Method and device for encoding image and method and device for decoding image on basis of sub-block

Abstract

A method of decoding an image according to an embodiment includes: when a size of a current block in the image is equal to or greater than a certain size, determining a candidate list including, as a candidate, a first reference block indicated by a temporal motion vector; when the first reference block is selected from among candidates included in the candidate list, determining motion vectors of sub-blocks in the current block by using motion vectors obtained from the first reference block; and reconstructing the current block based on sample values of a second reference block indicated by the motion vectors of the sub-blocks.

Description

Method and device for decoding an image based on a sub-block, and encoding method and device

[0001] The present disclosure relates to the field of image encoding and decoding. More specifically, the present disclosure relates to a method and device for encoding an image based on sub-blocks within a block, and a method and device for decoding the image.

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

[0003] Inter prediction is a method of compressing images by removing temporal redundancy between images, and motion estimation coding is a representative example. Motion estimation coding predicts blocks of the current image using at least one reference image. A reference block most similar to the current block can be searched for within a predetermined search range using a predetermined evaluation function. 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 and encode a residual block. At this time, in order to perform prediction more accurately, interpolation can be performed on the reference image to generate pixels of sub-pel units smaller than integer pel units, and inter prediction can be performed based on the pixels of the sub-pel units.

[0004] Codecs such as H.264 AVC (Advanced Video Coding) and HEVC (High Efficiency Video Coding) use the motion vectors of previously encoded blocks adjacent to the current block or blocks included in a previously encoded image as the prediction motion vector of the current block to predict the motion vector of the current block. The differential motion vector, which is the difference between the motion vector of the current block and the predicted motion vector, is signaled to the decoder side through a predetermined method.

[0005] A video decoding device and method according to one embodiment, and a video encoding device and method have as their technical task the accurate restoration of motion information of a block within an image.

[0006] In addition, the image decoding device and method according to one embodiment and the image encoding device and method have as a technical task the reduction of the complexity of image encoding and decoding by limiting the size of a block.

[0007] A method for decoding an image according to one embodiment may include: determining a candidate list including a first reference block indicated by a temporal motion vector as a candidate when a size of a current block in the image is greater than or equal to a predetermined size; determining motion vectors of sub-blocks in the current block using motion vectors obtained from the first reference block when the first reference block is selected from among candidates included in the candidate list; and restoring the current block based on sample values ​​of a second reference block indicated by the motion vectors of the sub-blocks.

[0008] An image decoding device and method according to one embodiment, and an image encoding device and method can accurately restore motion information of a block in an image.

[0009] In addition, the image decoding device and method and the image encoding device and method according to one embodiment can reduce the complexity of image encoding and decoding by limiting the size of a block.

[0010] However, the effects that can be achieved by the image decoding device and method and the image encoding device and method according to one embodiment are not limited to those mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0011] To facilitate a more thorough understanding of the drawings cited herein, a brief description of each drawing is provided.

[0012] FIG. 1 is a block diagram of an image decoding device according to one embodiment.

[0013] FIG. 2 is a block diagram of an image encoding device according to one embodiment.

[0014] FIG. 3 illustrates a process in which an image decoding device divides a current encoding unit to determine at least one encoding unit according to one embodiment.

[0015] FIG. 4 illustrates a process in which an image decoding device determines at least one encoding unit by dividing a non-square encoding unit according to one embodiment.

[0016] FIG. 5 illustrates a process in which an image decoding device divides an encoding unit based on at least one of block shape information and division shape mode information, according to one embodiment.

[0017] FIG. 6 illustrates a method for a video decoding device to determine a predetermined encoding unit among an odd number of encoding units according to one embodiment.

[0018] FIG. 7 illustrates the order in which multiple encoding units are processed when an image decoding device determines multiple encoding units by dividing a current encoding unit according to one embodiment.

[0019] FIG. 8 illustrates a process for 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.

[0020] FIG. 9 illustrates a process in which an image decoding device divides a first encoding unit to determine at least one encoding unit according to one embodiment.

[0021] FIG. 10 illustrates that, according to one embodiment, a video decoding device 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 satisfies a predetermined condition.

[0022] FIG. 11 illustrates a process of a video decoding device dividing 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.

[0023] FIG. 12 illustrates that, according to one embodiment, the processing order between multiple encoding units may vary depending on the process of dividing the encoding units.

[0024] 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.

[0025] 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.

[0026] FIG. 15 illustrates that a plurality of encoding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment.

[0027] FIG. 16 illustrates a processing block that serves as a criterion for determining the order of determination of reference coding units included in a picture according to one embodiment.

[0028] FIG. 17 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.

[0029] FIG. 18 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.

[0030] FIG. 19 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.

[0031] Figure 20 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0032] Fig. 21 is a block diagram illustrating the configuration of an image decoding device according to one embodiment.

[0033] Figure 22 is a diagram showing a candidate list according to one embodiment.

[0034] Figure 23 is a diagram illustrating a first reference block pointed to by a temporal motion vector.

[0035] Figure 24 is a diagram for explaining a method for determining motion vectors of sub-blocks within the current block.

[0036] Figure 25 is a drawing to explain the restoration process of the current block.

[0037] Figure 26 is an exemplary drawing showing the locations of surrounding blocks adjacent to the current block.

[0038] Figure 27 is an exemplary drawing showing the positions of surrounding blocks according to the shape of the current block.

[0039] Figure 28 is a drawing for explaining a deblocking process according to one embodiment.

[0040] Figure 29 is a flowchart for explaining a method for decoding an image according to one embodiment.

[0041] Fig. 30 is a block diagram illustrating a configuration of an image encoding device according to one embodiment.

[0042] FIG. 31 is a drawing for explaining an image encoding method according to one embodiment.

[0043] A method for decoding an image according to one embodiment may include: determining a candidate list including a first reference block indicated by a temporal motion vector as a candidate when a size of a current block in the image is greater than or equal to a predetermined size; determining motion vectors of sub-blocks in the current block using motion vectors obtained from the first reference block when the first reference block is selected from among candidates included in the candidate list; and restoring the current block based on sample values ​​of a second reference block indicated by the motion vectors of the sub-blocks.

[0044] The method for decoding the above image may further include a step of obtaining a filtered current block by deblocking filtering sample values ​​of the sub-blocks based on a boundary between the sub-blocks within the restored current block.

[0045] The step of determining the candidate list may include a step of determining the candidate list when the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of a candidate included in the candidate list.

[0046] The method for decoding the above image may further include a step of determining a motion vector of a surrounding block spatially adjacent to the current block as the temporal motion vector.

[0047] The step of determining the temporal motion vector may include a step of determining a predetermined motion vector as the temporal motion vector when there is no availability of the surrounding block.

[0048] The step of determining the temporal motion vector may include a step of determining a predetermined motion vector instead of the motion vector of the surrounding block as the temporal motion vector when the image indicated by the motion vector of the surrounding block is different from a predetermined collocated image.

[0049] The method for decoding the above image may further include a step of determining a predetermined motion vector as the temporal motion vector when the current block is a predetermined block unit.

[0050] The method for decoding the above image may further include a step of determining a candidate list including blocks other than the first reference block as candidates when the size of the current block is smaller than the predetermined size.

[0051] Among the candidates included in the above candidate list, an index with the smallest value can be assigned to the first reference block.

[0052] The method for decoding the above image may further include a step of determining a motion vector corresponding to a center sample among the samples of the first reference block as a representative motion vector.

[0053] The method for decoding the above image may further include the step of determining sub-regions corresponding to the sub-blocks in the first reference block; and the step of determining a motion vector of a sub-region from which a motion vector cannot be obtained among the sub-regions as the representative motion vector.

[0054] The step of determining the candidate list may include a step of determining the candidate list including blocks other than the first reference block as candidates when there is no motion vector corresponding to a center sample among the samples of the first reference block.

[0055] According to one embodiment, a video decoding device may include a motion information determining unit that determines a candidate list including a first reference block indicated by a temporal motion vector as a candidate when a size of a current block in the video is greater than or equal to a predetermined size, and, when the first reference block is selected from among candidates included in the candidate list, determines motion vectors of sub-blocks in the current block using motion vectors obtained from the first reference block; and a restoration unit that restores the current block based on sample values ​​of a second reference block indicated by the motion vectors of the sub-blocks.

[0056] A method for encoding an image according to one embodiment includes the steps of: determining a candidate list including a first reference block indicated by a temporal motion vector as a candidate when a size of a current block in the image is greater than or equal to a predetermined size; selecting a candidate used to determine a motion vector of the current block from among candidates included in the candidate list; and generating a bitstream including information indicating the selected candidate, wherein motion vectors obtained from the first reference block can be used to determine motion vectors of sub-blocks in the current block.

[0057] The present disclosure may be subject to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments of the present disclosure, and it should be understood that the present disclosure encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the various embodiments.

[0058] 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 throughout the description of the specification are merely identifiers used to distinguish one component from another.

[0059] Additionally, in this specification, when a component is referred to as being “connected” or “connected” to another component, it should be understood that the component may be directly connected or connected to the other component, but may also be connected or connected via another component in between, unless there is a specific description to the contrary.

[0060] In addition, components expressed as 'unit', 'module', etc. in this specification may be two or more components combined into one component, or one component may be divided into two or more components with more detailed functions. 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 of course, some of the main functions performed by each component may be performed exclusively by other components.

[0061] Additionally, in this specification, 'image' or 'picture' may refer to a still image of a video or a moving image, i.e., the video itself.

[0062] Additionally, in this specification, "sample" or "signal" refers to data assigned to a sampling location in an image and is the subject of processing. For example, pixel values ​​in a spatial domain image or transform coefficients in a transform domain may be samples. A unit containing at least one such sample may be defined as a block.

[0063] Hereinafter, with reference to FIGS. 1 to 20, an image encoding method and device based on a tree-structured encoding unit and a transformation unit, and an image decoding method and device are disclosed according to an embodiment. Each of the image encoding device (200) and the image decoding device (100) to be described with reference to FIGS. 1 to 20 may include each of the image encoding device (2900) and the image decoding device (2100) to be described with reference to FIGS. 21 to 31.

[0064] FIG. 1 illustrates a block diagram of an image decoding device (100) according to one embodiment.

[0065] 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.

[0066] 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.

[0067] To describe in detail the operation of the video decoding device (100), the bitstream acquisition unit (110) can receive a bitstream.

[0068] 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.

[0069] Below, the division of encoding units according to one embodiment of the present disclosure is described in detail.

[0070] 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 Coding Tree Units (CTUs). The concept that contrasts with a Coding Tree Block (CTB) is a Coding Tree Block (CTB).

[0071] A maximum coding block (CTB) is an N x N block containing N x N samples (where N is an integer). Each color component can be divided into one or more maximum coding blocks.

[0072] 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 the picture and samples of the picture.

[0073] A single maximum coding block (CTB) can be partitioned into M x N coding blocks containing M x N samples (M, N are integers).

[0074] 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 samples. 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 the picture and samples of the picture.

[0075] 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.

[0076] 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.

[0077] 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 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, 128 x 128, and 256 x 256.

[0078] 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.

[0079] 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. In contrast, the maximum size of a 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 32 x 32, and the maximum size of a luma coding block capable of ternary splitting in a P picture or a B picture may be 64 x 64.

[0080] 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.

[0081] 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.

[0082] 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 whether it will be binary / ternary split.

[0083] 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.

[0084] 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.

[0085] 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 ternaries in the horizontal direction can be determined as 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 ternaries in the vertical direction can be determined as ternary vertical split (SPLIT_BT_VER).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The shape and size of the transformation block and the prediction block may be unrelated.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The block shape may include 4N x 4N, 4N x 2N, 2N x 4N, 4N x N, N x 4N, 32N x N, N x 32N, 16N x N, N x 16N, 8N x N or N x 8N, 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.

[0094] 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 4N x 4N), 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.

[0095] When the width and height of the encoding unit are different (i.e., when the block shape of the encoding unit is 4N x 2N, 2N x 4N, 4N x N, N x 4N, 32N x N, N x 32N, 16N x N, N x 16N, 8N x N, or N x 8N), 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.

