Image encoding device and image decoding device using triangular prediction mode, and image encoding method and image decoding method performed by same

Abstract

Disclosed in one embodiment is an image decoding method comprising the steps of: acquiring information related to a triangular prediction mode for a current block from a bitstream; dividing the current block into two triangular partitions according to the information related to the triangular prediction mode; constructing a merge list for the triangular prediction mode according to a merge list construction method in a conventional merge mode; selecting a motion vector for the two triangular partitions according to information indicating a motion vector among the motion vectors included in the merge list; obtaining prediction blocks corresponding to the two triangular partitions from a reference image based on the motion vector; and reconstructing the current block based on the final prediction block.

Description

[0001] This application is a divisional application of a patent application with an application date of December 20, 2019, application number 201980085114.1, and titled "Image encoding device and image decoding device using a triangle prediction mode and image encoding method and image decoding method executed by them". Technical Field

[0002] The present disclosure relates to the field of image encoding and decoding. More specifically, the present disclosure relates to an apparatus for encoding and decoding an image by using a triangle prediction mode and a method for encoding and decoding an image by the apparatus. Background Art

[0003] In the method of encoding and decoding an image, each block may be predictively encoded and predictively decoded by inter-frame prediction or intra-frame prediction.

[0004] Intra-frame prediction refers to a method of compressing an image by removing spatial redundancy in the image, and inter-frame prediction refers to a method of compressing an image by removing temporal redundancy between images. A representative example of inter-frame prediction is motion estimation coding. In motion estimation coding, a block of a current image is predicted by using at least one reference image. A reference block most similar to the current block can be searched within a preset search range by using a preset evaluation function. The current block is predicted based on the reference block, and a residual block is generated by subtracting a prediction block generated as a result of the prediction from the current block, and then the residual block is encoded. Here, in order to further accurately perform prediction, interpolation may be performed on the reference image so as to generate pixels in sub-pixel units that are smaller than integer pixel units, and inter-frame prediction may be performed based on pixels in sub-pixel units.

[0005] In codecs such as H.264 Advanced Video Coding (AVC) and High Efficiency Video Coding (HEVC), a motion vector of a previously encoded block adjacent to a current block or blocks included in a previously encoded picture is used as a predicted motion vector of the current block in order to predict the motion vector of the current block. A differential motion vector, which is a difference between the motion vector of the current block and the predicted motion vector, is signaled to a decoder according to a preset scheme. In a merge mode of inter-frame prediction, instead of signaling the differential motion vector to the decoder, information indicating a motion vector candidate to be used as the motion vector of the current block among motion vector candidates included in a merge list generated according to a preset rule is signaled to the decoder. Summary of the invention

[0006] Technical issues

[0007] According to technical purposes, the image decoding apparatus and method and the image encoding apparatus and method according to the embodiments may set restrictions on a prediction mode of a current block, thereby preventing unnecessary information from being included in a bitstream.

[0008] In addition, according to technical purposes, the image decoding apparatus and method and the image encoding apparatus and method according to the embodiments can simplify the process of encoding and decoding an image.

[0009] Solution to the problem

[0010] According to an embodiment, an image decoding method may include: obtaining information related to a triangle prediction mode for a current block divided from an image from a bitstream; dividing the current block into two triangle partitions according to the information related to the triangle prediction mode; generating a merge list for the triangle prediction mode according to a merge list generation method in a normal merge mode, wherein, in the normal merge mode, the current block is reconstructed without being divided into triangle partitions; selecting motion vectors for the two triangle partitions according to information indicating a motion vector among motion vectors included in the merge list, the information being included in the information related to the triangle prediction mode; obtaining a prediction block corresponding to the two triangle partitions from a reference image based on the selected motion vector; and reconstructing the current block based on a final prediction block obtained as a combination of the prediction blocks.

[0011] Disclosure of beneficial effects

[0012] According to an embodiment, an image decoding apparatus and method and an image encoding apparatus and method may set a restriction on a prediction mode of a current block, thereby preventing unnecessary information from being included in a bitstream.

[0013] In addition, according to the embodiments, the image decoding apparatus and method and the image encoding apparatus and method can simplify the process of encoding and decoding an image.

[0014] However, the effects that can be achieved by the apparatus and method for decoding an image and the apparatus and method for encoding an image according to the embodiments are not limited to those described above, and other effects not mentioned can be clearly understood by a person of ordinary skill in the art from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A brief description of each figure is provided to provide a better understanding of the drawings referenced herein.

[0016] Figure 1 is a block diagram of an image decoding apparatus according to an embodiment.

[0017] Figure 2 is a block diagram of an image encoding apparatus according to an embodiment.

[0018] Figure 3 A process of determining at least one coding unit by splitting a current coding unit, performed by an image decoding apparatus according to an embodiment, is illustrated.

[0019] Figure 4 A process of determining at least one coding unit by splitting a non-square coding unit, performed by an image decoding apparatus according to an embodiment, is illustrated.

[0020] Figure 5 A process of splitting a coding unit based on at least one of block shape information and division shape pattern information, performed by an image decoding apparatus according to an embodiment, is illustrated.

[0021] Figure 6 A method of determining a preset coding unit from among odd-numbered coding units, performed by an image decoding apparatus according to an embodiment, is illustrated.

[0022] Figure 7 An order in which a plurality of coding units are processed when an image decoding apparatus determines a plurality of coding units by splitting a current coding unit according to an embodiment is illustrated.

[0023] Figure 8 A process of determining that a current coding unit is to be split into an odd number of coding units, performed by an image decoding apparatus when coding units cannot be processed in a preset order, according to an embodiment is illustrated.

[0024] Fig. 9 A process of determining at least one coding unit by splitting a first coding unit, performed by an image decoding apparatus according to an embodiment, is illustrated.

[0025] Fig.10 It is shown that shapes into which the second coding unit may be split are restricted when a second coding unit having a non-square shape determined by splitting the first coding unit by an image decoding apparatus satisfies a preset condition according to an embodiment.

[0026] Fig.11 A process of splitting a square coding unit performed by an image decoding apparatus when division shape pattern information indicates that the square coding unit is not to be split into four square coding units according to an embodiment is illustrated.

[0027] Fig.12 It is shown that a processing order among a plurality of coding units may be changed according to a process of dividing the coding units according to an embodiment.

[0028] Fig.13 A process of determining a depth of a coding unit as a shape and a size of a coding unit change when a coding unit is recursively split so that a plurality of coding units are determined according to an embodiment is illustrated.

[0029] Fig.14 Depth that may be determined based on the shape and size of a coding unit and a partial index (PID) for distinguishing coding units according to an embodiment are illustrated.

[0030] Fig.15 It is illustrated that a plurality of coding units are determined based on a plurality of preset data units included in a picture according to an embodiment.

[0031] Fig.16 A processing block serving as a unit for determining an order of reference coding units included in a picture according to an embodiment is illustrated.

[0032] Fig.17 Coding units that may be determined for each picture in a picture when a division shape combination of coding units varies for each picture according to an embodiment are illustrated.

[0033] Fig.18 Various shapes of coding units that may be determined based on division shape pattern information that may be represented as a binary code according to an embodiment are illustrated.

[0034] Fig.19 Other shapes of coding units that may be determined based on division shape pattern information that may be represented as a binary code according to an embodiment are illustrated.

[0035] Fig. 20 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0036] Fig.21 is a block diagram showing the configuration of an image decoding device according to an embodiment.

[0037] Fig. 22 An example of a syntax structure for parsing information related to a triangle prediction mode according to an embodiment is shown.

[0038] Fig.23 is a diagram for describing a method for generating a merge list in a normal merge mode.

[0039] Fig.24 An example for describing a method of generating a merge list for a triangle prediction mode from a merge list for a normal merge mode is shown.

[0040] Fig.25 An example for describing a method of generating a merge list for a triangle prediction mode from a merge list for a normal merge mode is shown.

[0041] Fig.26 is a diagram for describing a method of determining a prediction block corresponding to two triangular partitions divided from a current block.

[0042] Fig. 27 is a diagram for describing a method of generating a final prediction block by combining prediction blocks corresponding to two triangle partitions.

[0043] Fig.28 is a flowchart of an image decoding method according to an embodiment.

[0044] Fig.29 is a block diagram of a configuration of an image encoding device according to an embodiment.

[0045] Fig.30 is a flowchart of an image encoding method according to an embodiment.

[0046] Best Mode

[0047] According to an embodiment, an image decoding method may include: obtaining information related to a triangle prediction mode for a current block divided from an image from a bitstream; dividing the current block into two triangle partitions according to the information related to the triangle prediction mode; generating a merge list for the triangle prediction mode according to a merge list generation method in a normal merge mode, wherein, in the normal merge mode, the current block is reconstructed without being divided into triangle partitions; selecting a motion vector for the two triangle partitions according to information indicating a motion vector among motion vectors included in the merge list, wherein the information is included in the information related to the triangle prediction mode; obtaining a prediction block corresponding to the two triangle partitions from a reference image based on the selected motion vector; and reconstructing the current block based on a final prediction block obtained as a combination of the prediction blocks.

[0048] In an embodiment, the merge list generation method in the normal merge mode may be a method of generating a merge list including motion vectors of blocks that can be used among spatial blocks spatially related to the current block and temporal blocks temporally related to the current block.

[0049] The step of obtaining information related to the triangle prediction mode from the bitstream may include: comparing the size of the current block with a first threshold; and when the comparison result satisfies a preset condition, obtaining information related to the triangle prediction mode for the current block from the bitstream.

[0050] The obtaining of information related to the triangle prediction mode from the bitstream may include obtaining information related to the triangle prediction mode from the bitstream when a height of the current block is less than a first threshold and a width of the current block is less than the first threshold.

[0051] The comparing step may include comparing the size of the current block with a second threshold, and the step of obtaining information related to the triangle prediction mode from the bitstream may include obtaining information related to the triangle prediction mode from the bitstream when the comparison result between the size of the current block and the first threshold and the comparison result between the size of the current block and the second threshold meet the preset condition.

[0052] Comparing the size of the current block with the second threshold may include comparing a value obtained by multiplying a height of the current block by a width of the current block with the second threshold.

[0053] The first threshold may be greater than the second threshold.

[0054] The obtaining of the information related to the triangle prediction mode from the bitstream may include obtaining the information related to the triangle prediction mode from the bitstream when the prediction mode of the current block is not the inter-intra combination mode.

[0055] When the prediction mode of the current block is a merge mode using a differential motion vector, information related to the triangle prediction mode may not be obtained from a bitstream, and the image decoding method may further include reconstructing the current block according to the merge mode using the differential motion vector.

[0056] The step of reconstructing the current block may include generating a final prediction block according to a weighted sum of sample point values ​​included in the prediction blocks respectively corresponding to the two triangular partitions.

[0057] The step of dividing the current block into two triangular partitions may include dividing the current block from an upper left corner of the current block toward a lower right corner of the current block, or dividing the current block from an upper right corner of the current block toward a lower left corner of the current block.

[0058] According to an embodiment, an image decoding device may include: an entropy decoder configured to obtain information related to a triangle prediction mode for a current block partitioned from an image from a bitstream; and a prediction decoder configured to perform the following operations: partitioning the current block into two triangle partitions according to the information related to the triangle prediction mode; generating a merge list for the triangle prediction mode according to a merge list generation method in a normal merge mode, wherein, in the normal merge mode, the current block is reconstructed without being divided into triangle partitions; selecting a motion vector for the two triangle partitions according to information indicating a motion vector in the motion vectors included in the merge list, wherein the information is included in the information related to the triangle prediction mode; obtaining a prediction block corresponding to the two triangle partitions from a reference image based on the selected motion vector; and reconstructing the current block based on a final prediction block obtained as a combination of the prediction blocks.

[0059] According to an embodiment, an image encoding method may include: determining a prediction mode of a current block as a triangle prediction mode, wherein the current block is partitioned from an image; dividing the current block into two triangle partitions; generating a merge list for the triangle prediction mode according to a merge list generation method in a normal merge mode, wherein, in the normal merge mode, the current block is reconstructed without being divided into triangle partitions; selecting motion vectors for the two triangle partitions from motion vectors included in the merge list; and generating a bit stream including information related to the triangle prediction mode, wherein the information related to the triangle prediction mode includes information indicating the selected motion vector.

[0060] The step of determining the prediction mode of the current block as the triangle prediction mode may include: comparing the size of the current block with a first threshold; and when the comparison result satisfies a preset condition, determining the prediction mode of the current block as the triangle prediction mode. DETAILED DESCRIPTION

[0061] Since the present disclosure allows various changes and many examples, specific embodiments will be shown in the drawings and described in detail in the written description. However, this is not intended to limit the present disclosure to a specific mode of practice, and it will be understood that all changes, equivalents and substitutions that do not depart from the spirit and technical scope of the various embodiments are included in the present disclosure.

[0062] In the description of the embodiment, when it is considered that the specific detailed explanation of the related art may unnecessarily obscure the essence of the present disclosure, the specific detailed explanation of the related art is omitted. In addition, the numerals (e.g., first, second, etc.) used in the description of the specification are merely identifiers for distinguishing one element from another.

[0063] Further, in the present specification, it will be understood that when elements are “connected” or “coupled” to each other, the elements may be directly connected or coupled to each other, but may be connected or coupled to each other through intermediate elements between the elements, unless otherwise specified.

[0064] In this specification, with respect to an element represented as a "unit" or a "module", two or more elements may be combined into one element, or one element may be divided into two or more elements according to subdivided functions. In addition, each element described below may additionally perform some or all of the functions performed by another element in addition to its own main function, and some of the main functions of each element may be completely performed by another element.

[0065] In addition, in this specification, "image" or "screen" may indicate a static image. Alternatively, "image" or "screen" may indicate each frame constituting a video or the video itself.

[0066] In addition, in this specification, "sample" or "signal" indicates data assigned to a sampling position of an image, that is, data to be processed. For example, in an image, a pixel value in a spatial domain and a transform coefficient on a transform domain may be a sample. A unit including at least one such sample may be defined as a block.

[0067] In the following, reference is made to Figures 1 to 20 , provide an image encoding method and device based on tree-structured coding units and transformation units according to an embodiment, as well as an image decoding method and device.

[0068] Figure 1 A block diagram of an image decoding apparatus 100 according to an embodiment is shown.

[0069] The image decoding apparatus 100 may include a bitstream obtainer 110 and a decoder 120. The bitstream obtainer 110 and the decoder 120 may include at least one processor. In addition, the bitstream obtainer 110 and the decoder 120 may include a memory storing instructions to be executed by the at least one processor.

[0070] The bitstream obtainer 110 may receive a bitstream. The bitstream includes information of an image encoded by the image encoding device 200 described below. In addition, the bitstream may be sent from the image encoding device 200. The image encoding device 200 and the image decoding device 100 may be connected by wire or wirelessly, and the bitstream obtainer 110 may receive the bitstream by wire or wirelessly. The bitstream obtainer 110 may receive the bitstream from a storage medium such as an optical medium or a hard disk. The decoder 120 may reconstruct the image based on the information obtained from the received bitstream. The decoder 120 may obtain syntax elements for reconstructing the image from the bitstream. The decoder 120 may reconstruct the image based on the syntax elements.

[0071] In further description of the operation of the image decoding apparatus 100 , the bitstream obtainer 110 may receive a bitstream.

[0072] The image decoding apparatus 100 may perform an operation of obtaining a binary bit string corresponding to a division shape pattern of a coding unit from a bitstream. The image decoding apparatus 100 may perform an operation of determining a division rule of a coding unit. In addition, the image decoding apparatus 100 may perform an operation of dividing a coding unit into a plurality of coding units based on at least one of a division rule and a binary bit string corresponding to a division shape pattern. The image decoding apparatus 100 may determine an allowable first range of a size of a coding unit according to an aspect ratio of the coding unit in order to determine the division rule. The image decoding apparatus 100 may determine an allowable second range of a size of a coding unit according to a division shape pattern of the coding unit in order to determine the division rule.

[0073] Hereinafter, the division of coding units will be described in detail according to an embodiment of the present disclosure.

[0074] First, a picture may be divided into one or more slices or one or more tiles. A slice or a tile may be a sequence of one or more maximum coding units (coding tree units (CTUs)). There is a maximum coding block (coding tree block (CTB)) conceptually comparable to the maximum coding unit (CTU).

[0075] A maximum coding block (CTB) represents an N×N block including N×N samples (where N is an integer). Each color component may be divided into one or more maximum coding blocks.

[0076] When a picture has three sample arrays (sample arrays for Y, Cr, and Cb components), the maximum coding unit (CTU) includes a maximum coding block of luma samples, two corresponding maximum coding blocks of chroma samples, and a syntax structure for encoding luma samples and chroma samples. When the picture is a monochrome picture, the maximum coding unit includes a maximum coding block of monochrome samples and a syntax structure for encoding monochrome samples. When the picture is a picture encoded in a color plane separated according to color components, the maximum coding unit includes a syntax structure for encoding the picture and the samples of the picture.

[0077] One maximum coding block (CTB) may be divided into M×N coding blocks including M×N samples (M and N are integers).

[0078] When a picture has sample arrays for Y, Cr, and Cb components, a coding unit (CU) includes a coding block of luma samples, two corresponding coding blocks of chroma samples, and a syntax structure for encoding luma samples and chroma samples. When the picture is a monochrome picture, the coding unit includes a coding block of monochrome samples and a syntax structure for encoding monochrome samples. When the picture is a picture coded in a color plane separated according to color components, the coding unit includes a syntax structure for encoding the picture and the samples of the picture.

[0079] As described above, the maximum coding block and the maximum coding unit are conceptually distinguished from each other, and the coding block and the coding unit are conceptually distinguished from each other. That is, the (maximum) coding unit refers to a data structure including a (maximum) coding block including corresponding samples and a syntax element corresponding to the (maximum) coding block. However, because a person of ordinary skill in the art understands that a (maximum) coding unit or a (maximum) coding block refers to a block of a preset size including a preset number of samples, unless otherwise described, the maximum coding block and the maximum coding unit or the coding block and the coding unit are mentioned in the following description without distinction.

[0080] The image may be divided into maximum coding units (CTUs). The size of each maximum coding unit may be determined based on information obtained from the bitstream. The shape of each maximum coding unit may be a square shape of the same size. However, the embodiment is not limited thereto.

[0081] For example, information about the maximum size of the luma coding block may 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 may be one of 4×4, 8×8, 16×16, 32×32, 64×64, 128×128, and 256×256.

[0082] For example, information about the luminance block size difference and the maximum size of the luminance coding block that can be divided into two may be obtained from the bitstream. The information about the luminance block size difference may refer to the size difference between the luminance maximum coding unit and the maximum luminance coding block that can be divided into two. Therefore, when the information about the maximum size of the luminance coding block that can be divided into two obtained from the bitstream and the information about the luminance block size difference are combined with each other, the size of the luminance maximum coding unit may be determined. The size of the chrominance maximum coding unit may be determined by using the size of the luminance maximum coding unit. For example, when the Y:Cb:Cr ratio is 4:2:0 according to the color format, the size of the chrominance block may be half the size of the luminance block, and the size of the chrominance maximum coding unit may be half the size of the luminance maximum coding unit.

[0083] According to an embodiment, since information about the maximum size of a brightness coding block that can be divided into two is obtained from a bitstream, the maximum size of a brightness coding block that can be divided into two can be variably determined. In contrast, the maximum size of a brightness coding block that can be divided into three can be fixed. For example, the maximum size of a brightness coding block that can be divided into three in an I slice can be 32×32, and the maximum size of a brightness coding block that can be divided into three in a P slice or a B slice can be 64×64.

[0084] In addition, the maximum coding unit may be hierarchically split into coding units based on the split shape pattern information obtained from the bitstream. At least one of information indicating whether to perform four-partitioning, information indicating whether to perform multi-partitioning, split direction information, and split type information may be obtained from the bitstream as the split shape pattern information.

[0085] For example, the information indicating whether to perform four-division may indicate whether the current coding unit is to be four-divided (QUAD_SPLIT) or not to be four-divided.

