Method and apparatus for encoding / decoding image using quantization parameter

Abstract

The invention discloses a method and apparatus for encoding / decoding an image using a quantization parameter, and provides an image encoding / decoding method and apparatus. The image decoding method includes: decoding size information of a quantization group from a bitstream; obtaining a difference quantization parameter of the current block based on the size information of the quantization group; and deriving a quantization parameter of the current block based on the differential quantization parameter.

Description

[0001] This application is a divisional application of a patent application with an application date of June 25, 2019, application number 201980043298.5, and invention name “Method and device for encoding / decoding an image using quantization parameters”. Technical Field

[0002] The present invention relates to an image encoding / decoding method and apparatus and a recording medium storing a bit stream. More particularly, the present invention relates to an image encoding / decoding method and apparatus using a quantization parameter and a recording medium storing a bit stream. Background Art

[0003] Recently, the demand for high-resolution and high-quality images such as high-definition (HD) or ultra-high-definition (UHD) images has increased in various applications. 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 sent 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.

[0004] 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 of the energy of compressed residual signals, and entropy coding techniques that assign shorter codes to frequently occurring pixel values ​​and longer codes to less frequently occurring pixel values.

[0005] In the conventional technology for video encoding / decoding methods and apparatuses using quantization parameters, only quadtree blocks are considered. Therefore, it is difficult for the conventional technology to process encoding or decoding of differential quantization parameters for blocks having various tree structures. Summary of the invention

[0006] Technical issues

[0007] An object of the present invention is to provide an image encoding / decoding method and device using a quantization parameter.

[0008] Another object of the present invention is to provide an image encoding / decoding method and device that adaptively determines the appropriate size of a block for which a differential quantization parameter is to be signaled based on the block structure and the size information of the quantization group encoded / decoded at a high level, so as to improve the operation of signaling the quantization parameter and the encoding efficiency of the quantization parameter.

[0009] Another object of the present invention is to provide an image encoding / decoding method and device for determining a quantization parameter for a current block based on quantization parameters of adjacent quantization groups to reduce the number of bits required for encoding / decoding a differential quantization parameter.

[0010] Another object of the present invention is to provide a recording medium storing a bit stream generated by an image encoding / decoding method or apparatus.

[0011] Technical Solution

[0012] According to the present invention, an image decoding method is provided, comprising: decoding size information of a quantization group from a bit stream; obtaining a differential quantization parameter of a current block based on the size information of the quantization group; and deriving a quantization parameter for the current block based on the differential quantization parameter.

[0013] According to one embodiment, the size information of the quantization group includes one or more pieces of information selected from depth information, length information, area information, ratio information, shape information, and sub-division information of the quantization group.

[0014] According to one embodiment, the quantization group comprises a square shape or a non-square shape.

[0015] According to one embodiment, the non-square shape is any shape based on a binary tree, a ternary tree, or both a binary tree and a ternary tree.

[0016] According to one embodiment, the step of obtaining the differential quantization parameter of the current block includes: determining the size of the quantization group based on the size information of the quantization group; and obtaining the differential quantization parameter of the current block based on the size of the quantization group.

[0017] According to one embodiment, the differential quantization parameter of the current block is obtained based on the relationship between the depth of the current block and the depth information of the quantization group.

[0018] According to an embodiment, the differential quantization parameter of the current block is obtained based on the size relationship between the area of ​​the current block and the area information of the quantization group.

[0019] According to one embodiment, the differential quantization parameter of the current block is obtained based on the relationship between the sub-division value of the current block and the sub-division information of the quantization group.

[0020] According to one embodiment, when the current block is a block generated by quadtree partitioning, the sub-division value of the current block is a value equal to the original sub-division value before partitioning of the current block plus 2.

[0021] According to one embodiment, when the current block is a block generated by binary tree partitioning, the sub-division value of the current block is a value equal to the original sub-division value before partitioning of the current block plus 1.

[0022] In addition, according to the present invention, an image encoding method is provided, comprising: determining the size of a quantization group; determining a quantization parameter of a current block based on the size of the quantization group; deriving a differential quantization parameter of the current block based on the quantization parameter; and encoding the size information of the quantization group.

[0023] According to one embodiment, the size information of the quantization group includes one or more pieces of information selected from depth information, length information, area information, ratio information, shape information, and sub-division information of the quantization group.

[0024] According to one embodiment, the quantization group comprises a square shape or a non-square shape.

[0025] According to one embodiment, the non-square shape is any shape based on a binary tree, a ternary tree, or both a binary tree and a ternary tree.

[0026] According to one embodiment, the differential quantization parameter of the current block is obtained based on the relationship between the depth of the current block and the depth information of the quantization group.

[0027] According to an embodiment, the differential quantization parameter of the current block is obtained based on the size relationship between the area of ​​the current block and the area information of the quantization group.

[0028] According to one embodiment, the differential quantization parameter of the current block is derived based on the relationship between the sub-division value of the current block and the sub-division information of the quantization group.

[0029] According to one embodiment, when the current block is a block generated by quadtree partitioning, the sub-division value of the current block is a value equal to the original sub-division value of the current block before partitioning plus 2.

[0030] According to one embodiment, when the current block is a block generated by binary tree partitioning, the sub-division value of the current block is a value equal to the original sub-division value before partitioning of the current block plus 1.

[0031] In addition, according to the present invention, a computer-readable non-temporary recording medium storing image data used in an image decoding method is provided, wherein the image data includes size information of a quantization group, and in the image decoding method, the size information of the quantization group is used to obtain a differential quantization parameter of a current block, and is used to derive a quantization parameter of the current block based on the differential quantization parameter.

[0032] Beneficial Effects

[0033] According to the present invention, there can be provided an image encoding / decoding method and apparatus using a quantization parameter.

[0034] According to the present invention, there can be provided an image encoding / decoding method and apparatus for adaptively determining an appropriate size of a block for which a differential quantization parameter is to be signaled according to size information of a quantization group encoded / decoded at a high level.

[0035] According to the present invention, an image encoding / decoding method and apparatus for determining a quantization parameter for a current block using quantization parameters of neighboring quantization groups can be provided.

[0036] According to the present invention, there can be provided a recording medium storing a bit stream generated by the encoding / decoding method or apparatus according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a block diagram showing the configuration of one embodiment of an encoding device to which the present invention is applied;

[0038] Figure 2 is a block diagram showing the configuration of one embodiment of a decoding device to which the present invention is applied;

[0039] Figure 3 is a schematic diagram showing a screen partition structure used when encoding and decoding an image;

[0040] Figure 4 is a diagram illustrating one embodiment of an intra prediction process;

[0041] Figure 5 is a diagram illustrating one embodiment of an inter-frame prediction process;

[0042] Figure 6 is a diagram for describing transform and quantization processing.

[0043] Figure 7 is a diagram for describing available reference samples for intra prediction;

[0044] Figure 8 is a diagram illustrating an image encoding / decoding process performed based on a CTU according to an embodiment of the present invention;

[0045] Figure 9a is a flowchart illustrating an image decoding method according to an embodiment of the present invention;

[0046] Figure 9b is a flowchart illustrating an image encoding method according to an embodiment of the present invention;

[0047] Fig.10 is a diagram illustrating a process of deriving a predicted quantization parameter of a current quantization group according to one embodiment of the present invention;

[0048] Fig.11is a diagram illustrating a process of deriving a predicted quantization parameter of a current quantization group according to another embodiment of the present invention;

[0049] Fig.12 is a diagram illustrating a process of deriving a predicted quantization parameter of a current quantization group according to yet another embodiment of the present invention;

[0050] Fig.13 is a diagram illustrating a process of deriving a predicted quantization parameter of a current quantization group according to yet another embodiment of the present invention;

[0051] Fig.14 is a diagram showing the order of encoding / decoding for a case where a CU has a square shape and a non-square shape according to an embodiment of the present invention;

[0052] Fig.15 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that may be set when the size of a CTU is 256×256 and diff_cu_qp_delta_depth is 2;

[0053] Fig.16 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 256×256 and log2_diff_cu_qp_delta_length is 1;

[0054] Fig.17 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that may be set when the size of a CTU is 128×128 and diff_cu_qp_delta_depth is 2;

[0055] Fig.18 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 128×128 and log2_diff_cu_qp_delta_length is 2;

[0056] Fig.19 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and log2_diff_cu_qp_delta_length is 3;

[0057] Fig. 20 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and diff_cu_qp_delta_area is 3;

[0058] Fig.21 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and diff_cu_qp_delta_area is 4;

[0059] Fig. 22 is a diagram showing blocks for each of which a delta quantization parameter is signaled and various quantization groups that may be set when the size of a CTU is 64×64 and cu_qp_delta_subdiv is 3;

[0060] Fig.23 is a diagram showing blocks for each of which a delta quantization parameter is signaled and various quantization groups that may be set when the size of a CTU is 64×64 and cu_qp_delta_subdiv is 4;

[0061] Fig.24 is a diagram illustrating a method for determining a quantization parameter using length information of a quantization group according to an embodiment of the present invention;

[0062] Fig.25 is a diagram illustrating a method for determining a quantization parameter using area information of a quantization group according to an embodiment of the present invention;

[0063] Fig.26 is a diagram illustrating a method for determining a quantization parameter using length information of a quantization group according to another embodiment of the present invention;

[0064] Fig. 27 is a diagram illustrating a method for determining a quantization parameter using area information of a quantization group according to yet another embodiment of the present invention;

[0065] Fig.28 is a diagram illustrating a method for determining a quantization parameter using depth information of a quantization group according to an embodiment of the present invention;

[0066] Fig.29 is a diagram illustrating a method for determining a quantization parameter using depth information of a quantization group according to another embodiment of the present invention;

[0067] Fig.30 is a diagram illustrating a method of determining a quantization parameter using depth information of a quantization group according to still another embodiment of the present invention; and

[0068] Fig.31 and Fig.32 : is a diagram showing an example of syntax element information required for entropy encoding / decoding of a differential quantization parameter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0069] 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 and described in detail with reference to the accompanying drawings. However, 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, the present invention is not limited thereto. Similar figure numerals refer to the same or similar functions in various aspects. 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 showing specific embodiments in which the present invention can be practiced by way of illustration. 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, do not necessarily exclude each other. 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 considered as limiting, and the scope of the present disclosure is limited only by the full range of the appended claims and the equivalents claimed by the claims, which are properly interpreted.

[0070] The terms "first", "second", etc. used in the specification may be used to describe various components, but the components should not be interpreted as limited to the terms. The terms are only used to distinguish one component from other components. For example, without departing from the scope of the present invention, the "first" component may be referred to as the "second" component, and the "second" component may also be similarly referred to as the "first" component. The term "and / or" includes a combination of multiple items or any one of the multiple terms.

[0071] It will be understood that when an element is simply referred to as being “connected to” or “coupled to” another element in this specification rather than being “directly connected to” or “directly coupled to” another element, it 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.

[0072] 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 separated hardware or software as a constituent unit. In other words, for convenience, each component includes each of the listed components. Therefore, at least two components in each component can be combined to form a component, or a component can be divided into multiple components to perform each function. Without departing from the essence of the present invention, the embodiments in which each component is combined and the embodiments in which a component is divided are also included in the scope of the present invention.

[0073] The terms used in this specification are only used to describe specific embodiments and are not intended to limit the present invention. Expressions used in the singular form cover expressions in the plural form unless it has a significantly different meaning in the context. In this specification, it is to be understood that terms such as "including", "having" and the like are intended to indicate the existence 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", elements other than the corresponding element are not excluded, but additional elements may be included in embodiments of the present invention or in the scope of the present invention.

[0074] In addition, some components may not be indispensable components for performing the necessary functions of the present invention, but selective components that only improve the performance thereof. The present invention may be realized by only including the indispensable constituent parts for realizing the essence of the present invention except the components for improving the performance. A structure including only the indispensable components except the selective components for only improving the performance is also included in the scope of the present invention.

[0075] 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 structures may unnecessarily obscure the understanding of the present invention, so well-known functions or structures will not be described in detail. 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.

[0076] Hereinafter, an image may refer to a picture constituting a video, or may refer to a video itself. For example, "encoding or decoding of an image, or both encoding and decoding" may refer to "encoding or decoding of a moving picture, or both encoding and decoding", and may refer to "encoding or decoding of one image among a plurality of images of a moving picture, or both encoding and decoding".

[0077] Hereinafter, the terms "motion picture" and "video" may be used as the same meaning and replaced with each other.

[0078] Hereinafter, a target image may be an encoding target image as a target of encoding and / or a decoding target image as a target of decoding. In addition, the 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.

[0079] Hereinafter, the terms "image", "picture", "frame" and "screen" may be used as the same meaning and replaced with each other.

[0080] Hereinafter, the target block may be an encoding target block as a target of encoding and / or a decoding target block as a target of decoding. 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.

[0081] Hereinafter, the terms "block" and "unit" may be used as the same meaning and replaced with each other. Alternatively, a "block" may refer to a specific unit.

[0082] In the following, the terms "region" and "segment" may be used interchangeably.

[0083] 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.

[0084] 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.

[0085] When the variable i or j is used to represent a column, row, or index, the value of i may be an integer equal to or greater than 0 or equal to or greater than 1. That is, the column, row, index, etc. may be counted from 0 or may be counted from 1.

[0086] Description of terms

[0087] Encoder: This refers to the device that performs encoding. In other words, it refers to the encoding device.

[0088] Decoder: refers to a device that performs decoding. In other words, it refers to a decoding device.

[0089] Block: is an M×N array of samples. Here, M and N may represent positive integers, and a block may represent an array of samples 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.

[0090] Sample: It is a basic unit constituting a block. Samples can be represented as values ​​from 0 to 2Bd-1 according to the bit depth (Bd). In the present invention, sample can be used as the meaning of pixel. That is, sample, pel, pixel can have the same meaning as each other.

[0091] Unit: may refer to a coding unit and a 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 forms, and in particular, the form of a unit may be a two-dimensional geometric figure such as a square shape, a rectangular shape, a trapezoidal shape, a triangular shape, a pentagonal shape, 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.

[0092] 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 a lower-level unit such as a coding unit, a prediction unit, a transform unit, 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.

[0093] When the size of the coding block is within a predetermined range, it can be divided 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 can be signaled through a bitstream, and the information can be signaled in units of at least one 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 can be divided using only quadtree partitioning. Optionally, when the size of the coding block is larger than the size of the maximum transform block, it can be divided 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 may be divided 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.

[0094] Coding tree block: may be used as a term for designating any one of a Y coding tree block, a Cb coding tree block, and a Cr coding tree block.

[0095] 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 horizontally adjacent to the current block or a block that is horizontally adjacent to a neighboring block vertically adjacent to the current block.

[0096] Reconstructed neighboring block: may refer to 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 refer to a reconstructed neighboring unit. The reconstructed spatial neighboring block may be a block within the current picture that 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.

[0097] 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 highest node can have a depth of 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 expressed as a tree structure, the level at which the unit is located can represent the unit depth.

[0098] Bitstream: can represent a stream of bits including coded image information.

[0099] Parameter set: corresponds to header information in the configuration within 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 parallel block group header, and parallel block header information. The term "parallel block group" means a group of parallel blocks and has the same meaning as a slice.

[0100] Parsing: may mean determining the value of a syntax element by performing entropy decoding, or may mean the entropy decoding itself.

[0101] 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.

[0102] Prediction mode: may be information indicating a mode of encoding / decoding using intra-frame prediction or a mode of encoding / decoding using inter-frame prediction.

[0103] 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 prediction units of lower levels. Multiple partitions may be basic units when performing prediction or compensation. Partitions generated by splitting a prediction unit may also be prediction units.

[0104] Prediction unit partition: may represent a form obtained by partitioning a prediction unit.

[0105] A reference picture list may refer to a list including one or more reference pictures used for inter prediction or motion compensation. There are multiple types of available reference picture lists, including LC (List Combination), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3).

[0106] The inter prediction indicator may refer to the direction of inter prediction (unidirectional prediction, bidirectional prediction, etc.) of the current block. Alternatively, it may refer to the number of reference pictures used to generate the prediction block of the current block. Alternatively, it may refer to the number of prediction blocks used when performing inter prediction or motion compensation on the current block.

[0107] 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), this 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), this indicates that the reference picture list is used to generate the prediction block.

[0108] Reference picture index: may refer to an index indicating a specific reference picture in a reference picture list.

[0109] 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 may be interchanged.

[0110] 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.

[0111] The search range may be a two-dimensional area that is searched to retrieve a motion vector during inter prediction. For example, the size of the search range may be M×N. Here, M and N are both integers.

[0112] When a motion vector is predicted, the motion vector candidate may refer to a prediction candidate block or a motion vector of the prediction candidate block. In addition, the motion vector candidate may be included in a motion vector candidate list.

[0113] The motion vector candidate list may mean a list consisting of one or more motion vector candidates.

[0114] The motion vector candidate index may represent an indicator indicating a motion vector candidate in the motion vector candidate list. Alternatively, the motion vector candidate index may be an index of a motion vector predictor.

[0115] The motion information may represent information including at least one of the following items: 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.

[0116] The merge candidate list may mean a list consisting of one or more merge candidates.

[0117] 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.

[0118] The merge index may represent an indicator indicating a merge candidate in the merge candidate list. Optionally, the merge index may indicate a block from which a merge candidate has been derived in a reconstructed block that is spatially / temporally adjacent to the current block. Optionally, the merge index may indicate at least one piece of motion information of the merge candidate.

[0119] Transform unit: may represent a basic unit when performing encoding / decoding (such as transformation, inverse transformation, quantization, inverse quantization, and transformation coefficient encoding / decoding of 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 primary transform / primary inverse transform and a secondary transform / secondary inverse transform.

[0120] 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.

[0121] Quantization parameter: may represent a value used when a transform coefficient is used to generate a quantized level during quantization. The quantization parameter may also represent 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 on a quantization step size.

[0122] Differential quantization parameter: can represent the difference between the predicted quantization parameter and the quantization parameter of the encoding / decoding target unit.

[0123] 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 referred to as scanning, and changing a one-dimensional matrix of coefficients to a two-dimensional matrix may be referred to as scanning or inverse scanning.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] Quantization matrix: may refer to a matrix used in a quantization process or an inverse quantization process performed to improve subjective or objective image quality. A quantization matrix may also be referred to as a scaling list.

[0128] Quantization matrix coefficients: can represent each element in the quantization matrix. Quantization matrix coefficients can also be called matrix coefficients.

[0129] Default matrix: may represent a predetermined quantization matrix predefined in an encoder or a decoder.

[0130] Non-default matrix: may represent a quantization matrix that is not predefined in the encoder or decoder but is signaled by the user.

[0131] 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, sum value, weighted average value, weighted sum value, minimum value, maximum value, most frequent value, median value, and interpolation value of the corresponding specific value.

[0132] Figure 1 is a block diagram showing a configuration of an encoding device according to an embodiment to which the present invention is applied.

[0133] 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.

[0134] 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.

[0135] 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 encoded 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 be switched to the intra mode. Alternatively, when the inter mode is used as a prediction mode, the switch 115 may be switched 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 a residual block using a residual of the prediction block and the input block after the prediction block is generated. 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.

[0136] 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 generate prediction samples of the input block by performing spatial prediction for the current block using the reference samples or by performing spatial prediction. Here, intra prediction may refer to prediction within a frame.

[0137] 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 the 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 for the reference image is performed, the reference image may be stored in the reference picture buffer 190.

[0138] The motion compensation unit 112 may generate a prediction 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.

[0139] 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 of a skip mode, a merge mode, an advanced motion vector prediction (AMVP) mode, and a 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.

[0140] The subtractor 125 may generate a residual block by using the difference between the prediction block and the input 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.

[0141] The transform unit 130 may generate a transform coefficient by performing a transform of the residual block and output the generated transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing a transform of the residual block. When the transform skip mode is applied, the transform unit 130 may skip the transform of the residual block.

[0142] The quantized level may be generated by applying quantization to a transform coefficient or a residual signal. Hereinafter, the quantized level may also be referred to as a transform coefficient in an embodiment.

[0143] 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.

[0144] 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.

