Apparatus and method for encoding and decoding image by using template matching

Abstract

A method for decoding an image, according to an embodiment, may comprise the steps of: determining a transformed template of the current block by performing transformation on a template of the current block, and determining transformed templates of a plurality of candidate blocks by performing transformation on templates of the plurality of candidate blocks within a search area; comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks; on the basis of the result of the comparison, determining a reference block of the current block from among the plurality of candidate blocks; generating a prediction block of the current block by using the reference block; and reconstructing the current block by using the prediction block of the current block.

Description

Device and method for encoding and decoding images using template matching

[0001] The present disclosure relates to the field of video encoding and decoding, and more particularly, to a device and method for encoding and decoding a video by performing intra prediction using template matching.

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

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

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

[0005] Intra prediction is a technique for compressing images by removing spatial redundancy within the image. Intra prediction generates a predicted block based on the surrounding pixels of the current block, depending on the intra prediction mode. Then, the predicted block is subtracted from the current block to generate a residual block.

[0006] The residual block generated through inter-prediction or intra-prediction can be transformed and quantized and then passed to a decoder. The decoder can dequantize and inversely transform the residual block, and combine the predicted block of the current block with the residual block to reconstruct the current block. In certain cases, the decoder can filter the reconstructed current block to remove artifacts within it.

[0007] A method for decoding an image according to one embodiment may include determining a transformed template of a current block by performing a transformation on a template of a current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on templates of a plurality of candidate blocks within a search region.

[0008] A method of decoding an image according to one embodiment may include a step of comparing a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0009] A method for decoding an image according to one embodiment may include a step of determining a reference block of a current block among a plurality of candidate blocks based on a comparison result.

[0010] A method of decoding an image according to one embodiment may include a step of generating a prediction block of a current block using a reference block.

[0011] A method of decoding an image according to one embodiment may include a step of restoring a current block using a prediction block of the current block.

[0012] An image decryption device according to one embodiment may include at least one memory storing at least one instruction; and at least one processor operating according to at least one instruction.

[0013] In one embodiment, at least one processor can determine a transformed template of the current block by performing a transformation on a template of the current block, and determine transformed templates of a plurality of candidate blocks by performing a transformation on templates of the plurality of candidate blocks within the search region.

[0014] In one embodiment, at least one processor can compare a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0015] In one embodiment, at least one processor can determine a reference block of the current block from among a plurality of candidate blocks based on a comparison result.

[0016] In one embodiment, at least one processor may generate a prediction block of a current block using a reference block.

[0017] In one embodiment, at least one processor can reconstruct the current block using a predicted block of the current block.

[0018] A method of encoding an image according to one embodiment may include determining a transformed template of a current block by performing a transformation on a template of a current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on templates of a plurality of candidate blocks within a search area.

[0019] A method of encoding an image according to one embodiment may include a step of comparing a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0020] A method for encoding an image according to one embodiment may include a step of determining a reference block of a current block among a plurality of candidate blocks based on a comparison result.

[0021] A method of encoding an image according to one embodiment may include a step of generating a prediction block of a current block using a reference block.

[0022] A method of encoding an image according to one embodiment may include a step of restoring a current block using a prediction block of the current block.

[0023] An image encoding device according to one embodiment may include at least one memory storing at least one instruction; and at least one processor operating according to at least one instruction.

[0024] In one embodiment, at least one processor can determine a transformed template of the current block by performing a transformation on a template of the current block, and determine transformed templates of a plurality of candidate blocks by performing a transformation on templates of the plurality of candidate blocks within the search region.

[0025] In one embodiment, at least one processor can compare a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0026] In one embodiment, at least one processor can determine a reference block of the current block from among a plurality of candidate blocks based on a comparison result.

[0027] In one embodiment, at least one processor may generate a prediction block of a current block using a reference block.

[0028] In one embodiment, at least one processor can encode the current block using a prediction block of the current block.

[0029] In a computer-readable recording medium having recorded thereon a bitstream according to one embodiment, the bitstream may include an encoding result of a current block.

[0030] In one embodiment, the encoding result of the current block can be generated by determining a transformed template of the current block by performing a transformation on the template of the current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on the templates of a plurality of candidate blocks within the search area.

[0031] In one embodiment, the encoding result of the current block can be generated by comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks.

[0032] In one embodiment, the encoding result of the current block can be generated by determining a reference block of the current block among a plurality of candidate blocks based on a comparison result.

[0033] In one embodiment, the encoding result of the current block can be generated by generating a prediction block of the current block using a reference block.

[0034] In one embodiment, the encoding result of the current block can be generated by encoding the current block using a prediction block of the current block.

[0035] FIG. 1 is a block diagram of an image decoding device according to one embodiment.

[0036] FIG. 2 is a block diagram of an image encoding device according to one embodiment.

[0037] FIG. 3 illustrates a process of dividing a current encoding unit to determine at least one encoding unit according to one embodiment.

[0038] FIG. 4 illustrates a process of dividing a non-square coding unit to determine at least one coding unit according to one embodiment.

[0039] FIG. 5 illustrates a process of dividing an encoding unit based on at least one of block shape information and segmentation shape mode information according to one embodiment.

[0040] FIG. 6 illustrates a method for determining a predetermined coding unit among an odd number of coding units according to one embodiment.

[0041] FIG. 7 illustrates the order in which multiple encoding units are processed when a current encoding unit is divided to determine multiple encoding units according to one embodiment.

[0042] FIG. 8 illustrates a process for determining that a current encoding unit is split into an odd number of encoding units when encoding units cannot be processed in a predetermined order according to one embodiment.

[0043] FIG. 9 illustrates a process of dividing a first encoding unit to determine at least one encoding unit according to one embodiment.

[0044] FIG. 10 illustrates that, according to one embodiment, the shapes into which a first encoding unit can be divided are limited when a second encoding unit of a non-square shape determined by splitting the first encoding unit satisfies a predetermined condition.

[0045] FIG. 11 illustrates a process of splitting a square-shaped encoding unit when the split shape mode information cannot represent splitting into four square-shaped encoding units according to one embodiment.

[0046] FIG. 12 illustrates that, according to one embodiment, the processing order between multiple encoding units may vary depending on the process of splitting the encoding units.

[0047] FIG. 13 illustrates a process in which the depth of an encoding unit is determined as the shape and size of the encoding unit change when the encoding unit is recursively split to determine a plurality of encoding units according to one embodiment.

[0048] FIG. 14 illustrates an index (part index, hereinafter referred to as PID) for depth and encoding unit distinction that can be determined according to the shape and size of encoding units according to one embodiment.

[0049] FIG. 15 illustrates that a plurality of coding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment.

[0050] FIG. 16 illustrates encoding units that can be determined for each picture when the combination of forms into which encoding units can be divided is different for each picture according to one embodiment.

[0051] FIG. 17 illustrates various forms of encoding units that can be determined based on segmentation form mode information expressed in binary code according to one embodiment.

[0052] FIG. 18 illustrates another form of a coding unit that can be determined based on segmentation mode information expressed in binary code according to one embodiment.

[0053] FIG. 19 is a block diagram of an image encoding and decoding system that performs loop filtering according to one embodiment.

[0054] FIG. 20 is a block diagram illustrating the configuration of an image decoding device (2000) according to one embodiment.

[0055] FIG. 21 is a diagram for explaining a template matching prediction method according to one embodiment.

[0056] FIG. 22 is a diagram for explaining a template matching prediction method using a converted template according to one embodiment.

[0057] FIG. 23 is a diagram for explaining template matching prediction using a transformed sub-template according to one embodiment.

[0058] FIG. 24 is a diagram for explaining template matching prediction using a transformed sub-template according to one embodiment.

[0059] FIG. 25 is a diagram illustrating a process of generating a prediction block by combining transformed reference blocks according to one embodiment.

[0060] Fig. 26 is a diagram for explaining a template matching prediction process according to one embodiment.

[0061] Figure 27 is a flowchart of an image decoding method according to one embodiment.

[0062] Fig. 28 is a block diagram illustrating a configuration of an image encoding device according to one embodiment.

[0063] Figure 29 is a flowchart of an image encoding method according to one embodiment.

[0064] A method for decoding an image according to one embodiment may include determining a transformed template of a current block by performing a transformation on a template of a current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on templates of a plurality of candidate blocks within a search area.

[0065] A method of decoding an image according to one embodiment may include a step of comparing a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0066] A method for decoding an image according to one embodiment may include a step of determining a reference block of a current block among a plurality of candidate blocks based on a comparison result.

[0067] A method of decoding an image according to one embodiment may include a step of generating a prediction block of a current block using a reference block.

[0068] A method of decoding an image according to one embodiment may include a step of restoring a current block using a prediction block of the current block.

[0069] The present disclosure may be subject to various modifications and various embodiments. Examples are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the embodiments of the present disclosure, and the present disclosure may include all modifications, equivalents, and alternatives that fall within the spirit and technical scope of the various embodiments.

[0070] When describing embodiments, detailed descriptions of related known technologies may be omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, numbers (e.g., "first," "second," etc.) used in the description of embodiments may correspond to identification symbols used to distinguish one component from another.

[0071] In this disclosure, the expression “at least one of a, b or c” may refer to “a”, “b”, “c”, “a and b”, “a and c”, “b and c”, “all of a, b and c”, or variations thereof.

[0072] In the present disclosure, when a component is referred to as being “connected” or “connected” to another component, the component may be directly connected or connected to the other component, but unless there is a specific description to the contrary, the component may also be connected or connected via another component in between.

[0073] In the present disclosure, components expressed as "units", "modules", etc. may be two or more components combined into a single component, or a single component may be divided into two or more more detailed components. In addition, each component described below may additionally perform some or all of the functions performed by other components in addition to its own main function, and some of the main functions performed by each component may be exclusively performed by other components.

[0074] In the present disclosure, 'image' may refer to a picture, a still image, a frame, a moving image composed of a plurality of consecutive still images, or a video.

[0075] In this disclosure, "sample" may refer to data assigned to a sampling location in an image and thus to be processed. For example, a pixel within a frame in a spatial domain may correspond to a sample. A unit containing multiple samples may be defined as a block.

[0076] In the present disclosure, entropy decoding for a block or unit may mean a process of obtaining a syntax element of the block or unit from a bitstream (or bits included in the bitstream), or a process of obtaining an empty string corresponding to the syntax element.

[0077] In the present disclosure, entropy encoding for a block or unit may mean a process of generating a bitstream (or bits constituting a bitstream) from a syntax element of a block or unit, or a process of generating a bitstream (or bits constituting a bitstream) from an empty string corresponding to a syntax element.

[0078] Hereinafter, with reference to FIGS. 1 to 19, an image encoding method and device based on a tree-structured encoding unit and a transformation unit according to one embodiment, and an image decoding method and device are disclosed.

[0079] FIG. 1 illustrates a block diagram of an image decoding device (100) according to one embodiment.

[0080] The video decoding device (100) may include a bitstream acquisition unit (110) and a decoding unit (120). The bitstream acquisition unit (110) and the decoding unit (120) may include at least one processor. In addition, the bitstream acquisition unit (110) and the decoding unit (120) may include a memory that stores commands to be executed by at least one processor.

[0081] The bitstream acquisition unit (110) can receive a bitstream. The bitstream includes information obtained by encoding an image by an image encoding device (200) described below. In addition, the bitstream can be transmitted from the image encoding device (200). The image encoding device (200) and the image decoding device (100) can be connected by wire or wirelessly, and the bitstream acquisition unit (110) can receive the bitstream by wire or wirelessly. The bitstream acquisition unit (110) can receive the bitstream from a storage medium such as an optical medium, a hard disk, etc. The decoding unit (120) can restore the image based on information obtained from the received bitstream. The decoding unit (120) can obtain syntax elements for restoring the image from the bitstream. The decoding unit (120) can restore the image based on the syntax elements.

[0082] To describe in detail the operation of the video decoding device (100), the bitstream acquisition unit (110) can receive a bitstream.

[0083] The image decoding device (100) may perform an operation of obtaining a binstring corresponding to a splitting shape mode of an encoding unit from a bitstream. In addition, the image decoding device (100) may perform an operation of determining a splitting rule of the encoding unit. In addition, the image decoding device (100) may perform an operation of splitting the encoding unit into a plurality of encoding units based on at least one of the binstring corresponding to the splitting shape mode and the splitting rule. In order to determine the splitting rule, the image decoding device (100) may determine a first allowable range of the size of the encoding unit according to a ratio of the width and height of the encoding unit. In order to determine the splitting rule, the image decoding device (100) may determine a second allowable range of the size of the encoding unit according to the splitting shape mode of the encoding unit.

[0084] Below, the division of encoding units according to one embodiment of the present disclosure is described in detail.

[0085] First, a picture can be divided into one or more slices or one or more tiles. A slice or a tile can be a sequence of one or more maximum coding tree units (CTUs). Depending on the implementation, a slice may include one or more tiles, and a slice may include one or more maximum coding units. A slice including one or more tiles can be determined within a picture.

[0086] The maximum coding block (Coding Tree Block; CTB) is a concept that contrasts with the maximum coding unit (CTU). A CTB is an NxN block containing NxN samples (N is an integer). Each color component can be divided into one or more CTBs.

[0087] When a picture has three sample arrays (sample arrays for Y, Cr, and Cb components), a maximum coding unit (CTU) is a unit that includes a maximum coding block of luma samples, two maximum coding blocks of corresponding chroma samples, and syntax structures used to encode the luma samples and chroma samples. When a picture is a monochrome picture, a maximum coding unit is a unit that includes a maximum coding block of monochrome samples and syntax structures used to encode the monochrome samples. When a picture is a picture that is encoded with a color plane that is separated by color components, a maximum coding unit is a unit that includes syntax structures used to encode the picture and samples of the picture.

[0088] A single maximum coding block (CTB) can be divided into MxN coding blocks containing MxN samples (M, N are integers).

[0089] When a picture has a sample array for each Y, Cr, and Cb component, a coding unit (CU) is a unit that includes a coding block for a luma sample and two coding blocks for corresponding chroma samples, and syntax structures used to encode the luma sample and the chroma samples. When a picture is a monochrome picture, a coding unit is a unit that includes a coding block for a monochrome sample and syntax structures used to encode the monochrome samples. When a picture is a picture that is encoded with a color plane that is separated by color component, a coding unit is a unit that includes syntax structures used to encode the picture and samples of the picture.

[0090] As explained above, the maximum coding block and the maximum coding unit are distinct concepts, and the coding block and the coding unit are distinct concepts. That is, the (maximum) coding unit refers to a data structure including a (maximum) coding block including the corresponding sample and a syntax structure corresponding to it. However, since a person skilled in the art can understand that the (maximum) coding unit or the (maximum) coding block refers to a block of a predetermined size including a predetermined number of samples, the following specification will refer to the maximum coding block and the maximum coding unit, or the coding block and the coding unit, without distinction unless there are special circumstances.

[0091] An image can be divided into Coding Tree Units (CTUs). The size of the CTUs can be determined based on information obtained from the bitstream. The shape of the CTUs can be a square of equal size, but is not limited thereto.

[0092] For example, information about the maximum size of a luma coding block can be obtained from the bitstream. For example, the maximum size of the luma coding block indicated by the information about the maximum size of the luma coding block can be one of 4x4, 8x8, 16x16, 32x32, 64x64, 128x128, and 256x256.

[0093] For example, information about the maximum size of a luma coding block capable of being split into two and the luma block size difference can be obtained from the bitstream. The information about the luma block size difference can indicate the size difference between a luma maximum coding unit and a maximum luma coding block capable of being split into two. Therefore, by combining the information about the maximum size of a luma coding block capable of being split into two obtained from the bitstream and the information about the luma block size difference, the size of the luma maximum coding unit can be determined. Using the size of the luma maximum coding unit, the size of the chroma maximum coding unit can also be determined. For example, if the Y: Cb: Cr ratio is 4:2:0 according to the color format, the size of the chroma block can be half the size of the luma block, and similarly, the size of the chroma maximum coding unit can be half the size of the luma maximum coding unit.

[0094] According to one embodiment, since information about the maximum size of a luma coding block capable of binary splitting is obtained from a bitstream, the maximum size of the luma coding block capable of binary splitting can be determined variably. In contrast, the maximum size of a luma coding block capable of ternary splitting can be fixed. For example, the maximum size of a luma coding block capable of ternary splitting in an I picture may be 32x32, and the maximum size of a luma coding block capable of ternary splitting in a P picture or a B picture may be 64x64.

[0095] Additionally, the maximum coding unit can be hierarchically divided into coding units based on the division shape mode information obtained from the bitstream. As the division shape mode information, at least one of information indicating whether quad division is performed, information indicating whether multi-division is performed, division direction information, and division type information can be obtained from the bitstream.

[0096] For example, information indicating whether a quad split is present may indicate whether the current encoding unit is to be quad split (QUAD_SPLIT) or not to be quad split.

[0097] If the current encoding unit is not quad-split, the information indicating whether it is multi-split may indicate whether the current encoding unit will not be split any further (NO_SPLIT) or whether it will be binary / ternary split.

[0098] When the current encoding unit is binary or ternary split, the split direction information indicates that the current encoding unit is split in either the horizontal or vertical direction.

[0099] When the current encoding unit is split in the horizontal or vertical direction, the split type information indicates that the current encoding unit is split into binary split or ternary split.

[0100] Depending on the split direction information and the split type information, the split mode of the current encoding unit can be determined. The split mode when the current encoding unit is split into binaries in the horizontal direction can be determined as binary horizontal split (SPLIT_BT_HOR), the split mode when the current encoding unit is split into ternary horizontal split (SPLIT_TT_HOR), the split mode when the current encoding unit is split into binaries in the vertical direction can be determined as binary vertical split (SPLIT_BT_VER), and the split mode when the current encoding unit is split into ternary vertical split (SPLIT_TT_VER).

[0101] The image decoding device (100) can obtain segmentation shape mode information from a bitstream from a single binstring. The format of the bitstream received by the image decoding device (100) can include a fixed length binary code, a unary code, a truncated unary code, a predetermined binary code, etc. The binstring represents information as a series of binary numbers. The binstring can be composed of at least one bit. The image decoding device (100) can obtain segmentation shape mode information corresponding to the binstring based on a segmentation rule. The image decoding device (100) can determine whether to quad-segment an encoding unit, whether not to quad-segment, or the segmentation direction and segmentation type based on a single binstring.

[0102] The coding unit may be smaller than or equal to the maximum coding unit. For example, the maximum coding unit is also a coding unit with the maximum size, so it is a coding unit. If the split shape mode information for the maximum coding unit indicates that it is not split, the coding unit determined from the maximum coding unit has the same size as the maximum coding unit. If the split shape mode information for the maximum coding unit indicates that it is split, the maximum coding unit may be split into coding units. In addition, if the split shape mode information for the coding unit indicates splitting, the coding units may be split into coding units of smaller sizes. However, the splitting of the image is not limited thereto, and the maximum coding unit and the coding units may not be distinguished. The splitting of the coding unit is described in more detail with reference to FIGS. 3 to 16.

[0103] Additionally, one or more prediction blocks for prediction may be determined from the coding unit. The prediction blocks may be equal to or smaller than the coding unit. Additionally, one or more transformation blocks for transformation may be determined from the coding unit. The transformation blocks may be equal to or smaller than the coding unit.

[0104] The shape and size of the transformation block and the prediction block may be unrelated.

[0105] In another embodiment, prediction may be performed using the encoding unit as a prediction block. Transformation may also be performed using the encoding unit as a transform block.

[0106] The division of a coding unit is described in more detail with reference to FIGS. 3 to 16. The current block and neighboring blocks of the present disclosure may represent one of a maximum coding unit, a coding unit, a prediction block, and a transform block. In addition, the current block or the current coding unit is a block currently being decoded or encoded, or a block currently being divided. The neighboring block may be a block reconstructed before the current block. The neighboring block may be spatially or temporally adjacent to the current block. The neighboring block may be located on one of the lower left, left, upper left, upper right, upper right, right, and lower right sides of the current block.

[0107] FIG. 3 illustrates a process in which an image decoding device (100) divides a current encoding unit to determine at least one encoding unit according to one embodiment.

[0108] The block shape may include 4Nx4N, 4Nx2N, 2Nx4N, 4NxN, Nx4N, 32NxN, Nx32N, 16NxN, Nx16N, 8NxN or Nx8N, where N may be a positive integer. The block shape information is information indicating at least one of the shape, direction, width and height ratio or size of the encoding unit.

[0109] The shape of the encoding unit may include square and non-square. When the width and height of the encoding unit are equal (i.e., when the block shape of the encoding unit is 4Nx4N), the image decoding device (100) may determine the block shape information of the encoding unit as square. The image decoding device (100) may determine the shape of the encoding unit as non-square.

[0110] When the width and height of the encoding unit are different (i.e., when the block shape of the encoding unit is 4Nx2N, 2Nx4N, 4NxN, Nx4N, 32NxN, Nx32N, 16NxN, Nx16N, 8NxN, or Nx8N), the image decoding device (100) may determine the block shape information of the encoding unit to be non-square. When the shape of the encoding unit is non-square, the image decoding device (100) may determine the ratio of the width and height among the block shape information of the encoding unit to be at least one of 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, 1:32, and 32:1. Additionally, based on the width length and height length of the encoding unit, the image decoding device (100) can determine whether the encoding unit is in the horizontal or vertical direction. Additionally, based on at least one of the width length, height length, or area of ​​the encoding unit, the image decoding device (100) can determine the size of the encoding unit.

[0111] According to one embodiment, the image decoding device (100) can determine the shape of an encoding unit using block shape information, and can determine the shape into which the encoding unit is divided using segmentation shape mode information. That is, the splitting method of the encoding unit indicated by the segmentation shape mode information can be determined depending on which block shape the block shape information used by the image decoding device (100) indicates.

[0112] The image decoding device (100) can obtain the segmentation shape mode information from the bitstream. However, the present invention is not limited thereto, and the image decoding device (100) and the image encoding device (200) can determine the pre-agreed segmentation shape mode information based on the block shape information. The image decoding device (100) can determine the pre-agreed segmentation shape mode information for the maximum coding unit or the minimum coding unit. For example, the image decoding device (100) can determine the segmentation shape mode information for the maximum coding unit as quad split. In addition, the image decoding device (100) can determine the segmentation shape mode information for the minimum coding unit as “not split.” Specifically, the image decoding device (100) can determine the size of the maximum coding unit as 256x256. The image decoding device (100) can determine the pre-agreed segmentation shape mode information as quad split. Quad splitting is a splitting mode that divides both the width and height of an encoding unit in half. The image decoding device (100) can obtain a coding unit of size 128x128 from a maximum coding unit of size 256x256 based on the splitting mode information. In addition, the image decoding device (100) can determine the size of the minimum coding unit as 4x4. The image decoding device (100) can obtain splitting mode information indicating "not splitting" for the minimum coding unit.

[0113] According to one embodiment, the image decoding device (100) may use block shape information indicating that the current encoding unit is a square shape. For example, the image decoding device (100) may determine whether to not split a square encoding unit, to split it vertically, to split it horizontally, to split it into four encoding units, etc., according to the split shape mode information. Referring to FIG. 3, when the block shape information of the current encoding unit (300) indicates a square shape, the decoding unit (120) may not split an encoding unit (310a) having the same size as the current encoding unit (300) according to the split shape mode information indicating that it is not split, or may determine a split encoding unit (310b, 310c, 310d, 310e, 310f, etc.) based on the split shape mode information indicating a predetermined splitting method.