[0086] When the current coding unit is not divided into four parts, the information indicating whether multi-split is performed may indicate whether the current coding unit is no longer split (NO_SPLIT) or is divided into two parts / three parts.

[0087] When the current coding unit is two-partitioned or three-partitioned, the split direction information indicates that the current coding unit is split in one direction of a horizontal direction and a vertical direction.

[0088] When the current coding unit is split in the horizontal direction or the vertical direction, the split type information indicates whether the current coding unit is split into two or three.

[0089] The split mode of the current coding unit may be determined according to the split direction information and the split type information. The split mode when the current coding unit is split into two in the horizontal direction may be determined as a horizontal two-split mode (SPLIT_BT_HOR), the split mode when the current coding unit is split into three in the horizontal direction may be determined as a horizontal three-split mode (SPLIT_TT_HOR), the split mode when the current coding unit is split into two in the vertical direction may be determined as a vertical two-split mode (SPLIT_BT_VER), and the split mode when the current coding unit is split into three in the vertical direction may be determined as a vertical three-split mode (SPLIT_TT_VER).

[0090] The image decoding device 100 may obtain the division shape pattern information from a binary bit string from the bit stream. The form of the bit stream received by the image decoding device 100 may include a fixed-length binary code, a unary code, a truncated unary code, a predetermined binary code, etc. The binary bit string is information of a binary number. The binary bit string may include at least one bit. The image decoding device 100 may obtain the division shape pattern information corresponding to the binary bit string based on the division rule. The image decoding device 100 may determine whether to divide the coding unit into four, whether to not divide the coding unit, the division direction, and the division type based on a binary bit string.

[0091] The coding unit may be smaller than or equal to the maximum coding unit. For example, since the maximum coding unit is a coding unit having the maximum size, the maximum coding unit is one of the coding units. When the division shape pattern information about the maximum coding unit indicates that division is not performed, the coding unit determined in the maximum coding unit has the same size as the maximum coding unit. When the division shape pattern information about the maximum coding unit indicates that division is performed, the maximum coding unit may be divided into coding units. In addition, when the division shape pattern information about the coding unit indicates that division is performed, the coding unit may be divided into smaller coding units. However, the division of the image is not limited thereto, and the maximum coding unit and the coding unit may not be distinguished. Reference will be made to Figures 3 to 16 The division of coding units is described in detail.

[0092] In addition, one or more prediction blocks for prediction may be determined from the coding unit. The prediction block may be equal to or smaller than the coding unit. In addition, one or more transform blocks for transformation may be determined from the coding unit. The transform block may be equal to or smaller than the coding unit.

[0093] The shapes and sizes of the transform block and the prediction block may be unrelated to each other.

[0094] In another embodiment, prediction may be performed by using a coding unit as a prediction unit. In addition, transformation may be performed by using a coding unit as a transformation block.

[0095] Will refer to Figures 3 to 16 The division of the coding unit is described in detail. The current block and the neighboring block of the present disclosure may indicate one of the maximum coding unit, the coding unit, the prediction block, and the transformation block. In addition, the current block of 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 adjacent to the current block in space or time. The neighboring block may be located at one of the lower left, left side, upper left, upper, upper right, right side, and lower right side of the current block.

[0096] Figure 3 A process of determining at least one coding unit by splitting a current coding unit, performed by the image decoding apparatus 100 according to an embodiment, is illustrated.

[0097] The block shape may include 4N×4N, 4N×2N, 2N×4N, 4N×N, N×4N, 32N×N, N×32N, 16N×N, N×16N, 8N×N, or N×8N. Here, N may be a positive integer. The block shape information is information indicating at least one of a shape, a direction, an aspect ratio, or a size of a coding unit.

[0098] The shape of the coding unit may include a square and a non-square. When the width length and height length of the coding unit are the same (that is, when the block shape of the coding unit is 4N×4N), the image decoding apparatus 100 may determine the block shape information of the coding unit as a square. The image decoding apparatus 100 may determine the shape of the coding unit as a non-square.

[0099] When the width and height of the coding unit are different from each other (that is, when the block shape of the coding unit is 4N×2N, 2N×4N, 4N×N, N×4N, 32N×N, N×32N, 16N×N, N×16N, 8N×N, or N×8N), the image decoding apparatus 100 may determine the block shape information of the coding unit as a non-square shape. When the shape of the coding unit is non-square, the image decoding apparatus 100 may determine the aspect ratio in the block shape information of the coding unit as 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. In addition, the image decoding apparatus 100 may determine whether the coding unit is in the horizontal direction or in the vertical direction based on the width length and height length of the coding unit. In addition, the image decoding apparatus 100 may determine the size of the coding unit based on at least one of the width length, height length, or area of ​​the coding unit.

[0100] According to an embodiment, the image decoding apparatus 100 may determine the shape of the coding unit by using the block shape information, and may determine the division method of the coding unit by using the division shape pattern information. That is, the coding unit division method indicated by the division shape pattern information may be determined based on the block shape indicated by the block shape information used by the image decoding apparatus 100.

[0101] The image decoding device 100 may obtain the division shape pattern information from the bitstream. However, the embodiment is not limited thereto, and the image decoding device 100 and the image encoding device 200 may determine the pre-agreed division shape pattern information based on the block shape information. The image decoding device 100 may determine the pre-agreed division shape pattern information for the maximum coding unit or the minimum coding unit. For example, the image decoding device 100 may determine the division shape pattern information for the maximum coding unit as four divisions. In addition, the image decoding device 100 may determine the division shape pattern information about the minimum coding unit as "no division is performed". Specifically, the image decoding device 100 may determine the size of the maximum coding unit to be 256×256. The image decoding device 100 may determine the pre-agreed division shape pattern information to be four divisions. Four divisions are division shape patterns in which the width and height of the coding unit are both divided into two equal parts. The image decoding device 100 may obtain a coding unit of a size of 128×128 from a maximum coding unit of a size of 256×256 based on the division shape pattern information. In addition, the image decoding device 100 may determine the size of the minimum coding unit to be 4×4. The image decoding apparatus 100 may obtain division shape pattern information indicating “do not perform division” for a minimum coding unit.

[0102] According to an embodiment, the image decoding apparatus 100 may use block shape information indicating that the current coding unit has a square shape. For example, the image decoding apparatus 100 may determine whether to not split the square coding unit, whether to vertically split the square coding unit, whether to horizontally split the square coding unit, or whether to split the square coding unit into four coding units based on the split shape mode information. Figure 3 , when the block shape information of the current coding unit 300 indicates a square shape, the decoder 120 may not divide the coding unit 310a having the same size as the current coding unit 300 based on the division shape pattern information indicating that division is not performed, or may determine the coding units 310b, 310c, 310d, 310e or 310f divided based on the division shape pattern information indicating a preset division method.

[0103] Reference Figure 3 According to an embodiment, the image decoding apparatus 100 may determine two coding units 310b obtained by dividing the current coding unit 300 in the vertical direction based on the division shape pattern information indicating that division is performed in the vertical direction. The image decoding apparatus 100 may determine two coding units 310c obtained by dividing the current coding unit 300 in the horizontal direction based on the division shape pattern information indicating that division is performed in the horizontal direction. The image decoding apparatus 100 may determine four coding units 310d obtained by dividing the current coding unit 300 in the vertical and horizontal directions based on the division shape pattern information indicating that division is performed in the vertical and horizontal directions. According to an embodiment, the image decoding apparatus 100 may determine three coding units 310e obtained by dividing the current coding unit 300 in the vertical direction based on the division shape pattern information indicating that three divisions are performed in the vertical direction. The image decoding apparatus 100 may determine three coding units 310f obtained by dividing the current coding unit 300 in the horizontal direction based on the division shape pattern information indicating that three divisions are performed in the horizontal direction. However, the division method of the square coding unit is not limited to the above method, and the division shape pattern information may indicate various methods. A preset division method for dividing a square coding unit will be described in detail below with respect to various embodiments.

[0104] Figure 4 A process of determining at least one coding unit by splitting a non-square coding unit, performed by the image decoding apparatus 100 according to an embodiment, is illustrated.

[0105] According to an embodiment, the image decoding apparatus 100 may use block shape information indicating that the current coding unit has a non-square shape. The image decoding apparatus 100 may determine whether to not split the non-square current coding unit or whether to split the non-square current coding unit by using a preset splitting method based on the splitting shape pattern information. Figure 4 , when the block shape information of the current coding unit 400 or 450 indicates a non-square shape, the image decoding apparatus 100 may determine a coding unit 410 or 460 having the same size as the current coding unit 400 or 450 based on the division shape pattern information indicating that division is not performed, or may determine coding units 420a and 420b, 430a to 430c, 470a and 470b, or 480a to 480c divided based on the division shape pattern information indicating a preset division method. The preset division method for dividing the non-square coding unit will be described in detail with respect to various embodiments below.

[0106] According to an embodiment, the image decoding apparatus 100 may determine a splitting method of a coding unit by using splitting shape pattern information, and in this case, the splitting shape pattern information may indicate the number of one or more coding units generated by splitting the coding unit. Figure 4 When the division shape pattern information indicates that the current coding unit 400 or 450 is divided into two coding units, the image decoding device 100 can determine the two coding units 420a and 420b or 470a and 470b included in the current coding unit 400 or 450 by dividing the current coding unit 400 or 450 based on the division shape pattern information.

[0107] According to an embodiment, when the image decoding apparatus 100 splits the non-square current coding unit 400 or 450 based on the split shape pattern information, the image decoding apparatus 100 may split the current coding unit in consideration of the position of the long side of the non-square current coding unit 400 or 450. For example, the image decoding apparatus 100 may determine a plurality of coding units by splitting the current coding unit 400 or 450 in a direction in which the long side of the current coding unit 400 or 450 is split in consideration of the shape of the current coding unit 400 or 450.

[0108] According to an embodiment, when the division shape pattern information indicates that the coding unit is divided (three-divided) into an odd number of blocks, the image decoding apparatus 100 may determine the odd number of coding units included in the current coding unit 400 or 450. For example, when the division shape pattern information indicates that the current coding unit 400 or 450 is divided into three coding units, the image decoding apparatus 100 may divide the current coding unit 400 or 450 into three coding units 430a, 430b, and 430c or 480a, 480b, and 480c.

[0109] According to an embodiment, the aspect ratio of the current coding unit 400 or 450 may be 4:1 or 1:4. When the aspect ratio is 4:1, since the width length is longer than the height length, the block shape information may indicate the horizontal direction. When the aspect ratio is 1:4, since the width length is shorter than the height length, the block shape information may indicate the vertical direction. The image decoding apparatus 100 may determine the current coding unit to be divided into an odd number of blocks based on the division shape mode information. In addition, the image decoding apparatus 100 may determine the division direction of the current coding unit 400 or 450 based on the block shape information of the current coding unit 400 or 450. For example, when the current coding unit 400 is in the vertical direction, the image decoding apparatus 100 may determine the coding units 430a, 430b, and 430c by dividing the current coding unit 400 in the horizontal direction. In addition, when the current coding unit 450 is in the horizontal direction, the image decoding apparatus 100 may determine the coding units 480a, 480b, and 480c by dividing the current coding unit 450 in the vertical direction.

[0110] According to an embodiment, the image decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 400 or 450, and not all determined coding units may have the same size. For example, a preset coding unit 430b or 480b among the determined odd number of coding units 430a, 430b, and 430c or 480a, 480b, and 480c may have a size different from that of other coding units 430a and 430c or 480a and 480c. That is, the coding unit determined by dividing the current coding unit 400 or 450 may have a plurality of sizes, and in some cases, all odd number of coding units 430a, 430b, and 430c or 480a, 480b, and 480c may have different sizes.

[0111] According to an embodiment, when the division shape pattern information indicates that the coding unit is divided into an odd number of blocks, the image decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 400 or 450, and further, may apply a preset restriction to at least one of the odd number of coding units generated by dividing the current coding unit 400 or 450. Figure 4, the image decoding apparatus 100 may set a decoding process for a coding unit 430b or 480b to be different from a decoding process of other coding units 430a and 430c or 480a and 480c, wherein the coding unit 430b or 480b is located at the center of three coding units 430a, 430b, and 430c or 480a, 480b, and 480c generated by dividing the current coding unit 400 or 450. For example, unlike other coding units 430a and 430c or 480a and 480c, the image decoding apparatus 100 may limit the coding unit 430b or 480b at the center position from being further divided or being divided only a preset number of times.

[0112] Figure 5 A process of splitting a coding unit based on at least one of block shape information and division shape pattern information, performed by the image decoding apparatus 100 according to an embodiment, is illustrated.

[0113] According to an embodiment, the image decoding apparatus 100 may determine whether to divide the square first coding unit 500 into coding units or not to divide the square first coding unit 500 based on at least one of the block shape information and the division shape mode information. According to an embodiment, when the division shape mode information indicates that the first coding unit 500 is divided in the horizontal direction, the image decoding apparatus 100 may determine the second coding unit 510 by dividing the first coding unit 500 in the horizontal direction. The first coding unit, the second coding unit, and the third coding unit used according to the embodiment are terms for understanding the relationship before and after the coding unit is divided. For example, the second coding unit may be determined by dividing the first coding unit, and the third coding unit may be determined by dividing the second coding unit. It will be understood that the relationship between the first coding unit, the second coding unit, and the third coding unit follows the above description.

[0114] According to an embodiment, the image decoding apparatus 100 may determine whether to split the determined second coding unit 510 into coding units or not to split the determined second coding unit 510 based on the division shape pattern information. Figure 5, the image decoding apparatus 100 may split the non-square second coding unit 510 determined by splitting the first coding unit 500 into one or more third coding units 520a, 520b, 520c, and 520d based on at least one of the split shape pattern information and the block shape information, or may not split the non-square second coding unit 510. The image decoding apparatus 100 may obtain the split shape pattern information, and may obtain a plurality of second coding units (for example, 510) of various shapes by splitting the first coding unit 500 based on the obtained split shape pattern information, and may split the second coding unit 510 by using the split method of the first coding unit 500 based on the split shape pattern information. According to an embodiment, when the first coding unit 500 is split into the second coding unit 510 based on the split shape pattern information of the first coding unit 500, the second coding unit 510 may also be split into the third coding units (for example, 520a, or 520b, 520c, and 520d) based on the split shape pattern information of the second coding unit 510. That is, the coding unit may be recursively split based on the split shape pattern information of each coding unit. Thus, a square coding unit may be determined by splitting a non-square coding unit, and a non-square coding unit may be determined by recursively splitting a square coding unit.

[0115] Reference Figure 5 , the preset coding units (e.g., coding units at the center position or square coding units) in the odd number of third coding units 520b, 520c, and 520d determined by dividing the non-square second coding unit 510 may be recursively divided. According to an embodiment, the square third coding unit 520c in the odd number of third coding units 520b, 520c, and 520d may be divided into a plurality of fourth coding units in the horizontal direction. The non-square fourth coding unit 530b or 530d in the plurality of fourth coding units 530a, 530b, 530c, and 530d may be divided into a plurality of coding units again. For example, the non-square fourth coding unit 530b or 530d may be divided into an odd number of coding units again. A method that can be used to recursively divide coding units will be described below with respect to various embodiments.

[0116] According to an embodiment, the image decoding apparatus 100 may divide each of the third coding unit 520a, or 520b, 520c, and 520d into coding units based on the division shape pattern information. In addition, the image decoding apparatus 100 may determine not to divide the second coding unit 510 based on the division shape pattern information. According to an embodiment, the image decoding apparatus 100 may divide the non-square second coding unit 510 into an odd number of third coding units 520b, 520c, and 520d. The image decoding apparatus 100 may impose a preset restriction on a preset third coding unit among the odd number of third coding units 520b, 520c, and 520d. For example, the image decoding apparatus 100 may limit the third coding unit 520c at the center position among the odd number of third coding units 520b, 520c, and 520d to no longer be divided or to be divided a set number of times.

[0117] Reference Figure 5 , the image decoding apparatus 100 may limit the third coding unit 520c at the center position among the odd number of third coding units 520b, 520c, and 520d included in the non-square second coding unit 510 to no longer be divided, to be divided by using a preset division method (e.g., only divided into four coding units or divided by using the division method of the second coding unit 510), or to be divided only a preset number of times (e.g., only divided n times (where n>0)). However, the limitation on the third coding unit 520c at the center position is not limited to the above example, and may include various limitations for decoding the third coding unit 520c at the center position differently from the other third coding units 520b and 520d.

[0118] According to an embodiment, the image decoding apparatus 100 may obtain split shape pattern information for splitting the current coding unit from a preset position in the current coding unit.

[0119] Figure 6 A method of determining a preset coding unit from among odd-numbered coding units, performed by the image decoding apparatus 100 according to an embodiment, is illustrated.

[0120] Reference Figure 6 , the division shape pattern information of the current coding unit 600 or 650 may be obtained from a sample at a preset position (e.g., a sample 640 or 690 at a center position) among a plurality of samples included in the current coding unit 600 or 650. However, the preset position in the current coding unit 600 where the division shape pattern information can be obtained is not limited to Figure 6, and may include various positions (e.g., top, bottom, left, right, top left, bottom left, top right, bottom right, etc.) included in the current coding unit 600. The image decoding apparatus 100 may obtain the division shape pattern information from a preset position, and may determine whether to divide the current coding unit into coding units of various shapes and sizes or not to divide the current coding unit.

[0121] According to an embodiment, when the current coding unit is divided into a preset number of coding units, the image decoding apparatus 100 may select one of the coding units. As will be described below with respect to various embodiments, various methods may be used to select one of the plurality of coding units.

[0122] According to an embodiment, the image decoding apparatus 100 may split a current coding unit into a plurality of coding units, and may determine a coding unit at a preset position.

[0123] According to an embodiment, the image decoding apparatus 100 may determine a coding unit at a center position among the odd-numbered coding units using information indicating the positions of the odd-numbered coding units. Figure 6 , the image decoding apparatus 100 may determine the odd number of coding units 620a, 620b, and 620c or the odd number of coding units 660a, 660b, and 660c by dividing the current coding unit 600 or the current coding unit 650. The image decoding apparatus 100 may determine the intermediate coding unit 620b or the intermediate coding unit 660b by using information about the positions of the odd number of coding units 620a, 620b, and 620c or the odd number of coding units 660a, 660b, and 660c. For example, the image decoding apparatus 100 may determine the coding unit 620b of the center position by determining the positions of the coding units 620a, 620b, and 620c based on information indicating the positions of preset samples included in the coding units 620a, 620b, and 620c. In detail, the image decoding apparatus 100 may determine the coding unit 620b at the center position by determining the positions of the coding units 620a, 620b, and 620c based on information indicating the positions of the upper left samples 630a, 630b, and 630c of the coding units 620a, 620b, and 620c.

[0124] According to an embodiment, the information indicating the positions of the upper left sample points 630a, 630b, and 630c respectively included in the coding units 620a, 620b, and 620c may include information about the positions or coordinates of the coding units 620a, 620b, and 620c in the picture. According to an embodiment, the information indicating the positions of the upper left sample points 630a, 630b, and 630c respectively included in the coding units 620a, 620b, and 620c may include information indicating the width or height of the coding units 620a, 620b, and 620c included in the current coding unit 600, and the width or height may correspond to the information indicating the difference between the coordinates of the coding units 620a, 620b, and 620c in the picture. That is, the image decoding apparatus 100 may determine the coding unit 620b at the center position by directly using the information about the positions or coordinates of the coding units 620a, 620b, and 620c in the picture or by using the information about the width or height of the coding unit corresponding to the difference between the coordinates.

