Image decoding method for chroma component and apparatus therefor

Abstract

The present invention provides an image decoding method for chroma components and an apparatus therefor. An image decoding method performed by a decoding device according to the present document comprises the steps of: acquiring chroma quantization parameter data including at least one chroma QP mapping table for a chroma component, and prediction information and residual information on the chroma component; deriving a chroma QP mapping table based on the chroma quantization parameter data; deriving a chroma quantization parameter for the chroma component based on a chroma QP mapping table; deriving a prediction sample for the chroma component based on the prediction information; deriving a residual sample based on the residual information and the chroma quantization parameter; and generating a reconstructed picture based on the prediction sample and the residual sample.

Description

[0001] This application is a divisional application of the patent application with application number 202080059781.5 (PCT / KR2020 / 008736), application date July 3, 2020, and title "Image Decoding Method and Apparatus for Chrominance Components", which was filed on February 23, 2022. Technical Field

[0002] The present disclosure relates to image coding technology, and more particularly, to an image decoding method and apparatus that uses a chrominance QP mapping table derived based on signaled chrominance quantization parameter data in an image coding system. Background Art

[0003] Recently, in various fields, the demand for high-resolution and high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images is increasing. Since image data has high resolution and high quality, the amount of information or bits to be transmitted increases compared to traditional image data. Therefore, when transmitting image data using a medium such as a traditional wired / wireless broadband line or storing image data using an existing storage medium, the transmission cost and storage cost increase.

[0004] Accordingly, there is a need for an efficient image compression technology for effectively transmitting, storing, and reproducing information of high-resolution and high-quality images. Summary of the Invention

[0005] Technical Problem

[0006] A technical object of the present disclosure is to provide a method and apparatus for improving image coding efficiency.

[0007] Another technical object of the present disclosure is to provide a method and apparatus for improving data coding efficiency for deriving quantization parameters for chrominance components.

[0008] Technical Solution

[0009] According to an embodiment of the present disclosure, there is provided an image decoding method performed by a decoding device. The method includes: obtaining image information, the image information including prediction information and residual information for a chrominance component and chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for the chrominance component; deriving a chrominance QP mapping table based on the chrominance quantization parameter data; deriving a chrominance quantization parameter for the chrominance component based on the chrominance QP mapping table; deriving a predicted sample for the chrominance component based on the prediction information; deriving transform coefficients for the chrominance component based on the residual information; deriving a residual sample by dequantizing the transform coefficients based on the chrominance quantization parameter; and generating a reconstructed picture based on the predicted sample and the residual sample, wherein the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP mapping table, a syntax element for an increment value (delta value) of an input coordinate of a target point used to derive the chrominance QP mapping table, and a syntax element for an increment value of an output coordinate of the target point used to derive the chrominance QP mapping table.

[0010] According to another embodiment of the present disclosure, there is provided a decoding device for performing image decoding. The decoding device includes: an entropy coder configured to obtain image information, the image information including prediction information and residual information for a chrominance component and chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for the chrominance component; a predictor configured to derive a predicted sample for the chrominance component based on the prediction information; a residual processor configured to derive a chrominance QP mapping table based on the chrominance quantization parameter data, derive a chrominance quantization parameter for the chrominance component based on the chrominance QP mapping table, derive transform coefficients for the chrominance component based on the residual information, derive a residual sample by dequantizing the transform coefficients based on the chrominance quantization parameter, and generate a reconstructed picture based on the predicted sample and the residual sample, wherein the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP mapping table, a syntax element for an increment value of an input coordinate of a target point used to derive the chrominance QP mapping table, and a syntax element for an increment value of an output coordinate of the target point used to derive the chrominance QP mapping table.

[0011] According to another embodiment of the present disclosure, there is provided a video encoding method performed by an encoding device. The method includes: deriving a prediction sample for a chrominance component based on inter-frame prediction or intra-frame prediction; deriving a residual sample for the chrominance component based on the prediction sample; generating chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance component; and encoding prediction information for the chrominance component, residual information for the chrominance component, and the chrominance quantization parameter data, where the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP mapping table, a syntax element for an increment value of an input coordinate of a target point used to derive the chrominance QP mapping table, and a syntax element for an increment value of an output coordinate of the target point used to derive the chrominance QP mapping table.

[0012] According to another embodiment of the present disclosure, there is provided a video encoding device. The encoding device includes: a predictor configured to derive a prediction sample for a chrominance component based on inter-frame prediction or intra-frame prediction; a residual processor configured to derive a residual sample for the chrominance component based on the prediction sample, and generate chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance component; and an entropy encoder configured to encode prediction information for the chrominance component, residual information for the chrominance component, and the chrominance quantization parameter data, where the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP mapping table, a syntax element for an increment value of an input coordinate of a target point used to derive the chrominance QP mapping table, and a syntax element for an increment value of an output coordinate of the target point used to derive the chrominance QP mapping table.

[0013] Beneficial effects

[0014] According to the present disclosure, when deriving a chrominance quantization parameter for a chrominance component, a chrominance QP mapping table derived using chrominance quantization parameter data signaled can be used instead of a default chrominance QP mapping table to derive the chrominance quantization parameter for the chrominance component, and in this way, the encoding efficiency can be improved by performing encoding based on quantization parameters according to the characteristics of the image.

[0015] According to the present disclosure, a chrominance QP mapping table can be derived based on a syntax element representing an increment value of an input coordinate of a point used to derive the chrominance QP mapping table and / or a syntax element representing an increment value of an output coordinate of a point used to derive the chrominance QP mapping table, and the encoding efficiency can be improved by performing encoding based on a chrominance QP mapping table that more specifically reflects the characteristics of the image. Brief description of the drawings

[0016] Figure 1 Examples of video / image encoding devices to which embodiments of the present disclosure can be applied are briefly illustrated.

[0017] Figure 2 It is a schematic diagram illustrating the configuration of a video / image encoding device to which embodiments of the present disclosure can be applied.

[0018] Figure 3 It is a schematic diagram illustrating the configuration of a video / image decoding device to which embodiments of the present disclosure can be applied.

[0019] Figure 4 An example of a video / image encoding method based on inter-frame prediction is illustrated.

[0020] Figure 5 An example of a video / image decoding method based on inter-frame prediction is illustrated.

[0021] Figure 6 The inter-frame prediction process is schematically shown.

[0022] Figure 7 The image encoding method of the encoding device according to this document is schematically shown.

[0023] Figure 8 The encoding device for performing the image encoding method according to this document is schematically shown.

[0024] Figure 9 The image decoding method of the decoding device according to this document is schematically shown.

[0025] Figure 10 The decoding device for performing the image decoding method according to this document is schematically shown.

[0026] Figure 11 The structural diagram of a content stream system applying the present disclosure is illustrated. Detailed Embodiments

[0027] The present disclosure can be modified in various forms, and its specific embodiments will be described and illustrated in the accompanying drawings. However, the embodiments are not intended to limit the present disclosure. The terms used in the following description are only for describing specific embodiments and are not intended to limit the present disclosure. As long as it is clearly understood in a different way, singular expressions include plural expressions. Terms such as "including" and "having" are intended to indicate the presence of features, numbers, steps, operations, elements, components, or combinations thereof used in the following description, and thus it should be understood that there is no exclusion of the possibility of the presence or addition of one or more different features, numbers, steps, operations, elements, components, or combinations thereof.

[0028] In addition, the elements in the drawings described in the present disclosure are independently drawn for the convenience of explaining different specific functions, and do not mean that these elements are embodied by independent hardware or independent software. For example, two or more of the elements may be combined to form a single element, or one element may be divided into multiple elements. The implementation manners of combining elements and / or dividing elements belong to the present disclosure without departing from the concept of the present disclosure.

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, throughout the drawings, like reference numerals are used to indicate like elements, and the same description of like elements will be omitted.

[0030] Figure 1 An example of a video / image compilation device to which embodiments of the present disclosure can be applied is briefly illustrated.

[0031] Referring to Figure 1 , a video / image compilation system may include a first device (source device) and a second device (receiving device). The source device may send encoded video / image information or data to the receiving device in the form of a file or a stream via a digital storage medium or a network.

[0032] The source device may include a video source, an encoding device, and a transmitter. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be referred to as a video / image encoding device, and the decoding device may be referred to as a video / image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display, and the display may be configured as a separate device or an external component.

[0033] The video source may obtain video / images through processes such as capturing, synthesizing, or generating video / images. The video source may include a video / image capturing device and / or a video / image generating device. The video / image capturing device may include, for example, one or more cameras, a video / image archive including previously captured video / images, etc. The video / image generating device may include, for example, a computer, a tablet, and a smart phone, and may (electronically) generate video / images. For example, virtual video / images may be generated by a computer or the like. In this case, the video / image capturing process may be replaced by a process of generating relevant data.

[0034] The encoding device may encode the input video / images. The encoding device may perform a series of processes such as prediction, transformation, and quantization to achieve compression and compilation efficiency. The encoded data (encoded video / image information) can be output in the form of a bit stream.

[0035] The transmitter can send the encoded image / image information or data output in the form of a bitstream to the receiver of the receiving device in the form of a file or a stream via a digital storage medium or a network. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter can include elements for generating a media file in a predetermined file format and can include elements for transmitting via a broadcast / communication network. The receiver can receive / extract the bitstream and send the received bitstream to the decoding device.

[0036] The decoding device can decode the video / image by performing a series of processes such as dequantization, inverse transformation, and prediction corresponding to the operations of the encoding device.

[0037] The renderer can render the decoded video / image. The rendered video / image can be displayed via a display.

[0038] This disclosure relates to video / image compilation. For example, the methods / embodiments disclosed in this disclosure can be applied to the methods disclosed in Versatile Video Coding (VVC), Efficient Video Coding (EVC) standard, AOMedia Video 1 (AV1) standard, Second Generation Audio Video Coding Standard (AVS2), or the next-generation video / image compilation standards (e.g., H.267, or H.268, etc.).

[0039] This disclosure presents various embodiments of video / image compilation, and unless otherwise mentioned, the embodiments can be executed in combination with each other.

[0040] In the present disclosure, a video may refer to a series of images over time. Generally, a picture refers to a unit representing an image in a specific time zone, and a sub-picture / slice / tile is a unit that forms part of a picture being compiled. A sub-picture / slice / tile may include one or more Compilation Tree Units (CTUs). A picture may be composed of one or more sub-pictures / slices / tile. A picture may be composed of one or more tile groups. A tile group may include one or more tiles. A brick may represent a rectangular region of CTU rows within a tile in a picture. A tile may be partitioned into multiple bricks, each brick consisting of one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. Brick scan may sort CTUs in a specific order for CTUs partitioning a picture, where CTUs are sorted continuously in raster scan order within a brick, bricks within a tile are sorted continuously in raster scan order of the tiles of the picture, and tiles in a picture are sorted continuously in raster scan order of the tiles of the picture. Additionally, a sub-picture may represent a rectangular region of one or more slices within a picture. That is, a sub-picture contains one or more slices that jointly cover a rectangular region of the picture. A tile is a rectangular region of CTUs within a specific tile column and a specific tile row in a picture. A tile column is a rectangular region of CTUs, the height of which is equal to the height of the picture and the width of which is specified by a syntax element in the picture parameter set. A tile row is a rectangular region of CTUs, the height of which is specified by a syntax element in the picture parameter set and the width of which is equal to the width of the picture. Tile scan is a specific order sorting of CTUs partitioning a picture, where CTUs may be sorted continuously in raster scan order within a tile, while tiles in a picture may be sorted continuously in raster scan order of the tiles of the picture. A slice includes an integer number of bricks that can be exclusively included in a single NAL unit of a picture. A slice may be composed of multiple complete tiles or only of a continuous sequence of complete bricks of one tile. In the present disclosure, tile groups and slices may be used interchangeably. For example, in the present disclosure, a tile group / tile group header may be referred to as a slice / slice header.

[0041] A pixel or pel may represent the smallest unit that makes up a picture (or image). Additionally, "sample" may be used as a term corresponding to a pixel. A sample generally may represent a pixel or a pixel value and may represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chrominance component.

[0042] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of a picture and information related to the area. A unit may include a luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit may be used interchangeably with terms such as a block or a region. Generally, an M×N block may include a set (or array) of samples (or a sample array) of M columns and N rows or a set (or array) of transform coefficients.

[0043] In this specification, "A or B" may mean "only A", "only B", or "A and B". In other words, in this specification, "A or B" may be interpreted as "A and / or B". For example, "A, B, or C" herein means "only A", "only B", "only C", or "any one and any combination of A, B, and C".

[0044] The slashes ( / ) or commas used in this specification may mean "and / or". For example, "A / B" may mean "A and / or B". Thus, "A / B" may mean "only A", "only B", or "A and B". For example, "A, B, C" may mean "A, B, or C".

[0045] In this specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". Additionally, in this specification, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted as the same as "at least one of A and B".

[0046] Furthermore, in this specification, "at least one of A, B, and C" means "only A", "only B", "only C", or "any combination of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B, and / or C" may mean "at least one of A, B, and C".

[0047] Moreover, the parentheses used in this specification may mean "for example". Specifically, when indicating "prediction (intra prediction)", "intra prediction" may be presented as an example of "prediction". In other words, "prediction" in this specification is not limited to "intra prediction", and "intra prediction" may be presented as an example of "prediction". Additionally, even when indicating "prediction (i.e., intra prediction)", "intra prediction" may also be presented as an example of "prediction".

[0048] In this specification, the technical features described separately in a figure may be implemented separately or may be implemented simultaneously.

[0049] The following drawings are created to explain specific examples of this specification. Since the names of specific devices or the names of specific signals / messages / fields described in the drawings are presented by way of example, the technical features of this specification are not limited to the specific names used in the following drawings.

[0050] Figure 2 is a schematic diagram illustrating the configuration of a video / image encoding device to which embodiments of the present disclosure can be applied. Hereinafter, the video encoding device may include an image encoding device.

[0051] Referring to Figure 2 , the encoding device 200 includes an image splitter 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter-frame predictor 221 and an intra-frame predictor 222. The residual processor 230 may include a transformer 232, a quantizer 233, an inverse quantizer 234, and an inverse transformer 235. The residual processor 230 may further include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstruction block generator. According to an embodiment, the image splitter 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250, and the filter 260 may be constituted by at least one hardware component (e.g., an encoder chipset or a processor). Additionally, the memory 270 may include a decoded picture buffer (DPB) or may be constituted by a digital storage medium. The hardware component may further include the memory 270 as an internal / external component.

[0052] The image splitter 210 may split an input image (or picture or frame) input to the encoding device 200 into one or more processors. For example, the processors may be referred to as compile units (CUs). In this case, the compile units may be recursively split from compile tree units (CTUs) or largest compile units (LCUs) according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, a compile unit may be split into multiple deeper compile units based on a quadtree structure, a binary tree structure, and / or a ternary structure. In this case, for example, the quadtree structure may be applied first, and then the binary tree structure and / or the ternary structure may be applied. Alternatively, the binary tree structure may be applied first. The compile process according to the present disclosure may be performed based on the final compile units that are no longer split. In this case, the largest compile unit may be used as the final compile unit based on compile efficiency according to image characteristics, or if necessary, the compile units may be recursively split into deeper compile units and the compile units having an optimal size may be used as the final compile units. Here, the compile process may include processes of prediction, transformation, and reconstruction, which will be described later. As another example, the processor may further include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may be separated or split from the above-mentioned final compile units. The prediction unit may be a unit for sample prediction, and the transformation unit may be a unit for deriving transformation coefficients and / or a unit for deriving a residual signal from the transformation coefficients.

[0053] In some cases, a unit may be used interchangeably with terms such as a block or a region. In general, an M×N block may represent a set of samples or transformation coefficients composed of M columns and N rows. A sample may generally represent a pixel or a pixel value, a pixel / pixel value representing only a luminance component, or a pixel / pixel value representing only a chrominance component. A sample may be used as a term corresponding to a picture (or image) of a pixel or a pixel element.

[0054] In the encoding device 200, a prediction signal (prediction block, prediction sample array) output from the inter-frame predictor 221 or the intra-frame predictor 222 is subtracted from the input image signal (original block, original sample array) to generate a residual signal (residual block, residual sample array), and the generated residual signal is sent to the transformer 232. In this case, as shown in the figure, the unit in the encoding device 200 for subtracting the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) may be referred to as the subtractor 231. The predictor may perform prediction on a block to be processed (hereinafter referred to as the current block) and generate a prediction block including the prediction samples of the current block. The predictor is capable of determining whether to apply intra-frame prediction or inter-frame prediction based on the current block or CU. As described later in the description of each prediction mode, the predictor may generate various information related to the prediction, such as prediction mode information, and send the generated information to the entropy encoder 240. The information about the prediction may be encoded in the entropy encoder 240 and output in the form of a bitstream.

[0055] The intra-frame predictor 222 may predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the samples referred to may be located near the current block or may be far from the current block. In intra-frame prediction, the prediction mode may include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes may include, for example, the DC mode and the planar mode. Depending on the level of detail of the prediction direction, the directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes may be used depending on the settings. The intra-frame predictor 222 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0056] The inter - frame predictor 221 can derive a predicted block of a current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. Here, in order to reduce the amount of motion information transmitted in the inter - frame prediction mode, the motion information can be predicted in units of blocks, sub - blocks, or samples based on the correlation of the motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include inter - frame prediction direction (L0 prediction, L1 prediction, Bi - prediction, etc.) information. In the case of inter - frame prediction, neighboring blocks can include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block can be the same or different. The temporal neighboring block can be referred to as a collocated reference block, a co - located CU (colCU), etc., and the reference picture including the temporal neighboring block can be referred to as a collocated picture (colPic). For example, the inter - frame predictor 221 can configure a motion information candidate list based on neighboring blocks, and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter - frame prediction can be performed based on various prediction modes. For example, in the skip mode and the merge mode, the inter - frame predictor 221 can use the motion information of neighboring blocks as the motion information of the current block. In the skip mode, different from the merge mode, it may not be possible to transmit a residual signal. In the case of the motion vector prediction (MVP) mode, the motion vector of a neighboring block can be used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling a motion vector difference.

[0057] The predictor 220 can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra - frame prediction or inter - frame prediction to predict a block, but also apply both intra - frame prediction and inter - frame prediction simultaneously. This can be referred to as combined intra - inter - prediction (CIIP). Additionally, the predictor can predict a block based on the intra - block copy (IBC) prediction mode or the palette mode. The IBC prediction mode or the palette mode can be used for content image / video compilation such as games, for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but can perform IBC similar to inter - frame prediction because the reference block is derived in the current picture. That is, IBC can use at least one of the inter - frame prediction techniques described in this disclosure. The palette mode can be regarded as an example of intra - frame compilation or intra - frame prediction. When the palette mode is applied, the sample values within the picture can be signaled based on information about the palette table and the palette index.