[0096] According to one embodiment, 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.

[0097] The image decoding device (100) can obtain the split 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 split shape mode information based on the block shape information. The image decoding device (100) can determine the pre-agreed split shape mode information for the maximum coding unit or the minimum coding unit. For example, the image decoding device (100) can determine the split shape mode information for the maximum coding unit as quad split. In addition, the image decoding device (100) can determine the split 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 256 x 256. The image decoding device (100) can determine the pre-agreed split 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 128 x 128 from a maximum coding unit of size 256 x 256 based on the splitting mode information. In addition, the image decoding device (100) can determine the size of the minimum coding unit as 4 x 4. The image decoding device (100) can obtain splitting mode information indicating "not splitting" for the minimum coding unit.

[0098] According to one embodiment, 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.

[0099] Referring to FIG. 3, the image decoding device (100) may determine two coding units (310b) by vertically dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is vertically divided, according to an embodiment. The image decoding device (100) may determine two coding units (310c) by horizontally dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is horizontally divided, according to an embodiment. The image decoding device (100) may determine four coding units (310d) by vertically and horizontally dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is vertically and horizontally divided, according to an embodiment. The image decoding device (100) may determine three coding units (310e) by vertically dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is ternary divided, according to an embodiment. The image decoding device (100) can determine three coding units (310f) into which the current coding unit (300) is horizontally divided based on the division shape mode information indicating that the ternary division is horizontally divided. However, the division shapes into which a square coding unit can be divided should not be interpreted as being limited to the above-described shapes, and may include various shapes that can be indicated by the division shape mode information. Specified division shapes into which a square coding unit is divided will be specifically described below through various embodiments.

[0100] 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.

[0101] According to one embodiment, the image decoding device (100) may utilize block shape information indicating that the current encoding unit is non-square. The image decoding device (100) may determine whether to not split the current non-square 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. The predetermined splitting method by which a non-square encoding unit is split will be described in detail through various embodiments below.

[0102] According to one embodiment, the image decoding device (100) may determine a form in which an encoding unit is split using split form mode information, and in this case, the split form mode information may indicate the number of at least one encoding unit generated by splitting the encoding unit. Referring to FIG. 4, when the split form mode information indicates that the current encoding unit (400 or 450) is split into two encoding units, the image decoding device (100) may split the current encoding unit (400 or 450) based on the split form mode information to determine two encoding units (420a, 420b, or 470a, 470b) included in the current encoding unit.

[0103] According to one embodiment, 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.

[0104] According to one embodiment, if the split shape mode information indicates that the coding unit is split into an odd number of blocks (ternary splitting), the image decoding device (100) may determine an odd number of coding units included in the current coding unit (400 or 450). For example, if the split shape mode information indicates that the current coding unit (400 or 450) is split into three coding units, the image decoding device (100) may split the current coding unit (400 or 450) into three coding units (430a, 430b, 430c, 480a, 480b, 480c).

[0105] According to one embodiment, 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 block shape information may be in the horizontal direction because the length of the width is longer than the length of the height. When the ratio of the width and height is 1:4, the block shape information may be in the vertical direction because the length of the width is shorter than the length of the height. 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).

[0106] According to one embodiment, 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.

[0107] According to one embodiment, 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.

[0108] 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.

[0109] According to one embodiment, 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. According to one embodiment, when the split shape mode information indicates splitting the first coding unit (500) in the horizontal direction, 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 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. Hereinafter, the relationship between the first coding unit, the second coding unit, and the third coding unit used may be understood to follow the above-described characteristics.

[0110] According to one embodiment, the image decoding device (100) may determine to split or not split the determined second encoding unit (510) into encoding units based on the split shape mode information. Referring to FIG. 5, the image decoding device (100) may split the first encoding unit (500) based on the split 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, 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.

[0111] 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 an embodiment, the square third coding unit (520c), 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. Methods that can be used for recursive division of coding units will be described later through various embodiments.

[0112] According to one embodiment, the image decoding device (100) may split each of the third encoding units (520a, 520b, 520c, 520d, etc.) into encoding units based on the split shape mode information. In addition, the image decoding device (100) may determine not to split the second encoding unit (510) based on the split shape mode information. According to one embodiment, 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.

[0113] 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).

[0114] According to one embodiment, 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.

[0115] 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.

[0116] 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.

[0117] According to one embodiment, 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 descriptions of such methods will be provided later through various embodiments.

[0118] According to one embodiment, the image decoding device (100) can divide the current encoding unit into a plurality of encoding units and determine an encoding unit at a predetermined position.

[0119] According to one embodiment, 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 divide 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).

[0120] According to one embodiment, 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, 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.

[0121] According to one embodiment, information indicating the position of the sample (630a) at the upper left of the upper encoding unit (620a) may represent (xa, ya) coordinates, information indicating the position of the sample (530b) at the upper left of the middle encoding unit (620b) may represent (xb, yb) coordinates, and information indicating the position of the sample (630c) at the upper left of the lower encoding unit (620c) may represent (xc, yc) coordinates. The image decoding device (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.

[0122] According to one embodiment, the image decoding device (100) may 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) may select an encoding unit (620b) having a different size from among the encoding units (620a, 620b, 620c).

[0123] According to one embodiment, the image decoding device (100) may 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, 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, 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, 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.

[0124] 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).

[0125] According to one embodiment, the image decoding device (100) may determine the width of the left encoding unit (660a) as xe-xd. The image decoding device (100) may determine the height of the left encoding unit (660a) as the height of the current encoding unit (650). According to one embodiment, the image decoding device (100) may determine the width of the middle encoding unit (660b) as xf-xe. The image decoding device (100) may determine the height of the middle encoding unit (660b) as the height of the current encoding unit (600). According to one embodiment, the image decoding device (100) may determine the width or height of the right encoding unit (660c) using the width or height of the current encoding unit (650) and the widths and heights of the left encoding unit (660a) and the middle encoding 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.

[0126] 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.

[0127] According to one embodiment, the image decoding device (100) may select an encoding unit at a predetermined position from among an odd number of encoding units determined by splitting the current encoding unit, taking into consideration the shape of the current encoding unit. For example, if the current encoding unit has a non-square shape in which the width is longer than the height, the image decoding device (100) may determine an encoding unit at a predetermined position in the horizontal direction. That is, the image decoding device (100) may determine one of the encoding units whose positions vary in the horizontal direction and place a restriction on the corresponding encoding unit. If the current encoding unit has a non-square shape in which the height is longer than the width, the image decoding device (100) may determine an encoding unit at a predetermined position in the vertical direction. That is, the image decoding device (100) may determine one of the encoding units whose positions vary in the vertical direction and place a restriction on the corresponding encoding unit.

[0128] According to one embodiment, the image decoding device (100) may use information indicating the positions of each of the even-numbered coding units to determine the coding unit at a predetermined position among the even-numbered coding units. The image decoding device (100) may determine the even-numbered coding units by dividing the current coding unit (binary dividing) and may determine the coding unit at a predetermined position using information about the positions of the even-numbered coding units. A specific process for this may be a process corresponding to the process of determining the coding unit at a predetermined position (e.g., the center position) among the odd-numbered coding units described above in FIG. 6, and thus will be omitted.

[0129] According to one embodiment, 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.

[0130] 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.

[0131] According to one embodiment, 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 device (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 one embodiment, 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 such a 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.

[0132] According to one embodiment, 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, the 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.

[0133] According to one embodiment, when the image decoding device (100) divides the current encoding unit into a plurality of encoding units, the image decoding device (100) may use the split shape mode information to determine the encoding unit at a predetermined position among the plurality of encoding units. According to one embodiment, 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 the 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 the 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.

[0134] According to one embodiment, 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).

[0135] FIG. 7 illustrates the order in which multiple encoding units are processed when an image decoding device (100) divides a current encoding unit to determine multiple encoding units according to one embodiment.

[0136] According to one embodiment, 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).

[0137] 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.

[0138] According to one embodiment, the image decoding device (100) can recursively split the encoding units. Referring to FIG. 7, the image decoding device (100) can split the 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).

[0139] According to one embodiment, 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.

[0140] According to one embodiment, the processing order of the 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 device (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.

[0141] FIG. 8 illustrates a process for 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 invention.

[0142] According to one embodiment, 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, 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).

[0143] According to one embodiment, 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.

[0144] According to one embodiment, the image decoding device (100) may 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 may 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 an embodiment, the image decoding device (100) may place a predetermined restriction on an encoding unit at a predetermined position among the divided encoding units when the encoding unit is divided into an odd number of encoding units. Since the contents of such restrictions or predetermined positions have been described above through various embodiments, a detailed description thereof will be omitted.

[0145] 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.

[0146] According to one embodiment, the image decoding device (100) may 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 may be split into four coding units having a square shape or may 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) may split the first coding unit (900) into a plurality of non-square coding units. 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.

[0147] According to one embodiment, 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 allows them to 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 units (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 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. 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, the image decoding device (100) may place a predetermined restriction on an encoding unit at a predetermined position among the divided encoding units when the encoding unit is divided into an odd number of encoding units. Since the contents of such restrictions or predetermined positions, etc. have been described above through various embodiments, a detailed description thereof will be omitted.

[0148] According to one embodiment, the image decoding device (100) can divide the first encoding unit to determine encoding units of various shapes.

[0149] 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.

[0150] FIG. 10 illustrates that, according to one embodiment, 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 splitting a first encoding unit (1000) satisfies a predetermined condition.

[0151] According to one embodiment, 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 split independently. 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, the image decoding device (100) may determine third encoding units (1012a, 1012b) by horizontally dividing the left second encoding unit (1010a) having a non-square shape determined by vertically dividing the first encoding unit (1000). However, when the image decoding device (100) divides the left second encoding unit (1010a) in the horizontal direction, the right second encoding unit (1010b) may be restricted from being horizontally divided in the same direction as the direction in which the left second encoding 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.

[0152] According to one embodiment, 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.

[0153] 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.

[0154] According to one embodiment, 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.

[0155] According to one embodiment, 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.

[0156] 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).

[0157] 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).

[0158] FIG. 12 illustrates that, according to one embodiment, the processing order between multiple encoding units may vary depending on the process of dividing the encoding units.

[0159] According to one embodiment, the image decoding device (100) may 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) may 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 may 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 horizontally 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.

[0160] According to one embodiment, 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, 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.

[0161] According to one embodiment, the image decoding device (100) may 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) may 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.

[0162] According to one embodiment, the image decoding device (100) may 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) may 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.

[0163] 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.

[0164] 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.

[0165] According to one embodiment, 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, an encoding unit with an increased depth is expressed as an encoding unit of a lower depth.

[0166] Referring to FIG. 13, according to one embodiment, 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 2N x 2N, 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 N x N. 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 / 2 x N / 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.

[0167] In one embodiment, 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.

[0168] The image decoding device (100) can determine a second encoding unit (e.g., 1302, 1312, 1322, etc.) by dividing at least one of the width and height of the first encoding unit (1310) having a size of N x 2N. That is, the image decoding device (100) can determine a second encoding unit (1302) having a size of N x N or a second encoding unit (1322) having a size of N x N / 2 by dividing the first encoding unit (1310) in the horizontal direction, and can also determine a second encoding unit (1312) having a size of N / 2 x N by dividing it in the horizontal direction and the vertical direction.

[0169] According to one embodiment, the image decoding device (100) may determine a second encoding unit (e.g., 1302, 1312, 1322, etc.) by splitting at least one of the width and the height of the first encoding unit (1320) having a size of 2N x N. That is, the image decoding device (100) may split the first encoding unit (1320) in the vertical direction to determine a second encoding unit (1302) having a size of N x N or a second encoding unit (1312) having a size of N / 2 x N, and may split the first encoding unit (1320) in the horizontal direction and the vertical direction to determine a second encoding unit (1322) having a size of N x N / 2.

[0170] According to one embodiment, 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 N x N. 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 / 2 x N / 2, a third encoding unit (1314) having a size of N / 4 x N / 2, or a third encoding unit (1324) having a size of N / 2 x N / 4.