[0114] Referring to FIG. 3, the image decoding device (100) may determine two coding units (310b) by vertically dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is vertically divided, according to an embodiment. The image decoding device (100) may determine two coding units (310c) by horizontally dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is horizontally divided, according to an embodiment. The image decoding device (100) may determine four coding units (310d) by vertically and horizontally dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is vertically and horizontally divided, according to an embodiment. The image decoding device (100) may determine three coding units (310e) by vertically dividing the current coding unit (300) based on the split shape mode information indicating that the current coding unit (300) is ternary divided, according to an embodiment. The image decoding device (100) can determine three coding units (310f) into which the current coding unit (300) is horizontally divided based on the division shape mode information indicating that the ternary division is horizontally divided. However, the division shapes into which a square coding unit can be divided should not be interpreted as being limited to the above-described shapes, and may include various shapes that can be indicated by the division shape mode information. Specified division shapes into which a square coding unit is divided will be specifically described below through various embodiments.

[0115] FIG. 4 illustrates a process in which an image decoding device (100) divides a non-square coding unit to determine at least one coding unit according to one embodiment.

[0116] According to one embodiment, the image decoding device (100) may utilize block shape information indicating that the current encoding unit is non-square. The image decoding device (100) may determine whether to not split the current non-square encoding unit or to split it using a predetermined method based on the split shape mode information. Referring to FIG. 4, when the block shape information of the current encoding unit (400 or 450) indicates a non-square shape, the image decoding device (100) may determine an encoding unit (410 or 460) having the same size as the current encoding unit (400 or 450) according to the split shape mode information indicating that it is not split, or may determine a split encoding unit (420a, 420b, 430a, 430b, 430c, 470a, 470b, 480a, 480b, 480c) based on the split shape mode information indicating a predetermined splitting method. The predetermined splitting method by which a non-square encoding unit is split will be described in detail through various embodiments below.

[0117] According to one embodiment, the image decoding device (100) may determine a form in which an encoding unit is split using split form mode information, and in this case, the split form mode information may indicate the number of at least one encoding unit generated by splitting the encoding unit. Referring to FIG. 4, when the split form mode information indicates that the current encoding unit (400 or 450) is split into two encoding units, the image decoding device (100) may split the current encoding unit (400 or 450) based on the split form mode information to determine two encoding units (420a, 420b, or 470a, 470b) included in the current encoding unit.

[0118] According to one embodiment, when the image decoding device (100) splits a current encoding unit (400 or 450) having a non-square shape based on split shape mode information, the image decoding device (100) may split the current encoding unit by considering the position of the long side of the non-square current encoding unit (400 or 450). For example, the image decoding device (100) may split the current encoding unit (400 or 450) in a direction that splits the long side of the current encoding unit (400 or 450) by considering the shape of the current encoding unit (400 or 450) to determine a plurality of encoding units.

[0119] According to one embodiment, if the split shape mode information indicates that the coding unit is split into an odd number of blocks (ternary splitting), the image decoding device (100) may determine an odd number of coding units included in the current coding unit (400 or 450). For example, if the split shape mode information indicates that the current coding unit (400 or 450) is split into three coding units, the image decoding device (100) may split the current coding unit (400 or 450) into three coding units (430a, 430b, 430c, 480a, 480b, 480c).

[0120] According to one embodiment, the ratio of the width and height of the current encoding unit (400 or 450) may be 4:1 or 1:4. When the ratio of the width and height is 4:1, the block shape information may be in the horizontal direction because the length of the width is longer than the length of the height. When the ratio of the width and height is 1:4, the block shape information may be in the vertical direction because the length of the width is shorter than the length of the height. The image decoding device (100) may determine to split the current encoding unit into an odd number of blocks based on the split shape mode information. In addition, the image decoding device (100) may determine the splitting direction of the current encoding unit (400 or 450) based on the block shape information of the current encoding unit (400 or 450). For example, if the current encoding unit (400) is in the vertical direction, the image decoding device (100) can divide the current encoding unit (400) in the horizontal direction to determine encoding units (430a, 430b, 430c). Also, if the current encoding unit (450) is in the horizontal direction, the image decoding device (100) can divide the current encoding unit (450) in the vertical direction to determine encoding units (480a, 480b, 480c).

[0121] According to one embodiment, the image decoding device (100) may determine an odd number of coding units included in the current coding unit (400 or 450), and the sizes of the determined coding units may not all be the same. For example, among the determined odd number of coding units (430a, 430b, 430c, 480a, 480b, 480c), the size of a given coding unit (430b or 480b) may have a different size from the other coding units (430a, 430c, 480a, 480c). That is, the encoding units into which the current encoding unit (400 or 450) can be divided and determined can have multiple types of sizes, and in some cases, an odd number of encoding units (430a, 430b, 430c, 480a, 480b, 480c) can each have different sizes.

[0122] According to one embodiment, when the split shape mode information indicates that the coding unit is split into an odd number of blocks, the image decoding device (100) can determine an odd number of coding units included in the current coding unit (400 or 450), and further, the image decoding device (100) can place a predetermined restriction on at least one coding unit among the odd number of coding units generated by splitting. Referring to FIG. 4, the image decoding device (100) can perform a decoding process for a coding unit (430b, 480b) located in the center among three coding units (430a, 430b, 430c, 480a, 480b, 480c) generated by splitting the current coding unit (400 or 450) differently from the decoding process for other coding units (430a, 430c, 480a, 480c). For example, the image decoding device (100) can restrict the encoding unit (430b, 480b) located in the center from being split any further, unlike other encoding units (430a, 430c, 480a, 480c), or can restrict it to be split only a predetermined number of times.

[0123] FIG. 5 illustrates a process in which an image decoding device (100) divides an encoding unit based on at least one of block shape information and division shape mode information according to one embodiment.

[0124] According to one embodiment, the image decoding device (100) may determine whether to split or not to split a first coding unit (500) having a square shape into coding units based on at least one of block shape information and split shape mode information. According to one embodiment, when the split shape mode information indicates splitting the first coding unit (500) in the horizontal direction, the image decoding device (100) may split the first coding unit (500) in the horizontal direction to determine a second coding unit (510). The first coding unit, the second coding unit, and the third coding unit used according to one embodiment are terms used to understand the relationship before and after splitting between coding units. For example, when the first coding unit is split, the second coding unit may be determined, and when the second coding unit is split, the third coding unit may be determined. Hereinafter, the relationship between the first coding unit, the second coding unit, and the third coding unit used may be understood to follow the above-described characteristics.

[0125] According to one embodiment, the image decoding device (100) may determine to split or not split the determined second encoding unit (510) into encoding units based on the split shape mode information. Referring to FIG. 5, the image decoding device (100) may split the first encoding unit (500) based on the split shape mode information to split the determined second encoding unit (510) of a non-square shape into at least one third encoding unit (520a, 520b, 520c, 520d, etc.) or may not split the second encoding unit (510). The image decoding device (100) can obtain split shape mode information, and the image decoding device (100) can split the first encoding unit (500) based on the obtained split shape mode information to split a plurality of second encoding units (e.g., 510) of various shapes, and the second encoding unit (510) can be split according to the way in which the first encoding unit (500) is split based on the split shape mode information. According to one embodiment, when the first encoding unit (500) is split into the second encoding unit (510) based on the split shape mode information for the first encoding unit (500), the second encoding unit (510) can also be split into the third encoding unit (e.g., 520a, 520b, 520c, 520d, etc.) based on the split shape mode information for the second encoding unit (510). That is, the coding unit can be recursively split based on the split shape mode information associated with each coding unit. Accordingly, a square coding unit can be determined from a non-square coding unit, and such a square coding unit can be recursively split to determine a non-square coding unit.

[0126] Referring to FIG. 5, among the odd number of third coding units (520b, 520c, 520d) determined by splitting the second coding unit (510) having a non-square shape, a predetermined coding unit (e.g., a coding unit located in the middle or a coding unit having a square shape) may be split recursively. According to an embodiment, the non-square third coding unit (520c), which is one of the odd number of third coding units (520b, 520c, 520d), may be split horizontally into a plurality of fourth coding units. The non-square fourth coding unit (530b or 530d), which is one of the plurality of fourth coding units (530a, 530b, 530c, 530d), may be split again into a plurality of coding units. For example, the fourth coding unit (530b or 530d) having a non-square shape may be further divided into an odd number of coding units. Methods that can be used for recursive division of coding units will be described later through various embodiments.

[0127] According to one embodiment, the image decoding device (100) may split each of the third encoding units (520a, 520b, 520c, 520d, etc.) into encoding units based on the split shape mode information. In addition, the image decoding device (100) may determine not to split the second encoding unit (510) based on the split shape mode information. According to one embodiment, the image decoding device (100) may split the second encoding unit (510) having a non-square shape into an odd number of third encoding units (520b, 520c, 520d). The image decoding device (100) may place a predetermined restriction on a predetermined third encoding unit among the odd number of third encoding units (520b, 520c, 520d). For example, the image decoding device (100) can limit the encoding unit (520c) located in the middle among an odd number of third encoding units (520b, 520c, 520d) to not be divided any further or to be divided a settable number of times.

[0128] Referring to FIG. 5, the image decoding device (100) may limit the coding unit (520c) located in the middle among the odd number of third coding units (520b, 520c, 520d) included in the second coding unit (510) having a non-square shape to not be split any further, or to be split in a predetermined split form (for example, to be split only into four coding units or to be split in a form corresponding to the split form of the second coding unit (510), or to be split only a predetermined number of times (for example, to be split only n times, where n>0). However, the above limitations on the coding unit (520c) located in the middle are merely simple embodiments and should not be interpreted as being limited to the above-described embodiments, but should be interpreted as including various limitations in which the coding unit (520c) located in the middle can be decoded differently from the other coding units (520b, 520d).

[0129] According to one embodiment, the image decoding device (100) can obtain the segmentation shape mode information used to segment the current encoding unit from a predetermined location within the current encoding unit.

[0130] FIG. 6 illustrates a method for an image decoding device (100) to determine a predetermined encoding unit among an odd number of encoding units according to one embodiment.

[0131] Referring to FIG. 6, the split shape mode information of the current encoding unit (600, 650) can be obtained from a sample at a predetermined position among a plurality of samples included in the current encoding unit (600, 650) (for example, a sample (640, 690) located in the center). However, the predetermined position within the current encoding unit (600) from which at least one of the split shape mode information can be obtained should not be interpreted as being limited to the center position illustrated in FIG. 6, but should be interpreted as including various positions (for example, top, bottom, left, right, upper left, lower left, upper right, or lower right, etc.) that can be included within the current encoding unit (600). The image decoding device (100) can obtain the split shape mode information obtained from the predetermined position and determine whether or not to split the current encoding unit into encoding units of various shapes and sizes.

[0132] According to one embodiment, the image decoding device (100) may select one of the coding units when the current coding unit is divided into a predetermined number of coding units. Various methods may be used to select one of the multiple coding units, and descriptions of such methods will be provided later through various embodiments.

[0133] According to one embodiment, the image decoding device (100) can divide the current encoding unit into a plurality of encoding units and determine an encoding unit at a predetermined position.

[0134] According to one embodiment, the image decoding device (100) may use information indicating the positions of each of the odd-numbered coding units to determine an coding unit located in the middle of the odd-numbered coding units. Referring to FIG. 6, the image decoding device (100) may divide the current coding unit (600) or the current coding unit (650) to determine odd-numbered coding units (620a, 620b, 620c) or odd-numbered coding units (660a, 660b, 660c). The image decoding device (100) may use information about the positions of the odd-numbered coding units (620a, 620b, 620c) or odd-numbered coding units (660a, 660b, 660c) to determine the middle coding unit (620b) or the middle coding unit (660b). For example, the image decoding device (100) can determine the coding unit (620b) located in the center by determining the positions of the coding units (620a, 620b, 620c) based on information indicating the positions of predetermined samples included in the coding units (620a, 620b, 620c). Specifically, the image decoding device (100) can determine the coding unit (620b) located in the center by determining the positions of the coding units (620a, 620b, 620c) based on information indicating the positions of samples (630a, 630b, 630c) at the upper left of the coding units (620a, 620b, 620c).

[0135] According to one embodiment, information indicating the positions of the upper left samples (630a, 630b, 630c) included in each of the coding units (620a, 620b, 620c) may include information on the positions or coordinates of the coding units (620a, 620b, 620c) within the picture. According to one embodiment, information indicating the positions of the upper left samples (630a, 630b, 630c) included in each of the coding units (620a, 620b, 620c) may include information indicating the width or height of the coding units (620a, 620b, 620c) included in the current coding unit (600), and this width or height may correspond to information indicating the difference between the coordinates of the coding units (620a, 620b, 620c) within the picture. That is, the image decoding device (100) can determine the encoding unit (620b) located in the center by directly using information about the positions or coordinates of the encoding units (620a, 620b, 620c) within the picture or by using information about the width or height of the encoding unit corresponding to the difference between the coordinates.

[0136] According to one embodiment, information indicating the position of the sample (630a) at the upper left of the upper encoding unit (620a) may represent (xa, ya) coordinates, information indicating the position of the sample (530b) at the upper left of the middle encoding unit (620b) may represent (xb, yb) coordinates, and information indicating the position of the sample (630c) at the upper left of the lower encoding unit (620c) may represent (xc, yc) coordinates. The image decoding device (100) may determine the middle encoding unit (620b) using the coordinates of the upper left samples (630a, 630b, 630c) included in the encoding units (620a, 620b, 620c), respectively. For example, when the coordinates of the samples (630a, 630b, 630c) on the upper left are sorted in ascending or descending order, the encoding unit (620b) including the coordinates (xb, yb) of the sample (630b) located in the center can be determined as the encoding unit located in the center among the encoding units (620a, 620b, 620c) determined by dividing the current encoding unit (600). However, the coordinates indicating the positions of the upper left samples (630a, 630b, 630c) may indicate coordinates indicating the absolute positions within the picture, and further, based on the position of the upper left sample (630a) of the upper left coding unit (620a), the (dxb, dyb) coordinates, which are information indicating the relative position of the sample (630b) of the upper left of the middle coding unit (620b), and the (dxc, dyc) coordinates, which are information indicating the relative position of the sample (630c) of the upper left of the lower coding unit (620c), may be used. In addition, the method of determining the coding unit of a given position by using the coordinates of the corresponding sample as information indicating the position of the sample included in the coding unit should not be interpreted as being limited to the above-described method, but should be interpreted as various arithmetic methods that can utilize the coordinates of the sample.

[0137] According to one embodiment, the image decoding device (100) may divide the current encoding unit (600) into a plurality of encoding units (620a, 620b, 620c), and select an encoding unit from among the encoding units (620a, 620b, 620c) according to a predetermined criterion. For example, the image decoding device (100) may select an encoding unit (620b) having a different size from among the encoding units (620a, 620b, 620c).

[0138] According to one embodiment, the image decoding device (100) may determine the width or height of each of the encoding units (620a, 620b, 620c) by using the (xa, ya) coordinate, which is information indicating the position of the sample (630a) at the upper left of the upper encoding unit (620a), the (xb, yb) coordinate, which is information indicating the position of the sample (630b) at the upper left of the middle encoding unit (620b), and the (xc, yc) coordinate, which is information indicating the position of the sample (630c) at the upper left of the lower encoding unit (620c). The image decoding device (100) can determine the size of each of the encoding units (620a, 620b, 620c) using coordinates (xa, ya), (xb, yb), (xc, yc) indicating the positions of the encoding units (620a, 620b, 620c). According to one embodiment, the image decoding device (100) can determine the width of the upper encoding unit (620a) as the width of the current encoding unit (600). The image decoding device (100) can determine the height of the upper encoding unit (620a) as yb-ya. According to one embodiment, the image decoding device (100) can determine the width of the middle encoding unit (620b) as the width of the current encoding unit (600). The image decoding device (100) may determine the height of the middle encoding unit (620b) as yc-yb. According to one embodiment, the image decoding device (100) may determine the width or height of the lower encoding unit using the width or height of the current encoding unit and the width and height of the upper encoding unit (620a) and the middle encoding unit (620b). The image decoding device (100) may determine an encoding unit having a different size from other encoding units based on the width and height of the determined encoding units (620a, 620b, 620c).Referring to FIG. 6, the image decoding device (100) can determine the middle encoding unit (620b) having a different size from the sizes of the upper encoding unit (620a) and the lower encoding unit (620c) as the encoding unit of a predetermined position. However, the process by which the image decoding device (100) described above determines the encoding unit having a different size from other encoding units is merely an embodiment of determining the encoding unit of a predetermined position using the size of the encoding unit determined based on sample coordinates, and therefore, various processes of determining the encoding unit of a predetermined position by comparing the sizes of the encoding units determined according to predetermined sample coordinates can be used.

[0139] The image decoding device (100) can determine the width or height of each of the encoding units (660a, 660b, 660c) by using the (xd, yd) coordinate, which is information indicating the position of the sample (670a) at the upper left of the left encoding unit (660a), the (xe, ye) coordinate, which is information indicating the position of the sample (670b) at the upper left of the middle encoding unit (660b), and the (xf, yf) coordinate, which is information indicating the position of the sample (670c) at the upper left of the right encoding unit (660c). The image decoding device (100) can determine the size of each of the encoding units (660a, 660b, 660c) by using the (xd, yd), (xe, ye), (xf, yf), which are coordinates indicating the positions of the encoding units (660a, 660b, 660c).

[0140] According to one embodiment, the image decoding device (100) may determine the width of the left encoding unit (660a) as xe-xd. The image decoding device (100) may determine the height of the left encoding unit (660a) as the height of the current encoding unit (650). According to one embodiment, the image decoding device (100) may determine the width of the middle encoding unit (660b) as xf-xe. The image decoding device (100) may determine the height of the middle encoding unit (660b) as the height of the current encoding unit (600). According to one embodiment, the image decoding device (100) may determine the width or height of the right encoding unit (660c) using the width or height of the current encoding unit (650) and the widths and heights of the left encoding unit (660a) and the middle encoding unit (660b). The image decoding device (100) can determine an encoding unit having a different size from other encoding units based on the width and height of the determined encoding units (660a, 660b, 660c). Referring to FIG. 6, the image decoding device (100) can determine a middle encoding unit (660b) having a different size from the sizes of the left encoding unit (660a) and the right encoding unit (660c) as an encoding unit at a predetermined position. However, the process of the image decoding device (100) described above determining an encoding unit having a different size from other encoding units is merely an embodiment of determining an encoding unit at a predetermined position using the size of the encoding unit determined based on sample coordinates, and therefore, various processes of determining an encoding unit at a predetermined position by comparing the sizes of the encoding units determined according to predetermined sample coordinates can be used.

[0141] However, the location of the sample considered for determining the location of the encoding unit should not be interpreted as being limited to the upper left corner described above, and it can be interpreted that information on the location of any sample included in the encoding unit can be used.

[0142] According to one embodiment, the image decoding device (100) may select an encoding unit at a predetermined position from among an odd number of encoding units determined by splitting the current encoding unit, taking into consideration the shape of the current encoding unit. For example, if the current encoding unit has a non-square shape in which the width is longer than the height, the image decoding device (100) may determine an encoding unit at a predetermined position in the horizontal direction. That is, the image decoding device (100) may determine one of the encoding units whose positions vary in the horizontal direction and place a restriction on the corresponding encoding unit. If the current encoding unit has a non-square shape in which the height is longer than the width, the image decoding device (100) may determine an encoding unit at a predetermined position in the vertical direction. That is, the image decoding device (100) may determine one of the encoding units whose positions vary in the vertical direction and place a restriction on the corresponding encoding unit.

[0143] According to one embodiment, the image decoding device (100) may use information indicating the positions of each of the even-numbered coding units to determine the coding unit at a predetermined position among the even-numbered coding units. The image decoding device (100) may determine the even-numbered coding units by dividing the current coding unit (binary dividing) and may determine the coding unit at a predetermined position using information about the positions of the even-numbered coding units. A specific process for this may be a process corresponding to the process of determining the coding unit at a predetermined position (e.g., the center position) among the odd-numbered coding units described above in FIG. 6, and thus will be omitted.

[0144] According to one embodiment, when a current encoding unit having a non-square shape is split into a plurality of encoding units, predetermined information about the encoding unit at a predetermined position may be used during the splitting process to determine an encoding unit at a predetermined position among the plurality of encoding units. For example, the image decoding device (100) may use at least one of block shape information and split shape mode information stored in a sample included in a middle encoding unit during the splitting process to determine an encoding unit located in the middle among the encoding units into which the current encoding unit is split.

[0145] Referring to FIG. 6, the image decoding device (100) can split the current encoding unit (600) into a plurality of encoding units (620a, 620b, 620c) based on the split shape mode information, and can determine the encoding unit (620b) located in the middle among the plurality of encoding units (620a, 620b, 620c). Furthermore, the image decoding device (100) can determine the encoding unit (620b) located in the middle by considering the position where the split shape mode information is acquired. That is, the split shape mode information of the current encoding unit (600) can be obtained from a sample (640) located in the center of the current encoding unit (600), and when the current encoding unit (600) is split into a plurality of encoding units (620a, 620b, 620c) based on the split shape mode information, the encoding unit (620b) including the sample (640) can be determined as the encoding unit located in the center. However, the information used to determine the encoding unit located in the center should not be interpreted as being limited to the split shape mode information, and various types of information can be used in the process of determining the encoding unit located in the center.

[0146] According to one embodiment, predetermined information for identifying a coding unit at a predetermined position may be obtained from a predetermined sample included in the coding unit to be determined. Referring to FIG. 6, the image decoding device (100) may use split shape mode information obtained from a sample at a predetermined position within the current coding unit (600) (e.g., a sample located at the center of the current coding unit (600)) to determine a coding unit at a predetermined position among a plurality of coding units (620a, 620b, 620c) determined by splitting the current coding unit (600) (e.g., a coding unit located at the center of the coding units split into multiple units). That is, the image decoding device (100) can determine the sample at the predetermined position by considering the block shape of the current encoding unit (600), and the image decoding device (100) can determine an encoding unit (620b) that includes a sample from which predetermined information (e.g., division shape mode information) can be obtained among a plurality of encoding units (620a, 620b, 620c) determined by dividing the current encoding unit (600), and can set a predetermined restriction. Referring to FIG. 6, according to one embodiment, the image decoding device (100) can determine a sample (640) located at the center of the current encoding unit (600) as a sample from which predetermined information can be obtained, and the image decoding device (100) can set a predetermined restriction on the encoding unit (620b) that includes such a sample (640) during the decoding process. However, the location of the sample from which certain information can be obtained should not be interpreted as being limited to the above-described location, but may be interpreted as samples at any location included in the encoding unit (620b) to be determined in order to set a limitation.

