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

Abstract

Provided are an image encoding method and an image encoding device, the image encoding method comprising the steps of: using a prediction mode of a block to acquire the current reconstruction block including a center sample; determining a plurality of difference values between the center sample and a plurality of nearby samples of the center sample; acquiring, on the basis of the prediction mode, at least one lookup table for filtering; using the plurality of difference values and the at least one lookup table to determine a plurality of modifier values; determining at least one filtering parameter on the basis of the sum of the plurality of modifier values; determining an offset value on the basis of the at least one filtering parameter; and using the center sample and the offset value to acquire a filtered sample.

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 a device and method for encoding and decoding images using filtering.

[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, a video decoding method is provided. The video decoding method may include a step of obtaining a current reconstructed block including a center sample using a prediction mode of the block. The video decoding method may include a step of determining a plurality of difference values ​​between the center sample and a plurality of surrounding samples of the center sample. The video decoding method may include a step of obtaining at least one lookup table for filtering based on the prediction mode. The video decoding method may include a step of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table. The video decoding method may include a step of determining at least one filtering parameter based on a sum of the plurality of modifier values. The video decoding method may include a step of determining an offset value based on the at least one filtering parameter. The video decoding method may include a step of obtaining a filtered sample using the center sample and the offset value.

[0007] In one embodiment of the present disclosure, a video encoding method is provided. The video encoding method may include a step of obtaining a current reconstructed block including a center sample using a prediction mode of a block. The video encoding method may include a step of determining a plurality of difference values ​​between a center sample and a plurality of surrounding samples of the center sample. The video encoding method may include a step of obtaining at least one lookup table for filtering based on the prediction mode. The video encoding method may include a step of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table. The video encoding method may include a step of determining at least one filtering parameter based on a sum of the plurality of modifier values. The video encoding method may include a step of determining an offset value based on the at least one filtering parameter. The video encoding method may include a step of obtaining a filtered sample using the center sample and the offset value.

[0008] In one embodiment of the present disclosure, a computer-readable storage medium is provided that stores at least one of a bitstream encoded by the image encoding method or a bitstream decoded by the image decoding device.

[0009] FIG. 1 is a block diagram of an image decoding device according to one embodiment of the present disclosure.

[0010] FIG. 2 is a block diagram of an image encoding device according to one embodiment of the present disclosure.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] FIG. 20 is a block diagram showing the configuration of an image decoding device according to one embodiment of the present disclosure.

[0029] Fig. 21 is a block diagram showing the configuration of a loop filtering unit according to one embodiment of the present disclosure.

[0030] FIG. 22 is a drawing for explaining the shape of a bidirectional filter according to one embodiment of the present disclosure.

[0031] FIG. 23 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0032] FIG. 24 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents the CIIP mode.

[0033] FIG. 25 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents the GPM mode.

[0034] FIG. 26 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents the IBC mode.

[0035] FIG. 27 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents a template matching prediction mode.

[0036] Fig. 28 is a block diagram showing the configuration of a loop filtering unit according to one embodiment of the present disclosure.

[0037] FIG. 29 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0038] FIG. 30 is a drawing for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0039] FIG. 31 is a drawing for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0040] FIG. 32 is a diagram for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0041] FIG. 33 is a diagram for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0042] FIG. 34 is a block diagram showing the configuration of an image encoding device according to one embodiment of the present disclosure.

[0043] FIG. 35 is a flowchart illustrating an image encoding method according to one embodiment of the present disclosure.

[0044] 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.

[0045] In describing the embodiments, detailed descriptions of related known technologies are 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 the embodiments correspond to identification symbols used to distinguish one component from another.

[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, 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.

[0048] In the present disclosure, components expressed as "units", "modules", etc. may be two or more components combined into a single component, or a single 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] FIG. 1 illustrates a block diagram of an image decoding device (100) according to one embodiment of the present disclosure.

[0053] 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.

[0054] 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.

[0055] To describe in detail the operation of the video decoding device (100), the bitstream acquisition unit (110) can receive a bitstream.

[0056] 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.

[0057] Below, the division of encoding units according to one embodiment of the present disclosure is described in detail.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] A single maximum coding block (CTB) can be divided into MxN coding blocks containing MxN samples (M, N are integers).

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] For example, information about the maximum size of a luma coding block capable of being 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 capable of being split into two. Therefore, by combining the information about the maximum size of a luma coding block capable of being 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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).

[0074] 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.

[0075] 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.

[0076] 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 transformation blocks for transformation may be determined from the coding unit. The transformation blocks may be equal to or smaller than the coding unit.

[0077] The shape and size of the transformation block and the prediction block may be unrelated.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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 syntax elements based on a context model. In addition, the image encoding device (200) can transmit the bitstream to the image decoding device (100).

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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).

[0106] 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).

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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).

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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).

[0121] 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.

[0122] 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.

[0123] 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).

[0124] 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.

[0125] 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).

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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).

[0136] 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.

[0137] 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).

[0138] 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.

[0139] 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).

[0140] 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.

[0141] 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.

[0142] 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).

[0143] 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).

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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).

[0158] 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).

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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 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.

[0173] 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.

[0174] 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).

[0175] 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.

[0176] 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.

[0177] 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).

[0178] 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).

[0179] 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).

[0180] 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.

[0181] 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).

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] Hereinafter, a method for determining a partitioning rule according to one embodiment of the present disclosure will be described in detail.

[0197] 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.

[0198] 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).

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] Additionally, the image decoding device (100) may 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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).

[0218] 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.

[0219] 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.

[0220] 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.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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).

[0225] Figure 19 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0226] 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).

[0227] 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 transformation coefficients of residual data between the prediction data and the current input image. The entropy encoding unit (1925) encodes and transforms the quantized transformation coefficients and outputs them as a bitstream. The quantized transformation coefficients are restored to spatial domain data through the inverse quantization and inverse transformation unit (1930), and the restored spatial domain data are output as a restored image through the deblocking filtering unit (1935) and the loop filtering unit (1940). The restored image can be used as a reference image of the next input image through the prediction encoding unit (1915).

[0228] 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).

[0229] 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).

[0230] FIG. 20 is a block diagram showing the configuration of an image decoding device according to one embodiment of the present disclosure.

[0231] Referring to FIG. 20, the image decoding device (2000) may include an acquisition unit (2010) and a prediction decoding unit (2020).

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] 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 partitioned from a current image to be decoded. In one embodiment of the present disclosure, a prediction mode such as an intra mode, an inter mode, a combined mode, a geometric partitioning mode, and / or an intra block copy may be used for prediction of the current block. In one embodiment, the intra mode may be performed according to a template matching-based prediction method. In one embodiment, the block copy mode may include an intra block copy mode. In one embodiment, the template matching-based prediction mode may include a template matching-based intra prediction mode. The combined mode may include a Combined Inter-Intra Prediction (CIIP) mode that performs prediction by combining prediction according to an intra mode and prediction according to an inter mode. The geometric partitioning mode may include a mode that partitions to include directionality within a block. The geometric segmentation mode can perform prediction using inter-prediction or intra-prediction for each of the blocked segmented regions. A prediction mode according to an embodiment of the present disclosure will be described below.

[0237] 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.

[0238] 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.

[0239] 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. The prediction decoding unit (2020) can perform intra prediction according to the planar mode. The prediction decoding unit (2020) can perform inter prediction using a motion vector. 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 has been intra predicted.

[0240] 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.

[0241] 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, the prediction decoding unit (2020) can determine a prediction block based on the reference block. For example, the prediction decoding unit (2020) can determine a prediction block that is identical to the reference block or by performing filtering on the reference block.

[0242] In one embodiment of the present disclosure, when the prediction mode of the current block is a template matching prediction mode, the prediction decoding unit (2020) can reconstruct the current block using a reference block included in the current image. The prediction decoding unit (2020) can determine the prediction block by performing template matching-based intra prediction on the current image.

[0243] 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, 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.

[0244] In intra mode, a prediction block of a current block can be generated based on surrounding samples of the current block according to the intra prediction mode, assuming that there will be continuity between surrounding samples of the current block and samples within the current block. The prediction decoding unit (2020) according to an embodiment of the present disclosure can use not only surrounding samples of the current block included in the current image but also 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 samples of the current block using not only 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.

[0245] The prediction decoding unit (2020) can perform deblocking filtering. The deblocking filter can improve image quality by smoothing the edges between blocks.

[0246] 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.

[0247] 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.

[0248] Fig. 21 is a block diagram showing the configuration of a loop filtering unit according to one embodiment of the present disclosure.

[0249] Referring to FIG. 21, the loop filtering unit (1940) can generate filtered samples by performing filtering on restored samples. In one embodiment of the present disclosure, the loop filtering unit (1940) can include a bidirectional filtering unit (2110), a sample adaptive offset filtering unit (2120), and an adaptive loop filtering unit (2130).

[0250] In one embodiment of the present disclosure, the reconstructed sample may be a sample on which deblocking filtering has been performed. The deblocking filter may modify the values ​​of a plurality of samples near the boundaries of the current block and surrounding blocks. The deblocking filter may modify the values ​​of the samples by applying deblocking filter coefficients to the samples near the boundaries of the current block and the samples near the boundaries of the surrounding blocks.

[0251] The bidirectional filtering unit (2110) can perform filtering on the current sample using surrounding samples of the current sample. The bidirectional filtering unit (2110) can perform filtering on samples of the luma component and samples of the chroma component. The bidirectional filtering unit (2110) can filter the BIF offset value (△I) for the current sample. BIF) can be determined. The offset value may include the amount of change in the current sample due to filtering. The bidirectional filtering unit (2110) may determine the filtering strength based on the difference value between the current sample and the surrounding samples. For example, the bidirectional filtering unit (2110) may apply stronger filtering as the difference between the current sample and the surrounding samples increases. That is, the bidirectional filtering unit (2110) may have a large difference between the current sample before and after filtering. A bidirectional filter according to an embodiment of the present disclosure is described in detail with reference to FIGS. 22 to 33.

[0252] The sample adaptive offset filtering unit (2120) calculates the SAO offset value (△I) for the current sample. SAO ) can be determined. The sample adaptive offset filtering unit (2120) can determine an edge offset or a band offset. The sample adaptive offset filtering unit (2120) can determine whether the sample adaptive offset type of the current block is an edge offset.

[0253] In one embodiment of the present disclosure, the sample adaptive offset filtering unit (2120) can obtain an edge offset class from a bitstream. The edge offset class can represent a representative edge among a horizontal edge, a vertical edge, a 135 degree edge, or a 45 degree edge. The sample adaptive offset filtering unit (2120) can determine an edge offset category based on a category condition. The category condition can include a size condition between values ​​of samples at positions determined based on the edge offset class. The sample adaptive offset filtering unit (2120) can determine an offset based on the edge offset category.

[0254] In one embodiment of the present disclosure, the sample adaptive offset filtering unit (2120) can determine a plurality of bands based on the brightness of a pixel. The sample adaptive offset filtering unit (2120) can obtain offset values ​​corresponding to the plurality of bands from a bitstream. The plurality of bands can include continuous bands. The sample adaptive offset filtering unit (2120) can determine a band corresponding to a current sample. The sample adaptive offset filtering unit (2120) can determine an offset value corresponding to the determined band as an offset value for the current sample.

[0255] In one embodiment of the present disclosure, a filtered current sample may be determined using a BIF offset value determined by a bidirectional filtering unit (2110) and an SAO offset value determined by a sample adaptive offset filtering unit (2120). For example, the filtered current sample may be determined as the sum of the restored current sample, the BIF offset value, and the SAO offset value. The filtered current sample cannot be larger than the bit depth of the image.

