Device and method for encoding motion vector, and device and method for decoding motion vector

Abstract

A method, perfonned by an image decoding apparatus (2000), of decoding a motion vector, including obtaining infonnation indicating a motion vector resolution of a current block from a bitstream; selecting (S2410) a first neighboring block from among neighboring blocks adjacent to the current block, by using the obtained information indicating the motion vector resolution of the current block; based on the current block referring to a reference picture in a list 0, and the first neighboring block referring to the reference picture in the list 0, determining a prediction motion vector of the current block using a motion vector of the first neighboring block; based on the current block refen-ing to the reference picture in the list 0 and the first neighboring block referring to a reference picture in a list 1, selecting a motion vector of a second neighboring block among the neighboring blocks as a basic motion vector, and detennining the prediction motion vector of the current block using the detennined basic motion vector; and determining (S2420, S2430) a motion vector of the current block using the prediction motion vector of the current block.

Description

Motion vector encoding device and method, and motion vector decoding device and method

[0001] The present disclosure relates to the field of video encoding and decoding. More specifically, the present disclosure relates to a device and method for encoding and decoding a current motion vector using surrounding motion vectors.

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

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

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

[0005] A motion vector encoding device and method according to one embodiment, and a motion vector decoding device and method, have as a technical task the improvement of the prediction accuracy of the motion vector of the current block.

[0006] In addition, a motion vector encoding device and method according to one embodiment, and a motion vector decoding device and method have as a technical task the reduction of the size of a differential motion vector included in a bitstream.

[0007] A method for decoding a motion vector according to one embodiment may include: selecting a first neighboring block among neighboring blocks adjacent to a current block according to information obtained from a bitstream; identifying that the first neighboring block is available using information indicating availability of the first neighboring block, and if a motion vector of the first neighboring block in a prediction direction identical to that of the current block does not exist, obtaining a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block; and obtaining a motion vector of the current block by combining the predicted motion vector and the differential motion vector of the current block.

[0008] A motion vector encoding device and method according to one embodiment, and a motion vector decoding device and method can improve the prediction accuracy of a motion vector of a current block.

[0009] In addition, the motion vector encoding device and method according to one embodiment, and the motion vector decoding device and method can reduce the size of a differential motion vector included in a bitstream.

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

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

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

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

[0014] FIG. 3 illustrates a process of dividing a current encoding unit to determine at least one encoding unit according to one embodiment.

[0015] FIG. 4 illustrates a process of dividing a non-square coding unit to determine at least one coding unit according to one embodiment.

[0016] 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.

[0017] FIG. 6 illustrates a method for determining a predetermined coding unit among an odd number of coding units according to one embodiment.

[0018] 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.

[0019] 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.

[0020] FIG. 9 illustrates a process of dividing a first encoding unit to determine at least one encoding unit according to one embodiment.

[0021] 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.

[0022] 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.

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

[0024] FIG. 13 illustrates a process in which the depth of an encoding unit is determined as the shape and size of the encoding unit change when the encoding unit is recursively divided to determine a plurality of encoding units according to one embodiment.

[0025] FIG. 14 illustrates an index (part index, hereinafter referred to as PID) for depth and encoding unit distinction that can be determined according to the shape and size of encoding units according to one embodiment.

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

[0027] FIG. 16 illustrates 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.

[0028] 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.

[0029] 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.

[0030] Figure 19 is a block diagram showing a video encoding and decoding system.

[0031] Fig. 20 is a block diagram illustrating a configuration of an image decoding device according to one embodiment.

[0032] Figure 21a is an exemplary diagram showing the positions of surrounding blocks when the left block of the current block is available.

[0033] Figure 21b is an exemplary diagram showing the positions of surrounding blocks when the left and right blocks of the current block are available.

[0034] Figure 21c is a diagram showing the positions of surrounding blocks when the block to the right of the current block is available.

[0035] Figure 22 is a diagram showing the mapping relationship between indices indicating motion vector resolution, motion vector resolutions, and locations of surrounding blocks.

[0036] FIG. 23a is a diagram illustrating a case where the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value.

[0037] FIG. 23b is a diagram illustrating a case in which the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block is equal to a predetermined value.

[0038] FIG. 23c is a diagram illustrating a case in which, when the prediction direction of the current block is bidirectional, one of the reference image index in the list 0 direction of the first surrounding block and the reference image index in the list 1 direction is equal to a predetermined value, and the other is not equal to the predetermined value.

[0039] Fig. 24 is a flowchart showing a method for decoding a motion vector according to one embodiment.

[0040] Fig. 25 is a block diagram illustrating a configuration of an image encoding device according to one embodiment.

[0041] Fig. 26 is a flowchart showing a method of encoding a motion vector according to one embodiment.

[0042] Fig. 27 is a diagram for explaining a process of obtaining a predicted motion vector according to one embodiment.

[0043] Fig. 28 is a diagram for explaining a process of obtaining a predicted motion vector according to one embodiment.

[0044] A method for decoding a motion vector according to one embodiment may include: selecting a first neighboring block among neighboring blocks adjacent to a current block according to information obtained from a bitstream; identifying that the first neighboring block is available using information indicating availability of the first neighboring block, and if a motion vector of the first neighboring block in a prediction direction identical to that of the current block does not exist, obtaining a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block; and obtaining a motion vector of the current block by combining the predicted motion vector and the differential motion vector of the current block.

[0045] If the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is -1, the motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block may not exist.

[0046] The availability of the first peripheral block may be determined based on at least one of whether a tile including the first peripheral block and a tile including the current block are different from each other, whether the first peripheral block is located outside the current image, whether the first peripheral block is intra-predicted, and whether restoration of the first peripheral block is complete.

[0047] The step of obtaining the predicted motion vector of the current block may include a step of obtaining the predicted motion vector of the current block from the motion vector of the first neighboring block, if the first neighboring block is identified as being available using information indicating the availability of the first neighboring block, and a motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block exists.

[0048] The information obtained from the bitstream includes information indicating a motion vector resolution of the current block among a plurality of motion vector resolutions, and the plurality of motion vector resolutions can be mapped to surrounding blocks at different locations.

[0049] The location of the second peripheral block may vary depending on information indicating the availability of the left and right peripheral blocks of the current block.

[0050] The step of obtaining the predicted motion vector of the current block may include a step of obtaining the predicted motion vector of the current block from the motion vector of the second neighboring block, if the second neighboring block is identified as being available using information indicating the availability of the second neighboring block, and if a reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is the same as the reference image index of the current block, or if a motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block exists.

[0051] The step of obtaining the predicted motion vector of the current block may include a step of obtaining the predicted motion vector of the current block from a motion vector of a block decoded before the current block, if the second neighboring block is identified as not being available using information indicating the availability of the second neighboring block, or if there is no motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block.

[0052] The step of obtaining a predicted motion vector of the current block may include a step of obtaining a predicted motion vector of the current block from a motion vector of the second neighboring block when the first neighboring block is identified as unavailable.

[0053] According to one embodiment, an image decoding device may include a motion vector prediction unit that selects a first neighboring block among neighboring blocks adjacent to a current block according to information obtained from a bitstream, identifies the first neighboring block as available using information indicating availability of the first neighboring block, and obtains a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block when a motion vector of the first neighboring block in a prediction direction identical to a prediction direction of the current block does not exist; and a motion vector restoration unit that obtains a motion vector of the current block by combining the predicted motion vector of the current block and a differential motion vector.

[0054] A method for encoding a motion vector according to one embodiment may include: when a first neighboring block selected from neighboring blocks adjacent to a current block is identified as available and a motion vector of the first neighboring block in a prediction direction identical to that of the current block does not exist, obtaining a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block; and generating a bitstream including a differential motion vector between the motion vector of the current block and the predicted motion vector, and information for indicating the first neighboring block.

[0055] The present disclosure may be subject to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments of the present disclosure, and it should be understood that the present disclosure encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the various embodiments.