[0125] According to an embodiment, information indicating the position of the upper left sample point 630a of the upper coding unit 620a may include coordinates (xa, ya), information indicating the position of the upper left sample point 630b of the center coding unit 620b may include coordinates (xb, yb), and information indicating the position of the upper left sample point 630c of the lower coding unit 620c may include coordinates (xc, yc). The image decoding apparatus 100 may determine the intermediate coding unit 620b by using the coordinates of the upper left sample points 630a, 630b, and 630c respectively included in the coding units 620a, 620b, and 620c. For example, when the coordinates of the upper left sample points 630a, 630b, and 630c are sorted in ascending or descending order, the coding unit 620b including the coordinates (xb, yb) of the sample point 630b at the center position may be determined as the coding unit at the center position among the coding units 620a, 620b, and 620c determined by dividing the current coding unit 600. However, the coordinates indicating the positions of the upper left sample points 630a, 630b, and 630c may include coordinates indicating absolute positions in the picture, or coordinates (dxb, dyb) indicating the relative position of the upper left sample point 630b of the middle coding unit 620b relative to the position of the upper left sample point 630a of the upper coding unit 620a and coordinates (dxc, dyc) indicating the relative position of the upper left sample point 630c of the lower coding unit 620c relative to the position of the upper left sample point 630a of the upper coding unit 620a may be used. The method of determining the coding unit at a preset position by using the coordinates of the sample points included in the coding unit as information indicating the positions of the sample points is not limited to the above method, and may include various arithmetic methods capable of using the coordinates of the sample points.

[0126] According to an embodiment, the image decoding apparatus 100 may divide the current coding unit 600 into a plurality of coding units 620a, 620b, and 620c, and may select one of the coding units 620a, 620b, and 620c based on a preset criterion. For example, the image decoding apparatus 100 may select a coding unit 620b having a size different from that of other coding units from among the coding units 620a, 620b, and 620c.

[0127] According to an embodiment, the image decoding apparatus 100 may determine the width or height of each of the coding units 620a, 620b, and 620c by using the coordinates (xa, ya) as information indicating the position of the upper left sample point 630a of the upper coding unit 620a, the coordinates (xb, yb) as information indicating the position of the upper left sample point 630b of the middle coding unit 620b, and the coordinates (xc, yc) as information indicating the position of the upper left sample point 630c of the lower coding unit 620c. The image decoding apparatus 100 may determine the size of each of the coding units 620a, 620b, and 620c by using the coordinates (xa, ya), (xb, yb), and (xc, yc) indicating the positions of the coding units 620a, 620b, and 620c. According to an embodiment, the image decoding apparatus 100 may determine the width of the upper coding unit 620a as the width of the current coding unit 600. The image decoding apparatus 100 may determine the height of the upper coding unit 620a as yb-ya. According to an embodiment, the image decoding apparatus 100 may determine the width of the intermediate coding unit 620b as the width of the current coding unit 600. The image decoding apparatus 100 may determine the height of the intermediate coding unit 620b as yc-yb. According to an embodiment, the image decoding apparatus 100 may determine the width or height of the lower coding unit 620c by using the width or height of the current coding unit 600 or the width or height of the upper coding unit 620a and the intermediate coding unit 620b. The image decoding apparatus 100 may determine a coding unit having a size different from sizes of other coding units based on the determined width and height of the coding units 620a, 620b, and 620c. Referring to Figure 6 , the image decoding apparatus 100 may determine the middle coding unit 620b having a size different from the sizes of the upper coding unit 620a and the lower coding unit 620c as the coding unit at the preset position. However, the above-mentioned method of determining the coding unit having a size different from the sizes of other coding units performed by the image decoding apparatus 100 corresponds only to an example of determining the coding unit at the preset position by using the size of the coding unit determined based on the coordinates of the sample points, and therefore, various methods of determining the coding unit at the preset position by comparing the size of the coding unit determined based on the coordinates of the preset sample points may be used.

[0128] The image decoding apparatus 100 may determine the width or height of each of the coding units 660a, 660b, and 660c by using the coordinates (xd, yd) as information indicating the position of the upper left sample point 670a of the left coding unit 660a, the coordinates (xe, ye) as information indicating the position of the upper left sample point 670b of the middle coding unit 660b, and the coordinates (xf, yf) as information indicating the position of the upper left sample point 670c of the right coding unit 660c. The image decoding apparatus 100 may determine the size of each of the coding units 660a, 660b, and 660c by using the coordinates (xd, yd), (xe, ye), and (xf, yf) indicating the positions of the coding units 660a, 660b, and 660c.

[0129] According to an embodiment, the image decoding device 100 may determine the width of the left coding unit 660a as xe-xd. The image decoding device 100 may determine the height of the left coding unit 660a as the height of the current coding unit 650. According to an embodiment, the image decoding device 100 may determine the width of the middle coding unit 660b as xf-xe. The image decoding device 100 may determine the height of the middle coding unit 660b as the height of the current coding unit 650. According to an embodiment, the image decoding device 100 may determine the width or height of the right coding unit 660c by using the width or height of the current coding unit 650 or the width or height of the left coding unit 660a and the middle coding unit 660b. The image decoding device 100 may determine a coding unit whose size is different from that of other coding units based on the determined width and height of the coding units 660a, 660b, and 660c. Refer to Figure 6 , the image decoding apparatus 100 may determine the middle coding unit 660b having a size different from the sizes of the left coding unit 660a and the right coding unit 660c as the coding unit at the preset position. However, the above-mentioned method of determining the coding unit having a size different from the sizes of other coding units, performed by the image decoding apparatus 100, corresponds only to an example of determining the coding unit at the preset position by using the size of the coding unit determined based on the coordinates of the sample points, and therefore, various methods of determining the coding unit at the preset position by comparing the size of the coding unit determined based on the coordinates of the preset sample points may be used.

[0130] However, the position of the sample considered in determining the position of the coding unit is not limited to the above-mentioned upper left position, and information on arbitrary positions of the samples included in the coding unit may be used.

[0131] According to an embodiment, the image decoding apparatus 100 may select a coding unit at a preset position from an odd number of coding units determined by dividing the current coding unit, taking into account the shape of the current coding unit. For example, when the current coding unit has a non-square shape with a width greater than a height, the image decoding apparatus 100 may determine a coding unit at a preset position along the horizontal direction. That is, the image decoding apparatus 100 may determine one of the coding units at different positions along the horizontal direction and may impose restrictions on the coding unit. When the current coding unit has a non-square shape with a height greater than a width, the image decoding apparatus 100 may determine a coding unit at a preset position along the vertical direction. That is, the image decoding apparatus 100 may determine one of the coding units at different positions along the vertical direction and may impose restrictions on the coding unit.

[0132] According to an embodiment, the image decoding apparatus 100 may use information indicating respective positions of even-numbered coding units to determine a coding unit at a preset position among the even-numbered coding units. The image decoding apparatus 100 may determine the even-numbered coding units by dividing (dividing) the current coding unit, and may determine the coding unit at the preset position by using information about the positions of the even-numbered coding units. The operations related thereto may be the same as those already described above with respect to Figure 6 The operation of determining a coding unit at a preset position (eg, a center position) among odd-numbered coding units corresponds to the operation described in detail, and thus a detailed description thereof is not provided here.

[0133] According to an embodiment, when a non-square current coding unit is split into a plurality of coding units, a coding unit at a preset position among the plurality of coding units may be determined using preset information about the coding unit at a preset position in a splitting operation. For example, the image decoding apparatus 100 may determine a coding unit at a center position among the plurality of coding units determined by splitting the current coding unit using at least one of block shape information and split shape pattern information stored in samples included in an intermediate coding unit in a splitting operation.

[0134] Reference Figure 6, the image decoding apparatus 100 may divide the current coding unit 600 into a plurality of coding units 620a, 620b, and 620c based on the division shape pattern information, and may determine the coding unit 620b at the center position among the plurality of coding units 620a, 620b, and 620c. In addition, the image decoding apparatus 100 may determine the coding unit 620b at the center position in consideration of the position where the division shape pattern information is obtained. That is, the division shape pattern information of the current coding unit 600 may be obtained from the sample point 640 at the center position of the current coding unit 600, and when the current coding unit 600 is divided into a plurality of coding units 620a, 620b, and 620c based on the division shape pattern information, the coding unit 620b including the sample point 640 may be determined as the coding unit at the center position. However, information for determining the coding unit at the center position is not limited to the division shape pattern information, and the coding unit at the center position may be determined using various types of information.

[0135] According to an embodiment, preset information for identifying a coding unit at a preset position may be obtained from preset samples included in a coding unit to be determined. Figure 6 , the image decoding apparatus 100 may use the division shape pattern information obtained from the sample at the preset position in the current coding unit 600 (for example, the sample at the center position of the current coding unit 600) to determine the coding unit at the preset position (for example, the coding unit at the center position of the divided multiple coding units) among the multiple coding units 620a, 620b, and 620c determined by dividing the current coding unit 600. That is, the image decoding apparatus 100 may determine the sample at the preset position by considering the block shape of the current coding unit 600, may determine the coding unit 620b including the sample for which the preset information (for example, the division shape pattern information) may be obtained from the multiple coding units 620a, 620b, and 620c determined by dividing the current coding unit 600, and may impose a preset restriction on the coding unit 620b. Referring to Figure 6 According to an embodiment, in a decoding operation, the image decoding apparatus 100 may determine a sample 640 at a center position of a current coding unit 600 as a sample from which preset information may be obtained, and may impose a preset restriction on a coding unit 620b including the sample 640. However, the position of the sample from which preset information may be obtained is not limited to the above-mentioned position, and may include any position included in the coding unit 620b to be determined as a sample for restriction.

[0136] According to an embodiment, the position of the sample at which the preset information can be obtained may be determined based on the shape of the current coding unit 600. According to an embodiment, the block shape information may indicate whether the current coding unit has a square shape or a non-square shape, and the position of the sample at which the preset specific information can be determined based on the shape. For example, the image decoding apparatus 100 may determine a sample located on a boundary for dividing at least one of the width and the height of the current coding unit in half as a sample at which the preset specific information can be obtained by using at least one of the information about the width of the current coding unit and the information about the height of the current coding unit. As another example, when the block shape information of the current coding unit indicates a non-square shape, the image decoding apparatus 100 may determine one of the samples adjacent to the boundary dividing the long side of the current coding unit in half as a sample at which the preset information can be obtained.

[0137] According to an embodiment, when a current coding unit is divided into a plurality of coding units, the image decoding device 100 may use division shape pattern information to determine a coding unit at a preset position in the plurality of coding units. According to an embodiment, the image decoding device 100 may obtain division shape pattern information from a sample at a preset position in a coding unit, and may divide a plurality of coding units generated by dividing the current coding unit by using the division shape pattern information, wherein the division shape pattern information is obtained from a sample at a preset position in each of the plurality of coding units. That is, the coding unit may be recursively divided based on the division shape pattern information, wherein the division shape pattern information is obtained from a sample at a preset position in each coding unit. As has been described above, Figure 5 An operation of recursively splitting the coding unit is described, and thus a detailed description thereof will not be provided here.

[0138] According to an embodiment, the image decoding apparatus 100 may determine one or more coding units by splitting a current coding unit, and may determine an order in which to decode the one or more coding units based on a preset block (for example, the current coding unit).

[0139] Figure 7 An order in which a plurality of coding units are processed when the image decoding apparatus 100 determines a plurality of coding units by splitting a current coding unit according to an embodiment is illustrated.

[0140] According to an embodiment, based on the division shape pattern information, the image decoding device 100 can determine the second coding units 710a and 710b by dividing the first coding unit 700 in a vertical direction, determine the second coding units 730a and 730b by dividing the first coding unit 700 in a horizontal direction, or determine the second coding units 750a, 750b, 750c and 750d by dividing the first coding unit 700 in vertical and horizontal directions.

[0141] Reference Figure 7 , the image decoding apparatus 100 may determine to process the second coding units 710a and 710b determined by dividing the first coding unit 700 in the vertical direction in a horizontal direction order 710c. The image decoding apparatus 100 may determine to process the second coding units 730a and 730b determined by dividing the first coding unit 700 in the horizontal direction in a vertical direction order 730c. The image decoding apparatus 100 may determine the second coding units 750a, 750b, 750c, and 750d determined by dividing the first coding unit 700 in the vertical direction and the horizontal direction according to a preset order (for example, in a raster scan order or a zigzag scan order 750e), wherein the coding units in one row are processed according to the preset order and then the coding units in the next row are processed.

[0142] According to an embodiment, the image decoding apparatus 100 may recursively divide the coding unit. Figure 7 , the image decoding apparatus 100 may determine a plurality of coding units 710a and 710b, 730a and 730b, or 750a, 750b, 750c, and 750d by dividing the first coding unit 700, and may recursively divide each of the determined plurality of coding units 710a, 710b, 730a, 730b, 750a, 750b, 750c, and 750d. A division method of the plurality of coding units 710a and 710b, 730a and 730b, or 750a, 750b, 750c, and 750d may correspond to a division method of the first coding unit 700. Therefore, each of the plurality of coding units 710a and 710b, 730a and 730b, or 750a, 750b, 750c, and 750d may be independently divided into a plurality of coding units. Referring to Figure 7 , the image decoding apparatus 100 may determine the second coding units 710a and 710b by splitting the first coding unit 700 in a vertical direction, and may determine whether to independently split or not split each of the second coding units 710a and 710b.

[0143] According to an embodiment, the image decoding apparatus 100 may determine the third coding units 720a and 720b by splitting the left second coding unit 710a in a horizontal direction, and may not split the right second coding unit 710b.

[0144] According to an embodiment, the processing order of the coding units may be determined based on the operation of dividing the coding units. In other words, the processing order of the coding units after the division may be determined based on the processing order of the coding units immediately before the division. The image decoding apparatus 100 may determine the processing order of the third coding units 720a and 720b determined by dividing the left second coding unit 710a independently of the right second coding unit 710b. Since the third coding units 720a and 720b are determined by dividing the left second coding unit 710a in the horizontal direction, the third coding units 720a and 720b may be processed in a vertical direction order 720c. Since the left second coding unit 710a and the right second coding unit 710b are processed in a horizontal direction order 710c, the right second coding unit 710b may be processed after the third coding units 720a and 720b included in the left second coding unit 710a are processed in a vertical direction order 720c. The operation of determining the processing order of coding units based on the coding units before splitting is not limited to the above example, and coding units split and determined to be various shapes may be independently processed in a preset order using various methods.

[0145] Figure 8 1 and 2. A process of determining that a current coding unit is to be split into an odd number of coding units, performed by the image decoding apparatus 100, is illustrated when coding units cannot be processed in a preset order according to an embodiment.

[0146] According to an embodiment, the image decoding apparatus 100 may determine that the current coding unit is to be split into an odd number of coding units based on the obtained split shape pattern information. Figure 8 , the square first coding unit 800 may be divided into non-square second coding units 810a and 810b, and the second coding units 810a and 810b may be independently divided into third coding units 820a and 820b and 820c, 820d, and 820e. According to an embodiment, the image decoding apparatus 100 may determine a plurality of third coding units 820a and 820b by dividing the left second coding unit 810a in the horizontal direction, and may divide the right second coding unit 810b into an odd number of third coding units 820c, 820d, and 820e.

[0147] According to an embodiment, the image decoding apparatus 100 may determine whether any coding unit is split into an odd number of coding units by determining whether the third coding units 820a and 820b and 820c, 820d, and 820e can be processed in a preset order. Figure 8 , the image decoding apparatus 100 may determine the third coding units 820a and 820b and 820c, 820d, and 820e by recursively dividing the first coding unit 800. The image decoding apparatus 100 may determine whether any one of the following coding units is divided into an odd number of coding units based on at least one of the block shape information and the division shape mode information: the first coding unit 800, the second coding units 810a and 810b, the third coding units 820a and 820b, and 820c, 820d, and 820e. For example, the coding unit located on the right side of the second coding units 810a and 810b may be divided into an odd number of third coding units 820c, 820d, and 820e. The processing order of the multiple coding units included in the first coding unit 800 can be a preset order (for example, a zigzag scanning order 830), and the image decoding device 100 can determine whether the third coding units 820c, 820d and 820e determined by dividing the right second coding unit 810b into an odd number of coding units meet the conditions for processing in the preset order.

[0148] According to an embodiment, the image decoding apparatus 100 may determine whether the third coding units 820a and 820b and 820c, 820d, and 820e included in the first coding unit 800 satisfy a condition for processing in a preset order, and the condition is related to whether at least one of the width and height of the second coding units 810a and 810b will be divided in half along the boundary of the third coding units 820a and 820b and 820c, 820d, and 820e. For example, the third coding units 820a and 820b determined when the height of the left second coding unit 810a of a non-square shape is divided in half may satisfy the condition. Because the boundaries of the third coding units 820c, 820d, and 820e determined when the right second coding unit 810b is divided into three coding units fail to divide the width or height of the right second coding unit 810b in half, it may be determined that the third coding units 820c, 820d, and 820e do not satisfy the condition. When the condition is not satisfied as described above, the image decoding apparatus 100 may determine that the scanning order is discontinuous, and may determine that the right second coding unit 810b is to be divided into an odd number of coding units based on the determination result. According to an embodiment, when the coding unit is divided into an odd number of coding units, the image decoding apparatus 100 may impose a preset restriction on the coding unit at a preset position in the divided coding unit. The restriction or the preset position has been described above with respect to various embodiments, and therefore a detailed description thereof will not be provided here.

[0149] Fig. 9 A process of determining at least one coding unit by splitting the first coding unit 900 , performed by the image decoding apparatus 100 according to an embodiment, is illustrated.

[0150] According to an embodiment, the image decoding apparatus 100 may divide the first coding unit 900 based on the division shape pattern information obtained by the bitstream obtainer 110. The square first coding unit 900 may be divided into four square coding units, or may be divided into a plurality of non-square coding units. Fig. 9 , when the first coding unit has a square shape and the division shape pattern information indicates that the first coding unit 900 is divided into non-square coding units, the image decoding apparatus 100 may divide the first coding unit 900 into a plurality of non-square coding units. In detail, when the division shape pattern information indicates that an odd number of coding units is determined by dividing the first coding unit 900 in a horizontal direction or a vertical direction, the image decoding apparatus 100 may divide the square first coding unit 900 into an odd number of coding units (for example, second coding units 910a, 910b, and 910c determined by dividing the square first coding unit 900 in a vertical direction, or second coding units 920a, 920b, and 920c determined by dividing the square first coding unit 900 in a horizontal direction).

[0151] According to an embodiment, the image decoding apparatus 100 may determine whether the second coding units 910a, 910b, 910c, 920a, 920b, and 920c included in the first coding unit 900 satisfy a condition for processing in a preset order, and the condition is related to whether at least one of the width and height of the first coding unit 900 will be divided in half along the boundary of the second coding units 910a, 910b, 910c, 920a, 920b, and 920c. Fig. 9, because the boundaries of the second coding units 910a, 910b, and 910c determined by dividing the first coding unit 900 in the vertical direction do not divide the width of the first coding unit 900 in half, it can be determined that the first coding unit 900 does not meet the condition for processing in a preset order. In addition, because the boundaries of the second coding units 920a, 920b, and 920c determined by dividing the first coding unit 900 in the horizontal direction do not divide the height of the first coding unit 900 in half, it can be determined that the first coding unit 900 does not meet the condition for processing in a preset order. When the condition is not satisfied as described above, the image decoding apparatus 100 may determine that the scanning order is not continuous, and may determine that the first coding unit 900 is to be divided into an odd number of coding units based on the determination result. According to an embodiment, when the coding unit is divided into an odd number of coding units, the image decoding apparatus 100 may impose a preset restriction on the coding unit at a preset position in the divided coding unit. The restriction or the preset position has been described above with respect to various embodiments, so a detailed description thereof will not be provided here.

[0152] According to an embodiment, the image decoding apparatus 100 may determine coding units of various shapes by splitting the first coding unit.

[0153] Reference Fig. 9 , the image decoding apparatus 100 may divide the square first coding unit 900 or the non-square first coding unit 930 or 950 into coding units of various shapes.

[0154] Fig.10 It is shown that shapes into which the second coding unit may be split are restricted when a second coding unit having a non-square shape determined by splitting the first coding unit 1000 by the image decoding apparatus 100 satisfies a preset condition according to an embodiment.