[0256] The adaptive loop filtering unit (2130) can determine filter coefficients that minimize the error between the original image and the reconstructed image. The adaptive loop filtering unit (2130) can determine a class and filter coefficients based on the characteristics of the current block. For example, the adaptive loop filtering unit (2130) can determine a class of an N x N block and determine filter coefficients based on the class. The class of the block can be determined based on the direction and activity of pixels within the block. The adaptive loop filtering unit (2130) can perform a geometric transformation on the filter based on the gradient within the block. The gradient within the block can include a horizontal gradient, a vertical gradient, and two diagonal gradients. The geometric transformation can include at least one of a diagonal symmetry transformation, a vertical symmetry transformation, or a rotation transformation. The adaptive loop filtering unit (2130) can perform filtering using the filter coefficients. The adaptive loop filtering unit (2130) can perform filtering by applying a filter coefficient to the difference between the values ​​of the current sample and the surrounding samples.

[0257] In one embodiment of the present disclosure, the loop filtering unit (1940) may not include at least some of the bidirectional filtering unit (2110), the sample adaptive offset filtering unit (2120), and the adaptive loop filtering unit (2130). For example, the reconstructed sample may only undergo bidirectional filtering by the bidirectional filtering unit (2110). Whether the bidirectional filtering unit (2110), the sample adaptive offset filtering unit (2120), and the adaptive loop filtering unit (2130) perform filtering can be obtained through the bitstream. Whether the bidirectional filtering unit (2110) and the sample adaptive offset filtering unit (2120) perform filtering can be determined using Rate Distortion Optimization (RDO). That is, whether to apply filtering can be determined through an optimization process using the quality of the image and the number of bits included in the bitstream. The image decoding device (2000) can obtain information indicating whether filtering is performed from the bitstream. The image decoding device (2000) can perform filtering based on the acquired information. In one embodiment of the present disclosure, the bidirectional filtering unit (2110) and the sample adaptive offset filtering unit (2120) may be performed sequentially rather than in parallel.

[0258] In one embodiment of the present disclosure, the loop filtering unit (1970) may be configured to be identical to the loop filtering unit (1940). The loop filtering unit (1970) may include a bidirectional filtering unit, a sample adaptive offset filtering unit, and / or an adaptive loop filtering unit.

[0259] FIG. 22 is a drawing for explaining the shape of a bidirectional filter according to one embodiment of the present disclosure.

[0260] Referring to FIG. 22, the bidirectional filter (2200) may be a 5 x 5 diamond-shaped filter. However, the bidirectional filter is not limited thereto and may be an N x N diamond-shaped filter, such as a 3 x 3 or 7 x 7.

[0261] A bidirectional filter (2200) according to one embodiment of the present disclosure may include a center sample and surrounding samples. The center sample (I C ) may refer to the current sample on which filtering is performed. The surrounding samples are upper samples (I) located above the center sample. A ), the left sample (I) located to the left of the center sample L ), the lower sample (I) located below the central sample B ), the right sample (I) located to the right of the central sample R ) may be included. The surrounding samples are the Northwest sample (I) located at the upper left of the central sample. NW ), the Southwest sample (I) located at the lower left of the central sample SW ), the SouthEast sample (I) located at the lower right of the central sample SE ), the NorthEast sample (I) located at the upper right of the central sample NE ) may be included. The surrounding sample is an above-above sample (I) located above the upper sample. AA ), the left-left sample (I) located to the left of the left sample LL ), the below-below sample (I) located below the lower sample BB ), the right-right sample (I) located to the right of the right sample RR ) may be included.

[0262] The video decoding device (2000) can determine the difference value between the center sample and the surrounding samples. For example, the difference value (△I) between the center sample and the right sample R ) can be determined as in mathematical expression 1.

[0263] [Mathematical Formula 1]

[0264] △I R = (|I R -I C | + 2 n-8 ) >> (n-7)

[0265] Here, | ` | represents an absolute value, and n represents the bit depth of the image. According to one embodiment of the present disclosure, mathematical expression 1 represents the difference value (△I R ) can be calculated as the difference between the center sample and the surrounding samples, shifted right by n bits, and rounded. For example, in a 10-bit image, the difference value (△I R ) is (|I R -I C | + 4) >> 3 can be determined. In one embodiment of the present disclosure, the difference value can be expressed as a quantized absolute value of the difference between the center sample and the surrounding samples.

[0266] In one embodiment of the present disclosure, the image decoding device (2000) may determine an offset value using a difference value between a center sample and surrounding samples. The image decoding device (2000) may obtain a predefined look-up table (LUT). The look-up table may include a plurality of indices and a plurality of values ​​corresponding to each of the plurality of indices. For example, the look-up table may include 16 values ​​of {0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}. LUT[i] refers to a value corresponding to index i, and LUT[0] refers to 0, which is the 0th value of the look-up table, that is, the leftmost value. In one embodiment of the present disclosure, the look-up table may be determined based on a quantization parameter. In one embodiment of the present disclosure, the look-up table may be determined according to a prediction mode.

[0267] In one embodiment of the present disclosure, the image decoding device (2000) can determine a modifier value (μ) according to a difference value using a lookup table. In one embodiment of the present disclosure, the modifier value (μ) corresponding to the right sample △IR ) is the difference value (△I) between the center sample and the right sample R ) can be determined as the output value of the lookup table corresponding to LUT[△I R ] can be determined.

[0268] In one embodiment of the present disclosure, a modifier value (μ) corresponding to the right sample △IR ) can be determined based on the number of values ​​contained in the lookup table. For example, the modifier value is LUT[min(15, △I R)] can be determined. If the number of values ​​included in the lookup table is 16, the upper limit is determined to be 15, so one of 0 to 15 can be determined as the index of the lookup table. Accordingly, even if the difference between the central sample and the surrounding samples is greater than a predetermined value, the modifier value can be obtained from the lookup table.

[0269] In one embodiment of the present disclosure, a modifier value (μ) corresponding to the right sample △IR ) can be determined based on whether the difference between the center sample and the right sample is greater than 0. For example, if the difference between the center sample and the right sample is less than 0, the modifier value (μ △IR ) can be determined by the negative of the output value of the lookup table.

[0270] In one embodiment of the present disclosure, the modifier value may be determined based on the distance between the surrounding sample and the center sample. In one embodiment of the present disclosure, when the distance between the center sample and the surrounding sample is 2, the modifier value may be a value obtained by dividing the value obtained according to the lookup table by 2. For example, the modifier value (μ) corresponding to the imaginary side sample △AA ) is LUT[△I AA ] >> can be determined as 1. In one embodiment of the present disclosure, a lookup table may be applied to the modifier value according to the distance between the surrounding sample and the center sample. For example, the modifier value may be determined through different lookup tables for the surrounding sample with a distance of 1 from the center sample and the surrounding sample with a distance of 2.

[0271] According to one embodiment of the present disclosure, the process of determining a modifier value has been described with reference to the upper sample, but is not limited thereto and can be equally applied to other surrounding samples.

[0272] In one embodiment of the present disclosure, the image decoding device (2000) can determine an offset value based on a modifier value. The image decoding device (2000) can determine a sum of modifier values. In one embodiment of the present disclosure, the image decoding device (2000) can combine the sum of modifier values ​​for surrounding samples included in a bilateral filter. For example, the image decoding device (2000) can combine the sum (m) of modifier values ​​(μ) corresponding to surrounding samples as in Equation 2. sum ) can be determined.

[0273] [Equation 2]

[0274] m sum = μ △A + μ △B + μ △L + μ △R + μ △NW + μ △NE + μ △SW + μ △SE + μ △AA + μ △BB + μ △LL + μ △RR

[0275] The video decoding device (2000) can determine an offset value based on the sum of the modifier values. The video decoding device (2000) can determine a filtering parameter based on the sum of the modifier values.

[0276] In one embodiment of the present disclosure, the image decoding device (2000) may determine a multiplier value. In the present disclosure, the multiplier value may be referred to as a "c parameter." The image decoding device (2000) may determine the multiplier value based on at least some of the width of a block including a center sample, the height of the block, the minimum values ​​of the width and height of the block, or the prediction mode of the block. For example, the image decoding device (2000) may determine one of the predetermined multiplier values ​​based on the minimum values ​​of the width and height of the block. For example, the image decoding device (2000) may determine the predetermined multiplier value corresponding to whether the prediction mode of the block indicates an inter prediction mode or an intra prediction mode. The multiplier value may be determined as one of predetermined values. For example, the multiplier value may be determined as one of 1, 2, or 3.

[0277] In one embodiment of the present disclosure, the image decoding device (2000) can determine a filtering parameter based on the sum of the multiplier value and the modifier values. The filtering parameter can be determined by multiplying the multiplier value by the sum of the modifier values.

[0278] The image decoding device (2000) can determine an offset value based on a filtering parameter. In one embodiment of the present disclosure, the image decoding device (2000) can determine an offset value based on a bilateral filter strength. The image decoding device (2000) can obtain the filtering strength. The image decoding device (2000) can determine the offset value by adjusting the filtering parameter according to the filtering strength. For example, the image decoding device (2000) can determine the filtering parameter as in Equation 3.

[0279] [Equation 3]

[0280] r add=214-n-bilateral_filter_strength

[0281] r shift =15-n-bilateral_filter_strength

[0282] △I BIF = (c v + r add ) >> r shift

[0283] Here, n represents the bit depth of the image, and bilateral_filter_strength represents the bilateral filtering strength. The bilateral filtering strength can represent a value of 0 or 1. In one embodiment of the present disclosure, the bilateral filtering strength can be signaled through a picture parameter set (PPS) of the bitstream.

[0284] The image decoding device (2000) can obtain filtered samples using the center sample and offset value. The image decoding device (2000) can perform filtering by combining the center sample and offset value. For example, the image decoding device (2000) can perform filtering as shown in Equation 4.

[0285] [Equation 4]

[0286] I out = clip3(0, (1< <BitDepth)-1, I C + △I BIF )

[0287] Here, the clip3(x, y, z) function is a function that outputs the value of the variable z between the lower limit x and the upper limit y. If the variable z is less than the lower limit x, the lower limit x is output, and if the variable z is greater than the upper limit y, the upper limit y is output. Here, I out is the value of the filtered sample, I C is the value of the central sample, △I BIF represents the offset value for the bidirectional filter.

[0288] In one embodiment of the present disclosure, the image decoding device (2000) can obtain filtered samples using a sample adaptive offset (SAO) filter. For example, the image decoding device (2000) can perform filtering as in Equation 5 using a bilateral filter and a sample adaptive offset filter.

[0289] [Equation 5]

[0290] I out = clip3(0, (1< <BitDepth)-1, I C + △I BIF + △I SAO )

[0291] Here, △I BIF represents the offset value for the sample adaptive offset (SAO) filter.

[0292] FIG. 23 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0293] Referring to FIG. 23, in step S2310, the image decoding device (2000) can obtain a current reconstructed block including a center sample using the prediction mode of the block. In one embodiment of the present disclosure, the current reconstructed block may include a block on which deblocking filtering has been performed.

[0294] In step S2320, the image decoding device (2000) may determine a plurality of difference values ​​between a central sample and a plurality of surrounding samples of the central sample. For example, the image decoding device (2000) may determine a difference value for each of the central sample and the surrounding samples. In one embodiment of the present disclosure, the image decoding device (2000) may determine a rounded difference value between the central sample and the surrounding samples.

[0295] In step S2330, the image decoding device (2000) may obtain at least one lookup table for filtering based on the prediction mode. In one embodiment of the present disclosure, the image decoding device (2000) may obtain at least one lookup table according to the prediction mode from among a plurality of lookup tables. For example, the image decoding device (2000) may obtain a lookup table corresponding to the intra block copy mode from among the plurality of lookup tables based on the prediction mode being the intra block copy mode.

