Method and apparatus for video decoding, and method and apparatus for video encoding

Abstract

Suggested are a method and an apparatus for performing intra-prediction during video encoding and decoding processes by configuring an additional mode set on the basis of MPM modes of a current block, and determining an intra-prediction mode of the current block on the basis of the MPM modes and the additional mode set. In order to resolve the technical problem, a video decoding method suggested in this disclosure may comprise the steps of: configuring an additional mode set on the basis of MPM modes of a current block; determining an intra-prediction mode of the current block on the basis of the MPM modes and the additional mode set; and performing intra-prediction of the current block on the basis of the intra-prediction mode.

Description

Video decoding method and device, video encoding method and device

[0001] The present disclosure relates to a video decoding method and a video decoding device, and proposes a method and device for performing intra prediction of a current block by configuring an additional mode set based on MPM modes of a current block and determining an intra prediction mode of the current block based on the MPM modes and the additional mode set.

[0002] Video data is encoded using a codec according to a given data compression standard, such as the MPEG (Moving Picture Expert Group) standard, and then stored on a recording medium in the form of a bitstream or transmitted through a communication channel.

[0003] With the development and widespread adoption of hardware capable of playing and storing high-resolution or high-definition video content, the need for codecs that effectively encode or decode such content is increasing. Encoded video content can be played back by decoding it. Recently, methods for effectively compressing such high-resolution or high-definition video content have been developed. For example, video compression techniques have been proposed to effectively implement video compression by arbitrarily segmenting the video to be encoded or manipulating the data.

[0004] As one of the data manipulation techniques, it is common to use two or more MPMs (most probable modes) for intra prediction and signal the other modes by coding them under the same conditions.

[0005] During a video encoding and decoding process, a method and device are proposed for constructing an additional mode set based on MPM modes of a current block, determining an intra prediction mode based on the MPM modes and the constructed additional mode set, and performing prediction of the current block using the determined intra prediction mode.

[0006] In order to solve the above technical problem, the video decoding method proposed in the present disclosure may include the steps of: configuring an additional mode set based on MPM modes of a current block; determining an intra prediction mode of the current block based on the MPM modes and the additional mode set; and performing intra prediction of the current block based on the intra prediction mode.

[0007] In order to solve the above technical problem, the video decoding device proposed in the present disclosure comprises: a memory; and at least one processor connected to the memory, wherein the at least one processor is configured to: configure an additional mode set based on MPM modes of a current block; determine an intra prediction mode of the current block based on the MPM modes and the additional mode set; and perform intra prediction of the current block based on the intra prediction mode.

[0008] In order to solve the above technical problem, the video encoding method proposed in the present disclosure may include the steps of: configuring an additional mode set based on MPM modes of a current block; determining an intra prediction mode of the current block based on the MPM modes and the additional mode set; and performing intra prediction of the current block based on the intra prediction mode.

[0009] In order to solve the above technical problem, the video encoding device proposed in the present disclosure comprises: a memory; and at least one processor connected to the memory, wherein the at least one processor is configured to: configure an additional mode set based on MPM modes of a current block; determine an intra prediction mode of the current block based on the MPM modes and the additional mode set; and perform intra prediction of the current block based on the intra prediction mode.

[0010] During the video encoding and decoding process, an additional mode set is configured based on the MPM modes of the current block, and prediction of the current block is performed using an intra prediction mode determined based on the MPM modes and the additional mode set, thereby improving performance by making intra prediction accurate and reducing the amount of bits generated during intra prediction mode coding, thereby improving the efficiency of mode signaling and increasing reliability.

[0011] FIG. 1 illustrates a schematic block diagram of an image decoding device (100) according to one embodiment.

[0012] FIG. 2 illustrates a flowchart of an image decoding method according to one embodiment.

[0013] FIG. 3 illustrates a process in which an image decoding device divides a current encoding unit to determine at least one encoding unit according to one embodiment.

[0014] FIG. 4 illustrates a process in which an image decoding device determines at least one encoding unit by dividing a non-square encoding unit according to one embodiment.

[0015] FIG. 5 illustrates a process in which an image decoding device divides an encoding unit based on at least one of block shape information and division shape mode information, according to one embodiment.

[0016] FIG. 6 illustrates a method for a video decoding device to determine a predetermined encoding unit among an odd number of encoding units according to one embodiment.

[0017] FIG. 7 illustrates the order in which multiple encoding units are processed when an image decoding device determines multiple encoding units by dividing a current encoding unit according to one embodiment.

[0018] 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.

[0019] FIG. 9 illustrates a process in which an image decoding device divides a first encoding unit to determine at least one encoding unit according to one embodiment.

[0020] FIG. 10 illustrates that, according to one embodiment, a video decoding device limits the shapes into which a second encoding unit can be divided when a non-square shape of a second encoding unit determined by dividing a first encoding unit satisfies a predetermined condition.

[0021] FIG. 11 illustrates a process of a video decoding device dividing a square-shaped encoding unit when the split shape mode information cannot indicate that the encoding unit is divided into four square-shaped encoding units according to one embodiment.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] FIG. 16 illustrates a processing block that serves as a criterion for determining the order of determination of reference coding units included in a picture according to one embodiment.

[0027] FIG. 17 illustrates a block diagram of a video decoding device according to one embodiment.

[0028] FIG. 18 illustrates a flowchart of a video decoding method according to one embodiment.

[0029] FIG. 19 illustrates a block diagram of a video encoding device according to one embodiment.

[0030] FIG. 20 illustrates a flowchart of a video encoding method according to one embodiment.

[0031] Figure 21 illustrates an embodiment of the mode set of the surrounding blocks on the left and upper sides and the mode set of the current block.

[0032] Figure 22 illustrates an embodiment of an intra prediction mode direction.

[0033] Figure 23 illustrates one embodiment of an additional mode set.

[0034] Figure 24 illustrates an embodiment of intra prediction mode signaling syntax.

[0035] A video decoding method according to one embodiment proposed in the present disclosure may include: configuring an additional mode set based on MPM modes of a current block; determining an intra prediction mode of the current block based on the MPM modes and the additional mode set; and performing intra prediction of the current block based on the intra prediction mode.