[0147] According to one embodiment, the position of a sample from which predetermined information can be obtained may be determined according to the shape of the current encoding unit (600). According to one embodiment, the block shape information may determine whether the shape of the current encoding unit is square or non-square, and may determine the position of a sample from which predetermined information can be obtained according to the shape. For example, the image decoding apparatus (100) may determine a sample located on a boundary that divides at least one of the width and height of the current encoding unit in half as a sample from which predetermined information can be obtained, using at least one of information about the width and information about the height of the current encoding unit. As another example, when the block shape information related to the current encoding unit indicates that the shape is non-square, the image decoding apparatus (100) may determine one of the samples adjacent to the boundary that divides the long side of the current encoding unit in half as a sample from which predetermined information can be obtained.

[0148] According to one embodiment, when the image decoding device (100) divides the current encoding unit into a plurality of encoding units, the image decoding device (100) may use the split shape mode information to determine the encoding unit at a predetermined position among the plurality of encoding units. According to one embodiment, the image decoding device (100) may obtain the split shape mode information from a sample at a predetermined position included in the encoding unit, and the image decoding device (100) may divide the plurality of encoding units generated by splitting the current encoding unit using the split shape mode information obtained from the sample at a predetermined position included in each of the plurality of encoding units. That is, the encoding unit may be recursively divided using the split shape mode information obtained from the sample at a predetermined position included in each of the encoding units. Since the recursive division process of the encoding unit has been described above with reference to FIG. 5, a detailed description thereof will be omitted.

[0149] According to one embodiment, the image decoding device (100) can divide a current encoding unit to determine at least one encoding unit, and can determine the order in which the at least one encoding unit is decoded according to a predetermined block (e.g., the current encoding unit).

[0150] FIG. 7 illustrates the order in which multiple encoding units are processed when an image decoding device (100) divides a current encoding unit to determine multiple encoding units according to one embodiment.

[0151] According to one embodiment, the image decoding device (100) may determine second encoding units (710a, 710b) by vertically splitting the first encoding unit (700) according to the splitting shape mode information, determine second encoding units (730a, 730b) by horizontally splitting the first encoding unit (700), or determine second encoding units (750a, 750b, 750c, 750d) by vertically and horizontally splitting the first encoding unit (700).

[0152] Referring to FIG. 7, the image decoding device (100) can determine the order in which the second encoding units (710a, 710b) determined by vertically dividing the first encoding unit (700) are processed in the horizontal direction (710c). The image decoding device (100) can determine the order in which the second encoding units (730a, 730b) determined by horizontally dividing the first encoding unit (700) are processed in the vertical direction (730c). The image decoding device (100) can determine the second encoding units (750a, 750b, 750c, 750d) determined by dividing the first encoding unit (700) in the vertical and horizontal directions according to a predetermined order (e.g., raster scan order (750e) or z scan order (z scan order)) in which encoding units located in one row are processed and then encoding units located in the next row are processed.

[0153] According to one embodiment, the image decoding device (100) can recursively split the encoding units. Referring to FIG. 7, the image decoding device (100) can split the first encoding unit (700) to determine a plurality of encoding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d), and can recursively split each of the determined plurality of encoding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d). A method for splitting a plurality of coding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d) may be a method corresponding to a method for splitting the first coding unit (700). Accordingly, the plurality of coding units (710a, 710b, 730a, 730b, 750a, 750b, 750c, 750d) may each be independently split into a plurality of coding units. Referring to FIG. 7, the image decoding device (100) may split the first coding unit (700) in the vertical direction to determine the second coding units (710a, 710b), and further may determine to independently split or not split each of the second coding units (710a, 710b).

[0154] According to one embodiment, the image decoding device (100) may horizontally divide the second encoding unit (710a) on the left into third encoding units (720a, 720b), and may not divide the second encoding unit (710b) on the right.

[0155] According to one embodiment, the processing order of the coding units may be determined based on the splitting process of the coding units. In other words, the processing order of the split coding units may be determined based on the processing order of the coding units immediately before splitting. The image decoding device (100) may determine the processing order of the third coding units (720a, 720b) ​​determined by splitting the second coding unit (710a) on the left, independently from the second coding unit (710b) on the right. Since the second coding unit (710a) on the left is split horizontally and the third coding units (720a, 720b) ​​are determined, the third coding units (720a, 720b) ​​may be processed in the vertical direction (720c). In addition, since the order in which the second encoding unit (710a) on the left and the second encoding unit (710b) on the right are processed corresponds to the horizontal direction (710c), the right encoding unit (710b) can be processed after the third encoding units (720a, 720b) ​​included in the second encoding unit (710a) on the left are processed in the vertical direction (720c). Since the above-described content is intended to explain the process in which the processing order of the encoding units is determined according to the encoding units before splitting, it should not be interpreted as being limited to the above-described embodiment, but should be interpreted as being used in various ways in which encoding units that are split and determined in various forms can be independently processed according to a predetermined order.

[0156] FIG. 8 illustrates a process for determining that a current encoding unit is divided into an odd number of encoding units when the encoding units cannot be processed in a predetermined order, according to one embodiment of the present invention.

[0157] According to one embodiment, the image decoding device (100) may determine that the current encoding unit is split into an odd number of encoding units based on the acquired split shape mode information. Referring to FIG. 8, a first encoding unit (800) having a square shape may be split into second encoding units (810a, 810b) having a non-square shape, and the second encoding units (810a, 810b) may each be independently split into third encoding units (820a, 820b, 820c, 820d, 820e). According to one embodiment, the image decoding device (100) can determine a plurality of third encoding units (820a, 820b) by horizontally dividing the left encoding unit (810a) among the second encoding units, and can divide the right encoding unit (810b) into an odd number of third encoding units (820c, 820d, 820e).

[0158] According to one embodiment, the image decoding device (100) can determine whether there is an odd number of split encoding units by determining whether the third encoding units (820a, 820b, 820c, 820d, 820e) can be processed in a predetermined order. Referring to FIG. 8, the image decoding device (100) can determine the third encoding units (820a, 820b, 820c, 820d, 820e) by recursively splitting the first encoding unit (800). The image decoding device (100) can determine whether the first encoding unit (800), the second encoding unit (810a, 810b), or the third encoding unit (820a, 820b, 820c, 820d, 820e) is divided into an odd number of encoding units based on at least one of the block shape information and the split shape mode information. For example, the encoding unit located on the right side of the second encoding unit (810a, 810b) can be divided into an odd number of third encoding units (820c, 820d, 820e). The order in which the plurality of encoding units included in the first encoding unit (800) are processed can be a predetermined order (e.g., z-scan order (830)), and the image decoding device (100) can determine whether the third encoding unit (820c, 820d, 820e) determined by dividing the second encoding unit (810b) on the right into odd numbers satisfies the condition that it can be processed according to the predetermined order.

[0159] According to one embodiment, the image decoding device (100) may determine whether the third encoding units (820a, 820b, 820c, 820d, 820e) included in the first encoding unit (800) satisfy a condition that they can be processed in a predetermined order, and the condition is related to whether at least one of the width and height of the second encoding unit (810a, 810b) is split in half according to the boundary of the third encoding unit (820a, 820b, 820c, 820d, 820e). For example, the third encoding unit (820a, 820b) determined by splitting the height of the left second encoding unit (810a) of a non-square shape in half may satisfy the condition. Since the boundaries of the third encoding units (820c, 820d, 820e) determined by dividing the right second encoding unit (810b) into three encoding units do not divide the width or height of the right second encoding unit (810b) in half, it may be determined that the third encoding units (820c, 820d, 820e) do not satisfy the condition. In the case where this condition is not satisfied, the image decoding device (100) may determine that there is a disconnection in the scanning order, and may determine that the right second encoding unit (810b) is divided into an odd number of encoding units based on the determination result. According to an embodiment, the image decoding device (100) may place a predetermined restriction on an encoding unit at a predetermined position among the divided encoding units when the encoding unit is divided into an odd number of encoding units. Since the contents of such restrictions or predetermined positions have been described above through various embodiments, a detailed description thereof will be omitted.

[0160] FIG. 9 illustrates a process in which an image decoding device (100) divides a first encoding unit (900) to determine at least one encoding unit according to one embodiment.

[0161] According to one embodiment, the image decoding device (100) may split the first coding unit (900) based on the split shape mode information acquired through the bitstream acquisition unit (110). The first coding unit (900) having a square shape may be split into four coding units having a square shape or may be split into a plurality of coding units having a non-square shape. For example, referring to FIG. 9, when the first coding unit (900) is square and the split shape mode information indicates that it is split into non-square coding units, the image decoding device (100) may split the first coding unit (900) into a plurality of non-square coding units. Specifically, when the split shape mode information indicates that the first encoding unit (900) is split in the horizontal direction or the vertical direction to determine an odd number of encoding units, the image decoding device (100) can split the first encoding unit (900) having a square shape into second encoding units (910a, 910b, 910c) determined by splitting them in the vertical direction into an odd number of encoding units or second encoding units (920a, 920b, 920c) determined by splitting them in the horizontal direction.

[0162] According to one embodiment, the image decoding device (100) can determine whether the second encoding units (910a, 910b, 910c, 920a, 920b, 920c) included in the first encoding unit (900) satisfy a condition that allows them to be processed in a predetermined order, and the condition is related to whether at least one of the width and height of the first encoding unit (900) is split in half according to the boundary of the second encoding units (910a, 910b, 910c, 920a, 920b, 920c). Referring to FIG. 9, since the boundaries of the second coding units (910a, 910b, 910c) determined by vertically dividing the first coding unit (900) in a square shape do not divide the width of the first coding unit (900) in half, it may be determined that the first coding unit (900) does not satisfy the condition that it can be processed in a predetermined order. In addition, since the boundaries of the second coding units (920a, 920b, 920c) determined by horizontally dividing the first coding unit (900) in a square shape do not divide the height of the first coding unit (900) in half, it may be determined that the first coding unit (900) does not satisfy the condition that it can be processed in a predetermined order. If such a condition is not satisfied, the image decoding device (100) may determine that the scan order is disconnected, and based on the determination result, may determine that the first encoding unit (900) is divided into an odd number of encoding units. According to one embodiment, the image decoding device (100) may place a predetermined restriction on an encoding unit at a predetermined position among the divided encoding units when the encoding unit is divided into an odd number of encoding units. Since the contents of such restrictions or predetermined positions, etc. have been described above through various embodiments, a detailed description thereof will be omitted.

[0163] According to one embodiment, the image decoding device (100) can divide the first encoding unit to determine encoding units of various shapes.

[0164] Referring to FIG. 9, the image decoding device (100) can divide the first encoding unit (900) having a square shape and the first encoding unit (930 or 950) having a non-square shape into encoding units of various shapes.

[0165] FIG. 10 illustrates that, according to one embodiment, a video decoding device (100) limits the shapes into which a second encoding unit can be divided when a non-square shape of a second encoding unit determined by splitting a first encoding unit (1000) satisfies a predetermined condition.

[0166] According to one embodiment, the image decoding device (100) may determine to split a first coding unit (1000) having a square shape into second coding units (1010a, 1010b, 1020a, 1020b) having a non-square shape based on the split shape mode information acquired through the bitstream acquisition unit (110). The second coding units (1010a, 1010b, 1020a, 1020b) may be split independently. Accordingly, the image decoding device (100) may determine to split or not split into a plurality of coding units based on the split shape mode information related to each of the second coding units (1010a, 1010b, 1020a, 1020b). According to one embodiment, the image decoding device (100) may determine third encoding units (1012a, 1012b) by horizontally dividing the left second encoding unit (1010a) having a non-square shape determined by vertically dividing the first encoding unit (1000). However, when the image decoding device (100) divides the left second encoding unit (1010a) in the horizontal direction, the right second encoding unit (1010b) may be restricted from being horizontally divided in the same direction as the direction in which the left second encoding unit (1010a) is divided. If the second encoding unit on the right (1010b) is split in the same direction to determine the third encoding unit (1014a, 1014b), the second encoding unit on the left (1010a) and the second encoding unit on the right (1010b) may be independently split in the horizontal direction to determine the third encoding unit (1012a, 1012b, 1014a, 1014b). However, this is the same result as the image decoding device (100) splitting the first encoding unit (1000) into four square-shaped second encoding units (1030a, 1030b, 1030c, 1030d) based on the split shape mode information, which may be inefficient in terms of image decoding.

[0167] According to one embodiment, the image decoding device (100) may determine third coding units (1022a, 1022b, 1024a, 1024b) by vertically dividing a second coding unit (1020a or 1020b) having a non-square shape determined by dividing a first coding unit (1000) in a horizontal direction. However, when the image decoding device (100) vertically divides one of the second coding units (e.g., the upper second coding unit (1020a)), the other second coding units (e.g., the lower coding unit (1020b)) may be restricted from being vertically divided in the same direction as the direction in which the upper second coding unit (1020a) is divided, for the reasons described above.

[0168] FIG. 11 illustrates a process in which an image decoding device (100) divides a square-shaped encoding unit when the split shape mode information cannot indicate that the encoding unit is divided into four square-shaped encoding units according to one embodiment.

[0169] According to one embodiment, the image decoding device (100) may split the first encoding unit (1100) based on the split shape mode information to determine the second encoding units (1110a, 1110b, 1120a, 1120b, etc.). The split shape mode information may include information about various shapes into which the encoding unit may be split, but the information about various shapes may not include information for splitting the encoding unit into four encoding units having a square shape. According to this split shape mode information, the image decoding device (100) cannot split the first encoding unit (1100) having a square shape into four second encoding units having a square shape (1130a, 1130b, 1130c, 1130d). Based on the segmentation shape mode information, the image decoding device (100) can determine a second encoding unit (1110a, 1110b, 1120a, 1120b, etc.) of a non-square shape.

[0170] According to one embodiment, the image decoding device (100) can independently split each of the second encoding units (1110a, 1110b, 1120a, 1120b, etc.) having a non-square shape. Each of the second encoding units (1110a, 1110b, 1120a, 1120b, etc.) can be split in a predetermined order using a recursive method, which may be a splitting method corresponding to a method in which the first encoding unit (1100) is split based on splitting shape mode information.

[0171] For example, the image decoding device (100) can determine third coding units (1112a, 1112b) having a square shape by splitting the left second coding unit (1110a) in the horizontal direction, and can determine third coding units (1114a, 1114b) having a square shape by splitting the right second coding unit (1110b) in the horizontal direction. Furthermore, the image decoding device (100) can also determine third coding units (1116a, 1116b, 1116c, 1116d) having a square shape by splitting both the left second coding unit (1110a) and the right second coding unit (1110b) in the horizontal direction. In this case, the encoding unit can be determined in the same form as the first encoding unit (1100) being divided into four square-shaped second encoding units (1130a, 1130b, 1130c, 1130d).

[0172] As another example, the image decoding device (100) may determine third coding units (1122a, 1122b) having a square shape by vertically splitting the upper second coding unit (1120a), and may determine third coding units (1124a, 1124b) having a square shape by vertically splitting the lower second coding unit (1120b). Furthermore, the image decoding device (100) may determine third coding units (1126a, 1126b, 1126a, 1126b) having a square shape by vertically splitting both the upper second coding unit (1120a) and the lower second coding unit (1120b). In this case, the encoding unit can be determined in the same form as the first encoding unit (1100) being divided into four square-shaped second encoding units (1130a, 1130b, 1130c, 1130d).

[0173] FIG. 12 illustrates that, according to one embodiment, the processing order between multiple encoding units may vary depending on the process of dividing the encoding units.

[0174] According to one embodiment, the image decoding device (100) may split the first encoding unit (1200) based on the split shape mode information. If the block shape is square and the split shape mode information indicates that the first encoding unit (1200) is split in at least one of the horizontal direction and the vertical direction, the image decoding device (100) may split the first encoding unit (1200) to determine second encoding units (e.g., 1210a, 1210b, 1220a, 1220b, etc.). Referring to FIG. 12, the second encoding units (1210a, 1210b, 1220a, 1220b) having a non-square shape determined by splitting the first encoding unit 1200 only in the horizontal direction or the vertical direction may be independently split based on the split shape mode information for each. For example, the image decoding device (100) can determine third encoding units (1216a, 1216b, 1216c, 1216d) by horizontally dividing second encoding units (1210a, 1210b) generated by vertically dividing the first encoding unit (1200), and can determine third encoding units (1226a, 1226b, 1226c, 1226d) by vertically dividing second encoding units (1220a, 1220b) generated by horizontally dividing the first encoding unit (1200). Since the process of dividing the second encoding units (1210a, 1210b, 1220a, 1220b) has been described above with reference to FIG. 11, a detailed description thereof will be omitted.

[0175] According to one embodiment, the image decoding device (100) can process encoding units according to a predetermined order. Since the characteristics of processing encoding units according to a predetermined order have been described above with reference to FIG. 7, a detailed description thereof will be omitted. Referring to FIG. 12, the image decoding device (100) can divide a first encoding unit (1200) having a square shape and determine four third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) having a square shape. According to one embodiment, the image decoding device (100) can determine the processing order of the third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) depending on the form in which the first encoding unit (1200) is divided.

[0176] According to one embodiment, the image decoding device (100) may determine third encoding units (1216a, 1216b, 1216c, 1216d) by horizontally dividing the second encoding units (1210a, 1210b) generated by vertically dividing them, and the image decoding device (100) may process the third encoding units (1216a, 1216b, 1216c, 1216d) according to an order (1217) of first processing the third encoding units (1216a, 1216c) included in the left second encoding unit (1210a) in the vertical direction and then processing the third encoding units (1216b, 1216d) included in the right second encoding unit (1210b) in the vertical direction.

[0177] According to one embodiment, the image decoding device (100) may determine third encoding units (1226a, 1226b, 1226c, 1226d) by vertically dividing the second encoding units (1220a, 1220b) generated by being divided in the horizontal direction, and the image decoding device (100) may process the third encoding units (1226a, 1226b, 1226c, 1226d) according to an order (1227) of first processing the third encoding units (1226a, 1226b) included in the upper second encoding unit (1220a) in the horizontal direction and then processing the third encoding units (1226c, 1226d) included in the lower second encoding unit (1220b) in the horizontal direction.

[0178] Referring to FIG. 12, the second encoding units (1210a, 1210b, 1220a, 1220b) can be divided into third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) having a square shape. The second encoding units (1210a, 1210b) determined by being split in the vertical direction and the second encoding units (1220a, 1220b) determined by being split in the horizontal direction are split into different shapes, but according to the third encoding units (1216a, 1216b, 1216c, 1216d, 1226a, 1226b, 1226c, 1226d) determined later, the first encoding unit (1200) is ultimately split into encoding units of the same shape. Accordingly, even if the image decoding device (100) determines encoding units of the same shape as a result by recursively splitting the encoding units through different processes based on the split shape mode information, it can process a plurality of encoding units determined in the same shape in different orders.

[0179] FIG. 13 illustrates a process in which the depth of an encoding unit is determined as the shape and size of the encoding unit change when the encoding unit is recursively divided to determine a plurality of encoding units according to one embodiment.

[0180] According to one embodiment, the image decoding device (100) may determine the depth of an encoding unit according to a predetermined criterion. For example, the predetermined criterion may be the length of a long side of the encoding unit. If the length of the long side of the current encoding unit is split to be 2n (n>0) times the length of the long side of the encoding unit before splitting, the image decoding device (100) may determine that the depth of the current encoding unit is increased by n compared to the depth of the encoding unit before splitting. Hereinafter, an encoding unit with an increased depth is expressed as an encoding unit of a lower depth.

[0181] Referring to FIG. 13, according to one embodiment, based on block shape information indicating a square shape (for example, the block shape information may indicate '0: SQUARE'), the image decoding device (100) may divide a first coding unit (1300) having a square shape to determine a second coding unit (1302), a third coding unit (1304), etc. of a lower depth. If the size of the first coding unit (1300) having a square shape is 2Nx2N, the second coding unit (1302) determined by dividing the width and height of the first coding unit (1300) by half may have a size of NxN. Furthermore, the third coding unit (1304) determined by dividing the width and height of the second coding unit (1302) by half may have a size of N / 2xN / 2. In this case, the width and height of the third encoding unit (1304) correspond to 1 / 4 of the width and height of the first encoding unit (1300). When the depth of the first encoding unit (1300) is D, the depth of the second encoding unit (1302), which is 1 / 2 of the width and height of the first encoding unit (1300), may be D+1, and the depth of the third encoding unit (1304), which is 1 / 4 of the width and height of the first encoding unit (1300), may be D+2.

[0182] In one embodiment, based on block shape information indicating a non-square shape (for example, the block shape information may indicate '1: NS_VER' indicating a non-square shape in which the height is longer than the width or '2: NS_HOR' indicating a non-square shape in which the width is longer than the height), the image decoding device (100) may split a first coding unit (1310 or 1320) having a non-square shape to determine a second coding unit (1312 or 1322), a third coding unit (1314 or 1324) of a lower depth, etc.

[0183] The image decoding device (100) can determine a second encoding unit (e.g., 1302, 1312, 1322, etc.) by splitting at least one of the width and height of the first encoding unit (1310) having a size of Nx2N. That is, the image decoding device (100) can split the first encoding unit (1310) in the horizontal direction to determine a second encoding unit (1302) having a size of NxN or a second encoding unit (1322) having a size of NxN / 2, and can also split the first encoding unit (1310) in the horizontal direction and the vertical direction to determine a second encoding unit (1312) having a size of N / 2xN.

[0184] According to one embodiment, the image decoding device (100) may determine a second coding unit (e.g., 1302, 1312, 1322, etc.) by splitting at least one of the width and the height of the first coding unit (1320) having a size of 2NxN. That is, the image decoding device (100) may split the first coding unit (1320) in the vertical direction to determine a second coding unit (1302) having a size of NxN or a second coding unit (1312) having a size of N / 2xN, and may split the first coding unit (1320) in the horizontal direction and the vertical direction to determine a second coding unit (1322) having a size of NxN / 2.

[0185] According to one embodiment, the image decoding device (100) may determine a third encoding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second encoding unit (1302) having a size of NxN. That is, the image decoding device (100) may split the second encoding unit (1302) in the vertical direction and the horizontal direction to determine a third encoding unit (1304) having a size of N / 2xN / 2, a third encoding unit (1314) having a size of N / 4xN / 2, or a third encoding unit (1324) having a size of N / 2xN / 4.

[0186] According to one embodiment, the image decoding device (100) may determine a third encoding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second encoding unit (1312) having a size of N / 2xN. That is, the image decoding device (100) may split the second encoding unit (1312) in the horizontal direction to determine a third encoding unit (1304) having a size of N / 2xN / 2 or a third encoding unit (1324) having a size of N / 2xN / 4, or split the second encoding unit (1312) in the vertical direction and the horizontal direction to determine a third encoding unit (1314) having a size of N / 4xN / 2.

[0187] According to one embodiment, the image decoding device (100) may determine a third encoding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second encoding unit (1322) having a size of NxN / 2. That is, the image decoding device (100) may split the second encoding unit (1322) in the vertical direction to determine a third encoding unit (1304) having a size of N / 2xN / 2 or a third encoding unit (1314) having a size of N / 4xN / 2, or split the second encoding unit (1322) in the vertical direction and the horizontal direction to determine a third encoding unit (1324) having a size of N / 2xN / 4.

[0188] According to one embodiment, the image decoding device (100) may split a square-shaped encoding unit (e.g., 1300, 1302, 1304) in a horizontal direction or a vertical direction. For example, a first encoding unit (1300) having a size of 2Nx2N may be split in the vertical direction to determine a first encoding unit (1310) having a size of Nx2N, or may be split in the horizontal direction to determine a first encoding unit (1320) having a size of 2NxN. According to one embodiment, when the depth is determined based on the length of the longest side of the encoding unit, the depth of the encoding unit determined by splitting the first encoding unit (1300) having a size of 2Nx2N in the horizontal direction or the vertical direction may be the same as the depth of the first encoding unit (1300).