[0171] According to one embodiment, 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 (1312) having a size of N / 2 x N. That is, the image decoding device (100) may split the second encoding unit (1312) in the horizontal direction to determine a third encoding unit (1304) having a size of N / 2 x N / 2 or a third encoding unit (1324) having a size of N / 2 x N / 4, or may split the second encoding unit (1312) in the vertical direction and the horizontal direction to determine a third encoding unit (1314) having a size of N / 4 x N / 2.

[0172] According to one embodiment, 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 (1322) having a size of N x N / 2. That is, the image decoding device (100) may split the second encoding unit (1322) in the vertical direction to determine a third encoding unit (1304) having a size of N / 2 x N / 2 or a third encoding unit (1314) having a size of N / 4 x N / 2, or may split the second encoding unit (1322) in the vertical direction and the horizontal direction to determine a third encoding unit (1324) having a size of N / 2 x N / 4.

[0173] According to one embodiment, 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 2N x 2N can be split in the vertical direction to determine a first encoding unit (1310) having a size of N x 2N, or can be split in the horizontal direction to determine a first encoding unit (1320) having a size of 2N x N. According to one embodiment, when the depth is determined based on the length of the longest side of the encoding unit, the depth of the encoding unit determined by splitting the first encoding unit (1300) having a size of 2N x 2N in the horizontal direction or the vertical direction can be the same as the depth of the first encoding unit (1300).

[0174] According to one embodiment, 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.

[0175] 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.

[0176] According to one embodiment, the image decoding device (100) may 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) may 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).

[0177] According to one embodiment, 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).

[0178] According to one embodiment, the image decoding device (100) may split a first encoding unit (1410) having a height greater than its width into a plurality of second encoding units (1412a, 1412b, 1414a, 1414b, 1414c) in a horizontal direction according to the splitting shape mode information. According to one embodiment, the image decoding device (100) may split a first encoding unit (1420) having a width greater than its height into a plurality of second encoding units (1422a, 1422b, 1424a, 1424b, 1424c) in a vertical direction according to the splitting shape mode information.

[0179] According to one embodiment, the depth of the second coding unit (1412a, 1412b, 1414a, 1414b, 1414c. 1422a, 1422b, 1424a, 1424b, 1424c) determined based on the split shape mode information for the first coding unit (1410 or 1420) of a non-square shape may be determined based on the length of the long side. 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.

[0180] 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).

[0181] According to one embodiment, when determining an index (PID) for distinguishing divided coding units, the image decoding device (100) may determine the index based on a size ratio between the coding units when the coding units divided into an odd number are not of the same size. Referring to FIG. 14, among the coding units (1414a, 1414b, 1414c) divided into an odd number, 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 index value. According to one embodiment, 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.

[0182] According to one embodiment, the image decoding device (100) may determine whether the image is divided into a specific split shape based on the value of an index for distinguishing a plurality of coding units that are divided from the current coding unit. Referring to FIG. 14, the image decoding device (100) may divide a first coding unit (1410) having a rectangular shape in which the height is longer than the width, to determine an even number of coding units (1412a, 1412b) or an odd number of coding units (1414a, 1414b, 1414c). The image decoding device (100) may use an index (PID) indicating each coding unit to distinguish each of the plurality of coding units. According to one embodiment, the PID may be obtained from a sample (for example, an upper left sample) at a predetermined position of each coding unit.

[0183] According to one embodiment, the image decoding device (100) may 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, 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) may divide the first coding unit (1410) into three coding units (1414a, 1414b, 1414c). The image decoding device (100) may assign an index to each of the three coding units (1414a, 1414b, 1414c). The image decoding device (100) may 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, 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, 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.

[0184] According to one embodiment, the image decoding device (100) may utilize a predetermined data unit from which recursive division of the encoding unit begins.

[0185] FIG. 15 illustrates that a plurality of encoding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment.

[0186] According to one embodiment, 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.

[0187] According to one embodiment, the reference data unit may exhibit a predetermined size and shape. According to one embodiment, the reference coding unit may include M x N 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 exhibit a square or non-square shape, and may be subsequently divided into an integer number of coding units.

[0188] According to one embodiment, the video decoding device (100) can divide the current picture into a plurality of reference data units. According to one embodiment, the video decoding device (100) can divide the plurality of reference data units into which the current picture is divided using division type mode information for each reference data unit. This division process of the reference data units can correspond to a division process using a quad-tree structure.

[0189] According to one embodiment, the image decoding device (100) may predetermine the minimum size that a reference data unit included in the current picture may have. Accordingly, the image decoding device (100) may determine reference data units of various sizes having a size greater than or equal to the minimum size, and may determine at least one encoding unit using segmentation mode information based on the determined reference data unit.

[0190] 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, 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.

[0191] According to one embodiment, 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.

[0192] According to one embodiment, the image decoding device (100) may use an index for identifying the size and shape of the reference coding unit 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.

[0193] According to one embodiment, the image decoding device (100) may use at least one reference coding unit included in one maximum coding unit. That is, a maximum coding unit for dividing an image may include at least one reference coding unit, and a coding unit may be determined through a recursive splitting process of each reference coding unit. According to one embodiment, at least one of the width and the height of the maximum coding unit 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, the size of the reference coding unit may be a size obtained by splitting the maximum coding unit n times according to a quad tree structure. That is, the image decoding device (100) may split the maximum coding unit n times according to the quad tree structure to determine the reference coding unit, and may split the reference coding unit based on at least one of block shape information and split shape mode information according to various embodiments.

[0194] FIG. 16 illustrates a processing block that serves as a criterion for determining the order of determination of reference encoding units included in a picture (1600) according to one embodiment.

[0195] According to one embodiment, the image decoding apparatus (100) may determine at least one processing block for dividing a picture. The processing block is a data unit including at least one reference coding unit for dividing an image, and at least one reference coding unit included in the processing block may be determined in a specific order. That is, the determination order of at least one reference coding unit determined in each processing block may correspond to one of various types of orders in which the reference coding unit may be determined, and the determination order of the reference coding unit determined in each processing block may be different for each processing block. The determination order of the reference coding unit determined for each processing block may be one of various orders such as raster scan, Z-scan, N-scan, up-right diagonal scan, horizontal scan, and vertical scan, but the order in which it may be determined should not be interpreted as being limited to the above scan orders.

[0196] According to one embodiment, the image decoding device (100) can obtain information about the size of a processing block to determine the size of at least one processing block included in an image. The image decoding device (100) can obtain information about the size of a processing block from a bitstream to determine the size of at least one processing block included in an image. The size of the processing block may be a predetermined size of a data unit indicated by the information about the size of the processing block.

[0197] According to one embodiment, the bitstream acquisition unit (110) of the image decoding device (100) can acquire information about the size of a processing block from the bitstream for each specific data unit. For example, the information about the size of a processing block can be acquired from the bitstream for each data unit such as an image, a sequence, a picture, a slice, a slice segment, a tile, a tile group, etc. That is, the bitstream acquisition unit (110) can acquire information about the size of a processing block from the bitstream for each of the above-described multiple data units, and the image decoding device (100) can determine the size of at least one processing block for dividing a picture using the acquired information about the size of the processing block, and the size of the processing block can be an integer multiple of a reference coding unit.

[0198] According to one embodiment, the image decoding device (100) may determine the size of the processing block (1602, 1612) included in the picture (1600). For example, the image decoding device (100) may determine the size of the processing block based on information about the size of the processing block obtained from the bitstream. Referring to FIG. 16, the image decoding device (100) may determine the horizontal size of the processing block (1602, 1612) to be four times the horizontal size of the reference coding unit, and the vertical size of the processing block (1602, 1612) to be four times the vertical size of the reference coding unit, according to one embodiment. The image decoding device (100) may determine the order in which at least one reference coding unit is determined within at least one processing block.

[0199] According to one embodiment, the video decoding device (100) may determine each processing block (1602, 1612) included in the picture (1600) based on the size of the processing block, and may determine the determination order of at least one reference coding unit included in the processing block (1602, 1612). According to one embodiment, the determination of the reference coding unit may include determining the size of the reference coding unit.

[0200] According to one embodiment, the image decoding device (100) can obtain information about a determination order of at least one reference coding unit included in at least one processing block from a bitstream, and can determine an order in which at least one reference coding unit is determined based on the obtained information about the determination order. The information about the determination order can be defined as an order or direction in which the reference coding units are determined within the processing block. That is, the order in which the reference coding units are determined can be independently determined for each processing block.

[0201] According to one embodiment, the image decoding device (100) can obtain information about the determination order of the reference coding unit for each specific data unit from the bitstream. For example, the bitstream acquisition unit (110) can obtain information about the determination order of the reference coding unit for each data unit such as an image, sequence, picture, slice, slice segment, tile, tile group, processing block, etc. from the bitstream. Since the information about the determination order of the reference coding unit indicates the determination order of the reference coding unit within the processing block, the information about the determination order can be obtained for each specific data unit including an integer number of processing blocks.

[0202] The image decoding device (100) can determine at least one reference encoding unit based on an order determined according to one embodiment.

[0203] According to one embodiment, the bitstream acquisition unit (110) may acquire information on the reference coding unit determination order as information related to the processing blocks (1602, 1612) from the bitstream, and the image decoding device (100) may determine the order in which at least one reference coding unit included in the processing blocks (1602, 1612) is determined and at least one reference coding unit included in the picture (1600) may be determined according to the determination order of the coding units. Referring to FIG. 16, the image decoding device (100) may determine the determination order (1604, 1614) of at least one reference coding unit related to each processing block (1602, 1612). For example, when information on the determination order of the reference coding unit is acquired for each processing block, the determination order of the reference coding unit related to each processing block (1602, 1612) may be different for each processing block. If the reference encoding unit determination order (1604) related to the processing block (1602) is a raster scan order, the reference encoding unit included in the processing block (1602) can be determined according to the raster scan order. In contrast, if the reference encoding unit determination order (1614) related to another processing block (1612) is a reverse order of the raster scan order, the reference encoding unit included in the processing block (1612) can be determined according to the reverse order of the raster scan order.

[0204] According to one embodiment, the image decoding device (100) can decode at least one determined reference coding unit. The image decoding device (100) can decode an image based on the determined reference coding unit through the above-described embodiment. The method of decoding the reference coding unit may include various methods of decoding an image.

[0205] According to one embodiment, the video decoding device (100) may obtain and use block shape information indicating the shape of the current encoding unit or split shape mode information indicating a method of splitting the current encoding unit from the bitstream. The split shape mode information may be included in a bitstream related to various data units. For example, the video decoding device (100) may 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) may obtain and use a syntax element corresponding to block shape information or split shape mode information from the bitstream for each maximum encoding unit, each reference encoding unit, and each processing block.

[0206] Hereinafter, a method for determining a partitioning rule according to one embodiment of the present disclosure will be described in detail.

[0207] 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.

[0208] 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).

[0209] The shape of the encoding unit may include a square and a non-square. 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.

[0210] The size of the encoding unit may include various sizes such as 4 x 4, 8 x 4, 4 x 8, 8 x 8, 16 x 4, 16 x 8, ..., 256 x 256. The size of the encoding unit may be classified according to the length of the long side, the length of the short side, or the width of the encoding unit. The image decoding device (100) may apply the same splitting rule to encoding units classified into the same group. For example, the image decoding device (100) may classify encoding 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 encoding units having the same long side length.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] Additionally, the image decoding device (100) can determine a splitting rule so that encoding units generated through different splitting paths do not have the same block shape. However, this is not limited thereto, and encoding units generated through different splitting paths may have the same block shape. Encoding units generated through different splitting paths may have different decoding processing orders. Since the decoding processing order has been described together with FIG. 12, a detailed description thereof will be omitted.

[0216] FIG. 17 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.