[0155] According to an embodiment, the image decoding apparatus 100 may determine to divide the square first coding unit 1000 into non-square second coding units 1010a and 1010b, or 1020a and 1020b, based on the division shape pattern information obtained by the bitstream obtainer 110. The second coding units 1010a and 1010b, or 1020a and 1020b may be independently divided. In this way, the image decoding apparatus 100 may determine to divide each of the second coding units 1010a and 1010b, or 1020a and 1020b into a plurality of coding units or not to divide each of the second coding units 1010a and 1010b, or 1020a and 1020b, based on the division shape pattern information of each of the second coding units 1010a and 1010b, or 1020a and 1020b. According to an embodiment, the image decoding apparatus 100 may determine the third coding units 1012a and 1012b by splitting the non-square left second coding unit 1010a determined by splitting the first coding unit 1000 in the vertical direction in the horizontal direction. However, when the left second coding unit 1010a is split in the horizontal direction, the image decoding apparatus 100 may limit the right second coding unit 1010b to not be split in the horizontal direction in which the left second coding unit 1010a is split. When the third coding units 1014a and 1014b are determined by splitting the right second coding unit 1010b in the same direction, since the left second coding unit 1010a and the right second coding unit 1010b are independently split in the horizontal direction, the third coding units 1012a and 1012b, or 1014a and 1014b may be determined. However, this case has the same effect as the case where the image decoding apparatus 100 divides the first coding unit 1000 into four square second coding units 1030a, 1030b, 1030c, and 1030d based on the division shape pattern information, and may be inefficient in image decoding.

[0156] According to an embodiment, the image decoding apparatus 100 may determine the third coding units 1022a and 1022b, or 1024a and 1024b, by vertically splitting the non-square second coding unit 1020a or 1020b determined by horizontally splitting the first coding unit 1000. However, when the second coding unit (e.g., the upper second coding unit 1020a) is split in the vertical direction, the image decoding apparatus 100 may limit another second coding unit (e.g., the lower second coding unit 1020b) to not be split in the vertical direction in which the upper second coding unit 1020a is split for the above-mentioned reason.

[0157] Fig.11A process of splitting a square coding unit performed by the image decoding apparatus 100 when the division shape pattern information indicates that the square coding unit is not to be split into four square coding units according to an embodiment is illustrated.

[0158] According to an embodiment, the image decoding apparatus 100 may determine the second coding units 1110a and 1110b, or 1120a and 1120b, etc. by dividing the first coding unit 1100 based on the division shape pattern information. The division shape pattern information may include information about various methods of dividing the coding unit, but the information about the various division methods may not include information for dividing the coding unit into four square coding units. According to such division shape pattern information, the image decoding apparatus 100 may not divide the square first coding unit 1100 into four square coding units 1130a, 1130b, 1130c, and 1130d. The image decoding apparatus 100 may determine the non-square second coding units 1110a and 1110b, or 1120a and 1120b, etc. based on the division shape pattern information.

[0159] According to an embodiment, the image decoding apparatus 100 may independently divide the non-square second coding units 1110a and 1110b, or 1120a and 1120b, etc. Each of the second coding units 1110a and 1110b, or 1120a and 1120b, etc. may be recursively divided in a preset order, and the division method may correspond to the method of dividing the first coding unit 1100 based on the division shape pattern information.

[0160] For example, the image decoding apparatus 100 may determine square third coding units 1112a and 1112b by dividing the left second coding unit 1110a in the horizontal direction, and may determine square third coding units 1114a and 1114b by dividing the right second coding unit 1110b in the horizontal direction. In addition, the image decoding apparatus 100 may determine square third coding units 1116a, 1116b, 1116c, and 1116d by dividing both the left second coding unit 1110a and the right second coding unit 1110b in the horizontal direction. In this case, coding units having the same shape as the four square second coding units 1130a, 1130b, 1130c, and 1130d divided from the first coding unit 1100 may be determined.

[0161] As another example, the image decoding apparatus 100 may determine the third coding units 1122a and 1122b of the square shape by dividing the upper second coding unit 1120a in the vertical direction, and may determine the third coding units 1124a and 1124b of the square shape by dividing the lower second coding unit 1120b in the vertical direction. In addition, the image decoding apparatus 100 may determine the third coding units 1126a, 1126b, 1126c, and 1126d of the square shape by dividing both the upper second coding unit 1120a and the lower second coding unit 1120b in the vertical direction. In this case, a coding unit having the same shape as the four square second coding units 1130a, 1130b, 1130c, and 1130d divided from the first coding unit 1100 may be determined.

[0162] Fig.12 It is shown that a processing order among a plurality of coding units according to an embodiment may be changed according to a process of dividing the coding units.

[0163] According to an embodiment, the image decoding apparatus 100 may divide the first coding unit 1200 based on the division shape pattern information. When the block shape indicates a square shape and the division shape pattern information indicates that the first coding unit 1200 is divided in at least one of the horizontal direction and the vertical direction, the image decoding apparatus 100 may determine the second coding units 1210a and 1210b, or 1220a and 1220b, etc. by dividing the first coding unit 1200. Fig.12 , the non-square second coding units 1210a and 1210b, or 1220a and 1220b determined by dividing the first coding unit 1200 only in the horizontal direction or the vertical direction may be independently divided based on the division shape pattern information of each coding unit. For example, the image decoding device 100 may determine the third coding units 1216a, 1216b, 1216c, and 1216d by dividing the second coding units 1210a and 1210b generated by dividing the first coding unit 1200 in the vertical direction in the horizontal direction, and may determine the third coding units 1226a, 1226b, 1226c, and 1226d by dividing the second coding units 1220a and 1220b generated by dividing the first coding unit 1200 in the horizontal direction in the vertical direction. As has been described above, Fig.11 An operation of dividing the second coding units 1210a and 1210b, or 1220a and 1220b is described, and thus a detailed description thereof will not be provided here.

[0164] According to an embodiment, the image decoding apparatus 100 may process the coding units in a preset order. Figure 7The operation of processing the encoding units in a preset order is described, and thus a detailed description thereof will not be provided here. Fig.12 , the image decoding apparatus 100 may determine four square third coding units 1216a, 1216b, 1216c, and 1216d and 1226a, 1226b, 1226c, and 1226d by dividing the square first coding unit 1200. According to an embodiment, the image decoding apparatus 100 may determine a processing order of the third coding units 1216a, 1216b, 1216c, and 1216d and 1226a, 1226b, 1226c, and 1226d based on a division shape of dividing the first coding unit 1200.

[0165] According to an embodiment, the image decoding device 100 can determine the third coding units 1216a, 1216b, 1216c and 1216d by dividing the second coding units 1210a and 1210b generated by dividing the first coding unit 1200 in the vertical direction in the horizontal direction, and can process the third coding units 1216a, 1216b, 1216c and 1216d in the following processing order 1217: first, the third coding units 1216a and 1216c included in the left second coding unit 1210a are processed in the vertical direction, and then the third coding units 1216b and 1216d included in the right second coding unit 1210b are processed in the vertical direction.

[0166] According to an embodiment, the image decoding device 100 can determine the third coding units 1226a, 1226b, 1226c and 1226d by dividing the second coding units 1220a and 1220b generated by dividing the first coding unit 1200 in the horizontal direction in the vertical direction, and can process the third coding units 1226a, 1226b, 1226c and 1226d in the following processing order 1227: first, the third coding units 1226a and 1226b included in the upper second coding unit 1220a are processed in the horizontal direction, and then the third coding units 1226c and 1226d included in the lower second coding unit 1220b are processed in the horizontal direction.

[0167] Reference Fig.12, square third coding units 1216a, 1216b, 1216c and 1216d and 1226a, 1226b, 1226c and 1226d may be determined by dividing the second coding units 1210a and 1210b, and 1220a and 1220b, respectively. Although the second coding units 1210a and 1210b determined by splitting the first coding unit 1200 in the vertical direction are different from the second coding units 1220a and 1220b determined by splitting the first coding unit 1200 in the horizontal direction, the third coding units 1216a, 1216b, 1216c, and 1216d and the third coding units 1226a, 1226b, 1226c, and 1226d split from the second coding units 1210a and 1210b and the second coding units 1220a and 1220b ultimately show the same shape of coding units split from the first coding unit 1200. In this way, by recursively splitting the coding units in different ways based on the split shape pattern information, even if the coding units are ultimately determined to be the same shape, the image decoding apparatus 100 may process a plurality of coding units in different orders.

[0168] Fig.13 A process of determining a depth of a coding unit as a shape and a size of a coding unit change when a coding unit is recursively split to determine a plurality of coding units according to an embodiment is illustrated.

[0169] According to an embodiment, the image decoding apparatus 100 may determine the depth of the coding unit based on a preset standard. For example, the preset standard may be the length of the long side of the coding unit. When the length of the long side of the coding unit before being divided is 2n (n>0) times the length of the long side of the current coding unit after being divided, the image decoding apparatus 100 may determine that the depth of the current coding unit is increased by n compared to the depth of the coding unit before being divided. In the following description, a coding unit with an increased depth is represented as a coding unit of a lower depth.

[0170] Reference Fig.13According to an embodiment, the image decoding apparatus 100 may determine a second coding unit 1302 and a third coding unit 1304 of a lower depth by dividing a square first coding unit 1300 based on block shape information indicating a square shape (for example, the block shape information may be represented as "0: SQUARE"). Assuming that the size of the square first coding unit 1300 is 2N×2N, the second coding unit 1302 determined by dividing the width and height of the first coding unit 1300 into 1 / 2 may have a size of N×N. In addition, the third coding unit 1304 determined by dividing the width and height of the second coding unit 1302 into 1 / 2 may have a size of N / 2×N / 2. In this case, the width and height of the third coding unit 1304 are 1 / 4 of the width and height of the first coding unit 1300. When the depth of the first coding unit 1300 is D, the depth of the second coding unit 1302 whose width and height are 1 / 2 of the width and height of the first coding unit 1300 may be D+1, and the depth of the third coding unit 1304 whose width and height are 1 / 4 of the width and height of the first coding unit 1300 may be D+2.

[0171] According to an embodiment, the image decoding device 100 can determine the second coding unit 1312 or 1322 of the lower depth, and the third coding unit 1314 or 1324 by dividing the non-square first coding unit 1310 or 1320 based on block shape information indicating a non-square shape (for example, the block shape information may be represented as "1: NS_VER" indicating a non-square shape in which the height is longer than the width, or may be represented as "2: NS_HOR" indicating a non-square shape in which the width is longer than the height).

[0172] The image decoding apparatus 100 may determine the second coding unit 1302, 1312, or 1322 by splitting at least one of the width and the height of the first coding unit 1310 having a size of N×2N. That is, the image decoding apparatus 100 may determine the second coding unit 1302 having a size of N×N or the second coding unit 1322 having a size of N×N / 2 by splitting the first coding unit 1310 in a horizontal direction, or may determine the second coding unit 1312 having a size of N / 2×N by splitting the first coding unit 1310 in horizontal and vertical directions.

[0173] According to an embodiment, the image decoding apparatus 100 may determine the second coding unit 1302, 1312, or 1322 by dividing at least one of the width and the height of the first coding unit 1320 having a size of 2N×N. That is, the image decoding apparatus 100 may determine the second coding unit 1302 having a size of N×N or the second coding unit 1312 having a size of N / 2×N by dividing the first coding unit 1320 in a vertical direction, or may determine the second coding unit 1322 having a size of N×N / 2 by dividing the first coding unit 1320 in horizontal and vertical directions.

[0174] According to an embodiment, the image decoding apparatus 100 may determine the third coding unit 1304, 1314, or 1324 by dividing at least one of the width and the height of the second coding unit 1302 having a size of N×N. That is, the image decoding apparatus 100 may determine the third coding unit 1304 having a size of N / 2×N / 2, the third coding unit 1314 having a size of N / 4×N / 2, or the third coding unit 1324 having a size of N / 2×N / 4 by dividing the second coding unit 1302 in the vertical direction and the horizontal direction.

[0175] According to an embodiment, the image decoding apparatus 100 may determine the third coding unit 1304, 1314, or 1324 by dividing at least one of the width and the height of the second coding unit 1312 having a size of N / 2×N. That is, the image decoding apparatus 100 may determine the third coding unit 1304 having a size of N / 2×N / 2 or the third coding unit 1324 having a size of N / 2×N / 4 by dividing the second coding unit 1312 in a horizontal direction, or may determine the third coding unit 1314 having a size of N / 4×N / 2 by dividing the second coding unit 1312 in a vertical direction and a horizontal direction.

[0176] According to an embodiment, the image decoding apparatus 100 may determine the third coding unit 1304, 1314, or 1324 by dividing at least one of the width and the height of the second coding unit 1322 having a size of N×N / 2. That is, the image decoding apparatus 100 may determine the third coding unit 1304 having a size of N / 2×N / 2 or the third coding unit 1314 having a size of N / 4×N / 2 by dividing the second coding unit 1322 in a vertical direction, or may determine the third coding unit 1324 having a size of N / 2×N / 4 by dividing the second coding unit 1322 in a vertical direction and a horizontal direction.

[0177] According to an embodiment, the image decoding apparatus 100 may split the square coding unit 1300, 1302, or 1304 in a horizontal direction or a vertical direction. For example, the image decoding apparatus 100 may determine the first coding unit 1310 having a size of N×2N by splitting the first coding unit 1300 having a size of 2N×2N in a vertical direction, or may determine the first coding unit 1320 having a size of 2N×N by splitting the first coding unit 1300 in a horizontal direction. According to an embodiment, when the depth is determined based on the length of the longest side of the coding unit, the depth of the coding unit determined by splitting the first coding unit 1300 having a size of 2N×2N in a horizontal direction or a vertical direction may be the same as the depth of the first coding unit 1300.

[0178] According to an embodiment, the width and height of the third coding unit 1314 or 1324 may be 1 / 4 of the width and height 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 whose width and height are 1 / 2 of 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 whose width and height are 1 / 4 of the width and height of the first coding unit 1310 or 1320 may be D+2.

[0179] Fig.14 Depth that may be determined based on the shape and size of a coding unit and a partial index (PID) for distinguishing coding units according to an embodiment are illustrated.

[0180] According to an embodiment, the image decoding apparatus 100 may determine second coding units of various shapes by dividing the square first coding unit 1400. Fig.14 , the image decoding apparatus 100 may determine the second coding units 1402a and 1402b, the second coding units 1404a and 1404b, and the second coding units 1406a, 1406b, 1406c, and 1406d by dividing the first coding unit 1400 in at least one of the vertical direction and the horizontal direction based on the division shape pattern information. That is, the image decoding apparatus 100 may determine the second coding units 1402a and 1402b, 1404a and 1404b, and 1406a, 1406b, 1406c, and 1406d based on the division shape pattern information of the first coding unit 1400.

[0181] According to an embodiment, the depths of the second coding units 1402a and 1402b, the second coding units 1404a and 1404b, and the second coding units 1406a, 1406b, 1406c, and 1406d determined based on the division shape pattern information of the square first coding unit 1400 may be determined based on the lengths of their long sides. For example, since the length of the side of the square first coding unit 1400 is equal to the length of the long side of the non-square second coding units 1402a and 1402b and 1404a and 1404b, the first coding unit 1400 and the non-square second coding units 1402a and 1402b and 1404a and 1404b may have the same depth, for example, D. However, when the image decoding device 100 divides the first coding unit 1400 into four square second coding units 1406a, 1406b, 1406c and 1406d based on the division shape pattern information, because the length of the side of the square second coding units 1406a, 1406b, 1406c and 1406d is 1 / 2 of the length of the side of the first coding unit 1400, the depth of the second coding units 1406a, 1406b, 1406c and 1406d can be D+1 which is 1 deeper than the depth D of the first coding unit 1400.

[0182] According to an embodiment, the image decoding apparatus 100 may determine a plurality of second coding units 1412a and 1412b and 1414a, 1414b, and 1414c by horizontally dividing the first coding unit 1410 whose height is longer than the width based on the division shape pattern information. According to an embodiment, the image decoding apparatus 100 may determine a plurality of second coding units 1422a and 1422b and 1424a, 1424b, and 1424c by vertically dividing the first coding unit 1420 whose width is longer than the height based on the division shape pattern information.

[0183] According to an embodiment, the depth of the second coding units 1412a and 1412b and 1414a, 1414b and 1414c, or 1422a and 1422b and 1424a, 1424b and 1424c determined based on the division shape pattern information of the non-square first coding unit 1410 or 1420 may be determined based on the length of their long sides. For example, since the length of the side of the square second coding units 1412a and 1412b is 1 / 2 of the length of the long side of the first coding unit 1410 having a non-square shape whose height is longer than the width, the depth of the square second coding units 1412a and 1412b is D+1 which is 1 deeper than the depth D of the non-square first coding unit 1410.

[0184] In addition, the image decoding apparatus 100 may divide the non-square first coding unit 1410 into an odd number of second coding units 1414a, 1414b, and 1414c based on the division shape pattern information. The odd number of second coding units 1414a, 1414b, and 1414c may include the non-square second coding units 1414a and 1414c and the square second coding unit 1414b. In this case, since the length of the long side of the non-square second coding units 1414a and 1414c and the length of the side of the square second coding unit 1414b are 1 / 2 of the length of the long side of the first coding unit 1410, the depth of the second coding units 1414a, 1414b, and 1414c may be D+1 which is 1 deeper than the depth D of the non-square first coding unit 1410. The image decoding apparatus 100 may determine the depths of coding units split from the first coding unit 1420 having a non-square shape having a width longer than a height by using the above-described method of determining the depths of coding units split from the first coding unit 1410 .

[0185] According to an embodiment, when the odd-numbered divided coding units do not have equal sizes, the image decoding apparatus 100 may determine a PID for identifying the divided coding units based on a size ratio between the coding units. Fig.14 , the width of the coding unit 1414b at the center position among the odd-numbered divided coding units 1414a, 1414b, and 1414c may be equal to the width of the other coding units 1414a and 1414c and its height may be twice the height of the other coding units 1414a and 1414c. That is, in this case, the coding unit 1414b at the center position may include two other coding units 1414a or 1414c. Therefore, when the PID of the coding unit 1414b at the center position is 1 based on the scanning order, the PID of the coding unit 1414c located at a position adjacent to the coding unit 1414b may increase by 2 and may thus be 3. That is, there may be discontinuity in the PID value. According to an embodiment, the image decoding apparatus 100 may determine whether the odd-numbered divided coding units do not have equal sizes based on whether there is discontinuity in the PID for identifying the divided coding units.

[0186] According to an embodiment, the image decoding apparatus 100 may determine whether to use a specific splitting method based on a PID value for identifying a plurality of coding units determined by splitting a current coding unit. Fig.14, the image decoding apparatus 100 may determine even-numbered coding units 1412a and 1412b or odd-numbered coding units 1414a, 1414b, and 1414c by dividing the first coding unit 1410 having a rectangular shape whose height is longer than its width. The image decoding apparatus 100 may use a PID indicating a corresponding coding unit in order to identify the corresponding coding unit. According to an embodiment, the PID may be obtained from a sample point at a preset position of each coding unit (e.g., an upper left sample point).

