Device and method for adaptively filtering image

Abstract

An image filtering method according to an embodiment comprises the steps of: calculating a first directional feature value and a second directional feature value of the current block in the current image; determining a directional value of the current block on the basis of a comparison result of a first threshold value and a first ratio between a first maximum feature value corresponding to a larger value of the first directional feature value and the second directional feature value and a first minimum feature value corresponding to a smaller value of the first directional feature value and the second directional feature value, and a comparison result of the first maximum feature value and a second threshold value; determining a class corresponding to the current block among a plurality of classes on the basis of the directional value; and filtering samples in the current block by using a filter configured according to the determined class.

Description

Adaptive filtering device and method for video

[0001] The present disclosure relates to the field of image filtering, and more specifically, to a device and method for adaptively filtering an image by using a classification result for the image during an image encoding or decoding process.

[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 can be a technique for compressing images by removing temporal redundancy between images. Inter prediction can predict blocks in the current image 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 can be predicted based on the reference block, and the predicted block generated as a result of the prediction can be subtracted from the current block to generate a residual block.

[0004] Intra prediction can be a technique for compressing images by removing spatial redundancy within the image. Intra prediction can generate a predicted block based on the surrounding pixels of the current block, depending on the intra prediction mode. Then, the predicted block can be subtracted from the current block to generate a residual block. The intra prediction mode used to generate the predicted block can be signaled to the decoder through a predetermined method.

[0005] The residual block generated through inter prediction or intra prediction can be transformed and quantized and then passed to the decoder.

[0006] The encoder and decoder can reconstruct the current block by combining the predicted block and the residual block of the current block. The encoder and decoder can apply a deblocking filter and / or an adaptive loop filter to the reconstructed current block to remove artifacts within the current block.

[0007] A method for filtering an image by a filtering device according to one embodiment may include a step of calculating a first direction feature value and a second direction feature value of a current block in a current image.

[0008] A method for filtering an image by a filtering device according to one embodiment may include a step of determining a directionality value of a current block based on a result of comparing a first ratio between a first maximum feature value corresponding to a larger value of a first direction feature value and a second direction feature value and a first minimum feature value corresponding to a smaller value of a first direction feature value and a second direction feature value with a first threshold value, and a result of comparing the first maximum feature value with a second threshold value.

[0009] A method for filtering an image by a filtering device according to one embodiment may include a step of determining a class corresponding to a current block among a plurality of classes based on a determined directionality value.

[0010] A method for filtering an image by a filtering device according to one embodiment may include a step of filtering a sample within a current block using a filter configured according to a determined class.

[0011] A filtering device according to one embodiment may include a directionality determination unit that calculates a first directionality feature value and a second directionality feature value of a current block in a current image, and determines a directionality value of the current block based on a comparison result between a first ratio between a first maximum feature value corresponding to a larger value of the first directionality feature value and the second directionality feature value and a first minimum feature value corresponding to a smaller value of the first directionality feature value and the second directionality feature value and a first threshold value, and a comparison result between the first maximum feature value and the second threshold value.

[0012] A filtering device according to one embodiment may include a class determination unit that determines a class corresponding to a current block among a plurality of classes based on a determined directional value.

[0013] A filtering device according to one embodiment may include a filter unit that filters samples within a current block using a filter configured according to a determined class.

[0014] A computer-readable recording medium according to one embodiment may include a bitstream.

[0015] In one embodiment, the bitstream may include filter information used to filter the current image according to a filtering method.

[0016] In one embodiment, the filtering method may include the step of calculating a first direction feature value and a second direction feature value of a current block within a current image.

[0017] In one embodiment, the filtering method may include determining a directionality value of the current block based on a comparison result between a first ratio between a first maximum feature value corresponding to a larger value of the first directional feature value and a first minimum feature value corresponding to a smaller value of the first directional feature value and the second directional feature value and a first threshold value, and a comparison result between the first maximum feature value and the second threshold value.

[0018] In one embodiment, the filtering method may include determining a class corresponding to the current block among a plurality of classes based on the determined directional value.

[0019] In one embodiment, the filtering method may include filtering samples within a current block using a filter configured according to determined class and filter information.

[0020] FIG. 1 is a block diagram of an image decoding device according to one embodiment.

[0021] FIG. 2 is a block diagram of an image encoding device according to one embodiment.

[0022] FIG. 3 illustrates a process of dividing a current encoding unit to determine at least one encoding unit according to one embodiment.

[0023] FIG. 4 illustrates a process of dividing a non-square coding unit to determine at least one coding unit according to one embodiment.

[0024] 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.

[0025] FIG. 6 illustrates a method for determining a predetermined coding unit among an odd number of coding units according to one embodiment.

[0026] 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.

[0027] 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.

[0028] FIG. 9 illustrates a process of dividing a first encoding unit to determine at least one encoding unit according to one embodiment.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] FIG. 19 is a block diagram of an image encoding and decoding system according to one embodiment.

[0039] Fig. 20 is a block diagram illustrating a configuration of a filtering device according to one embodiment.

[0040] FIG. 21 is a diagram illustrating a filter according to one embodiment.

[0041] Fig. 22 is a block diagram illustrating the configuration of a classifier according to one embodiment.

[0042] FIG. 23 is a diagram for explaining a method for calculating direction feature values ​​of a current block according to one embodiment.

[0043] FIG. 24 is a diagram for explaining a method for determining a directionality value of a current block according to one embodiment.

[0044] FIG. 25 is a diagram for explaining a method for determining a directionality value of a current block according to one embodiment.

[0045] FIG. 26 is a diagram illustrating a method for determining a directionality value of a current block according to one embodiment.

[0046] FIG. 27 is a diagram illustrating a method for classifying a current block based on sample feature values ​​of the current block according to one embodiment.

[0047] FIG. 28 is a diagram illustrating a histogram of sample feature values ​​according to one embodiment.

[0048] Fig. 29 is a block diagram illustrating the configuration of a classifier according to one embodiment.

[0049] FIG. 30 is a diagram illustrating a histogram constructed based on sample feature values ​​derived from a current image according to one embodiment.

[0050] FIG. 31 is a diagram illustrating a method for clustering candidate values ​​based on temporary representative values ​​according to one embodiment.

[0051] FIG. 32 is a diagram illustrating a method for determining new temporary representative values ​​in the sub-ranges illustrated in FIG. 31.

[0052] FIG. 33 is a diagram illustrating a method for clustering candidate values ​​based on the new temporary representative values ​​illustrated in FIG. 32.

[0053] FIG. 34 is a diagram illustrating a lookup table constructed based on the clustering results of candidate values ​​according to one embodiment.

[0054] Figure 35 is a flowchart for explaining a method of filtering an image according to one embodiment.

[0055] Figure 36 is a flowchart for explaining a method of filtering an image according to one embodiment.

[0056] A method for filtering an image by a filtering device according to one embodiment may include a step of calculating a first direction feature value and a second direction feature value of a current block in a current image.

[0057] A method for filtering an image by a filtering device according to one embodiment may include a step of determining a directionality value of a current block based on a result of comparing a first ratio between a first maximum feature value corresponding to a larger value of a first direction feature value and a second direction feature value and a first minimum feature value corresponding to a smaller value of a first direction feature value and a second direction feature value with a first threshold value, and a result of comparing the first maximum feature value with a second threshold value.

[0058] A method for filtering an image by a filtering device according to one embodiment may include a step of determining a class corresponding to a current block among a plurality of classes based on a determined directionality value.

[0059] A method for filtering an image by a filtering device according to one embodiment may include a step of filtering a sample within a current block using a filter configured according to a determined class.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] In this 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 performed by other components.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] FIG. 1 illustrates a block diagram of an image decoding device (100) according to one embodiment.

[0069] 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.

[0070] 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.

[0071] To describe in detail the operation of the video decoding device (100), the bitstream acquisition unit (110) can receive a bitstream.

[0072] 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.

[0073] Below, the division of encoding units according to one embodiment of the present disclosure is described in detail.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] A single maximum coding block (CTB) can be divided into MxN coding blocks containing MxN samples (M, N are integers).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] If the current encoding unit is not quad-split, the information indicating whether it is multi-split may indicate whether the current encoding unit will not be split any further (NO_SPLIT) or will be binary / ternary split.

[0087] 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.

[0088] 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.

[0089] 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).

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The shape and size of the transformation block and the prediction block may be unrelated.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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).

[0109] 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).

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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 obtain 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.

[0115] 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 (520b), which is one of the odd number of third coding units (520b, 520c, 520d), may be split horizontally into a plurality of fourth coding units. The non-square fourth coding unit (530b or 530d), which is one of the plurality of fourth coding units (530a, 530b, 530c, 530d), may be split again into a plurality of coding units. For example, the fourth coding unit (530b or 530d) having a non-square shape may be further divided into an odd number of coding units. Methods that can be used for recursive division of coding units will be described later through various embodiments.

[0116] 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.

[0117] 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).

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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).

[0124] 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.

[0125] 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.

[0126] 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).

[0127] 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.

[0128] 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).

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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).

[0139] 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.

[0140] 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).

[0141] 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.

[0142] 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).

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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).

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] According to one embodiment, the image decoding device (100) can divide the first encoding unit to determine encoding units of various shapes.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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).

[0161] 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).

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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 also split the first coding unit (1320) in the horizontal direction and the vertical direction to determine a second coding unit (1322) having a size of NxN / 2.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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).

[0178] 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.

[0179] 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.

[0180] 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).

[0181] 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).

[0182] 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.

[0183] 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.

[0184] 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).

[0185] 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.

[0186] 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.

[0187] 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.

[0188] According to one embodiment, the image decoding device (100) may utilize a predetermined data unit from which recursive division of the encoding unit begins.

[0189] FIG. 15 illustrates that a plurality of encoding units are determined according to a plurality of predetermined data units included in a picture according to one embodiment.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] Hereinafter, a method for determining a partitioning rule according to one embodiment of the present disclosure will be described in detail.

[0200] 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.

[0201] 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).

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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).