[0036] According to one embodiment, the MPM modes of the current block may include a prediction mode of a neighboring block adjacent to the left of the current block and a prediction mode of a neighboring block adjacent to the upper side of the current block.

[0037] In one embodiment, a neighboring block adjacent to the right side of the current block and a neighboring block adjacent to the upper side of the current block are restored before the current block, and the MPM modes of the current block may include a prediction mode of a neighboring block adjacent to the right side of the current block and a prediction mode of a neighboring block adjacent to the upper side of the current block.

[0038] In one embodiment, an additional set of modes may be determined based on the types of the MPM modes.

[0039] In one embodiment, if all of the MPM modes are non-directional, the additional mode set may include at least one of a DC mode, a planar mode, a vertical mode, a horizontal mode, and a diagonal mode.

[0040] In one embodiment, when all of the MPM modes are directional modes, the additional mode set may include at least one of a DC mode, a planar mode, and intra prediction modes having an index that is n times the index of the MPM modes, where n is a non-zero integer.

[0041] In one embodiment, when all of the MPM modes are directional modes, the additional mode set may include at least one of a DC mode, a planar mode, an intra prediction mode having an index increased by 1 from the index of the MPM modes, an intra prediction mode having an index decreased by 1 from the index of the MPM modes, and an intra prediction mode having an index decreased by 2 from the index of the MPM modes.

[0042] In one embodiment, when the intra prediction mode of the left adjacent neighboring block of the current block and the intra prediction mode of the above adjacent neighboring block of the current block are the same and are directional modes, the MPM modes and the additional mode set may include the intra prediction mode of the left adjacent neighboring block, a DC mode, a planar mode, a mode that increases the index of the intra prediction mode of the left adjacent neighboring block by 1, an intra prediction mode having an index that decreases the index of the intra prediction mode of the left adjacent neighboring block by 1, and an intra prediction mode having an index that decreases the index of the intra prediction mode of the left adjacent neighboring block by 2.

[0043] In one embodiment, when the first MPM mode among the MPM modes is a non-directional mode and the second MPM mode is a directional mode, the additional mode set may include at least one of a DC mode and a planar mode other than the first MPM mode, an intra prediction mode having an index increased by n from the index of the second MPM mode, a vertical mode, and a horizontal mode, where n is a non-zero integer.

[0044] A video encoding method according to one embodiment proposed in the present disclosure may include: configuring an additional mode set based on MPM modes of a current block; determining an intra prediction mode of the current block based on the MPM modes and the additional mode set; and performing intra prediction of the current block based on the intra prediction mode.

[0045] A video decoding device according to one embodiment proposed in the present disclosure comprises: a memory; and at least one processor connected to the memory, wherein the at least one processor is configured to: configure an additional mode set based on MPM modes of a current block; determine an intra prediction mode of the current block based on the MPM modes and the additional mode set; and perform intra prediction of the current block based on the intra prediction mode.

[0046] A video encoding device according to one embodiment proposed in the present disclosure comprises: a memory; and at least one processor connected to the memory, wherein the at least one processor is configured to: configure an additional mode set based on MPM modes of a current block; determine an intra prediction mode of the current block based on the MPM modes and the additional mode set; and perform intra prediction of the current block based on the intra prediction mode.

[0047] The advantages and features of the disclosed embodiments, and the methods for achieving them, will become clearer with reference to the embodiments described below, along with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure the completeness of the disclosure and to fully inform those skilled in the art of the present disclosure of the scope of the invention.

[0048] The terms used in this specification will be briefly explained, and the disclosed embodiments will be described in detail.

[0049] The terms used in this specification have been selected from widely used, current terms, taking into account the functions of the present disclosure. However, these terms may vary depending on the intentions of engineers working in the relevant fields, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this disclosure should not be defined simply as names, but rather based on the meanings of the terms and the overall content of the present disclosure.

[0050] In this specification, singular expressions include plural expressions unless the context clearly specifies that they are singular.

[0051] When a part of a specification is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0052] Also, the term "part" used in the specification means a software or hardware component, and the "part" performs certain functions. However, the "part" is not limited to software or hardware. The "part" may be configured to reside on an addressable storage medium and may be configured to execute one or more processors. Thus, by way of example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts."

[0053] According to one embodiment of the present disclosure, a "unit" may be implemented as a processor and a memory. The term "processor" should be broadly interpreted to include a general-purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and the like. In some circumstances, a "processor" may also refer to an application-specific integrated circuit (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), and the like. The term "processor" may also refer to a combination of processing devices, such as, for example, a combination of a DSP and a microprocessor, a combination of a plurality of microprocessors, a combination of one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0054] The term "memory" should be interpreted broadly to include any electronic component capable of storing electronic information. The term memory may also refer to various types of processor-readable media, such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, etc. Memory is said to be in electronic communication with the processor if the processor can read information from the memory and / or write information to the memory. Memory integrated in a processor is in electronic communication with the processor.

[0055] Hereinafter, “image” may refer to a static image such as a still image of a video, or a dynamic image such as a moving image, i.e., the video itself.

[0056] Hereinafter, "sample" 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 transformation coefficients in a transformation domain may be samples. A unit containing at least one such sample may be defined as a block.

[0057] Below, with reference to the attached drawings, embodiments are described in detail so that those skilled in the art can easily implement the present disclosure. Furthermore, in order to clearly illustrate the present disclosure in the drawings, parts irrelevant to the description are omitted.

[0058] Hereinafter, with reference to FIGS. 1 to 16, an image encoding apparatus and an image decoding apparatus, an image encoding method, and an image decoding method according to an embodiment will be described in detail. With reference to FIGS. 3 to 16, a method for determining a data unit of an image according to an embodiment will be described, and with reference to FIGS. 17 to 24, a method for configuring an additional mode set based on MPM modes of a current block of the present invention, determining an intra prediction mode of the current block based on the MPM modes and the additional mode set, and performing intra prediction of the current block based on the determined intra prediction mode will be described below according to an embodiment.