[0056] In describing the embodiments, detailed descriptions of related known technologies are omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, numbers (e.g., "first," "second," etc.) used throughout the description of the specification are merely identifiers used to distinguish one component from another.

[0057] Additionally, in this specification, when a component is referred to as being “connected” or “connected” to another component, it should be understood that the component may be directly connected or connected to the other component, but may also be connected or connected via another component in between, unless there is a specific description to the contrary.

[0058] In addition, components expressed as 'unit', 'module', etc. in this specification may be two or more components combined into one component, or one component may be divided into two or more components with more detailed functions. In addition, each component described below may additionally perform some or all of the functions performed by other components in addition to its own main function, and of course, some of the main functions performed by each component may be performed exclusively by other components.

[0059] Additionally, in this specification, 'image' or 'picture' may represent a still image or moving image (video) of a video.

[0060] Additionally, in this specification, "sample" or "signal" refers to data assigned to a sampling location in an image and is the subject of processing. For example, pixel values ​​in a spatial domain image or transform coefficients in a transform domain may be samples. A unit containing at least one such sample may be defined as a block.

[0061] 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.

[0062] FIG. 1 illustrates a block diagram of an image decoding device (100) according to one embodiment.

[0063] 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.

[0064] 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.

[0065] To describe in detail the operation of the video decoding device (100), the bitstream acquisition unit (110) can receive a bitstream.

[0066] 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.

[0067] Below, the division of encoding units according to one embodiment of the present disclosure is described in detail.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] A single maximum coding block (CTB) can be divided into MxN coding blocks containing MxN samples (M, N are integers).

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] For example, information about the maximum size of a luma coding block that can be 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 that can be split into two. Therefore, by combining the information about the maximum size of a luma coding block that can be 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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).

[0084] 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.

[0085] 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.

[0086] 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.

[0087] The shape and size of the transformation block and the prediction block may be unrelated.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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).

[0103] 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).

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] According to one embodiment, the image decoding device (100) may determine to split or not split the determined second encoding unit (510) into encoding units based on the split shape mode information. Referring to FIG. 5, the image decoding device (100) may split the first encoding unit (500) based on the split shape mode information to split the determined second encoding unit (510) of a non-square shape into at least one third encoding unit (520a, 520b, 520c, 520d, etc.) or may not split the second encoding unit (510). The image decoding device (100) can obtain split shape mode information, and the image decoding device (100) can split the first encoding unit (500) based on the obtained split shape mode information to split a plurality of second encoding units (e.g., 510) of various shapes, and the second encoding unit (510) can be split according to the way in which the first encoding unit (500) is split based on the split shape mode information. According to one embodiment, when the first encoding unit (500) is split into the second encoding unit (510) based on the split shape mode information for the first encoding unit (500), the second encoding unit (510) can also be split into the third encoding unit (e.g., 520a, 520b, 520c, 520d, etc.) based on the split shape mode information for the second encoding unit (510). That is, the coding unit can be recursively split based on the split shape mode information associated with each coding unit. Accordingly, a square coding unit can be determined from a non-square coding unit, and such a square coding unit can be recursively split to determine a non-square coding unit.

[0109] Referring to FIG. 5, among the odd number of third coding units (520b, 520c, 520d) determined by splitting the second coding unit (510) having a non-square shape, a predetermined coding unit (e.g., a coding unit located in the middle or a coding unit having a square shape) may be split recursively. According to an embodiment, the non-square third coding unit (520c), which is one of the odd number of third coding units (520b, 520c, 520d), may be split horizontally into a plurality of fourth coding units. The non-square fourth coding unit (530b or 530d), which is one of the plurality of fourth coding units (530a, 530b, 530c, 530d), may be split again into a plurality of coding units. For example, the fourth coding unit (530b or 530d) having a non-square shape may be further divided into an odd number of coding units. Methods that can be used for recursive division of coding units will be described later through various embodiments.

[0110] 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.

[0111] 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).

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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).

[0118] 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.

[0119] 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.

[0120] 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).

[0121] 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.

[0122] 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).

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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).

[0133] 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.

[0134] 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).

[0135] 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.

[0136] 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).

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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).

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] According to one embodiment, the image decoding device (100) can divide the first encoding unit to determine encoding units of various shapes.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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).

[0155] 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).

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] According to one embodiment, the image decoding device (100) may determine a third encoding unit (e.g., 1304, 1314, 1324, etc.) by splitting at least one of the width and the height of the second encoding unit (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.

[0171] 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).

[0172] 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.

[0173] 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.

[0174] 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).

[0175] 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).

[0176] 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.

[0177] 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.

[0178] 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).

[0179] 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.

[0180] 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.

[0181] 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.

[0182] According to one embodiment, the image decoding device (100) may utilize a predetermined data unit from which recursive division of the encoding unit begins.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] Hereinafter, a method for determining a partitioning rule according to one embodiment of the present disclosure will be described in detail.

[0194] 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.

[0195] 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).

[0196] The shape of the encoding unit may include a square and a non-square shape. If the width and height of the encoding unit are equal, the image decoding device (100) may determine the shape of the encoding unit as a square. In addition, if the width and height of the encoding unit are not equal, the image decoding device (100) may determine the shape of the encoding unit as a non-square shape.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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).

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] 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).

[0222] Figure 19 is a block diagram showing a video encoding and decoding system.

[0223] The encoder (1910) of the image encoding and decoding system (1900) transmits an encoded bitstream of an image, and the decoder (1950) receives the bitstream and decodes it to output a restored image. Here, the decoder (1950) may have a configuration similar to that of the image decoding device (100).

[0224] In the encoding unit (1910), the inter prediction encoding unit (1905) generates motion information of the current block that points to a reference block of a reference picture that is temporally adjacent to the current picture when the prediction mode of the current block is the inter prediction mode. The inter prediction encoding unit (1905) can determine prediction samples of the current block using samples of the reference blocks. The intra prediction encoding unit (1910) can determine intra prediction information that indicates a direction in which neighboring samples similar to the current block are located or a method of determining prediction samples so that the prediction samples of the current block can be determined using neighboring samples that are spatially adjacent to the current block.

[0225] The inter prediction encoding unit (1905) can determine reference samples to be used for prediction of the current block among the previously restored samples stored in the DPB (Decoded Picture Buffer) (1948).

[0226] The transform unit (1920) performs a transform on the residual sample values ​​obtained by subtracting the prediction samples generated by the inter prediction encoding unit (1905) or the intra prediction encoding unit (1910) from the original sample of the current block, and outputs transform coefficients. The quantization unit (1925) quantizes the transform coefficients output from the transform unit (1920) and outputs the quantized transform coefficients. The entropy encoding unit (1930) can encode the quantized transform coefficients into residual syntax elements including level values ​​and output them in the form of a bitstream.

[0227] The quantized transform coefficients output from the quantization unit (1925) can be dequantized and inversely transformed through the inverse quantization unit (1933) and inverse transformation unit (1935) to generate residual sample values ​​again.

[0228] In the adder (1915), residual sample values ​​and predicted sample values ​​are combined to output restored sample values. The post-restoration filtering unit (1940) performs post-restoration filtering on the restored samples, and the restored sample values ​​updated through the post-restoration filtering can be used as reference sample values ​​for intra prediction to be performed in the intra prediction unit (1910). The post-restoration filtering unit (1940) can perform Hadamard transform domain filtering or bilateral filtering on the restored sample values.

[0229] The in-loop filtering unit (1945) can perform at least one of deblocking filtering and adaptive loop filtering on restored samples updated through post-restoration filtering. Restored sample values ​​updated through filtering by the in-loop filtering unit (1945) can be stored in the DPB (1948) and used as reference sample values ​​for inter prediction to be performed by the inter prediction unit (1905).