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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).

[0228] FIG. 19 is a block diagram of an image encoding and decoding system according to one embodiment.

[0229] 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).

[0230] 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).

[0231] 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).

[0232] 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).

[0233] 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.

[0234] 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.

[0235] 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.

[0236] 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).

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] 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.

[0245] 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.

[0246] Fig. 20 is a block diagram illustrating the configuration of a filtering device (2000) according to one embodiment.

[0247] Referring to FIG. 20, the filtering device (2000) may include a classifier (2010) and a filter unit (2030).

[0248] The classifier (2010) and filter unit (2030) may be implemented with at least one processor. At least one processor may include processing circuitry.

[0249] The classifier (2010) and the filter unit (2030) can operate according to at least one instruction stored in at least one memory.

[0250] The filtering device (2000) may include at least one memory for storing input / output data of the classifier (2010) and the filter unit (2030). The filtering device (2000) may include a memory control unit for controlling data input / output of at least one memory.

[0251] In one embodiment, the filtering device (2000) may correspond to the loop filtering unit (1940, 1970) illustrated in FIG. 19. In one embodiment, the filtering device (2000) may be included in each of the image decoding device (100) and the image encoding device (200).

[0252] In one embodiment, the filtering device (2000) can generate a filtered image from an input image. The filtering device (2000) can classify samples or blocks included in the image according to their characteristics, and filter the samples included in the image using a filter appropriate for the classification result.

[0253] For example, the classifier (2010) may determine which class among multiple classes each of the blocks or samples included in the image belongs to. In one embodiment, the classifier (2010) may determine a class corresponding to a block or sample among multiple classes based on feature values ​​of the block or sample within the image.

[0254] The filter unit (2030) can determine filter coefficients to be used for filtering samples within a block by considering at least one of the classification results or filter information by the classifier (2010). The filter unit (2030) can apply the adaptively determined filter coefficients to one sample and its surrounding samples to generate a filtered sample.

[0255] In one embodiment, if the classification process by the classifier (2010) is performed on a block-by-block basis, the same filter may be applied to samples included in the same block. In one embodiment, if the classification process by the classifier (2010) is performed on a sample-by-sample basis, a filter independently determined for each sample in the image may be applied.

[0256] In one embodiment, the image classified by the classifier (2010) may include at least one of a reconstructed image, a deblocking filtered reconstructed image, a reconstructed image with a fixed filter applied, a predicted image, a residual image, a predicted image with a fixed filter applied, or a residual image with a fixed filter applied.

[0257] Here, the predicted image may be an image generated through intra-prediction or inter-prediction for blocks, and the residual image may be an image corresponding to the difference between the original image and the predicted image. Furthermore, the restored image may be an image generated by combining the predicted image and the residual image.

[0258] A deblocking filter may be applied to a restored image to remove artifacts between blocks. A fixed filter may refer to a filter whose filter coefficients are agreed upon in advance between an image encoding device (200) and an image decoding device (100).

[0259] In one embodiment, the image filtered by the filter unit (2030) may include at least one of a restored image, a deblocking filtered restored image, a restored image with a fixed filter applied, a predicted image, a residual image, a predicted image with a fixed filter applied, or a residual image with a fixed filter applied.

[0260] In one embodiment, when multiple images are classified by the classifier (2010), the classification results of the multiple images can be combined to obtain a final classification result. For example, the class to which each block within different images belongs can be determined. The class indicated by the average value of the values ​​representing the classes to which each of the multiple blocks belongs can be obtained as the final classification result.

[0261] In one embodiment, when feature values ​​(e.g., directional feature values ​​or sample feature values ​​described below) are derived from a plurality of images for classification of the plurality of images, a final classification result may be obtained based on a value obtained by combining the derived feature values.

[0262] In one embodiment, when multiple images are filtered by the filter unit (2030), the filtered images may be combined (e.g., weighted combined) to obtain a final filtered image.

[0263] In one embodiment, the types of images classified by the classifier (2010) and the types of images filtered by the filter unit (2030) may be different. For example, a deblocking-filtered restored image may be filtered based on the classification result for the residual image. As another example, at least one of the restored image, the deblocking-filtered restored image, the restored image with a fixed filter applied, the residual image, or the residual image with a fixed filter applied may be filtered based on the classification result for the deblocking-filtered restored image or the residual image.

[0264] In one embodiment, the types of images classified by the classifier (2010) and images filtered by the filter unit (2030) may be the same.

[0265] In the following, it is described that the current image is input to the classifier (2010) and the filter unit (2030), but the type of image input to the classifier (2010) and the type of image input to the filter unit (2030) may be the same or different from each other.

[0266] When the classification result of the current image is obtained by the classifier (2010), the filter unit (2030) can determine a filter suitable for filtering samples within the current image based on the classification result and / or filter information. Then, the filter unit (2030) can filter samples within the current image using the determined filter.

[0267] In one embodiment, when the filtering device (200) is included in the image decoding device, filter information can be obtained from the bitstream. In one embodiment, when the filtering device (200) is included in the image encoding device, the filtering device (200) can generate filter information by referring to the filtering result for the image, and include the generated filter information in the bitstream.

[0268] In one embodiment, the bitstream may correspond to the encoding result of the image. In one embodiment, the bitstream may be generated by the image encoding device (200) and transmitted to the image decoding device (100).

[0269] In one embodiment, the bitstream may be stored on a storage medium such as an optical media, a hard disk, or the like.

[0270] In one embodiment, the filter information may include at least one of information indicating whether adaptive filtering is applied to the current image or a block within the current image (e.g., a slice or a maximum coding unit, etc.), information indicating which of several adaptation parameter sets (APS) included in the bitstream is used for the current image or a block within the current image, or information indicating which of several filter sets is used for the current image or a block within the current image.

[0271] In one embodiment, the APS may include information about filter coefficients, and filter coefficients identified from the classification results by the classifier (2010) may be applied to samples in the current image.

[0272] FIG. 21 is a diagram illustrating a filter according to one embodiment.

[0273] In one embodiment, a first filter (2110) and a second filter (2130) may be used to filter an image. curr included in the first filter (2110) and the second filter (2130) may represent a sample to be filtered.

[0274] In one embodiment, the first filter (2110) may be applied to a deblocking filtered reconstructed image, and the second filter (2130) may be applied to a fixed filtered reconstructed image.

[0275] The filter unit (2030) can determine filter coefficients included in the first filter (2110) and the second filter (2130) based on the classification result and / or filter information of the classifier (2010). For example, based on the class to which a block or sample in the current image belongs and the filter set used for filtering the current image, filter coefficients 0 to 9 of the first filter (2110) and filter coefficients 10 to 27 of the second filter (2130) can be determined.

[0276] Although FIG. 21 discloses only two filters (2110, 2130), in one embodiment, more than one filter may be used to filter the image.

[0277] The filtering device (2000) illustrated in FIG. 20 includes one classifier (2010), and the number of classifiers (2010) included in the filtering device (2000) may be multiple.

[0278] For example, if the filtering device (2000) includes a first classifier, a second classifier, and a third classifier, the first classifier, the second classifier, and the third classifier can classify blocks of the current image in different ways.

[0279] In one embodiment, if the filtering device (2000) includes one classifier, the classifier can classify a block of the current image based on the directional feature values ​​described below.

[0280] In one embodiment, when the filtering device (2000) includes a first classifier and a second classifier, the first classifier can classify a block of the current image based on a directional feature value described below, and the second classifier can classify a block of the current image based on a sample feature value described below.

[0281] In one embodiment, when the filtering device (2000) includes a first classifier, a second classifier, and a third classifier, the first classifier may classify a block of the current image based on a directional feature value of the block in the deblocking filtered restored image, the second classifier may classify a block of the current image based on a sample feature value in the deblocking filtered restored image, and the third classifier may classify a block of the current image based on a sample feature value in the residual image.

[0282] In one embodiment, when the filtering device (2000) includes a first classifier, a second classifier, a third classifier, and a fourth classifier, the first classifier may classify a block of the current image based on a directional feature value of the block in the deblocking filtered reconstructed image, the second classifier and the third classifier may classify a block of the current image based on a sample feature value in the deblocking filtered reconstructed image, and the fourth classifier may classify a block of the current image based on a sample feature value in the residual image. Here, the second classifier may classify a block of the current image by dividing the entire range including candidate values ​​into several sub-ranges of the same size, as described with reference to FIG. 27. And, the third classifier may classify a block of the current image by adaptively dividing the entire range including candidate values ​​into several sub-ranges, as described with reference to FIGS. 30 to 33.

[0283] In one embodiment, when a filtering device (2000) includes a plurality of classifiers (2010), one of the plurality of classifiers (2010) may be selected, and a classification result by the selected classifier (2010) may be transmitted to the filter unit (2030). When the filtering device (2000) is included in the image decoding device (100), information indicating one of the plurality of classifiers (2010) may be obtained from a bitstream.

[0284] In one embodiment, if the filtering device (2000) includes multiple classifiers (2010), the classification results from the multiple classifiers (2010) may be combined to obtain a final classification result. For example, if the current block is classified by multiple classifiers (2010), values ​​representing the classes to which the current block belongs may be obtained, and a class corresponding to the average value of the obtained values ​​may be determined as the final class of the current block.

[0285] Below, a classifier (2010) that classifies the current block based on the directional feature value is described with reference to FIGS. 22 to 26.

[0286] The current block may be a slice, tile, maximum coding unit, encoding unit, prediction unit, or transform unit segmented from the current image. In one embodiment, the size of the current block may be greater than 1x1. For example, the size of the current block may be 2x2 or 4x4.

[0287] FIG. 22 is a block diagram illustrating the configuration of a classifier (2200) according to one embodiment.

[0288] Referring to FIG. 22, the classifier (2200) may include a directionality determination unit (2210), an activity determination unit (2230), and a class determination unit (2250).

[0289] The directionality determination unit (2210) can determine the directionality value of the current block to be classified, and the activity determination unit (2230) can determine the activity value of the current block.