[0296] In step S2340, the image decoding device (2000) may determine a plurality of modifier values ​​using a plurality of difference values ​​and at least one lookup table. In one embodiment of the present disclosure, the image decoding device (2000) may obtain a modifier value of the lookup table corresponding to each difference value. For example, the image decoding device (2000) may determine a difference value as an index value of the lookup table, and obtain an output value of the lookup table corresponding to the index value as a modifier value.

[0297] In step S2350, the image decoding device (2000) may determine at least one filtering parameter based on the sum of multiple modifier values. In one embodiment of the present disclosure, the number of filtering parameters may be determined according to the prediction mode.

[0298] In step S2360, the image decoding device (2000) may determine an offset value based on at least one filtering parameter. In one embodiment of the present disclosure, the larger the filtering parameter, the larger the offset value. In one embodiment of the present disclosure, the offset value may include the amount of change in the current sample value due to filtering.

[0299] In step S2370, the image decoding device (2000) can obtain a filtered sample using the center sample and offset value. In one embodiment of the present disclosure, the image decoding device (2000) can perform adaptive loop filtering using the filtered sample.

[0300] In one embodiment of the present disclosure, the image decoding device (2000) can perform filtering based on a prediction mode. The process of the image decoding device (2000) performing filtering based on the prediction mode is described in detail with reference to FIGS. 24 to 33.

[0301] FIG. 24 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents the CIIP mode.

[0302] The video decoding device (2000) can identify that the prediction mode of the block (2410) including the current sample indicates the CIIP mode. In one embodiment of the present disclosure, the block (2410) can include a coding unit. The video decoding device (2000) can determine the prediction mode of the block (2410) based on at least one of the number of samples included in the block (2410), the width of the block (2410), or the height of the block (2410). In one embodiment of the present disclosure, the video decoding device (2000) can obtain a flag regarding the CIIP mode. For example, the video decoding device (2000) can obtain a flag regarding the CIIP mode when the number of samples included in the block (2410) is 64 or more, and the width of the block (2410) and the height of the block (2410) are both less than 128. The flag for CIIP mode may be a flag indicating whether CIIP prediction is applied to the block (2410).

[0303] The video decoding device (2000) can perform prediction by combining inter prediction and intra prediction when the prediction mode indicates the CIIP mode. The video decoding device (2000) can perform intra prediction using the Planar mode. The video decoding device (2000) can obtain a prediction sample for the CIIP mode as a weighted sum of prediction samples by inter prediction and prediction samples by intra prediction. For example, a prediction sample P by CIIP CIIP is ((4-w)*P inter + w*P intra )>>2. The weight (w) can be determined based on the prediction mode of the upper peripheral location (2420) and the left peripheral location (2430). For example, if both the upper peripheral location (2420) and the left peripheral location (2430) have performed intra prediction, the weight w can be determined as 3. The more intra predictions there are for peripheral locations, the greater the weight for intra prediction can be. For example, if both the upper peripheral location (2420) and the left peripheral location (2430) have not performed intra prediction, the weight w can be determined as 1.

[0304] In one embodiment of the present disclosure, when the prediction mode indicates the CIIP mode, the image decoding device (2000) can obtain at least one of an inter lookup table corresponding to the inter prediction mode, an intra lookup table corresponding to the intra prediction mode, or a lookup table predetermined according to the CIIP prediction mode.

[0305] In one embodiment of the present disclosure, the video decoding device (2000) can perform filtering by combining filtering according to inter prediction and filtering according to intra prediction. In one embodiment of the present disclosure, the video decoding device (2000) can obtain a CIIP filtering parameter as a weighted sum of an inter filtering parameter according to inter prediction and an intra filtering parameter according to intra prediction. For example, the video decoding device (2000) can determine the CIIP filtering parameter as expressed in Equation 6.

[0306] [Equation 6]

[0307] BIF CIIP = ((4-w)*BIF inter + w*BIF intra ) >> 2

[0308] Here, BIF X represents a filtering parameter for prediction mode X. By determining the intra filtering parameter as in mathematical expression 6, the characteristics of the CIIP mode can be well reflected, thereby obtaining a high image quality improvement effect. In one embodiment of the present disclosure, the weight may be the same as the determination condition in the CIIP prediction. For example, the weight (w) may be determined based on the prediction mode of the upper peripheral location (2420) and the left peripheral location (2430).

[0309] In one embodiment of the present disclosure, the image decoding device (2000) can determine the CIIP filtering parameter as an average of the inter-filtering parameter according to inter-prediction and the intra-filtering parameter according to intra-prediction. By determining the CIIP filtering parameter as an average of the inter-filtering parameter and the intra-filtering parameter, features for both inter-prediction and intra-prediction can be considered while saving time and resources compared to determining the filtering parameter by weighted sum.

[0310] In one embodiment of the present disclosure, the video decoding device (2000) can obtain an inter lookup table corresponding to inter prediction and an intra lookup table corresponding to intra prediction. The video decoding device (2000) can obtain an inter filtering parameter according to the inter lookup table. The video decoding device (2000) can obtain an intra filtering parameter according to the intra lookup table. The video decoding device (2000) can determine a CIIP filtering parameter based on the inter filtering parameter and the intra filtering parameter. The video decoding device (2000) can determine an offset value based on the CIIP filtering parameter. According to one embodiment of the present disclosure, a process in which the video decoding device (2000) determines an offset value using the lookup table has been described above, and therefore, will be omitted.

[0311] In one embodiment of the present disclosure, the image decoding device (2000) can obtain filtering parameters of a reference block. For example, the image decoding device (2000) can determine filtering parameters of a reference block referenced in inter prediction as inter filtering parameters.

[0312] In one embodiment of the present disclosure, the image decoding device (2000) can obtain a lookup table predetermined according to the CIIP. The CIIP lookup table can be predetermined separately from the inter lookup table and the intra lookup table.

[0313] In one embodiment of the present disclosure, the CIIP lookup table can be obtained as a linear combination (or weighted sum) of an inter lookup table and an intra lookup table. The linear coefficients (or weights) for the inter lookup table and the intra lookup table can be predetermined values.

[0314] In one embodiment of the present disclosure, the CIIP lookup table may have a distribution of output values ​​that corresponds to a linear, logistic, or sinusoidal distribution below a predetermined index value, and may have a value of 0 when the predetermined index value is exceeded. For example, the CIIP lookup table may be {1, 2, 3, 4, 5, 0, 0, 0} having a linear distribution of output values ​​below a predetermined index value of 4.

[0315] In one embodiment of the present disclosure, the CIIP lookup table may be determined as a linear combination of multiple lookup tables. For example, if the first, second, and third lookup tables each exhibit a linear distribution, a logistic distribution, and a sinusoidal distribution below a predetermined index value, the CIIP lookup table may be determined as a weighted combination of the first, second, and third lookup tables. The weights among the multiple lookup tables may be experimentally predetermined values.

[0316] In one embodiment of the present disclosure, the video decoding device (2000) can obtain information about bidirectional filtering applied to a block from a bitstream. For example, the video decoding device (2000) can obtain information about a method for determining a CIIP filtering parameter from the bitstream. The information about the method for determining the CIIP filtering parameter may include index information indicating a type of lookup table. For example, the information about the method for determining the CIIP filtering parameter may include index information indicating at least one of: i) whether the CIIP filtering parameter is determined as a weighted sum of inter-filtering parameters and intra-filtering parameters, ii) whether the CIIP filtering parameter is determined as an average of inter-filtering parameters and intra-filtering parameters, or iii) whether the CIIP filtering parameter is determined using a lookup table predetermined for a CIIP mode. The information about bidirectional filtering may be determined for a coding unit, a maximum coding unit, a slice unit, or a picture unit and transmitted through a bitstream.

[0317] FIG. 25 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents the GPM mode.

[0318] The image decoding device (2000) can identify that the prediction mode of the block (2510) including the current sample indicates the GPM (Geometric Partitioning Mode) mode. In one embodiment of the present disclosure, the block (2510) can include an encoding unit. If the prediction mode is the GPM mode, the image decoding device (2000) can divide the block into a plurality of regions. The image decoding device (2000) can determine the boundary to be divided based on the distance and angle with respect to the boundary to be divided. In one embodiment of the present disclosure, the image decoding device (2000) can determine the prediction mode for the divided region within the block (2510). The image decoding device (2000) can obtain the prediction mode information for the region from the bitstream. Image

[0319] In one embodiment of the present disclosure, the prediction mode of block (2510) may include an inter-prediction mode and an intra-prediction mode. One of the divided regions of block (2510) may be predicted by inter-prediction, and another region may be predicted by intra-prediction. According to one embodiment of the present disclosure, block (2510) may be divided into a first region where intra-prediction is performed and a second region where inter-prediction is performed.

[0320] In one embodiment of the present disclosure, when the prediction mode indicates the GPM mode, the image decoding device (2000) can obtain at least one of an inter lookup table corresponding to the inter prediction mode, an intra lookup table corresponding to the intra prediction mode, or a lookup table predetermined according to the GPM prediction mode.

[0321] In one embodiment of the present disclosure, the image decoding device (2000) can perform filtering based on the positions of the central sample and the surrounding samples. The image decoding device (2000) can determine a segmented region of a block (2510) that includes the positions of the central sample and the surrounding samples.

[0322] In one embodiment of the present disclosure, the image decoding device (2000) may include a filtering region (2520) including a center sample and surrounding samples in a first region where intra prediction is performed. In one embodiment of the present disclosure, when the entire filtering region (2520) is included in the first region, the image decoding device (2000) may determine a filtering parameter of an intra prediction mode using an intra lookup table. For example, the image decoding device (2000) may determine a filtering parameter of a prediction mode in the same manner as in the case of an intra prediction mode. In one embodiment of the present disclosure, when the entire filtering region (2520) is included in the first region, the image decoding device (2000) may determine a filtering parameter of a prediction mode by obtaining an intra filtering parameter. For example, the image decoding device (2000) may obtain a filtering parameter from a sample referenced for prediction of a center sample, and determine the obtained filtering parameter as a filtering parameter of a prediction mode.

[0323] In one embodiment of the present disclosure, the image decoding device (2000) may include a filtering region (2530) including a center sample and surrounding samples in a second region where inter prediction is performed. In one embodiment of the present disclosure, when the entire filtering region (2530) is included in the second region, the image decoding device (2000) may determine a filtering parameter of a prediction mode using an inter lookup table. For example, the image decoding device (2000) may determine a filtering parameter of a prediction mode in the same manner as in the case of an inter prediction mode. In one embodiment of the present disclosure, when the filtering region (2530) is included in the second region, the image decoding device (2000) may determine a filtering parameter of a prediction mode by obtaining an inter filtering parameter. For example, the image decoding device (2000) may obtain a filtering parameter from a sample referenced for prediction of a center sample, and determine the obtained filtering parameter as a filtering parameter of a prediction mode.

[0324] In one embodiment of the present disclosure, the image decoding device (2000) may be configured such that a filtering region (2540) including a center sample and peripheral samples may be located at a boundary between a first region where intra prediction is performed and a second region where inter prediction is performed. That is, a part of the filtering region (2540) may be included in the first region, and the remaining part may be included in the second region. In one embodiment of the present disclosure, the image decoding device (2000) may determine a filtering parameter of a prediction mode by using at least one of an inter lookup table, an intra lookup table, a CIIP lookup table, or a lookup table predetermined according to a GPM, when the filtering region (2530) is located at a boundary between the first region and the second region. In one embodiment of the present disclosure, the image decoding device (2000) may obtain an inter lookup table corresponding to inter prediction and an intra lookup table corresponding to intra prediction. The image decoding device (2000) may obtain an inter filtering parameter according to the inter lookup table. The image decoding device (2000) can obtain intra filtering parameters according to the intra lookup table. The image decoding device (2000) can obtain GPM filtering parameters according to the GPM lookup table. The image decoding device (2000) can determine GPM filtering parameters based on CIIP filtering parameters. The image decoding device (2000) can determine an offset value based on the GPM filtering parameters. According to one embodiment of the present disclosure, the process of the image decoding device (2000) determining an offset value using the lookup table has been described above, and therefore, is omitted.

