Inter-frame prediction information encoding / decoding method and device

Abstract

Disclosed are an image encoding / decoding method and device. An image decoding method includes: decoding a subblock merge mode indicator of a current block; if the subblock merge mode indicator does not indicate a subblock merge mode, decoding a normal merge mode indicator of the current block; and if the subblock merge mode indicator indicates a subblock merge mode, decoding subblock merge mode information of the current block.

Description

Technical Field

[0001] The present invention relates to an image encoding / decoding method and apparatus and a recording medium for storing a bit stream. More specifically, the present invention relates to an image encoding / decoding method and apparatus for encoding / decoding various inter-frame prediction modes. Background Art

[0002] Recently, in various applications, the demand for high-resolution and high-quality images such as high-definition (HD) or ultra-high-definition (UHD) images has increased. As the resolution and quality of images increase, the amount of data increases accordingly. This is one of the reasons for the increase in transmission cost and storage cost when image data is transmitted through existing transmission media such as wired or wireless broadband channels or when image data is stored. In order to solve these problems of high-resolution and high-quality image data, efficient image encoding / decoding technology is required.

[0003] There are various video compression techniques, such as inter-frame prediction techniques that predict the values ​​of pixels in a current picture from the values ​​of pixels in a previous picture or a subsequent picture, intra-frame prediction techniques that predict the values ​​of pixels in an area of ​​the current picture from the values ​​of pixels in another area of ​​the current picture, transformation and quantization techniques for compressing the energy of residual signals, and entropy coding techniques that assign shorter codes to frequently occurring pixel values ​​and longer codes to less frequently occurring pixel values.

[0004] As the inter prediction mode becomes diversified in order to improve the prediction performance of the image encoding device, data for representing the inter prediction mode may increase, resulting in an overhead of compression bits. Summary of the invention

[0005] Technical issues

[0006] An object of the present invention is to provide a method for efficiently encoding / decoding various inter-frame prediction modes.

[0007] Furthermore, another object of the present invention is to provide a recording medium for storing a bit stream generated by an image encoding / decoding method or apparatus.

[0008] Technical Solution

[0009] An image decoding method according to the present invention includes: decoding a subblock merge mode indicator of a current block, if the subblock merge mode indicator does not indicate a subblock merge mode, decoding a regular merge mode indicator of the current block, and if the subblock merge mode indicator indicates a subblock merge mode, decoding the subblock merge mode information of the current block.

[0010] In the image decoding method, the normal merge mode indicator may indicate, in the case of a first value, that the normal merge mode or the merge with motion vector difference (MMVD) mode is used to derive the inter-frame prediction information of the current block, and in the case of a second value, that the combined intra-frame merge mode or the geometric partition merge mode is used to derive the inter-frame prediction information of the current block.

[0011] In the image decoding method, whether the normal merge mode indicator is decoded may be determined based on a combined intra prediction usage indicator of the current block.

[0012] In the image decoding method, whether the normal merge mode indicator is decoded may be determined based on a skip indicator of the current block.

[0013] In the image decoding method, whether the normal merge mode indicator is decoded may be determined based on a slice type of the current block.

[0014] In the image decoding method, if at least one of a width of the current block or a height of the current block is greater than or equal to a predefined value, the normal merge mode indicator may not be decoded.

[0015] In the image decoding method, the image decoding method may further include: if the normal merge mode indicator has a first value, decoding the MMVD indicator of the current block, and if the normal merge mode indicator has a second value, decoding the combined intra-frame merge mode indicator of the current block.

[0016] In the image decoding method, if the MMVD indicator is not decoded in the decoding step, the MMVD indicator may be inferred to be a predefined value indicating a normal merge mode instead of an MMVD mode.

[0017] In the image decoding method, if the combined intra-frame merge mode indicator is not decoded in the decoding step, the MMVD indicator can be set based on at least one of the following items: a normal merge mode indicator, a combined intra-frame merge mode usage indicator, a skip indicator, or the size of the current block.

[0018] An image encoding method according to the present invention includes: encoding a subblock merge mode indicator of a current block, if the subblock merge mode indicator does not indicate a subblock merge mode, encoding a regular merge mode indicator of the current block, and if the subblock merge mode indicator indicates a subblock merge mode, encoding subblock merge mode information of the current block.

[0019] In the image encoding method, the normal merge mode indicator may indicate, in the case of a first value, that the normal merge mode or the merge with motion vector difference (MMVD) mode is used to derive the inter-frame prediction information of the current block, and in the case of a second value, that the combined intra-frame merge mode or the geometric partition merge mode is used to derive the inter-frame prediction information of the current block.

[0020] In the image encoding method, whether the normal merge mode indicator is encoded may be determined based on a combined intra prediction use indicator of the current block.

[0021] In the image encoding method, whether the normal merge mode indicator is encoded may be determined based on a skip indicator of the current block.

[0022] In the image encoding method, whether the normal merge mode indicator is encoded may be determined based on a slice type of the current block.

[0023] In the image encoding method, if at least one of a width of the current block or a height of the current block is greater than or equal to a predefined value, the normal merge mode indicator may not be encoded.

[0024] In the image encoding method, the image encoding method may further include: if the normal merge mode indicator has a first value, encoding the MMVD indicator of the current block, and if the normal merge mode indicator has a second value, encoding the combined intra-frame merge mode indicator of the current block.

[0025] Furthermore, the recording medium according to the present invention can store a bit stream generated by the image encoding method according to the present invention.

[0026] Beneficial Effects

[0027] According to the present invention, encoding efficiency can be improved by defining the encoding / decoding order of various inter-frame prediction mode information.

[0028] According to the present invention, encoding efficiency can be improved by encoding / decoding inter prediction mode information based on inter prediction mode enabling information encoded / decoded at a higher level.

[0029] Furthermore, according to the present invention, there can be provided a recording medium for storing a bit stream generated by an image encoding / decoding method or apparatus.

[0030] Furthermore, according to the present invention, image encoding and decoding efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1is a block diagram showing a configuration of an encoding device according to an embodiment to which the present invention is applied.

[0032] Figure 2 is a block diagram showing the configuration of a decoding device according to an embodiment and to which the present invention is applied.

[0033] Figure 3 is a diagram schematically showing a partition structure of an image when the image is encoded and decoded.

[0034] Figure 4 is a diagram illustrating an intra prediction process.

[0035] Figure 5 is a diagram illustrating an embodiment of an inter-picture prediction process.

[0036] Figure 6 is a diagram illustrating transform and quantization processing.

[0037] Figure 7 is a diagram showing reference samples that can be used for intra prediction.

[0038] Figure 8 is a flowchart illustrating an inter-frame prediction information encoding / decoding method according to an embodiment of the present invention.

[0039] Figures 9 to 12 is a diagram illustrating an inter prediction information syntax of a merge mode according to various embodiments of the present invention.

[0040] Fig.13 is a diagram showing the use of an indicator in a non-conventional merge mode where a sequence parameter set is entropy encoded.

[0041] Fig.14 is a diagram illustrating an inter prediction information syntax of a merge mode according to an exemplary embodiment of the present invention.

[0042] Fig.15 is a diagram illustrating an affine adaptive motion vector difference usage indicator for a sequence parameter set.

[0043] Fig.16 is a diagram illustrating an inter prediction information syntax of a merge mode according to an exemplary embodiment of the present invention.

[0044] Fig.17 is a diagram illustrating syntax elements indicating various inter prediction modes according to an exemplary embodiment.

[0045] Fig.18 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

[0046] Fig.19 is a flowchart illustrating an image encoding method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] Various modifications may be made to the present invention, and there are various embodiments of the present invention, wherein examples of various embodiments of the present invention will now be provided with reference to the accompanying drawings and described in detail. However, the present invention is not limited thereto, although the exemplary embodiments may be interpreted as including all modifications, equivalents or substitutions within the technical concept and technical scope of the present invention. In various aspects, similar figure numerals refer to the same or similar functions. In the accompanying drawings, the shapes and sizes of the elements may be exaggerated for clarity. In the following detailed description of the present invention, reference is made to the accompanying drawings that illustrate specific embodiments of the present invention in a graphical manner. These embodiments are described in sufficient detail to enable those skilled in the art to implement the present disclosure. It should be understood that the various embodiments of the present disclosure, although different, are not necessarily mutually exclusive. For example, without departing from the spirit and scope of the present disclosure, the specific features, structures and characteristics described herein in conjunction with one embodiment may be implemented in other embodiments. In addition, it should be understood that the position or arrangement of each element within each disclosed embodiment may be modified without departing from the spirit and scope of the present disclosure. Therefore, the following detailed description should not be regarded as having a limiting meaning, and the scope of the present disclosure is limited only by the appended claims (when properly interpreted, together with the full range of equivalents claimed by the claims).

[0048] The terms "first", "second", etc. used in the specification may be used to describe various components, but the components should not be interpreted as being limited to these terms. These terms are only used to distinguish one component from other components. For example, without departing from the scope of the present invention, a "first" component may be named a "second" component, and a "second" component may also be similarly named a "first" component. The term "and / or" includes a combination of multiple items or any one of the multiple items.

[0049] It will be understood that in this specification, when an element is simply referred to as being “connected to” or “coupled to” another element rather than being “directly connected to” or “directly coupled to” another element, the element may be “directly connected to” or “directly coupled to” another element, or connected to or coupled to another element with other elements interposed therebetween. Conversely, it will be understood that when an element is referred to as being “directly coupled to” or “directly connected to” another element, there are no intervening elements.

[0050] In addition, the components shown in the embodiments of the present invention are shown independently to represent the characteristic functions that are different from each other. Therefore, this does not mean that each component is composed of a separate hardware or software component unit. In other words, for convenience, each component includes each component in the listed components. Therefore, at least two components of each component can be combined to form a component, or a component can be divided into multiple components to perform each function. If it does not depart from the essence of the present invention, the embodiment in which each component is combined and the embodiment in which a component is divided are also included in the scope of the present invention.

[0051] The terms used in this specification are only used to describe specific embodiments and are not intended to limit the present invention. Unless there is a significantly different meaning in the context, the expression used in the singular includes the expression in the plural form. In this specification, it will be understood that terms such as "including", "having" etc. are intended to indicate the presence of features, numbers, steps, actions, elements, parts or combinations thereof disclosed in the specification, and are not intended to exclude the possibility that one or more other features, numbers, steps, actions, elements, parts or combinations thereof may exist or may be added. In other words, when a particular element is referred to as "included", it does not exclude elements other than the corresponding element, but may include other elements in an embodiment of the present invention or in the scope of the present invention.

[0052] In addition, some components may not be essential components for performing the basic functions of the present invention, but are selective components that only improve its performance. The present invention can be implemented by only including essential components for implementing the essence of the present invention without including components for improving performance. Structures that only include essential components without including selective components that only improve performance are also included in the scope of the present invention.

[0053] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. When describing the exemplary embodiments of the present invention, well-known functions or configurations will not be described in detail because they may unnecessarily obscure the understanding of the present invention. The same constituent elements in the accompanying drawings are represented by the same reference numerals, and repeated descriptions of the same elements will be omitted.

[0054] Hereinafter, an image may refer to a picture constituting a video, or may refer to the video itself. For example, "encoding or decoding an image or both encoding and decoding" may refer to "encoding or decoding a moving picture or both encoding and decoding", and may refer to "encoding or decoding one of the images of the moving picture or both encoding and decoding".

[0055] Hereinafter, the terms "motion picture" and "video" may be used as the same meaning and may be replaced with each other.

[0056] Hereinafter, a target image may be an encoding target image as an encoding target and / or a decoding target image as a decoding target. In addition, a target image may be an input image input to an encoding device, and an input image input to a decoding device. Here, the target image may have the same meaning as the current image.

[0057] Hereinafter, the terms "image", "picture", "frame" and "screen" may be used as the same meaning and may be replaced with each other.

[0058] Hereinafter, the target block may be an encoding target block as an encoding target and / or a decoding target block as a decoding target. In addition, the target block may be a current block as a target of current encoding and / or decoding. For example, the terms "target block" and "current block" may be used as the same meaning and may be replaced with each other.

[0059] Hereinafter, the terms "block" and "unit" may be used as the same meaning and may be replaced with each other. Alternatively, a "block" may refer to a specific unit.

[0060] In the following, the terms "region" and "segment" are used interchangeably.

[0061] Hereinafter, a specific signal may be a signal representing a specific block. For example, an original signal may be a signal representing a target block. A prediction signal may be a signal representing a prediction block. A residual signal may be a signal representing a residual block.

[0062] In an embodiment, each of the specific information, data, flags, indexes, elements, attributes, etc. may have a value. The value of the information, data, flags, indexes, elements, and attributes equal to "0" may represent a logical false or a first predefined value. In other words, the value "0", false, logical false, and the first predefined value may be replaced with each other. The value of the information, data, flags, indexes, elements, and attributes equal to "1" may represent a logical true or a second predefined value. In other words, the value "1", true, logical true, and the second predefined value may be replaced with each other.

[0063] When the variable i or j is used to represent a column, row, or index, the value of i can be an integer equal to or greater than 0, or an integer equal to or greater than 1. That is, the column, row, index, etc. can be counted from 0 or 1.

[0064] Description of terms

[0065] Encoder: This refers to a device that performs encoding. In other words, it refers to an encoding device.

[0066] Decoder: Refers to a device that performs decoding. In other words, it refers to a decoding device.

[0067] Block: is an M×N sample array. Here, M and N may represent positive integers, and a block may represent a sample array in a two-dimensional form. A block may refer to a unit. A current block may represent an encoding target block that becomes a target at the time of encoding, or a decoding target block that becomes a target at the time of decoding. In addition, the current block may be at least one of a coding block, a prediction block, a residual block, and a transform block.

[0068] Sample: It is the basic unit of a block. d ), the sample point can be represented from 0 to 2 Bd In the present invention, a sample point may be used as the meaning of a pixel. That is, a sample point, a pel, and a pixel may have the same meaning as each other.

[0069] Unit: may refer to a coding and decoding unit. When encoding and decoding an image, a unit may be a region generated by partitioning a single image. In addition, when a single image is partitioned into sub-division units during encoding or decoding, a unit may represent a sub-division unit. That is, an image may be partitioned into a plurality of units. When encoding and decoding an image, a predetermined process for each unit may be performed. A single unit may be partitioned into sub-units having a size smaller than that of the unit. According to the function, a unit may represent a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding block, a prediction unit, a prediction block, a residual unit, a residual block, a transform unit, a transform block, and the like. In addition, in order to distinguish a unit from a block, a unit may include a luminance component block, a chrominance component block associated with the luminance component block, and a syntax element for each color component block. A unit may have various sizes and shapes, and specifically, the shape of a unit may be a two-dimensional geometric figure such as a square, a rectangle, a trapezoid, a triangle, a pentagon, and the like. Also, the unit information may include at least one of a unit type indicating a coding unit, a prediction unit, a transformation unit, etc., and a unit size, a unit depth, an order of encoding and decoding of the unit, and the like.

[0070] Coding tree unit: A single coding tree block configured with a luminance component Y and two coding tree blocks associated with chrominance components Cb and Cr. In addition, the coding tree unit may represent a syntax element including a block and each block. Each coding tree unit may be partitioned by using at least one of a quadtree partitioning method, a binary tree partitioning method, and a ternary tree partitioning method to configure subordinate units such as coding units, prediction units, transform units, etc. The coding tree unit may be used as a term for specifying a sample block that becomes a processing unit when encoding / decoding an image as an input image. Here, the quadtree may represent a quadtree.

[0071] When the size of the coding block is within a predetermined range, it is possible to divide it using only quadtree partitioning. Here, the predetermined range may be defined as at least one of the maximum size and the minimum size of the coding block that can be divided using only quadtree partitioning. Information indicating the maximum / minimum size of the coding block that allows quadtree partitioning may be signaled through a bitstream, and the information may be signaled in at least one unit of a sequence, a picture parameter, a parallel block group, or a slice (fragment). Optionally, the maximum / minimum size of the coding block may be a fixed size predetermined in the encoder / decoder. For example, when the size of the coding block corresponds to 256×256 to 64×64, it is possible to divide it using only quadtree partitioning. Optionally, when the size of the coding block is larger than the size of the maximum conversion block, it is possible to divide it using only quadtree partitioning. Here, the block to be divided may be at least one of a coding block and a transform block. In this case, the information indicating the division of the coding block (e.g., split_flag) may be a flag indicating whether quadtree partitioning is performed. When the size of the coding block falls within a predetermined range, it is possible to divide it using only binary or ternary tree partitioning. In this case, the above description of the quadtree partition can be applied to the binary tree partition or the ternary tree partition in the same manner.

[0072] Coding tree block: may be used as a term used to designate any one of a Y coding tree block, a Cb coding tree block, and a Cr coding tree block.

[0073] Neighboring block: may refer to a block adjacent to the current block. The block adjacent to the current block may refer to a block that touches the boundary of the current block or a block that is located within a predetermined distance from the current block. The neighboring block may refer to a block adjacent to a vertex of the current block. Here, the block adjacent to a vertex of the current block may refer to a block that is vertically adjacent to a neighboring block that is horizontally adjacent to the current block or a block that is horizontally adjacent to a neighboring block that is vertically adjacent to the current block.

[0074] Reconstructed neighboring block: may represent a neighboring block that is adjacent to the current block and has been encoded or decoded in space / time. Here, the reconstructed neighboring block may represent a reconstructed neighboring unit. The reconstructed spatial neighboring block may be a block that is within the current picture and has been reconstructed by encoding or decoding or both encoding and decoding. The reconstructed temporal neighboring block is a block at a position corresponding to the current block of the current picture within the reference image or a neighboring block of the block.