[0290] The class determination unit (2250) may determine which class among multiple classes the current block belongs to by using at least one of a directionality value and an activity value. For example, the class determination unit (2250) may determine that the current block belongs to a class indicated by a value combining a directionality value and an activity value.

[0291] As described above, once the class corresponding to the current block is determined, the filter unit (2030) can obtain filter coefficients for filtering samples within the current block based on the class.

[0292] In one embodiment, the directionality determination unit (2210) can calculate a directionality feature value of the current block. A directionality value and an activity value can be determined based on the directionality feature value.

[0293] FIG. 23 is a diagram for explaining a method for calculating direction feature values ​​of a current block according to one embodiment.

[0294] In one embodiment, the directional feature values ​​may include gradient values ​​or Laplace values ​​representing the amount of change in the sample values.

[0295] In one embodiment, the gradient value of the first sample may correspond to the difference between the sample value of the first sample and the sample value of the second sample positioned after the first sample.

[0296] In one embodiment, the Laplace value of the first sample may correspond to a value obtained by subtracting a second difference between the sample value of the first sample and the sample value of the second sample located after the first sample from a first difference between the sample value of the third sample located before the first sample. The Laplace value of the first sample may correspond to a difference between the gradient value of the third sample and the gradient value of the first sample.

[0297] In one embodiment, positioning one sample next to another sample may mean, for example, that one sample is positioned to the right or below the other sample in raster scan order.

[0298] Referring to FIG. 23, in Step 1, at least one of a first direction feature value, a second direction feature value, a third direction feature value, or a fourth direction feature value can be obtained for each of the samples within the current block and the samples adjacent to the current block.

[0299] In one embodiment, the first direction feature value may be a horizontal direction feature value, the second direction feature value may be a vertical direction feature value, the third direction feature value may be a first diagonal direction feature value, and the fourth direction feature value may be a second diagonal direction feature value.

[0300] In one embodiment, the first diagonal direction may be a direction connecting the upper right sample and the lower left sample with respect to one sample, and the second diagonal direction may be a direction connecting the upper left sample and the lower right sample with respect to one sample.

[0301] According to Fig. 23, the first direction feature value is the horizontal direction Laplace value (H k,l ) and the second direction feature value is the Laplace value in the vertical direction (V k,l ) can be. In addition, the feature value in the first diagonal direction is the Laplace value (D0) in the first diagonal direction. k,l ), and the feature value in the second diagonal direction is the Laplace value in the second diagonal direction (D1 k,l ) can be. k, l can represent the location of the sample. In Fig. 23, R(k, l) can represent the sample value of the sample at the location (k, l).

[0302] In Step 2, the direction feature values ​​of each sample of the current block and the direction feature values ​​of each sample adjacent to the current block can be combined to produce the direction feature values ​​of the current block.

[0303] In one embodiment, the horizontal feature values ​​(H) of each sample in the current block k,l ) and the horizontal feature values ​​(H) of each sample adjacent to the current block. k,l ) can be combined to produce the horizontal feature value (gh) of the current block.

[0304] Additionally, in one embodiment, the vertical feature values ​​(V) of each sample in the current block k,l) and the vertical feature values ​​(V) of each sample adjacent to the current block. k,l ) can be combined to produce the vertical feature value (gv) of the current block.

[0305] Additionally, in one embodiment, the first diagonal feature value (D0) of each sample in the current block k,l ) and the first diagonal feature value (D0) of each sample adjacent to the current block k,l ) can be combined to produce the first diagonal feature value (gd0) of the current block.

[0306] Additionally, in one embodiment, the second diagonal feature value (D1) of each of the samples in the current block k,l ) and the second diagonal feature values ​​(D1) of each sample adjacent to the current block k,l ) can be combined to produce the second diagonal feature value (gd1) of the current block.

[0307] In Step 2 of Fig. 23, i and j may represent the positions of the upper left samples within the current block. In addition, in Step 2, the fact that k has values ​​from i-2 to i+5 and l has values ​​from j-2 to j+5 may mean that when the size of the current block is 4x4, the direction feature values ​​of the current block are calculated by adding up the direction feature values ​​of eight samples (four samples within the current block and four samples adjacent to the outside of the boundary of the current block).

[0308] In one embodiment, the number of samples used to obtain the direction feature value of the block can be determined in various ways, and accordingly, the range of k and the range of l in Step 2 can be changed in various ways.

[0309] In Step 3, a larger value between the horizontal feature value (gh) of the current block and the vertical feature value (gv) of the current block may be determined as a first maximum feature value (gmax0), and a smaller value between the horizontal feature value (gh) of the current block and the vertical feature value (gv) of the current block may be determined as a first minimum feature value (gmin0). In addition, a larger value between the first diagonal feature value (gd0) of the current block and the second diagonal feature value (gd1) of the current block may be determined as a second maximum feature value (gmax1), and a smaller value between the first diagonal feature value (gd0) of the current block and the second diagonal feature value (gd1) of the current block may be determined as a second minimum feature value (gmin1).

[0310] In one embodiment, the directionality determination unit (2210) can determine the directionality value of the current block using at least one of the first maximum feature value (gmax0), the first minimum feature value (gmin0), the second maximum feature value (gmax1), or the second minimum feature value (gmin1).

[0311] FIG. 24 is a diagram for explaining a method for determining a directionality value of a current block according to one embodiment.

[0312] Referring to FIG. 24, in Step 1, if the first maximum feature value (gmax0) is less than the product of the first predetermined threshold value (t0) and the first minimum feature value (gmin0), and the second maximum feature value (gmax1) is less than the product of the first threshold value (t0) and the second minimum feature value (gmin1), the directionality value (D) can be determined as 0.

[0313] In other words, in Step 1, the directionality value (D) may be determined as 0 when a first ratio between the first maximum feature value (gmax0) and the first minimum feature value (gmin0) (e.g., the first maximum feature value (gmax0) divided by the first minimum feature value (gmin0)) is less than a first threshold value (t0), and a second ratio between the second maximum feature value (gmax1) and the second minimum feature value (gmin1) (e.g., the second maximum feature value (gmax1) divided by the second minimum feature value (gmin1)) is less than a first threshold value (t0).

[0314] In one embodiment, a directionality value (D) of 0 may mean that there is no directionality among the sample values ​​within the current block. In other words, there may be no edges within the current block with a directionality value (D) of 0.

[0315] In one embodiment, the first threshold value (t0) compared with the first ratio and the first threshold value (t0) compared with the second ratio may be the same or different from each other.

[0316] In one embodiment, at least one of the first threshold value (t0) compared with the first ratio or the second threshold value (t0) compared with the second ratio may be adaptively determined based on a type of a slice including a current block, quantization parameters for blocks included in the slice, a size of a maximum coding unit, etc. The type of the slice may be, for example, any one of a bi-predictive slice, a predictive slice, and an intra slice.

[0317] In Step 1, if the first ratio is greater than or equal to the first threshold value (t0) or the second ratio is greater than or equal to the first threshold value (t0), it can be determined that an edge exists within the current block, and Step 2 can be performed.

[0318] In Step 2, the directionality of edges existing within the current block can be identified. In one embodiment, it can be determined whether a first ratio between a first maximum feature value (gmax0) and a first minimum feature value (gmin0) is greater than a second ratio between a second maximum feature value (gmax1) and a second minimum feature value (gmin1).

[0319] If the first ratio is greater than the second ratio, it is determined that there is a horizontal edge or a vertical edge within the current block, and Step 3 can be performed. If the first ratio is less than or equal to the second ratio, it is determined that there is a first diagonal edge or a second diagonal edge within the current block, and Step 4 can be performed.

[0320] In Step 3, if the first maximum feature value (gmax0) is greater than the first minimum feature value (gmin0) multiplied by the second threshold value (t1), the directionality value (D) may be determined as 2, and if the first maximum feature value (gmax0) is less than or equal to the first minimum feature value (gmin0) multiplied by the second threshold value (t1), the directionality value (D) may be determined as 1.

[0321] Step 3 can be understood as a process of determining whether the first ratio between the first maximum feature value (gmax0) and the first minimum feature value (gmin0) is greater than the second threshold value (t1).

[0322] In one embodiment, a directionality value (D) of 1 may mean that the strength of a horizontal edge or vertical edge within the current block is weak. Additionally, in one embodiment, a directionality value (D) of 2 may mean that the strength of a horizontal edge or vertical edge within the current block is strong.

[0323] In Step 4, if the second maximum feature value (gmax1) is greater than the second minimum feature value (gmin1) multiplied by the second threshold value (t1), the directionality value (D) may be determined as 4, and if the second maximum feature value (gmax1) is less than or equal to the second minimum feature value (gmin1) multiplied by the second threshold value (t1), the directionality value (D) may be determined as 3.

[0324] Step 4 can be understood as a process of determining whether the second ratio between the second maximum feature value (gmax1) and the second minimum feature value (gmin1) is greater than the second threshold value (t1).

[0325] In one embodiment, a directionality value (D) of 3 may mean that the strength of the first diagonal edge or the second diagonal edge within the current block is weak. Also, in one embodiment, a directionality value (D) of 4 may mean that the strength of the first diagonal edge or the second diagonal edge within the current block is strong.

[0326] In one embodiment, the second threshold value (t1) used in Step 3 and the second threshold value (t1) used in Step 4 may be the same or different from each other.

[0327] In one embodiment, at least one of the second threshold value (t1) used in Step 3 or the second threshold value (t1) used in Step 4 may be adaptively determined based on the type of the slice including the current block, the quantization parameters for the blocks included in the slice, the size of the maximum coding unit, etc.

[0328] According to the embodiment described with reference to FIG. 24, the directionality value (D) of the current block can be determined as any one of 0 to 4. In one embodiment, the size and / or number of values ​​that the directionality value (D) can have can be varied.

[0329] FIG. 25 is a diagram for explaining a method for determining a directionality value of a current block according to one embodiment.