[0059] Hereinafter, with reference to FIGS. 1 and 2, a method and apparatus for adaptively selecting a context model based on various types of encoding units according to one embodiment of the present disclosure are described.

[0060] FIG. 1 illustrates a schematic block diagram of an image decoding device (100) according to one embodiment.

[0061] The video decoding device (100) may include a receiving unit (110) and a decoding unit (120). The receiving unit (110) and the decoding unit (120) may include at least one processor. In addition, the receiving unit (110) and the decoding unit (120) may include a memory that stores instructions to be executed by at least one processor.

[0062] The receiving unit (110) can receive a bitstream. The bitstream includes information obtained by encoding an image by an image encoding device (2200) described below. In addition, the bitstream can be transmitted from the image encoding device (2200). The image encoding device (2200) and the image decoding device (100) can be connected by wire or wirelessly, and the receiving unit (110) can receive the bitstream by wire or wirelessly. The receiving unit (110) can receive the bitstream from a storage medium such as an optical medium or a hard disk. 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.

[0063] The operation of the video decoding device (100) will be described in more detail with reference to FIG. 2.

[0064] FIG. 2 illustrates a flowchart of an image decoding method according to one embodiment.

[0065] According to one embodiment of the present disclosure, the receiving unit (110) receives a bitstream.

[0066] The image decoding device (100) performs a step (210) of obtaining a binstring corresponding to a splitting shape mode of an encoding unit from a bitstream. The image decoding device (100) performs a step (220) of determining a splitting rule of the encoding unit. In addition, the image decoding device (100) performs a step (230) 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. A slice can be a sequence of one or more Coding Tree Units (CTUs). The concept that contrasts with a Coding Tree Block (CTB) is a Coding Tree Block (CTB).

[0069] A maximum coding block (CTB) is an NxN block containing NxN samples (where N is an integer). Each color component can be divided into one or more maximum coding blocks.

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

[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. Alternatively, the maximum size of the 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 slice may be 32x32, and the maximum size of a luma coding block capable of ternary splitting in a P slice or a B slice 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_BT_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 (2200) 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 third coding unit (520b) having a square shape, 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 fourth coding unit (530b or 530d) having a non-square shape, 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 correspond to a 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 coding units by determining whether the third coding units (820a, 820b, 820c, 820d, 820e) can be processed in a predetermined order. Referring to FIG. 8, the image decoding device (100) can determine the third coding units (820a, 820b, 820c, 820d, 820e) by recursively splitting the first coding unit (800). The image decoding device (100) can determine whether the first encoding unit (800), the second encoding unit (810a, 810b), or the third encoding unit (820a, 820b, 820c, 820d, 820e) is divided into an odd number of encoding units based on at least one of the block shape information and the split shape mode information. For example, the encoding unit located on the right side of the second encoding unit (810a, 810b) can be divided into an odd number of third encoding units (820c, 820d, 820e). The order in which the plurality of encoding units included in the first encoding unit (800) are processed can be a predetermined order (e.g., z-scan order (830)), and the image decoding device (100) can determine whether the third encoding unit (820c, 820d, 820e) determined by dividing the second encoding unit (810b) on the right into odd numbers satisfies the condition that it can be processed according to the predetermined order.

[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 encoding unit (900) based on the split shape mode information obtained through the receiver (110). The first encoding unit (900) having a square shape may be split into four square-shaped encoding units or may be split into a plurality of non-square encoding units. For example, referring to FIG. 9, when the first encoding unit (900) is square and the split shape mode information indicates that it is split into non-square encoding units, the image decoding device (100) may split the first encoding unit (900) into a plurality of non-square encoding 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 width of the first coding unit (900) in half, it may be determined that the first coding unit (900) does not satisfy the condition that it can be processed in a predetermined order. If such a condition is not satisfied, the image decoding device (100) may determine that the scan order is disconnected, and based on the determination result, may determine that the first encoding unit (900) is divided into an odd number of encoding units. According to one embodiment, the image decoding device (100) may place a predetermined restriction on an encoding unit at a predetermined position among the divided encoding units when the encoding unit is divided into an odd number of encoding units. Since the contents of such restrictions or predetermined positions, etc. have been described above through various embodiments, a detailed description thereof will be omitted.

[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 obtained through the receiver (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 horizontally dividing second encoding units (1220a, 1220b) generated by horizontally dividing the first encoding unit (1200). Since the process of dividing the second encoding units (1210a, 1210b, 1220a, 1220b) has been described above with reference to FIG. 11, a detailed description thereof will be omitted.

[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] According to 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) may 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) may include a non-square second encoding unit (1414a, 1414c) and a square second encoding unit (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 coding 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, maximum coding unit, etc.) that may include at least one reference coding unit.

[0189] According to one embodiment, the receiving unit (110) of the image decoding device (100) can obtain 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 receiving unit (110) may obtain only an index for identifying the size and shape of the reference coding unit for each slice, slice segment, maximum coding unit, etc., among the various data units (e.g., sequences, pictures, slices, slice segments, maximum coding units, etc.) from the bitstream, as a data unit that satisfies a predetermined condition (e.g., a data unit having a size smaller than a slice). 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] FIG. 16 illustrates a processing block that serves as a criterion for determining the order of determination of reference encoding units included in a picture (1600) according to one embodiment.

[0193] According to one embodiment, the image decoding apparatus (100) may determine at least one processing block for dividing a picture. The processing block is a data unit including at least one reference coding unit for dividing an image, and at least one reference coding unit included in the processing block may be determined in a specific order. That is, the determination order of at least one reference coding unit determined in each processing block may correspond to one of various types of orders in which the reference coding unit may be determined, and the determination order of the reference coding unit determined in each processing block may be different for each processing block. The determination order of the reference coding unit determined for each processing block may be one of various orders such as raster scan, Z-scan, N-scan, up-right diagonal scan, horizontal scan, and vertical scan, but the order in which it may be determined should not be interpreted as being limited to the above scan orders.

[0194] According to one embodiment, the image decoding device (100) can obtain information about the size of a processing block to determine the size of at least one processing block included in an image. The image decoding device (100) can obtain information about the size of a processing block from a bitstream to determine the size of at least one processing block included in an image. The size of the processing block may be a predetermined size of a data unit indicated by the information about the size of the processing block.