[0075] Unit depth: can represent the degree of partitioning of a unit. In a tree structure, the highest node (root node) can correspond to the first unit that is not partitioned. In addition, the highest node can have a minimum depth value. In this case, the depth of the highest node can be level 0. A node with a depth of level 1 can represent a unit generated by partitioning the first unit once. A node with a depth of level 2 can represent a unit generated by partitioning the first unit twice. A node with a depth of level n can represent a unit generated by partitioning the first unit n times. A leaf node can be the lowest node and a node that cannot be further partitioned. The depth of a leaf node can be the maximum level. For example, the predefined value of the maximum level can be 3. The depth of the root node can be the lowest, and the depth of the leaf node can be the deepest. In addition, when a unit is represented as a tree structure, the level at which the unit exists can represent the unit depth.

[0076] Bitstream: can represent a stream of bits including coded image information.

[0077] Parameter set: corresponds to header information among the configurations in the bitstream. At least one of a video parameter set, a sequence parameter set, a picture parameter set, and an adaptation parameter set may be included in the parameter set. In addition, the parameter set may include a slice header, a tile group header, and tile header information. The term "tile group" means a group of tiles and has the same meaning as a slice.

[0078] The adaptation parameter set may represent a parameter set that can be shared by being referenced in different pictures, sub-pictures, slices, tile groups, tiles, or bricks. In addition, information in the adaptation parameter set may be used by referring to different adaptation parameter sets for sub-pictures, slices, tile groups, tiles, or bricks within a picture.

[0079] Furthermore, regarding adaptation parameter sets, different adaptation parameter sets may be referenced by using identifiers of different adaptation parameter sets for a sub-picture, a slice, a tile group, a tile, or a partition within a picture.

[0080] Furthermore, regarding adaptation parameter sets, different adaptation parameter sets may be referenced by using identifiers of different adaptation parameter sets for slices, tile groups, tiles, or partitions within a sub-picture.

[0081] Furthermore, regarding adaptation parameter sets, different adaptation parameter sets may be referenced by using identifiers of different adaptation parameter sets for tiles or partitions within a slice.

[0082] Furthermore, with respect to adaptation parameter sets, different adaptation parameter sets may be referenced by using identifiers of different adaptation parameter sets for partitions within a tile.

[0083] Information about the adaptation parameter set identifier may be included in a header or a parameter set of a sub-picture, and an adaptation parameter set corresponding to the adaptation parameter set identifier may be used for the sub-picture.

[0084] Information about the adaptation parameter set identifier may be included in a header or a parameter set of a tile, and an adaptation parameter set corresponding to the adaptation parameter set identifier may be used for the tile.

[0085] Information about the adaptation parameter set identifier may be included in a header of the tile, and an adaptation parameter set corresponding to the adaptation parameter set identifier may be used for the tile.

[0086] A picture may be partitioned into one or more tile rows and one or more tile columns.

[0087] A sub-picture may be partitioned into one or more parallel block rows and one or more parallel block columns within a picture. A sub-picture may be an area having a rectangular / square form within a picture and may include one or more CTUs. In addition, at least one or more parallel blocks / blocks / strips may be included in a sub-picture.

[0088] A tile may be an area having a rectangular / square form within a picture and may include one or more CTUs. In addition, a tile may be partitioned into one or more partitions.

[0089] A partition may represent one or more CTU rows within a tile. A tile may be partitioned into one or more partitions, and each partition may have at least one or more CTU rows. A tile that is not partitioned into two or more may represent a partition.

[0090] A slice may include one or more tiles within a picture, and may include one or more partitions within a tile.

[0091] Parsing: may mean determining the value of a syntax element by performing entropy decoding, or may mean the entropy decoding itself.

[0092] Symbol: At least one of a syntax element, a coding parameter, and a transform coefficient value that can represent a coding / decoding target unit. In addition, the symbol can represent an entropy coding target or an entropy decoding result.

[0093] Prediction mode: may be information indicating a mode for encoding / decoding using intra prediction or a mode for encoding / decoding using inter prediction.

[0094] Prediction unit: may represent a basic unit when performing prediction (such as inter prediction, intra prediction, inter compensation, intra compensation, and motion compensation). A single prediction unit may be partitioned into multiple partitions of smaller size, or may be partitioned into multiple lower-level prediction units. Multiple partitions may be basic units when performing prediction or compensation. Partitions generated by splitting a prediction unit may also be prediction units.

[0095] Prediction unit partition: may represent a shape obtained by partitioning a prediction unit.

[0096] A reference picture list may refer to a list including one or more reference pictures used for inter prediction or motion compensation. There are several types of available reference picture lists, including LC (List Combination), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3).

[0097] The inter prediction indicator may refer to the direction of inter prediction of the current block (unidirectional prediction, bidirectional prediction, etc.). Alternatively, the inter prediction indicator may refer to the number of reference pictures used to generate the prediction block of the current block. Alternatively, the inter prediction indicator may refer to the number of prediction blocks used when performing inter prediction or motion compensation on the current block.

[0098] The prediction list utilization flag indicates whether at least one reference picture in a specific reference picture list is used to generate a prediction block. The prediction list utilization flag may be used to derive the inter prediction indicator, and conversely, the inter prediction indicator may be used to derive the prediction list utilization flag. For example, when the prediction list utilization flag has a first value of zero (0), it indicates that the reference picture in the reference picture list is not used to generate the prediction block. On the other hand, when the prediction list utilization flag has a second value of one (1), it indicates that the reference picture list is used to generate the prediction block.

[0099] The reference picture index may refer to an index indicating a specific reference picture in a reference picture list.

[0100] A reference picture may refer to a reference picture referenced by a specific block for the purpose of inter-frame prediction or motion compensation of the specific block. Alternatively, a reference picture may be a picture including a reference block referenced by a current block for inter-frame prediction or motion compensation. Hereinafter, the terms "reference picture" and "reference image" have the same meaning and are interchangeable.

[0101] A motion vector may be a two-dimensional vector used for inter-frame prediction or motion compensation. A motion vector may represent an offset between a coding / decoding target block and a reference block. For example, (mvX, mvY) may represent a motion vector. Here, mvX may represent a horizontal component, and mvY may represent a vertical component.

[0102] The search range may be a two-dimensional area that is searched during inter prediction to retrieve a motion vector. For example, the size of the search range may be M×N. Here, M and N are both integers.

[0103] The motion vector candidate may refer to a prediction candidate block or a motion vector of the prediction candidate block when predicting a motion vector. In addition, the motion vector candidate may be included in a motion vector candidate list.

[0104] The motion vector candidate list may mean a list consisting of one or more motion vector candidates.

[0105] The motion vector candidate index may represent an indicator indicating a motion vector candidate in the motion vector candidate list. Alternatively, it may be an index of a motion vector predictor.

[0106] The motion information may represent information including at least one of items including a motion vector, a reference picture index, an inter prediction indicator, a prediction list utilization flag, a reference picture list information, a reference picture, a motion vector candidate, a motion vector candidate index, a merge candidate, and a merge index.

[0107] The merge candidate list may mean a list consisting of one or more merge candidates.

[0108] The merge candidate may represent a spatial merge candidate, a temporal merge candidate, a combined merge candidate, a combined bi-prediction merge candidate, or a zero merge candidate. The merge candidate may include motion information such as an inter prediction indicator, a reference picture index for each list, a motion vector, a prediction list utilization flag, and an inter prediction indicator.

[0109] The merge index may represent an indicator indicating a merge candidate in the merge candidate list. Alternatively, the merge index may indicate a block in a reconstructed block that is spatially / temporally adjacent to the current block, from which the merge candidate has been derived. Alternatively, the merge index may indicate at least one piece of motion information of the merge candidate.

[0110] Transform unit: may represent a basic unit when encoding / decoding (such as transform, inverse transform, quantization, inverse quantization, transform coefficient encoding / decoding) is performed on a residual signal. A single transform unit may be partitioned into a plurality of lower-level transform units having a smaller size. Here, the transform / inverse transform may include at least one of a first transform / first inverse transform and a second transform / second inverse transform.

[0111] Scaling: may refer to the process of multiplying the level of quantization by a factor. Transform coefficients may be generated by scaling the level of quantization. Scaling may also be referred to as inverse quantization.

[0112] Quantization parameter: may indicate a value used when a transform coefficient is used to generate a quantized level during quantization. The quantization parameter may also indicate a value used when a transform coefficient is generated by scaling the quantized level during inverse quantization. The quantization parameter may be a value mapped to a quantization step size.

[0113] Delta quantization parameter: may represent the difference between the predicted quantization parameter and the quantization parameter of the encoding / decoding target unit.

[0114] Scan: may refer to a method of ordering coefficients within a cell, block, or matrix. For example, changing a two-dimensional matrix of coefficients to a one-dimensional matrix may be called scanning, and changing a one-dimensional matrix of coefficients to a two-dimensional matrix may be called scanning or inverse scanning.

[0115] Transform coefficient: may refer to a coefficient value generated after performing a transform in an encoder. Transform coefficient may refer to a coefficient value generated after performing at least one of entropy decoding and inverse quantization in a decoder. A quantization level obtained by quantizing a transform coefficient or a residual signal or a quantized transform coefficient level may also fall within the meaning of a transform coefficient.

[0116] Quantization level: may represent a value generated by quantizing a transform coefficient or a residual signal in an encoder. Alternatively, the quantization level may represent a value that is a dequantization target subjected to dequantization in a decoder. Similarly, the quantized transform coefficient level as a result of transformation and quantization may also fall within the meaning of the quantization level.

[0117] Non-zero transform coefficient: may refer to a transform coefficient having a value other than zero, or a transform coefficient level or quantization level having a value other than zero.

[0118] Quantization matrix: may refer to a matrix used in a quantization process or an inverse quantization process performed to improve subjective image quality or objective image quality. The quantization matrix may also be referred to as a scaling list.

[0119] Quantization matrix coefficients: can represent each element in the quantization matrix. Quantization matrix coefficients can also be called matrix coefficients.

[0120] Default matrix: may represent a predetermined quantization matrix predefined in an encoder or a decoder.

[0121] Non-default matrix: may denote a quantization matrix that is not predefined in the encoder or decoder but is signaled by the user.

[0122] Statistical value: The statistical value for at least one of a variable, a coding parameter, a constant value, etc. having a calculable specific value can be one or more of the average value, summed value, weighted average value, weighted sum value, minimum value, maximum value, most frequently occurring value, median value, and interpolation value of the corresponding specific value.

[0123] Figure 1 is a block diagram showing a configuration of an encoding device according to an embodiment to which the present invention is applied.

[0124] The encoding device 100 may be an encoder, a video encoding device, or an image encoding device. A video may include at least one image. The encoding device 100 may sequentially encode at least one image.

[0125] Reference Figure 1 , the encoding device 100 may include a motion prediction unit 111, a motion compensation unit 112, an intra-frame prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transform unit 170, an adder 175, a filter unit 180 and a reference picture buffer 190.

[0126] The encoding device 100 may perform encoding of an input image by using an intra mode or an inter mode or both an intra mode and an inter mode. In addition, the encoding device 100 may generate a bit stream including encoding information by encoding the input image, and output the generated bit stream. The generated bit stream may be stored in a computer-readable recording medium, or may be streamed through a wired / wireless transmission medium. When the intra mode is used as a prediction mode, the switch 115 may switch to the intra mode. Alternatively, when the inter mode is used as a prediction mode, the switch 115 may switch to the inter mode. Here, the intra mode may represent an intra prediction mode, and the inter mode may represent an inter prediction mode. The encoding device 100 may generate a prediction block for an input block of the input image. In addition, the encoding device 100 may encode the residual block using the residual of the input block and the prediction block after generating the prediction block. The input image may be referred to as a current image as a current encoding target. The input block may be referred to as a current block as a current encoding target, or may be referred to as an encoding target block.

[0127] When the prediction mode is the intra mode, the intra prediction unit 120 may use samples of a block that has been encoded / decoded and is adjacent to the current block as reference samples. The intra prediction unit 120 may perform spatial prediction on the current block by using the reference samples, or may generate prediction samples of the input block by performing spatial prediction. Here, intra prediction may refer to prediction within a frame.

[0128] When the prediction mode is the inter mode, the motion prediction unit 111 may retrieve the area that best matches the input block from the reference image when performing motion prediction, and derive a motion vector by using the retrieved area. In this case, the search area may be used as the area. The reference image may be stored in the reference picture buffer 190. Here, when encoding / decoding the reference image is performed, the reference image may be stored in the reference picture buffer 190.

[0129] The motion compensation unit 112 may generate a predicted block by performing motion compensation on the current block using a motion vector. Here, inter prediction may refer to prediction or motion compensation between frames.

[0130] When the value of the motion vector is not an integer, the motion prediction unit 111 and the motion compensation unit 112 may generate a prediction block by applying an interpolation filter to a partial area of ​​a reference picture. In order to perform inter-picture prediction or motion compensation on a coding unit, it may be determined which mode among the skip mode, merge mode, advanced motion vector prediction (AMVP) mode, and current picture reference mode is used for motion prediction and motion compensation of a prediction unit included in the corresponding coding unit. Then, inter-picture prediction or motion compensation may be performed differently according to the determined mode.

[0131] The subtractor 125 may generate a residual block by using the difference between the input block and the prediction block. The residual block may be referred to as a residual signal. The residual signal may represent the difference between the original signal and the prediction signal. In addition, the residual signal may be a signal generated by transforming or quantizing the difference between the original signal and the prediction signal, or by transforming and quantizing the difference between the original signal and the prediction signal. The residual block may be a residual signal of a block unit.

[0132] The transform unit 130 may generate a transform coefficient by performing a transform on the residual block and output the generated transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing a transform on the residual block. When the transform skip mode is applied, the transform unit 130 may skip the transform on the residual block.

[0133] The quantized level may be generated by applying quantization to a transform coefficient or to a residual signal. Hereinafter, the quantized level may also be referred to as a transform coefficient in an embodiment.

[0134] The quantization unit 140 may generate a quantization level by quantizing the transform coefficient or the residual signal according to the parameter and output the generated quantization level. Here, the quantization unit 140 may quantize the transform coefficient by using a quantization matrix.

[0135] The entropy encoding unit 150 may generate a bitstream by performing entropy encoding on the value calculated by the quantization unit 140 or the encoding parameter value calculated when encoding is performed according to the probability distribution, and output the generated bitstream. The entropy encoding unit 150 may perform entropy encoding on sample information of the image and information for decoding the image. For example, the information for decoding the image may include a syntax element.

[0136] When entropy coding is applied, symbols are represented so that a smaller number of bits are assigned to symbols with a high probability of generation, and a larger number of bits are assigned to symbols with a low probability of generation, and therefore, the size of the bit stream for the symbol to be encoded can be reduced. The entropy coding unit 150 may use a coding method for entropy coding such as exponential Golomb, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), etc. For example, the entropy coding unit 150 may perform entropy coding by using a variable length coding / code (VLC) table. In addition, the entropy coding unit 150 may derive a binarization method of a target symbol and a probability model of a target symbol / binary bit, and perform arithmetic coding by using the derived binarization method and context model.

[0137] In order to encode a transform coefficient level (quantized level), the entropy encoding unit 150 may change a coefficient in a two-dimensional block form into a one-dimensional vector form by using a transform coefficient scanning method.

[0138] The coding parameters may include information such as syntax elements (flags, indexes, etc.) that are encoded in the encoder and sent to the decoder by signaling, as well as information derived when performing encoding or decoding. The coding parameters may represent information required when encoding or decoding an image. For example, at least one value or combination of the following items may be included in the coding parameters: unit / block size, unit / block depth, unit / block partition information, unit / block shape, unit / block partition structure, whether to perform quadtree partitioning, whether to perform binary tree partitioning, binary tree partition direction (horizontal or vertical), binary tree partition form (symmetric partitioning or asymmetric partitioning), whether the current coding unit is partitioned by ternary tree partitioning, the direction of ternary tree partitioning (horizontal or vertical), the type of ternary tree partitioning (symmetric type or asymmetric type), whether the current coding unit is partitioned by multi-type tree partitioning, and the type of multi-type tree partitioning. direction (horizontal or vertical), type of multi-type tree partition (symmetric or asymmetric), tree (binary tree or ternary tree) structure of multi-type tree partition, prediction mode (intra-frame prediction or inter-frame prediction), luminance intra-frame prediction mode / direction, chrominance intra-frame prediction mode / direction, intra-frame partition information, inter-frame partition information, coding block partition flag, prediction block partition flag, transform block partition flag, reference sample filtering method, reference sample filter taps, reference sample filter coefficients, prediction block filtering method, prediction block filter taps, prediction block filter coefficients, prediction block boundary filtering method, prediction block boundary filter taps, prediction block boundary filter coefficients, intra-frame prediction mode , inter prediction mode, motion information, motion vector, motion vector difference, reference picture index, inter prediction angle, inter prediction indicator, prediction list utilization flag, reference picture list, reference picture, motion vector predictor index, motion vector predictor candidate, motion vector candidate list, whether to use merge mode, merge index, merge candidate, merge candidate list, whether to use skip mode, interpolation filter type, interpolation filter tap, interpolation filter coefficient, motion vector size, representation accuracy of motion vector, transform type, transform size, information on whether primary (first) transform is used, information on whether secondary transform is used, primary transform index, secondary transform index , information on whether a residual signal exists, coding block pattern, coding block flag (CBF), quantization parameter, quantization parameter residual, quantization matrix, whether to apply an intra-frame loop filter, intra-frame loop filter coefficients, intra-frame loop filter taps, intra-frame loop filter shape / form, whether to apply a deblocking filter, deblocking filter coefficients, deblocking filter taps, deblocking filter strength, deblocking filter shape / form, whether to apply adaptive sample offset, adaptive sample offset value, adaptive sample offset category, adaptive sample offset type, whether to apply an adaptive loop filter, adaptive loop filter coefficients, adaptive loop filter taps, adaptive loop filter shape / form,Binarization / debinarization method, context model determination method, context model update method, whether to execute normal mode, whether to execute bypass mode, context binary bit, bypass binary bit, valid coefficient flag, last valid coefficient flag, encoding flag for unit of coefficient group, position of last valid coefficient, flag on whether the value of coefficient is greater than 1, flag on whether the value of coefficient is greater than 2, flag on whether the value of coefficient is greater than 3, information on remaining coefficient values, sign information, reconstructed luminance sample, reconstructed chrominance sample, residual luminance sample, residual chrominance sample, luminance transform coefficient, chrominance transform coefficient, quantized luminance level, quantized chrominance level, transform coefficient level scanning method, motion vector search area on decoder side domain size, shape of a motion vector search area at a decoder side, number of motion vector searches at a decoder side, information on a CTU size, information on a minimum block size, information on a maximum block size, information on a maximum block depth, information on a minimum block depth, image display / output order, slice identification information, slice type, slice partition information, tile identification information, tile type, tile partition information, tile group identification information, tile group type, tile group partition information, picture type, bit depth of input samples, bit depth of reconstructed samples, bit depth of residual samples, bit depth of transform coefficients, bit depth of quantization levels, and information on a luminance signal or information on a chrominance signal.