[0230] The entropy decoding unit (1955) of the decoder (1950) can perform entropy decoding on the received bitstream to parse residual syntax elements including level values. Quantized transform coefficients can be restored from the residual syntax elements. The inverse quantization unit (1960) can perform inverse quantization on the quantized transform coefficients to output transform coefficients, and the inverse transform unit (1965) can perform inverse transformation on the transform coefficients to output residual sample values.

[0231] The inter prediction encoding unit (1970) of the decoder (1950) can determine a reference picture temporally adjacent to the current picture using the motion information of the current block parsed by the entropy decoding unit (1955), and can determine a reference block within the reference picture. The inter prediction encoding unit (1970) can determine prediction samples of the current block using samples of the reference blocks. The intra prediction encoding unit (1975) of the decoder (1950) can determine reference samples spatially adjacent to the current block using the intra prediction information using the motion information of the current block parsed by the entropy decoding unit (1955), and can determine prediction samples of the current block using the determined neighboring samples.

[0232] The inter prediction encoding unit (1970) can determine reference samples to be used for prediction of the current block among the previously restored samples stored in the DPB (Decoded Picture Buffer) (1990).

[0233] The adder (1995) of the decoder (1950) combines the residual sample values ​​and the predicted sample values ​​to output the restored sample values ​​of the current block. The post-restoration filtering unit (1980) of the decoder (1950) can perform Hadamard transform domain filtering or bilateral filtering on the restored sample values. The restored sample values ​​updated through the filtering of the post-restoration filtering unit (1980) can be used as reference sample values ​​for intra prediction to be performed in the intra prediction unit (1975).

[0234] The in-loop filtering unit (1985) of the decoder (1950) can perform at least one of deblocking filtering and adaptive loop filtering on restored samples updated through post-restoration filtering. The restored sample values ​​updated through filtering of the in-loop filtering unit (1985) are stored in the DPB (1990) and can be used as reference sample values ​​for inter prediction to be performed in the inter prediction unit (1970).

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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).

[0239] 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.

[0240] 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 the encoding unit.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] FIG. 20 is a block diagram illustrating the configuration of an image decoding device (2000) according to one embodiment.

[0249] Referring to FIG. 20, the image decoding device (2000) includes a bitstream acquisition unit (2010) and a prediction decoding unit (2030). The prediction decoding unit (2030) includes a motion vector prediction unit (2032) and a motion vector restoration unit (2034).

[0250] The bitstream acquisition unit (2010) illustrated in FIG. 20 corresponds to the bitstream acquisition unit (110) illustrated in FIG. 1, and the prediction decoding unit (2030) may correspond to the decoding unit (120) illustrated in FIG. 1.

[0251] According to one embodiment, the bitstream acquisition unit (2010) and the prediction decoding unit (2030) may be implemented with at least one processor. The image decoding device (2000) may include one or more memories (not shown) that store input / output data of the bitstream acquisition unit (2010) and the prediction decoding unit (2030). In addition, the image decoding device (2000) may include a memory control unit (not shown) that controls data input / output of the memory (not shown).

[0252] The bitstream acquisition unit (2010) acquires a bitstream generated as a result of encoding an image. The bitstream acquisition unit (2010) acquires syntax elements for decoding an image from the bitstream. Binary values ​​corresponding to the syntax elements may be included in the bitstream according to the hierarchical structure of the image. The bitstream acquisition unit (2010) may acquire the syntax elements by entropy decoding the binary values ​​included in the bitstream.

[0253] The bitstream may include information about the prediction mode of the current block within the current image. The current block may refer to a block of the largest coding unit, coding unit, or transform unit segmented from the current image to be decoded.

[0254] The prediction mode of the current block may include an intra-prediction mode or an inter-prediction mode. As described above, the inter-prediction mode is a mode that reconstructs the current block from a reference block pointed to by the motion vector of the current block within the reference image.

[0255] The prediction decoding unit (2030) can restore the current block using intra prediction or inter prediction depending on the prediction mode of the current block.

[0256] In inter-prediction mode, motion information can be used to reconstruct the current block. The motion information of the current block may include the prediction direction, reference image index, and motion vector of the current block. The prediction direction, reference image index, and motion vector of the current block can be identified from information included in the bitstream.

[0257] The prediction direction of the current block can be any one of the list 0 direction, the list 1 direction, and bidirectional. The prediction direction being the list 0 direction means that the image included in the reference image list 0 is used as the reference image in the list 0 direction, and the prediction direction being the list 1 direction means that the image included in the reference image list 1 is used as the reference image in the list 1 direction. In addition, the prediction direction being bidirectional means that the image included in the reference image list 0 is used as the reference image in the list 0 direction, and the image included in the reference image list 1 is used as the reference image in the list 1 direction.

[0258] The reference image index indicates an image used as a reference image of a block among the images included in reference image list 0 and / or reference image list 1. According to the reference image index in the list 0 direction, an image used as a reference image in the list 0 direction is specified among the images included in reference image list 0. In addition, according to the reference image index in the list 1 direction, an image used as a reference image in the list 1 direction is specified among the images included in reference image list 1.

[0259] A motion vector specifies the location of a reference block within a reference image. A motion vector in the list 0 direction refers to a motion vector pointing to a reference block within a reference image in the list 0 direction, and a motion vector in the list 1 direction refers to a motion vector pointing to a reference block within a reference image in the list 1 direction.

[0260] If the prediction direction of the current block is in the list 0 direction, the motion information of the current block includes at least one of information indicating that the prediction direction of the current block is in the list 0 direction, a reference image index in the list 0 direction, and a motion vector in the list 0 direction. In addition, if the current block is in the list 1 direction, the motion information of the current block includes at least one of information indicating that the prediction direction of the current block is in the list 1 direction, a reference image index in the list 1 direction, and a motion vector in the list 1 direction. In addition, if the current block is bidirectional, the motion information of the current block includes at least one of information indicating that the prediction direction of the current block is in the list 0 direction, a reference image index in the list 1 direction, a motion vector in the list 0 direction, and a motion vector in the list 1 direction.

[0261] In one embodiment, the bitstream acquisition unit (2010) may acquire information indicating the prediction direction of the current block and the reference image index of the current block from the bitstream when the prediction mode of the current block is the inter prediction mode. The prediction decoding unit (2030) may acquire the differential motion vector of the current block from the information included in the bitstream, and may obtain the motion vector of the current block by combining the predicted motion vector and the differential motion vector of the current block.

[0262] The prediction decoding unit (2030) can restore the current block based on the prediction direction, reference image index, and motion vector of the current block.

[0263] Below, the method by which the prediction decoding unit (2030) obtains the prediction motion vector of the current block is described in detail.

[0264] A motion vector prediction unit (2032) according to one embodiment can obtain a predicted motion vector using the motion vectors of neighboring blocks adjacent to the current block. Here, the neighboring blocks are blocks at predetermined locations used to obtain the predicted motion vector of the current block, and are included in the current image together with the current block.

[0265] The surrounding blocks may include A0 block, A1 block, B0 block, B1 block and B2 block at predetermined locations.

[0266] The motion vector prediction unit (2032) can identify the locations of the A0 block, the A1 block, the B0 block, the B1 block, and the B2 block based on information indicating the availability of the left block and the right block of the current block.

[0267] In a typical video codec, decoding is performed in the raster scan direction for the image. In this case, the block to the left of the current block is available because decoding was completed before the current block, and the block to the right of the current block is not available because decoding is not completed.

[0268] The present disclosure can adaptively determine the decoding direction of blocks segmented from an image. That is, instead of decoding all blocks segmented from an image along the raster scan direction, some blocks are decoded from right to left, thereby improving coding efficiency. Accordingly, the right block of the current block may be available, while the left block of the current block may not be available, or both the right and left blocks of the current block may be available.

[0269] Whether the left block and the right block are available can be determined in the same way as the availability of the first surrounding block described below.

[0270] The positions of surrounding blocks, which change depending on the availability of the blocks on the left and right of the current block, are described with reference to FIGS. 21a to 21c.