[0187] According to an embodiment, the image decoding apparatus 100 may determine a coding unit at a preset position among the divided coding units by using a PID for distinguishing coding units. According to an embodiment, when the division shape pattern information of the first coding unit 1410 having a rectangular shape having a height longer than a width indicates that the coding unit is divided into three coding units, the image decoding apparatus 100 may divide the first coding unit 1410 into three coding units 1414a, 1414b, and 1414c. The image decoding apparatus 100 may assign a PID to each of the three coding units 1414a, 1414b, and 1414c. The image decoding apparatus 100 may compare the PIDs of the odd-numbered divided coding units to determine a coding unit at a center position among the coding units. The image decoding apparatus 100 may determine the coding unit 1414b corresponding to the PID and the intermediate value among the PIDs of the coding units as the coding unit at the center position among the coding units determined by dividing the first coding unit 1410. According to an embodiment, when the divided coding units do not have equal sizes, the image decoding apparatus 100 may determine a PID for distinguishing the divided coding units based on a size ratio between the coding units. Fig.14, the width of the coding unit 1414b generated by dividing the first coding unit 1410 may be equal to the width of the other coding units 1414a and 1414c, and the height thereof may be twice the height of the other coding units 1414a and 1414c. In this case, when the PID of the coding unit 1414b at the center position is 1, the PID of the coding unit 1414c located at the adjacent position to the coding unit 1414b may increase by 2 and thus may be 3. When the PID is not uniformly increased as described above, the image decoding apparatus 100 may determine that the coding unit is divided into a plurality of coding units, wherein the plurality of coding units include coding units having sizes different from those of the other coding units. According to an embodiment, when the division shape pattern information indicates that the coding unit is divided into an odd number of coding units, the image decoding apparatus 100 may divide the current coding unit in such a manner that the coding unit at a preset position (e.g., the coding unit at the center position) among the odd number of coding units has a size different from that of the other coding units. In this case, the image decoding apparatus 100 may determine the coding units at the center position having different sizes by using the PIDs of the coding units. However, the PID of the encoding unit at the preset position and the size or position are not limited to the above examples, and various PIDs and various positions and sizes of the encoding unit may be used.

[0188] According to an embodiment, the image decoding apparatus 100 may use a preset data unit in which the coding unit is recursively split starting from the preset data unit.

[0189] Fig.15 It is illustrated that a plurality of coding units are determined based on a plurality of preset data units included in a picture according to an embodiment.

[0190] According to an embodiment, a preset data unit may be defined as a data unit for recursively dividing a coding unit starting by using division shape pattern information. That is, the preset data unit may correspond to a coding unit for determining a highest depth of a plurality of coding units divided from a current picture. In the following description, for ease of explanation, a preset data unit is referred to as a reference data unit.

[0191] According to an embodiment, the reference data unit may have a preset size and a preset shape. According to an embodiment, the reference coding unit may include M×N samples. Here, M and N may be equal to each other and may be an integer represented as a power of 2. That is, the reference data unit may have a square shape or a non-square shape and may be divided into an integer number of coding units.

[0192] According to an embodiment, the image decoding apparatus 100 may divide the current picture into a plurality of reference data units. According to an embodiment, the image decoding apparatus 100 may divide the plurality of reference data units divided from the current picture by using the division shape pattern information of each reference data unit. The operation of dividing the reference data unit may correspond to the division operation using a quadtree structure.

[0193] According to an embodiment, the image decoding apparatus 100 may predetermine a minimum size allowed for a reference data unit included in the current picture. Therefore, the image decoding apparatus 100 may determine various reference data units having a size equal to or larger than the minimum size, and may determine one or more coding units by using the division shape pattern information with reference to the determined reference data unit.

[0194] Reference Fig.15 , the image decoding apparatus 100 may use a square reference coding unit 1500 or a non-square reference coding unit 1502. According to an embodiment, the shape and size of the reference coding unit may be determined based on various data units (e.g., a sequence, a picture, a slice, a slice segment, a tile, a tile group, a maximum coding unit, etc.) that can include one or more reference coding units.

[0195] According to an embodiment, the bitstream obtainer 110 of the image decoding apparatus 100 may obtain at least one of reference coding unit shape information and reference coding unit size information for each of various data units from the bitstream. Figure 3 The operation of dividing the current coding unit 300 describes the operation of dividing the square reference coding unit 1500 into one or more coding units, and the above has been combined with Figure 4 The operation of splitting the current coding unit 400 or 450 describes an operation of splitting the non-square reference coding unit 1502 into one or more coding units. Therefore, a detailed description thereof will not be provided here.

[0196] According to an embodiment, the image decoding apparatus 100 may determine the size and shape of the reference coding unit using a PID for identifying the size and shape of the reference coding unit according to some data units predetermined based on a specific condition. That is, the bitstream obtainer 110 may obtain only the PID for identifying the size and shape of the reference coding unit for each slice, slice segment, tile, tile group, or maximum coding unit from the bitstream, wherein the slice, slice segment, tile, tile group, or maximum coding unit is a data unit (e.g., a data unit having a size equal to or smaller than a slice) among various data units (e.g., a sequence, a picture, a slice, a slice segment, a tile, a tile group, a maximum coding unit, etc.) that meets a preset condition. The image decoding apparatus 100 may determine the size and shape of the reference coding unit for each data unit that meets the preset condition by using the PID. When the reference coding unit shape information and the reference coding unit size information are obtained and used from the bitstream according to each data unit having a relatively small size, the efficiency of using the bitstream may not be high, and therefore, only the PID may be obtained and used instead of directly obtaining the reference coding unit shape information and the reference coding unit size information. In this case, at least one of the sizes and shapes of the reference coding units corresponding to the PID for identifying the sizes and shapes of the reference coding units may be predetermined. That is, the image decoding apparatus 100 may determine at least one of the sizes and shapes of the reference coding units included in the data unit serving as the unit for obtaining the PID by selecting at least one of the sizes and shapes of the reference coding units predetermined based on the PID.

[0197] According to an embodiment, the image decoding device 100 may use one or more reference coding units included in the maximum coding unit. That is, the maximum coding unit divided from the picture may include one or more reference coding units, and the coding unit may be determined by recursively dividing each reference coding unit. According to an embodiment, at least one of the width and height of the maximum coding unit may be an integer multiple of at least one of the width and height of the reference coding unit. According to an embodiment, the size of the reference coding unit may be obtained by dividing the maximum coding unit n times based on a quadtree structure. That is, according to various embodiments, the image decoding device 100 may determine the reference coding unit by dividing the maximum coding unit n times based on a quadtree structure, and the reference coding unit may be divided based on at least one of the block shape information and the division shape mode information.

[0198] Fig.16 A processing block serving as a unit for determining an order of reference coding units included in the picture 1600 according to an embodiment is illustrated.

[0199] According to an embodiment, the image decoding device 100 may determine one or more processing blocks divided from a picture. A processing block is a data unit including one or more reference coding units divided from a picture, and one or more reference coding units included in the processing block may be determined according to a specific order. That is, the determination order of one or more reference coding units determined in each processing block may correspond to one of various types of orders for determining reference coding units, and may vary according to the processing block. The determination order of the reference coding units determined for each processing block may be one of various orders (e.g., raster scanning order, zigzag scanning, N-shaped scanning, upper right diagonal scanning, horizontal scanning, and vertical scanning), but is not limited to the scanning order mentioned above.

[0200] According to an embodiment, the image decoding apparatus 100 may obtain processing block size information and may determine the size of one or more processing blocks included in the picture. The image decoding apparatus 100 may obtain processing block size information from a bitstream and may determine the size of one or more processing blocks included in the picture. The size of the processing block may be a preset size of a data unit indicated by the processing block size information.

[0201] According to an embodiment, the bitstream obtainer 110 of the image decoding device 100 may obtain processing block size information from the bitstream according to each specific data unit. For example, the processing block size information may be obtained from the bitstream according to data units such as an image, a sequence, a picture, a slice, a slice segment, a parallel block, or a parallel block group. That is, the bitstream obtainer 110 may obtain processing block size information from the bitstream according to each of the various data units, and the image decoding device 100 may determine the size of one or more processing blocks divided from the picture by using the obtained processing block size information. The size of the processing block may be an integer multiple of the size of the reference coding unit.

[0202] According to an embodiment, the image decoding apparatus 100 may determine the size of the processing blocks 1602 and 1612 included in the picture 1600. For example, the image decoding apparatus 100 may determine the size of the processing block based on the processing block size information obtained from the bitstream. Fig.16 According to an embodiment, the image decoding apparatus 100 may determine the width of the processing blocks 1602 and 1612 to be four times the width of the reference coding unit, and may determine the height of the processing blocks 1602 and 1612 to be four times the height of the reference coding unit. The image decoding apparatus 100 may determine the determination order of one or more reference coding units in one or more processing blocks.

[0203] According to an embodiment, the image decoding apparatus 100 may determine the processing blocks 1602 and 1612 included in the picture 1600 based on the size of the processing blocks, and may determine a determination order of one or more reference coding units in the processing blocks 1602 and 1612. According to an embodiment, the determination of the reference coding unit may include determining the size of the reference coding unit.

[0204] According to an embodiment, the image decoding apparatus 100 may obtain determination order information of one or more reference coding units included in one or more processing blocks from a bitstream, and may determine a determination order for the one or more reference coding units based on the obtained determination order information. The determination order information may be defined as an order or direction for determining the reference coding units in the processing block. That is, the determination order of the reference coding units may be determined independently for each processing block.

[0205] According to an embodiment, the image decoding apparatus 100 may obtain the determination order information of the reference coding unit from the bitstream according to each specific data unit. For example, the bitstream obtainer 110 may obtain the determination order information of the reference coding unit from the bitstream according to each data unit (such as an image, a sequence, a picture, a slice, a slice segment, a tile, a tile group, or a processing block). Because the determination order information of the reference coding unit indicates the order of the reference coding unit in the processing block, the determination order information may be obtained for each specific data unit including an integer number of processing blocks.

[0206] According to an embodiment, the image decoding apparatus 100 may determine one or more reference coding units based on the determined order.

[0207] According to an embodiment, the bitstream obtainer 110 may obtain determination order information of reference coding units from the bitstream as information related to the processing blocks 1602 and 1612, and the image decoding apparatus 100 may determine the determination order of one or more reference coding units included in the processing blocks 1602 and 1612, and determine one or more reference coding units included in the picture 1600 based on the determination order. Fig.16, the image decoding apparatus 100 may respectively determine determination orders 1604 and 1614 of one or more reference coding units in the processing blocks 1602 and 1612. For example, when determination order information of the reference coding units is obtained for each processing block, different types of determination order information of the reference coding units may be obtained for the processing blocks 1602 and 1612. When the determination order 1604 of the reference coding units in the processing block 1602 is a raster scan order, the reference coding units included in the processing block 1602 may be determined according to the raster scan order. Conversely, when the determination order 1614 of the reference coding units in another processing block 1612 is a reverse raster scan order, the reference coding units included in the processing block 1612 may be determined according to the reverse raster scan order.

[0208] According to an embodiment, the image decoding apparatus 100 may decode the determined one or more reference coding units. The image decoding apparatus 100 may decode the image based on the reference coding units determined as described above. The method of decoding the reference coding units may include various image decoding methods.

[0209] According to an embodiment, the image decoding device 100 may obtain block shape information indicating the shape of the current coding unit or division shape pattern information indicating the division method of the current coding unit from the bitstream, and may use the obtained information. The division shape pattern information may be included in the bitstream associated with various data units. For example, the image decoding device 100 may use the division shape pattern information included in a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a parallel block header, or a parallel block group header. In addition, the image decoding device 100 may obtain a syntax element corresponding to the block shape information or the division shape pattern information from the bitstream according to each maximum coding unit, each reference coding unit, or each processing block, and may use the obtained syntax element.

[0210] Hereinafter, a method for determining a division rule according to an embodiment of the present disclosure will be described in detail.

[0211] The image decoding apparatus 100 may determine a division rule of an image. The division rule may be predetermined between the image decoding apparatus 100 and the image encoding apparatus 200. The image decoding apparatus 100 may determine a division rule of an image based on information obtained from a bitstream. The image decoding apparatus 100 may determine a division 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 parallel block header, and a parallel block group header. The image decoding apparatus 100 may determine a division rule differently according to a frame, a slice, a parallel block, a temporal layer, a maximum coding unit, or a coding unit.

[0212] The image decoding device 100 may determine the division rule based on the block shape of the coding unit. The block shape may include the size, shape, aspect ratio, and direction of the coding unit. The image encoding device 200 and the image decoding device 100 may predetermine the division rule based on the block shape of the coding unit. However, the embodiment is not limited thereto. The image decoding device 100 may determine the division rule based on information obtained from the bit stream received from the image encoding device 200.

[0213] The shape of the coding unit may include a square and a non-square. When the width length and height length of the coding unit are the same, the image decoding apparatus 100 may determine that the shape of the coding unit is a square. In addition, when the width length and height length of the coding unit are different, the image decoding apparatus 100 may determine that the shape of the coding unit is a non-square.

[0214] The size of the coding unit may include various sizes such as 4×4, 8×4, 4×8, 8×8, 16×4, 16×8, ... and up to 256×256. The size of the coding unit may be classified based on the length of the long side, the length of the short side, or the area of ​​the coding unit. The image decoding device 100 may apply the same division rule to the coding units classified into the same group. For example, the image decoding device 100 may classify the coding units having the same long side length as having the same size. In addition, the image decoding device 100 may apply the same division rule to the coding units having the same long side length.

[0215] The aspect ratio of the coding unit may include 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, 32:1, 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 width length of the coding unit is longer than the height length of the coding unit. The vertical direction may indicate a case where the width length of the coding unit is shorter than the height length of the coding unit.

[0216] The image decoding apparatus 100 may adaptively determine the division rule based on the size of the coding unit. The image decoding apparatus 100 may determine the allowable division shape mode differently based on the size of the coding unit. For example, the image decoding apparatus 100 may determine whether to allow division based on the size of the coding unit. The image decoding apparatus 100 may determine the division direction according to the size of the coding unit. The image decoding apparatus 100 may determine the allowable division type according to the size of the coding unit.

[0217] The division rule determined based on the size of the coding unit may be a division rule predetermined between the image encoding apparatus 200 and the image decoding apparatus 100. Also, the image decoding apparatus 100 may determine the division rule based on information obtained from a bitstream.

[0218] The image decoding apparatus 100 may adaptively determine a split rule based on a location of a coding unit. The image decoding apparatus 100 may adaptively determine a split rule based on a location of a coding unit in an image.

[0219] In addition, the image decoding apparatus 100 may determine a division rule so that the coding units generated via different division paths do not have the same block shape. However, the embodiment is not limited thereto, and the coding units generated via different division paths have the same block shape. The coding units generated via different division paths may have different decoding processing orders. Fig.12 The decoding process order is described, so its details are not provided again.

[0220] Fig.17 Coding units that may be determined for each of pictures when a division shape combination for coding units varies for each picture according to an embodiment are illustrated.

[0221] Reference Fig.17 , the image decoding apparatus 100 may determine that the division shape combination for the coding unit is different in each picture. For example, the image decoding apparatus 100 may decode the image by using a picture 1700 that can be divided into 4 coding units, a picture 1710 that can be divided into 2 or 4 coding units, and a picture 1720 that can be divided into 2, 3, or 4 coding units among one or more pictures included in the image. In order to divide the picture 1700 into a plurality of coding units, the image decoding apparatus 100 may use only the division shape information indicating division into 4 square coding units. In order to divide the picture 1710, the image decoding apparatus 100 may use only the division shape information indicating division into 2 or 4 coding units. In order to divide the picture 1720, the image decoding apparatus 100 may use only the division shape information indicating division into 2, 3, or 4 coding units. The above-mentioned division shape combination is an embodiment for describing the operation of the image decoding apparatus 100, and thus the above-mentioned division shape combination should not be interpreted as being limited to the above-mentioned embodiment. It should be explained that various division shape combinations may be used for each preset data unit.

[0222] According to an embodiment, the bitstream obtainer 110 of the image decoding apparatus 100 may obtain a bitstream including an index representing a combination of division shape information for each preset data unit (e.g., a sequence, a picture, a slice, a slice segment, a tile, a tile group, etc.). For example, the bitstream obtainer 110 may obtain an index representing a combination of division shape information from a sequence parameter set, a picture parameter set, a slice header, a tile header, or a tile group header. The image decoding apparatus 100 may use the obtained index to determine, for each preset data unit, a division shape combination into which a coding unit may be divided, and thus may use a different division shape combination for each preset data unit.

[0223] Fig.18 Various shapes of coding units that may be determined based on division shape pattern information that may be represented as a binary code according to an embodiment are illustrated.

[0224] According to an embodiment, the image decoding apparatus 100 may divide the coding unit into various shapes by using the block shape information and the division shape pattern information obtained by the bitstream obtainer 110. The shapes into which the coding unit may be divided may correspond to various shapes including the shapes described above through the embodiments.

[0225] Reference Fig.18 , the image decoding apparatus 100 may divide the square coding unit in at least one of the horizontal direction and the vertical direction based on the division shape pattern information, and may divide the non-square coding unit in the horizontal direction or the vertical direction.

[0226] According to an embodiment, when the image decoding device 100 can obtain four square coding units by dividing a square coding unit in the horizontal direction and the vertical direction, the four division shapes can be indicated by the division shape pattern information for the square coding unit. According to an embodiment, the division shape pattern information can be represented as a 2-bit binary code, and the binary code can be assigned to each of the division shapes. For example, when the coding unit is not divided, the division shape pattern information can be represented as (00)b; when the coding unit is divided in the horizontal direction and the vertical direction, the division shape pattern information can be represented as (01)b, when the coding unit is divided in the horizontal direction, the division shape pattern information can be represented as (10)b, and when the coding unit is divided in the vertical direction, the division shape pattern information can be represented as (11)b.

[0227] According to an embodiment, when the image decoding apparatus 100 splits a non-square coding unit in a horizontal direction or a vertical direction, the type of the split shape that may be indicated by the split shape pattern information may be determined according to the number of coding units into which the coding unit is to be split. Fig.18 , according to an embodiment, the image decoding device 100 may divide the non-square coding unit into up to 3 coding units. In addition, the image decoding device 100 may divide the coding unit into two coding units, and in this case, the division shape pattern information may be represented as (10)b. The image decoding device 100 may divide the coding unit into three coding units, and in this case, the division shape pattern information may be represented as (11)b. The image decoding device 100 may determine not to divide the coding unit, and in this case, the division shape pattern information may be represented as (0)b. That is, the image decoding device 100 may use variable length coding (VLC) instead of fixed length coding (FLC) in order to use a binary code representing the division shape pattern information.

[0228] According to the embodiment, referring to Fig.18 , the binary code of the division shape mode information indicating that the coding unit is not to be divided can be represented as (0)b. In the case where the binary code of the division shape mode information indicating that the coding unit is not to be divided is set to (00)b, even when there is no division shape mode information set to (01)b, the 2-bit division shape mode information must be used in its entirety. However, if Fig.18 As shown in , in the case where three division shapes are used for non-square coding units, the image decoding apparatus 100 can determine that the coding unit will not be divided by using a 1-bit binary code (0)b as the division shape pattern information, thereby efficiently using the bitstream. However, the division shape of the non-square coding unit indicated by the division shape pattern information should not be interpreted as being limited to Fig.18 The three shapes shown in FIG. 1 should be interpreted as including various shapes of the above-mentioned embodiments.

[0229] Fig.19 Other shapes of coding units that may be determined based on division shape pattern information that may be represented as a binary code according to an embodiment are illustrated.

[0230] Reference Fig.19 , the image decoding device 100 may divide the square coding unit in the horizontal direction or the vertical direction based on the division shape pattern information, and may divide the non-square coding unit in the horizontal direction or the vertical direction. That is, the division shape pattern information may indicate that the square coding unit is divided in one direction. In this case, the binary code of the division shape pattern information indicating that the square coding unit will not be divided may be represented as (0)b. In the case where the binary code of the division shape pattern information indicating that the coding unit will not be divided is set to (00)b, even when there is no division shape pattern information set to (01)b, the binary code of the 2-bit division shape pattern information must be used in its entirety. However, as Fig.19 As shown in , in the case where three division shapes are used for square coding units, the image decoding apparatus 100 can determine that the coding unit will not be divided by using a 1-bit binary code (0)b as the division shape pattern information, thereby efficiently using the bit stream. However, the division shape of the square coding unit indicated by the division shape pattern information should not be interpreted as being limited to Fig.19 The three shapes shown in FIG. 1 should be interpreted as including various shapes of the above-mentioned embodiments.

[0231] According to an embodiment, block shape information or division shape mode information may be represented using a binary code, and such information may be directly generated as a bitstream. In addition, block shape information or division shape mode information represented using a binary code may not be directly generated as a bitstream, but may be used as a binary code input in context adaptive binary arithmetic coding (CABAC).