[0325] In one embodiment of the present disclosure, the image decoding device (2000) can determine GPM filtering parameters using CIIP filtering parameters. The image decoding device (2000) can determine filtering parameters using the process for determining filtering parameters described in FIG. 24. In one embodiment of the present disclosure, the image decoding device (2000) can determine filtering parameters using a CIIP lookup table.

[0326] In one embodiment of the present disclosure, the image decoding device (2000) may determine a filtering parameter using an inter lookup table determined according to an inter prediction mode and an intra lookup table determined according to an intra prediction mode. The image decoding device (2000) may determine a GPM filtering parameter as a weighted sum of the inter filtering parameter and the intra filtering parameter. The weight may be determined based on the number of samples included in the inter mode area of ​​the block (2510) and the number of samples included in the intra mode area. For example, the weight may be determined based on the ratio of the number of samples for which prediction was performed according to the inter mode to the number of samples for which prediction was performed according to the intra mode among the samples included in the block (2510). For example, the GPM filtering parameter may be determined as in Equation 7.

[0327] [Equation 7]

[0328] BIF GPM = (n inter *BIF inter + n intra *BIF intra ) >> (log2(n inter +n intra ))

[0329] Here, n inter is the number of samples contained in the inter-mode region of the block, and n intra is the number of samples contained in the intra-mode region of the block.

[0330] In one embodiment of the present disclosure, the image decoding device (2000) can determine filtering parameters using a lookup table predetermined according to GPM.

[0331] In one embodiment of the present disclosure, the image decoding device (2000) can determine filtering parameters based on the positions of the filtering regions (2520, 2530, 2540). In one embodiment of the present disclosure, the image decoding device (2000) can determine filtering parameters of an intra prediction mode using an intra lookup table when all of the filtering regions (2520) are included in the first region. In one embodiment of the present disclosure, the image decoding device (2000) can determine filtering parameters of a prediction mode by obtaining intra filtering parameters when all of the filtering regions (2520) are included in the first region.

[0332] In one embodiment of the present disclosure, the image decoding device (2000) can determine the filtering parameters of the prediction mode using the inter lookup table when the filtering region (2530) is entirely included in the second region. For example, the image decoding device (2000) can determine the filtering parameters of the prediction mode in the same manner as in the case of the inter prediction mode. In one embodiment of the present disclosure, the image decoding device (2000) can determine the filtering parameters of the prediction mode by obtaining the inter filtering parameters when the filtering region (2530) is included in the second region.

[0333] In one embodiment of the present disclosure, when the filtering region (2530) is located at the boundary between the first region and the second region, the image decoding device (2000) may determine a filtering parameter using an inter lookup table determined according to an inter prediction mode and an intra lookup table determined according to an intra prediction mode. The image decoding device (2000) may determine a GPM filtering parameter as a weighted sum of the inter filtering parameter and the intra filtering parameter. The weight may be determined based on the number of samples included in the inter mode region of the block (2510) and the number of samples included in the intra mode region. For example, the GPM filtering parameter may be determined as in Equation 7.

[0334] In one embodiment of the present disclosure, the image decoding device (2000) may determine filtering parameters using a lookup table predetermined according to the GPM when the location of the filtering area (2540) is the boundary between the first area and the second area. The image decoding device (2000) may determine inter-filtering parameters and intra-filtering parameters as GPM filtering parameters when the location of the filtering area (2520) is the first area or the location of the filtering area (2540) is the second area, respectively.

[0335] In one embodiment of the present disclosure, the image decoding device (2000) can determine filtering parameters using a lookup table predetermined according to the GPM, regardless of the location of the filtering region. For example, the image decoding device (2000) can determine filtering parameters using a lookup table predetermined according to the GPM, even if the location of the filtering region (2520) is the first region or the location of the filtering region (2540) is the second region.

[0336] In one embodiment of the present disclosure, the image decoding device (2000) can obtain information about bidirectional filtering applied to a block from a bitstream. For example, the image decoding device (2000) can obtain information about a method for determining a GPM filtering parameter from the bitstream. The information about the method for determining the GPM filtering parameter may include index information indicating a type of lookup table. For example, the information about the method for determining the GPM filtering parameter may include index information indicating at least one of i) whether the GPM filtering parameter is determined as a CIIP filtering parameter, ii) whether the GPM filtering parameter is determined as a weighted sum of an inter-filtering parameter and an intra-filtering parameter, or iii) whether the GPM filtering parameter is determined using a lookup table predetermined for a GPM mode. The information about bidirectional filtering may be determined on a coding unit, a maximum coding unit, a slice unit, or a picture unit and transmitted through a bitstream.

[0337] FIG. 26 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents the IBC mode.

[0338] The video decoding device (2000) can identify that the prediction mode of the current block (2610) including the current sample indicates an intra block copy (IBC) mode. In one embodiment of the present disclosure, the current block (2610) can include a coding unit.

[0339] In one embodiment of the present disclosure, the image decoding device (2000) can determine a reference block (2620) when the prediction mode of the current block (2610) is IBC. For example, the image decoding device (2000) can determine the reference block (2620) from vector information representing the reference block (2620). The image decoding device (2000) can predict the current block (2610) based on the reference block (2620). For example, the image decoding device (2000) can predict the current block (2610) in the same way as the reference block (2620).

[0340] In one embodiment of the present disclosure, when the prediction mode indicates the IBC mode, the image decoding device (2000) may obtain at least one of a reference lookup table corresponding to the reference block (2620) or a lookup table predetermined according to the IBC mode.

[0341] In one embodiment of the present disclosure, the image decoding device (2000) can perform filtering according to the IBC mode. In one embodiment of the present disclosure, the IBC mode can include at least one of IBC merge, IBC AMVP, IBC-TM merge, IBC-TM AMVP, IBC-CIIP, or IBC-GPM.

[0342] In one embodiment of the present disclosure, the image decoding device (2000) can obtain the filtering parameters of the reference block (2620). The image decoding device (2000) can determine the filtering parameters of the reference block (2620) as the filtering parameters of the current block (2610).

[0343] In one embodiment of the present disclosure, the image decoding device (2000) can obtain a lookup table of a reference block (2620). The image decoding device (2000) can determine the lookup table of the reference block (2620) as the lookup table of the current block (2610). The image decoding device (2000) can determine the filtering parameters of the current block (2610) using the determined lookup table.

[0344] In one embodiment of the present disclosure, the image decoding device (2000) can obtain a predetermined lookup table according to the IBC mode. The IBC lookup table can be predetermined separately from the inter lookup table and the intra lookup table. The image decoding device (2000) can determine an offset value using the IBC lookup table. The process by which the image decoding device (2000) determines an offset value using the lookup table has been described above, and therefore, a detailed description thereof will be omitted.

[0345] In one embodiment of the present disclosure, the video decoding device (2000) can obtain information about bidirectional filtering applied to a block from a bitstream. For example, the video decoding device (2000) can obtain information about a method for determining an IBC filtering parameter from the bitstream. The information about the method for determining the IBC filtering parameter may include index information indicating a type of lookup table. For example, the information about the method for determining the IBC filtering parameter may include index information indicating at least one of i) whether the IBC filtering parameter is determined as a filtering parameter of a reference block, or ii) whether the IBC filtering parameter is determined using a lookup table predetermined for the IBC mode. The information about bidirectional filtering may be determined for a coding unit, a maximum coding unit, a slice unit, or a picture unit and transmitted through a bitstream.

[0346] FIG. 27 is a diagram for explaining filtering when the prediction mode according to one embodiment of the present disclosure represents a template matching prediction mode.

[0347] The video decoding device (2000) can identify that the prediction mode of the current block (2710) including the current sample indicates a template matching mode. In one embodiment of the present disclosure, the current block (2710) can include an encoding unit.

[0348] In one embodiment of the present disclosure, the image decoding device (2000) may determine a reference block (2720) when the current block (2710) is in template matching mode. For example, the image decoding device (2000) may determine a template area similar to the template area of ​​the current block (2710) and determine a reference block (2720) corresponding to the determined template area. The image decoding device (2000) may predict the current block (2710) based on the reference block (2720). For example, the image decoding device (2000) may predict the current block (2710) in the same manner as the reference block (2720).

[0349] In one embodiment of the present disclosure, when the prediction mode indicates a template matching mode, the image decoding device (2000) may obtain at least one of a reference lookup table corresponding to the reference block (2720) or a lookup table predetermined according to the template matching mode.

[0350] In one embodiment of the present disclosure, the image decoding device (2000) can perform filtering according to a template matching mode.

[0351] In one embodiment of the present disclosure, the image decoding device (2000) can obtain the filtering parameters of the reference block (2720). The image decoding device (2000) can determine the filtering parameters of the reference block (2720) as the filtering parameters of the current block (2710).

[0352] In one embodiment of the present disclosure, the image decoding device (2000) can obtain a lookup table of a reference block (2720). The image decoding device (2000) can determine the lookup table of the reference block (2720) as the lookup table of the current block (2710). The image decoding device (2000) can determine the filtering parameters of the current block (2710) using the determined lookup table.

[0353] In one embodiment of the present disclosure, the image decoding device (2000) can obtain a predetermined lookup table according to a template matching mode. The template matching lookup table can be predetermined separately from the inter lookup table and the intra lookup table. The image decoding device (2000) can determine an offset value using the template matching lookup table. The process by which the image decoding device (2000) determines an offset value using the lookup table has been described above, and thus is omitted.

[0354] In one embodiment of the present disclosure, the image decoding device (2000) can predict the current block (2720) using a plurality of reference blocks (2720). For example, the image decoding device (2000) can predict the current block (2720) using a weighted sum of the plurality of reference blocks (2720). The image decoding device (2000) can determine the filtering parameter of the current block using a weighted sum of the filtering parameters of the plurality of reference blocks (2720). The weights for the plurality of reference blocks (2720) in the filtering step may be the same as the weights for the plurality of reference blocks (2720) in the prediction step.

[0355] In one embodiment of the present disclosure, the image decoding device (2000) can obtain information about bidirectional filtering applied to a block from a bitstream. For example, the image decoding device (2000) can obtain information about a method for determining template matching filtering parameters from the bitstream. The information about the method for determining template matching filtering parameters may include index information indicating a type of lookup table. For example, the information about the method for determining template matching filtering parameters may include index information indicating at least one of i) whether the template matching filtering parameters are determined as filtering parameters of a reference block, or ii) whether the template matching filtering parameters are determined using a lookup table predetermined for a template matching mode. The information about bidirectional filtering may be determined for a coding unit, a maximum coding unit, a slice unit, or a picture unit and transmitted through a bitstream.

[0356] Fig. 28 is a block diagram showing the configuration of a loop filtering unit according to one embodiment of the present disclosure.

[0357] Referring to FIG. 28, the loop filtering unit (1940) can generate a filtered sample by performing filtering on the restored sample. In one embodiment of the present disclosure, the loop filtering unit (1940) can perform filtering on a chroma sample. In one embodiment of the present disclosure, the loop filtering unit (1940) can include a chroma bidirectional filtering unit (2810), a sample adaptive offset filtering unit (2820), and an adaptive loop filtering unit (2840).