[0058] The prediction signal generated by a predictor (including the inter-frame predictor 221 and / or the intra-frame predictor 222) can be used to generate a reconstructed signal or to generate a residual signal. The transformer 232 can generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique can include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a karhunen-loève transform (KLT), a graph-based transform (GBT), or a conditional non-linear transform (CNT). Here, GBT represents a transform obtained from a graph when the relationship information between pixels is represented by the graph. CNT refers to a transform generated based on a prediction signal generated using all previously reconstructed pixels. Additionally, the transform process can be applied to square pixel blocks of the same size, or can be applied to blocks of variable size that are not square.

[0059] Quantizer 233 can quantize the transform coefficients and send them to entropy encoder 240, and entropy encoder 240 can encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. The information about the quantized transform coefficients can be referred to as residual information. Quantizer 233 can rearrange the block type quantized transform coefficients into a one-dimensional vector form based on the coefficient scan order, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. Information about the transform coefficients can be generated. Entropy encoder 240 can perform various encoding methods, such as, for example, Exponential Golomb, Context Adaptive Variable Length Coding (CAVLC), Context Adaptive Binary Arithmetic Coding (CABAC), etc. Entropy encoder 240 can encode the information required for video / image reconstruction other than the quantized transform coefficients (e.g., the values of syntax elements, etc.) together or separately. The encoded information (e.g., encoded video / image information) can be sent or stored in units of NAL (Network Abstraction Layer) in the form of a bitstream. The video / image information can also include information about various parameter sets such as Adaptive Parameter Set (APS), Picture Parameter Set (PPS), Sequence Parameter Set (SPS), or Video Parameter Set (VPS). Additionally, the video / image information can also include general constraint information. In the present disclosure, the information and / or syntax elements sent / signaled from the encoding device to the decoding device can be included in the video / picture information. The video / image information can be encoded through the above encoding process and included in the bitstream. The bitstream can be sent through a network or stored in a digital storage medium. The network can include a broadcast network and / or a communication network, and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) for sending the signal output from entropy encoder 240 and / or a storage unit (not shown) for storing the signal can be included as internal / external elements of encoding device 200, and alternatively, the transmitter can be included in entropy encoder 240.

[0060] The quantized transform coefficients output from the quantizer 233 can be used to generate a prediction signal. For example, the residual signal (residual block or residual sample) can be reconstructed by applying dequantization and inverse transformation to the quantized transform coefficients by using the dequantizer 234 and the inverse transformer 235. The adder 250 adds the reconstructed residual signal to the prediction signal output from the inter-frame predictor 221 or the intra-frame predictor 222 to generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). If the block to be processed has no residual (such as in the case where the skip mode is applied), the predicted block can be used as the reconstructed block. The adder 250 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture and can be used for inter-frame prediction of the next picture through filtering as described below.

[0061] In addition, during picture encoding and / or reconstruction, luminance mapping and chrominance scaling (LMCS) can be applied.

[0062] The filter 260 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 260 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and store the modified reconstructed picture in the memory 270 (specifically, the DPB of the memory 270). The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filter 260 can generate various information related to filtering and send the generated information to the entropy encoder 240, as described later in the description of various filtering methods. The information related to filtering can be encoded by the entropy encoder 240 and output in the form of a bitstream.

[0063] The modified reconstructed picture sent to the memory 270 can be used as a reference picture in the inter-frame predictor 221. When inter-frame prediction is applied by the encoding device, prediction mismatches between the encoding device 200 and the decoding device can be avoided, and the encoding efficiency can be improved.

[0064] The DPB of the memory 270 can store the modified reconstructed picture used as a reference picture in the inter-frame predictor 221. The memory 270 can store the motion information of the block from which the motion information in the current picture is derived (or encoded) and / or the motion information of the reconstructed blocks in the picture. The stored motion information can be sent to the inter-frame predictor 221 and used as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 270 can store the reconstructed samples of the reconstructed blocks in the current picture and can transmit the reconstructed samples to the intra-frame predictor 222.

[0065] Figure 3 is a schematic diagram illustrating the configuration of a video / image decoding device to which embodiments of the present disclosure can be applied.

[0066] Referring to Figure 3 , the decoding device 300 may include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-frame predictor 332 and an intra-frame predictor 331. The residual processor 320 may include a dequantizer 321 and an inverse transformer 322. According to an embodiment, the entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 may be constituted by hardware components (e.g., a decoder chipset or a processor). Additionally, the memory 360 may include a decoded picture buffer (DPB), or may be constituted by a digital storage medium. The hardware components may also include the memory 360 as an internal / external component.

[0067] When receiving a bitstream including video / image information, the decoding device 300 may reconstruct an image corresponding to the processing of the video / image information in the Figure 2 encoding device. For example, the decoding device 300 may derive units / blocks based on the block segmentation-related information obtained from the bitstream. The decoding device 300 may perform decoding using the processor applied in the encoding device. Thus, the decoding processor may be, for example, a compilation unit, and may divide the compilation unit from a compilation tree unit or a largest compilation unit according to a quadtree structure, a binary tree structure, and / or a ternary tree structure. One or more transform units may be derived from the compilation unit. The reconstructed image signal decoded and output by the decoding device 300 may be reproduced by a reproduction device.

[0068] The decoding device 300 may receive, in the form of a bitstream, from Figure 2The signal output by the encoding device, and the received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can parse the bitstream to derive the information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information can also include information about various parameter sets such as an Adaptive Parameter Set (APS), a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), or a Video Parameter Set (VPS). Additionally, the video / image information can also include general constraint information. The decoding device can also decode the picture based on the information about the parameter sets and / or the general constraint information. The signaled / received information and / or syntax elements described later in this disclosure can be decoded through the decoding process and obtained from the bitstream. For example, the entropy decoder 310 decodes the information in the bitstream based on coding methods such as Exponential Golomb coding, CAVLC, or CABAC, and outputs the syntax elements required for image reconstruction and the quantization values of the transform coefficients of the residuals. More specifically, the CABAC entropy decoding method can receive the bins corresponding to each syntax element in the bitstream, use the decoding target syntax element information, the decoding information of the decoding target block, or the information of the symbols / bins decoded in the previous stage to determine the context model, and perform arithmetic decoding on the bin by predicting the occurrence probability of the bin according to the determined context model, and generate the symbols corresponding to the values of each syntax element. In this case, after determining the context model, the CABAC entropy decoding method can update the context model by using the information of the decoded symbols / bins for the context model of the next symbol / bin. The information related to prediction among the information decoded by the entropy decoder 310 can be provided to the predictors (inter-frame predictor 332 and intra-frame predictor 331), and the residual values (i.e., the quantized transform coefficients and related parameter information) for which entropy decoding has been performed in the entropy decoder 310 can be input to the residual processor 320. The residual processor 320 can derive the residual signal (residual block, residual sample, residual sample array). Additionally, the information about filtering among the information decoded by the entropy decoder 310 can be provided to the filter 350. Furthermore, a receiver (not shown) for receiving the signal output by the encoding device can be further configured as an internal / external component of the decoding device 300, or the receiver can be a component of the entropy decoder 310. Additionally, the decoding device according to this disclosure can be referred to as a video / image / picture decoding device, and the decoding device can be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder can include the entropy decoder 310, and the sample decoder can include at least one of a dequantizer 321, an inverse transformer 322, an adder 340, a filter 350, a memory 360, an inter-frame predictor 332, and an intra-frame predictor 331.

[0069] The dequantizer 321 can dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 can rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement can be performed based on the coefficient scan order executed in the encoding device. The dequantizer 321 can dequantize the quantized transform coefficients by using quantization parameters (e.g., quantization step information) and obtain the transform coefficients.

[0070] The inverse transformer 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0071] The predictor can perform prediction on the current block and generate a prediction block including the prediction samples of the current block. The predictor can determine whether to apply intra prediction or inter prediction to the current block based on the information about prediction output from the entropy decoder 310, and can determine a specific intra / inter prediction mode.

[0072] The predictor 330 can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra prediction or inter prediction to predict a block, but also apply intra prediction and inter prediction simultaneously. This can be referred to as combined intra and inter prediction (CIIP). Additionally, the predictor can predict a block based on the intra block copy (IBC) prediction mode or the palette mode. The IBC prediction mode or the palette mode can be used for content image / video compilation such as games, for example, screen content compilation (SCC). IBC basically performs prediction in the current picture, but IBC can be performed similar to inter prediction because a reference block is derived in the current picture. That is, IBC can use at least one of the inter prediction techniques described in the present disclosure. The palette mode can be regarded as an example of intra compilation or intra prediction. When the palette mode is applied, the sample values within the picture can be signaled based on the information about the palette table and the palette index.

[0073] The intra predictor 331 can predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the samples referred to can be located near the current block or can be far from the current block. In intra prediction, the prediction mode can include multiple non - directional modes and multiple directional modes. The intra predictor 331 can determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0074] The inter - frame predictor 332 can derive a prediction block for a current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter - frame prediction mode, the motion information can be predicted in units of blocks, sub - blocks, or samples based on the correlation of the motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include inter - frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter - frame prediction, neighboring blocks can include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter - frame predictor 332 can configure a motion information candidate list based on neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter - frame prediction can be performed based on various prediction modes, and the information about the prediction can include information indicating the mode of inter - frame prediction for the current block.

[0075] The adder 340 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to a prediction signal (prediction block, prediction sample array) output from a predictor (including the inter - frame predictor 332 and / or the intra - frame predictor 331). If the block to be processed has no residual (e.g., when the skip mode is applied), the prediction block can be used as the reconstructed block.

[0076] The adder 340 can be referred to as a reconstructor or a reconstructed - block generator. The generated reconstructed signal can be used for intra - frame prediction of the next block to be processed in the current picture, can be output through filtering as described below, or can be used for inter - frame prediction of the next picture.

[0077] In addition, luminance mapping and chrominance scaling (LMCS) can be applied during picture decoding.

[0078] The filter 350 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 350 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and store the modified reconstructed picture in the memory 360 (specifically, the DPB of the memory 360). Various filtering methods can include, for example, de - blocking filtering, sample - adaptive offset, adaptive loop filter, bilateral filter, etc.

[0079] The (modified) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter-predictor 332. The memory 360 can store the motion information of the blocks from which the motion information in the current picture is derived (or decoded) and / or the motion information of the reconstructed blocks in the picture. The stored motion information can be sent to the inter-predictor 332 and utilized as the motion information of spatially neighboring blocks or temporally neighboring blocks. The memory 360 can store the reconstructed samples of the reconstructed blocks in the current picture and can transmit the reconstructed samples to the intra-predictor 331.

[0080] In the present disclosure, the embodiments described in the filter 260, the inter-predictor 221, and the intra-predictor 222 of the encoding device 200 can be the same as or respectively applied to correspond to the filter 350, the inter-predictor 332, and the intra-predictor 331 of the decoding device 300. The same content can also be applied to the inter-predictor 332 and the intra-predictor 331.

[0081] In the present disclosure, at least one of quantization / inverse quantization and / or transform / inverse transform can be omitted. When quantization / inverse quantization is omitted, the quantized transform coefficients can be referred to as transform coefficients. When transform / inverse transform is omitted, the transform coefficients can be referred to as coefficients or residual coefficients, or for the sake of uniformity of expression, can still be referred to as transform coefficients.

[0082] In the present disclosure, the quantized transform coefficients and the transform coefficients can be respectively referred to as transform coefficients and scaled transform coefficients. In this case, the residual information can include information about the transform coefficients, and the information about the transform coefficients can be signaled through the residual coding syntax. The transform coefficients can be derived based on the residual information (or the information about the transform coefficients), and the scaled transform coefficients can be derived by inverse-transforming (scaling) the transform coefficients. The residual samples can be derived based on inverse-transforming (transforming) the scaled transform coefficients. This can also be applied / expressed in other parts of the present disclosure.

[0083] Meanwhile, as described above, when performing video encoding, prediction is performed to improve the compression efficiency. By doing so, a prediction block including prediction samples for a current block can be generated as a block to be encoded (i.e., an encoding target block). Here, the prediction block includes prediction samples in the spatial domain (or pixel domain). The prediction block is derived in the same manner in the encoding device and the decoding device, and the encoding device can signal information (residual information) about the residual between the original block and the prediction block to the decoding device instead of the original sample values of the original block, thereby improving the image encoding efficiency. The decoding device can derive a residual block including residual samples based on the residual information, add the residual block and the prediction block to generate a reconstructed block including reconstructed samples, and generate a reconstructed picture including the reconstructed block.

[0084] Residual information can be generated through a transform and quantization process. For example, the encoding device can derive a residual block between the original block and the prediction block, can perform a transform process on the residual samples (residual sample array) included in the residual block to derive transform coefficients, can perform a quantization process on the transform coefficients to derive quantized transform coefficients, and can signal the relevant residual information (through a bitstream) to the decoding device. Here, the residual information can include value information such as the value information of the quantized transform coefficients, position information, transform technique, transform core, and quantization parameters. The decoding device can perform a dequantization / inverse transform process based on the residual information and derive residual samples (or a residual block). The decoding device can generate a reconstructed picture based on the prediction block and the residual block. In addition, for reference in inter prediction for future reference pictures, the encoding device can dequantize / inverse transform the quantized transform coefficients to derive a residual block and generate a reconstructed picture based on this.

[0085] Intra prediction can refer to generating a prediction of prediction samples for a current block based on reference samples in the picture to which the current block belongs (hereinafter referred to as the current picture). When intra prediction is applied to the current block, adjacent reference samples to be used for the intra prediction of the current block can be derived. The adjacent reference samples of the current block can include a total of 2xnH samples adjacent to the left boundary of the current block of size nWxnH and adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2xnW samples adjacent to the upper right, and samples adjacent to the upper left of the current block. Alternatively, the adjacent reference samples of the current block can include multiple columns of adjacent samples above and multiple rows of adjacent samples to the left. In addition, the adjacent reference samples of the current block can include a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the lower boundary of the current block, and samples adjacent to the lower right of the current block.

[0086] However, some neighboring reference samples of the current block have not been decoded or may not be available. In such cases, the decoder can construct the neighboring reference samples to be used for prediction by replacing the unavailable samples with available samples. Alternatively, the neighboring reference samples to be used for prediction can be configured by interpolation of available samples.

[0087] When deriving the neighboring reference samples, (i) the predicted sample can be derived based on the average or interpolation of the neighboring reference samples of the current block, or (ii) the predicted sample can be derived based on the reference samples present in a specific (prediction) direction with respect to the predicted sample among the neighboring reference samples of the current block. Case (i) can be referred to as the non-directional mode or non-angular mode, and case (ii) can be referred to as the directional mode or angular mode.

[0088] Additionally, the predicted sample can be generated by interpolation between a first neighboring sample located in the prediction direction of the intra prediction mode of the current block and a second neighboring sample located in the direction opposite to the prediction direction among the neighboring reference samples. The above case can be referred to as linear interpolation intra prediction (LIP). Furthermore, a linear model (LM) can be used to generate chrominance prediction samples based on luminance samples. This case can be referred to as the LM mode or chrominance component LM (CCLM) mode.

[0089] Additionally, a temporary prediction sample of the current block is derived based on the filtered neighboring reference samples, and the predicted sample of the current block can also be derived by weighted summing the temporary prediction sample and at least one reference sample derived according to the intra prediction mode among the existing neighboring reference samples (i.e., unfiltered neighboring reference samples). The above case can be referred to as position-dependent intra prediction (PDPC).

[0090] Additionally, the reference sample line with the highest prediction accuracy among the multiple neighboring reference sample lines of the current block is selected, and the predicted sample is derived using the reference sample located in the prediction direction in the selected line. In this case, intra prediction coding can be performed by indicating (signaling) the reference sample line used. The above case can be referred to as multi-reference line intra prediction or MRL-based intra prediction.

[0091] Additionally, the current block is divided into vertical or horizontal sub-partitions and intra prediction is performed based on the same intra prediction mode, but the neighboring reference samples can be derived and used on a sub-partition basis. That is, in this case, the intra prediction mode of the current block also applies to the sub-partitions, but in some cases, the intra prediction performance can be improved by deriving and using the neighboring reference samples on a sub-partition basis. This prediction method can be referred to as intra prediction based on intra sub-partition (ISP).

[0092] The above intra prediction method may be referred to as an intra prediction type to distinguish it from an intra prediction mode. The intra prediction type may be referred to by various terms, such as an intra prediction technique or an additional intra prediction mode. For example, the intra prediction type (or an additional intra prediction mode, etc.) may include at least one of the above LIP, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP may be referred to as a normal intra prediction type. When the above specific intra prediction types are not applied, the normal intra prediction type may generally be applied, and prediction may be performed based on the above intra prediction mode. Meanwhile, if necessary, post - processing filtering may be performed on the derived prediction samples.

[0093] Specifically, the intra prediction process may include an intra prediction mode / type determination step, an adjacent reference sample derivation step, and a prediction sample derivation step based on the intra prediction mode / type. In addition, if necessary, a post - filtering step may be performed on the derived prediction samples.

[0094] When intra prediction is applied, the intra prediction mode of a neighboring block may be used to determine the intra prediction mode applied to the current block. For example, the decoding device may select one of the MPM candidates in the most probable mode (MPM) list derived based on the intra prediction mode of the neighboring blocks (e.g., left and / or upper neighboring blocks) of the current block and additional candidate modes or select one of the remaining intra prediction modes not included in the MPM candidates (and the planar mode) based on the remaining intra prediction mode information. The MPM list may be configured to include or not include the planar mode as a candidate. For example, when the MPM list includes the planar mode as a candidate, the MPM list may have 6 candidates, and when the MPM list does not include the planar mode as a candidate, the MPM list may have 5 candidates. When the MPM list does not include the planar mode as a candidate, a non - planar flag (e.g., intra_luma_not_planar_flag) indicating whether the intra prediction mode of the current block is not the planar mode may be signaled. For example, the MPM flag may be signaled first, and when the value of the MPM flag is 1, the MPM index and the non - planar flag may be signaled. In addition, when the value of the non - planar flag is 1, the MPM index may be signaled. Here, the fact that the MPM list is configured not to include the planar mode as a candidate means that the planar mode is always considered as an MPM rather than not considering the planar mode as an MPM. Therefore, the flag (non - planar flag) is signaled first to check whether it is the planar mode.

[0095] For example, based on an MPM flag (e.g., intra_luma_mpm_flag), it can be indicated whether the intra prediction mode applied to the current block is among the MPM candidates (and the planar mode) or among the remaining modes. An MPM flag with a value of 1 can indicate that the intra prediction mode for the current block is within the MPM candidates (and the planar mode), and an MPM flag with a value of 0 can indicate that the intra prediction mode of the current block is not within the MPM candidates (and the planar mode). A non-planar flag with a value of 0 (e.g., intra_luma_not_planar_flag) can indicate that the intra prediction mode for the current block is the planar mode, and a non-planar flag with a value of 1 can indicate that the intra prediction mode for the current block is not the planar mode. The MPM index can be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information can be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information can indicate one of the remaining intra prediction modes not included in the MPM candidates (and the planar mode) among all the intra prediction modes by indexing in the order of the prediction mode numbers. The intra prediction mode can be the intra prediction mode for the luminance component (samples). Hereinafter, the intra prediction mode information can include at least one of the following: an MPM flag (e.g., intra_luma_mpm_flag), a non-planar flag (e.g., intra_luma_not_planar_flag), an MPM index (e.g., mpm_idx or intra_luma_mpm_idx), or the remaining intra prediction mode information (rem_intra_luma_luma_mpm_mode or intra_luma_mpminder). In the present disclosure, the MPM list can be referred to by various terms such as the MPM candidate list and the candModeList. When applying MIP to the current block, a separate MPM flag (e.g., intra_mip_mpm_flag), an MPM index (e.g., intra_mip_mpm_idx), and the remaining intra prediction mode information (e.g., intra_mip_mpm_remainder) for MIP can be signaled, and the non-planar flag can be not signaled.