[0232] According to an embodiment, the process of obtaining the syntax for block shape information or division shape mode information by CABAC by the image decoding device 100 will be described. The image decoding device 100 may obtain a bitstream including a binary code for the syntax through the bitstream obtainer 110. The image decoding device 100 may detect a syntax element indicating block shape information or division shape mode information by debinarizing a binary bit string included in the obtained bitstream. According to an embodiment, the image decoding device 100 may obtain a set of binary bit strings corresponding to syntax elements to be decoded, and may decode each binary bit in the binary bit by using probability information. The image decoding device 100 may repeat this operation until a binary bit string configured with decoded binary bits is identical to one of the binary bit strings obtained previously. The image decoding device 100 may determine the syntax element by debinarizing the binary bit string.

[0233] According to an embodiment, the image decoding apparatus 100 may perform a decoding process of adaptive binary arithmetic coding to determine a syntax for a binary bit string, and may update a probability model for a binary bit obtained by the bitstream obtainer 110. Fig.18 According to an embodiment, the bitstream obtainer 110 of the image decoding device 100 may obtain a bitstream indicating a binary code, wherein the binary code represents the division shape pattern information. The image decoding device 100 may determine the syntax for the division shape pattern information by using the obtained binary code of 1 bit or 2 bits. In order to determine the syntax for the division shape pattern information, the image decoding device 100 may update the probability of each bit in the 2-bit binary code. That is, the image decoding device 100 may update the probability that the next binary bit will have a value of 0 or 1 when decoding, according to whether the value of the first binary bit in the 2-bit binary code is 0 or 1.

[0234] According to an embodiment, in the process of determining the syntax, the image decoding apparatus 100 may update the probability of the bins used in the process of decoding the bins of the bin string for the syntax. In this regard, the image decoding apparatus 100 may not update the probability of a specific bit of the bin string and may determine that the specific bit has the same probability.

[0235] Reference Fig.18, in the process of determining the syntax by using a binary bit string representing the division shape pattern information for the non-square coding unit, the image decoding device 100 may determine the syntax for the division shape pattern information by using a binary bit having a value of 0 when the non-square coding unit is not divided. That is, when the block shape information indicates that the current coding unit has a non-square shape, the first binary bit of the binary bit string for the division shape pattern information may be 0 when the non-square coding unit will not be divided, and the first binary bit of the binary bit string for the division shape pattern information may be 1 when the non-square coding unit will be divided into two or three coding units. Therefore, the probability that the first binary bit of the binary bit string for the division shape pattern information for the non-square coding unit will be 0 may be 1 / 3, and the probability that the first binary bit will be 1 may be 2 / 3. As described above, the division shape pattern information indicating that the non-square coding unit will not be divided may be represented only as a binary bit string of 1 bit having a value of 0, so that the image decoding device 100 can determine the syntax for the division shape pattern information by determining whether the second binary bit is 0 or 1 only when the first binary bit of the division shape pattern information is 1. According to an embodiment, when the first binary bit of the division shape pattern information is 1, the image decoding apparatus 100 may determine that the probability that the second binary bit will be 0 is equal to the probability that the second binary bit will be 1, and may decode the next binary bit.

[0236] Therefore, in the process of determining the binary string for the division shape pattern information, the image decoding device 100 may use various probabilities for each of the binary bits. According to an embodiment, the image decoding device 100 may determine that the probability of the binary string for the division shape pattern information is different according to the direction of the non-square block. According to an embodiment, the image decoding device 100 may determine that the probability of the binary string for the division shape pattern information is different according to the width of the current coding unit or the length of the longer side of the current coding unit. According to an embodiment, the image decoding device 100 may determine that the probability of the binary string for the division shape pattern information is different according to at least one of the shape of the current coding unit and the length of the longer side of the current coding unit.

[0237] According to an embodiment, the image decoding apparatus 100 may determine that the probability of the binary bits for the division shape pattern information is the same for coding units equal to or greater than a preset size. For example, the image decoding apparatus 100 may determine that the probability of the binary bits for the division shape pattern information is the same for coding units whose lengths of the longer sides are equal to or greater than 64 samples.

[0238] According to an embodiment, the image decoding apparatus 100 may determine initial probabilities of bins constituting a bin string of division shape pattern information based on a slice type (eg, I slice, P slice, or B slice).

[0239] Fig. 20 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0240] The encoder 2010 of the image encoding and decoding system 2000 may transmit an encoded bitstream of an image, and the decoder 2050 may output a reconstructed image by receiving and decoding the bitstream. In this regard, the encoder 2010 may be a configuration similar to the image encoding apparatus 200 to be described below, and the decoder 2050 may be a configuration similar to the image decoding apparatus 100.

[0241] In the encoder 2010, the prediction encoder 2015 may output prediction data through inter-frame prediction and intra-frame prediction, and the transformer and quantizer 2020 may output quantized transform coefficients of residual data between the prediction data and the current input image. The entropy encoder 2025 may encode the quantized transform coefficients, and may output the encoded quantized transform coefficients as a bitstream. The quantized transform coefficients may be reconstructed into spatial domain data through the inverse quantizer and inverse transformer 2030, and the reconstructed spatial domain data may be output as a reconstructed image through the deblocking filter 2035 and the loop filter 2040. The prediction encoder 2015 may use the reconstructed image as a reference image for the next input image.

[0242] The encoded image data of the bit stream received by the decoder 2050 may be reconstructed as spatial domain residual data through the entropy decoder 2055 and the inverse quantizer and inverse transformer 2060. The prediction data output from the prediction decoder 2075 may be combined with the residual data to reconstruct the spatial domain image data, and the deblocking filter 2065 and the loop filter 2070 may perform filtering on the spatial domain image data, and may output a reconstructed image for the current original image. The prediction decoder 2075 may use the reconstructed image as a reference image for the next original image.

[0243] The loop filter 2040 of the encoder 2010 may perform loop filtering by using filter information input according to user input or system setting. The filter information used by the loop filter 2040 may be output to the entropy encoder 2025 and may be sent to the decoder 2050 together with the encoded image data. The loop filter 2070 of the decoder 2050 may perform loop filtering based on the filter information input from the decoder 2050.

[0244] The above-mentioned various embodiments describe operations related to the image decoding method performed by the image decoder 100. Hereinafter, operations of the image encoding apparatus 200 that performs the image encoding method corresponding to the reverse order of the image decoding method will be described through various embodiments.

[0245] Figure 2 is a block diagram of an image encoding apparatus 200 capable of encoding an image based on at least one of block shape information and division shape pattern information according to an embodiment.

[0246] The image encoding apparatus 200 may include an encoder 220 and a bitstream generator 210. The encoder 220 may receive an input image and may encode the input image. The encoder 220 may obtain at least one syntax element by encoding the input image. 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 quantization coefficient, a coding block pattern, a coding block flag, an intra prediction mode, a direct flag, a merge flag, a differential QP, a reference index, a prediction direction, and a transform index. The encoder 220 may determine a context model based on block shape information including at least one of a shape, a direction, an aspect ratio, and a size of a coding unit.

[0247] The bitstream generator 210 may generate a bitstream based on the encoded input image. For example, the bitstream generator 210 may generate a bitstream by entropy encoding syntax elements based on a context model. In addition, the image encoding apparatus 200 may transmit the bitstream to the image decoding apparatus 100.

[0248] According to an embodiment, the encoder 220 of the image encoding apparatus 200 may determine the shape of the coding unit. For example, the coding unit may have a square shape or a non-square shape, and information indicating such a shape may be included in the block shape information.

[0249] According to an embodiment, the encoder 220 may determine a shape into which the coding unit is to be divided. The encoder 220 may determine the shape of at least one coding unit included in the coding unit, and the bitstream generator 210 may generate a bitstream including division shape pattern information including information about the shape of the coding unit.

[0250] According to an embodiment, the encoder 220 may determine whether the coding unit is to be divided or not divided. When the encoder 220 determines that the coding unit includes only one coding unit or the coding unit is not divided, the bitstream generator 210 may generate a bitstream including division shape pattern information indicating that the coding unit is not divided. In addition, the encoder 220 may divide the coding unit into a plurality of coding units included in the coding unit, and the bitstream generator 210 may generate a bitstream including division shape pattern information indicating that the coding unit is to be divided into a plurality of coding units.

[0251] According to an embodiment, information indicating the number of coding units into which the coding unit is divided or the direction in which the coding unit is divided may be included in the division shape pattern information. For example, the division shape pattern information may indicate that division is performed in at least one of the vertical direction and the horizontal direction or may indicate that division is not performed.

[0252] The image encoding apparatus 200 may determine the division shape pattern information based on the division shape pattern of the coding unit. The image encoding apparatus 200 may determine the context model based on at least one of the shape, direction, aspect ratio, or size of the coding unit. In addition, the image encoding apparatus 200 may generate information about the division shape pattern for dividing the coding unit as a bitstream based on the context model.

[0253] In order to determine the context model, the image encoding apparatus 200 may obtain an arrangement for matching at least one of the shape, direction, aspect ratio, or size of the coding unit with an index for the context model. The image encoding apparatus 200 may obtain an index for the context model from the arrangement based on at least one of the shape, direction, aspect ratio, or size of the coding unit. The image encoding apparatus 200 may determine the context model based on the index for the context model.

[0254] In order to determine the context model, the image encoding apparatus 200 may further determine the context model based on block shape information including at least one of a shape, a direction, an aspect ratio, or a size of a neighboring coding unit adjacent to the coding unit. In addition, the neighboring coding unit may include at least one of coding units located at the lower left, left, upper left, upper, upper right, right, and lower right of the coding unit.

[0255] In addition, in order to determine the context model, the image encoding apparatus 200 may compare the width length of the upper adjacent coding unit with the width length of the coding unit. In addition, the image encoding apparatus 200 may compare the height lengths of the left adjacent coding unit and the right adjacent coding unit with the height length of the coding unit. In addition, the image encoding apparatus 200 may determine the context model based on the comparison result.

[0256] The operation of the image encoding device 200 includes the same Figures 3 to 20 The contents of the image decoding device 100 described are similar to those described above, and therefore a detailed description thereof is not provided.

[0257] In the following, reference will now be made to Figures 21 to 30 An image encoding device 2900 and an image decoding device 2100 for encoding and decoding an image in a triangle prediction mode are described.

[0258] Fig.21 is a block diagram showing the configuration of an image decoding apparatus 2100 according to an embodiment.

[0259] Reference Fig.21 , the image decoding apparatus 2100 according to an embodiment may include an entropy decoder 2110 and a prediction decoder 2130 .

[0260] The entropy decoder 2110 and the prediction decoder 2130 may correspond to Figure 1 The decoder 120 shown in FIG. In addition, the entropy decoder 2110 and the prediction decoder 2130 may correspond to Fig. 20 The entropy decoder 2055 and the prediction decoder 2075 shown in FIG. Fig.21 , but the image decoding device 2100 according to an embodiment may further include a bitstream obtainer for obtaining a bitstream generated as a result of image encoding.

[0261] The entropy decoder 2110 and the prediction decoder 2130 according to an embodiment may be implemented as at least one processor. The image decoding apparatus 2100 may include one or more memories (not shown) for storing input and output data of the entropy decoder 2110 and the prediction decoder 2130. In addition, the image decoding apparatus 2100 may include a memory controller (not shown) for controlling data input and output of the memory (not shown).

[0262] The entropy decoder 2110 entropy-decodes the binary value included in the bitstream, thereby obtaining a value corresponding to the syntax element. The entropy decoder 2110 may decode the bitstream through CABAC.

[0263] The bitstream may include a plurality of pieces of information to be used in reconstruction of the current block. The current block may be a block generated by splitting from an image according to a tree structure, and may correspond to a block such as a maximum coding unit, a coding unit, or a transformation unit.

[0264] The prediction decoder 2130 may determine the current block based on block shape information and / or partition shape mode information included in a bitstream corresponding to at least one level of a sequence parameter set, a picture parameter set, a video parameter set, a slice header, and a slice segment header.

[0265] The bitstream may include information indicating a prediction mode of the current block. The prediction mode of the current block may include an intra mode, an inter mode, etc. The inter mode may be a mode for predicting and reconstructing the current block based on a reference image in order to reduce temporal redundancy between images. The inter mode may include a conventional merge mode, a merge mode using a differential motion vector, a triangle prediction mode, etc., which will be described below.

[0266] When the prediction mode of the current block is determined, the prediction decoder 2130 reconstructs the current block according to the determined prediction mode. The reconstructed block may be used as a reference block for a block to be decoded later.

[0267] In the image decoding method according to the embodiment, the current block may be reconstructed according to the triangle prediction mode. The triangle prediction mode refers to a mode in which the current block is divided into two triangle partitions, prediction blocks corresponding to the two divided triangle partitions are combined according to the division shape to generate a final prediction block, and the current block is reconstructed based on the final prediction block. For example, the prediction decoder 2130 may determine the final prediction block as the reconstructed block. As another example, a result obtained by combining the final prediction block and the residual data obtained from the bitstream may be determined as the reconstructed block.

[0268] As will be referred to below Fig. 27 As described, the reason for dividing the current block into two triangular partitions according to the triangular prediction mode is to determine a combination scheme of prediction blocks corresponding to the two triangular partitions. Therefore, dividing the current block into two triangular partitions can be understood as a process of determining a combination scheme of prediction blocks corresponding to the two triangular partitions.

[0269] When the triangle prediction mode is applied to the current block, the current block having a square shape must be divided into two triangle partitions, and due to this limitation, applying the triangle prediction mode to the current block may be disadvantageous in terms of bit rate. In other words, information related to the triangle prediction mode must be obtained from the bitstream in order to reconstruct the current block according to the final prediction block, however, even in the case where the final prediction block will not be applied, the information related to the triangle prediction mode is included in the bitstream, so that the number of unnecessary bits may increase.

[0270] Therefore, in an embodiment, the entropy decoder 2110 may determine whether to obtain information related to the triangle prediction mode from the bitstream based on a preset condition, and only when the preset condition is satisfied, the entropy decoder 2110 may entropy decode the information related to the triangle prediction mode from the bitstream. Conversely, when the preset condition is not satisfied, the entropy decoder 2110 may not perform entropy decoding on the information related to the triangle prediction mode. The image encoding device 2900 may also determine whether to apply the triangle prediction mode to the current block based on a preset condition, and therefore, when the preset condition is not satisfied, the image encoding device 2900 may not add the information related to the triangle prediction mode to the bitstream.

[0271] The information related to the triangle prediction mode obtained by the entropy decoder 2110 from the bitstream may include information indicating whether the triangle prediction mode is applied, partition shape information, and information indicating motion vectors for triangle partitions. In an embodiment, when a preset condition is met, the entropy decoder 2110 may determine that the triangle prediction mode is to be applied to the current block, and may obtain the partition shape information and the information indicating motion vectors for triangle partitions from the bitstream as the information related to the triangle prediction mode.

[0272] In a first embodiment, the entropy decoder 2110 may compare the size of the current block with a first threshold value, and when the comparison result satisfies a preset condition, the entropy decoder 2110 may obtain information related to the triangle prediction mode for the current block from the bitstream. For example, when the height of the current block is less than the first threshold value and the width of the current block is less than the first threshold value, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream. On the contrary, when the height or width of the current block is equal to or greater than the first threshold value, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream. In addition, for example, when the height or width of the current block is less than the first threshold value, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream. On the contrary, when both the height and width of the current block are equal to or greater than the first threshold value, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream.

[0273] The first embodiment is provided to limit the triangle prediction mode to be applied to a current block of a large size. Because the sizes of the two triangle partitions obtained from the current block of a large size are large, the sameness between the final prediction block and the current block may be reduced compared to the case where the current block is divided into four or three. Therefore, in the first embodiment, when the size of the current block is equal to or greater than the first threshold, it is determined that the triangle prediction mode will not be applied to the current block, and information related to the triangle prediction mode may not be parsed from the bitstream.

[0274] In a second embodiment, the entropy decoder 2110 may compare the size of the current block with the second threshold value, and when the comparison result satisfies a preset condition, the entropy decoder 2110 may obtain information related to the triangle prediction mode for the current block from the bitstream. For example, when the value obtained by multiplying the height of the current block by the width of the current block is equal to or greater than the second threshold value, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream. On the contrary, when the value obtained by multiplying the height of the current block by the width of the current block is less than the second threshold value, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream. In addition, for example, when both the height and width of the current block are equal to or greater than the second threshold value, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream. On the contrary, when the height or width of the current block is less than the second threshold value, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream.

[0275] The second threshold value may be less than the first threshold value described with reference to the first embodiment. For example, the first threshold value may be 128, and the second threshold value may be 64. In another embodiment, the second threshold value and the first threshold value may be the same. For example, both the first threshold value and the second threshold value may be 64.

[0276] A second embodiment is provided to limit the triangle prediction mode to be applied to a current block of a small size. When a current block of a very small size is divided into two triangle partitions, the complexity of the encoding and decoding processes is large compared to the encoding efficiency of the encoding and decoding processes. Therefore, in the second embodiment, when the size of the current block is less than the second threshold, it may be determined that the triangle prediction mode will not be applied to the current block, and information related to the triangle prediction mode may not be parsed from the bitstream.

[0277] In the third embodiment, when the prediction mode of the current block is not the inter-intra combination mode, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream. Conversely, when the prediction mode of the current block is the inter-intra combination mode, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream.

[0278] The inter-intra combination mode refers to a mode in which a prediction block in a reference image is combined with a prediction block obtained from pixels in a current image so that the current block is reconstructed, wherein the prediction block in the reference image is indicated by a motion vector of the current block. That is, the current block is reconstructed by combining a prediction block obtained according to the inter mode with a prediction block obtained according to the intra mode.

[0279] In a conventional case where the current block is encoded without being partitioned or the current block is partitioned and then encoded according to the inter mode, when the cost (e.g., rate-distortion cost) is high, the inter-intra combination mode may be applied as the prediction mode of the current block. That is, the fact that the inter-intra combination mode is applied to the current block may indicate that the encoding efficiency is not good even when the current block is partitioned, so that when the prediction mode of the current block is the inter-intra combination mode, the entropy decoder 2110 does not obtain information related to the triangular prediction mode that requires partitioning the current block from the bitstream.

[0280] In the fourth embodiment, when the prediction mode of the current block is the merge mode using the differential motion vector, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream. Conversely, when the prediction mode of the current block is not the merge mode using the differential motion vector, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream.

[0281] First, the merge mode is described. The merge mode refers to a mode in which a merge list including motion vectors of a previously encoded block or a previously decoded block is generated to determine the motion vector of the current block, and then one of the motion vectors included in the merge list is determined as the motion vector of the current block. The image encoding device 2900 may send only the index of the motion vector indicating the motion vector to be used as the motion vector of the current block among the motion vectors included in the merge list to the image decoding device 2100, and the image decoding device 2100 may reconstruct the motion vector of the current block according to the received index. That is, the encoding of the motion vector is achieved only by using the index, so that the efficiency can be improved in terms of bit rate. The image decoding device 2100 may obtain the motion vector of the current block according to the index received from the image encoding device 2900, and may determine the reconstructed block based on the prediction block indicated by the obtained motion vector.

[0282] The merge mode using the differential motion vector determines one of the motion vectors included in the merge list as the motion vector of the current block, as in the merge mode, but is different in that the differential motion vector between the actual motion vector of the current block and the motion vector selected from the merge list is signaled to the image decoding apparatus 2100. The differential motion vector may be represented as a change distance and a change direction. That is, the image encoding apparatus 2900 may transmit information indicating the change distance and the change direction corresponding to the differential motion vector and an index indicating one of the motion vectors included in the merge list to the image decoding apparatus 2100, and the image decoding apparatus 2100 may select the motion vector indicated by the index from the motion vectors included in the merge list, may change the selected motion vector according to the change distance and the change direction, and thus may determine the motion vector of the current block.

[0283] The fact that the merge mode using the differential motion vector is applied to the current block indicates that when the current block is encoded / decoded by using the motion vector included in the merge list without partitioning the current block, efficiency is good. Therefore, when the merge mode using the differential motion vector is applied to the current block, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream.