[0358] In one embodiment of the present disclosure, the chroma bidirectional filtering unit (2810) may correspond to the bidirectional filtering unit (2110). In one embodiment of the present disclosure, the chroma bidirectional filtering unit (2110) may perform filtering on samples of chroma components. In one embodiment of the present disclosure, the sample adaptive offset filtering unit (2820) may correspond to the sample adaptive offset filtering unit (2120). In one embodiment of the present disclosure, the adaptive loop filtering unit (2840) may correspond to the adaptive loop filtering unit (2130). The loop filtering unit (1940) may further include a cross component sample adaptive offset (CCSAO) filtering unit (2830).

[0359] The CCSAO filtering unit (2830) calculates the CCSAO offset value (△I) for the current sample. CCSAO ) can be determined. The CCSAO filtering unit (2710) can determine the cross component offset. The CCSAO filtering unit (2830) can determine the CCSAO offset value (△I) using the luma sample and the chroma sample. CCSAO ) can be determined.

[0360] In one embodiment of the present disclosure, the chroma bidirectional filtering unit (2810) can perform filtering on the current sample using surrounding samples of the current sample. The chroma bidirectional filtering unit (2810) can perform filtering on samples of chroma components. The chroma bidirectional filtering unit (2810) can filter the BIF offset value (△I) for the current sample. BIF) can be determined. The offset value may include the amount of change in the current sample due to filtering. The chroma bidirectional filtering unit (2810) may determine the filtering strength based on the difference value between the current sample and surrounding samples. For example, the chroma bidirectional filtering unit (2810) may apply stronger filtering as the difference between the current sample and surrounding samples increases. That is, the chroma bidirectional filtering unit (2810) may have a large difference between the current sample before and after filtering.

[0361] In one embodiment of the present disclosure, the chroma bidirectional filtering unit (2810) can determine an offset value using a lookup table corresponding to chroma. The chroma bidirectional filtering unit (2810) can obtain a lookup table according to color components.

[0362] In one embodiment of the present disclosure, the chroma bidirectional filtering unit (2810) may perform filtering on chroma samples based on restored luma samples. The chroma bidirectional filtering unit (2810) may determine a lookup table to be applied to filtering of chroma samples based on the luma samples. The process of filtering chroma samples based on restored luma samples according to one embodiment of the present disclosure will be described in detail with reference to FIGS. 29 to 32.

[0363] In one embodiment of the present disclosure, the chroma bidirectional filtering unit (2810) may perform filtering on the first chroma sample based on the restored second chroma sample. The chroma bidirectional filtering unit (2810) may determine a lookup table to be applied to the filtering of the first chroma sample based on the second chroma sample. The process of filtering the first chroma sample based on the restored second chroma sample according to one embodiment of the present disclosure will be described in detail with reference to FIG. 33.

[0364] In one embodiment of the present disclosure, a filtered current sample may be determined using a BIF offset value determined by a chroma bidirectional filtering unit (2810), an SAO offset value determined by a sample adaptive offset filtering unit (2820), and a CCSAO offset value determined by a CCSAO filtering unit (2830). For example, the filtered current sample may be determined as the sum of the restored current sample, the BIF offset value, the SAO offset value, and the CCSAO offset value. The filtered current sample cannot be larger than the bit depth of the image.

[0365] In one embodiment of the present disclosure, the loop filtering unit (1940) may not include at least some of the chroma bidirectional filtering unit (2810), the sample adaptive offset filtering unit (2820), the CCSAO filtering unit (2830), and the adaptive loop filtering unit (2840). For example, the reconstructed sample may only undergo bidirectional filtering by the chroma bidirectional filtering unit (2810). Whether the chroma bidirectional filtering unit (2810), the sample adaptive offset filtering unit (2820), the CCSAO filtering unit (2830), and the adaptive loop filtering unit (2840) perform filtering can be obtained through the bitstream. Whether the chroma bidirectional filtering unit (2810), the sample adaptive offset filtering unit (2820), and the CCSAO filtering unit (2830) perform filtering can be determined using Rate Distortion Optimization (RDO). That is, whether or not to apply filtering can be determined through an optimization process using the quality of the image and the number of bits contained in the bitstream.

[0366] The video decoding device (2000) can obtain information indicating whether filtering is performed from a bitstream. The video decoding device (2000) can perform filtering based on the obtained information. In one embodiment of the present disclosure, the bidirectional filtering unit (2810), the sample adaptive offset filtering unit (2820), and the CCSAO filtering unit (2830) may be performed sequentially rather than in parallel.

[0367] In one embodiment of the present disclosure, the loop filtering unit (1970) may be configured to be identical to the loop filtering unit (1940). The loop filtering unit (1970) may include a bidirectional filtering unit, a sample adaptive offset filtering unit, and / or an adaptive loop filtering unit.

[0368] FIG. 29 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0369] Referring to FIG. 29, in step S2910, the video decoding device (2000) may obtain information regarding a chroma bidirectional filtering mode. For example, the video decoding device (2000) may obtain information regarding a method for determining a lookup table used in chroma bidirectional filtering from a bitstream. The information regarding the method for determining the lookup table may include index information indicating a method for determining the lookup table. For example, the information regarding the method for determining the lookup table may include index information indicating at least one of: i) a mode for determining the lookup table using a luma center sample, ii) a mode for determining the lookup table using a BIF offset value of a luma center sample, iii) a mode for determining the lookup table using a filtered luma center sample, or iv) a mode for determining the lookup table using a chroma center sample. The information regarding bidirectional filtering may be determined in units of coding units, maximum coding units, slice units, or picture units and transmitted through a bitstream. In one embodiment of the present disclosure, step S2910 may be omitted. If step S2910 is omitted, a lookup table may be determined using a predetermined mode.

[0370] In step S2920, the image decoding device (2000) can identify whether dual-tree partitioning is enabled. In one embodiment of the present disclosure, the image decoding device (2000) can determine a lookup table based on whether dual-tree partitioning is enabled. If dual-tree partitioning is enabled, the image decoding device (2000) can obtain a predetermined lookup table according to the dual-tree partitioning. In one embodiment of the present disclosure, step S2920 can be omitted. If step S2920 is omitted, a predetermined lookup table can be obtained.

[0371] In step S2930, the image decoding device (2000) can perform chroma bidirectional filtering. The image decoding device (2000) can perform chroma bidirectional filtering using a lookup table. The process by which the image decoding device (2000) performs bidirectional filtering has already been described, so a detailed description thereof will be omitted.

[0372] FIG. 30 is a drawing for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0373] Referring to FIG. 30, bidirectional filtering on a chroma sample can be performed using a luma sample. In one embodiment of the present disclosure, the chroma sample can include at least one of a sample of a Cb component or a sample of a Cr component.

[0374] In one embodiment of the present disclosure, the video decoding device (2000) can determine a lookup table for chroma samples using the restored luma sample. The video decoding device (2000) can determine a center luma sample corresponding to the current chroma sample for performing filtering. The video decoding device (2000) can determine a difference value between the center luma sample and surrounding luma samples.

[0375] In one embodiment of the present disclosure, the peripheral luma sample is a sample adjacent to the central luma sample and may have a shape of one of a 3 x 3 cross, a 3 x 3 square, a 3 x 3 diamond, or a 5 x 5 diamond. When the peripheral luma sample has a shape of a 3 x 3 cross, the peripheral luma sample may include samples positioned at the upper left, lower left, lower right, and upper right of the central luma sample. When the peripheral luma sample has a shape of a 3 x 3 square, the peripheral luma sample may include samples positioned at the upper left, left, lower left, lower right, right, upper right, and upper sides of the central luma sample. When the peripheral luma sample has a shape of a 3 x 3 diamond, the peripheral luma sample may include samples positioned at the left, lower, right, and upper sides of the central luma sample. If the shape of the surrounding luma sample is a 5 x 5 diamond, the surrounding luma sample can include 12 samples as described in FIG. 22.

[0376] In one embodiment of the present disclosure, the video decoding device (2000) may down-sample a luma block to determine a difference value between a central luma sample and surrounding luma samples. For example, when the color format is 4:2:2, the luma block may be downscaled by a factor of 2, and the difference value between the central luma sample of the downscaled luma block and the surrounding luma samples may be determined. For example, when the color format is 4:2:0, the luma block may be downscaled by a factor of 4, and the difference value between the central luma sample of the downscaled luma block and the surrounding luma samples may be determined. The video decoding device (2000) may determine a difference value between the central luma sample and the surrounding luma samples without performing down-sampling on the luma block. For example, the video decoding device (2000) may not perform down-scaling when the color format is 4:4:4. The video decoding device (2000) may not perform downscaling even when the color format is 4:2:2.

[0377] In one embodiment of the present disclosure, the video decoding device (2000) may determine a lookup table for filtering chroma samples using difference values. For example, the video decoding device (2000) may determine a chroma lookup table of chroma components using a luma center sample and a plurality of surrounding samples of the luma center sample. The video decoding device (2000) may determine an average or weighted sum of difference values ​​between the center luma sample and the surrounding luma samples. The video decoding device (2000) may determine a lookup table corresponding to the average or weighted sum of the difference values. In one embodiment of the present disclosure, the average or weighted sum of the difference values ​​may be quantized to be included in a predetermined range. For example, the average or weighted sum of the difference values ​​may be quantized to have one value from 0 to k-1.

[0378] In one embodiment of the present disclosure, the video decoding device (2000) can perform bidirectional filtering on a chroma sample using the determined lookup table. The video decoding device (2000) can determine a difference value between a current chroma sample and surrounding samples of the current chroma sample. The video decoding device (2000) can determine modifier values ​​corresponding to the difference values ​​using the determined lookup table. The video decoding device (2000) can determine a filtering parameter using the modifier values. The video decoding device (2000) can determine an offset value using the filtering parameter.

[0379] FIG. 31 is a drawing for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0380] Referring to FIG. 31, bidirectional filtering on a chroma sample can be performed using a BIF offset value of a luma sample. In one embodiment of the present disclosure, the chroma sample can include at least one of a sample of a Cb component or a sample of a Cr component.

[0381] The video decoding device (2000) can determine a luma sample corresponding to a current chroma sample for performing filtering. In one embodiment of the present disclosure, the video decoding device (2000) can obtain a BIF offset value of the luma sample. The video decoding device (2000) can determine a lookup table for a chroma sample using the BIF offset value of the luma sample. For example, the video decoding device (2000) can determine a chroma lookup table of a chroma component based on at least one of an offset value for a luma center sample or a filtered luma center sample.

[0382] In one embodiment of the present disclosure, a BIF offset value may be quantized to fall within a predetermined range. For example, the BIF offset value may be quantized to have a value between 0 and k-1. The image decoding device (2000) may obtain a lookup table corresponding to the quantized BIF offset value.

[0383] In one embodiment of the present disclosure, the video decoding device (2000) can perform bidirectional filtering on chroma samples using the determined lookup table. The video decoding device (2000) can determine chroma filtering parameters based on the lookup table. The video decoding device (2000) can determine a difference value between a current chroma sample and surrounding samples of the current chroma sample. The video decoding device (2000) can determine modifier values ​​corresponding to the difference values ​​using the determined lookup table. The video decoding device (2000) can determine a filtering parameter using the modifier values. The video decoding device (2000) can determine an offset value using the filtering parameter.

[0384] FIG. 32 is a diagram for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0385] Referring to FIG. 32, bidirectional filtering on a chroma sample can be performed using a luma sample on which BIF filtering has been performed. The image decoding device (2000) can perform bidirectional filtering on a chroma sample using a luma sample on which at least one of BIF filtering and SAO filtering has been performed. In one embodiment of the present disclosure, the chroma sample can include at least one of a sample of a Cb component or a sample of a Cr component.