[0330] According to Step 1 illustrated in FIG. 24, whether an edge exists within the current block is determined based on a first ratio between a first maximum feature value (gmax0) and a first minimum feature value (gmin0), and a second ratio between a second maximum feature value (gmax1) and a second minimum feature value (gmin1).

[0331] For example, in the case of Step 1 illustrated in Fig. 24, even if the first maximum feature value (gmax0) or the second maximum feature value (gmax1) is small, when the first minimum feature value (gmin0) or the second minimum feature value (gmin1) has a very small value close to 0, the first ratio or the second ratio may have a large value. Therefore, even if an edge does not actually exist, it is possible that an edge is determined to exist within the current block.

[0332] As another example, even if the first maximum feature value (gmax0) or the second maximum feature value (gmax1) has a large value, if the first minimum feature value (gmin0) or the second minimum feature value (gmin1) also has a large value, the first ratio or the second ratio may have a small value. Therefore, even if an edge actually exists, it is possible that it is determined that no edge exists within the current block.

[0333] In Step 1 illustrated in Figure 25, by considering the size of the first maximum feature value (gmax0) and the second maximum feature value (gmax1), it is possible to prevent the presence of an edge from being incorrectly determined, as in the example above.

[0334] In one embodiment, in Step 1, if the first maximum feature value (gmax0) is less than a product of a predetermined first threshold value (t0) and a first minimum feature value (gmin0), or if the first maximum feature value (gmax0) is less than a third threshold value (t2), and if the second maximum feature value (gmax1) is less than a product of the first threshold value (t0) and a second minimum feature value (gmin1), or if the second maximum feature value (gmax1) is less than a third threshold value (t2), the directionality value (D) may be determined to be 0.

[0335] In other words, the directionality value (D) may be determined as 0 when the first ratio between the first maximum feature value (gmax0) and the first minimum feature value (gmin0) is less than the first threshold value (t0) or the first maximum feature value (gmax0) is less than the third threshold value (t2), and the second ratio between the second maximum feature value (gmax1) and the second minimum feature value (gmin1) is less than the first threshold value (t0) or the second maximum feature value (gmax1) is less than the third threshold value (t2).

[0336] According to Step 1 illustrated in FIG. 25, the sizes of the first maximum feature value (gmax0) and the second maximum feature value (gmax1) themselves can be used to determine whether an edge exists. Therefore, when the first maximum feature value (gmax0) or the second maximum feature value (gmax1) is small, it is possible to prevent an error in determining that an edge exists within the current block.

[0337] In one embodiment, the first threshold value (t0) compared with the first ratio and the first threshold value (t0) compared with the second ratio may be the same or different from each other.

[0338] In one embodiment, at least one of the first threshold value (t0) compared with the first ratio or the first threshold value (t0) compared with the second ratio may be adaptively determined based on the type of slice containing the current block, quantization parameters for blocks contained in the slice, the size of the maximum coding unit, etc.

[0339] In one embodiment, the third threshold value (t2) compared with the first maximum feature value (gmax0) and the third threshold value (t2) compared with the second maximum feature value (gmax1) may be the same or different from each other.

[0340] In one embodiment, at least one of the third threshold value (t2) compared with the first maximum feature value (gmax0) or the third threshold value (t2) compared with the second maximum feature value (gmax1) may be adaptively determined based on the type of the slice including the current block, the quantization parameters for the blocks included in the slice, the size of the maximum coding unit, etc.

[0341] In one embodiment, the average value of the first maximum feature value (gmax0) and the first minimum feature value (gmin0) may be used instead of the first maximum feature value (gmax0) for comparison with the third threshold value (t2). Furthermore, in one embodiment, the average value of the second maximum feature value (gmax1) and the second minimum feature value (gmin1) may be used instead of the second maximum feature value (gmax1) for comparison with the third threshold value (t2).

[0342] In other words, in Step 1, the directionality value (D) can be determined as 0 if the first ratio is less than the first threshold value (t0) or the average of the first maximum feature value (gmax0) and the first minimum feature value (gmin0) is less than the third threshold value (t2), and if the second ratio is less than the first threshold value (t0) or the average of the second maximum feature value (gmax1) and the second minimum feature value (gmin1) is less than the third threshold value (t2).

[0343] Steps 2, 3 and 4 of Fig. 25 are identical to Steps 2, 3 and 4 described with respect to Fig. 24, so detailed descriptions are omitted here.

[0344] FIG. 26 is a diagram illustrating a method for determining a directionality value of a current block according to one embodiment.

[0345] Step 1, Step 3 and Step 4 of Fig. 26 are identical to Step 1, Step 3 and Step 4 described with respect to Fig. 24, so detailed descriptions are omitted here.

[0346] According to Step 2 illustrated in FIG. 24, the direction of the edge existing in the current block is determined according to a first ratio between the first maximum feature value (gmax0) and the first minimum feature value (gmin0), and a second ratio between the second maximum feature value (gmax1) and the second minimum feature value (gmin1). In this case, even if the first maximum feature value (gmax0) is small and the second maximum feature value (gmax1) is large, if the first minimum feature value (gmin0) is sufficiently small, it may be determined that a horizontal edge or a vertical edge exists in the current block. That is, even if a first diagonal edge or a second diagonal edge exists in the current block, it may be incorrectly determined that a horizontal edge or a vertical edge exists in the current block.

[0347] Conversely, even if the second maximum feature value (gmax1) is small and the first maximum feature value (gmax0) is large, if the second minimum feature value (gmin1) is sufficiently small, it can be determined that a first diagonal edge or a second diagonal edge exists within the current block.

[0348] In Step 2 illustrated in Figure 26, the direction of the edge existing within the current block can be more accurately determined by considering the ratio between the first maximum feature value (gmax0) and the second maximum feature value (gmax1).

[0349] In one embodiment, in Step 2, if a value obtained by combining the first maximum feature value (gmax0) divided by the second maximum feature value (gmax1) and the first ratio is greater than a value obtained by combining the second maximum feature value (gmax1) divided by the first maximum feature value (gmax0) and the second ratio, it may be determined that a horizontal edge or a vertical edge exists within the current block.

[0350] In one embodiment, if a value obtained by combining the first maximum feature value (gmax0) divided by the second maximum feature value (gmax1) and the first ratio is less than or equal to a value obtained by combining the second maximum feature value (gmax1) divided by the first maximum feature value (gmax0) and the second ratio, it may be determined that a first diagonal edge or a second diagonal edge exists within the current block.

[0351] α illustrated in FIG. 26 may be a predetermined weight. In one embodiment, the weight (α) applied to the value obtained by dividing the first maximum feature value (gmax0) by the second maximum feature value (gmax1) and the weight (α) applied to the value obtained by dividing the second maximum feature value (gmax1) by the first maximum feature value (gmax0) may be the same or different from each other.

[0352] In one embodiment, instead of the value obtained by dividing the first maximum feature value (gmax0) by the second maximum feature value (gmax1), a value obtained by dividing the average of the first maximum feature value (gmax0) and the first minimum feature value (gmin0) by the average of the second maximum feature value (gmax1) and the second minimum feature value (gmin1) may be used. Furthermore, instead of the value obtained by dividing the second maximum feature value (gmax1) by the first maximum feature value (gmax0), a value obtained by dividing the average of the second maximum feature value (gmax1) and the second minimum feature value (gmin1) by the average of the first maximum feature value (gmax0) and the first minimum feature value (gmin0) may be used.

[0353] In one embodiment, after Step 1 illustrated in FIG. 25 is performed, Steps 2, 3, and 4 illustrated in FIG. 26 may be performed.

[0354] In Step 1, Step 2, and Step 3 of FIGS. 24 to 26, it is determined whether one value is greater than or less than the other value in order to compare the sizes of two values. In one embodiment, this may be changed to determine whether one value is greater than or less than the other value. For example, in Step 1 of FIG. 26, it is determined whether the first ratio is less than the first threshold value (t0) and whether the second ratio is less than the first threshold value (t0). In one embodiment, it may be determined whether the first ratio is less than or equal to the first threshold value (t0) and whether the second ratio is less than or equal to the first threshold value (t0).

[0355] Referring again to FIG. 22, in one embodiment, the activity determining unit (2230) may determine the activity value of the current block using at least one of a horizontal feature value (gh), a vertical feature value (gv), a first diagonal feature value (gd0), or a second diagonal feature value (gd1).

[0356] In one embodiment, the activity determining unit (2230) may determine the activity value of the current block from the sum of the horizontal feature value (gh) and the vertical feature value (gv). For example, the activity determining unit (2230) may scale the sum of the horizontal feature value (gh) and the vertical feature value (gv) based on a predetermined value (e.g., bit depth) and map the scaled value to one of the predetermined candidate values. The mapped candidate value may be determined as the activity value of the current block.

[0357] In one embodiment, the activity determining unit (2230) may determine the activity value of the current block from the sum of the feature value (gd0) in the first diagonal direction and the feature value (gd1) in the second diagonal direction. For example, the activity determining unit (2230) may scale the sum of the feature value (gd0) in the first diagonal direction and the feature value (gd1) in the second diagonal direction based on a predetermined value (e.g., bit depth) and map the scaled value to one of the predetermined candidate values. The mapped candidate value may be determined as the activity value of the current block.

[0358] When determining the activity value of the current block, if only the horizontal feature value (gh) and the vertical feature value (gv) are used, the features in the first diagonal direction and the second diagonal direction within the current block are not considered. In addition, when determining the activity value of the current block, if only the first diagonal feature value (gd0) and the second diagonal feature value (gd1) are used, the horizontal and vertical features within the current block are not considered.

[0359] In one embodiment, if the direction of the edge within the current block is determined to be horizontal or vertical according to step 2 included in FIGS. 24, 25, and 26, the activity determination unit (2230) may determine the activity value of the current block from the sum of the horizontal direction feature value (gh) and the vertical direction feature value (gv) (or the average value of the horizontal direction feature value (gh) and the vertical direction feature value (gv)). If the direction of the edge within the current block is determined to be the first diagonal direction or the second diagonal direction, the activity determination unit (2230) may determine the activity value of the current block from the sum of the first diagonal direction feature value (gd0) and the second diagonal direction feature value (gd1) (or the average value of the first diagonal direction feature value (gd0) and the second diagonal direction feature value (gd1)).