[0195] According to one embodiment, the receiving unit (110) of the image decoding device (100) can obtain information about the size of a processing block from a bitstream for each specific data unit. For example, the information about the size of a processing block can be obtained from the bitstream for each data unit such as an image, a sequence, a picture, a slice, a slice segment, etc. That is, the receiving unit (110) can obtain information about the size of a processing block from the bitstream for each of the above-described multiple data units, and the image decoding device (100) can determine the size of at least one processing block for dividing a picture using the obtained information about the size of the processing block, and the size of the processing block can be an integer multiple of a reference coding unit.

[0196] According to one embodiment, the image decoding device (100) may determine the size of the processing block (1602, 1612) included in the picture (1600). For example, the image decoding device (100) may determine the size of the processing block based on information about the size of the processing block obtained from the bitstream. Referring to FIG. 16, the image decoding device (100) may determine the horizontal size of the processing block (1602, 1612) to be four times the horizontal size of the reference coding unit, and the vertical size of the processing block (1602, 1612) to be four times the vertical size of the reference coding unit, according to one embodiment. The image decoding device (100) may determine the order in which at least one reference coding unit is determined within at least one processing block.

[0197] According to one embodiment, the video decoding device (100) may determine each processing block (1602, 1612) included in the picture (1600) based on the size of the processing block, and may determine the determination order of at least one reference coding unit included in the processing block (1602, 1612). According to one embodiment, the determination of the reference coding unit may include determining the size of the reference coding unit.

[0198] According to one embodiment, the image decoding device (100) can obtain information about a determination order of at least one reference coding unit included in at least one processing block from a bitstream, and can determine an order in which at least one reference coding unit is determined based on the obtained information about the determination order. The information about the determination order can be defined as an order or direction in which the reference coding units are determined within the processing block. That is, the order in which the reference coding units are determined can be independently determined for each processing block.

[0199] According to one embodiment, the image decoding device (100) can obtain information about the determination order of the reference coding unit for each specific data unit from the bitstream. For example, the receiving unit (110) can obtain information about the determination order of the reference coding unit for each data unit such as an image, sequence, picture, slice, slice segment, processing block, etc. from the bitstream. Since the information about the determination order of the reference coding unit indicates the determination order of the reference coding unit within the processing block, the information about the determination order can be obtained for each specific data unit including an integer number of processing blocks.

[0200] The image decoding device (100) can determine at least one reference encoding unit based on an order determined according to one embodiment.

[0201] According to one embodiment, the receiver (110) may obtain information about the reference coding unit determination order as information related to the processing blocks (1602, 1612) from the bitstream, and the image decoding device (100) may determine the order in which at least one reference coding unit included in the processing blocks (1602, 1612) is determined and determine at least one reference coding unit included in the picture (1600) according to the determination order of the coding units. Referring to FIG. 16, the image decoding device (100) may determine the determination order (1604, 1614) of at least one reference coding unit related to each processing block (1602, 1612). For example, when information about the determination order of the reference coding unit is obtained for each processing block, the determination order of the reference coding unit related to each processing block (1602, 1612) may be different for each processing block. If the reference encoding unit determination order (1604) related to the processing block (1602) is a raster scan order, the reference encoding unit included in the processing block (1602) can be determined according to the raster scan order. In contrast, if the reference encoding unit determination order (1614) related to another processing block (1612) is a reverse order of the raster scan order, the reference encoding unit included in the processing block (1612) can be determined according to the reverse order of the raster scan order.

[0202] According to one embodiment, the image decoding device (100) can decode at least one determined reference coding unit. The image decoding device (100) can decode an image based on the determined reference coding unit through the above-described embodiment. The method of decoding the reference coding unit may include various methods of decoding an image.

[0203] According to one embodiment, the video decoding device (100) may obtain and use block shape information indicating the shape of a current encoding unit or split shape mode information indicating a method of splitting the current encoding unit from a 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, and a slice segment 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, reference encoding unit, and processing block.

[0204] Hereinafter, a method for determining a partitioning rule according to one embodiment of the present disclosure will be described in detail.

[0205] 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 (2200). 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, and a slice segment header. The video decoding device (100) can determine the segmentation rule differently depending on a frame, a slice, a temporal layer, a maximum coding unit, or an coding unit.

[0206] 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 (2200) 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 (2200).

[0207] The shape of the encoding unit may include a square and a non-square. If the width and height of the encoding unit are equal, the image decoding device (100) may determine the shape of the encoding unit as a square. In addition, if the width and height of the encoding unit are not equal, the image decoding device (100) may determine the shape of the encoding unit as a non-square.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] Determining the splitting rule based on the size of the encoding unit may be a splitting rule predetermined between the image encoding device (2200) 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.

[0212] 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.

[0213] 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.

[0214] Hereinafter, with reference to FIGS. 17 to 20, a method and apparatus for encoding or decoding a video by configuring an additional mode set based on MPM modes of a current block, determining an intra prediction mode of a current block based on the MPM modes and the additional mode set, and performing intra prediction of the current block based on the determined intra prediction mode are described in detail.

[0215] FIG. 17 illustrates a block diagram of a video decoding device (1700) according to one embodiment.

[0216] A video decoding device (1700) according to one embodiment may include a memory (1710) and at least one processor (1720) connected to the memory (1710). Operations of the video decoding device (1700) according to one embodiment may operate as individual processors or may be operated under the control of a central processor. In addition, the memory (1710) of the video decoding device (1700) may store data received from the outside and data generated by the processor, for example, information about MPM modes of the current block and information about configured additional mode sets.

[0217] A processor (172+0) of a video decoding device (1700) may configure an additional mode set including at least one candidate mode based on MPM modes of a current block, determine an intra prediction mode of the current block based on the MPM modes and the additional mode set, and perform intra prediction based on the intra prediction mode.

[0218] Referring to FIG. 18 below, a specific operation of a video decoding method in which a video decoding device (1700) according to one embodiment configures an additional mode set based on MPM modes of a current block, determines an intra prediction mode of the current block based on the MPM modes and the additional mode set, and performs intra prediction is described in detail.

