Encoding method, encoding device, decoding method, and decoding device for image

Abstract

Provided are an image decoding method, an image decoding device, an image encoding method, and an image encoding device, the image decoding method comprising the steps of: acquiring, from an encoding unit, one or more transform units including the current transform unit; acquiring a transform coefficient of a residual block corresponding to the current transform unit; acquiring a residual sample of the residual block on the basis of the transform coefficient of the residual block; when the size of the residual block is greater than the size of the current transform unit, determining a residual sample of the encoding unit by using a portion of the residual sample of the residual block; and reconstructing a sample of the encoding unit on the basis of the residual sample of the encoding unit.

Description

Image encoding method, encoding device, decoding method and decoding device

[0001] The present disclosure relates to the field of image encoding and decoding. More specifically, it relates to an encoding and decoding method and device for predicting image samples.

[0002] In image encoding and decoding, the image is divided into blocks, and each block is predicted and decoded through inter prediction or intra prediction.

[0003] Inter prediction is a technique for compressing images by removing temporal redundancy between images. Inter prediction uses a reference image to predict blocks in the current image. The reference block most similar to the current block can be searched within a predetermined search range within the reference image. The current block is predicted based on the reference block, and the predicted block generated as a result of the prediction is subtracted from the current block to generate a residual block.

[0004] Intra prediction is a technique for compressing images by removing spatial redundancy within the image. Intra prediction generates a predicted block based on the surrounding pixels of the current block, depending on the prediction mode. The predicted block is then subtracted from the current block to create a residual block.

[0005] The residual block generated through inter-prediction or intra-prediction undergoes transformation and quantization and is then passed to the decoder. The decoder dequantizes and inversely transforms the residual block, and combines the predicted block of the current block with the residual block to reconstruct the current block. The decoder can filter the reconstructed current block to remove artifacts within it.

[0006] In one embodiment of the present disclosure, an image decoding method is provided. The image decoding method may include a step of obtaining one or more transformation units including a current transformation unit from a coding unit. The image decoding method may include a step of obtaining a transform coefficient of a residual block corresponding to the current transformation unit. The image decoding method may include a step of obtaining a residual sample of the residual block based on the transform coefficient of the residual block. The image decoding method may include a step of determining a residual sample of the coding unit using a portion of the residual samples of the residual block when a size of the residual block is larger than a size of the current transformation unit. The image decoding method may include a step of reconstructing a sample of the coding unit based on the residual sample of the coding unit.

[0007] In one embodiment of the present disclosure, an image decoding device is provided. The image decoding device may include at least one processor including a memory storing one or more instructions and processing circuitry. The at least one processor may execute one or more instructions to enable the device to obtain one or more transformation units including a current transformation unit from an encoding unit. The at least one processor may execute one or more instructions to enable the device to obtain transform coefficients of a residual block corresponding to the current transformation unit. The at least one processor may execute one or more instructions to enable the device to obtain residual samples of the residual block based on the transform coefficients of the residual block. The at least one processor may execute one or more instructions to enable the device to determine residual samples of the encoding unit using some of the residual samples of the residual block when the size of the residual block is larger than the size of the current transformation unit. The at least one processor may execute one or more instructions to enable the device to reconstruct samples of the encoding unit based on the residual samples of the encoding unit.

[0008] In one embodiment of the present disclosure, a video encoding method is provided. The video encoding method may include a step of obtaining one or more transformation units including a current transformation unit from a coding unit. The video encoding method may include a step of obtaining a residual sample of the current transformation unit. The video encoding method may include a step of determining a residual sample of the residual block using the residual sample of the current transformation unit when a size of the residual block corresponding to the current transformation unit is larger than a size of the current transformation unit. The video encoding method may include a step of obtaining a transform coefficient of the residual block based on the residual sample of the residual block. The video encoding method may include a step of generating a bitstream including information in which the transform coefficient of the residual block is encoded.

[0009] In one embodiment of the present disclosure, a computer-readable storage medium for storing a bitstream generated by an image encoding method is provided. The image encoding method for generating the bitstream stored in the storage medium may include a step of obtaining one or more transformation units including a current transformation unit from an encoding unit. The image encoding method for generating the bitstream stored in the storage medium may include a step of obtaining a residual sample of the current transformation unit. The image encoding method for generating the bitstream stored in the storage medium may include a step of determining a residual sample of a residual block using a residual sample of the current transformation unit when a size of a residual block corresponding to the current transformation unit is larger than a size of the current transformation unit. The image encoding method for generating the bitstream stored in the storage medium may include a step of obtaining a transform coefficient of the residual block based on the residual sample of the residual block. The image encoding method for generating the bitstream stored in the storage medium may include a step of generating a bitstream including information in which transform coefficients of the residual block are encoded.

[0010] FIG. 1 is a block diagram of an image decoding device according to one embodiment of the present disclosure.

[0011] FIG. 2 is a block diagram of an image encoding device according to one embodiment of the present disclosure.

[0012] FIG. 3 illustrates a process of dividing a current encoding unit to determine at least one encoding unit according to one embodiment of the present disclosure.

[0013] FIG. 4 illustrates a process of dividing a non-square coding unit to determine at least one coding unit according to one embodiment of the present disclosure.

[0014] FIG. 5 illustrates a process of dividing an encoding unit based on at least one of block shape information and segmentation shape mode information according to one embodiment of the present disclosure.

[0015] FIG. 6 illustrates a method for determining a predetermined coding unit among an odd number of coding units according to one embodiment of the present disclosure.

[0016] FIG. 7 illustrates the order in which multiple encoding units are processed when a current encoding unit is divided to determine multiple encoding units according to one embodiment of the present disclosure.

[0017] FIG. 8 illustrates a process for determining that a current encoding unit is split into an odd number of encoding units when encoding units cannot be processed in a predetermined order according to one embodiment of the present disclosure.

[0018] FIG. 9 illustrates a process of dividing a first encoding unit to determine at least one encoding unit according to one embodiment of the present disclosure.

[0019] FIG. 10 illustrates that the shapes into which a second encoding unit of a non-square shape determined by splitting a first encoding unit is split are limited when a predetermined condition is satisfied, according to one embodiment of the present disclosure.

[0020] FIG. 11 illustrates a process of splitting a square-shaped encoding unit when the split shape mode information cannot represent splitting into four square-shaped encoding units according to one embodiment of the present disclosure.

[0021] FIG. 12 illustrates that the processing order between a plurality of encoding units may vary depending on the process of splitting the encoding units according to one embodiment of the present disclosure.

[0022] FIG. 13 illustrates a process in which the depth of an encoding unit is determined as the shape and size of the encoding unit change when the encoding unit is recursively divided to determine a plurality of encoding units according to one embodiment of the present disclosure.

[0023] FIG. 14 illustrates an index (part index, hereinafter referred to as PID) for depth and encoding unit distinction that can be determined according to the shape and size of encoding units according to one embodiment of the present disclosure.

[0024] FIG. 15 illustrates that a plurality of coding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment of the present disclosure.

[0025] FIG. 16 illustrates encoding units that can be determined for each picture when the combination of forms into which encoding units can be divided is different for each picture according to one embodiment of the present disclosure.

[0026] FIG. 17 illustrates various forms of encoding units that can be determined based on segmentation mode information expressed in binary code according to one embodiment of the present disclosure.

[0027] FIG. 18 illustrates another form of a coding unit that can be determined based on segmentation mode information expressed in binary code according to one embodiment of the present disclosure.

[0028] FIG. 19 is a block diagram of an image encoding and decoding system that performs loop filtering according to one embodiment of the present disclosure.

[0029] FIG. 20 is a block diagram showing the configuration of an image decoding device according to one embodiment of the present disclosure.

[0030] FIG. 21 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0031] FIG. 22 is a diagram for explaining an image encoding and decoding process according to one embodiment of the present disclosure.

[0032] FIG. 23 is a diagram for explaining an image encoding and decoding process according to one embodiment of the present disclosure.

[0033] FIG. 24 is a diagram for explaining a residual block corresponding to a transformation unit according to one embodiment of the present disclosure.

[0034] FIG. 25 is a diagram for explaining a residual block corresponding to a transformation unit according to one embodiment of the present disclosure.

[0035] FIG. 26 is a flowchart of a method for determining a conversion unit according to one embodiment of the present disclosure.

[0036] FIG. 27 is a diagram for explaining a process of determining a transformation unit having residual data according to one embodiment of the present disclosure.

[0037] FIG. 28 is a diagram for explaining a process of determining a transformation unit having residual data according to one embodiment of the present disclosure.

[0038] FIG. 29 is a diagram for explaining a process of determining a transformation unit having residual data according to one embodiment of the present disclosure.

[0039] FIG. 30 is a diagram illustrating a transformation unit having residual data according to one embodiment of the present disclosure.

[0040] FIG. 31 is a flowchart of a method for obtaining data of a conversion unit according to one embodiment of the present disclosure.

[0041] FIG. 32 is a diagram for explaining an image decoding method according to one embodiment of the present disclosure.

[0042] FIG. 33 is a block diagram showing the configuration of an image encoding device according to one embodiment of the present disclosure.

[0043] FIG. 34 is a flowchart illustrating an image encoding method according to one embodiment of the present disclosure.

[0044] FIG. 35 is a flowchart of a method for determining a conversion unit according to one embodiment of the present disclosure.

[0045] FIG. 36 is a flowchart of a method for determining data of a conversion unit according to one embodiment of the present disclosure.

[0046] In this disclosure, the expression “at least one of a, b or c” may refer to “a”, “b”, “c”, “a and b”, “a and c”, “b and c”, “all of a, b and c”, or variations thereof.

[0047] In the present disclosure, the expression "a, b and / or c" can be replaced with "at least one of a, b or c." That is, the expression "a, b and / or c" can refer to "a," "b," "c," "a and b," "a and c," "b and c," "all of a, b and c," or variations thereof.

[0048] The present disclosure may be subject to various modifications and various embodiments. Examples are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the embodiments of the present disclosure, and the present disclosure may include all modifications, equivalents, and alternatives that fall within the spirit and technical scope of the various embodiments.

[0049] The terms used in this disclosure are selected from widely used, common terms, taking into account the functions of the disclosure. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings can be understood through the relevant description. Therefore, the terms used in this disclosure should not be defined simply as names of terms, but rather based on the meanings of the terms and the overall content of the disclosure.

[0050] In this disclosure, singular expressions may include plural expressions unless the context clearly dictates otherwise. In describing embodiments, detailed descriptions of related known technologies will be omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, numbers (e.g., "first," "second," etc.) used in the description of embodiments serve as identifiers to distinguish one component from another.

[0051] In the present disclosure, when a component is referred to as being “connected” or “connected” to another component, the component may be directly connected or connected to the other component, but unless there is a specific description to the contrary, the component may also be connected or connected via another component in between.

[0052] When a part in this disclosure is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be further included, unless otherwise specifically stated. Components expressed as "unit", "module", etc. in this disclosure may be two or more components combined into one component, or one component may be divided into two or more more detailed components. In addition, each component described below may additionally perform some or all of the functions performed by other components in addition to its own main function, and some of the main functions performed by each component may be exclusively performed by other components.

[0053] The expression "configured to" as used herein can be used interchangeably with, for example, "suitable for", "having the capacity to", "designed to", "adapted to", "made to", or "capable of", depending on the context. The term "configured to" does not necessarily mean something is "specifically designed to" in terms of hardware. Alternatively, in some contexts, the expression "a system configured to" can include that the system is "capable of" in conjunction with other devices or components. For example, the phrase "a processor configured to perform A, B, and C" can include a dedicated processor for performing the operations (e.g., an embedded processor), or a general-purpose processor (e.g., a CPU or an application processor) that can perform the operations by executing one or more software programs stored in a memory.

[0054] At least one processor according to embodiments of the present disclosure may include various processing circuits and / or multiple processors. For example, the term "processor" as used herein, including in the claims, may include various processing circuits including at least one processor, one or more of which are configured to individually and / or collectively perform the various functions described herein in a distributed manner. As used herein, when "processor," "at least one processor," and "one or more processors" are described as being configured to perform various functions, these terms may include, for example, without limitation, a single processor performing some of the recited functions, other processor(s) performing other of the recited functions, and still other situations where a single processor can perform all of the recited functions. Additionally, the at least one processor may include a combination of processors that perform the various functions enumerated / disclosed, for example, in a distributed manner. The at least one processor may execute program instructions to achieve or perform the various functions.

[0055] In the present disclosure, an 'image' may include a picture, a still image, a frame, a moving image composed of a plurality of consecutive still images, or a video.

[0056] In the present disclosure, a "sample" may include data assigned to a sampling location in an image and may include data to be processed. For example, a sample may include pixels within a frame in a spatial domain. A block may refer to a unit including a plurality of samples.

[0057] Hereinafter, with reference to FIGS. 1 to 19, an image encoding method and device based on a tree-structured encoding unit and a transformation unit according to an embodiment of the present disclosure, and an image decoding method and device are disclosed.

[0058] FIG. 1 illustrates a block diagram of an image decoding device (100) according to one embodiment of the present disclosure.

[0059] The video decoding device (100) may include a bitstream acquisition unit (110) and a decoding unit (120). The bitstream acquisition unit (110) and the decoding unit (120) may include at least one processor. In addition, the bitstream acquisition unit (110) and the decoding unit (120) may include a memory that stores commands to be executed by at least one processor.

[0060] The bitstream acquisition unit (110) can receive a bitstream. The bitstream includes information obtained by encoding an image by an image encoding device (200) described below. In addition, the bitstream can be transmitted from the image encoding device (200). The image encoding device (200) and the image decoding device (100) can be connected by wire or wirelessly, and the bitstream acquisition unit (110) can receive the bitstream by wire or wirelessly. The bitstream acquisition unit (110) can receive the bitstream from a storage medium such as an optical medium, a hard disk, etc. The decoding unit (120) can restore the image based on information obtained from the received bitstream. The decoding unit (120) can obtain syntax elements for restoring the image from the bitstream. The decoding unit (120) can restore the image based on the syntax elements.

[0061] To describe in detail the operation of the video decoding device (100), the bitstream acquisition unit (110) can receive a bitstream.

[0062] The image decoding device (100) may perform an operation of obtaining a binstring corresponding to a splitting shape mode of an encoding unit from a bitstream. In addition, the image decoding device (100) may perform an operation of determining a splitting rule of the encoding unit. In addition, the image decoding device (100) may perform an operation of splitting the encoding unit into a plurality of encoding units based on at least one of the binstring corresponding to the splitting shape mode and the splitting rule. In order to determine the splitting rule, the image decoding device (100) may determine a first allowable range of the size of the encoding unit according to a ratio of the width and height of the encoding unit. In order to determine the splitting rule, the image decoding device (100) may determine a second allowable range of the size of the encoding unit according to the splitting shape mode of the encoding unit.

[0063] Below, the division of encoding units according to one embodiment of the present disclosure is described in detail.

[0064] First, a picture can be divided into one or more slices or one or more tiles. A slice or a tile can be a sequence of one or more maximum coding tree units (CTUs). Depending on the implementation, a slice may include one or more tiles, and a slice may include one or more maximum coding units. A slice including one or more tiles can be determined within a picture.

[0065] The concept of a maximum coding block (Coding Tree Block; CTB) contrasts with a maximum coding unit (CTU). A maximum coding block (CTB) is an NxN block containing NxN samples (N is an integer). Each color component can be divided into one or more maximum coding blocks.

[0066] When a picture has three sample arrays (sample arrays for Y, Cr, and Cb components), a maximum coding unit (CTU) is a unit that includes a maximum coding block of luma samples, two maximum coding blocks of corresponding chroma samples, and syntax structures used to encode the luma samples and chroma samples. When a picture is a monochrome picture, a maximum coding unit is a unit that includes a maximum coding block of monochrome samples and syntax structures used to encode the monochrome samples. When a picture is a picture that is encoded with a color plane that is separated by color components, a maximum coding unit is a unit that includes syntax structures used to encode samples of the picture and the image.

[0067] A single maximum coding block (CTB) may be partitioned into MxN coding blocks containing MxN samples (where M and N are integers). In one embodiment, a coding block may be referred to as a coding unit.

[0068] When a picture has a sample array for each Y, Cr, and Cb component, a coding unit (CU) is a unit that includes a coding block for a luma sample and two coding blocks for corresponding chroma samples, and syntax structures used to encode the luma sample and the chroma sample. When a picture is a monochrome picture, a coding unit is a unit that includes a coding block for a monochrome sample and syntax structures used to encode the monochrome samples. When a picture is a picture that is encoded with a color plane that is separated by color component, a coding unit is a unit that includes syntax structures used to encode samples of the picture and the image.

[0069] As explained above, the maximum coding block and the maximum coding unit are distinct concepts, and the coding block and the coding unit are distinct concepts. That is, the (maximum) coding unit refers to a data structure including a (maximum) coding block including the corresponding sample and a syntax structure corresponding to it. However, since a person skilled in the art can understand that the (maximum) coding unit or the (maximum) coding block refers to a block of a predetermined size including a predetermined number of samples, the following specification will refer to the maximum coding block and the maximum coding unit, or the coding block and the coding unit, without distinction unless there are special circumstances.

[0070] An image can be divided into Coding Tree Units (CTUs). The size of the CTUs can be determined based on information obtained from the bitstream. The shape of the CTUs can be a square of equal size, but is not limited thereto.

[0071] For example, information about the maximum size of a luma coding block can be obtained from the bitstream. For example, the maximum size of the luma coding block indicated by the information about the maximum size of the luma coding block can be one of 4x4, 8x8, 16x16, 32x32, 64x64, 128x128, and 256x256.

[0072] For example, information about the maximum size of a luma coding block that can be split into two and the luma block size difference can be obtained from the bitstream. The information about the luma block size difference can indicate the size difference between a luma maximum coding unit and a maximum luma coding block that can be split into two. Therefore, by combining the information about the maximum size of a luma coding block that can be split into two obtained from the bitstream and the information about the luma block size difference, the size of the luma maximum coding unit can be determined. Using the size of the luma maximum coding unit, the size of the chroma maximum coding unit can also be determined. For example, if the Y: Cb: Cr ratio is 4:2:0 according to the color format, the size of the chroma block can be half the size of the luma block, and similarly, the size of the chroma maximum coding unit can be half the size of the luma maximum coding unit.

[0073] According to one embodiment, since information about the maximum size of a luma coding block capable of binary splitting is obtained from a bitstream, the maximum size of the luma coding block capable of binary splitting can be determined variably. Alternatively, the maximum size of the luma coding block capable of ternary splitting can be fixed. For example, the maximum size of a luma coding block capable of ternary splitting in an I picture may be 32x32, and the maximum size of a luma coding block capable of ternary splitting in a P picture or a B picture may be 64x64.

[0074] Additionally, the maximum coding unit can be hierarchically divided into coding units based on the division shape mode information obtained from the bitstream. As the division shape mode information, at least one of information indicating whether quad division is performed, information indicating whether multi-division is performed, division direction information, and division type information can be obtained from the bitstream.

[0075] For example, information indicating whether a quad split is present may indicate whether the current encoding unit is to be quad split (QUAD_SPLIT) or not to be quad split.

[0076] If the current encoding unit is not quad-split, the information indicating whether it is multi-split may indicate whether the current encoding unit will not be split any further (NO_SPLIT) or will be binary / ternary split.

[0077] When the current encoding unit is binary or ternary split, the split direction information indicates that the current encoding unit is split in either the horizontal or vertical direction.

[0078] When the current encoding unit is split in the horizontal or vertical direction, the split type information indicates that the current encoding unit is split into binary split or ternary split.

[0079] Depending on the split direction information and the split type information, the split mode of the current encoding unit can be determined. The split mode when the current encoding unit is split into binaries in the horizontal direction can be determined as binary horizontal split (SPLIT_BT_HOR), the split mode when the current encoding unit is split into ternary horizontal split (SPLIT_TT_HOR), the split mode when the current encoding unit is split into binaries in the vertical direction can be determined as binary vertical split (SPLIT_BT_VER), and the split mode when the current encoding unit is split into ternary vertical split (SPLIT_TT_VER).

[0080] The image decoding device (100) can obtain segmentation shape mode information from a bitstream from a single binstring. The format of the bitstream received by the image decoding device (100) can include a fixed length binary code, a unary code, a truncated unary code, a predetermined binary code, etc. The binstring represents information as a series of binary numbers. The binstring can be composed of at least one bit. The image decoding device (100) can obtain segmentation shape mode information corresponding to the binstring based on a segmentation rule. The image decoding device (100) can determine whether to quad-segment an encoding unit, whether not to quad-segment, or the segmentation direction and segmentation type based on a single binstring.

[0081] The coding unit may be smaller than or equal to the maximum coding unit. For example, the maximum coding unit is also a coding unit with the maximum size, so it is a coding unit. If the split shape mode information for the maximum coding unit indicates that it is not split, the coding unit determined from the maximum coding unit has the same size as the maximum coding unit. If the split shape mode information for the maximum coding unit indicates that it is split, the maximum coding unit may be split into coding units. In addition, if the split shape mode information for the coding unit indicates splitting, the coding units may be split into coding units of smaller sizes. However, the splitting of the image is not limited thereto, and the maximum coding unit and the coding units may not be distinguished. The splitting of the coding unit is described in more detail with reference to FIGS. 3 to 16.

[0082] Additionally, one or more prediction blocks for prediction may be determined from the coding unit. The prediction blocks may be equal to or smaller than the coding unit. Additionally, one or more transform blocks for transformation may be determined from the coding unit. The transform blocks may be equal to or smaller than the coding unit. The transform blocks may be referred to as transform units.

[0083] The shape and size of the transformation block and the prediction block may be unrelated.

[0084] In another embodiment, prediction may be performed using the encoding unit as a prediction block. Transformation may also be performed using the encoding unit as a transform block.

[0085] The division of a coding unit is described in more detail with reference to FIGS. 3 to 16. The current block and neighboring blocks of the present disclosure may represent one of a maximum coding unit, a coding unit, a prediction block, and a transform block. In addition, the current block or the current coding unit is a block currently being decoded or encoded, or a block currently being divided. The neighboring block may be a block reconstructed before the current block. The neighboring block may be spatially or temporally adjacent to the current block. The neighboring block may be located on one of the lower left, left, upper left, upper right, upper right, right, and lower right sides of the current block.

[0086] The above-described embodiment describes operations related to an image decoding method performed by an image decoding device (100). Hereinafter, the operations of an image encoding device (200) that performs an image encoding method corresponding to the reverse process of the image decoding method will be described through one embodiment of the present disclosure.

[0087] FIG. 2 illustrates a block diagram of an image encoding device (200) capable of encoding an image based on at least one of block shape information and segmentation shape mode information according to one embodiment of the present disclosure.

[0088] The video encoding device (200) may include an encoding unit (220) and a bitstream generation unit (210). The encoding unit (220) may receive an input image and encode the input image. The encoding unit (220) may encode the input image to obtain at least one syntax element. The syntax element may include at least one of a skip flag, a prediction mode, a motion vector difference, a motion vector prediction method (or index), a transform quantized coefficient, a coded block pattern, a coded block flag, an intra prediction mode, a direct flag, a merge flag, a delta QP, a reference index, a prediction direction, and a transform index. The encoding unit (220) may determine a context model based on block shape information including at least one of a shape, a direction, a ratio of width and height, or a size of an encoding unit.

[0089] The bitstream generation unit (210) can generate a bitstream based on an encoded input image. For example, the bitstream generation unit (210) can generate a bitstream by entropy encoding a syntax element based on a context model. In one embodiment of the present disclosure, the image encoding device (100) can generate a bitstream according to an image encoding method to be described below. The image encoding device (100) can store the bitstream in a computer-readable storage medium.

[0090] In one embodiment of the present disclosure, the image encoding device (200) can transmit a bitstream to the image decoding device (100). For example, the image encoding device (200) can transmit a bitstream generated by a image encoding method.

[0091] According to one embodiment of the present disclosure, the encoding unit (220) of the image encoding device (200) can determine the shape of an encoding unit. For example, the encoding unit may be square or have a non-square shape, and information indicating such shape may be included in the block shape information.

[0092] According to one embodiment of the present disclosure, the encoding unit (220) can determine the shape into which the encoding unit is to be split. The encoding unit (220) can determine the shape of at least one encoding unit included in the encoding unit, and the bitstream generation unit (210) can generate a bitstream including split shape mode information including information about the shape of such encoding unit.

[0093] According to one embodiment of the present disclosure, the encoder (220) can determine whether the encoding unit is split or not. If the encoder (220) determines that the encoding unit includes only one encoding unit or that the encoding unit is not split, the bitstream generation unit (210) can generate a bitstream including split shape mode information indicating that the encoding unit is not split. In addition, the encoder (220) can split the encoding unit into a plurality of encoding units, and the bitstream generation unit (210) can generate a bitstream including split shape mode information indicating that the encoding unit is split into a plurality of encoding units.

[0094] According to one embodiment of the present disclosure, information indicating the number of coding units to be split into or the direction in which the coding unit is split may be included in the splitting mode information. For example, the splitting mode information may indicate splitting in at least one of the vertical and horizontal directions, or may indicate no splitting.

[0095] The video encoding device (200) determines information about the segmentation shape mode based on the segmentation shape mode of the encoding unit. The video encoding device (200) determines a context model based on at least one of the shape, direction, width, and height ratio or size of the encoding unit. Then, the video encoding device (200) generates information about the segmentation shape mode for segmenting the encoding unit based on the context model as a bitstream.

[0096] In order to determine a context model, the video encoding device (200) may obtain an array for matching at least one of the shape, direction, width and height ratio or size of the encoding unit with an index for the context model. The video encoding device (200) may obtain an index for the context model based on at least one of the shape, direction, width and height ratio or size of the encoding unit in the array. The video encoding device (200) may determine the context model based on the index for the context model.

[0097] The video encoding device (200) may further determine the context model based on block shape information including at least one of the shape, direction, width, and height ratio or size of a neighboring encoding unit adjacent to the encoding unit, in order to determine the context model. In addition, the neighboring encoding unit may include at least one of encoding units located on the lower left, left, upper left, upper right, right, or lower right of the encoding unit.

[0098] In addition, the video encoding device (200) may compare the length of the width of the upper peripheral encoding unit with the length of the width of the encoding unit to determine the context model. In addition, the video encoding device (200) may compare the length of the height of the left and right peripheral encoding units with the length of the height of the encoding unit. In addition, the video encoding device (200) may determine the context model based on the comparison results.

[0099] Since the operation of the video encoding device (200) includes similar contents to the operation of the video decoding device (100) described in FIGS. 3 to 19, a detailed description is omitted.

[0100] FIG. 3 illustrates a process in which an image decoding device (100) divides a current encoding unit to determine at least one encoding unit according to one embodiment of the present disclosure.

[0101] The block shape may include 4Nx4N, 4Nx2N, 2Nx4N, 4NxN, Nx4N, 32NxN, Nx32N, 16NxN, Nx16N, 8NxN or Nx8N, where N may be a positive integer. The block shape information is information indicating at least one of the shape, direction, width and height ratio or size of the encoding unit.

[0102] The shape of the encoding unit may include square and non-square. When the width and height of the encoding unit are equal (i.e., when the block shape of the encoding unit is 4Nx4N), the image decoding device (100) may determine the block shape information of the encoding unit as square. The image decoding device (100) may determine the shape of the encoding unit as non-square.