[0189] According to one embodiment, the width and height of the third coding unit (1314 or 1324) may be 1 / 4 times that of the first coding unit (1310 or 1320). When the depth of the first coding unit (1310 or 1320) is D, the depth of the second coding unit (1312 or 1322), which is 1 / 2 times the width and height of the first coding unit (1310 or 1320), may be D+1, and the depth of the third coding unit (1314 or 1324), which is 1 / 4 times the width and height of the first coding unit (1310 or 1320), may be D+2.

[0190] FIG. 14 illustrates an index (part index, hereinafter referred to as PID) for depth and encoding unit distinction that can be determined according to the shape and size of encoding units according to one embodiment.

[0191] According to one embodiment, the image decoding device (100) may split a first encoding unit (1400) having a square shape to determine second encoding units of various shapes. Referring to FIG. 14, the image decoding device (100) may split the first encoding unit (1400) in at least one of a vertical direction and a horizontal direction according to the split shape mode information to determine second encoding units (1402a, 1402b, 1404a, 1404b, 1406a, 1406b, 1406c, 1406d). That is, the image decoding device (100) can determine the second encoding unit (1402a, 1402b, 1404a, 1404b, 1406a, 1406b, 1406c, 1406d) based on the split shape mode information for the first encoding unit (1400).

[0192] According to one embodiment, the depth of the second coding units (1402a, 1402b, 1404a, 1404b, 1406a, 1406b, 1406c, 1406d) determined according to the split shape mode information for the first coding unit (1400) having a square shape may be determined based on the length of the long side. For example, since the length of one side of the first coding unit (1400) having a square shape and the length of the long side of the second coding unit (1402a, 1402b, 1404a, 1404b) having a non-square shape are the same, the depth of the first coding unit (1400) and the second coding units (1402a, 1402b, 1404a, 1404b) having a non-square shape may be considered to be the same as D. In contrast, when the image decoding device (100) divides the first encoding unit (1400) into four square-shaped second encoding units (1406a, 1406b, 1406c, 1406d) based on the split shape mode information, the length of one side of the square-shaped second encoding units (1406a, 1406b, 1406c, 1406d) is half the length of one side of the first encoding unit (1400), so the depth of the second encoding units (1406a, 1406b, 1406c, 1406d) may be a depth of D+1, which is one depth lower than D, the depth of the first encoding unit (1400).

[0193] According to one embodiment, the image decoding device (100) may split a first encoding unit (1410) having a height greater than its width into a plurality of second encoding units (1412a, 1412b, 1414a, 1414b, 1414c) in a horizontal direction according to the splitting shape mode information. According to one embodiment, the image decoding device (100) may split a first encoding unit (1420) having a width greater than its height into a plurality of second encoding units (1422a, 1422b, 1424a, 1424b, 1424c) in a vertical direction according to the splitting shape mode information.

[0194] According to one embodiment, the depth of the second coding unit (1412a, 1412b, 1414a, 1414b, 1414c. 1422a, 1422b, 1424a, 1424b, 1424c) determined based on the split shape mode information for the first coding unit (1410 or 1420) of a non-square shape may be determined based on the length of the long side. For example, since the length of one side of the second encoding unit (1412a, 1412b) in the shape of a square is half the length of one side of the first encoding unit (1410) in the shape of a non-square having a height longer than a width, the depth of the second encoding unit (1412a, 1412b) in the shape of a square is D+1, which is one depth lower than the depth D of the first encoding unit (1410) in the shape of a non-square.

[0195] Furthermore, the image decoding device (100) can split a non-square first encoding unit (1410) into an odd number of second encoding units (1414a, 1414b, 1414c) based on the split shape mode information. The odd number of second encoding units (1414a, 1414b, 1414c) can include non-square second encoding units (1414a, 1414c) and square second encoding units (1414b). In this case, since the length of the long side of the second encoding unit (1414a, 1414c) of a non-square shape and the length of one side of the second encoding unit (1414b) of a square shape are half the length of one side of the first encoding unit (1410), the depth of the second encoding unit (1414a, 1414b, 1414c) may be a depth of D+1, which is one depth lower than D, which is the depth of the first encoding unit (1410). The image decoding device (100) may determine the depth of the encoding units associated with the first encoding unit (1420) of a non-square shape, in which the width is longer than the height, in a manner corresponding to the above method of determining the depth of the encoding units associated with the first encoding unit (1410).

[0196] According to one embodiment, when determining an index (PID) for distinguishing divided coding units, the image decoding device (100) may determine the index based on a size ratio between the coding units when the coding units divided into an odd number are not of the same size. Referring to FIG. 14, among the coding units (1414a, 1414b, 1414c) divided into an odd number, the coding unit (1414b) located in the middle may have the same width as the other coding units (1414a, 1414c) but may have a height that is twice the height of the coding units (1414a, 1414c) that are different in height. That is, in this case, the coding unit (1414b) located in the middle may include two of the other coding units (1414a, 1414c). Accordingly, if the index (PID) of the encoding unit (1414b) located in the middle according to the scanning order is 1, the index of the encoding unit (1414c) located in the next order may be 3, which is an increase of 2. In other words, there may be a discontinuity in the index value. According to one embodiment, the image decoding device (100) may determine whether the encoding units divided into an odd number are not of the same size based on the presence or absence of discontinuity in the index for distinguishing between the divided encoding units.

[0197] According to one embodiment, the image decoding device (100) may determine whether the image is divided into a specific split shape based on the value of an index for distinguishing a plurality of coding units that are divided from the current coding unit. Referring to FIG. 14, the image decoding device (100) may divide a first coding unit (1410) having a rectangular shape in which the height is longer than the width, to determine an even number of coding units (1412a, 1412b) or an odd number of coding units (1414a, 1414b, 1414c). The image decoding device (100) may use an index (PID) indicating each coding unit to distinguish each of the plurality of coding units. According to one embodiment, the PID may be obtained from a sample (for example, an upper left sample) at a predetermined position of each coding unit.

[0198] According to one embodiment, the image decoding device (100) may determine an coding unit at a predetermined position among the coding units that are divided and determined using an index for distinguishing the coding units. According to one embodiment, when the split shape mode information for the first coding unit (1410) having a rectangular shape with a height longer than the width indicates that the first coding unit (1410) is divided into three coding units, the image decoding device (100) may divide the first coding unit (1410) into three coding units (1414a, 1414b, 1414c). The image decoding device (100) may assign an index to each of the three coding units (1414a, 1414b, 1414c). The image decoding device (100) may compare the indexes for each coding unit to determine the middle coding unit among the coding units divided into an odd number of coding units. The image decoding device (100) may determine a coding unit (1414b) having an index corresponding to a middle value among the indices of the coding units as a coding unit at a middle position among the coding units determined by splitting the first coding unit (1410). According to an embodiment, when determining an index for distinguishing the split coding units, the image decoding device (100) may determine the index based on a size ratio between the coding units when the coding units do not have the same size. Referring to FIG. 14, the coding unit (1414b) generated by splitting the first coding unit (1410) may have the same width as other coding units (1414a, 1414c) but may be twice the height of the coding units (1414a, 1414c) that are different in height. In this case, if the index (PID) of the encoding unit (1414b) located in the middle is 1, the index of the encoding unit (1414c) located in the next order may be 3, which is an increase of 2.In cases like this where the index increases uniformly and then the increase amount changes, the image decoding device (100) may determine that the current encoding unit is divided into a plurality of encoding units including encoding units having different sizes from other encoding units. According to one embodiment, when the split shape mode information indicates that the current encoding unit is divided into an odd number of encoding units, the image decoding device (100) may divide the current encoding unit into a form in which an encoding unit at a predetermined position among the odd number of encoding units (for example, a middle encoding unit) has a different size from the other encoding units. In this case, the image decoding device (100) may determine a middle encoding unit having a different size using an index (PID) for the encoding unit. However, the above-described index, the size or position of the encoding unit at the predetermined position to be determined are specific for explaining one embodiment and should not be interpreted as being limited thereto, and it should be interpreted that various indexes, positions and sizes of encoding units can be used.

[0199] According to one embodiment, the image decoding device (100) may utilize a predetermined data unit from which recursive division of the encoding unit begins.

[0200] FIG. 15 illustrates that a plurality of coding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment.

[0201] According to one embodiment, a predetermined data unit may be defined as a data unit from which a coding unit begins to be recursively split using split shape mode information. That is, it may correspond to a coding unit of the highest depth used in the process of determining multiple coding units for splitting the current picture. For convenience of explanation, this predetermined data unit will be referred to as a reference data unit hereinafter.

[0202] In one embodiment, the reference data unit may exhibit a predetermined size and shape. In one embodiment, the reference data unit may include MxN samples, where M and N may be the same and may be integers expressed as powers of 2. That is, the reference data unit may exhibit a square or non-square shape, and may be subsequently divided into an integer number of coding units.

[0203] According to one embodiment, the video decoding device (100) can divide the current picture into a plurality of reference data units. According to one embodiment, the video decoding device (100) can divide the plurality of reference data units into which the current picture is divided using division type mode information for each reference data unit. This division process of the reference data units can correspond to a division process using a quad-tree structure.

[0204] According to one embodiment, the image decoding device (100) may predetermine the minimum size that a reference data unit included in the current picture may have. Accordingly, the image decoding device (100) may determine reference data units of various sizes having a size greater than or equal to the minimum size, and may determine at least one encoding unit using segmentation mode information based on the determined reference data unit.

[0205] Referring to FIG. 15, the image decoding device (100) may use a reference coding unit (1500) having a square shape, or may use a reference coding unit (1502) having a non-square shape. According to one embodiment, the shape and size of the reference coding unit may be determined according to various data units (e.g., sequence, picture, slice, slice segment, tile, tile group, maximum coding unit, etc.) that may include at least one reference coding unit.

[0206] According to one embodiment, the bitstream acquisition unit (110) of the image decoding device (100) can acquire at least one of information on the shape of the reference coding unit and information on the size of the reference coding unit from the bitstream for each of the various data units. The process of determining at least one coding unit included in the square-shaped reference coding unit (1500) has been described above through the process of splitting the current coding unit (300) of FIG. 3, and the process of determining at least one coding unit included in the non-square-shaped reference coding unit (1502) has been described above through the process of splitting the current coding unit (400 or 450) of FIG. 4, so a detailed description thereof will be omitted.

[0207] According to one embodiment, the image decoding device (100) may use an index for identifying the size and shape of the reference coding unit to determine the size and shape of the reference coding unit according to some data units that are predetermined based on a predetermined condition. That is, the bitstream acquisition unit (110) may acquire only an index for identifying the size and shape of the reference coding unit for each slice, slice segment, tile, tile group, maximum coding unit, etc., among the various data units (e.g., sequences, pictures, slices, slice segments, tiles, tile groups, maximum coding units, etc.) that satisfy a predetermined condition (e.g., data units having a size smaller than a slice) from the bitstream. The image decoding device (100) may determine the size and shape of the reference data unit for each data unit that satisfies the predetermined condition by using the index. When information about the shape of the reference coding unit and information about the size of the reference coding unit are obtained from the bitstream for each relatively small-sized data unit and used, the efficiency of the bitstream may not be good. Therefore, instead of directly obtaining information about the shape of the reference coding unit and information about the size of the reference coding unit, only the index may be obtained and used. In this case, at least one of the size and shape of the reference coding unit corresponding to the index indicating the size and shape of the reference coding unit may be determined in advance. That is, the image decoding device (100) can determine at least one of the size and shape of the reference coding unit included in the data unit that serves as the basis for obtaining the index by selecting at least one of the sizes and shapes of the predetermined reference coding units according to the index.

[0208] According to one embodiment, the image decoding device (100) may use at least one reference coding unit included in one maximum coding unit. That is, a maximum coding unit for dividing an image may include at least one reference coding unit, and a coding unit may be determined through a recursive splitting process of each reference coding unit. According to one embodiment, at least one of the width and the height of the maximum coding unit may correspond to an integer multiple of at least one of the width and the height of the reference coding unit. According to one embodiment, the size of the reference coding unit may be a size obtained by splitting the maximum coding unit n times according to a quad tree structure. That is, the image decoding device (100) may split the maximum coding unit n times according to the quad tree structure to determine the reference coding unit, and may split the reference coding unit based on at least one of block shape information and split shape mode information according to various embodiments.

[0209] According to one embodiment, the video decoding device (100) may obtain and use block shape information indicating the shape of the current encoding unit or split shape mode information indicating a method of splitting the current encoding unit from the bitstream. The split shape mode information may be included in a bitstream related to various data units. For example, the video decoding device (100) may use split shape mode information included in a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a tile header, and a tile group header. Furthermore, the video decoding device (100) may obtain and use a syntax element corresponding to block shape information or split shape mode information from the bitstream for each maximum encoding unit and each reference encoding unit.

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

[0211] The video decoding device (100) can determine a segmentation rule of the video. The segmentation rule may be predetermined between the video decoding device (100) and the video encoding device (200). The video decoding device (100) can determine the segmentation rule of the video based on information obtained from a bitstream. The video decoding device (100) can determine the segmentation rule based on information obtained from at least one of a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a tile header, and a tile group header. The video decoding device (100) can determine the segmentation rule differently according to a frame, a slice, a tile, a temporal layer, a maximum coding unit, or an coding unit.

[0212] The image decoding device (100) can determine a segmentation rule based on the block shape of the encoding unit. The block shape can include the size, shape, width and height ratio, and direction of the encoding unit. The image encoding device (200) and the image decoding device (100) can determine in advance that the segmentation rule will be determined based on the block shape of the encoding unit. However, the present invention is not limited thereto. The image decoding device (100) can determine the segmentation rule based on information obtained from the bitstream received from the image encoding device (200).

[0213] The shape of the encoding unit may include a square and a non-square. If the width and height of the encoding unit are equal, the image decoding device (100) may determine the shape of the encoding unit as a square. In addition, if the width and height of the encoding unit are not equal, the image decoding device (100) may determine the shape of the encoding unit as a non-square.

[0214] The size of the coding unit may include various sizes such as 4x4, 8x4, 4x8, 8x8, 16x4, 16x8, ..., 256x256. The size of the coding unit may be classified according to the length of the long side, the length of the short side, or the area of ​​the coding unit. The image decoding device (100) may apply the same splitting rule to the coding units classified into the same group. For example, the image decoding device (100) may classify the coding units having the same long side length into the same size. In addition, the image decoding device (100) may apply the same splitting rule to the coding units having the same long side length.

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

[0216] The image decoding device (100) can adaptively determine a splitting rule based on the size of the encoding unit. The image decoding device (100) can determine a different allowable splitting mode based on the size of the encoding unit. For example, the image decoding device (100) can determine whether splitting is allowed based on the size of the encoding unit. The image decoding device (100) can determine a splitting direction based on the size of the encoding unit. The image decoding device (100) can determine an allowable splitting type based on the size of the encoding unit.

[0217] Determining the splitting rule based on the size of the encoding unit may be a splitting rule predetermined between the image encoding device (200) and the image decoding device (100). In addition, the image decoding device (100) may determine the splitting rule based on information obtained from the bitstream.

[0218] The image decoding device (100) can adaptively determine a segmentation rule based on the position of the encoding unit. The image decoding device (100) can adaptively determine a segmentation rule based on the position that the encoding unit occupies in the image.

[0219] Additionally, the image decoding device (100) can determine a splitting rule so that encoding units generated through different splitting paths do not have the same block shape. However, this is not limited thereto, and encoding units generated through different splitting paths may have the same block shape. Encoding units generated through different splitting paths may have different decoding processing orders. Since the decoding processing order has been described together with FIG. 12, a detailed description thereof will be omitted.

[0220] FIG. 16 illustrates encoding units that can be determined for each picture when the combination of forms into which encoding units can be divided is different for each picture according to one embodiment.

[0221] Referring to FIG. 16, the image decoding device (100) can determine a different combination of partitioning shapes into which encoding units can be partitioned for each picture. For example, the image decoding device (100) can decode an image using a picture (1600) that can be partitioned into four encoding units, a picture (1610) that can be partitioned into two or four encoding units, and a picture (1620) that can be partitioned into two, three, or four encoding units, among at least one picture included in the image. The image decoding device (100) can only use partitioning shape information indicating that the picture (1600) is partitioned into four square encoding units to partition the picture (1600) into a plurality of encoding units. The image decoding device (100) can only use partitioning shape information indicating that the picture (1610) is partitioned into two or four encoding units to partition the picture. The video decoding device (100) can only use the segmentation type information indicating that the picture (1620) is segmented into two, three, or four encoding units. The above-described combination of segmentation types is merely an example for explaining the operation of the video decoding device (100), and therefore the above-described combination of segmentation types should not be interpreted as being limited to the above-described example, but should be interpreted as being capable of using various combinations of segmentation types for each predetermined data unit.

[0222] According to one embodiment, the bitstream acquisition unit (110) of the image decoding device (100) can acquire a bitstream including an index indicating a combination of segmentation type information for each predetermined data unit (e.g., sequence, picture, slice, slice segment, tile, tile group, etc.). For example, the bitstream acquisition unit (110) can acquire an index indicating a combination of segmentation type information from a sequence parameter set, a picture parameter set, a slice header, a tile header, or a tile group header. The image decoding device (100) of the image decoding device (100) can determine a combination of segmentation types by which an encoding unit can be divided for each predetermined data unit using the acquired index, and thus can use different combinations of segmentation types for each predetermined data unit.

[0223] FIG. 17 illustrates various forms of encoding units that can be determined based on segmentation mode information that can be expressed in binary code according to one embodiment.

[0224] According to one embodiment, the image decoding device (100) can split an encoding unit into various shapes using block shape information and split shape mode information acquired through the bitstream acquisition unit (110). The shapes of the encoding unit that can be split may correspond to various shapes including the shapes described through the above-described embodiments.

[0225] Referring to FIG. 17, the image decoding device (100) can split a square-shaped encoding unit in at least one of the horizontal direction and the vertical direction based on the split shape mode information, and can split a non-square-shaped encoding unit in the horizontal direction or the vertical direction.

[0226] According to one embodiment, when the image decoding device (100) can divide a square-shaped encoding unit into four square encoding units by horizontally and vertically splitting the encoding unit, there may be four types of splitting modes that the splitting mode information for the square encoding unit can indicate. According to one embodiment, the splitting mode information may be expressed as a two-digit binary code, and a binary code may be assigned to each splitting mode. For example, when the encoding unit is not split, the splitting mode information may be expressed as (00)b, when the encoding unit is split in the horizontal direction and the vertical direction, the splitting mode information may be expressed as (01)b, when the encoding unit is split in the horizontal direction, the splitting mode information may be expressed as (10)b, and when the encoding unit is split in the vertical direction, the splitting mode information may be expressed as (11)b.

[0227] According to one embodiment, when the image decoding device (100) splits a non-square coding unit in a horizontal direction or a vertical direction, the type of split shape that the split shape mode information can indicate may be determined depending on the number of coding units into which the coding unit is split. Referring to FIG. 17, the image decoding device (100) may split a non-square coding unit into up to three according to one embodiment. The image decoding device (100) may split the coding unit into two coding units, in which case the split shape mode information may be expressed as (10)b. The image decoding device (100) may split the coding unit into three coding units, in which case the split shape mode information may be expressed as (11)b. The image decoding device (100) may determine not to split the coding unit, in which case the split shape mode information may be expressed as (0)b. That is, the image decoding device (100) can use variable length coding (VLC) rather than fixed length coding (FLC) to use a binary code representing segmentation mode information.

[0228] According to one embodiment, referring to FIG. 17, the binary code of the partition shape mode information indicating that the coding unit is not split may be expressed as (0)b. If the binary code of the partition shape mode information indicating that the coding unit is not split is set to (00)b, all binary codes of the 2-bit partition shape mode information must be used even if there is no partition shape mode information set to (01)b. However, as illustrated in FIG. 17, if three partition shapes for a non-square coding unit are used, the image decoding device (100) can determine that the coding unit is not split even if it uses a 1-bit binary code (0)b as the partition shape mode information, and thus can efficiently use the bitstream. However, the partition shapes of the non-square coding unit indicated by the partition shape mode information should not be interpreted as being limited to only the three shapes illustrated in FIG. 17, but should be interpreted as various shapes including the above-described embodiments.

[0229] FIG. 18 illustrates another form of a coding unit that can be determined based on segmentation mode information that can be expressed in binary code according to one embodiment.

[0230] Referring to FIG. 18, the image decoding device (100) can split a square-shaped encoding unit in the horizontal direction or the vertical direction based on the split shape mode information, and can split a non-square-shaped encoding unit in the horizontal direction or the vertical direction. That is, the split shape mode information can indicate that a square-shaped encoding unit is split in one direction. In this case, the binary code of the split shape mode information indicating that a square-shaped encoding unit is not split can be expressed as (0)b. If the binary code of the split shape mode information indicating that the encoding unit is not split is set to (00)b, all binary codes of the 2-bit split shape mode information must be used even though there is no split shape mode information set to (01)b. However, as illustrated in FIG. 18, if three types of division forms for a square-shaped encoding unit are used, the image decoding device (100) can determine that the encoding unit is not divided even if it uses a 1-bit binary code (0)b as the division form mode information, and thus can efficiently use the bitstream. However, the division forms of the square-shaped encoding unit indicated by the division form mode information should not be interpreted as being limited to only the three types illustrated in FIG. 18, but should be interpreted as various types including the embodiments described above.

[0231] In one embodiment, block shape information or segmentation shape mode information may be expressed using binary code, and such information may be directly generated as a bitstream. Furthermore, block shape information or segmentation shape mode information that may be expressed using binary code may not be directly generated as a bitstream, but may instead be used as a binary code input into CABAC (context adaptive binary arithmetic coding).

[0232] According to one embodiment, the image decoding device (100) describes a process of obtaining syntax for block shape information or segmentation shape mode information through CABAC. A bitstream including a binary code for the syntax can be obtained through a bitstream obtaining unit (110). The image decoding device (100) can detect a syntax element indicating block shape information or segmentation shape mode information by de-binarizing a bin string included in the obtained bitstream. According to one embodiment, the image decoding device (100) can obtain a set of binary bin strings corresponding to syntax elements to be decoded, and decode each bin using probability information, and the image decoding device (100) can repeat the process until a bin string composed of the decoded bins becomes equal to one of the previously obtained bin strings. The image decoding device (100) can determine syntax elements by performing inverse binarization of an empty string.

[0233] According to one embodiment, the image decoding device (100) may perform a decoding process of adaptive binary arithmetic coding to determine a syntax for a bin string, and the image decoding device (100) may update a probability model for bins acquired through the bitstream acquisition unit (110). Referring to FIG. 17, the bitstream acquisition unit (110) of the image decoding device (100) may acquire a bitstream representing a binary code representing segmentation mode information according to one embodiment. Using the acquired binary code having a size of 1 or 2 bits, the image decoding device (100) may determine a syntax for the segmentation mode information. In order to determine the syntax for the segmentation mode information, the image decoding device (100) may update a probability for each bit of the 2-bit binary code. That is, the image decoding device (100) can update the probability of having a value of 0 or 1 when decoding the next bin, depending on whether the value of the first bin among the 2-bit binary codes is 0 or 1.