[0219] FIG. 18 illustrates a flowchart of a video decoding method according to one embodiment.

[0220] Referring to FIG. 18, in step s1810, the video decoding device (1700) can configure an additional mode set based on the MPM modes of the current block.

[0221] According to one embodiment, the MPM modes of the current block may include a prediction mode of a neighboring block adjacent to the left of the current block and a prediction mode of a neighboring block adjacent to the upper side of the current block.

[0222] According to another embodiment, the neighboring blocks adjacent to the right side of the current block and the neighboring blocks adjacent to the upper side of the current block are reconstructed before the current block, and the MPM modes of the current block may include the prediction mode of the neighboring blocks adjacent to the right side of the current block and the prediction mode of the neighboring blocks adjacent to the upper side of the current block. When the neighboring blocks adjacent to the right side of the current block and the neighboring blocks adjacent to the upper side of the current block exist, and when the neighboring blocks adjacent to the left side of the current block exist at the same time, the MPM mode may be configured using the prediction mode information of the left block and the upper block, and then an additional mode set may be configured using the MPM mode information and the mode information of the right block. When the mode information of the neighboring blocks adjacent to the left, the upper, and the right all exist and some of the left, the upper, and the right blocks have the same mode, the mode set may be configured using only two different mode information, or the mode set may include more directional modes in directions closer to the indexes of the overlapping modes among the modes of the neighboring blocks.

[0223] In step s1830, the video decoding device (1700) can determine the intra prediction mode of the current block based on the MPM modes and the additional mode set.

[0224] According to one embodiment, the intra prediction mode of the current block can determine an optimal intra prediction mode for the current block among the MPM modes and modes of an additional mode set using information obtained from a bitstream.

[0225] In step s1850, the video decoding device (1700) can perform intra prediction of the current block based on the intra prediction mode.

[0226] In one embodiment, since the intra prediction mode of the current block may be highly correlated with the intra prediction modes of the surrounding blocks, N intra prediction modes that are highly likely to be the intra prediction modes of the current block may be configured as an additional mode set using the surrounding block mode information or the MPM information of the current block. The additional mode set may be configured with the intra prediction modes having indices increased by n from the intra prediction mode index of the left block mode and the intra prediction modes having indices increased by m from the intra prediction mode index of the upper block mode (n and m are non-zero integers). For example, when the left block and the upper block are directional modes, the additional mode set may be composed of an intra prediction mode with an index increased by 1 from the intra prediction mode index of the left block mode, an intra prediction mode with an index increased by 1 from the intra prediction mode index of the upper block mode, an intra prediction mode with an index decreased by 1 from the intra prediction mode index of the left block mode, and an intra prediction mode with an index decreased by 1 from the intra prediction mode index of the upper block mode, or the additional mode set may be composed of an intra prediction mode with an index increased by 1 from the intra prediction mode index of the upper block mode, an intra prediction mode with an index increased by 2 from the intra prediction mode index of the left block mode, an intra prediction mode with an index decreased by 1 from the intra prediction mode index of the left block mode, and an intra prediction mode with an index obtained by averaging and rounding off the intra prediction mode indices of each of the left block mode and the upper block mode.

[0227] Figure 21 illustrates an embodiment of the mode set of the surrounding blocks on the left and upper sides and the mode set of the current block.

[0228] Referring to FIG. 21, when the intra prediction modes of the upper peripheral block (2120) adjacent to the upper side of the current block (2110) and the left peripheral block (2130) adjacent to the left side of the current block (2110) are the vertical mode and the horizontal mode, respectively, the MPM mode of the current block is determined to be the vertical mode and the horizontal mode, and an additional mode set may include modes that are highly correlated with the MPM mode and close to the MPM mode among the modes between the vertical mode and the horizontal mode. For example, the additional mode set may be composed of an intra prediction mode with an index increased by 1 from the intra prediction mode index of the vertical mode, an intra prediction mode with an index increased by 2 from the intra prediction mode index of the vertical mode, an intra prediction mode with an index decreased by 2 from the intra prediction mode index of the horizontal mode, an intra prediction mode with an index that is obtained by averaging and rounding off the intra prediction mode indexes of each of the vertical mode and the horizontal mode, etc.

[0229] In one embodiment, the additional mode set may be composed of a predetermined integer N of modes depending on the number of intra prediction modes or the number of MPMs.

[0230] According to one embodiment, the additional mode sets may be configured differently, such as N or M (where N and M are positive integers) depending on the type of intra prediction mode of the neighboring blocks adjacent to the current block. Specifically, the additional mode sets may be different depending on whether the intra prediction mode of the neighboring blocks is an angular mode or a non-angular mode such as a DC mode or a planar mode.

[0231] Figure 22 illustrates an embodiment of an intra prediction mode direction.

[0232] Specifically, among the intra prediction directions of the intra prediction mode of FIG. 22, the vertical direction (2240), which is the positive direction of the y-axis, and the horizontal direction (2220), which is the negative direction of the x-axis, represent the vertical mode and the horizontal mode of the intra prediction mode, respectively. In addition, FIG. 22 illustrates a diagonal directional mode (2250) on the first quadrant, which is the last direction of the intra prediction directions, a diagonal directional mode (2210) on the third quadrant, which is the starting direction of the directional mode, and a diagonal mode (2230) (diagonal mode) perpendicular to the direction of the directional mode (2250) in the 45-degree direction. The direction of the directional mode (2250) among the intra prediction modes of FIG. 22 may be an angular direction other than the 45-degree direction.

[0233] According to one embodiment, the intra prediction modes may be composed of 67. Specifically, the intra prediction modes may be composed of a DC mode, a planar mode, and 65 directional modes, and the intra prediction modes may be distinguished by indicating the index of the intra prediction mode as 0 to 66 (0 is a planar mode, 1 is a DC mode, and 2 to 66 are directional modes).