[0271] FIG. 21a is an exemplary diagram showing the positions of surrounding blocks when the left block of the current block (2100) is available.

[0272] The locations of surrounding blocks when the left block of the current block (2100) is available may be the same as the locations of spatial surrounding blocks specified in the HEVC standard.

[0273] Referring to FIG. 21a, the surrounding blocks may include a lower left corner block (A0), a lower left block (A1), an upper right corner block (B0), an upper right block (B1), and an upper left corner block (B2) of the current block (2100). As illustrated in FIG. 21a, the lower left block (A1) may be located above the lower left corner block (A0), and the upper right block (B1) may be located to the left of the upper right corner block (B0).

[0274] FIG. 21b is an exemplary diagram showing the positions of surrounding blocks when the left block and right block of the current block (2100) are available.

[0275] Referring to FIG. 21b, the surrounding blocks may include an upper right corner block (A0), a lower left block (A1), an upper left block (B0), a lower right block (B1), and an upper left corner block (B2) of the current block (2100). As illustrated in FIG. 21b, the upper left corner block (B2) may be located to the left of the upper left block (B0).

[0276] Figure 21c is a diagram showing the positions of surrounding blocks when the right block of the current block (2100) is available.

[0277] Referring to FIG. 21c, the surrounding blocks may include a lower right corner block (A0), a lower right block (A1), an upper left corner block (B0), an upper left block (B1), and an upper right corner block (B2) of the current block (2100). As illustrated in FIG. 21c, the lower right block (A1) may be located above the lower right corner block (A0), and the upper left block (B1) may be located to the right of the upper left corner block (B0).

[0278] The positions of the peripheral blocks shown in FIGS. 21a to 21c are examples, and the positions and number of the peripheral blocks may vary depending on the implementation.

[0279] The motion vector prediction unit (2032) can determine the availability of the left and right blocks of the current block and specify the locations of surrounding blocks to be used to obtain a predicted motion vector of the current block from information indicating the availability of the left and right blocks.

[0280] In one embodiment, the motion vector prediction unit (2032) selects a first neighboring block from among neighboring blocks based on information obtained from the bitstream. The first neighboring block may be any one of the A0 block, the A1 block, the B0 block, the B1 block, and the B2 block corresponding to the neighboring blocks.

[0281] In one embodiment, the information obtained from the bitstream may be information indicating the motion vector resolution of the current block. The motion vector prediction unit (2032) may determine the motion vector resolution of the current block based on the information obtained from the bitstream among a plurality of predetermined motion vector resolutions, and select a first neighboring block for obtaining a predicted motion vector.

[0282] Motion vector resolution may refer to the precision of a pixel position that a motion vector determined through inter prediction can point to among pixels included in a reference image (or an interpolated reference image). If the motion vector resolution has N pixel units (N is a rational number), it means that the motion vector can have a precision of N pixel units. For example, a motion vector resolution of 1 / 4 pixel units may mean that a motion vector can point to a pixel of 1 / 4 pixel unit (i.e., a subpixel unit) in the interpolated reference image, and a motion vector resolution of 1 pixel unit may mean that a motion vector can point to a pixel corresponding to 1 pixel unit (i.e., an integer pixel unit) in the interpolated reference image. Among several motion vector resolutions, a motion vector resolution that can express the motion vector of the current block with a small number of bits may be adaptively determined.

[0283] In one embodiment, information indicating a motion vector resolution obtained from a bitstream may point to any one of several motion vector resolutions and may point to any one first neighboring block among neighboring blocks at different locations.

[0284] Figure 22 is a diagram showing the mapping relationship between indices indicating motion vector resolution, motion vector resolutions, and locations of surrounding blocks.

[0285] Referring to FIG. 22, it can be seen that the motion vector resolution and the neighboring block corresponding to the first neighboring block can be determined according to the value of the index (AMVR index). For example, if the index (AMVR index) is 0, the motion vector resolution of the current block can be selected in 1 / 4 pixel units (pel), and the first neighboring block can be selected as the A1 block. In addition, if the index (AMVR index) is 1, the motion vector resolution of the current block can be selected in 1 / 2 pixel units (pel), and the first neighboring block can be selected as the B1 block.

[0286] In the existing HEVC standard, multiple neighboring blocks are included in a candidate list, and the motion vectors of neighboring blocks in the candidate list selected from information signaled through the bitstream are used as predicted motion vectors. However, in the present disclosure, the first neighboring block used to obtain the predicted motion vector of the current block can be specified based on information obtained from the bitstream, i.e., information indicating the motion vector resolution of the current block. Accordingly, separate information (e.g., mvp_l0_flag, mvp_l1_flag in HEVC) indicating any one neighboring block included in the candidate list is not included in the bitstream.

[0287] The motion vector prediction unit (2032) determines the availability of the selected first neighboring block based on information indicating the motion vector resolution. Specifically, the motion vector prediction unit (2032) determines the availability of the first neighboring block based on at least one of whether a tile including the first neighboring block is different from a tile including the current block, whether the first neighboring block is located outside the current image, whether the first neighboring block is intra-predicted, and whether the restoration of the first neighboring block is complete.

[0288] For example, the motion vector prediction unit (2032) can determine that the first surrounding block is unavailable if any one of the following four conditions is satisfied.

[0289] (Condition 1) The tile containing the first surrounding block and the tile containing the current block are different from each other.

[0290] (Condition 2) The first surrounding block is located outside the current image.

[0291] (Condition 3) The first surrounding block is not restored.

[0292] (Condition 4) The first surrounding block is coded in intra prediction mode or IBC (intra block copy) mode.

[0293] IBC mode searches for a prediction block corresponding to the current block within the current image. The prediction block can be found through motion estimation of the current image. For example, the prediction block can be searched for on an integer pixel basis within the current image, and the positional relationship between the current block and the searched prediction block can be signaled to the decoder.

[0294] In one embodiment, the motion vector prediction unit (2032) can determine that the motion vector of the first neighboring block is available as a predicted motion vector if the first neighboring block is identified as available from information indicating the availability of the first neighboring block and the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value (e.g., -1). If the motion vector of the first neighboring block is available as a predicted motion vector, the motion vector prediction unit (2032) derives the predicted motion vector of the current block from the motion vector of the first neighboring block.

[0295] If the availability of the first neighboring block is identified as not being available from the information indicating the availability of the first neighboring block, or if the availability of the first neighboring block is identified but the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is equal to a predetermined value, the motion vector of the first neighboring block may be determined as not being available as a predicted motion vector. In this case, the motion vector prediction unit (2032) may obtain a default motion vector according to the derivation procedure of the default motion vector described below, and may obtain a predicted motion vector of the current block using the default motion vector.

[0296] If the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value, it may mean that there is a motion vector of the first neighboring block pointing to a reference image in the same prediction direction as the prediction direction of the current block. Conversely, if the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is equal to a predetermined value, it may mean that there is no motion vector of the first neighboring block pointing to a reference image in the same prediction direction as the prediction direction of the current block.

[0297] The reference image index of the first surrounding block includes a reference image index in the list 0 direction and a reference image index in the list 1 direction, and the values ​​of the reference image index in the list 0 direction and the reference image index in the list 1 direction can be determined according to the prediction direction of the first surrounding block.

[0298] For example, if the prediction direction of the first surrounding block is in the list 0 direction, the reference image index in the list 0 direction is set to the value of the index obtained from the bitstream (e.g., ref_idx_l0), and the reference image index in the list 1 direction is set to a predetermined value. Since the images included in the reference image list have indices from 0 to n (n is a natural number), the predetermined value may be a value different from 0 to n, for example, -1.

[0299] If the prediction direction of the first surrounding block is in the list 1 direction, the reference image index in the list 1 direction is set to the value of the index obtained from the bitstream (e.g., ref_idx_l1), and the reference image index in the list 0 direction is set to a predetermined value.