[0145] When entropy coding is applied, symbols are represented so that a smaller number of bits are allocated to symbols with a high chance of generation and a larger number of bits are allocated to symbols with a low chance of generation, and therefore, the size of the bitstream for the symbol to be encoded can be reduced. The entropy coding unit 150 can 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 can perform entropy coding by using a variable length coding / code (VLC) table. In addition, the entropy coding unit 150 can derive a binarization method of the target symbol and a probability model of the target symbol / binary bit, and perform arithmetic coding by using the derived binarization method and context model.

[0146] 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.

[0147] The coding parameters may include information such as syntax elements that are encoded in the encoder and sent to the decoder by signaling (flags, indexes, etc.) and 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 to partition the current coding unit by ternary tree partitioning, ternary tree partition direction (horizontal or vertical), ternary tree partition type (symmetric partitioning or asymmetric partitioning), whether to partition the current coding unit by multi-type tree partitioning, multi-type tree direction of partition (horizontal or vertical), type of multi-type tree partition (symmetric partition or asymmetric partition), tree structure (binary tree or ternary tree) 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 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, whether to use primary (first) transform information, whether to use secondary transform information, primary transform index, secondary transform index introduction, information on whether there is a residual signal, 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 updating method, whether to execute normal mode, whether to execute bypass mode, context binary bit, bypass binary bit, significant coefficient flag, last significant coefficient flag, encoding flag for unit of coefficient group, position of last significant coefficient, flag for whether coefficient value is greater than 1, flag for whether coefficient value is greater than 2, flag for whether coefficient value is greater than 3, information about remaining coefficient values, sign information, reconstructed luminance samples, reconstructed chrominance samples, residual luminance samples, residual chrominance samples, luminance transform coefficient, chrominance transform coefficient, quantized luminance level, quantized chrominance level, transform coefficient level scanning method, motion vector search area at decoder side size, shape of a motion vector search area at a decoder side, number of motion vector searches at a decoder side, information about a CTU size, information about a minimum block size, information about a maximum block size, information about a maximum block depth, information about 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 about a luminance signal or information about a chrominance signal.

[0148] Here, signaling a flag or an index may mean that the corresponding flag or index is entropy encoded by an encoder and included in a bitstream, and may mean that the corresponding flag or index is entropy decoded from the bitstream by a decoder.

[0149] 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.

[0150] The quantization level may be dequantized in the dequantization unit 160 or may be inversely transformed in the inverse transform unit 170. The dequantized coefficient or the inversely transformed coefficient or the coefficient that is both dequantized and inversely transformed may be added to the prediction block through the adder 175. By adding the dequantized coefficient or the inversely transformed coefficient or the coefficient that is both dequantized and inversely transformed to the prediction block, a reconstructed block may be generated. Here, the dequantized coefficient or the inversely transformed coefficient or the coefficient that is both dequantized and inversely transformed may represent a coefficient on which at least one of dequantization and inverse transformation is performed, and may represent a reconstructed residual block.

[0151] 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.

[0152] 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 samples included in a 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.

[0153] In order to compensate for the coding error, an appropriate offset value may be added to the sample value by using sample adaptive offset. Sample adaptive offset may correct the offset of the deblocked image and the original image in sample units. A method of partitioning the samples of the image into a predetermined number of regions, determining the regions to which the offset is applied, and applying the offset to the determined regions, or a method of applying the offset in consideration of edge information about each sample may be used.

[0154] The adaptive loop filter may perform filtering based on a comparison result of a filtered reconstructed image with 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 for each group. Information on whether ALF is applied may be signaled per coding unit (CU), and the form and coefficient of ALF to be applied to each block may vary.

[0155] 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.

[0156] 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.

[0157] The decoding device 200 may be a decoder, a video decoding device, or an image decoding device.

[0158] Reference Figure 2 , the decoding device 200 may include an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra-frame prediction unit 240, a motion compensation unit 250, an adder 225, a filter unit 260 and a reference picture buffer 270.

[0159] 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-frame mode or an inter-frame 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.

[0160] When the prediction mode used in decoding is intra mode, the switch may be switched to intra mode. Alternatively, when the prediction mode used in decoding is inter mode, the switch may be switched to inter mode.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] The quantized level may be inversely quantized in the inverse quantization unit 220, or may be inversely transformed in the inverse transform unit 230. The quantized level may be a result of inverse quantization or inverse transformation or both inverse quantization and inverse transformation, and may be generated as a reconstructed residual block. Here, the inverse quantization unit 220 may apply a quantization matrix to the quantized level.

[0165] When the intra mode is used, the intra prediction unit 240 may generate a predicted block by performing spatial prediction using sample values ​​of a block adjacent to the decoding target block and already decoded, with respect to the current block.

[0166] When the inter mode is used, the motion compensation unit 250 may generate a prediction block by performing motion compensation using a reference image and a motion vector stored in the reference picture buffer 270 on the current block.

[0167] The adder 225 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.

[0168] 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 cell into a plurality of lower-level cells is schematically shown.

[0169] In order to efficiently 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.

[0170] Reference Figure 3 , the image 300 is partitioned sequentially by the largest 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 mean partitioning a block associated with the unit. In the block partition information, information about the unit depth may be included. The depth information may indicate the number or degree of partitioning of the unit or both the number and degree. A single unit may be partitioned into a plurality of lower-level units hierarchically associated with the depth information based on a tree structure. In other words, the unit and the lower-level units generated by partitioning the unit may correspond to a node and a child node of the node, respectively. Each of the partitioned lower-level units may have depth information. The depth information may be information indicating the size of a CU and may be stored in each CU. The unit depth indicates the number and / or degree associated with partitioning the unit. Therefore, the partition information of the lower-level unit may include information about the size of the lower-level unit.

[0171] 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 a plurality of (positive integers equal to or greater than 2, including 2, 4, 8, 16, etc.) 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 a size smaller than the horizontal size and vertical size before partitioning, respectively, according to the number of partitioning times. The CU may be recursively partitioned into a plurality of 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 smallest 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. Starting partitioning from the LCU 310, as the horizontal size or vertical size or both the horizontal size and the vertical size of the CU decrease through partitioning, the CU depth increases by 1. For example, for each depth, a non-partitioned CU may have a size of 2N×2N. Also, in the case of a partitioned CU, a CU of size 2N×2N may be partitioned into four CUs of size N×N. The size of N may be reduced to half as the depth increases by 1.

[0172] In addition, information on whether a CU is partitioned may be indicated by using 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.

[0173] Reference Figure 3 , an LCU with a depth of 0 may be a 64×64 block. 0 may be the minimum depth. An SCU with a depth of 3 may be an 8×8 block. 3 may be the maximum depth. A CU with a block of 32×32 and a block of 16×16 may be represented as depth 1 and depth 2, respectively.

[0174] For example, when a single coding unit is partitioned into four coding units, the horizontal size and vertical size of the four partitioned coding units may be half the horizontal size and vertical size of the CU before partitioning. In one embodiment, when a coding unit of size 32×32 is partitioned into four coding units, each of the four partitioned coding units 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.

[0175] 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, it can be said that the coding unit is partitioned by binary partitioning or partitioning according to a binary tree partition structure.

[0176] 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 the horizontal size or the vertical size of 1:2:1. 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 ternary partitioned or partitioned in a ternary tree partition structure.

[0177] 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.

[0178] 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 by a binary tree partition structure or a ternary tree partition structure, or may not be further partitioned. Therefore, by preventing coding blocks generated by binary tree partitioning or ternary tree partitioning of coding units corresponding to leaf nodes of a quadtree from undergoing further quadtree partitioning, block partitioning and / or signaling of partition information may be efficiently performed.

[0179] The four partition information may be used to signal the fact that the coding unit corresponding to the node of the quadtree is partitioned. The four partition information having a first value (e.g., '1') may indicate that the current coding unit is partitioned in a quadtree partition structure. The four partition information having a second value (e.g., '0') may indicate that the current coding unit is not partitioned in a quadtree partition structure. The four partition information may be a flag having a predetermined length (e.g., one bit).

[0180] There may be no priority between the binary tree partition and the ternary tree partition. That is, the coding unit corresponding to the leaf node of the quadtree may further undergo any partition of the binary tree partition and the ternary tree partition. In addition, the coding unit generated by the binary tree partition or the ternary tree partition may undergo further binary tree partition or further ternary tree partition, or may not be further partitioned.

[0181] A tree structure in which there is no priority between a binary tree partition and a ternary tree partition is referred to as 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. For partitions of coding units corresponding to nodes of a multi-type tree, multi-type tree partition indication information, partition direction, and partition tree information may be sequentially signaled.

[0182] 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.

[0183] 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 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.

[0184] 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 for the partition of 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 the 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 the ternary tree partition structure.

[0185] The partition indication information, the partition tree information and the partition direction information may all be flags having a predetermined length (eg, one bit).

[0186] 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. For entropy encoding / decoding of those types of information, information about neighboring coding units adjacent to the current coding unit may be used. For example, the partition type (partition or non-partition, 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 likely to be 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 unit. The information about the neighboring coding unit 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.

[0187] 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, quadtree partitioning or binary tree partitioning may not be performed on the coding unit corresponding to the node of the ternary tree.

[0188] 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, the partition structure information and partition information for partitioning the coding unit into prediction units and / or transformation units may not be present in the bitstream.

[0189] 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 transformation. 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 transformation. In this case, the partition of the coding unit for transformation is not separately signaled and 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 bisected. For example, when the vertical size (length) of the coding unit is larger than the vertical size (length) of the maximum transform block, the coding unit may be horizontally bisected.

[0190] 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 a higher level of the coding unit. The higher 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 as 4×4. For example, the maximum size of a transform block may be determined as 64×64. For example, the minimum size of a transform block may be determined as 4×4.

[0191] 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 sent with a signal or determined at a higher level of the coding unit. For example, the higher level may be a sequence level, a picture level, a slice level, a parallel block group level, a parallel block level, etc. Information on the minimum size of the quadtree and / or information on the maximum depth of the multi-type tree may be sent with a signal or determined for each of an intra-picture slice and an inter-picture slice.

[0192] The difference information between the size of the CTU and the maximum size of the transform block may be signaled or determined at a higher level of the coding unit. For example, the higher 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.

[0193] 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.

[0194] 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 be included in the bitstream or may not be included in the bitstream.

[0195] 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 can be derived from the second value.

[0196] 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 by the binary tree or the ternary tree. Therefore, the multi-type tree partition indication information may not be signaled, but may be derived from the second value.

[0197] 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 by the binary tree or the ternary tree. Therefore, the multi-type tree partition indication information may not be sent by signal, but may be derived from the second value. This is because when the coding unit is partitioned by 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.

[0198] 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.

[0199] - N×M (N and / or M is 128) ternary tree partitions for coding units

[0200] - 128×N (N<=64) binary tree partitions in the horizontal direction for coding units

[0201] - N×128 (N<=64) binary tree partitions in the vertical direction for the coding unit

[0202] 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 binary tree partitioned and / or ternary tree partitioned. Therefore, the multi-type tree partition indication information may not be sent with a signal, but may be derived from the second value.

[0203] 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 the coding unit corresponding to the node of the multi-type tree, the multi-type tree partition indication information may be sent by signal. Otherwise, the coding unit may not be partitioned by the binary tree and / or the ternary tree. Therefore, the multi-type tree partition indication information may not be sent by signal, but may be derived from the second value.

[0204] Optionally, partition direction information may be signaled 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. Otherwise, the partition direction information may not be signaled, but may be derived from a value indicating a possible partition direction.

[0205] Optionally, partition tree information may be signaled 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 unit corresponding to a node of a multi-type tree. Otherwise, the partition tree information may not be signaled but may be derived from a value indicating a possible partition tree structure.

[0206] Figure 4 is a diagram illustrating an intra prediction process.

[0207] Figure 4 The arrows from the center to the outside in may represent the prediction direction of the intra prediction mode.

[0208] Intra-frame encoding and / or intra-frame 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 intra-frame decoding may be performed by using encoding parameters or values ​​of reference samples included in the reconstructed neighboring blocks.

[0209] 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.

[0210] 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.

[0211] The number of intra-frame prediction modes can be fixed to N, regardless of the block size. 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.

[0212] 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 with 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 greater than 1, including non-angle modes and angle modes.

[0213] In order to perform intra prediction on the 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 a sample that cannot be used as a reference sample of the current block exists, 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 at least one sample value of the samples included in the reconstructed neighboring block 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.

[0214] Figure 7 is a diagram showing reference samples that can be used for intra prediction.

[0215] 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 example, the samples of fragment A and fragment F may be filled with the samples closest to fragment B and fragment E, respectively, instead of being obtained from the reconstructed neighboring blocks. Index information indicating the reference sample line to be used for intra prediction of the current block may be signaled. When the upper boundary of the current block is the boundary of the CTU, only the reference sample line 0 is available. Therefore, in this case, the index information may not be signaled. When reference sample lines other than the reference sample line 0 are used, filtering for the prediction block, which will be described later, may not be performed.

[0216] 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.

[0217] In the case of the planar mode, when generating a 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 and left reference samples of the current sample and the upper right and lower left reference samples 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 and left reference samples 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, left, upper right and / or lower left reference samples of the current block. In order to generate the prediction sample value, interpolation of real number units may be performed.

[0218] In the case of intra prediction between color components, a prediction block for 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 neighboring samples and / or left neighboring samples of the current block and upper neighboring samples and / or left neighboring samples of a reconstruction block of the first color component corresponding thereto. For example, the parameters of the linear model may be derived using a sample value of the first color component having a maximum value among the samples in the template and a sample value of the second color component corresponding thereto, and a sample value of the first color component having a minimum value among the samples in the template and a sample value of the second color component corresponding thereto. When the parameters of the linear model are derived, the corresponding reconstruction block may be applied to the linear model to generate a prediction block for the current block. Depending on the video format, subsampling may be performed on the reconstruction block of the first color component and the neighboring samples of 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.

[0219] The current block may be partitioned into two or four sub-blocks in the horizontal direction or the vertical direction. The partitioned sub-blocks may be reconstructed in sequence. 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 the sub-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 about whether intra prediction is performed based on sub-blocks and / or partition directions (horizontal or vertical) may be signaled. 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.

[0220] The final prediction block may be generated by performing filtering on the intra-predicted prediction block. Filtering may be performed by applying predetermined weights to the filtering target sample, the left reference sample, the upper reference sample, and / or the upper left reference sample. The weights and / or reference samples (range, position, etc.) used for filtering may be determined based on at least one of the block size, the intra-prediction mode, and the position of the filtering target sample in the prediction block. Filtering may be performed only in the case of a predetermined intra-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.

[0221] The intra-frame prediction mode of the current block may be entropy encoded / decoded by predicting the intra-frame prediction mode of a block adjacent to the current block. When the intra-frame prediction modes of the current block and the adjacent block are the same, information that the intra-frame prediction modes of the current block and the adjacent block are the same 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 adjacent blocks may be signaled. When the intra-frame prediction modes of the current block and the adjacent block are different, 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 adjacent block.

[0222] Figure 5 is a diagram illustrating an embodiment of an inter-picture prediction process.

[0223] exist Figure 5 In , a rectangle can represent a picture. Figure 5In FIG, the arrow indicates the prediction direction. Pictures can be classified into intra-pictures (I pictures), predicted pictures (P pictures) and bi-predicted pictures (B pictures) according to their coding types.

[0224] I pictures may be encoded by intra prediction without inter-picture prediction. P pictures may be encoded by inter-picture prediction using reference pictures existing in one direction (i.e., forward or backward) for the current block. B pictures may be encoded by inter-picture prediction using reference pictures existing in two directions (i.e., forward and backward) for 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.

[0225] Next, embodiments of inter-picture prediction will be described in detail.

[0226] Reference pictures and motion information may be used to perform inter-picture prediction or motion compensation.

[0227] 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, a co-located block (also referred to as a col block or a co-located block), and / or motion information of a block adjacent to the co-located block. The co-located block may represent a block within 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.

[0228] The derivation method of motion information may be different according to the prediction mode of the current block. For example, the prediction modes applied for inter-frame prediction include AMVP mode, merge mode, skip mode, merge mode with motion vector difference, sub-block merge mode, triangle partition mode, inter-intra combined prediction mode, affine mode, etc. Here, the merge mode may be referred to as motion merge mode.

[0229] For example, when AMVP is used as a prediction mode, at least one of the motion vector of the reconstructed neighboring block, the motion vector of the co-located block, the motion vector of the block adjacent to the co-located block, and the (0,0) motion vector may be determined as a motion vector candidate for the current block, and a motion vector candidate list is generated by using the motion vector candidate. The motion vector candidate of 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 the 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.

[0230] 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 an optimal motion vector candidate among motion vector candidates included in a 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.

[0231] In addition, the encoding apparatus 100 may perform entropy encoding on the calculated resolution information of the MVD. The decoding apparatus 200 may adjust the resolution of the entropy-decoded MVD using the MVD resolution information.

[0232] 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 through the sum of the entropy-decoded MVD and the affine controlled motion vector candidate.

[0233] 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.

[0234] 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 multiple blocks. The merge mode may represent a mode of deriving motion information of a current block from motion information of neighboring blocks. When the merge mode is applied, the motion information of reconstructed neighboring blocks and / or the motion information of the same-positioned blocks 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).

[0235] 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 in a reference picture of the current block (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.

[0236] 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 on the left side of the current block, an upper neighboring block set above the current block, and a temporal neighboring block temporally adjacent to the current block.

[0237] 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 sends it to the decoding device 200 by signal. The decoding device 200 may correct the motion vector of the merge candidate selected according to 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 sent by the signal may be referred to as a merge mode with a motion vector difference.

[0238] 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.

[0239] 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.

[0240] The triangular partition mode may represent a mode of performing the following operations: deriving motion information by partitioning the current block along a diagonal direction, deriving each prediction sample using each of the derived motion information, and deriving the prediction sample of the current block by weighting each of the derived prediction samples.

[0241] 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 an inter prediction and a prediction sample generated by an intra prediction.

[0242] 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.

[0243] The decoding apparatus 200 may use the optical flow to compensate for the prediction samples derived through the inter-frame prediction.

[0244] Figure 6 is a diagram illustrating transform and quantization processing.

[0245] 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 produces a transform coefficient, and the secondary transform of the transform coefficient produces a secondary transform coefficient.

[0246] 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 used 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.

[0247] A quantized level signal (quantized coefficient) may be generated by performing quantization on a residual signal or a result of performing a primary transform and / or a secondary transform. 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, depending on the intra prediction mode or block size / shape of the block. For example, when the coefficients are scanned according to a diagonal upper right scan, the coefficients in block form become 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 size of the transform block. The scanned quantized level coefficients may be entropy encoded to be inserted into a bitstream.

[0248] The decoder entropy decodes the bit stream to obtain quantization level coefficients. The quantization level coefficients may 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 may be used.

[0249] The quantization level coefficients may then be dequantized, then inverse transformed twice as needed, and finally inverse transformed once as needed to generate a reconstructed residual signal.

[0250] Inverse mapping of 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. An 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 into a mapping area via mapping using the mapping function, and then used to generate a 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 a reconstructed block without mapping / inverse mapping.

[0251] 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 the 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 a 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 switched to the 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.

[0252] Information indicating whether mapping / inverse mapping of luma components and chroma components is available may be signaled through a set of sequence parameters.

[0253] 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 a coding unit of M×N (M<=64, N<=64). The IBC mode may include a skip mode, a merge mode, an AMVP mode, and the like. In the case of the skip mode or the merge mode, a merge candidate list is constructed and a merge index is signaled so that one merge candidate may 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.

[0254] Figure 8 is a diagram illustrating an image encoding / decoding process performed based on a CTU according to an embodiment of the present invention.

[0255] The image encoding / decoding apparatus divides an input picture into coding tree units (CTUs) and performs encoding / decoding based on the CTUs. Figure 8 , a CTU of 64×64 size may be divided into quadtree (QT) coding units (CUs), and encoding / decoding may be performed on a CU basis. For example, starting from the top left CU, CUs are encoded / decoded in the order indicated by the solid lines. Figure 8 The encoding / decoding order shown in is called a zigzag scanning order. Figure 8 In FIG. 1 , the dotted line indicates the progress of encoding / decoding from the current CTU to the next CTU. That is, when the encoding / decoding of the current CTU is completed, the next CTU is encoded / decoded.