[0217] Referring to FIG. 17, the image decoding device (100) can determine a different combination of partitioning shapes into which a coding unit can be partitioned for each picture. For example, the image decoding device (100) can decode an image using a picture (1700) that can be partitioned into four coding units, a picture (1710) that can be partitioned into two or four coding units, and a picture (1720) that can be partitioned into two, three, or four coding units, among at least one picture included in the image. The image decoding device (100) can use only partitioning shape information indicating that the picture (1700) is partitioned into four square coding units to partition the picture (1700) into a plurality of coding units. The image decoding device (100) can use only partitioning shape information indicating that the picture (1710) is partitioned into two or four coding units to partition the picture. The video decoding device (100) can only use the segmentation type information indicating that the picture (1720) 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.

[0218] According to one embodiment, 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., sequence, picture, slice, slice segment, tile, 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) of 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.

[0219] FIG. 18 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.

[0220] According to one embodiment, 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.

[0221] Referring to FIG. 18, 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.

[0222] According to one embodiment, when the image decoding device (100) can divide a square-shaped encoding unit into four square encoding units by horizontally and vertically splitting the encoding unit, there may be four types of splitting modes that the splitting mode information for the square encoding unit can indicate. According to one embodiment, the splitting mode information may be expressed as a two-digit binary code, and a binary code may be assigned to each splitting mode. For example, when the encoding unit is not split, the splitting mode information may be expressed as (00)b, when the encoding unit is split in the horizontal direction and the vertical direction, the splitting mode information may be expressed as (01)b, when the encoding unit is split in the horizontal direction, the splitting mode information may be expressed as (10)b, and when the encoding unit is split in the vertical direction, the splitting mode information may be expressed as (11)b.

[0223] According to one embodiment, 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. 18, the image decoding device (100) may split a non-square coding unit into up to three according to one embodiment. 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.

[0224] According to one embodiment, referring to FIG. 18, 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. 18, 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 partition shapes of the non-square coding unit indicated by the partition shape mode information should not be interpreted as being limited to only the three shapes illustrated in FIG. 18, but should be interpreted as various shapes including the above-described embodiments.

[0225] FIG. 19 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.

[0226] Referring to FIG. 19, 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. 19, 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. 19, but should be interpreted as various types including the embodiments described above.

[0227] In one embodiment, block shape information or segmentation shape mode information may be expressed using binary code, and such information may be directly generated as a bitstream. Furthermore, block shape information or segmentation shape mode information that may be expressed using binary code may not be directly generated as a bitstream, but may instead be used as a binary code input into CABAC (context adaptive binary arithmetic coding).

[0228] According to one embodiment, the image 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 image 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, the image 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 image 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.

[0229] According to one embodiment, 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. 18, 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. 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.

[0230] According to one embodiment, the image decoding device (100) may, in the process of determining the syntax, update the probability for the bins used in the process of decoding the bins of the empty string for the syntax, and the image decoding device (100) may determine that certain bits among the empty strings have the same probability without updating the probability.

[0231] Referring to FIG. 18, 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, the image decoding device (100) can decode the bin by considering that the probability that the second bin is 0 or 1 when the first bin for the partition shape mode information is 1 is the same probability.

[0232] According to one embodiment, the image decoding device (100) may use 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, 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, 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, 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.

[0233] According to one embodiment, the image decoding device (100) may determine that the bin probability for the segmentation shape mode information is the same for encoding units of a predetermined size or larger. For example, the bin probability for the segmentation 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.

[0234] According to one embodiment, 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).

[0235] Figure 20 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0236] The encoding unit (2010) of the video encoding and decoding system (2000) transmits an encoded bitstream of the video, and the decoding unit (2050) receives the bitstream and decodes it to output a restored video. Here, the encoding unit (2010) may have a configuration similar to that of the video encoding device (200) described below, and the decoding unit (2050) may have a configuration similar to that of the video decoding device (100).

[0237] In the encoding unit (2010), the prediction encoding unit (2015) outputs prediction data through inter prediction and intra prediction, and the transformation and quantization unit (2020) outputs quantized transformation coefficients of residual data between the prediction data and the current input image. The entropy encoding unit (2025) 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 (2030), and the restored spatial domain data are output as a restored image through the deblocking filtering unit (2035) and the loop filtering unit (2040). The restored image can be used as a reference image of the next input image through the prediction encoding unit (2015).

[0238] The encoded image data among the bitstreams received by the decoding unit (2050) is restored to residual data in the spatial domain through the entropy decoding unit (2055) and the inverse quantization and inverse transformation unit (2060). The prediction data and residual data output from the prediction decoding unit (2075) are combined to form image data in the spatial domain, and the deblocking filtering unit (2065) and the loop filtering unit (2070) 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 (2075).

[0239] The loop filtering unit (2040) of the encoding unit (2010) performs loop filtering using filter information input according to user input or system settings. The filter information used by the loop filtering unit (2040) is output to the entropy encoding unit (2025) and transmitted to the decoding unit (2050) together with the encoded image data. The loop filtering unit (2070) of the decoding unit (2050) can perform loop filtering based on the filter information input from the decoding unit (2050).

[0240] The various embodiments described above describe operations related to the image decoding method performed by the image decoding device (100). Hereinafter, the operations of the image encoding device (200), which performs the image encoding method corresponding to the reverse process of the image decoding method, will be described through various embodiments.

[0241] 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.

[0242] 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.

[0243] 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).

[0244] According to one embodiment, 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.

[0245] According to one embodiment, 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.

[0246] According to one embodiment, the encoder (220) may 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) may generate a bitstream including split shape mode information indicating that the encoding unit is not split. In addition, the encoder (220) may split the encoding unit into a plurality of encoding units, and the bitstream generation unit (210) may generate a bitstream including split shape mode information indicating that the encoding unit is split into a plurality of encoding units.

[0247] According to one embodiment, information indicating the number of encoding units to be split into or the direction in which the encoding unit is to be 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.

[0248] 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.

[0249] 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.

[0250] 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.

[0251] 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.

[0252] 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 20, a detailed description is omitted.

[0253] FIG. 21 is a block diagram illustrating the configuration of an image decoding device (2100) according to one embodiment.

[0254] Referring to FIG. 21, the video decoding device (2100) includes an acquisition unit (2110), a motion information determination unit (2130), a restoration unit (2150), and a deblocking unit (2170). The acquisition unit (2110) illustrated in FIG. 21 corresponds to the bitstream acquisition unit (110) illustrated in FIG. 1, and the motion information determination unit (2130), the restoration unit (2150), and the deblocking unit (2170) may correspond to the decoding unit (120) illustrated in FIG. 1.

[0255] According to one embodiment, the acquisition unit (2110), the motion information determination unit (2130), the restoration unit (2150), and the deblocking unit (2170) may be implemented with at least one processor. The image decoding device (2100) may include one or more data storage units (not shown) that store input / output data of the acquisition unit (2110), the motion information determination unit (2130), the restoration unit (2150), and the deblocking unit (2170). In addition, the image decoding device (2100) may also include a memory control unit (not shown) that controls data input / output of the data storage unit (not shown).

[0256] The acquisition unit (2110) receives a bitstream generated as a result of encoding an image. The bitstream may include information for determining a motion vector used for inter prediction of the current block. The current block is a block generated by dividing the image according to a tree structure, and may correspond to a block unit such as a maximum coding unit, an coding unit, or a transformation unit, for example.

[0257] The motion information determination unit (2130) can determine the current block based on block shape information and / or information about a segmentation shape mode included in at least one of a sequence parameter set, a picture parameter set, a video parameter set, a slice header, and a slice segment header. Furthermore, the acquisition unit (2110) can obtain syntax elements corresponding to block shape information or information about a segmentation shape mode for each maximum coding unit, reference coding unit, and processing block from a bitstream, and the motion information determination unit (2130) can use the obtained information to determine the current block.

[0258] The bitstream may include information indicating the prediction mode of the current block, and the prediction mode of the current block may include intra mode, inter mode, merge mode, AMVP (advanced motion vector prediction) mode, direct mode, skip mode, etc.

[0259] In one embodiment, the motion information determination unit (2130) may determine a candidate list including a first reference block indicated by a temporal motion vector as a candidate when the size of the current block is greater than or equal to a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.). The candidate list may include a predetermined number of candidates. Each candidate may represent a block at a specific location. Alternatively, each candidate may represent a motion vector of a block at a specific location. That is, the inclusion of a predetermined block as a candidate in the candidate list may mean that the motion vector of the predetermined block is included as a candidate in the candidate list.

[0260] In the present disclosure, the first reference block refers to a block for extracting a motion vector used to determine the motion vector of the current block. When comparing the size of the current block with a predetermined size, the motion information determination unit (2130) may compare one of the horizontal and vertical sizes of the current block (e.g., a smaller size) with the predetermined size. For example, when the size of the current block is 4 x 16 and the predetermined size is 8 x 8, since the horizontal size of the current block, 4, is smaller than 8, which represents the size of one side in the predetermined size, the size of the current block may be determined to be smaller than the predetermined size.

[0261] In one embodiment, the motion information determination unit (2130) may determine a candidate list including blocks other than the first reference block as candidates if the size of the current block is smaller than a predetermined size. The first reference block may or may not be included in the candidate list based on the size of the current block.

[0262] In one embodiment, the motion information determination unit (2130) may determine a first candidate list including the first reference block as a candidate when the size of the current block is greater than or equal to a predetermined size, and may determine a second candidate list including a block other than the first reference block as a candidate when the size of the current block is smaller than the predetermined size.

[0263] The motion information determination unit (2130) can determine the candidate list when the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of the candidate included in the candidate list. Information (e.g., a flag or an index) indicating the prediction mode of the current block can be obtained from the bitstream. The motion information determination unit (2130) can determine the candidate list when the flag indicating whether the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of the candidate included in the candidate list is 1.

[0264] The mode for determining the motion vector of the current block using the motion vector of the candidate included in the candidate list may include, for example, skip mode, merge mode, and AMVP mode. In skip mode and merge mode, the motion vector of the candidate included in the candidate list is determined as the motion vector of the current block, and in AMVP mode, the value obtained by applying a residual motion vector (difference motion vector) to the motion vector of the candidate included in the candidate list is determined as the motion vector of the current block. Information indicating the residual motion vector is obtained from the bitstream.

[0265] Figure 22 is a diagram showing a candidate list according to one embodiment.

[0266] Referring to FIG. 22, the candidate list may include a first reference block, a first spatial neighboring block, a second spatial neighboring block, a third spatial neighboring block, a temporal neighboring block, etc. as candidates. An index may be assigned to each candidate, and in one embodiment, an index with the smallest value may be assigned to the first reference block.

[0267] In FIG. 22, the spatial surrounding blocks represent surrounding blocks that are spatially adjacent to the current block within the current image, and the temporal surrounding blocks may include blocks located at the same point as the current block within the collocated image, or blocks located to the lower right of blocks located at the same point as the current block.

[0268] FIG. 22 illustrates that the first reference block and the temporal surrounding blocks are included together as candidates in the candidate list. If the first reference block is included in the candidate list, the temporal surrounding blocks may not be included in the candidate list, and conversely, if the temporal surrounding blocks are included in the candidate list, the first reference block may not be included in the candidate list.

[0269] In one embodiment, the minimum number of spatial surrounding blocks and the minimum number of temporal surrounding blocks (including the first reference block) that must be included as candidates in the candidate list may be predetermined.

[0270] Before constructing a candidate list, the motion information determination unit (2130) can determine the availability of predetermined blocks (including the first reference block) and sequentially include blocks with availability in the candidate list. If the number of candidates included in the candidate list is less than the predetermined number, the motion information determination unit (2130) can include a default motion vector in the candidate list. If a block is inter-predicted, the block can be determined to be available.

[0271] The default motion vector may include, for example, a zero vector, a temporal motion vector pointing to the first reference block, a representative motion vector of the first reference block, or a value combining motion vectors of blocks already included in the candidate list.

[0272] The order of blocks included in the candidate list may be predetermined. For example, as illustrated in FIG. 22, blocks may be included in the candidate list according to availability in the following order: first reference block → spatial surrounding block → temporal surrounding block, or may be included in the candidate list according to availability in the following order: spatial surrounding block → first reference block → temporal reference block. Alternatively, blocks may be included in the candidate list according to availability in the following order: first spatial surrounding block → first reference block → second spatial surrounding block → third spatial surrounding block → temporal surrounding block. Alternatively, blocks may be included in the candidate list in the following order: first available spatial surrounding block among spatial surrounding blocks → first reference block → remaining spatial surrounding blocks among spatial surrounding blocks → temporal surrounding block.