[0300] If the prediction direction of the first surrounding block is bidirectional, both the reference image index in the list 0 direction and the reference image index in the list 1 direction are set to the values ​​of the indices obtained from the bitstream (e.g., ref_idx_l0, ref_idx_l1).

[0301] Hereinafter, a case in which the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block is equal to or not equal to a predetermined value is described with reference to FIGS. 23a to 23c.

[0302] FIG. 23a is a diagram illustrating a case where the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value.

[0303] Referring to FIG. 23A, the prediction directions of the current block (2312) and the first neighboring block (2314) are both in the list 0 direction. Therefore, the motion vector (MV) of the first neighboring block (2314) points to a reference block in the reference image (2330) included in the reference image list 0. The reference image index of the first neighboring block (2314) in the list 0 direction is set according to information obtained from the bitstream, and the reference image index of the first neighboring block (2314) in the list 1 direction is set to a predetermined value. The motion vector prediction unit (2032) obtains the predicted motion vector of the current block (2312) using the motion vector (MV) of the first neighboring block (2314) because the reference image index of the first neighboring block (2314) in the list 0 direction, which is the same prediction direction as that of the current block (2312), is not equal to the predetermined value.

[0304] Similarly, when the prediction directions of the current block (2312) and the first surrounding block (2314) are both in the list 1 direction, the motion vector prediction unit (2032) obtains the predicted motion vector of the current block (2312) using the motion vector (MV) of the first surrounding block (2314), since the reference image index of the first surrounding block (2314) in the same prediction direction as the prediction direction of the current block (2312), i.e., in the list 1 direction, is not equal to a predetermined value.

[0305] FIG. 23b is a diagram illustrating a case in which the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block is equal to a predetermined value.

[0306] Referring to FIG. 23b, the prediction direction of the current block (2312) is in the list 1 direction, and the prediction direction of the first neighboring block (2314) is in the list 0 direction. The motion vector (MV) of the first neighboring block (2314) points to a reference block in the reference image (2330) included in the reference image list 0. The reference image index of the first neighboring block (2314) in the list 0 direction is set according to information obtained from the bitstream, and the reference image index of the first neighboring block (2314) in the list 1 direction is set to a predetermined value. Since the reference image index of the first neighboring block (2314) in the same prediction direction as the prediction direction of the current block (2312), i.e., in the list 1 direction, is equal to the predetermined value, the motion vector prediction unit (2032) obtains the predicted motion vector of the current block (2312) using the default motion vector described below.

[0307] Similarly, if the prediction direction of the current block (2312) is in the list 0 direction and the prediction direction of the first surrounding block (2314) is in the list 1 direction, the motion vector prediction unit (2032) obtains the prediction motion vector of the current block (2312) using the default motion vector since the reference image index of the first surrounding block (2314) in the list 0 direction, which is the same prediction direction as that of the current block (2312), is equal to a predetermined value.

[0308] FIG. 23c is a diagram illustrating a case in which, when the prediction direction of the current block is bidirectional, one of the reference image index in the list 0 direction of the first surrounding block and the reference image index in the list 1 direction is equal to a predetermined value, and the other is not equal to the predetermined value.

[0309] Referring to FIG. 23c, the prediction direction of the current block (2312) is bidirectional, and the prediction direction of the first neighboring block (2314) is in the list 1 direction. The motion vector (MV) of the first neighboring block (2314) points to a reference block in a reference image (2350) included in the reference image list 1. The reference image index in the list 0 direction of the first neighboring block (2314) is set to a predetermined value, and the reference image index in the list 1 direction is set according to information obtained from the bitstream. As described above, the prediction direction being bidirectional includes both the list 0 direction and the list 1 direction. The motion vector prediction unit (2032) obtains a predicted motion vector of the current block (2312) in the list 0 direction using the default motion vector because the reference image index of the first peripheral block (2314) in the list 0 direction is equal to a predetermined value, and obtains a predicted motion vector of the current block (2312) using the motion vector (MV) of the first peripheral block (2314) in the list 1 direction because the reference image index of the first peripheral block (2314) in the list 1 direction is not equal to a predetermined value.

[0310] When the prediction direction of the current block (2312) is bidirectional and the prediction direction of the first surrounding block (2314) is in the list 0 direction, the motion vector prediction unit (2032) obtains a prediction motion vector in the list 0 direction of the current block (2312) using the motion vector (MV) in the list 0 direction of the first surrounding block (2314), and obtains a prediction motion vector in the list 1 direction of the current block (2312) using the default motion vector.

[0311] In the present disclosure, if a first neighboring block is available and a reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value, the motion vector of the first neighboring block is determined to be available as a predicted motion vector. Then, the predicted motion vector of the current block is obtained from the motion vector of the first neighboring block.

[0312] If the motion vector of the first neighboring block is determined to be available as a predicted motion vector only under the condition that the first neighboring block must be available, there is a possibility that the predicted motion vector of the current block may be set to a zero vector, i.e., (0, 0). In other words, if the first neighboring block is available, but there is no motion vector of the first neighboring block in the same prediction direction as that of the current block, the motion vector of the first neighboring block cannot be used as the predicted motion vector of the current block. Therefore, the predicted motion vector of the current block may be determined to be a zero vector, which ultimately increases the number of bits required to express the differential motion vector.

[0313] In the present disclosure, the motion vector of the first neighboring block is used to obtain the predicted motion vector of the current block when both the condition that the first neighboring block must be available and the condition that the motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block are satisfied, so that the number of bits required to express the differential motion vector can be reduced.

[0314] Below, the process of deriving a default motion vector when the motion vector of the first surrounding block is not available as a predicted motion vector is described.

[0315] In one embodiment, the motion vector prediction unit (2032) may set the motion vector of a second neighboring block at a predetermined location as a default motion vector if the motion vector of the first neighboring block is not available as a predicted motion vector. The number of second neighboring blocks may be plural, and in this case, the motion vector of any one of the second neighboring blocks may be set as the default motion vector by determining the availability of the plurality of second neighboring blocks.

[0316] The second peripheral block may correspond to at least one of the peripheral blocks. For example, the second peripheral block may include block A1 and block B1. In another example, the location of the second peripheral block may differ from the locations of the aforementioned blocks A0, A1, B0, B1, and B2.

[0317] When the second surrounding block includes block A1 and block B1, the positions of block A1 and block B1 may vary depending on the availability of the left and right blocks of the current block, as described above. Specifically, referring to FIGS. 21A to 21C , if the left block of the current block is available, block A1 may be located at the lower left of the current block, and block B1 may be located at the upper right of the current block. In addition, if both the left and right blocks of the current block are available, block A1 may be located at the lower left of the current block, and block B1 may be located at the lower right of the current block. In addition, if the right block of the current block is available, block A1 may be located at the lower right of the current block, and block B1 may be located at the upper left of the current block.

[0318] The motion vector prediction unit (2032) determines the availability of the A1 block, and if the A1 block is identified as available based on information indicating whether the A1 block is available, the motion vector of the A1 block can be determined as a default motion vector. If the A1 block is not available, the motion vector prediction unit (2032) determines the availability of the B1 block, and if the B1 block is identified as available based on information indicating whether the B1 block is available, the motion vector of the B1 block can be determined as a default motion vector. That is, the motion vector prediction unit (2032) can check whether the motion vectors of the A1 block and the B1 block can be used as default motion vectors in the order of the A1 block → the B1 block.

[0319] The availability of block A1 and the availability of block B1 can be determined based on the four conditions for determining the availability of the first peripheral block described above.

[0320] In one embodiment, the motion vector prediction unit (2032) may set the motion vector of the second neighboring block as a default motion vector when the second neighboring block is identified as available from information indicating the availability of the second neighboring block, and the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is the same as the reference image index of the current block, or the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value (i.e., when the motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block exists).

[0321] The motion vector prediction unit (2032) may set the motion vector of a block decoded before the current block as a default motion vector if the second neighboring block is identified as unavailable from information indicating the availability of the second neighboring block, or if there is no motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block.