[0360] In one embodiment, the activity determination unit (2230) may determine the activity value of the current block from the first maximum feature value (gmax0) (or a value obtained by multiplying the first maximum feature value (gmax0) by a predetermined weight) when the direction of the edge within the current block is determined to be horizontal or vertical according to step 2 included in FIGS. 24, 25, and 26. For example, the activity determination unit (2230) may scale the first maximum feature value (gmax0) (or a value obtained by multiplying the first maximum feature value (gmax0) by a predetermined weight) based on a predetermined value (e.g., a bit depth) and map the scaled value to one of the predetermined candidate values. The mapped candidate value may be determined as the activity value of the current block.

[0361] If the direction of the edge within the current block is determined to be the first diagonal direction or the second diagonal direction, the activity determining unit (2230) can determine the activity value of the current block from the second maximum feature value (gmax1) (or a value obtained by multiplying the second maximum feature value (gmax1) by a predetermined weight). For example, the activity determining unit (2230) can scale the second maximum feature value (gmax1) (or a value obtained by multiplying the second maximum feature value (gmax1) by a predetermined weight) based on a predetermined value (e.g., a bit depth) and map the scaled value to one of the predetermined candidate values. The mapped candidate value can be determined as the activity value of the current block.

[0362] In one embodiment, the activity value of the current block may be determined as any one of 0 to 4. In one embodiment, the size and / or number of candidate values ​​that the activity value may have may vary.

[0363] In one embodiment, once the directionality and activity values ​​of the current block are derived, the class determination unit (2250) may determine which of the multiple classes the current block belongs to using at least one of the directionality and activity values. For example, the class determination unit (2250) may determine that the current block belongs to a class indicated by a combined value of the directionality and activity values.

[0364] In one embodiment, the class determination unit (2250) may derive a value between 0 and 24 by multiplying the directionality value by 5 and adding the activity value. The derived value may indicate the class to which the current block belongs. In one embodiment, the class determination unit (2250) may also derive a value between 0 and 24 by multiplying the activity value by 5 and adding the directionality value.

[0365] Below, we describe a method for classifying the current block based on the sample feature values ​​of the current block.

[0366] FIG. 27 is a diagram illustrating a method for classifying a current block based on sample feature values ​​of the current block according to one embodiment.

[0367] Sample feature values ​​of the current block can be obtained for classification of the current block.

[0368] In one embodiment, the sample feature value may correspond to a sum of the sample values ​​within the current block or an average of the sample values ​​within the current block.

[0369] Once the sample feature values ​​of the current block are calculated, the class of the current block can be determined based on the magnitude of the sample feature values ​​of the current block. In one embodiment, the sample feature values ​​of the current block are scaled based on a predetermined value, and the class indicated by the scaled value can be determined as the class of the current block.

[0370] Since the range of sample values ​​is limited, the sample feature values ​​can also fall within a predetermined range. In other words, the sample feature values ​​can correspond to any one of several values ​​within the predetermined range.

[0371] As illustrated in FIG. 27, when a sample feature value can have any one of the values ​​from 0 to z, it is identified which sub-range among several equally spaced sub-ranges included in the entire range including 0 to z the sample feature value of the current block belongs to, and the class of the current block can be determined according to the identified sub-range.

[0372] In Fig. 27, sub-ranges can correspond to multiple classes. Fig. 27 illustrates that there are k classes, where k can be a natural number greater than 1 (e.g., 25).

[0373] For example, if the sample feature value of the current block falls within a sub-range of 0 to a, the current block can be classified into a first class, and if the sample feature value of the current block falls within a sub-range of a to b, the current block can be classified into a second class.

[0374] Here, the fact that the sample feature value of the current block belongs to a sub-range may mean that the sample feature value of the current block corresponds to any one of the values ​​including the minimum value and the maximum value of the corresponding sub-range.

[0375] In one embodiment, if a sample feature value can have any one of the values ​​included in a predetermined overall range, the predetermined overall range can be divided into multiple equally spaced sub-ranges. However, if the overall range is divided into equally spaced sub-ranges without considering image characteristics, blocks that should be filtered by the same or similar filters may end up being filtered by entirely different filters.

[0376] FIG. 28 is a diagram illustrating a histogram of sample feature values ​​according to one embodiment.

[0377] The histogram shown in Figure 28 represents the frequencies of sample feature values ​​included in the image.

[0378] Typically, the number of blocks located within the boundary of an object within an image may be greater than the number of blocks located on the boundary of the object. Furthermore, the sample feature values ​​of blocks located within the boundary of the object may be more similar to each other.

[0379] That is, since the sample feature values ​​with a high frequency on the histogram are likely to have been derived from blocks located inside the object boundary, it may be desirable to filter blocks with high-frequency sample feature values ​​with the same or similar filter, because the blocks are likely to constitute the same object.

[0380] Referring to FIG. 28, since the frequency of sample feature values ​​belonging to area A is greater than the frequency of sample feature values ​​belonging to area B, blocks having sample feature values ​​belonging to area A may be located inside the boundary of the object, and blocks having sample feature values ​​belonging to area B may be located on the boundary of the object. However, since blocks having sample feature values ​​belonging to area A and blocks having sample feature values ​​belonging to area B are both classified into the second class, a problem may arise in which blocks having different characteristics are filtered by the same filter.

[0381] In addition, since the frequency of sample feature values ​​belonging to region C is high, it may be desirable to classify blocks having sample feature values ​​belonging to region C into the same class. However, according to Fig. 28, some of the sample feature values ​​belonging to region C are classified into the second class, and other some of the sample feature values ​​belonging to region C are classified into the third class, so the consistency of filtering for the same object may not be maintained.

[0382] In one embodiment, classification accuracy can be improved by classifying each block by considering the tendency or characteristics of the blocks included in the image.

[0383] FIG. 29 is a block diagram illustrating the configuration of a classifier (2900) according to one embodiment.

[0384] Referring to FIG. 29, the classifier (2900) may include a histogram construction unit (2910), a clustering unit (2930), and a class determination unit (2950).

[0385] The histogram construction unit (2910) can generate a histogram based on the sample feature values ​​of blocks included in the current image. Here, the process of generating the histogram can be understood as a process of calculating the frequency of the sample feature values ​​of blocks included in the current image.

[0386] Hereinafter, the histogram is described as being generated for the current image, but the histogram may also be generated for the upper blocks of blocks within the current image. For example, when sample feature values ​​of coding units are calculated, the histogram may be generated for the largest coding unit or slice comprising multiple coding units.

[0387] In one embodiment, the histogram construction unit (2910) can obtain the frequency of each candidate value that the sample feature value may have, calculated from the sample feature values ​​of blocks in the current image.

[0388] The histogram construction unit (2910) can identify, for example, the number of blocks having a sample feature value of 1, the number of blocks having a sample feature value of 2, and the number of blocks having a sample feature value of 3 when there are candidate values ​​of 1, 2, and 3.

[0389] The clustering unit (2930) can divide the entire range containing candidate values ​​into multiple sub-ranges by considering the frequency of each candidate value. The multiple sub-ranges can correspond to multiple classes. In other words, the clustering unit (2930) can group candidate values ​​into multiple classes.

[0390] In one embodiment, the clustering unit (2930) may divide the entire range into multiple sub-ranges according to an unsupervised algorithm. The unsupervised algorithm may include, for example, a k-means clustering algorithm.

[0391] The class determination unit (2950) can determine which sub-range among a plurality of sub-ranges the sample feature value of the current block belongs to, and determine the class corresponding to the sub-range to which the sample feature value of the current block belongs as the class of the current block.

[0392] In one embodiment, the process of determining which sub-range among the plurality of sub-ranges the sample feature value of the current block belongs to may be understood as a process of determining which representative value among the representative values ​​of each of the plurality of sub-ranges the sample feature value of the current block is most similar to. Here, the representative value may also be referred to as a centroid value.

[0393] Hereinafter, with reference to FIGS. 30 to 33, a method of dividing the entire range including candidate values ​​into multiple sub-ranges will be described.

[0394] FIG. 30 is a diagram illustrating a histogram constructed based on sample feature values ​​derived from a current image according to one embodiment.

[0395] In one embodiment, it is assumed that the sample feature values ​​can have candidate values ​​within the full range from 10 to 100.

[0396] The histogram construction unit (2910) can calculate sample feature values ​​of blocks within the current image and identify the frequency with which each candidate value is calculated as a sample feature value. Since the candidate value of 90 in FIG. 30 has the highest frequency, it can be seen that the sample feature values ​​of a large number of blocks within the current image are 90.

[0397] In one embodiment, the histogram construction unit (2910) updates the frequency of candidate values ​​each time a sample feature value of each block in the current image is calculated, and deletes the sample feature value used for the frequency update from the memory, thereby preventing a large number of sample feature values ​​from being stored in the memory.

[0398] For example, when a sample feature value of a block is calculated, the histogram construction unit (2910) can increase the frequency of a candidate value corresponding to the calculated sample feature value and delete the sample feature value of the block from the memory. In addition, the histogram construction unit (2910) can increase the frequency of the candidate value by calculating the sample feature value of the next block.

[0399] In one embodiment, the clustering unit (2930) may determine a plurality of temporary representative values ​​within the entire range including candidate values ​​from 10 to 100. The number of temporary representative values ​​may be equal to the number of classes.

[0400] Multiple temporary representative values ​​can be determined in various ways. For example, candidate values ​​selected in descending order of frequency from among candidate values ​​can be determined as multiple temporary representative values. Alternatively, multiple temporary representative values ​​can be determined at equal intervals within the entire range encompassing the candidate values.

[0401] Referring to FIG. 30, a first temporary representative value (C1) may be determined between 20 and 30, a second temporary representative value (C2) may be determined between 50 and 60, and a third temporary representative value (C3) may be determined between 80 and 90.