[0234] According to one embodiment, the image decoding device (100) may, in the process of determining the syntax, update the probability for the bins used in the process of decoding the bins of the empty string for the syntax, and the image decoding device (100) may determine that certain bits among the empty strings have the same probability without updating the probability.

[0235] Referring to FIG. 17, in the process of determining a syntax using an empty string indicating split shape mode information for a non-square coding unit, the image decoding device (100) may determine the syntax for the split shape mode information using one bin having a value of 0 when the non-square coding unit is not split. That is, when the block shape information indicates that the current coding unit is a non-square shape, the first bin of the empty string for the split shape mode information may be 0 when the non-square coding unit is not split, and may be 1 when it is split into 2 or 3 coding units. Accordingly, the probability that the first bin of the empty string of the split shape mode information for the non-square coding unit is 0 may be 1 / 3, and the probability that it is 1 may be 2 / 3. As described above, the image decoding device (100) can only express a 1-bit empty string having a value of 0 for the partition shape mode information indicating that a non-square-shaped encoding unit is not partitioned, so the image decoding device (100) can determine the syntax for the partition shape mode information by determining whether the second bin is 0 or 1 only when the first bin of the partition shape mode information is 1. According to one embodiment, the image decoding device (100) can decode the bin by considering that the probability that the second bin is 0 or 1 when the first bin for the partition shape mode information is 1 is the same probability.

[0236] According to one embodiment, the image decoding device (100) may use various probabilities for each bin in the process of determining a bin of a bin string for the partition shape mode information. According to one embodiment, the image decoding device (100) may determine the probability of a bin for the partition shape mode information differently depending on the direction of a non-square block. According to one embodiment, the image decoding device (100) may determine the probability of a bin for the partition shape mode information differently depending on the area or the length of the long side of the current encoding unit. According to one embodiment, the image decoding device (100) may determine the probability of a bin for the partition shape mode information differently depending on at least one of the shape and the length of the long side of the current encoding unit.

[0237] According to one embodiment, the image decoding device (100) may determine that the bin probability for the segmentation shape mode information is the same for encoding units of a predetermined size or larger. For example, the bin probability for the segmentation shape mode information may be determined to be the same for encoding units of a size of 64 samples or larger based on the length of the long side of the encoding unit.

[0238] According to one embodiment, the image decoding device (100) may determine the initial probability for bins constituting the empty string of the segmentation shape mode information based on the slice type (e.g., I slice, P slice, or B slice).

[0239] Figure 19 is a block diagram of an image encoding and decoding system that performs loop filtering.

[0240] The encoding unit (1910) of the image encoding and decoding system (1900) transmits an encoded bitstream of an image, and the decoding unit (1950) receives the bitstream and decodes it to output a restored image. Here, the encoding unit (1910) may have a configuration similar to that of the image encoding device (200) described below, and the decoding unit (1950) may have a configuration similar to that of the image decoding device (100).

[0241] In the encoding unit (1910), the prediction encoding unit (1915) outputs prediction data through inter prediction and intra prediction, and the transformation and quantization unit (1920) outputs quantized transformation coefficients of residual data between the prediction data and the current input image. The entropy encoding unit (1925) encodes and transforms the quantized transformation coefficients and outputs them as a bitstream. The quantized transformation coefficients are restored to spatial domain data through the inverse quantization and inverse transformation unit (1930), and the restored spatial domain data are output as a restored image through the deblocking filtering unit (1935) and the loop filtering unit (1940). The restored image can be used as a reference image of the next input image through the prediction encoding unit (1915).

[0242] The encoded image data among the bitstreams received by the decoding unit (1950) is restored to residual data in the spatial domain through the entropy decoding unit (1955) and the inverse quantization and inverse transformation unit (1960). The prediction data and residual data output from the prediction decoding unit (1975) are combined to form image data in the spatial domain, and the deblocking filtering unit (1965) and the loop filtering unit (1970) can perform filtering on the image data in the spatial domain to output a restored image for the current original image. The restored image can be used as a reference image for the next original image by the prediction decoding unit (1975).

[0243] The loop filtering unit (1940) of the encoding unit (1910) performs loop filtering using filter information input according to user input or system settings. The filter information used by the loop filtering unit (1940) is output to the entropy encoding unit (1925) and transmitted to the decoding unit (1950) together with the encoded image data. The loop filtering unit (1970) of the decoding unit (1950) can perform loop filtering based on the filter information input from the decoding unit (1950).

[0244] The various embodiments described above describe operations related to the image decoding method performed by the image decoding device (100). Hereinafter, the operations of the image encoding device (200), which performs the image encoding method corresponding to the reverse process of the image decoding method, will be described through various embodiments.

[0245] FIG. 2 illustrates a block diagram of an image encoding device (200) capable of encoding an image based on at least one of block shape information and segmentation shape mode information according to one embodiment.

[0246] The video encoding device (200) may include an encoding unit (220) and a bitstream generation unit (210). The encoding unit (220) may receive an input image and encode the input image. The encoding unit (220) may encode the input image to obtain at least one syntax element. The syntax element may include at least one of a skip flag, a prediction mode, a motion vector difference, a motion vector prediction method (or index), a transform quantized coefficient, a coded block pattern, a coded block flag, an intra prediction mode, a direct flag, a merge flag, a delta QP, a reference index, a prediction direction, and a transform index. The encoding unit (220) may determine a context model based on block shape information including at least one of a shape, a direction, a ratio of width and height, or a size of an encoding unit.

[0247] The bitstream generation unit (210) can generate a bitstream based on an encoded input image. For example, the bitstream generation unit (210) can generate a bitstream by entropy encoding syntax elements based on a context model. In addition, the image encoding device (200) can transmit the bitstream to the image decoding device (100).

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

[0249] According to one embodiment, the encoding unit (220) can determine the shape into which the encoding unit is to be split. The encoding unit (220) can determine the shape of at least one encoding unit included in the encoding unit, and the bitstream generation unit (210) can generate a bitstream including split shape mode information including information about the shape of such encoding unit.

[0250] According to one embodiment, the encoder (220) may determine whether the encoding unit is split or not. If the encoder (220) determines that the encoding unit includes only one encoding unit or that the encoding unit is not split, the bitstream generation unit (210) may generate a bitstream including split shape mode information indicating that the encoding unit is not split. In addition, the encoder (220) may split the encoding unit into a plurality of encoding units, and the bitstream generation unit (210) may generate a bitstream including split shape mode information indicating that the encoding unit is split into a plurality of encoding units.

[0251] According to one embodiment, information indicating the number of encoding units to be split into or the direction in which the encoding unit is to be split may be included in the splitting mode information. For example, the splitting mode information may indicate splitting in at least one of the vertical and horizontal directions, or may indicate no splitting.

[0252] The video encoding device (200) determines information about the segmentation shape mode based on the segmentation shape mode of the encoding unit. The video encoding device (200) determines a context model based on at least one of the shape, direction, width, and height ratio or size of the encoding unit. Then, the video encoding device (200) generates information about the segmentation shape mode for segmenting the encoding unit based on the context model as a bitstream.

[0253] In order to determine a context model, the video encoding device (200) may obtain an array for matching at least one of the shape, direction, width and height ratio or size of the encoding unit with an index for the context model. The video encoding device (200) may obtain an index for the context model based on at least one of the shape, direction, width and height ratio or size of the encoding unit in the array. The video encoding device (200) may determine the context model based on the index for the context model.

[0254] The video encoding device (200) may further determine the context model based on block shape information including at least one of the shape, direction, width, and height ratio or size of a neighboring encoding unit adjacent to the encoding unit, in order to determine the context model. In addition, the neighboring encoding unit may include at least one of encoding units located on the lower left, left, upper left, upper right, right, or lower right of the encoding unit.

[0255] In addition, the video encoding device (200) may compare the length of the width of the upper peripheral encoding unit with the length of the width of the encoding unit to determine the context model. In addition, the video encoding device (200) may compare the length of the height of the left and right peripheral encoding units with the length of the height of the encoding unit. In addition, the video encoding device (200) may determine the context model based on the comparison results.

[0256] Since the operation of the video encoding device (200) includes similar contents to the operation of the video decoding device (100) described in FIGS. 3 to 19, a detailed description is omitted.

[0257] FIG. 20 is a block diagram illustrating the configuration of an image decoding device (2000) according to one embodiment.

[0258] Referring to FIG. 20, the image decoding device (2000) may include an acquisition unit (2010) and a prediction decoding unit (2030).

[0259] According to one embodiment, the acquisition unit (2010) and the prediction decoding unit (2030) may be implemented with at least one processor. In one embodiment, the acquisition unit (2010) and the prediction decoding unit (2030) may operate according to at least one instruction stored in at least one memory.

[0260] The image decoding device (2000) may include at least one memory for storing input / output data of the acquisition unit (2010) and the prediction decoding unit (2030). In addition, the image decoding device (2000) may include a memory control unit for controlling data input / output of at least one memory.

[0261] In one embodiment, the acquisition unit (2010) may correspond to the entropy decoding unit (1955) illustrated in FIG. 19, and the prediction decoding unit (2030) may correspond to the prediction decoding unit (1975) illustrated in FIG. 19.

[0262] The acquisition unit (2010) can acquire a bitstream generated as a result of encoding a picture. The bitstream can include an encoding result for a current block. The current block can be a maximum coding unit, coding unit, transformation unit, or prediction unit divided from the current picture to be decoded.

[0263] In one embodiment, the acquisition unit (2010) can receive a bitstream from an image encoding device over a network.

[0264] In one embodiment, the acquisition unit (2010) may acquire a bitstream from a data storage medium including a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape, an optical recording medium such as a CD-ROM and a DVD, a magneto-optical medium such as a floptical disk, and the like.

[0265] The acquisition unit (2010) can acquire syntax elements for decoding a picture from a bitstream. Values ​​corresponding to the syntax elements can be included in the bitstream according to the hierarchical structure of the picture.

[0266] The acquisition unit (2010) can obtain syntax elements by entropy decoding the bins included in the bitstream.

[0267] In one embodiment, the bitstream may include information regarding the prediction mode of the current block within the current picture. The prediction mode of the current block may be any one of a plurality of prediction modes, including an intra mode and an inter mode. As an example, the intra mode may include a template matching prediction mode.

[0268] In this disclosure, a method of generating a predictor based on template matching is referred to as template matching prediction. Template matching-based prediction may also be referred to as template matching prediction, template matching mode, template matching prediction mode, intra-template matching prediction, intra-template matching mode, or intra-template matching prediction mode.

[0269] Alternatively, in one embodiment, the prediction mode of the current block may be any one of a plurality of prediction modes including at least one of an intra mode, an inter mode, or a template matching prediction mode.

[0270] The prediction decoding unit (2030) can perform intra prediction or inter prediction on the current block according to the prediction mode of the current block to generate a prediction block of the current block, and restore the current block using the prediction block.

[0271] In one embodiment, the prediction decoding unit (2030) can determine a reference block of the current block within a search region by performing template matching when the prediction mode of the current block is a template matching prediction mode.

[0272] In one embodiment, the acquisition unit (2010) may acquire information about the intra prediction mode of the current block from the bitstream when the prediction mode of the current block is the intra mode. As an example, the information about the intra prediction mode may include information about the template matching prediction mode. As an example, the information about the template matching prediction mode may include information indicating whether the template matching prediction mode is applied. Alternatively, as an example, the information about the template matching prediction mode may include information specifying one of a plurality of template matching prediction modes. An embodiment thereof is described in detail below with reference to FIG. 25.

[0273] In one embodiment, information about the intra prediction mode may be included in a sequence parameter set, a picture parameter set, a slice header, or slice data of a bitstream. As an example, the slice data may include information signaled at the coding tree, coding unit, transform tree, or transform unit level.

[0274] When a prediction block is generated through intra prediction for the current block, the prediction decoding unit (2030) can obtain a restored current block using the prediction block.

[0275] In one embodiment, the prediction decoding unit (2030) can determine the prediction block as the restored current block.

[0276] In one embodiment, the prediction decoding unit (2030) can combine residual data obtained from the bitstream by the acquisition unit (2010) with the prediction block to generate a reconstructed current block.

[0277] In one embodiment, when template matching prediction is applied to a current block, a reference block within a predefined search area can be specified by performing template matching, and a prediction block for the current block can be generated using the specified reference block.

[0278] Hereinafter, with reference to FIGS. 21 to 27, the template matching prediction process performed for the current block is described in detail.

[0279] FIG. 21 is a diagram for explaining a template matching prediction method according to one embodiment.

[0280] Referring to FIG. 21, the image decoding device (2000) can generate a prediction block of the current block (2100) based on template matching.

[0281] In one embodiment, when template matching prediction is used, the image decoding device (2000) can generate a predictor of the current block (2100) on its own through a search process. In other words, the image decoding device (2000) can specify a reference block (2120) within a search area through a search process, and generate a prediction block (or prediction sample) of the current block (2100) using the specified reference block (2120).

[0282] The image decoding device (2000) can determine the reference block (2120) of the current block (2100) by comparing the template (2101) of the current block (2100) with the template (2121) of the reference block (2120) within the search area. As an example, the image decoding device (2000) can calculate a cost between the template (2101) of the current block (2100) and the template (2121) of the reference block (2120), and determine the reference block (2120) of the current block (2100) using the calculated cost. In the present disclosure, the cost (i.e., template matching cost) can be expressed as a difference between templates.

[0283] The video decoding device (2000) can determine a reference block (2120) of the current block (2100) through a differential comparison between templates. When template matching prediction is applied to the current block (2100), a candidate block that minimizes the differential can be determined as the reference block (2120) of the current block (2100). Alternatively, when template matching prediction is applied to the current block (2100), a predetermined number of candidate blocks that minimize the differential can be determined as the reference blocks (2120) of the current block (2100).

[0284] In the present disclosure, a candidate block may refer to a block having a template for which a differential comparison is performed with a template (2101) of the current block (2100) within a search area of ​​the current block (2100). In addition, in the present disclosure, a reference block may refer to a candidate block specified for prediction of the current block (2100) among the candidate blocks, or may collectively refer to all candidate blocks for which a differential comparison is performed.

[0285] In one embodiment, a search area for template matching prediction may be predefined. Furthermore, in one embodiment, multiple search areas for template matching prediction may be predefined. In this case, a search order among the multiple search areas may be predefined. The image decoding device (2000) may sequentially search the search areas according to the defined search order and determine a reference block having a template most similar to the template (2101) of the current block (2100).

[0286] In one embodiment, as illustrated in FIG. 21, the search area may include a first area (2130), a second area (2131), a third area (2132), and a fourth area (2133). The search area of ​​FIG. 21 is merely an example, and the search area for template matching prediction is not limited to the area illustrated in FIG. 21. In addition to the area illustrated in FIG. 21, additional areas may be included as search areas, and the area illustrated in FIG. 21 may be segmented in a manner different from that illustrated in FIG. 21.

[0287] In one embodiment, the first region (2130) may be an upper left region of the current block (2101) within the current coding tree unit (CTU) (2110) to which the current block (2101) belongs. Alternatively, the first region (2130) may be an region adjacent to the upper left of the template (2101) of the current block (2101) within the current CTU (2110) to which the current block (2101) belongs. Alternatively, the first region (2130) may be a surrounding region of the current block (2101) within the current coding tree unit (CTU) (2110) to which the current block (2101) belongs.

[0288] In one embodiment, a search order among the first region (2130), the second region (2131), the third region (2132), and the fourth region (2133) may be defined. In one embodiment, the second region (2131), the third region (2132), and the fourth region (2133) may be the upper left, upper, and left CTUs of the current CTU (2110), respectively. For example, candidate blocks or reference blocks may be searched in the order of the first region (2130), the second region (2131), the third region (2132), and the fourth region (2133). Alternatively, candidate blocks or reference blocks may be searched in the order of the first region (2130), the fourth region (2133), the third region (2132), and the second region (2131). Alternatively, candidate blocks or reference blocks may be searched in the order of the first area (2130), the third area (2132), the fourth area (2133), and the second area (2131).

[0289] In one embodiment, the image decoding device (2000) may determine a predetermined number of candidate blocks within each search area. As an example, a candidate list including a predetermined number of candidate blocks may be constructed. As an example, each candidate included in the candidate list may include a block vector indicating the respective candidate block. In the present disclosure, a block vector for specifying a candidate block or reference block used for template matching prediction may be referred to as a template matching block vector.

[0290] In one embodiment, the image decoding device (2000) may determine a predetermined number of candidate blocks with the smallest difference among the plurality of searched candidate blocks as reference blocks. As an example, the image decoding device (2000) may determine one candidate block with the smallest difference among the plurality of searched candidate blocks as a reference block. Alternatively, the image decoding device (2000) may determine a plurality of candidate blocks as reference blocks. An embodiment related to this will be described in detail below with reference to Mathematical Formula 4.

[0291] The video decoding device (2000) can search for a reference block (2120) having a template (2121) most similar to the template (2101) of the current block (2100) within the search area. The video decoding device (2000) can calculate a difference between the template (2101) of the current block (2100) and the template (2121) of the reference block (2120) to find a similar template. Generally, the sum of absolute difference (SAD) can be used as a method for calculating the difference.

[0292] In one embodiment, when SAD is used, the image decoding device (2000) may select a reference block (2120) having a template (2121) with the smallest SAD within the search area. In other words, when SAD is used, the image decoding device (2000) may determine a candidate block having a template (2121) that minimizes SAD within the search area as the reference block (2120).

[0293] In one embodiment, the template matching cost can be calculated based on various criteria (or cost functions). In other words, various metrics can be used to calculate the difference. For example, the difference can be calculated using the sum of squared error (SSE), mean-removed SAD (MR-SAD), or sum of absolute transformed difference (SATD) in addition to the aforementioned SAD. Alternatively, the difference can be calculated using partial SAD, which calculates the SAD for only a portion of the template.

[0294] Meanwhile, the reference block (2120) with the smallest SAD value cannot be considered the block most similar to the current block (2100) in any case. In addition, template matching prediction using SAD, which simply compares pixel values ​​in the spatial domain, may have lower prediction accuracy than template matching prediction, which compares coefficient values ​​in the frequency domain.

[0295] In this disclosure, we propose a prediction method that performs template matching in the frequency domain, which can increase the accuracy of prediction while considering a wider variety of predictors in prediction, taking these points into account.

[0296] In the frequency domain, low-frequency components represent areas where pixel values ​​differ little from the surrounding area, while high-frequency components represent areas where pixel values ​​differ greatly from the surrounding area. Low-frequency components represent broad areas, such as the overall information of the image, while high-frequency components represent detailed areas, including corners or boundaries with significant changes.

[0297] Hereinafter, a template matching prediction method considering the characteristics according to the above-described frequency band is described with reference to FIGS. 22 to 25. As an example, template matching prediction can be performed based on a template converted into the frequency domain.

[0298] By performing template matching prediction considering the characteristics according to the above-described frequency band, the accuracy of prediction can be increased, and compression efficiency can be improved by considering a wider variety of predictors in the prediction.

[0299] FIG. 22 is a diagram for explaining a template matching prediction method using a converted template according to one embodiment.

[0300] Referring to FIG. 22, the image decoding device (2000) can determine a reference block by performing a differential comparison using templates (2220, 2221) converted to the frequency domain. In FIG. 22, only the transformation for the templates (2210, 2211) of the current block (2100) is shown, but the transformation for the template of the candidate block (or reference block) of the current block (2100) can also be performed in the same manner. That is, the template of the candidate block corresponding to the templates (2210, 2211) of the current block (2100) can be transformed in the same manner as the templates (2210, 2211) of the current block (2100), so that the transformed template can be determined.

[0301] Specifically, the image decoding device (2000) can obtain a transformed template (2220, 2221) of the current block and a transformed template of the candidate block by performing transformation on the template (2210, 2211) of the current block (2100) and the template of the candidate block, respectively.

[0302] In one embodiment, the template (2210, 2211) of the current block (2100) may include at least one of the left template (2210) or the upper template (2211). The template of the candidate block may be determined as an area corresponding to the template (2210, 2211) of the current block. The transformed template (2220, 2221) of the current block may include at least one of the left transformed template (2220) or the upper transformed template (2221).

[0303] The image decoding device (2000) can determine a left transformed template (2220) by performing a transformation on the left template (2210), and can determine an upper transformed template (2221) by performing a transformation on the upper template (2211).

[0304] In one embodiment, the image decoding device (2000) can perform a differential comparison between the transformed templates (2220, 2221) of the current block and the transformed templates of the candidate block. By performing the differential comparison in the frequency domain, a more sophisticated predictor can be obtained compared to the SAD-based template matching prediction that calculates the differential in the spatial domain described in the embodiment of FIG. 21 above.

[0305] In one embodiment, the image decoding device (2000) can obtain a transformed template (2220, 2221) of the current block (2100) in the frequency domain by performing a transformation on the template (2210, 2211) of the current block (2100) in the spatial domain using a predefined transformation. Similarly, the image decoding device (2000) can obtain a transformed template of the candidate block in the frequency domain by performing a transformation on the template of the candidate block in the spatial domain using a predefined transformation.

[0306] In one embodiment, various transforms (or transform kernels, transform types, and transform matrices) may be defined for the transformation. For example, the predefined transforms may include at least one of a Hadamard transform, a Discrete Cosine Transform (DCT)-based transform, a Discrete Sine Transform (DST)-based transform, a Discrete Fourier transform (DFT)-based transform, a Wavelet Transform, or a Karhunen-Löve Transform (KLT).

[0307] In one embodiment, the image decoding device (2000) can determine a reference block of the current block (2100) among candidate blocks by performing a differential comparison between the transformed templates (2220, 2221) of the current block (2100) and the transformed templates of the candidate blocks. As an example, for the differential comparison, the sum of the absolute values ​​of the differences between the transform coefficients of the transformed templates (2220, 2221) of the current block (2100) and the transform coefficients of the transformed templates of the candidate blocks can be calculated.

[0308] In one embodiment, in calculating the difference between the transformed templates of the current block (2100) and the candidate block, the image decoding device (2000) may add the sum of the absolute values ​​of the differences between the left transformed template (2220) of the current block (2100) and the left transformed template of the candidate block and the sum of the absolute values ​​of the differences between the upper transformed template (2221) of the current block (2100) and the upper transformed template of the candidate block. That is, calculation of the difference between the transformed templates of the candidate block corresponding to the transformed templates (2220, 2221) of the current block (2100) may be performed.

[0309] Meanwhile, considering the characteristics according to the aforementioned frequency band, a region in which differential calculation (or differential comparison) is performed can be defined. That is, the difference can be calculated between predetermined regions within the transformed template or between predetermined transform coefficients.

[0310] In one embodiment, a differential calculation is performed considering only a predetermined frequency band, and a reference block can be determined among candidate blocks based on the calculated differential. In other words, an area corresponding to a predetermined frequency band can be predefined within the transformed template, and the differential between the transform coefficients contained in that area can be calculated.