[0322] The motion vector prediction unit (2032) can determine the motion vector of the first surrounding block or the default motion vector as the predicted motion vector of the current block.

[0323] When the motion vector of the first surrounding block is determined as the predicted motion vector, the motion vector prediction unit (2032) can update the predicted motion vector of the current block by scaling the predicted motion vector of the current block according to the distance between the current image and the reference image of the current block and the distance between the current image and the reference image of the first surrounding block, if the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block and the reference image index of the current block are not the same.

[0324] In one embodiment, the motion vector prediction unit (2032) may determine the default motion vector as the predicted motion vector of the current block if the reference image index of the second neighboring block (or the block decoded before the current block, which is used to obtain the default motion vector) in the same prediction direction as the prediction direction of the current block is the same as the reference image index of the current block. In addition, the motion vector prediction unit (2032) may scale the default motion vector according to the distance between the current image and the reference image of the current block and the distance between the current image and the reference image of the second neighboring block (or the block decoded before the current block) in the same prediction direction as the prediction direction of the current block, and determine the scaled default motion vector as the predicted motion vector of the current block if the reference image index of the second neighboring block (or the block decoded before the current block, which is used to obtain the default motion vector) is not the same as the reference image index of the current block.

[0325] After obtaining the predicted motion vector of the current block, the motion vector prediction unit (2032) can adjust the predicted motion vector of the current block if the motion vector resolution of the current block is different from a predetermined motion vector resolution (e.g., the minimum motion vector resolution among a plurality of motion vector resolutions). The reason for adjusting the predicted motion vector is to match the motion vector resolution of the current block and the resolution of the predicted motion vector.

[0326] The motion vector prediction unit (2032) can adjust the predicted motion vector, which is expressed as a coordinate within an interpolated image according to the minimum motion vector resolution, to the motion vector resolution of the current block, so as to point to surrounding pixels instead of the pixel pointed to by the predicted motion vector.

[0327] For example, the motion vector prediction unit (2032) can adjust the predicted motion vector of (19, 27) so that the predicted motion vector becomes (20, 28) when the minimum motion vector resolution is 1 / 4 pixel unit and the motion vector resolution of the current block is 1 pixel unit. This is because when the minimum motion vector resolution is 1 / 4 pixel unit, an integer pixel has coordinates of (4n, 4m) in the interpolated image.

[0328] In one embodiment, the motion vector prediction unit (2032) may cause the adjusted predicted motion vector to point to a pixel located at the upper right of the pixel pointed to by the predicted motion vector before adjustment when adjusting the predicted motion vector according to the motion vector resolution of the current block. In another embodiment, the motion vector prediction unit (2032) may cause the adjusted predicted motion vector to point to a pixel located at the upper left, lower left, or lower right of the pixel pointed to by the predicted motion vector before adjustment.

[0329] To summarize the above according to one embodiment, if the motion vector of the first neighboring block is available as a predicted motion vector, the motion vector of the first neighboring block is determined as the predicted motion vector of the current block. Then, if the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is not the same as the reference image index of the current block, the predicted motion vector is scaled. If the motion vector resolution of the current block is not the same as a predetermined motion vector resolution among a plurality of motion vector resolutions, the predicted motion vector or the scaled predicted motion vector is adjusted according to the motion vector resolution of the current block.

[0330] In addition, if the motion vector of the first neighboring block is not available as a predicted motion vector, a default motion vector is derived. And, if the reference image index of a block (a block used to derive the default motion vector) having the same prediction direction as that of the current block is not the same as the reference image index of the current block, the default motion vector is scaled, and the scaled default motion vector is determined as the predicted motion vector of the current block. If the motion vector resolution of the current block is not the same as a predetermined motion vector resolution among a plurality of motion vector resolutions, the predicted motion vector is adjusted according to the motion vector resolution of the current block.

[0331] The motion vector restoration unit (2034) obtains the motion vector of the current block by combining the predicted motion vector of the current block and the differential motion vector obtained from the bitstream. The motion vector restoration unit (2034) can obtain the motion vector of the current block by adding the predicted motion vector of the current block and the differential motion vector.

[0332] The prediction decoding unit (2030) can restore the current block by inter-predicting the current block according to the prediction direction, reference image index, and motion vector of the current block.

[0333] Fig. 24 is a flowchart showing a method for decoding a motion vector according to one embodiment.

[0334] In step S2410, the image decoding device (2000) determines the availability of a first neighboring block selected from among neighboring blocks adjacent to the current block based on information obtained from the bitstream.

[0335] In one embodiment, information obtained from the bitstream may include information indicating a motion vector resolution of a current block among a plurality of motion vector resolutions.

[0336] At step S2420, the image decoding device (2000) determines whether a first surrounding block is available and whether a motion vector of the first surrounding block in the same prediction direction as the prediction direction of the current block exists.

[0337] At step S2430, the image decoding device (2000) obtains a predicted motion vector of the current block from the motion vector of the first surrounding block, if the first surrounding block is available and there is a motion vector of the first surrounding block in the same prediction direction as the prediction direction of the current block.

[0338] In step S2440, the image decoding device (2000) obtains a predicted motion vector of the current block from a motion vector of a second neighboring block when the first neighboring block is not available or when a motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block does not exist.

[0339] As described above, if the availability of the second neighboring block is not available, the predicted motion vector of the current block can be obtained from the motion vector of the block decoded before the current block.

[0340] At step S2450, the image decoding device (2000) obtains a motion vector of the current block by combining the predicted motion vector and the differential motion vector of the current block.

[0341] FIG. 25 is a block diagram illustrating the configuration of an image encoding device (2500) according to one embodiment.

[0342] Referring to FIG. 25, the image encoding device (2500) includes a prediction encoding unit (2510) and a bitstream generation unit (2530). The prediction encoding unit (2510) may include a motion vector prediction unit (2512) and a motion vector encoding unit (2514).

[0343] The prediction encoding unit (2510) may correspond to the encoding unit (220) of FIG. 2, and the bitstream generation unit (2530) may correspond to the bitstream generation unit (210) of FIG. 2.

[0344] According to one embodiment, the prediction encoding unit (2510) and the bitstream generation unit (2530) may be implemented with at least one processor. The video encoding device (2500) may include one or more memories (not shown) that store input / output data of the prediction encoding unit (2510) and the bitstream generation unit (2530). In addition, the video encoding device (2500) may also include a memory control unit (not shown) that controls data input / output of the memory (not shown).

[0345] The prediction encoding unit (2510) encodes an image according to a prediction mode, and the bitstream generation unit (2530) generates a bitstream including information generated as a result of encoding the image.

[0346] The prediction encoding unit (2510) can determine the prediction mode of the current block within the current image. If the prediction mode of the current block is determined to be an inter prediction mode, the bitstream generation unit (2530) includes information indicating motion information of the current block in the bitstream.

[0347] The motion vector prediction unit (2512) predicts the motion vector of the current block encoded in inter prediction mode.

[0348] A motion vector prediction unit (2512) according to one embodiment can obtain a predicted motion vector using the motion vectors of neighboring blocks adjacent to the current block. Since the locations of the neighboring blocks have been described above, a detailed description thereof will be omitted.

[0349] In one embodiment, the motion vector prediction unit (2512) selects a first neighboring block from among neighboring blocks. The first neighboring block may be any one of the A0 block, the A1 block, the B0 block, the B1 block, and the B2 block corresponding to the neighboring blocks.

[0350] In one embodiment, the motion vector prediction unit (2512) can select a first neighboring block mapped to the motion vector resolution of the current block among a plurality of motion vector resolutions.

[0351] The motion vector prediction unit (2512) determines the availability of the first surrounding block. Specifically, the motion vector prediction unit (2512) determines the availability of the first surrounding block based on at least one of whether a tile including the first surrounding block is different from a tile including the current block, whether the first surrounding block is located outside the current image, whether the first surrounding block is intra-predicted, and whether the restoration of the first surrounding block is complete.