[0103] When the width and height of the encoding unit are different (i.e., when the block shape of the encoding unit is 4Nx2N, 2Nx4N, 4NxN, Nx4N, 32NxN, Nx32N, 16NxN, Nx16N, 8NxN, or Nx8N), the image decoding device (100) may determine the block shape information of the encoding unit to be non-square. When the shape of the encoding unit is non-square, the image decoding device (100) may determine the ratio of the width and height among the block shape information of the encoding unit to be at least one of 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, 1:32, and 32:1. Additionally, based on the width length and height length of the encoding unit, the image decoding device (100) can determine whether the encoding unit is in the horizontal or vertical direction. Additionally, based on at least one of the width length, height length, or area of ​​the encoding unit, the image decoding device (100) can determine the size of the encoding unit.

[0104] According to one embodiment of the present disclosure, the image decoding device (100) can determine the shape of an encoding unit using block shape information, and can determine the shape into which the encoding unit is divided using segmentation shape mode information. That is, the splitting method of the encoding unit indicated by the segmentation shape mode information can be determined depending on which block shape the block shape information used by the image decoding device (100) indicates.

[0105] The image decoding device (100) can obtain the segmentation shape mode information from the bitstream. However, the present invention is not limited thereto, and the image decoding device (100) and the image encoding device (200) can determine the pre-agreed segmentation shape mode information based on the block shape information. The image decoding device (100) can determine the pre-agreed segmentation shape mode information for the maximum coding unit or the minimum coding unit. For example, the image decoding device (100) can determine the segmentation shape mode information for the maximum coding unit as quad split. In addition, the image decoding device (100) can determine the segmentation shape mode information for the minimum coding unit as “not split.” Specifically, the image decoding device (100) can determine the size of the maximum coding unit as 256x256. The image decoding device (100) can determine the pre-agreed segmentation shape mode information as quad split. Quad splitting is a splitting mode that divides both the width and height of an encoding unit in half. The image decoding device (100) can obtain a coding unit of size 128x128 from a maximum coding unit of size 256x256 based on the splitting mode information. In addition, the image decoding device (100) can determine the size of the minimum coding unit as 4x4. The image decoding device (100) can obtain splitting mode information indicating "not splitting" for the minimum coding unit.

[0106] According to one embodiment of the present disclosure, the image decoding device (100) may use block shape information indicating that the current encoding unit is a square shape. For example, the image decoding device (100) may determine whether to not split a square encoding unit, to split it vertically, to split it horizontally, to split it into four encoding units, etc., according to the split shape mode information. Referring to FIG. 3, when the block shape information of the current encoding unit (300) indicates a square shape, the decoding unit (120) may not split an encoding unit (310a) having the same size as the current encoding unit (300) according to the split shape mode information indicating that it is not split, or may determine a split encoding unit (310b, 310c, 310d, 310e, 310f, etc.) based on the split shape mode information indicating a predetermined splitting method.

[0107] Referring to FIG. 3, the image decoding device (100) may determine two encoding units (310b) by vertically dividing the current encoding unit (300) based on the split shape mode information indicating that the current encoding unit (300) is split in the vertical direction according to one embodiment of the present disclosure. The image decoding device (100) may determine two encoding units (310c) by horizontally dividing the current encoding unit (300) based on the split shape mode information indicating that the current encoding unit (300) is split in the horizontal direction. The image decoding device (100) may determine four encoding units (310d) by vertically dividing the current encoding unit (300) and the horizontal direction based on the split shape mode information indicating that the current encoding unit (300) is split in the vertical direction and the horizontal direction. The image decoding device (100) may determine three coding units (310e) into which the current coding unit (300) is vertically divided based on the partition shape mode information indicating that the current coding unit (300) is ternary divided in the vertical direction according to one embodiment of the present disclosure. The image decoding device (100) may determine three coding units (310f) into which the current coding unit (300) is horizontally divided based on the partition shape mode information indicating that the current coding unit (300) is ternary divided in the horizontal direction. However, the partition shapes into which a square coding unit may be divided should not be interpreted as being limited to the above-described shapes, and may include various shapes that the partition shape mode information may indicate. Specified partition shapes into which a square coding unit is divided will be specifically described below through one embodiment of the present disclosure.

[0108] FIG. 4 illustrates a process in which an image decoding device (100) divides a non-square coding unit to determine at least one coding unit according to one embodiment of the present disclosure.

[0109] According to one embodiment of the present disclosure, an image decoding device (100) may utilize block shape information indicating that a current encoding unit is non-square in shape. The image decoding device (100) may determine whether to not split a non-square current encoding unit or to split it using a predetermined method based on the split shape mode information. Referring to FIG. 4, when the block shape information of the current encoding unit (400 or 450) indicates a non-square shape, the image decoding device (100) may determine an encoding unit (410 or 460) having the same size as the current encoding unit (400 or 450) according to the split shape mode information indicating that it is not split, or may determine a split encoding unit (420a, 420b, 430a, 430b, 430c, 470a, 470b, 480a, 480b, 480c) based on the split shape mode information indicating a predetermined splitting method. A predetermined splitting method by which a non-square encoding unit is split will be described in detail below through an embodiment of the present disclosure.

[0110] According to one embodiment of the present disclosure, the image decoding device (100) can determine a form in which an encoding unit is split using split shape mode information, and in this case, the split shape mode information can indicate the number of at least one encoding unit generated by splitting the encoding unit. Referring to FIG. 4, when the split shape mode information indicates that the current encoding unit (400 or 450) is split into two encoding units, the image decoding device (100) can split the current encoding unit (400 or 450) based on the split shape mode information to determine two encoding units (420a, 420b, or 470a, 470b) included in the current encoding unit.

[0111] According to one embodiment of the present disclosure, when the image decoding device (100) splits a current encoding unit (400 or 450) having a non-square shape based on split shape mode information, the image decoding device (100) may split the current encoding unit by considering the position of the long side of the non-square current encoding unit (400 or 450). For example, the image decoding device (100) may split the current encoding unit (400 or 450) in a direction that splits the long side of the current encoding unit (400 or 450) by considering the shape of the current encoding unit (400 or 450) to determine a plurality of encoding units.

[0112] According to one embodiment of the present disclosure, if the splitting shape mode information indicates that the encoding unit is split into an odd number of blocks (ternary splitting), the image decoding device (100) may determine an odd number of encoding units included in the current encoding unit (400 or 450). For example, if the splitting shape mode information indicates that the current encoding unit (400 or 450) is split into three encoding units, the image decoding device (100) may split the current encoding unit (400 or 450) into three encoding units (430a, 430b, 430c, 480a, 480b, 480c).

[0113] According to one embodiment of the present disclosure, the ratio of the width and height of the current encoding unit (400 or 450) may be 4:1 or 1:4. When the ratio of the width and height is 4:1, the length of the width is longer than the length of the height, so the block shape information may be in the horizontal direction. When the ratio of the width and height is 1:4, the length of the width is shorter than the length of the height, so the block shape information may be in the vertical direction. The image decoding device (100) may determine to split the current encoding unit into an odd number of blocks based on the split shape mode information. In addition, the image decoding device (100) may determine the splitting direction of the current encoding unit (400 or 450) based on the block shape information of the current encoding unit (400 or 450). For example, if the current encoding unit (400) is in the vertical direction, the image decoding device (100) can divide the current encoding unit (400) in the horizontal direction to determine encoding units (430a, 430b, 430c). Also, if the current encoding unit (450) is in the horizontal direction, the image decoding device (100) can divide the current encoding unit (450) in the vertical direction to determine encoding units (480a, 480b, 480c).

[0114] According to one embodiment of the present disclosure, the image decoding device (100) may determine an odd number of coding units included in the current coding unit (400 or 450), and the sizes of the determined coding units may not all be the same. For example, among the determined odd number of coding units (430a, 430b, 430c, 480a, 480b, 480c), the size of a given coding unit (430b or 480b) may have a different size from the other coding units (430a, 430c, 480a, 480c). That is, the encoding units into which the current encoding unit (400 or 450) can be divided and determined can have multiple types of sizes, and in some cases, an odd number of encoding units (430a, 430b, 430c, 480a, 480b, 480c) can each have different sizes.

[0115] According to one embodiment of the present disclosure, when the split shape mode information indicates that the coding unit is split into an odd number of blocks, the image decoding device (100) can determine an odd number of coding units included in the current coding unit (400 or 450), and further, the image decoding device (100) can place a predetermined restriction on at least one coding unit among the odd number of coding units generated by splitting. Referring to FIG. 4, the image decoding device (100) can perform a decoding process for a coding unit (430b, 480b) located in the center among three coding units (430a, 430b, 430c, 480a, 480b, 480c) generated by splitting the current coding unit (400 or 450) differently from the decoding process for other coding units (430a, 430c, 480a, 480c). For example, the image decoding device (100) can restrict the encoding unit (430b, 480b) located in the center from being split any further, unlike other encoding units (430a, 430c, 480a, 480c), or can restrict it to be split only a predetermined number of times.

[0116] FIG. 5 illustrates a process in which an image decoding device (100) divides an encoding unit based on at least one of block shape information and division shape mode information according to one embodiment of the present disclosure.

[0117] According to one embodiment of the present disclosure, the image decoding device (100) may determine whether to split or not to split a first coding unit (500) having a square shape into coding units based on at least one of block shape information and split shape mode information. If the split shape mode information indicates that the first coding unit (500) is split in the horizontal direction according to one embodiment of the present disclosure, the image decoding device (100) may split the first coding unit (500) in the horizontal direction to determine a second coding unit (510). The first coding unit, the second coding unit, and the third coding unit used according to one embodiment of the present disclosure are terms used to understand the relationship before and after splitting between coding units. For example, when the first coding unit is split, the second coding unit may be determined, and when the second coding unit is split, the third coding unit may be determined. In the following, the relationship between the first encoding unit, the second encoding unit, and the third encoding unit used can be understood as following the above-described characteristics.

[0118] According to one embodiment of the present disclosure, the image decoding device (100) may determine to split or not split the determined second encoding unit (510) into encoding units based on the splitting shape mode information. Referring to FIG. 5, the image decoding device (100) may split the first encoding unit (500) based on the splitting shape mode information to split the determined second encoding unit (510) of a non-square shape into at least one third encoding unit (520a, 520b, 520c, 520d, etc.) or may not split the second encoding unit (510). The image decoding device (100) can obtain split shape mode information, and the image decoding device (100) can split the first encoding unit (500) based on the obtained split shape mode information to split a plurality of second encoding units (e.g., 510) of various shapes, and the second encoding unit (510) can be split according to the way in which the first encoding unit (500) is split based on the split shape mode information. According to one embodiment of the present disclosure, when the first encoding unit (500) is split into the second encoding unit (510) based on the split shape mode information for the first encoding unit (500), the second encoding unit (510) can also be split into the third encoding unit (e.g., 520a, 520b, 520c, 520d, etc.) based on the split shape mode information for the second encoding unit (510). That is, the coding unit can be recursively split based on the split shape mode information associated with each coding unit. Accordingly, a square coding unit can be determined from a non-square coding unit, and such a square coding unit can be recursively split to determine a non-square coding unit.

[0119] Referring to FIG. 5, among the odd number of third coding units (520b, 520c, 520d) into which the non-square second coding unit (510) is split, a predetermined coding unit (e.g., a coding unit located in the middle or a square coding unit) may be split recursively. According to one embodiment of the present disclosure, the non-square third coding unit (520b), which is one of the odd number of third coding units (520b, 520c, 520d), may be split horizontally into a plurality of fourth coding units. The non-square fourth coding unit (530b or 530d), which is one of the plurality of fourth coding units (530a, 530b, 530c, 530d), may be split again into a plurality of coding units. For example, the fourth coding unit (530b or 530d) having a non-square shape may be further divided into an odd number of coding units. A method that can be used for recursive division of coding units will be described later through an embodiment of the present disclosure.

[0120] According to one embodiment of the present disclosure, the image decoding device (100) may split each of the third encoding units (520a, 520b, 520c, 520d, etc.) into encoding units based on the splitting shape mode information. In addition, the image decoding device (100) may determine not to split the second encoding unit (510) based on the splitting shape mode information. According to one embodiment of the present disclosure, the image decoding device (100) may split the second encoding unit (510) having a non-square shape into an odd number of third encoding units (520b, 520c, 520d). The image decoding device (100) may place a predetermined restriction on a predetermined third encoding unit among the odd number of third encoding units (520b, 520c, 520d). For example, the image decoding device (100) can limit the encoding unit (520c) located in the middle among an odd number of third encoding units (520b, 520c, 520d) to not be divided any further or to be divided a settable number of times.

[0121] Referring to FIG. 5, the image decoding device (100) may limit the coding unit (520c) located in the middle among the odd number of third coding units (520b, 520c, 520d) included in the second coding unit (510) having a non-square shape to not be split any further, or to be split in a predetermined split form (for example, to be split only into four coding units or to be split in a form corresponding to the split form of the second coding unit (510), or to be split only a predetermined number of times (for example, to be split only n times, where n>0). However, the above limitations on the coding unit (520c) located in the middle are merely simple embodiments and should not be interpreted as being limited to the above-described embodiments, but should be interpreted as including various limitations in which the coding unit (520c) located in the middle can be decoded differently from the other coding units (520b, 520d).

[0122] According to one embodiment of the present disclosure, the image decoding device (100) can obtain the segmentation shape mode information used to segment the current encoding unit from a predetermined location within the current encoding unit.

[0123] FIG. 6 illustrates a method for an image decoding device (100) to determine a predetermined encoding unit among an odd number of encoding units according to one embodiment of the present disclosure.

[0124] Referring to FIG. 6, the split shape mode information of the current encoding unit (600, 650) can be obtained from a sample at a predetermined position among a plurality of samples included in the current encoding unit (600, 650) (for example, a sample (640, 690) located in the center). However, the predetermined position within the current encoding unit (600) from which at least one of the split shape mode information can be obtained should not be interpreted as being limited to the center position illustrated in FIG. 6, but should be interpreted as including various positions (for example, top, bottom, left, right, upper left, lower left, upper right, or lower right, etc.) that can be included within the current encoding unit (600). The image decoding device (100) can obtain the split shape mode information obtained from the predetermined position and determine whether or not to split the current encoding unit into encoding units of various shapes and sizes.

[0125] According to one embodiment of the present disclosure, the image decoding device (100) may select one of the coding units when the current coding unit is divided into a predetermined number of coding units. Various methods may be used to select one of the multiple coding units, and a description of such methods will be provided later through one embodiment of the present disclosure.

[0126] According to one embodiment of the present disclosure, an image decoding device (100) can divide a current encoding unit into a plurality of encoding units and determine an encoding unit at a predetermined position.

[0127] According to one embodiment of the present disclosure, the image decoding device (100) may use information indicating the positions of each of the odd-numbered coding units to determine an coding unit located in the middle of the odd-numbered coding units. Referring to FIG. 6, the image decoding device (100) may split the current coding unit (600) or the current coding unit (650) to determine odd-numbered coding units (620a, 620b, 620c) or odd-numbered coding units (660a, 660b, 660c). The image decoding device (100) may use information about the positions of the odd-numbered coding units (620a, 620b, 620c) or odd-numbered coding units (660a, 660b, 660c) to determine the middle coding unit (620b) or the middle coding unit (660b). For example, the image decoding device (100) can determine the coding unit (620b) located in the center by determining the positions of the coding units (620a, 620b, 620c) based on information indicating the positions of predetermined samples included in the coding units (620a, 620b, 620c). Specifically, the image decoding device (100) can determine the coding unit (620b) located in the center by determining the positions of the coding units (620a, 620b, 620c) based on information indicating the positions of samples (630a, 630b, 630c) at the upper left of the coding units (620a, 620b, 620c).

[0128] According to one embodiment of the present disclosure, information indicating the positions of the upper left samples (630a, 630b, 630c) included in each of the coding units (620a, 620b, 620c) may include information on the positions or coordinates of the coding units (620a, 620b, 620c) within the picture. According to one embodiment of the present disclosure, information indicating the positions of the upper left samples (630a, 630b, 630c) included in each of the coding units (620a, 620b, 620c) may include information indicating the width or height of the coding units (620a, 620b, 620c) included in the current coding unit (600), and this width or height may correspond to information indicating the difference between the coordinates of the coding units (620a, 620b, 620c) within the picture. That is, the image decoding device (100) can determine the encoding unit (620b) located in the center by directly using information about the positions or coordinates of the encoding units (620a, 620b, 620c) within the picture or by using information about the width or height of the encoding unit corresponding to the difference between the coordinates.

[0129] According to one embodiment of the present disclosure, information indicating the position of the sample (630a) at the upper left of the upper encoding unit (620a) may represent coordinates (xa, ya), information indicating the position of the sample (530b) at the upper left of the middle encoding unit (620b) may represent coordinates (xb, yb), and information indicating the position of the sample (630c) at the upper left of the lower encoding unit (620c) may represent coordinates (xc, yc). The image decoding apparatus (100) may determine the middle encoding unit (620b) using the coordinates of the upper left samples (630a, 630b, 630c) included in the encoding units (620a, 620b, 620c), respectively. For example, when the coordinates of the samples (630a, 630b, 630c) on the upper left are sorted in ascending or descending order, the encoding unit (620b) including the coordinates (xb, yb) of the sample (630b) located in the center can be determined as the encoding unit located in the center among the encoding units (620a, 620b, 620c) determined by dividing the current encoding unit (600). However, the coordinates indicating the positions of the upper left samples (630a, 630b, 630c) may indicate coordinates indicating the absolute positions within the picture, and further, based on the position of the upper left sample (630a) of the upper left coding unit (620a), the (dxb, dyb) coordinates, which are information indicating the relative position of the sample (630b) of the upper left of the middle coding unit (620b), and the (dxc, dyc) coordinates, which are information indicating the relative position of the sample (630c) of the upper left of the lower coding unit (620c), may be used. In addition, the method of determining the coding unit of a given position by using the coordinates of the corresponding sample as information indicating the position of the sample included in the coding unit should not be interpreted as being limited to the above-described method, but should be interpreted as various arithmetic methods that can utilize the coordinates of the sample.

[0130] According to one embodiment of the present disclosure, the image decoding device (100) can divide the current encoding unit (600) into a plurality of encoding units (620a, 620b, 620c), and select an encoding unit from among the encoding units (620a, 620b, 620c) according to a predetermined criterion. For example, the image decoding device (100) can select an encoding unit (620b) having a different size from among the encoding units (620a, 620b, 620c).

[0131] According to one embodiment of the present disclosure, the image decoding device (100) can determine the width or height of each of the encoding units (620a, 620b, 620c) by using the (xa, ya) coordinate, which is information indicating the position of the sample (630a) at the upper left of the upper encoding unit (620a), the (xb, yb) coordinate, which is information indicating the position of the sample (630b) at the upper left of the middle encoding unit (620b), and the (xc, yc) coordinate, which is information indicating the position of the sample (630c) at the upper left of the lower encoding unit (620c). The image decoding device (100) can determine the size of each of the encoding units (620a, 620b, 620c) using coordinates (xa, ya), (xb, yb), (xc, yc) indicating the positions of the encoding units (620a, 620b, 620c). According to one embodiment of the present disclosure, the image decoding device (100) can determine the width of the upper encoding unit (620a) as the width of the current encoding unit (600). The image decoding device (100) can determine the height of the upper encoding unit (620a) as yb-ya. According to one embodiment of the present disclosure, the image decoding device (100) can determine the width of the middle encoding unit (620b) as the width of the current encoding unit (600). The image decoding device (100) may determine the height of the middle encoding unit (620b) as yc-yb. According to one embodiment of the present disclosure, the image decoding device (100) may determine the width or height of the lower encoding unit using the width or height of the current encoding unit and the width and height of the upper encoding unit (620a) and the middle encoding unit (620b). The image decoding device (100) may determine an encoding unit having a different size from other encoding units based on the width and height of the determined encoding units (620a, 620b, 620c).Referring to FIG. 6, the image decoding device (100) can determine the middle encoding unit (620b) having a different size from the sizes of the upper encoding unit (620a) and the lower encoding unit (620c) as the encoding unit of a predetermined position. However, the process by which the image decoding device (100) described above determines the encoding unit having a different size from other encoding units is merely an embodiment of determining the encoding unit of a predetermined position using the size of the encoding unit determined based on sample coordinates, and therefore, various processes of determining the encoding unit of a predetermined position by comparing the sizes of the encoding units determined according to predetermined sample coordinates can be used.

[0132] The image decoding device (100) can determine the width or height of each of the encoding units (660a, 660b, 660c) by using the (xd, yd) coordinate, which is information indicating the position of the sample (670a) at the upper left of the left encoding unit (660a), the (xe, ye) coordinate, which is information indicating the position of the sample (670b) at the upper left of the middle encoding unit (660b), and the (xf, yf) coordinate, which is information indicating the position of the sample (670c) at the upper left of the right encoding unit (660c). The image decoding device (100) can determine the size of each of the encoding units (660a, 660b, 660c) by using the (xd, yd), (xe, ye), (xf, yf), which are coordinates indicating the positions of the encoding units (660a, 660b, 660c).

[0133] According to one embodiment of the present disclosure, the image decoding device (100) may determine the width of the left coding unit (660a) as xe-xd. The image decoding device (100) may determine the height of the left coding unit (660a) as the height of the current coding unit (650). According to one embodiment of the present disclosure, the image decoding device (100) may determine the width of the middle coding unit (660b) as xf-xe. The image decoding device (100) may determine the height of the middle coding unit (660b) as the height of the current coding unit (600). According to one embodiment of the present disclosure, the image decoding device (100) may determine the width or height of the right coding unit (660c) using the width or height of the current coding unit (650) and the widths and heights of the left coding unit (660a) and the middle coding unit (660b). The image decoding device (100) can determine an encoding unit having a different size from other encoding units based on the width and height of the determined encoding units (660a, 660b, 660c). Referring to FIG. 6, the image decoding device (100) can determine a middle encoding unit (660b) having a different size from the sizes of the left encoding unit (660a) and the right encoding unit (660c) as an encoding unit at a predetermined position. However, the process of the image decoding device (100) described above determining an encoding unit having a different size from other encoding units is merely an embodiment of determining an encoding unit at a predetermined position using the size of the encoding unit determined based on sample coordinates, and therefore, various processes of determining an encoding unit at a predetermined position by comparing the sizes of the encoding units determined according to predetermined sample coordinates can be used.

[0134] However, the location of the sample considered for determining the location of the encoding unit should not be interpreted as being limited to the upper left corner described above, and it can be interpreted that information on the location of any sample included in the encoding unit can be used.

[0135] According to one embodiment of the present disclosure, the image decoding device (100) may select an coding unit at a predetermined position from among an odd number of coding units determined by splitting the current coding unit, taking into consideration the shape of the current coding unit. For example, if the current coding unit has a non-square shape in which the width is longer than the height, the image decoding device (100) may determine an coding unit at a predetermined position in the horizontal direction. That is, the image decoding device (100) may determine one of the coding units whose positions vary in the horizontal direction and place a restriction on the corresponding coding unit. If the current coding unit has a non-square shape in which the height is longer than the width, the image decoding device (100) may determine an coding unit at a predetermined position in the vertical direction. That is, the image decoding device (100) may determine one of the coding units whose positions vary in the vertical direction and place a restriction on the corresponding coding unit.

[0136] According to one embodiment of the present disclosure, the image decoding device (100) may use information indicating the positions of each of the even-numbered coding units to determine an coding unit at a predetermined position among an even-numbered coding unit. The image decoding device (100) may determine an even-numbered coding unit by dividing the current coding unit (binary dividing) and may determine an coding unit at a predetermined position using information about the positions of the even-numbered coding units. A specific process for this may correspond to a process of determining an coding unit at a predetermined position (e.g., a center position) among an odd-numbered coding unit described above in FIG. 6, and thus will be omitted.

[0137] According to one embodiment of the present disclosure, when a current encoding unit having a non-square shape is split into a plurality of encoding units, predetermined information about the encoding unit at a predetermined position may be used during the splitting process to determine an encoding unit at a predetermined position among the plurality of encoding units. For example, the image decoding device (100) may use at least one of block shape information and split shape mode information stored in a sample included in a middle encoding unit during the splitting process to determine an encoding unit located in the middle among the encoding units into which the current encoding unit is split.

[0138] Referring to FIG. 6, the image decoding device (100) can split the current encoding unit (600) into a plurality of encoding units (620a, 620b, 620c) based on the split shape mode information, and can determine the encoding unit (620b) located in the middle among the plurality of encoding units (620a, 620b, 620c). Furthermore, the image decoding device (100) can determine the encoding unit (620b) located in the middle by considering the position where the split shape mode information is acquired. That is, the split shape mode information of the current encoding unit (600) can be obtained from a sample (640) located in the center of the current encoding unit (600), and when the current encoding unit (600) is split into a plurality of encoding units (620a, 620b, 620c) based on the split shape mode information, the encoding unit (620b) including the sample (640) can be determined as the encoding unit located in the center. However, the information used to determine the encoding unit located in the center should not be interpreted as being limited to the split shape mode information, and various types of information can be used in the process of determining the encoding unit located in the center.

[0139] According to one embodiment of the present disclosure, predetermined information for identifying a coding unit at a predetermined position may be obtained from a predetermined sample included in the coding unit to be determined. Referring to FIG. 6, the image decoding apparatus (100) may use split shape mode information obtained from a sample at a predetermined position within the current coding unit (600) (e.g., a sample located at the center of the current coding unit (600)) to determine a coding unit at a predetermined position among a plurality of coding units (620a, 620b, 620c) determined by splitting the current coding unit (600) (e.g., a coding unit located at the center of the coding units split into multiple units). That is, the image decoding device (100) can determine the sample at the predetermined position by considering the block shape of the current encoding unit (600), and the image decoding device (100) can determine an encoding unit (620b) that includes a sample from which predetermined information (e.g., division shape mode information) can be obtained among a plurality of encoding units (620a, 620b, 620c) determined by dividing the current encoding unit (600), and can set a predetermined restriction. Referring to FIG. 6, according to an embodiment of the present disclosure, the image decoding device (100) can determine a sample (640) located at the center of the current encoding unit (600) as a sample from which predetermined information can be obtained, and the image decoding device (100) can set a predetermined restriction on the encoding unit (620b) that includes this sample (640) during the decoding process. However, the location of the sample from which certain information can be obtained should not be interpreted as being limited to the above-described location, but may be interpreted as samples at any location included in the encoding unit (620b) to be determined in order to set a limitation.

[0140] According to one embodiment of the present disclosure, the position of a sample from which predetermined information can be obtained may be determined according to the shape of the current encoding unit (600). According to one embodiment of the present disclosure, block shape information may determine whether the shape of the current encoding unit is square or non-square, and may determine the position of a sample from which predetermined information can be obtained according to the shape. For example, the image decoding apparatus (100) may determine a sample located on a boundary that divides at least one of the width and height of the current encoding unit in half as a sample from which predetermined information can be obtained, using at least one of information about the width and information about the height of the current encoding unit. As another example, when the block shape information related to the current encoding unit indicates that the shape is non-square, the image decoding apparatus (100) may determine one of the samples adjacent to the boundary that divides the long side of the current encoding unit in half as a sample from which predetermined information can be obtained.