[0096] In other words, generally, when performing block segmentation for an image, the current block to be compiled and the neighboring blocks have similar image features. Therefore, it is highly likely that the current block and the neighboring blocks have the same or similar intra prediction modes. Thus, the encoder can use the intra prediction mode of the neighboring blocks to encode the intra prediction mode of the current block.

[0097] For example, a decoding device / encoding device may construct a Most Probable Mode (MPM) list for a current block. The MPM list may be referred to as an MPM candidate list. Here, the MPM may refer to a mode that is used to improve the compilation efficiency by considering the similarity between the current block and neighboring blocks during the in-frame prediction mode compilation. As described above, the MPM list may be constructed to include the planar mode, or may be constructed to exclude the planar mode. For example, when the MPM list includes the planar mode, the number of candidates in the MPM list may be 6. And when the MPM list does not include the planar mode, the number of candidates in the MPM list may be 5.

[0098] The encoder / decoder may construct an MPM list including 5 or 6 MPMs.

[0099] To construct the MPM list, three modes may be considered: the default in-frame mode, the neighboring in-frame mode, and the derived in-frame mode.

[0100] For the neighboring in-frame mode, two neighboring blocks may be considered, namely the left neighboring block and the upper neighboring block.

[0101] As described above, if the MPM list is constructed to exclude the planar mode, the planar mode is excluded from the list, and the number of MPM list candidates may be set to 5.

[0102] In addition, in the in-frame prediction mode, the non-directional mode (or non-angle mode) may include a DC mode based on the average of the neighboring reference samples of the current block or an interpolated planar mode.

[0103] Meanwhile, when inter-frame prediction is applied, the predictor of the encoding device / decoding device can derive a predicted sample by performing inter-frame prediction on a block-by-block basis. When performing prediction on a current block, inter-frame prediction can be applied. That is, the predictor of the encoding / decoding device (more specifically, the inter-frame predictor) can derive a predicted sample by performing inter-frame prediction on a block-by-block basis. Inter-frame prediction can represent a prediction derived by a method that depends on data elements (e.g., sample values or motion information) of (one or more) pictures other than the current picture. When applying inter-frame prediction to the current block, a predicted block (predicted sample array) for the current block can be derived based on a reference block (reference sample array) specified by a motion vector on a reference picture indicated by a reference picture index. In this case, in order to reduce the amount of motion information transmitted in the inter-frame prediction mode, the motion information of the current block can be predicted on a block, sub-block, or sample basis based on the correlation of the motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include inter-frame prediction type (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of applying inter-frame prediction, neighboring blocks can include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block can be the same as or different from each other. The temporal neighboring block can be referred to by names such as a collocated reference block, a collocated CU (ColCU), etc., and the reference picture including the temporal neighboring block can be referred to as a collocated picture (ColPic). For example, a motion information candidate list can be configured based on neighboring blocks of the current block, and a flag or index information indicating which candidate is selected (used) can be signaled in order to derive the motion vector and / or reference picture index of the current block. Inter-frame prediction can be performed based on various prediction modes, and for example, in the case of the skip mode and the merge mode, the motion information of the current block can be the same as the motion information of the selected neighboring block. In the case of the skip mode, different from the merge mode, a residual signal may not be sent. In the case of the motion vector prediction (MVP) mode, the motion vector of the selected neighboring block can be used as a motion vector predictor, and a motion vector difference can be signaled. In this case, the motion vector of the current block can be derived by using the sum of the motion vector predictor and the motion vector difference.

[0104] Depending on the inter - frame prediction type (L0 prediction, L1 prediction, Bi - prediction, etc.), the motion information may further include L0 motion information and / or L1 motion information. The L0 - direction motion vector may be referred to as the L0 motion vector or MVL0, and the L1 - direction motion vector may be referred to as the L1 motion vector or MVL1. The prediction based on the L0 motion vector may be called L0 prediction, the prediction based on the L1 motion vector may be called L1 prediction, and the prediction based on both the L0 motion vector and the L1 motion vector may be called bi - prediction. Here, the L0 motion vector may indicate a motion vector associated with the reference picture list L0, and the L1 motion vector may indicate a motion vector associated with the reference picture list L1. The reference picture list L0 may include pictures that are before the current picture in the output order, and the reference picture list L1 may include pictures that are after the current picture in the output order as reference pictures. The previous pictures may be called forward (reference) pictures, and the subsequent pictures may be called backward (reference) pictures. The reference picture list L0 may further include pictures that are after the current picture in the output order as reference pictures. In this case, the previous pictures may be indexed first in the reference picture list L0, and then the subsequent pictures may be indexed. The reference picture list L1 may further include pictures that are before the current picture in the output order as reference pictures. In this case, the subsequent pictures may be indexed first in the reference picture list L1, and then the previous pictures may be indexed. Here, the output order may correspond to the picture order count (POC) order.

[0105] The video / image encoding process based on inter - frame prediction may schematically include, for example, the following.

[0106] Figure 4 An example of a video / image encoding method based on inter - frame prediction is illustrated.

[0107] The encoding device performs inter prediction on the current block (S400). The encoding device can derive the inter prediction mode and motion information of the current block and generate the prediction samples of the current block. Here, the inter prediction mode determination process, the motion information derivation process, and the prediction sample generation process can be performed simultaneously, and any one of the processes can be performed earlier than the other processes. For example, the inter prediction unit of the encoding device can include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit. The prediction mode determination unit can determine the prediction mode for the current block, the motion information derivation unit can derive the motion information of the current block, and the prediction sample derivation unit can derive the prediction samples of the current block. For example, the inter prediction unit of the encoding device can search for a block similar to the current block in a predetermined region (search region) of the reference picture through motion estimation and derive a reference block with the smallest difference from the current block or equal to or less than a predetermined criterion. The reference picture index of the reference picture where the reference block is located can be indicated based on this derivation, and the motion vector can be derived based on the position difference between the reference block and the current block. The encoding device can determine the mode applied to the current block among various prediction modes. The encoding device can compare the RD costs of various prediction modes and determine the best prediction mode for the current block.

[0108] For example, when the skip mode or the merge mode is applied to the current block, the encoding device can configure a merge candidate list to be described below and derive a reference block with the smallest difference from the current block or equal to or less than a predetermined criterion among the reference blocks indicated by the merge candidates included in the merge candidate list. In this case, the merge candidate associated with the derived reference block can be selected, and the merge index information indicating the selected merge candidate can be generated and signaled to the decoding device. The motion information of the current block can be derived by using the motion information of the selected merge candidate.

[0109] As another example, when the (A)MVP mode is applied to the current block, the encoding device can configure an (A)MVP candidate list to be described below and use the motion vector of the selected mvp candidate among the motion vector predictors (mvps) included in the (A)MVP candidate list as the mvp of the current block. In this case, for example, the motion vector of the reference block derived through motion estimation can be used as the motion vector of the current block, and the mvp candidate with the smallest difference from the motion vector of the current block among the mvp candidates can become the selected mvp candidate. The motion vector difference (MVD), which is the difference obtained by subtracting the mvp from the motion vector of the current block, can be derived. In this case, the information about the MVD can be signaled to the decoding device. In addition, when the (A)MVP mode is applied, the value of the reference picture index can be configured as reference picture index information and signaled to the decoding device separately.

[0110] The encoding device may derive a residual sample based on a prediction sample (S410). The encoding device may derive a residual sample by comparing an original sample of a current block and a prediction sample.

[0111] The encoding device encodes image information including prediction information and residual information (S420). The encoding device can output the encoded image information in the form of a bitstream. The prediction information may include information about prediction mode information (e.g., a skip flag, a merge flag, or a mode index, etc.) and information about motion information, as information related to the prediction process. The information about motion information may include candidate selection information (e.g., a merge index, an mvp flag, or an mvp index), which is information for deriving a motion vector. In addition, the information about motion information may include information about an MVD and / or reference picture index information. In addition, the information about motion information may include information indicating whether to apply L0 prediction, L1 prediction, or bi-prediction. The residual information is information about residual samples. The residual information may include information about quantization transform coefficients for the residual samples.

[0112] The output bitstream may be stored in a (digital) storage medium and transmitted to the decoding device, or transmitted to the decoding device via a network.

[0113] Meanwhile, as described above, the encoding device may generate a reconstructed picture (including reconstructed samples and reconstructed blocks) based on reference samples and residual samples. This is to derive the same prediction result as the prediction result executed by the decoding device, and as a result, the compilation efficiency can be improved. Therefore, the encoding device may store the reconstructed picture (or reconstructed samples or reconstructed blocks) in a memory and use the reconstructed picture as a reference picture. As described above, in-loop filtering processing may be further applied to the reconstructed picture.

[0114] The video / image decoding process based on inter-frame prediction may schematically include, for example, the following.

[0115] Figure 5 An example of a video / image decoding method based on inter-frame prediction is illustrated.

[0116] Refer to Figure 5 , the decoding device may perform an operation corresponding to the operation performed by the encoding device. The decoding device may perform prediction on a current block based on the received prediction information and derive a prediction sample.

[0117] Specifically, the decoding device may determine a prediction mode of a current block based on the received prediction information (S500). The decoding device may determine which inter-frame prediction mode to apply to the current block based on the prediction mode information in the prediction information.

[0118] For example, it can be determined whether the merge mode or (A)MVP mode is applied to the current block based on the merge flag. Alternatively, one of various inter prediction mode candidates can be selected based on the mode index. The inter prediction mode candidates can include the skip mode, the merge mode, and / or the (A)MVP mode, or can include various inter prediction modes to be described below.

[0119] The decoding apparatus derives the motion information of the current block based on the determined inter prediction mode (S510). For example, when the skip mode or the merge mode is applied to the current block, the decoding apparatus can configure a merge candidate list to be described below and select one merge candidate among the merge candidates included in the merge candidate list. Here, the selection can be performed based on the selection information (merge index). The motion information of the current block can be derived by using the motion information of the selected merge candidate. The motion information of the selected merge candidate can be used as the motion information of the current block.

[0120] As another example, when the (A)MVP mode is applied to the current block, the decoding apparatus can configure an (A)MVP candidate list to be described below and use the motion vector of the selected mvp candidate among the motion vector predictor (mvp) candidates included in the (A)MVP candidate list as the mvp of the current block. Here, the selection can be performed based on the selection information (mvp flag or mvp index). In this case, the MVD of the current block can be derived based on the information about the MVD, and the motion vector of the current block can be derived based on the mvp and the MVD of the current block. In addition, the reference picture index of the current block can be derived based on the reference picture index information. The picture indicated by the reference picture index in the reference picture list for the current block can be derived as the reference picture referred to for the inter prediction of the current block.

[0121] Meanwhile, as described below, the motion information of the current block can be derived without configuring a candidate list, and in this case, the motion information of the current block can be derived according to the process disclosed in the prediction mode. In this case, the candidate list configuration can be omitted.

[0122] The decoding apparatus can generate a prediction sample for the current block based on the motion information of the current block (S520). In this case, the reference picture can be derived based on the reference picture index of the current block, and the prediction sample of the current block can be derived by using the samples of the reference block indicated by the motion vector of the current block on the reference picture. In this case, in some cases, a prediction sample filtering process for all or some of the prediction samples of the current block can be further performed.

[0123] For example, the inter - frame prediction unit of the decoding device may include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit. The prediction mode determination unit may determine a prediction mode for a current block based on the received prediction mode information. The motion information derivation unit may derive the motion information (motion vector and / or reference picture index) of the current block based on information about the received motion information. And the prediction sample derivation unit may derive the prediction samples of the current block.

[0124] The decoding device generates residual samples for the current block based on the received residual information (S530). The decoding device may generate reconstruction samples for the current block based on the prediction samples and the residual samples, and generate a reconstructed picture based on the generated reconstruction samples (S540). Thereafter, as described above, an in - loop filtering process may be further applied to the reconstructed picture.

[0125] Figure 6 The inter - frame prediction process is schematically shown.

[0126] Reference Figure 6 , as described above, the inter - frame prediction process may include an inter - frame prediction mode determination step, a motion information derivation step according to the determined prediction mode, and a prediction process (prediction sample generation) step based on the derived motion information. The inter - frame prediction process may be executed by the encoding device and the decoding device as described above. Herein, the compiling device may include an encoding device and / or a decoding device.

[0127] Refer to Figure 6 , the compiling device determines the inter - frame prediction mode of the current block (S600). Various inter - frame prediction modes may be used for predicting the current block in a picture. For example, various modes such as a merge mode, a skip mode, a motion vector prediction (MVP) mode, an affine mode, a sub - block merge mode, a merge with MVD (MMVD) mode, and a history motion vector prediction (HMVP) mode may be used. Decoder - side motion vector refinement (DMVR) mode, adaptive motion vector resolution (AMVR) mode, bi - prediction with CU - level weight (BCW), and bi - directional optical flow (BDOF), etc. may be further used as additional modes. The affine mode may also be referred to as an affine motion prediction mode. The MVP mode may also be referred to as an advanced motion vector prediction (AMVP) mode. Herein, some modes and / or candidates of motion information derived from some modes may also be included in one of the motion information - related candidates in other modes. For example, the HMVP candidate may be added to the merge candidates of the merge / skip mode, or added to the mvp candidates of the MVP mode. If the HMVP candidate is used as a motion information candidate for the merge mode or the skip mode, the HMVP candidate may be referred to as an HMVP merge candidate.

[0128] Prediction mode information indicating the inter - frame prediction mode of the current block can be signaled from an encoding device to a decoding device. In this case, the prediction mode information can be included in a bitstream and received by the decoding device. The prediction mode information can include index information indicating one of a plurality of candidate modes. Alternatively, the inter - frame prediction mode can be indicated by hierarchical signaling of flag information. In this case, the prediction mode information can include one or more flags. For example, it can be indicated whether to apply the skip mode by signaling a skip flag. When the skip mode is not applied, it can be indicated whether to apply the merge mode by signaling a merge flag. And when the merge mode is not applied, it can be indicated to apply the MVP mode or additional flags for further differentiation can be signaled. The affine mode can be signaled as an independent mode or as a dependent mode with respect to the merge mode or the MVP mode. For example, the affine mode can include an affine merge mode and an affine MVP mode.

[0129] The encoding device derives motion information for the current block (S610). The motion information derivation can be based on the inter - frame prediction mode.

[0130] The encoding device can use the motion information of the current block to perform inter - frame prediction. The encoding device can derive the best motion information for the current block through a motion estimation process. For example, the encoding device can search for a similar reference block with high correlation in a predetermined search range in a reference picture using the original block in the original picture for the current block, in units of fractional pixels, and derive the motion information through the searched reference block. The similarity of the block can be derived based on the difference in sample values based on phase. For example, the similarity of the block can be calculated based on the sum of absolute differences (SAD) between the current block (or a template of the current block) and the reference block (or a template of the reference block). In this case, the motion information can be derived based on the reference block with the minimum SAD in the search area. The derived motion information can be signaled to the decoding device according to various methods based on the inter - frame prediction mode.

[0131] The encoding device performs inter - frame prediction based on the motion information for the current block (S620). The encoding device can derive the (one or more) prediction samples for the current block based on the motion information. The current block including the prediction samples can be referred to as a prediction block.

[0132] Meanwhile, as described above, the quantizer of the encoding device can derive quantized transform coefficients by applying quantization to the transform coefficients. The de - quantizer of the encoding device or the de - quantizer of the decoding device can derive the transform coefficients by applying de - quantization to the quantized transform coefficients.

[0133] Generally, in video / image compilation, the quantization ratio can be changed, and the changed quantization ratio can be used to adjust the compression ratio. In terms of implementation, the quantization parameter (QP) can be used by considering the complexity instead of directly using the quantization ratio. For example, a quantization parameter with an integer value from 0 to 63 can be used, and each quantization parameter value can correspond to an actual quantization ratio. Additionally, for example, the quantization parameter QP Y for the luminance component and the quantization parameter QP C for the chrominance component can be configured differently.

[0134] In the quantization process, the transform coefficient C can be the input, the quantization ratio (Q step ) can be divided, and the quantized transform coefficient C` can be obtained based on the quantization ratio. In this case, by considering the computational complexity, multiplying the quantization ratio by a scale can produce the quantization ratio in integer form, and a shift operation can be performed with a value corresponding to the scale value. The quantization scale can be derived based on the product of the quantization ratio and the scale value. That is, the quantization scale can be derived based on QP. For example, the quantization scale can be applied to the transform coefficient C`, and the quantized transform coefficient C` can be derived based on the applied result.

[0135] The dequantization process is the inverse process of the quantization process. In this process, the quantized transform coefficient C` can be multiplied by the quantization ratio (Q step ), and the reconstructed transform coefficient C`` can be obtained based on the result of the multiplication. In this case, the level scale can be derived based on the quantization parameter, the level scale can be applied to the quantized transform coefficient C`, and the reconstructed transform coefficient C`` can be derived. Due to the loss in the transform and / or quantization process, the reconstructed transform coefficient C`` may be somewhat different from the first transform coefficient C. Therefore, dequantization is performed in the encoding device as well as in the decoding device.

[0136] Meanwhile, an adaptive frequency weighted quantization technique for adjusting quantization strength according to frequency can be applied. The adaptive frequency weighted quantization technique is a method of applying quantization strength differently to each frequency. In adaptive frequency weighted quantization, a predefined quantization scaling matrix can be used to apply quantization strength for each frequency differently. That is, the above quantization / dequantization process can be performed based on the quantization scaling matrix. For example, in order to generate the size of the current block and / or the residual signal of the current block, different quantization scaling matrices can be used depending on whether the prediction mode applied to the current block is inter prediction or intra prediction. The quantization scaling matrix can be referred to as a quantization matrix or a scaling matrix. The quantization scaling matrix can be predefined. In addition, for frequency adaptive scaling, quantization scale information for each frequency of the quantization scaling matrix can be constructed / encoded in the encoding device and signaled to the decoding device. The quantization scale information for each frequency can be referred to as quantization scaling information. The quantization scale information for each frequency can include scaling_list_data. A (modified) quantization scaling matrix can be derived based on the scaling_list_data. In addition, the quantization scale information for each frequency can include presence flag information indicating whether the scaling_list_data exists. Alternatively, if the scaling_list_data is signaled at a higher level (e.g., SPS), information indicating whether the scaling_list_data is modified at a lower level (e.g., PPS or slice group header, etc.) in the higher level can also be included.