[0234] Referring to FIG. 22, a mode having an index of 2 in the intra prediction mode may be a directional mode (2210) in the opposite direction of a directional mode (2250) in the 45 degree direction, a mode having an index of 34 in the intra prediction mode may be a diagonal mode (2230) perpendicular to the direction of the directional mode (2250) in the 45 degree direction, a mode having an index of 66 in the intra prediction mode may be an intra prediction mode in the 45 degree direction (2250), an index of a horizontal mode (2220) in the negative direction of the x-axis may be 18, and an index of a vertical mode (2240) in the positive direction of the y-axis may be 50.

[0235] In one embodiment, when the number of MPM modes is 2 and the remaining intra prediction modes are 65, the additional mode sets may be composed of 4 or 8 depending on the type of mode selected as the MPM mode.

[0236] Table 1 below shows an example of an additional mode set configured according to the type of the two MPM modes, where MPM[0] and MPM[1] each denote an intra prediction mode designated as an MPM mode.

[0237] When both MPMs are non-directional mode, when both MPMs are directional mode, DC or planar mode, Planar mode, Vertical mode, DC mode, Horizontal mode, MPM[0]-2, Diagonal mode, MPM[0]-1, MPM[0]+1, MPM[1]-2, MPM[1]-1, MPM[1]+1

[0238] Specifically, if both MPM modes are non-directional, the additional mode set may include four modes: DC or planar mode, vertical mode, horizontal mode, and diagonal mode. Alternatively, the additional mode set may include at least one of DC or planar mode, vertical mode, horizontal mode, and diagonal mode.

[0239] In another embodiment, when both MPM modes are non-directional, the additional mode set may include at least one of a DC or planar mode, a vertical mode, a horizontal mode, an intra prediction mode with an index increased by 4 from the intra prediction mode index of the horizontal mode, and an intra prediction mode with an index decreased by 4 from the intra prediction mode index of the horizontal mode.

[0240] Additionally, when both MPM modes are directional modes, the additional mode set may include eight modes: a planar mode, a DC mode, an intra prediction mode whose index is decreased by 2 from the mode index of MPM[0] (MPM[0]-2), an intra prediction mode whose index is decreased by 1 from the mode index of MPM[0] (MPM[0]-1), an intra prediction mode whose index is increased by 1 from the mode index of MPM[0] (MPM[0]+1), an intra prediction mode whose index is decreased by 2 from the mode index of MPM[1] (MPM[1]-2), an intra prediction mode whose index is decreased by 1 from the mode index of MPM[1] (MPM[1]-1), and an intra prediction mode whose index is increased by 1 from the mode index of MPM[1] (MPM[1]+1). Alternatively, the additional mode set may include at least one of a planar mode, a DC mode, an intra prediction mode with an index reduced by 2 from the mode index of MPM[0] (MPM[0]-2), an intra prediction mode with an index reduced by 1 from the mode index of MPM[0] (MPM[0]-1), an intra prediction mode with an index increased by 1 from the mode index of MPM[0] (MPM[0]+1), an intra prediction mode with an index reduced by 2 from the mode index of MPM[1] (MPM[1]-2), an intra prediction mode with an index reduced by 1 from the mode index of MPM[1] (MPM[1]-1), and an intra prediction mode with an index increased by 1 from the mode index of MPM[1] (MPM[1]+1).

[0241] In addition, if the intra prediction mode of the neighboring block adjacent to the left side of the current block (a candidate for MPM[0]) and the intra prediction mode of the neighboring block adjacent to the upper side of the current block (a candidate for MPM[1]) are the same and are directional modes, MPM[0] is determined as the intra prediction mode of the neighboring block adjacent to the left side of the current block, and the remaining MPM modes and the additional mode set may include five modes: a planar mode, a DC mode, an intra prediction mode of an index decreased by 2 from the mode index of MPM[0] (MPM[0]-2), an intra prediction mode of an index decreased by 1 from the mode index of MPM[0] (MPM[0]-1), and an intra prediction mode of an index increased by 1 from the mode index of MPM[0] (MPM[0]+1). Alternatively, MPM[0] is determined as an intra prediction mode of a neighboring block adjacent to the left of the current block, and the remaining MPM modes and additional mode sets may include at least one of a planar mode, a DC mode, an intra prediction mode with an index decreased by 2 from the mode index of MPM[0] (MPM[0]-2), an intra prediction mode with an index decreased by 1 from the mode index of MPM[0] (MPM[0]-1), and an intra prediction mode with an index increased by 1 from the mode index of MPM[0] (MPM[0]+1).

[0242] In another embodiment, when both MPM modes are directional modes, the additional mode set may include at least one of a DC mode, a planar mode, an intra-prediction mode whose index is increased by 1 from the mode index of the MPM mode having a larger intra-prediction mode index among the MPM modes and an intra-prediction mode whose index is decreased by 1 from the mode index of the MPM mode having a larger intra-prediction mode index among the MPM modes, or an intra-prediction mode whose index is increased by 2 from the mode index of the MPM mode having a larger intra-prediction mode index among the MPM modes and an intra-prediction mode whose index is decreased by 2 from the mode index of the MPM mode having a larger intra-prediction mode index among the MPM modes.

[0243] In another embodiment, when both MPM modes are directional modes, the additional mode set may include at least one of the DC mode, the planar mode, and the intra prediction modes whose index is increased by n from the index of the MPM modes, where n is a non-zero integer.

[0244] Table 2 below shows an example of an additional mode set that would be configured if one of the MPM modes is a non-directional mode and the other is a directional mode, i.e., MPM[0] is a non-directional mode and MPM[1] is a directional mode.

[0245] In case of directional + non-directional mode (4 modes) In case of directional + non-directional mode (8 modes) DC or planar mode (different mode than MPM[0]) DC or planar mode (different mode than MPM[0]) MPM[1]-2 MPM[1]+2 MPM[1]+2 MPM[1]+1 Default mode MPM[1]-1 MPM[1]-2 Default mode Default mode Default mode

[0246] Specifically, when one of the two MPM modes is a non-directional mode and the other is a directional mode, the additional mode set may be composed of four modes: a mode other than MPM[0] which is a non-directional mode among “DC or planar mode”, an intra prediction mode whose index is decreased by 2 from the mode index of MPM[1] which is a directional mode, an intra prediction mode whose index is increased by 2 from the mode index of MPM[1], and a default mode. Alternatively, the additional mode set may be composed of at least one mode other than MPM[0] which is a non-directional mode among “DC or planar mode”, an intra prediction mode whose index is decreased by 2 from the mode index of MPM[1] which is a directional mode, an intra prediction mode whose index is increased by 2 from the mode index of MPM[1], and a default mode.