[0386] The video decoding device (2000) can determine a luma sample corresponding to a current chroma sample for performing filtering. In one embodiment of the present disclosure, the video decoding device (2000) can obtain a BIF offset value of the luma sample. In one embodiment of the present disclosure, the video decoding device (2000) can obtain an SAO offset value of the luma sample. The video decoding device (2000) can obtain a filtered luma sample using at least one of the BIF offset value or the SAO offset value of the luma sample.

[0387] The video decoding device (2000) may determine a lookup table for a chroma sample using the filtered luma sample. For example, the video decoding device (2000) may determine a chroma lookup table of a chroma component based on at least one of an offset value for a luma center sample or a filtered luma center sample. The video decoding device (2000) may determine a difference value between a value of the filtered luma sample and a value of the center luma sample. In one embodiment of the present disclosure, the difference value between the value of the filtered luma sample and the value of the center luma sample may be quantized to be included in a predetermined range. For example, the difference value between the value of the filtered luma sample and the value of the center luma sample may be quantized to have one of 0 to k-1. The video decoding device (2000) may obtain a lookup table corresponding to the quantized difference value.

[0388] In one embodiment of the present disclosure, the video decoding device (2000) can perform bidirectional filtering on a chroma sample using the determined lookup table. The video decoding device (2000) can determine a difference value between a current chroma sample and surrounding samples of the current chroma sample. The video decoding device (2000) can determine modifier values ​​corresponding to the difference values ​​using the determined lookup table. The video decoding device (2000) can determine a filtering parameter using the modifier values. The video decoding device (2000) can determine an offset value using the filtering parameter.

[0389] FIG. 33 is a diagram for explaining a chroma bidirectional filter according to one embodiment of the present disclosure.

[0390] Referring to FIG. 33, bidirectional filtering on a chroma sample can be performed using another chroma sample. In one embodiment of the present disclosure, the chroma sample can include at least one of a sample of a Cb component or a sample of a Cr component. Bidirectional filtering on a Cb sample can be performed using a Cr sample.

[0391] In one embodiment of the present disclosure, the video decoding device (2000) may determine a lookup table for the first chroma sample using the restored second chroma sample. The video decoding device (2000) may determine a second chroma sample corresponding to the current second chroma sample for performing filtering. The video decoding device (2000) may determine a difference value between the second chroma sample and surrounding samples of the second chroma sample.

[0392] In one embodiment of the present disclosure, the surrounding samples of the second chroma sample are samples adjacent to the second chroma sample and may have one of a 3 x 3 cross, a 3 x 3 square, a 3 x 3 diamond, and a 5 x 5 diamond shape. When the shape of the surrounding samples of the second chroma sample is a 3 x 3 cross, the surrounding samples may include samples positioned at the upper left, lower left, lower right, and upper right of the second chroma sample. When the shape of the surrounding samples of the second chroma sample is a 3 x 3 square, the surrounding samples may include samples positioned at the upper left, left, lower left, lower right, right, upper right, and upper sides of the second chroma sample. When the shape of the surrounding samples of the second chroma sample is a 3 x 3 diamond, the surrounding samples may include samples positioned at the left, lower, right, and upper sides of the second chroma sample. If the shape of the surrounding sample of the second chroma sample is a 5 x 5 diamond, the surrounding sample may include 12 samples as described in FIG. 22.

[0393] In one embodiment of the present disclosure, the video decoding device (2000) may determine a lookup table for filtering chroma samples using difference values. The video decoding device (2000) may determine an average or a weighted sum of difference values ​​between a second chroma sample and surrounding samples. The video decoding device (2000) may determine a lookup table corresponding to the average or weighted sum of the difference values. In one embodiment of the present disclosure, the average or weighted sum of the difference values ​​may be quantized to be included in a predetermined range. For example, the average or weighted sum of the difference values ​​may be quantized to have one of a value from 0 to k-1.

[0394] In one embodiment of the present disclosure, the video decoding device (2000) can perform bidirectional filtering on the first chroma sample using the determined lookup table. The video decoding device (2000) can determine a difference value between the first chroma sample and surrounding samples of the first chroma sample. The video decoding device (2000) can determine modifier values ​​corresponding to the difference values ​​using the determined lookup table. The video decoding device (2000) can determine a filtering parameter using the modifier values. The video decoding device (2000) can determine an offset value using the filtering parameter.

[0395] In one embodiment of the present disclosure, the video decoding device (2000) can determine a lookup table for a second chroma sample using the reconstructed first chroma sample. The video decoding device (2000) can determine a lookup table for the second chroma sample using the first chroma sample in the same way as it determines a lookup table for the first chroma sample using the second chroma sample. The video decoding device (2000) can perform filtering on the second chroma sample using the lookup table determined using the first chroma sample.

[0396] FIG. 34 is a block diagram showing the configuration of an image encoding device according to one embodiment of the present disclosure.

[0397] Referring to FIG. 34, the image encoding device (3400) may include a prediction encoding unit (3410) and a generation unit (3420).

[0398] In one embodiment of the present disclosure, the prediction encoding unit (3410) and the generation unit (3420) may be implemented with at least one processor. In one embodiment of the present disclosure, the video encoding device (3400) may include a memory that stores input and output data of the prediction encoding unit (3410) and the generation unit (3420). The prediction encoding unit (3410) and the generation unit (3420) may operate according to instructions stored in the memory. In one embodiment of the present disclosure, the video encoding device (3400) may include a memory control unit that controls data input and output of the memory.

[0399] In one embodiment of the present disclosure, the prediction encoding unit (3410) may correspond to the prediction encoding unit (1915) illustrated in FIG. 19. In one embodiment of the present disclosure, the generation unit (3420) may correspond to the entropy encoding unit (1925) illustrated in FIG. 19.

[0400] The prediction encoding unit (3410) may determine the prediction mode of the current block. The current block may include at least one of a maximum coding unit, an encoding unit, a transformation unit, or a prediction unit divided from the current image (2200) to be encoded. In one embodiment of the present disclosure, the prediction mode of the current block may include an intra mode, an inter mode, a combined mode, a geometric partitioning mode, and / or an intra block copy. In one embodiment, the intra mode may include a template matching-based prediction 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 submode 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-based prediction mode may include a template matching-based 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 segmentation mode may include a mode that segments to include directionality within a block. The geometric segmentation mode may perform prediction using inter prediction or intra prediction for each segmented region of the block.

[0401] In one embodiment of the present disclosure, when the prediction mode of the current block is the CIIP mode, the prediction encoding unit (3410) can perform prediction on the current block by combining inter prediction and intra prediction. The prediction encoding unit (3410) can perform intra prediction according to the Planar mode. The prediction encoding unit (3410) can determine a motion vector of a reference block for the current block. The prediction encoding unit (3410) can perform inter prediction using the motion vector. The prediction encoding unit (3410) 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).

[0402] In one embodiment of the present disclosure, when the prediction mode of the current block is a geometric segmentation mode, the prediction encoding unit (3410) can perform prediction by segmenting the current block. The prediction encoding unit (3410) 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 (3410) can segment the current block based on the segmentation angle and the segmentation distance. The prediction encoding unit (3410) 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 (3410) 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.

[0403] In one embodiment of the present disclosure, the prediction encoding unit (3410) can determine the intra prediction mode of the current block when the prediction mode of the current block is the intra mode.

[0404] In one embodiment of the present disclosure, the prediction encoding unit (3410) can determine information about a block vector representing a reference block when the prediction mode of the current block is a block copy mode.

[0405] In one embodiment of the present disclosure, the prediction encoding unit (3410) 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.

[0406] In one embodiment of the present disclosure, when the prediction mode of the current block is block copy mode, the prediction encoding unit (3410) may determine a prediction block from a reference block. For example, the prediction encoding unit (3410) may determine a prediction block that is identical to the reference block or by performing filtering on the reference block.

[0407] 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 (3410) can reconstruct the current block using a reference block. The prediction encoding unit (3410) can determine a prediction block using the reference block.

[0408] The predictive encoding unit (3410) can perform deblocking filtering. The deblocking filter can improve image quality by smoothing edges between blocks.

[0409] The prediction encoding unit (3410) 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.

[0410] The predictive encoding unit (3410) 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.

[0411] 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.

[0412] In one embodiment of the present disclosure, the prediction encoding unit (3410) 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.

[0413] The generation unit (3420) can generate a bitstream including the encoding result of the image. The bitstream can include the encoding result for the current block.

[0414] In one embodiment of the present disclosure, the generation unit (3420) 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.

[0415] In one embodiment of the present disclosure, the generation unit (3420) can transmit the bitstream to the image decoding device (2000) via a network.

[0416] In one embodiment of the present disclosure, the generation unit (3420) 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.

[0417] The generation unit (3420) 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.

[0418] The generation unit (3420) can obtain bins included in the bitstream by entropy encoding syntax elements.

[0419] In one embodiment of the present disclosure, the bitstream may include information about a prediction mode of a current block within a current image.

[0420] 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.

[0421] In intra mode, a prediction block of a current block can be generated based on surrounding samples of the current block according to the intra prediction mode, assuming that there will be continuity between surrounding samples of the current block and samples within the current block. The prediction encoding unit (3410) according to an embodiment of the present disclosure can use not only surrounding samples of the current block included in the current image but also 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 samples of the current block using not only 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 (3400) 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 (3400) according to an embodiment of the present disclosure can improve compression efficiency by increasing the efficiency of intra prediction.

[0422] FIG. 35 is a flowchart illustrating an image encoding method according to one embodiment of the present disclosure.

[0423] Referring to FIG. 35, in step S3510, the image encoding device (3400) may obtain a current restoration block including a center sample using the prediction mode of the block. In one embodiment of the present disclosure, the current restoration block may include a block on which deblocking filtering has been performed.

[0424] In step S3520, the image encoding device (3400) may determine a plurality of difference values ​​between a central sample and a plurality of surrounding samples of the central sample. For example, the image encoding device (3400) may determine a difference value for each of the central sample and the surrounding samples. In one embodiment of the present disclosure, the image encoding device (3400) may determine a rounded difference value between the central sample and the surrounding samples.

[0425] In step S3530, the video encoding device (3400) may obtain at least one lookup table for filtering based on the prediction mode. In one embodiment of the present disclosure, the video encoding device (3400) may obtain at least one lookup table according to the prediction mode from among a plurality of lookup tables. For example, the video encoding device (3400) may obtain a lookup table corresponding to the intra block copy mode from among the plurality of lookup tables based on the prediction mode being the intra block copy mode.

[0426] In step S3540, the video encoding device (3400) may determine a plurality of modifier values ​​using a plurality of difference values ​​and at least one lookup table. In one embodiment of the present disclosure, the video encoding device (3400) may obtain a modifier value of the lookup table corresponding to each difference value. For example, the video encoding device (3400) may determine a difference value as an index value of the lookup table, and obtain an output value of the lookup table corresponding to the index value as a modifier value.

[0427] In step S3550, the image encoding device (3400) may determine at least one filtering parameter based on the sum of multiple modifier values. In one embodiment of the present disclosure, the number of filtering parameters may be determined according to the prediction mode.

[0428] In step S3560, the video encoding device (3400) may determine an offset value based on at least one filtering parameter. In one embodiment of the present disclosure, the larger the filtering parameter, the larger the offset value. In one embodiment of the present disclosure, the offset value may include the amount of change in the current sample value due to filtering.

[0429] In step S3570, the image encoding device (3400) may obtain a filtered sample using the center sample and offset value. In one embodiment of the present disclosure, the image encoding device (3400) may perform adaptive loop filtering using the filtered sample.