[0256] The maximum size of the CTU and the minimum size of the CU vary according to a value signaled in a high-level syntax such as a sequence parameter set (SPS), an adaptation parameter set (APS), a picture parameter set (PPS), a sub-picture header, a tile header, a tile group header, or a sequence parameter set. A residual signal, which is a difference between an input picture (input signal) and a prediction signal, undergoes transformation, quantization, and entropy encoding in the order of transformation, quantization, and entropy encoding, and the resulting signal is transmitted to an image decoding apparatus.

[0257] Here, the term "adaptive parameter set" refers to a parameter set referenced by several pictures, several sub-pictures, several tile groups, several tiles, several slices, several CTU lines, several CTUs, etc.

[0258] The term APS also refers to a parameter set referenced and shared by different pictures, sub-pictures, slices, tile groups, tiles, or CTU lines. In addition, sub-pictures, slices, tile groups, tiles, or CTU lines in a picture can reference different adaptation parameter sets to use information in different adaptation parameter sets.

[0259] For adaptation parameter sets, a sub-picture, slice, tile group, tile or CTU line in a picture can refer to different adaptation parameter sets using an adaptation parameter set identifier.

[0260] For adaptation parameter sets, a slice, tile group, tile or CTU line in a sub-picture can refer to a different adaptation parameter set using an adaptation parameter set identifier.

[0261] For adaptation parameter sets, a tile or CTU line in a slice can refer to different adaptation parameter sets using an adaptation parameter set identifier.

[0262] For adaptation parameter sets, CTU lines in a tile can refer to different adaptation parameter sets using adaptation parameter set identifiers.

[0263] The parameter set or header of the sub-picture contains information of the adaptation parameter set identifier, so that the adaptation parameter set corresponding to the adaptation parameter set identifier can be used for processing the sub-picture.

[0264] The parameter set or header of the tile contains an adaptation parameter set identifier, so that the adaptation parameter set corresponding to the adaptation parameter set identifier can be used for processing the tile.

[0265] The header of the CTU line includes an adaptation parameter set identifier so that an adaptation parameter set corresponding to the adaptation parameter set identifier can be used for processing of the CTU line.

[0266] A picture may be divided into one or more tile rows and one or more tile columns.

[0267] A sub-picture in a picture can be divided into one or more tile rows and one or more tile columns. A sub-picture is a rectangular or square area in a picture and includes one or more CTUs. A sub-picture can be one or more tiles, CTU lines and / or strips.

[0268] A tile is a rectangular or square area in a picture and includes one or more CTUs. A tile may be divided into one or more CTU lines.

[0269] A CTU line may represent one or more CTU rows in a parallel block. A parallel block may be divided into one or more CTU lines, and each CTU line may include one or more CTU rows. A parallel block that is not divided into two or more CTU lines is also referred to as a CTU line. A CTU line may include one or more CTU rows.

[0270] A slice in a picture may include one or more tiles. A slice in a tile may include one or more CTU lines.

[0271] In the quantization process, quantization is performed on the transform coefficient, wherein the quantized transform coefficient (level) is determined by a quantization parameter (QP). Here, the term "quantization parameter" means a parameter of quantization.

[0272] In order to use the quantization parameter on a block basis, the delta quantization parameter enabled flag cu_qp_delta_enabled_flag is signaled in the high-level syntax element.

[0273] When the flag has a first value of 1, quantization group size information diff_cu_qp_delta_depth may be signaled. Here, the quantization group size information diff_cu_qp_delta_depth represents depth information of the quantization group. Optionally, the first value may be 0 or an integer. For example, the first value may be 1.

[0274] According to one embodiment of the present invention, the size of a quantization group (QG) may be determined based on size information of the quantization group. A differential quantization parameter may be signaled for each quantization group size.

[0275] Table 1 shows the quantization group size determined based on the size of the CTU and the size information of the quantization group.

[0276] [Table 1]

[0277]

[0278] The delta quantization parameter may be signaled as a syntax element cu_qb_delta_abs specifying an absolute value of the delta quantization parameter and / or a syntax element cu_qb_delta_sign_flag specifying a sign of the delta quantization parameter. At least one of the syntax elements of the delta quantization parameter may be signaled based on a quantization group defined as diff_cu_qb_delta_depth, where diff_cu_qb_delta_depth is size information of the quantization group.

[0279] According to one embodiment, when the size of the block is equal to or greater than the size of the quantization group, at least one differential quantization parameter may be signaled for the block. One or more blocks in the block located in the quantization group may share the same differential quantization parameter. The predicted quantization parameter of one or more blocks in the block located in the quantization group may be derived from one or more quantization parameters of the corresponding adjacent quantization group. When at least one adjacent quantization group in the adjacent quantization group is not available, the quantization parameter that is signaled by the syntax element of the immediately preceding quantization in the encoding / decoding order or by a higher level (such as a picture, a sub-picture, a slice, a parallel block group, a parallel block, a CTU column, a CTU row, or a CTU line) is used instead of the quantization parameter of the non-existent quantization group. In addition, one or more blocks in the block arranged in the quantization group may share a predicted quantization parameter equal to the predicted quantization parameter. The quantization parameter is obtained by adding the differential quantization parameter to the predicted quantization parameter. Therefore, one or more blocks in the block arranged in the quantization group may share the same quantization parameter.

[0280] According to an embodiment of the present invention, when the size of the block is smaller than the size of the quantization group, the differential quantization parameter may be signaled from the first block in the quantization group, wherein the first block has a coded block flag coded_block_flag other than the first value. Here, the first value may be 0.

[0281] For example, when the coded block flag of the block is not the second value, the differential quantization parameter may not be signaled. Here, the second value may be 1.

[0282] Specifically, for example, in the case where the CTU size is 64×64, where the quantization group size information is diff_cu_qp_delta_depth=1, and there are four 16×16 blocks in a 32×32 quantization group, the quantization parameter is signaled only from the first block in the quantization group, and at least one of the other blocks in the quantization group shares the differential quantization parameter signaled from the first block. Here, the first block may represent the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0283] For another specific example, in the case where the CTU size is 64×64, where the quantization group size information is diff_cu_qp_delta_depth=1, and there are four 16×16 blocks in one 32×32 quantization group, only the nth block in the quantization group is signaled, and at least one of the other blocks in the quantization group shares the delta quantization parameter signaled from the nth block. Here, the nth block may represent the nth block whose coding block flag is not the first value. Here, the first value may be 0. Here, n is an integer greater than 1.

[0284] The coded block flag may indicate a coded block flag for at least one of a luma signal (Y) and chroma signals Cb and Cr.

[0285] Figure 9a is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

[0286] Reference Figure 9a , the image decoding apparatus decodes size information of a quantization group from a bit stream (S901).

[0287] Here, the size information of the quantization group includes at least one of depth information of the quantization group, length information of the quantization group, area information of the quantization group, ratio information of the quantization group, type information of the quantization group, and sub-division information of the quantization group.

[0288] The quantization groups may include square quantization groups or non-square quantization groups.

[0289] The non-square quantization group may have a shape based on at least one of a binary tree structure and a ternary tree structure.

[0290] The image decoding apparatus may acquire a differential quantization parameter of the current block from size information of the quantization group (S902).

[0291] For example, the size of the quantization group may be determined based on the size information of the quantization group, and the differential quantization parameter of the current block may be obtained based on the size of the quantization group. In this case, the differential quantization parameter of the current block may be decoded based on the size of the quantization group.

[0292] The image decoding apparatus may derive a quantization parameter of the current block from the size information of the quantization group (S903).

[0293] For example, the differential quantization parameter of the current block may be obtained based on the relationship between the depth of the current block and the depth information of the quantization group.

[0294] For example, the differential quantization parameter of the current block may be acquired based on a size relationship of the quantization group set between the area of ​​the current block and area information of the quantization group.

[0295] For example, the differential quantization parameter of the current block is obtained based on the relationship between the sub-division value of the current block and the sub-division information of the quantization group.

[0296] Here, when the current block is partitioned by a quadtree, the sub-division value of the current block is equal to 2 plus the value before sub-division.

[0297] When the current block is partitioned by a binary tree, the sub-partition value of the current block is equal to 1 plus the value before sub-partitioning.

[0298] The differential quantization parameter and the predicted quantization parameter may be added to derive the quantization parameter of the current block.

[0299] Figure 9b is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

[0300] Reference Figure 9b , the image encoding apparatus determines the size of the quantization group (S911).

[0301] Here, the size information of the quantization group includes at least one of depth information of the quantization group, length information of the quantization group, area information of the quantization group, ratio information of the quantization group, type information of the quantization group, and sub-division information of the quantization group.

[0302] The quantization groups may include square quantization groups or non-square quantization groups.

[0303] The non-square quantization group may have a shape based on at least one of a binary tree structure and a ternary tree structure.

[0304] The image encoding apparatus may determine a quantization parameter of the current block based on the size of the quantization group (S912).

[0305] The image encoding apparatus may derive a differential quantization parameter of the current block from the quantization parameter (S913).

[0306] For example, the differential quantization parameter of the current block may be derived based on the relationship between the depth of the current block and the depth information of the quantization group.

[0307] For example, the differential quantization parameter of the current block may be derived based on a size relationship of the quantization group set between the area of ​​the current block and area information of the quantization group.

[0308] For example, the differential quantization parameter of the current block may be derived based on the relationship between the sub-division value of the current block and the sub-division information of the quantization group.

[0309] Here, when the current block is partitioned by a quadtree, the sub-division value of the current block is equal to 2 plus the value before sub-division.

[0310] When the current block is partitioned by a binary tree, the sub-partition value of the current block is equal to 1 plus the value before sub-partitioning.

[0311] The differential quantization parameter may be derived by subtracting the predicted quantization parameter from the quantization parameter of the current block.

[0312] The image encoding apparatus may encode size information of the quantization group (S914). A differential quantization parameter of the current block may be encoded based on the size information of the quantization group.

[0313] According to an embodiment of the present invention, an image encoding / decoding method and apparatus performs the following steps: determining the size of a quantization group, determining a quantization parameter, and / or encoding / decoding the size information of the quantization group and / or the differential quantization parameter information. The encoding / decoding may represent entropy encoding / decoding.

[0314] Hereinafter, the steps of determining the size of the quantization group will be described.

[0315] The encoder / decoder may determine the size of the quantization group.

[0316] For example, the encoder determines the size of the quantization group to be used in encoding / decoding by using a size set by a user or a size determined by a predetermined rule.

[0317] Alternatively, the decoder may determine the size of the quantization group based on at least one of various sizes indicated by quantization group size information obtained by entropy decoding the bitstream.

[0318] Further optionally, the decoder may determine the size of the quantization group according to a predetermined rule.

[0319] Still further optionally, the encoder / decoder may determine the size of the quantization group based on a previously set size.

[0320] Here, the term "quantization group" refers to a region where one or more processing units share the same quantization parameter. A quantization group may include at least one CU, PU, ​​TU and / or block. Therefore, the CU, PU, ​​TU and / or block within the quantization group use the same quantization parameter. The block may be a predefined block.

[0321] The size of the quantization group (hereinafter, for convenience of description, 'the size of the quantization group' will be referred to as the quantization group size) may be determined according to at least one selected from depth, length, area, ratio, shape, and sub-division.

[0322] The size information of the quantization group may refer to at least one of depth information, length information, area information, ratio information, shape information, and sub-division information of the quantization group. The quantization group may have a square shape or a non-square shape such as a rectangular shape and a triangular shape.

[0323] Examples of the non-square shape include a binary tree, a ternary tree, and at least one block generated by partitioning the binary tree or the ternary tree.

[0324] The size information of the quantization group may refer to any combination of depth information, length information, area information, ratio information, shape information, and sub-division information of the quantization group.

[0325] The multi-type tree may refer to a binary tree, a ternary tree, or both a binary tree and a ternary tree.

[0326] The block depth (ie, the depth of the block) may mean at least one of the depth of a quadtree, the depth of a binary tree, and the depth of a ternary tree, or the sum of the depths of two or more of these trees.

[0327] The depth of the multi-type tree may represent at least one of the depth of the binary tree and the depth of the ternary tree, or the sum of the depths of two or more trees. The depth of the multi-type tree may represent the depth of the binary tree. The depth of the multi-type tree may represent the depth of the ternary tree.

[0328] For example, when the block may have a square shape and a non-square shape, the depth of the block may represent at least one of the depth of the quadtree and the depth of the multi-type tree, or the sum of the depths of two or more trees. That is, the depth of the block may represent at least one of the depth of the quadtree, the depth of the binary tree, and the depth of the ternary tree, or the sum of the depths of two or more trees thereof.

[0329] On the other hand, when a block can have only a square shape, the depth of the block only represents the depth of the quadtree.

[0330] On the other hand, when the block can only have a non-square shape, the depth of the block only represents the depth of the multi-type tree. That is, the depth of the block can represent at least one of the depth of the binary tree and the depth of the ternary tree, or can represent the sum of the depths of two or more trees therein.

[0331] Hereinafter, the steps of determining the quantization parameter will be described.

[0332] At the encoder / decoder, a quantization parameter may be determined.

[0333] For example, at an encoder, the quantization parameter may be set by a user or may be determined according to a predetermined rule.

[0334] For example, at the decoder, the quantization parameter may be obtained by adding a predicted quantization parameter derived by prediction based on neighboring quantization groups of the current quantization group to the differential quantization parameter. The differential quantization parameter may represent information of the differential quantization parameter obtained by decoding the bitstream.

[0335] When at least one of the neighboring quantization groups of the current quantization group is unavailable, the quantization parameter of the quantization group corresponding to the previous position in encoding / decoding rather than the quantization parameter of the neighboring quantization group corresponding to the unavailable position may be used as the predicted quantization parameter of the current quantization group.

[0336] When at least one of the neighboring quantization groups of the current quantization group is unavailable, the quantization parameters of the quantization group corresponding to the previous position in encoding / decoding rather than the quantization parameters of the neighboring quantization group corresponding to the unavailable position may be used as the quantization parameters for calculating the predicted quantization parameters of the current quantization group.

[0337] When at least one of the neighboring quantization groups of the current quantization group does not exist, the quantization parameter of the quantization group corresponding to the previous position in the encoding / decoding order, rather than the quantization parameter of the non-existent neighboring quantization group, may be used as the quantization parameter to be used to calculate the predicted quantization parameter of the current quantization group. At this time, when a specific neighboring quantization group exists, the quantization parameter sent by the high-level syntax element may be used as the predicted quantization parameter. The high-level syntax element may be at least one of a picture, a sub-picture, a slice, a tile, a tile group, a CTU line, a CTU row, a CTU column, and a CTU.

[0338] Here, the expression that the neighboring quantization group does not exist means that the current quantization group is located at a boundary of at least one of a picture, a sub-picture, a slice, a tile, a tile group, a CTU line, a CTU row, a CTU column, and a CTU.

[0339] Here, the expression that the neighboring quantization group does not exist means that the neighboring quantization group is located outside the boundary of at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU.

[0340] Here, the expression that the neighboring quantization group does not exist means that the neighboring quantization group is different from the current quantization group in at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU.

[0341] For example, when the current quantization group is the first quantization group in at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU, at least one of a picture-based quantization parameter, a sub-picture-based quantization parameter, a slice-based quantization parameter, a tile group-based quantization parameter, a tile block-based quantization parameter, and a CTU line-based quantization parameter may be used as a predicted quantization parameter.

[0342] For example, when the current quantization group is the last quantization group in at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU, at least one of a picture-based quantization parameter, a sub-picture-based quantization parameter, a slice-based quantization parameter, a tile group-based quantization parameter, a tile block-based quantization parameter, and a CTU line-based quantization parameter may be used as a predicted quantization parameter.

[0343] For example, when the current quantization group is the first quantization group in at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU, at least one of a picture-based quantization parameter, a sub-picture-based quantization parameter, a slice-based quantization parameter, a tile group-based quantization parameter, a tile block-based quantization parameter, and a CTU line-based quantization parameter may be used as a quantization parameter for calculating a predicted quantization parameter.

[0344] For example, when the current quantization group is the first quantization group in the first CTU row, at least one of the quantization parameter of the picture, the quantization parameter of the sub-picture, the quantization parameter of the slice, the quantization parameter of the parallel block group, the quantization parameter of the parallel block, and the quantization parameter of the CTU line may be used as a quantization parameter for calculating the predicted quantization parameter.

[0345] Optionally, when the current quantization group is the first quantization group in a CTU line, at least one of a quantization parameter of a picture, a quantization parameter of a sub-picture, a quantization parameter of a slice, a quantization parameter of a parallel block group, a quantization parameter of a parallel block, and a quantization parameter of a CTU line may be used as a quantization parameter for calculating a predicted quantization parameter.

[0346] For example, when the current quantization group is the last quantization group in at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU, at least one of a quantization parameter of the picture, a quantization parameter of the sub-picture, a quantization parameter of the slice, a quantization parameter of the tile group, a quantization parameter of the tile, and a quantization parameter of the CTU line may be used as a quantization parameter for calculating a predicted quantization parameter.

[0347] Here, the term "quantization group" means a block or a region.

[0348] At the decoder, the quantization parameter may be determined by a predetermined rule.

[0349] According to one embodiment, for the current quantization group or at least one block in the quantization group, at least one of the quantization parameters of neighboring quantization groups of the current quantization group, the quantization parameters of previous quantization groups in the coding / decoding order, and the quantization parameters signaled at the picture level, sub-picture level, slice level, parallel block group level, parallel block level, CTU line level, CTU row level, CTU column level, and CTU level may be used to derive a predicted quantization parameter.

[0350] For example, the predicted quantization parameter of the current quantization group may be derived from at least one quantization parameter among the quantization parameters of the corresponding neighboring quantization groups of the current quantization group. The process of deriving the predicted quantization parameter for the current quantization group will be described with reference to Figures 10 to 13 FIG.

[0351] Fig.10 FIG. is a diagram illustrating a process of deriving a predicted quantization parameter for a current quantization group according to an embodiment of the present invention.

[0352] In Fig.10 , the unit size of the quantization group is defined by a thick solid line. Sub-blocks generated from the division of the block are defined by thin solid lines. The relatively bright solid line defines the minimum size of the block to be encoded / decoded. Here, the minimum block size may be set to M×N, where M or N is an integer. For example, the minimum block size for the luminance component may be 4×4, and the minimum block size for the chrominance component may be 2×2. The upper left position in quantization group A may be represented as (x, y). In addition, curQGwidth and curQGheight represent the horizontal size (width) and vertical size (height) of the current quantization group.

[0353] In Fig.10 of (a), A represents the current quantization group. Each of B and C represents the position of a block or sample for deriving the predicted quantization parameter or the position of a neighboring quantization group located around the current quantization group. The predicted quantization parameter of the current quantization group may be derived by using the quantization parameters of the quantization group corresponding to at least one of the positions B and C.

[0354] For example, the position B may be represented as (x, y-(1<<minBlklog2size)). The position C may be represented as (x-(1<<minBlklog2size), y).

[0355] Optionally, the position B may be represented as (x, y-1). The position C may be represented as (x-1, y).

[0356] The quantization parameters existing at positions B and C are represented as QP_B and QP_C, respectively.

[0357] At least one of quantization parameters QP_B and QP_C, or at least one of statistical values of quantization parameters QP_B and QP_C, can be used to derive a predicted quantization parameter for the current quantization group.

[0358] For example, as shown in Expression 1, the average value of QP_B and QP_C can be used to derive a predicted quantization parameter for the current quantization group.

[0359] [Expression 1]

[0360] predcurQP = (QP_B + QP_C + 1) >> 1

[0361] In Fig.10 in (b) of , A represents the current quantization group. Each of B, C, D, and E represents the position of a block or sample for deriving a predicted quantization parameter or the position of an adjacent quantization group around the current quantization group. The predicted quantization parameter for the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B, C, D, and E.

[0362] For example, position B can be represented as (x, y - (1 << minBlklog2size)). Position C can be represented as (x - (1 << minBlklog2size), y). Position D can be represented as (x + (curQGwidth >> 1), y - (1 << minBlklog2size)). Position E can be represented as (x - (1 << minBlklog2size), y + (curQGheight >> 1)).

[0363] Optionally, position B can be represented as (x, y - 1). Position C can be represented as (x - 1, y). Position D can be represented as (x + (curQGwidth ≥ 1), y - 1). Position E can be represented as (x - 1, y + (curQGheight >> 1)).