[0273] However, the candidate list illustrated in FIG. 22 is only an example, and the number and types of candidates included in the candidate list may vary depending on the implementation. For example, the candidate list may include at least one of a zero vector, a temporal motion vector pointing to the first reference block, a representative motion vector of the first reference block, and a value obtained by combining motion vectors of blocks already included in the candidate list.

[0274] A motion information determination unit (2130) obtains information (e.g., a flag or index) indicating one of the candidates included in the candidate list from a bitstream, and determines a motion vector of the current block using the motion vector of the candidate indicated by the obtained information.

[0275] According to one embodiment of the present disclosure, when a first reference block is selected from among candidates included in a candidate list, the motion vectors of sub-blocks within the current block are determined through a sub-block-based prediction process. This will be described with reference to FIGS. 23 and 24.

[0276] FIG. 23 is a drawing illustrating a first reference block (2330) pointed to by a temporal motion vector (2320), and FIG. 24 is a drawing for explaining a method for determining motion vectors of sub-blocks (2312, 2314, 2316, 2318) within a current block (2310).

[0277] The motion information determination unit (2130) determines a temporal motion vector (2320) for determining the first reference block (2330). A specific method for determining the temporal motion vector (2320) will be described later.

[0278] Once the temporal motion vector (2320) is determined, a first reference block (2330) pointed to by the temporal motion vector (2320) with respect to the current block (2310) within the first reference picture is determined. The size of the first reference block (2330) may be determined to be the same as that of the current block (2310).

[0279] When determining the motion vector of the current block (2310) based on the first reference block (2330), in one embodiment of the present disclosure, sub-blocks are determined within the current block (2310) and the motion vector is determined in units of sub-blocks.

[0280] Referring to FIG. 24, the current block (2310) can be divided into a plurality of sub-blocks (2312, 2314, 2316, 2318). Each of the sub-blocks (2312, 2314, 2316, 2318) can have a predetermined size. For example, the size of the sub-block can be 4 x 4, 8 x 8, 16 x 16, 32 x 32, or 64 x 64.

[0281] The size of a sub-block can be determined by GOP (group of picture), picture, tile, maximum coding unit, or coding unit.

[0282] A sub-block may have a predetermined size depending on the value of the temporal layer of the pictures constituting the GOP. Specifically, in an image where the value of the temporal layer is from 0 to n (where n is an integer), a sub-block may have a size of 4 x 4, in an image where the value of the temporal layer is from n+1 to m (where m is an integer), a sub-block may have a size of 8 x 8, and in an image where the value of the temporal layer is from m+1 to l (where l is an integer), a sub-block may have a size of 16 x 16. That is, as the value of the temporal layer increases, the size of the sub-block may also increase.

[0283] In one example, the size of a sub-block may be determined based on the size of the current block. Specifically, if the size of the current block is M x N, the sub-block may have a size of M / 4 x N / 4. In this case, if the size of the sub-block is smaller than a predetermined minimum size of the sub-block, the size of the sub-block within the current block may be determined as the minimum size of the sub-block.

[0284] In another example, if the size of the current block is M x N, and the larger of M and N is K, the sub-block may have a size of K / 4 x K / 4.

[0285] FIG. 24 illustrates that four sub-blocks (2312, 2314, 2316, 2318) are determined within the current block (2310), but the number of sub-blocks may vary depending on the size of the sub-block and the size of the current block.

[0286] Sub-regions (2332, 2334, 2336, 2338) are determined within the first reference block (2330) corresponding to each sub-block (2312, 2314, 2316, 2318), and motion vectors (mv1', mv2', mv3', mv4') of each sub-block (2312, 2314, 2316, 2318) can be determined based on motion vectors (mv1, mv2, mv3, mv4) extracted from each sub-region (2332, 2334, 2336, 2338).

[0287] For example, based on the motion vector (mv1) extracted from the first sub-region (2332) in the first reference block (2330), the motion vector (mv1') of the first sub-block (2312) in the current block (2310) is determined, based on the motion vector (mv2) extracted from the second sub-region (2334), the motion vector (mv2') of the second sub-block (2314) in the current block (2310) is determined, based on the motion vector (mv3) extracted from the third sub-region (2336), the motion vector (mv3') of the third sub-block (2316) in the current block (2310) is determined, and based on the motion vector (mv4) extracted from the fourth sub-region (2338), the motion vector (mv4') of the fourth sub-block (2318) in the current block (2310) is determined.

[0288] The motion vectors (mv1, mv2, mv3, mv4) of each sub-region (2332, 2334, 2336, 2338) can be extracted based on the center pixel of each sub-region (2332, 2334, 2336, 2338).

[0289] Motion vectors used in the video decoding process are stored based on blocks of a predetermined size (e.g., 16 x 16 blocks in the HEVC codec, hereinafter referred to as storage blocks). In one embodiment of the present disclosure, the size of the storage block may be, but is not limited to, 4 x 4, 8 x 8, 16 x 16, or 32 x 32.

[0290] The motion information determination unit (2130) can determine the motion vector of the storage block including the center pixel of the sub-regions (2332, 2334, 2336, 2338) within the first reference block (2330) as the motion vector of the sub-regions (2332, 2334, 2336, 2338). The motion vector of the storage block including the center pixel of the first sub-region (2332) can be determined as the motion vector of the first sub-region (2332), and the motion vector of the storage block including the center pixel of the second sub-region (2334) can be determined as the motion vector of the second sub-region (2334).

[0291] If the positions of pixels in a region are (0,0) to (n-1, n-1), the position of the center pixel can be (n / 2, n / 2), ((n-2) / 2), (n-2) / 2)), (n / 2, (n-2) / 2)), or ((n-2) / 2), n / 2).

[0292] In determining the motion vector of each sub-region (2332, 2334, 2336, 2338), a motion vector may not exist in a storage block including a center pixel of any of the sub-regions (2332, 2334, 2336, 2338). For example, if all samples of a storage block including a center pixel of a sub-region are intra-predicted, a motion vector may not exist in the corresponding storage block. To this end, the motion information determination unit (2130) may determine the motion vector of the storage block including the center pixel of the first reference block (2330) as a representative motion vector, and may determine the motion vector of a sub-region for which the motion vector cannot be determined as a representative motion vector. As described below, a motion vector corresponding to the center pixel of the first reference block (2330) may not exist. In this case, the first reference block (2330) may be determined to have no availability and may not be included in the candidate list.

[0293] In one embodiment, when the size of the storage block (e.g., 8 x 8) is larger than the size of the sub-block (e.g., 4 x 4), the motion information determination unit (2130) may determine the motion vector of at least one of the sub-regions (2332, 2334, 2336, 2338) corresponding to the sub-blocks (2312, 2314, 2316, 2318) as a combined value (e.g., an average value) of the motion vectors of adjacent sub-regions. This is to prevent the motion vectors of a large number of sub-regions from being determined to have the same value because the center pixels of all of the sub-regions are included in one storage block. For example, when the center pixels of a predetermined number of sub-regions among all the sub-regions in the current block are all included in one storage block, the motion vector of some of the predetermined number of sub-regions may be determined as an average value of the motion vectors of the adjacent sub-regions.

[0294] When the motion vectors of the sub-blocks (2312, 2314, 2316, 2318) within the current block (2310) are determined, the restoration unit (2150) restores the sub-blocks (2312, 2314, 2316, 2318) based on the sample values ​​of the second reference block pointed to by the motion vectors of the sub-blocks (2312, 2314, 2316, 2318). As a result, the current block (2310) is restored. In the present disclosure, the second reference block means a block used for motion compensation of the current block.

[0295] FIG. 25 is a drawing for explaining the restoration process of the current block, and the restoration unit (2150) can determine the sample values ​​of the second reference blocks (2512, 2514, 2516, 2518) pointed to by the motion vectors (mv1', mv2', mv3', mv4') of the sub blocks (2312, 2314, 2316, 2318) as the sample values ​​of the sub blocks (2312, 2314, 2316, 2318).

[0296] In one embodiment, the restoration unit (2150) may determine the sample values ​​of the sub-blocks (2312, 2314, 2316, 2318) by applying residual data obtained from the bitstream according to the prediction mode of the current block (2310) to each of the sample values ​​of the second reference blocks (2512, 2514, 2516, 2518) pointed to by the motion vectors (mv1', mv2', mv3', mv4') of the sub-blocks (2312, 2314, 2316, 2318).

[0297] In one embodiment, when the current block (2310) becomes a reference block of a subsequent block, the motion vector of the subsequent block may be determined according to the representative motion vector of the first reference block (2330) described above. In another embodiment, when the current block (2310) becomes a reference block of a subsequent block, the motion vector of the subsequent block may be determined according to the motion vector of any one of the sub-blocks (2312, 2314, 2316, 2318) within the current block (2310).

[0298] In one embodiment, when the restoration unit (2150) stores the motion vectors determined within the current image after the decoding of the current image is completed, the motion vectors of all sub-blocks within the current block may be stored. However, depending on which temporal layer value the current image has within the GOP, the motion vectors of the sub-blocks may be converted and stored with a predetermined precision. Here, the precision may be expressed in pixel units. For example, 1 pixel precision indicates that the motion vector is expressed in units of one integer pixel, and 1 / 4 pixel precision indicates that the motion vector is expressed in units of 1 / 4 pixel (i.e., sub-pixel). Compared to 1 pixel precision, 1 / 4 pixel precision can express the motion vector more precisely.

[0299] The restoration unit (2150) can store the motion vectors of the sub-blocks with a lower precision as the temporal layer value of the current image is lower. If the motion vectors of the sub-blocks are determined with a 1 / 4 pixel precision, the restoration unit (2150) can convert and store the motion vectors of the sub-blocks with, for example, a 1 pixel precision if the temporal layer value of the current image is the same as the predetermined value. If the motion vector of a certain sub-block is (16, 16) with a 1 / 4 pixel precision, the corresponding motion vector can be stored as (4, 4) with a 1 pixel precision. This is to improve the data processing speed because the lower the temporal layer value of an image, the more frequently it is referenced from other images.

[0300] When storing the motion vectors of sub-blocks with low precision, the restoration unit (2150) can apply rounding to store the motion vectors as integer values. For example, if the motion vector of a sub-block is (17, 17) with 1 / 4 pixel precision, the motion vector can be stored as (4, 4) with 1 pixel precision (i.e., an integer value that rounds up 17 / 4).

[0301] In one embodiment of the present disclosure, when a first reference block is selected from among candidates included in a candidate list, an image can be accurately decoded in units of sub blocks by performing a motion vector determination process and a sample value restoration process on a sub block basis.

[0302] According to one embodiment of the present disclosure, when a candidate other than the first reference block is selected from among the candidates included in the candidate list, the current block may be restored through a process different from the processes described above with respect to FIGS. 23 to 25. For example, when a specific spatial neighboring block is selected from among the candidates included in the candidate list, the motion information determination unit (2130) may determine the motion vector of the current block using the motion vector of the spatial neighboring block, and may restore the current block using the sample values ​​of the reference block indicated by the motion vector of the current block. That is, when selecting a spatial neighboring block, the motion vector determination process and restoration process may be performed based on the current block.

[0303] Meanwhile, the first reference block may or may not be included in the candidate list, and whether the first reference block is included in the candidate list may be based on various conditions.

[0304] For example, if the size of the current block is smaller than a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the size of the current block is larger than the predetermined size, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0305] Also, as an example, if the size of the current block is smaller than a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.) and the temporal motion vector obtained through the temporal motion vector determination process described below is a predetermined motion vector (e.g., a zero vector), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporal neighboring blocks within the predetermined collocated image as candidates. Conversely, if the size of the current block is larger than the predetermined size or the temporal motion vector is not the predetermined motion vector, the candidate list may include the first reference block, and temporal neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be the size of a sub-block.