[0141] According to one embodiment of the present disclosure, when the image decoding device (100) divides a current encoding unit into a plurality of encoding units, the image decoding device (100) may use the split shape mode information to determine an encoding unit at a predetermined position among the plurality of encoding units. According to one embodiment of the present disclosure, the image decoding device (100) may obtain the split shape mode information from a sample at a predetermined position included in the encoding unit, and the image decoding device (100) may divide the plurality of encoding units generated by splitting the current encoding unit using the split shape mode information obtained from a sample at a predetermined position included in each of the plurality of encoding units. That is, the encoding unit may be recursively divided using the split shape mode information obtained from a sample at a predetermined position included in each of the encoding units. Since the recursive division process of the encoding unit has been described above with reference to FIG. 5, a detailed description thereof will be omitted.

[0142] According to one embodiment of the present disclosure, the image decoding device (100) can divide a current encoding unit to determine at least one encoding unit, and can determine the order in which the at least one encoding unit is decoded according to a predetermined block (e.g., the current encoding unit).

[0143] FIG. 7 illustrates the order in which multiple encoding units are processed when an image decoding device (100) determines multiple encoding units by dividing a current encoding unit according to one embodiment of the present disclosure.

[0144] According to one embodiment of the present disclosure, the image decoding device (100) may determine second encoding units (710a, 710b) by vertically splitting the first encoding unit (700) according to the splitting shape mode information, determine second encoding units (730a, 730b) by horizontally splitting the first encoding unit (700), or determine second encoding units (750a, 750b, 750c, 750d) by vertically and horizontally splitting the first encoding unit (700).

[0145] Referring to FIG. 7, the image decoding device (100) can determine the order in which the second encoding units (710a, 710b) determined by vertically dividing the first encoding unit (700) are processed in the horizontal direction (710c). The image decoding device (100) can determine the order in which the second encoding units (730a, 730b) determined by horizontally dividing the first encoding unit (700) are processed in the vertical direction (730c). The image decoding device (100) can determine the second encoding units (750a, 750b, 750c, 750d) determined by dividing the first encoding unit (700) in the vertical and horizontal directions according to a predetermined order (e.g., raster scan order (750e) or z scan order (z scan order)) in which encoding units located in one row are processed and then encoding units located in the next row are processed.

[0146] According to one embodiment of the present disclosure, the image decoding device (100) can recursively split encoding units. Referring to FIG. 7, the image decoding device (100) can split a first encoding unit (700) to determine a plurality of encoding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d), and can recursively split each of the determined plurality of encoding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d). A method for splitting a plurality of coding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d) may be a method corresponding to a method for splitting the first coding unit (700). Accordingly, the plurality of coding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d) may each be independently split into a plurality of coding units. Referring to FIG. 7, the image decoding device (100) may split the first coding unit (700) in the vertical direction to determine the second coding units (710a, 710b), and further may determine to independently split or not split each of the second coding units (710a, 710b).

[0147] According to one embodiment of the present disclosure, the image decoding device (100) may horizontally divide the second encoding unit (710a) on the left into third encoding units (720a, 720b), and may not divide the second encoding unit (710b) on the right.

[0148] According to one embodiment of the present disclosure, the processing order of coding units may be determined based on the splitting process of the coding units. In other words, the processing order of the split coding units may be determined based on the processing order of the coding units immediately before splitting. The image decoding apparatus (100) may determine the processing order of the third coding units (720a, 720b) ​​determined by splitting the second coding unit (710a) on the left, independently from the second coding unit (710b) on the right. Since the second coding unit (710a) on the left is split horizontally and the third coding units (720a, 720b) ​​are determined, the third coding units (720a, 720b) ​​may be processed in the vertical direction (720c). In addition, since the order in which the second encoding unit (710a) on the left and the second encoding unit (710b) on the right are processed corresponds to the horizontal direction (710c), the right encoding unit (710b) can be processed after the third encoding units (720a, 720b) ​​included in the second encoding unit (710a) on the left are processed in the vertical direction (720c). Since the above-described content is intended to explain the process in which the processing order of the encoding units is determined according to the encoding units before splitting, it should not be interpreted as being limited to the above-described embodiment, but should be interpreted as being used in various ways in which encoding units that are split and determined in various forms can be independently processed according to a predetermined order.

[0149] FIG. 8 illustrates a process of determining that a current encoding unit is divided into an odd number of encoding units when the encoding units cannot be processed in a predetermined order, according to one embodiment of the present disclosure, by an image decoding device (100).

[0150] According to one embodiment of the present disclosure, the image decoding device (100) may determine that the current encoding unit is split into an odd number of encoding units based on the acquired split shape mode information. Referring to FIG. 8, a first encoding unit (800) having a square shape may be split into second encoding units (810a, 810b) having a non-square shape, and the second encoding units (810a, 810b) may each be independently split into third encoding units (820a, 820b, 820c, 820d, 820e). According to one embodiment of the present disclosure, the image decoding device (100) can determine a plurality of third encoding units (820a, 820b) by horizontally dividing the left encoding unit (810a) among the second encoding units, and can divide the right encoding unit (810b) into an odd number of third encoding units (820c, 820d, 820e).

[0151] According to one embodiment of the present disclosure, the image decoding device (100) can determine whether there is an odd number of split coding units by determining whether the third coding units (820a, 820b, 820c, 820d, 820e) can be processed in a predetermined order. Referring to FIG. 8, the image decoding device (100) can determine the third coding units (820a, 820b, 820c, 820d, 820e) by recursively splitting the first coding unit (800). The image decoding device (100) can determine whether the first encoding unit (800), the second encoding unit (810a, 810b), or the third encoding unit (820a, 820b, 820c, 820d, 820e) is divided into an odd number of encoding units based on at least one of the block shape information and the split shape mode information. For example, the encoding unit located on the right side of the second encoding unit (810a, 810b) can be divided into an odd number of third encoding units (820c, 820d, 820e). The order in which the plurality of encoding units included in the first encoding unit (800) are processed can be a predetermined order (e.g., z-scan order (830)), and the image decoding device (100) can determine whether the third encoding unit (820c, 820d, 820e) determined by dividing the second encoding unit (810b) on the right into odd numbers satisfies the condition that it can be processed according to the predetermined order.

[0152] According to one embodiment of the present disclosure, the image decoding device (100) can determine whether the third encoding units (820a, 820b, 820c, 820d, 820e) included in the first encoding unit (800) satisfy a condition that they can be processed in a predetermined order, and the condition is related to whether at least one of the width and height of the second encoding unit (810a, 810b) is split in half according to the boundary of the third encoding unit (820a, 820b, 820c, 820d, 820e). For example, the third encoding unit (820a, 820b) determined by splitting the height of the left second encoding unit (810a) of a non-square shape in half can satisfy the condition. Since the boundaries of the third encoding units (820c, 820d, 820e) determined by dividing the right second encoding unit (810b) into three encoding units do not divide the width or height of the right second encoding unit (810b) in half, it may be determined that the third encoding units (820c, 820d, 820e) do not satisfy the condition. In the case where this condition is not satisfied, the image decoding device (100) may determine that there is a disconnection in the scanning order, and may determine that the right second encoding unit (810b) is divided into an odd number of encoding units based on the determination result. According to one embodiment of the present disclosure, when the image decoding device (100) is divided into an odd number of encoding units, a predetermined restriction may be placed on an encoding unit at a predetermined position among the divided encoding units. Since the contents of such restrictions or predetermined positions, etc. have been described above through one embodiment of the present disclosure, a detailed description thereof will be omitted.

[0153] FIG. 9 illustrates a process in which an image decoding device (100) divides a first encoding unit (900) to determine at least one encoding unit according to one embodiment of the present disclosure.

[0154] According to one embodiment of the present disclosure, the image decoding device (100) can split the first coding unit (900) based on the split shape mode information acquired through the bitstream acquisition unit (110). The first coding unit (900) having a square shape can be split into four coding units having a square shape or can be split into a plurality of coding units having a non-square shape. For example, referring to FIG. 9, when the first coding unit (900) is square and the split shape mode information indicates that it is split into coding units having a non-square shape, the image decoding device (100) can split the first coding unit (900) into a plurality of coding units having a non-square shape. Specifically, when the split shape mode information indicates that the first encoding unit (900) is split in the horizontal direction or the vertical direction to determine an odd number of encoding units, the image decoding device (100) can split the first encoding unit (900) having a square shape into second encoding units (910a, 910b, 910c) determined by splitting them in the vertical direction into an odd number of encoding units or second encoding units (920a, 920b, 920c) determined by splitting them in the horizontal direction.

[0155] According to one embodiment of the present disclosure, the image decoding device (100) can determine whether the second encoding units (910a, 910b, 910c, 920a, 920b, 920c) included in the first encoding unit (900) satisfy a condition that they can be processed in a predetermined order, and the condition is related to whether at least one of the width and height of the first encoding unit (900) is split in half according to the boundary of the second encoding unit (910a, 910b, 910c, 920a, 920b, 920c). Referring to FIG. 9, since the boundaries of the second coding units (910a, 910b, 910c) determined by vertically dividing the first coding unit (900) in a square shape do not divide the width of the first coding unit (900) in half, it may be determined that the first coding unit (900) does not satisfy the condition that it can be processed in a predetermined order. In addition, since the boundaries of the second coding units (920a, 920b, 920c) determined by horizontally dividing the first coding unit (900) in a square shape do not divide the height of the first coding unit (900) in half, it may be determined that the first coding unit (900) does not satisfy the condition that it can be processed in a predetermined order. If such a condition is not satisfied, the image decoding device (100) may determine that the scan order is disconnected, and based on the determination result, may determine that the first encoding unit (900) is divided into an odd number of encoding units. According to one embodiment of the present disclosure, when the image decoding device (100) is divided into an odd number of encoding units, a predetermined restriction may be placed on an encoding unit at a predetermined position among the divided encoding units. Since the contents of such restriction or the predetermined position, etc. have been described above through one embodiment of the present disclosure, a detailed description thereof will be omitted.

[0156] According to one embodiment of the present disclosure, the image decoding device (100) can divide the first encoding unit to determine encoding units of various shapes.

[0157] Referring to FIG. 9, the image decoding device (100) can divide the first encoding unit (900) having a square shape and the first encoding unit (930 or 950) having a non-square shape into encoding units of various shapes.

[0158] FIG. 10 illustrates that, according to one embodiment of the present disclosure, a video decoding device (100) limits the shapes into which a second encoding unit can be divided when a non-square shape of a second encoding unit determined by dividing a first encoding unit (1000) satisfies a predetermined condition.

[0159] According to one embodiment of the present disclosure, the image decoding device (100) may determine to split a first coding unit (1000) having a square shape into second coding units (1010a, 1010b, 1020a, 1020b) having a non-square shape based on the split shape mode information acquired through the bitstream acquisition unit (110). The second coding units (1010a, 1010b, 1020a, 1020b) may be independently split. Accordingly, the image decoding device (100) may determine to split or not split into a plurality of coding units based on the split shape mode information related to each of the second coding units (1010a, 1010b, 1020a, 1020b). According to one embodiment of the present disclosure, the image decoding device (100) may determine third coding units (1012a, 1012b) by horizontally dividing the left second coding unit (1010a) having a non-square shape determined by vertically dividing the first coding unit (1000). However, when the image decoding device (100) horizontally divides the left second coding unit (1010a), the right second coding unit (1010b) may be restricted from being horizontally divided in the same direction as the direction in which the left second coding unit (1010a) is divided. If the second encoding unit on the right (1010b) is split in the same direction to determine the third encoding unit (1014a, 1014b), the second encoding unit on the left (1010a) and the second encoding unit on the right (1010b) may be independently split in the horizontal direction to determine the third encoding unit (1012a, 1012b, 1014a, 1014b). However, this is the same result as the image decoding device (100) splitting the first encoding unit (1000) into four square-shaped second encoding units (1030a, 1030b, 1030c, 1030d) based on the split shape mode information, which may be inefficient in terms of image decoding.

[0160] According to one embodiment of the present disclosure, the image decoding device (100) may determine third coding units (1022a, 1022b, 1024a, 1024b) by vertically dividing a second coding unit (1020a or 1020b) having a non-square shape determined by dividing a first coding unit (1000) in a horizontal direction. However, when the image decoding device (100) vertically divides one of the second coding units (e.g., the upper second coding unit (1020a)), the other second coding units (e.g., the lower coding unit (1020b)) may be restricted from being vertically divided in the same direction as the direction in which the upper second coding unit (1020a) is divided, for the reasons described above.

[0161] FIG. 11 illustrates a process in which an image decoding device (100) divides a square-shaped encoding unit when the split shape mode information cannot indicate that the encoding unit is divided into four square-shaped encoding units according to one embodiment of the present disclosure.

[0162] According to one embodiment of the present disclosure, the image decoding device (100) may split the first encoding unit (1100) based on the split shape mode information to determine the second encoding units (1110a, 1110b, 1120a, 1120b, etc.). The split shape mode information may include information about various shapes into which the encoding unit may be split, but the information about various shapes may not include information for splitting the encoding unit into four encoding units having a square shape. According to this split shape mode information, the image decoding device (100) cannot split the first encoding unit (1100) having a square shape into four second encoding units having a square shape (1130a, 1130b, 1130c, 1130d). Based on the segmentation shape mode information, the image decoding device (100) can determine a second encoding unit (1110a, 1110b, 1120a, 1120b, etc.) of a non-square shape.

[0163] According to one embodiment of the present disclosure, the image decoding device (100) can independently split each of the second encoding units (1110a, 1110b, 1120a, 1120b, etc.) having a non-square shape. Each of the second encoding units (1110a, 1110b, 1120a, 1120b, etc.) can be split in a predetermined order using a recursive method, which may be a splitting method corresponding to a method in which the first encoding unit (1100) is split based on splitting shape mode information.

[0164] For example, the image decoding device (100) can determine third coding units (1112a, 1112b) having a square shape by splitting the left second coding unit (1110a) in the horizontal direction, and can determine third coding units (1114a, 1114b) having a square shape by splitting the right second coding unit (1110b) in the horizontal direction. Furthermore, the image decoding device (100) can also determine third coding units (1116a, 1116b, 1116c, 1116d) having a square shape by splitting both the left second coding unit (1110a) and the right second coding unit (1110b) in the horizontal direction. In this case, the encoding unit can be determined in the same form as the first encoding unit (1100) being divided into four square-shaped second encoding units (1130a, 1130b, 1130c, 1130d).

[0165] As another example, the image decoding device (100) may determine third coding units (1122a, 1122b) having a square shape by vertically splitting the upper second coding unit (1120a), and may determine third coding units (1124a, 1124b) having a square shape by vertically splitting the lower second coding unit (1120b). Furthermore, the image decoding device (100) may determine third coding units (1126a, 1126b, 1126a, 1126b) having a square shape by vertically splitting both the upper second coding unit (1120a) and the lower second coding unit (1120b). In this case, the encoding unit can be determined in the same form as the first encoding unit (1100) being divided into four square-shaped second encoding units (1130a, 1130b, 1130c, 1130d).

[0166] FIG. 12 illustrates that the processing order between a plurality of encoding units may vary depending on the process of splitting the encoding units according to one embodiment of the present disclosure.

[0167] According to one embodiment of the present disclosure, the image decoding device (100) can split the first encoding unit (1200) based on the split shape mode information. If the block shape is square and the split shape mode information indicates that the first encoding unit (1200) is split in at least one of the horizontal direction and the vertical direction, the image decoding device (100) can split the first encoding unit (1200) to determine second encoding units (e.g., 1210a, 1210b, 1220a, 1220b, etc.). Referring to FIG. 12, the second encoding units (1210a, 1210b, 1220a, 1220b) having a non-square shape determined by splitting the first encoding unit (1200) only in the horizontal direction or the vertical direction can be independently split based on the split shape mode information for each. For example, the image decoding device (100) can determine third encoding units (1216a, 1216b, 1216c, 1216d) by horizontally dividing second encoding units (1210a, 1210b) generated by vertically dividing the first encoding unit (1200), and can determine third encoding units (1226a, 1226b, 1226c, 1226d) by vertically dividing second encoding units (1220a, 1220b) generated by horizontally dividing the first encoding unit (1200). Since the process of dividing the second encoding units (1210a, 1210b, 1220a, 1220b) has been described above with reference to FIG. 11, a detailed description thereof will be omitted.

[0168] According to one embodiment of the present disclosure, the image decoding device (100) can process encoding units according to a predetermined order. Since the characteristics of processing encoding units according to a predetermined order have been described above with reference to FIG. 7, a detailed description thereof will be omitted. Referring to FIG. 12, the image decoding device (100) can divide a first encoding unit (1200) having a square shape and determine four third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) having a square shape. According to one embodiment of the present disclosure, the image decoding device (100) can determine the processing order of the third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) depending on the form in which the first encoding unit (1200) is divided.

[0169] According to one embodiment of the present disclosure, the image decoding device (100) can determine third encoding units (1216a, 1216b, 1216c, 1216d) by horizontally dividing the second encoding units (1210a, 1210b) generated by vertically dividing them, and the image decoding device (100) can process the third encoding units (1216a, 1216b, 1216c, 1216d) according to an order (1217) of first processing the third encoding units (1216a, 1216c) included in the left second encoding unit (1210a) in the vertical direction and then processing the third encoding units (1216b, 1216d) included in the right second encoding unit (1210b) in the vertical direction.

[0170] According to one embodiment of the present disclosure, the image decoding device (100) can determine third encoding units (1226a, 1226b, 1226c, 1226d) by vertically dividing the second encoding units (1220a, 1220b) generated by being divided in the horizontal direction, and the image decoding device (100) can process the third encoding units (1226a, 1226b, 1226c, 1226d) according to an order (1227) of first processing the third encoding units (1226a, 1226b) included in the upper second encoding unit (1220a) in the horizontal direction and then processing the third encoding units (1226c, 1226d) included in the lower second encoding unit (1220b) in the horizontal direction.

[0171] Referring to FIG. 12, the second encoding units (1210a, 1210b, 1220a, 1220b) can be divided into third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) having a square shape. The second encoding units (1210a, 1210b) determined by being split in the vertical direction and the second encoding units (1220a, 1220b) determined by being split in the horizontal direction are split into different shapes, but according to the third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) determined later, the first encoding unit (1200) is ultimately split into encoding units of the same shape. Accordingly, even if the image decoding device (100) determines encoding units of the same shape as a result by recursively splitting the encoding units through different processes based on the split shape mode information, it can process a plurality of encoding units determined in the same shape in different orders.

[0172] FIG. 13 illustrates a process in which the depth of an encoding unit is determined as the shape and size of the encoding unit change when the encoding unit is recursively divided to determine a plurality of encoding units according to one embodiment of the present disclosure.

[0173] According to one embodiment of the present disclosure, the image decoding device (100) may determine the depth of an encoding unit according to a predetermined criterion. For example, the predetermined criterion may be the length of a long side of the encoding unit. If the length of the long side of the current encoding unit is split to be 2n (n>0) times the length of the long side of the encoding unit before splitting, the image decoding device (100) may determine that the depth of the current encoding unit is increased by n compared to the depth of the encoding unit before splitting. Hereinafter, the encoding unit with increased depth will be expressed as an encoding unit of a lower depth.

[0174] Referring to FIG. 13, according to one embodiment of the present disclosure, based on block shape information indicating a square shape (for example, the block shape information may indicate '0: SQUARE'), the image decoding device (100) may divide a first coding unit (1300) having a square shape to determine a second coding unit (1302), a third coding unit (1304), etc. of a lower depth. If the size of the first coding unit (1300) having a square shape is 2Nx2N, the second coding unit (1302) determined by dividing the width and height of the first coding unit (1300) by half may have a size of NxN. Furthermore, the third coding unit (1304) determined by dividing the width and height of the second coding unit (1302) by half may have a size of N / 2xN / 2. In this case, the width and height of the third encoding unit (1304) correspond to 1 / 4 of the width and height of the first encoding unit (1300). When the depth of the first encoding unit (1300) is D, the depth of the second encoding unit (1302), which is 1 / 2 of the width and height of the first encoding unit (1300), may be D+1, and the depth of the third encoding unit (1304), which is 1 / 4 of the width and height of the first encoding unit (1300), may be D+2.

[0175] According to one embodiment of the present disclosure, based on block shape information indicating a non-square shape (for example, the block shape information may indicate '1: NS_VER' indicating a non-square shape in which the height is longer than the width or '2: NS_HOR' indicating a non-square shape in which the width is longer than the height), the image decoding device (100) may split a first coding unit (1310 or 1320) having a non-square shape to determine a second coding unit (1312 or 1322), a third coding unit (1314 or 1324) of a lower depth, etc.

[0176] The image decoding device (100) can determine a second encoding unit (e.g., 1302, 1312, 1322, etc.) by splitting at least one of the width and height of the first encoding unit (1310) having a size of Nx2N. That is, the image decoding device (100) can split the first encoding unit (1310) in the horizontal direction to determine a second encoding unit (1302) having a size of NxN or a second encoding unit (1322) having a size of NxN / 2, and can also split the first encoding unit (1310) in the horizontal direction and the vertical direction to determine a second encoding unit (1312) having a size of N / 2xN.

[0177] According to one embodiment of the present disclosure, the image decoding device (100) may determine a second coding unit (e.g., 1302, 1312, 1322, etc.) by splitting at least one of the width and the height of the first coding unit (1320) having a size of 2NxN. That is, the image decoding device (100) may split the first coding unit (1320) in the vertical direction to determine a second coding unit (1302) having a size of NxN or a second coding unit (1312) having a size of N / 2xN, and may also split the first coding unit (1320) in the horizontal direction and the vertical direction to determine a second coding unit (1322) having a size of NxN / 2.

[0178] According to one embodiment of the present disclosure, the image decoding device (100) may determine a third encoding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second encoding unit (1302) having a size of NxN. That is, the image decoding device (100) may split the second encoding unit (1302) in the vertical direction and the horizontal direction to determine a third encoding unit (1304) having a size of N / 2xN / 2, a third encoding unit (1314) having a size of N / 4xN / 2, or a third encoding unit (1324) having a size of N / 2xN / 4.

[0179] According to one embodiment of the present disclosure, the image decoding device (100) may determine a third coding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second coding unit (1312) having a size of N / 2xN. That is, the image decoding device (100) may split the second coding unit (1312) in the horizontal direction to determine a third coding unit (1304) having a size of N / 2xN / 2 or a third coding unit (1324) having a size of N / 2xN / 4, or may split the second coding unit (1312) in the vertical direction and the horizontal direction to determine a third coding unit (1314) having a size of N / 4xN / 2.

[0180] According to one embodiment of the present disclosure, the image decoding device (100) may determine a third coding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second coding unit (1322) having a size of NxN / 2. That is, the image decoding device (100) may split the second coding unit (1322) in the vertical direction to determine a third coding unit (1304) having a size of N / 2xN / 2 or a third coding unit (1314) having a size of N / 4xN / 2, or split the second coding unit (1322) in the vertical direction and the horizontal direction to determine a third coding unit (1324) having a size of N / 2xN / 4.

[0181] According to one embodiment of the present disclosure, the image decoding device (100) can split a square-shaped encoding unit (e.g., 1300, 1302, 1304) in a horizontal direction or a vertical direction. For example, a first encoding unit (1300) having a size of 2Nx2N can be split in the vertical direction to determine a first encoding unit (1310) having a size of Nx2N, or can be split in the horizontal direction to determine a first encoding unit (1320) having a size of 2NxN. When the depth is determined based on the length of the longest side of the encoding unit according to one embodiment of the present disclosure, the depth of the encoding unit determined by splitting the first encoding unit (1300) having a size of 2Nx2N in the horizontal direction or the vertical direction can be the same as the depth of the first encoding unit (1300).

[0182] According to one embodiment of the present disclosure, the width and height of the third coding unit (1314 or 1324) may be 1 / 4 times that of the first coding unit (1310 or 1320). When the depth of the first coding unit (1310 or 1320) is D, the depth of the second coding unit (1312 or 1322), which is 1 / 2 times the width and height of the first coding unit (1310 or 1320), may be D+1, and the depth of the third coding unit (1314 or 1324), which is 1 / 4 times the width and height of the first coding unit (1310 or 1320), may be D+2.

[0183] FIG. 14 illustrates an index (part index, hereinafter referred to as PID) for depth and encoding unit distinction that can be determined according to the shape and size of encoding units according to one embodiment of the present disclosure.

[0184] According to one embodiment of the present disclosure, the image decoding device (100) can split a first encoding unit (1400) having a square shape to determine second encoding units of various shapes. Referring to FIG. 14, the image decoding device (100) can split the first encoding unit (1400) in at least one of a vertical direction and a horizontal direction according to the split shape mode information to determine second encoding units (1402a, 1402b, 1404a, 1404b, 1406a, 1406b, 1406c, 1406d). That is, the image decoding device (100) can determine the second encoding unit (1402a, 1402b, 1404a, 1404b, 1406a, 1406b, 1406c, 1406d) based on the split shape mode information for the first encoding unit (1400).

[0185] According to one embodiment of the present disclosure, the depth of the second coding units (1402a, 1402b, 1404a, 1404b, 1406a, 1406b, 1406c, 1406d) determined according to the split shape mode information for the first coding unit (1400) having a square shape may be determined based on the length of the long side. For example, since the length of one side of the first coding unit (1400) having a square shape and the length of the long side of the second coding unit (1402a, 1402b, 1404a, 1404b) having a non-square shape are the same, the depth of the first coding unit (1400) and the second coding units (1402a, 1402b, 1404a, 1404b) having a non-square shape may be considered to be the same as D. In contrast, when the image decoding device (100) divides the first encoding unit (1400) into four square-shaped second encoding units (1406a, 1406b, 1406c, 1406d) based on the split shape mode information, the length of one side of the square-shaped second encoding units (1406a, 1406b, 1406c, 1406d) is half the length of one side of the first encoding unit (1400), so the depth of the second encoding units (1406a, 1406b, 1406c, 1406d) may be a depth of D+1, which is one depth lower than D, the depth of the first encoding unit (1400).

[0186] According to one embodiment of the present disclosure, the image decoding device (100) can horizontally split a first encoding unit (1410) having a height longer than width according to split shape mode information into a plurality of second encoding units (1412a, 1412b, 1414a, 1414b, 1414c). According to one embodiment of the present disclosure, the image decoding device (100) can vertically split a first encoding unit (1420) having a width longer than height according to split shape mode information into a plurality of second encoding units (1422a, 1422b, 1424a, 1424b, 1424c).

[0187] According to one embodiment of the present disclosure, the second coding units (1412a, 1412b, 1414a, 1414b, 1414c. 1422a, 1422b, 1424a, 1424b, 1424c) determined according to the split shape mode information for the first coding unit (1410 or 1420) of a non-square shape may have their depths determined based on the length of their long sides. For example, since the length of one side of the second encoding unit (1412a, 1412b) in the shape of a square is half the length of one side of the first encoding unit (1410) in the shape of a non-square having a height longer than a width, the depth of the second encoding unit (1412a, 1412b) in the shape of a square is D+1, which is one depth lower than the depth D of the first encoding unit (1410) in the shape of a non-square.

[0188] Furthermore, the image decoding device (100) can split a non-square first encoding unit (1410) into an odd number of second encoding units (1414a, 1414b, 1414c) based on the split shape mode information. The odd number of second encoding units (1414a, 1414b, 1414c) can include non-square second encoding units (1414a, 1414c) and square second encoding units (1414b). In this case, since the length of the long side of the second encoding unit (1414a, 1414c) of a non-square shape and the length of one side of the second encoding unit (1414b) of a square shape are half the length of one side of the first encoding unit (1410), the depth of the second encoding unit (1414a, 1414b, 1414c) may be a depth of D+1, which is one depth lower than D, which is the depth of the first encoding unit (1410). The image decoding device (100) may determine the depth of the encoding units associated with the first encoding unit (1420) of a non-square shape, in which the width is longer than the height, in a manner corresponding to the above method of determining the depth of the encoding units associated with the first encoding unit (1410).