[0364] The quantization parameters existing at positions B, C, D, and E are respectively represented as QP_B, QP_C, QP_D, and QP_E.

[0365] At least one of quantization parameters QP_B, QP_C, QP_D, and QP_E, or at least one of statistical values of quantization parameters QP_B, QP_C, QP_D, and QP_E, can be used to derive a predicted quantization parameter for the current quantization group.

[0366] For example, as shown in Expression 2, the average value of QP_B, QP_C, QP_D, and QP_E can be used to derive a predicted quantization parameter for the current quantization group.

[0367] [Expression 2]

[0368] predcurQP = (QP_B + QP_C + QP_D + QP_E + 2) >> 2

[0369] In Fig.10 in (c) of, A represents the current quantization group. Each of B and C represents the position of a block or sample for deriving a predicted quantization parameter or the position of an adjacent quantization group around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B and C.

[0370] For example, the position B can be represented as (x + (curQGwidth >> 1), y - (curQGheight >> 1)). The position C can be represented as (x - (curQGwidth >> 1), y + (curQGheight >> 1)).

[0371] The quantization parameters existing at the positions B and C are represented as QP_B and QP_C respectively.

[0372] At least one of QP_B and QP_C or at least one of their statistical values can be used to derive the predicted quantization parameter of the current quantization group.

[0373] For example, as shown in Expression 3, the average value of QP_B and QP_C can be used to derive the predicted quantization parameter of the current quantization group.

[0374] [Expression 3]

[0375] predcurQP = (QP_B + QP_C + 1) >> 1

[0376] In Fig.10 in (d) of, A represents the current quantization group. Each of B and C represents the position of a block or sample for deriving a predicted quantization parameter or the position of an adjacent quantization group around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B and C.

[0377] For example, the position B can be represented as (x + curQGwidth - (1 << minBlklog2size), y - (1 << minBlklog2size)). The position C can be represented as (x - (1 << minBlklog2size), y + curQGheight - (1 << minBlklog2size)).

[0378] Optionally, position B can be represented as (x + curQGwidth - 1, y - 1). Position C can be represented as (x - 1, y + curQGheight - 1).

[0379] The quantization parameters existing at positions B and C are represented as QP_B and QP_C, respectively.

[0380] At least one of QP_B and QP_C or at least one of their statistical values can be used to derive the predicted quantization parameter of the current quantization group.

[0381] For example, as shown in Expression 4, the average value of QP_B and QP_C can be used to derive the predicted quantization parameter of the current quantization group.

[0382] [Expression 4]

[0383] predcurQP = (QP_B + QP_C + 1) >> 1

[0384] Fig.11 is a diagram showing the process of deriving the predicted quantization parameter for the current quantization group according to another embodiment of the present invention.

[0385] In Fig.11 , the unit size of the quantization group is defined by a thick solid line. The sub-blocks generated from the division of the blocks are defined by thin solid lines. The relatively bright solid line defines the minimum size of the block to be encoded / decoded. Here, the minimum block size can be set to M×N, where M or N is an integer. For example, the minimum block size for the luminance component can be 4×4, and the minimum block size for the chrominance component can be 2×2. The upper left position in quantization group A can be represented as (x, y). In addition, curQGwidth and curQGheight represent the horizontal size (width) and vertical size (height) of the current quantization group. In addition, A represents the first quantization group in a predetermined CTU row. Optionally, A represents the first quantization group in at least one CTU row included in the CTU line.

[0386] In Fig.11 of (a), A represents the current quantization group. Each of B and C represents the position of the block or sample point for deriving the predicted quantization parameter or the position of the neighboring quantization group around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B and C.

[0387] For example, position B can be represented as (x, y - (1 << minBlklog2size)). Position C can be represented as (x - (1 << minBlklog2size), y).

[0388] Alternatively, position B may be represented as (x, y-1). Position C may be represented as (x-1, y).

[0389] Here, the position B may be located outside the boundary of the picture, sub-picture, slice, tile, tile group, tile, CTU line, CTU row, CTU column, or CTU where the current quantization group is located.

[0390] For example, since the quantization group corresponding to position B is located outside the boundary, the quantization parameter of position B may not be used when deriving the predicted quantization parameter. The quantization parameter of position C may be denoted as QP_C.

[0391] By using QP_C, the predicted quantization parameter of the current quantization group can be derived.

[0392] For example, as shown in Expression 5, QP_C may be used to derive a predicted quantization parameter of the current quantization group.

[0393] [Expression 5]

[0394] predcurQP=QP_C

[0395] For example, since the quantization group corresponding to position B is located outside the boundary, the quantization parameter of position B may be replaced with the quantization parameter of the previous quantization group in the encoding / decoding order, or replaced with an advanced quantization parameter, and the replaced quantization parameter may be used. The quantization parameter of the previous quantization group in the encoding / decoding order or the advanced quantization parameter may be represented as QP_B. The quantization parameter of position C may be represented as QP_C.

[0396] In the current embodiment and / or other embodiments of the present invention, the advanced quantization parameter may represent at least one of a quantization parameter of a picture, a quantization parameter of a sub-picture, a quantization parameter of a slice, a quantization parameter of a parallel block group, a quantization parameter of a parallel block, and a quantization parameter of a CTU line.

[0397] At least one of QP_B and QP_C or at least one of their statistical values ​​may be used to derive a predicted quantization parameter of a current quantization group.

[0398] For example, as shown in Expression 6, the average value of QP_B and QP_C may be used to derive the predicted quantization parameter of the current quantization group.

[0399] [Expression 6]

[0400] predcurQP=(QP_B+QP_C+1)>>1

[0401] Alternatively, a weighted average may be used to derive the predicted quantization parameter of the current quantization group. In this case, the weighting factor of QP-B may be set to be smaller than the weighting factor of QP_C.

[0402] In Fig.11 (b) of, A represents the current quantization group. Each of B, C, D, and E represents the position of a block or sample for deriving a predicted quantization parameter or the position of an adjacent quantization group around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B, C, D, and E.

[0403] For example, the position B can be represented as (x, y-(1<<minBlklog2size)). The position C can be represented as (x-(1<<minBlklog2size), y). The position D can be represented as (x+(curQGwidth>>1), y-(1<<minBlklog2size)). The position E can be represented as (x-(1<<minBlklog2size), y+(curQGheight>>1)).

[0404] Optionally, the position B can be represented as (x, y-1). The position C can be represented as (x-1, y). The position D can be represented as (x+(curQGwidth≥1), y-1). The position E can be represented as (x-1, y+(curQGheight>>1)).

[0405] Here, at least one of the positions of B and D may be outside the boundaries of the picture, sub-picture, slice, parallel block, parallel block group, parallel block, CTU line, CTU row, CTU column, or CTU including the current quantization group.

[0406] For example, since the quantization group corresponding to at least one of the positions B and D is outside the said boundary, the quantization parameters at one or more of the positions B and D may not be used when deriving the predicted quantization parameter. The quantization parameters at positions C and E can be represented as QP_C and QP_E respectively.

[0407] At least one of QP_C and QP_E or at least one of their statistical values can be used to derive the predicted quantization parameter of the current quantization group.

[0408] For example, as shown in Expression 7, the average value of QP_C and QP_E can be used to derive the predicted quantization parameter of the current quantization group.

[0409] [Expression 7]

[0410] predcurQP = (QP_C + QP_E + 1) >> 1

[0411] Optionally, since the quantization group corresponding to the position of at least one of B and D is outside the boundary, the quantization parameter of the position of at least one of B and D can be replaced with the quantization parameter of the previous quantization group in the encoding / decoding order or with an advanced quantization parameter, and the replaced quantization parameter can be used. The quantization parameter of the previous quantization group in the encoding / decoding order or the advanced quantization parameter can be represented as QP_B and QP_D. The quantization parameters at positions C and E can be represented as QP_C and QP_E respectively.

[0412] In this case, at least one of QP_B, QP_C, QP_D, and QP_E or at least one of their statistical values can be used to derive the predicted quantization parameter of the current quantization group.

[0413] For example, as in the example represented by Expression 8, the average value of QP_B, QP_C, QP_D, and QP_E can be used to derive the predicted quantization parameter of the current quantization group.

[0414] [Expression 8]

[0415] predcurQP = (QP_B + QP_C + QP_D + QP_E + 2) >> 2

[0416] Optionally, a weighted average value can be used to derive the predicted quantization parameter of the current quantization group. In this case, at least one of the weighting factors of QP_B and QP_D can be set to be less than at least one of the weighting factors of QP_C and QP_E.

[0417] In Fig.11 of (c), A represents the current quantization group. A can represent the first quantization group in a predetermined CTU row. Optionally, A can represent the first quantization group in at least one CTU row included in the CTU line. Optionally, A can represent at least one of the first quantization group in a predetermined strip, the first quantization group in a predetermined sub-picture, the first quantization group in a predetermined parallel block group, and the first quantization group in a predetermined parallel block.

[0418] Each of B and C represents the position of a block or sample for deriving the predicted quantization parameter or the position of an adjacent quantization group around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B and C.

[0419] For example, the position B can be represented as (x, y-(1<<minBlklog2size)). The position C can be represented as (x-(1<<minBlklog2size), y).

[0420] Alternatively, position B may be represented as (x, y-1). Position C may be represented as (x-1, y).

[0421] Here, the position C may be outside the boundary of the picture, sub-picture, slice, tile, tile group, tile, CTU line, CTU row, CTU column, or CTU where the current quantization group is located.

[0422] For example, since the quantization group corresponding to position C is located outside the boundary, the quantization parameter of position C may not be used for derivation of the predicted quantization parameter. The quantization parameter at position B may be denoted as QP_B.

[0423] By using QP_B, the predicted quantization parameter of the current quantization group can be derived.

[0424] For example, as in the example represented by Expression 9, QP_B may be used to derive a predicted quantization parameter of the current quantization group.

[0425] [Expression 9]

[0426] predcurQP=QP_B

[0427] For example, since the quantization group corresponding to position C is located outside the boundary, the quantization parameter of position C may be replaced with the quantization parameter of the previous quantization group in the encoding / decoding order or with an advanced quantization parameter, and the replaced quantization parameter may be used. The quantization parameter of the previous quantization group in the encoding / decoding order or the advanced quantization parameter may be represented as QP_C. The quantization parameter at position B may be represented as QP_B.

[0428] At least one of QP_B and QP_C or at least one of their statistical values ​​may be used to derive a predicted quantization parameter of a current quantization group.

[0429] For example, as in the example represented by Expression 10, the average value of QP_B and QP_C may be used to derive the predicted quantization parameter of the current quantization group.

[0430] [Expression 10]

[0431] predcurQP=(QP_B+QP_C+1)>>1

[0432] Alternatively, a weighted average may be used to derive the predicted quantization parameter of the current quantization group. In this case, the weighting factor of QP_B may be set to be smaller than the weighting factor of QP_B.

[0433] exist Fig.11In (d) above, A represents the current quantization group. Each of B and C represents the position of a block or sample for deriving the predicted quantization parameter or the position of an adjacent quantization group surrounding the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B and C.

[0434] For example, position B can be represented as (x + curQGwidth - (1 << minBlklog2size), y - (1 << minBlklog2size)). Position C can be represented as (x - (1 << minBlklog2size), y + curQGheight - (1 << minBlklog2size)).

[0435] Optionally, position B can be represented as (x + curQGwidth - 1, y - 1). Position C can be represented as (x - 1, y + curQGheight - 1).

[0436] Here, position C can be outside the boundaries of the picture, sub - picture, slice, parallel block, parallel block group, parallel block, CTU line, CTU row, CTU column or CTU where the current quantization group is located.

[0437] For example, since the quantization group corresponding to position C is outside the said boundary, the quantization parameter of position C may not be used for deriving the predicted quantization parameter. The quantization parameter at position B can be represented as QP_B.

[0438] By using QP_B, the predicted quantization parameter of the current quantization group can be derived.

[0439] For example, as shown in Expression 11, QP_B can be used to derive the predicted quantization parameter of the current quantization group.

[0440] [Expression 11]

[0441] predcurQP = QP_B

[0442] For example, since the quantization group corresponding to position C is outside the said boundary, the quantization parameter of position C can be replaced by the quantization parameter of the previous quantization group in the coding / decoding order or by an advanced quantization parameter, and the replaced quantization parameter can be used. The quantization parameter of the previous quantization group in the coding / decoding order or the advanced quantization parameter can be represented as QP_C. The quantization parameter at position B can be represented as QP_B.

[0443] At least one of QP_B and QP_C or at least one of their statistical values can be used to derive the predicted quantization parameter of the current quantization group.

[0444] For example, as shown in Expression 12, the average value of QP_B and QP_C can be used to derive the predicted quantization parameter of the current quantization group.

[0445] [Expression 12]

[0446] predcurQP = (QP_B + QP_C + 1) >> 1

[0447] Optionally, a weighted average value can be used to derive the predicted quantization parameter of the current quantization group. In this case, the weighting factor of QP_C can be set to be smaller than the weighting factor of QP_B.

[0448] Fig.12 is a diagram showing the process of deriving the predicted quantization parameter for the current quantization group according to another embodiment of the present invention.

[0449] In Fig.12 , the unit size of the quantization group is defined by a thick solid line. The sub-blocks generated from the division of the block are defined by thin solid lines. The relatively bright solid line defines the minimum size of the block to be encoded / decoded. Here, the minimum block size can be set to M×N, where M or N is an integer. For example, the minimum block size for the luminance component can be 4×4, and the minimum block size for the chrominance component can be 2×2. The upper left position in quantization group A can be represented as (x, y). In addition, curQGwidth and curQGheight respectively represent the horizontal size (width) and vertical size (height) of the current quantization group.

[0450] In Fig.12 's (a), A represents the current quantization group. Each of B, C, D, and E represents the position of the block or sample point for deriving the predicted quantization parameter or the position of the neighboring quantization group around the current quantization group. In this case, the quantization parameters of the quantization group corresponding to at least one of the positions B, C, D, and E can be used to derive the predicted quantization parameter for the current quantization group. The current quantization group A can have a non-square shape. The method for deriving the quantization parameter for a non-square quantization group can be similar to the method for deriving the quantization parameter for a square quantization group.

[0451] For example, the position B can be represented as (x, y-(1<<minBlklog2size)). The position C can be represented as (x-(1<<minBlklog2size), y). The position D can be represented as (x+(curQGwidth>>1), y-(1<<minBlklog2size)). The position E can be represented as (x-(1<<minBlklog2size), y+(curQGheight>>1)).

[0452] Alternatively, position B may be represented as (x, y-1). Position C may be represented as (x-1, y). Position D may be represented as (x+(curQGwidth>>1), y-1). Position E may be represented as (x-1, y+(curQGheight>>1)).

[0453] Quantization parameters existing at positions B, C, D, and E are represented as QP_B, QP_C, QP_D, and QP_E, respectively.

[0454] At least one of QP_B, QP_C, QP_D, and QP_E, or at least one of their statistical values, may be used to derive a predicted quantization parameter of a current quantization group.

[0455] For example, as shown in Expression 13, the average value of QP_B, QP_C, QP_D, and QP_E may be used to derive the predicted quantization parameter of the current quantization group.

[0456] [Expression 13]

[0457] predcurQP=(QP_B+QP_C+QP_D+QP_E+2)>>2

[0458] exist Fig.12 In (b), A represents the current quantization group. Each of B and C represents the position of a block or sample point from which a predicted quantization parameter is derived or the position of a neighboring quantization group located around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of the quantization group corresponding to at least one of the positions B and C. The current quantization group A may have a non-square shape. The method for deriving the quantization parameter for a non-square quantization group may be similar to the method for deriving the quantization parameter for a square quantization group. Optionally, the predicted quantization parameter for a non-square quantization group may be derived based on the width and / or height of the non-square quantization group.

[0459] For example, position B may be represented as (x+(BQGwidth>>1), y-(BQGheight>>1)). Position C may be represented as (x-(CQGwidth>>1), y+(CQGheight>>1)). Here, XQGwidth and XQGheight may represent the width and height of adjacent quantization groups located around the current quantization group, respectively. For example, the width and height of the quantization group at position B may be represented by replacing the character "X" with the character "B", for example, BQGwidth and BQGheight, respectively. The width and height of the quantization group at position C may be represented by replacing the character "X" with the character "C", for example, CQGwidth and CQGheight, respectively.

[0460] The quantization parameters existing at positions B and C are respectively represented as QP_B and QP_C.

[0461] At least one of QP_B and QP_C or at least one of their statistical values can be used to derive the predicted quantization parameter of the current quantization group.

[0462] For example, as shown in Expression 14, the average value of QP_B and QP_C can be used to derive the predicted quantization parameter of the current quantization group.

[0463] [Expression 14]

[0464] predcurQP = (QP_B + QP_C + 1) >> 1

[0465] In Fig.12 (c) of, A represents the current quantization group. Each of B, C, D, E, and F represents the position of a block or sample point for deriving the predicted quantization parameter or the position of an adjacent quantization group around the current quantization group. The predicted quantization parameter of the current quantization group can be derived by using the quantization parameter of at least one quantization group corresponding to at least one of B, C, D, E, and F.

[0466] For example, position B can be represented as (x - (1 << minBlklog2size), y + curQGheight - (1 << minBlklog2size)). The position of C can be represented as (x + curQGwidth - (1 << minBlklog2size), y - (1 << minBlklog2size)). The position of D can be represented as (x + curQGwidth, y - (1 << minBlklog2size)). The position of E can be represented as (x - (1 << minBlklog2size), y + curQGheight). The position of F can be represented as (x - (1 << minBlklog2size), y - (1 << minBlklog2size)).

[0467] Optionally, position B can be represented as (x - 1, y + curQGheight - 1). The position of C can be represented as (x + curQGwidth - 1, y - 1). The position of D can be represented as (x + curQGwidth, y - 1). The position of E can be represented as (x - 1, y + curQGheight). The position of F can be represented as (x - 1, y - 1).

[0468] The quantization parameters existing at positions B, C, D, E, and F can be respectively represented as QP_B, QP_C, QP_D, QP_E, and QP_F.

[0469] At least N quantization parameters among QP_B, QP_C, QP_D, QP_E and QP_F or statistical values ​​of at least N quantization parameters among QP_B, QP_C, QP_D, QP_E and QP_F can be used to derive the predicted quantization parameter of the current quantization group. Here, N is a positive integer.

[0470] The N quantization parameters may be selected according to a specific order. The specific order may be an encoding / decoding order or an order of specific positions processed in an encoder / decoder. The specific order may represent the order of B, C, D, E, and F.

[0471] For example, as shown in Expression 15, a statistical value (eg, an average value) of two quantization parameters QP_B and QP_C among the quantization parameters QP_B, QP_C, QP_D and QP_E, QP_F may be used to derive a predicted quantization parameter of the current quantization group.

[0472] [Expression 15]

[0473] predcurQP=(QP_B+QP_C+1)>>1

[0474] exist Fig.12 In (d), A represents the current quantization group. Each of B and C represents the position of the block or sample from which the predicted quantization parameter is derived or the position of the neighboring quantization group located around the current quantization group. Here, when the current quantization group is the quantization group located in the upper left corner or the first quantization group in at least one of the picture, sub-picture, slice, parallel block group, parallel block, CTU line, CTU row and CTU column, there may be no quantization group at positions B and C. In this case, the predicted quantization parameter of the current quantization group may be a value sent from an advanced syntax element. Here, the value sent from the advanced syntax element may represent at least one of the advanced quantization parameters.

[0475] The high-level syntax element may be at least one of a picture, a sub-picture, a slice, a tile, a tile group, a tile, a CTU line, a CTU row, a CTU column, and a CTU.

[0476] For example, when the value of the transmitted quantization parameter in the picture is picQP, the predicted quantization parameter of the current quantization group can be derived as in the example of Expression 16.

[0477] [Expression 16]

[0478] predcurQP=picQP

[0479] Alternatively, when the value of the transmitted quantization parameter in the slice is sliceQP, the predicted quantization parameter of the current quantization group may be derived as in the example of Expression 17.

[0480] [Expression 17]

[0481] predcurQP=sliceQP

[0482] Further optionally, when the value of the transmitted quantization parameter in the tile group is tilegroupQP, the predicted quantization parameter of the current quantization group may be derived as in the example of Expression 18.