[0430] In one embodiment of the present disclosure, a video decoding method is provided. The video decoding method may include a step of obtaining a current reconstructed block including a center sample using a prediction mode of the block. The video decoding method may include a step of determining a plurality of difference values ​​between the center sample and a plurality of surrounding samples of the center sample. The video decoding method may include a step of obtaining at least one lookup table for filtering based on the prediction mode. The video decoding method may include a step of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table. The video decoding method may include a step of determining at least one filtering parameter based on a sum of the plurality of modifier values. The video decoding method may include a step of determining an offset value based on the at least one filtering parameter. The video decoding method may include a step of obtaining a filtered sample using the center sample and the offset value.

[0431] In one embodiment of the present disclosure, the step of determining at least one filtering parameter may include the step of determining a multiplier value based on at least one of a prediction mode, a width of a transform block including a center sample, or a height of the transform block. The step of determining at least one filtering parameter may include the step of determining at least one filtering parameter using the sum of the multiplier value and a plurality of modifier values.

[0432] In one embodiment of the present disclosure, when the prediction mode represents a Combined Inter and Intra Prediction mode (CIIP) mode or a Geometric Partitioning Mode (GPM), at least one lookup table may include at least one of an inter lookup table corresponding to the inter prediction mode, an intra lookup table corresponding to the intra prediction mode, or a lookup table predetermined according to the prediction mode.

[0433] In one embodiment of the present disclosure, when the lookup table includes an inter lookup table and an intra lookup table, the step of determining a plurality of modifier values ​​may include a step of determining a plurality of inter modifier values ​​using a plurality of difference values ​​and the inter lookup table. The step of determining a plurality of modifier values ​​may include a step of determining a plurality of intra modifier values ​​using a plurality of difference values ​​and the intra lookup table.

[0434] The step of obtaining at least one filtering parameter may include a step of obtaining an inter-filtering parameter based on a sum of a plurality of inter-modifier values. The step of obtaining at least one filtering parameter may include a step of obtaining an intra-filtering parameter based on a sum of a plurality of intra-modifier values. The step of determining an offset value may include a step of determining an offset value based on the inter-filtering parameter and the intra-filtering parameter.

[0435] In one embodiment of the present disclosure, when the prediction mode indicates an Intra Block Copy (IBC) mode or an Intra Template Matching prediction mode, at least one lookup table may include at least one of a lookup table used for filtering a reference block corresponding to the block or a lookup table predetermined according to the prediction mode.

[0436] In one embodiment of the present disclosure, a video decoding method may include a step of obtaining index information indicating the type of a lookup table from a bitstream. The video decoding method may include a step of determining a lookup table based on the index information.

[0437] In one embodiment of the present disclosure, the step of determining a plurality of difference values ​​may include the step of performing deblocking filtering on a current reconstructed block. The step of determining a plurality of difference values ​​may include the step of obtaining a plurality of difference values ​​between a deblocking-filtered center sample and a plurality of deblocking-filtered surrounding samples. The image decoding method may include the step of performing adaptive loop filtering on the filtered sample.

[0438] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, the video decoding method may include a step of determining a chroma lookup table of a chroma component using the luma center sample and a plurality of surrounding samples of the luma center sample. The video decoding method may include a step of obtaining a chroma filtering parameter based on the chroma lookup table of the chroma component. The video decoding method may include a step of obtaining a filtered chroma sample based on the chroma filtering parameter.

[0439] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, the video decoding method may include a step of determining a chroma lookup table of the chroma component based on at least one of an offset value or a filtered sample. The video decoding method may include a step of obtaining a chroma filtering parameter based on the chroma lookup table of the chroma component. The video decoding method may include a step of obtaining a filtered chroma sample based on the chroma filtering parameter.

[0440] In one embodiment of the present disclosure, when the center sample represents a first chroma center sample of a first chroma component, the video decoding method may include a step of determining a chroma lookup table of a second chroma component using the first chroma center sample and a plurality of surrounding samples of the first chroma center sample. The video decoding method may include a step of obtaining a chroma filtering parameter based on the chroma lookup table of the second chroma component. The video decoding method may include a step of obtaining a filtered chroma sample corresponding to a sample of the second chroma component based on the chroma filtering parameter.

[0441] In one embodiment of the present disclosure, a video encoding method is provided. The video encoding method may include a step of obtaining a current reconstructed block including a center sample using a prediction mode of a block. The video encoding method may include a step of determining a plurality of difference values ​​between a center sample and a plurality of surrounding samples of the center sample. The video encoding method may include a step of obtaining at least one lookup table for filtering based on the prediction mode. The video encoding method may include a step of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table. The video encoding method may include a step of determining at least one filtering parameter based on a sum of the plurality of modifier values. The video encoding method may include a step of determining an offset value based on the at least one filtering parameter. The video encoding method may include a step of obtaining a filtered sample using the center sample and the offset value.

[0442] In one embodiment of the present disclosure, the step of determining at least one filtering parameter may include the step of determining a multiplier value based on at least one of a prediction mode, a width of a transform block including a center sample, or a height of the transform block. The step of determining at least one filtering parameter may include the step of determining at least one filtering parameter using the sum of the multiplier value and a plurality of modifier values.

[0443] In one embodiment of the present disclosure, when the prediction mode represents a Combined Inter and Intra Prediction mode (CIIP) mode or a Geometric Partitioning Mode (GPM), at least one lookup table may include at least one of an inter lookup table corresponding to the inter prediction mode, an intra lookup table corresponding to the intra prediction mode, or a lookup table predetermined according to the prediction mode.

[0444] In one embodiment of the present disclosure, when the lookup table includes an inter lookup table and an intra lookup table, the step of determining a plurality of modifier values ​​may include a step of determining a plurality of inter modifier values ​​using a plurality of difference values ​​and the inter lookup table. The step of determining a plurality of modifier values ​​may include a step of determining a plurality of intra modifier values ​​using a plurality of difference values ​​and the intra lookup table.

[0445] The step of obtaining at least one filtering parameter may include a step of obtaining an inter-filtering parameter based on a sum of a plurality of inter-modifier values. The step of obtaining at least one filtering parameter may include a step of obtaining an intra-filtering parameter based on a sum of a plurality of intra-modifier values. The step of determining an offset value may include a step of determining an offset value based on the inter-filtering parameter and the intra-filtering parameter.

[0446] In one embodiment of the present disclosure, when the prediction mode indicates an Intra Block Copy (IBC) mode or an Intra Template Matching prediction mode, at least one lookup table may include at least one of a lookup table used for filtering a reference block corresponding to the block or a lookup table predetermined according to the prediction mode.

[0447] In one embodiment of the present disclosure, a video encoding method may include a step of obtaining index information indicating the type of a lookup table from a bitstream. The video encoding method may include a step of determining a lookup table based on the index information.

[0448] In one embodiment of the present disclosure, the step of determining a plurality of difference values ​​may include a step of performing deblocking filtering on a current reconstructed block. The step of determining a plurality of difference values ​​may include a step of obtaining a plurality of difference values ​​between a deblocking-filtered center sample and a plurality of deblocking-filtered surrounding samples. The video encoding method may include a step of performing adaptive loop filtering on the filtered sample.

[0449] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, the video encoding method may include a step of determining a chroma lookup table of a chroma component using the luma center sample and a plurality of surrounding samples of the luma center sample. The video encoding method may include a step of obtaining a chroma filtering parameter based on the chroma lookup table of the chroma component. The video encoding method may include a step of obtaining a filtered chroma sample based on the chroma filtering parameter.

[0450] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, the video encoding method may include a step of determining a chroma lookup table of the chroma component based on at least one of an offset value or a filtered sample. The video encoding method may include a step of obtaining a chroma filtering parameter based on the chroma lookup table of the chroma component. The video encoding method may include a step of obtaining a filtered chroma sample based on the chroma filtering parameter.

[0451] In one embodiment of the present disclosure, when the center sample represents a first chroma center sample of a first chroma component, the video encoding method may include a step of determining a chroma lookup table of a second chroma component using the first chroma center sample and a plurality of surrounding samples of the first chroma center sample. The video encoding method may include a step of obtaining a chroma filtering parameter based on the chroma lookup table of the second chroma component. The video encoding method may include a step of obtaining a filtered chroma sample corresponding to a sample of the second chroma component based on the chroma filtering parameter.

[0452] In one embodiment of the present disclosure, a computer-readable storage medium is provided that stores at least one of a bitstream encoded by the image encoding method or a bitstream decoded by the image decoding device.

[0453] In one embodiment of the present disclosure, an image decoding device is provided. The image decoding device may include at least one processor and a memory. The at least one processor may obtain a current reconstructed block including a center sample by executing one or more instructions stored in the memory, using a prediction mode of the block. The at least one processor may determine a plurality of difference values ​​between the center sample and a plurality of surrounding samples of the center sample. The at least one processor may obtain at least one lookup table for filtering based on the prediction mode. The at least one processor may determine a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table. The at least one processor may determine at least one filtering parameter based on a sum of the plurality of modifier values. The at least one processor may determine an offset value based on the at least one filtering parameter. The at least one processor may obtain a filtered sample using the center sample and the offset value.

[0454] In one embodiment of the present disclosure, at least one processor may determine a multiplier value based on at least one of a prediction mode, a width of a transform block including a center sample, or a height of the transform block. At least one processor may determine at least one filtering parameter using the sum of the multiplier value and a plurality of modifier values.

[0455] In one embodiment of the present disclosure, when the prediction mode represents a Combined Inter and Intra Prediction mode (CIIP) mode or a Geometric Partitioning Mode (GPM), at least one lookup table may include at least one of an inter lookup table corresponding to the inter prediction mode, an intra lookup table corresponding to the intra prediction mode, or a lookup table predetermined according to the prediction mode.

[0456] In one embodiment of the present disclosure, when the lookup table includes an inter lookup table and an intra lookup table, at least one processor can determine a plurality of inter modifier values ​​using a plurality of difference values ​​and the inter lookup table. At least one processor can determine a plurality of intra modifier values ​​using a plurality of difference values ​​and the intra lookup table.

[0457] At least one processor can obtain an inter-filtering parameter based on a sum of a plurality of inter-modifier values. At least one processor can obtain an intra-filtering parameter based on a sum of a plurality of intra-modifier values. At least one processor can determine an offset value based on the inter-filtering parameter and the intra-filtering parameter.

[0458] In one embodiment of the present disclosure, when the prediction mode indicates an Intra Block Copy (IBC) mode or an Intra Template Matching prediction mode, at least one lookup table may include at least one of a lookup table used for filtering a reference block corresponding to the block or a lookup table predetermined according to the prediction mode.

[0459] In one embodiment of the present disclosure, at least one processor can obtain index information indicating the type of lookup table from a bitstream. Based on the index information, the at least one processor can determine the lookup table.

[0460] In one embodiment of the present disclosure, at least one processor may perform deblocking filtering on a current reconstructed block. The at least one processor may obtain a plurality of difference values ​​between a deblocking-filtered center sample and a plurality of deblocking-filtered surrounding samples. The at least one processor may perform adaptive loop filtering on the filtered sample.

[0461] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, at least one processor may determine a chroma lookup table of a chroma component using the luma center sample and a plurality of surrounding samples of the luma center sample. The at least one processor may obtain a chroma filtering parameter based on the chroma lookup table of the chroma component. The at least one processor may obtain a filtered chroma sample based on the chroma filtering parameter.

[0462] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, at least one processor may determine a chroma lookup table of the chroma component based on at least one of an offset value or a filtered sample. At least one processor may obtain a chroma filtering parameter based on the chroma lookup table of the chroma component. At least one processor may obtain a filtered chroma sample based on the chroma filtering parameter.

[0463] In one embodiment of the present disclosure, when the center sample represents a first chroma center sample of a first chroma component, at least one processor can determine a chroma lookup table of a second chroma component using the first chroma center sample and a plurality of surrounding samples of the first chroma center sample. The at least one processor can obtain a chroma filtering parameter based on the chroma lookup table of the second chroma component. The at least one processor can obtain a filtered chroma sample corresponding to a sample of the second chroma component based on the chroma filtering parameter.