[0189] According to one embodiment of the present disclosure, when determining an index (PID) for distinguishing split coding units, the image decoding device (100) may determine the index based on a size ratio between the coding units when the coding units split into an odd number of units do not have the same size. Referring to FIG. 14, among the coding units (1414a, 1414b, 1414c) split into an odd number of units, the coding unit (1414b) located in the middle may have the same width as the other coding units (1414a, 1414c) but may have a height that is twice the height of the coding units (1414a, 1414c) that are different in height. That is, in this case, the coding unit (1414b) located in the middle may include two of the other coding units (1414a, 1414c). Accordingly, if the index (PID) of the encoding unit (1414b) located in the middle according to the scanning order is 1, the index of the encoding unit (1414c) located in the next order may be 3, which is an increase of 2. In other words, there may be a discontinuity in the value of the index. According to one embodiment of the present disclosure, the image decoding device (100) may determine whether the encoding units divided into an odd number are not of the same size based on the presence or absence of discontinuity in the index for distinguishing between the divided encoding units.

[0190] According to one embodiment of the present disclosure, the image decoding device (100) may determine whether the current encoding unit is divided into a specific split shape based on the value of an index for distinguishing a plurality of encoding units determined by division. Referring to FIG. 14, the image decoding device (100) may divide a first encoding unit (1410) having a rectangular shape in which a height is longer than a width, to determine an even number of encoding units (1412a, 1412b) or an odd number of encoding units (1414a, 1414b, 1414c). The image decoding device (100) may use an index (PID) indicating each encoding unit to distinguish each of the plurality of encoding units. According to one embodiment of the present disclosure, the PID may be obtained from a sample (e.g., an upper left sample) at a predetermined position of each encoding unit.

[0191] According to one embodiment of the present disclosure, the image decoding device (100) can determine an coding unit at a predetermined position among the coding units that are divided and determined using an index for distinguishing the coding units. According to one embodiment of the present disclosure, when the split shape mode information for the first coding unit (1410) having a rectangular shape with a height longer than the width indicates that the first coding unit (1410) is divided into three coding units, the image decoding device (100) can divide the first coding unit (1410) into three coding units (1414a, 1414b, 1414c). The image decoding device (100) can assign an index to each of the three coding units (1414a, 1414b, 1414c). The image decoding device (100) can compare the indexes for each coding unit to determine the middle coding unit among the coding units divided into an odd number of coding units. The image decoding device (100) may determine a coding unit (1414b) having an index corresponding to a middle value among the indices of the coding units as a coding unit at a middle position among the coding units determined by splitting the first coding unit (1410). According to an embodiment of the present disclosure, when determining an index for distinguishing the split coding units, the image decoding device (100) may determine the index based on a size ratio between the coding units when the coding units do not have the same size. Referring to FIG. 14, the coding unit (1414b) generated by splitting the first coding unit (1410) may have the same width as other coding units (1414a, 1414c) but may be twice the height of the coding units (1414a, 1414c) that are different in height. In this case, if the index (PID) of the encoding unit (1414b) located in the middle is 1, the index of the encoding unit (1414c) located in the next order may be 3, which is an increase of 2.In cases like this where the index increases uniformly and then the increase amount changes, the image decoding device (100) may determine that the current encoding unit is divided into a plurality of encoding units including encoding units having different sizes from other encoding units. According to one embodiment of the present disclosure, when the split shape mode information indicates that the current encoding unit is divided into an odd number of encoding units, the image decoding device (100) may divide the current encoding unit into a form in which an encoding unit at a predetermined position among the odd number of encoding units (for example, a middle encoding unit) has a different size from the other encoding units. In this case, the image decoding device (100) may determine a middle encoding unit having a different size using an index (PID) for the encoding unit. However, the above-described index, the size or position of the encoding unit at the predetermined position to be determined are specific for explaining one embodiment and should not be interpreted as being limited thereto, and it should be interpreted that various indexes, positions and sizes of encoding units can be used.

[0192] According to one embodiment of the present disclosure, an image decoding device (100) can use a predetermined data unit from which recursive division of an encoding unit begins.

[0193] FIG. 15 illustrates that a plurality of coding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment of the present disclosure.

[0194] According to one embodiment of the present disclosure, a predetermined data unit may be defined as a data unit from which a coding unit begins to be recursively split using split shape mode information. That is, it may correspond to a coding unit of the highest depth used in the process of determining multiple coding units for splitting the current picture. For convenience of explanation, this predetermined data unit will be referred to as a reference data unit hereinafter.

[0195] According to one embodiment of the present disclosure, a reference data unit may have a predetermined size and shape. According to one embodiment of the present disclosure, the reference data unit may include MxN samples, where M and N may be the same and may be integers expressed as powers of 2. That is, the reference data unit may have a square or non-square shape, and may be subsequently divided into an integer number of coding units.

[0196] According to one embodiment of the present disclosure, an image decoding device (100) may divide a current picture into a plurality of reference data units. According to one embodiment of the present disclosure, an image decoding device (100) may divide a plurality of reference data units into which a current picture is divided using division shape mode information for each reference data unit. This division process of the reference data units may correspond to a division process using a quad-tree structure.

[0197] According to one embodiment of the present disclosure, the image decoding device (100) can determine in advance the minimum size that a reference data unit included in a current picture can have. Accordingly, the image decoding device (100) can determine reference data units of various sizes having a size greater than or equal to the minimum size, and can determine at least one encoding unit using segmentation mode information based on the determined reference data unit.

[0198] Referring to FIG. 15, the image decoding device (100) may use a reference coding unit (1500) having a square shape, or may use a reference coding unit (1502) having a non-square shape. According to one embodiment of the present disclosure, the shape and size of the reference coding unit may be determined according to various data units (e.g., sequence, picture, slice, slice segment, tile, tile group, maximum coding unit, etc.) that may include at least one reference coding unit.

[0199] According to one embodiment of the present disclosure, the bitstream acquisition unit (110) of the image decoding device (100) can acquire at least one of information on the shape of the reference coding unit and information on the size of the reference coding unit from the bitstream for each of the various data units. The process of determining at least one coding unit included in the square-shaped reference coding unit (1500) has been described above through the process of splitting the current coding unit (300) of FIG. 3, and the process of determining at least one coding unit included in the non-square-shaped reference coding unit (1502) has been described above through the process of splitting the current coding unit (400 or 450) of FIG. 4, so a detailed description thereof will be omitted.

[0200] According to one embodiment of the present disclosure, the image decoding device (100) may use an index for identifying the size and shape of the reference coding unit in order to determine the size and shape of the reference coding unit according to some data units that are predetermined based on a predetermined condition. That is, the bitstream acquisition unit (110) may acquire only an index for identifying the size and shape of the reference coding unit for each slice, slice segment, tile, tile group, maximum coding unit, etc., among the various data units (e.g., sequences, pictures, slices, slice segments, tiles, tile groups, maximum coding units, etc.) that satisfy a predetermined condition (e.g., data units having a size smaller than a slice) from the bitstream. The image decoding device (100) may determine the size and shape of the reference data unit for each data unit that satisfies the predetermined condition by using the index. When information about the shape of the reference coding unit and information about the size of the reference coding unit are obtained from the bitstream for each relatively small-sized data unit and used, the efficiency of the bitstream may not be good. Therefore, instead of directly obtaining information about the shape of the reference coding unit and information about the size of the reference coding unit, only the index may be obtained and used. In this case, at least one of the size and shape of the reference coding unit corresponding to the index indicating the size and shape of the reference coding unit may be determined in advance. That is, the image decoding device (100) can determine at least one of the size and shape of the reference coding unit included in the data unit that serves as the basis for obtaining the index by selecting at least one of the sizes and shapes of the predetermined reference coding units according to the index.

[0201] According to one embodiment of the present disclosure, the image decoding device (100) may use at least one reference coding unit included in one maximum coding unit (1510). That is, the maximum coding unit (1510) for dividing an image may include at least one reference coding unit, and the coding unit may be determined through a recursive splitting process of each reference coding unit. According to one embodiment of the present disclosure, at least one of the width and the height of the maximum coding unit (1510) may correspond to an integer multiple of at least one of the width and the height of the reference coding unit. According to one embodiment of the present disclosure, the size of the reference coding unit may be a size obtained by splitting the maximum coding unit (1510) n times according to a quad tree structure. That is, the image decoding device (100) may determine the reference coding unit by splitting the maximum coding unit (1510) n times according to the quad tree structure, and may split the reference coding unit based on at least one of block shape information and split shape mode information according to one embodiment of the present disclosure.

[0202] According to one embodiment of the present disclosure, the video decoding device (100) can obtain and use block shape information indicating the shape of a current encoding unit or split shape mode information indicating a method of splitting the current encoding unit from a bitstream. The split shape mode information may be included in a bitstream related to various data units. For example, the video decoding device (100) can use split shape mode information included in a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a tile header, and a tile group header. Furthermore, the video decoding device (100) can obtain and use a syntax element corresponding to block shape information or split shape mode information from the bitstream for each maximum encoding unit and each reference encoding unit.

[0203] Hereinafter, a method for determining a partitioning rule according to one embodiment of the present disclosure will be described in detail.

[0204] The video decoding device (100) can determine a segmentation rule of the video. The segmentation rule may be predetermined between the video decoding device (100) and the video encoding device (200). The video decoding device (100) can determine the segmentation rule of the video based on information obtained from a bitstream. The video decoding device (100) can determine the segmentation rule based on information obtained from at least one of a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a tile header, and a tile group header. The video decoding device (100) can determine the segmentation rule differently according to a frame, a slice, a tile, a temporal layer, a maximum coding unit, or an coding unit.

[0205] The image decoding device (100) can determine a segmentation rule based on the block shape of the encoding unit. The block shape can include the size, shape, width and height ratio, and direction of the encoding unit. The image encoding device (200) and the image decoding device (100) can determine in advance that the segmentation rule will be determined based on the block shape of the encoding unit. However, the present invention is not limited thereto. The image decoding device (100) can determine the segmentation rule based on information obtained from the bitstream received from the image encoding device (200).

[0206] The shape of the encoding unit may include a square and a non-square shape. If the width and height of the encoding unit are equal, the image decoding device (100) may determine the shape of the encoding unit as a square. In addition, if the width and height of the encoding unit are not equal, the image decoding device (100) may determine the shape of the encoding unit as a non-square shape.

[0207] The size of the coding unit may include various sizes such as 4x4, 8x4, 4x8, 8x8, 16x4, 16x8, ..., 256x256. The size of the coding unit may be classified according to the length of the long side, the length of the short side, or the area of ​​the coding unit. The image decoding device (100) may apply the same splitting rule to the coding units classified into the same group. For example, the image decoding device (100) may classify the coding units having the same long side length into the same size. In addition, the image decoding device (100) may apply the same splitting rule to the coding units having the same long side length.

[0208] The ratio of the width to the height of the coding unit may include 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, 32:1, or 1:32, etc. In addition, the direction of the coding unit may include a horizontal direction and a vertical direction. The horizontal direction may indicate a case where the length of the width of the coding unit is longer than the length of the height. The vertical direction may indicate a case where the length of the width of the coding unit is shorter than the length of the height.

[0209] The image decoding device (100) can adaptively determine a splitting rule based on the size of the encoding unit. The image decoding device (100) can determine a different allowable splitting mode based on the size of the encoding unit. For example, the image decoding device (100) can determine whether splitting is allowed based on the size of the encoding unit. The image decoding device (100) can determine a splitting direction based on the size of the encoding unit. The image decoding device (100) can determine an allowable splitting type based on the size of the encoding unit.

[0210] Determining the splitting rule based on the size of the encoding unit may be a splitting rule predetermined between the image encoding device (200) and the image decoding device (100). In addition, the image decoding device (100) may determine the splitting rule based on information obtained from the bitstream.

[0211] The image decoding device (100) can adaptively determine a segmentation rule based on the position of the encoding unit. The image decoding device (100) can adaptively determine a segmentation rule based on the position that the encoding unit occupies in the image.

[0212] Additionally, the image decoding device (100) can determine a splitting rule so that encoding units generated through different splitting paths do not have the same block shape. However, this is not limited thereto, and encoding units generated through different splitting paths may have the same block shape. Encoding units generated through different splitting paths may have different decoding processing orders. Since the decoding processing order has been described together with FIG. 12, a detailed description thereof will be omitted.

[0213] FIG. 16 illustrates encoding units that can be determined for each picture when the combination of forms into which encoding units can be divided is different for each picture according to one embodiment of the present disclosure.

[0214] Referring to FIG. 16, the image decoding device (100) can determine a different combination of partitioning shapes into which encoding units can be partitioned for each picture. For example, the image decoding device (100) can decode an image using a picture (1600) that can be partitioned into four encoding units, a picture (1610) that can be partitioned into two or four encoding units, and a picture (1620) that can be partitioned into two, three, or four encoding units, among at least one picture included in the image. The image decoding device (100) can only use partitioning shape information indicating that the picture (1600) is partitioned into four square encoding units to partition the picture (1600) into a plurality of encoding units. The image decoding device (100) can only use partitioning shape information indicating that the picture (1610) is partitioned into two or four encoding units to partition the picture. The video decoding device (100) can only use the segmentation type information indicating that the picture (1620) is segmented into two, three, or four encoding units. The above-described combination of segmentation types is merely an example for explaining the operation of the video decoding device (100), and therefore the above-described combination of segmentation types should not be interpreted as being limited to the above-described example, but should be interpreted as being capable of using various combinations of segmentation types for each predetermined data unit.

[0215] According to one embodiment of the present disclosure, the bitstream acquisition unit (110) of the image decoding device (100) can acquire a bitstream including an index indicating a combination of segmentation type information for each predetermined data unit (e.g., a sequence, a picture, a slice, a slice segment, a tile, a tile group, etc.). For example, the bitstream acquisition unit (110) can acquire an index indicating a combination of segmentation type information from a sequence parameter set, a picture parameter set, a slice header, a tile header, or a tile group header. The image decoding device (100) can determine a combination of segmentation types by which an encoding unit can be divided for each predetermined data unit using the acquired index, and thus can use different combinations of segmentation types for each predetermined data unit.

[0216] FIG. 17 illustrates various forms of encoding units that can be determined based on segmentation mode information that can be expressed in binary code according to one embodiment of the present disclosure.

[0217] According to one embodiment of the present disclosure, the image decoding device (100) can split an encoding unit into various shapes using block shape information and split shape mode information acquired through the bitstream acquisition unit (110). The shapes of the encoding unit that can be split may correspond to various shapes including the shapes described through the above-described embodiments.

[0218] Referring to FIG. 17, the image decoding device (100) can split a square-shaped encoding unit in at least one of the horizontal direction and the vertical direction based on the split shape mode information, and can split a non-square-shaped encoding unit in the horizontal direction or the vertical direction.

[0219] According to one embodiment of the present disclosure, when the image decoding device (100) can divide a square-shaped encoding unit into four square encoding units by horizontally and vertically dividing the square-shaped encoding unit, there may be four types of division forms that the division shape mode information for the square encoding unit can indicate. According to one embodiment of the present disclosure, the division shape mode information may be expressed as a two-digit binary code, and a binary code may be assigned to each division form. For example, when the encoding unit is not divided, the division shape mode information may be expressed as (00)b, when the encoding unit is divided in the horizontal direction and the vertical direction, the division shape mode information may be expressed as (01)b, when the encoding unit is divided in the horizontal direction, the division shape mode information may be expressed as (10)b, and when the encoding unit is divided in the vertical direction, the division shape mode information may be expressed as (11)b.

[0220] According to one embodiment of the present disclosure, when the image decoding device (100) splits a non-square coding unit in a horizontal direction or a vertical direction, the type of split shape that the split shape mode information can indicate may be determined depending on the number of coding units into which the coding unit is split. Referring to FIG. 17, the image decoding device (100) may split a non-square coding unit into up to three according to one embodiment of the present disclosure. The image decoding device (100) may split the coding unit into two coding units, in which case the split shape mode information may be expressed as (10)b. The image decoding device (100) may split the coding unit into three coding units, in which case the split shape mode information may be expressed as (11)b. The image decoding device (100) may determine not to split the coding unit, in which case the split shape mode information may be expressed as (0)b. That is, the image decoding device (100) can use variable length coding (VLC) rather than fixed length coding (FLC) to use a binary code representing segmentation mode information.

[0221] According to one embodiment of the present disclosure, referring to FIG. 17, the binary code of the partition shape mode information indicating that the coding unit is not split may be expressed as (0)b. If the binary code of the partition shape mode information indicating that the coding unit is not split is set to (00)b, all binary codes of the 2-bit partition shape mode information must be used even if there is no partition shape mode information set to (01)b. However, as illustrated in FIG. 17, if three partition shapes for a non-square coding unit are used, the image decoding device (100) can determine that the coding unit is not split even if it uses a 1-bit binary code (0)b as the partition shape mode information, and thus can efficiently use the bitstream. However, the division form of the non-square-shaped encoding unit indicated by the division form mode information should not be interpreted as being limited to only the three forms illustrated in FIG. 17, but should be interpreted as various forms including the embodiments described above.

[0222] FIG. 18 illustrates another form of a coding unit that can be determined based on segmentation mode information that can be expressed in binary code according to one embodiment of the present disclosure.

[0223] Referring to FIG. 18, the image decoding device (100) can split a square-shaped encoding unit in the horizontal direction or the vertical direction based on the split shape mode information, and can split a non-square-shaped encoding unit in the horizontal direction or the vertical direction. That is, the split shape mode information can indicate that a square-shaped encoding unit is split in one direction. In this case, the binary code of the split shape mode information indicating that a square-shaped encoding unit is not split can be expressed as (0)b. If the binary code of the split shape mode information indicating that the encoding unit is not split is set to (00)b, all binary codes of the 2-bit split shape mode information must be used even though there is no split shape mode information set to (01)b. However, as illustrated in FIG. 18, if three types of division forms for a square-shaped encoding unit are used, the image decoding device (100) can determine that the encoding unit is not divided even if it uses a 1-bit binary code (0)b as the division form mode information, and thus can efficiently use the bitstream. However, the division forms of the square-shaped encoding unit indicated by the division form mode information should not be interpreted as being limited to only the three types illustrated in FIG. 18, but should be interpreted as various types including the embodiments described above.

[0224] According to one embodiment of the present disclosure, block shape information or segmentation shape mode information can be expressed using binary code, and such information can be directly generated as a bitstream. In addition, block shape information or segmentation shape mode information that can be expressed using binary code may not be directly generated as a bitstream, but may be used as a binary code input in CABAC (context adaptive binary arithmetic coding).

[0225] According to one embodiment of the present disclosure, a video decoding device (100) describes a process of obtaining syntax for block shape information or segmentation shape mode information through CABAC. A bitstream including a binary code for the syntax can be obtained through a bitstream obtaining unit (110). The video decoding device (100) can detect a syntax element indicating block shape information or segmentation shape mode information by de-binarizing a bin string included in the obtained bitstream. According to one embodiment of the present disclosure, the video decoding device (100) can obtain a set of binary bin strings corresponding to syntax elements to be decoded, and decode each bin using probability information, and the video decoding device (100) can repeat the process until a bin string composed of the decoded bins becomes equal to one of the previously obtained bin strings. The image decoding device (100) can determine syntax elements by performing inverse binarization of an empty string.

[0226] According to one embodiment of the present disclosure, the image decoding device (100) may perform a decoding process of adaptive binary arithmetic coding to determine a syntax for a bin string, and the image decoding device (100) may update a probability model for bins acquired through the bitstream acquisition unit (110). Referring to FIG. 17, the bitstream acquisition unit (110) of the image decoding device (100) may acquire a bitstream representing a binary code representing segmentation mode information according to one embodiment of the present disclosure. Using the acquired binary code having a size of 1 or 2 bits, the image decoding device (100) may determine a syntax for the segmentation mode information. In order to determine the syntax for the segmentation mode information, the image decoding device (100) may update a probability for each bit of the 2-bit binary code. That is, the image decoding device (100) can update the probability of having a value of 0 or 1 when decoding the next bin, depending on whether the value of the first bin among the 2-bit binary codes is 0 or 1.

[0227] According to one embodiment of the present disclosure, the image decoding device (100) can, in the process of determining a syntax, update the probability for bins used in the process of decoding bins of an empty string for the syntax, and the image decoding device (100) can determine that certain bits among the empty strings have the same probability without updating the probability.

[0228] Referring to FIG. 17, in the process of determining a syntax using an empty string indicating split shape mode information for a non-square coding unit, the image decoding device (100) may determine the syntax for the split shape mode information using one bin having a value of 0 when the non-square coding unit is not split. That is, when the block shape information indicates that the current coding unit is a non-square shape, the first bin of the empty string for the split shape mode information may be 0 when the non-square coding unit is not split, and may be 1 when it is split into 2 or 3 coding units. Accordingly, the probability that the first bin of the empty string of the split shape mode information for the non-square coding unit is 0 may be 1 / 3, and the probability that it is 1 may be 2 / 3. As described above, the image decoding device (100) can only express a 1-bit empty string having a value of 0 for the partition shape mode information indicating that a non-square-shaped encoding unit is not partitioned, so the image decoding device (100) can determine the syntax for the partition shape mode information by determining whether the second bin is 0 or 1 only when the first bin of the partition shape mode information is 1. According to one embodiment of the present disclosure, when the first bin for the partition shape mode information is 1, the image decoding device (100) can decode the bin by considering that the probability that the second bin is 0 or 1 is the same probability.

[0229] According to one embodiment of the present disclosure, the image decoding device (100) may utilize various probabilities for each bin in the process of determining a bin of a bin string for the partition shape mode information. According to one embodiment of the present disclosure, the image decoding device (100) may determine the probability of a bin for the partition shape mode information differently depending on the direction of a non-square block. According to one embodiment of the present disclosure, the image decoding device (100) may determine the probability of a bin for the partition shape mode information differently depending on the area or the length of the long side of the current encoding unit. According to one embodiment of the present disclosure, the image decoding device (100) may determine the probability of a bin for the partition shape mode information differently depending on at least one of the shape and the length of the long side of the current encoding unit.

[0230] According to one embodiment of the present disclosure, the image decoding device (100) may determine that the bin probability for the partition shape mode information is the same for encoding units of a predetermined size or larger. For example, the bin probability for the partition shape mode information may be determined to be the same for encoding units of a size of 64 samples or larger based on the length of the long side of the encoding unit.

[0231] According to one embodiment of the present disclosure, the image decoding device (100) may determine the initial probability for bins constituting the empty string of the segmentation shape mode information based on the slice type (e.g., I slice, P slice, or B slice).

[0232] Figure 19 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0233] The encoding unit (1910) of the image encoding and decoding system (1900) transmits an encoded bitstream of an image, and the decoding unit (1950) receives the bitstream and decodes it to output a restored image. Here, the encoding unit (1910) may have a configuration similar to that of the image encoding device (200) described below, and the decoding unit (1950) may have a configuration similar to that of the image decoding device (100).

[0234] In the encoding unit (1910), the prediction encoding unit (1915) outputs prediction data through inter prediction and intra prediction, and the transformation and quantization unit (1920) outputs quantized transformed coefficients (or quantized coefficients) of residual data between the prediction data and the current input image. For example, the transform coefficients may be generated using a transform kernel including at least one of a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), a Hadamard transform, a Karhunen-Loeve Transform (KLT), or a Wavelet Transform. The residual data may have information compressed by performing the transformation. For example, the residual data may be expressed using a small number of frequencies by performing the transformation. In one embodiment, the transform and quantization unit (1920) may omit transforming the residual data between the prediction data and the current input image. For example, if the distribution of the residual data makes it inefficient to perform transform, the transform process for the residual data may be omitted and the quantization process may be performed. In one embodiment, whether transform is omitted (or whether transform is performed) may be transmitted to the decoding unit (1950) through the bitstream. The entropy encoding unit (1925) encodes and transforms the quantized transform coefficients and outputs them as a bitstream. The quantized transform coefficients may be restored to data in the spatial domain through the inverse quantization and inverse transform unit (1930). The inverse quantization and inverse transform unit (1930) may perform inverse quantization on the quantized transform coefficients and apply a transform kernel to determine the residual data. In one embodiment, the inverse quantization and inverse transform unit (1930) may not perform inverse transform.For example, if transformation on residual data is omitted, the inverse quantization and inverse transformation unit (1930) may not perform inverse transformation. The inverse quantization and inverse transformation unit (1930) may determine residual data by performing inverse quantization on quantized transform coefficients. The data of the restored spatial domain is output as a restored image through the deblocking filtering unit (1935) and the loop filtering unit (1940). The restored image may be used as a reference image for the next input image through the predictive encoding unit (1915).

[0235] The encoded image data among the bitstreams received by the decoding unit (1950) is restored to residual data in the spatial domain through the entropy decoding unit (1955) and the inverse quantization and inverse transformation unit (1960). The prediction data and residual data output from the prediction decoding unit (1975) are combined to form image data in the spatial domain, and the deblocking filtering unit (1965) and the loop filtering unit (1970) can perform filtering on the image data in the spatial domain to output a restored image for the current original image. The restored image can be used as a reference image for the next original image by the prediction decoding unit (1975).

[0236] The loop filtering unit (1940) of the encoding unit (1910) performs loop filtering using filter information input according to user input or system settings. The filter information used by the loop filtering unit (1940) is output to the entropy encoding unit (1925) and transmitted to the decoding unit (1950) together with the encoded image data. The loop filtering unit (1970) of the decoding unit (1950) can perform loop filtering based on the filter information input from the decoding unit (1950).

[0237] FIG. 20 is a block diagram showing the configuration of an image decoding device according to one embodiment of the present disclosure.

[0238] Referring to FIG. 20, the image decoding device (2000) may include an acquisition unit (2010) and a prediction decoding unit (2020).

[0239] In one embodiment of the present disclosure, the acquisition unit (2010) and the prediction decoding unit (2020) may be implemented with at least one processor. In one embodiment of the present disclosure, the image decoding device (2000) may include a memory that stores at least one of input / output data or instructions of the acquisition unit (2010) and the prediction decoding unit (2020). The acquisition unit (2010) and the prediction decoding unit (2020) may operate according to the instructions stored in the memory. In one embodiment of the present disclosure, the image decoding device (2000) may include a memory control unit that controls data input / output of the memory.

[0240] In one embodiment of the present disclosure, the acquisition unit (2010) may correspond to the entropy decoding unit (1955) illustrated in FIG. 19. In one embodiment of the present disclosure, the prediction decoding unit (2020) may correspond to the prediction decoding unit (1975) illustrated in FIG. 19.

[0241] The acquisition unit (2010) can acquire a bitstream generated as a result of encoding an image. The bitstream can include an encoding result for a current block. In one embodiment of the present disclosure, the acquisition unit (2010) can receive the bitstream from an image encoding device via a network. In one embodiment of the present disclosure, the acquisition unit (2010) can acquire the bitstream from a data storage medium including at least one of a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape, an optical recording medium such as a CD-ROM and a DVD, or a magneto-optical medium such as a floptical disk.

[0242] The acquisition unit (2010) can acquire syntax elements for decoding an image from a bitstream. The values ​​corresponding to the syntax elements can be included in the bitstream according to the hierarchical structure of the image. In one embodiment of the present disclosure, the acquisition unit (2010) can acquire the syntax elements by entropy decoding bins included in the bitstream.