[0402] The fact that three temporary representative values ​​(C1, C2, C3) are selected within the entire range may mean that the number of classes is three.

[0403] FIG. 31 is a diagram illustrating a method of dividing an entire area including candidate values ​​according to one embodiment into sub-ranges (3110, 3120, 3130) based on temporary representative values.

[0404] The clustering unit (2930) can identify which temporary representative value each of the plurality of candidate values ​​is closest to based on the distance between each of the plurality of candidate values ​​and the temporary representative values ​​(C1, C2, C3). The candidate values ​​identified as being closest to a particular temporary representative value can form a sub-range corresponding to a particular class.

[0405] In one embodiment, the distance between the temporary representative value and the candidate value may correspond to the difference between the temporary representative value and the candidate value.

[0406] Referring to FIG. 31, a first sub-range (3110) can be identified from candidate values ​​of 10, 20, 30, and 40 that are closest to the first temporary representative value (C1), and a second sub-range (3120) can be identified from candidate values ​​of 50, 60, and 70 that are closest to the second temporary representative value (C2). Additionally, a third sub-range (3130) can be identified from candidate values ​​of 80, 90, and 100 that are closest to the third temporary representative value (C3).

[0407] In other words, candidate values ​​of 10, 20, 30, and 40 may be included in one group, candidate values ​​of 50, 60, and 70 may be included in another group, and candidate values ​​of 80, 90, and 100 may be included in yet another group.

[0408] When multiple sub-ranges (3110, 3120, 3130) are identified based on multiple temporary representative values ​​(C1, C2, C3), the clustering unit (2930) can determine new temporary representative values ​​in each of the multiple sub-ranges (3110, 3120, 3130).

[0409] FIG. 32 is a drawing for explaining a method of determining new temporary representative values ​​(C1', C2', C3') in the sub-ranges (3110, 3120, 3130) illustrated in FIG. 31.

[0410] In one embodiment, the clustering unit (2930) may determine new temporary representative values ​​(C1', C2', C3') in each sub-range (3110, 3120, 3130) by weighting the candidate values ​​belonging to each sub-range (3110, 3120, 3130) according to their frequencies. In one embodiment, when determining the new temporary representative values ​​(C1', C2', C3'), the frequencies may be applied as weights to the candidate values.

[0411] For example, when the frequencies of candidate values ​​of 50, 60, and 70 included in the second sub-range (3120) are a, b, and c, respectively, the new temporary representative value (C2') can be calculated as (50*a+60*b+70*c). In one embodiment, the new temporary representative value (C2') can also be calculated as (50*a+60*b+70*c) / (a+b+c).

[0412] When new temporary representative values ​​(C1', C2', C3') are determined in each of the plurality of sub-ranges (3110, 3120, 3130), the clustering unit (2930) can update the sub-ranges (3110, 3120, 3130) based on the new temporary representative values ​​(C1', C2', C3').

[0413] FIG. 33 is a diagram for explaining a method of updating sub-ranges (3110, 3120, 3130) based on new temporary representative values ​​(C1', C2', C3') illustrated in FIG. 32.

[0414] The clustering unit (2930) can identify which temporary representative value each of the plurality of candidate values ​​is closest to based on the distance between each of the plurality of candidate values ​​and the new temporary representative values ​​(C1', C2', C3'). The candidate values ​​identified as being closest to a particular temporary representative value can form a sub-range corresponding to a particular class.

[0415] Referring to FIG. 33, a first sub-range (3310) can be identified that includes candidate values ​​of 10, 20, 30, 40, and 50 that are closest to a first temporary representative value (C1'), a second sub-range (3320) can be identified that includes candidate values ​​of 60 and 70 that are closest to a second temporary representative value (C2'), and a third sub-range (3330) can be identified that includes candidate values ​​of 80, 90, and 100 that are closest to a third temporary representative value (C3').

[0416] Compared to FIG. 32, it can be seen that the first sub-range (3110) illustrated in FIG. 32 includes four candidate values, and the first sub-range (3310) illustrated in FIG. 33 includes five candidate values. In addition, it can be seen that the second sub-range (3120) illustrated in FIG. 32 includes three candidate values, and the second sub-range (3320) illustrated in FIG. 33 includes two candidate values.

[0417] When new sub-ranges (3310, 3320, 3330) are identified, the clustering unit (2930) can repeat the process of updating the temporary representative values ​​and the process of updating the sub-ranges described with respect to FIGS. 32 and 33 until the temporary representative values ​​no longer change.

[0418] The class determination unit (2950) can compare the sample feature values ​​of the current block with a plurality of representative values ​​finally determined by the clustering unit (2930) to determine which representative value the current block corresponds to.

[0419] In one embodiment, the class determination unit (2950) can identify a representative value among a plurality of representative values ​​that has the smallest difference from the sample feature value of the current block, and determine a class corresponding to the identified representative value as the class of the current block.

[0420] According to one embodiment, sub-ranges or representative values ​​are adaptively determined based on the frequency of sample feature values ​​produced within the current image, so that filtering suitable for the features of the current image can be performed for each block.

[0421] FIG. 34 is a diagram illustrating a lookup table constructed based on clustering results according to one embodiment.

[0422] In one embodiment, when a plurality of representative values ​​are determined, the clustering unit (2930) can identify in advance which representative value each of the candidate values ​​corresponds to, or in other words, which class each of the candidate values ​​corresponds to.

[0423] As previously illustrated in FIG. 33, if the candidate values ​​of 10, 20, 30, 40, and 50 correspond to the first representative value (C1'), the clustering unit (2930) can determine that the candidate values ​​of 10, 20, 30, 40, and 50 belong to the class corresponding to the first temporary representative value (C1').

[0424] In one embodiment, a lookup table is constructed to determine which class each candidate value belongs to, so that it can be quickly determined which class the current block belongs to.

[0425] For example, referring to the lookup table illustrated in FIG. 34, if the sample feature value of the current block is 30, the current block may be determined to belong to class 0, and if the sample feature value of the current block is 80, the current block may be determined to belong to class 2.

[0426] Figure 35 is a flowchart for explaining a method of filtering an image according to one embodiment.

[0427] At step S3510, the filtering device (2000) can produce a first direction feature value and a second direction feature value of a current block in a current image.

[0428] The first direction feature value may be, for example, a Laplace value in the horizontal direction, and the second direction feature value may be, for example, a Laplace value in the vertical direction. In one embodiment, the first direction feature value may be, for example, a Laplace value in the first diagonal direction, and the second direction feature value may be, for example, a Laplace value in the second diagonal direction.

[0429] In one embodiment, the size of the current block may be 1x1 or larger. A block of size 1x1 may represent a sample.

[0430] In one embodiment, the filtering device (2000) can further obtain a third direction feature value and a fourth direction feature value together with the first direction feature value and the second direction feature value. When the first direction feature value is a horizontal Laplace value and the second direction feature value is a vertical Laplace value, the third direction feature value and the fourth direction feature value may be a first diagonal Laplace value and a second diagonal Laplace value, respectively. Conversely, when the first direction feature value is a first diagonal Laplace value and the second direction feature value is a second diagonal Laplace value, the third direction feature value and the fourth direction feature value may be a horizontal Laplace value and a vertical Laplace value, respectively.

[0431] In step S3520, the filtering device (2000) can determine the directionality value of the current block based on the comparison result between the first ratio and the first threshold value, and the comparison result between the first maximum feature value and the second threshold value.

[0432] The first maximum feature value may represent a larger value between the first directional feature value and the second directional feature value. If the smaller value between the first directional feature value and the second directional feature value is the first minimum feature value, the first ratio may correspond to a ratio between the first maximum feature value and the first minimum feature value.

[0433] The first threshold value may correspond to the first threshold value (t0) illustrated in FIG. 25, and the second threshold value may correspond to the third threshold value (t2).

[0434] In one embodiment, if the first ratio is less than the first threshold value or the first maximum feature value is less than the second threshold value, the filtering device (2000) may determine that there is no directionality of the sample values ​​in the current block and determine the directionality value to be 0.

[0435] In one embodiment, the filtering device (2000) may determine that there is directionality in the sample values ​​within the current block if the first ratio is greater than or equal to a first threshold value and the first maximum feature value is greater than or equal to a second threshold value.

[0436] In one embodiment, when a third direction feature value and a fourth direction feature value are further acquired by the filtering device (2000), a larger value of the third direction feature value and the fourth direction feature value may correspond to a second maximum feature value, and a smaller value of the third direction feature value and the fourth direction feature value may correspond to a second minimum feature value. A ratio between the second maximum feature value and the second minimum feature value may correspond to a second ratio.

[0437] In one embodiment, the filtering device (2000) can determine the directionality value of the current block based on a comparison result between the first ratio and the first threshold value, a comparison result between the second ratio and the first threshold value, a comparison result between the first maximum feature value and the second threshold value, and a comparison result between the second maximum feature value and the second threshold value.

[0438] In one embodiment, if there is a directionality of sample values ​​within the current block, the filtering device (2000) can determine the directionality value based on a comparison result of a first result value that combines a value obtained by dividing the first maximum feature value by the second maximum feature value and a first ratio, and a second result value that combines a value obtained by dividing the second maximum feature value by the first maximum feature value and a second ratio.

[0439] In one embodiment, if the first result value is greater than the second result value and the first ratio is greater than the third threshold value, it may mean that the horizontal or vertical directionality of the sample values ​​within the current block is strong. In one embodiment, if the first result value is greater than the second result value and the first ratio is less than or equal to the third threshold value, it may mean that the horizontal or vertical directionality of the sample values ​​within the current block is weak. If the horizontal or vertical directionality of the sample values ​​within the current block is strong, the directionality value may be determined as 2, and if the horizontal or vertical directionality of the sample values ​​within the current block is weak, the directionality value may be determined as 1.