[0139] Here, signaling a flag or an index may mean entropy encoding the corresponding flag or index by an encoder and including it in a bitstream, and may mean entropy decoding the corresponding flag or index from the bitstream by a decoder.

[0140] When the encoding apparatus 100 performs encoding by inter-frame prediction, the encoded current image may be used as a reference image for another image that is subsequently processed. Therefore, the encoding apparatus 100 may reconstruct or decode the encoded current image, or store the reconstructed or decoded image as a reference image in the reference picture buffer 190.

[0141] The quantized level may be dequantized in the dequantization unit 160 or may be inversely transformed in the inverse transform unit 170. The dequantized or inversely transformed coefficient or the dequantized and inversely transformed coefficient may be added to the prediction block by the adder 175. By adding the dequantized or inversely transformed coefficient or the dequantized and inversely transformed coefficient to the prediction block, a reconstructed block may be generated. Here, the dequantized or inversely transformed coefficient or the dequantized and inversely transformed coefficient may mean a coefficient on which at least one of dequantization and inverse transformation is performed, and may mean a reconstructed residual block.

[0142] The reconstructed block may pass through the filter unit 180. The filter unit 180 may apply at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed sample, the reconstructed block, or the reconstructed image. The filter unit 180 may be referred to as an in-loop filter.

[0143] The deblocking filter may remove block distortion generated in the boundary between blocks. In order to determine whether to apply the deblocking filter, it may be determined whether to apply the deblocking filter to the current block based on the samples included in the number of rows or columns included in the block. When the deblocking filter is applied to the block, another filter may be applied according to the required deblocking filter strength.

[0144] In order to compensate for the coding error, a suitable offset value may be added to the sample value by using sample adaptive offset. Sample adaptive offset can correct the offset of the deblocked image from the original image in units of samples. A method of applying the offset in consideration of edge information about each sample may be used, or a method of partitioning the samples of the image into a predetermined number of regions, determining the region to which the offset is applied, and applying the offset to the determined region may be used.

[0145] The adaptive loop filter may perform filtering based on a comparison result of a filtered reconstructed image and an original image. Samples included in an image may be partitioned into predetermined groups, a filter to be applied to each group may be determined, and differential filtering may be performed on each group. Information on whether ALF is applied may be signaled by a coding unit (CU), and the form and coefficient of ALF to be applied to each block may vary.

[0146] The reconstructed block or the reconstructed image that has passed through the filter unit 180 may be stored in the reference picture buffer 190. The reconstructed block processed by the filter unit 180 may be a part of the reference image. That is, the reference image is a reconstructed image composed of the reconstructed blocks processed by the filter unit 180. The stored reference image may be used later in inter-frame prediction or motion compensation.

[0147] Figure 2 is a block diagram showing the configuration of a decoding device according to an embodiment and to which the present invention is applied.

[0148] The decoding device 200 may be a decoder, a video decoding device, or an image decoding device.

[0149] Reference Figure 2 , the decoding device 200 may include an entropy decoding unit 210, a dequantization unit 220, an inverse transform unit 230, an intra-frame prediction unit 240, a motion compensation unit 250, an adder 255, a filter unit 260 and a reference picture buffer 270.

[0150] The decoding device 200 may receive a bit stream output from the encoding device 100. The decoding device 200 may receive a bit stream stored in a computer-readable recording medium, or may receive a bit stream streamed through a wired / wireless transmission medium. The decoding device 200 may decode the bit stream by using an intra mode or an inter mode. In addition, the decoding device 200 may generate a reconstructed image or a decoded image generated by decoding, and output the reconstructed image or the decoded image.

[0151] When the prediction mode used in decoding is the intra mode, the switch may be switched to the intra mode. Alternatively, when the prediction mode used in decoding is the inter mode, the switch may be switched to the inter mode.

[0152] The decoding device 200 can obtain a reconstructed residual block by decoding the input bit stream and generate a prediction block. When the reconstructed residual block and the prediction block are obtained, the decoding device 200 can generate a reconstructed block that becomes a decoding target by adding the reconstructed residual block to the prediction block. The decoding target block may be referred to as a current block.

[0153] The entropy decoding unit 210 may generate symbols by entropy decoding the bit stream according to the probability distribution. The generated symbols may include symbols in the form of quantized levels. Here, the entropy decoding method may be an inverse process of the above entropy encoding method.

[0154] In order to decode the transform coefficient levels (quantized levels), the entropy decoding unit 210 may change the coefficients in the form of a one-way vector into a two-dimensional block form by using a transform coefficient scanning method.

[0155] The quantized level may be dequantized in the dequantization unit 220, or the quantized level may be inversely transformed in the inverse transform unit 230. The quantized level may be a result of dequantization or inverse transformation or both, and may be generated as a reconstructed residual block. Here, the dequantization unit 220 may apply a quantization matrix to the quantized level.

[0156] When the intra mode is used, the intra prediction unit 240 may generate a predicted block by performing spatial prediction on the current block, wherein the spatial prediction uses sample values ​​of a block that is adjacent to the decoding target block and has been decoded.

[0157] When the inter mode is used, the motion compensation unit 250 may generate a prediction block by performing motion compensation on the current block, wherein the motion compensation uses a motion vector and a reference image stored in the reference picture buffer 270 .

[0158] The adder 255 can generate a reconstructed block by adding the reconstructed residual block to the prediction block. The filter unit 260 can apply at least one of a deblocking filter, a sample adaptive offset, and an adaptive loop filter to the reconstructed block or the reconstructed image. The filter unit 260 can output the reconstructed image. The reconstructed block or the reconstructed image can be stored in the reference picture buffer 270 and used when performing inter-frame prediction. The reconstructed block processed by the filter unit 260 can be a part of the reference image. That is, the reference image is a reconstructed image composed of the reconstructed blocks processed by the filter unit 260. The stored reference image can be used later in inter-frame prediction or motion compensation.

[0159] Figure 3 is a diagram schematically showing a partition structure of an image when the image is encoded and decoded. Figure 3 An example of partitioning a single unit into a plurality of subordinate units is schematically shown.

[0160] In order to effectively partition an image, a coding unit (CU) may be used when encoding and decoding. A coding unit may be used as a basic unit when encoding / decoding an image. In addition, a coding unit may be used as a unit for distinguishing an intra prediction mode from an inter prediction mode when encoding / decoding an image. A coding unit may be a basic unit for prediction, transformation, quantization, inverse transformation, inverse quantization, or encoding / decoding processing of a transform coefficient.

[0161] Reference Figure 3 , the image 300 is partitioned sequentially according to the maximum coding unit (LCU), and the LCU unit is determined as a partition structure. Here, the LCU may be used in the same meaning as the coding tree unit (CTU). Unit partitioning may represent partitioning of a block associated with the unit. In the block partition information, information about the unit depth may be included. The depth information may represent the number or degree of the unit being partitioned or both the number and degree of the unit being partitioned. A single unit may be partitioned into a plurality of subordinate units hierarchically associated with the depth information based on a tree structure. In other words, the unit and the subordinate units generated by partitioning the unit may correspond to a node and a child node of the node, respectively. Each of the partitioned subordinate units may have depth information. The depth information may be information representing the size of a CU and may be stored in each CU. The unit depth represents the number and / or degree associated with partitioning the unit. Therefore, the partition information of the subordinate unit may include information about the size of the subordinate unit.

[0162] The partition structure may represent the distribution of coding units (CUs) within the LCU 310. Such distribution may be determined according to whether a single CU is partitioned into multiple (including 2, 4, 8, 16, etc., positive integers equal to or greater than 2) CUs. The horizontal size and vertical size of the CU generated by partitioning may be half of the horizontal size and vertical size of the CU before partitioning, respectively, or may have sizes smaller than the horizontal size and vertical size before partitioning, respectively, according to the number of partitioning. The CU may be recursively partitioned into multiple CUs. By recursive partitioning, at least one of the height and width of the CU after partitioning may be reduced compared to at least one of the height and width of the CU before partitioning. The partitioning of the CU may be recursively performed until a predefined depth or a predefined size. For example, the depth of the LCU may be 0, and the depth of the minimum coding unit (SCU) may be a predefined maximum depth. Here, as described above, the LCU may be a coding unit having a maximum coding unit size, and the SCU may be a coding unit having a minimum coding unit size. Partitioning starts from the LCU 310, and when the horizontal size or the vertical size or both the horizontal size and the vertical size of the CU are reduced by partitioning, the CU depth increases by 1. For example, for each depth, the size of the non-partitioned CU may be 2N×2N. In addition, in the case of a partitioned CU, a CU of size 2N×2N may be partitioned into four CUs of size N×N. As the depth increases by 1, the size of N may be halved.

[0163] In addition, information on whether a CU is partitioned may be indicated by using the partition information of the CU. The partition information may be 1-bit information. All CUs except the SCU may include partition information. For example, when the value of the partition information is a first value, the CU may not be partitioned, and when the value of the partition information is a second value, the CU may be partitioned.

[0164] Reference Figure 3 , an LCU with a depth of 0 may be a block of 64×64. 0 may be the minimum depth. An SCU with a depth of 3 may be a block of 8×8. 3 may be the maximum depth. A CU of a block of 32×32 and a CU of a block of 16×16 may be represented as depth 1 and depth 2, respectively.

[0165] For example, when a single coding unit is partitioned into four coding units, the horizontal size and vertical size of the four coding units partitioned may be half the size of the horizontal size and vertical size of the CU before being partitioned. In one embodiment, when a coding unit of size 32×32 is partitioned into four coding units, each of the four coding units partitioned may have a size of 16×16. When a single coding unit is partitioned into four coding units, it can be said that the coding unit can be partitioned into a quadtree form.

[0166] For example, when one coding unit is partitioned into two sub-coding units, the horizontal size or vertical size (width or height) of each of the two sub-coding units may be half of the horizontal size or vertical size of the original coding unit. For example, when a coding unit of size 32×32 is partitioned vertically into two sub-coding units, each of the two sub-coding units may have a size of 16×32. For example, when a coding unit of size 8×32 is partitioned horizontally into two sub-coding units, each of the two sub-coding units may have a size of 8×16. When one coding unit is partitioned into two sub-coding units, the coding unit may be said to be partitioned into two or partitioned according to a binary tree partition structure.

[0167] For example, when one coding unit is partitioned into three sub-coding units, the horizontal size or the vertical size of the coding unit may be partitioned at a ratio of 1:2:1, thereby generating three sub-coding units having a ratio of 1:2:1 in the horizontal size or the vertical size. For example, when a coding unit having a size of 16×32 is partitioned horizontally into three sub-coding units, the three sub-coding units may have sizes of 16×8, 16×16, and 16×8, respectively, in order from the uppermost sub-coding unit to the lowermost sub-coding unit. For example, when a coding unit having a size of 32×32 is partitioned vertically into three sub-coding units, the three sub-coding units may have sizes of 8×32, 16×32, and 8×32, respectively, in order from the left sub-coding unit to the right sub-coding unit. When one coding unit is partitioned into three sub-coding units, the coding unit may be said to be partitioned into three sub-coding units or partitioned according to a ternary tree partition structure.

[0168] exist Figure 3 , a coding tree unit (CTU) 320 is an example of a CTU to which a quadtree partition structure, a binary tree partition structure, and a ternary tree partition structure are all applied.

[0169] As described above, in order to partition a CTU, at least one of a quadtree partition structure, a binary tree partition structure, and a ternary tree partition structure may be applied. Various tree partition structures may be sequentially applied to a CTU according to a predetermined priority order. For example, a quadtree partition structure may be preferentially applied to a CTU. Coding units that can no longer be partitioned using a quadtree partition structure may correspond to leaf nodes of a quadtree. Coding units corresponding to leaf nodes of a quadtree may be used as root nodes of a binary and / or ternary tree partition structure. That is, coding units corresponding to leaf nodes of a quadtree may be further partitioned according to a binary tree partition structure or a ternary tree partition structure, or may not be further partitioned. Therefore, by preventing coding units obtained from binary tree partitions or ternary tree partitions of coding units corresponding to leaf nodes of a quadtree from undergoing further quadtree partitions, block partitioning operations and / or operations of signaling partition information may be effectively performed.

[0170] The fact that the coding unit corresponding to the node of the quadtree is partitioned may be signaled using the four partition information. The four partition information having a first value (e.g., '1') may indicate that the current coding unit is partitioned according to the quadtree partition structure. The four partition information having a second value (e.g., '0') may indicate that the current coding unit is not partitioned according to the quadtree partition structure. The four partition information may be a flag having a predetermined length (e.g., one bit).

[0171] There may be no priority between binary tree partitioning and ternary tree partitioning. That is, the coding unit corresponding to the leaf node of the quadtree may further undergo any partitioning of the binary tree partitioning and the ternary tree partitioning. In addition, the coding unit generated by the binary tree partitioning or the ternary tree partitioning may undergo further binary tree partitioning or further ternary tree partitioning, or may not be further partitioned.

[0172] A tree structure in which there is no priority between binary tree partitions and ternary tree partitions is called a multi-type tree structure. A coding unit corresponding to a leaf node of a quadtree may be used as a root node of a multi-type tree. At least one of multi-type tree partition indication information, partition direction information, and partition tree information may be used to signal whether to partition a coding unit corresponding to a node of a multi-type tree. In order to partition a coding unit corresponding to a node of a multi-type tree, multi-type tree partition indication information, partition direction information, and partition tree information may be sequentially signaled.

[0173] The multi-type tree partition indication information having a first value (eg, '1') may indicate that the current coding unit will undergo multi-type tree partitioning. The multi-type tree partition indication information having a second value (eg, '0') may indicate that the current coding unit will not undergo multi-type tree partitioning.

[0174] When a coding unit corresponding to a node of a multi-type tree is further partitioned according to a multi-type tree partition structure, the coding unit may include partition direction information. The partition direction information may indicate in which direction the current coding unit will be partitioned for the multi-type tree partition. The partition direction information having a first value (e.g., "1") may indicate that the current coding unit will be partitioned vertically. The partition direction information having a second value (e.g., "0") may indicate that the current coding unit will be partitioned horizontally.

[0175] When the coding unit corresponding to the node of the multi-type tree is further partitioned according to the multi-type tree partition structure, the current coding unit may include partition tree information. The partition tree information may indicate a tree partition structure to be used to partition the node of the multi-type tree. The partition tree information having a first value (e.g., "1") may indicate that the current coding unit will be partitioned according to a binary tree partition structure. The partition tree information having a second value (e.g., "0") may indicate that the current coding unit will be partitioned according to a ternary tree partition structure.

[0176] The partition indication information, partition tree information and partition direction information may all be flags with a predetermined length (eg, one bit).

[0177] At least any one of the quadtree partition indication information, the multi-type tree partition indication information, the partition direction information, and the partition tree information may be entropy encoded / decoded. In order to entropy encode / decode those types of information, information about neighboring coding units adjacent to the current coding unit may be used. For example, there is a high probability that the partition type (partitioned or not partitioned, partition tree, and / or partition direction) of the left neighboring coding unit and / or the upper neighboring coding unit of the current coding unit is similar to the partition type of the current coding unit. Therefore, context information for entropy encoding / decoding the information about the current coding unit may be derived from the information about the neighboring coding units. The information about the neighboring coding units may include at least any one of the quadtree partition information, the multi-type tree partition indication information, the partition direction information, and the partition tree information.

[0178] As another example, among binary tree partitioning and ternary tree partitioning, binary tree partitioning may be preferentially performed. That is, the current coding unit may first undergo binary tree partitioning, and then the coding unit corresponding to the leaf node of the binary tree may be set as the root node for the ternary tree partitioning. In this case, for the coding unit corresponding to the node of the ternary tree, neither quadtree partitioning nor binary tree partitioning may be performed.

[0179] A coding unit that cannot be partitioned according to a quadtree partition structure, a binary tree partition structure, and / or a ternary tree partition structure becomes a basic unit for encoding, prediction, and / or transformation. That is, the coding unit cannot be further partitioned for prediction and / or transformation. Therefore, partition structure information and partition information for partitioning a coding unit into a prediction unit and / or a transformation unit may not exist in the bitstream.

[0180] However, when the size of the coding unit (i.e., the basic unit for partitioning) is larger than the size of the maximum transform block, the coding unit may be recursively partitioned until the size of the coding unit is reduced to be equal to or smaller than the size of the maximum transform block. For example, when the size of the coding unit is 64×64 and when the size of the maximum transform block is 32×32, the coding unit may be partitioned into four 32×32 blocks for transforming. For example, when the size of the coding unit is 32×64 and the size of the maximum transform block is 32×32, the coding unit may be partitioned into two 32×32 blocks for transforming. In this case, the partitioning of the coding unit for transforming is not separately signaled, and the partitioning of the coding unit for transforming may be determined by comparison between the horizontal size or vertical size of the coding unit and the horizontal size or vertical size of the maximum transform block. For example, when the horizontal size (width) of the coding unit is larger than the horizontal size (width) of the maximum transform block, the coding unit may be vertically divided into two equal parts. For example, when the vertical size (height) of the coding unit is larger than the vertical size (height) of the maximum transform block, the coding unit may be horizontally divided into two equal parts.