[0306] Also, for example, if the size of the current block is larger than a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the size of the current block is smaller than the predetermined size, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0307] Also, as an example, if the size of the current block is equal to a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the size of the current block is not equal to the predetermined size, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0308] Also, for example, if the size of the current block is different from a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the size of the current block is equal to the predetermined size, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0309] Additionally, for example, if the current block is a predetermined block unit (e.g., a maximum coding unit), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the current block is not a predetermined block unit, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0310] Additionally, as an example, if the size of the current block is at least k times (where k is a predetermined integer) larger than the size of the sub-block, a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within the predetermined collocated image as candidates. Conversely, if the size of the current block is not at least k times larger than the size of the predetermined block, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0311] In addition, for example, in a case where candidates for a candidate list are sequentially determined based on the availability of multiple blocks including a first reference block, if the first reference block is determined as the first candidate in the candidate list, the first reference block may be excluded from the candidate list. For example, in a situation where the first spatial neighboring block, the first reference block, and the second spatial neighboring block are included in the candidate list in the order of their availability, if the first spatial neighboring block is unavailable and the first reference block is included in the candidate list as the first candidate, the first reference block may be excluded from the candidate list.

[0312] Additionally, as an example, within a GOP including the current picture, if the value of the temporal layer of the current picture is equal to a predetermined value (e.g., the largest value), a candidate list including blocks other than the first reference block as candidates can be determined.

[0313] In addition, as an example, if the temporal motion vector obtained through the temporal motion vector determination process described below is a predetermined motion vector (e.g., a zero vector), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within the predetermined collocated image as candidates. Conversely, if the temporal motion vector obtained through the temporal motion vector determination process is different from the predetermined motion vector, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0314] In addition, as an example, if the temporal motion vector obtained through the temporal motion vector determination process described below is different from a predetermined motion vector (e.g., a zero vector), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within the predetermined collocated image as candidates. Conversely, if the temporal motion vector obtained through the temporal motion vector determination process is identical to the predetermined motion vector, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0315] Additionally, for example, if there is no motion vector corresponding to the center pixel of the first reference block, a candidate list including blocks other than the first reference block as candidates may be determined. Conversely, if there is a motion vector corresponding to the center pixel of the first reference block, the candidate list may include the first reference block.

[0316] Below, a method for determining a temporal motion vector pointing to a first reference block by a motion information determination unit (2130) is described.

[0317] The motion information determination unit (2130) may determine a temporal motion vector before determining the candidate list if it is confirmed that the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of a candidate included in the candidate list (for example, if sub-block_merge_flag is 1). Alternatively, the motion information determination unit (2130) may determine a temporal motion vector in order to determine the availability of the first reference block in the middle of determining the candidate list. If the availability of the first reference block is not present (for example, if a representative motion vector does not exist), a candidate list having blocks other than the first reference block as candidates may be determined.

[0318] The motion information determination unit (2130) may scan at least one predetermined surrounding block in a predetermined order and determine the motion vector of the first available surrounding block as a temporal motion vector. Referring to FIG. 26, the surrounding blocks of the current block (2310) may include spatial surrounding blocks (A0, A1, B0, B1, B2) that are spatially adjacent to the current block (2310) and temporal surrounding blocks (Col, Br) that are temporally adjacent to the current block (2310). Specifically, the surrounding blocks may include a lower left outer block (A0) of the current block (2310), a lower left block (A1) of the current block (2310), an upper right outer block (B0) of the current block (2310), an upper right block (B1) of the current block (2310), an upper left outer block (B2) of the current block (2310), a block (Col) located at the same point as the current block (2310) in the collocated image, and a lower right outer block (Br) of the block (Col) at the same point.

[0319] The position of the pixel located at the far left of the top of the current block (2310) is referred to as (xCb, yCb), and the horizontal and vertical lengths of the current block (2310) are referred to as cbWidth and cbHeight in pixels, respectively. Block A1 is a block that includes a pixel at the position (xCb-1, yCb+cbHeight-1), and block A0 is a block that includes a pixel at the position (xCb-1, yCb+cbHeight). In addition, block B1 is a block that includes a pixel at the position (xCb+cbWidth-1, yCb-1), and block B0 is a block that includes a pixel at the position (xCb+cbWidth, yCb-1). In addition, block B2 is a block that includes a pixel at the position (xCb-1, yCb-1). However, the positions of the surrounding blocks illustrated in FIG. 26 are only an example and may vary depending on the implementation.

[0320] The motion information determination unit (2130) may determine a predetermined motion vector (e.g., a zero vector) as a temporal motion vector when there is no availability of at least one predetermined surrounding block.

[0321] The motion information determination unit (2130) may determine that a surrounding block to be scanned is not available if the surrounding block to be scanned is intra-predicted. The motion information determination unit (2130) may determine that a corresponding block is not available if the image pointed to by the surrounding block to be scanned is different from a predetermined collocated image, and may determine that a corresponding block is available if the image pointed to by the surrounding block to be scanned is the same as the predetermined collocated image. In addition, the motion information determination unit (2130) may determine the availability of a surrounding block by considering the size of a storage block. For example, when the size of a storage block is M x M, the motion information determination unit (2130) may determine that a corresponding block is not available if the x component value or the y component value of the motion vector of a surrounding block to be scanned is less than M. As another example, when the size of the storage block is M x M, the motion information determination unit (2130) may determine that the block is not available if the x component value or the y component value of the motion vector of the surrounding block to be scanned is less than M / 2.

[0322] In one embodiment, the motion information determination unit (2130) may scan in the order of a surrounding block (A0 or A1) located to the left of the current block → a surrounding block (B0, B1, or B2) located above the current block, and determine the motion vector of an available surrounding block as a temporal motion vector. If the left and upper surrounding blocks are not available, the motion vector determination unit may determine a predetermined motion vector (e.g., a zero vector) as the temporal motion vector.

[0323] In one embodiment, the motion information determination unit (2130) may scan a neighboring block (A0 or A1) located on the left side of the current block, and if the left neighboring block is available, determine the motion vector of the left neighboring block as the temporal motion vector. If the left neighboring block is not available, the motion vector determination unit may determine a predetermined motion vector (e.g., a zero vector) as the temporal motion vector. In addition, in one embodiment, the left neighboring block (A0 or A1) of the current block → upper neighboring block (B0, B1 or B1) → temporal neighboring block (Col or Br) may be scanned in that order, and the motion vector of the neighboring block that is available may be determined as the temporal motion vector.

[0324] In one embodiment, the motion information determination unit (2130) may determine the location and scanning order of the surrounding blocks to be scanned based on the shape of the current block (2310), which will be described with reference to FIG. 27. In FIG. 27, (a) illustrates a case where the current block (2310) has a square shape, (b) illustrates a case where the horizontal length of the current block (2310) is greater than the vertical length, and (c) illustrates a case where the vertical length of the current block (2310) is greater than the horizontal length.

[0325] First, the positions of the surrounding blocks illustrated in Fig. 27 will be described. The position of the pixel located at the far left of the top of the current block (2310) is referred to as (xCb, yCb), and the horizontal and vertical lengths of the current block (2310) are referred to as cbWidth and cbHeight in pixels, respectively. Block A1 is a block that includes a pixel at a position (xCb-1, yCb+cbHeight-1), and block A0 is a block that includes a pixel at a position (xCb-1, yCb+cbHeight). In addition, block B1 is a block that includes a pixel at a position (xCb+cbWidth-1, yCb-1), and block B0 is a block that includes a pixel at a position (xCb+cbWidth, yCb-1). Additionally, block A2 is a block containing pixels at positions (xCb-1, yCb+cbHeight / 2-1), and block B3 is a block containing pixels at positions (xCb+cbWidth / 2-1, yCb-1). However, the positions of the surrounding blocks illustrated in Fig. 27 are only examples and may vary depending on the implementation.

[0326] For example, if the current block (2310) has a square shape, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of a left peripheral block (A0 or A1) of the current block (2310). In addition, if the horizontal length of the current block (2310) is greater than the vertical length, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of an upper peripheral block (B0 or ​​B1) of the current block (2310), and if the vertical length of the current block (2310) is greater than the horizontal length, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of a left peripheral block (A0 or A1) of the current block (2310).

[0327] As another example, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of a left peripheral block (A0 or A1) of the current block (2310) when the current block (2310) has a square shape. In addition, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of a left peripheral block (A0 or A1) of the current block (2310) when the horizontal length of the current block (2310) is greater than the vertical length, and can determine a temporal motion vector by determining the availability of an upper peripheral block (B0 or ​​B1) of the current block (2310) when the vertical length of the current block (2310) is greater than the horizontal length.

[0328] As another example, the motion information determination unit (2130) can determine a temporal motion vector by determining availability in the order of A1 block → B1 block → B0 block → A0 block when the current block (2310) has a square shape or the vertical length of the current block (2310) is greater than the horizontal length, and can determine a temporal motion vector by determining availability in the order of B1 block → A1 block → B0 block → A0 block when the horizontal length of the current block (2310) is greater than the vertical length.

[0329] As another example, the motion information determination unit (2130) determines the temporal motion vector by determining availability in the order of A1 block → B1 block → B0 block → A0 block when the current block (2310) has a square shape, and determines the temporal motion vector by determining availability in the order of B1 block → B0 block → A1 block → A0 block when the vertical length of the current block (2310) is greater than the horizontal length or the horizontal length is greater than the vertical length.

[0330] As another example, if the current block (2310) has a square shape, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the left peripheral block (A0 or A1) and the upper peripheral block (B0 or ​​B1) of the current block (2310), and if the horizontal length of the current block (2310) is greater than the vertical length, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the upper peripheral block (B0 or ​​B1) of the current block (2310). In addition, if the vertical length of the current block (2310) is greater than the horizontal length, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the left peripheral block (A0 or A1) of the current block (2310).

[0331] As another example, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the left peripheral block (A0 or A1) and the upper peripheral block (B0 or ​​B1) when the current block (2310) has a square shape. The motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the left peripheral block (A0 or A1) and the upper peripheral block (B3) when the horizontal length of the current block (2310) is greater than the vertical length. Here, the B3 block is a block located at the upper right of the left block determined by vertically dividing the current block (2310) in two. In addition, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the upper peripheral block (B0 or ​​B1) and the left peripheral block (A2) of the current block (2310) when the vertical length of the current block (2310) is greater than the horizontal length. Here, block A2 is a block located at the lower left of the upper block determined by dividing the current block (2310) into two horizontal parts.

[0332] As another example, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the A1 block, the B1 block, the A0 block, and the B0 block when the current block (2310) has a square shape. The motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the A1 block, the B3 block, the A0 block, and the B0 block when the horizontal length of the current block (2310) is greater than the vertical length. In addition, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the A2 block, the B1 block, the A0 block, and the B0 block when the vertical length of the current block (2310) is greater than the horizontal length. Here, the A0 block and the B0 block may be excluded from the scanning target regardless of the shape of the current block (2310).

[0333] As another example, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the A1 block, the B1 block, the A0 block, and the B0 block when the current block (2310) has a square shape. The motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the A1 block, the B3 block, the B1 block, and the A0 block when the horizontal length of the current block (2310) is greater than the vertical length. In addition, the motion information determination unit (2130) can determine a temporal motion vector by determining the availability of the B1 block, the A1 block, the A2 block, and the B0 block when the vertical length of the current block (2310) is greater than the horizontal length.

[0334] As another example, the motion information determination unit (2130) can determine the temporal motion vector by determining the availability in the order of A1 block → B1 block → B0 block → A0 block when the current block (2310) has a square shape. The motion information determination unit (2130) can determine the temporal motion vector by determining the availability in the order of B1 block → B0 block → B3 block → A1 block when the horizontal length of the current block (2310) is greater than the vertical length. In addition, the motion information determination unit (2130) can determine the temporal motion vector by determining the availability in the order of A1 block → A2 block → A0 block → B1 block when the vertical length of the current block (2310) is greater than the horizontal length.