[0311] In one embodiment, a region corresponding to a low-frequency band (or low-frequency component) within a transformed template may be defined as the region for which a difference is calculated. Alternatively, as an example, a difference between a specific region in the upper left corner of the transformed template may be calculated. For example, if the size of the transformed template is WxH, a cost comparison may be performed between the MxN regions in the upper left corner of the transformed template. In this case, W >= M and H >= N may be satisfied.

[0312] In one embodiment, only a predetermined number of transform coefficients within the transformed template may be used for the differential comparison between templates. For example, a predetermined number of transform coefficients determined according to a predefined scan order starting from the upper left of the transformed template may be used for the differential comparison. For example, the scan order may include at least one of a z-scan order, a raster scan order, a zig-zag scan order, an up-right diagonal scan order, a horizontal scan order, or a vertical scan order.

[0313] Additionally, in one embodiment, a search area may be predefined. The search area may be defined as multiple areas. Reference blocks may be sequentially searched according to a defined search order among the multiple search areas. In this case, the embodiment described above in FIG. 21 may be applied, and any redundant descriptions related thereto will be omitted.

[0314] Meanwhile, in performing template matching prediction using a transformed template, candidate blocks within the search area can be determined (or searched) in a variety of ways.

[0315] In one embodiment, the image decoding device (2000) can determine all blocks corresponding to the current block (2100) in units of one pixel within the search area as candidate blocks. The image decoding device (2000) can perform transformation on the template of the candidate block while moving in units of pixels, and perform template matching prediction using the transformed template.

[0316] In one embodiment, the image decoding device (2000) may determine a candidate block in units of 1 pixel from the upper left initial position within the search area. As an example, the upper left initial position may be determined based on the height of the upper template and the width of the left template. For example, when the upper left pixel position of the search area is (0, 0), the height of the upper template is H, and the width of the left template is W, the upper left initial position may be (W, H). Alternatively, as an example, the upper left initial position may be the upper left pixel position of the search area.

[0317] However, the above-described embodiment may increase complexity as transformations are required for all possible blocks within the search area on a pixel-by-pixel basis. Considering this point, embodiments of determining candidate blocks for template matching prediction in the frequency domain are described below.

[0318] In one embodiment, a candidate block may be searched for in units of a predetermined number of pixels within the search area. In other words, the position of the candidate block within the search area may be determined in units of a predetermined number of pixels. For example, the predetermined number may be 2, 4, 8, 16, or 64. For example, the candidate block may be determined at distances of 2, 4, 8, 16, or 64 pixels in the horizontal / vertical direction from the initial position at the upper left within the search area. As an example, the initial position at the upper left may be determined based on the height of the upper template and the width of the left template. For example, when the initial position at the upper left of the search area is (0, 0), the height of the upper template is H, and the width of the left template is W, the initial position at the upper left may be (W, H). Or, as an example, the initial position at the upper left may be the initial position at the upper left of the search area.

[0319] In one embodiment, candidate blocks may be selected based on template matching predictions in the spatial domain within the search region. In this case, the embodiment described above in FIG. 21 may be applied. For example, the image decoding device (2000) may determine multiple candidate blocks by performing template matching predictions in the spatial domain.

[0320] In one embodiment, the number of candidate blocks determined by template matching prediction in the spatial domain may be predefined. As an example, a candidate list including a predetermined number of candidate blocks may be constructed. Each candidate included in the candidate list may include a block vector indicating the candidate block.

[0321] In one embodiment, template matching prediction in the spatial domain can be performed based on SAD, i.e., a predetermined number of candidate blocks with the smallest SAD values ​​within the search region can be determined.

[0322] The image decoding device (2000) can determine a plurality of candidate blocks by template matching prediction in the spatial domain, and perform template matching prediction in the frequency domain based on the determined plurality of candidate blocks. The image decoding device (2000) can determine the transformed template of each candidate block by performing transformation on the template of the determined candidate blocks.

[0323] The image decoding device (2000) can compare the transformed template of the current block (2100) with the transformed template of each of a plurality of candidate blocks, and determine a reference block of the current block (2100) from among the plurality of candidate blocks based on the result of the comparison. That is, the image decoding device (2000) can determine a candidate block having a transformed template that is most similar to the transformed template of the current block (2100) from among the plurality of candidate blocks as the reference block of the current block (2100).

[0324] FIG. 23 is a diagram for explaining template matching prediction using a transformed sub-template according to one embodiment.

[0325] Referring to FIG. 23, the image decoding device (2000) can perform template matching prediction in the frequency domain in units of sub-templates (2321, 2322) divided from the transformed template (2310) by considering characteristics according to frequency components. In other words, the image decoding device (2000) can perform differential comparison in units of sub-templates (2321, 2322) to determine a candidate block having a sub-template most similar to each sub-template (2321, 2322) as a reference block.

[0326] In one embodiment, the template (2300) illustrated in FIG. 23 may be a template of the current block (2100) or a template of a candidate block (or reference block). The transformed template of the candidate block corresponding to the transformed template of the current block (2100) may have the same sub-template division structure.

[0327] In one embodiment, the image decoding device (2000) can determine a plurality of reference blocks by performing a differential comparison between the corresponding sub-templates in the current block (2100) and the candidate blocks. The image decoding device (2000) can determine two candidate blocks having sub-templates that minimize the differential with each of the sub-templates (2321, 2322) of the current block (2100) as reference blocks of the current block. In addition, the image decoding device (2000) can generate a prediction block of the current block (2100) through a weighted sum of the determined plurality of reference blocks.

[0328] In one embodiment, the image decoding device (2000) can obtain a transformed template (2310) by transforming the template (2300) of the current block (2100). The image decoding device (2000) can divide the transformed template (2310) into a first sub-template (2321) and a second sub-template (2322) by considering the frequency band (or frequency component). The image decoding device (2000) can obtain an optimal predictor for each frequency band by performing a differential comparison based on the transform coefficients included in each of the first sub-template (2321) and the second sub-template (2322), and can improve the accuracy of the prediction by using a wider variety of predictors for the prediction.

[0329] In one embodiment, the image decoding device (2000) can obtain a first sub-template (2321) and a second sub-template (2322) by vertically dividing the transformed template (2310) into two, as illustrated in FIG. 23. As an example, the first sub-template (2321) may be an area including low-frequency components, and the second sub-template (2322) may be an area including high-frequency components.

[0330] In one embodiment, the first sub-template (2321) may include transform coefficients having a relatively lower frequency than the transform coefficients included in the second sub-template (2322). As an example, the first sub-template (2321) may include transform coefficients corresponding to a first frequency band, and the second sub-template (2322) may include transform coefficients corresponding to a second frequency band. In this case, the first frequency band may be a lower frequency band than the second frequency band.

[0331] In one embodiment, the image decoding device (2000) can obtain two reference blocks through differential comparison between the current block (2100) and the corresponding sub-templates in the candidate block.

[0332] In one embodiment, the image decoding device (2000) may determine a candidate block having a first sub-template (2321) that minimizes the difference between the first sub-templates (2321) as a first reference block. That is, a candidate block having a first sub-template (2321) that is most similar to the first sub-template (2321) of the current block (2100) may be determined as the first reference block.

[0333] Additionally, in one embodiment, the image decoding device (2000) may determine a candidate block having a second sub-template (2322) that minimizes the difference between the second sub-templates (2322) as a second reference block. A candidate block having a second sub-template (2322) that is most similar to the second sub-template (2322) of the current block (2100) may be determined as the second reference block.

[0334] In one embodiment, the image decoding device (2000) can generate a prediction block of the current block (2100) by weighting the first reference block and the second reference block.

[0335] The segmentation of the transformed template (2310) illustrated in FIG. 23 can be performed on the transformed template (2310) of the current block (2100) and the corresponding transformed template (2310) of the candidate block. In addition, as an example, the transformed template (2310) may be the left transformed template (2310) of the current block (2100) and the candidate block, or may be the upper transformed template (2310).

[0336] In Fig. 23, the case where the converted template (2310) is vertically divided into two is mainly described, but this is not limited thereto. Even when the converted template (2310) is horizontally divided into two, a differential comparison between corresponding sub-templates can be performed in substantially the same manner.

[0337] In one embodiment, when divided into two in the horizontal direction, the transformed template (2310) may be divided into an upper sub-template and a lower sub-template. At this time, the upper sub-template may be a region including low-frequency components, and the lower sub-template may be a region including high-frequency components. As an example, the upper sub-template may include transform coefficients having a relatively lower frequency than transform coefficients included in the lower sub-template. The upper sub-template may include transform coefficients corresponding to a first frequency band, and the lower sub-template may include transform coefficients corresponding to a second frequency band. At this time, the first frequency band may be a lower frequency band than the second frequency band.

[0338] In one embodiment, when divided into two in the horizontal direction, the upper sub-template may correspond to the first sub-template (2321) when divided into two in the vertical direction, and the lower sub-template may correspond to the second sub-template (2322) when divided into two in the vertical direction.

[0339] In one embodiment, a split direction (or split structure) for the left and upper transformed templates (2310) may be defined. As an example, the split directions for the left and upper transformed templates (2310) may be the same. For example, both the left and upper transformed templates (2310) may be split in two in the vertical direction, as illustrated in FIG. 23 . Alternatively, both the left and upper transformed templates (2310) may be split in two in the horizontal direction.

[0340] Additionally, in one embodiment, the left and top transformed templates (2310) may be split in different directions. For example, the left transformed template (2310) may be split horizontally, and the top transformed template (2310) may be split vertically. Alternatively, for example, the top transformed template (2310) may be split vertically, and the top transformed template (2310) may be split horizontally.

[0341] In one embodiment, when the left and upper transformed templates (2310) are each divided into two sub-templates, differential comparison may be performed in units of sub-template sets including corresponding sub-templates in the left and upper transformed templates (2310). That is, the image decoding device (2000) may obtain two reference blocks through differential comparison between the current block (2100) and the corresponding sub-template sets in the candidate blocks. The sub-template sets may include sub-templates in the left and upper transformed templates (2310), as follows.

[0342] For example, if the left and top transformed templates (2310) are equally vertically divided, the first sub-template set may include the first sub-template (2321) of the left and top transformed templates (2310), and the second sub-template set may include the second sub-template (2322) of the left and top transformed templates (2310).

[0343] For example, if the left and top transformed templates (2310) are equally divided in the horizontal direction, the first sub-template set may include the top sub-templates of the left and top transformed templates (2310), and the second sub-template set may include the bottom sub-templates of the left and top transformed templates (2310).

[0344] For example, if the left transformed template (2310) is split horizontally and the upper transformed template (2310) is split vertically, the first sub-template set may include the upper sub-template of the left transformed template (2310) and the first sub-template (2321) of the upper transformed template (2310), and the second sub-template set may include the lower sub-template of the left transformed template (2310) and the second sub-template (2322) of the upper transformed template (2310).

[0345] In addition, although FIG. 23 assumes that the transformed template (2310) is symmetrically divided into two, it is not limited thereto. It may also be asymmetrically divided into two considering the positions of the transformation coefficients according to the frequency band. For example, the ratio of the width of the first sub-template (2321) to the width of the second sub-template (2322) may be 1:3.

[0346] The video decoding device (2000) can generate a prediction block of the current block (2100) through a weighted sum of the first reference block and the second reference block. At this time, the prediction block of the current block (2100) can be generated using the following mathematical expression 1.

[0347]

[0348] Referring to mathematical expression 1, the predicted sample (P) of the current sample in the current block (2100) is a sample (RB) corresponding to the current sample in the first reference block. f1 ) and a sample corresponding to the current sample in the second reference block (RB f2 ) can be obtained by a weighted sum. w1 represents a first weight applied to a sample in a first reference block, and w2 represents a second weight applied to a sample in a second reference block.

[0349] As an example, the first weight and the second weight may be 1. That is, the prediction block of the current block (2100) may be generated by averaging the first reference block and the second reference block.

[0350] Alternatively, as an example, the first weight and the second weight may be predefined fixed values, or may be values ​​determined based on encoding information of the current block (2100). The encoding information may include a search area to which the reference block to which the weight is applied belongs, the position / size of the sub-template, the division structure of the sub-template, a frequency band corresponding to the sub-template, etc.

[0351] FIG. 24 is a diagram for explaining template matching prediction using a transformed sub-template according to one embodiment.

[0352] Referring to FIG. 24, the image decoding device (2000) can perform template matching prediction in the frequency domain in units of sub-templates (2421, 2422, 2423, 2424) divided from the transformed template (2410) by considering characteristics according to frequency components. In other words, the image decoding device (2000) can perform differential comparison in units of sub-templates (2421, 2422, 2423, 2424), thereby determining a candidate block having a sub-template most similar to each sub-template (2421, 2422, 2423, 2424) as a reference block.

[0353] In one embodiment, the template (2400) illustrated in FIG. 24 may be a template of the current block (2100) or a template of a candidate block (or reference block). The transformed template of the candidate block corresponding to the transformed template of the current block (2100) may have the same sub-template division structure.

[0354] In one embodiment, the image decoding device (2000) can determine a plurality of reference blocks by performing a differential comparison between the corresponding sub-templates in the current block (2100) and the candidate blocks. The image decoding device (2000) can determine four candidate blocks having sub-templates that minimize the differential with each of the sub-templates (2421, 2422, 2423, 2424) of the current block (2100) as reference blocks of the current block. In addition, the image decoding device (2000) can generate a prediction block of the current block (2100) through a weighted sum of the determined plurality of reference blocks.

[0355] In one embodiment, the image decoding device (2000) can obtain a transformed template (2410) by transforming the template (2400) of the current block (2100). The image decoding device (2000) can divide the transformed template (2410) into a first sub-template (2421), a second sub-template (2422), a third sub-template (2423), and a fourth sub-template (2424) by considering the frequency band (or frequency component). The image decoding device (2000) can obtain an optimal predictor for each frequency band by performing a differential comparison based on the transform coefficients included in each of the first sub-template (2421), the second sub-template (2422), the third sub-template (2423), and the fourth sub-template (2424), and can improve the accuracy of the prediction by using a wider variety of predictors for the prediction.

[0356] In one embodiment, the image decoding device (2000) may obtain a first sub-template (2421), a second sub-template (2422), a third sub-template (2423), and a fourth sub-template (2424) by dividing the transformed template (2410) into four in the vertical and horizontal directions, as illustrated in FIG. 24. As an example, the first sub-template (2421), the second sub-template (2422), the third sub-template (2423), and the fourth sub-template (2424) may include transform coefficients having relatively low frequencies in that order.

[0357] As an example, a first sub-template (2421) may include transform coefficients corresponding to a first frequency band, a second sub-template (2422) may include transform coefficients corresponding to a second frequency band, a third sub-template (2423) may include transform coefficients corresponding to a third frequency band, and a fourth sub-template (2424) may include transform coefficients corresponding to a fourth frequency band. In this case, the lowest frequency band may be assigned to the first frequency band, and higher frequency bands may be sequentially assigned up to the fourth frequency band. As an example, the first sub-template (2421) may be an area including low-frequency components, and the fourth sub-template (2424) may be an area including high-frequency components.

[0358] In one embodiment, the image decoding device (2000) can obtain four reference blocks through differential comparison between the current block (2100) and the corresponding sub-templates in the candidate blocks.

[0359] In one embodiment, the image decoding device (2000) may determine a candidate block having a first sub-template (2421) that minimizes the difference between the first sub-templates (2421) as a first reference block. That is, a candidate block having a first sub-template (2421) that is most similar to the first sub-template (2421) of the current block (2100) may be determined as the first reference block.

[0360] Additionally, in one embodiment, the image decoding device (2000) may determine a candidate block having a second sub-template (2422) that minimizes the difference between the second sub-templates (2422) as a second reference block. A candidate block having a second sub-template (2422) that is most similar to the second sub-template (2422) of the current block (2100) may be determined as the second reference block.

[0361] Additionally, in one embodiment, the image decoding device (2000) may determine a candidate block having a third sub-template (2423) that minimizes the difference between the third sub-templates (2423) as a third reference block. A candidate block having a third sub-template (2423) that is most similar to the third sub-template (2423) of the current block (2100) may be determined as the third reference block.

[0362] Additionally, in one embodiment, the image decoding device (2000) may determine a candidate block having a fourth sub-template (2424) that minimizes the difference between the fourth sub-templates (2424) as a fourth reference block. A candidate block having a fourth sub-template (2422) that is most similar to the second sub-template (2424) of the current block (2100) may be determined as the fourth reference block.

[0363] In one embodiment, the image decoding device (2000) can generate a prediction block of the current block (2100) by weighting the first reference block to the fourth reference block.

[0364] The segmentation of the transformed template (2410) illustrated in FIG. 24 can be performed on the transformed template (2410) of the current block (2100) and the corresponding transformed template (2410) of the candidate block. In addition, as an example, the transformed template (2410) may be the left transformed template (2410) of the current block (2100) and the candidate block, or may be the upper transformed template (2410).

[0365] In one embodiment, when the left and upper transformed templates (2410) are each divided into four sub-templates, differential comparison may be performed in units of sub-template sets including corresponding sub-templates in the left and upper transformed templates (2410). That is, the image decoding device (2000) may obtain four reference blocks through differential comparison between the current block (2100) and the corresponding sub-template sets in the candidate blocks. The sub-template sets may include sub-templates in the left and upper transformed templates (2310), as follows.

[0366] For example, a first sub-template set may include a first sub-template (2421) of the left and top transformed template (2410), a second sub-template set may include a second sub-template (2422) of the left and top transformed template (2410), a third sub-template set may include a third sub-template (2423) of the left and top transformed template (2410), and a fourth sub-template set may include a fourth sub-template (2424) of the left and top transformed template (2410).

[0367] In addition, although FIG. 24 assumes that the transformed template (2410) is symmetrically divided into four, it is not limited thereto. It may also be asymmetrically divided into four considering the positions of the transformation coefficients according to the frequency band. For example, the ratio of the width of the first sub-template (2421) to the width of the second sub-template (2422) may be 1:3, and the ratio of the height of the first sub-template (2421) to the height of the third sub-template (2423) may be 1:3.

[0368] The video decoding device (2000) can generate a prediction block of the current block (2100) through a weighted sum of the first to fourth reference blocks. At this time, the following mathematical expression 2 can be applied.

[0369]

[0370] In mathematical expression 2, RB f1 represents the first reference block, and RB f2 represents the second reference block, and RB f3 represents the third reference block, and RB f4 represents a fourth reference block. w1 represents a first weight applied to the first reference block, w2 represents a second weight applied to the second reference block, w3 represents a third weight applied to the third reference block, and w4 represents a fourth weight applied to the fourth reference block.

[0371] As an example, the first to fourth weights may be 1. That is, the prediction block of the current block (2100) may be generated by averaging the first to fourth reference blocks.

[0372] Alternatively, as an example, the first to fourth weights may be predefined fixed values, or may be values ​​determined based on encoding information of the current block (2100). The encoding information may include a search area to which the reference block to which the corresponding weight is applied belongs, the position / size of the sub-template, the division structure of the sub-template, a frequency band corresponding to the sub-template, etc.

[0373] Meanwhile, the division of the transformed templates (2310, 2410) described in FIGS. 23 and 24 is not limited to the above-described embodiments, and may be performed in various other ways. For example, the transformed template of the current block (2100) may be divided uniformly or non-uniformly. The transformed template of the candidate block may be divided into the same structure as the transformed template of the current block (2100).

[0374] In one embodiment, the image decoding device (2000) may non-uniformly divide the converted template into an upper left region and a remaining region. The converted template may be divided into a first sub-template including the upper left region and a second sub-template including the remaining region excluding the upper left region. As an example, the first sub-template may include the first sub-template (2421) of FIG. 24. The second sub-template may include the second to fourth sub-templates (2422, 2423, 2424) of FIG. 24.

[0375] Additionally, in one embodiment, the image decoding device (2000) may divide regions in order from the low frequency within the transformed template. For example, a first sub-template may be determined as a region including a predetermined number of transform coefficients from the low frequency, and a second sub-template may be determined as a region including the remaining transform coefficients. At this time, the region division of the transform coefficients may be determined according to a predefined scan order. For example, the scan order may include at least one of a z-scan order, a raster scan order, a zig-zag scan order, an up-right diagonal scan order, a horizontal scan order, or a vertical scan order.

[0376] Additionally, in one embodiment, the image decoding device (2000) may not perform a search for a specific frequency band during the process of dividing the transformed template to determine a sub-template. For example, the image decoding device (2000) may not perform a differential comparison for the second sub-template (2422) or the third sub-template (2423) of FIG. 24. That is, the reference block (i.e., the second reference block or the third reference block) may not be acquired based on the second sub-template (2422) or the third sub-template (2423).

[0377] In one embodiment, the image decoding device (2000) may set the transform coefficient corresponding to a specific frequency band to 0 so as not to perform a search for the specific frequency band. For example, the image decoding device (2000) may set the transform coefficient included in the second sub-template (2422) or the third sub-template (2423) of FIG. 24 to 0.

[0378] The above described embodiments perform template matching prediction based on differential comparisons between specific regions or specific frequency bands of templates converted to the frequency domain. According to the above-described embodiments, template matching prediction can be performed while considering characteristics according to frequency bands, thereby improving prediction accuracy.

[0379] Meanwhile, even when obtaining a predicted block from a reference block, considering characteristics according to frequency bands can improve compression efficiency by allowing for a wider variety of predictors to be considered in the prediction. Below, a method for generating a predicted block using a reference block in the frequency domain, taking into account characteristics according to frequency bands, is described.

[0380] FIG. 25 is a diagram illustrating a process of generating a prediction block by combining transformed reference blocks according to one embodiment.

[0381] Referring to FIG. 25, the image decoding device (2000) performs transformation on reference blocks (2510, 2520) to obtain transformed reference blocks (2511, 2521), and within the transformed reference blocks, generates a prediction block of the current block (2100) based on an area corresponding to a sub-template used for determining each reference block (i.e., a first area (2512) and a second area (2522) as hatched areas in FIG. 25).

[0382] Specifically, the image decoding device (2000) can obtain a transformed first reference block (2511) and a transformed second reference block (2521) by transforming the first reference block (2510) and the second reference block (2520), respectively. The image decoding device (2000) can combine regions (i.e., the hatched regions in FIG. 25, the first region (2512) and the second region (2522)) corresponding to the sub-templates used for differential comparison within the transformed first reference block (2511) and the transformed second reference block (2521). The image decoding device (2000) can generate a prediction block of the current block (2100) by performing an inverse transformation on the combined regions.

[0383] In one embodiment, the region corresponding to the sub-template used for the differential comparison may be a region including transform coefficients corresponding to the frequency band of the sub-template used for the differential comparison.

[0384] In Fig. 25, it is assumed that the converted first reference block (2511) and the converted second reference block (2521) are vertically divided into two, but this is not limited thereto, and the converted reference blocks (2511, 2521) may be divided into a structure corresponding to the division structure of the converted template.

[0385] In one embodiment, the image decoding device (2000) may determine a first reference block (2510) and a second reference block (2520). At this time, the method described above in FIG. 23 may be applied. If the transformed template is divided into four parts, four reference blocks may be determined. In this case, the method described above in FIG. 24 may be applied.