[0243] In one embodiment of the present disclosure, a bitstream may include information about a prediction mode of a current block in a current image. The current block may include at least one of a maximum coding unit, an encoding unit, a transformation unit, or a prediction unit segmented from a current image to be decoded. In one embodiment of the present disclosure, the prediction mode of the current block may include at least one of an intra mode, an inter mode, a combined mode, a geometric partitioning mode, a block copy mode, or a template matching prediction mode.

[0244] In one embodiment of the present disclosure, the intra mode may include an intra planar mode of 0 (Intra_Planar) that is non-directional, an intra DC mode of 1 (Intra_DC), intra directional modes of 2 to 66 (Intra_Angular2.. Intra_Angular66) that are directional, and intra wide directional modes of -14 to -1 and 67 to 80 (Intra_Wide_Angular). In one embodiment of the present disclosure, the intra planar mode may refer to a mode that determines a prediction sample based on a weighted average value according to a distance of a left reference sample, an upper reference sample, a lower-left sample of a current block, and an upper-right sample. In one embodiment of the present disclosure, the intra DC mode may refer to a mode that determines an average value of reference samples as a prediction sample. In one embodiment of the present disclosure, in intra directional modes, the positions of reference samples for generating prediction samples of samples within a current block can be identified by considering the direction indicated by the intra directional modes. For example, in mode 34, reference samples located at a 45 degree upper left direction with respect to samples within the current block can be identified. Intra wide directional modes can be used to identify reference samples of samples within a non-square current block. In one embodiment of the present disclosure, the prediction decoding unit (2020) can determine one of the intra wide directional modes as an intra prediction mode of a non-square current block. The number and types of intra prediction modes that can be used in the intra mode by the prediction decoding unit (2020) according to one embodiment of the present disclosure can be set in various ways.

[0245] In one embodiment of the present disclosure, the prediction decoding unit (2020) can determine an intra prediction mode using MPM (most probable modes). The prediction decoding unit (2020) can determine whether to use MPM. The acquisition unit (2010) can obtain information related to whether to use MPM from a bitstream. The prediction decoding unit (2020) can determine a candidate mode list. The prediction decoding unit (2020) can determine the candidate mode list based on the intra mode of the upper block of the current block and the intra mode of the left block. The prediction decoding unit (2020) can determine one of the candidate mode lists as the intra prediction mode of the current block. The prediction decoding unit (2020) can obtain information indicating the intra prediction mode of the current block from the bitstream from the candidate mode list.

[0246] In one embodiment of the present disclosure, the prediction decoding unit (2020) may determine an intra prediction mode using a template. The prediction decoding unit (2020) may determine a template of a current block. The template of the current block may include a left sample, an upper-left sample, and / or an upper sample of the current block. The prediction decoding unit (2020) may determine surrounding samples of the template of the current block. The surrounding samples of the template may include a left sample, an upper-left sample, and / or an upper sample of the template. The prediction decoding unit (2020) may perform prediction on the template using the surrounding samples of the template as reference samples. In one embodiment of the present disclosure, the process of determining an intra prediction mode by the prediction decoding unit (2020) performing prediction on the template may be referred to as template-based intra mode derivation (TIMD).

[0247] In one embodiment of the present disclosure, the prediction decoding unit (2020) can infer an intra prediction mode of the current block using surrounding samples of the current block. The prediction decoding unit (2020) can determine a slope using the surrounding samples of the current block. The prediction decoding unit (2020) can determine a plurality of 3 x 3 blocks adjacent to the current block. The prediction decoding unit (2020) can obtain horizontal variations and vertical variations of samples included in each of the determined 3 x 3 blocks. The prediction decoding unit (2020) can determine a slope based on the horizontal variations and vertical variations. The prediction decoding unit (2020) can determine the horizontal variations and vertical variations using a Sobel filter. The prediction decoding unit (2020) can determine an intra prediction mode corresponding to the slope. The prediction decoding unit (2020) may determine the intra prediction mode of the current block based on a plurality of intra prediction modes determined for a plurality of 3 x 3 blocks. In one embodiment of the present disclosure, the prediction decoding unit (2020) may determine the intra prediction mode that is determined most frequently as the intra prediction mode of the current block. In one embodiment of the present disclosure, the prediction decoding unit (2020) may determine an amplitude based on horizontal variation and vertical variation. The prediction decoding unit (2020) may determine the intra prediction mode of the current block based on the amplitude. The prediction decoding unit (2020) may determine a weight of the intra prediction mode corresponding to the slope as the amplitude. For example, the prediction decoding unit (2020) may increase the weight of the intra prediction mode determined based on the slope as the horizontal variation and vertical variation increase. The prediction decoding unit (2020) can determine the intra prediction mode of the current block based on the result reflecting the weight determined according to the size.In one embodiment of the present disclosure, the process by which the prediction decoding unit (2020) determines an intra prediction mode based on a slope may be referred to as decoder side intra mode derivation (DIMD).

[0248] In one embodiment of the present disclosure, the block copy mode may include an intra block copy mode. In one embodiment, the block copy mode may include an intra block copy mode. In one embodiment, the intra block copy mode may be a sub-mode of the intra mode, but is not limited thereto, and may represent a mode separate from the intra mode. In one embodiment, the template matching prediction mode may include a template matching intra prediction mode. The combined mode may include a Combined Inter-Intra Prediction (CIIP) mode that performs prediction by combining prediction according to the intra mode and prediction according to the inter mode. The geometric partitioning mode may include a mode that partitions to include directionality within a block. The geometric partitioning mode may perform prediction using inter prediction or intra prediction for each of the divided regions that are blocked.

[0249] The prediction decoding unit (2020) can restore the current block by performing prediction according to the prediction mode for the current block according to the prediction mode of the current block.

[0250] In one embodiment of the present disclosure, the acquisition unit (2010) can acquire information regarding the prediction mode of the current block from the bitstream. For example, the acquisition unit (2010) can acquire index information indicating the prediction mode of the current block from the bitstream.

[0251] In one embodiment of the present disclosure, when the prediction mode of the current block is the CIIP mode, the prediction decoding unit (2020) can reconstruct the current block by combining inter prediction and intra prediction. For example, the prediction decoding unit (2020) can perform intra prediction according to the planar mode. For example, the prediction decoding unit (2020) can perform inter prediction using a motion vector (MV). The prediction decoding unit (2020) can reconstruct the current block using a weighted sum of a prediction block according to inter prediction and a prediction block according to intra prediction. The weight can be determined based on whether a block adjacent to the current block was intra predicted.

[0252] In one embodiment of the present disclosure, when the prediction mode of the current block is a geometric segmentation mode, the prediction decoding unit (2020) can perform prediction by segmenting the current block. The prediction decoding unit (2020) can obtain a segmentation angle and a segmentation distance for a boundary at which segmentation is performed within the current block. The prediction decoding unit (2020) can segment the current block based on the segmentation angle and the segmentation distance. The prediction decoding unit (2020) can perform inter-prediction or intra-prediction on each of the segmented regions within the current block to reconstruct the current block. The prediction decoding unit (2020) can (i) perform intra-prediction on both segmented regions, (ii) perform inter-prediction on one region and intra-prediction on the other region, or (iii) perform inter-prediction on both segmented regions.

[0253] In one embodiment of the present disclosure, when the prediction mode of the current block is block copy mode, the prediction decoding unit (2020) can reconstruct the current block based on a reference block included in the current image. In one embodiment of the present disclosure, when the prediction mode of the current block is block copy mode, the prediction decoding unit (2020) can determine information about a block vector (BV) representing the reference block. In one embodiment of the present disclosure, the prediction decoding unit (2020) can determine the prediction block based on the reference block. For example, the prediction decoding unit (2020) can determine the prediction block by being identical to the reference block or by performing filtering on the reference block.

[0254] In one embodiment of the present disclosure, when the prediction mode of the current block is the template matching prediction mode, the prediction decoding unit (2020) can reconstruct the current block using a reference block. The acquisition unit (2010) can acquire information related to whether the template matching prediction mode is used. The prediction decoding unit (2020) can determine whether the template matching prediction mode is used based on the acquired information. The reference block can be determined based on at least one of a region included in the current image or a region included in a previously decoded image. In one embodiment of the present disclosure, the prediction decoding unit (2020) can determine the reference block using a cost function. The cost function can include at least one of a sum of absolute difference (SAD), a sum of squared difference (SSD), a sum of absolute transformed difference (SATD), a sum of squared error (SSE), or a mean removed SAD (MR-SAD). For example, the prediction decoding unit (2020) can determine the error between templates using at least one cost function among SAD, SATD, SSE, and MR-SAD. When the cost function is SAD, the prediction decoding unit (2020) can determine the error based on the sum of the absolute values ​​of the differences between each sample of the template of the current block and each sample of the template of the candidate block. When the cost function is SSD, the prediction decoding unit (2020) can determine the error based on the sum of the squares of the differences between each sample of the template of the current block and each sample of the template of the candidate block. The cost function may include a function representing the number of identical samples. The prediction decoding unit (2020) can determine a block with a small error among the candidate blocks as a reference block. The prediction decoding unit (2020) can determine a prediction block by performing template matching intra prediction on the current image.In the present disclosure, the process of determining a reference block for a current block using a template may be referred to as template matching (TM). In the present disclosure, performing a prediction for a current block based on template matching may be referred to as template matching prediction (TMP) or intra-template matching prediction (ITEM).

[0255] The prediction decoding unit (2020) can generate a reconstructed current block using the prediction block. In one embodiment of the present disclosure, the prediction decoding unit (2020) can determine the prediction block as the reconstructed current block. In one embodiment of the present disclosure, the prediction decoding unit (2020) can generate a reconstructed current block by combining the prediction block with residual data acquired from the bitstream by the acquisition unit (2010). The reconstructed current block can be used as a reference block for the next block.

[0256] In one embodiment, the acquisition unit (2010) can acquire residual data from the bitstream. The residual data can include information about the difference between an original image (or an original sample) and a predicted image (or a predicted sample). In one embodiment, the acquisition unit (2010) can acquire transform coefficients of a residual block corresponding to a transform unit from the bitstream. In one embodiment, the prediction decoding unit (2020) can acquire residual samples of the residual block based on the transform coefficients of the residual block. For example, the prediction decoding unit (2020) can acquire residual samples of the residual block by performing at least one of inverse quantization or inverse transformation on the transform coefficients of the residual block. In one embodiment, the prediction decoding unit (2020) can determine the residual sample of the coding unit using at least a portion of a portion of the residual samples of the residual block. If the size of the residual block is larger than the size of the transformation unit, the prediction decoding unit (2020) may determine some of the residual samples of the residual block as residual samples of the coding unit. Alternatively, the prediction decoding unit (2020) may determine some of the residual samples of the residual block on which filtering has been performed as residual samples of the coding unit. The prediction decoding unit (2020) may reconstruct the samples of the coding unit based on the residual samples of the coding unit.

[0257] In a prediction mode (e.g., intra mode) that uses reference samples included in a current image, a prediction block of the current block can be generated based on the surrounding samples of the current block according to the prediction mode, assuming that there will be continuity between the surrounding samples of the current block and the samples within the current block. The prediction decoding unit (2020) according to an embodiment of the present disclosure can use not only the surrounding samples of the current block included in the current image but also the spatial reference samples included in the current image for intra prediction. When using samples reconstructed before the current block, the size of the residual data can be reduced by predicting the samples of the current block using not only the samples immediately adjacent to the current block but also samples far from the current block. In an embodiment of the present disclosure, the image decoding apparatus (2000) performs intra prediction using a reference block including unreconstructed samples, thereby increasing the range of an area that can be determined as a reference block. The image decoding apparatus (2000) according to an embodiment of the present disclosure can improve compression efficiency by increasing the efficiency of intra prediction.

[0258] In a prediction mode (e.g., inter mode) that utilizes reference samples included in a reference image rather than the current image, a prediction block of the current block can be generated based on a reference block (or reference sample) of the reference image according to the prediction mode, under the assumption that there will be continuity between the current image and the reference image. An image decoding apparatus (2000) according to an embodiment of the present disclosure can improve compression efficiency by increasing the efficiency of intra prediction.

[0259] The image decoding device (2000) can improve prediction accuracy by considering both a reference block (or reference sample) included in the current image and a reference block (or reference sample) included in an image other than the current image. The image decoding device (2000) according to one embodiment of the present disclosure can improve prediction accuracy by considering both the current image and an image other than the current image.

[0260] The prediction decoding unit (2020) can perform deblocking filtering. The deblocking filter can improve image quality by smoothing the edges between blocks.

[0261] The prediction decoding unit (2020) may perform filtering on samples of the current block on which deblocking filtering has been performed using a sample adaptive offset (SAO) filter and / or a bilateral filter (BIF). The SAO filter and BIF may improve image quality by reducing the error between the restored image and the original image. The SAO filter and BIF may perform filtering on a sample-by-sample basis.

[0262] The predictive decoding unit (2020) can perform filtering using an adaptive loop filter (ALF). ALF can improve image quality by reducing the error between the reconstructed image and the original image. ALF filtering can be performed on a block-by-block basis.

[0263] FIG. 21 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0264] In one embodiment of the present disclosure, the image decoding method may be performed by the image decoding device (2000). For example, the image decoding device (2000) may perform each step of the image decoding method by having the processor of the image decoding device (2000) execute at least one instruction contained in a memory.

[0265] In step S2110, the image decoding device (2000) can obtain one or more transformation units including the current transformation unit from the encoding unit. The image decoding device (2000) can divide the encoding unit into one or more transformation units.

[0266] In one embodiment, when a subblock transform (SBT) is applied to an encoding unit, the image decoding device (2000) may split the encoding unit into one or more transform units. In one embodiment, “subblock transform” may indicate that the encoding unit is split into a plurality of transform units, and some of the split transform units are subjected to transform and the rest are not subjected to transform. In one embodiment, the image decoding device (2000) may determine the coefficient of a transform unit on which a transform is not performed as a predetermined value (e.g., 0). In one embodiment, the image decoding device (2000) may obtain information about a transform unit on which a transform is not performed from a bitstream. The image decoding device (2000) may obtain information indicating whether a subblock transform is applied from the bitstream. The image decoding device (2000) may determine whether a subblock transform is applied based on the information obtained from the bitstream.

[0267] In one embodiment, the image decoding device (2000) may obtain a transformation unit that is the same as the coding unit. The image decoding device (2000) may determine not to split the coding unit based on at least one of the width of the coding unit or the height of the coding unit. For example, the image decoding device (2000) may determine not to split the coding unit when the width of the coding unit is less than or equal to a predetermined first value (e.g., the maximum size of the transformation unit) and the height of the coding unit is less than or equal to a predetermined second value (e.g., the maximum size of the transformation unit). When the image decoding device (2000) determines not to split the coding unit, it may obtain a transformation unit that is the same as the coding unit.

[0268] In one embodiment, the current transformation unit may represent a transformation unit having residual data among one or more transformation units of the encoding unit. For example, the current transformation unit may refer to a transformation unit whose bitstream includes residual data. The residual data may include at least one of residual data on which transformation has been performed or residual data on which transformation has not been performed.

[0269] In step S2120, the image decoding apparatus (2000) may obtain a transform coefficient of a residual block corresponding to a current transformation unit. In one embodiment, the residual block may include information related to a residual sample of the coding unit. For example, the residual sample of the coding unit may be determined based on a residual sample of the residual block. In one embodiment, the transformation unit included in the coding unit may include at least one of a transformation unit having a residual block (or residual data) on which transformation has been performed, a transformation unit having a residual block on which transformation has been omitted, or a transformation unit not having a residual block. In one embodiment, the image decoding apparatus (2000) may determine a residual sample value of a coding unit corresponding to a transformation unit not having a residual block to be 0. In one embodiment, the residual data may include information about a residual sample of the coding unit. The residual block may include residual data. In one embodiment, the residual sample can be obtained by performing at least one of entropy decoding, inverse quantization, or inverse transformation on the residual data.

[0270] The image decoding device (2000) can obtain information related to transform coefficients of a residual block from a bitstream. The information related to the transform coefficients can include at least one of information related to the size of the transform coefficients or information related to the sign of the transform coefficients. The information related to the size of the transform coefficients can include information related to whether the transform coefficients are greater than a predetermined value (e.g., 0, 1, 3). The information related to the size of the transform coefficients can include information indicating a difference between the transform coefficients and the predetermined value (e.g., 0, 1, 3).

[0271] The video decoding device (2000) can determine a transform coefficient based on information obtained from a bitstream.

[0272] In step S2130, the image decoding device (2000) can obtain a residual sample of the residual block based on the transform coefficient of the residual block. The image decoding device (2000) can obtain the residual sample of the residual block by performing an inverse transform on the transform coefficient of the residual block. The image decoding device (2000) can perform the inverse transform using a transform kernel.

[0273] The image decoding device (2000) may perform inverse transformation using one or more transform kernels among a plurality of predetermined transform kernels. In one embodiment, the predetermined transform kernels may include at least one of DCT-2, DCT-7, DCT-8, or Identity Transform. For example, the image decoding device (2000) may perform inverse transformation using DCT-2.

[0274] In one embodiment, the image decoding device (2000) may determine the transform kernel based on at least one of the size (e.g., width, height, or area) of the residual block, the ratio between the width of the residual block and the height of the residual block, the size of the transform unit, the ratio between the width of the transform unit and the height of the transform unit, or the position of the transform unit (or residual block) within the coding unit. For example, the image decoding device (2000) may perform an inverse transform using a transform kernel determined in advance according to a predetermined condition.

[0275] In one embodiment, the image decoding device (2000) can obtain information about a transform kernel from a bitstream. The image decoding device (2000) can determine a transform kernel based on the information obtained from the bitstream.

[0276] In one embodiment, the image decoding device (2000) can determine vertical and horizontal transformation kernels, respectively. The image decoding device (2000) can obtain index information indicating the vertical and horizontal transformation kernels from a bitstream. The image decoding device (2000) can determine the vertical and horizontal transformation kernels based on the index information.

[0277] In step S2140, the image decoding device (2000) may determine residual samples of the encoding unit by using some of the residual samples of the residual block when the size of the residual block is larger than the size of the current transformation unit. In one embodiment, the size of the residual block may be larger than or equal to the size of the transformation unit corresponding to the residual block. For example, the size of the residual block corresponding to the current transformation unit may be larger than or equal to the size of the current transformation unit. The size of the block or unit may include at least one of the width, height, and area of ​​the block or unit.

[0278] In one embodiment of the present disclosure, when the size of the residual block is larger than the size of the current transformation unit, the image decoding device (2000) may select a portion of residual samples of the residual block. For example, when the size of the residual block is N times larger than the current transformation unit, the image decoding device (2000) may select from among the residual samples of the residual block at a ratio of 1 / N. For example, when the size of the residual block is twice larger than the current transformation unit, the image decoding device (2000) may select half of the residual samples of the residual block. A process of selecting a portion of residual samples of the residual block by the image decoding device (2000) according to one embodiment of the present disclosure may be described with reference to FIGS. 23 to 25.

[0279] The image decoding device (2000) may determine residual samples of an encoding unit using some residual samples of a selected residual block. In one embodiment, the image decoding device (2000) may determine residual samples of an encoding unit identical to some residual samples of a selected residual block. In one embodiment, the image decoding device (2000) may determine residual samples of an encoding unit identical to samples obtained by performing filtering on some residual samples of a selected residual block.

[0280] In step S2150, the image decoding device (2000) can reconstruct a sample of the encoding unit based on a residual sample of the encoding unit. In one embodiment, the image decoding device (2000) can obtain a prediction sample based on information obtained from a bitstream. For example, the image decoding device (2000) can obtain a prediction sample according to a prediction mode of the encoding unit. The image decoding device (2000) can reconstruct a sample of the encoding unit based on the prediction sample and the residual sample. For example, the image decoding device (2000) can obtain a reconstructed sample by adding the prediction sample and the residual sample.

[0281] An image decoding method according to one embodiment of the present disclosure can improve compression efficiency by increasing the performance of residual coding.

[0282] FIG. 22 is a diagram for explaining an image encoding and decoding process according to one embodiment of the present disclosure.

[0283] Referring to FIG. 22, residual samples of a coding unit can be obtained through encoding and decoding processes. In one embodiment of the present disclosure, an original image may include multiple coding units. For example, a coding unit (2210) may represent one of multiple coding units included in the original image. A coding unit (2210) may include multiple transformation units.

[0284] The image decoding device (2000) may split the encoding unit (2210) into a plurality of transformation units based on a predetermined condition or information obtained from a bitstream. For example, the transformation unit (2215) may be one of the transformation units included in the encoding unit (2210), and the transformation unit (2215) may be obtained by splitting the encoding unit (2210) in a horizontal direction. For example, the width of the transformation unit (2215) may be the same as the width of the encoding unit (2210), and the height of the transformation unit (2215) may be half the height of the encoding unit (2210).

[0285] In one embodiment, the transformation unit (2215) may be a transformation unit having residual data (or residual block) among the transformation units included in the encoding unit (2210). For example, the encoding unit (2210) may be a transformation unit to which a subblock transform is applied, and the transformation unit (2215) may be a transformation unit having residual data among the transformation units of the encoding unit (2210). For example, the transformation unit (2215) may be determined based on at least one of information about a split size of the encoding unit (2210) (e.g., cu_sbt_quad_flag), information about a split direction of the encoding unit (2210) (e.g., cu_sbt_horizontal_flag), and information about a position of the transformation unit having residual data (e.g., cu_sbt_pos_flag).

[0286] In one embodiment, the residual block (2220) corresponding to the transformation unit (2215) may have the same size as the transformation unit (2215). For example, the height and width of the residual block (2220) may be the same as the height and width of the transformation unit (2215). The transformation unit may refer to a block (or unit) containing transformation data. In one embodiment, the residual block (2220) may have a different size from the transformation unit (2215). An example of increasing the size of the residual block (2220) will be described with reference to FIG. 23.

[0287] In one embodiment, the residual data of the residual block (2220) may be encoded by an image encoding device. For example, the residual block (2220) may be encoded by performing at least one of transformation, quantization, or entropy coding. The encoded information may be transmitted to the image decoding device (2000) via a bitstream.

[0288] In one embodiment, the image decoding device (2000) can determine the encoding unit (2250), the transformation unit (2255), and the residual block (2240) of the current image. The image decoding device (2000) can obtain the encoding unit (2250), the transformation unit (2255), and the residual block (2240) from the current image based on information obtained through the bitstream.

[0289] In one embodiment, the image decoding device (2000) can obtain encoded information from a bitstream. The encoded information can include a transform coefficient of a residual block (2240) (or, a transform unit). The image decoding device (2000) can obtain a residual sample of the residual block (2240) based on the transform coefficient of the residual block (2240). In one embodiment, the image decoding device (2000) can obtain a residual sample of the residual block (2240) by performing at least some of entropy decoding, inverse quantization, and inverse transformation on the transform coefficient of the residual block (2240). In one embodiment, the image decoding device (2000) can determine a residual coefficient of an encoding unit (2250) using the residual sample of the residual block (2240). The video decoding device (2000) can determine the sample of the transformation unit (2240) corresponding to the residual block (2240) (or the sample of the encoding unit (2250)) to be the same as the residual sample of the residual block (2240).

[0290] FIG. 23 is a diagram for explaining an image encoding and decoding process according to one embodiment of the present disclosure.

[0291] Referring to FIG. 23, the residual blocks (2320, 2340) of the encoding unit may have a larger size than the residual blocks (2220, 2240) corresponding to the transformation unit. For example, the residual blocks (2320, 2340) of the encoding unit may have a size that is N times (e.g., 2 times, 4 times, etc.) larger than the residual blocks (2220, 2240) corresponding to the transformation unit. In one embodiment, when the size of the residual blocks (2320, 2340) of the encoding unit is larger than the residual blocks (2220, 2240) corresponding to the transformation unit, the residual blocks (2320, 2340) of the encoding unit may be referred to as enlarged residual blocks. For convenience of explanation, the contents described in FIG. 22 may be omitted.

[0292] In one embodiment, the video encoding device and / or the video decoding device (2000) may enlarge a residual block (2220, 2240) corresponding to a transformation unit. Referring to FIG. 23, the residual block (2320, 2340) of the encoding unit may be a residual block (2220, 2240) corresponding to the transformation unit enlarged by twice. The residual block (2320, 2340) may be enlarged in at least one of the height or the width. In one embodiment, the process of obtaining the enlarged residual block (2320) from the residual block (2220) may be referred to as up-sampling. In one embodiment, the process of obtaining the residual block (2240) corresponding to the transformation unit (2255) from the enlarged residual block (2340) may be referred to as down-sampling.

[0293] In one embodiment, the video encoding device and / or the video decoding device (2000) can obtain an enlarged residual block (2320, 2340) corresponding to the transformation unit (2215, 2255). The video decoding device (2000) can omit the operation of determining the residual block (2220, 2240) and determine the enlarged residual block (2320, 2340) corresponding to the transformation unit (2215, 2255).

[0294] In one embodiment, the residual samples of the enlarged residual block (2320) may be determined based on the residual samples of the residual block (2220). For example, some of the residual samples of the enlarged residual block (2320) may be determined as the residual samples of the residual block (2220), and the remaining residual samples may be determined through interpolation of the residual samples of the residual block (2220). In one embodiment of the present disclosure, an operation of generating the enlarged residual block (2320) from the residual block (2220) is described in detail with reference to FIG. 24.

[0295] In one embodiment, the residual data of the enlarged residual block (2320) may be encoded. For example, encoded information may be generated by performing at least one of transformation, quantization, or entropy coding on the residual data of the enlarged residual block (2320). The encoded information according to the enlarged residual block (2320) may be transmitted to the image decoding device (2000) via a bitstream.

[0296] In one embodiment, the image decoding device (2000) can obtain encoded information from a bitstream. The image decoding device (2000) can obtain residual data of a residual block (2340) by decoding the encoded information.

[0297] In one embodiment, the image decoding device (2000) may determine the residual block (2240) using a portion of the residual block (2340). For example, the image decoding device (2000) may determine a portion of the residual samples of the residual block (2340) as the residual samples of the residual block (2240). In one embodiment, the image decoding device (2000) may determine the residual samples of a residual block for which residual data is not obtained through a bitstream to be 0.

[0298] In one embodiment, without any separate conditions, the image decoding device (2000) may determine that the residual block (2340) is enlarged. In one embodiment, if only some transformation units (2255) of the coding unit (2250) have residual data, the image decoding device (2000) may determine that the residual block (2340) is enlarged. In one embodiment, if only some transformation units (2255) of the coding unit (2250) have residual data, the image decoding device (2000) may obtain information on whether the residual block (2340) is enlarged through a bitstream. The image decoding device (2000) may determine whether the residual block (2340) is enlarged based on the obtained information.

[0299] In one embodiment, the image decoding device (2000) may determine whether the residual block (2340) is enlarged based on at least one of the size of the residual block (2340), the ratio between the width and height of the residual block (2340), the size of the transformation unit (2255), the ratio between the width and height of the transformation unit (2255), or the prediction mode of the encoding unit (2250).

[0300] In one embodiment, whether to apply a method of expanding a residual block (2340) (i.e., upsampling) may be included in a header of a bitstream (e.g., Sequence Parameter Set, Video Parameter Set, Picture Header, Slice Header, CTU (coding tree unit) unit, CU (coding unit) unit, PU (prediction unit), TU (transform unit)), and whether to apply upsampling may be determined for a specific unit.