[0352] In one embodiment, the motion vector prediction unit (2512) may determine that the motion vector of the first neighboring block is available as a predicted motion vector if the first neighboring block is identified as available from information indicating the availability of the first neighboring block, and if the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value (i.e., if there is a motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block), the motion vector prediction unit (2512) may determine that the motion vector of the first neighboring block is available as a predicted motion vector. The predetermined value may be, for example, -1. If the motion vector of the first neighboring block is available as a predicted motion vector, the motion vector prediction unit (2512) derives the predicted motion vector of the current block from the motion vector of the first neighboring block.

[0353] If the availability of the first neighboring block is identified as not being available from the information indicating the availability of the first neighboring block, or if the reference image index of the first neighboring block in the same prediction direction as the prediction direction of the current block is equal to a predetermined value, the motion vector of the first neighboring block may be determined as not being available as a predicted motion vector. In this case, the motion vector prediction unit (2512) may obtain the predicted motion vector of the current block using the default motion vector.

[0354] In one embodiment, the motion vector prediction unit (2512) may set the motion vector of a second neighboring block at a predetermined location as a default motion vector if the motion vector of the first neighboring block is not available as a predicted motion vector. The number of second neighboring blocks may be plural, and in this case, the motion vector of any one of the second neighboring blocks may be set as the default motion vector by determining the availability of the plurality of second neighboring blocks.

[0355] If the second surrounding block includes the A1 block and the B1 block, the motion vector prediction unit (2512) determines the availability of the A1 block, and if the A1 block is identified as available based on information indicating whether the A1 block is available, the motion vector of the A1 block can be determined as a default motion vector. If the A1 block is not available, the motion vector prediction unit (2512) determines the availability of the B1 block, and if the B1 block is identified as available based on information indicating whether the B1 block is available, the motion vector of the B1 block can be determined as a default motion vector. That is, the motion vector prediction unit (2512) can check whether the motion vectors of the A1 block and the B1 block can be used as default motion vectors in the order of the A1 block → the B1 block.

[0356] In one embodiment, the motion vector prediction unit (2512) may set the motion vector of the second neighboring block as a default motion vector if the second neighboring block is identified as available from information indicating the availability of the second neighboring block, and if the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is the same as the reference image index of the current block, or if the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is not equal to a predetermined value (i.e., if the motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block exists).

[0357] The motion vector prediction unit (2512) can set the motion vector of a block encoded before the current block as a default motion vector if the second neighboring block is identified as unavailable from information indicating the availability of the second neighboring block, or if the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is equal to a predetermined value.

[0358] The motion vector prediction unit (2512) can determine the motion vector of the first surrounding block or the default motion vector as the predicted motion vector of the current block.

[0359] When the motion vector of the first surrounding block is determined as the predicted motion vector, the motion vector prediction unit (2512) can update the predicted motion vector of the current block by scaling the predicted motion vector of the current block according to the distance between the current image and the reference image of the current block and the distance between the current image and the reference image of the first surrounding block, if the reference image index of the first surrounding block in the same prediction direction as the prediction direction of the current block is not the same as the reference image index of the current block.

[0360] When a default motion vector is obtained, in one embodiment, the motion vector prediction unit (2512) may determine the default motion vector as the predicted motion vector of the current block if the reference image index of the second neighboring block (or, the block used to obtain the default motion vector and decoded before the current block) in the same prediction direction as the prediction direction of the current block is the same as the reference image index of the current block. If the reference image index of the second neighboring block (or, the block used to obtain the default motion vector and decoded before the current block) in the same prediction direction as the prediction direction of the current block is not the same as the reference image index of the current block, the motion vector prediction unit (2512) may scale the default motion vector according to the distance between the current image and the reference image of the current block and the distance between the current image and the reference image of the second neighboring block (or, the block decoded before the current block), and determine the scaled default motion vector as the predicted motion vector of the current block.

[0361] After the predicted motion vector of the current block is obtained, the motion vector prediction unit (2512) can adjust the predicted motion vector of the current block if the motion vector resolution of the current block is different from a predetermined motion vector resolution (e.g., the minimum motion vector resolution among a plurality of motion vector resolutions).

[0362] The motion vector encoding unit (2514) obtains a differential motion vector between the motion vector of the current block and the predicted motion vector. The motion vector encoding unit (2514) can obtain the differential motion vector by subtracting the predicted motion vector from the motion vector of the current block.

[0363] The bitstream generation unit (2530) generates a bitstream including information indicating a differential motion vector of the current block and information indicating a first neighboring block among neighboring blocks. As described above, the information indicating the first neighboring block may be information indicating a motion vector resolution of the current block among a plurality of motion vector resolutions.

[0364] Fig. 26 is a flowchart showing a method of encoding a motion vector according to one embodiment.

[0365] In step S2610, the video encoding device (2500) determines the availability of a first neighboring block selected from among neighboring blocks adjacent to the current block. In one embodiment, the video encoding device (2500) may select a first neighboring block corresponding to the motion vector resolution of the current block.

[0366] At step S2620, the video encoding device (2500) determines whether a first surrounding block is available and whether a motion vector of the first surrounding block in the same prediction direction as the prediction direction of the current block exists.

[0367] In step S2630, if the first peripheral block of the video encoding device (2500) is available and there is a motion vector of the first peripheral block in the same prediction direction as the prediction direction of the current block, the predicted motion vector of the current block is obtained from the motion vector of the first peripheral block.

[0368] In step S2640, the video encoding device (2500) obtains a predicted motion vector of the current block from a motion vector of a second neighboring block if the first neighboring block is not available or if there is no motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block.

[0369] If the availability of the second neighboring block is not available, the predicted motion vector of the current block can be obtained from the motion vector of the block encoded before the current block.

[0370] In step S2650, the video encoding device (2500) obtains a differential motion vector between the motion vector of the current block and the predicted motion vector, and generates a bitstream including information indicating the differential motion vector and information indicating a first neighboring block. The information indicating the first neighboring block may be information indicating a motion vector resolution of the current block among a plurality of motion vector resolutions.

[0371] FIG. 27 and FIG. 28 are diagrams for explaining a process of obtaining a predicted motion vector according to one embodiment.

[0372] Figures 27 and 28 specifically illustrate an example of the above-described embodiments. In Figures 27 and 28, LX included in mvpLX, mvLX, etc. represents the prediction direction of the current block. That is, if the prediction direction of the current block is in the L0 direction, X is 0, and if the prediction direction of the current block is in the L1 direction, X is 1. If the prediction direction of the current block is bidirectional, X can sequentially have the values ​​0 and 1.

[0373] In S2710, the flag indicating the availability of predicted motion vectors (mvpAvailFlag) is set to 0.

[0374] In S2720, a block to be used for obtaining a predicted motion vector of the current block is specified according to information (amvr_idx) indicating the motion vector resolution of the current block. If amvr_idx is 1, the B1 block is selected. Then, the availability of the B1 block is determined. The availability of the B1 block can be determined according to the four conditions for determining the availability of the first surrounding block described above. In Fig. 27, only the process when amvr_idx is 1 is illustrated to omit redundant description, and blocks at different locations are selected according to the value of amvr_idx. For example, as illustrated in Fig. 22, a block mapped to amvr_idx can be selected.

[0375] In S2730, if the B1 block is identified as available from information (availableB1) indicating availability of the B1 block, and the reference picture index (RefIdxLX) of the B1 block in the same prediction direction as the prediction direction of the current block is not equal to -1, a flag (mvpAvailFlag) indicating availability of the predicted motion vector is set to 1, and the motion vector of the B1 block is set as the predicted motion vector (mvpLX).