[0386] FIG. 25 assumes a case where a first reference block (2510) is obtained through a differential comparison between the current block (2100) and the first sub-template (2321) of the candidate block, as described in FIG. 23 described above, and a second reference block (2520) is obtained through a differential comparison between the current block (2100) and the second sub-template (2322) of the candidate block. In this case, the first area (2512) in the transformed first reference block (2511) may be an area corresponding to the first sub-template (2321), and the second area (2522) in the transformed second reference block (2521) may be an area corresponding to the second sub-template (2322).

[0387] In one embodiment, the image decoding device (2000) can obtain a combined reference block (2530) by combining a first region (2512) within a transformed first reference block (2511) and a second region (2522) within a transformed second reference block (2521).

[0388] In one embodiment, the location of the first region (2512) within the combined reference block (2530) may correspond to the location of the first sub-template (2321) within the transformed template (2310). That is, the first region (2512) may be located on the left within the combined reference block (2530).

[0389] Similarly, the location of the second region (2522) within the combined reference block (2530) may correspond to the location of the second sub-template (2322) within the transformed template (2310). That is, the second region (2522) may be located on the right within the combined reference block (2530).

[0390] In one embodiment, the image decoding device (2000) can derive an inversely transformed reference block (2540) by performing an inverse transformation on the combined reference block (2530). The inversely transformed reference block (2540) can be determined as a prediction block of the current block (2100). The image decoding device (2000) can generate a prediction block of the current block (2100) by performing an inverse transformation on the combined reference block (2530).

[0391] In one embodiment, a transform applied to a reference block may be predefined. Various transforms (or transform kernels, transform types, and transform matrices) may be defined for transforming the reference block. For example, the predefined transform may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a DFT-based transform, a wavelet transform, or a KLT. In addition, as an example, the transform applied to the reference block may be the same as the transform applied to the templates of the current block (2100) and the candidate block. Alternatively, as an example, the transform applied to the reference block may be different from the transform applied to the templates of the current block (2100) and the candidate block.

[0392] As described above, the partition structure of the converted reference block (2510, 2520) may correspond to the partition structure of the converted template.

[0393] In one embodiment, when a transformed template is divided into N regions, N reference blocks can be determined. In this case, the image decoding device (2000) can determine N transformed reference blocks by performing transformation on the N reference blocks. The image decoding device (2000) can combine regions each corresponding to a sub-template within the N transformed reference blocks. Then, the image decoding device (2000) can inversely transform the combined reference blocks to generate a prediction block of the current block (2100).

[0394] In one embodiment, when a transformed template is divided into four as in the embodiment described above in FIG. 24, the image decoding device (2000) can determine four reference blocks based on a differential comparison between the four sub-templates. The image decoding device (2000) can determine four transformed reference blocks by performing transformation on each of the four reference blocks. The image decoding device (2000) can determine a combined reference block by combining areas corresponding to the sub-templates used for determining each reference block within the four transformed reference blocks. The image decoding device (2000) can determine a prediction block of the current block (2100) by inversely transforming the combined reference block.

[0395] Meanwhile, according to the embodiments described above in FIGS. 22 to 25, a transformation is performed on a template or reference block for template matching prediction in the frequency domain. At this time, the complexity may increase as the unit to which the transformation is applied becomes larger. Therefore, considering this, the size of the unit to which the transformation is applied can be defined in advance. For example, when the size of the template or reference block is WxH, the transformation kernel (or transformation matrix) is defined as MxN, and the transformation can be performed in units of blocks of size MxN.

[0396] In one embodiment, when the current block (2100) is WxH and the upper and left templates are Wx4 and 4xH, respectively, the image decoding device (2000) can perform transformation on the template of the current block (2100) in 4x4 units. The image decoding device (2000) can obtain 4x4-sized sub-templates by performing transformation on the upper and left templates in 4x4 units. The image decoding device (2000) can determine a plurality of reference blocks by performing differential comparison in units of 4x4-sized sub-templates, and can generate a prediction block through a weighted sum of the reference blocks.

[0397] In addition, in one embodiment, when the reference block is WxH, the image decoding device (2000) can perform transformation on the reference block in 4x4 units. For example, the size of the transformation applied to the reference block may be the same as the size of the transformation applied to the template. The image decoding device (2000) can obtain a combined reference block by combining areas corresponding to the sub-templates used for determining each reference block within the transformed reference block. The image decoding device (2000) can determine the prediction block of the current block (2100) by inversely transforming the combined reference block. For example, within the combined reference block, areas corresponding to the sub-templates used for determining each reference block may be allocated to a predetermined location.

[0398] In one embodiment, the frequency domain template matching prediction method described above in FIGS. 22 to 25 may be optionally used with the spatial domain template matching prediction method described above in FIG. 21. As an example, a SATD-based template matching prediction mode and a SAD-based template matching prediction mode may be defined and optionally used.

[0399] In one embodiment, multiple template matching prediction modes may be defined. The multiple template matching prediction modes may include a SATD-based template matching prediction mode and a SAD-based template matching prediction mode. As an example, a syntax element indicating a specific template matching prediction mode among the multiple template matching prediction modes may be signaled through the bitstream. In this case, the syntax element may be a flag or an index.

[0400] Additionally, in one embodiment, the plurality of template matching prediction modes may include a SAD-based template matching prediction mode, a SATD-based template matching prediction mode, or a combination template matching prediction mode. Here, the combination template matching prediction mode represents a method of determining a candidate block based on SAD and determining a final reference block based on SATD among the determined candidate blocks, as described above with reference to FIGS. 21 and 25. As an example, a syntax element indicating a specific template matching prediction mode among the plurality of template matching prediction modes may be signaled through a bitstream. In this case, the syntax element may be an index.

[0401] Additionally, in one embodiment, syntax elements indicating the partition structure of the transformed template, the number of sub-templates, the partition structure of the transformed reference block, and weight information applied to the reference block may be signaled through the bitstream.

[0402] Meanwhile, as described above in FIG. 22, the image decoding device (2000) can determine the final candidate block by performing SATD-based template matching prediction on the candidate determined by SAD-based template matching prediction. In the present disclosure, SAD-based template matching prediction may refer to the spatial domain-based template matching prediction described above in FIG. 21, and SATD-based template matching prediction may refer to the frequency domain-based template matching prediction described above in FIGS. 22 to 25.

[0403] As described above, when performing frequency domain-based template matching prediction, a search for differential comparison can be performed on candidate blocks at all pixel locations within the search area. At this time, the image decoding device (2000) can perform transformation on the templates of all candidate blocks within the search area while moving pixel by pixel, and perform template matching prediction using the transformed template.

[0404] However, as previously mentioned, complexity may increase as transformations are required for all possible blocks within the search area at the pixel level. Therefore, candidate blocks for template matching prediction can be defined as blocks at a predetermined location sampled within the search area, and may be determined by SAD-based template matching prediction.

[0405] In one embodiment, a candidate block for which SATD-based template matching prediction is performed may be selected by performing SAD-based template matching prediction within the search region. In this case, the embodiment described above in FIG. 21 may be applied.

[0406] In one embodiment, the number of candidate blocks determined by SAD-based template matching prediction may be predefined. As an example, a candidate list including a predetermined number of candidate blocks may be constructed. Each candidate included in the candidate list may include a block vector indicating the candidate block. In other words, a candidate list including a predetermined number of candidate blocks with the lowest SAD value within the search region may be constructed.

[0407] In one embodiment, the image decoding device (2000) may determine the candidate block having the smallest SATD value within the candidate list as a reference block. As shown in FIGS. 23 to 25 above, when performing template matching prediction on a sub-template basis, the image decoding device (2000) may determine the candidate block having the smallest SATD value within the candidate list as a reference block on a sub-template basis.

[0408] Additionally, in one embodiment, the image decoding device (2000) can perform differential comparison using both the spatial domain inter-template difference and the frequency domain inter-template difference. That is, the image decoding device (2000) can obtain inter-template differences using SAD and SATD, and determine a candidate block that minimizes the obtained difference as a reference block. As an example, the following mathematical expression 3 can be used.

[0409]

[0410] Referring to Equation 3, the difference between templates can be calculated using the SAD value and the SATD value. For example, a reference block having a template that minimizes the sum of the SAD value and the SATD value multiplied by λ can be determined. In Equation 3, λ is a variable applied to the SATD value and can be a predefined constant. The reference block can be determined by comparing the differences obtained using Equation 3.

[0411] Meanwhile, the embodiment of obtaining a prediction block by inversely transforming a reference block in the frequency domain described in FIG. 25 above can be used in substantially the same manner for IBC (Intra block copy) prediction or inter prediction. For example, the transformation can be performed on a plurality of reference blocks obtained based on IBC prediction or inter prediction. In one embodiment, in the case of IBC prediction, a reference block can be specified within a current picture by a block vector, and in the case of inter prediction, a reference block can be specified within a reference picture by a motion vector.

[0412] In one embodiment, the image decoding device (2000) can obtain a combined reference block by combining predetermined areas (or frequency bands) within each transformed reference block, and generate a prediction block by performing inverse transformation on the combined reference block.

[0413] In one embodiment, the image decoding device (2000) may transform a first reference block to obtain a first transformed reference block. The image decoding device (2000) may divide the first transformed reference block into two frequency domains. That is, the first transformed reference block may be divided into a region corresponding to a first frequency domain and a region corresponding to a second frequency domain.

[0414] Similarly, the image decoding device (2000) can transform the second reference block to obtain a second transformed reference block. The image decoding device (2000) can divide the second transformed reference block into two frequency domains. The second transformed reference block can be divided into a region corresponding to the first frequency domain and a region corresponding to the second frequency domain.

[0415] The image decoding device (2000) can obtain a combined reference block by combining an area corresponding to a first frequency area within a first transformed reference block and an area corresponding to a second frequency area within a second transformed reference block. The image decoding device (2000) can inversely transform the combined reference block to generate a prediction block.

[0416] Below, various extended embodiments for performing spatial domain-based template matching prediction are described.

[0417] In the spatial domain-based template matching prediction according to the embodiment described in FIG. 21, a single candidate block with the smallest inter-template difference is determined as a reference block. That is, a single reference block is searched within the search area. In one embodiment, the image decoding device (2000) may generate a prediction block through a weighted sum of multiple reference blocks when performing spatial domain-based template matching prediction.

[0418] In one embodiment, the image decoding device (2000) may determine a predetermined number of reference blocks in the search area in descending order of SAD. The image decoding device (2000) may generate a prediction block of the current block (2100) through a weighted sum of the determined reference blocks. At this time, the following mathematical expression 4 may be used.

[0419]

[0420] In Equation 4, RB1 represents the reference block with the smallest SAD value, RB2 represents the reference block with the second smallest SAD value, and RB3 represents the reference block with the third smallest SAD value. For example, w1+w2+w3+…+w n =1. That is, the sum of the weights applied to the reference blocks may be 1. Or, as an example, the weights applied to the reference blocks may be the same. That is, the predicted block may be generated by averaging the reference blocks. Or, as an example, the weights applied to the reference blocks may be different. Or, as an example, the weights applied to the reference blocks may be set such that when x <= y, w*x >= w*y always. Or, as an example, the weights applied to the reference blocks may be determined according to the cost function used.

[0421] Fig. 26 is a diagram for explaining a template matching prediction process according to one embodiment.

[0422] Referring to FIG. 26, the image decoding device (2000) can determine a reference block through a cascaded search for candidate blocks in a search area.

[0423] Specifically, the image decoding device (2000) can determine a first reference block (2620) having a template (2621) that minimizes the difference between the template (2601) of the current block (2600) and the template within the search area. Thereafter, the image decoding device (2000) can additionally perform template matching prediction using the template (2621) of the first reference block (2620) within the search area. That is, the image decoding device (2000) can determine a second reference block (2622) having a template (2623) that minimizes the difference between the template (2621) of the first reference block (2620) and the template within the search area.

[0424] In one embodiment, the image decoding device (2000) can determine a predetermined number of reference blocks of the current block (2600) by repeatedly performing the above-described process in a chain. The image decoding device (2000) can generate a prediction block of the current block (2100) through a weighted sum of the determined reference blocks. At this time, the following mathematical expression 5 can be used.

[0425]

[0426] Referring to mathematical expression 5, RB1 represents a first reference block (2620) having a template (2621) that minimizes the inter-template difference from the template (2601) of the current block (2600), RB2 represents a second reference block (2622) having a template (2623) that minimizes the inter-template difference from the template (2621) of the first reference block (2620), and RB3 represents a third reference block having a template (2623) that minimizes the inter-template difference from the template (2622).

[0427] In one embodiment, w1+w2+w3+…+w n=1. That is, the sum of the weights applied to the reference blocks may be 1. Alternatively, as an example, the weights applied to the reference blocks may be the same. That is, the predicted block may be generated by averaging the reference blocks. Alternatively, as an example, the weights applied to the reference blocks may be different.

[0428] In addition, in one embodiment, considering that template matching prediction is performed within a search area, which is an already restored area, after the determination of the first reference block (2620), subsequent reference block searches may be performed through differential comparison between reference blocks rather than differential comparison between templates. That is, the image decoding device (2000) may determine a block that minimizes the difference from the first reference block (2620) as a second reference block (2622), and may determine a block that minimizes the difference from the second reference block (2622) as a third reference block.

[0429] In one embodiment, a search area may be predefined. The search area may be defined as multiple areas. Reference blocks may be sequentially searched according to a search order defined among the multiple search areas. In this case, the embodiment described above in FIG. 21 may be applied, and any redundant descriptions related thereto will be omitted.

[0430] Figure 27 is a flowchart of an image decoding method according to one embodiment.

[0431] In step S2710, the image decoding device (2000) can determine a transformed template of the current block by performing transformation on the template of the current block (2100), and can determine transformed templates of a plurality of candidate blocks by performing transformation on the templates of a plurality of candidate blocks within the search area.

[0432] In one embodiment, a variety of predefined transforms may be used for the transformation. For example, the predefined transforms may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0433] In one embodiment, when performing template matching prediction using a transformed template, candidate blocks within the search area can be determined in a variety of ways. In this case, the embodiments described above in FIGS. 22 and 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0434] In one embodiment, the positions of the multiple candidate blocks may be determined in pixel units starting from an initial position in the upper left corner within the search area. As an example, the initial position in the upper left corner may be determined based on the height of the upper template of the current block (2100) and the width of the left template of the current block (2100).

[0435] Additionally, the locations of multiple candidate blocks can be determined based on comparison results performed based on SAD within the search area.

[0436] At step S2720, the image decoding device (2000) can compare the transformed template of the current block (2100) with the transformed template of each of the plurality of candidate blocks.

[0437] In one embodiment, the image decoding device (2000) may divide the transformed template of the current block (2100) and the transformed templates of multiple candidate blocks into multiple sub-templates. In this case, the embodiments described above in FIGS. 23 to 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0438] In one embodiment, the image decoding device (2000) can calculate a difference between a current sub-template within a transformed template of a current block (2100) and a sub-template corresponding to the current sub-template within the transformed template of a first candidate block. For example, the difference can be calculated using SATD.

[0439] In one embodiment, the transformed template of the current block (2100) may include a first sub-template including transform coefficients corresponding to a first frequency band (or frequency component) and a second sub-template including transform coefficients corresponding to a second frequency band. In other words, the transformed template of the current block (2100) may include a first sub-template corresponding to the first frequency band and a second sub-template corresponding to the second frequency band.

[0440] Similarly, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band. In other words, the transformed templates of the plurality of candidate blocks may each include a third sub-template corresponding to the first frequency band and a fourth sub-template corresponding to the second frequency band.

[0441] In step S2730, the image decoding device (2000) can determine a reference block of the current block (2100) among a plurality of candidate blocks based on the results compared in step S2720.

[0442] In one embodiment, the image decoding device (2000) may perform a differential comparison on a divided sub-template basis, thereby determining a candidate block having a sub-template most similar to each sub-template in the transformed template of the current block (2100) as a reference block of the current block (2100). In this case, the embodiments described above in FIGS. 23 to 25 may be applied. Here, any redundant descriptions related thereto will be omitted.

[0443] In one embodiment, the image decoding device (2000) may determine a candidate block that minimizes the difference between the first sub-template of the current block (2100) and the third sub-template of the candidate block as a first reference block. The image decoding device (2000) may determine a candidate block that minimizes the difference between the second sub-template of the current block (2100) and the fourth sub-template of the candidate block as a second reference block.

[0444] At step S2740, the image decoding device (2000) can generate a prediction block of the current block (2100) using a reference block.

[0445] In one embodiment, the image decoding device (2000) can generate a prediction block of the current block (2100) by performing a weighted sum of a first reference block and a second reference block.

[0446] Additionally, in one embodiment, the image decoding device (2000) may obtain a reference block transformed from a reference block, combine regions corresponding to sub-templates used to determine each reference block within the transformed reference block, and generate a prediction block of the current block (2100) based on the combined regions. At this time, the embodiment described in FIG. 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0447] In one embodiment, the image decoding device (2000) can determine a first transformed reference block and a second transformed reference block by performing transformation on the first reference block and the second reference block, respectively.

[0448] In one embodiment, the image decoding device (2000) can combine a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0449] In one embodiment, the image decoding device (2000) can generate a prediction block of the current block (2100) by performing an inverse transformation on the combined region.

[0450] At step S2750, the image decoding device (2000) can restore the current block (2100) using the prediction block of the current block (2100).

[0451] In one embodiment, the image decoding device (2000) can reconstruct the current block (2100) using the prediction block.

[0452] In one embodiment, the video decoding device (2000) can determine the predicted block as the reconstructed current block (2100).

[0453] In one embodiment, the image decoding device (2000) can generate a reconstructed current block (2100) by combining residual data obtained from a bitstream and a prediction block.

[0454] Fig. 28 is a block diagram illustrating a configuration of an image encoding device according to one embodiment.

[0455] Referring to FIG. 28, the image encoding device (2800) may include a prediction encoding unit (2810) and a generation unit (2820).

[0456] According to one embodiment, the prediction encoding unit (2810) and the generation unit (2820) may be implemented with at least one processor. In one embodiment, the prediction encoding unit (2810) and the generation unit (2820) may operate according to at least one instruction stored in at least one memory.

[0457] The image encoding device (2800) may include at least one memory that stores input / output data of the prediction encoding unit (2810) and the generation unit (2820). In addition, the image encoding device (2800) may include a memory control unit that controls data input / output of the memory.

[0458] In one embodiment, the prediction encoding unit (2810) may correspond to the prediction encoding unit (1915) illustrated in FIG. 19, and the generation unit (2820) may correspond to the entropy encoding unit (1925) illustrated in FIG. 19.

[0459] The prediction encoding unit (2810) can determine the prediction mode of the current block. The current block may be a maximum coding unit, coding unit, transformation unit, or prediction unit divided from the current picture to be encoded.

[0460] In one embodiment, the prediction mode of the current block may be determined as one of a plurality of prediction modes, including an intra mode and an inter mode. As an example, the intra mode may include a template matching prediction mode.

[0461] Alternatively, in one embodiment, the prediction mode of the current block may be determined as any one of a plurality of prediction modes including at least one of an intra mode, an inter mode, or a template matching prediction mode.

[0462] The prediction encoding unit (2810) can perform intra prediction or inter prediction on the current block according to the prediction mode of the current block to generate a prediction block of the current block, and encode the current block using the prediction block.

[0463] In one embodiment, the prediction encoding unit (2810) can determine a reference block of the current block within the search area by performing template matching when the prediction mode of the current block is a template matching prediction mode.

[0464] When a prediction block is generated through intra prediction for the current block, the prediction encoding unit (2810) can encode the current block using the prediction block.

[0465] In one embodiment, encoding of a current block may refer to a process of generating information that enables the image decoding device (2000) to restore the current block. The information generated through encoding may be included in a bitstream.

[0466] In one embodiment, when template matching prediction is applied to a current block, the prediction encoding unit (2810) can perform template matching to specify a reference block within a predefined search area and generate a prediction block for the current block using the specified reference block.

[0467] The specific embodiment of performing template matching prediction described above with reference to FIGS. 20 to 27 can be applied in a substantially identical manner in the prediction encoding unit (2810). Any duplicate descriptions in this regard will be omitted.

[0468] In one embodiment, the prediction encoding unit (2810) may perform a differential comparison on a per-sub-template basis to determine a candidate block having a sub-template most similar to each sub-template within the transformed template of the current block as the reference block of the current block. In this case, the embodiments described above in FIGS. 23 to 25 may be applied. Here, any redundant descriptions related thereto will be omitted.

[0469] Additionally, in one embodiment, the prediction encoding unit (2810) may obtain a reference block transformed from a reference block, combine regions corresponding to sub-templates used to determine each reference block within the transformed reference block, and generate a prediction block of the current block based on the combined regions. In this case, the embodiment described in FIG. 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0470] In one embodiment, the prediction encoding unit (2810) may generate residual data corresponding to the difference between the predicted block and the current block. If the predicted block is determined to be the current block, residual data may not be generated.

[0471] In one embodiment, the prediction encoding unit (2810) may encode the current block using the prediction block. A bitstream may be generated as a result of encoding the current block. In one embodiment, the image encoding device (2800) may obtain residual data corresponding to the difference between the prediction block and the original block, and information about the residual data may be included in the bitstream.

[0472] In one embodiment, the operation of the prediction encoding unit (4010) of the image encoding device (2800) may be identical to the operation of the prediction decoding unit (2030) of the image decoding device (2000), and therefore, the description of the operation of the prediction decoding unit (2030) described above may be equally applied to the prediction encoding unit (2810).

[0473] The generation unit (2820) can generate a bitstream including the encoding result of the picture. The bitstream can include the encoding result for the current block.

[0474] In one embodiment, the generation unit (2820) can transmit the bitstream to the image decoding device (2000) over a network.

[0475] In one embodiment, the generation unit (2820) may store the bitstream on a data storage medium including a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape, an optical recording medium such as a CD-ROM and a DVD, a magneto-optical medium such as a floptical disk, and the like.

[0476] The generation unit (2820) can generate a bitstream including syntax elements generated through encoding of a picture. Values ​​corresponding to the syntax elements can be included in the bitstream according to the hierarchical structure of the picture.

[0477] The generation unit (2820) can obtain bins included in the bitstream by entropy encoding syntax elements.

[0478] In one embodiment, the bitstream may include information about the prediction mode of the current block within the current picture.

[0479] In one embodiment, information about the prediction mode may be included in a sequence parameter set, a picture parameter set, a slice header, or slice data of the bitstream. As an example, the slice data may include information signaled at the coding tree, coding unit, transform tree, or transform unit level.

[0480] Figure 29 is a flowchart of an image encoding method according to one embodiment.

[0481] In step S2910, the image encoding device (2800) can determine a transformed template of the current block by performing transformation on the template of the current block, and can determine transformed templates of a plurality of candidate blocks by performing transformation on the templates of a plurality of candidate blocks within the search area.

[0482] The specific embodiments of template matching prediction described above with reference to FIGS. 21 to 27 can be applied in substantially the same manner to the image encoding device (4000). Any duplicate descriptions in this regard will be omitted.

[0483] In one embodiment, a variety of predefined transforms may be used for the transformation. For example, the predefined transforms may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0484] In one embodiment, when performing template matching prediction using a transformed template, candidate blocks within the search area can be determined in a variety of ways. In this case, the embodiments described above in FIGS. 22 and 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0485] In one embodiment, the positions of the multiple candidate blocks may be determined in pixels starting from the initial position in the upper left corner within the search area. As an example, the initial position in the upper left corner may be determined based on the height of the upper template of the current block and the width of the left template of the current block.