[0181] Information on the maximum and / or minimum size of a coding unit and information on the maximum and / or minimum size of a transform block may be signaled or determined at an upper level of the coding unit. The upper level may be, for example, a sequence level, a picture level, a slice level, a tile group level, a tile block level, etc. For example, the minimum size of a coding unit may be determined to be 4×4. For example, the maximum size of a transform block may be determined to be 64×64. For example, the minimum size of a transform block may be determined to be 4×4.

[0182] Information on the minimum size of the coding unit corresponding to the leaf node of the quadtree (quadtree minimum size) and / or information on the maximum depth from the root node of the multi-type tree to the leaf node (maximum tree depth of the multi-type tree) may be signaled or determined at an upper level of the coding unit. For example, the upper level may be a sequence level, a picture level, a slice level, a tile group level, a tile level, etc. Information on the minimum size of the quadtree and / or information on the maximum depth of the multi-type tree may be signaled or determined for each of the intra-picture slice and the inter-picture slice.

[0183] The difference information between the size of the CTU and the maximum size of the transform block may be signaled or determined at the upper level of the coding unit. For example, the upper level may be a sequence level, a picture level, a slice level, a parallel block group level, a parallel block level, etc. The information of the maximum size of the coding unit corresponding to each node of the binary tree (hereinafter referred to as the maximum size of the binary tree) may be determined based on the size of the coding tree unit and the difference information. The maximum size of the coding unit corresponding to each node of the ternary tree (hereinafter referred to as the maximum size of the ternary tree) may vary according to the type of the slice. For example, for an intra-picture slice, the maximum size of the ternary tree may be 32×32. For example, for an inter-picture slice, the maximum size of the ternary tree may be 128×128. For example, the minimum size of the coding unit corresponding to each node of the binary tree (hereinafter referred to as the minimum size of the binary tree) and / or the minimum size of the coding unit corresponding to each node of the ternary tree (hereinafter referred to as the minimum size of the ternary tree) may be set to the minimum size of the coding block.

[0184] As another example, the maximum size of the binary tree and / or the maximum size of the ternary tree may be signaled or determined at the slice level. Alternatively, the minimum size of the binary tree and / or the minimum size of the ternary tree may be signaled or determined at the slice level.

[0185] According to the sizes and depth information of the above-mentioned various blocks, quad partition information, multi-type tree partition indication information, partition tree information and / or partition direction information may or may not be included in the bitstream.

[0186] For example, when the size of the coding unit is not greater than the minimum size of the quadtree, the coding unit does not include the quad partition information. Therefore, the quad partition information may be inferred as the second value.

[0187] For example, when the size (horizontal size and vertical size) of the coding unit corresponding to the node of the multi-type tree is greater than the maximum size (horizontal size and vertical size) of the binary tree and / or the maximum size (horizontal size and vertical size) of the ternary tree, the coding unit may not be partitioned into two or three partitions. Therefore, the multi-type tree partition indication information may not be signaled, but the multi-type tree partition indication information may be inferred as the second value.

[0188] Optionally, when the size (horizontal size and vertical size) of the coding unit corresponding to the node of the multi-type tree is the same as the maximum size (horizontal size and vertical size) of the binary tree and / or is twice as large as the maximum size (horizontal size and vertical size) of the ternary tree, the coding unit may not be further partitioned into two or three partitions. Therefore, the multi-type tree partition indication information may not be signaled, but the multi-type tree partition indication information may be inferred as a second value. This is because when the coding unit is partitioned according to the binary tree partition structure and / or the ternary tree partition structure, a coding unit smaller than the minimum size of the binary tree and / or the minimum size of the ternary tree is generated.

[0189] Optionally, the binary tree partition or ternary tree partition may be limited based on the size of the virtual pipeline data unit (hereinafter, the pipeline buffer size). For example, when the coding unit is divided into sub-coding units that do not fit the pipeline buffer size by binary tree partition or ternary tree partition, the corresponding binary tree partition or ternary tree partition may be limited. The pipeline buffer size may be the size of the maximum transform block (e.g., 64×64). For example, when the pipeline buffer size is 64×64, the following division may be limited.

[0190] - N×M (N and / or M is 128) ternary tree partitions for coding units

[0191] - 128×N (N<=64) binary tree partitions in the horizontal direction for coding units

[0192] - N×128 (N<=64) binary tree partitions in the vertical direction for coding units

[0193] Optionally, when the depth of the coding unit corresponding to the node of the multi-type tree is equal to the maximum depth of the multi-type tree, the coding unit may not be further partitioned into two and / or three partitions. Therefore, the multi-type tree partition indication information may not be sent by a signal, but the multi-type tree partition indication information may be inferred as the second value.

[0194] Optionally, only when at least one of vertical binary tree partitioning, horizontal binary tree partitioning, vertical ternary tree partitioning, and horizontal ternary tree partitioning is possible for a coding unit corresponding to a node of a multi-type tree, a multi-type tree partition indication information may be sent by a signal. Otherwise, the coding unit may not be partitioned into two and / or three partitions. Therefore, the multi-type tree partition indication information may not be sent by a signal, but the multi-type tree partition indication information may be inferred as a second value.

[0195] Optionally, only when both vertical binary tree partitioning and horizontal binary tree partitioning or both vertical ternary tree partitioning and horizontal ternary tree partitioning are possible for the coding unit corresponding to the node of the multi-type tree, the partition direction information can be sent by signal. Otherwise, the partition direction information may not be sent by signal, but the partition direction information may be inferred as a value indicating a possible partition direction.

[0196] Optionally, only when both vertical binary tree partitioning and vertical ternary tree partitioning or both horizontal binary tree partitioning and horizontal ternary tree partitioning are possible for a coding tree corresponding to a node of a multi-type tree, partition tree information may be signaled. Otherwise, partition tree information may not be signaled, but the partition tree information may be inferred as a value indicating a possible partition tree structure.

[0197] Figure 4 is a diagram illustrating an intra prediction process.

[0198] Figure 4 The arrows from the center to the outside in FIG. 1 represent the prediction direction of the intra prediction mode.

[0199] Intra-frame encoding and / or decoding may be performed by using reference samples of neighboring blocks of the current block. The neighboring blocks may be reconstructed neighboring blocks. For example, intra-frame encoding and / or decoding may be performed by using values ​​of reference samples or encoding parameters included in the reconstructed neighboring blocks.

[0200] The prediction block may represent a block generated by performing intra prediction. The prediction block may correspond to at least one of a CU, a PU, and a TU. The unit of the prediction block may have a size of one of a CU, a PU, and a TU. The prediction block may be a square block of a size of 2×2, 4×4, 16×16, 32×32, or 64×64, etc., or may be a rectangular block of a size of 2×8, 4×8, 2×16, 4×16, and 8×16, etc.

[0201] Intra-prediction may be performed according to an intra-prediction mode for the current block. The number of intra-prediction modes that the current block may have may be a fixed value, and may be a value determined differently according to properties of the prediction block. For example, the properties of the prediction block may include the size of the prediction block, the shape of the prediction block, and the like.

[0202] Regardless of the block size, the number of intra-frame prediction modes can be fixed to N. Alternatively, the number of intra-frame prediction modes can be 3, 5, 9, 17, 34, 35, 36, 65 or 67, etc. Optionally, the number of intra-frame prediction modes can vary according to the block size or the color component type or both the block size and the color component type. For example, the number of intra-frame prediction modes can vary depending on whether the color component is a luminance signal or a chrominance signal. For example, as the block size becomes larger, the number of intra-frame prediction modes can increase. Optionally, the number of intra-frame prediction modes of the luminance component block can be greater than the number of intra-frame prediction modes of the chrominance component block.

[0203] The intra prediction mode may be a non-angle mode or an angle mode. The non-angle mode may be a DC mode or a planar mode, and the angle mode may be a prediction mode having a specific direction or angle. The intra prediction mode may be represented by at least one of a mode number, a mode value, a mode number, a mode angle, and a mode direction. The number of intra prediction modes may be M, which is greater than 1, including non-angle modes and angle modes. In order to perform intra prediction on a current block, a step of determining whether a sample included in a reconstructed neighboring block can be used as a reference sample of the current block may be performed. When there are samples that cannot be used as reference samples of the current block, a value obtained by copying or interpolating at least one sample value of the samples included in the reconstructed neighboring block, or by both copying and interpolating, may be used to replace the unavailable sample value of the sample, so that the replaced sample value is used as the reference sample of the current block.

[0204] Figure 7 is a diagram showing reference samples that can be used for intra prediction.

[0205] like Figure 7 As shown in , at least one of the reference sample line 0 to the reference sample line 3 can be used for intra prediction of the current block. Figure 7 In , the samples of fragment A and fragment F can be filled with the samples of the closest fragment B and fragment E, respectively, instead of retrieving from the reconstructed neighboring blocks. The index information indicating the reference sample line to be used for intra prediction of the current block can be sent by signaling. For example, in Figure 7 In the example, reference sample line indicators 0, 1, and 2 may be signaled as index information indicating reference sample line 0, reference sample line 1, and reference sample line 2. When the upper boundary of the current block is the boundary of the CTU, only reference sample line 0 may be available. Therefore, in this case, index information may not be signaled. When reference sample lines other than reference sample line 0 are used, filtering for a prediction block, which will be described later, may not be performed.

[0206] When intra prediction is performed, a filter may be applied to at least one of a reference sample and a prediction sample based on an intra prediction mode and a current block size.

[0207] In the case of the planar mode, when generating the prediction block of the current block, according to the position of the prediction target sample in the prediction block, the sample value of the prediction target sample may be generated by using the weighted sum of the upper reference sample and the left reference sample of the current block and the upper right reference sample and the lower left reference sample of the current block. In addition, in the case of the DC mode, when generating the prediction block of the current block, the average value of the upper reference sample and the left reference sample of the current block may be used. In addition, in the case of the angular mode, the prediction block may be generated by using the upper reference sample, the left reference sample, the upper right reference sample and / or the lower left reference sample of the current block. In order to generate the prediction sample value, interpolation of real number units may be performed.

[0208] In the case of intra prediction between color components, a prediction block of a current block of a second color component may be generated based on a corresponding reconstruction block of a first color component. For example, the first color component may be a luminance component, and the second color component may be a chrominance component. For intra prediction between color components, parameters of a linear model between the first color component and the second color component may be derived based on a template. The template may include upper and / or left neighboring samples of the current block and upper and / or left neighboring samples of a reconstruction block of the first color component corresponding thereto. For example, the sample value of the first color component having the maximum value among the samples in the template and the sample value of the second color component corresponding thereto, and the sample value of the first color component having the minimum value among the samples in the template and the sample value of the second color component corresponding thereto may be used to derive the parameters of the linear model. When deriving the parameters of the linear model, the corresponding reconstruction block may be applied to the linear model to generate a prediction block of the current block. Depending on the video format, subsampling may be performed on the neighboring samples of the reconstruction block of the first color component and the corresponding reconstruction block. For example, when one sample of the second color component corresponds to four samples of the first color component, the four samples of the first color component may be subsampled to calculate one corresponding sample. In this case, parameter derivation of the linear model and intra prediction between color components may be performed based on the corresponding subsampled samples. Whether to perform intra prediction between color components and / or the range of the template may be signaled as an intra prediction mode.

[0209] The current block may be partitioned into two sub-blocks or four sub-blocks in the horizontal direction or the vertical direction. The partitioned sub-blocks may be reconstructed sequentially. That is, intra prediction may be performed on the sub-block to generate a sub-prediction block. In addition, inverse quantization and / or inverse transformation may be performed on the sub-block to generate a sub-residual block. The reconstructed sub-block may be generated by adding the sub-prediction block to the sub-residual block. The reconstructed sub-block may be used as a reference sample for intra prediction of a subsequent sub-block. The sub-block may be a block including a predetermined number (e.g., 16) or more samples. Thus, for example, when the current block is an 8×4 block or a 4×8 block, the current block may be partitioned into two sub-blocks. In addition, when the current block is a 4×4 block, the current block may not be partitioned into sub-blocks. When the current block has other sizes, the current block may be partitioned into four sub-blocks. Information on whether intra prediction is performed based on sub-blocks and / or partition directions (horizontal or vertical) may be sent by a signal. Intra prediction based on sub-blocks may be performed only when reference sample line 0 is used. When subblock-based intra prediction is performed, filtering for a prediction block, which will be described later, may not be performed.

[0210] The final prediction block may be generated by performing filtering on the prediction block predicted by the intra-frame. The filtering may be performed by applying a predetermined weight to the filtering target sample, the left reference sample, the upper reference sample, and / or the upper left reference sample. The weight and / or reference sample (range, position, etc.) used for filtering may be determined based on at least one of the block size, the intra-frame prediction mode, and the position of the filtering target sample in the prediction block. The filtering may be performed only in the case of a predetermined intra-frame prediction mode (e.g., DC, plane, vertical, horizontal, diagonal, and / or adjacent diagonal mode). The adjacent diagonal mode may be a mode in which k is added to the diagonal mode or subtracted from the diagonal mode. For example, k may be a positive integer of 8 or less.

[0211] The intra-frame prediction mode of the current block may be entropy encoded / decoded by predicting the intra-frame prediction mode of a block existing adjacent to the current block. When the intra-frame prediction mode of the current block is the same as that of the neighboring block, information that the intra-frame prediction mode of the current block is the same as that of the neighboring block may be signaled by using predetermined flag information. In addition, indicator information of the intra-frame prediction mode that is the same as the intra-frame prediction mode of the current block among the intra-frame prediction modes of multiple neighboring blocks may be signaled. When the intra-frame prediction mode of the current block is different from that of the neighboring block, the intra-frame prediction mode information of the current block may be entropy encoded / decoded by performing entropy encoding / decoding based on the intra-frame prediction mode of the neighboring block.

[0212] Figure 5 is a diagram illustrating an embodiment of an inter-picture prediction process.

[0213] exist Figure 5 In , a rectangle can represent a picture. Figure 5In FIG. 1 , the arrow indicates the prediction direction. According to the encoding type of the picture, the picture can be classified into an intra picture (I picture), a predicted picture (P picture) and a bi-predicted picture (B picture).

[0214] An I picture may be encoded by intra prediction without requiring inter-picture prediction. A P picture may be encoded by inter-picture prediction using a reference picture existing in one direction (i.e., forward or backward) relative to the current block. A B picture may be encoded by inter-picture prediction using a reference picture existing in two directions (i.e., forward and backward) relative to the current block. When inter-picture prediction is used, the encoder may perform inter-picture prediction or motion compensation, and the decoder may perform corresponding motion compensation.

[0215] Hereinafter, embodiments of inter-picture prediction will be described in detail.

[0216] Reference pictures and motion information may be used to perform inter-picture prediction or motion compensation.

[0217] The motion information of the current block may be derived during inter-picture prediction by each of the encoding device 100 and the decoding device 200. The motion information of the current block may be derived by using the motion information of a reconstructed neighboring block, the motion information of a co-located block (also referred to as a col block or a co-located block), and / or the motion information of a block adjacent to the co-located block. The co-located block may represent a block in a previously reconstructed co-located picture (also referred to as a col picture or a co-located picture) that is spatially located at the same position as the current block. The co-located picture may be one of one or more reference pictures included in a reference picture list.

[0218] The derivation method of motion information may be different according to the prediction mode of the current block. For example, the prediction modes applied to inter prediction include AMVP mode, merge mode, skip mode, merge mode with motion vector difference, sub-block merge mode, geometric partition mode, combined inter-intra prediction mode, affine mode, etc. Here, the merge mode may be referred to as motion merge mode.

[0219] For example, when AMVP is used as a prediction mode, at least one of a motion vector of a reconstructed neighboring block, a motion vector of a co-located block, a motion vector of a block adjacent to the co-located block, and a (0,0) motion vector may be determined as a motion vector candidate for the current block, and a motion vector candidate list may be generated by using the motion vector candidate. The motion vector candidate for the current block may be derived by using the generated motion vector candidate list. The motion information of the current block may be determined based on the derived motion vector candidate. The motion vector of the co-located block or the motion vector of a block adjacent to the co-located block may be referred to as a temporal motion vector candidate, and the motion vector of the reconstructed neighboring block may be referred to as a spatial motion vector candidate.

[0220] The encoding device 100 may calculate a motion vector difference (MVD) between a motion vector of a current block and a motion vector candidate, and may perform entropy coding on the motion vector difference (MVD). In addition, the encoding device 100 may perform entropy coding on a motion vector candidate index and generate a bitstream. The motion vector candidate index may indicate the best motion vector candidate among the motion vector candidates included in the motion vector candidate list. The decoding device may perform entropy decoding on the motion vector candidate index included in the bitstream, and may select a motion vector candidate of a decoding target block from the motion vector candidates included in the motion vector candidate list by using the entropy-decoded motion vector candidate index. In addition, the decoding device 200 may add the entropy-decoded MVD to the motion vector candidate extracted by entropy decoding, thereby deriving a motion vector of the decoding target block.

[0221] In addition, the encoding apparatus 100 may perform entropy encoding on the resolution information of the calculated MVD. The decoding apparatus 200 may adjust the resolution of the entropy-decoded MVD using the MVD resolution information.

[0222] In addition, the encoding device 100 calculates a motion vector difference (MVD) between a motion vector in the current block and a motion vector candidate based on an affine model, and performs entropy encoding on the MVD. The decoding device 200 derives a motion vector based on each sub-block by deriving an affine controlled motion vector of a decoding target block according to the sum of the entropy-decoded MVD and the affine controlled motion vector candidate.

[0223] The bitstream may include a reference picture index indicating a reference picture. The reference picture index may be entropy encoded by the encoding apparatus 100 and then signaled as a bitstream to the decoding apparatus 200. The decoding apparatus 200 may generate a prediction block of a decoding target block based on the derived motion vector and the reference picture index information.