[0137] As described above, quantization / dequantization can be applied to the luminance component and the chrominance component based on quantization parameters.

[0138] Quantization parameters for a compilation unit can be determined based on information signaled at the picture and / or slice level. For example, quantization parameters can be derived as described later.

[0139] For example, information related to the derivation of quantization parameters can be signaled through a sequence parameter set (SPS) as shown in the following table.

[0140] [Table 1]

[0141]

[0142] The semantics of the syntax elements in Table 1 can be the same as those in the following table.

[0143] [Table 2]

[0144]

[0145]

[0146] For example, the syntax element bit_depth_luma_minus8 can represent BitDepth Y i.e., the bit depth of the samples of the luma array, and QpBdOffset Y i.e., the luma quantization parameter range offset. That is to say, for example, BitDepth Y and QpBdOffset Y can be derived based on the syntax element bit_depth_luma_minus8. For example, BitDepth Y can be derived as the value obtained by adding 8 to the value of the syntax element bit_depth_luma_minus8. QpBdOffset Y can be derived as the value obtained by multiplying the value of the syntax element bit_depth_luma_minus8 by 6. In addition, bit_depth_luma_minus8 can be in the range of 0 to 8.

[0147] In addition, for example, the syntax element bit_depth_chroma_minus8 can represent BitDepth C i.e., the bit depth of the samples of the chroma array, and QpBdOffset C i.e., the chroma quantization parameter range offset. That is to say, for example, BitDepth C and QpBdOffset C can be derived based on the syntax element bit_depth_chroma_minus8. For example, BitDepth C can be derived as the value obtained by adding 8 to the value of the syntax element bit_depth_chroma_minus8. QpBdOffset C can be derived as the value obtained by multiplying the value of the syntax element bit_depth_chroma_minus8 by 6. In addition, bit_depth_chroma_minus8 can be in the range of 0 to 8.

[0148] In addition, information related to the derivation of quantization parameters can be signaled, for example, through a picture parameter set (PPS) as shown in the following table. This information can include chroma Cb offset, chroma Cr offset, combined chroma offset, and initial quantization parameter. That is to say, this information can include syntax elements for chroma Cb offset, chroma Cr offset, combined chroma offset, and initial quantization parameter.

[0149] [Table 3]

[0150]

[0151] The semantics of the syntax elements in Table 3 can be the same as those in the following table.

[0152] [Table 4]

[0153]

[0154] For example, the value obtained by adding 26 to the syntax element init_qp_minus26 can represent the SliceQp for each slice of the reference PPS Y initial value. If a non-zero value of slice_qp_delta is decoded, the initial value of SliceQp Y can be modified in the slice layer. init_qp_minus26 0 can be in the range of -(26 + QpBdOffset Y ).

[0155] In addition, for example, the syntax elements pps_cb_qp_offset and pps_cr_qp_offset can represent the offsets for deriving Qp’ Cb and Qp’ Cr of the luma quantization parameter Qp’ Y respectively. pps_cb_qp_offset and pps_cr_qp_offset can be in the range of -12 to +12. In addition, when ChromaArrayType is 0, during the decoding process, pps_cb_qp_offset and pps_cr_qp_offset may not be used, and the decoding device can ignore the values of these syntax elements.

[0156] In addition, for example, the syntax element pps_joint_cbcr_qp_offset can represent the offset for deriving Qp’ CbCr of the luma quantization parameter Qp’ Y respectively. pps_joint_cbcr_qp_offset can be in the range of -12 to +12. In addition, when ChromaArrayType is 0, during the decoding process, pps_joint_cbcr_qp_offset may not be used, and the decoding device can ignore the values of these syntax elements.

[0157] In addition, for example, the syntax element pps_slice_chroma_qp_offsets_present_flag can indicate whether the syntax elements slice_cb_qp_offset and slice_cr_qp_offset are present in the slice header associated with the syntax elements slice_cb_qp_offset and slice_cr_qp_offset. For example, a pps_slice_chroma_qp_offsets_present_flag having a value of 1 can indicate that the syntax elements slice_cb_qp_offset and slice_cr_qp_offset are present in the slice header associated with the syntax elements slice_cb_qp_offset and slice_cr_qp_offset. In addition, for example, a pps_slice_chroma_qp_offsets_present_flag having a value of 0 can indicate that the syntax elements slice_cb_qp_offset and slice_cr_qp_offset are not present in the slice header associated with the syntax elements slice_cb_qp_offset and slice_cr_qp_offset. In addition, when ChromaArrayType is 0, during the decoding process, the pps_slice_chroma_qp_offsets_present_flag can be the same as 0.

[0158] As in the foregoing, the syntax elements parsed in the PPS can be init_qp_minus26, pps_cb_qp_offset_pps_cr_qp_offset, pps_joint_cbcr_qp_offset, and pps_slice_chroma_qp_offsets_present_flag. The syntax element init_qp_minus26 can represent the initial value of SliceQp Y for each slice that refers to the PPS. In addition, the syntax elements pps_cb_qp_offset, pps_cr_qp_offset, and pps_joint_cbcr_qp_offset can represent the offset for the luma quantization parameter Qp’ Y . In addition, the syntax element pps_slice_chroma_qp_offsets_present_flag can indicate whether the offset parameter is present in the slice header.

[0159] In addition, for example, information related to the derivation of quantization parameters can be signaled through the slice header as shown in the following table.

[0160] [Table 5]

[0161]

[0162] The semantics of the syntax elements in Table 5 can be the same as those in the following table.

[0163] [Table 6]

[0164]

[0165]

[0166]

[0167] For example, slice_qp_delta can represent the initial value of Qp to be used in the coding block within a slice until it is modified by the value of CuQpDeltaVal at the compilation unit layer. For example, the initial value of Qp for a slice Y SliceQp can be derived as 26 + init_qp_minus26 + slice_qp_delta. The value of SliceQpY can be in the range of -QpBdOffset Y to +63. Y to +63. Y to +63.

[0168] In addition, for example, slice_cb_qp_offset can represent the difference to be added to the value of pps_cb_qp_offset when determining the value of the quantization parameter Qp'. Cb The value of slice_cb_qp_offset can be in the range of -12 to +12. In addition, for example, if slice_cb_qp_offset does not exist, slice_cb_qp_offset can be inferred as 0. The value of pps_cb_qp_offset + slice_cb_qp_offset can be in the range of 12 to +12.

[0169] In addition, for example, slice_cr_qp_offset can represent the difference to be added to the value of pps_cr_qp_offset when determining the value of the quantization parameter Qp'. Cr The value of slice_cr_qp_offset can be in the range of -12 to +12. In addition, for example, if slice_cr_qp_offset does not exist, slice_cr_qp_offset can be inferred as 0. The value of pps_cr_qp_offset + slice_cr_qp_offset can be in the range of 12 to +12.

[0170] In addition, for example, slice_cbcr_qp_offset may represent the difference to be added to the value of pps_cbcr_qp_offset when determining the value of quantization parameter Qp'. The value of slice_cbcr_qp_offset may be in the range of -12 to +12. In addition, for example, if slice_cbcr_qp_offset does not exist, slice_cbcr_qp_offse may be inferred as 0. The value of pps_cbcr_qp_offset + slice_cbcr_qp_offset may be in the range of 12 to +12. CbCr The value of slice_cbcr_qp_offset may be the difference to be added to the value of pps_cbcr_qp_offset when determining the value of quantization parameter Qp'. The value of slice_cbcr_qp_offset may be in the range of -12 to +12. In addition, for example, if slice_cbcr_qp_offset does not exist, slice_cbcr_qp_offse may be inferred as 0. The value of pps_cbcr_qp_offset + slice_cbcr_qp_offset may be in the range of 12 to +12.

[0171] The derivation process for the luminance and chrominance quantization parameters may be started based on the following fact:

[0172] The input to this process is the luminance position, parameters for specifying the width and height of the current coding block, and a parameter for specifying a single tree or a double tree. At the same time, as in the foregoing, the luminance quantization parameter, the chrominance quantization parameter, and the joint chrominance quantization parameter may be represented as Qp' Y 、Qp' Cb 、Qp' Cr and Qp' CbCr .

[0173] At the same time, for example, the syntax element cu_qp_delta_sign_flag representing the sign of CuQpDeltaVal may be parsed. For example, cu_qp_delta_sign_flag may represent the sign of CuQpDeltaVal as follows.

[0174] For example, when cu_qp_delta_sign_flag is 0, the CuQpDeltaVal corresponding to cu_qp_delta_sign_flag may have a positive value. Alternatively, for example, when cu_qp_delta_sign_flag is 1, the CuQpDeltaVal corresponding to cu_qp_delta_sign_flag may have a negative value. In addition, if cu_qp_delta_sign_flag does not exist, cu_qp_delta_sign_flag may be inferred as 0.

[0175] In addition, for example, if cu_qp_delta_abs exists, the parameter IsCuQpDeltaCoded

[0176] may be derived as 1. The parameter CuQpDeltaVal may be derived as cu_qp_delta_abs

[0177] *(1 - 2 * cu_qp_delta_sign_flag). CuQpDeltaVal can be in the range of -(32 +

[0178] QpBdOffsetY / 2) to +(31 + QpBdOffsetY / 2).

[0179] Thereafter, for example, the luma quantization parameter Qp’ Y can be derived as in the following equation.

[0180] [Equation 1]

[0181] Qp Y = ((qP Y_PRED + CuQpDeltaVal + 64 + 2 * QpBdOffset Y ) % (64 + QpBdOffset Y )) - QpBdOffset Y

[0182] In addition, if ChromaArrayType is not 0 and treeType is SINGLE_TREE or DUAL_TREE_CHROMA, the following can be applied.

[0183] - When treeType is equal to DUAL_TREE_CHROMA, the parameter Qp Y can be set the same as the luma quantization parameter Qp of the luma coding unit including the luma position QpY(xCb + cbWidth / 2, yCb + cbHeight / 2). Y

[0184] - The parameters qP Cb , qP Cr and qP CbCr can be derived as follows.

[0185] [Equation 2]

[0186] qPi Cb = Clip3(-QpBdOffset C , 69, Qp Y + pps_cb_qp_offset + slice_cb_qp_offset)

[0187] qPi Cr = Clip3(-QpBdOffset C , 69, Qp Y + pps_cr_qp_offset + slice_cr_qp_offset)​

[0188] qPi CbCr = Clip3(-QpBdOffsct C , 69, Qp Y +pps_joint_cbcr_qp_offsct+slice_joint_cbcr_qp_offsct)

[0189] For example, when ChromaArrayType is 1, the parameter qP Cb , qP Cr and qP CbCr can be set to be the same as the QpC value specified in Table 7 based on the index qPi that is the same as qPi Cb , qPi Cr and qPi CbCr respectively.

[0190] [Table 7]

[0191] qPi ＜30 30 31 32 33 34 35 36 37 38 39 40 41 42 43 ＞43 <![CDATA[Qp C > = qPi 29 30 31 32 33 33 34 34 35 35 36 36 37 37 = qPi - 6

[0192] Alternatively, when ChromaArrayType is not 1, the parameter qP Cb , qP Cr and qP CbCr can be set to be the same as Min(qPi, 63) based on the index qPi that is the same as qPi Cb , qPi Cr and qPi CbC respectively.

[0193] - The chrominance quantization parameters Qp' Cb and Qp' Cr for the Cb and Cr components, and the chrominance quantization parameter Qp' CbCr for joint Cb - Cr coding can be derived as follows.

[0194] [Equation 3]

[0195] Qp' Cb = qP Cb + QpBdOffset C

[0196] Qp′ Cr = qP Cr + QpBdOffset C

[0197] Qp′ CbCr = qP CbCr + QpBdOffset C

[0198] Meanwhile, the document proposes a solution for improving the compilation efficiency in quantization / dequantization processing.

[0199] In an embodiment, this document proposes a method for defining and using a user-defined chroma quantization mapping table, rather than a method of obtaining a chroma quantization parameter value from a luma quantization parameter value through a pre-defined chroma quantization mapping table in the existing VVCDraft5 v.7 when ChromaArrayType is not 0 (e.g., when ChromaArrayType is 1). In the VVC specification text (e.g., VVC Draft5 v.7), when a given qPi (luma quantization parameter value) is provided, Qpc (chroma quantization parameter value) is derived through a pre-defined chroma quantization table (e.g., Table 7), but this document proposes a method of deriving Qpc from qPi based on a newly user-defined chroma quantization mapping table. According to an embodiment of this document, a method is proposed in which the Qpc value can be derived through a functional relationship of the qPi value, and the function can be signaled as a syntax such as APS, SPS, or PPS through a user-defined functional method. The functional relationship sends the value of a pre-defined syntax element, and the user defines the chroma quantization table mapping based on the sent value. For example, since the Qpc value can be derived through a functional relationship of the qPi value, if the syntax element value representing the corresponding function is sent, the user-defined chroma quantization mapping table can be derived in the form of Table 7.

[0200] In an embodiment, a solution is proposed for signaling information about a syntax element (Qpc_data) in an Adaptive Parameter Set (APS), which represents a function related to chroma quantization mapping as shown in the following table to be described later.

[0201] [Table 8]

[0202]

[0203] Referring to Table 8, if aps_params_type represents Qpc_APS, for example, when the value of aps_params_type is 2, Qpc_data() can be signaled.

[0204] The semantics of the syntax elements in Table 8 can be the same as those in the following table.

[0205] [Table 9]

[0206]

[0207] For example, the syntax element adaptation_parameter_set_id can provide an identifier of the APS referenced by other syntax elements.

[0208] In addition, for example, the syntax element aps_extension_flag may indicate whether the aps_extension_data_flag syntax element is present in the APS RBSP syntax structure. For example, the syntax element aps_extension_flag with a value of 1 may indicate that the aps_extension_data_flag syntax element is present in the APS RBSP syntax structure. The syntax element aps_extension_flag with a value of 0 may indicate that the aps_extension_data_flag syntax element is not present in the APS RBSP syntax structure.

[0209] In addition, for example, the syntax element aps_extension_data_flag may have any value. The presence (existence and value) of aps_extension_data_flag may not affect the decoding compliance of the profiles specified in the version of this standard. For example, a decoding device following the version of this standard may ignore all syntax elements aps_extension_data_flag.

[0210] In addition, for example, the syntax element aps_params_type may indicate the type of APS parameters included in the APS, as shown in Table 10.

[0211] [Table 10]

[0212]

[0213] For example, referring to Table 10, when the value of the syntax element aps_params_type is 0, the syntax element aps_params_type may indicate that the type of APS parameter is an ALF parameter. When the value of the syntax element aps_params_type is 1, the syntax element aps_params_type may indicate that the type of APS parameter is an LMCS parameter. When the value of the syntax element aps_params_type is 2, the syntax element aps_params_type may indicate that the type of APS parameter is a Qpc data parameter. The Qpc data parameter may indicate a chrominance quantization data parameter.

[0214] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0215] For example, this embodiment presents a method for signaling user-defined Qp in the Picture Parameter Set (PPS) CA solution for data. As an example for implementing the solution proposed in this embodiment, a flag indicating whether the PPS includes user - defined data in the SPS can be introduced. That is, a flag indicating whether the PPS includes user - defined data in the SPS can be signaled. In addition, according to this embodiment, user - defined data can be signaled in the PPS. Alternatively, user - defined data can be signaled in the slice header and / or another header set.

[0216] A flag indicating whether the PPS includes user - defined data can be signaled as shown in the following table.

[0217] [Table 11]

[0218]

[0219] For example, the syntax element Qpc_data_default_flag can be the syntax element of the aforementioned flag. The syntax element Qpc_data_default_flag can indicate whether the Qpc_data() parameter exists in the PPS RBSP syntax structure. For example, Qpc_data_default_flag being 0 can indicate that the Qpc_data() parameter does not exist in the PPS RBSP syntax structure, and the default table is used to assist in the determination of chroma quantization. In this case, the default table can be the same as Table 7. In addition, for example, Qpc_data_default_flag being 1 can indicate that the Qpc_data() parameter can exist in the PPS RBSP syntax structure.

[0220] In addition, the user - defined data signaled in the PPS according to this embodiment can be the same as the following table.

[0221] [Table 12]

[0222]

[0223] Meanwhile, for example, Qpc_data() can include information required for chroma quantization derivation when ChromaArrayType is 1.

[0224] In addition, this document proposes another embodiment in which information for quantization parameters is signaled.

[0225] For example, this embodiment proposes a flexible structure for chroma quantization parameter (QP) derivation and combined chroma QP derivation. This embodiment proposes a solution for signaling an initial flag that indicates whether there is a user - defined mode in which parameters representing functions for deriving chroma quantization parameters (QP) in the SPS and / or PPS can be used.

[0226] For example, the flag information signaled in the high-level syntax proposed in this embodiment may be the same as the table described later.

[0227] [Table 13]

[0228]

[0229] For example, Qpc_data_present_flag may indicate whether the parameter for deriving the chrominance quantization parameter exists in the high-level syntax RBSP syntax structure. For example, Qpc_data_present_flag with a value of 0 may indicate that the chrominance quantization parameter does not exist in the high-level syntax RBSP syntax structure. Additionally, for example, Qpc_data_present_flag with a value of 1 may indicate that the chrominance quantization parameter exists in the high-level syntax RBSP syntax structure.

[0230] Alternatively, the syntax element Qpc_data_present_flag may be used in the bitstream to indicate the scheme used for chrominance quantization derivation. For example, the syntax element Qpc_data_present_flag may represent the tool for chrominance quantization derivation or the use of the following user-defined mode.

[0231] For example, Qpc_data_present_flag in the bitstream may indicate whether user-defined chrominance quantization is used. For example, Qpc_data_present_flag with a value of 0 may indicate that user-defined chrominance quantization is not used in the bitstream. Additionally, for example, Qpc_data_present_flag with a value of 1 may indicate that user-defined chrominance quantization is used alone or in combination with another flag.

[0232] Furthermore, this document presents another embodiment in which information for quantization parameters is signaled.

[0233] For example, this embodiment presents how the user-defined information signaled in a function can be used to derive the chrominance quantization parameter (QP) (i.e., Qp` Cb 、Qp` Cr and Qp` CbCr ). For example, according to this embodiment, data representing the function for deriving the chrominance quantization parameter (QP) can be signaled, and the chrominance quantization parameter can be derived based on the chrominance quantization data. The data for chrominance quantization parameter derivation (or the user-defined QP mapping table) can be signaled as shown in the following table.

[0234] [Table 14]

[0235]

[0236] The semantics of the syntax elements in Table 14 can be the same as those in the following table.

[0237] [Table 15]

[0238]

[0239] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chroma quantization.

[0240] In addition, for example, the syntax element qPi_delta_max_idx can represent the incremental value between Qpi_min_idx and the maximum qPi index used in the derivation of chroma Qp c The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. For example, the maximum index qPiMaxIdx used in the derivation of Qp c can be derived as in the following equation.

[0241] [Equation 4]

[0242] qPiMaxIdx = qPi_min_idx + qPi_delta_max_idx

[0243] In addition, for example, the syntax element Qp C _qPi_val[i] can represent the Qp value for the i-th index. C value.