[0483] [Expression 18]

[0484] predcurQP=tilegroupQP

[0485] Further optionally, when the value of the transmitted quantization parameter in the tile is tileQP, the predicted quantization parameter of the current quantization group may be derived as in the example of Expression 19.

[0486] [Expression 19]

[0487] predcurQP=tileQP

[0488] Fig.13 is a diagram illustrating a process of deriving a predicted quantization parameter of a current quantization group according to yet another embodiment of the present invention.

[0489] exist Fig.13 In the figure, the unit size of the quantization group is bounded by a thick solid line. The sub-blocks resulting from the partition of the block are bounded by a thin solid line. The relatively bright solid line defines the minimum size of the block being encoded / decoded. Here, the minimum block size can be set to M×N, where M or N is an integer. For example, the minimum block size for the luma component can be 4×4, and the minimum block size for the chroma component can be 2×2. The upper left position in the quantization group A can be represented as (x, y). In addition, curQGwidth and curQGheight represent the horizontal size (width) and vertical size (height) of the current quantization group, respectively.

[0490] exist Fig.13 In (a), A represents the current quantization group. At least one of B, C, D, E, and F represents the position of a block or sample point from which a predicted quantization parameter is derived or may represent the position of a neighboring quantization group located around the current quantization group. Here, the quantization parameter of the quantization group corresponding to at least one of the positions B, C, D, E, and F may be used to derive the predicted quantization parameter of the current quantization group.

[0491] For example, position B can be represented as (x - (1 << minBlklog2size), y + curQGheight - (1 << minBlklog2size)). The position of C can be represented as (x + curQGwidth - (1 << minBlklog2size), y - (1 << minBlklog2size)). The position of D can be represented as (x + curQGwidth, y - (1 << minBlklog2size)). The position of E can be represented as (x - (1 << minBlklog2size), y + curQGheight). The position of F can be represented as (x - (1 << minBlklog2size), y - (1 << minBlklog2size)).

[0492] Optionally, position B can be represented as (x - 1, y + curQGheight - 1). The position of C can be represented as (x + curQGwidth - 1, y - 1). The position of D can be represented as (x + curQGwidth, y - 1). The position of E can be represented as (x - 1, y + curQGheight). The position of F can be represented as (x - 1, y - 1).

[0493] At least one of the positions B, E, and F can be outside the boundary of at least one of the current picture, sub - picture, slice, parallel block group, parallel block, CTU line, CTU row, CTU column, and CTU.

[0494] Since the quantization group corresponding to at least one of the positions B, E, and F is outside the boundary, the quantization parameters at one or more of the positions B, E, and F are not used to derive the predicted quantization parameters of the current quantization group. On the other hand, the quantization parameters at positions C and D can be represented as QP_C and QP_D respectively.

[0495] At least one of QP_C and QP_D or at least one statistical value of QP_C and QP_D can be used to derive the predicted quantization parameters of the current quantization group.

[0496] For example, as in the example of Expression 20, the average value of QP_C and QP_D can be used to derive the predicted quantization parameters of the current quantization group.

[0497] [Expression 20]

[0498] predcurQP = (QP_C + QP_D + 1) >> 1

[0499] As another example, since the quantization group corresponding to at least one of the positions B, E, and F is outside the boundary, the quantization parameter corresponding to at least one of the positions B, E, and F may be replaced with the quantization parameter of the previous quantization group in the encoding / decoding order or with a higher-level quantization parameter. At this time, the quantization parameter of the previous quantization group in the encoding / decoding order or the higher-level quantization parameter may be expressed as QP_B, QP_E, and QP_F. In addition, the quantization parameters at positions C and D may be expressed as QP_C and QP_D, respectively.

[0500] On the other hand, at least N quantization parameters among QP_B, QP_C, QP_D, QP_E and QP_F or statistical values ​​of the at least N quantization parameters may be used to derive the predicted quantization parameter of the current quantization group. Here, N is a positive integer.

[0501] The N quantization parameters may be selected according to a specific order. The specific order is the encoding / decoding order or the order of specific positions processed in the encoder / decoder. The specific order may represent the order of B, C, D, E, and F.

[0502] For example, as shown in Expression 21, the predicted quantization parameter of the current quantization group may be derived using statistical values ​​(eg, average values) of two quantization parameters QP_B and QP_C among QP_B, QP_C, QP_D, QP_E, and QP_F.

[0503] [Expression 21]

[0504] predcurQP=(QP_B+QP_C+1)>>1

[0505] Alternatively, a weighted average may be used to derive the predicted quantization parameter of the current quantization group. In this case, a weighting factor of at least one of QP_B, QP_E, and QP_F may be set to be smaller than a weighting factor of at least one of QP_C and QP_D.

[0506] exist Fig.13 In (b), A represents the current quantization group. At least one of B, C, D, E, and F may represent the position of a block or sample point from which a predicted quantization parameter is derived or may represent the position of a neighboring quantization group located around the current quantization group. Here, the quantization parameter of the quantization group corresponding to at least one of the positions B, C, D, E, and F may be used to derive the predicted quantization parameter of the current quantization group.

[0507] For example, position B can be represented as (x - (1 << minBlklog2size), y + curQGheight - (1 << minBlklog2size)). Position C can be represented as (x + curQGwidth - (1 << minBlklog2size), y - (1 << minBlklog2size)). Position D can be represented as (x + curQGwidth, y - (1 << minBlklog2size)). Position E can be represented as (x - (1 << minBlklog2size), y + curQGheight). Position F can be represented as (x - (1 << minBlklog2size), y - (1 << minBlklog2size)).

[0508] Optionally, position B can be represented as (x - 1, y + curQGheight - 1). Position C can be represented as (x + curQGwidth - 1, y - 1). Position D can be represented as (x + curQGwidth, y - 1). Position E can be represented as (x - 1, y + curQGheight). Position F can be represented as (x - 1, y - 1).

[0509] At least one of positions C, D, and F can be outside the boundary of at least one of the current picture, sub - picture, slice, parallel block group, parallel block, CTU line, CTU row, CTU column, and CTU.

[0510] For example, since the quantization group corresponding to at least one of positions C, D, and F is outside the boundary, the quantization parameter of at least one of positions C, D, and F may not be used to derive the predicted quantization parameter of the current quantization group. The quantization parameters at positions B and E can be represented as QP_B and QP_E respectively.

[0511] At least one of QP_B and QP_C or at least one of the statistical values of QP_B and QP_C can be used to derive the predicted quantization parameter of the current quantization group.

[0512] For example, as shown in Expression 22, the average value of QP_C and QP_E can be used to derive the predicted quantization parameter of the current quantization group.

[0513] [Expression 22]

[0514] predcurQP = (QP_B + QP_E + 1) >> 1

[0515] As another example, since the quantization group corresponding to at least one of the positions C, D, and F is outside the boundary, the quantization parameter corresponding to at least one of the positions C, D, and F may be replaced with the quantization parameter of the previous quantization group in the encoding / decoding order or with a higher-level quantization parameter. At this time, the quantization parameter of the previous quantization group in the encoding / decoding order or the higher-level quantization parameter may be represented as QP_C, QP_D, and QP_F. The quantization parameters at positions B and E may be represented as QP_B and QP_E, respectively.

[0516] On the other hand, at least N quantization parameters among QP_B, QP_C, QP_D, QP_E and QP_F or statistical values ​​of the at least N quantization parameters may be used to derive the predicted quantization parameter of the current quantization group. Here, N is a positive integer.

[0517] The N quantization parameters may be selected according to a specific order. The specific order may be an encoding / decoding order or an order of specific positions processed in an encoder / decoder. The specific order may represent the order of B, C, D, E, and F.

[0518] For example, as shown in Expression 23, the predicted quantization parameter of the current quantization group may be derived using statistical values ​​(eg, average values) of four quantization parameters QP_B, QP_C, QP_D, QP_E, and QP_F.

[0519] [Expression 23]

[0520] predcurQP=(QP_B+QP_C+QP_D+QP_E+2)>>2

[0521] Alternatively, a weighted average may be used to derive the predicted quantization parameter of the current quantization group. In this case, a weighting factor of at least one of QP_C, QP_D, and QP_F may be set to be smaller than a weighting factor of at least one of QP_B and QP_E.

[0522] exist Fig.13 In (c), A represents the current quantization group. Each of B, C, D, E and F may represent the position of a block or sample point from which a predicted quantization parameter is derived or the position of a neighboring quantization group located around the current quantization group. Here, the quantization parameter of the quantization group corresponding to at least one of the positions B, C, D, E and F may be used to derive the predicted quantization parameter of the current quantization group. The current quantization group A may have a non-square shape. The method for deriving the quantization parameter for a non-square quantization group may be similar to the method for deriving the quantization parameter for a square quantization group.

[0523] For example, position B can be represented as (x - (1 << minBlklog2size), y + curQGheight - (1 << minBlklog2size)). Position C can be represented as (x + curQGwidth - (1 << minBlklog2size), y - (1 << minBlklog2size)). Position D can be represented as (x + curQGwidth, y - (1 << minBlklog2size)). Position E can be represented as (x - (1 << minBlklog2size), y + curQGheight). Position F can be represented as (x - (1 << minBlklog2size), y - (1 << minBlklog2size)).

[0524] Optionally, position B can be represented as (x - 1, y + curQGheight - 1). Position C can be represented as (x + curQGwidth - 1, y - 1). Position D can be represented as (x + curQGwidth, y - 1). Position E can be represented as (x - 1, y + curQGheight). Position F can be represented as (x - 1, y - 1).

[0525] Here, position E can be outside the boundaries of the picture, sub - picture, slice, parallel block, parallel block group, parallel block, CTU line, CTU row, CTU column, or CTU where the current quantization group is located.

[0526] For example, since the quantization group corresponding to position E is outside the said boundaries, the quantization parameter of position E may not be used to derive the predicted quantization parameter. The quantization parameters existing at positions B, C, D, and F are represented as QP_B, QP_C, QP_D, and QP_F respectively.

[0527] At least one of QP_B, QP_C, QP_D, and QP_F or at least one of the statistical values of QP_B, QP_C, QP_D, and QP_F can be used to derive the predicted quantization parameter of the current quantization group.

[0528] For example, as shown in Expression 24, the average value of QP_B, QP_C, QP_D, and QP_F can be used to derive the predicted quantization parameter of the current quantization group.

[0529] [Expression 24]

[0530] predcurQP = (QP_B + QP_C + QP_D + QP_F + 2) >> 2

[0531] For example, since the quantization group corresponding to position E is located outside the boundary, the quantization parameter of position E may be replaced with the quantization parameter of the previous quantization group in the encoding / decoding order or with an advanced quantization parameter, and the replaced quantization parameter may be used. The quantization parameter of the previous quantization group in the encoding / decoding order or the advanced quantization parameter may be represented as QP_E. The quantization parameters present at positions B, C, D, and F are represented as QP_B, QP_C, QP_D, and QP_F, respectively.

[0532] On the other hand, at least N quantization parameters among QP_B, QP_C, QP_D, QP_E and QP_F or statistical values ​​of the at least N quantization parameters may be used to derive the predicted quantization parameter of the current quantization group. Here, N is a positive integer.

[0533] The N quantization parameters may be selected according to a specific order. The specific order may be an encoding / decoding order or an order of specific positions processed in an encoder / decoder. The specific order may represent the order of B, C, D, E, and F.

[0534] For example, as shown in Expression 25, the predicted quantization parameter of the current quantization group may be derived using statistical values ​​(eg, average values) of four quantization parameters QP_B, QP_C, QP_D, QP_E, and QP_F.

[0535] [Expression 25]

[0536] predcurQP=(QP_B+QP_C+QP_D+QP_E+2)>>2

[0537] Alternatively, a weighted average may be used to derive the predicted quantization parameter of the current quantization group. In this case, the weighting factor of QP_E may be set to be smaller than at least one of the weighting factors of QP_B, QP_C, QP_D, and QP_F.

[0538] Hereinafter, steps of encoding / decoding size information of a quantization group and / or information of a differential quantization parameter will be described below.

[0539] The size information of the quantization group may be entropy encoded in the encoder. Here, the size information of the quantization group may be entropy encoded to the bitstream at the level of a video parameter set (VPS), a sequence parameter set (SPS), an adaptation parameter set (APS), a picture parameter set (PPS), a sub-picture header, a slice header, a tile group header, a CTU line, a CTU row, a CTU column, a CTU or a block.

[0540] For example, the size of each unit or block for which the differential quantization parameter is signaled may be entropy encoded using at least one of the depth, length, area, ratio, shape, and sub-division of the size of the specified quantization group as shown in Table 2. Table 2 shows an example of the size of each unit or block for which the differential quantization parameter determined from the quantization group size determination information is signaled. Here, the size of each unit or block for which the differential quantization parameter is signaled may represent the size information of the quantization group.

[0541] As another example, the size information of the quantization group may be entropy-encoded using at least one of a ratio and a shape specifying the size of the quantization group.

[0542] The size information of the quantization group may be entropy encoded in the encoder. Here, the size information of the quantization group may be entropy decoded from the bitstream at the level of a video parameter set (VPS), a sequence parameter set (SPS), an adaptation parameter set (APS), a picture parameter set (PPS), a sub-picture header, a slice header, a tile group header, a CTU line, a CTU row, a CTU column, a CTU or a block.

[0543] For example, as shown in Table 2, the size of each unit or block for which the differential quantization parameter is signaled may be entropy decoded using at least one of the depth, length, area, ratio, shape, and sub-division that specifies the size of the quantization group. Here, the size of each unit or block for which the differential quantization parameter is signaled may represent size information of the quantization group.

[0544] As another example, the size information of the quantization group may be entropy-decoded using at least one of a ratio and a shape specifying the size of the quantization group.

[0545] [Table 2]

[0546]

[0547]

[0548]

[0549] The differential quantization parameter information may be entropy encoded in the encoder. At least one item of the differential quantization parameter information may be entropy encoded on at least one of a quantization group basis, a CU basis, a PU basis, a TU basis, and a block basis.

[0550] The differential quantization parameter information may be entropy decoded in a decoder. At least one item of the differential quantization parameter information may be entropy decoded on at least one of a quantization group basis, a CU basis, a PU basis, a TU basis, and a block basis.

[0551] At least one differential quantization parameter may be entropy encoded / decoded for each quantization group.

[0552] At least one differential quantization parameter may be entropy encoded / decoded for each quantization group by setting whether the differential quantization parameter is entropy encoded / decoded in the quantization group using a variable or flag such as IsCuDeltaQPCoded. That is, when the differential quantization parameter is entropy encoded / decoded in the quantization group, the flag or value IsCuDeltaQPCoded is set to a first value. Here, the first value may be 1. Depending on the shape of each quantization group in the quantization group, at least one differential quantization parameter may be entropy encoded / decoded for a corresponding one of the quantization groups.

[0553] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 1, when the block depth of the current block is 1 (i.e., the depth of the quadtree is 1 and the size is 32×32), the delta quantization parameter of the current block may be entropy encoded / encoded. That is, after the delta quantization parameter of the current block is entropy encoded / decoded, the flag or value IsCuDeltaQPCoded may be set to a first value. When diff_cu_qp_delta_depth is 1, the size of the quantization group may be set to 32×32.

[0554] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 1, when the block depth of the current block is 2 (i.e., the depth of the quadtree depth is 1 and the block size is 16×16), the differential quantization parameter may be entropy encoded / encoded for the first block of the blocks generated by partitioning at the same depth 1 as the depth information of the quantization group. After the differential quantization parameter for the current block is entropy encoded / entropy decoded, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter does not need to be entropy encoded / entropy decoded for the other blocks in the quantization group. Therefore, the blocks in one quantization group may share the same differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. When diff_cu_qp_delta_depth is 1, the size of the quantization group may be set to 32×32. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter. Furthermore, other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter.

[0555] For example, when the size of the CTU is 128×128 and diff_cu_qp_delta_depth is 1, when the block depth of the current block is 3 (i.e., the depth of the quadtree is 2, the depth of the binary tree is 1, and the size is 32×16), the delta quantization parameter of the current block may be entropy encoded / encoded. After entropy encoding / decoding the delta quantization parameter of the current block, the flag or value IsCuDeltaQPCoded may be set to a first value. In this case, the size of the quantization group may be set to the size of the current block.

[0556] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 3, when the block depth of the current block is 2 (i.e., the depth of the quadtree is 1, the depth of the binary tree is 1, and the size is 32×16), the delta quantization parameter of the current block may be entropy encoded / encoded. After entropy encoding / decoding the delta quantization parameter of the current block, the flag or value IsCuDeltaQPCoded may be set to a first value. In this case, the size of the quantization group may be set to the size of the current block.

[0557] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 3, when the block depth of the current block is 2 (i.e., the depth of the quadtree is 1, the depth of the multi-type tree is 1, and the block size is 32×16), the delta quantization parameter of the current block may be entropy encoded / encoded. After entropy encoding / decoding the delta quantization parameter of the current block, the flag or value IsCuDeltaQPCoded may be set to a first value. In this case, the size of the quantization group may be set to the size of the current block.

[0558] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 2, when the block depth of the current block is 3 (i.e., the depth of the quadtree depth is 1, the depth of the binary tree is 1, the depth of the ternary tree is 3, and the block size is 8×16), the differential quantization parameter may be entropy encoded / encoded for the first block of the blocks generated by partitioning at the same depth 2 as the depth information of the quantization group. After entropy encoding / decoding the differential quantization parameter for the current block, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameters for other blocks in the quantization group do not need to be entropy encoded / decoded. Therefore, blocks having a depth that is the same as or greater than the depth information of the quantization group may share the differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. The size of the quantization group may be set based on the quantization group depth information diff_cu_qp_delta_depth.

[0559] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 2, when the block depth of the current block is 3 (i.e., the depth of the quadtree depth is 1, the depth of the multi-type tree is 2, and the block size is 8×16), the differential quantization parameter may be entropy encoded / encoded for the first block of the blocks generated by partitioning at the same depth 1 as the depth information of the quantization group. After entropy encoding / decoding the differential quantization parameter for the current block, the variable or flag IsCuDeltaQPCoded may be set to a first value so that it is not necessary to entropy encode / decode the differential quantization parameters for other blocks in the quantization group. Therefore, blocks having a depth that is the same as or greater than the depth information of the quantization group may share the differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. The size of the quantization group may be set based on the quantization group depth information diff_cu_qp_delta_depth.

[0560] Further optionally, for example, when the size of the CTU is 32×32 and log2_diff_cu_qp_delta_length (quantization group length information) is 1, the size of the quantization group may be set to 16×16. When the size of the current block is 4×12, the differential quantization parameter for the first block in the quantization group may be entropy encoded / decoded. After the differential quantization parameter is entropy encoded / decoded, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameters for other blocks in the quantization group do not need to be entropy encoded / decoded. Therefore, the blocks in one quantization group may share the same differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter.

[0561] Further optionally, for example, when the size of the CTU is 128×128 and log2_diff_cu_qp_delta_length (quantization group length information) is 2, the size of the quantization group may be set to 32×32. When the size of the current block is 16×8, the differential quantization parameter for the first block in the quantization group may be entropy encoded / decoded. After the differential quantization parameter is entropy encoded / decoded, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameters for other blocks in the quantization group do not need to be entropy encoded / decoded. Therefore, the blocks in one quantization group may share the same differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter.

[0562] Further optionally, for example, when the size of the CTU is 32×32 and log2_diff_cu_qp_delta_length (quantization group length information) is 1, the size of the quantization group may be set to 16×16. When the size of the current block is 16×8, the differential quantization parameter for the first block in the quantization group may be entropy encoded / decoded. After the differential quantization parameter is entropy encoded / decoded, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameters for other blocks in the quantization group do not need to be entropy encoded / decoded. Therefore, the blocks in one quantization group may share the same differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter.

[0563] Further optionally, for example, when the size of the CTU is 64×64 and log2_diff_cu_qp_delta_length (quantization group length information) is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 32×16, the differential quantization parameter for the current block may be entropy encoded / decoded. When the maximum length (maximum value) of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, the size of the quantization group may be set to the size of the current block. Since the maximum length (maximum value) of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, after IsCuDeltaQPCoded is set to the first value, the differential quantization parameter for the current block is entropy encoded / decoded. When the size of the quantization group is within the size range of the current block, the size of the quantization group may be set to the size of the current block.