[0224] Another example of a method of deriving motion information of a current block may be a merge mode. The merge mode may represent a method of merging motions of a plurality of blocks. The merge mode may represent a mode of deriving motion information of a current block from motion information of a neighboring block. When the merge mode is applied, the motion information of the reconstructed neighboring block and / or the motion information of the same-position block may be used to generate a merge candidate list. The motion information may include at least one of a motion vector, a reference picture index, and an inter-picture prediction indicator. The prediction indicator may indicate unidirectional prediction (L0 prediction or L1 prediction) or bidirectional prediction (L0 prediction and L1 prediction).

[0225] The merge candidate list may be a list of stored motion information. The motion information included in the merge candidate list may be at least one of the following: motion information of a neighboring block adjacent to the current block (spatial merge candidate), motion information of a co-located block of the current block in a reference picture (temporal merge candidate), new motion information generated by combining motion information present in the merge candidate list, motion information of a block encoded / decoded before the current block (historical-based merge candidate), and a zero merge candidate.

[0226] The encoding device 100 may generate a bitstream by performing entropy encoding on at least one of a merge flag and a merge index, and may signal the bitstream to the decoding device 200. The merge flag may be information indicating whether a merge mode is performed for each block, and the merge index may be information indicating which neighboring block among neighboring blocks of the current block is a merge target block. For example, the neighboring blocks of the current block may include a left neighboring block located on the left side of the current block, an upper neighboring block arranged above the current block, and a temporal neighboring block temporally adjacent to the current block.

[0227] In addition, the encoding device 100 performs entropy encoding on the correction information for correcting the motion vector in the motion information of the merge candidate, and transmits it to the decoding device 200 by signal. The decoding device 200 may correct the motion vector of the merge candidate selected by the merge index based on the correction information. Here, the correction information may include at least one of information on whether to perform correction, correction direction information, and correction size information. As described above, the prediction mode in which the motion vector of the merge candidate is corrected based on the correction information transmitted by the signal may be referred to as a merge mode with a motion vector difference.

[0228] The skip mode may be a mode in which the motion information of the neighboring blocks is applied to the current block as it is. When the skip mode is applied, the encoding apparatus 100 may perform entropy encoding on information of the fact of which block's motion information is to be used as the motion information of the current block to generate a bitstream, and may signal the bitstream to the decoding apparatus 200. The encoding apparatus 100 may not signal a syntax element regarding at least any one of the motion vector difference information, the coded block flag, and the transform coefficient level to the decoding apparatus 200.

[0229] The sub-block merge mode may represent a mode for deriving motion information in units of sub-blocks of a coding block (CU). When the sub-block merge mode is applied, the sub-block merge candidate list may be generated using motion information of a sub-block co-located with the current sub-block in a reference image (sub-block based temporal merge candidates) and / or affine control point motion vector merge candidates.

[0230] The geometric partition mode may denote a mode in which motion information is derived by partitioning the current block in a predetermined direction, each prediction sample is derived using each of the derived motion information, and a prediction sample of the current block is derived by weighting each of the derived prediction samples.

[0231] The inter-intra combined prediction mode may mean a mode of deriving a prediction sample of a current block by weighting a prediction sample generated by inter prediction and a prediction sample generated by intra prediction.

[0232] The decoding apparatus 200 may correct the derived motion information by itself. The decoding apparatus 200 may search for a predetermined area based on a reference block indicated by the derived motion information, and derive motion information having a minimum SAD as the corrected motion information.

[0233] The decoding apparatus 200 may compensate for prediction samples derived through inter-frame prediction using optical flow.

[0234] Figure 6 is a diagram illustrating transform and quantization processing.

[0235] like Figure 6 As shown in , a transform process and / or a quantization process is performed on the residual signal to generate a quantized level signal. The residual signal is the difference between the original block and the prediction block (i.e., an intra-frame prediction block or an inter-frame prediction block). The prediction block is a block generated by intra-frame prediction or inter-frame prediction. The transform can be a primary transform, a secondary transform, or both a primary transform and a secondary transform. The primary transform of the residual signal generates a transform coefficient, and the secondary transform of the transform coefficient generates a secondary transform coefficient.

[0236] At least one scheme selected from various predefined transform schemes is used to perform the primary transform. For example, examples of the predefined transform schemes include discrete cosine transform (DCT), discrete sine transform (DST) and Karhunen-Loève transform (KLT). The transform coefficients generated by the primary transform may undergo a secondary transform. The transform scheme for the primary transform and / or the secondary transform may be determined based on the coding parameters of the current block and / or the neighboring blocks of the current block. Optionally, transform information indicating the transform scheme may be sent by a signal. DCT-based transforms may include, for example, DCT-2, DCT-8, etc. DST-based transforms may include, for example, DST-7.

[0237] A quantized level signal (quantized coefficient) may be generated by performing quantization on a residual signal or on a result of performing a primary transform and / or a secondary transform. Depending on the intra prediction mode of the block or the block size / shape, the quantized level signal may be scanned according to at least one of a diagonal upper right scan, a vertical scan, and a horizontal scan. For example, when the coefficients are scanned according to a diagonal upper right scan, the coefficients in block form are changed to a one-dimensional vector form. In addition to the diagonal upper right scan, a horizontal scan that scans the coefficients in a two-dimensional block form horizontally or a vertical scan that scans the coefficients in a two-dimensional block form vertically may be used according to the intra prediction mode and / or the size of the transform block. The scanned quantized level coefficients may be entropy encoded for insertion into a bitstream.

[0238] The decoder performs entropy decoding on the bit stream to obtain quantized level coefficients. The quantized level coefficients can be arranged in a two-dimensional block form by inverse scanning. For the inverse scanning, at least one of diagonal upper right scanning, vertical scanning, and horizontal scanning can be used.

[0239] The quantized level coefficients may then be dequantized, then inversely transformed secondary if necessary, and finally inversely transformed primary if necessary to generate a reconstructed residual signal.

[0240] Inverse mapping in the dynamic range can be performed for the luminance component reconstructed by intra-frame prediction or inter-frame prediction before in-loop filtering. The dynamic range can be divided into 16 equal segments, and the mapping function for each segment can be sent by signal. The mapping function can be sent by signal at the slice level or parallel block group level. The inverse mapping function for performing inverse mapping can be derived based on the mapping function. In-loop filtering, reference picture storage and motion compensation are performed in the inverse mapping area, and the prediction block generated by inter-frame prediction is converted to the mapping area via mapping using the mapping function, and then used to generate the reconstructed block. However, since intra-frame prediction is performed in the mapping area, the prediction block generated by intra-frame prediction can be used to generate the reconstructed block without mapping / inverse mapping.

[0241] When the current block is a residual block of a chroma component, the residual block can be converted to an inverse mapping area by performing scaling on the chroma component of the mapping area. The availability of scaling can be signaled at the slice level or the parallel block group level. Scaling can be applied only when mapping for the luminance component is available and the division of the luminance component and the division of the chroma component follow the same tree structure. Scaling can be performed based on the average value of the sample value of the luminance prediction block corresponding to the chroma block. In this case, when the current block uses inter-frame prediction, the luminance prediction block can represent the mapped luminance prediction block. The value required for scaling can be derived by using the index reference lookup table of the fragment to which the average value of the sample value of the luminance prediction block belongs. Finally, the residual block can be converted to an inverse mapping area by scaling the residual block using the derived value. Then, chroma component block recovery, intra-frame prediction, inter-frame prediction, in-loop filtering, and reference picture storage can be performed in the inverse mapping area.

[0242] Information indicating whether mapping / inverse mapping of luma components and chroma components is available may be signaled through a sequence parameter set.

[0243] The prediction block of the current block may be generated based on a block vector indicating the displacement between the current block and the reference block in the current picture. In this way, the prediction mode for generating the prediction block with reference to the current picture is called an intra-block copy (IBC) mode. The IBC mode may be applied to M×N (M<=64, N<=64) coding units. The IBC mode may include a skip mode, a merge mode, an AMVP mode, and the like. In the case of a skip mode or a merge mode, a merge candidate list is constructed, and a merge index is signaled so that a merge candidate can be specified. The block vector of the specified merge candidate may be used as the block vector of the current block. The merge candidate list may include at least one of a spatial candidate, a history-based candidate, a candidate based on the average of two candidates, and a zero merge candidate. In the case of the AMVP mode, a difference block vector may be signaled. In addition, a prediction block vector may be derived from the left neighboring block and the upper neighboring block of the current block. The index of the neighboring block to be used may be signaled. The prediction block in the IBC mode is included in the current CTU or the left CTU and is limited to blocks in the reconstructed area. For example, the value of the block vector may be limited so that the prediction block of the current block is located in the region of three 64×64 blocks preceding the 64×64 block to which the current block belongs in the encoding / decoding order. By limiting the value of the block vector in this way, the memory consumption and device complexity of the implementation according to the IBC mode may be reduced.

[0244] Hereinafter, a method of encoding inter-frame prediction information according to the present invention will be described.

[0245] Figure 8 is a flowchart illustrating an inter-frame prediction information encoding / decoding method according to an embodiment of the present invention.

[0246] Reference Figure 8 , the inter-frame prediction information encoding / decoding may include [D1] prediction mode information encoding / decoding step and [D2] inter-frame prediction information encoding / decoding step. Hereinafter, each step will be described in detail.

[0247] [D1] Prediction mode information encoding / decoding steps

[0248] When encoding and decoding the inter-frame prediction mode for a block to be currently encoded / decoded (hereinafter referred to as the "current block"), encoding and decoding of the prediction mode information may be performed using at least one of a skip indicator (e.g., cu_skip_flag), a prediction mode indicator (e.g., pred_mode_flag), or a prediction mode IBC indicator (e.g., pred_mode_ibc_flag).

[0249] The prediction mode information according to an embodiment of the present invention may indicate whether to perform a skip mode, an inter-frame prediction mode, an intra-frame prediction mode, a prediction mode based on intra-frame block copying, and a palette mode of the current block. In addition, the prediction mode information may include at least one of a skip indicator, a prediction mode indicator, or a prediction mode IBC indicator.

[0250] The skip indicator cu_skip_flag may indicate that there is no residual signal for the current block. Therefore, entropy encoding / decoding, quantization / dequantization, and transformation / inverse transformation of the residual signal may not be performed. The skip indicator may have a single bit "0" or "1". In addition, the skip indicator may indicate whether inter-frame prediction or intra-frame block copy-based prediction is performed for the current block.

[0251] For example, if the skip indicator 'cu_skip_flag' decoded by the decoder is '1', inter prediction information (eg, merge_idx) may be decoded.

[0252] For example, if the skip indicator 'cu_skip_flag' decoded by the decoder is '1' and the current slice type is an 'I' (intra) slice, intra block copy-based prediction skip information may be decoded.

[0253] If the slice type of the current block is an 'I' slice and the width or height of the target block is greater than 64, the skip indicator may not be entropy decoded. In other words, this may mean that intra block copy-based prediction skip mode is not allowed for blocks having the above conditions.

[0254] For example, if the skip indicator 'cu_skip_flag' decoded by the decoder is '1', entropy decoding of the residual signal may not be performed.

[0255] For example, if the skip indicator 'cu_skip_flag' decoded by the decoder is '1', inverse quantization and inverse transform may not be performed.

[0256] For example, if the skip indicator 'cu_skip_flag' decoded by the decoder is '0', the prediction mode indicator or the prediction mode IBC indicator may be decoded.

[0257] The prediction mode indicator pred_mode_flag may indicate whether inter prediction or intra prediction is performed on the current block. The prediction mode indicator may have a single bit 0 or 1.

[0258] For example, if the prediction mode indicator decoded by the decoder is '0', entropy encoding of inter prediction mode related information may be performed.

[0259] For example, if the prediction mode indicator decoded by the decoder is '1', entropy decoding of intra prediction mode related information may be performed.

[0260] The prediction mode IBC indicator pred_mode_ibc_flag may indicate whether intra block copy based prediction of the current block is performed. The prediction mode indicator may have a single bit 0 or 1.

[0261] For example, if the intra block copy prediction mode indicator pred_mode_ibc_flag decoded by the decoder is '1', entropy decoding of the intra block copy prediction mode may be performed.

[0262] For example, if the intra block copy prediction mode indicator pred_mode_ibc_flag decoded by the decoder is '0', entropy decoding of inter prediction mode related information or intra prediction mode related information may be performed.

[0263] If the width or height of the current block is greater than 64, the intra block copy prediction mode indicator may not be entropy decoded. In other words, this may mean that if the width or height of the target block is greater than 64, this may mean that intra block copy-based prediction is not allowed.

[0264] When performing entropy encoding / decoding of prediction mode information, entropy encoding / decoding may be adaptively performed using prediction information of spatial neighboring blocks in different ways. The prediction information of the spatial neighboring blocks may include at least one of a skip indicator of the spatial neighboring blocks, a prediction mode indicator, a prediction mode IBC indicator, or a residual signal presence indicator cbf.

[0265] For example, in CABAC entropy encoding / decoding of the skip indicator, different probability models may be used according to the number of cases where the skip indicator of the spatially neighboring blocks is "1".

[0266] For example, in entropy encoding / decoding of the skip indicator, when the number of cases where the skip indicator of the spatially neighboring blocks is '1' is greater than a certain threshold, CABAC may be performed, and otherwise, bypass encoding may be performed.

[0267] [D2] Inter-frame prediction information encoding / decoding

[0268] Encoding and decoding of inter prediction information of the current block may be performed.

[0269] The inter-frame prediction mode may include at least one of a general merge mode and an inter-frame mode (advanced motion vector prediction (AMPV) mode), wherein the general merge mode is used to infer the motion information of the current block from the motion information of the neighboring blocks, and the inter-frame mode (advanced motion vector prediction (AMPV) mode) is used to derive the motion information of the current block by adding the entropy-decoded motion vector difference information and the predicted motion vector.

[0270] The general merge mode may be indicated by a general merge mode indicator (eg, general_merge_flag) value.

[0271] For example, if the entropy-decoded 'general_merge_flag' is '1' as the first value, this may indicate that the current block is decoded in a general merge mode, which may indicate that the current block is decoded in at least one of the following modes: an intra-block copy-based merge mode, a regular merge mode, a merge mode with MVD (motion vector difference), a sub-block merge mode, a combined intra-frame merge mode, or a triangle partitioning mode.

[0272] For example, if the entropy-decoded 'general_merge_flag' is '0' as the second value, this may mean that the current block is decoded in the AMVP mode or the intra block copy-based inter mode.

[0273] If the skip indicator 'cu_skip_flag' decoded by the decoder is '1' which is the first value, the general merge mode indicator general_merge_flag may be inferred as '1' which is the first value without being entropy decoded.

[0274] As prediction modes applied to the general merge mode, there may be a merge mode based on intra block copy, a regular merge mode, a merge with MVD (MMVD) mode, a sub-block merge mode, a combined intra merge mode (or a combined inter intra prediction (CIIP) mode), a triangle partition (or a geometric partition mode (GPM)), and the like.

[0275] In addition, as a prediction mode applied to the skip mode, there may be an intra block copy-based merge mode, a normal merge mode, a merge mode with MVD, a subblock merge mode, a triangle partition mode (or a geometric partition mode), and the like.

[0276] In the normal merge mode, the motion information of the merge candidate selected by the decoded merge index may be used as the motion information of the current block. Here, the normal merge mode may represent Figure 5 The merge mode described in .

[0277] The regular merge mode may be indicated by a regular merge mode indicator (eg, regular_merge_flag) value, and the indicator may be entropy encoded / decoded.

[0278] For example, if the entropy-decoded 'regular_merge_flag' is '1' as the first value, this may indicate that the current block is decoded in the regular merge mode. If 'regular_merge_flag' is '1' as the first value, the merge index information may be entropy encoded / decoded.

[0279] For example, if the entropy-decoded 'regular_merge_flag' is '0' as the second value, this may mean that the current block is decoded in at least one of the MMVD mode, the subblock merge mode, the combined intra merge mode, or the geometric partition mode, rather than the regular merge mode.

[0280] If the general merge mode indicator (general_merge_flag) value is "1" as the first value and at least one of the following conditions (condition 1 or condition 2) is satisfied, the normal merge mode indicator may be derived as "1" as the first value without entropy encoding / decoding. In other words, this may indicate that the current block is always in normal merge mode.

[0281] Condition 1: In the case where the following indicator values ​​entropy-decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, a slice header, etc.) all have "0" as the second value,

[0282] MMVD mode usage indicator (e.g., sps_mmvd_enabled_flag),

[0283] Sub-block unit temporal motion vector prediction usage indicator (e.g., sps_sbtmvp_enabled_flag)

[0284] Affine transform model prediction usage indicator (e.g., sps_affine_enabled_flag)

[0285] Combined intra prediction usage indicator (e.g., sps_ciip_enabled_flag)

[0286] Triangle partition merging mode using indicator (e.g., sps_triangle_enabled_flag)

[0287] In addition, if the above indicator value is '0' as the second value, this may mean that the corresponding merge mode is not used.

[0288] Condition 2: In the case where the MMVD mode usage indicator sps_mmvd_enabled_flag has a second value of "0" and the product of the width and height of the current block is 32 when the higher level (such as sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), sub-picture, tile group, slice header, etc.) is entropy decoded

[0289] In another example, if the general merge mode indicator (general_merge_flag) value is "1" as the first value and at least one of the following conditions (condition 1 or condition 2) is satisfied, the normal merge mode indicator may be derived as "1" as the first value without being entropy encoded / decoded. In other words, this may indicate that the current block is always in normal merge mode.