[0244] In addition, for example, the syntax element QpOffset C can represent the offset value used for the derivation of Qp C value.

[0245] In addition, for example, the parameter Qp C Idx[qPi] for qPi can be derived as follows. In this case, qPi can be from 0 to qPiMaxIdx.

[0246] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set to be the same as qPi.

[0247] - When qPi = qPi_min_idx... qPiMaxIdx, Qp C Idx[qPi] can be set the same as Qp C _qPi_val[qPi].

[0248] - When qPi > qPiMaxIdx, Qp CIdx[qPi] can be set to qPi - QpOffset C 。

[0249] After that, the value of Qp C can be derived as Qp C Idx[qPi].

[0250] For example, according to this embodiment, if the process of deriving quantization parameters is described in a standard format, the process can be as shown in the following table.

[0251] [Table 16]

[0252]

[0253]

[0254]

[0255]

[0256] Referring to Table 16, the process of deriving quantization parameters for luminance and chrominance can be started based on the following facts: the inputs for this process are the luminance position (xCb, yCb), the parameters cbWidth and cbHeight specifying the width and height of the current coded block, and the parameter treeType specifying single tree or double tree. Also, as in the foregoing, the luminance quantization parameter and the chrominance quantization parameter can be represented as Qp’ Y 、Qp’ Cb and Qp’ Cr 。

[0257] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0258] For example, this embodiment presents an example in which there is a user - defined mode or a default mode as a flag within the SPS, so as to use syntax elements that can be used to control the derivation of quantization parameters. Examples of syntax elements that can be used to derive quantization parameters can be the same as those in the following table. Also, the structure of the syntax elements is not limited to, for example, the structure illustrated in the following table.

[0259] [Table 17]

[0260]

[0261] [Table 18]

[0262]

[0263] [Table 19]

[0264]

[0265] For example, the syntax element Qpc_data_default_flag may indicate whether a user - defined mode is used to derive quantization parameters. For example, a Qpc_data_default_flag with a value of 0 may indicate that the user - defined mode is used to derive quantization parameters. Additionally, for example, a Qpc_data_default_flag with a value of 1 may indicate that a default table is used to derive chrominance quantization parameters. In this case, the default table may be the same as Table 7. Further, if the syntax element Qpc_data_default_flag does not exist, the syntax element Qpc_data_default_flag may be inferred as 1.

[0266] Meanwhile, if the user - defined mode is used, the corresponding slice header, tile group / header, or another appropriate header may be used to signal the APS ID. For example, as shown in Table 18, a syntax element representing the APS ID may be signaled through the slice header.

[0267] For example, the syntax element slice_Qp c _aps_id may represent the adaptation_parameter_set_id of the Qp c APS referred to by the slice. The TemporalId of a Qp c _aps_id) with an adaptation_parameter_set_id (such as slice_Qp c APS NAL unit may be less than or equal to the TemporalId of the coded slice NAL unit. If multiple Qp c APSs with an adaptation_parameter_set_id including the same value are referred to by two or more slices of the same image, then multiple Qp c APSs with an adaptation_parameter_set_id including the same value may have the same content.

[0268] In addition, the APS structure for transmitting chrominance quantization data proposed in this embodiment may be the same as Table 19.

[0269] For example, the syntax element adaptation_parameter_set_id may provide an identifier of the APS referred to by other syntax elements.

[0270] In addition, for example, the syntax element aps_extension_flag may indicate whether the aps_extension_data_flag syntax element is present in the APS RBSP syntax structure. For example, the syntax element aps_extension_flag with a value of 1 may indicate that the aps_extension_data_flag syntax element is present in the APS RBSP syntax structure. The syntax element aps_extension_flag with a value of 0 may indicate that the aps_extension_data_flag syntax element is not present in the APS RBSP syntax structure.

[0271] In addition, for example, the syntax element aps_extension_data_flag may have any value. The presence (existence and value) of aps_extension_data_flag may not affect the decoding compliance of the profiles specified in this version of the standard. For example, a decoding device following this version of the standard may ignore all syntax elements aps_extension_data_flag.

[0272] In addition, for example, the syntax element aps_extension_flag may indicate the type of APS parameters included in the APS, as shown in Table 10.

[0273] The Qpc_data() disclosed in Table 19 may be signaled as shown in the following table.

[0274] [Table 20]

[0275]

[0276] For example, the syntax element qPi_min_idx may indicate the minimum qPi index used in chrominance quantization.

[0277] In addition, for example, the syntax element qPi_delta_max_idx may indicate the incremental value between Qpi_min_idx and the maximum qPi index used in the derivation of the chrominance Qp c The value of qPiMaxIdx may be greater than or equal to qPi_min_idx. For example, the maximum index qPiMaxIdx used in the derivation of Qp c may be derived as shown in Equation 4.

[0278] In addition, for example, the value obtained by adding 1 to the syntax element Qp c _prec_minus1 may indicate the number of bits used to represent the syntax lmcs_delta_abs_cw[i]. Qp cThe value of _prec_minus1 can be in the range of 0 to BitDepth Y -2.

[0279] In addition, for example, the syntax element Qp c _init_val can represent the Qp corresponding to qPi_min_idx C value.

[0280] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the increment of the Qp value for the i-th index C value.

[0281] In addition, for example, the syntax element QpOffset C can represent the offset value used to derive Qp c value.

[0282] For example, the parameter Qp C Idx[qPi] for qPi can be derived as follows. In this case, qPi can be from 0 to qPiMaxIdx.

[0283] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set to be the same as qPi.

[0284] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] can be set to Qp c _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0285] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - QpOffset C .

[0286] Thereafter, the value of Qp C can be derived as Qp C Idx[qPi].

[0287] As in the foregoing embodiments, the chrominance quantization parameter, i.e., Qp’ Cb , Qp’ Cr and Qp’ CbCr , can be derived using the signaled user-defined information or the default values illustrated in a default table such as Table 7.

[0288] For example, in this embodiment, if the process of deriving quantization parameters is written in a standard format, the process can be represented as in the following table.

[0289] [Table 21]

[0290]

[0291]

[0292]

[0293]

[0294] Referring to Table 21, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameters qP Cb 、qP Cr and qP CbCr can be derived based on the signaling user - defined information proposed in this embodiment. When ChromaArrayType is 1 and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameters qP Cb 、qP Cr and qP CbCr can be derived respectively based on the same index qPi Cb 、qPi Cr and qPi CbCr from the default table.

[0295] In addition, this document presents another embodiment in which information for quantizing parameters is signaled.

[0296] For example, this embodiment proposes a syntax element that can be used to control the derivation of quantization parameters by indicating a user - defined mode or a default mode via a flag in the SPS. Specifically, this embodiment proposes a scheme for signaling the following syntax structure. At the same time, the structure of the syntax element is an example and is not limited to the structure illustrated in the following table.

[0297] [Table 22]

[0298]

[0299] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chroma quantization.

[0300] In addition, for example, the syntax element qPi_delta_max_idx can represent the increment value between Qpi_min_idx and the maximum qPi index used in the derivation. The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. For example, Qp c In the derivation, the maximum qPi index qPiMaxIdx used can be derived as in Equation 4. c In addition, for example, the syntax element Qp

[0301] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the increment of the Qp value at the i-th index. C In addition, for example, the syntax element QpOffset can represent an offset value used in the derivation of Qp, such as the foregoing.

[0302] In addition, for example, the syntax element QpOffset C can represent an offset value used in the derivation of Qp c as described above.

[0303] As in the foregoing embodiments, the chroma quantization parameters, i.e., Qp’ Cb 、Qp’ Cr and Qp’ CbCr can be derived using the signaled user-defined information or the default values used in a default table such as Table 7.

[0304] For example, in this embodiment, if the process of deriving the quantization parameters is written in a standard format, the process can be represented as in the following table.

[0305] [Table 23]

[0306]

[0307]

[0308]

[0309]

[0310] Referring to Table 23, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameters qP Cb 、qP Cr and qP CbCr can be derived based on the signaled user-defined information proposed in this embodiment. For example, when ChromaArrayType is 1 and Qpc When _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameter qP Cb 、qP Cr and qP CbCr can be derived identically based on the index qPi Cb 、qPi Cr and qPi CbCr that is the same as Qp C respectively, as follows.

[0311] For example, the parameter Qp C Idx[i] can be derived as follows.

[0312] - When i < qPi_min_idx, Qp C Idx[qPi] can be set identically to qPi.

[0313] - When i = qPi_min_idx…qPiMaxIdx, Qp C Idx[i] can be set to Qp C _qPi_delta_val[i] + Qp C Idx[i - 1].

[0314] - When i > qPiMaxIdx, Qp C Idx[i] can be set to qPi - QpOffset C .

[0315] Thereafter, Qp C can be set to Qp C Idx[i].

[0316] In addition, referring to Table 23, when ChromaArrayType is 1 and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameter qP Cb 、qP Cr and qP CbCr can be derived from the default table based on the index qPi Cb 、qPi Cr and qPi CbCr that is the same respectively.

[0317] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0318] For example, the present embodiment proposes a syntax element for a derivation parameter of chrominance quantization (Qp C ) in an Adaptive Parameter Set (APS). For example, the APS ID can be signaled in the slice header. Additionally, for example, a flag can be proposed within the Picture Parameter Set (PPS), which indicates whether to use the default table or a table derived from the information signaled in the APS. Additionally, for example, if the default table is not used, an additional control scheme for supporting access to the APS including Qp C data can be added to the slice header.

[0319] Meanwhile, according to existing video / image standards, the chrominance QP can be derived from the luma QP and can be updated by an additionally signaled chrominance QP offset. The existing chrominance quantization parameter Qp C table can be a default table such as Table 7.

[0320] The present embodiment proposes to add a function for signaling the chrominance quantization parameter Qp C as a function of the index qPi. The APS can be used for integrating the signaling scheme of Qp C values.

[0321] For example, the APS according to the present embodiment can be the same as the following table.

[0322] [Table 24]

[0323]

[0324] For example, the syntax element adaptation_parameter_set_id can provide an identifier of the APS referenced by other syntax elements.

[0325] Additionally, for example, the syntax element aps_params_type can represent the type of APS parameters included in the APS, as shown in Table 10.

[0326] Additionally, for example, the syntax element aps_extension_flag can indicate whether the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure. For example, the syntax element aps_extension_flag with a value of 1 can indicate that the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure. The syntax element aps_extension_flag with a value of 0 can indicate that the aps_extension_data_flag syntax element does not exist in the APS RBSP syntax structure.

[0327] In addition, for example, the syntax element aps_extension_data_flag can have any value. The presence (presence and value) of aps_extension_data_flag may not affect the decoding suitability of the profiles specified in this version of the standard. For example, a decoding device that complies with this version of the standard may ignore all syntax elements aps_extension_data_flag.

[0328] The Qp disclosed in Table 24 c _data() can be signaled as shown in the following table.

[0329] [Table 25]

[0330]

[0331] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chrominance quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0332] In addition, for example, the syntax element qPi_delta_max_idx can represent the incremental value between Qpi_min_idx and the maximum qPi index used in chrominance Qp c derivation. The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. In addition, for example, the value of qPi_delta_max_idx can be in the range of 0 to 63. For example, the maximum index qPiMaxIdx used in Qp c derivation can be derived as in Equation 4.

[0333] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the difference between the Qp C values of the i-th index. This difference can also be referred to as an increment.

[0334] In addition, for example, the syntax element Qp C Offset C _present_flag can represent whether QpOffset C exists in the bitstream. For example, Qp with a value of 1 C Offset C _present_flag can represent that QpOffset C exists in the bitstream. In addition, for example, Qp with a value of 0 C Offset C _present_flag can represent that QpOffset CIt does not exist in the bitstream. When Qp C Offset C _present_flag does not exist, Qp C Offset C _present_flag can be inferred to be 0.

[0335] In addition, for example, the syntax element QpOffset C can represent the offset value used in the derivation of Qp c .

[0336] For example, the parameter Qp C Idx[qPi] of qPi can be derived as follows. In this case, qPi can be from 0 to 63.

[0337] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0338] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] can be set to Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0339] - If qPi > qPiMaxIdx, then when Qp C Offset C _present_flag is 1, Qp C Idx[qPi] can be set to qPi - QpOffset C . If Qp C Offset C _present_flag is not 1, that is, if Qp C Offset C _present_flag is 0, then Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0340] After that, the value of Qp C can be derived as Qp C Idx[qPi].

[0341] In addition, this embodiment proposes signaling as the flag of PPS as shown in the following table.

[0342] [Table 26]

[0343]

[0344] For example, the syntax element Qp c _data_default_flag can indicate whether the user - defined mode is used for quantization parameter derivation. For example, a Qp with a value of 0 c _data_default_flag can indicate that the user - defined mode is used for quantization parameter derivation. In addition, for example, a Qp with a value of 1 c _data_default_flag can indicate that the above - mentioned default table is used for quantization parameter derivation. The default table can be the same as Table 7. If the Qp c _data_default_flag does not exist, then the Qp c _data_default_flag can be inferred as 1.

[0345] In addition, this embodiment proposes signaling in the following table as a syntax element of the slice header.

[0346] [Table 27]

[0347]

[0348] For example, the syntax element slice_Qp c _aps_id can indicate the adaptation_parameter_set_id of the Qp referenced by the slice c APS. The TemporalId of the Qp with an adaptation_parameter_set_id (such as slice_Qp c _aps_id) of the APS NAL unit can be less than or the same as the TemporalId of the compiled slice NAL unit. If there are multiple Qp c APSs with adaptation_parameter_set_id including the same value and they are referenced by two or more slices of the same image, then multiple Qp c APSs with adaptation_parameter_set_id including the same value c APSs can have the same content.

[0349] For example, in this embodiment, if the process of deriving quantization parameters is written in a standard format, the process can be represented as in the following table.

[0350] [Table 28]

[0351]

[0352]

[0353]

[0354]

[0355] Referring to Table 28, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameter qP Cb , qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. Further, for example, when ChromaArrayType is 1 and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameter qP Cb , qP Cr and qP CbCr can be derived respectively based on the same index qPi as qPi Cb , qPi Cr and qPi CbCr through a default table.

[0356] Further, this document presents another embodiment in which information for quantizing parameters is signaled.

[0357] For example, in this embodiment, a user - defined derivation of chroma quantization signaled in the SPS is presented as follows. For example, this embodiment presents user - defined chroma quantization (Qp C ). For example, the flag in the SPS can indicate whether the default table is used for chroma quantization derivation or the content of the table for chroma quantization derivation is derived in the information signaled in the SPS.

[0358] For example, this embodiment presents a scheme for performing chroma quantization according to the index qPi by using the syntax elements shown in the following table.

[0359] [Table 29]

[0360]

[0361] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chrominance quantization. The value of qPi_min_idx may be in the range of 0 to 63.

[0362] In addition, for example, the syntax element qPi_delta_max_idx may represent the incremental value between Qpi_min_idx and the maximum qPi index used in the Qp c derivation. The value of qPiMaxIdx may be greater than or equal to qPi_min_idx. The value of qPi_delta_max_idx may be in the range of 0 to 63. For example, in the Qp c derivation, the maximum index qPiMaxIdx used may be derived as in Equation 4.

[0363] In addition, for example, the syntax element Qp C _qPi_delta_val[i] may represent the increment of the Qp value for the i-th index. C

[0364] For example, the parameter Qp C Idx[qPi] may be derived as follows.

[0365] - When qPi < qPi_min_idx, Qp C Idx[qPi] may be set the same as qPi.

[0366] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] may be set to Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0367] - When qPi > qPiMaxIdx, Qp C Idx[qPi] may be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0368] Thereafter, Qp C may be set to Qp C Idx[qPi].

[0369] In addition, the flag of the SPS that represents whether the default table is used for chrominance quantization derivation or whether the signaling information is used for chrominance quantization derivation proposed in this embodiment may be the same as the following table.

[0370] [Table 30]

[0371]

[0372] For example, the syntax element Qp c _data_default_flag can indicate whether the user-defined mode is used to derive quantization parameters. For example, Qp with a value of 0 c _data_default_flag can indicate that the user-defined mode is used to derive quantization parameters. In addition, for example, Qp with a value of 1 c _data_default_flag can indicate that the default table is used to derive quantization parameters. The default table can be the same as Table 7. In addition, if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred as 1.

[0373] For example, according to this embodiment, if the process of deriving quantization parameters is written in a standard format, the process can be represented as in the following table.

[0374] [Table 31]

[0375]

[0376]

[0377]

[0378]

[0379] Referring to Table 31, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameters qP Cb 、qP Cr and qP CbCr can be derived based on the signaled user-defined information as proposed in this embodiment. In addition, for example, when ChromaArrayType is 1 and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameters qP Cb 、qP Cr and qP CbCr can be based on qPi Cb 、qPi Cr and qPi CbCrThe same index qPi is derived through the default table.

[0380] In addition, this document presents another embodiment in which information for quantized parameters is signaled.

[0381] For example, this embodiment proposes adding a function for signaling the chrominance quantization parameter Qp as a function of the index qPi. C For example, a syntax element scheme for signaling a user - defined table for quantized parameter derivation in the PPS can be proposed. Thus, flexibility regarding changing the user - defined table and the default table for each picture of the reference PPS can be provided.

[0382] The syntax element of the user - defined table for signaling in the PPS proposed in this embodiment can be the same as the following table.

[0383] [Table 32]

[0384]

[0385] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chrominance quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0386] In addition, for example, the syntax element qPi_delta_max_idx can represent the incremental value between Qpi_min_idx and the maximum qPi index used in chrominance Qp c derivation. The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. The value of qPi_delta_max_idx can be in the range of 0 to 63. For example, the maximum index qPiMaxIdx used in Qp c derivation can be derived as in Equation 4.

[0387] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the increment of the Qp C value for the i - th index.

[0388] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0389] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0390] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] can be set to QpC _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0391] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0392] After that, Qp C can be set to Qp C Idx[qPi].

[0393] In addition, in this embodiment, the flag in the SPS indicating whether the default table is used for chrominance quantization derivation or whether the signaling information is used for chrominance quantization derivation can be the same as the following table.

[0394] [Table 33]

[0395]

[0396] For example, the syntax element Qp c _data_default_flag can indicate whether the user - defined mode is used for deriving the quantization parameter. For example, Qp with a value of 0 c _data_default_flag can indicate that the user - defined mode is used for deriving the quantization parameter. That is, for example, Qp with a value of 0 c _data_default_flag can indicate using the chrominance quantization parameter data Qp c _data(). When Qp c _data_default_flag is 0, the chrominance quantization parameter data Qp c _data() can be signaled. In addition, for example, Qp with a value of 1 c _data_default_flag can indicate using the default table to derive the quantization parameter. The default table can be the same as Table 7. In addition, if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred as 1.

[0397] For example, in this embodiment, if the process of deriving the quantization parameter is written in a standard format, the process can be represented as in the following table.

[0398] [Table 34]

[0399]

[0400]

[0401]

[0402]

[0403]

[0404] Referring to Table 34, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameter qP Cb 、qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. Further, for example, when ChromaArrayType is 1, and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameter qP Cb 、qP Cr and qP CbCr can be derived from the default table based on the same index qPi Cb 、qPi Cr and qPi CbCr respectively as qPi.