[0564] Further optionally, for example, when the size of the CTU is 256×256 and log2_diff_cu_qp_delta_length (quantization group length information) is 2, the size of the quantization group may be set to 32×32. When the size of the current block is 64×16, the differential quantization parameter for the current block may be entropy encoded / decoded. When the maximum length (maximum value) of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, the size of the quantization group may be set to the size of the current block. Since the maximum length of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, after IsCuDeltaQPCoded is set to the first value, the differential quantization parameter for the current block may be entropy encoded / decoded.

[0565] Further optionally, for example, when the size of the CTU is 32×32 and log2_diff_cu_qp_delta_length (quantization group length information) is 2, the size of the quantization group may be set to 8×8. When the size of the current block is 4×16, the differential quantization parameter for the current block may be entropy encoded / decoded. When the maximum length of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, the size of the quantization group may be set to the size of the current block. Since the maximum length of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, after IsCuDeltaQPCoded is set to the first value, the differential quantization parameter for the current block may be entropy encoded / decoded.

[0566] Further optionally, for example, when the size of the CTU is 32×32 and log4_diff_cu_qp_delta_area (quantization group area information) is 1, the size of the quantization group may be set to 16×16. When the size of the current block is 16×16, the differential quantization parameter for the current block may be entropy encoded / decoded.

[0567] Further optionally, for example, when the size of the CTU is 128×128 and log4_diff_cu_qp_delta_area (quantization group area information) is 2, the size of the quantization group may be set to 32×32. When the size of the current block is 16×16, the differential quantization parameter for the first block in the quantization group may be entropy encoded / decoded. After the differential quantization parameter is entropy encoded / decoded, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameters for other blocks in the quantization group do not need to be entropy encoded / decoded. Therefore, the blocks in one quantization group may share the same differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter.

[0568] Further optionally, for example, when the size of the CTU is 64×64 and log4_diff_cu_qp_delta_area (quantization group area information) is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 32×16, the differential quantization parameter for the current block may be entropy encoded / decoded. When the area of ​​the current block is larger than the area of ​​the quantization group, the size of the quantization group is set to the size of the current block. Since the maximum length of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, after IsCuDeltaQPCoded is set to the first value, the differential quantization parameter for the current block may be entropy encoded / decoded.

[0569] Here, the first block may refer to the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0570] In this case, the size of the quantization group may be set to the size of the current block.

[0571] Further optionally, for example, when the size of the CTU is 64×64 and log4_diff_cu_qp_delta_area (quantization group area information) is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 16×32, the differential quantization parameter for the current block may be entropy encoded / decoded. When the area of ​​the current block is larger than the area of ​​the quantization group, the size of the quantization group is set to the size of the current block. Since the maximum length of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, after IsCuDeltaQPCoded is set to the first value, the differential quantization parameter for the current block may be entropy encoded / decoded.

[0572] Further optionally, for example, when the size of the CTU is 32×32 and the ratio information specifying the size of the quantization group is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 4×12, the differential quantization parameter for the first block in the quantization group may be entropy encoded / decoded. After the differential quantization parameter is entropy encoded / decoded, the variable or flag IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameters for other blocks in the quantization group do not need to be entropy encoded / decoded. Therefore, the blocks in one quantization group may share the same differential quantization parameter. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter. In addition, the other blocks in the quantization group may determine their differential quantization parameters based on the differential quantization parameter.

[0573] Further optionally, for example, when the size of the CTU is 32×32 and the ratio information specifying the size of the quantization group is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 32×16, the differential quantization parameter for the current block may be entropy encoded / decoded. When the maximum length (maximum value) of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, the size of the quantization group may be set to the size of the current block. Since the maximum length of the horizontal length (width) and the vertical length (height) of the current block is longer than the length of the quantization group, after IsCuDeltaQPCoded is set to the first value, the differential quantization parameter for the current block may be entropy encoded / decoded.

[0574] When a predetermined condition is met, entropy encoding / decoding may not be performed on the differential quantization parameter for each quantization group. In this case, when the predetermined condition is met, IsCuDeltaQPCoded is set to 1, so that entropy encoding / decoding may not be performed on the differential quantization parameter. Here, the first value may be 1. The predetermined condition will be described below.

[0575] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 1, when the block depth of the current block is 2 (i.e., a block of size 16×16), since the depth of the current block is greater than the depth of the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / encoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / entropy decoded. In this case, a quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter for the current block. That is, without performing entropy encoding / entropy decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter for the current block as is. When diff_cu_qp_delta_depth is 1, the size of the quantization group may be set to 32×32.

[0576] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 1, when the block depth of the current block is 2 (i.e., the depth of the quadtree is 1, the depth of the binary tree is 1, and the block size is 32×16), since the depth of the current block is greater than the depth of the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / entropy encoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / entropy decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / entropy decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter for the current block as it is. The size of the quantization group may be set based on the quantization group depth information diff_cu_qp_delta_depth.

[0577] For example, when the size of the CTU is 64×64 and diff_cu_qp_delta_depth is 1, when the block depth of the current block is 2 (i.e., the depth of the quadtree is 1, the depth of the multi-type tree is 1, and the block size is 32×16), since the depth of the current block is greater than the depth of the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / entropy encoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / entropy decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / entropy decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as it is. The size of the quantization group may be set based on the quantization group depth information diff_cu_qp_delta_depth.

[0578] Further optionally, for example, when the size of the CTU is 128×128 and log2_diff_cu_qp_delta_length (quantization group length information) is 3, the size of the quantization group may be set to 16×16. When the size of the current block is 4×8, since the maximum length of the horizontal length and the vertical length of the current block is less than the length of the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0579] Further optionally, for example, when the size of the CTU is 32×32 and log2_diff_cu_qp_delta_length (quantization group length information) is 1, the size of the quantization group may be set to 16×16. When the size of the current block is 8×4, since the maximum length of the horizontal length and the vertical length of the current block is less than the length of the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0580] Further optionally, for example, when the size of the CTU is 128×128 and log4_diff_cu_qp_delta_area (quantization group area information) is 4, the size of the quantization group may be set to 8×8. When the size of the current block is 4×4, since the area of ​​the current block is smaller than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, entropy encoding / decoding may not be performed on the differential quantization parameters for other blocks in the quantization group. In this case, a quantization parameter may be derived from at least one of the neighboring quantization groups to determine the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0581] Further optionally, for example, when the size of the CTU is 64×64 and log4_diff_cu_qp_delta_area (quantization group area information) is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 16×8, since the area of ​​the current block is smaller than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0582] Further optionally, for example, when the size of the CTU is 32×32 and log4_diff_cu_qp_delta_area (quantization group area information) is 1, the size of the quantization group may be set to 16×16. When the size of the current block is 32×4, since the area of ​​the current block is smaller than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0583] Further optionally, for example, when the size of the CTU is 64×64 and log4_diff_cu_qp_delta_area (quantization group area information) is 2, the size of the quantization group may be set to 16×16. When the size of the current block is 8×16, since the area of ​​the current block is smaller than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0584] Further optionally, for example, when the size of the CTU is 32×32 and log4_diff_cu_qp_delta_area (quantization group area information) is 1, the size of the quantization group may be set to 16×16. When the size of the current block is 4×32, since the area of ​​the current block is smaller than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value so that the differential quantization parameter for the current block may not be entropy encoded / decoded. In this case, since IsCuDeltaQPCoded is set to the first value, the differential quantization parameters for other blocks in the quantization group may not be entropy encoded / decoded. In this case, the quantization parameter may be derived from at least one of the neighboring quantization groups, and the derived quantization parameter may be determined as the quantization parameter of the current block. That is, without performing entropy encoding / decoding on the differential quantization parameter, the predicted quantization parameter may be used as the quantization parameter of the current block as is.

[0585] Further optionally, for example, according to a predetermined priority among depth information, length information, area information, ratio information, and shape information of a quantization group, entropy encoding / decoding may not be performed on the differential quantization parameter.

[0586] The following will refer to Figures 14 to 23 A method for efficiently signaling a differential quantization parameter using quantization group size information in a block structure where non-square blocks (eg, M×N blocks) exist is described in detail. Figures 14 to 23 In , M and N are positive integers and can have different values.

[0587] Fig.14 2 is a diagram illustrating encoding / decoding orders for a case where a CU has a square shape and a case where the CU has a non-square shape according to an embodiment of the present invention.

[0588] The size of the quantization group may be determined based on size information, depth information, length information, area information, ratio information, shape information, and sub-division information of the quantization group. In this embodiment and / or other embodiments of the present invention, the area may represent a region.

[0589] For example, the size of the quantization group may be determined using depth information diff_cu_qp_delta_depth of the quantization group, and whether to signal a delta quantization parameter may be determined according to the depth information of the quantization group and a depth value of the current M×N block.

[0590] As another example, the size of the quantization group may be determined using log2_diff_cu_qp_delta_length as length information of the quantization group, and whether to signal a differential quantization parameter may be determined based on the length information of the quantization group and a statistical value of a minimum or maximum value among the horizontal length (M) and vertical length (N) of the current M×N block.

[0591] As another example, the size of the quantization group may be determined using log4_diff_cu_qp_delta_area as area information of the quantization group, and whether to signal a differential quantization parameter may be determined based on the area information of the quantization group and the product of the horizontal length (M) and the vertical length (N) of the current M×N block.

[0592] As another example, the size of the quantization group may be determined using sub-division information cu_qp_delta_subdiv of the quantization group, and whether to signal a delta quantization parameter may be determined by comparing the sub-division information of the quantization group with CbSubdiv which is a sub-division value of a currently encoded / decoded block.

[0593] The delta quantization parameter may be signaled for a block generated from a quadtree partition, a binary tree partition, or a ternary tree partition. Whether to signal the delta quantization parameter may be determined by comparing the depth of the block with diff_cu_qp_delta_depth, which is quantization depth information.

[0594] For example, the quantization parameter may be signaled when the depth of the block is less than or equal to the quantization depth information.

[0595] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and depth information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0596] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape. When the current block is a block generated from multi-type tree partitioning, the shape of the quantization group for the current block may be a non-square shape.

[0597] As another example, when the depth of the block is greater than the depth information of the quantization group, the quantization parameter may be signaled from the first block of the blocks generated by the partition. The other blocks generated by the partition except the first block may share the differential quantization parameter of the first block. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. The depth of the block may be at least one of the depth of the binary tree or the depth of the ternary tree, or may be the sum of at least one of the depths of the tree. The depth of the block may be at least one of the depth of the binary tree and the depth of the ternary tree or the sum of at least two of the depths of the tree.

[0598] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, depth information of the quantization group, a size of the current block, and a size of at least one of the parent nodes of the current block. The size of the quantization group for the current block may be set equal to a size of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group.

[0599] The shape of the quantization group for the current block may be the same as the shape of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group. The quantization group for the current block may have a non-square shape.

[0600] As another example, a differential quantization parameter may be signaled for each quadtree block. That is, a differential quantization parameter may not be signaled for a binary tree block or a ternary tree block. A binary tree block or a ternary tree block may use a differential quantization parameter signaled for a quadtree block. A binary tree block or a ternary tree block may share a differential quantization parameter signaled for a quadtree block. Alternatively, a quantization parameter of a binary tree block or a ternary tree block may be determined based on a quantization parameter of a quadtree block. Alternatively, a quantization parameter of a quadtree block may be determined as a quantization parameter of a binary tree block or a ternary tree block.

[0601] As another example, the quantization parameter may be signaled when the depths of the quadtree block and the binary tree block are less than or equal to the quantization depth information.

[0602] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and depth information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0603] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape. When the current block is a block generated from binary tree partitioning, the shape of the quantization group for the current block may have a non-square shape.

[0604] As another example, when the depth of the block generated by binary tree partitioning is greater than the depth of the quantization group, a differential quantization parameter may be signaled for only one of the two blocks. The other block may share the differential quantization parameter signaled. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. The only one block may be the first block of the two blocks generated by binary tree partitioning. Here, the first block may represent the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0605] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, depth information of the quantization group, a size of the current block, and a size of at least one of the parent nodes of the current block. The size of the quantization group for the current block may be set equal to a size of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group.

[0606] The shape of the quantization group for the current block may be the same as the shape of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group. The quantization group for the current block may have a non-square shape.

[0607] As another example, when the depth of a block generated by quadtree partitioning or ternary tree partitioning is less than or equal to the quantization depth information, a differential quantization parameter may be signaled.

[0608] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and depth information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0609] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape. When the current block is a block generated from ternary tree partitioning, the shape of the quantization group for the current block may be a non-square shape.

[0610] As another example, when the depth of the blocks generated by ternary tree partitioning is greater than the depth of the quantization group, the differential quantization parameter may be signaled for only one of the three blocks. The other blocks may share the differential quantization parameter signaled. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. The only one block may be the first of the two blocks generated by ternary tree partitioning. The only one block may be the block with the largest area among the three blocks generated by ternary tree partitioning.

[0611] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, depth information of the quantization group, a size of the current block, and a size of at least one of the parent nodes of the current block. The size of the quantization group for the current block may be set equal to a size of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group.

[0612] The shape of the quantization group for the current block may be the same as the shape of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group. The quantization group for the current block may have a non-square shape.

[0613] As another example, when the depth of a block generated by quadtree partitioning or multi-type tree partitioning is less than or equal to quantization depth information, a differential quantization parameter may be signaled.

[0614] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and depth information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0615] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape. When the current block is a block generated from multi-type tree partitioning, the shape of the quantization group for the current block may be a non-square shape.

[0616] As another example, when the depth of a block generated by quadtree partitioning or multi-type partitioning is greater than the depth of a quantization group, a differential quantization parameter may be signaled for only one of the two or more blocks. The other blocks may share the differential quantization parameter signaled. Since the blocks in a quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in a quantization group. The only one block may be the first block of the two or more blocks generated by partitioning. The only one block may be the block with the largest area of ​​the two or more blocks generated by partitioning. The only one block may be the block with the smallest area of ​​the two or more blocks generated by partitioning.

[0617] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, depth information of the quantization group, a size of the current block, and a size of at least one of the parent nodes of the current block. The size of the quantization group for the current block may be set equal to a size of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group.

[0618] The shape of the quantization group for the current block may be the same as the shape of at least one of the parent nodes of the current block corresponding to the depth information of the quantization group. The quantization group for the current block may have a non-square shape.

[0619] The delta quantization parameter may be signaled for a block generated from quadtree partitioning, binary tree partitioning, or ternary tree partitioning. Whether to signal the delta quantization parameter may be determined by comparing the area of ​​the block with the size of the quantization group set according to diff_cu_qp_delta_area, which is area information of the quantization group.

[0620] For example, when the area of ​​the block is less than or equal to the size of the quantization group, a differential quantization parameter may be signaled.

[0621] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and area information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0622] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape. When the current block is a block generated from multi-type tree partitioning, the shape of the quantization group for the current block may be a non-square shape.

[0623] As another example, when the area of ​​a block generated by binary tree partitioning is larger than the size of the quantization group, a differential quantization parameter may be signaled for only one of the two blocks generated from the binary tree partitioning. A quantization parameter for the other block may be determined based on the signaled differential quantization parameter.

[0624] As another example, when the area of ​​the block is less than the size of the quantization group, the quantization parameter may be signaled from the first block of the blocks generated by the partition. Blocks other than the first block generated from the partition may share the differential quantization parameter of the first block. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. Here, the area of ​​the block may be the area of ​​a quadtree or the area of ​​a multi-type tree.

[0625] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, area information of the quantization group, an area of ​​the current block, and a size of at least one of the parent nodes of the current block. The size of the quantization group for the current block may be set equal to a size of at least one of the parent nodes of the current block corresponding to the area information of the quantization group.

[0626] The shape of the quantization group for the current block may be the same as the shape of at least one of the parent nodes corresponding to the area information of the quantization group of the current block. The quantization group for the current block may have a non-square shape.

[0627] As another example, when the area of ​​the block generated from the ternary tree partition is less than the size of the quantization group, the differential quantization parameter may be signaled for only one of the three blocks having the largest area. The other blocks may share the signaled differential quantization parameter. As another example, when the area of ​​the block generated from the ternary tree partition is less than the size of the quantization group, the differential quantization parameter may be signaled for only one of the three blocks having the smallest area. The other blocks may share the differential quantization parameter of the block having the smallest area.

[0628] On the other hand, the shape of the current block being encoded / decoded may be a quadtree, a binary tree, or a ternary tree. When the shape is a quadtree, the area difference diff_cur_block_area_minus4 between quadtree blocks may be obtained by Expression 26.

[0629] [Expression 26]

[0630] diff_cur_block_area_minus4=2*log2_ctu_size_minus2-log2_current_block_area_minus4

[0631] In Expression 26, log2_ctu_size_minus2 represents a value obtained by performing a log2 function on the maximum CTU size and then subtracting 2 from the result of the log2 function. log2_current_block_area_minus4 is a value obtained by performing a log2 function on the product of the horizontal length and the vertical length of the current block and subtracting 4 from the result of the log2 function.

[0632] For example, when the current block is a block generated from quadtree partitioning, in the case where diff_cur_block_area_minus4 is less than or equal to the area information of the quantization group, a differential quantization parameter may be signaled.

[0633] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and area information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0634] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape.

[0635] For example, when the current block is a block generated from binary tree partitioning, in the case where diff_cur_block_area_minus4 is less than or equal to the area information of the quantization group, a differential quantization parameter may be signaled.

[0636] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and area information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0637] When the current block is a block generated from binary tree partitioning, the shape of a quantization group for the current block may have a non-square shape.

[0638] For example, when the current block is a block generated from ternary tree partitioning, in the case where diff_cur_block_area_minus4 is less than or equal to the area information of the quantization group, a differential quantization parameter may be signaled.

[0639] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information about whether to signal the differential quantization parameter, and area information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0640] When the current block is a block generated from ternary-tree partitioning, the shape of a quantization group for the current block may be a non-square shape.

[0641] For example, when the current block is a block generated from ternary tree partitioning, in the case where diff_cur_block_area_minus4 is greater than the area information of the quantization group, the differential quantization parameter may be signaled from the first block of the blocks generated from the ternary tree partitioning. In this case, in the case of a middle block among the three blocks generated from the ternary tree partitioning, even if diff_cur_block_area_minus4 is less than or equal to the area information of the quantization group, the differential quantization parameter may not be signaled but may be predicted or derived from an already encoded / decoded block. In the case of the last block among the three blocks generated from the ternary tree partitioning, the differential quantization parameter may not be signaled but may be predicted or derived from an already encoded / decoded block.

[0642] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and area information of the quantization group.

[0643] When the current block is a block generated from ternary-tree partitioning, the shape of a quantization group for the current block may be a non-square shape.

[0644] For example, when the current block is a block generated from ternary tree partitioning, in the case where diff_cur_block_area_minus4 is greater than the area information of the quantization group, the differential quantization parameter may be signaled from the first block of the blocks generated from the ternary tree partitioning. In this case, in the case of a middle block among the three blocks generated from the ternary tree partitioning, even if diff_cur_block_area_minus4 is less than or equal to the area information of the quantization group, the differential quantization parameter may not be signaled. In the case of the last block among the three blocks generated from the ternary tree partitioning, the differential quantization parameter may not be signaled but may be predicted or derived from a block that has already been encoded / decoded.

[0645] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and area information of the quantization group.

[0646] When the current block is a block generated from ternary-tree partitioning, the shape of a quantization group for the current block may be a non-square shape.

[0647] The delta quantization parameter may be signaled for a block generated from quadtree partitioning, binary tree partitioning, or ternary tree partitioning. Whether to signal the delta quantization parameter may be determined by comparing a sub-division value of the block with diff_cu_qp_delta_subdiv as sub-division information of a quantization group.

[0648] For example, the differential quantization parameter may be signaled when the sub-division value of the current block is less than or equal to the sub-division information of the quantization group.

[0649] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and sub-division information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0650] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape. When the current block is a block generated from multi-type tree partitioning, the shape of the quantization group for the current block may be a non-square shape.