[0290] Condition 1: In the case where the following indicator values ​​entropy-decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, a slice header, etc.) all have "0" as the second value and the maximum candidate number information MaxNumSubblockMergeCand of the sub-block merging mode is 0 (MaxNumSubblockMergeCand=0), the MMVD mode uses an indicator (e.g., sps_mmvd_enabled_flag),

[0291] Combined intra prediction usage indicator (e.g., sps_ciip_enabled_flag)

[0292] Triangle partition merging mode using indicator (e.g., sps_triangle_enabled_flag)

[0293] Condition 2: In the case where the MMVD mode usage indicator sps_mmvd_enabled_flag has a second value of "0" and the product of the width and height of the current block is 32 when the higher level (such as sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), sub-picture, tile group, slice header, etc.) is entropy decoded

[0294] In another example, if the general merge mode indicator (general_merge_flag) value is "1" as the first value and at least one of the following conditions (condition 1 or condition 2) is satisfied, the normal merge mode indicator may be derived as "1" as the first value without being entropy encoded / decoded. In other words, this may indicate that the current block is always in normal merge mode.

[0295] Condition 1: In the case where the following indicator values ​​entropy-decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, a slice header, etc.) all have "0" as the second value and the maximum candidate number information MaxNumTriangleMergeCand of the triangle partition merging mode is 0 (MaxNumTriangleMergeCand=0), the MMVD mode uses an indicator (e.g., sps_mmvd_enabled_flag),

[0296] Sub-block unit temporal motion vector prediction usage indicator (e.g., sps_sbtmvp_enabled_flag)

[0297] Affine transform model prediction usage indicator (e.g., sps_affine_enabled_flag)

[0298] Combined intra prediction usage indicator (e.g., sps_ciip_enabled_flag)

[0299] Condition 2: In the case where the MMVD mode usage indicator sps_mmvd_enabled_flag has a second value of "0" and the product of the width and height of the current block is 32 when the higher level (such as sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), sub-picture, tile group, slice header, etc.) is entropy decoded

[0300] In another example, if the general merge mode indicator (general_merge_flag) value is "1" as the first value and at least one of the following conditions (condition 1 or condition 2) is satisfied, the normal merge mode indicator may be derived as "1" as the first value without being entropy encoded / decoded. In other words, this may indicate that the current block is always in normal merge mode.

[0301] Condition 1: In the case where the following indicator values ​​entropy-decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, a slice header, etc.) all have "0" as the second value, the maximum candidate number information MaxNumSubblockMergeCand of the sub-block merge mode is "0" (MaxNumSubblockMergeCand=0), and the maximum candidate number information MaxNumTriangleMergeCand of the triangle partition merge mode is "0" (MaxNumTriangleMergeCand=0),

[0302] MMVD mode usage indicator (e.g., sps_mmvd_enabled_flag),

[0303] Combined intra prediction usage indicator (e.g., sps_ciip_enabled_flag)

[0304] Condition 2: In the case where the MMVD mode usage indicator sps_mmvd_enabled_flag has a second value of "0" and the product of the width and height of the current block is 32 when the higher level (such as sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), sub-picture, tile group, slice header, etc.) is entropy decoded

[0305] In another example, if the general merge mode indicator general_merge_flag value is "1" as a first value, and the sub-block merge mode indicator (e.g., merge_subblock_flag) is "0" as a second value (not indicating the sub-block merge mode), the normal merge mode indicator may be derived as "1" as a first value without being entropy encoded / decoded. In other words, this may indicate that the current block is always in normal merge mode.

[0306] In addition, a regular merge mode indicator (eg, regular_merge_flag) may indicate a regular merge mode or an MMVD mode.

[0307] For example, if the entropy-decoded 'regular_merge_flag' is '1' as the first value, this may mean that the current block is decoded in the regular merge mode or the MMVD mode.

[0308] The skip / merge mode based on intra block copy can be determined based on the entropy-encoded prediction mode information (skip indicator or prediction mode IBC indicator), and the motion information of the merge mode selected by the decoded merge index can be used as the motion information of the current block, that is, the block vector.

[0309] In intra block copy based skip / merge mode, only merge index information may be entropy decoded.

[0310] Figures 9 to 12 is a diagram illustrating an inter prediction information syntax of a merge mode according to various embodiments of the present invention.

[0311] Fig. 9 An example of a syntax table for inter prediction mode information that is entropy decoded when the current block is encoded / decoded in general merge mode (ie, general_merge_flag=1) is shown.

[0312] like Fig. 9 As shown in , if at least one of the indicators "sps_mmvd_enabled_flag", "sps_sbtmvp_enabled_flag", "sps_affine_enabled_flag", "sps_ciip_enabled_flag" or "sps_triangle_enabled_flag" entropy decoded at a higher level (e.g., sequence level) is "1", that is, only when the corresponding mode is allowed to be used, the regular merge mode indicator regular_merge_flag may be entropy decoded. In other cases, entropy decoding may not be performed, and the regular merge mode indicator value may always be inferred to be "1".

[0313] Furthermore, if at least one of indicators 'sps_mmvd_enabled_flag', 'sps_sbtmvp_enabled_flag', 'sps_affine_enabled_flag', 'sps_ciip_enabled_flag', or 'sps_triangle_enabled_flag' is '1', additionally, entropy decoding of the normal merge mode indicator may be determined based on the width and height of the current block.

[0314] For example, Fig. 9As shown in , the normal merge mode indicator may be entropy decoded only when the product of the width and height of the current block is not 32. In other words, if the product of the width and height is 32, entropy decoding may not be performed, and the normal merge mode indicator value may always be inferred to be "1". That is, it may be inferred that the current block is in normal merge mode.

[0315] Furthermore, if at least one of the indicators "sps_mmvd_enabled_flag", "sps_sbtmvp_enabled_flag", "sps_affine_enabled_flag", "sps_ciip_enabled_flag", or "sps_triangle_enabled_flag" is "1", then additionally, when "sps_mmvd_enabled_flag" is "1" which is the first value, as Fig. 9 As shown in , the regular merge mode indicator can always be entropy decoded regardless of the width and height of the current block.

[0316] Fig.10 Another example of a syntax table for inter prediction mode information that is entropy decoded when the current block is encoded / decoded in the general merge mode (ie, general_merge_flag=1) is shown.

[0317] and Fig. 9 Differently, the indicators "sps_sbtmvp_enabled_flag" and "sps_affine_enabled_flag" entropy decoded at a higher level (e.g., sequence level) are not directly used, and whether the regular merge mode indicator regular_merge_flag is entropy decoded can be determined based on the maximum number information MaxNumSubblockMergeCand of sub-block merge modes entropy decoded at another higher level (e.g., sequence level, picture level, or slice header).

[0318] MaxNumSubblockMergeCand may have a value from 0 to 5, and may be derived through 'five_minus_max_num_subblock_merge_cand' information as follows.

[0319] MaxNumSubblockMergeCand=5-five_minus_max_num_subblock_merge_cand

[0320] If MaxNumSubblockMergeCand has a value of '0', this may mean that the subblock-unit merge mode is not used for the current slice.

[0321] like Fig.10 As shown in , if the maximum number information of subblock merge modes of the current block is greater than 0 or at least one of the indicators "sps_mmvd_enabled_flag", "sps_ciip_enabled_flag" or "sps_triangle_enabled_flag" entropy-decoded at a higher level is "1", the regular merge mode indicator regular_merge_flag can be entropy decoded.

[0322] Fig.11 Another example of a syntax table for inter prediction mode information that is entropy decoded when the current block is encoded / decoded in the general merge mode (ie, general_merge_flag=1) is shown.

[0323] and Fig. 9 Differently, the indicator "sps_triangle_enabled_flag" entropy-decoded at a higher level (e.g., sequence level) is not directly used, and whether the regular merge mode indicator regular_merge_flag is entropy-decoded may be determined based on the maximum number information MaxNumTriangleMergeCand of the triangle partition merge mode entropy-decoded at another higher level (e.g., slice header). Here, the triangle partition merge mode may be a geometry partition merge mode.

[0324] MaxNumTriangleMergeCand may be derived through 'max_num_merge_cand_minus_max_num_triangle_cand' information decoded at a slice level as follows.

[0325] MaxNumTriangleMergeCand=MaxNumMergeCand-max_num_merge_cand_minus_max_num_triangle_cand

[0326] MaxNumMergeCand may represent the number of merge candidates derived from 'six_minus_max_num_merge_cand' decoded at the slice level.

[0327] If MaxNumTriangleMergeCand has a value of '0', this may indicate that the triangle partition merge mode is not used for the current stripe.

[0328] like Fig.11As shown in , if the maximum number information of the triangle merge mode of the current block is greater than 1 or at least one of the indicators "sps_mmvd_enabled_flag", "sps_sbtmvp_enabled_flag", "sps_affine_enabled_flag" or "sps_ciip_enabled_flag" entropy decoded at a higher level is "1", the regular merge mode indicator regular_merge_flag can be entropy decoded.

[0329] Fig.12 Another example of a syntax table for inter prediction mode information that is entropy decoded when the current block is encoded / decoded in the general merge mode (ie, general_merge_flag=1) is shown.

[0330] and Fig. 9 Differently, the indicators “sps_sbtmvp_enabled_flag”, “sps_affine_enabled_flag” and “sps_triangle_enabled_flag” entropy decoded at a higher level (e.g., sequence level) are not directly used, and whether the regular merge mode indicator regular_merge_flag is entropy decoded can be determined based on the maximum number information MaxNumSubblockMergeCand of sub-block merge modes and the maximum number information MaxNumTriangleMergeCand of triangle partition merge modes entropy decoded at another higher level (e.g., sequence level, picture level, or slice header).

[0331] MaxNumSubblockMergeCand may have a value from 0 to 5, and may be derived through 'five_minus_max_num_subblock_merge_cand' information as follows.

[0332] MaxNumSubblockMergeCand=5-five_minus_max_num_subblock_merge_cand

[0333] If MaxNumSubblockMergeCand has a value of '0', this may mean that the subblock-unit merge mode is not used for the current block.

[0334] MaxNumTriangleMergeCand may be derived through 'max_num_merge_cand_minus_max_num_triangle_cand' information decoded at a slice level as follows.

[0335] MaxNumTriangleMergeCand=MaxNumMergeCand-max_num_merge_cand_minus_max_num_triangle_cand

[0336] MaxNumMergeCand may represent the number of merge candidates derived from 'six_minus_max_num_merge_cand' decoded at the slice level.

[0337] If MaxNumTriangleMergeCand has a value of '0', this may indicate that the triangle partition merge mode is not used for the current stripe.

[0338] like Fig.12 As shown in , if the maximum number information of the triangle partition merge mode of the current block is greater than 1, the maximum number of sub-block merge modes is greater than 0, or the value of at least one of the indicators "sps_mmvd_enabled_flag" or "sps_ciip_enabled_flag" entropy decoded at a higher level is "1", the regular merge mode indicator regular_merge_flag can be entropy decoded.

[0339] Fig.13 is a diagram showing an example of a syntax table for using an indicator for a non-conventional merge mode entropy decoded in a sequence parameter set.

[0340] If the value of the non-regular merge mode usage indicator (e.g., sps_non_regular_merge_enabled_flag) is "1" as the first value, at least one of the following indicators may be entropy decoded: a merge mode usage indicator with MVD, a sub-block unit temporal motion vector prediction usage indicator, an affine model transform based prediction usage indicator, a combined intra-frame merge mode usage indicator, or a triangle partition merge mode usage indicator.

[0341] If the value of the non-regular merge mode usage indicator (e.g., sps_non_regular_merge_enabled_flag) is "0" as the second value, at least one of the following indicators may not be entropy decoded and may be inferred to be "0" as the second value (which may indicate that the corresponding prediction mode is not used): a merge mode usage indicator with MVD, a sub-block unit temporal motion vector prediction usage indicator, an affine model transform based prediction usage indicator, a combined intra-frame merge mode usage indicator, or a triangle partition merge mode usage indicator.

[0342] Fig.14 is a diagram showing an example of a syntax table for inter prediction mode information that is entropy decoded when a current block is encoded / decoded in a general merge mode (ie, general_merge_flag=1).

[0343] Whether to entropy decode the regular merge mode indicator regular_merge_flag may be determined based on a non-regular merge mode usage indicator entropy decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header).

[0344] For example, the regular merge mode indicator regular_merge_flag may be entropy decoded only when the value of the non-regular merge mode usage indicator (e.g., sps_non_regular_merge_enabled_flag) is "1" as the first value and only at least one of two conditions is satisfied ("sps_mmvd_enabled_flag" decoded at a higher level is "1" as the first value and the product of the width and height of the current block is not 32).

[0345] Hereinafter, the merge mode with MVD, the subblock merge mode, the combined intra merge mode, and the triangle partition mode will be described in detail.

[0346] In the merge with MVD (MMVD) mode, the motion vector of the motion information of the merge candidate selected by the decoded merge index may be corrected based on the correction information and then used as the motion information of the current block. Here, the correction information may include at least one of the correction direction information mmvd_direction_idx or the correction distance information. Motion vector difference information may be derived through the correction information, and the motion information obtained by adding the derived motion vector difference information to the motion vector of the motion information of the merge candidate selected by the merge index may be used as the motion information of the current block.

[0347] The MMVD mode may be indicated by an MMVD mode indicator (eg, mmvd_merge_flag) value, and the indicator may be entropy encoded / decoded.

[0348] For example, if the entropy-decoded 'mmvd_merge_flag' has '1' as the first value, this may indicate that the current block is decoded in the MMVD mode. If 'mmvd_merge_flag' has '1' as the first value, 'mmvd_cand_flag' corresponding to the merge index information, the correction distance information mmvd_distance_idx, and the correction direction information mmvd_direction_idx may be entropy-decoded.

[0349] For example, if the entropy-decoded 'mmvd_merge_flag' is '0' as the second value, this may mean that the current block is decoded in at least one of the normal merge mode, the subblock merge mode, the combined intra merge mode, or the triangle partition merge mode, rather than the MMVD mode.

[0350] For example, if the entropy-decoded 'mmvd_merge_flag' is '0' as the second value, this may mean that the current block is decoded in the normal merge mode, rather than being decoded in the MMVD mode.

[0351] The indicator may not be entropy decoded based on a motion vector difference merge mode using an indicator value that is entropy decoded at a higher level, such as a sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), sub-picture, tile group, or slice header.

[0352] For example, only when an MMVD use indicator (eg, sps_mmvd_enabled_flag) entropy-decoded in an SPS has '1' as a first value (indicating that the MMVD mode is used), 'mmvd_merge_flag' may be entropy-decoded.

[0353] If the indicator mmvd_merge_flag is not entropy decoded, a value of '0' may be set. In other words, this may indicate that the MMVD mode is not applied to the block currently to be decoded.

[0354] The sub-block merge mode may represent a mode for deriving motion information in units of sub-blocks of the current block. When the sub-block merge mode is applied, the sub-block merge candidate list may be generated using motion information of a sub-block corresponding (co-located) to the current sub-block in the reference image (sub-block-based temporal merge candidates) and / or affine control point motion vector merge candidates.

[0355] The sub-block merge mode may be indicated by a value of a sub-block merge mode indicator (eg, merge_subblock_flag), and the indicator may be entropy encoded / decoded.

[0356] For example, if the entropy-decoded 'merge_subblock_flag' has '1' as the first value, this may indicate that the current block is decoded in the subblock merge mode. If 'merge_sublock_flag' has '1' as the first value, the subblock merge index information merge_subblock_idx may be entropy-decoded.

[0357] For example, if the entropy-decoded 'merge_subblock_flag' is '0' as the second value, this may mean that the current block is decoded in at least one of the normal merge mode, the MMVD mode, the combined intra merge mode, or the triangle partition merge mode, rather than the subblock merge mode.

[0358] The indicator may not be entropy decoded based on at least one of a sub-block unit temporal motion vector prediction usage indicator or an affine transformation model based prediction usage indicator entropy decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header).

[0359] For example, if a sub-block-unit temporal motion vector prediction use indicator (eg, sps_sbtmvp_enabled_flag) entropy-decoded in an SPS has '1' as a first value (indicating use of a sub-block-unit temporal motion vector), the indicator 'merge_subblock_flag' may be entropy-decoded.

[0360] For example, if an affine transformation model prediction use indicator (eg, sps_affine_enabled_flag) entropy-decoded in an SPS has '1' as a first value (indicating use of an affine transformation model), the indicator 'merge_subblock_flag' may be entropy-decoded.

[0361] For example, if both 'sps_sbtmvp_enabled_flag' and 'sps_affine_enabled_flag' entropy-decoded in the SPS have '0' as the second value (indicating that sub-block-unit temporal motion vector prediction and affine transformation model prediction are not used), the indicator 'merge_subblock_flag' may not be entropy-decoded.

[0362] The indicator may be entropy-decoded based on the maximum number information MaxNumSubblockMergeCand of the subblock merge modes. For example, if MaxNumSubblockMergeCand has '0', the indicator 'merge_subblock_flag' may not be entropy-decoded.

[0363] If the indicator merge_subblock_flag is not entropy decoded, a value of '0' may be set. In other words, this may indicate that the sub-block-unit merge mode is not applied to the block currently to be decoded.

[0364] The combined intra merge mode (or combined inter intra prediction mode, CIIP mode, combined inter intra prediction mode) may denote a mode in which prediction samples of a current block are derived by weighted summing of prediction samples generated by inter prediction and prediction samples generated by intra prediction.

[0365] The combined intra merge mode may be indicated by a value of a combined intra merge mode indicator (eg, ciip_flag), and the indicator may be entropy encoded / decoded.

[0366] For example, if the entropy-decoded 'ciip_flag' has '1' as the first value, this may indicate that the current block is decoded in the combined intra merge mode. If 'ciip_flag' has '1' as the first value, merge index information merge_idx for generating inter prediction samples may be entropy-decoded.

[0367] For example, if the entropy-decoded 'ciip_flag' has '0' as the second value, this may mean that the current block is decoded in at least one of the normal merge mode, the MMVD mode, the subblock merge mode, or the triangle partition merge mode, rather than the combined intra merge mode.

[0368] The indicator may not be entropy decoded using an indicator value based on a combined intra merge mode that is entropy decoded at a higher level, such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header.