[0464] In one embodiment of the present disclosure, a video encoding device is provided. The video encoding device may include at least one processor and a memory. The at least one processor may obtain a current reconstructed block including a center sample by executing one or more instructions stored in the memory, using a prediction mode of the block. The at least one processor may determine a plurality of difference values ​​between the center sample and a plurality of surrounding samples of the center sample. The at least one processor may obtain at least one lookup table for filtering based on the prediction mode. The at least one processor may determine a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table. The at least one processor may determine at least one filtering parameter based on a sum of the plurality of modifier values. The at least one processor may determine an offset value based on the at least one filtering parameter. The at least one processor may obtain a filtered sample using the center sample and the offset value.

[0465] In one embodiment of the present disclosure, at least one processor may determine a multiplier value based on at least one of a prediction mode, a width of a transform block including a center sample, or a height of the transform block. At least one processor may determine at least one filtering parameter using the sum of the multiplier value and a plurality of modifier values.

[0466] In one embodiment of the present disclosure, when the prediction mode represents a Combined Inter and Intra Prediction mode (CIIP) mode or a Geometric Partitioning Mode (GPM), at least one lookup table may include at least one of an inter lookup table corresponding to the inter prediction mode, an intra lookup table corresponding to the intra prediction mode, or a lookup table predetermined according to the prediction mode.

[0467] In one embodiment of the present disclosure, when the lookup table includes an inter lookup table and an intra lookup table, at least one processor can determine a plurality of inter modifier values ​​using a plurality of difference values ​​and the inter lookup table. At least one processor can determine a plurality of intra modifier values ​​using a plurality of difference values ​​and the intra lookup table.

[0468] At least one processor can obtain an inter-filtering parameter based on a sum of a plurality of inter-modifier values. At least one processor can obtain an intra-filtering parameter based on a sum of a plurality of intra-modifier values. At least one processor can determine an offset value based on the inter-filtering parameter and the intra-filtering parameter.

[0469] In one embodiment of the present disclosure, when the prediction mode indicates an Intra Block Copy (IBC) mode or an Intra Template Matching prediction mode, at least one lookup table may include at least one of a lookup table used for filtering a reference block corresponding to the block or a lookup table predetermined according to the prediction mode.

[0470] In one embodiment of the present disclosure, at least one processor can obtain index information indicating the type of lookup table from a bitstream. Based on the index information, the at least one processor can determine the lookup table.

[0471] In one embodiment of the present disclosure, at least one processor may perform deblocking filtering on a current reconstructed block. The at least one processor may obtain a plurality of difference values ​​between a deblocking-filtered center sample and a plurality of deblocking-filtered surrounding samples. The at least one processor may perform adaptive loop filtering on the filtered sample.

[0472] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, at least one processor may determine a chroma lookup table of a chroma component using the luma center sample and a plurality of surrounding samples of the luma center sample. The at least one processor may obtain a chroma filtering parameter based on the chroma lookup table of the chroma component. The at least one processor may obtain a filtered chroma sample based on the chroma filtering parameter.

[0473] In one embodiment of the present disclosure, when the center sample represents a luma center sample of a luma component, at least one processor may determine a chroma lookup table of the chroma component based on at least one of an offset value or a filtered sample. At least one processor may obtain a chroma filtering parameter based on the chroma lookup table of the chroma component. At least one processor may obtain a filtered chroma sample based on the chroma filtering parameter.

[0474] In one embodiment of the present disclosure, when the center sample represents a first chroma center sample of a first chroma component, at least one processor can determine a chroma lookup table of a second chroma component using the first chroma center sample and a plurality of surrounding samples of the first chroma center sample. The at least one processor can obtain a chroma filtering parameter based on the chroma lookup table of the second chroma component. The at least one processor can obtain a filtered chroma sample corresponding to a sample of the second chroma component based on the chroma filtering parameter.

[0475] The image decoding method, image decoding device, image encoding method, and image encoding device according to one embodiment of the present disclosure can improve the quality of a restored image by improving the performance of filtering by determining filtering parameters corresponding to a prediction mode more detailed than the inter prediction mode and the intra prediction mode. However, the technical effect of the image decoding method according to one embodiment of the present disclosure is not limited to the contents described above, and may include technical features generated according to the present disclosure.

[0476] The image decoding method, image decoding device, image encoding method, and image encoding device according to one embodiment of the present disclosure can improve the performance of filtering and thus the quality of restored images by determining filtering parameters for chroma samples using information on samples that are not targets of filtering. However, the technical effects of the image decoding method according to one embodiment of the present disclosure are not limited to the contents described above, and may include technical features generated according to the present disclosure.

[0477] A device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, the term "non-transitory storage medium" simply means a tangible device that does not contain signals (e.g., electromagnetic waves). This term does not distinguish between cases where data is permanently stored in the storage medium and cases where data is temporarily stored. For example, a "non-transitory storage medium" may include a buffer in which data is temporarily stored.

[0478] According to one embodiment, the method according to various embodiments disclosed in the present document may be provided as included in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) through an application store or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored or temporarily generated in a machine-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

Claims

1. In the video decryption method, A step (S2310) of obtaining a current restoration block including a center sample by using the prediction mode of the block; A step (S2320) of determining a plurality of difference values ​​between the central sample and a plurality of surrounding samples of the central sample; A step (S2330) of obtaining at least one lookup table for filtering based on the above prediction mode; A step (S2340) of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table; A step (S2350) of determining at least one filtering parameter based on the sum of the above multiple modifier values; Step (S2360) of determining an offset value based on at least one of the above filtering parameters; and A method comprising a step (S2370) of obtaining a filtered sample by using the above center sample and the above offset value.

2. In paragraph 1, The step (S2350) of determining at least one filtering parameter is: determining a multiplier value based on at least one of the prediction mode, the width of the transform block including the center sample, or the height of the transform block; and A method comprising the step of determining the at least one filtering parameter using the sum of the multiplier value and the plurality of modifier values.

3. In any one of paragraphs 1 and 2, A method wherein, when the above prediction mode represents a Combined Inter and Intra Prediction mode (CIIP) mode or a Geometric Partitioning Mode (GPM), the at least one lookup table includes at least one of an inter lookup table corresponding to an inter prediction mode, an intra lookup table corresponding to an intra prediction mode, or a lookup table predetermined according to the prediction mode.

4. In paragraph 3, If the above lookup table includes an inter lookup table and an intra lookup table, The step (S2340) of determining the above multiple modifier values ​​is A step of determining a plurality of inter modifier values ​​using the plurality of difference values ​​and the inter lookup table; and A step of determining a plurality of intra modifier values ​​using the plurality of difference values ​​and the intra lookup table, The step (S2350) of obtaining at least one filtering parameter is: A step of obtaining an inter filtering parameter based on the sum of the above multiple inter modifier values; and A step of obtaining an intra filtering parameter based on a sum of the above multiple intra modifier values, The step (S2360) of determining the above offset value is A method comprising the step of determining an offset value based on the inter-filtering parameter and the intra-filtering parameter.

5. In any one of paragraphs 1 to 4, A method wherein, when the above prediction mode indicates an IBC (Intra Block Copy) mode or an intra template matching prediction mode, the at least one lookup table includes at least one of a lookup table used for filtering a reference block corresponding to the block or a lookup table predetermined according to the prediction mode.

6. In any one of paragraphs 1 to 5, A step of obtaining index information indicating the type of the above lookup table from a bitstream; and A method comprising the step of determining the lookup table based on the index information.

7. In any one of paragraphs 1 to 6, The step (S2330) of determining the above plural difference values ​​is A step of performing deblocking filtering on the current restoration block; and Comprising a step of obtaining the plurality of difference values ​​between the deblocking filtered central sample and the plurality of deblocking filtered peripheral samples, A method further comprising the step of performing adaptive loop filtering on the filtered sample.

8. In any one of paragraphs 1 to 7, If the above center sample represents the luma center sample of the luma component, A step of determining a chroma lookup table of chroma components using the luma center sample and a plurality of surrounding samples of the luma center sample; A step of obtaining chroma filtering parameters based on the chroma lookup table of the above chroma components; and A method comprising the step of obtaining a filtered chroma sample based on the above chroma filtering parameters.

9. In any one of paragraphs 1 to 8, If the above center sample represents the luma center sample of the luma component, determining a chroma lookup table of chroma components based on at least one of the offset values ​​or the filtered samples; A step of obtaining chroma filtering parameters based on the chroma lookup table of the above chroma components; A method comprising the step of obtaining a filtered chroma sample based on the above chroma filtering parameters.

10. In any one of paragraphs 1 to 9, If the above center sample represents the first chroma center sample of the first chroma component, A step of determining a chroma lookup table of a second chroma component using the first chroma center sample and a plurality of surrounding samples of the first chroma center sample; A step of obtaining chroma filtering parameters based on the chroma lookup table of the second chroma component; A method comprising the step of obtaining a filtered chroma sample corresponding to a sample of a second chroma component based on the above chroma filtering parameters.

11. In the video encoding method, A step (S3510) of obtaining a current restoration block including a center sample by using the prediction mode of the block; A step (S3520) of determining a plurality of difference values ​​between the central sample and a plurality of surrounding samples of the central sample; A step (S3530) of obtaining at least one lookup table for filtering based on the above prediction mode; A step (S3540) of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table; A step (S3550) of determining at least one filtering parameter based on the sum of the above multiple modifier values; Step (S3560) of determining an offset value based on at least one of the above filtering parameters; and A method comprising a step (S3570) of obtaining a filtered sample by using the above center sample and the above offset value.

12. In paragraph 11, The step (S3550) of determining at least one filtering parameter is: a step of determining a multiplier value based on at least one of the prediction mode, the width of the transform block including the center sample, or the height of the transform block; and A method comprising the step of determining the at least one filtering parameter using the sum of the multiplier value and the plurality of modifier values.

13. In any one of paragraphs 11 to 12, A method wherein, when the above prediction mode represents a Combined Inter and Intra Prediction mode (CIIP) mode or a Geometric Partitioning Mode (GPM), the at least one lookup table includes at least one of an inter lookup table corresponding to an inter prediction mode, an intra lookup table corresponding to an intra prediction mode, or a lookup table predetermined according to the prediction mode.

14. In paragraph 13, If the above lookup table includes an inter lookup table and an intra lookup table, The step (S3540) of determining the above multiple modifier values ​​is A step of determining a plurality of inter modifier values ​​using the plurality of difference values ​​and the inter lookup table; and A step of determining a plurality of intra modifier values ​​using the plurality of difference values ​​and the intra lookup table, The step (S3550) of obtaining at least one filtering parameter is: A step of obtaining an inter filtering parameter based on the sum of the above multiple inter modifier values; and A step of obtaining an intra filtering parameter based on a sum of the above multiple intra modifier values, The step (S3560) of determining the above offset value is A method comprising the step of determining an offset value based on the inter-filtering parameter and the intra-filtering parameter.

15. A step of obtaining a current restoration block including a center sample by using the prediction mode of the block; A step of determining a plurality of differences between the central sample and a plurality of surrounding samples of the central sample; A step of obtaining at least one look-up table for filtering based on the above prediction mode; A step of determining a plurality of modifier values ​​using the plurality of difference values ​​and the at least one lookup table; and A step of determining at least one filtering parameter based on a sum of the plurality of modifier values; determining an offset value based on at least one of the filtering parameters; and A computer-readable storage medium storing a bitstream encoded by an image encoding method, the method comprising the step of obtaining a filtered sample using the center sample and the offset value.

Images