[0440] In one embodiment, if the second result value is greater than the first result value and the second ratio is greater than the third threshold value, this may mean that the diagonal directionality of the sample values ​​within the current block is strong. In one embodiment, if the second result value is greater than the first result value and the second ratio is less than or equal to the third threshold value, this may mean that the diagonal directionality of the sample values ​​within the current block is weak. When the diagonal directionality of the sample values ​​within the current block is strong, the directionality value may be determined as 4, and when the diagonal directionality of the sample values ​​within the current block is weak, the directionality value may be determined as 3.

[0441] At step S3530, the filtering device (2000) can determine a class corresponding to the current block among multiple classes based on the directionality value.

[0442] The filtering device (2000) may determine an activity value of the current block and may also determine a class corresponding to the current block based on at least one of the directional value and the activity value.

[0443] In one embodiment, the filtering device (2000) can determine the activity value of the current block from the sum of the first direction feature value and the second direction feature value.

[0444] In one embodiment, the filtering device (2000) can determine the activity value of the current block from the sum of the third direction feature value and the fourth direction feature value.

[0445] In one embodiment, the filtering device (2000) can determine the activity value of the current block from the sum of the first direction feature value and the second direction feature value (or the average value of the first direction feature value and the second direction feature value) when the direction of the edge within the current block is determined to be the first direction or the second direction. The filtering device (2000) can determine the activity value of the current block from the sum of the third direction feature value and the fourth direction feature value (or the average value of the third direction feature value and the fourth direction feature value) when the direction of the edge within the current block is determined to be the third direction or the fourth direction.

[0446] In one embodiment, the filtering device (2000) can determine the activity value of the current block from the first maximum feature value (or the value obtained by multiplying the first maximum feature value by a predetermined weight) when the direction of the edge within the current block is determined to be the first direction or the second direction. The filtering device (2000) can determine the activity value of the current block from the second maximum feature value (or the value obtained by multiplying the second maximum feature value by a predetermined weight) when the direction of the edge within the current block is determined to be the third direction or the fourth direction.

[0447] In one embodiment, once the class corresponding to the current block is determined, each sample of the current block may be determined to belong to the class corresponding to the current block. In other words, the class determined for the current block may be shared among the samples within the current block.

[0448] At step S3540, the filtering device (2000) can filter samples within the current block using a filter configured according to a class corresponding to the current block.

[0449] The filter may include filter coefficients obtained based on a class corresponding to the current block. The current sample may be filtered by applying the filter coefficients to the current sample and its surrounding samples.

[0450] In one embodiment, when samples within a current image are filtered, the filtered image can be used as a reference image for the next image. For example, the filtered image can be used as a reference image for inter prediction of blocks within the next image.

[0451] Figure 36 is a flowchart for explaining a method of filtering an image according to one embodiment.

[0452] In one embodiment, if FIG. 35 illustrates a filtering method when a first classification process is applied to the current block, FIG. 36 may be said to illustrate a filtering method when a second classification process is applied to the current block.

[0453] In step S3610, the filtering device (2000) can determine a plurality of representative values ​​corresponding to a plurality of classes within a range including candidate values ​​that the sample feature values ​​of the block may have.

[0454] The sample feature values ​​of a block may correspond to the sum of the sample values ​​within the block or the average of the sample values ​​within the block.

[0455] In one embodiment, the filtering device (2000) can determine a plurality of representative values ​​corresponding to a plurality of classes based on a k-means clustering algorithm.

[0456] In one embodiment, the filtering device (2000) can determine a plurality of representative values ​​corresponding to a plurality of classes by repeatedly performing i) the process of determining temporary representative values ​​and ii) the process of determining sub-ranges until there is no change in the temporary representative values.

[0457] To elaborate on the process of determining multiple representative values, in one embodiment, the filtering device (2000) can select multiple temporary representative values ​​within the entire range that includes candidate values ​​that the sample feature values ​​of the block can have.

[0458] Multiple interim representative values ​​can be determined for each of the identified sub-ranges based on previous interim representative values. If no previous interim representative values ​​exist, multiple interim representative values ​​can be determined within the entire range in various ways. For example, multiple interim representative values ​​can be selected from among candidate values ​​based on a predetermined criterion. Alternatively, multiple interim representative values ​​can be determined randomly within the entire range.

[0459] The filtering device (2000) can divide the entire range into a plurality of sub-ranges corresponding to each of the plurality of temporary representative values ​​by considering the differences between the plurality of temporary representative values ​​and the candidate values.

[0460] The filtering device (2000) can determine a new temporary representative value in each of the plurality of sub-ranges by calculating a weighted average of candidate values ​​included in each of the plurality of sub-ranges. If the new temporary representative values ​​are identical to the immediately previous temporary representative values, the new temporary representative values ​​can be determined as the final representative values. If the new temporary representative values ​​are not identical to the immediately previous temporary representative values, the plurality of sub-ranges can be determined again based on the new temporary representative values.

[0461] In one embodiment, a frequency may be considered in calculating a weighted average of candidate values ​​included in each of a plurality of sub-ranges. Here, the frequency may be a frequency calculated for each candidate value using sample feature values ​​of blocks within the current image.

[0462] In step S3620, the filtering device (2000) can compare the sample feature value of the current block with a plurality of representative values ​​to identify the representative value corresponding to the current block.

[0463] In one embodiment, the filtering device (2000) can identify a representative value having the smallest difference from a sample feature value of the current block among a plurality of representative values ​​as the representative value corresponding to the current block.

[0464] At step S3630, the filtering device (2000) can determine the class corresponding to the identified representative value as the class corresponding to the current block.

[0465] In one embodiment, the filtering device (2000) can compare candidate values ​​that a sample feature value of a block may have with a plurality of representative values ​​to determine a class corresponding to each candidate value. The correspondence between the candidate values ​​and the classes may be configured as a lookup table. The filtering device (2000) can determine a class corresponding to the sample feature value of the current block based on the lookup table.

[0466] At step S3640, the filtering device (2000) can filter samples within the current block using a filter configured according to a class.

[0467] The filter may include filter coefficients obtained based on a class corresponding to the current block. The current sample may be filtered by applying the filter coefficients to the current sample and its surrounding samples.

[0468] In one embodiment, when samples within a current image are filtered, the filtered image can be used as a reference image for the next image. For example, the filtered image can be used as a reference image for inter prediction of blocks within the next image.

[0469] One embodiment challenges the task of accurately classifying blocks or samples within a current image for filtering purposes.

[0470] One embodiment aims to improve the quality of an image output through a decryption process.

[0471] One embodiment aims to improve the encoding and decoding efficiency of a next image when a filtered current image is used as a reference image for the next image.

[0472] 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.

[0473] A method for filtering an image by a filtering device (2000) according to one embodiment may include a step of calculating a first direction feature value and a second direction feature value of a current block in a current image.

[0474] A method for filtering an image by a filtering device (2000) according to one embodiment may include a step of determining a directionality value of the current block based on a result of comparing a first ratio between a first maximum feature value corresponding to a larger value of the first directional feature value and the second directional feature value and a first minimum feature value corresponding to a smaller value of the first directional feature value and the second directional feature value with a first threshold value, and a result of comparing the first maximum feature value with a second threshold value.

[0475] A method for filtering an image by a filtering device (2000) according to one embodiment may include a step of determining a class corresponding to the current block among a plurality of classes based on the determined directionality value.

[0476] A method for filtering an image by a filtering device (2000) according to one embodiment may include a step of filtering a sample within the current block using a filter configured according to the determined class.

[0477] According to one embodiment, the directional value of the current block can be more accurately calculated by considering the size of the first maximum feature value itself.

[0478] In one embodiment, if the first ratio is less than the first threshold value or the first maximum feature value is less than the second threshold value, the directionality value may be determined as the first value.

[0479] According to one embodiment, it can be accurately determined whether an edge exists within the current block based on the size of the first maximum feature value.

[0480] In one embodiment, the method for filtering an image further includes a step of calculating a third direction feature value and a fourth direction feature value of the current block, wherein a larger value of the third direction feature value and the fourth direction feature value corresponds to a second maximum feature value, and a smaller value of the third direction feature value and the fourth direction feature value corresponds to a second minimum feature value, and when the first ratio is greater than or equal to the first threshold value and the first maximum feature value is greater than or equal to the second threshold value, the step of determining the directionality value may include a step of determining the directionality value based on a comparison result of a first result value obtained by combining a value obtained by dividing the first maximum feature value by the second maximum feature value and the first ratio, and a second result value obtained by combining a value obtained by dividing the second maximum feature value by the first maximum feature value and a second ratio between the second maximum feature value and the second minimum feature value.

[0481] According to one embodiment, the direction of an edge within a current block can be more accurately determined based on a ratio between a first maximum feature value and a second maximum feature value.

[0482] In one embodiment, if the first result value is greater than the second result value, the directionality value may be determined as a second value, and if the first result value is less than or equal to the second result value, the directionality value may be determined as a third value.

[0483] In one embodiment, the directionality value may be determined differently depending on the direction of the edge within the current block.

[0484] In one embodiment, the step of determining a class corresponding to the current block includes the step of determining a class corresponding to the current block among the plurality of classes based on the determined directionality value and the activity value of the current block, wherein if the first result value is greater than the second result value, the activity value may be determined based on the first maximum feature value, and if the first result value is less than or equal to the second result value, the activity value may be determined based on the second maximum feature value.

[0485] According to one embodiment, the horizontal / vertical direction characteristics and diagonal direction characteristics of the current block may be appropriately considered in determining the activity value.

[0486] In one embodiment, a class indicated by a value combining the directional value and the activity value among the plurality of classes may be determined as the class corresponding to the current block.

[0487] In one embodiment, the method for filtering an image further includes a step of selecting a classifier for determining a class corresponding to the current block from among a plurality of classifiers, and when the classifier is selected as a first classifier, the class corresponding to the current block can be determined based on a directionality value of the current block.

[0488] In one embodiment, the current block can be classified based on multiple classifiers, thereby making the classification result more accurate.