[0335] As another example, the motion information determination unit (2130) can determine the temporal motion vector by determining the availability in the order of A1 block → B1 block → B0 block → A0 block when the current block (2310) has a square shape. The motion information determination unit (2130) can determine the temporal motion vector by determining the availability in the order of B1 block → B0 block when the horizontal length of the current block (2310) is greater than the vertical length. In addition, the motion information determination unit (2130) can determine the temporal motion vector by determining the availability of A1 block → A0 block when the vertical length of the current block (2310) is greater than the horizontal length.

[0336] As another example, the motion information determination unit (2130) can determine the temporal motion vector by judging the availability in the order of the left peripheral block (A1 or A0) → upper peripheral block (B1 or B0) when the current block (2310) has a square shape. The motion information determination unit (2130) can determine the temporal motion vector by judging the availability of the upper peripheral block (B0 or ​​B1) when the horizontal length of the current block (2310) is greater than the vertical length. In addition, the motion information determination unit (2130) can determine the temporal motion vector by judging the availability of the left peripheral block (A1 or A0 block) when the vertical length of the current block (2310) is greater than the horizontal length.

[0337] When determining a temporal motion vector through the above-described scanning process, the motion information determination unit (2130) may determine a temporal motion vector by converting the motion vector of the surrounding block to a B pixel (B is a rational number) precision different from the A pixel precision when the precision of the motion vector of the surrounding block that is available is A pixel (A is a rational number).

[0338] The motion information determination unit (2130) can determine the precision of the temporal motion vector based on at least one of the size of the storage block, which is a unit for storing the motion vector, and the size of the sub-block within the current block. For example, when the size of the storage block is M x M, the motion information determination unit (2130) can convert the motion vector of the surrounding block to an M / 2 pixel precision or an M pixel precision and determine it as a temporal motion vector. At this time, the motion information determination unit (2130) can divide the motion vector of the surrounding block by a predetermined value to convert the motion vector of the surrounding block of high precision to a low precision, and then round the resulting value up, down, or up to determine a low-precision motion vector in integer units, and determine the determined low-precision motion vector as the temporal motion vector. When the size of the storage block is M x M, the motion information determination unit (2130) can omit pixel-unit position calculation for extracting motion vectors of sub-regions within the first reference region by converting the motion vector of the surrounding block to M / 2 pixel precision or M pixel precision.

[0339] As another example, when the size of the sub-block is M x M, the motion information determination unit (2130) can determine the motion vector of the surrounding block as a temporal motion vector by converting it to an M / 2 pixel precision or an M pixel precision. At this time, in order to convert the motion vector of the surrounding block of high precision into a low precision, the motion information determination unit (2130) can divide the motion vector of the surrounding block by a predetermined value, and then round the resulting value up, down, or up to determine a low precision motion vector in integer units, and determine the determined low precision motion vector as a temporal motion vector.

[0340] As another example, the motion information determination unit (2130) may determine a temporal motion vector by converting the motion vector of a surrounding block with a pixel precision pre-mapped for the size of the storage block and the size of the sub-block.

[0341] In one embodiment, the motion information determination unit (2130) may determine a temporal motion vector based on a history of motion vectors. The motion information determination unit (2130) may store a predetermined number of motion vectors used in the decoding process of previous blocks, and may determine at least one motion vector used in the decoding process of the previous block as a temporal motion vector when decoding the current block. For example, the motion information determination unit (2130) may determine a motion vector used in the decoding process of the block immediately preceding the current block as a temporal motion vector. As another example, the motion information determination unit (2130) may determine a motion vector indicated by information included in the bitstream among the motion vectors stored as a history as a temporal motion vector. The motion information determination unit (2130) may store a predetermined number of motion vectors of previous blocks for each maximum coding unit, slice unit, and picture unit.

[0342] In another embodiment, the motion information determination unit (2130) may determine a global motion vector obtained from a bitstream as a temporal motion vector. In this case, the global motion vector may be included in the bitstream with a predetermined pixel precision. The global motion vector may be used to decode a picture including the current block, a slice including the current block, or blocks within a maximum coding unit including the current block.

[0343] In another embodiment, the motion information determination unit (2130) may determine a predetermined motion vector (e.g., a zero vector) as a temporal motion vector.

[0344] In another embodiment, the motion information determination unit (2130) may determine the temporal motion vector based on at least one of the size of the storage block and the size of the sub-block. For example, when the size of the storage block is M x M, the motion information determination unit (2130) may determine (M, M) or (M / 2, M / 2) as the temporal motion vector with 1 pixel precision. In addition, for example, when the size of the sub-block is M x M, the motion information determination unit (2130) may determine (M, M) or (M / 2, M / 2) as the temporal motion vector with 1 pixel precision. As another example, when the size of the storage block is M x M and the size of the sub-block is M x M, the motion information determination unit (2130) may determine (M, M) or (M / 2, M / 2) as the temporal motion vector with 1 pixel precision. As another example, the motion information determination unit (2130) may determine a motion vector mapped in advance for the size of the storage block and the size of the sub-block as a temporal motion vector.

[0345] As another example, when the motion vector determined based on at least one of the size of the storage block and the size of the sub-block is (I, J), the motion information determination unit (2130) may determine not only (I, J) but also a motion vector transformed from (I, J) (for example, at least one of (-I, J), (I, -J), (-I, -J), (I, 0), (-I, 0), (0, J), (0, -J), and (0, 0)) as a candidate, and may determine any one of the motion vectors determined as a candidate as a temporal motion vector.

[0346] In another embodiment, the motion information determination unit (2130) may determine a predetermined motion vector (e.g., a zero vector) as a temporal motion vector when the current block is a predetermined block unit (e.g., a maximum coding unit). When the current block is not a predetermined block unit (e.g., a maximum coding unit), a temporal motion vector may be determined through a scanning process of a predetermined block.

[0347] When the restoration of the current block is completed by the restoration unit (2150), the deblocking unit (2170) can deblock filter the sample values ​​of the blocks based on the boundaries between the blocks to remove artifacts in the image.

[0348] Figure 28 is a drawing for explaining a deblocking process according to one embodiment.

[0349] Referring to FIG. 28, the current image (2700) includes a current block (2310) and surrounding blocks (2730, 2750). In one embodiment, the deblocking unit (2170) deblocks sample values ​​adjacent to the boundary (2735, 2755) between the current block (2310) and the surrounding blocks (2730, 2750). Specifically, deblocking filtering may be performed to change the values ​​of samples within the current block (2310) and samples within the right block (2730) adjacent to the boundary (2735) based on the boundary (2735) between the current block (2310) and the right block (2730). Additionally, based on the boundary (2755) between the current block (2310) and the sub-block (2750), deblocking filtering can be performed to change the values ​​of samples in the current block (2310) and samples in the sub-block (2750) adjacent to the boundary (2755).

[0350] Additionally, in one embodiment, the deblocking unit (2170) can also perform deblocking on sub-blocks (2312, 2314, 2316, 2318) within the current block (2310). Specifically, the sample values ​​of the sub-blocks (2312, 2314, 2316, 2318) can be deblocked and filtered based on the boundaries (2311, 2313, 2315, 2317) between the sub-blocks (2312, 2314, 2316, 2318), thereby determining the filtered current block. Accordingly, deblocking filtering may be performed to change the values ​​of samples within the first sub-block (2312) and samples within the second sub-block (2314) adjacent to the boundary (2311) based on the boundary (2311) between the first sub-block (2312) and the second sub-block (2314). In addition, deblocking filtering may be performed to change the values ​​of samples within the first sub-block (2312) and samples within the third sub-block (2316) adjacent to the boundary (2313) based on the boundary (2313) between the first sub-block (2312) and the third sub-block (2316). Similarly, deblocking filtering can be performed on the boundary (2317) between the second sub-block (2314) and the fourth sub-block (2318), and the boundary (2317) between the third sub-block (2316) and the fourth sub-block (2318).

[0351] In one embodiment, the deblocking unit (2170) may deblock filter the sub-blocks (2312, 2314, 2316, 2318) in the current block (2310) if the size of the sub-blocks (2312, 2314, 2316, 2318) is less than or equal to a predetermined size (e.g., 8 x 8 or 16 x 16, etc.), and may not perform deblock filtering if the size of the sub-blocks (2312, 2314, 2316, 2318) is greater than the predetermined size.

[0352] Additionally, in one embodiment, the deblocking unit (2170) may deblock filter the sub-blocks (2312, 2314, 2316, 2318) in the current block (2310) if the size of the sub-blocks (2312, 2314, 2316, 2318) is greater than or equal to a predetermined size (e.g., 8 x 8 or 16 x 16, etc.), and may not perform deblock filtering if the size of the sub-blocks (2312, 2314, 2316, 2318) is smaller than the predetermined size.

[0353] Figure 29 is a flowchart for explaining a method for decoding an image according to one embodiment.

[0354] In step S2810, the image decoding device (2100) determines a temporal motion vector, and in step S2820, determines a candidate list including a first reference block pointed to by the temporal motion vector as a candidate.

[0355] The video decoding device (2100) can determine a temporal motion vector and a candidate list when the size of the current block is greater than a predetermined size and the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of a candidate included in the candidate list.

[0356] The process of determining the temporal motion vector and candidate list has been described in detail above, so its description is omitted here.

[0357] In step S2830, when a first reference block is selected from among candidates included in the candidate list, the image decoding device (2100) determines motion vectors of sub-blocks within the current block using motion vectors obtained from the first reference block.

[0358] In step S2840, the image decoding device (2100) can restore the current block based on the sample values ​​of the second reference block pointed to by the motion vectors of the sub blocks.

[0359] Once the current block is restored, the image decoding device (2100) can obtain a filtered current block by deblocking filtering the sample values ​​of the sub-blocks based on the boundaries between the sub-blocks within the restored current block. The filtered current block can be used as a reference block for the next block.

[0360] Fig. 30 is a block diagram illustrating the configuration of an image encoding device (2900) according to one embodiment.

[0361] The video encoding device (2900) includes an encoding unit (2910) and a generation unit (2930). The encoding unit (2910) and the generation unit (2930) according to one embodiment may be implemented with at least one processor. The video encoding device (2900) may include one or more data storage units (not shown) that store input / output data of the encoding unit (2910) and the generation unit (2930). In addition, the video encoding device (2900) may also include a memory control unit (not shown) that controls data input / output of the data storage unit (not shown).

[0362] The encoding unit (2910) encodes the image, and the generation unit (2930) generates a bitstream including information generated as a result of encoding the image. The encoding unit (2910) and the generation unit (2930) illustrated in FIG. 30 may correspond to the encoding unit (220) and the bitstream generation unit (210) illustrated in FIG. 2, respectively.

[0363] The encoding unit (2910) can determine the prediction mode of the current block determined within the current image. The prediction mode of the current block can include intra mode, inter mode, merge mode, AMVP mode, direct mode, skip mode, etc.

[0364] The encoding unit (2910) may determine a candidate list including a first reference block pointed to by a temporal motion vector as a candidate when the size of the current block is greater than or equal to a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.). The candidate list may include a predetermined number of candidates.

[0365] The first reference block refers to a block for extracting a motion vector used to determine the motion vector of the current block.

[0366] When comparing the size of the current block with the predetermined size, the encoding unit (2910) may compare one of the horizontal and vertical sizes of the current block (e.g., a smaller size) with the predetermined size. For example, when the size of the current block is 4 x 16 and the predetermined size is 8 x 8, since the horizontal size of the current block, 4, is smaller than 8, which represents the size of one side of the predetermined size, the size of the current block may be determined to be smaller than the predetermined size.

[0367] In one embodiment, the encoder (2910) may determine a candidate list including blocks other than the first reference block as candidates when the size of the current block is smaller than a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.). That is, the first reference block may or may not be included in the candidate list based on the size of the current block.

[0368] In one embodiment, the encoder (2910) may determine a first candidate list including the first reference block as a candidate when the size of the current block is greater than or equal to a predetermined size, and may determine a second candidate list including blocks other than the first reference block as candidates when the size of the current block is smaller than the predetermined size.