[0376] In S2740, if the reference picture index (refIdxLX) of the current block and the reference picture index (RefIdxLX[xNbB1][yNbB1]) of the B1 block are not the same, the predicted motion vector (mvpLX) is scaled according to the ratio (distScaleFactorLX) of the distance (currPocDiffLX) between the current picture and the reference picture (RefPicListX[RefIdxLX[xNbB1][yNbB1]]) of the B1 block and the distance (targetPocDiffLX) between the current picture and the reference picture (RefPicListX[refIdxLX]) of the current block.

[0377] In S2750, if amvr_idx is not 0, i.e., if the motion vector resolution of the current block is different from a predetermined motion vector resolution (e.g., minimum motion vector resolution), adjustment of the predicted motion vector (mvpLX) is performed. If amvr_idx is 0, i.e., if the predicted motion vector is obtained from the motion vector of the A1 block, the process of adjusting the predicted motion vector is not performed.

[0378] Next, referring to FIG. 28, in S2810, if the flag (mvpAvailFlag) indicating the availability of the predicted motion vector is 0, that is, if the B1 block is identified as not available from the information (availableB1) indicating the availability of the B1 block, or if the reference picture index (RefIdxLX[xNbB1][yNbB1]) of the B1 block in the same prediction direction as the prediction direction of the current block is equal to -1, the default motion vector derivation procedure of S2820 to S2890 is performed.

[0379] In S2820, the availability of blocks A1 and B1 is determined. The availability of blocks A1 and B1 can be determined based on the four conditions for determining the availability of the first peripheral block described above.

[0380] In S2830, both the x-axis and y-axis components of the default motion vector (DefaultMvLX) are set to 0.

[0381] In S2840, if the A1 block is identified as available from information indicating the availability of the A1 block (availableA1), and the reference picture index (refIdxLX) of the current block and the reference picture index (RefIdxLX[xNbA1][yNbA1]) of the A1 block are the same, the motion vector of the A1 block is set as the default motion vector.

[0382] In S2850, if the condition described in S2840 is not satisfied, and the B1 block is identified as available from information indicating the availability of the B1 block (availableB1), and the reference picture index (refIdxLX) of the current block and the reference picture index (RefIdxLX[xNbB1][yNbB1]) of the B1 block are the same, the motion vector of the B1 block is set as the default motion vector.

[0383] In S2860, if the conditions described in S2850 are not satisfied, and the A1 block is identified as available from information indicating the availability of the A1 block (availableA1), and the reference picture index of the A1 block (RefIdxLX[xNbA1][yNbA1]) is not equal to -1, the motion vector of the A1 block is set as the default motion vector.

[0384] In S2870, if the condition described in S2860 is not satisfied, and the B1 block is identified as available from information indicating the availability of the B1 block (availableB1), and the reference picture index of the B1 block (RefIdxLX[xNbB1][yNbB1]) is not equal to -1, the motion vector of the B1 block is set as the default motion vector.

[0385] In S2880, if the motion vector of block A1 or block B1 is not set as the default motion vector, the motion vector of the block decoded before the current block is set as the default motion vector.

[0386] In S2890, if the reference picture index (refIdxLX) of the current block and the default reference picture index (DefaultRefIdxLX) are not the same, the default motion vector is scaled according to the ratio (distScaleFactorLX) of the distance (currPocDiffLX) between the current picture and the picture pointed to by the default reference picture index (RefPicListX[DefaultRefIdxLX]) and the distance (targetPocDiffLX) between the current picture and the reference picture of the current block (RefPicListX[refIdxLX]). Here, the default reference picture index (DefaultRefIdxLX) may mean the reference picture index of the block used to obtain the default motion vector.

[0387] In S2895, the default motion vector (DefaultMvLX) is set to the predicted motion vector (mvpLX) of the current block.

[0388] Although not shown in Fig. 28, if amvr_idx is not 0, i.e., if the motion vector resolution of the current block is different from a predetermined motion vector resolution (e.g., minimum motion vector resolution), adjustment of the predicted motion vector (mvpLX) is performed.

[0389] 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 medium.

[0390] A medium may be something that permanently stores a computer-executable program, or may be something that temporarily stores it for execution or download. Furthermore, the medium may be a variety of recording or storage means, including a single or multiple hardware components, and is not limited to media directly connected to a computer system, but may also be distributed across a network. Examples of media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and anything configured to store program instructions, including ROM, RAM, and flash memory. Furthermore, other examples of media may include recording or storage media managed by app stores that distribute applications, sites that supply or distribute various software, or servers.

[0391] 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. A method for decoding a motion vector using an image decoding device, A step of selecting a first neighboring block among neighboring blocks adjacent to a current block based on information obtained from a bitstream; A step of obtaining a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block, if the first neighboring block is identified as available using information indicating the availability of the first neighboring block and there is no motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block; and A method for decoding a motion vector, comprising the step of obtaining a motion vector of the current block by combining a predicted motion vector and a differential motion vector of the current block.

2. In paragraph 1, A method for decoding a motion vector, wherein if the reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is -1, the motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block does not exist.

3. In paragraph 1, The availability of the above first peripheral block is, A method for decoding a motion vector, wherein it is determined based on at least one of whether a tile including the first peripheral block and a tile including the current block are different from each other, whether the first peripheral block is located outside the current image, whether the first peripheral block is intra-predicted, and whether restoration of the first peripheral block is complete.

4. In paragraph 1, The step of obtaining the predicted motion vector of the current block is: A method for decoding a motion vector, comprising: a step of identifying that the first peripheral block is available using information indicating the availability of the first peripheral block, and obtaining a predicted motion vector of the current block from the motion vector of the first peripheral block if a motion vector of the first peripheral block in the same prediction direction as the prediction direction of the current block exists.

5. In paragraph 1, The information obtained from the above bitstream includes information indicating the motion vector resolution of the current block among multiple motion vector resolutions, A method for decoding motion vectors, wherein the above plurality of motion vector resolutions are mapped to surrounding blocks at different locations.

6. In paragraph 1, The location of the above second peripheral block is, A method for decoding a motion vector, which varies depending on information indicating the availability of surrounding blocks on the left and right sides of the current block.

7. In paragraph 1, The step of obtaining the predicted motion vector of the current block is: A method for decoding a motion vector, comprising: a step of obtaining a predicted motion vector of the current block from the motion vector of the second neighboring block, if the second neighboring block is identified as available using information indicating the availability of the second neighboring block, and a reference image index of the second neighboring block in the same prediction direction as the prediction direction of the current block is identical to the reference image index of the current block, or a motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block exists.

8. In paragraph 7, The step of obtaining the predicted motion vector of the current block is: A method for decoding a motion vector, comprising the step of obtaining a predicted motion vector of the current block from a motion vector of a block decoded before the current block, if the second neighboring block is identified as unavailable by using information indicating the availability of the second neighboring block, or if there is no motion vector of the second neighboring block in the same prediction direction as the prediction direction of the current block.

9. In paragraph 1, The step of obtaining the predicted motion vector of the current block is: A method for decoding a motion vector, comprising the step of obtaining a predicted motion vector of the current block from a motion vector of the second surrounding block if the first surrounding block is identified as unavailable.

10. A motion vector prediction unit for selecting a first neighboring block among neighboring blocks adjacent to a current block according to information obtained from a bitstream, identifying that the first neighboring block is available using information indicating availability of the first neighboring block, and obtaining a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block if there is no motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block; and An image decoding device, comprising a motion vector restoration unit that obtains a motion vector of the current block by combining a predicted motion vector and a differential motion vector of the current block.

11. A method for encoding a motion vector by a video encoding device, A step of obtaining a predicted motion vector of the current block from a motion vector of a second neighboring block at a predetermined position adjacent to the current block, if a first neighboring block selected from neighboring blocks adjacent to the current block is identified as available and there is no motion vector of the first neighboring block in the same prediction direction as the prediction direction of the current block; and A method for encoding a motion vector, comprising the step of generating a bitstream including a differential motion vector between the motion vector of the current block and the predicted motion vector, and information for pointing to the first surrounding block.