[0301] The video decoding device (2000) can obtain information (e.g., transform_skip_flag) indicating whether a transformation has been applied to a transformation unit (2255) or a residual block (2340) from the bitstream. In one embodiment, when the residual block (2340) is enlarged, the video decoding device (2000) can determine that a transformation has been performed on the transformation unit (2255) or the residual block (2340) without obtaining information indicating whether a transformation has been applied from the bitstream.

[0302] The residual block (2320) can be transformed into a frequency domain. The residual block (2320) can include a plurality of transform coefficients in the frequency domain. In one embodiment, the image encoding device can discard the transform coefficients of the high frequency region of the residual block (2320). For example, the image encoding device can determine (or change) the transform coefficients of the high frequency region of the residual block (2320) to 0. In one embodiment, the image encoding device (3300) can delete the transform coefficients of the residual block (2320) that are outside the transform unit (2215) or the residual block (2220). For example, the image decoding device (2000) can delete the transform coefficients of the horizontally divided lower wxh / 2 region of the residual block (2320), where the size of the residual block (2320) is wxh and the size of the residual block (2220) is wxh / 2. In one embodiment, the image encoding device may not transmit information about the deleted high-frequency region. The bitstream may not include transform coefficients for the deleted high-frequency region. In one embodiment, the image decoding device (2000) may determine the transform coefficients for the high-frequency region of the residual block (2340) to be 0.

[0303] According to one embodiment, a video encoding method and a video decoding method can improve coding efficiency such as precision of transform coefficients, peak signal-to-noise ratio (PSNR), and energy compaction by performing transformation by enlarging residual data.

[0304] FIG. 24 is a diagram for explaining a residual block corresponding to a transformation unit according to one embodiment of the present disclosure.

[0305] Referring to FIG. 24, the height of the encoding unit (2410) according to one embodiment is 8, the height of the transformation unit (2415) is 4, and the height of the residual block (2420) is 8. However, the present invention is not limited thereto, and the height of the transformation unit (2415) may be a value obtained by dividing the height of the encoding unit (2410) by N (where N is an integer, for example, N is 2, 4), and the height of the residual block (2420) may be M times the height of the transformation unit (2415) (where M is an integer, for example, M is 2, 4). In one embodiment, the size of the residual block (2420) may be smaller than or equal to the encoding unit (2410). When the size of the residual block (2420) is smaller than or equal to the encoding unit (2410), coding efficiency can be improved without increasing complexity.

[0306] In one embodiment, the size (e.g., height, width) of the residual block (2420) may be larger than the transformation unit (2415). The image decoding device (2000) may determine the residual sample of the residual block (2420) based on the transformation unit (2415).

[0307] The image decoding device (2000) can determine a residual sample of a residual block (2420) based on a residual sample of a transformation unit (2415). The image decoding device (2000) can determine a part of the residual samples of the residual block (2420) based on the residual samples of the transformation unit (2415). For example, the residual sample of the 2Lth row of the residual block (2420) can be determined as a residual sample of the Lth row of the transformation unit (2415). For example, the residual sample of the 4th row of the residual block (2420) can be determined as a residual sample of the 2nd row of the transformation unit (2415).

[0308] The video decoding device (2000) can determine the remaining residual samples of the residual block (2420) based on the residual samples of the transformation unit (2415).

[0309] In one embodiment, the image decoding device (2000) may determine a residual sample of a residual block (2420) by using interpolation between residual samples of a transformation unit (2415). For example, the image decoding device (2000) may determine a residual sample of a first row of the residual block (2420) by using interpolation between the residual sample of the 0th row and the residual sample of the second row.

[0310] In one embodiment, the image decoding device (2000) may determine the residual samples of the residual block (2420) to be identical to the residual samples of the transformation unit (2415). For example, the residual samples of the 2L-th row and the 2L+1-th row of the residual block (2420) may be determined as the residual samples of the L-th row of the transformation unit (2415). For example, the image decoding device (2000) may determine the residual samples of the 1st row of the residual block (2420) to be identical to the 0th row.

[0311] In one embodiment, the image decoding device (2000) may determine the samples of the residual block (2420) as predetermined values. For example, the image decoding device (2000) may determine the residual samples of the last row of the residual block (2420) as 0.

[0312] FIG. 25 is a diagram for explaining a residual block corresponding to a transformation unit according to one embodiment of the present disclosure.

[0313] Referring to FIG. 25, a process of obtaining a residual sample of an encoding unit from the extended residual block of FIG. 24 is illustrated. An image decoding device (2000) according to one embodiment can obtain a residual sample of an encoding unit (2510).

[0314] The image decoding device (2000) can determine a residual sample of an encoding unit (2410) or a residual sample of a transformation unit (2515) based on a residual sample of a residual block (2520). The image decoding device (2000) can determine a residual sample of an encoding unit (2510) or a residual sample of a transformation unit (2515) based on some of the residual samples of the residual block (2520).

[0315] In one embodiment, the image decoding device (2000) may determine a residual sample of the same encoding unit (2510) or a residual sample of the transformation unit (2515) as some of the residual samples of the residual block (2520). For example, the image decoding device (2000) may determine a residual sample of the L-th row of the same transformation unit (2515) as a residual sample of the 2L-th row of the residual block (2520). For example, a residual sample of the 4th row of the residual block (2520) may be determined as a residual sample of the 2nd row of the transformation unit (2515).

[0316] In one embodiment, the image decoding device (2000) may determine the residual sample of the encoding unit (2510) based on the size ratio of the residual block (2520) and the transformation unit (2515). The size ratio of the residual block (2520) and the transformation unit (2515) may include at least one of a height ratio, a width ratio, or an area ratio between the residual block (2520) and the transformation unit (2515). The image decoding device (2000) may select some residual samples from among the residual samples of the residual block (2520) by using the size ratio of the residual block (2520) and the transformation unit (2515). For example, the image decoding device (2000) may select the residual samples of the residual block (2520) at a ratio interval. For example, when the ratio of the size of the residual block (2520) to the size of the transformation unit (2515) is 2, residual samples at two-line intervals (e.g., 0th, 2nd, 4th, etc.) of the residual block (2520) can be selected. The image decoding device (2000) can determine the residual sample of the encoding unit (2520) using the selected residual sample.

[0317] In one embodiment, the image decoding device (2000) may determine the filtered sample for the residual sample of the residual block (2520) as the residual sample of the encoding unit (2510) or the residual sample of the transformation unit (2515). In one embodiment, if there is no information for performing filtering, the image decoding device (2000) may perform filtering using the boundary value of the residual sample of the transformation unit (2515). In one embodiment, if there is no information for performing filtering, the image decoding device (2000) may perform filtering using a predetermined value (e.g., “0”).

[0318] In one embodiment, the image decoding device (2000) may determine a quantization parameter based on the size of the residual block (2520). The image decoding device (2000) may determine the quantization parameter based on whether the residual block is extended. The image decoding device (2000) may determine a quantization parameter offset value based on whether the size of the residual block (2520) is larger than the transformation unit (2515). For example, the image decoding device (2000) may determine the quantization parameter offset value to be a value greater than 0 when the size of the residual block (2520) is larger than the transformation unit (2515). For example, the image decoding device (2000) may determine the quantization parameter offset value to be 0 when the size of the residual block (2520) is the same as the transformation unit (2515). However, without being limited thereto, the quantization parameter offset value determined when the size of the residual block (2520) is larger than the transformation unit (2515) may be determined to be larger than the quantization parameter offset value determined when the size of the residual block (2520) is smaller than or equal to the transformation unit (2515).

[0319] When the residual block is enlarged, the residual energy may increase, and thus the quantization parameter may be determined to be larger than before. For example, if the quantization parameter of the non-enlarged residual block is QP, the quantization parameter of the enlarged residual block (2520) may be determined as QP + A. Here, A may represent a quantization parameter offset value. In one embodiment, the quantization parameter offset value may be determined based on the size of the residual block (2520) or the ratio of the size of the residual block (2520) to the size of the transformation unit (2515). The quantization parameter offset value may be determined to be larger as the size of the residual block (2520) is larger or the ratio of the size of the residual block (2520) to the size of the transformation unit (2515) is larger. The image decoding device (2000) may determine a quantization step. For example, if the quantization step of the non-enlarged residual block is S, the quantization step of the enlarged residual block (2520) can be determined as S * R. Here, R can mean a real value greater than 0. The image decoding device (2000) can determine a quantization parameter for obtaining a residual sample of the residual block (2520) based on the parameter offset value.

[0320] FIG. 26 is a flowchart of a method for determining a conversion unit according to one embodiment of the present disclosure.

[0321] In one embodiment of the present disclosure, a method for determining a transformation unit may be performed by an image decoding device (2000). For example, the image decoding device (2000) may perform each step of the method for determining a transformation unit by having a processor of the image decoding device (2000) execute at least one instruction contained in a memory.

[0322] In step S2610, the image decoding device (2000) can obtain information regarding whether sub-block transformation is applied to the encoding unit. For example, the image decoding device (2000) can obtain information (e.g., cu_sbt_flag) regarding whether sub-block transformation is applied through the bitstream.

[0323] In one embodiment, the sub-block transform may include splitting a coding unit horizontally or vertically and acquiring residual data only from a portion of the split region. The value of the residual data not acquired in the sub-block transform may be determined to be 0.

[0324] In one embodiment, the video decoding device (2000) can obtain information on whether sub-block transformation is applied when the slice type is inter-slice. In one embodiment, the video decoding device (2000) can obtain information on whether sub-block transformation is applied when the slice type is inter-slice or intra-slice. For example, the video decoding device (2000) can obtain information on whether sub-block transformation is applied when the prediction mode of the encoding unit is block copy mode (or intra-block copy mode) or template matching based prediction mode (or intra-template matching based prediction mode).

[0325] In step S2620, the image decoding device (2000) may obtain at least one of information related to a split size of a coding unit, information related to a split direction of the coding unit, or information related to a position of a current transformation unit within the coding unit from a bitstream. In one embodiment, the current transformation unit may represent a transformation unit having residual data. In one embodiment, the image decoding device (2000) may obtain information related to a split size of a coding unit, information related to a split direction of the coding unit, and / or information related to a position of a current transformation unit within the coding unit from a bitstream when subblock transformation is applied to the coding unit (e.g., cu_sbt_flag == 1).

[0326] In one embodiment, the information related to the split size of the coding unit may include at least one of a size ratio between transformation units split from the coding unit or a ratio between the size of the current transformation unit and the coding unit including the transformation unit. For example, the information related to the split size of the coding unit may include at least one of whether the size ratio between the transformation units is 1:2:1, 1:1, or 1:3. For example, the information related to the split size of the coding unit may include information about whether the size of the transformation unit is 1 / 4 or 1 / 2 of the coding unit.

[0327] In one embodiment, information about the splitting direction of the encoding unit may include information about the direction of a transform unit split from the encoding unit.

[0328] Information regarding the splitting direction of a coding unit may indicate whether the coding unit is split in a predetermined direction or the direction in which the coding unit is split into transformation units. For example, information regarding the splitting direction of a coding unit may include at least one of horizontal splitting, vertical splitting, or diagonal splitting.

[0329] In one embodiment, information about the position of a current transformation unit within a coding unit may include information indicating a relative position of the current transformation unit (e.g., a transformation unit having residual data) within the coding unit. For example, information about the position of the current transformation unit within the coding unit may include information about whether the current transformation unit is located on the left, right, above, middle, or below the coding unit.

[0330] In step S2630, the image decoding device (2000) can determine the current transformation unit within the encoding unit based on the acquired information. The image decoding device (2000) can determine the current transformation unit by dividing the encoding unit based on the acquired information. In one embodiment, the image decoding device (2000) can determine the transformation unit having residual data included within the encoding unit based on the acquired information.

[0331] An image decoding device (2000) according to one embodiment can perform the image decoding method of FIG. 21 by combining the method of determining a transformation unit of FIG. 26. For example, the image decoding device (2000) can obtain one or more transformation units including a current transformation unit from an encoding unit, as described in step S2110. Here, the image decoding device (2000) can determine the current transformation unit through steps S2610 to S2630.

[0332] FIG. 27 is a diagram for explaining a process of determining a transformation unit having residual data according to one embodiment of the present disclosure.

[0333] In one embodiment of the present disclosure, an encoding unit may be split into one or more transformation units. One or more transformation units of the encoding unit may include a transformation unit having residual data (e.g., the current transformation unit of FIG. 26). The image decoding device (2000) may determine a transformation unit having residual data included in the encoding unit based on information obtained from a bitstream.

[0334] In one embodiment, the image decoding device (2000) may obtain at least one of information related to the split size of an encoding unit, information related to the split direction of an encoding unit, or information related to the position of a current transformation unit within an encoding unit from a bitstream. For convenience of explanation, the information obtained from the bitstream, as described with reference to FIG. 26, is omitted.

[0335] In one embodiment, information about the split size (cu_sbt_quad_flag) may indicate the size of a transformation unit having a residual block. For example, the image decoding device (2000) may determine, based on the information about the split size, whether the size of the transformation unit having the residual block corresponds to half (e.g., cu_sbt_quad_flag == 0) or 1 / 4 (e.g., cu_sbt_quad_flag == 1) of the width of the coding unit.

[0336] In one embodiment, the image decoding device (2000) can determine the size of a transformation unit having a residual block without obtaining information about the split size. The image decoding device (2000) can determine the split size based on at least one of the height or the width of the coding unit. For example, the image decoding device (2000) can determine the size of the transformation unit to be 1 / 4 of the coding unit when the height of the coding unit in the horizontal split is greater than or equal to a predetermined value. For example, the image decoding device (2000) can determine the size of the transformation unit to be 1 / 2 of the coding unit when the height of the coding unit in the horizontal split is less than a predetermined value. In one embodiment, the residual block can be obtained by dividing the coding unit into N equal parts (e.g., N is a power of 2).

[0337] In one embodiment, information about the splitting direction (cu_sbt_horizontal_flag) may indicate the splitting direction of the encoding unit. For example, the image decoding device (2000) may determine whether to split the encoding unit in the horizontal direction (e.g., cu_sbt_horizontal_flag == 0) or the vertical direction (e.g., cu_sbt_horizontal_flag == 1) based on the information about the splitting direction.

[0338] In one embodiment, information about the position of a transformation unit (cu_sbt_pos_flag) may indicate the position of a transformation unit having residual data in a split encoding unit. For example, the image decoding device (2000) may determine, based on the information about the position of the transformation unit, that the position of the transformation unit having residual data is one of the upper, lower, left, or right sides.

[0339] Referring to FIG. 27, a transformation unit may be determined based on information about a split size (cu_sbt_quad_flag), information about a split direction (cu_sbt_horizontal_flag), and information about a position of a transformation unit (cu_sbt_pos_flag). In one embodiment, a hatched area of ​​a coding unit in FIG. 27 may represent a transformation unit having residual data. A square area outside the hatched area may represent a coding unit. Although the coding unit in FIG. 27 according to one embodiment is illustrated as a square, the present invention is not limited thereto, and the coding unit may be a rectangle.

[0340] Referring to FIG. 27, in one embodiment, when a transformation unit having residual data is half of an encoding unit (cu_sbt_quad_flag==0), the encoding unit is horizontally divided (cu_sbt_horizontal_flag==1), and the transformation unit having residual data is located below the encoding unit (cu_sbt_pos_flag==1), the image decoding device (2000) can perform decoding on residual data located below the encoding unit.

[0341] FIG. 28 is a diagram for explaining a process of determining a transformation unit having residual data according to one embodiment of the present disclosure.

[0342] The image decoding device (2000) can determine a transformation unit having residual data included in an encoding unit based on information obtained from a bitstream.

[0343] In one embodiment, the image decoding device (2000) may obtain at least one of information related to the split size of an encoding unit, information related to the split direction of an encoding unit, or information related to the position of a current transformation unit within an encoding unit from a bitstream. For convenience of explanation, the contents described with reference to FIGS. 26 and 27 among the information obtained from the bitstream are omitted.

[0344] In one embodiment, information about the position of a transformation unit (cu_sbt_pos_flag) may indicate the position of a transformation unit having residual data in a split encoding unit. For example, the image decoding device (2000) may determine, based on the information about the position of the transformation unit, that the position of the transformation unit having residual data is at least one of the upper side, the middle side, the lower side, the left side, or the right side. In one embodiment, the information about the position of the transformation unit may be expressed as index information, cu_sbt_pos_idx.

[0345] Referring to FIG. 28, a transformation unit may be determined based on information about a split size (cu_sbt_quad_flag), information about a split direction (cu_sbt_horizontal_flag), and information about the position of a transformation unit (cu_sbt_pos_flag). In one embodiment, the hatched area of ​​the encoding unit in FIG. 28 may represent a transformation unit having residual data.

[0346] Referring to FIG. 28, in one embodiment, when a transformation unit having residual data is half of an encoding unit (cu_sbt_quad_flag==0), the encoding unit is horizontally divided (cu_sbt_horizontal_flag==1), and the transformation unit having residual data is located in the middle of the encoding unit (cu_sbt_pos_flag==1), the image decoding device (2000) can perform decoding on residual data located in the middle area of ​​the encoding unit.

[0347] Referring to FIG. 28, in one embodiment, when a transformation unit having residual data is 1 / 4 of a coding unit (cu_sbt_quad_flag==1), the coding unit is vertically divided (cu_sbt_horizontal_flag==0), and the transformation unit having residual data is located at the right edge of the coding unit (cu_sbt_pos_flag==3), the image decoding device (2000) can perform decoding on residual data located at the right edge area of ​​the coding unit.

[0348] In one embodiment, a transform tree syntax structure may be expressed as shown in Table 1. In the transform tree syntax, a transform unit may be determined based on information related to a split size of a coding unit (cu_sbt_quad_flag), information related to a split direction of the coding unit (cu_sbt_horizontal_flag), and information related to a position of a current transform unit within the coding unit (cu_sbt_pos_flag). For example, when cu_sbt_horizontal_flag == 0 and cu_sbt_pos_flag = = 1, the coding unit is split into three transform units, and the width ratio of each transform unit is 1:2:1.

[0349] transform_tree( x0, y0, tbWidth, tbHeight, treeType, chType ) {DescriptorInferTuCbfLuma = 1if( IntraSubPartitionsSplitType = = ISP_NO_SPLIT && !cu_sbt_flag ) {...}} else if( cu_sbt_flag ) {if( !cu_sbt_horizontal_flag ) {if( cu_sbt_pos_flag = = 0 ) {...} else if( cu_sbt_pos_flag = = 1 ) {if( cu_sbt_quad_flag = = 0 ) {transform_unit( x0, y0, tbWidth / 4, tbHeight, treeType, 0, 0, 1 )transform_unit( x0 + tbWidth / 4, y0, tbWidth / 2, tbHeight, treeType, 1, 0, 0 )transform_unit( x0 + tbWidth * 3 / 4, y0, tbWidth / 4, tbHeight, treeType, 2, 0, 1 )} else { / ( cu sbt_quad_flag = = 1 )transform_unit( x0, y0, tbWidth / 4, tbHeight, treeType, 0, 0, 1 )transform_unit( x0 + tbWidth / 4, y0, tbWidth / 4, tbHeight, treeType, 1, 0, 0 )transform_unit( x0 + tbWidth / 2, y0, tbWidth / 2, tbHeight, treeType, 2, 0, 1 )}} else if( cu_sbt_pos_flag = = 2 ) {...}} else { / ( cu_sbt_pos_flag = = 3 )...}}} else { / horizontal split cases}...}

[0350] In one embodiment, information about the position of the transformation unit (cu_sbt_pos_flag) may indicate that the transformation unit having the residual block is located above, below, left, and right of the coding unit, as shown in FIG. 27. In this example, information about the position of the transformation unit may be expressed with 1 bit. In one embodiment, information about the position of the transformation unit (cu_sbt_pos_flag) may indicate that the transformation unit having the residual block is located at least one of the above, middle, below, left, and right of the coding unit, as shown in FIG. 28. In this example, information about the position of the transformation unit may be expressed with 2 bits.

[0351] In one embodiment, whether information about the position of a transformation unit indicates that the transformation unit is located in the middle region of a coding unit (e.g., whether information about the position of the transformation unit is expressed with 1 bit as in FIG. 27 or with 2 bits as in FIG. 28) may be included in a header of a bitstream (e.g., Sequence Parameter Set, Video Parameter Set, Picture Header, Slice Header, CTU (coding tree unit) unit, CU (coding unit) unit, PU (prediction unit), TU (transform unit)). It may be determined whether information about the position of a transformation unit for a specific unit indicates that the transformation unit is located in the middle region of a coding unit.

[0352] In one embodiment, information about the position of a transformation unit is expressed as 1 bit as in FIG. 26, and an extension flag indicating whether the transformation unit represents the middle region and / or both edge regions of the encoding unit may be used. For example, when the extension flag is 0, the image decoding device (2000) may determine a transformation unit having residual data as in FIG. 27. For example, when the extension flag is 1, the image decoding device (2000) may determine a transformation unit having residual data that is not expressed according to FIG. 27 among FIG. 28.

[0353] According to one embodiment, the image encoding method and the image decoding method can perform encoding and decoding even when residual data is located in the middle area of ​​an encoding unit or in an edge area excluding the middle area, so that coding efficiency can be improved according to the image encoding method and the image decoding method.

[0354] FIG. 29 is a diagram for explaining a process of determining a transformation unit having residual data according to one embodiment of the present disclosure.

[0355] In one embodiment, the height and width of a transformation unit having residual data may be smaller than that of a coding unit. Referring to FIGS. 26 and 27, the width or height of a transformation unit having residual data according to one embodiment is the same as that of a coding unit, but as in FIG. 29, the width and height of a transformation unit having residual data according to one embodiment may be smaller than that of a coding unit.

[0356] In one embodiment, the width of a transformation unit having residual data may be 1 / N of a coding unit, and the height of the transformation unit may be 1 / M of a coding unit. For example, the width and height of the transformation unit having residual data may be half of the width and height of the coding unit, respectively (e.g., N = 2, M = 2). FIG. 29 is an example of a case where the width and height of a transformation unit having residual data are half of the width and height of the coding unit, respectively, according to one embodiment of the present disclosure, and the hatched area may represent a transformation unit having residual data.

[0357] In one embodiment, the information about the split size may include information about the split ratio of the height of the encoding unit and the split ratio of the width of the encoding unit. For example, the information about the split size may include information indicating values ​​of N and M (e.g., N is the ratio of the width of the transform unit to the width of the encoding unit, and M is the ratio of the height).

[0358] In one embodiment, the image decoding device (2000) may omit information about the splitting direction and determine the transformation unit based on information about the position of the transformation unit. Information about the position of the transformation unit may indicate one of the positions of the predetermined transformation unit. For example, referring to FIG. 29, information about the position of the transformation unit may indicate one of the positions of nine transformation units (2910-2990). In one embodiment, transformation units (2910, 2920, 2930, 2940) may be adjacent to two edges of the encoding unit. In one embodiment, transformation units (2950, ​​2960, 2970, 2980) may be adjacent to one edge of the encoding unit. In one embodiment, transformation unit (2990) may not be adjacent to an edge.

[0359] FIG. 30 is a diagram illustrating a transformation unit having residual data according to one embodiment of the present disclosure.

[0360] In one embodiment, the transformation unit having residual data may have various shapes other than those described in FIGS. 27 to 29. In one embodiment, the transformation unit having residual data may be obtained by diagonally dividing the encoding unit. For example, transformation units (3010, 3020, 3030, 3040) may be determined by diagonally dividing the encoding unit. Information about the division direction may include the diagonal direction. Information about the position of the transformation unit may include upper left, upper right, upper left, and lower left.

[0361] In one embodiment, a transformation unit having residual data may include two non-adjacent transformation units within an encoding unit. For example, transformation units (3050, 3060, 3070, 3080) may include two non-adjacent transformation units within an encoding unit. The image decoding apparatus (2000) may obtain information regarding whether an encoding unit includes a plurality of transformation units that do not have residual data.

[0362] In one embodiment, the image decoding device (2000) may determine a transformation type based on the shape of the transformation unit. For example, if the transformation unit is diagonally divided, the image decoding device (2000) may select a transformation type from among predetermined transformation types according to the diagonal division.

[0363] FIG. 31 is a flowchart of a method for obtaining data of a conversion unit according to one embodiment of the present disclosure.

[0364] In one embodiment of the present disclosure, acquisition of data of a conversion unit may be performed by an image decoding device (2000). For example, the image decoding device (2000) may perform each step of acquiring data of a conversion unit by having a processor of the image decoding device (2000) execute at least one instruction contained in a memory.

[0365] In step S3110, the image decoding device (2000) may determine at least one of whether to acquire residual data for one or more transformation units excluding the current transformation unit or whether transformation is performed on the residual data. In one embodiment, the current transformation unit may mean a transformation unit that includes residual data included in an encoding unit determined through a bitstream.

[0366] In one embodiment, the image decoding device (2000) may not obtain residual data for transformation units other than the current transformation unit. The image decoding device (2000) may not obtain residual data from the bitstream for transformation units other than the current transformation unit of the encoding unit, and may determine the value of the transformation unit to be 0.

[0367] In one embodiment, the image decoding device (2000) may obtain residual data for transformation units excluding the current transformation unit. In one embodiment, the image decoding device (2000) may determine that transformation is skipped for transformation units excluding the current transformation unit. For example, the image decoding device (2000) may determine information (e.g., transform_skip_flag=1) indicating whether transformation is applied to a transformation unit for transformation units excluding the current transformation unit. The image decoding device (2000) may obtain residual data for transformation units excluding the current transformation unit in which transformation is skipped. For example, the image decoding device (2000) may call syntax (e.g., residual_ts_coding()) for transformation units in which transformation is skipped for transformation units excluding the current transformation unit. The image decoding device (2000) may skip inverse transformation for the transformation units.

[0368] In one embodiment, the image decoding device (2000) can obtain information from the bitstream indicating whether a transform is used (or whether an inverse transform is performed) for each of one or more transform units. The image decoding device (2000) can determine whether a transform is used (or whether an inverse transform is performed) for each of one or more transform units of an encoding unit based on the information obtained from the bitstream. The image decoding device (2000) can obtain residual data (e.g., residual_coding()) on which a transform is performed for a transform unit on which a transform is performed, and can obtain residual data (e.g., residual_ts_coding()) on which a transform is omitted for a transform unit on which a transform is omitted.

[0369] In one embodiment, the image decoding device (2000) can obtain information from the bitstream indicating whether each of one or more transformation units has residual data for which transformation has been performed or does not have residual data. The image decoding device (2000) can determine whether to obtain residual data for each of one or more transformation units of an encoding unit based on the information obtained from the bitstream.

[0370] In one embodiment, the image decoding device (2000) can obtain information indicating whether transformation is performed or not for the current transformation unit. The image decoding device (2000) can obtain information indicating whether transformation includes residual data for which transformation is not performed for a transformation unit other than the current transformation unit or does not include residual data.

[0371] In one embodiment, the image decoding device (2000) may determine that the current transformation unit has residual data on which transformation is not performed. The image decoding device (2000) may determine that one or more transformation units other than the current transformation unit have residual data on which transformation is performed.

[0372] In one embodiment, the image decoding device (2000) may determine that transformation is omitted for a transformation unit among one or more transformation units in which at least one of the width or height is not a power of 2. For example, the image decoding device (2000) may determine that transformation of the transformation unit is omitted when the height of the transformation unit is 12.