[0284] The entropy decoder 2110 may combine the conditions described above with reference to the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment in order to determine whether to obtain information related to the triangular prediction mode from a bitstream.

[0285] For example, when the comparison result between the size of the current block and the first threshold and the comparison result between the size of the current block and the second threshold meet the preset conditions, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream. For example, when the height and width of the current block are less than the first threshold, and the result obtained by multiplying the height of the current block by the width of the current block is equal to or greater than the second threshold, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream.

[0286] As another example, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream based on a comparison result between the size of the current block and the first threshold value and whether the prediction mode of the current block is an inter-intra combination mode. For example, when the height and width of the current block are less than the first threshold value and the prediction mode of the current block is not an inter-intra combination mode, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream.

[0287] As another example, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream based on a comparison result between the size of the current block and the first threshold and whether the prediction mode of the current block is a merge mode using a differential motion vector. For example, when the height or width of the current block is equal to or greater than the first threshold, or the prediction mode of the current block is a merge mode using a differential motion vector, the entropy decoder 2110 may not obtain information related to the triangle prediction mode from the bitstream.

[0288] As another example, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream based on a comparison result between the size of the current block and the first threshold, a comparison result between the size of the current block and the second threshold, and whether the prediction mode of the current block is an inter-intra combination mode. For example, when the height and width of the current block are less than the first threshold, a value obtained by multiplying the height of the current block by the width of the current block is equal to or greater than the second threshold, and the prediction mode of the current block is not an inter-intra combination mode, the entropy decoder 2110 may obtain information related to the triangle prediction mode from the bitstream.

[0289] Fig. 22 An example of a syntax structure for parsing information related to a triangle prediction mode according to an embodiment is shown.

[0290] At S2201, the entropy decoder 2110 determines whether the prediction mode of the current block is a normal merge mode. The normal merge mode refers to a mode in which a merge list including motion vectors of a previously encoded block or a previously decoded block is generated to determine a motion vector of the current block, and then one of the motion vectors included in the merge list is determined as the motion vector of the current block. In addition, the normal merge mode refers to a mode in which information related to the triangle prediction mode is not used and the current block is reconstructed from a prediction block indicated by one of the motion vectors included in the merge list.

[0291] When the prediction mode of the current mode is the normal merge mode, one of the motion vectors included in the merge list may be selected according to the index (merge_idx) of the motion vector indicating the current block, and a reconstructed block may be generated based on the prediction block indicated by the selected motion vector. The normal merge mode is different from the triangle prediction mode in that the current block is not divided into two triangle partitions. That is, in the normal merge mode, the current block is reconstructed from the prediction block without considering the shape of the triangle partition.

[0292] At S2202 , when the prediction mode of the current block is the normal merge mode, the entropy decoder 2110 obtains a flag (mmvd_merge_flag) indicating whether the prediction mode of the current block is the merge mode using the differential motion vector from the bitstream.

[0293] In S2203, when the prediction mode of the current block is a merge mode using a differential motion vector, the entropy decoder 2110 obtains information (mmvd_cand_flag) indicating one of the motion vectors included in the merge list from the bitstream, and obtains change distance information (mmvd_distance_idx) and change direction information (mmvd_direction_idx) as information indicating the differential motion vector from the bitstream. The prediction decoder 2130 reconstructs the current block according to the merge mode using the differential motion vector by using mmvd_cand_flag, mmvd_distance_idx, and mmvd_direction_idx.

[0294] At S2204, when the prediction mode of the current block is not a merge mode using a differential motion vector, that is, when the prediction mode of the current block is a normal merge mode, the entropy decoder 2110 obtains information (merge_idx) indicating one of the motion vectors included in the merge list from the bitstream. The prediction decoder 2130 reconstructs the current block by using merge_idx according to the normal merge mode.

[0295] At S2205, the entropy decoder 2110 determines whether the values ​​of multiple variables (sps_clip_enabled_flag, sps_triangle_enabled_flag, MaxNumTriangleMergeCand, silce_type, and cu_skip_flag) meet the preset conditions. In addition, the entropy decoder 2110 determines whether the comparison result between the size of the current block and the first threshold and the comparison result between the size of the current block and the second threshold meet the preset conditions. Specifically, according to condition A, when the value obtained by multiplying the width (cbWidth) of the current block by the height (cbHeight) of the current block is equal to or greater than 64, and the width (cbWidth) and height (cbHeight) of the current block are both less than 128, at S2206, the entropy decoder 2110 obtains a flag (ciip_flag) indicating whether the prediction mode of the current block is an inter-frame-intra-frame combination mode from the bitstream. When the prediction mode of the current block is the inter-intra combination mode, the prediction decoder 2130 reconstructs the current block by combining a prediction block obtained in a reference image with a prediction block obtained in a current image according to the inter-intra combination mode.

[0296] In S2207, when the prediction mode of the current block is not the inter-intra combination mode, the entropy decoder 2110 obtains the current block partition shape information (merge_triangle_split_dir) and the information indicating the motion vector included in the merge list for the triangle prediction mode to be used as the motion vector of the triangle partition (merge_triangle_idx0, merge_triangle_idxl) from the bitstream as information related to the triangle prediction mode.

[0297] The current block partition shape information may indicate whether the current block is partitioned from its upper left corner to its lower right corner or whether the current block is partitioned from its upper right corner to its lower left corner.

[0298] exist Fig. 22 In the embodiment, according to the condition that the information related to the triangle prediction mode (merge_triangle_split_dir, merge_triangle_idx0, merge_triangle_idx1) is not obtained from the bitstream, first, in S2202, when the prediction mode of the current block is the merge mode using the differential motion vector, the information related to the triangle prediction mode is not obtained from the bitstream. In addition, in S2205, when the value obtained by multiplying the width of the current block by the height of the current block is less than 64, the width of the current block is equal to or greater than 128, or the height of the current block is equal to or greater than 128, the information related to the triangle prediction mode is not obtained from the bitstream. In addition, in S2207, when the prediction mode of the current block is the inter-intra combination mode, the information related to the triangle prediction mode is not obtained from the bitstream.

[0299] In the following, reference will now be made to Figure 23 to Figure 27 A method in which the prediction decoder 2130 reconstructs the current block according to the triangle prediction mode when the prediction mode of the current block is the triangle prediction mode and the entropy decoder 2110 obtains information related to the triangle prediction mode from a bitstream is described.

[0300] Fig.23 is a diagram for describing a method for generating a merge list in a normal merge mode.

[0301] In an embodiment, when the prediction mode of the current block 2310 is the triangle prediction mode, the prediction decoder 2130 may generate a merge list for the normal merge mode according to the merge list generation method in the normal merge mode, and may determine the merge list for the triangle prediction mode by using the merge list for the normal merge mode.

[0302] In an embodiment, the prediction decoder 2130 may determine the merge list for the normal merge mode as the merge list for the triangle prediction mode without change.

[0303] In another embodiment, the prediction decoder 2130 may determine the merge list for the triangle prediction mode by modifying the merge list for the normal merge mode. In this regard, the fact that the merge list for the normal merge mode is modified may indicate that the order of motion vectors included in the merge list for the normal merge mode may be changed, some motion vectors may be excluded, or new motion vectors not present in the merge list may be added.

[0304] First, a method of generating a merge list for a normal merge mode will now be described.

[0305] The prediction decoder 2130 may generate a merge list including motion vectors of blocks that can be used among a spatial block spatially related to the current block 2310 and a temporal block temporally related to the current block 2310. The spatial block and the temporal block may include a block decoded before the current block 2310.

[0306] Reference Fig.23 , the temporal block may include at least one of a block (Col) co-located with the current block 2310 and a block (Br) spatially adjacent to the co-located block (Col) in a reference image having a picture order count (POC) different from that of the current block 2310. The block (Br) may be located at the lower right side of the block (Col) co-located with the current block 2310. The block (Col) co-located with the current block 2310 may be a block including a pixel corresponding to a center pixel in the current block 2310 and from among pixels included in the reference image.

[0307] The spatial blocks spatially related to the current block 2310 may include at least one of a lower left corner block A0, a lower left corner block A1, an upper right corner block B0, an upper right corner block B1, and an upper left corner block B2.

[0308] Fig.23 The positions of the time blocks and spatial blocks shown in are merely examples, and in another embodiment, the positions and numbers of the time blocks and spatial blocks may vary.

[0309] The prediction decoder 2130 may determine that a block is available, which is inter-predicted from the temporal block and the spatial block. The prediction decoder 2130 may add the motion vectors of the available blocks to the merge list according to a predetermined order. When the motion vector of a specific available block is equal to the motion vector previously included in the merge list, the motion vector of the specific available block may not be included in the merge list.

[0310] When the number of motion vectors included in the merge list is less than a preset number, the prediction decoder 2130 may generate a new motion vector by combining the motion vectors included in the merge list, and may add the generated motion vector to the merge list. When the number of motion vectors included in the merge list is less than a preset number, the prediction decoder 2130 may add a zero vector to the merge list until the number of motion vectors included in the merge list reaches the preset number.

[0311] When the generation of the merge list for the normal merge mode is completed, the prediction decoder 2130 may determine the merge list for the normal merge mode as a merge list for the triangle prediction mode, and may select a motion vector to be used as a motion vector for the triangle partition from the motion vectors included in the merge list based on information related to the triangle prediction mode.

[0312] In an embodiment, when the generation of the merge list for the normal merge mode is completed, the prediction decoder 2130 can determine the merge list for the triangle prediction mode by modifying the merge list for the normal merge mode, and can select a motion vector to be used as a motion vector for the triangle partition from the motion vectors included in the merge list based on information related to the triangle prediction mode.

[0313] Now refer to Fig.24 and Fig.25 A method of determining a merge list for a triangle prediction mode by modifying a merge list for a normal merge mode is described.

[0314] Fig.24 and Fig.25 An example for describing a method of generating a merge list for a triangle prediction mode from a merge list for a normal merge mode is shown.

[0315] First, in Fig.24 , the merge list shown on the left is for the normal merge mode, where B1, B0, A0 and B2 represent the motion vectors of the available spatial blocks, and Co1 represents the motion vectors of the available temporal blocks.

[0316] The prediction decoder 2130 adds a unidirectional motion vector among the motion vectors included in the merge list to the merge list for the triangle prediction mode. The unidirectional motion vector refers to a motion vector indicating a block in the reference image included in list 0 or indicating a block in the reference image included in list 1. Conversely, the bidirectional motion vector refers to a motion vector indicating a block in the reference image included in list 0 and a block in the reference image included in list 1.

[0317] When B1, A0, B2 and Co1 among B1, B0, A0, B2 and Co1 are unidirectional motion vectors, such as Fig.24 As shown on the right side of , the prediction decoder 2130 adds B1, A0, B2, and Co1 to the merge list for the triangle prediction mode. When the number of motion vectors included in the merge list for the triangle prediction mode is less than a preset number (e.g., 5), the prediction decoder 2130 generates a new bidirectional motion vector by combining the motion vectors already included in the merge list according to a predetermined criterion, and adds the generated motion vector to the merge list. Fig.24 Obviously, B1+A0 generated by combining B1 and A0 is added to the merge list as the final candidate.

[0318] Next, refer to Fig.25 , the prediction decoder 2130 may generate a merge list for the triangle prediction mode by considering only a predetermined number of motion vectors from among the motion vectors included in the merge list for the normal merge mode. For example, in order to generate a merge list for the triangle prediction mode, the prediction decoder 2130 may use only four of the five motion vectors included in the merge list for the normal merge mode, in the order in which the four motion vectors are included in the merge list. Therefore, the prediction decoder 2130 adds a unidirectional motion vector to the merge list for the triangle prediction mode, wherein the unidirectional motion vector is from among B1, B0, A0, and B2, which are the four motion vectors included in the merge list for the normal merge mode. When B1, A0, and B2 among B1, B0, A0, and B2 are unidirectional motion vectors, as Fig.25 As shown on the right side of , the prediction decoder 2130 adds B1, A0, and B2 to the merge list for the triangle prediction mode. Then, when the number of motion vectors included in the merge list for the triangle prediction mode is less than a preset number (e.g., 5), the prediction decoder 2130 generates a new bidirectional motion vector by combining the motion vectors already included in the merge list according to a predetermined criterion, and adds the generated motion vector to the merge list. Fig.25 Obviously, B1+A0 generated by combining B1 and A0 and B1+B2 generated by combining B1 and B2 are added to the merge list for the triangle prediction mode after B2.

[0319] Reference Fig.24 and Fig.25 , in the case where a new motion vector (B1+A0, B1+B2, etc.) generated as a result of the combination of unidirectional motion vectors is added to the merge list for the triangle prediction mode, the prediction decoder 2130 may add the new motion vector to the merge list for the triangle prediction mode only when the new motion vector is not equal to the motion vector previously added to the merge list.

[0320] In this regard, in an embodiment, the prediction decoder 2130 may add a new motion vector to the merge list for the triangle prediction mode only when the new motion vector is not equal to all motion vectors previously added to the merge list.

[0321] However, determining whether the new motion vector is not equal to all motion vectors previously added to the merge list increases the encoding / decoding complexity, and therefore, in another embodiment, when the new motion vector is not equal to the motion vector most recently added to the merge list, the prediction decoder 2130 may add the new motion vector to the merge list for the triangle prediction mode.

[0322] When the generation of the merge list for the triangle prediction mode is completed, the prediction decoder 2130 determines the motion vector of the triangle partition based on the information related to the triangle prediction mode. In detail, the prediction decoder 2130 may obtain information (e.g., an index) indicating a motion vector to be used as a motion vector of the triangle partition among the motion vectors included in the merge list, and may determine the motion vector indicated by the information as the motion vector of the triangle partition. For example, according to the reference Fig.25 , when the index indicating the motion vector of the triangle partition indicates 0 and 1, the prediction decoder 2130 may determine B1 as the motion vector of one triangle partition, and may determine A0 as the motion vector of another triangle partition.

[0323] When the motion vector of the triangle partition is determined, the prediction decoder 2130 determines a prediction block indicated by the motion vector in the reference image.

[0324] Fig.26 2 is a diagram for describing a method of determining prediction blocks 2612 and 2614 corresponding to two triangular partitions 2312 and 2314 divided from a current block 2310. Fig.26 As shown in , the prediction decoder 2130 can obtain a first prediction block 2612 indicated by a motion vector mv1 of a first triangle partition 2312 and a second prediction block 2614 indicated by a motion vector mv2 of a second triangle partition 2314 .

[0325] Fig.26 It is shown that the first prediction block 2612 and the second prediction block 2614 are included in one reference image, but this is merely an example, and thus, the first prediction block 2612 and the second prediction block 2614 may be located in different reference images, respectively.

[0326] When the prediction blocks 2612 and 2614 corresponding to the triangle partitions 2312 and 2314 are obtained, the prediction decoder 2130 generates a final prediction block by combining the prediction blocks 2612 and 2614. Fig. 27 Describe this.

[0327] Fig. 27 27 is a diagram for describing a method of generating a final prediction block 2710 by combining prediction blocks 2612 and 2614 corresponding to two triangle partitions 2312 and 2314 .

[0328] The prediction decoder 2130 may generate a final prediction block 2710 by weighted summing the first sample value P1 included in the first prediction block 2612 and the second sample value P2 included in the second prediction block 2614 , wherein the first prediction block 2612 and the second prediction block 2614 correspond to the first triangle partition 2312 and the second triangle partition 2314 .

[0329] Reference Fig. 27 , when the current block 2310 is divided into two triangular partitions along its upper left corner and its lower right corner, the first sample value P1 and the second sample value P2 located on the boundary 2315 are summed by applying weights (4 / 8, 4 / 8) to the first sample value P1 and the second sample value P2 located on the boundary 2315, which are among the first sample value P1 included in the first prediction block 2612 and the second sample value P2 included in the second prediction block 2614. Then, a higher weight may be applied to the first sample value P1 in the direction from the boundary 2315 toward the upper right corner, and a higher weight may be applied to the second sample value P2 in the direction from the boundary 2315 toward the lower left corner. The first sample value P1 is assigned to the sample adjacent to the upper right corner among the samples of the final prediction block 2710, and the second sample value P2 is assigned to the sample adjacent to the lower left corner among the samples of the final prediction block 2710.

[0330] Reference Fig.26 and Fig. 27 , describes the case where the current block 2310 is divided into two triangular partitions relative to the upper left corner and the lower right corner. However, even when the current block 2310 is divided into two triangular partitions relative to its upper right corner and its lower left corner, the final prediction block can be generated in the same manner.

[0331] Fig.28 is a flowchart of an image decoding method according to an embodiment.

[0332] In operation S2810, the image decoding apparatus 2100 obtains information related to a triangle prediction mode with respect to a current block split from a current image from a bitstream.

[0333] When the comparison result between the size of the current block and the first threshold satisfies a preset condition, the image decoding device 2100 may obtain information related to the triangle prediction mode for the current block from the bitstream. In detail, when the width of the current block is less than the first threshold and the height of the current block is less than the first threshold, the image decoding device 2100 may obtain information related to the triangle prediction mode from the bitstream. Conversely, when the width of the current block is equal to or greater than the first threshold or the height of the current block is equal to or greater than the first threshold, the image decoding device 2100 may obtain information related to the triangle prediction mode from the bitstream.

[0334] In an embodiment, the image decoding device 2100 may compare the size of the current block with the second threshold value, and when the comparison result satisfies a preset condition, the image decoding device 2100 may obtain information related to the triangle prediction mode for the current block from the bitstream. In detail, when the value obtained by multiplying the width of the current block by the height of the current block is equal to or greater than the second threshold value, the image decoding device 2100 may obtain information related to the triangle prediction mode from the bitstream. Conversely, when the value obtained by multiplying the width of the current block by the height of the current block is less than the second threshold value, the image decoding device 2100 may not obtain information related to the triangle prediction mode from the bitstream.

[0335] When the prediction mode of the current block is not an inter-intra combination mode, the image decoding device 2100 may obtain information related to the triangle prediction mode for the current block from the bitstream. Conversely, when the prediction mode of the current block is an inter-intra combination mode, the image decoding device 2100 may not obtain information related to the triangle prediction mode for the current block from the bitstream.

[0336] In addition, when the prediction mode of the current block is the merge mode using the differential motion vector, the image decoding apparatus 2100 may not obtain information related to the triangle prediction mode for the current block from the bitstream. Conversely, when the prediction mode of the current block is not the merge mode using the differential motion vector, the image decoding apparatus 2100 may obtain information related to the triangle prediction mode for the current block from the bitstream.

[0337] The information related to the triangle prediction mode may include at least one of information indicating whether the triangle prediction mode is to be applied to the current block, current block partition shape information, and information indicating a motion vector of the triangle partition. The current block partition shape information may indicate whether the current block is partitioned along a boundary connecting the upper left corner and the lower right corner of the current block or whether the current block is partitioned along a boundary connecting the upper right corner and the lower left corner of the current block.

[0338] In operation S2820, the image decoding apparatus 2100 generates a merge list for a triangle prediction mode according to a merge list generation method in a normal merge mode in which a current block is reconstructed without being divided into triangle partitions.

[0339] In an embodiment, the image decoding apparatus 2100 may determine the merge list for the normal merge mode as the merge list for the triangle prediction mode without change.

[0340] In another embodiment, the image decoding apparatus 2100 may determine the merge list for the triangle prediction mode by modifying the merge list for the normal merge mode. In this regard, the fact that the merge list for the normal merge mode is modified may indicate that the order of motion vectors included in the merge list for the normal merge mode may be changed, some motion vectors may be excluded, or new motion vectors not existing in the merge list may be added.

[0341] The merge list generation method in the normal merge mode may indicate a method of generating a merge list including motion vectors of blocks that can be used among a spatial block spatially related to a current block and a temporal block temporally related to the current block.