[0651] As another example, when the sub-division value of the block is greater than the sub-division information of the quantization group, the quantization parameter may be signaled from the first block of the blocks generated by the partition. Blocks other than the first block generated from the partition may share the differential quantization parameter of the first block. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group. Here, the area of ​​the block may be the area of ​​a quadtree or the area of ​​a multi-type tree.

[0652] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, sub-division information of the quantization group, a sub-division value of the current block, and a size of at least one of the parent nodes of the current block. The size of the quantization group for the current block may be set equal to a size of at least one of the parent nodes of the current block corresponding to the sub-division information of the quantization group.

[0653] The shape of the quantization group for the current block may be the same as the shape of at least one of the parent nodes corresponding to the sub-division information of the quantization group of the current block. The quantization group for the current block may have a non-square shape.

[0654] On the other hand, a sub-division value may be assigned to each block and may be used together with a depth value of the block.

[0655] Furthermore, the sub-division values ​​may be calculated in the manner described below.

[0656] The shape of the current block may be at least one of a quadtree, a binary tree, or a ternary tree, and the current block may be partitioned into a quadtree form, a binary tree form, or a ternary tree form.

[0657] For example, when the current block is partitioned in a quadtree form, the sub-division value of each sub-block generated from the quadtree partitioning may be set to a value obtained by adding 2 to the sub-division value of the current block.

[0658] As another example, when the current block is partitioned in a binary tree form, the sub-partition value of each sub-block generated from the binary tree partitioning may be set to a value obtained by adding 1 to the sub-partition value of the current block.

[0659] As another example, when the current block is partitioned into a ternary tree form, the sub-division value of each of the left sub-block and the right sub-block of the three sub-blocks generated from the ternary tree partitioning may be set to a value obtained by adding 2 to the sub-division value of the current block, and the sub-division value of the middle sub-block of the three sub-blocks generated from the ternary tree partitioning may be set to a value obtained by adding 1 to the sub-division value of the current block.

[0660] As another example, when the current block is partitioned into a ternary tree form, whether to signal a differential quantization parameter can be determined by comparing the sub-division information of the quantization group with a value obtained by adding 2 to the sub-division value of the current block that has not yet been partitioned (hereinafter, also referred to as the original sub-division value).

[0661] As another example, when the current block is a block generated from quadtree partitioning, in case a sub-division value of the current block is less than or equal to sub-division information of a quantization group, a differential quantization parameter may be signaled.

[0662] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and sub-division information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0663] When the current block is a block generated from quadtree partitioning, the shape of the quantization group for the current block may be a square shape.

[0664] As another example, when the current block is a block generated from binary tree partitioning, in case a sub-division value of the current block is less than or equal to sub-division information of a quantization group, a differential quantization parameter may be signaled.

[0665] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and sub-division information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0666] When the current block is a block generated from binary tree partitioning, the shape of a quantization group for the current block may have a non-square shape.

[0667] As another example, when the current block is a block generated from ternary tree partitioning, in case a sub-division value of the current block is less than or equal to sub-division information of a quantization group, a differential quantization parameter may be signaled.

[0668] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and sub-division information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0669] When the current block is a block generated from ternary-tree partitioning, the shape of a quantization group for the current block may be a non-square shape.

[0670] As another example, when the current block is a block generated from ternary tree partitioning, in the case where the sub-division value of the current block is greater than the sub-division information of the quantization group, the differential quantization parameter may be signaled from the first block of the blocks generated from the partitioning. In this case, in the case of a middle block among the three blocks generated from the ternary tree partitioning, even if the sub-division value of the block is less than or equal to the sub-division information of the quantization group, the differential quantization parameter may not be signaled, but may be predicted or derived from a block that has already been encoded / decoded. In the case of the last block among the three blocks generated from the ternary tree partitioning, the differential quantization parameter may not be signaled, but may be predicted or derived from a block that has already been encoded / decoded.

[0671] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and sub-division information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0672] When the current block is a block generated from ternary-tree partitioning, the shape of a quantization group for the current block may be a non-square shape.

[0673] As another example, when the current block is a block generated from ternary tree partitioning, in the case where the sub-division value of the block is greater than the sub-division information of the quantization group, the delta quantization parameter may be signaled from the first block of the blocks generated from the partitioning. In the case of a middle block among three blocks generated from the ternary tree partitioning, the delta quantization parameter may be signaled even if cu_qp_delta_subdiv is less than or equal to the sub-division information of the quantization group. In the case of the last block among three blocks generated from the ternary tree partitioning, the delta quantization parameter may not be signaled but may be predicted or derived from a block that has already been encoded / decoded.

[0674] Here, the size of the quantization group for the current block may be set according to at least one of a differential quantization parameter utilization flag, information on whether to signal the differential quantization parameter, and sub-division information of the quantization group. In this case, the size of the quantization group for the current block may be set equal to the size of the current block.

[0675] When the current block is a block generated from ternary-tree partitioning, the shape of a quantization group for the current block may be a non-square shape.

[0676] On the other hand, the differential quantization parameter may be signaled on a per transform unit (TU) basis, on a per block basis, or on a per coding unit (CU) basis. The size of the TU may be equal to the size of the CU. Alternatively, the size of the TU may be smaller than the size of the CU.

[0677] Here, the first block may refer to the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0678] In addition, the differential quantization parameter utilization flag may be cu_qp_delta_enabled_flag.

[0679] Furthermore, whether to signal the delta quantization parameter may be at least one of cu_qp_delta_enabled_flag and IsCuDeltaQPCoded.

[0680] The differential quantization parameter may be signaled according to the size of the CTU, diff_cu_qp_delta_depth as depth information of the quantization group, log2_diff_cu_qp_delta_length as length information of the quantization group, diff_cu_qp_delta_area as area information of the quantization group, cu_qp_delta_subdiv as sub-division information of the quantization group, and / or the size of the quantization group.

[0681] Hereinafter, an embodiment of signaling a differential quantization parameter will be described in more detail for a case where the size of a CTU is 128×128 and diff_cu_qp_delta_depth as depth information of a quantization group is 2. In this case, the size of the quantization group may be set to the size of the current block.

[0682] For example, when the current block is partitioned by quadtree partitioning twice and by binary tree partitioning once, the current block may have a depth of 3 and a size of 32×16 or 16×32. When the depth information of the quantization group is 2, since the depth information of the quantization group is less than or equal to the depth of the current block, a differential quantization parameter for the first block of the blocks generated from the binary tree partitioning may be signaled. In addition, the differential quantization parameter of the first block may be shared by other blocks of the block having a depth of 2 generated from the binary tree partitioning. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group.

[0683] As another example, when the current block is partitioned by one quadtree partitioning, the current block may have a depth of 1 and a size of 64×64. When the depth information of the quantization group is 2, since the depth information of the quantization group is greater than the depth of the current block, a differential quantization parameter for the current block may be signaled.

[0684] As another example, when the current block is partitioned by one quadtree partition, one binary tree partition, and one ternary tree partition, the current block may have a depth of 3 and a size of 16×32 or 32×16. When the depth information of the quantization group is 2, since the depth information of the quantization group is less than or equal to the depth of the current block, a differential quantization parameter for the first block of the blocks with a depth of 2 generated from the ternary tree partition may be signaled. The differential quantization parameter for the first block may be shared by other blocks of the blocks with a depth of 2 generated from the ternary tree partition. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group.

[0685] As another example, when the current block is partitioned by quadtree partitioning once and by multi-type tree partitioning twice, the current block may have a depth of 3 and a size of 16×16. When the depth information of the quantization group is 2, since the depth information of the quantization group is less than or equal to the depth of the current block, a differential quantization parameter for the first block of the blocks with a depth of 2 generated from the multi-type tree partitioning may be signaled. The differential quantization parameter for the first block may be shared by other blocks of the blocks with a depth of 2 generated from the multi-type tree partitioning. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group.

[0686] As another example, when the current block is partitioned by three quadtree partitions and once by ternary tree partitions, the current block may have a depth of 4 and a size of 4×16. When the depth information of the quantization group is 2, since the depth information of the quantization group is less than or equal to the depth of the current block, a differential quantization parameter for the first block of the blocks generated from the quadtree partition may be signaled. The differential quantization parameter of the first block may be shared by other blocks of the block having a depth of 2 generated from the binary tree partition. Since the blocks in one quantization group use the same predicted quantization parameter, the same quantization parameter may also be shared by the blocks in one quantization group.

[0687] When the depth information of the current block is greater than the depth information of the quantization group, the depth information of the quantization group may be set as a basic unit based on which encoding / decoding is performed. The size of the quantization group may be set using the depth information of the quantization group.

[0688] When the depth information of the current block is equal to or less than the depth information of the quantization group, the current block may be set as a basic unit based on which encoding / decoding is performed. The size of the current block may be set as the size of the quantization group.

[0689] The current block may be partitioned in the order of quadtree partitioning, binary tree partitioning, and ternary tree partitioning.

[0690] Here, the first block may refer to the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0691] Hereinafter, for a case where the size of a CTU is 128×128 and log2_diff_cu_qp_delta_length as length information of a quantization group is 2, an embodiment of signaling a differential quantization parameter will be described in more detail. In this case, the size of the quantization group may be determined to be 32×32. That is, as shown in Table 3, the horizontal length or the vertical length of the quantization group may be determined to be 32, and the size of the quantization group may be determined to be 32×32.

[0692] [Table 3]

[0693]

[0694] For example, when the size of the current block generated from the binary tree partition is 32×64, since the maximum length of the horizontal length and the vertical length of the current block is greater than the length of the quantization group, the differential quantization parameter for the current block can be sent by signal. In this case, the size of the quantization group can be set to the size of the current block.

[0695] As another example, when the size of the current block generated from the vertical ternary tree partition is 24×32, since the maximum length of the horizontal length and the vertical length of the current block is greater than the length of the quantization group, the differential quantization parameter for the current block may be sent by signal. In this case, the size of the quantization group may be set to the size of the current block. For an 8×32 block adjacent to the current block and generated from a binary tree partition of the same parent node as the current block, the differential quantization parameter may not be sent by signal. The 8×32 block may use the differential quantization parameter of the current block as is. That is, the quantization parameter may be shared by the 24×32 block and the 8×32 block. In another case, that is, for an 8×32 block adjacent to the current block and generated from a binary tree partition of the same parent node as the current block, the differential quantization parameter may not be sent by signal. The differential quantization parameter for the 8×32 block may be determined based on the differential quantization parameter of the current block.

[0696] As another example, when the size of the current block is 32×16, since the maximum length of the horizontal length and the vertical length of the current block is greater than the length of the quantization group, the differential quantization parameter for the current block may be sent by signal. In this case, the size of the quantization group may be set to the size of the current block. In this case, for a 32×16 block adjacent to the current block and generated from a binary tree partition of the same parent node as the current block, the differential quantization parameter may not be sent by signal. The 32×16 block and the current block may share the same differential quantization parameter. That is, the quantization parameter may be shared by two blocks of size 32×16. In another case, that is, for a 32×16 block adjacent to the current block and generated from a binary tree partition of the same parent node as the current block, the differential quantization parameter may not be sent by signal. The 32×16 block and the current block may share the same differential quantization parameter.

[0697] As another example, when the size of the current block generated from the horizontal ternary tree partition is 16×64, since the maximum length of the horizontal length and the vertical length of the current block is greater than the length of the quantization group, the differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0698] As another example, when the size of the current block generated from the vertical ternary tree partition is 8×32, since the maximum length of the horizontal length and the vertical length of the current block is greater than the length of the quantization group, the differential quantization parameter for the current block may be sent by signal. In this case, the size of the quantization group may be set to the size of the current block. For 8×32 blocks and 16×32 blocks adjacent to the current block and generated from the ternary tree partition of the same parent node as the current block, the differential quantization parameter may not be sent by signal. These blocks may share the differential quantization parameter of the current block. That is, the quantization parameter may be shared by two 8×32 blocks and one 16×32 block. In another case, that is, for 16×32 blocks and 8×32 blocks adjacent to the current block and generated from the ternary tree partition of the same parent node as the current block, the differential quantization parameter may not be sent by signal. The differential quantization parameter may be determined based on the differential quantization parameter of the current block.

[0699] When a maximum length among a horizontal length and a vertical length of the current block is greater than a length of the quantization group, the size of the quantization group may be set to the size of the current block.

[0700] Also, when the maximum length of the horizontal length and the vertical length of the current block is equal to the length of the quantization group, the size of the quantization group may be set according to log2_diff_cu_qp_delta_length, which is the length information of the quantization group.

[0701] In addition, when the maximum length of the horizontal length and the vertical length of the current block has a predetermined relationship with the length of the quantization group, the size of the quantization group may be set according to log2_diff_cu_qp_delta_length as the length information of the quantization group. For example, the predetermined relationship may be one of multiples of 2.

[0702] Hereinafter, for a case where the size of a CTU is 128×128 and diff_cu_qp_delta_area as area information of a quantization group is 3, an embodiment of signaling a differential quantization parameter will be described in more detail. As shown in Table 4, the area of ​​a quantization group may be 2 11 .

[0703] [Table 4]

[0704]

[0705] For example, when the size of the current block generated from the quadtree partition is 64×64, the area difference value diff_cur_block_area_minus4 of the current block may be 2. At this time, since the area difference value is less than or equal to the area information of the quantization group, the differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0706] As another example, when the size of the current block generated from the quadtree partition is 32×32, the area difference value diff_cur_block_area_minus4 of the current block may be 4. At this time, since the area difference value is less than or equal to the area information of the quantization group, the differential quantization parameter for the first block in the blocks generated from the quadtree partition may be signaled. The other blocks may use the differential quantization parameter signaled from the first block. In this case, the size of the quantization group may be set to 64×64, which is the size of the parent block of the current block.

[0707] As another example, when the size of the current block generated from the binary tree partition is 32×64, the area difference value diff_cur_block_area_minus4 of the current block may be 3. At this time, since the area difference value is less than or equal to the area information of the quantization group, the differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0708] As another example, when the size of the current block generated from the binary tree partition is 32×16, the area difference value diff_cur_block_area_minus4 of the current block may be 5. In this case, since the area difference value is greater than the area information of the quantization group, a differential quantization parameter for the first block in the blocks generated from the binary tree partition may be signaled. The other blocks may share the differential quantization parameter of the first block. In this case, the size of the quantization group is 32×32, which is the size of the first parent block of the current block. That is, the size of the quantization group is greater than the area information of the quantization group. Therefore, the size of the quantization group may be set to 64×64, which is the second parent block.

[0709] As another example, when the size of the current block generated from the ternary tree partition is 16×64, the area difference value diff_cur_block_area_minus4 of the current block may be 4. In this case, since the area difference value is greater than the area information of the quantization group, when the current block is the first block among the blocks generated from the ternary tree partition, the differential quantization parameter may be signaled. Other blocks of size 16×64 may use the differential quantization parameter of the first block. In the case of an intermediate block of size 32×64, the area difference value of the intermediate block is 3. That is, the area difference value is less than or equal to the area information of the quantization group. However, since whether to signal the differential quantization parameter for the intermediate block is determined based on whether to signal the differential quantization parameter for the first block among the blocks generated from the ternary tree partition, the differential quantization parameter for the intermediate block may not be signaled, and the differential quantization parameter for another block within the same quantization group may be shared.

[0710] As another example, when the size of the current block generated from the ternary tree partition is 64×32, the area difference value diff_cur_block_area_minus4 of the current block may be 3. In this case, since the area difference value is less than or equal to the area information of the quantization group, a differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0711] When the area information of the current block is smaller than the area information of the quantization group, the current block may be set as a basic unit based on which encoding / decoding is performed. The size of the current block may be set to the size of the quantization group.

[0712] The current block may be partitioned by quadtree partitioning, binary tree partitioning, and ternary tree partitioning in the order of quadtree partitioning, binary tree partitioning, and ternary tree partitioning.

[0713] Here, the first block may refer to the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0714] Hereinafter, an embodiment of signaling a differential quantization parameter will be described in more detail for a case where the size of a CTU is 128×128 and diff_cu_qp_delta_subdiv as sub-division information of a quantization group is 3. In this embodiment, a sub-division value cbSubdiv of a current block to be encoded / decoded may be used.

[0715] For example, when the size of the current block generated from the quadtree partition is 64×64, the sub-division value cbSubdiv of the current block may be 2. In this case, since the sub-division value of the current block is less than or equal to the sub-division information of the quantization group, a differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0716] As another example, when the size of the current block generated from the quadtree partition is 32×32, the sub-division value cbSubdiv of the current block may be 4. In this case, since the sub-division value is greater than the sub-division information of the quantization group, a differential quantization parameter for the first block of the blocks generated from the quadtree partition may be signaled. The other blocks may use the differential quantization parameter signaled from the first block. In this case, the size of the quantization group may be set to 64×64, which is the size of the parent block of the current block.

[0717] As another example, when the size of the current block generated from the binary tree partition is 32×64, the sub-division value cbSubdiv of the current block may be 3. In this case, since the sub-division value is equal to the sub-division information of the quantization group, a differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0718] As another example, when the size of the current block generated from the binary tree partition is 32×16, the sub-division value cbSubdiv of the current block may be 5. In this case, since the sub-division value is greater than the sub-division information of the quantization group, a differential quantization parameter for the first block in the blocks generated from the binary tree partition may be signaled. The other blocks may share the differential quantization parameter of the first block. In this case, the size of the quantization group is 32×32, which is the size of the first parent block of the current block. That is, the size of the quantization group is greater than the area information of the quantization group. Therefore, the size of the quantization group may be set to 64×64, which is the second parent block.

[0719] As another example, when the size of the current block generated from the ternary tree partition is 16×64, the sub-division value cbSubdiv of the current block may be 4. In this case, since the sub-division value is greater than the sub-division information of the quantization group, when the current block is the first block among the blocks generated from the ternary tree partition, the differential quantization parameter may be signaled. Other blocks of size 16×64 may use the differential quantization parameter of the first block. In the case of the middle block, it has a size of 32×64. Therefore, the sub-division value of the middle block is 3. That is, the sub-division value of the middle block is less than or equal to the sub-division information of the quantization group. However, since whether to signal the differential quantization parameter for the middle block is determined based on whether to signal the differential quantization parameter for the first block among the blocks generated from the ternary tree partition, the differential quantization parameter for the middle block may not be signaled, and the differential quantization parameter for another block within the same quantization group may be shared.

[0720] As another example, when the size of the current block generated from the ternary tree partition is 64×32, the sub-division value cbSubdiv of the current block may be 3. In this case, since the sub-division value of the current block is less than or equal to the sub-division information of the quantization group, a differential quantization parameter for the current block may be signaled. In this case, the size of the quantization group may be set to the size of the current block.

[0721] When sub-division information of the current block is smaller than sub-division information of the quantization group, the current block may be set as a basic unit based on which encoding / decoding is performed. The size of the current block may be set to the size of the quantization group.

[0722] The current block may be partitioned in the order of quadtree partitioning, binary tree partitioning, and ternary tree partitioning.

[0723] Here, the first block may refer to the first block in which the coded block flag in the block is not the first value. Here, the first value may be 0.

[0724] Fig.15 2 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 256×256 and diff_cu_qp_delta_depth is 2. Fig.15 , each block for which a differential quantization parameter is signaled is shown in grey, and each quantization group is bounded by a thick solid line.

[0725] Fig.16 2 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 256×256 and log2_diff_cu_qp_delta_length is 1. Fig.16, each block for which a differential quantization parameter is signaled is colored grey, and each quantization group is bounded by a thick solid line.

[0726] Fig.17 2 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 128×128 and diff_cu_qp_delta_depth is 2. Fig.17 , each block for which a differential quantization parameter is signaled is colored grey, and each quantization group is bounded by a thick solid line.

[0727] Fig.18 2 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 128×128 and log2_diff_cu_qp_delta_length is 2. Fig.18 , each block for which a differential quantization parameter is signaled is colored grey, and each quantization group is bounded by a thick solid line.

[0728] Fig.19 2 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and log2_diff_cu_qp_delta_length is 3. Fig.19 , each block for which a differential quantization parameter is signaled is shown in grey, and each quantization group is bounded by a thick solid line.

[0729] Fig. 20 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and diff_cu_qp_delta_area is 3. Fig. 20 , each block for which a differential quantization parameter is signaled is shown in grey, and each quantization group is bounded by a thick solid line.