[0405] In addition, this document presents another embodiment in which information for quantizing parameters is signaled.

[0406] For example, this embodiment proposes a normal mode in which chroma quantization parameter Qp C is derived and signaled.

[0407] The chroma quantization parameter data Qp c _data() for chroma quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0408] [Table 35]

[0409]

[0410] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0411] In addition, for example, the syntax element qPi_delta_max_idx may represent the incremental value between the maximum qPi index used in the derivation and Qpi_min_idx and the chroma Qp c The value of qPiMaxIdx may be greater than or equal to qPi_min_idx. The value of qPi_delta_max_idx may range from 0 to 63. For example, in the Qp c The maximum index qPiMaxIdx used in the derivation may be derived as in Equation 4.

[0412] In addition, for example, the syntax element Qp C _qPi_delta_val[i] may represent the increment of the Qp value of the i-th index. C

[0413] For example, the parameter Qp C Idx[qPi] may be derived as follows.

[0414] - When qPi < qPi_min_idx, Qp C Idx[qPi] may be set the same as qPi.

[0415] - When qPi = qPi_min_idx... qPiMaxIdx, Qp C Idx[qPi] may be set to Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0416] - When qPi > qPiMaxIdx, Qp C Idx[qPi] may be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0417] Thereafter, Qp C may be set to Qp C Idx[qPi].

[0418] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chroma quantization derivation or whether the signaled information is used for chroma quantization derivation. The flag may be signaled through a high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through the high-level syntax may be the same as the following table.

[0419] [Table 36]

[0420] ​

[0421] For example, the syntax element Qp c _data_default_flag may indicate whether the user-defined mode is used to derive the quantization parameter. For example, Qp with a value of 0 c _data_default_flag may indicate that the user-defined mode is used to derive the quantization parameter. That is, for example, Qp with a value of 0 c _data_default_flag may indicate the use of the chrominance quantization parameter data Qp c _data(). When Qp c _data_default_flag is 0, the chrominance quantization parameter data Qp c _data() may be signaled. In addition, for example, Qp with a value of 1 c _data_default_flag may indicate that the default table is used to derive the quantization parameter. The default table may be the same as Table 7. In addition, if Qp c _data_default_flag does not exist, then Qp c _data_default_flag may be inferred to be 1.

[0422] For example, in this embodiment, if the process of deriving the quantization parameter is written in a standard format, the process may be represented as in the following table.

[0423] [Table 37]

[0424]

[0425]

[0426]

[0427]

[0428]

[0429] Referring to Table 37, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameters qP Cb 、qP Cr and qP CbCrcan be derived based on the signaling user - defined information as proposed in this embodiment. Additionally, for example, when ChromaArrayType is 1 and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameter qP Cb 、qP Cr and qP CbCr can be derived based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively through a default table.

[0430] Additionally, this document presents another embodiment in which information for quantizing parameters is signaled.

[0431] For example, this embodiment proposes a scheme for deriving a chroma quantization parameter Qp C table without offset. This embodiment can be proposed for use with APS or independently. For example, the syntax structure of APS integrated with chroma quantization data can be the same as the following table.

[0432] [Table 38]

[0433]

[0434] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0435] Additionally, for example, the syntax element qPi_delta_max_idx can represent the incremental value between Qpi_min_idx and the maximum qPi index used in chroma Qp c derivation. The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. The value of qPi_delta_max_idx can be in the range of 0 to 63. For example, the maximum index qPiMaxIdx used in Qp c derivation can be derived as in Equation 4.

[0436] Additionally, for example, the syntax element Qp C _qPi_delta_val[i] can represent the difference between the Qp C values of the i - th index. This difference can also be referred to as an increment.

[0437] For example, the parameter Qp CIdx[qPi] can be derived as follows. In this case, qPi can be from 0 to 63.

[0438] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0439] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] can be set to Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0440] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0441] After that, Qp C can be set to Qp C Idx[qPi].

[0442] In addition, this document presents another embodiment in which information for quantized parameters is signaled.

[0443] For example, this embodiment presents a scheme in which the increment (or difference) between consecutive Qp C values is limited to 1 as an example.

[0444] For example, this embodiment presents a scheme in which user-defined chroma quantization (Qp C ) is additionally included in existing image / video standards. For example, the flag in the sequence parameter set (SPS) presented in this embodiment can indicate whether the existing default table is used for chroma quantization parameter derivation or whether the content of the table is derived based on the information signaled in the SPS. According to this embodiment, a scheme suitable for encoding an image can be selected by adapting user-defined chroma quantization, and the encoding efficiency can be improved.

[0445] For example, this embodiment presents a function for signaling chroma quantization Qp C as a function of the index qPi by using the syntax elements in the following table.

[0446] [Table 39]

[0447]

[0448] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chrominance quantization. The value of qPi_min_idx may be in the range of 1 to 63.

[0449] In addition, for example, the syntax element qPi_delta_max_idx may represent the incremental value between Qpi_min_idx and the maximum qPi index used in the Qp c derivation. The value of qPiMaxIdx may be greater than or equal to qPi_min_idx. The value of qPi_delta_max_idx may be in the range of 1 to 63. For example, in the Qp c derivation, the maximum index qPiMaxIdx used may be derived as in Equation 4.

[0450] In addition, for example, the syntax element QpC_qPi_flag[i] may represent whether the Qp C value is incremented by 1. That is, for example, the syntax element QpC_qPi_flag[i] may represent the i-th Qp C value and the (i - 1)-th Qp C value compared to whether it is incremented by 1. For example, QpC_qPi_flag[i] with a value of 1 may represent that the Qp C value is incremented by 1. QpC_qPi_flag[i] with a value of 0 may represent that the Qp C value is not incremented.

[0451] For example, the parameter Qp C Idx[qPi] can be derived as follows. In this case, qPi can be 0 to 63.

[0452] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0453] - When qPi = qPi_min_idx... qPiMaxIdx, Qp C Idx[qPi] can be set to Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0454] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0455] Thereafter, Qp C can be set to QpC Idx[qPi].

[0456] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chrominance quantization derivation or whether the signaled information is used for chrominance quantization derivation. This flag can be signaled through high-level syntax such as the Sequence Parameter Set (SPS) or the Picture Parameter Set (PPS). The flag signaled through high-level syntax can be the same as the following table.

[0457] [Table 40]

[0458]

[0459] For example, the syntax element Qp c _data_default_flag can indicate whether the user-defined mode is used for deriving the quantization parameter. For example, Qp c _data_default_flag with a value of 0 can indicate that the user-defined mode is used for deriving the quantization parameter. That is, for example, Qp c _data_default_flag with a value of 0 can indicate that the chrominance quantization parameter data Qp c _data() is used. When Qp c _data_default_flag is 0, the chrominance quantization parameter data Qp c _data() can be signaled. In addition, for example, Qp c _data_default_flag with a value of 1 can indicate that the default table is used for deriving the quantization parameter. The default table can be the same as Table 7. In addition, if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred as 1.

[0460] For example, in this embodiment, if the process of deriving the quantization parameter is written in the standard format, the process can be represented as in the following table.

[0461] [Table 41]

[0462]

[0463]

[0464]

[0465]

[0466] Referring to Table 41, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), the parameters qP Cb 、qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. In addition, for example, when ChromaArrayType is 1 and Qp c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), the parameters qP Cb 、qP Cr and qP CbCr can be derived based on the default table with the same index qPi Cb 、qPi Cr and qPi CbCr respectively.

[0467] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters.

[0468] For example, this embodiment proposes an example of a data signaling structure for chroma QP derivation. Specifically, this embodiment proposes a scheme for adding chroma_qp_mapping_flag as a new syntax element in the SPS. For example, if the chroma_qp_mapping_flag value is 0, the default chroma QP mapping table can be used to derive chroma quantization parameters. In addition, for example, if the chroma_qp_mapping_flag value is 1, the syntax elements for deriving the chroma QP mapping table can be signaled as in the following table.

[0469] [Table 42]

[0470]

[0471] For example, the syntax element Qp C _data_default_flag can indicate whether the user - defined mode is used to derive quantization parameters. For example, Qp C _data_default_flag with a value of 0 can indicate that the user - defined mode is used to derive quantization parameters. That is, for example, Qp C_data_default_flag can indicate that the chrominance QP mapping table derived from the chrominance quantization parameter data shown in Table 42 as described above is used to derive the chrominance quantization parameters. If Qp C _data_default_flag is 0, the chrominance quantization parameter data shown in Table 42 as described above can be signaled. In addition, for example, Qp with a value of 1 C _data_default_flag can indicate that the default table is used to derive the quantization parameters. The default table can be the same as the default table in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred as 1.

[0472] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can indicate the number of points where the mapping function does not increase.

[0473] In addition, for example, the syntax element qPi_min_idx_minus1 can indicate the first element of the set of points where its mapping function does not increase.

[0474] In addition, for example, the syntax element Qp C _qPi_flag[i] can indicate the incremental value between the i-th element and the (i - 1)-th element of the set of points where the mapping function does not increase.

[0475] The chrominance QP mapping table can be derived as follows based on the chrominance quantization parameter data shown in Table 42.

[0476] For example, the variable cQpFatSize can be derived as in the following equation.

[0477] [Equation 5]

[0478] cQpFlatSize = qPi_delta_max_idx_minus1 + 1

[0479] In addition, for example, the variable cQpFlat[] can be derived as in the following table.

[0480] [Table 43]

[0481]

[0482] Thereafter, based on the variable cQpFlatSize and the variable cQpFlat[], the chrominance QP mapping table can be derived as in the following table.

[0483] [Table 44]

[0484]

[0485] In addition, the present disclosure presents another embodiment for signaling information about quantization parameters.

[0486] For example, this embodiment presents a scheme for adding chroma_qp_mapping_flag as a new syntax element in SPS. For example, if the chroma_qp_mapping_flag value is 0, the default chroma QP mapping table can be used to derive the chroma quantization parameters. In addition, for example, if the chroma_qp_mapping_flag value is 1, the syntax elements for deriving the chroma QP mapping table can be signaled as shown in the following table.

[0487] [Table 45]

[0488]

[0489] For example, the syntax element Qp C _data_default_flag can indicate whether the user-defined mode is used to derive the quantization parameters. For example, Qp with a value of 0 C _data_default_flag can indicate that the user-defined mode is used to derive the quantization parameters. That is, for example, Qp with a value of 0 C _data_default_flag can indicate that the chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 42 above is used to derive the chroma quantization parameters. If Qp C _data_default_flag is 0, the chroma quantization parameter data shown in Table 42 above can be signaled. In addition, for example, Qp with a value of 1 C _data_default_flag can indicate that the default table is used to derive the quantization parameters. The default table can be as shown in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred as 1.

[0490] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can indicate the number of points where the mapping function does not increase.

[0491] In addition, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 can represent the first element of the set of points where the mapping table does not increase.

[0492] In addition, for example, by adding 1 to the syntax element Qp C _qPi_idx_minus1[i], the obtained value can represent the incremental value between the i-th element and the (i - 1)-th element of the set of points where the mapping function does not increase.

[0493] The chrominance QP mapping table can be derived as follows based on the chrominance quantization parameter data shown in Table 45.

[0494] For example, the variable cQpFlatSize can be derived as in Equation 5 as described above.

[0495] In addition, for example, the variable cQpFlat[] can be derived as in the following table.

[0496] [Table 46]

[0497]

[0498] Thereafter, based on the variable cQpFlatSize and the variable cQpFlat[], the chrominance QP mapping table can be derived. For example, the chrominance QP mapping table can be derived as in Table 44 as described above.

[0499] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters.

[0500] For example, this embodiment proposes a scheme for signaling a separate table for each chrominance component. That is, for example, this embodiment proposes a scheme for signaling the syntax elements for deriving the chrominance QP mapping table for the corresponding chrominance component.

[0501] For example, the chrominance QP mapping table for the corresponding chrominance component can be derived, and the syntax elements for the corresponding chrominance component can be signaled as in the following table.

[0502] [Table 47]

[0503]

[0504] For example, the syntax element qp_luma_to_chroma_joint_map_flag can indicate whether the common luma-chroma quantization parameter mapping table is used for the chroma components Cb, Cr, and CbCr. That is, for example, the syntax element qp_luma_to_chroma_joint_map_flag can indicate whether a luma-chroma quantization parameter mapping table is applied to the Cb residual, Cr residual, and CbCr residual. For example, if the value of qp_luma_to_chroma_joint_map_flag is 1, the common luma-chroma quantization parameter mapping table can be used for the chroma components Cb, Cr, and CbCr, and if the value of qp_luma_to_chroma_joint_map_flag is 0, separate luma-chroma quantization parameter mapping tables can be used for each of the chroma components Cb, Cr, and CbCr.

[0505] In addition, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 can indicate the minimum qPi index used for chroma quantization. The qPi_min_idx_minus1 value can be in the range of 1 to 63.

[0506] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can indicate the incremental value between Qpi_min_idx and the maximum qPi index derived for chroma Qp C The qPiMaxIdx value can be equal to or greater than the qPi_min_idx value. For example, the qPi_delta_max_idx_minus1 value can be in the range of 1 to 63. The maximum index qPiMaxIdx derived for Qp C can be derived as in the following equation.

[0507] [Equation 6]

[0508] for(i = 0; i < 3; i++){qPiMaxIdx[i] = qPi_min_idx_minus1[i] + 1 + qPi_delta_max_idx_minus1[i] + 1

[0509] In addition, for example, the syntax element Qp C _qPi_flag[j] can indicate whether the Qp C value is incremented by 1, that is, for example, the syntax element QpC_qPi_flag[i][j] can indicate the j-th Qp of the i-th chroma component C value and the (j - 1)-th Qp CWhether the value is increased by 1 compared to. For example, QpC_qPi_flag[j] equal to 1 can indicate Qp C The value is increased by 1, and QpC_qPi_flag[j] equal to 0 can indicate Qp C The value is not increased.

[0510] For example, the variable Qp C Idx[i][qPi] can be derived as follows. Here, when the value is 0, qPi can be maxQp.

[0511] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0512] - When qPi = qPi_min_idx_minus1 + 1...qPiMaxIdx, Qp C Idx[qPi] can be configured as QpC_qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0513] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0514] Thereafter, Qp C The value can be derived as QpCIdx[i][qPi].

[0515] Meanwhile, according to this embodiment, a flag indicating whether to signal a syntax element for deriving the chrominance QP mapping table in SPS or to use the default table can be signaled. For example, the flag can be signaled as shown in the following table.

[0516] [Table 48]

[0517]

[0518] The syntax element Qp C _data_default_flag can indicate whether the user - defined mode is used to derive the quantization parameter. For example, Qp C _data_default_flag with a value of 0 can indicate that the user - defined mode is used to derive the quantization parameter. That is, for example, Qp C_data_default_flag can indicate that the chroma QP mapping table derived from the chroma quantization parameter data shown in Table 47 as described above is used to derive the chroma quantization parameter. If Qp C _data_default_flag is 0, the chroma quantization parameter data shown in Table 47 as described above can be signaled. In addition, for example, Qp with a value of 1 C _data_default_flag can indicate that the default table is used to derive the quantization parameter. The default table can be the same as the default table in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred as 1.

[0519] For example, according to this embodiment, through the description in the standard format, the process of deriving the quantization parameter can be represented as shown in the following table.

[0520] [Table 49]

[0521]

[0522]

[0523]

[0524]

[0525] Referring to Table 49 as described above, if ChromaArrayType is 1 and Qp C _data_default_flag indicates false (for example, if Qp C _data_default_flag is 0), then the variables qP Cb 、qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. In addition, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (for example, if Qp C _data_default_flag is 1), then the variables qP Cb 、qP Cr and qP CbCr can be derived through the default table based on the qPi Cb 、qPi Cr and qPi CbCr with the same index qPi respectively.

[0526] In addition, the present disclosure presents another embodiment for signaling information about quantization parameters. This embodiment presents a scheme for signaling the maximum difference between a start point and an end point by signaling the end point as an increment for the maximum QP. That is, for example, according to this embodiment, a syntax element representing the increment value between the maxQp for deriving the chrominance Qp C and the maximum qPi index can be signaled.

[0527] The chrominance quantization parameter data Qp for the chrominance quantization parameters proposed in this embodiment can be signaled as shown in the following table C _data().

[0528] [Table 50]

[0529]

[0530] For example, the syntax element qPi_min_idx can represent the minimum qPi index for chrominance quantization. The qPi_min_idx value can be in the range of 0 to 63.

[0531] In addition, for example, the syntax element qPi_delta_max_idx can represent the increment value between the maxQp and the maximum qPi index for deriving the chrominance Qp C . The qPiMaxIdx value can be equal to or greater than the qPi_min_Idx value. The qPi_delta_max_idx value can be in the range of 1 to 63. For example, the maximum index qPiMaxIdx for deriving Qp C can be derived as shown in the following equation.

[0532] [Equation 7]

[0533] qPiMaxIdx = maxQp - qPi_delta_max_idx

[0534] In addition, for example, the syntax element Qp C _qPi_flag[i] can represent whether the Qp C value is incremented by 1. That is, for example, the syntax element QpC_qPi_flag[i] can represent whether the i-th Qp C value is incremented by 1 compared to the (i - 1)-th Qp C value. For example, QpC_qPi_flag[i] with a value of 1 can represent that the Qp C value is incremented by 1, and QpC_qPi_flag[i] with a value of 0 can represent that the Qp C value is not incremented.

[0535] For example, variable Qp C Idx[qPi] can be derived as follows. Here, qPi can range from 0 to 63.

[0536] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be configured to be the same as qPi.

[0537] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] can be configured to be QpC_qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0538] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured to be qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0539] After that, Qp C can be configured to be Qp C Idx[qPi].

[0540] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or the information used to derive chrominance quantization is used. The flag can be signaled through a high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through the high-level syntax can be as shown in the following table.

[0541] [Table 51]

[0542]

[0543] For example, the syntax element Qp C _data_default_flag can indicate whether a user-defined mode is used to derive quantization parameters. For example, Qp C _data_default_flag with a value of 0 can indicate that a user-defined mode is used to derive quantization parameters. That is, for example, Qp C _data_default_flag with a value of 0 can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp C_data(). Additionally, for example, Qp with a value of 1 C _data_default_flag may indicate that the default table is used to derive quantization parameters. The default table may be as in Table 7 described above. Additionally, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag may be inferred as 1.

[0544] For example, according to this embodiment, through the description in the standard format, the process of deriving quantization parameters can be represented as in the following table.

[0545] [Table 52]

[0546]

[0547]

[0548]

[0549]

[0550] Referring to Table 52 described above, if ChromaArrayType is 1 and Qp C _data_default_flag indicates false (for example, if Qp C _data_default_flag is 0), then the variables qP Cb 、qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. Additionally, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (for example, if Qp C _data_default_flag is 1), then the variables qP Cb 、qP Cr and qP CbCr can be derived based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr through the default table.