[0489] In one embodiment, when the classifier is selected as a second classifier, the step of determining a class corresponding to the current block may include: determining a plurality of representative values ​​corresponding to a plurality of classes within a range including candidate values ​​that the sample feature values ​​of the block may have; identifying a representative value corresponding to the current block by comparing the sample feature values ​​of the current block with the plurality of representative values; and determining a class corresponding to the identified representative value as the class corresponding to the current block.

[0490] In one embodiment, the step of determining the plurality of representative values ​​may include the step of calculating sample feature values ​​of blocks in the current image; the step of obtaining a frequency of each of the candidate values ​​calculated as sample feature values ​​of the blocks; and the step of determining the plurality of representative values ​​within the range, taking into account the frequency of each of the candidate values.

[0491] According to one embodiment, a plurality of representative values ​​are adaptively determined based on the frequencies of candidate values, so that the class of the current block can be determined more accurately.

[0492] In one embodiment, the step of determining the plurality of representative values ​​may include: selecting a plurality of temporary representative values ​​within the range; dividing the range into a plurality of sub-ranges corresponding to each of the plurality of temporary representative values ​​by considering differences between the plurality of temporary representative values ​​and candidate values; and determining a representative value for each of the plurality of sub-ranges through a weighted average of the candidate values ​​included in each of the plurality of sub-ranges.

[0493] In one embodiment, the class of the current block can be more accurately determined through the process of updating the representative value.

[0494] In one embodiment, candidate values ​​included in each of the plurality of sub-ranges may be weighted averaged based on the frequency.

[0495] In one embodiment, when the classifier is selected as a second classifier, the step of determining a class corresponding to the current block may include: determining a plurality of representative values ​​corresponding to a plurality of classes within a range including candidate values ​​that the sample feature values ​​of the block may have; comparing the candidate values ​​with the plurality of representative values ​​to determine a class corresponding to each of the candidate values; and determining a class of a candidate value corresponding to the sample feature value of the current block among the candidate values ​​as the class corresponding to the current block.

[0496] In one embodiment, the current block can be classified more quickly by pre-constructing a lookup table.

[0497] In one embodiment, the sample feature value of the block may be a sum of the sample values ​​of the samples within the block or an average of the sample values ​​of the samples within the block.

[0498] A filtering device (200) according to one embodiment may include a directionality determination unit (2210) that calculates a first directionality feature value and a second directionality feature value of a current block in a current image, and determines a directionality value of the current block based on a result of comparing a first ratio between a first maximum feature value corresponding to a larger value between the first directionality feature value and the second directionality feature value and a first minimum feature value corresponding to a smaller value between the first directionality feature value and the second directionality feature value and a first threshold value, and a result of comparing the first maximum feature value and the second threshold value.

[0499] A filtering device (200) according to one embodiment may include a class determination unit (2250) that determines a class corresponding to the current block among a plurality of classes based on the determined directionality value.

[0500] A filtering device (200) according to one embodiment may include a filter unit (2030) that filters samples within the current block using a filter configured according to the determined class.

[0501] According to one embodiment, the directional value of the current block can be more accurately calculated by considering the size of the first maximum feature value itself.

[0502] A computer-readable recording medium according to one embodiment can store a bitstream.

[0503] In one embodiment, the bitstream may include filter information used to filter the current image according to a filtering method.

[0504] In one embodiment, the filtering method may include a step of calculating a first direction feature value and a second direction feature value of a current block in the current image.

[0505] In one embodiment, the filtering method may include a step of determining a directionality value of the current block based on a comparison result between a first ratio between a first maximum feature value corresponding to a larger value of the first directional feature value and the second directional feature value and a first minimum feature value corresponding to a smaller value of the first directional feature value and the second directional feature value and a first threshold value, and a comparison result between the first maximum feature value and the second threshold value.

[0506] In one embodiment, the filtering method may include a step of determining a class corresponding to the current block among a plurality of classes based on the determined directional value.

[0507] In one embodiment, the filtering method may include a step of filtering samples within the current block using a filter configured according to the determined class and the filter information.

[0508] According to one embodiment, the directional value of the current block can be more accurately calculated by considering the size of the first maximum feature value itself.

[0509] One embodiment can accurately classify blocks or samples within a current image for filtering the current image.

[0510] One embodiment may improve the quality of an image output through a decryption process.

[0511] One embodiment can improve the encoding and decoding efficiency of the next image when the filtered current image is used as a reference image for the next image.

[0512] 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.

[0513] 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.

[0514] 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.

[0515] 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.

[0516] Above, the technical idea of ​​the present disclosure has been described in detail with reference to preferred embodiments, but the technical idea of ​​the present disclosure is not limited to the above embodiments, and various modifications and changes are possible by a person having ordinary knowledge in the art within the scope of the technical idea of ​​the present disclosure.

Claims

1. In a method of filtering an image using a filtering device (2000), A step of calculating a first direction feature value and a second direction feature value of a current block in a current image; A step of determining a directionality value of the current block based on a comparison result between a first ratio between a first maximum feature value corresponding to a larger value of the first directional feature value and the second directional feature value and a first minimum feature value corresponding to a smaller value of the first directional feature value and the second directional feature value and a first threshold value, and a comparison result between the first maximum feature value and the second threshold value; A step of determining a class corresponding to the current block among a plurality of classes based on the determined directional value; and A method for filtering an image, comprising the step of filtering samples within the current block using a filter configured according to the determined class.

2. In paragraph 1, A method for filtering an image, wherein if the first ratio is less than the first threshold value or the first maximum feature value is less than the second threshold value, the directionality value is determined as the first value.

3. In any one of paragraphs 1 and 2, The filtering method of the above video is: Further comprising a step of calculating a third direction feature value and a fourth direction feature value of the current block, The larger value among the third direction feature value and the fourth direction feature value corresponds to the second maximum feature value, and the smaller value among the third direction feature value and the fourth direction feature value corresponds to the second minimum feature value. When the first ratio is greater than or equal to the first threshold value and the first maximum feature value is greater than or equal to the second threshold value, the step of determining the directionality value comprises: A method for filtering an image, comprising the step of determining the directionality value based on a comparison result of a first result value that combines a value obtained by dividing the first maximum feature value by the second maximum feature value and the first ratio, and a second result value that combines a value obtained by dividing the second maximum feature value by the first maximum feature value and a second ratio between the second maximum feature value and the second minimum feature value.

4. In any one of the clauses 1 to 3, If the first result value is greater than the second result value, the directionality value is determined as the second value, A method for filtering an image, wherein if the first result value is less than or equal to the second result value, the directionality value is determined as a third value.

5. In any one of paragraphs 1 to 4, The step of determining the class corresponding to the current block is: A step of determining a class corresponding to the current block among the plurality of classes based on the determined directionality value and the activity value of the current block, If the first result value is greater than the second result value, the activity value is determined based on the first maximum feature value, A method for filtering an image, wherein the activity value is determined based on the second maximum feature value if the first result value is less than or equal to the second result value.

6. In any one of paragraphs 1 to 5, A method for filtering an image, wherein a class indicated by a value combining the directional value and the activity value among the plurality of classes is determined as a class corresponding to the current block.

7. In any one of paragraphs 1 to 6, The filtering method of the above video is: Further comprising a step of selecting a classifier for determining a class corresponding to the current block among a plurality of classifiers, A method for filtering an image, wherein a class corresponding to the current block is determined based on a directionality value of the current block when the above classifier is selected as a first classifier.

8. In any one of paragraphs 1 to 7, If the above classifier is selected as the second classifier, the step of determining the class corresponding to the current block is: A step of determining a plurality of representative values corresponding to a plurality of classes within a range including candidate values that the sample feature value of the block may have; A step of comparing the sample feature value of the current block with the plurality of representative values to identify the representative value corresponding to the current block; and A method for filtering an image, comprising a step of determining a class corresponding to the identified representative value as a class corresponding to the current block.

9. In any one of paragraphs 1 to 8, The step of determining the above multiple representative values is: A step of calculating sample feature values of blocks in the current image; A step of obtaining a frequency calculated from the sample feature values of the blocks for each of the above candidate values; and A method for filtering an image, comprising a step of determining the plurality of representative values within the range by considering the frequency of each of the candidate values.

10. In any one of paragraphs 1 to 9, The step of determining the above multiple representative values is: A step of selecting multiple temporary representative values within the above range; A step of dividing the range into a plurality of sub-ranges corresponding to each of the plurality of temporary representative values, taking into account the differences between the plurality of temporary representative values and the candidate values; and A method for filtering an image, comprising the step of determining a representative value of each of a plurality of sub-ranges through a weighted average of candidate values included in each of the plurality of sub-ranges.

11. In any one of paragraphs 1 to 10, A method for filtering an image, wherein candidate values included in each of the plurality of sub-ranges are weighted and averaged based on the frequency.

12. In any one of paragraphs 1 to 11, If the above classifier is selected as the second classifier, the step of determining the class corresponding to the current block is: A step of determining a plurality of representative values corresponding to a plurality of classes within a range including candidate values that the sample feature values of the block may have; A step of comparing the candidate values with the plurality of representative values to determine a class corresponding to each of the candidate values; and A method for filtering an image, comprising a step of determining a class of a candidate value corresponding to a sample feature value of the current block among the candidate values as a class corresponding to the current block.

13. In any one of paragraphs 1 to 12, The sample feature values of the above block are: A method for filtering an image, wherein the sample values of the samples within the block are the sum or the average of the sample values of the samples within the block.

14. A direction determination unit (2210) that calculates a first direction feature value and a second direction feature value of a current block in a current image, and determines a direction value of the current block based on a comparison result between a first ratio between a first maximum feature value corresponding to a larger value between the first direction feature value and the second direction feature value and a first minimum feature value corresponding to a smaller value between the first direction feature value and the second direction feature value and a first threshold value, and a comparison result between the first maximum feature value and the second threshold value; A class determination unit (2250) that determines a class corresponding to the current block among a plurality of classes based on the determined directionality value; and An image filtering device including a filter unit (2030) that filters samples within the current block using a filter configured according to the determined class.

15. A method for transmitting a bitstream generated according to the filtering method of paragraph 1.

Images