[0730] Fig.21 is a diagram showing blocks for each of which a differential quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and diff_cu_qp_delta_area is 4. Fig.21 , each block for which a differential quantization parameter is signaled is shown in grey, and each quantization group is bounded by a thick solid line.

[0731] Fig. 22is a diagram showing blocks for each of which a delta quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and cu_qp_delta_subdiv is 3. Fig. 22 , each block for which a differential quantization parameter is signaled is shown in grey, and each quantization group is bounded by a thick solid line.

[0732] Fig.23 is a diagram showing blocks for each of which a delta quantization parameter is signaled and various quantization groups that can be set when the size of a CTU is 64×64 and cu_qp_delta_subdiv is 4. Fig.23 , each block for which a differential quantization parameter is signaled is shown in grey, and each quantization group is bounded by a thick solid line.

[0733] Fig.24 is a diagram illustrating a method of determining a quantization parameter using length information of a quantization group according to an embodiment of the present invention.

[0734] In step S2401, cu_qp_delta_enabled_flag may be entropy encoded / decoded. When cu_qp_delta_enabled_flag is the first value ( Fig.24 , the delta quantization parameter may not be entropy encoded / decoded. On the other hand, when cu_qp_delta_enabled_flag is the second value ( Fig.24 When the parameter “No” is used in the answer, the differential quantization parameter may be entropy encoded / decoded.

[0735] When cu_qp_delta_enabled_flag is the second value, in step S2402 , log2_diff_cu_qp_delta_length, which is length information of the quantization group, may be entropy encoded / decoded.

[0736] Therefore, in step S2403, at least one of the length of the quantization group (QG_length) and the size of the quantization group may be determined based on log2_diff_cu_qp_delta_length which is the length information of the quantization group.

[0737] In step S2401, encoding / decoding may be performed on a CTU. In this step, a CTU may be recursively partitioned into coding units (CUs), and may be partitioned CU by CU. Here, a CU may represent at least one of a prediction unit (PU), a transform unit (TU), and a block. In this step, IsCuDeltaQPCoded may be set to a second value.

[0738] In step S2405, when the maximum length (maximum value) of the horizontal length (CU_width) and the vertical length (CU_height) of the current block is equal to or greater than the length of the quantization group, IsCuDeltaQPCoded may be set to a first value in step S2406.

[0739] In step S2407, when CU_split_flag is entropy encoded / decoded to the second value ( Fig.24 In step S2407, when CU_split_flag is entropy encoded / decoded to the first value ( Fig.24 When the parameter is "No" in the code), the coded block flag coded_block_flag can be entropy encoded / decoded.

[0740] In step S2408, when the coded block flag is the first value ( Fig.24 In step S2409, a flag (IsLastCuCoded) indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0741] In step S2409, when IsLastCuCoded is the second value ( Fig.24 When IsLastCuCoded is the first value ( Fig.24 When the value is “Yes” in the command output, the next target CU is encoded / decoded.

[0742] In step S2408, when the coded block flag is the second value ( Fig.24 When the value is "No" in IsCuDeltaQPCoded, it can be checked whether IsCuDeltaQPCoded is set to the first value or the second value.

[0743] In step S2410, when IsCuDeltaQPCoded is set to the second value ( Fig.24 When the value is "No" in the CTU, a flag (IsLastCuCoded) indicating whether the last CU in the CTU has been encoded / decoded can be checked.

[0744] In step S2410, when IsCuDeltaQPCoded is set to the first value ( Fig.24 , when the value is "Yes" in the parameter list, the differential quantization parameter may be entropy encoded / decoded in step S2411, and then IsCuDeltaQPCoded may be set to a second value.

[0745] In step S2412, a predicted quantization parameter may be determined using a neighboring quantization group.

[0746] In step S2413, the differential quantization parameter and the predicted quantization parameter are added to determine the quantization parameter.

[0747] In step S2409 , a flag (IsLastCuCoded) indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0748] Here, IsCuDeltaQPCoded may be set for each block or each quantization group. At this time, it may be checked whether the delta quantization parameter is entropy encoded / decoded for each block or each quantization group by using a flag or variable such as IsCuDeltaQPCoded.

[0749] In the above-described embodiment, the first value may be 0, and the second value may be 1. Conversely, the first value may be 1, and the second value may be 0.

[0750] Fig.25 is a diagram illustrating a method of determining a quantization parameter using area information of a quantization group according to an embodiment of the present invention.

[0751] In step S2501, cu_qp_delta_enabled_flag may be entropy encoded / decoded. When cu_qp_delta_enabled_flag is the first value ( Fig.25 , the delta quantization parameter may not be entropy encoded / decoded. On the other hand, when cu_qp_delta_enabled_flag is the second value ( Fig.25 When the parameter “No” is used in the answer, the differential quantization parameter may be entropy encoded / decoded.

[0752] When cu_qp_delta_enabled_flag is the second value, in step S2502 , log4_diff_cu_qp_delta_area, which is area information of the quantization group, may be entropy encoded / decoded.

[0753] Therefore, in step S2503, at least one of the area of ​​the quantization group (QG_area) and the size of the quantization group may be determined based on the area information of the quantization group (ie, at least one of diff_cu_qp_delta_area and log4_diff_cu_qp_delta_area).

[0754] In step S2504, encoding / decoding may be performed on the CTU. In this step, the CTU may be recursively partitioned into coding units (CUs) and then encoded / decoded CU by CU. Here, CU may represent at least one of a prediction unit (PU), a transform unit (TU), and a block. In this step, IsCuDeltaQPCoded may be set to a second value.

[0755] In step S2505, when the area CU_area of ​​the current block is equal to or greater than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value in step S2506.

[0756] In step S2507, when CU_split_flag is entropy encoded / decoded to the second value ( Fig.25 In step S2507, when CU_split_flag is entropy encoded / decoded to the first value ( Fig.25 When the value is "No" in the code block flag coded_block_flag, entropy encoding / entropy decoding can be performed.

[0757] In step S2508, when the coded block flag is the first value ( Fig.25 In step S2509, a flag (IsLastCuCoded) indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0758] In step S2509, when IsLastCuCoded is the second value ( Fig.25 When IsLastCuCoded is the first value ( Fig.25 When the value is “Yes” in the command output, the next target CU is encoded / decoded.

[0759] In step S2508, when the coded block flag is the second value ( Fig.25 When the value is "No" in IsCuDeltaQPCoded, it can be checked whether IsCuDeltaQPCoded is set to the first value or the second value.

[0760] In step S2510, when IsCuDeltaQPCoded is set to the second value ( Fig.25 When the value is "No" in the CTU, the flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded can be checked.

[0761] In step S2510, when IsCuDeltaQPCoded is set to the first value ( Fig.25 When the value is "Yes" in the parameter list, the differential quantization parameter may be entropy encoded / decoded in step S2511, and then IsCuDeltaQPCoded may be set to a second value.

[0762] In step S2512, a predicted quantization parameter may be determined using a neighboring quantization group.

[0763] In step S2513, the differential quantization parameter and the predicted quantization parameter may be added to determine the quantization parameter.

[0764] In step S2509 , a flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0765] Here, IsCuDeltaQPCoded may be set for each block or each quantization group. At this time, it may be checked whether the delta quantization parameter is entropy encoded / decoded for each block or each quantization group by using a flag or variable such as IsCuDeltaQPCoded.

[0766] In the above-described embodiment, the first value may be 0, and the second value may be 1. Conversely, the first value may be 1, and the second value may be 0.

[0767] Fig.26 is a diagram illustrating a method of determining a quantization parameter using length information of a quantization group according to another embodiment of the present invention.

[0768] In step S2601, the flag cu_qp_delta_enabled_flag may be entropy encoded / decoded. When cu_qp_delta_enabled_flag is the first value ( Fig.26 , the delta quantization parameter may not be entropy encoded / decoded. On the other hand, when cu_qp_delta_enabled_flag is the second value ( Fig.26 When the parameter “No” is used in the answer, the differential quantization parameter may be entropy encoded / decoded.

[0769] When cu_qp_delta_enabled_flag is the second value, log2_diff_cu_qp_delta_length as the length information of the quantization group may be entropy encoded / decoded in step S2602.

[0770] Therefore, in step S2603, at least one of the length of the quantization group (QG_length) and the size of the quantization group may be determined based on log2_diff_cu_qp_delta_length which is the length information of the quantization group.

[0771] In step S2604, encoding / decoding may be performed on the CTU. In this step, the CTU may be recursively partitioned into coding units (CUs) and then encoded / decoded CU by CU. Here, CU may represent at least one of a prediction unit (PU), a transform unit (TU), and a block. In this step, IsCuDeltaQPCoded may be set to a second value.

[0772] In step S2605, when the maximum length (maximum value) of the horizontal length (CU_width) and the vertical length (CU_height) of the current block is equal to or greater than the length of the quantization group, IsCuDeltaQPCoded may be set to a first value in step S2606.

[0773] In step S2605, when the maximum length (maximum value) of the horizontal length (CU_width) and the vertical length (CU_height) of the current block is less than the length of the quantization group, IsCuDeltaQPCoded may be set to a second value in step S2606.

[0774] In step S2607, when CU_split_flag is entropy encoded / decoded to the second value ( Fig.26 In step S2607, when CU_split_flag is entropy encoded / decoded to the first value ( Fig.26 When the parameter is "No" in the code), the coded block flag coded_block_flag can be entropy encoded / decoded.

[0775] In step S2608, when the coded block flag is the first value ( Fig.26 In step S2609, a flag (IsLastCuCoded) indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0776] In step S2609, when IsLastCuCoded is the second value ( Fig.26 When IsLastCuCoded is the first value ( Fig.26 When the value is “Yes” in the command output, the next target CU is encoded / decoded.

[0777] In step S2608, when the coded block flag is the second value ( Fig.26 When the value is "No" in IsCuDeltaQPCoded, it can be checked whether IsCuDeltaQPCoded is set to the first value or the second value.

[0778] In step S2610, when IsCuDeltaQPCoded is set to the second value ( Fig.26 When the value is "No" in the CTU, the flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded can be checked.

[0779] In step S2610, when IsCuDeltaQPCoded is set to the first value ( Fig.26 When the value is "Yes" in the parameter list, the differential quantization parameter may be entropy encoded / decoded in step S2611, and then IsCuDeltaQPCoded may be set to a second value.

[0780] In step S2612, a predicted quantization parameter may be determined using a neighboring quantization group.

[0781] In step S2613, the differential quantization parameter and the predicted quantization parameter may be added to determine the quantization parameter.

[0782] In step S2609 , a flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0783] Here, IsCuDeltaQPCoded may be set for each block or each quantization group. At this time, it may be checked whether the delta quantization parameter is entropy encoded / decoded for each block or each quantization group by using a flag or variable such as IsCuDeltaQPCoded.

[0784] In the above-described embodiment, the first value may be 0, and the second value may be 1. Conversely, the first value may be 1, and the second value may be 0.

[0785] Fig. 27 is a diagram illustrating a method of determining a quantization parameter using area information of a quantization group according to still another embodiment of the present invention.

[0786] In step S2701, the flag cu_qp_delta_enabled_flag may be entropy encoded / decoded. When cu_qp_delta_enabled_flag is the first value ( Fig. 27 , the delta quantization parameter may not be entropy encoded / decoded. On the other hand, when cu_qp_delta_enabled_flag is the second value ( Fig. 27 When the parameter “No” is used in the answer, the differential quantization parameter may be entropy encoded / decoded.

[0787] When cu_qp_delta_enabled_flag is the second value, log4_diff_cu_qp_delta_area as the area information of the quantization group may be entropy encoded / decoded in step S2702 .

[0788] Therefore, in step S2703, at least one of the area of ​​the quantization group (QG_area) and the size of the quantization group may be determined based on the area information of the quantization group (ie, at least one of diff_cu_qp_delta_area and log4_diff_cu_qp_delta_area). Fig.25 is a diagram of an example in which log4_diff_cu_qp_delta_area is used as area information of a quantization group, Fig. 27 diff_cu_qp_delta_area is shown as another example of the area information.

[0789] In step S2704, encoding / decoding may be performed on the CTU. In this step, the CTU may be recursively partitioned into coding units (CUs) and then encoded / decoded CU by CU. Here, CU may represent at least one of a prediction unit (PU), a transform unit (TU), and a block. In this step, IsCuDeltaQPCoded may be set to a second value.

[0790] In step S2705, when the area CU_area of ​​the current block is equal to or greater than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a first value in step S2706.

[0791] In step S2705, when the area CU_area of ​​the current block is smaller than the area of ​​the quantization group, IsCuDeltaQPCoded may be set to a second value in step S2706.

[0792] In step S2707, when CU_split_flag is entropy encoded / decoded to the second value ( Fig. 27 In step S2707, when CU_split_flag is entropy encoded / decoded to the first value ( Fig. 27 When the parameter is "No" in the code), the coded block flag coded_block_flag can be entropy encoded / decoded.

[0793] In step S2708, when the coded block flag is the first value ( Fig. 27 In step S2709, a flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0794] In step S2709, when IsLastCuCoded is the second value ( Fig. 27 When IsLastCuCoded is the first value ( Fig. 27 When the value is “Yes” in the command output, the next target CU is encoded / decoded.

[0795] In step S2708, when the coded block flag is the second value ( Fig. 27 When the value is "No" in IsCuDeltaQPCoded, it can be checked whether IsCuDeltaQPCoded is set to the first value or the second value.

[0796] In step S2710, when IsCuDeltaQPCoded is set to the second value ( Fig. 27 When the value is "No" in the CTU, the flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded can be checked.

[0797] In step S2710, when IsCuDeltaQPCoded is set to the first value ( Fig. 27 When the value is "Yes" in the parameter list, the differential quantization parameter may be entropy encoded / decoded in step S2711, and then IsCuDeltaQPCoded may be set to a second value.

[0798] In step S2712, a predicted quantization parameter may be determined using a neighboring quantization group.

[0799] In step S2713, the differential quantization parameter and the predicted quantization parameter may be added to determine the quantization parameter.

[0800] In step S2709 , a flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0801] Here, IsCuDeltaQPCoded may be set for each block or each quantization group. At this time, it may be checked whether the delta quantization parameter is entropy encoded / decoded for each block or each quantization group by using a flag or variable such as IsCuDeltaQPCoded.

[0802] In the above-described embodiment, the first value may be 0, and the second value may be 1. Conversely, the first value may be 1, and the second value may be 0.

[0803] Fig.28 is a diagram illustrating a method of determining a quantization parameter using depth information of a quantization group according to an embodiment of the present invention.

[0804] In step S2801, the flag cu_qp_delta_enabled_flag may be entropy encoded / decoded. When cu_qp_delta_enabled_flag is the first value ( Fig.28 , the delta quantization parameter may not be entropy encoded / decoded. On the other hand, when cu_qp_delta_enabled_flag is the second value ( Fig.28 When the parameter “No” is used in the answer, the differential quantization parameter may be entropy encoded / decoded.

[0805] When cu_qp_delta_enabled_flag is the second value, diff_cu_qp_delta_depth as depth information of the quantization group may be entropy encoded / decoded in step S2802. Thus, a basic unit on which a signaling operation is performed during encoding / decoding may be set based on diff_cu_qp_delta_depth as depth information of the quantization group and the depth of the block.

[0806] In step S2804, encoding / decoding may be performed on the CTU. In this step, the CTU may be recursively partitioned into coding units (CUs) and then encoded / decoded CU by CU. Here, CU may represent at least one of a prediction unit (PU), a transform unit (TU), and a block. In this step, IsCuDeltaQPCoded may be set to a second value.

[0807] In step S2805, when the depth of the current block is less than or equal to the depth information of the quantization group, IsCuDeltaQPCoded may be set to a first value in step S2806.

[0808] In step S2807, when CU_split_flag is entropy encoded / decoded to the second value ( Fig.28 In step S2807, when CU_split_flag is entropy encoded / decoded to the first value ( Fig.28 When the value is "No" in the code block flag coded_block_flag, entropy encoding / entropy decoding can be performed.

[0809] In step S2808, when the coded block flag is the first value ( Fig.28 In step S2809, a flag IsLastCuCoded indicating whether the last CU in the CTU has been encoded / decoded may be checked.

[0810] In step S2809, when IsLastCuCoded is the second value ( Fig.28 When IsLastCuCoded is the first value ( Fig.28 When the value is “Yes” in the command output, the next target CU is encoded / decoded.

[0811] In step S2808, when the coded block flag...

Claims

1. An image decoding method, comprising: Decoding sub-division information of the quantization group from the bitstream, wherein the sub-division information indicates a maximum sub-division value of the quantization group; In response to a sub-division value of the current block being equal to or less than a maximum sub-division value of the quantization group, setting quantization parameter encoding information to a first value, wherein the quantization parameter encoding information indicates whether a quantization parameter is encoded; In response to the quantization parameter encoding information indicating a first value, obtaining a differential quantization parameter of the current block, and setting the quantization parameter encoding information to a second value; and deriving a quantization parameter of the current block based on the differential quantization parameter, The differential quantization parameter is determined based on absolute value information of the differential quantization parameter and sign information of the differential quantization parameter.

2. The image decoding method according to claim 1, wherein: The sub-partition value is related to the ratio of the area between the current block and the coding tree block.

3. The image decoding method according to claim 1, wherein: When the current block is obtained from the parent block partition of the current block according to the quadtree partitioning, the sub-division value of the current block is determined by adding two to the sub-division value of the parent block of the current block.

4. The image decoding method according to claim 1, wherein: When the current block is obtained from the parent block partition of the current block according to the binary tree partition, the sub-division value of the current block is determined by adding one to the sub-division value of the parent block of the current block.

5. The image decoding method according to claim 1, wherein: In the case where the current block is partitioned from the parent block of the current block according to the ternary tree partitioning, the sub-division value of the current block is determined by the following operations: When the current block is the middle block of the blocks partitioned from the parent block of the current block, the sub-division value of the parent block of the current block is increased by one, and When the current block is not a middle block among the blocks partitioned from the parent block of the current block, the sub-division value of the parent block of the current block is increased by two.

6. The image decoding method according to claim 1, wherein: Sub-division information of the quantization group indicating the maximum sub-division value of the quantization group is decoded in units of pictures.

7. The image decoding method according to claim 1, further comprising: In response to the current quantization group of the current block being the first quantization group in the coding tree block CTB row, determining a predicted quantization parameter of the current block based on a quantization parameter of an upper quantization group, in, The upper quantization group is located directly above the current quantization group, and The quantization parameter of the current block is derived based on the predicted quantization parameter of the current block and the differential quantization parameter.

8. The image decoding method according to claim 1, wherein: The current block is included in the current quantization group, and The quantization parameter of the current block is applied to multiple blocks in the current quantization group.

9. An image encoding method, comprising: determining a maximum subdivision value of the quantized group; Determine a quantization parameter for the current block; In response to a sub-division value of the current block being equal to or less than a maximum sub-division value of the quantization group, setting quantization parameter encoding information to a first value, wherein the quantization parameter encoding information indicates whether a quantization parameter is encoded; In response to the quantization parameter encoding information indicating a first value, encoding a differential quantization parameter of the current block and setting the quantization parameter encoding information to a second value; and encoding sub-division information of the quantization group indicating a maximum sub-division value of the quantization group, The encoding of the differential quantization parameter includes encoding absolute value information of the differential quantization parameter and sign information of the differential quantization parameter.

10. A method for sending a bit stream, comprising: obtaining a bitstream for an image, wherein the bitstream is generated by an image encoding method; and Send bitstream, Wherein, the image encoding method comprises: determining a maximum subdivision value of the quantized group; Determine a quantization parameter for the current block; In response to a sub-division value of the current block being equal to or less than a maximum sub-division value of the quantization group, setting quantization parameter encoding information to a first value, wherein the quantization parameter encoding information indicates whether a quantization parameter is encoded; In response to the quantization parameter encoding information indicating a first value, encoding a differential quantization parameter of the current block and setting the quantization parameter encoding information to a second value; and encoding sub-division information of the quantization group indicating a maximum sub-division value of the quantization group, The encoding of the differential quantization parameter includes encoding absolute value information of the differential quantization parameter and sign information of the differential quantization parameter.

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