[0551] Furthermore, this disclosure presents another embodiment for signaling information about quantization parameters. This embodiment proposes a scheme for signaling the maximum difference between a starting point and an ending point by signaling the ending point as an increment to the maximum QP or as the difference between the starting point and the value obtained by adding the increment to the starting point.

[0552] The chrominance quantization parameter data Qp for the chrominance quantization parameter proposed in this embodiment C _data() can be signaled as shown in the following table.

[0553] [Table 53]

[0554]

[0555] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 can represent the minimum qPi index for chrominance quantization. The qPi_min_idx value can be in the range of 1 to maxQp.

[0556] In addition, for example, the syntax element is_delta_maxQp can represent whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, is_delta_maxQp with a value of 1 can represent that qPiMaxIdx is derived from the maxQp value. In addition, for example, is_delta_maxQp with a value of 0 can represent that qPiMaxIdx is derived from the syntax element qPi_min_idx_minus1.

[0557] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can represent the incremental value between maxQp and the maximum qPi index used to derive the chrominance Qp C . The qPiMaxIdx value can be equal to or greater than qPi_min_idx. For example, the qPi_delta_max_idx_minus1 value can be in the range of 1 to 63. The maximum index qPiMaxIdx used for Qp C derivation can be derived as shown in the following table.

[0558] [Table 54]

[0559]

[0560] In addition, for example, the syntax element Qp C _qPi_flag[i] can represent whether the Qp C value increases by 1. That is, for example, the syntax element QpC_qPi_flag[i] can represent whether the i-th Qp C value increases by 1 compared to the (i - 1)-th Qp C value. For example, QpC_qPi_flag[i] with a value of 1 can represent that the Qp C value increases by 1, and QpC_qPi_flag[i] with a value of 0 can represent that the QpC The value is not increased.

[0561] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to maxQp.

[0562] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0563] - When qPi = qPi_min_idx_minus1…qPiMaxIdx, Qp C Idx[qPi] can be configured to Qp C _qPi_flag[qPi] + QpCIdx[qPi - 1].

[0564] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0565] Thereafter, Qp C can be configured to Qp C Idx[qPi].

[0566] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or information used to derive chrominance quantization is used. The flag can be signaled through a high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through the high-level syntax can be as shown in the following table.

[0567] [Table 55]

[0568]

[0569] For example, the syntax element Qp C _data_default_flag can indicate whether a user-defined mode is used to derive the quantization parameter. For example, Qp C _data_default_flag with a value of 0 can indicate that the user-defined mode is used to derive the quantization parameter. That is, for example, Qp C _data_default_flag with a value of 0 can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp CIf _data_default_flag is 0, a signal can be sent to notify the chrominance quantization parameter data Qp C _data(). In addition, for example, a Qp with a value of 1 C _data_default_flag can indicate that the default table is used to derive the quantization parameter. The default table can be like that in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred as 1.

[0570] For example, according to this embodiment, through the description in the standard format, the process of deriving the quantization parameter can be represented as in the following table.

[0571] [Table 56]

[0572]

[0573]

[0574]

[0575]

[0576] Referring to Table 56 as described above, if ChromaArrayType is 1 and Qp C _data_default_flag indicates false (for example, if Qp C _data_default_flag is 0), then the variables qP Cb 、qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. In addition, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (for example, if Qp C _data_default_flag is 1), then the variables qP Cb 、qP Cr and qP CbCr can be derived through the default table based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively.

[0577] In addition, the present disclosure presents another embodiment for signaling information about quantization parameters. This embodiment presents a scheme for signaling the maximum difference between a start point and an end point by signaling the end point as an increment of the maximum QP or as the difference between the start point and the value obtained by adding the increment to the start point.

[0578] The chrominance quantization parameter data Qp C _data() for chrominance quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0579] [Table 57]

[0580]

[0581] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 can represent the minimum qPi index for chrominance quantization. The qPi_min_idx value can be in the range of 1 to maxQp.

[0582] In addition, for example, the syntax element is_delta_maxQp can represent whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, is_delta_maxQp with a value of 1 can represent that qPiMaxIdx is derived from the maxQp value. In addition, for example, is_delta_maxQp with a value of 0 can represent that qPiMaxIdx is derived from the syntax element qPi_min_idx_minus1.

[0583] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can represent the incremental value between maxQp and the maximum qPi index for deriving chrominance Qp C . The qPiMaxIdx value can be equal to or greater than qPi_min_idx. For example, the qPi_delta_max_idx_minus1 value can be in the range of 1 to 63. The maximum index qPiMaxIdx for deriving Qp C can be derived as described above as shown in Table 54.

[0584] In addition, for example, the syntax element Qp C _qPi_flag[i] can represent whether the Qp C value is incremented by 1. That is, for example, the syntax element QpC_qPi_flag[i] can represent whether the i-th Qp C value is incremented by 1 compared to the (i - 1)-th Qp C value. For example, QpC_qPi_flag[i] with a value of 1 can represent QpC The value is incremented by 1, and QpC_qPi_flag[i] with a value of 0 can indicate Qp C The value is not incremented.

[0585] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can range from 0 to maxQp.

[0586] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0587] - When qPi = qPi_min_idx_minus1…qPiMaxIdx, Qp C Idx[qPi] can be configured as Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0588] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0589] After that, Qp C can be configured as Qp C Idx[qPi].

[0590] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or information used to derive chrominance quantization is used. The flag can be signaled through a high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through the high-level syntax can be the same as those in the following table.

[0591] [Table 58]

[0592]

[0593] For example, the syntax element Qp C _data_default_flag can indicate whether a user-defined mode is used to derive quantization parameters. For example, Qp C _data_default_flag with a value of 0 can indicate that the user-defined mode is used to derive quantization parameters. That is, for example, Qp C_data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp C _data() can be signaled. In addition, for example, a Qp with a value of 1 C _data_default_flag can indicate that the default table is used to derive the quantization parameter. The default table can be like that in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be considered to be 1.

[0594] For example, according to this embodiment, through the description in the standard format, the process of deriving the quantization parameter can be represented as in the following table.

[0595] [Table 59]

[0596]

[0597]

[0598]

[0599]

[0600] Referring to Table 59 as described above, if ChromaArrayType is 1 and Qp C _data_default_flag indicates false (for example, if Qp C _data_default_flag is 0), then the variables qP Cb 、qP Cr and qP CbCr can be derived based on the user-defined information signaled as proposed in this embodiment. In addition, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (for example, if Qp C _data_default_flag is 1), then the variables qP Cb 、qP Cr and qP CbCr can be derived through the default table based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively.

[0601] In addition, the present disclosure presents another embodiment for signaling information about quantization parameters. This embodiment presents a scheme for signaling the index of the chrominance QP mapping table by using the minus1 nomenclature instead of real values.

[0602] The chrominance quantization parameter data Qp C _data() for the chrominance quantization parameter proposed in this embodiment can be signaled as shown in the following table.

[0603] [Table 60]

[0604]

[0605] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 can represent the minimum qPi index for chrominance quantization. The qPi_min_idx value can be in the range of 1 to 63.

[0606] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can represent the incremental value between qPi_min_idx and the maximum qPi index used to derive the chrominance Qp C . The qPiMaxIdx value can be equal to or greater than qPi_min_idx. The qPi_delta_max_idx value can be in the range of 1 to 63. For example, the maximum index qPiMaxIdx used to derive Qp C can be derived as shown in the following equation.

[0607] [Equation 8]

[0608] qPiMaxIdx = qPi_min_idx_minus1 + 1 + qPi_delta_max_idx_minus1 + 1

[0609] In addition, for example, the syntax element Qp C _qPi_flag[i] can represent whether the Qp C value increases by 1. That is, for example, the syntax element QpC_qPi_flag[i] can represent whether the i-th Qp C value increases by 1 compared to the (i - 1)-th Qp C value. For example, QpC_qPi_flag[i] with a value of 1 can represent that the Qp C value increases by 1, while QpC_qPi_flag[i] with a value of 0 can represent that the Qp C value does not increase.

[0610] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to 63.

[0611] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0612] - When qPi = qPi_min_idx_minus1 + 1...qPiMaxIdx, Qp C Idx[qPi] can be configured to be Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0613] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured to be qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0614] After that, Qp C can be configured to be Qp C Idx[qPi].

[0615] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for deriving chrominance quantization or the information used for deriving chrominance quantization is used. This flag can be signaled through a high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through the high-level syntax can be as shown in the following table.

[0616] [Table 61]

[0617]

[0618] For example, the syntax element Qp C _data_default_flag can indicate whether a user-defined mode is used for deriving quantization parameters. For example, Qp C _data_default_flag with a value of 0 can indicate that the user-defined mode is used for deriving quantization parameters. That is, for example, Qp C _data_default_flag with a value of 0 can indicate that chrominance quantization parameter data Qp C _data() is used. If Qp C _data_default_flag is 0, then chrominance quantization parameter data Qp can be signaledC _data(). In addition, for example, Qp with a value of 1 C _data_default_flag can indicate that the default table is used for deriving quantization parameters. The default table can be like that in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be considered as 1.

[0619] For example, according to this embodiment, through the description in the standard format, the process of deriving quantization parameters can be represented as in the following table.

[0620] [Table 62]

[0621]

[0622]

[0623]

[0624]

[0625] Referring to Table 62 as described above, if ChromaArrayType is 1 and Qp C _data_default_flag indicates false (for example, if Qp C _data_default_flag is 0), then the variables qP Cb 、qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. In addition, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (for example, if Qp C _data_default_flag is 1), then the variables qP Cb 、qP Cr and qP CbCr can be derived through the default table based on the qPi Cb 、qPi Cr and qPi CbCr with the same index qPi respectively.

[0626] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. This embodiment proposes a scheme in which separate chroma quantization tables are used for each chroma component.

[0627] The chrominance quantization parameter data for the chrominance quantization parameter proposed in this embodiment can be signaled as shown in the following table.

[0628] [Table 63]

[0629]

[0630] For example, the syntax element Qp C _data_default_flag can indicate whether to use the default chrominance quantization parameter table. For example, Qp with a value of 1 C _data_default_flag can indicate that the default chrominance quantization parameter table is used to derive the chrominance quantization parameter. The default table can be as shown in Table 7 above. In addition, for example, Qp with a value of 0 C _data_default_flag can indicate that the default chrominance quantization parameter table is not used to derive the chrominance quantization parameter. That is, for example, Qp with a value of 0 C _data_default_flag can indicate that the chrominance quantization parameter table derived based on the signaled chrominance quantization parameter data for deriving the chrominance quantization parameter is used.

[0631] In addition, for example, the syntax element sps_separate_qpc_table_flag can indicate whether two separate Qp C tables are used for Cb samples and Cr samples. That is, for example, the syntax element sps_separate_qpc_table_flag can indicate whether separate luminance-chrominance quantization parameter mapping tables are used for Cb residuals and Cr residuals respectively. For example, sps_separate_qpc_table_flag with a value of 1 can indicate that separate Qp C tables are used for Cb samples and Cr samples respectively, while sps_separate_qpc_table_flag with a value of 0 can indicate that one Qp C table is used for both Cb samples and Cr samples.

[0632] Meanwhile, for example, the variable Qp Cb [i] can represent the Qp C table for Cb samples. In addition, for example, the variable Qp Cr [i] can represent the Qp C table for Cr samples. In addition, for example, if the value of sps_separate_qpc_table_flag is 0, then Qp Cr [i] can be the same as Qp Cb [i]. Here, i can be from 0 to 69.

[0633] In addition, for example, the value obtained by adding 1 to the syntax element qPi_Cb_min_idx_minus1 may represent the minimum qPi index for the Cb chrominance component. The value of qPi_Cb_min_idx_minus1 may be in the range of 1 to 69.

[0634] In addition, for example, the value obtained by adding 1 to the syntax element qPi_Cb_delta_max_idx_minus1 may represent the incremental value between qPi_Cb_min_idx_minus1 and the maximum value qPi_Cb_delta_max_idx_minus1 used for deriving the Cb chrominance Qp C The qPiMaxIdx value may be equal to or greater than qPi_min_idx. The value of qPi_Cb_delta_max_idx_minus1 may be in the range of 1 to 69. For example, the maximum index qPiMaxIdxcb for deriving the Qp of the Cb component may be derived as in the following equation. C The maximum index qPiMaxIdxcb for deriving the Qp of the Cb component may be derived as in the following equation.

[0635] [Equation 9]

[0636] qPiMaxIdxCb = qPi_cb_min_idx_minus1 + 1 + qPi_cb_delta_max_idx_minus1 + 1 In addition, for example, the syntax element Qp C _cb_qPi_flag[i] may represent the incremental value between the i-th Qp C value Qp Cb [i] of the Cb component and the (i - 1)-th Qp C value Qp Cb [i - 1].

[0637] Qp C The value of _cb_qPi_flag[i] may be in the range of 0 to 1.

[0638] For example, the variable Qp Cb [i] may be derived as follows. Here, i may be from 0 to 69.

[0639] - When i = 0...qPiMaxIdxCb, Qp Cb [i] may be configured to be the same as i.

[0640] - When i = qPi_cb_min_idx_minus1 + 1 + 1...qPiMaxIdxCb, Qp Cb [i] may be configured to be Qp Cb [i - 1] + Qp C_cb_qPi_flag[i].

[0641] - When i = qPiMaxIdxCb + 1...69, Qp Cb [i] can be configured as i - deltaEnd, and deltaEnd can be derived as qPiMaxIdxCb - Qp Cb [qPiMaxIdxCb].

[0642] In addition, for example, qPi_cr_min_idx_minus1, qPiMaxIdxCr, and Qp, which are syntax elements of the Cr component C _cr_qPi_flag[i] can have the same meaning as the syntax elements of the Cb component.

[0643] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. For example, this embodiment proposes a scheme for signaling parameters of multiple chroma QP tables. In addition, this embodiment can be connected to at least one of the embodiments described above. That is, for example, the embodiments of the present disclosure can be applied jointly.

[0644] Specifically, for example, this embodiment proposes to include user - defined chroma quantization parameters (Qp C ) in the VVC specification text. For example, according to this embodiment, the flag in the sequence parameter set (SPS) can indicate whether the default table is used to derive the chroma quantization parameters or the chroma QP mapping table is derived based on the information signaled in the SPS. Thus, the user - defined chroma quantization parameters can be used in image encoding considering the content characteristics of the image, and the encoding efficiency can be improved. In addition, this embodiment can provide flexibility through an option where one user - defined table is used for the chroma component and an option where separate user - defined tables are used for the Cb and Cr components.

[0645] For example, the chroma quantization parameter data Qp for the chroma quantization parameters proposed in this embodiment can be signaled as shown in the following table C _data().

[0646] [Table 64]

[0647]

[0648] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 can represent the minimum qPi index for chroma quantization. The qPi_min_idx value can be in the range of 1 to 69.

[0649] In addition, for example, the syntax element qPi_delta_max_idx can represent the incremental value between qPi_min_idx and the maximum qPi index used to derive the chroma Qp C The qPiMaxIdx value can be equal to or greater than qPi_min_idx. The qPi_delta_max_idx value can be in the range of 0 to 69. For example, the maximum index qPiMaxIdx used to derive Qp C can be derived as described above, such as in Equation 4.

[0650] In addition, for example, the syntax element Qp C _qPi_flag[i] can represent whether the Qp C value increases by 1. That is, for example, the syntax element QpC_qPi_flag[i] can represent whether the i-th Qp C value increases by 1 compared to the (i - 1)-th Qp C value. For example, QpC_qPi_flag[i] with a value of 1 can represent that the Qp C value increases by 1, while QpC_qPi_flag[i] with a value of 0 can represent that the Qp C value does not increase.

[0651] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to 69.

[0652] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be configured to be the same as qPi.

[0653] - When qPi = qPi_min_idx...qPiMaxIdx, Qp C Idx[qPi] can be configured to be Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0654] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured to be qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0655] Thereafter, Qp C can be configured to be Qp C Idx[qPi].

[0656] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chroma quantization or a chroma QP mapping table derived based on the signaled information is used. This flag can be signaled through high-level syntax such as the Sequence Parameter Set (SPS) or the Picture Parameter Set (PPS). The flag signaled through high-level syntax can be as shown in the following table.

[0657] [Table 65]

[0658]

[0659] For example, the syntax element Qp C _data_default_flag can indicate whether the user-defined mode is used to derive the quantization parameter. For example, Qp C _data_default_flag with a value of 0 can indicate that the user-defined mode is used to derive the quantization parameter. That is, for example, Qp C _data_default_flag with a value of 0 can indicate that chroma quantization parameter data Qp C _data() is used. If Qp C _data_default_flag is 0, then chroma quantization parameter data Qp C _data() can be signaled. In addition, for example, Qp C _data_default_flag with a value of 1 can indicate that the default table is used to derive the quantization parameter. The default table can be like that in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred as 1.

[0660] For example, according to this embodiment, through the description in the standard format, the process of deriving the quantization parameter can be represented as shown in the following table.

[0661] [Table 66]

[0662]

[0663]

[0664]

[0665]

[0666] Referring to Table 66 as described above, if ChromaArrayType is 1 and Qp C_data_default_flag indicates false (e.g., if Qp C _data_default_flag is 0), then the variable qP Cb 、qP Cr and qP CbCr can be derived based on the signaling user - defined information as proposed in this embodiment. Additionally, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (e.g., if Qp C _data_default_flag is 1), then the variable qP Cb 、qP Cr and qP CbCr can be derived based on the default table with the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively.

[0667] Furthermore, for example, the chroma quantization parameter data Qp C _data() in the case of using separate user - defined tables for the respective chrominance components as proposed in this embodiment can be signaled as shown in the following table.

[0668] [Table 67]

[0669]

[0670] For example, the syntax element is_separate_chroma_table can indicate whether the parameters related to separate chroma quantization tables are signaled for the Cb component and the Cr component. That is, for example, the syntax element is_separate_chroma_table can indicate whether two separate chroma quantization parameter mapping tables are used for the Cb component and the Cr component. For example, the syntax element is_separate_chroma_table can indicate whether separate luma - chroma quantization parameter mapping tables are used for the Cb residual and the Cr residual respectively. For example, is_separate_chroma_table with a value of 1 can indicate that separate chroma quantization parameter mapping tables are signaled for the Cb component and the Cr component, and is_separate_chroma_table with a value of 0 can indicate that one chroma quantization parameter mapping table is used for the Cb element, the Cr element, and the combined CbCr element. For example, if the is_separate_chroma_table value is 1, then Pi_min_idx_minus1[i], qPi_delta_max_idx[i], and Qp for the Cb component can be signaled.C _qPi_flag[i][j], and qPi_min_idx_minus1[i], qPi_delta_max_idx[i], and Qp for the Cr component C _qPi_flag[i][j]. Further, for example, if the value of is_separate_chroma_table is 0, qPi_min_idx_minus1[i], qPi_delta_max_idx[i], and Qp for the Cb component, the Cr component, and the combined CbCr component can be signaled C _qPi_flag[i][j].