[0369] For example, only when a combined intra merge mode use indicator (eg, sps_ciip_enabled_flag) in which an SPS is entropy-decoded has '1' as a first value (indicating that the combined intra merge mode is used), 'ciip_flag' may be entropy-decoded.

[0370] If the indicator is not entropy decoded, the value of the combined intra merge mode indicator may be set based on at least one of the combined intra merge mode usage indicator sps_ciip_enabled_flag, the regular merge mode indicator regular_merge_flag, the skip indicator cu_skip_flag, or the size of the current block.

[0371] The triangle partition merge mode (or geometric partition mode, GPM) may represent a mode in which motion information is derived by partitioning the current block, each prediction sample is derived using the derived motion information, and the prediction sample of the current block is derived by weighted summing the derived prediction samples. Here, the geometric partition mode may represent a mode in which the current block is partitioned into asymmetric sub-blocks and the current block is predicted.

[0372] The triangle partition merge mode may be indicated by a value of a triangle partition merge mode indicator (eg, triangle_merge_flag), and the indicator may be entropy encoded / decoded.

[0373] For example, if the entropy-decoded 'triangle_merge_flag' has '1' as a first value, this may mean that the current block is decoded in the triangle partition merging mode.

[0374] For example, if the entropy-decoded 'triangle_merge_flag' has '0' as the second value, this may mean that the current block is decoded in at least one of normal merge mode, MMVD mode, subblock merge mode, or combined intra merge mode, rather than triangle partition merge mode.

[0375] The indicator may be entropy decoded based on the value of the triangle partition merge mode usage indicator that is entropy decoded at a higher level, such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header.

[0376] For example, “triange_merge_flag” may be entropy decoded only when a triangle partition merge mode use indicator (eg, sps_triangle_enabled_flag) entropy-decoded in an SPS has “1” as a first value (indicating use of the triangle partition merge mode).

[0377] If the indicator is not entropy decoded, a value of “0” may be set. In other words, this may mean that the triangle partition merge mode is not applied to the block currently to be decoded.

[0378] In addition, whether the triangle partition merge mode is performed may be determined by the value of the combined intra-frame merge mode indicator (e.g., ciip_flag). For example, if the combined intra-frame merge mode indicator (ciip_flag) has "0" as the second value (not indicating the combined intra-frame merge mode), the current block may be determined to be in the triangle partition merge mode, and the triangle partition merge prediction information may be entropy decoded.

[0379] In addition, whether the geometric partition merge mode is performed may be determined based on the value of the combined intra-frame merge mode indicator (e.g., ciip_flag). For example, if the combined intra-frame merge mode indicator ciip_flag has "0" as the second value (not indicating the combined intra-frame merge mode), the geometric partition merge prediction information may be entropy decoded.

[0380] The triangle partition merge mode may be indicated by the value of the triangle partition merge mode indicator, and if the following conditions are met without performing entropy encoding / decoding, the indicator (e.g., MergeTriangleFlag) of the current block may be set to "1". Here, the triangle partition merge mode may represent the geometry partition merge mode. That is, the triangle partition merge mode usage indicator, the maximum number of triangle partition merge modes, and the triangle partition merge mode indicator may represent the geometry partition merge mode usage indicator, the maximum number of geometry partition merge modes, and the geometry partition merge mode indicator, respectively.

[0381] If at least one of the following conditions is not met, the value of 'MergeTriangleFlag' may be set to '0.' In other words, this may mean that the triangle partition merging mode is not allowed for the current block.

[0382] If the value of the triangle partition merging mode usage indicator (e.g., sps_triangle_enabled_flag) decoded at a higher level is "1",

[0383] If the stripe type of the current block is B stripe,

[0384] If the value of the general merge mode indicator general_merge_flag is "1",

[0385] If the maximum allowable number of candidates for the triangle partition merge mode MaxNumTriangleMergeCand is greater than or equal to 2,

[0386] If the product of the width and height of the current block is greater than or equal to 64,

[0387] If the value of the regular merge mode indicator regular_merge_flag is "0",

[0388] If the value of the MMVD mode indicator mmvd_merge_flag is "0",

[0389] If the value of the sub-block merge mode indicator merge_subblock_flag is "0",

[0390] If the value of the combined intra-frame merging mode indicator ciip_flag is "0",

[0391] If MergeTriangleFlag is '1' which is a first value, partition direction information indicator merge_triangle_split_dir and merge index information merge_triangle_idx0 and merge_triangle_idx1 of two subblocks may be entropy encoded / decoded.

[0392] If the maximum allowable number MaxNumTriangleMergeCand of candidates of the triangle partition merge mode is 2, 'merge_triangle_idx1' may not be entropy encoded / decoded, and other candidates except the candidate indicated by 'merge_triangle_idx0' may be used.

[0393] If the encoded / decoded general merge mode general_merge_flag of the current block has '1' as a first value and all following merge mode indicator values ​​are '0' as a second value, the merge index information merge_idx of the current block may be inferred to be '0' without being entropy decoded.

[0394] Regular merge mode indicator (e.g., regular_merge_flag)

[0395] MMVD mode indicator (e.g., mmvd_merge_flag)

[0396] Subblock merge mode indicator (e.g., merge_subblock_flag)

[0397] Combined intra-frame merging mode indicator (e.g., ciip_flag)

[0398] Triangle partition merge mode indicator (e.g., MergeTriangleFlag)

[0399] If the above conditions are met and thus the value of the general merge mode general_merge_flag is '1' as the first value and the merge index information is inferred to be '0', the motion information of the first candidate among the motion information stored in the merge candidate list may be used as the motion information of the current block.

[0400] The motion information stored in the merge candidate list may be at least one of the following: motion information of a neighboring block adjacent to the current block (spatial merge candidate), motion information of a block in a reference image corresponding to (co-located with) the current block (temporal merge candidate), new motion information generated by combining motion information already existing in the merge candidate list, motion information of a block encoded / decoded before the current block (historical-based merge candidate), or a zero merge candidate.

[0401] In another example, if the encoded / decoded general merge mode general_merge_flag of the current block has "1" as the first value and all following merge mode indicator values ​​have "0" as the second value, the current block may be set to the fallback merge mode, and after configuring the merge list with zero merge candidates, the motion information of the first candidate may be used as the motion information of the current block.

[0402] Regular merge mode indicator regular_merge_flag

[0403] MMVD mode indicator mmvd_merge_flag

[0404] Sub-block merge mode indicator merge_subblock_flag

[0405] Combined intra-frame merging mode indicator ciip_flag

[0406] Triangle partition merge mode indicator MergeTriangleFlag

[0407] If the above conditions are met, the general merge mode general_merge_flag has '1' as the first value, and the merge index information is inferred to be '0', additional correction may not be performed based on a motion vector derived from the corresponding index information.

[0408] If the above conditions are met, the general merge mode general_merge_flag has '1' as the first value, and the current block is set to the fallback merge mode, additional correction may not be performed.

[0409] The additional correction may mean a process (Decoder Motion Vector Correction (DMVR)) of correcting motion information having a minimum SAD in a decoder by searching a predefined area based on a reference block indicated by motion information derived from merge index information '0'.

[0410] The additional correction may mean a process (bidirectional optical flow (BDOF)) of compensating the prediction samples derived through inter-frame prediction using the optical flow based on the motion information derived from the merge index information '0' in the decoder.

[0411] The prediction modes applied to the inter-frame mode (or AMVP mode or advanced motion vector prediction mode) may include the inter-frame mode based on intra-frame block copy, the general AMVP mode, the affine inter-frame mode using the affine transformation mode, the symmetric motion vector difference (SMVD) mode for deriving the L1 direction MVD based on the L0 direction MVD, the adaptive motion vector resolution (AMVR) mode for adjusting the resolution of the MVD, and the like.

[0412] The intra block copy inter mode can be determined based on the entropy decoded prediction mode information (prediction mode IBC indicator, e.g., pred_mode_ibc_flag), and the motion vector obtained by adding the decoded block vector difference (BVD) to the motion vector prediction candidate selected by the decoded motion vector index (e.g., mvp_l0_flag) can be used as the motion vector of the current block, i.e., the block vector.

[0413] In general AMVP mode, a motion vector obtained by adding the decoded L0 / L1 motion vector difference to a motion vector prediction candidate selected by a motion vector index (e.g., mvp_lX_flag, X=0 or 1) decoded in the L0 direction and the L1 direction may be used as the L0 / L1 motion vector of the current block.

[0414] An inter prediction indicator inter_pred_idc indicating L0 or L1 unidirectional inter prediction or L0 / L1 bidirectional inter prediction, a reference image index ref_idx in L0 and L1 directions, and horizontal / vertical motion vector difference information in L0 and L1 directions may be entropy encoded / decoded.

[0415] If the motion vector difference value in at least one of the horizontal or vertical motion vector difference values ​​in the L0 and L1 directions is not "0", the adaptive motion vector difference indicator amvr_flag can be entropy decoded, and if the corresponding indicator value is "1", the indicator amvr_precision_flag for 1 / 16 pixel, 1 / 2 pixel, 1 pixel or 4 pixel resolution can be entropy decoded.

[0416] For example, if 'amver_flag' has '1' as a first value and 'amvr_precision_flag' has '0' as a second value, this may indicate that the motion vector difference value is 1 (integer) pixel resolution. If 'amver_flag' has '1' as a first value and 'amvr_precision_flag' has '1' as a first value, this may indicate that the motion vector difference value is 4 (integer) pixel resolution. If 'amvr_flag' has '0' as a second value, the motion vector difference value has 1 / 4 pixel resolution.

[0417] In the affine inter mode, the motion vector obtained by adding the decoded L0 / L1 affine control point motion vector difference and the affine control point motion vector prediction candidate selected by the motion vector index decoded in each direction of the L0 direction and the L1 direction (e.g., mvp_lX_flag, X=0 or 1) can be used as the L0 / L1 affine control point motion vector of the current block.

[0418] The affine inter mode indicator inter_affine_flag indicating whether the current block is in the affine inter mode may be entropy encoded / decoded.

[0419] If the indicator inter_affine_flag has '1' as a first value, the affine type information cu_affine_type_flag indicating 4 parameters using two affine control point motion vectors or 6 parameters using three affine control point motion vectors may be entropy encoded / decoded.

[0420] If 'cu_affine_type_flag' has '1' as the first value, this may mean that 6 parameters of three affine control point motion vectors are used.

[0421] If 'cu_affine_type_flag' has '0' as the second value, this may mean that 4-parameters using two affine control point motion vectors are used.

[0422] Whether the affine type information cu_affine_type_flag is entropy encoded / decoded may be determined based on a 6-parameter usage indicator (e.g., sps_affine_type_flag) that is entropy decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header).

[0423] For example, if sps_affine_type_flag entropy-decoded in an SPS has '1' and an affine inter mode indicator 'inter_affine_flag' of a block to be currently decoded has '1', cu_affine_type_flag may be encoded / decoded.

[0424] If the affine type information does not exist, "0" (ie, 4 parameters) as the second value may be inferred.

[0425] An inter prediction indicator inter_pred_idc indicating L0 or L1 unidirectional inter prediction or L0 / L1 bidirectional inter prediction, a reference image index ref_idx in L0 and L1 directions, and horizontal / vertical motion vector difference information in L0 and L1 directions may be entropy encoded / decoded.

[0426] If the motion vector difference value of at least one of the two or three horizontal or vertical motion vector difference values ​​in the L0 and L1 directions is not "0", the adaptive motion vector difference indicator amvr_flag can be entropy decoded, and if the corresponding indicator value has "1", the indicator amvr_precision_flag for 1 pixel or 1 / 16 pixel resolution can be entropy decoded.

[0427] If 'amver_flag' has '1' as a first value and 'amvr_precision_flag' has '0' as a second value, this may mean that the motion vector difference value is 1 / 16 pixel resolution.

[0428] If 'amver_flag' has '1' as a first value and 'amvr_precision_flag' has '1' as a first value, this may mean that the motion vector difference value is 1 (integer) pixel resolution.

[0429] If 'amvr_flag' has '0' as the second value, this may mean that the motion vector difference is 1 / 4 pixel resolution.

[0430] Whether the adaptive motion vector difference indicator amvr_flag is entropy encoded / decoded may be determined based on an affine adaptive motion vector difference usage indicator (e.g., sps_affine_amvr_enabled_flag) that is entropy decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header).

[0431] like Fig.15As shown in , the affine adaptive motion vector difference use indicator sps_affine_amvr_enabled_flag may be entropy encoded / decoded only in a case where the value of the affine transformation model prediction use indicator sps_affine_enabled_flag is '1' which is the first value.

[0432] For example, if 'sps_affine_amvr_enabled_flag' when SPS is encoded / decoded has '1' as the first value, the affine inter mode indicator 'inter_affine_flag' of the current block has '1' as the first value, and the motion vector difference in at least one of the two or three horizontal or vertical motion vector differences in the L0 and L1 directions is not '0', the adaptive motion vector difference indicator amvr_flag may be entropy encoded / decoded.

[0433] In SMVD mode, entropy encoding / decoding of reference image index information ref_idx in each of the L0 and L1 directions may not be performed, and reference image index information derived at the slice level may be used. In addition, the horizontal / vertical motion vector difference in the L1 direction may not be entropy encoded / decoded, and a symmetric value of the horizontal / vertical motion vector difference in the L0 direction that has been entropy encoded / decoded may be used as the horizontal / vertical motion vector difference in the L1 direction.

[0434] The symmetric MVD mode indicator sym_mvd_flag indicating whether the current block is in the SMVD mode may be entropy encoded / decoded.

[0435] Whether the indicator sym_mvd_flag is entropy encoded / decoded may be determined based on at least one of the following items: a symmetric MVD mode usage indicator sps_smvd_enabled_flag entropy decoded at a higher level (such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a sub-picture, a tile group, or a slice header), an inter-frame prediction indicator inter_pred_idc indicating L0 or L1 unidirectional inter-frame prediction or L0 / L1 bidirectional inter-frame prediction, or mvd_l1_zero_flag indicating whether the motion vector difference in the L1 direction is used as "0" when it is not entropy decoded by performing entropy encoding / decoding on the slice header.

[0436] For example, if the decoded 'sps_smvd_enabled_flag' in the SPS has '1' as the first value (enabling symmetric MVD) and the decoded 'mvd_l1_zero_flag' has '0' as the second value, and the inter prediction indicator of the current block is bidirectional prediction, the indicator sym_mvd_flag may be entropy encoded / decoded.

[0437] For example, if the decoded 'sps_smvd_enabled_flag' in the SPS has '1' as the first value (symmetric MVD is enabled), and the decoded 'mvd_l1_zero_flag' has '1' as the first value, and the inter prediction indicator of the current block is bidirectional prediction, the indicator sym_mvd_flag may not be entropy encoded / decoded.

[0438] If the value of "sym_mvd_flag" is not present, it may mean that the corresponding indicator value is inferred to be "0" and symmetric MVD of the current block is not allowed.

[0439] Fig.16 is a diagram illustrating an inter prediction information syntax of a merge mode according to an exemplary embodiment of the present invention.

[0440] Fig.16 An example of a syntax table for inter prediction mode information that is entropy decoded when the current block is encoded / decoded in general merge mode (ie, general_merge_flag=1) is shown.

[0441] Whether the subblock merge indicator merge_subblock_flag is entropy decoded may be determined based on at least one of maximum number information MaxNumSubblockMergeCand of subblock merge modes entropy decoded at a higher level (eg, sequence level or picture level), a width of a current block, or a height of a current block.

[0442] For example, if MaxNumSubblockMergeCand is greater than '0' and both the width and height of the current block are equal to or greater than 8, the subblock merge indicator may be entropy decoded.

[0443] Whether the regular merge mode indicator regular_merge_flag is entropy decoded can be determined based on at least one of the following items: the sub-block merge mode indicator merge_subblock_flag, the skip indicator cu_skip_flag, the combined intra-frame prediction usage indicator sps_ciip_enabled_flag, the width cbWidth of the current block, the height cbHeight of the current block, the area cbWidth*cbHeight of the current block, the slice type slice_type, or the maximum number MaxNumTriangleMergeCand of triangle partition merge candidates.

[0444] For example, if the subblock merge mode indicator merge_subblock_flag has '1' as a first value (indicating the subblock merge mode), the regular merge mode indicator regular_merge_flag may not be entropy-decoded.

[0445] For example, if the combined intra prediction use indicator sps_ciip_enabled_flag has '1' as a first value (indicating that combined intra prediction is allowed to be used) and the skip indicator cu_skip_flag has '0' as a second value (not indicating skip mode), the regular merge mode indicator regular_merge_flag may be entropy decoded.

[0446] For example, if the slice type is a B slice and the maximum number of triangle partition merge candidates is greater than or equal to a predefined value (e.g., 2), the regular merge mode indicator regular_merge_flag may be entropy decoded. If the maximum number of triangle partition merge candidates is less than the predefined value, this may indicate that the triangle partition merge mode is not performed. For example, if the slice type is a B slice and the triangle partition merge mode is performed, the regular merge mode indicator regular_merge_flag may be entropy decoded.

[0447] For example, if the slice type indicates an I slice or a P slice, and the skip indicator cu_skip_flag has '1' as a first value (indicating a skip mode), the regular merge mode indicator regular_merge_flag may not be entropy-decoded.

[0448] For example, if the slice type indicates an I slice or a P slice and the combined intra prediction use indicator sps_ciip_enabled_flag has '0' as the second value (not indicating that the use of combined intra prediction is allowed), the regular merge mode indicator regular_merge_flag may not be entropy-decoded.

[0449] For example, if at least one of the width or the height of the current block is greater than or equal to a predefined value (eg, 128), the regular merge mode indicator regular_merge_flag may not be entropy decoded.

[0450] In addition, if Fig.16 If the conditions described in , the regular merge mode indicator regular_merge_flag can be entropy decoded.

[0451] If the normal merge mode indicator has '1' as a first value (indicating the normal merge mode) and the MMVD mode use indicator sps_mmvd_enabled_flag has '1' as a first value (indicating the use of the MMVD mode), the MMVD mode indicator mmvd_merge_flag may be entropy decoded.