[0247] Additionally, the additional mode set may be composed of eight modes, including three default modes, a mode other than MPM[0] which is a non-directional mode, an intra prediction mode whose index is decreased by 2 from the mode index of MPM[1] which is a directional mode, an intra prediction mode whose index is decreased by 1 from the mode index of MPM[1], an intra prediction mode whose index is increased by 1 from the mode index of MPM[1], and an intra prediction mode whose index is increased by 2 from the mode index of MPM[1]. Alternatively, the additional mode set may be composed of at least one mode among three default modes, a mode other than MPM[0] which is a non-directional mode, a mode which decreases the mode index of MPM[1] which is a directional mode by 2, a mode which decreases the mode index of MPM[1] which is a directional mode by 1, a mode which increases the mode index of MPM[1] by 1, and a mode which increases the mode index of MPM[1] by 2.

[0248] In another embodiment, the additional mode set may be composed of at least one of a non-directional mode MPM[0] among “DC or planar mode”, an intra prediction mode with an index decreased by 2 from the mode index of MPM[1], a directional mode, an intra prediction mode with an index decreased by 1 from the mode index of MPM[1], and an intra prediction mode with an index increased by 1 from the mode index of MPM[1].

[0249] In another embodiment, when the first MPM mode among the MPM modes is a non-directional mode and the second MPM mode is a directional mode, the additional mode set may include at least one of a DC mode and a planar mode other than the first MPM mode, an intra prediction mode having an index increased by n from the index of the second MPM mode, a vertical mode, and a horizontal mode, where n is a non-zero integer.

[0250] In one embodiment, the default mode may be selected from a pre-configured list of default mode candidates in case the number of candidates to be included in the additional mode set is reduced, such as when at least two candidate modes overlap or when at least one mode or MPM mode of a surrounding block is configured as a non-directional mode. Specifically, the list of default mode candidates may be composed of intra prediction modes that are statistically frequently selected, and the order of the candidates included in the list may be listed in order of the mode with the highest probability of being selected.

[0251] In another embodiment, the default mode can be configured to form additional mode sets by adaptively selecting frequently selected intra prediction modes by counting the modes used up to the current block within the current frame. Alternatively, the default mode can be selected by utilizing the history of intra prediction modes selected from previous intra blocks of the current block in the current frame, or by prioritizing the modes of blocks close to the current block.

[0252] Figure 23 illustrates one embodiment of an additional mode set.

[0253] Referring to FIG. 23, the additional mode set may be composed of a vertical mode (2340) in the positive direction of the y-axis, a horizontal mode (2320) in the negative direction of the x-axis, a directional mode (2350) in the 45 degree direction, a directional mode (2310) in the opposite direction of the directional mode (2350) in the 45 degree direction, a diagonal mode (2330) in the direction perpendicular to the direction of the directional mode (2350) in the 45 degree direction, a directional mode (2370) in the direction that bisects the angle between the vertical mode (2340) and the directional mode (2350) in the 45 degree direction, and a directional mode (2360) in the direction that bisects the angle between the horizontal mode (2320) and the directional mode (2310) in the opposite direction of the directional mode (2350) in the 45 degree direction. When the angle between two directional modes is divided in half, if there is no exactly corresponding direction, the directional mode of the closest direction can be used, or the intra prediction mode with an index obtained by rounding off the average of each intra prediction mode index can be used.

[0254] FIG. 19 and FIG. 20 illustrate a block diagram of a video decoding device (1900) according to an embodiment corresponding to the video decoding device and video decoding method described above, respectively, and a flowchart of a video decoding method according to an embodiment.

[0255] A video encoding device (1900) according to one embodiment may include a memory (1910) and at least one processor (1920) connected to the memory (1910). Operations of the video encoding device (1900) according to one embodiment may operate as individual processors or may be operated under the control of a central processor. In addition, the memory (1910) of the video encoding device (1900) may store data received from the outside and data generated by the processor, for example, information about MPM modes of the current block and information about configured additional mode sets.

[0256] The processor (1920) of the video encoding device (1900) can configure an additional mode set based on the MPM modes of the current block, determine an intra prediction mode of the current block based on the MPM modes and the additional mode set, and perform intra prediction based on the intra prediction mode.

[0257] Referring to FIG. 20 below, a specific operation of a video encoding method in which a video encoding device (1900) according to one embodiment configures an additional mode set based on MPM modes of a current block, and determines an intra prediction mode of the current block based on the MPM modes and the additional mode set to perform intra prediction is described in detail.

[0258] FIG. 20 illustrates a flowchart of a video encoding method according to one embodiment.

[0259] In step s2010, the video encoding device (1900) can configure an additional mode set based on the MPM modes of the current block.

[0260] In one embodiment, the MPM modes of the current block can be determined using the prediction modes of the surrounding blocks.

[0261] In step s2030, the video encoding device (1900) can determine the intra prediction mode of the current block based on the MPM modes and the additional mode set.

[0262] According to one embodiment, the video encoding device (1900) can encode intra prediction mode information by comparing the MPM modes and modes of an additional mode set with the optimal intra prediction mode determined for the current block. The optimal intra prediction mode for the current block can be determined by calculating the rate-distortion cost for the current block.

[0263] In step s2050, the video encoding device (1900) can perform intra prediction of the current block based on the intra prediction mode.

[0264] Figure 24 illustrates an embodiment of intra prediction mode signaling syntax.

[0265] Referring to Fig. 24, when the MPM flag is 1, intra prediction is performed using the MPM mode, and when the MPM flag is 0, the flag of the additional mode set is checked, and when the additional mode set flag is 1, intra prediction is performed using N modes of the additional mode set, and when the additional mode set flag is 0, intra prediction can be performed using the remaining other intra prediction modes. The additional mode set flag can be coded and signaled by allocating log2(N) bits when the number of modes in the additional mode set is N.