[0369] Also, in one embodiment, if the size of the current block is smaller than a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.) and the temporal motion vector is a predetermined motion vector (e.g., a zero vector), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporal neighboring blocks within the predetermined collocated image as candidates. Conversely, if the size of the current block is larger than the predetermined size or the temporal motion vector is not the predetermined motion vector, the candidate list may include the first reference block, and temporal neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0370] Additionally, in one embodiment, if the size of the current block is greater than a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporal neighboring blocks within a predetermined collocated image as candidates. Conversely, if the size of the current block is less than or equal to the predetermined size, the candidate list may include the first reference block, and temporal neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0371] Additionally, in one embodiment, if the size of the current block is equal to a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. Conversely, if the size of the current block is not equal to the predetermined size, the candidate list may include the first reference block. In this case, temporally neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be the size of a sub-block.

[0372] Additionally, in one embodiment, if the size of the current block is different from a predetermined size (e.g., 4 x 4, 8 x 8, 16 x 16, 32 x 32, 64 x 64, or 128 x 128, etc.), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the size of the current block is equal to the predetermined size, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list. The predetermined size may be a size of a sub-block.

[0373] Additionally, in one embodiment, if the current block is a predetermined block unit (e.g., a maximum coding unit), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within a predetermined collocated image as candidates. Conversely, if the current block is not a predetermined block unit, the candidate list may include the first reference block, and temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0374] Additionally, in one embodiment, if the size of the current block is at least k times (where k is a predetermined integer) larger than the size of the sub-block, a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporally neighboring blocks within the predetermined collocated image as candidates. Conversely, if the size of the current block is not at least k times larger than the size of the predetermined block, the candidate list may include the first reference block, and in this case, temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0375] Additionally, in one embodiment, when candidates for a candidate list are sequentially determined based on the availability of multiple blocks including a first reference block, if the first reference block is determined as the first candidate in the candidate list, the first reference block may be excluded from the candidate list. For example, in a situation where the first spatial neighboring block, the first reference block, and the second spatial neighboring block are included in the candidate list in the order of their availability, if the first spatial neighboring block is unavailable and the first reference block is included in the candidate list as the first candidate, the first reference block may be excluded from the candidate list.

[0376] Additionally, in one embodiment, within the GOP including the current picture, a candidate list including blocks other than the first reference block as candidates may be determined if the value of the temporal layer of the current picture is equal to a predetermined value (e.g., the largest value).

[0377] Additionally, in one embodiment, if the temporal motion vector is a predetermined motion vector (e.g., a zero vector), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporal neighboring blocks within the predetermined collocated image as candidates. Conversely, if the temporal motion vector is different from the predetermined motion vector, the candidate list may include the first reference block, and in this case, temporal neighboring blocks within the collocated image may not be included in the candidate list.

[0378] Additionally, in one embodiment, if the temporal motion vector is different from a predetermined motion vector (e.g., a zero vector), a candidate list including blocks other than the first reference block as candidates may be determined. In this case, the candidate list may include temporal neighboring blocks within the predetermined collocated image as candidates. Conversely, if the temporal motion vector is identical to the predetermined motion vector, the candidate list may include the first reference block, and in this case, temporal neighboring blocks within the collocated image may not be included in the candidate list.

[0379] Additionally, in one embodiment, if there is no motion vector corresponding to the center pixel of the first reference block, a candidate list including blocks other than the first reference block as candidates may be determined. Conversely, if there is a motion vector corresponding to the center pixel of the first reference block, the candidate list may include the first reference block, in which case temporally neighboring blocks within the collocated image may not be included in the candidate list.

[0380] The encoding unit (2910) can determine the candidate list when the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of a candidate included in the candidate list.

[0381] The method for determining the candidate list by the encoding unit (2910) is the same as the method for determining the candidate list by the motion information determination unit (2130) described above, so a detailed description is omitted here.

[0382] In one embodiment, the encoding unit (2910) determines a temporal motion vector pointing to the first reference block. The method for determining the temporal motion vector is the same as the method for determining the temporal motion vector of the motion information determination unit (2130) described above, and thus a detailed description thereof is omitted here.

[0383] The encoding unit (2910) can assign indices to candidates included in the candidate list. For example, the index with the lowest value can be assigned to the first reference block. The encoding unit (2910) determines a motion vector of the current block or motion vectors of sub-blocks within the current block, and selects one of the candidates included in the candidate list to encode the motion vector of the current block. When the first reference block is selected, the first reference block can be used to determine the motion vectors of the sub-blocks within the current block. For example, when the first reference block is selected, the motion vectors of the sub-regions within the first reference block can be determined as the motion vectors of the sub-blocks within the current block. Since the method for determining the motion vectors of the sub-regions within the first reference block has been described above, a detailed description thereof will be omitted.

[0384] The generation unit (2930) generates a bitstream including information generated as a result of encoding an image. The bitstream may include at least one of information indicating a prediction mode of a current block, information indicating one of the candidates included in a candidate list, information indicating a temporal motion vector, a residual motion vector between the motion vector of the current block and the motion vector of the candidate included in the candidate list, and residual data between sample values ​​of a second reference block and sample values ​​of the current block.

[0385] The encoding unit (2910) may also perform the functions of the motion information determination unit (2130), the restoration unit (2150), and the deblocking unit (2170) of the aforementioned video decoding device (2100). Accordingly, the encoding unit (2910) may determine the motion vector of the current block using the motion vector of a candidate selected from the candidate list, and restore the current block through motion compensation of the current block.

[0386] The encoding unit (2910) can apply deblocking filtering to the current image including the reconstructed current block. The encoding unit (2910) can deblocking filter the current block and the surrounding blocks based on the boundary between the current block and the surrounding blocks. In addition, the encoding unit (2910) can deblocking filter the sub-blocks based on the boundary between the sub-blocks within the current block. The deblocking filtered current block can be used for encoding the subsequent block. When the current block becomes a reference block of a subsequent block, the motion vector of the subsequent block can be determined according to the representative motion vector of the first reference block described above. In another embodiment, when the current block becomes a reference block of a subsequent block, the motion vector of the subsequent block can also be determined according to the motion vector of any one of the sub-blocks within the current block.

[0387] FIG. 31 is a drawing for explaining an image encoding method according to one embodiment.

[0388] In step S3010, the video encoding device (2900) determines a temporal motion vector, and in step S3020, determines a candidate list including a first reference block pointed to by the temporal motion vector as a candidate.

[0389] The video encoding device (2900) can determine a temporal motion vector and a candidate list when the size of the current block is greater than or equal to a predetermined size and the prediction mode of the current block is a mode that determines the motion vector of the current block using the motion vector of a candidate included in the candidate list.

[0390] The process of determining the temporal motion vector and candidate list has been described in detail above, so its description is omitted here.

[0391] In step S3030, the video encoding device (2900) determines the motion vector of the current block and selects a candidate to be used in determining the motion vector of the current block from the candidate list. The video encoding device (2900) can determine one candidate based on the cost corresponding to each candidate included in the candidate list. A rate-distortion cost may be used when calculating the cost.

[0392] In step S3040, the video encoding device (2900) generates a bitstream including information indicating a candidate selected from the candidate list. If a first reference block is selected from the candidate list, motion vectors obtained from the first reference block can be used to determine motion vectors of sub-blocks within the current block.

[0393] As described above, in addition to information indicating a candidate selected from the candidate list, the bitstream may further include at least one of information indicating a prediction mode of the current block (e.g., sub-block_merge_flag), information indicating a temporal motion vector, a residual motion vector between the motion vector of the current block and the motion vector of the candidate included in the candidate list, and residual data between sample values ​​of a second reference block pointed to by the motion vector of the current block and sample values ​​of the current block.

[0394] Meanwhile, the embodiments of the present disclosure described above can be written as a program or instruction that can be executed on a computer, and the written program can be stored in a medium or a computer program product.

[0395] A medium may be something that permanently stores a computer-executable program, or may be something that temporarily stores it for execution or download. Furthermore, the medium may be a variety of recording or storage means, including a single piece of hardware or a combination of several pieces, and is not limited to media directly connected to a computer system, but may also be distributed across a network. Examples of media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and anything configured to store program instructions, including ROM, RAM, and flash memory. Furthermore, other examples of media may include recording or storage media managed by app stores that distribute applications, sites that supply or distribute various software, servers, etc.

[0396] Above, the technical idea of ​​the present disclosure has been described in detail with reference to preferred embodiments, but the technical idea of ​​the present disclosure is not limited to the above embodiments, and various modifications and changes are possible by a person having ordinary knowledge in the art within the scope of the technical idea of ​​the present disclosure.

Claims

1. In the method of decrypting the video, A step of determining a candidate list including a first reference block pointed to by a temporal motion vector as a candidate when the size of the current block in the above image is greater than or equal to a predetermined size; A step of determining motion vectors of sub-blocks within the current block using motion vectors obtained from the first reference block when the first reference block is selected from among candidates included in the candidate list; and A method for decoding an image, comprising the step of restoring the current block based on sample values ​​of a second reference block pointed to by the motion vectors of the sub-blocks.

2. In paragraph 1, The method of decrypting the above video is as follows: A method for decoding an image, further comprising a step of obtaining a filtered current block by deblocking filtering sample values ​​of the sub-blocks based on a boundary between the sub-blocks in the restored current block.

3. In paragraph 1, The step of determining the above candidate list is: A method for decoding an image, comprising a step of determining a candidate list, when the prediction mode of the current block is a mode for determining a motion vector of the current block using a motion vector of a candidate included in the candidate list.

4. In paragraph 1, The method of decrypting the above video is as follows: A method for decoding an image, further comprising a step of determining a motion vector of a surrounding block spatially adjacent to the current block as the temporal motion vector.

5. In paragraph 1, The above surrounding blocks are, A method for decoding an image, comprising a lower left block of the current block.

6. In paragraph 4, The step of determining the above temporal motion vector is: A method for decoding an image, comprising the step of determining a predetermined motion vector as the temporal motion vector when the availability of the surrounding blocks is not available.

7. In paragraph 4, The step of determining the above temporal motion vector is: A method for decoding an image, comprising the step of determining a predetermined motion vector instead of the motion vector of the surrounding block as the temporal motion vector when the image indicated by the motion vector of the surrounding block is different from a predetermined collocated image.

8. In paragraph 1, The method of decrypting the above video is as follows: A method for decoding an image, further comprising a step of determining a predetermined motion vector as the temporal motion vector when the current block is a predetermined block unit.

9. In paragraph 1, A method for decoding an image, wherein an index having the smallest value among the candidates included in the above candidate list is assigned to the first reference block.

10. In paragraph 1, The method of decrypting the above video is as follows: A method for decoding an image, further comprising the step of determining a motion vector corresponding to a center sample among samples of the first reference block as a representative motion vector.

11. In paragraph 10, The method of decrypting the above video is as follows: A step of determining sub-regions corresponding to the above sub-blocks in the first reference block; and A method for decoding an image, further comprising a step of determining a motion vector of a sub-region from which a motion vector cannot be obtained among the above sub-regions as the representative motion vector.

12. In paragraph 1, The step of determining the above candidate list is: A method for decoding an image, comprising the step of determining a candidate list including blocks other than the first reference block as candidates when a motion vector corresponding to a center sample among samples of the first reference block does not exist.

13. A computer-readable recording medium recording a program for executing the method for decrypting the video of paragraph 1.

14. In a video decryption device including at least one processor, A motion information determination unit that determines a candidate list including a first reference block indicated by a temporal motion vector as a candidate when the size of the current block in the image is greater than a predetermined size, and when the first reference block is selected from among the candidates included in the candidate list, determines motion vectors of sub-blocks in the current block using motion vectors obtained from the first reference block; and An image decoding device, comprising a restoration unit that restores the current block based on sample values ​​of a second reference block pointed to by the motion vectors of the sub-blocks.

15. In the method of encoding an image, A step of determining a candidate list including a first reference block pointed to by a temporal motion vector as a candidate when the size of the current block in the above image is greater than or equal to a predetermined size; A step of selecting a candidate used to determine the motion vector of the current block among the candidates included in the candidate list; and A step of generating a bitstream including information indicating the selected candidate, A method for encoding an image, wherein motion vectors obtained from the first reference block are used to determine motion vectors of sub-blocks within the current block.