[0452] Whether the combined intra-frame merge mode indicator ciip_flag is entropy decoded may be determined based on at least one of the following items: a regular merge mode indicator regular_merge_flag, a skip indicator cu_skip_flag, a combined intra-frame prediction use indicator sps_ciip_enabled_flag, a width cbWidth of a current block, a height cbHeight of a current block, a slice type slice_type, or a maximum number MaxNumTriangleMergeCand of triangle partition merge candidates. If the regular merge mode indicator has "0" as a second value (not indicating a regular merge mode), the combined intra-frame merge mode indicator ciip_flag may be entropy decoded.

[0453] If the maximum number of triangle partition merge candidates MaxNumTriangleMergeCand is less than 2, the combined intra merge mode indicator ciip_flag may not be entropy decoded. If the maximum number of triangle partition merge candidates MaxNumTriangleMergeCand is less than 2, this may mean that the triangle partition merge mode is not performed.

[0454] If the slice type indicates an I slice or a P slice, the combined intra merge mode indicator ciip_flag may not be entropy-decoded.

[0455] If the combined intra merge mode indicator ciip_flag has '1' as a first value (indicating the combined intra merge mode) and the maximum number of merge candidates MaxNumMergeCand is greater than 1, the merge index information merge_idx may be entropy-decoded.

[0456] If the combined intra merge mode indicator ciip_flag is not entropy decoded, the value of the combined intra merge mode indicator may be set based on at least one of the combined intra merge mode usage indicator sps_ciip_enabled_flag, the regular merge mode indicator regular_merge_flag, the skip indicator cu_skip_flag, or the size of the current block.

[0457] Therefore, even if the combined intra merge mode indicator ciip_flag is not entropy decoded, the value of the combined intra merge mode indicator ciip_flag may be set to '1' as the first value. Therefore, even if the combined intra merge mode indicator is not entropy decoded, the merge index information merge_idx may be entropy decoded.

[0458] Whether the triangle partition merge mode is performed may be determined based on the value of the combined intra merge mode indicator ciip_flag. For example, if the combined intra merge mode indicator ciip_flag has "0" as the second value (not indicating the combined intra merge mode), the triangle partition merge prediction information (merge_tranagle_split_dir, merge_triangle_idx0, or merge_triagle_idx1) may be entropy decoded. Here, the triangle partition merge mode may be a geometry partition merge mode.

[0459] Fig.17 is a diagram illustrating syntax elements indicating various inter prediction modes according to an exemplary embodiment.

[0460] If the value of the regular merge mode indicator regular_merge_flag is '1', this may indicate that the regular merge mode or the MMVD mode is used to derive inter prediction information. If the value of the regular merge mode indicator regular_merge_flag is '0', this may indicate that the combined intra merge mode or the geometric partition merge mode is used to derive inter prediction information.

[0461] If the value of the MMVD mode indicator mmvd_merge_flag is '1', this may indicate that the MMVD mode is used to derive inter prediction information. If the value of the MMVD mode indicator mmvd_merge_flag is '0', this may indicate that the normal merge mode is used to derive inter prediction information.

[0462] In addition, if the MMVD mode indicator mmvd_merge_flag is not entropy decoded, a value of “0” may be set. In other words, this may indicate that the MMVD mode is not applied to the block currently to be decoded and the normal merge mode is applied.

[0463] The combined intra merge mode indicator ciip_flag may indicate whether a combination of inter prediction and intra prediction is applied.

[0464] In addition, if the combined intra merge mode indicator ciip_flag is not entropy decoded, the value of the combined intra merge mode indicator may be set based on at least one of the following items: the combined intra merge mode usage indicator sps_ciip_enabled_flag, the regular merge mode indicator regular_merge_flag, the skip indicator cu_skip_flag, or the size of the current block.

[0465] Fig.18 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

[0466] Reference Fig.18 , the decoder may decode a sub-block merge mode indicator (eg, merge_subblock_flag) of the current block (S1801).

[0467] Furthermore, if the subblock merge mode indicator does not indicate the subblock merge mode ( S1802 —No), the decoder may decode a regular merge mode indicator (eg, regular_merge_flag) of the current block ( S1803 ).

[0468] Here, the normal merge mode indicator may indicate, in the case of a first value (e.g., "1"), that the normal merge mode or the MMVD mode is used to derive the inter-frame prediction information of the current block, and in the case of a second value (e.g., "0"), that the combined intra-frame merge mode or the geometric partition merge mode is used to derive the inter-frame prediction information of the current block.

[0469] Whether the normal merge mode indicator is decoded may be determined based on a combined intra prediction usage indicator (eg, sps_ciip_enabled_flag) of the current block.

[0470] Whether the normal merge mode indicator is decoded may be determined based on a skip indicator (eg, cu_skip_flag) of the current block.

[0471] Whether the normal merge mode indicator is decoded may be determined based on a slice type (eg, slice_type) of the current block.

[0472] If at least one of the width or height of the current block is greater than or equal to a predefined value (eg, 128), the normal merge mode indicator may not be decoded.

[0473] In addition, if the subblock merge mode indicator indicates the subblock merge mode (S1802-Yes), the decoder may decode the subblock merge mode information of the current block (S1804). Here, the subblock merge mode information may be a subblock merge index (eg, merge_subblock_idx).

[0474] In addition, if the normal merge mode indicator has a first value (e.g., "1"), the decoder may decode the MMVD mode indicator mmvd_merge_flag of the current block. In addition, if the normal merge mode indicator has a second value (e.g., "0"), the decoder may decode the combined intra-frame merge mode indicator (e.g., ciip_flag) of the current block.

[0475] If the MMVD mode indicator is not entropy decoded, the MMVD mode indicator may be inferred to be a predefined value (eg, “0”) indicating the normal merge mode instead of the MMVD mode.

[0476] If the combined intra merge mode indicator is not entropy decoded, the combined intra merge mode indicator may be set based on at least one of: a normal merge mode indicator, a combined intra merge mode usage indicator, a skip indicator, or a size of the current block.

[0477] Fig.19 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

[0478] Reference Fig.19 , the encoder may encode a subblock merge mode indicator (eg, merge_subblock_flag) of the current block (S1901).

[0479] In addition, if the subblock merge mode indicator does not indicate the subblock merge mode ( S1902 —No), the encoder may encode a regular merge mode indicator regular_merge_flag of the current block ( S1903 ).

[0480] Here, the normal merge mode indicator may indicate, in the case of a first value (e.g., "1"), that the normal merge mode or the MMVD mode is used to derive the inter-frame prediction information of the current block, and in the case of a second value (e.g., "0"), that the combined intra-frame merge mode or the geometric partition merge mode is used to derive the inter-frame prediction information of the current block.

[0481] Whether the normal merge mode indicator is encoded may be determined based on a combined intra prediction usage indicator (eg, sps_ciip_enabled_flag) of the current block.

[0482] Whether the normal merge mode indicator is encoded may be determined based on a skip indicator (eg, cu_skip_flag) of the current block.

[0483] Whether the normal merge mode indicator is encoded may be determined based on a slice type (eg, slice_type) of the current block.

[0484] If at least one of the width or height of the current block is greater than or equal to a predefined value (eg, 128), the normal merge mode indicator may not be encoded.

[0485] In addition, if the subblock merge mode indicator indicates the subblock merge mode (S1902-Yes), the encoder may encode the subblock merge mode information of the current block (S1904). Here, the subblock merge mode information may be a subblock merge index (eg, merge_subblock_idx).

[0486] In addition, if the normal merge mode indicator has a first value (e.g., "1"), the encoder may encode the MMVD mode indicator mmvd_merge_flag of the current block. In addition, if the normal merge mode indicator has a second value (e.g., "0"), the encoder may encode the combined intra-frame merge mode indicator (e.g., ciip_flag) of the current block.

[0487] The non-transitory computer-readable recording medium according to the present invention may store Fig.19 Describes the bitstream generated by the image encoding method.

[0488] Specifically, in a non-temporary computer-readable recording medium for storing a bit stream generated by an image encoding method, the image encoding method includes: encoding a subblock merge mode indicator of a current block, if the subblock merge mode indicator does not indicate a subblock merge mode, encoding a normal merge mode indicator of the current block, and if the subblock merge mode indicator indicates a subblock merge mode, encoding subblock merge mode information of the current block.

[0489] The above embodiments may be performed in the same way in an encoder and a decoder.

[0490] At least one embodiment or a combination of the above embodiments may be used to encode / decode a video.

[0491] The order applied to the above embodiments may be different between the encoder and the decoder, or the order applied to the above embodiments may be the same in the encoder and the decoder.

[0492] The above embodiments may be performed on each of the luminance signal and the chrominance signal, or may be performed identically on the luminance signal and the chrominance signal.

[0493] The block form to which the above embodiment of the present invention is applied may have a square form or a non-square form.

[0494] At least one of the syntax elements (flags, indices, etc.) entropy encoded in the encoder and entropy decoded in the decoder may use at least one of the following binarization, debinarization, entropy encoding / entropy decoding methods.

[0495] Truncated Rice Binarization Method

[0496] k-order Exp_Golomb binarization method

[0497] Finite k-order Exp_Golomb binarization method

[0498] Fixed-length binarization method

[0499] Unary Binarization Method

[0500] Truncated Unary Binarization Method

[0501] Truncated Binary Binarization Method

[0502] The above-mentioned embodiments of the present invention may be applied according to the size of at least one of a coding block, a prediction block, a transform block, a block, a current block, a coding unit, a prediction unit, a transform unit, a unit, and a current unit. Here, the size may be defined as a minimum size or a maximum size or both a minimum size and a maximum size so that the above-mentioned embodiments are applied, or the size may be defined as a fixed size to which the above-mentioned embodiments are applied. In addition, in the above-mentioned embodiments, the first embodiment may be applied to a first size, and the second embodiment may be applied to a second size. In other words, the above-mentioned embodiments may be applied in combination according to the size. In addition, the above-mentioned embodiments may be applied when the size is equal to or greater than the minimum size and equal to or less than the maximum size. In other words, the above-mentioned embodiments may be applied when the block size is included in a specific range.

[0503] For example, when the size of the current block is 8×8 or larger, the above embodiment may be applied. For example, when the size of the current block is only 4×4, the above embodiment may be applied. For example, when the size of the current block is 16×16 or smaller, the above embodiment may be applied. For example, when the size of the current block is equal to or larger than 16×16 and equal to or smaller than 64×64, the above embodiment may be applied.

[0504] The above-described embodiments of the present invention may be applied according to time layers. In order to identify the time layers to which the above-described embodiments may be applied, a corresponding identifier may be signaled, and the above-described embodiments may be applied to the specified time layers identified by the corresponding identifier. Here, the identifier may be defined as the lowest layer or the highest layer or both the lowest layer and the highest layer to which the above-described embodiments may be applied, or may be defined as a specific layer to which the embodiments may be applied. In addition, a fixed time layer to which the embodiments may be applied may be defined.

[0505] For example, when the temporal layer of the current image is the lowest layer, the above embodiment may be applied. For example, when the temporal layer identifier of the current image is 1, the above embodiment may be applied. For example, when the temporal layer of the current image is the highest layer, the above embodiment may be applied.

[0506] A slice type or a tile group type to which the above-described embodiments of the present invention are applied may be defined, and the above-described embodiments may be applied according to the corresponding slice type or tile group type.

[0507] In the above embodiments, the method is described based on a flowchart having a series of steps or units, but the present invention is not limited to the order of the steps, but some steps may be performed simultaneously with other steps or in a different order. In addition, it should be understood by those skilled in the art that the steps in the flowchart are not mutually exclusive, and other steps may be added to the flowchart, or some steps may be deleted from the flowchart without affecting the scope of the present invention.

[0508] The embodiments include various aspects of the examples. All possible combinations for various aspects may not be described, but those skilled in the art will be able to recognize different combinations. Therefore, the present invention may include all substitutions, modifications and changes within the scope of the claims.

[0509] Embodiments of the present invention can be implemented in the form of program instructions that can be executed by various computer components and recorded in a computer-readable recording medium. The computer-readable recording medium may include a separate program instruction, a data file, a data structure, etc. or a combination of program instructions, data files, data structures, etc. The program instructions recorded in the computer-readable recording medium may be specially designed and constructed for the present invention, or known to those of ordinary skill in the field of computer software technology. Examples of computer-readable recording media include magnetic recording media (such as hard disks, floppy disks, and tapes), optical data storage media (such as CD-ROMs or DVD-ROMs), magneto-optical media (such as floppy disks), and hardware devices (such as read-only memory (ROM), random access memory (RAM), flash memory, etc.) that are specifically constructed to store and implement program instructions. Examples of program instructions include not only machine language codes formatted by a compiler, but also high-level language codes that can be implemented by a computer using an interpreter. The hardware device may be configured to be operated by one or more software modules to perform processing according to the present invention, or vice versa.

[0510] Although the present invention has been described according to specific items such as detailed elements and limited embodiments and drawings, they are provided only to help a greater understanding of the present invention, and the present invention is not limited to the above embodiments. It will be appreciated by those skilled in the art that various modifications and changes can be made from the above description.

[0511] Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and the entire scope of the claims and their equivalents will fall within the scope and spirit of the present invention.

[0512] Industrial Applicability

[0513] The present invention can be used to encode or decode images.

Claims

1. An image decoding method, comprising: Decoding a sub-block merge mode indicator of a current block; and If the subblock merge mode indicator indicates that the subblock merge mode is not applied to the current block, decoding a normal merge mode indicator of the current block, Wherein, when the sub-block merge mode indicator indicates that the sub-block merge mode is applied to the current block, the sub-block merge mode information of the current block is decoded, wherein, when the normal merge mode indicator indicates that neither the normal merge mode nor the merged MMVD mode with motion vector difference is applied to the current block, the combined intra merge mode indicator is selectively decoded from the bitstream, Therein, even if decoding of the combined intra merge mode indicator is omitted, when the value of the combined intra merge mode indicator is inferred to indicate that the combined intra merge mode is applied to the current block, the merge index information is explicitly decoded from the bitstream.

2. The image decoding method according to claim 1, in, When the normal merge mode indicator has a first value, one of the normal merge mode and the MMVD mode is used to derive inter prediction information of the current block, and Wherein, when the normal merge mode indicator has a second value, one of the combined intra-frame merge mode and the geometric partition merge mode is used to derive the inter-frame prediction information of the current block.

3. The image decoding method according to claim 1, wherein: Whether the normal merge mode indicator is decoded from the bitstream is determined based on the combined intra merge mode enable indicator.

4. The image decoding method according to claim 1, wherein: Whether the normal merge mode indicator is decoded from the bitstream is determined based on the skip indicator of the current block.

5. The image decoding method according to claim 1, wherein: Whether the normal merge mode indicator is decoded from a bitstream is determined based on a slice type of the current block.

6. The image decoding method according to claim 1, wherein: When at least one of the width of the current block or the height of the current block is greater than or equal to a predefined value, the normal merge mode indicator is not decoded from the bitstream.

7. The image decoding method according to claim 2, further comprising: When the normal merge mode indicator has a first value, the MMVD indicator of the current block is selectively decoded from a bitstream.

8. The image decoding method according to claim 7, wherein: When decoding of the MMVD indicator is omitted, the value of the MMVD indicator is inferred to indicate that the MMVD mode is not applied to the current block.

9. An image encoding method, comprising: Encoding a sub-block merge mode indicator of the current block; and If the subblock merge mode indicator is encoded using a value indicating that the subblock merge mode is not applied to the current block, encoding a normal merge mode indicator for the current block, wherein, when the subblock merge mode indicator is encoded using a value indicating that the subblock merge mode is applied to the current block, subblock merge mode information of the current block is also encoded, wherein, when the normal merge mode indicator is encoded using a value indicating that neither the normal merge mode nor the merge MMVD mode with motion vector difference is applied to the current block, the combined intra merge mode indicator is selectively encoded into the bitstream, Therein, even if encoding of the combined intra merge mode indicator is omitted, when the value of the combined intra merge mode indicator is inferred to indicate that the combined intra merge mode is applied to the current block, the merge index information is explicitly encoded into the bitstream.

10. The image encoding method according to claim 9, in, When the normal merge mode indicator is encoded using a first value, one of the normal merge mode and the MMVD mode is used to derive inter prediction information of the current block, and Wherein, when the normal merge mode indicator is encoded using a second value, one of the combined intra-frame merge mode and the geometric partition merge mode is used to derive inter-frame prediction information of the current block.

11. The image encoding method according to claim 9, wherein: Whether the normal merge mode indicator is encoded into the bitstream is determined based on the combined intra merge mode enable indicator of the current block.

12. The image encoding method according to claim 9, wherein: Whether the normal merge mode indicator is encoded into the bitstream is determined based on the skip indicator of the current block.

13. The image encoding method according to claim 9, wherein: Whether the normal merge mode indicator is encoded into the bitstream is determined based on the slice type of the current block.

14. An apparatus for transmitting compressed video data, comprising: A processor configured to obtain the compressed video data; as well as a sending unit, configured to send the compressed video data, Wherein, obtaining the compressed video data comprises: encoding a sub-block merge mode indicator for the current block; and If the subblock merge mode indicator is encoded using a value indicating that the subblock merge mode is not applied to the current block, encoding a normal merge mode indicator for the current block, wherein, when the subblock merge mode indicator is encoded using a value indicating that the subblock merge mode is applied to the current block, subblock merge mode information of the current block is also encoded, wherein, when the normal merge mode indicator is encoded using a value indicating that neither the normal merge mode nor the merge MMVD mode with motion vector difference is applied to the current block, the combined intra merge mode indicator is selectively encoded into the bitstream, Therein, even if encoding of the combined intra merge mode indicator is omitted, when the value of the combined intra merge mode indicator is inferred to indicate that the combined intra merge mode is applied to the current block, the merge index information is explicitly encoded into the bitstream.

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