[0266] In one embodiment, the number of additional mode sets and the selection probability of the modes may be adjusted to reduce the bit count using unary coding or truncated unary coding.

[0267] In one embodiment, the same bits can be allocated to additional mode sets and each bit can be efficiently coded and signaled using context modeling.

[0268] In one embodiment, when an intra prediction mode other than the MPM mode and the modes in the additional mode set is selected, bits can be allocated excluding the MPM mode and the modes in the additional mode set to efficiently code and signal.

[0269] In one embodiment, an additional set of mode flags may be used, identical to the MPM flags, as per-block flags.

[0270] In one embodiment, it may be determined whether to use only MPM or an additional set of modes depending on the image.

[0271] In one embodiment, a flag may be transmitted on a frame-by-frame basis to determine whether to use an additional set of modes.

[0272] In one embodiment, the use of an additional mode set and the number of modes in the additional mode set may be applied differently depending on the size of the block.

[0273] The present disclosure has been described with a focus on various embodiments. Those skilled in the art will appreciate that the present disclosure can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than restrictive. The scope of the present disclosure is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present disclosure.

[0274] Meanwhile, the embodiments of the present disclosure described above can be written as computer-executable programs and implemented in a general-purpose digital computer that executes the programs using a computer-readable recording medium. The computer-readable recording medium includes storage media such as magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical readable media (e.g., CD-ROMs, DVDs, etc.).

Claims

1. A step of constructing an additional mode set based on the MPM modes of the current block; determining an intra prediction mode of the current block based on the MPM modes and the additional mode set; and A video decoding method, comprising the step of performing intra prediction of the current block based on the intra prediction mode.

2. In paragraph 1, A video decoding method, wherein the MPM modes of the current block include a prediction mode of a neighboring block adjacent to the left of the current block and a prediction mode of a neighboring block adjacent to the upper side of the current block.

3. In paragraph 1, The surrounding blocks adjacent to the right of the current block and the surrounding blocks adjacent to the upper side of the current block are restored before the current block, A video decoding method, wherein the MPM modes of the current block include a prediction mode of a neighboring block adjacent to the right of the current block and a prediction mode of a neighboring block adjacent to the upper side of the current block.

4. In paragraph 2, A video decoding method, wherein the above additional mode set is determined according to the type of the above MPM modes.

5. In paragraph 4, If all of the above MPM modes are non-directional modes, A video decoding method, wherein the additional mode set includes at least one of a DC mode, a planar mode, a vertical mode, a horizontal mode, and a diagonal mode.

6. In paragraph 4, If all of the above MPM modes are directional modes, The above additional mode set includes at least one of DC mode, planar mode, and intra prediction modes whose index is increased by n from the index of the above MPM modes, A video decoding method where n is a non-zero integer.

7. In paragraph 4, If all of the above MPM modes are directional modes, A video decoding method, wherein the additional mode set includes at least one of a DC mode, a planar mode, an intra prediction mode having an index increased by 1 from the index of the MPM modes, an intra prediction mode having an index decreased by 1 from the index of the MPM modes, and an intra prediction mode having an index decreased by 2 from the index of the MPM modes.

8. In paragraph 4, If the intra prediction mode of the surrounding block adjacent to the left of the current block and the intra prediction mode of the surrounding block adjacent to the upper side of the current block are the same and are directional modes, A video decoding method, wherein the MPM modes and the additional mode set include an intra prediction mode of the left adjacent neighboring block, a DC mode, a planar mode, a mode whose index is increased by 1 from the index of the intra prediction mode of the left adjacent neighboring block, an intra prediction mode whose index is decreased by 1 from the index of the intra prediction mode of the left adjacent neighboring block, and an intra prediction mode whose index is decreased by 2 from the index of the intra prediction mode of the left adjacent neighboring block.

9. In paragraph 4, If among the above MPM modes, the first MPM mode is a non-directional mode and the second MPM mode is a directional mode, The additional mode set includes at least one of a DC mode and a planar mode, a mode different from the first MPM mode, an intra prediction mode with an index increased by n from the index of the second MPM mode, a vertical mode, and a horizontal mode, A video decoding method where n is a non-zero integer.

10. Memory; and comprising at least one processor connected to the memory, At least one processor of the above: Construct an additional set of modes based on the MPM modes of the current block, Based on the above MPM modes and the additional mode set, determine the intra prediction mode of the current block, A video decoding device that performs intra prediction of the current block based on the intra prediction mode.

11. In paragraph 10, A video decoding device, wherein the MPM modes of the current block include a prediction mode of a neighboring block adjacent to the left of the current block and a prediction mode of a neighboring block adjacent to the upper side of the current block.

12. In paragraph 11, A video decoding device, wherein the above additional mode set is determined according to the type of the above MPM modes.

13. In paragraph 12, If all of the above MPM modes are directional modes, A video decoding device, wherein the additional mode set includes at least one of a DC mode, a planar mode, an intra prediction mode having an index increased by 1 from the index of the MPM modes, an intra prediction mode having an index decreased by 1 from the index of the MPM modes, and an intra prediction mode having an index decreased by 2 from the index of the MPM modes.

14. In paragraph 12, If the intra prediction mode of the surrounding block adjacent to the left of the current block and the intra prediction mode of the surrounding block adjacent to the upper side of the current block are the same and are directional modes, A video decoding device, wherein the MPM modes and the additional mode set include an intra prediction mode of the left adjacent neighboring block, a DC mode, a planar mode, a mode that increases the index of the intra prediction mode of the left adjacent neighboring block by 1, an intra prediction mode of an index that decreases the index of the intra prediction mode of the left adjacent neighboring block by 1, and an intra prediction mode of an index that decreases the index of the intra prediction mode of the left adjacent neighboring block by 2.

15. A step of constructing an additional mode set based on the MPM modes of the current block; A step of determining an intra prediction mode of the current block based on the above MPM modes and an additional mode set; A video encoding method, comprising the step of performing intra prediction of the current block based on the intra prediction mode.

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