[0486] Additionally, the locations of multiple candidate blocks can be determined based on comparison results performed based on SAD within the search area.

[0487] In step S2920, the image encoding device (2800) can compare the transformed template of the current block with the transformed template of each of the plurality of candidate blocks.

[0488] In one embodiment, the video encoding device (2800) may divide the transformed template of the current block and the transformed templates of multiple candidate blocks into multiple sub-templates. In this case, the embodiments described above in FIGS. 23 to 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0489] In one embodiment, the video encoding device (2800) can calculate a difference between a current sub-template within a transformed template of a current block and a sub-template corresponding to the current sub-template within the transformed template of a first candidate block. For example, the difference can be calculated using SATD.

[0490] In one embodiment, the transformed template of the current block may include a first sub-template including transform coefficients corresponding to a first frequency band (or frequency component) and a second sub-template including transform coefficients corresponding to a second frequency band. In other words, the transformed template of the current block may include a first sub-template corresponding to the first frequency band and a second sub-template corresponding to the second frequency band.

[0491] Similarly, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band. In other words, the transformed templates of the plurality of candidate blocks may each include a third sub-template corresponding to the first frequency band and a fourth sub-template corresponding to the second frequency band.

[0492] In step S2930, the video encoding device (2800) can determine a reference block of the current block among a plurality of candidate blocks based on the results compared in step S2920.

[0493] In one embodiment, the video encoding device (2800) can determine a candidate block having a sub-template most similar to each sub-template in the transformed template of the current block as a reference block of the current block by performing a differential comparison on a divided sub-template basis. In this case, the embodiments described above in FIGS. 23 to 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0494] In one embodiment, the video encoding device (2800) may determine a candidate block that minimizes the difference between the first sub-template of the current block and the third sub-template of the candidate block as a first reference block. The video encoding device (2800) may determine a candidate block that minimizes the difference between the second sub-template of the current block and the fourth sub-template of the candidate block as a second reference block.

[0495] At step S2940, the image encoding device (2800) can generate a prediction block of the current block using a reference block.

[0496] In one embodiment, the video encoding device (2800) can generate a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0497] Additionally, in one embodiment, the video encoding device (2800) may obtain a reference block transformed from a reference block, combine regions corresponding to sub-templates used to determine each reference block within the transformed reference block, and generate a prediction block of the current block based on the combined regions. In this case, the embodiment described in FIG. 25 may be applied. Here, any redundant descriptions related thereto are omitted.

[0498] In one embodiment, the video encoding device (2800) can determine a first transformed reference block and a second transformed reference block by performing transformation on the first reference block and the second reference block, respectively.

[0499] In one embodiment, the video encoding device (2800) can combine a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0500] In one embodiment, the image encoding device (2800) can generate a prediction block of the current block by performing an inverse transformation on the combined region.

[0501] At step S2950, ​​the image encoding device (2800) can encode the current block using the prediction block of the current block. A bitstream can be generated as a result of encoding the current block.

[0502] In one embodiment, the video encoding device (2800) can determine the predicted block as the reconstructed current block.

[0503] In one embodiment, the video encoding device (2800) can obtain residual data corresponding to the difference between the predicted block and the original block, and information about the residual data can be included in the bitstream.

[0504] A method and device for encoding an image (2800) and a method and device for decoding an image (2000) according to one embodiment have the task of improving the performance of predictive encoding and predictive decoding for a current block.

[0505] A method and device for encoding an image (2800) and a method and device for decoding an image (2000) according to one embodiment have the task of reducing the amount of data required for signaling an intra prediction mode.

[0506] A method and device for encoding an image (2800) and a method and device for decoding an image (2000) according to one embodiment have the task of reducing the bit rate of a bitstream.

[0507] The technical problems to be achieved through the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure pertains from the description below.

[0508] A method for decoding an image according to one embodiment may include determining a transformed template of a current block by performing a transformation on a template of a current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on templates of a plurality of candidate blocks within a search area.

[0509] In one embodiment, the transformation can be performed using a predefined transformation.

[0510] According to one embodiment, the predefined transform may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0511] According to one embodiment, the positions of the plurality of candidate blocks within the search area can be determined in units of pixels from the initial position on the upper left side within the search area.

[0512] According to one embodiment, the upper left initial position may be determined based on the height of the upper template of the current block and the width of the left template of the current block.

[0513] According to one embodiment, the positions of a plurality of candidate blocks within a search area may be determined based on comparison results performed based on SAD within the search area.

[0514] A method of decoding an image according to one embodiment may include a step of comparing a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0515] According to one embodiment, the step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks may include the step of dividing the transformed template of the current block and the transformed templates of the plurality of candidate blocks into a plurality of sub-templates, respectively.

[0516] According to one embodiment, the step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks may include the step of calculating a difference between the current sub-template and a sub-template corresponding to the current sub-template in the transformed template of the first candidate block.

[0517] In one embodiment, the difference can be computed based on SATD.

[0518] According to one embodiment, the transformed template of the current block may include a first sub-template including transform coefficients corresponding to a first frequency band and a second sub-template including transform coefficients corresponding to a second frequency band.

[0519] According to one embodiment, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band.

[0520] A method for decoding an image according to one embodiment may include a step of determining a reference block of a current block among a plurality of candidate blocks based on a comparison result.

[0521] According to one embodiment, the step of determining a reference block of the current block may include the step of determining a candidate block that minimizes the difference between the first sub-template and the third sub-template as the first reference block, and determining a candidate block that minimizes the difference between the second sub-template and the fourth sub-template as the second reference block.

[0522] A method of decoding an image according to one embodiment may include a step of generating a prediction block of a current block using a reference block.

[0523] According to one embodiment, the step of generating a prediction block of the current block may include the step of generating a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0524] According to one embodiment, the step of generating a prediction block of the current block may include the step of generating a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0525] According to one embodiment, the step of generating a prediction block of the current block may include the step of determining a first transformed reference block and a second transformed reference block by performing a transformation on the first reference block and the second reference block.

[0526] According to one embodiment, the step of generating a prediction block of a current block may include the step of combining a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0527] According to one embodiment, the step of generating a prediction block of the current block may include the step of generating the prediction block of the current block by performing an inverse transformation on a region that combines the first region and the second region.

[0528] A method of decoding an image according to one embodiment may include a step of restoring a current block using a prediction block of the current block.

[0529] An image decryption device according to one embodiment may include at least one memory storing at least one instruction; and at least one processor operating according to at least one instruction.

[0530] In one embodiment, at least one processor can determine a transformed template of the current block by performing a transformation on a template of the current block, and determine transformed templates of a plurality of candidate blocks by performing a transformation on templates of the plurality of candidate blocks within the search region.

[0531] In one embodiment, the transformation can be performed using a predefined transformation.

[0532] According to one embodiment, the predefined transform may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0533] According to one embodiment, the positions of the plurality of candidate blocks within the search area can be determined in units of pixels from the initial position on the upper left side within the search area.

[0534] According to one embodiment, the upper left initial position may be determined based on the height of the upper template of the current block and the width of the left template of the current block.

[0535] According to one embodiment, the positions of a plurality of candidate blocks within a search area may be determined based on comparison results performed based on SAD within the search area.

[0536] In one embodiment, at least one processor can compare a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0537] According to one embodiment, at least one processor can divide the transformed template of the current block and the transformed templates of the plurality of candidate blocks into a plurality of sub-templates, respectively.

[0538] According to one embodiment, at least one processor can compute a difference between a current sub-template and a sub-template corresponding to the current sub-template within a transformed template of the first candidate block.

[0539] In one embodiment, the difference can be computed based on SATD.

[0540] According to one embodiment, the transformed template of the current block may include a first sub-template including transform coefficients corresponding to a first frequency band and a second sub-template including transform coefficients corresponding to a second frequency band.

[0541] According to one embodiment, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band.

[0542] In one embodiment, at least one processor can determine a reference block of the current block from among a plurality of candidate blocks based on a comparison result.

[0543] According to one embodiment, at least one processor may determine a candidate block that minimizes the difference between the first sub-template and the third sub-template as a first reference block, and may determine a candidate block that minimizes the difference between the second sub-template and the fourth sub-template as a second reference block.

[0544] In one embodiment, at least one processor may generate a prediction block of a current block using a reference block.

[0545] According to one embodiment, at least one processor can generate a prediction block of a current block by performing a weighted sum of a first reference block and a second reference block.

[0546] According to one embodiment, at least one processor can generate a prediction block of a current block by performing a weighted sum of a first reference block and a second reference block.

[0547] According to one embodiment, at least one processor can determine a first transformed reference block and a second transformed reference block by performing a transformation on the first reference block and the second reference block.

[0548] According to one embodiment, at least one processor can combine a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0549] According to one embodiment, at least one processor can generate a prediction block of a current block by performing an inverse transformation on a region that combines the first region and the second region.

[0550] In one embodiment, at least one processor can reconstruct the current block using a predicted block of the current block.

[0551] A method of encoding an image according to one embodiment may include determining a transformed template of a current block by performing a transformation on a template of a current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on templates of a plurality of candidate blocks within a search area.

[0552] In one embodiment, the transformation can be performed using a predefined transformation.

[0553] According to one embodiment, the predefined transform may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0554] According to one embodiment, the positions of the plurality of candidate blocks within the search area can be determined in units of pixels from the initial position on the upper left side within the search area.

[0555] According to one embodiment, the upper left initial position may be determined based on the height of the upper template of the current block and the width of the left template of the current block.

[0556] According to one embodiment, the positions of a plurality of candidate blocks within a search area may be determined based on comparison results performed based on SAD within the search area.

[0557] A method of encoding an image according to one embodiment may include a step of comparing a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0558] According to one embodiment, the step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks may include the step of dividing the transformed template of the current block and the transformed templates of the plurality of candidate blocks into a plurality of sub-templates, respectively.

[0559] According to one embodiment, the step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks may include the step of calculating a difference between the current sub-template and a sub-template corresponding to the current sub-template in the transformed template of the first candidate block.

[0560] In one embodiment, the difference can be computed based on SATD.

[0561] According to one embodiment, the transformed template of the current block may include a first sub-template including transform coefficients corresponding to a first frequency band and a second sub-template including transform coefficients corresponding to a second frequency band.

[0562] According to one embodiment, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band.

[0563] A method for encoding an image according to one embodiment may include a step of determining a reference block of a current block among a plurality of candidate blocks based on a comparison result.

[0564] According to one embodiment, the step of determining a reference block of the current block may include the step of determining a candidate block that minimizes the difference between the first sub-template and the third sub-template as the first reference block, and determining a candidate block that minimizes the difference between the second sub-template and the fourth sub-template as the second reference block.

[0565] A method of encoding an image according to one embodiment may include a step of generating a prediction block of a current block using a reference block.

[0566] According to one embodiment, the step of generating a prediction block of the current block may include the step of generating a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0567] According to one embodiment, the step of generating a prediction block of the current block may include the step of generating a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0568] According to one embodiment, the step of generating a prediction block of the current block may include the step of determining a first transformed reference block and a second transformed reference block by performing a transformation on the first reference block and the second reference block.

[0569] According to one embodiment, the step of generating a prediction block of a current block may include the step of combining a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0570] According to one embodiment, the step of generating a prediction block of the current block may include the step of generating the prediction block of the current block by performing an inverse transformation on a region that combines the first region and the second region.

[0571] A method of encoding an image according to one embodiment may include a step of encoding a current block using a prediction block of the current block.

[0572] An image encoding device according to one embodiment may include at least one memory storing at least one instruction; and at least one processor operating according to at least one instruction.

[0573] In one embodiment, at least one processor can determine a transformed template of the current block by performing a transformation on a template of the current block, and determine transformed templates of a plurality of candidate blocks by performing a transformation on templates of the plurality of candidate blocks within the search region.

[0574] In one embodiment, the transformation can be performed using a predefined transformation.

[0575] According to one embodiment, the predefined transform may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0576] According to one embodiment, the positions of the plurality of candidate blocks within the search area can be determined in units of pixels from the initial position on the upper left side within the search area.

[0577] According to one embodiment, the upper left initial position may be determined based on the height of the upper template of the current block and the width of the left template of the current block.

[0578] According to one embodiment, the positions of a plurality of candidate blocks within a search area may be determined based on comparison results performed based on SAD within the search area.

[0579] In one embodiment, at least one processor can compare a transformed template of a current block with a transformed template of each of a plurality of candidate blocks.

[0580] According to one embodiment, at least one processor can divide the transformed template of the current block and the transformed templates of the plurality of candidate blocks into a plurality of sub-templates, respectively.

[0581] According to one embodiment, at least one processor can compute a difference between a current sub-template and a sub-template corresponding to the current sub-template within a transformed template of the first candidate block.

[0582] In one embodiment, the difference can be computed based on SATD.

[0583] According to one embodiment, the transformed template of the current block may include a first sub-template including transform coefficients corresponding to a first frequency band and a second sub-template including transform coefficients corresponding to a second frequency band.

[0584] According to one embodiment, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band.

[0585] In one embodiment, at least one processor can determine a reference block of the current block from among a plurality of candidate blocks based on a comparison result.

[0586] According to one embodiment, at least one processor may determine a candidate block that minimizes the difference between the first sub-template and the third sub-template as a first reference block, and may determine a candidate block that minimizes the difference between the second sub-template and the fourth sub-template as a second reference block.

[0587] In one embodiment, at least one processor may generate a prediction block of a current block using a reference block.

[0588] According to one embodiment, at least one processor can generate a prediction block of a current block by performing a weighted sum of a first reference block and a second reference block.

[0589] According to one embodiment, at least one processor can generate a prediction block of a current block by performing a weighted sum of a first reference block and a second reference block.

[0590] According to one embodiment, at least one processor can determine a first transformed reference block and a second transformed reference block by performing a transformation on the first reference block and the second reference block.

[0591] According to one embodiment, at least one processor can combine a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0592] According to one embodiment, at least one processor can generate a prediction block of a current block by performing an inverse transformation on a region that combines the first region and the second region.

[0593] In one embodiment, at least one processor can encode the current block using a prediction block of the current block.

[0594] In a computer-readable recording medium having recorded thereon a bitstream according to one embodiment, the bitstream may include an encoding result of a current block.

[0595] In one embodiment, the encoding result of the current block can be generated by determining a transformed template of the current block by performing a transformation on the template of the current block, and determining transformed templates of a plurality of candidate blocks by performing a transformation on the templates of a plurality of candidate blocks within the search area.

[0596] In one embodiment, the transformation can be performed using a predefined transformation.

[0597] According to one embodiment, the predefined transform may include at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a wavelet transform, or a KLT.

[0598] According to one embodiment, the positions of the plurality of candidate blocks within the search area can be determined in units of pixels from the initial position on the upper left side within the search area.

[0599] According to one embodiment, the upper left initial position may be determined based on the height of the upper template of the current block and the width of the left template of the current block.

[0600] According to one embodiment, the positions of a plurality of candidate blocks within a search area may be determined based on comparison results performed based on SAD within the search area.

[0601] In one embodiment, the encoding result of the current block can be generated by comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks.

[0602] According to one embodiment, the encoding result of the current block can be generated by dividing the transformed template of the current block and the transformed templates of the plurality of candidate blocks into a plurality of sub-templates.

[0603] According to one embodiment, the encoding result of the current block can be generated by calculating the difference between the current sub-template and a sub-template corresponding to the current sub-template in the transformed template of the first candidate block.

[0604] In one embodiment, the difference can be computed based on SATD.

[0605] According to one embodiment, the transformed template of the current block may include a first sub-template including transform coefficients corresponding to a first frequency band and a second sub-template including transform coefficients corresponding to a second frequency band.

[0606] According to one embodiment, the transformed templates of the plurality of candidate blocks may each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band.

[0607] In one embodiment, the encoding result of the current block can be generated by determining a reference block of the current block among a plurality of candidate blocks based on a comparison result.

[0608] According to one embodiment, the encoding result of the current block can be generated by determining a candidate block that minimizes the difference between the first sub-template and the third sub-template as a first reference block, and determining a candidate block that minimizes the difference between the second sub-template and the fourth sub-template as a second reference block.

[0609] In one embodiment, the encoding result of the current block can be generated by generating a prediction block of the current block using a reference block.

[0610] According to one embodiment, the encoding result of the current block can be generated by generating a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0611] According to one embodiment, the encoding result of the current block can be generated by generating a prediction block of the current block by performing a weighted sum of a first reference block and a second reference block.

[0612] According to one embodiment, the encoding result of the current block can be generated by determining the first transformed reference block and the second transformed reference block by performing a transformation on the first reference block and the second reference block.

[0613] According to one embodiment, the encoding result of the current block can be generated by combining a first region including transform coefficients corresponding to a first frequency band within a first transformed reference block, and a second region including transform coefficients corresponding to a second frequency band within a second transformed reference block.

[0614] According to one embodiment, the encoding result of the current block can be generated by generating a prediction block of the current block by performing an inverse transformation on a region that combines the first region and the second region.

[0615] In one embodiment, the encoding result of the current block can be generated by encoding the current block using a prediction block of the current block.

[0616] A method and device for encoding an image (2800) and a method and device for decoding an image (2000) according to one embodiment can improve the performance of predictive encoding and predictive decoding for a current block.

[0617] A method and device for encoding an image (2800) and a method and device for decoding an image (2000) according to one embodiment can reduce the amount of data required for signaling an intra prediction mode.

[0618] A method and device for encoding an image (2800) and a method and device for decoding an image (2000) according to one embodiment can reduce the bit rate of a bitstream.

[0619] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0620] Meanwhile, the embodiments of the present disclosure described above can be written as a program that can be executed on a computer, and the written program can be stored in a storage medium that can be read by a device.

[0621] A device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, the term "non-transitory storage medium" simply means a tangible device that does not contain signals (e.g., electromagnetic waves). This term does not distinguish between cases where data is permanently stored in the storage medium and cases where data is temporarily stored. For example, a "non-transitory storage medium" may include a buffer in which data is temporarily stored.

[0622] According to one embodiment, the method according to various embodiments disclosed in the present document may be provided as included in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) through an application store or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored or temporarily generated in a machine-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

Claims

1. In the method of decrypting the video, A step of determining a transformed template of a current block by performing a transformation on a template of the current block, and determining transformed templates of a plurality of candidate blocks within a search region by performing a transformation on the templates of the plurality of candidate blocks; A step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks; A step of determining a reference block of the current block among the plurality of candidate blocks based on the results of the comparison; A step of generating a prediction block of the current block using the reference block; and A method for decoding an image, comprising the step of restoring the current block using a prediction block of the current block.

2. In paragraph 1, The step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks is: A step of dividing the transformed template of the current block and the transformed templates of the plurality of candidate blocks into a plurality of sub-templates; and A method for decoding an image, comprising the step of calculating a difference between a current sub-template in a transformed template of the current block and a sub-template corresponding to the current sub-template in a transformed template of a first candidate block.

3. In paragraph 2, The transformed template of the current block includes a first sub-template including transform coefficients corresponding to a first frequency band and a second sub-template including transform coefficients corresponding to a second frequency band, A method for decoding an image, wherein the transformed templates of the plurality of candidate blocks each include a third sub-template including transform coefficients corresponding to the first frequency band and a fourth sub-template including transform coefficients corresponding to the second frequency band.

4. In paragraph 3, The step of determining the reference block of the current block is: A step of determining a candidate block that minimizes the difference between the first sub-template and the third sub-template as a first reference block; and A method for decoding an image, comprising the step of determining a candidate block that minimizes the difference between the second sub-template and the fourth sub-template as a second reference block.

5. In paragraph 4, The step of generating a prediction block of the current block is: A method for decoding an image, comprising the step of generating a prediction block of the current block by performing a weighted sum of the first reference block and the second reference block.

6. In paragraph 4, The step of generating a prediction block of the current block is: A step of determining a first transformed reference block and a second transformed reference block by performing a transformation on the first reference block and the second reference block; A step of combining a first region including transform coefficients corresponding to the first frequency band within the first transformed reference block, and a second region including transform coefficients corresponding to the second frequency band within the second transformed reference block; and A method for decoding an image, comprising the step of generating a prediction block of the current block by performing an inverse transformation on the combined region.

7. In paragraph 1, The above transformation is performed using a predefined transformation, A method for decoding an image, wherein the above predefined transform comprises at least one of a Hadamard transform, a DCT-based transform, a DST-based transform, a Wavelet Transform or a Karhunen Loeve Transform (KLT).

8. In paragraph 2, A method for decoding an image, wherein the above difference is calculated based on the Sum of Absolute Transformed Difference (SATD).

9. In paragraph 1, The positions of the above multiple candidate blocks are determined in pixel units from the initial position on the upper left side within the search area, A method for decoding an image, wherein the upper left initial position is determined based on the height of the upper template of the current block and the width of the left template of the current block.

10. In paragraph 1, A method for decoding an image, wherein the positions of the plurality of candidate blocks are determined based on a comparison result performed based on a Sum of Absolute Difference (SAD) within the search area.

11. In a video decryption device, At least one memory storing at least one instruction; and comprising at least one processor operating in accordance with at least one instruction; At least one processor of the above, Determine the transformed template of the current block by performing a transformation on the template of the current block, Determine transformed templates of multiple candidate blocks by performing transformation on templates of multiple candidate blocks within a search area, Compare the transformed template of the current block with the transformed template of each of the plurality of candidate blocks, Based on the results of the comparison, a reference block of the current block is determined among the plurality of candidate blocks, Generate a prediction block of the current block using the above reference block, An image decoding device that restores the current block using a prediction block of the current block.

12. In the method of encoding an image, A step of determining a transformed template of the current block by performing a transformation on the template of the current block, and determining transformed templates of a plurality of candidate blocks within the search area by performing a transformation on the templates of the plurality of candidate blocks; A step of comparing the transformed template of the current block with the transformed template of each of the plurality of candidate blocks; A step of determining a reference block of the current block among the plurality of candidate blocks based on the results of the comparison; A step of generating a prediction block of the current block using the reference block; and A method for encoding an image, comprising the step of encoding the current block using a prediction block of the current block.

13. In a video encoding device, At least one memory storing at least one instruction; and comprising at least one processor operating in accordance with at least one instruction; At least one processor of the above, Determine the transformed template of the current block by performing a transformation on the template of the current block, Determine transformed templates of multiple candidate blocks by performing transformation on templates of multiple candidate blocks within a search area, Compare the transformed template of the current block with the transformed template of each of the plurality of candidate blocks, Based on the results of the comparison, a reference block of the current block is determined among the plurality of candidate blocks, Generate a prediction block of the current block using the above reference block, An image encoding device that encodes the current block using a prediction block of the current block.

14. In a computer-readable recording medium that records a bitstream, The above bitstream contains the encoding result of the current block, The encoding result of the current block above is, Determine the transformed template of the current block by performing a transformation on the template of the current block, Determine transformed templates of multiple candidate blocks by performing transformation on templates of multiple candidate blocks within a search area, Compare the transformed template of the current block with the transformed template of each of the plurality of candidate blocks, Based on the results of the comparison, a reference block of the current block is determined among the plurality of candidate blocks, Generate a prediction block of the current block using the above reference block, A recording medium generated by encoding the current block using a prediction block of the current block.

Images