[0373] In one embodiment, the image decoding device (2000) can obtain information from a bitstream indicating whether a transformation unit among one or more transformation units, of which at least one of the width or height is not a power of 2, has residual data with omitted transformation or has no residual data.

[0374] In one embodiment, the image decoding device (2000) can perform transformations in multiple directions. For example, the image decoding device (2000) can perform transformations in the vertical direction and the horizontal direction. The image decoding device (2000) can determine whether transformation is omitted based on the height or width according to the direction. For example, for vertical transformation, if the height of the transformation unit is not a power of 2, the image decoding device (2000) can determine that transformation is omitted. For example, for horizontal transformation, if the width of the transformation unit is not a power of 2, the image decoding device (2000) can determine that transformation is omitted.

[0375] In one embodiment, a method for determining whether a transform unit has residual data on which a transform has been performed, residual data on which a transform has been omitted, or no residual data may be included in a header of a bitstream (e.g., a Sequence Parameter Set, a Video Parameter Set, a Picture Header, a Slice Header, a CTU (coding tree unit) unit, a CU (coding unit) unit, a PU (prediction unit), a TU (transform unit)), and whether a method for determining residual data of a transform unit is applied to a specific unit may be determined.

[0376] In step S3120, the image decoding device (2000) can obtain residual data corresponding to the transformation unit. In one embodiment, the image decoding device (2000) can obtain residual data of the transformation unit determined in step S3110 from the bitstream. For example, the image decoding device (2000) can obtain transformation-omitted residual data for a transformation unit in which transformation is omitted.

[0377] In one embodiment, when the image decoding device (2000) does not obtain residual data for one or more transformation units other than the current transformation unit, the image decoding device (2000) may determine at least one of a quantization parameter or a quantization interval. For example, the image decoding device (2000) may determine at least one of a quantization parameter or a quantization interval based on a ratio of an area of ​​a coding unit to an area of ​​a current transformation unit. For example, when the ratio of an area of ​​a coding unit to an area of ​​a current transformation unit is 1 / 2, the image decoding device (2000) may set the quantization parameter to be N smaller than an existing quantization parameter (e.g., QP-N). For example, when the ratio of an area of ​​a coding unit to an area of ​​a current transformation unit is 1 / 4, the image decoding device (2000) may set the quantization parameter to be 2*N smaller than an existing quantization parameter (e.g., QP-2*N). The image decoding device (2000) can improve the prediction accuracy of residual data by setting at least one of a quantization parameter or a quantization interval.

[0378] A video decoding method according to one embodiment of the present disclosure can improve coding efficiency by encoding some of a coding unit as residual data on which transformation has been performed, and encoding some of a coding unit as residual data on which transformation has been omitted. As the size of a coding unit increases, the characteristics of residual samples within the coding unit can be more diverse. For example, when a coding unit includes both a camera-captured video and a computer-generated video, the characteristics of both types of videos can be included. In such examples, there are cases where performing a transformation process is advantageous for compression efficiency, and conversely, there are cases where not performing a transformation is advantageous for compression efficiency.

[0379] Therefore, compression performance can be improved by encoding encoding units differently (e.g., determining differently whether to perform transformation within encoding) depending on the distribution of residual samples.

[0380] In one embodiment, the image decoding device (2000) may perform a combination of the image decoding method of FIG. 21 and the method of acquiring data of a transformation unit of FIG. 31. For example, the image decoding device (2000) may determine a residual sample of an encoding unit corresponding to a current transformation unit using steps S2110 to S2150 of FIG. 21. The image decoding device (2000) may determine a residual sample of an encoding unit corresponding to a transformation unit of an encoding unit other than the current transformation unit using steps S3110 and S3120 of FIG. 31.

[0381] In one embodiment, the video decoding device (2000) can obtain first information from the bitstream regarding whether upsampling is applied (i.e., whether the size of the residual block is or can be larger than the size of the transform unit). For example, the video decoding device (2000) can obtain a flag indicating whether upsampling is applied from the bitstream.

[0382] In one embodiment, the image decoding device (2000) may determine that upsampling is to be applied without obtaining first information from the bitstream. For example, the image decoding device (2000) may determine that upsampling is to be always applied.

[0383] In one embodiment, when upsampling is applied (e.g., when first information obtained from a bitstream indicates that upsampling is applied), the image decoding device (2000) can perform the image decoding method of FIG. 21. When upsampling is not applied, the image decoding device (2000) can obtain residual coefficients of a transform unit by inversely transforming and inversely quantizing residual coefficients of a residual block.

[0384] In one embodiment, if the first information obtained from the bitstream indicates that upsampling is not applied, the image decoding device (2000) can obtain second information from the bitstream regarding whether a transform has been applied to a transform unit or a residual block. The image decoding device (2000) can determine whether a transform is performed based on the information obtained from the bitstream. If the first information obtained from the bitstream indicates that upsampling is applied, the image decoding device (2000) can determine that a transform has not been applied to a transform unit or a residual block (e.g., transform skip) without obtaining the second information from the bitstream.

[0385] In one embodiment, the image decoding device (2000) may determine that a transformation has been applied to a transformation unit or a residual block without obtaining the second information regardless of the first information. The image decoding device (2000) may obtain third information from the bitstream, which indicates whether residual data for the remaining transformation blocks of the coding unit excluding the current transformation block is included in the bitstream. If the third information indicates that residual data for the remaining transformation blocks is included in the bitstream, the image decoding device (2000) may obtain residual data for the remaining transformation blocks from the bitstream.

[0386] In one embodiment, the image decoding device (2000) may determine that no transformation is applied to residual data of the remaining transformation blocks except for the current transformation block of the encoding unit.

[0387] In one embodiment, the image decoding device (2000) can obtain information from the bitstream indicating whether the bitstream does not include residual data of the remaining transform blocks excluding the current transform block of the encoding unit or whether the bitstream includes residual data to which no transform has been applied.

[0388] In one embodiment, the image decoding device (2000) can perform the method of determining the transformation unit of FIG. 26 by combining the method of obtaining data of the transformation unit of FIG. 31. For example, the image decoding device (2000) can determine the current transformation unit through steps S2610 to S2630 of FIG. 26. The image decoding device (2000) can determine a residual sample of an encoding unit corresponding to a transformation unit of an encoding unit excluding the current transformation unit by using steps S3110 and S3120 of FIG. 31. In one embodiment, the image decoding device (2000) can determine that a transformation is used for the current transformation unit. The image decoding device (2000) can obtain information indicating whether residual data of a transformation unit or a residual block is included in a bitstream from a bitstream. If the information obtained from the bitstream indicates that residual data of a transformation unit or a residual block is included in the bitstream, the residual data can be obtained from the bitstream.

[0389] In one embodiment, the image decoding device (2000) can obtain information from the bitstream indicating whether residual data regarding the coding unit is included in the bitstream. If the obtained information indicates that residual data regarding the coding unit is included in the bitstream, the image decoding device (2000) can obtain information regarding at least one of the aforementioned coding unit, transformation unit, or residual block from the bitstream.

[0390] In one embodiment, the image decoding device (2000) can perform the image decoding method of FIG. 21, the method of determining a transformation unit of FIG. 26, and the method of obtaining data of a transformation unit of FIG. 31 in combination. For example, the image decoding device (2000) can determine a current transformation unit through steps S2610 to S2630 of FIG. 26. The image decoding device (2000) can determine a residual sample of a coding unit corresponding to the current transformation unit using steps S2110 to S2150 of FIG. 21. The image decoding device (2000) can determine a residual sample of a coding unit corresponding to a transformation unit of a coding unit other than the current transformation unit using steps S3110 and S3120 of FIG. 31.

[0391] FIG. 32 is a diagram for explaining an image decoding method according to one embodiment of the present disclosure.

[0392] In one embodiment of the present disclosure, the image decoding method may be performed by the image decoding device (2000). For example, the image decoding device (2000) may perform each step of the image decoding method by having the processor of the image decoding device (2000) execute at least one instruction contained in a memory.

[0393] In step S3210, the image decoding device (2000) can identify whether residual data for the coding unit exists. In one embodiment, the image decoding device (2000) can obtain information regarding whether the bitstream includes residual data for the coding unit. If the obtained information indicates that the bitstream includes residual data for the coding unit, the process proceeds to step S3220. If the obtained information indicates that the bitstream does not include residual data for the coding unit, the process proceeds to step S3290.

[0394] In step S3220, the image decoding device (2000) can identify whether the encoding unit includes multiple transformation units. In one embodiment, the image decoding device (2000) can obtain segmentation information of the encoding unit from the bitstream. The segmentation information of the encoding unit can include information on which transformation unit is used to determine the encoding unit. If the encoding unit includes multiple transformation units, the process proceeds to step S3230. If the encoding unit does not include multiple transformation units, the process proceeds to step S3260.

[0395] In step S3230, the image decoding device (2000) may split the encoding unit into a plurality of transformation units. In one embodiment, the image decoding device (2000) may split the encoding unit as in step S2110 of FIG. 21. The plurality of transformation units may have residual data for which transformation is used or residual data for which transformation is not used. The residual data for which transformation is used may be decoded by the image decoding device (2000) through step S3240. The residual data for which transformation is not used may be decoded by the image decoding device (2000) through step S3250. Although steps S3240 and S3250 are expressed as being performed in parallel, they are not limited and may be performed sequentially.

[0396] In step S3240, the image decoding device (2000) may perform decoding using transformation on some transformation units. In one embodiment, some of the transformation units may include transformation units having residual data on which transformation is used. The image decoding device (2000) may perform decoding including inverse transformation. The image decoding device (2000) may obtain residual samples corresponding to some of the transformation units.

[0397] In step S3250, the image decoding device (2000) may perform decoding without using transformation on the remaining transformation units. In one embodiment, the remaining transformation units may include transformation units having residual data for which transformation is not used. The image decoding device (2000) may perform decoding excluding inverse transformation. The image decoding device (2000) may obtain residual samples corresponding to the remaining transformation units. The image decoding device (2000) may obtain residual samples of the encoding unit using steps S3240 and S3250.

[0398] In step S3260, the image decoding device (2000) can identify whether transformation is omitted in a transformation unit of the encoding unit. In one embodiment, the image decoding device (2000) can identify whether one transformation unit of the encoding unit has residual data for which transformation is used or residual data for which transformation is not used. If one transformation unit of the encoding unit has residual data for which transformation is not used, the process proceeds to step S3270. If one transformation unit of the encoding unit has residual data for which transformation is used, the process proceeds to step S3280.

[0399] In step S3270, the image decoding device (2000) can perform decoding without using transformation on the encoding unit. In one embodiment, the image decoding device (2000) can perform decoding excluding inverse transformation. The image decoding device (2000) can obtain a residual sample corresponding to the encoding unit.

[0400] In step S3280, the image decoding device (2000) may perform decoding using transformation on the encoding unit. In one embodiment, the image decoding device (2000) may perform decoding including inverse transformation. The image decoding device (2000) may obtain a residual sample corresponding to the encoding unit.

[0401] In step S3290, the image decoding device (2000) may determine the residual sample value of the encoding unit as 0. In one embodiment, based on the determination that there is no residual data in step S3210, the image decoding device (2000) may determine the residual sample of the encoding unit as 0.

[0402] In one embodiment, the video decoding device (2000) may obtain information on whether residual data for the remaining transformation units is included in the bitstream from the bitstream before step S3250. If the residual data for the remaining transformation units is included in the bitstream, the video decoding device (2000) may proceed to step S3250. In one embodiment, the information on whether residual data for the remaining transformation units is included in the bitstream may be included in a slice header or a picture header of the bitstream. In one embodiment, the video decoding device (2000) may obtain information on whether residual data for the remaining transformation units is included in the bitstream from the bitstream when the prediction mode of the coding unit includes at least one of a block copy mode and a palette mode.

[0403] FIG. 33 is a block diagram showing the configuration of an image encoding device according to one embodiment of the present disclosure.

[0404] Referring to FIG. 33, the image encoding device (3300) may include a prediction encoding unit (3310) and a generation unit (3320).

[0405] In one embodiment of the present disclosure, the prediction encoding unit (3310) and the generation unit (3320) may be implemented with at least one processor. In one embodiment of the present disclosure, the video encoding device (3300) may include a memory that stores input and output data of the prediction encoding unit (3310) and the generation unit (3320). The prediction encoding unit (3310) and the generation unit (3320) may operate according to instructions stored in the memory. In one embodiment of the present disclosure, the video encoding device (3300) may include a memory control unit that controls data input and output of the memory.

[0406] In one embodiment of the present disclosure, the prediction encoding unit (3310) may correspond to the prediction encoding unit (1915) illustrated in FIG. 19. In one embodiment of the present disclosure, the generation unit (3320) may correspond to the entropy encoding unit (1925) illustrated in FIG. 19.

[0407] The prediction encoding unit (3310) can determine the prediction mode of the current block. The current block can include at least one of a maximum coding unit, an encoding unit, a transformation unit, or a prediction unit segmented from the current image to be encoded. In one embodiment of the present disclosure, the prediction mode of the current block can include at least one of an intra mode, an inter mode, a combined mode, a geometric partitioning mode, a block copy mode, or a template matching prediction mode.

[0408] In one embodiment of the present disclosure, the intra mode may include a planar mode (Intra_Planar), a DC mode (Intra_DC), directional modes (Intra_Angular2.. Intra_Angular66), and wide directional modes (Intra_Wide_Angular) of numbers -14 to -1 and numbers 67 to 80. In one embodiment of the present disclosure, the planar mode may refer to a mode that determines a prediction sample based on a weighted average value according to the distance of a left reference sample, an upper reference sample, a lower-left sample, and an upper-right sample of a current block. In one embodiment of the present disclosure, the DC mode may refer to a mode that determines an average value of reference samples as a prediction sample. In one embodiment of the present disclosure, in the directional modes, the positions of reference samples for generating prediction samples of samples within a current block may be identified by considering the direction indicated by the intra directional modes. The wide directional modes may be used to identify reference samples of samples within a non-square current block. In one embodiment of the present disclosure, the prediction encoding unit (3310) may determine one of the wide directional modes as the intra prediction mode of the current non-square block. The number and types of intra prediction modes available to the prediction encoding unit (3310) in the intra mode according to one embodiment of the present disclosure may be set in various ways.

[0409] In one embodiment of the present disclosure, the prediction encoding unit (3310) may determine an intra prediction mode using MPM (most probable modes). The prediction encoding unit (3310) may determine whether to use MPM. The generation unit (3320) may generate a bitstream including information related to whether to use MPM. The prediction encoding unit (3310) may determine a candidate mode list. The prediction encoding unit (3310) may determine the candidate mode list based on the intra mode of the upper block of the current block and the intra mode of the left block. The prediction encoding unit (3310) may determine one of the candidate mode lists as the intra prediction mode of the current block. The prediction encoding unit (3310) may generate a bitstream including information indicating the intra prediction mode of the current block from the candidate mode list.

[0410] In one embodiment of the present disclosure, the prediction encoding unit (3310) may determine an intra prediction mode using a template. The prediction encoding unit (3310) may determine a template of a current block. The template of the current block may include a left sample, an upper left sample, and / or an upper sample of the current block. The prediction encoding unit (3310) may determine surrounding samples of the template of the current block. The surrounding samples of the template may include a left sample, an upper left sample, and / or an upper sample of the template. The prediction encoding unit (3310) may perform prediction on the template using the surrounding samples of the template as reference samples. The prediction encoding unit (3310) may compare the predicted template with the template of the reconstructed current block to determine an intra mode for the reference block. The prediction encoding unit (3310) may determine an intra mode with the smallest error between the predicted template and the template of the reconstructed current block as the intra mode for the reference block. In one embodiment of the present disclosure, the process of determining an intra prediction mode by the prediction encoding unit (3310) performing prediction on a template may be referred to as template-based intra mode derivation (TIMD).

[0411] In one embodiment of the present disclosure, the prediction encoding unit (3310) can infer an intra prediction mode of the current block using surrounding samples of the current block. The prediction encoding unit (3310) can determine a slope using the surrounding samples of the current block. The prediction encoding unit (3310) can determine a plurality of 3 x 3 blocks adjacent to the current block. The prediction encoding unit (3310) can obtain horizontal variations and vertical variations of samples included in each of the determined 3 x 3 blocks. The prediction encoding unit (3310) can determine a slope based on the horizontal variations and vertical variations. The prediction encoding unit (3310) can determine the horizontal variations and vertical variations using a Sobel filter. The prediction encoding unit (3310) can determine an intra prediction mode corresponding to the slope. The prediction encoding unit (3310) can determine the intra prediction mode of the current block based on a plurality of intra prediction modes determined for the plurality of 3 x 3 blocks. In one embodiment of the present disclosure, the prediction encoding unit (3310) may determine the intra prediction mode that is most frequently determined as the intra prediction mode of the current block. In one embodiment of the present disclosure, the prediction encoding unit (3310) may determine the size based on the horizontal variation and the vertical variation. The prediction encoding unit (3310) may determine the intra prediction mode of the current block based on the size. The prediction encoding unit (3310) may determine the weight of the intra prediction mode corresponding to the slope as the size. For example, the prediction encoding unit (3310) may increase the weight of the intra prediction mode determined based on the slope as the horizontal variation and the vertical variation increase. The prediction encoding unit (3310) may determine the intra prediction mode of the current block based on the result in which the weight determined according to the size is reflected.In one embodiment of the present disclosure, the process by which the prediction encoding unit (3310) determines an intra prediction mode based on a slope may be referred to as decoder side intra mode derivation (DIMD).

[0412] In one embodiment of the present disclosure, the block copy mode may include an intra block copy mode. In one embodiment, the block copy mode may include an intra block copy mode. In one embodiment, the intra block copy mode may be a sub-mode of the intra mode, but is not limited thereto, and may represent a mode separate from the intra mode. In one embodiment, the template matching prediction mode may include a template matching intra prediction mode. The combined mode may include a Combined Inter-Intra Prediction (CIIP) mode that performs prediction by combining prediction according to the intra mode and prediction according to the inter mode. The geometric partitioning mode may include a mode that partitions to include directionality within a block. The geometric partitioning mode may perform prediction using inter prediction or intra prediction for each of the divided regions that are blocked.

[0413] In one embodiment of the present disclosure, when the prediction mode of the current block is the CIIP mode, the prediction encoding unit (3310) can perform prediction on the current block by combining inter prediction and intra prediction. For example, the prediction encoding unit (3310) can perform intra prediction according to the Planar mode. For example, the prediction encoding unit (3310) can determine a motion vector of a reference block for the current block. The prediction encoding unit (3310) can perform inter prediction using the motion vector. The prediction encoding unit (3310) can predict the current block using a weighted sum of a prediction block according to inter prediction and a prediction block according to intra prediction. The weight can be determined based on whether a block adjacent to the current block was intra-predicted (or inter-predicted).

[0414] In one embodiment of the present disclosure, when the prediction mode of the current block is a geometric segmentation mode, the prediction encoding unit (3310) can perform prediction by segmenting the current block. The prediction encoding unit (3310) can determine a segmentation angle and a segmentation distance for a boundary at which segmentation is performed within the current block. The prediction encoding unit (3310) can segment the current block based on the segmentation angle and the segmentation distance. The prediction encoding unit (3310) can predict the current block by performing inter prediction or intra prediction on each of the segmented regions within the current block. The prediction encoding unit (3310) can (i) perform intra prediction on both segmented regions, (ii) perform inter prediction on one region and intra prediction on the other region, or (iii) perform inter prediction on both segmented regions.

[0415] In one embodiment of the present disclosure, when the prediction mode of the current block is the template matching prediction mode, the prediction encoding unit (3310) can reconstruct the current block using a reference block. The generation unit (3320) can generate information related to whether the template matching prediction mode is used. The prediction encoding unit (3310) can determine whether the template matching prediction mode is used based on the acquired information. The reference block can be determined based on at least one of a region included in the current image or a region included in a previously decoded image. In one embodiment of the present disclosure, the prediction encoding unit (3310) can determine the reference block using a cost function. The cost function can include at least one of a sum of absolute difference (SAD), a sum of squared difference (SSD), a sum of absolute transformed difference (SATD), a sum of squared error (SSE), or a mean removed SAD (MR-SAD). For example, the prediction encoding unit (3310) may determine the error between templates using at least one cost function among SAD, SATD, SSE, and MR-SAD. When the cost function is SAD, the prediction encoding unit (3310) may determine the error based on the sum of the absolute values ​​of the differences between each sample of the template of the current block and each sample of the template of the candidate block. When the cost function is SSD, the prediction encoding unit (3310) may determine the error based on the sum of the squares of the differences between each sample of the template of the current block and each sample of the template of the candidate block. The cost function may include a function representing the number of identical samples. The prediction encoding unit (3310) may determine a block with a small error among the candidate blocks as a reference block. The prediction encoding unit (3310) may determine a prediction block by performing template matching intra prediction on the current image.In the present disclosure, the process of determining a reference block for a current block using a template may be referred to as template matching (TM). In the present disclosure, performing a prediction for a current block based on template matching may be referred to as template matching prediction (TMP) or intra-template matching prediction (ITEM).

[0416] In one embodiment of the present disclosure, the prediction encoding unit (3310) can determine the intra prediction mode of the current block when the prediction mode of the current block is the intra mode.

[0417] In one embodiment of the present disclosure, the prediction encoding unit (3310) can determine information about a block vector representing a reference block when the prediction mode of the current block is a block copy mode.

[0418] In one embodiment of the present disclosure, the prediction encoding unit (3310) may perform intra prediction or inter prediction on the current block according to the prediction mode of the current block, and may encode the current block using a prediction block generated as a result of performing intra prediction or inter prediction.

[0419] In one embodiment of the present disclosure, when the prediction mode of the current block is block copy mode, the prediction encoding unit (3310) can determine a prediction block from a reference block. For example, the prediction encoding unit (3310) can determine a prediction block that is identical to the reference block or by performing filtering on the reference block. The reference block can be determined based on at least one of a region included in the current image or a region included in a previously decoded image.

[0420] In one embodiment of the present disclosure, when the prediction mode of the current block is a template matching prediction mode, the prediction encoding unit (3310) can reconstruct the current block using a reference block. The prediction encoding unit (3310) can determine a prediction block using the reference block.

[0421] The predictive encoding unit (3310) can perform deblocking filtering. The deblocking filter can improve image quality by smoothing edges between blocks.

[0422] The prediction encoding unit (3310) may perform filtering on samples of the current block on which deblocking filtering has been performed using a Sample Adaptive Offset (SAO) filter and / or a Bilateral Filter (BIF). The SAO filter and BIF may improve image quality by reducing the error between the restored image and the original image. The SAO filter and BIF may perform filtering on a sample-by-sample basis.

[0423] The predictive encoding unit (3310) can perform filtering using an adaptive loop filter (ALF). ALF can improve image quality by reducing the error between the restored image and the original image. ALF filtering can be performed on a block-by-block basis.

[0424] In one embodiment of the present disclosure, encoding of a current block may refer to a process of generating information that enables an image decoding device (2000) to restore the current block. The information generated through encoding may be included in a bitstream.

[0425] In one embodiment of the present disclosure, the prediction encoding unit (3310) may generate residual data corresponding to the difference between the predicted block and the current block. If the predicted block is determined to be the current block, residual data may not be generated.

[0426] The generation unit (3320) can generate a bitstream including the encoding result of the image. The bitstream can include the encoding result for the current block.

[0427] In one embodiment, the generation unit (3320) may generate a bitstream including residual data. The residual data may include information regarding a difference between an original image (or an original sample) and a predicted image (or a predicted sample). In one embodiment, the generation unit (3320) may generate a bitstream including transform coefficients of a residual block corresponding to a transform unit. In one embodiment, the prediction encoding unit (3310) may obtain transform coefficients of the residual block based on residual samples of the residual block. For example, the prediction encoding unit (3310) may obtain transform coefficients of the residual block by performing at least one of transforming or quantizing the residual samples of the residual block. In one embodiment, the prediction encoding unit (3310) may determine the transform coefficient of the residual block using the residual sample of the transformation unit. If the size of the residual block corresponding to the transformation unit is larger than the size of the transformation unit, the prediction encoding unit (3310) may determine some of the residual samples of the residual block as residual samples of the transformation unit. Alternatively, the prediction encoding unit (3310) may determine the residual samples of the residual block as residual samples of the transformation unit on which filtering is performed. The generation unit (3320) may generate a bitstream including the residual samples of the transformation unit.

[0428] In one embodiment of the present disclosure, the generation unit (3320) can generate a bitstream including information about a block vector representing a reference block when the prediction mode of the current block is a block copy mode.

[0429] In one embodiment of the present disclosure, the generation unit (3320) can transmit the bitstream to the image decoding device (2000) via a network.

[0430] In one embodiment of the present disclosure, the generation unit (3320) may store the bitstream in a data storage medium including at least one of a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape, an optical recording medium such as a CD-ROM and a DVD, or a magneto-optical medium such as a floptical disk.

[0431] The generation unit (3320) can generate a bitstream including syntax elements generated through encoding of an image. Values ​​corresponding to the syntax elements can be included in the bitstream according to the hierarchical structure of the image.

[0432] The generation unit (3320) can obtain bins included in the bitstream by entropy encoding syntax elements.

[0433] In one embodiment of the present disclosure, the bitstream may include information about a prediction mode of a current block within a current image.

[0434] In one embodiment of the present disclosure, when the prediction mode of the current block is an intra mode, the bitstream may include information indicating the intra prediction mode of the current block.

[0435] In a prediction mode (e.g., intra mode) that uses reference samples included in a current image, a prediction block of the current block can be generated based on the surrounding samples of the current block according to the intra prediction mode, assuming that there will be continuity between the surrounding samples of the current block and the samples within the current block. The prediction encoding unit (3310) according to an embodiment of the present disclosure can use not only the surrounding samples of the current block included in the current image but also the spatial reference samples included in the current image for intra prediction. When using samples reconstructed before the current block, the size of residual data can be reduced by predicting the samples of the current block using not only the samples immediately adjacent to the current block but also samples far from the current block. In an embodiment of the present disclosure, the image encoding apparatus (3300) performs intra prediction using a reference block including unreconstructed samples, thereby increasing the range of an area that can be determined as a reference block. The image encoding apparatus (3300) according to an embodiment of the present disclosure can improve compression efficiency by increasing the efficiency of intra prediction.

[0436] In a prediction mode (e.g., inter mode) that utilizes reference samples included in a reference image rather than the current image, a prediction block of the current block can be generated based on a reference block (or reference sample) of the reference image according to the prediction mode, under the assumption that there will be continuity between the current image and the reference image. An image encoding apparatus (3300) according to an embodiment of the present disclosure can improve compression efficiency by increasing the efficiency of intra prediction.

[0437] The image encoding device (3300) can improve prediction accuracy by considering both a reference block (or reference sample) included in the current image and a reference block (or reference sample) included in an image other than the current image. The image encoding device (3300) according to one embodiment of the present disclosure can improve prediction accuracy by considering both the current image and an image other than the current image.

[0438] FIG. 34 is a flowchart illustrating an image encoding method according to one embodiment of the present disclosure.

[0439] In one embodiment of the present disclosure, the image encoding method may be performed by the image encoding device (3300). For example, the image encoding device (3300) may perform each step of the image decoding method by having the processor of the image encoding device (3300) execute at least one instruction contained in the memory. For convenience of explanation, the details described through the aforementioned image decoding method are omitted.