[0342] In operation S2830, the image decoding device 2100 divides the current block into two triangular partitions according to the information related to the triangular prediction mode. The image decoding device 2100 may divide the current block from the upper left corner of the current block toward the lower right corner of the current block, or may divide the current block from the upper right corner of the current block toward the lower left corner of the current block. The reason for dividing the current block into two triangular partitions according to the triangular prediction mode is to determine a combination scheme of prediction blocks corresponding to the two triangular partitions. Therefore, dividing the current block into two triangular partitions can be understood as an operation of determining a combination scheme of prediction blocks corresponding to the two triangular partitions.

[0343] In operation S2840, the image decoding apparatus 2100 selects motion vectors for two triangle partitions according to information indicating a motion vector among motion vectors included in a merge list for a triangle prediction mode, the information being included in information related to the triangle prediction mode.

[0344] In operation S2850, the image decoding apparatus 2100 obtains a prediction block indicated by a motion vector for two triangle partitions from a reference image.

[0345] In operation S2860, the image decoding apparatus 2100 combines the prediction blocks corresponding to the two triangle partitions. Then, the image decoding apparatus 2100 reconstructs the current block based on the final prediction block generated as a result of the combination of the prediction blocks.

[0346] In an embodiment, the image decoding apparatus 2100 may determine the final prediction block as the reconstructed block. In another embodiment, the image decoding apparatus 2100 may combine the final prediction block with a residual block obtained based on information included in a bitstream, and may determine the combined block as the reconstructed block.

[0347] Fig.29 is a block diagram of a configuration of an image encoding device 2900 according to an embodiment.

[0348] Reference Fig.29 , the image encoding apparatus 2900 may include a prediction encoder 2910 and an entropy encoder 2930. The prediction encoder 2910 and the entropy encoder 2930 may correspond to Figure 2 The encoder 220 and the bitstream generator 210 shown in FIG. In addition, the prediction encoder 2910 and the entropy encoder 2930 may correspond to Fig. 20 The prediction encoder 2015 and entropy encoder 2025 shown in .

[0349] The prediction encoder 2910 and the entropy encoder 2930 according to an embodiment may be implemented as at least one processor. The image encoding apparatus 2900 may include one or more memories (not shown) for storing input and output data of the prediction encoder 2910 and the entropy encoder 2930. In addition, the image encoding apparatus 2900 may include a memory controller (not shown) for controlling data input and output of the memory (not shown).

[0350] The prediction encoder 2910 determines a prediction mode of the current block. The prediction encoder 2910 may determine the prediction mode of the current block to be a normal merge mode, a merge mode using a differential motion vector, an inter-intra combination mode, a triangle prediction mode, or an intra mode.

[0351] The prediction encoder 2910 may encode the current block according to the triangle prediction mode. Specifically, when the prediction mode of the current block is determined to be the triangle prediction mode, the prediction encoder 2910 generates a merge list for the triangle prediction mode. Figure 23 to Figure 25 The method described is the same, and therefore a detailed description thereof is not provided here. The prediction encoder 2910 divides the current block into two triangle partitions, and selects a motion vector to be used as a motion vector of the two triangle partitions from the motion vectors included in the merge list. The prediction encoder 2910 sends information related to the triangle prediction mode (specifically, information indicating the motion vectors of the two triangle partitions and information indicating the division shape of the current block) to the image decoding device 2100 by a signal.

[0352] In certain cases, encoding the current block in the triangle prediction mode may be poor in encoding efficiency, and in this case, when information related to the triangle prediction mode is included in a bitstream, the number of unnecessary bits may increase.

[0353] Therefore, in an embodiment, before generating information related to the triangle prediction mode, it can be first determined based on preset conditions whether it is appropriate to encode the current block in the triangle prediction mode, and then, it can be adaptively determined whether to generate information related to the triangle prediction mode according to the determination result.

[0354] In the first embodiment, the prediction encoder 2910 may compare the size of the current block with the first threshold value, and when the comparison result satisfies the preset condition, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. For example, when the height of the current block is less than the first threshold value and the width of the current block is less than the first threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. On the contrary, when the height or width of the current block is equal to or greater than the first threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as a mode other than the triangle prediction mode. In addition, for example, when the height or width of the current block is less than the first threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. On the contrary, when both the height and width of the current block are equal to or greater than the first threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as a mode other than the triangle prediction mode.

[0355] The first embodiment is provided to limit the triangle prediction mode to be applied to a current block of a large size. Since the sizes of the two triangle partitions obtained from the current block of a large size are large, the sameness between the final prediction block and the current block may be reduced compared to the case where the current block is divided into four or three. Therefore, in the first embodiment, when the size of the current block is equal to or greater than the first threshold, it is determined that the triangle prediction mode will not be applied to the current block, and information related to the triangle prediction mode may not be generated.

[0356] In the second embodiment, the prediction encoder 2910 may compare the size of the current block with the second threshold value, and when the comparison result satisfies the preset condition, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. For example, when the value obtained by multiplying the height of the current block by the width of the current block is equal to or greater than the second threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. On the contrary, when the value obtained by multiplying the height of the current block by the width of the current block is less than the second threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as a mode other than the triangle prediction mode. In addition, for example, when both the height and the width of the current block are equal to or greater than the second threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. On the contrary, when the height or the width of the current block is less than the second threshold value, the prediction encoder 2910 may determine the prediction mode of the current block as a mode other than the triangle prediction mode.

[0357] The second threshold value may be less than the first threshold value described with reference to the first embodiment. For example, the first threshold value may be 128, and the second threshold value may be 64. In another embodiment, the second threshold value and the first threshold value may be the same. For example, both the first threshold value and the second threshold value may be 64.

[0358] The second embodiment is provided to limit the triangle prediction mode to be applied to the current block of a small size. When the current block of a very small size is divided into two triangle partitions, the complexity of the encoding and decoding processes is large compared to the encoding efficiency of the encoding and decoding processes. Therefore, in the second embodiment, when the size of the current block is less than the second threshold, it may be determined that the triangle prediction mode will not be applied to the current block, and information related to the triangle prediction mode may not be generated.

[0359] In the third embodiment, when the prediction mode of the current block is not the inter-intra combination mode, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. Conversely, when the prediction mode of the current block is the inter-intra combination mode, the prediction encoder 2910 may not determine whether to encode the current block in the triangle prediction mode.

[0360] In a conventional case where the current block is encoded without being partitioned or the current block is partitioned and then encoded according to the inter mode, when the cost (e.g., rate-distortion cost) is high, the inter-intra combination mode may be applied as the prediction mode of the current block. That is, the fact that the inter-intra combination mode is applied to the current block may indicate that the encoding efficiency is not good even when the current block is partitioned, so that only when the prediction mode of the current block is not the inter-intra combination mode, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode, and may generate information related to the triangle prediction mode.

[0361] In the fourth embodiment, when the prediction mode of the current block is the merge mode using the differential motion vector, the prediction encoder 2910 may not determine whether to encode the current block according to the triangle prediction mode. Conversely, when the prediction mode of the current block is not the merge mode using the differential motion vector, the prediction encoder 2910 may determine the prediction mode of the current block to be the triangle prediction mode.

[0362] The fact that the merge mode using the differential motion vector is applied to the current block indicates that when the current block is encoded / decoded by using the motion vector included in the merge list without partitioning the current block, efficiency is good. Therefore, when the merge mode using the differential motion vector is applied to the current block, the prediction encoder 2910 may not determine whether to encode the current block in the triangle prediction mode.

[0363] The prediction encoder 2910 may combine the conditions described above with reference to the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment in order to determine whether to encode the current block in the triangular prediction mode.

[0364] For example, when the comparison result between the size of the current block and the first threshold and the comparison result between the size of the current block and the second threshold meet the preset condition, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode. For example, when the height and width of the current block are less than the first threshold, and the result obtained by multiplying the height of the current block by the width of the current block is equal to or greater than the second threshold, the prediction encoder 2910 may determine the prediction mode of the current block as the triangle prediction mode.

[0365] As another example, the prediction encoder 2910 may determine whether to encode the current block in the triangle prediction mode according to the comparison result between the size of the current block and the first threshold value and whether the prediction mode of the current block is the inter-intra combination mode. For example, when the height and width of the current block are less than the first threshold value and the prediction mode of the current block is not the inter-intra combination mode, the prediction encoder 2910 may determine the prediction mode of the current block to be the triangle prediction mode.

[0366] As another example, the prediction encoder 2910 may determine whether to encode the current block in the triangle prediction mode according to a comparison result between the size of the current block and the first threshold value and whether the prediction mode of the current block is a merge mode using a differential motion vector. For example, when the height or width of the current block is equal to or greater than the first threshold value, or the prediction mode of the current block is a merge mode using a differential motion vector, the prediction encoder 2910 may not determine whether to encode the current block in the triangle prediction mode.

[0367] As another example, the prediction encoder 2910 may determine whether to encode the current block in the triangle prediction mode based on a comparison result between the size of the current block and the first threshold, a comparison result between the size of the current block and the second threshold, and whether the prediction mode of the current block is the inter-intra combination mode. For example, when the height and width of the current block are less than the first threshold, a value obtained by multiplying the height of the current block by the width of the current block is equal to or greater than the second threshold, and the prediction mode of the current block is not the inter-intra combination mode, the prediction encoder 2910 may determine the prediction mode of the current block to be the triangle prediction mode.

[0368] In an embodiment, the predictive encoder 2910 may be based on Fig. 22 The syntax elements (mmvd_merge_flag, mmvd_cand_flag, mmvd_distance_idx, mmvd_direction_idx, merge_idx, ciip_flag, merge_triangle_split_dir, merge_triangle_idx0, and merge_triangle_idx1) are generated using the syntax structure shown in . The syntax elements may be entropy encoded by the entropy encoder 2930 and may then be included in the bitstream.

[0369] The entropy encoder 2930 may generate a bitstream by entropy encoding a value corresponding to a syntax element. The entropy encoder 2930 may encode a value corresponding to a syntax element according to CABAC.

[0370] The bitstream may include a plurality of pieces of information to be used in reconstruction of the current block. The current block may be a block generated by splitting from an image according to a tree structure, and may correspond to a block such as a maximum coding unit, a coding unit, or a transformation unit.

[0371] A bitstream corresponding to at least one level of a sequence parameter set, a picture parameter set, a video parameter set, a slice header, and a slice segment header may include block shape information and / or division shape pattern information, and the image decoding device 2100 may determine the current block in the current image based on the block shape information and / or division shape pattern information.

[0372] The bitstream may include information indicating a prediction mode of the current block. The prediction mode of the current block may include a normal merge mode, a merge mode using a differential motion vector, an inter-intra combination mode, a triangle prediction mode, or an intra mode.

[0373] In addition, when the prediction mode of the current block is determined to be the triangle prediction mode, the bitstream may include information related to the triangle prediction mode. The information related to the triangle prediction mode may include at least one of information indicating whether the prediction mode of the current block is the triangle prediction mode, partition shape information for partitioning the current block into two triangle partitions, and information indicating motion vectors of the two triangle partitions.

[0374] Fig.30 is a flowchart of an image encoding method according to an embodiment.

[0375] In S3010, the image encoding apparatus 2900 determines a prediction mode of a current block as a triangle prediction mode, the current block being split from a current image.

[0376] When the comparison result between the size of the current block and the first threshold satisfies a preset condition, the image encoding apparatus 2900 may determine the prediction mode of the current block as the triangle prediction mode. In detail, when the width of the current block is less than the first threshold and the height of the current block is less than the first threshold, the image encoding apparatus 2900 may determine the prediction mode of the current block as the triangle prediction mode. Conversely, when the width of the current block is equal to or greater than the first threshold or the height of the current block is equal to or greater than the first threshold, the image encoding apparatus 2900 may determine the prediction mode of the current block as a mode other than the triangle prediction mode.

[0377] In an embodiment, the image encoding apparatus 2900 may compare the size of the current block with the second threshold value, and when the comparison result satisfies a preset condition, the image encoding apparatus 2900 may determine the prediction mode of the current block as the triangle prediction mode. In detail, when the value obtained by multiplying the width of the current block by the height of the current block is equal to or greater than the second threshold value, the image encoding apparatus 2900 may determine the prediction mode of the current block as the triangle prediction mode. Conversely, when the value obtained by multiplying the width of the current block by the height of the current block is less than the second threshold value, the image encoding apparatus 2900 may determine the prediction mode of the current block as a mode other than the triangle prediction mode.

[0378] When the prediction mode of the current block is not an inter-intra combination mode, the image encoding device 2900 may determine the prediction mode of the current block as a triangle prediction mode. Conversely, when the prediction mode of the current block is an inter-intra combination mode, the image encoding device 2900 may not determine whether to encode the current block in the triangle prediction mode.

[0379] In addition, when the prediction mode of the current block is a merge mode using a differential motion vector, the image encoding apparatus 2900 may not determine whether to encode the current block in a triangle prediction mode. Conversely, when the prediction mode of the current block is not a merge mode using a differential motion vector, the image encoding apparatus 2900 may determine the prediction mode of the current block to be a triangle prediction mode.

[0380] At S3020 , the image encoding apparatus 2900 generates a merge list for a triangle prediction mode according to a merge list generation method in a normal merge mode in which a current block is encoded without being divided into triangle partitions.

[0381] In an embodiment, the image encoding apparatus 2900 may determine the merge list for the normal merge mode as the merge list for the triangle prediction mode without change.

[0382] In another embodiment, the image encoding apparatus 2900 may determine the merge list for the triangle prediction mode by modifying the merge list for the normal merge mode. In this regard, the fact that the merge list for the normal merge mode is modified may indicate that the order of motion vectors included in the merge list for the normal merge mode may be changed, some motion vectors may be excluded, or new motion vectors not existing in the merge list may be added.

[0383] The merge list generation method in the normal merge mode may indicate a method of generating a merge list including motion vectors of blocks that can be used among a spatial block spatially related to a current block and a temporal block temporally related to the current block.

[0384] At S3030, the image encoding apparatus 2900 divides the current block into two triangular partitions. The image encoding apparatus 2900 may divide the current block from the upper left corner toward the lower right corner of the current block, or may divide the current block from the upper right corner toward the lower left corner of the current block.

[0385] In operation S3040, the image encoding apparatus 2900 selects a motion vector to be used as a motion vector for two triangle partitions from the motion vectors included in the merge list for the triangle prediction mode. The image encoding apparatus 2900 may select a motion vector that generates a minimum cost (e.g., rate-distortion cost) for the two triangle partitions from the motion vectors included in the merge list.

[0386] In operation S3050, the image encoding apparatus 2900 generates a bitstream including information related to a triangle prediction mode.

[0387] The information related to the triangle prediction mode may include at least one of information indicating whether the triangle prediction mode is to be applied to the current block, current block partition shape information, and information indicating a motion vector of a triangle partition. The current block partition shape information may indicate whether the current block is partitioned along a boundary connecting the upper left corner and the lower right corner of the current block or whether the current block is partitioned along a boundary connecting the upper right corner and the lower left corner of the current block.

[0388] In addition, the embodiments of the present disclosure may be written as a program executable on a computer, and the program may be stored in a medium.

[0389] The medium can store computer executable programs continuously, or can temporarily store computer executable programs for execution or downloading. In addition, the medium can be any of various recording media or storage media combined with single or multiple pieces of hardware, and the medium is not limited to those directly connected to a specific computer system, but can be distributed over a network. Examples of media include magnetic media (such as hard disks, floppy disks, and tapes) configured to store program instructions, optical recording media (such as compact disk read-only memories (CD-ROMs) and digital versatile disks (DVDs)), magneto-optical media (such as floppy disks, read-only memories (ROMs), random access memories (RAMs), flash memories, etc.). In addition, other examples of media include recording media and storage media managed by application stores that distribute applications or by websites, servers, etc. that provide or distribute various other types of software.

[0390] Although one or more embodiments of the present disclosure are described in detail above with reference to exemplary embodiments, persons skilled in the art will understand that the present disclosure is not limited to the embodiments and that various changes in form and details may be made in the present disclosure without departing from the spirit and scope of the present disclosure.

Claims

1. An image decoding method performed by an image decoding device, the image decoding method comprising: obtaining information indicating whether an inter-intra combination mode is applied to a current block; When the information indicates that the inter-intra combination mode is not applied to the current block, obtaining partition shape information for the current block, first motion vector related information for the first partition, and second motion vector related information for the second partition from a bitstream; generating a merge list including motion vectors of a plurality of candidate blocks using neighboring blocks adjacent to the current block; obtaining a first prediction sample using a motion vector of a first candidate block indicated by first motion vector related information among the motion vectors of the plurality of candidate blocks included in the merge list; obtaining a second prediction sample using a motion vector of a second candidate block indicated by second motion vector related information among the motion vectors of the plurality of candidate blocks included in the merge list; Determine weight values ​​for the first prediction sample point and the second prediction sample point using the partition shape information; obtaining a third prediction sample point by combining the first prediction sample point with the second prediction sample point using the weight value; and By using the third prediction sample to reconstruct the current block, The adjacent blocks include adjacent blocks located on the left side of the current block.

2. An image decoding device, comprising: an entropy decoder configured to obtain information indicating whether the inter-intra combination mode is applied to the current block, and when the information indicates that the inter-intra combination mode is not applied to the current block, obtain partition shape information for the current block, first motion vector related information for the first partition, and second motion vector related information for the second partition from a bitstream; as well as a prediction decoder configured to generate a merge list including motion vectors of a plurality of candidate blocks using neighboring blocks adjacent to a current block, obtain a first prediction sample using a motion vector of a first candidate block indicated by first motion vector related information among the motion vectors of the plurality of candidate blocks included in the merge list, obtain a second prediction sample using a motion vector of a second candidate block indicated by second motion vector related information among the motion vectors of the plurality of candidate blocks included in the merge list, determine a weight value for the first prediction sample and the second prediction sample using the partition shape information, obtain a third prediction sample by combining the first prediction sample with the second prediction sample using the weight value, and reconstruct the current block using the third prediction sample, The adjacent blocks include adjacent blocks located on the left side of the current block.

3. An image encoding method performed by an image encoding device, the image encoding method comprising: determining whether an inter-intra combination mode is applied to a current block; When it is determined that the inter-intra combination mode is not applied to the current block, determining a partition shape for the current block, generating a merge list including motion vectors of a plurality of candidate blocks using neighboring blocks adjacent to the current block, and selecting a motion vector for a first candidate block for a first partition and a motion vector for a second candidate block for a second partition from among the motion vectors of the plurality of candidate blocks included in the merge list; as well as generating a bitstream, the bitstream including information indicating whether the inter-intra combination mode is applied to the current block, first motion vector related information indicating a motion vector of a first candidate block, second motion vector related information indicating a motion vector of a second candidate block, and partition shape information for the current block, The current block corresponds to a third prediction sample point obtained by combining the first prediction sample point with the second prediction sample point, The first prediction sample is determined based on the motion vector of the first candidate block, and the second prediction sample is determined based on the motion vector of the second candidate block. wherein the first prediction sample point and the second prediction sample point are combined based on a weight value determined using the partition shape information, The adjacent blocks include adjacent blocks located on the left side of the current block.

4. A non-transitory computer-readable storage medium recording a bit stream generated by a video encoding method, the video encoding method comprising: determining whether an inter-intra combination mode is applied to a current block; When it is determined that the inter-intra combination mode is not applied to the current block, determining a partition shape for the current block, generating a merge list including motion vectors of a plurality of candidate blocks using neighboring blocks adjacent to the current block, and selecting a motion vector for a first candidate block for a first partition and a motion vector for a second candidate block for a second partition from among the motion vectors of the plurality of candidate blocks included in the merge list; as well as generating a bitstream, the bitstream including information indicating whether the inter-intra combination mode is applied to the current block, first motion vector related information indicating a motion vector of a first candidate block, second motion vector related information indicating a motion vector of a second candidate block, and partition shape information for the current block, The current block corresponds to a third prediction sample point obtained by combining the first prediction sample point with the second prediction sample point, The first prediction sample is determined based on the motion vector of the first candidate block, and the second prediction sample is determined based on the motion vector of the second candidate block. wherein the first prediction sample point and the second prediction sample point are combined based on a weight value determined using the partition shape information, The adjacent blocks include adjacent blocks located on the left side of the current block.

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