[0440] In step S3410, the image encoding device (3300) can obtain one or more transformation units including the current transformation unit from the encoding unit. The image encoding device (3300) can divide the encoding unit into one or more transformation units.

[0441] In one embodiment, the video encoding device (3300) can determine whether a sub-block transform is applied. When a sub-block transform is applied to an encoding unit, the video encoding device (3300) can split the encoding unit into one or more transform units. In one embodiment, the video encoding device (3300) can determine a coefficient of a transform unit on which a transform is not performed as a predetermined value (e.g., 0). In one embodiment, the video encoding device (3300) can generate a bitstream including information about a transform unit on which a transform is not performed. The video encoding device (3300) can generate a bitstream including information indicating whether a sub-block transform is applied.

[0442] In step S3420, the image encoding device (3300) can obtain a residual sample of the current transformation unit. The image encoding device (3300) can obtain the residual sample by using the difference between the original image and the predicted image. For example, the difference between the original sample of the original image corresponding to the current transformation unit and the predicted sample of the predicted image can be determined as the residual sample of the current transformation unit. For example, the image encoding device (3300) can obtain the predicted sample according to the prediction mode of the coding unit. The image encoding device (3300) can determine the residual sample of the coding unit based on the original sample and the predicted sample.

[0443] In step S3430, the image encoding device (3300) may determine a residual sample of a residual block using a residual sample of the current transformation unit. When the size of the residual block corresponding to the current transformation unit is larger than the size of the current transformation unit, the image encoding device (3300) may determine a residual sample of the residual block using the residual sample of the current transformation unit.

[0444] In one embodiment of the present disclosure, when the size of the residual block is larger than the size of the current transformation unit, the image encoding device (3300) may determine some of the residual samples of the residual block as residual samples of the current transformation unit. For example, when the size of the residual block is N times larger than the current transformation unit, the image encoding device (3300) may determine 1 / N of the residual samples of the residual block as residual samples of the current transformation unit. For example, when the size of the residual block is twice larger than the current transformation unit, the image encoding device (3300) may determine that half of the residual samples of the residual block are identical to the residual samples of the current transformation unit.

[0445] In one embodiment, the video encoding device (3300) can determine a ratio of the size of a residual block and the size of a current transformation unit. The video encoding device (3300) can use the ratio to determine a portion of the residual samples of the residual block as residual samples of the current transformation unit. The video encoding device (3300) can obtain the remaining portion of the residual samples of the residual block by interpolating the residual samples of the current transformation unit.

[0446] In step S3440, the image encoding device (3300) may obtain transform coefficients of the residual block based on residual samples of the residual block. In one embodiment, the image encoding device (3300) may obtain transform coefficients by performing at least one of transform and quantization on the residual samples. The image encoding device (3300) may perform inverse transform using a transform kernel.

[0447] The image encoding device (3300) can perform the transformation using one or more transformation kernels among a plurality of predetermined transformation kernels. For example, the image encoding device (3300) can perform the transformation using DCT-2.

[0448] In one embodiment, the video encoding device (3300) may perform a transformation using a predetermined transformation kernel according to a predetermined condition. For example, the video encoding device (3300) may determine the transformation kernel based on at least one of the size of the residual block (e.g., width, height, or area), the ratio between the width of the residual block and the height of the residual block, the size of the transformation unit, the ratio between the width of the transformation unit and the height of the transformation unit, or the position of the transformation unit (or residual block) within the coding unit.

[0449] In one embodiment, the video encoding device (3300) can generate a bitstream including information about a transform kernel. The video encoding device (3300) can generate the bitstream based on the determined transform kernel.

[0450] In one embodiment, the image encoding device (3300) can determine vertical and horizontal transformation kernels, respectively. The image encoding device (3300) can generate a bitstream including index information indicating the vertical and horizontal transformation kernels.

[0451] In step S3450, the image encoding device (3300) may generate a bitstream including encoded information of the transform coefficients of the residual block. In one embodiment, the image encoding device (3300) may obtain encoded information by performing entropy coding on the transform coefficients.

[0452] An image encoding method according to one embodiment of the present disclosure can improve compression efficiency by increasing the performance of residual coding.

[0453] FIG. 35 is a flowchart of a method for determining a conversion unit according to one embodiment of the present disclosure.

[0454] In one embodiment of the present disclosure, a method for determining a transformation unit may be performed by an image encoding device (3300). For example, the image encoding device (3300) may perform each step of the method for determining a transformation unit by having a processor of the image encoding device (3300) execute at least one instruction contained in a memory.

[0455] In step S3510, the image encoding device (3300) can determine the current transformation unit within the encoding unit. The image encoding device (3300) can determine one or more transformation units including the current transformation unit within the encoding unit based on the loss rate.

[0456] In step S3520, the video encoding device (3300) may determine information regarding whether sub-block transformation is applied to the encoding unit. For example, the video encoding device (3300) may determine information (e.g., cu_sbt_flag) regarding whether sub-block transformation is applied. For example, the video encoding device (3400) may determine whether sub-block transformation is applied to the determined encoding unit.

[0457] In one embodiment, the video encoding device (3300) may determine information regarding whether sub-block transformation is applied when the slice type is inter-slice. In one embodiment, the video encoding device (3300) may determine information regarding whether sub-block transformation is applied when the slice type is inter-slice or intra-slice. For example, the video encoding device (3300) may determine information regarding whether sub-block transformation is applied when the prediction mode of the encoding unit is block copy mode (or intra-block copy mode) or template matching based prediction mode (or intra-template matching based prediction mode).

[0458] In step S3530, the image encoding device (3300) may determine at least one of information related to a split size of the encoding unit, information related to a split direction of the encoding unit, or information related to a position of the current transformation unit within the encoding unit. In one embodiment, the image encoding device (3300) may determine information related to a split size of the encoding unit, information related to a split direction of the encoding unit, and / or information related to a position of the current transformation unit within the encoding unit when subblock transformation is applied to the encoding unit (e.g., cu_sbt_flag == 1).

[0459] In one embodiment, the video encoding device (3400) can generate a bitstream including the information determined in steps S3520 and S3530.

[0460] An image encoding device (3300) according to one embodiment can perform the image decoding method of FIG. 34 by combining the method of determining a transformation unit of FIG. 35. For example, the image encoding device (3300) can obtain one or more transformation units including a current transformation unit from the coding unit, as described in steps S3410 and S3510. Here, the image encoding device (3300) can determine information about the coding unit through steps S3520 to S3530.

[0461] FIG. 36 is a flowchart of a method for determining data of a conversion unit according to one embodiment of the present disclosure.

[0462] In one embodiment of the present disclosure, acquisition of data of a transformation unit may be performed by an image encoding device (3300). For example, the image encoding device (3300) may perform each step of acquiring data of a transformation unit by having a processor of the image encoding device (3300) execute at least one instruction contained in a memory.

[0463] In step S3610, the image encoding device (3300) can obtain one or more transformation units included in the encoding unit.

[0464] In step S3620, the image encoding device (3300) may determine at least one of whether to acquire residual data for one or more transformation units excluding the current transformation unit or whether transformation is performed on the residual data. In one embodiment, the current transformation unit may mean a transformation unit that includes residual data included in the encoding unit.

[0465] In one embodiment, the video encoding device (3300) may not generate residual data for transformation units other than the current transformation unit. For example, the video encoding device (3300) may generate a bitstream without including residual data for transformation units other than the current transformation unit. The video encoding device (3300) may not generate residual data for transformation units other than the current transformation unit of the encoding unit in the bitstream, and may determine the value of the transformation unit to be 0.

[0466] In one embodiment, the video encoding device (3300) may generate residual data for transformation units excluding the current transformation unit. In one embodiment, the video encoding device (3300) may determine that transformation is skipped for transformation units excluding the current transformation unit. For example, the video encoding device (3300) may determine information (e.g., transform_skip_flag=1) indicating whether transformation is applied to transformation units excluding the current transformation unit. The video encoding device (3300) may generate residual data in which transformation is skipped for transformation units excluding the current transformation unit. For example, the video encoding device (3300) may call syntax (e.g., residual_ts_coding()) regarding transformation units in which transformation is skipped for transformation units excluding the current transformation unit. The video encoding device (3300) may skip transformation for transformation units.

[0467] In one embodiment, the video encoding device (3300) can determine whether a transform is used (or whether a transform is performed) for each of one or more transformation units of an encoding unit. The video encoding device (3300) can generate a bitstream including information indicating whether a transform is used (or whether a transform is performed) for each of one or more transformation units. The video encoding device (3300) can obtain residual data (e.g., residual_coding()) on which a transform is performed for a transformation unit on which a transform is performed, and can obtain residual data (e.g., residual_ts_coding()) on which a transform is omitted for a transformation unit on which a transform is omitted.

[0468] In one embodiment, the video encoding device (3300) may determine whether to obtain residual data for each of one or more transformation units of the encoding unit. The video encoding device (3300) may generate a bitstream including information indicating whether each of one or more transformation units has residual data for which transformation has been performed or does not have residual data.

[0469] In one embodiment, the video encoding device (3300) may generate a bitstream including information indicating whether a transformation is performed or not performed on the current transformation unit. The video encoding device (3300) may generate a bitstream including information indicating whether a transformation unit other than the current transformation unit includes residual data for which a transformation is not performed or does not include residual data.

[0470] In one embodiment, the image encoding device (3300) may determine that the current transformation unit has residual data on which transformation is not performed. The image encoding device (3300) may determine that one or more transformation units other than the current transformation unit have residual data on which transformation is performed.

[0471] In one embodiment, the video encoding device (3300) may determine that transformation is omitted for a transformation unit among one or more transformation units in which at least one of the width or height is not a power of 2. For example, the video encoding device (3300) may determine that transformation of the transformation unit is omitted when the height of the transformation unit is 12.

[0472] In one embodiment, the video encoding device (3300) can generate a bitstream including information indicating whether a transformation unit among one or more transformation units, of which at least one of the width or height is not a power of 2, has residual data with omitted transformation or has no residual data.

[0473] In one embodiment, the video encoding device (3300) can perform transformations in multiple directions. For example, the video encoding device (3300) can perform transformations in the vertical direction and the horizontal direction. The video encoding device (3300) can determine whether transformations are omitted based on the height or width according to the direction. For example, for vertical transformation, if the height of the transformation unit is not a power of 2, the video encoding device (3300) can determine that transformations are omitted. For example, for horizontal transformation, if the width of the transformation unit is not a power of 2, the video encoding device (3300) can determine that transformations are omitted.

[0474] In one embodiment, a method for determining whether a transform unit has residual data on which a transform has been performed, residual data on which a transform has been omitted, or no residual data may be included in a header of a bitstream (e.g., a Sequence Parameter Set, a Video Parameter Set, a Picture Header, a Slice Header, a CTU (coding tree unit) unit, a CU (coding unit) unit, a PU (prediction unit), a TU (transform unit)), and whether a method for determining residual data of a transform unit is applied to a specific unit may be determined.

[0475] In one embodiment, when the video encoding device (3300) does not obtain residual data for one or more transformation units other than the current transformation unit, the video encoding device (3300) may determine at least one of a quantization parameter or a quantization interval. For example, the video encoding device (3300) may determine at least one of a quantization parameter or a quantization interval based on a ratio of an area of ​​the coding unit to an area of ​​the current transformation unit. For example, when the ratio of the area of ​​the coding unit to an area of ​​the current transformation unit is 1 / 2, the video encoding device (3300) may set the quantization parameter to be N smaller than an existing quantization parameter (e.g., QP-N). For example, when the ratio of the area of ​​the coding unit to an area of ​​the current transformation unit is 1 / 4, the video encoding device (3300) may set the quantization parameter to be 2*N smaller than an existing quantization parameter (e.g., QP-2*N). The image encoding device (3300) can improve the prediction accuracy of residual data by setting at least one of a quantization parameter or a quantization interval.

[0476] A video encoding method according to one embodiment of the present disclosure can improve coding efficiency by encoding some of a coding unit as residual data on which transformation has been performed, and encoding some of a coding unit as residual data on which transformation has been omitted. As the size of a coding unit increases, the characteristics of residual samples within the coding unit can be more diverse. For example, when a coding unit includes both a camera-captured video and a computer-generated video, the characteristics of both types of videos can be included. In such examples, there are cases where performing a transformation process is advantageous for compression efficiency, and conversely, there are cases where not performing a transformation is advantageous for compression efficiency.

[0477] Therefore, compression performance can be improved by encoding encoding units differently (e.g., determining differently whether to perform transformation within encoding) depending on the distribution of residual samples.

[0478] In one embodiment, the image encoding device (3300) can perform the image decoding method of FIG. 34 in combination with the method of acquiring data of the transformation unit of FIG. 36. For example, the image encoding device (3300) can determine the transformation coefficient of the current transformation unit using steps S2110 to S2150 of FIG. 34. The image encoding device (3300) can determine the transformation coefficient of the transformation unit of the encoding unit excluding the current transformation unit using steps S3110 and S3120 of FIG. 36.

[0479] In one embodiment, the video encoding device (3300) may generate a bitstream including first information regarding whether upsampling is applied (i.e., whether the size of the residual block is or can be larger than the size of the transformation unit). For example, the video encoding device (3300) may generate a bitstream including a flag indicating whether upsampling is applied.

[0480] In one embodiment, the video encoding device (3300) may determine that upsampling is to be applied without generating first information in the bitstream. For example, the video encoding device (3300) may determine that upsampling is to be always applied.

[0481] In one embodiment, if it indicates that upsampling is not applied, the video encoding device (3300) can determine whether a transform is performed. The video encoding device (3300) can generate a bitstream including second information regarding whether a transform is applied to a transform unit or a residual block. If it indicates that upsampling is applied, the video encoding device (3300) can determine that a transform is not applied to a transform unit or a residual block (e.g., transform skip) without generating the second information in the bitstream.

[0482] In one embodiment, the video encoding device (3300) may determine that a transformation has been applied to a transformation unit or a residual block without generating the second information regardless of the first information. The video encoding device (3300) may generate a bitstream including third information indicating whether residual data for the remaining transformation blocks of the coding unit excluding the current transformation block is included in the bitstream. If the residual data is included in the bitstream, the video encoding device (3300) may generate a bitstream including residual data for the remaining transformation blocks.

[0483] In one embodiment, the video encoding device (3300) may determine that no transformation is applied to residual data of the remaining transformation blocks except for the current transformation block of the encoding unit.

[0484] In one embodiment, the video encoding device (3300) can generate a bitstream including information indicating whether the bitstream does not include residual data of transform blocks other than the current transform block of the encoding unit or whether it includes residual data to which no transform has been applied.

[0485] In one embodiment, the video encoding device (3300) can perform the method of determining the transformation unit of FIG. 35 and the method of obtaining data of the transformation unit of FIG. 36 in combination. For example, the video encoding device (3300) can determine the current transformation unit through steps S3510 to S3530 of FIG. 35. The video encoding device (3300) can determine a residual sample of an encoding unit corresponding to a transformation unit of an encoding unit other than the current transformation unit using steps S3610 and S3620 of FIG. 36. In one embodiment, the video encoding device (3300) can determine that a transformation is used for the current transformation unit. The video encoding device (3300) can generate a bitstream including information indicating whether residual data of a transformation unit or a residual block is included in a bitstream. If residual data of a transformation unit or a residual block is included in the bitstream, the video encoding device (3300) can generate a bitstream including the residual data.

[0486] In one embodiment, the video encoding device (3300) may generate a bitstream including information indicating whether residual data regarding a coding unit is included in the bitstream. If residual data regarding a coding unit is included in the bitstream, the video encoding device (3300) may generate a bitstream including information regarding at least one of the coding unit, transformation unit, or residual block described above from the bitstream.

[0487] In one embodiment, the image encoding device (3300) may perform a combination of the image decoding method of FIG. 34, the method of determining a transformation unit of FIG. 35, and the method of obtaining data of a transformation unit of FIG. 36. For example, the image encoding device (3300) may determine a current transformation unit through steps S2610 to S2630 of FIG. 26. The image encoding device (3300) may determine a residual sample of an encoding unit corresponding to the current transformation unit using steps S2110 to S2150 of FIG. 21. The image encoding device (3300) may determine a residual sample of an encoding unit corresponding to a transformation unit of an encoding unit other than the current transformation unit using steps S3110 and S3120 of FIG. 31.

[0488] For example, the video encoding device (3300) can determine the current transformation unit through steps S3510 to S3530 of FIG. 35. The video encoding device (3300) can determine the transformation coefficient of the current transformation unit using steps S2110 to S2150 of FIG. 34. The video encoding device (3300) can determine the residual sample of the coding unit corresponding to the transformation unit of the coding unit excluding the current transformation unit using steps S3610 and S3620 of FIG. 36.

[0489] In one embodiment of the present disclosure, an image decoding method is provided. The image decoding method may include a step of obtaining one or more transformation units including a current transformation unit from a coding unit. The image decoding method may include a step of obtaining a transform coefficient of a residual block corresponding to the current transformation unit. The image decoding method may include a step of obtaining a residual sample of the residual block based on the transform coefficient of the residual block. The image decoding method may include a step of determining a residual sample of the coding unit using a portion of the residual samples of the residual block when a size of the residual block is larger than a size of the current transformation unit. The image decoding method may include a step of reconstructing a sample of the coding unit based on the residual sample of the coding unit.

[0490] In one embodiment of the present disclosure, the step of determining a residual sample of a coding unit using a portion of residual samples of a residual block may include a step of determining a ratio of a size of the residual block and a size of a current transformation unit. The step of determining a residual sample of a coding unit using a portion of residual samples of the residual block may include a step of selecting some residual samples from among the residual samples of the residual block using a ratio. The step of determining a residual sample of a coding unit using a portion of residual samples of the residual block may include a step of determining a residual sample of a coding unit using the selected residual sample.

[0491] In one embodiment of the present disclosure, an image decoding method may include a step of determining a quantization parameter offset value based on whether a size of a residual block is larger than a current transform unit. The image decoding method may include a step of determining a quantization parameter for obtaining a residual sample of the residual block.

[0492] In one embodiment of the present disclosure, the image decoding method may include a step of determining a transform kernel based on at least one of a size of a residual block, a ratio between a width and a height of the residual block, a size of a current transform unit, a ratio between a width and a height of the current transform unit, and a position of the current transform unit within an encoding unit.

[0493] In one embodiment of the present disclosure, a method for decoding an image may include a step of obtaining, from a bitstream, at least one of information related to a split size of a coding unit, information related to a split direction of the coding unit, or information related to a position of a current transformation unit within the coding unit. The current transformation unit may be determined based on at least one of information related to a split size of the coding unit, information related to a split direction of the coding unit, or information related to a position of the current transformation unit within the coding unit.

[0494] In one embodiment of the present disclosure, information related to a split size of a coding unit may indicate at least one of a size ratio between one or more transformation units or a ratio between a size of a current transformation unit and a coding unit including the current transformation unit. Information related to a splitting direction of the coding unit may indicate whether the coding unit is split in a predetermined direction. The predetermined direction may include at least one of a vertical direction, a horizontal direction, or a diagonal direction. Information related to a position of a current transformation unit within a coding unit may indicate a relative position of the current transformation unit within the coding unit.

[0495] In one embodiment of the present disclosure, a video decoding method may include a step of obtaining information about whether a sub-block transform is applied to the encoding unit from a bitstream when the prediction mode of the encoding unit is an inter mode, a block copy mode, or a template matching mode.

[0496] In one embodiment of the present disclosure, the image decoding method may include a step of determining that a transformation unit other than the current transformation unit among one or more transformation units is not subject to transformation.

[0497] In one embodiment of the present disclosure, a method of decoding an image may include obtaining information from a bitstream indicating whether a transform is applied to each of one or more transform units.

[0498] In one embodiment of the present disclosure, a transformation unit among one or more transformation units in which at least one of the width or height is not a power of 2 may be determined as not having transformation applied.

[0499] In one embodiment of the present disclosure, an image decoding device is provided. The image decoding device may include at least one processor including a memory storing one or more instructions and processing circuitry. The at least one processor may execute one or more instructions to enable the device to obtain one or more transformation units including a current transformation unit from an encoding unit. The at least one processor may execute one or more instructions to enable the device to obtain transform coefficients of a residual block corresponding to the current transformation unit. The at least one processor may execute one or more instructions to enable the device to obtain residual samples of the residual block based on the transform coefficients of the residual block. The at least one processor may execute one or more instructions to enable the device to determine residual samples of the encoding unit using some of the residual samples of the residual block when the size of the residual block is larger than the size of the current transformation unit. The at least one processor may execute one or more instructions to enable the device to reconstruct samples of the encoding unit based on the residual samples of the encoding unit.

[0500] In one embodiment of the present disclosure, a video encoding method is provided. The video encoding method may include a step of obtaining one or more transformation units including a current transformation unit from a coding unit. The video encoding method may include a step of obtaining a residual sample of the current transformation unit. The video encoding method may include a step of determining a residual sample of the residual block using the residual sample of the current transformation unit when a size of the residual block corresponding to the current transformation unit is larger than a size of the current transformation unit. The video encoding method may include a step of obtaining a transform coefficient of the residual block based on the residual sample of the residual block. The video encoding method may include a step of generating a bitstream including information in which the transform coefficient of the residual block is encoded.

[0501] In one embodiment of the present disclosure, the step of determining a residual sample of a residual block using a residual sample of a current transformation unit may include the step of determining a ratio of a size of the residual block and a size of the current transformation unit. The step of determining a residual sample of the residual block using the residual sample of the current transformation unit may include the step of determining a part of the residual samples of the residual block as residual samples of the current transformation unit using the ratio. The step of determining a residual sample of the residual block using the residual sample of the current transformation unit may include the step of obtaining a remaining part of the residual samples of the residual block using interpolation of the residual samples of the current transformation unit.

[0502] In one embodiment of the present disclosure, an image encoding method may include a step of determining a quantization parameter offset value based on whether a size of a residual block is larger than a current transform unit. The image encoding method may include a step of determining a quantization parameter for quantizing a residual sample of the residual block.

[0503] In one embodiment of the present disclosure, a video encoding method may include a step of determining a transform kernel based on at least one of a size of a residual block, a ratio between a width and a height of the residual block, a size of a current transform unit, a ratio between a width and a height of the current transform unit, and a position of the current transform unit within an encoding unit.

[0504] In one embodiment of ...

Claims

1. In the video decryption method, A step (S2110) of obtaining one or more transformation units including the current transformation unit from the encoding unit; A step of obtaining a transformation coefficient of a residual block corresponding to the current transformation unit (S2120); A step of obtaining a residual sample of the residual block based on the transformation coefficient of the residual block (S2130); When the size of the residual block is larger than the size of the current transformation unit, a step (S2140) of determining a residual sample of the encoding unit using some of the residual samples of the residual block; and A method comprising a step (S2150) of restoring a sample of the encoding unit based on a residual sample of the encoding unit.

2. In the first paragraph, the step of determining the residual sample of the encoding unit using a portion of the residual sample of the residual block comprises: A step of determining a ratio of the size of the residual block and the size of the current transformation unit; A step of selecting some residual samples from among the residual samples of the residual block using the above ratio; and A method comprising the step of determining a residual sample of the encoding unit using the selected residual sample.

3. In any one of paragraphs 1 and 2, determining a quantization parameter offset value based on whether the size of the residual block is larger than the current transformation unit; and A method further comprising the step of determining quantization parameters for obtaining residual samples of the residual block.

4. In any one of paragraphs 1 to 3, A method further comprising the step of determining a transform kernel based on at least one of a size of the residual block, a ratio between a width and a height of the residual block, a size of the current transform unit, a ratio between a width and a height of the current transform unit, and a position of the current transform unit within the encoding unit.

5. In any one of paragraphs 1 to 4, A step of obtaining at least one of information related to a split size of the encoding unit from a bitstream, information related to a split direction of the encoding unit, or information related to a position of the current transformation unit within the encoding unit, A method, characterized in that the current conversion unit is determined based on at least one of information related to a split size of the encoding unit, information related to a split direction of the encoding unit, or information related to a position of the current conversion unit within the encoding unit.

6. In paragraph 5, Information related to the division size of the above encoding unit is: Indicates at least one of a size ratio between the one or more conversion units or a ratio between the size of the current conversion unit and the encoding unit including the current conversion unit, Information related to the division direction of the above encoding unit is: Indicates whether the above encoding unit is divided in a predetermined direction, wherein the predetermined direction includes at least one of a vertical direction, a horizontal direction, or a diagonal direction, Information related to the position of the current conversion unit within the above encoding unit, A method comprising information indicating the relative position of the current conversion unit within the encoding unit.

7. In any one of paragraphs 1 to 6, A method further comprising a step of obtaining information on whether a subblock transform is applied to the encoding unit from a bitstream when the prediction mode of the encoding unit is an inter mode, a block copy mode, or a template matching mode.

8. In any one of paragraphs 1 to 7, A method comprising a step of determining that a conversion unit other than the current conversion unit among the one or more conversion units is not subject to conversion.

9. In any one of paragraphs 1 to 8, A method comprising the step of obtaining information from a bitstream indicating whether a transformation is applied to each of the one or more transformation units.

10. In any one of paragraphs 1 to 9, A method characterized in that, among the one or more transformation units, a transformation unit whose width or height is not a power of 2 is determined as not subject to transformation.

11. In the video decryption device, Memory that stores one or more instructions; and comprising at least one processor comprising processing circuitry; The at least one processor executes the one or more instructions, thereby causing the device to: Obtain one or more transformation units including the current transformation unit from the encoding unit, Obtain the transformation coefficient of the residual block corresponding to the current transformation unit, Based on the transformation coefficient of the residual block, a residual sample of the residual block is obtained, When the size of the residual block is larger than the size of the current transformation unit, a residual sample of the encoding unit is determined using a portion of the residual samples of the residual block, A device for restoring a sample of the encoding unit based on a residual sample of the encoding unit.

12. In the video encoding method, A step (S3410) of obtaining one or more transformation units including the current transformation unit from the encoding unit; A step of obtaining a residual sample of the current conversion unit (S3420); When the size of the residual block corresponding to the current conversion unit is larger than the size of the current conversion unit, a step (S3430) of determining a residual sample of the residual block using the residual sample of the current conversion unit; A step (S3440) of obtaining a transform coefficient of the residual block based on the residual sample of the residual block; and A method comprising a step (S3450) of generating a bitstream including encoded information of the transform coefficients of the residual block.

13. In the 12th paragraph, the step of determining the residual sample of the residual block using the residual sample of the current transformation unit is as follows: A step of determining a ratio of the size of the residual block and the size of the current transformation unit; A step of determining a portion of the residual samples of the residual block as residual samples of the current transformation unit using the above ratio; and A method comprising the step of obtaining the remaining part of the residual samples of the residual block by using interpolation of the residual samples of the current transformation unit.

14. In any one of paragraphs 12 to 13, determining a quantization parameter offset value based on whether the size of the residual block is larger than the current transformation unit; and A method further comprising the step of determining a quantization parameter for quantizing a residual sample of the residual block.

15. A step of obtaining one or more transformation units including the current transformation unit from the encoding unit; A step of obtaining a residual sample of the current conversion unit; A step of determining a residual sample of the residual block using a residual sample of the current transformation unit when the size of the residual block corresponding to the current transformation unit is larger than the size of the current transformation unit; A step of obtaining a transform coefficient of the residual block based on a residual sample of the residual block; and A computer-readable storage medium storing a bitstream generated by an image encoding method, the method comprising the step of generating a bitstream including encoded information of transform coefficients of the residual block.

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