[0671] Further, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1[i] can represent the minimum qPi index for chrominance quantization. The qPi_min_idx value can be in the range of 1 to 69. The variable qPi_min_idx[i] can be configured to be the same as the value obtained by adding 1 to qPi_min_idx_minus1[i].

[0672] Further, for example, the syntax element qPi_delta_max_idx can represent the increment value between qPi_min_idx[i] and the maximum qPi index for deriving the chrominance Qp C . The qPiMaxIdx[i] value can be equal to or greater than qPi_min_idx[i]. The qPi_delta_max_idx value can be in the range of 0 to 69. For example, the maximum index qPiMaxIdx[i] for deriving Qp C can be derived as in the following equation.

[0673] [Equation 10]

[0674] qPiMaxIdx[i] = qPi_min_idx[i] + qPi_delta_max_idx_minus1[i] + 1

[0675] The qPiMaxIdx[i] value can be equal to or greater than qPi_min_idx_minus1[i].

[0676] Further, for example, the syntax element Qp C _qPi_flag[i][j] can represent whether the j-th Qp C value of the i-th chrominance component is incremented by 1. That is, for example, the syntax element QpC_qPi_flag[i][j] can represent the j-th Qp C value of the i-th chrominance component and the (j - 1)-th QpC whether the value has increased by 1 compared to the previous value. For example, QpC_qPi_flag[j] with a value of 1 can indicate that the j-th Qp of the i-th chrominance component C has its value increased by 1, while QpC_qPi_flag[j] with a value of 0 can indicate that the j-th Qp of the i-th chrominance component C has not had its value increased.

[0677] For example, the variable Qp C Idx[i][qPi] can be derived as shown in the following table. Here, qPi can range from 0 to 69.

[0678] [Table 68]

[0679]

[0680] Referring to Table 68, if the value of is_separate_chroma_table is 1, the 0-th (i = 0) chrominance quantization parameter data and the 1-st (i = 1) chrominance quantization parameter data can be signaled. Here, for example, the 0-th (i = 0) chrominance quantization parameter data can be the chrominance quantization parameter data for deriving the chrominance quantization parameter mapping table of the Cb component, and the 1-st (i = 0) chrominance quantization parameter data can be the chrominance quantization parameter data for deriving the chrominance quantization parameter mapping table of the Cr component.

[0681] In addition, referring to Table 68, if the value of is_separate_chroma_table is 0, only the 0-th (i = 0) chrominance quantization parameter data can be signaled. Here, for example, the 0-th (i = 0) chrominance quantization parameter data can be the chrominance quantization parameter data for deriving the chrominance quantization parameter mapping tables of the Cb component, the Cr component, and the combined CbCr component. That is, one chrominance quantization parameter mapping table can be used for the chrominance components.

[0682] In addition, referring to Table 68, Qp C Idx[i][qPi] can be derived as follows.

[0683] - When qPi < qPi_min_idx[i], Qp C Idx[i][qPi] can be configured to be the same as qPi.

[0684] - When qPi = qPi_min_idx[i]...qPiMaxIdx[i], Qp C Idx[qPi] can be configured to be Qp C _qPi_flag[i][qPi] + Qp C Idx[i][qPi - 1].

[0685] - When qPi > qPiMaxIdx, Qp C Idx[i][qPi] can be configured as qPi - (qPiMaxIdx[i] - Qp C Idx[i][qPiMaxIdx]).

[0686] Thereafter, Qp C value can be derived as Qp C Idx[i][qPi].

[0687] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or the information used to derive chrominance quantization is used. The flag can be signaled through a high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through the high-level syntax can be the same as the flag in the following table.

[0688] [Table 69]

[0689]

[0690] For example, the syntax element Qp C _data_default_flag can indicate whether the user-defined mode is used to derive quantization parameters. For example, Qp C _data_default_flag with a value of 0 can indicate that the user-defined mode is used to derive quantization parameters. That is, for example, Qp C _data_default_flag with a value of 0 can indicate that chrominance quantization parameter data Qp C _data() is used. If Qp C _data_default_flag is 0, then chrominance quantization parameter data Qp C _data() can be signaled. In addition, for example, Qp C _data_default_flag with a value of 1 can indicate that the default table is used to derive quantization parameters. The default table can be like that in Table 7 as described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred as 1.

[0691] For example, according to this embodiment, through the description in the standard format, the process of deriving quantization parameters can be represented as in the following table.

[0692] [Table 70]

[0693]

[0694]

[0695]

[0696]

[0697] Referring to Table 70 as described above, if ChromaArrayType is 1 and Qp C _data_default_flag indicates false (e.g., if Qp C _data_default_flag is 0), then the variable qP Cb , qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. Additionally, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (e.g., if Qp C _data_default_flag is 1), then the variable qP Cb , qP Cr and qP CbCr can be derived through the default table based on the same index qPi Cb , qPi Cr and qPi CbCr respectively.

[0698] Furthermore, the present disclosure presents another embodiment for signaling information regarding quantization parameters. For example, this embodiment presents a scheme for signaling parameters for a chrominance QP table without default configuration. Additionally, this embodiment can be connected to at least one of the above - mentioned embodiments. That is, for example, the embodiments of the present disclosure can be applied jointly.

[0699] The chrominance quantization parameter data of the chrominance quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0700] [Table 71]

[0701]

[0702] For example, the syntax element is_same_qp_table_for_cb_cr may indicate whether a single chrominance QP mapping table is signaled and applied for the Cb component, the Cr component, and the combined CbCr component. That is, for example, the syntax element is_same_qp_table_for_cb_cr may indicate whether parameters related to a single chrominance QP mapping table are signaled for the Cb component, the Cr component, and the combined CbCr component, and a chrominance QP mapping table is applied. For example, is_same_qp_table_for_cb_cr with a value of 1 may indicate that a single chrominance QP mapping table is signaled and applied for the Cb component, the Cr component, and the combined CbCr component. That is, for example, is_same_qp_table_for_cb_cr with a value of 1 may indicate that parameters related to a single chrominance QP mapping table are signaled for the Cb component, the Cr component, and the combined CbCr component, and a chrominance QP mapping table is applied. Additionally, for example, is_same_qp_table_for_cb_cr with a value of 0 may indicate that multiple chrominance QP mapping tables are signaled and applied for the Cb component, the Cr component, and the combined CbCr component. That is, for example, is_same_qp_table_for_cb_cr with a value of 0 may indicate that parameters related to multiple chrominance QP mapping tables are signaled for the Cb component, the Cr component, and the combined CbCr component, and multiple chrominance QP mapping tables are applied. For example, is_same_qp_table_for_cb_cr with a value of 0 may indicate that three chrominance QP mapping tables are signaled and applied for the Cb component, the Cr component, and the combined CbCr component.

[0703] Additionally, for example, the syntax element qPi_table_len_idx[i] may indicate the number of points used to interpret the i-th chrominance QP mapping table. That is, for example, qPi_table_len_idx[i] may indicate the number of indices of the i-th chrominance QP mapping table. The value of qPi_table_len_idx[i] may be in the range of 0 to 69 + QpBdOffsetC.

[0704] Additionally, for example, the syntax element qpC_qPi_in_idx[i][j] may indicate the incremental value of the input coordinates for deriving the j-th pivot point of the i-th chrominance QP mapping table.

[0705] Additionally, for example, the syntax element qpC_qPi_out_idx[i][j] may indicate the incremental value of the output coordinates for deriving the j-th pivot point of the i-th chrominance QP mapping table.

[0706] Based on the above-mentioned syntax elements, the i-th QP mapping table cQPTable[i] can be derived as shown in the following table. Here, if same_qp_table_for_cb_cr is 1, i can be 0, and if same_qp_table_for_cb_cr is not 1, i can be one of 0 to 2.

[0707] [Table 72]

[0708]

[0709]

[0710] Referring to Table 72 as described above, the input coordinates of the j-th pivot point of the i-th chroma QP mapping table can be derived based on qp C _qPi_in_idx[i][j]. The qpVal[i][j] illustrated in Table 72 as described above can represent the input coordinates of the j-th pivot point. In addition, referring to Table 72 as described above, the output coordinates of the j-th pivot point of the i-th chroma QP mapping table can be derived based on qp C _qPi_out_idx[i][j]. The cQPTable[i][j] illustrated in Table 72 as described above can represent the output coordinates of the j-th pivot point.

[0711] In addition, according to this embodiment, the following changes can be made to derive the chroma QP. For example, the restrictions in the following table can be added.

[0712] [Table 73]

[0713]

[0714] Referring to Table 73 as described above, the qpVal[i][j] value can be greater than the value of qpVal[i][j–1]. Here, j can be any one of 1 to qPi_table_len_idx[i].

[0715] In addition, if the chroma type is not 0, for example, if the chroma type is 1, when chroma_qp_table_present_flag is equal to 1, the variables qP Cb and qP Cr can be respectively configured to be the same as ChromaQpTable[0][qPiCb], ChromaQpTable[1][qPiCr], and ChromaQpTable[1][qPiCbCr].

[0716] In addition, the present disclosure presents another embodiment for signaling information about quantization parameters. This embodiment can be connected to at least one of the above-described embodiments. For example, this embodiment presents a scheme for restricting the range of the signaled qp index. As an example, this embodiment can signal the syntax element qPi_table_len_idx in the previous example as described above, as follows.

[0717] For example, the syntax element qPi_table_len_idx[i] can represent the number of points for interpreting the chrominance QP mapping table. In addition, the value of the syntax element qPi_table_len_idx[i] can be in the range of 0 to 69 + QpBdOffsetC.

[0718] As described above, this embodiment can present a scheme for restricting a parameter (e.g., the number of points of the chrominance QP mapping table represented by qPi_table_len_idx[i]) to the minimum range that can be signaled or inferred in another way.

[0719] Figure 7 An image encoding method of an encoding device according to this document is schematically shown. Figure 7 The method disclosed in Figure 2 can be executed by the encoding device disclosed in Figure 7 Specifically, for example, S700 of Figure 7 can be executed by the predictor of the encoding device, S710 to S720 of

[0720] can be executed by the residual processor of the encoding device, and S730 can be executed by the entropy encoder of the encoding device. In addition, although not shown, the process of generating a reconstructed sample and a reconstructed picture based on the residual sample and the predicted sample for the chrominance component can be executed by the adder of the encoding device.

[0721] The encoding device derives a predicted sample for the chrominance component based on inter-frame prediction or intra-frame prediction (S700). The encoding device can derive a predicted sample for the chrominance component based on the prediction mode. That is, for example, the encoding device can derive a predicted sample for the current block of the chrominance component based on the prediction mode. In this case, various prediction methods disclosed in the present disclosure, such as inter-frame prediction or intra-frame prediction, can be applied. The chrominance component can include a Cb component, a Cr component, and / or a combined CbCr component.

[0722] The encoding device derives residual samples for the chrominance component based on prediction samples (S710). For example, the encoding device can derive residual samples by subtracting the prediction samples from the original samples of the current block for the chrominance component in the current picture.

[0723] The encoding device generates chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance component (S720).

[0724] The encoding device can generate chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance component. The default chrominance QP mapping table for the chrominance component may not be used. That is, if chrominance quantization parameters for the chrominance component are used, the encoding device can generate chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance component. The picture information may include chrominance quantization parameter data for at least one chrominance QP mapping table for the chrominance component. In addition, for example, the chrominance component may include a Cb component, a Cr component, and / or a combined CbCr component. In addition, for example, the chrominance quantization parameter data may include a syntax element representing the number of points in the chrominance QP mapping table, a syntax element representing an incremental value of the input coordinates for deriving the target points of the chrominance QP mapping table, and / or a syntax element representing an incremental value of the output coordinates for deriving the target points of the chrominance QP mapping table. In addition, for example, the value of the syntax element representing the number of points in the chrominance QP mapping table may be in the range from 0 to a specific value. The specific value may be 69 + QpBdOffsetC. In addition, for example, the syntax element representing the number of points in the chrominance QP mapping table may be qPi_table_len_idx[i] as described above, and the syntax element representing the incremental value of the input coordinates for deriving the target points of the chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinates for deriving the target points of the chrominance QP mapping table may be qp C _qPi_out_idx[i][j].

[0725] In addition, for example, the encoding device can determine whether a chrominance QP mapping table is applied to the chrominance component, and can generate a flag indicating whether a chrominance QP mapping table is applied to the chrominance component. The picture information may include a flag indicating whether a chrominance QP mapping table is applied to the chrominance component.

[0726] For example, the encoding device may generate a flag indicating whether a chroma QP mapping table is applied to a chroma component based on the chroma type. Here, the chroma type may mean ChromaArrayType as described above. For example, if the chroma type value is not 0, the encoding device may generate a flag indicating whether a chroma QP mapping table is applied to the chroma component. For example, if the chroma type value is 1, the encoding device may generate a flag indicating whether a chroma QP mapping table is applied to the chroma component. Here, if the chroma type value is 0, the chroma type may be a monochrome format, and if the chroma type value is 1, the chroma type may be a 4:2:0 format. If the chroma type value is 2, the chroma type may be a 4:2:2 format, and if the chroma type value is 3, the chroma type may be a 4:4:4 format. For example, the syntax element of the flag may be the above-mentioned qp_luma_to_chroma_joint_map_flag, sps_separate_qpc_table_flag, is_separate_chroma_table, or is_same_qp_table_for_cb_cr.

[0727] For example, if the flag value is 1, the flag may indicate that a chroma QP mapping table is applied to the chroma component. Additionally, for example, if the flag value is 0, the flag may indicate that multiple chroma QP mapping tables are applied to the chroma component. That is, for example, if the flag value is 0, the flag may indicate that separate chroma QP mapping tables are applied to each chroma component.

[0728] Therefore, for example, if the flag value is 1, the chroma quantization parameter data for one chroma QP mapping table for the chroma component may be signaled, and if the flag value is 0, the chroma quantization parameter data for multiple chroma QP mapping tables for the chroma component may be signaled. That is, for example, if the flag value is 0, the chroma quantization parameter data for separate chroma QP mapping tables for each chroma component may be signaled.

[0729] Additionally, for example, the flag may be signaled through the high-level syntax. For example, the flag may be signaled through the Sequence Parameter Set (SPS), Picture Parameter Set (PPS), slice header, or Adaptive Parameter Set (APS).

[0730] Furthermore, for example, the encoding device may generate the chroma quantization parameter data for the chroma component based on the flag.

[0731] For example, the chroma quantization parameter data of multiple chroma QP mapping tables for chroma components may include the first chroma quantization parameter data of the first chroma QP mapping table for the Cb component and the second chroma quantization parameter data of the second chroma QP mapping table for the Cr component. Further, for example, the chroma quantization parameter data may include the first chroma quantization parameter data of the first chroma QP mapping table for the Cb component, the second chroma quantization parameter data of the second chroma QP mapping table for the Cr component, and / or the third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component.

[0732] Meanwhile, for example, the encoding device may generate a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component. That is, for example, the encoding device may determine whether there is third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component, and may generate a combined CbCr enable flag. Further, for example, the encoding device may generate a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component based on the chroma type. Here, the chroma type may mean ChromaArrayType as described above. For example, if the chroma type value is not 0, the encoding device may generate a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component. For example, if the chroma type value is 1, the encoding device may generate a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component. Further, for example, the combined CbCr enable flag may be signaled by the high-level syntax. For example, the combined CbCr enable flag may be signaled by the sequence parameter set (SPS), the picture parameter set (PPS), the slice header, or the adaptive parameter set (APS).

[0733] In this case, if the flag value is 0 (i.e., it is determined that multiple chroma QP mapping tables are applied to the chroma component) and the value of the combined CbCr enable flag is 1 (i.e., it is determined that there is third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component), the chroma quantization parameter data may include the first chroma quantization parameter data of the first chroma QP mapping table for the Cb component, the second chroma quantization parameter data of the second chroma QP mapping table for the Cr component, and the third chroma quantization parameter data of the third chroma QP mapping table for the combined CbCr component.

[0734] In addition, for example, the first chrominance quantization parameter data may include a syntax element representing the number of points of the first chrominance QP mapping table for the Cb component, a syntax element representing an incremental value of the input coordinates of the target point for deriving the first chrominance QP mapping table, and / or a syntax element representing an incremental value of the output coordinates of the target point for deriving the first chrominance QP mapping table. The syntax element representing the number of points of the first chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element representing the incremental value of the input coordinates of the target point for deriving the first chrominance QP mapping table may be qpC_qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinates of the target point for deriving the first chrominance QP mapping table may be qp C _qPi_out_idx[i][j]. In addition, for example, the first chrominance quantization parameter data may be signaled by high-level syntax. For example, the first chrominance quantization parameter data may be signaled by a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, or an Adaptive Parameter Set (APS).

[0735] In addition, for example, the second chrominance quantization parameter data may include a syntax element representing the number of points of the second chrominance QP mapping table for the Cr component, a syntax element representing an incremental value of the input coordinates of the target point for deriving the second chrominance QP mapping table, and / or a syntax element representing an incremental value of the output coordinates of the target point for deriving the second chrominance QP mapping table. The syntax element representing the number of points of the second chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element representing the incremental value of the input coordinates of the target point for deriving the second chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinates of the target point for deriving the second chrominance QP mapping table may be qp C _qPi_out_idx[i][j]. In addition, for example, the second chrominance quantization parameter data may be signaled by high-level syntax. For example, the second chrominance quantization parameter data may be signaled by a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, or an Adaptive Parameter Set (APS).

[0736] In addition, for example, the third chrominance quantization parameter data may include a syntax element representing the number of points of a third chrominance QP mapping table for the combined CbCr components, a syntax element representing an incremental value of an input coordinate for deriving a target point of the third chrominance QP mapping table, and / or a syntax element representing an incremental value of an output coordinate for deriving a target point of the third chrominance QP mapping table. The syntax element representing the number of points of the third chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element representing the incremental value of the input coordinate for deriving a target point of the third chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinate for deriving a target point of the third chrominance QP mapping table may be qp C _qPi_out_idx[i][j]. In addition, for example, the third chrominance quantization parameter data may be signaled by an advanced syntax. For example, the third chrominance quantization parameter data may be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0737] In addition, for example, if the flag value is 1 (i.e., it is determined that one chrominance QP mapping table is applied to the chrominance components), the chrominance quantization parameter data may include chrominance quantization parameter data for one chrominance QP mapping table for the Cb component, the Cr component, and the combined CbCr components.

[0738] The encoding device encodes prediction information for the chrominance components, residual information for the chrominance components, and chrominance quantization parameter data (S730). The encoding device may encode chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance components. The image information may include chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance components.

[0739] In addition, for example, the encoding device may encode a flag indicating whether one chrominance QP mapping table is applied to the chrominance components and / or a combined CbCr enable flag. The image information may include a flag indicating whether one chrominance QP mapping table is applied to the chrominance components and / or a combined CbCr enable flag.

[0740] In addition, for example, the encoding device may encode a flag indicating whether one chrominance QP mapping table is applied to the chrominance components and / or a combined CbCr enable flag. The image information may include a flag indicating whether one chrominance QP mapping table is applied to the chrominance components and / or a combined CbCr enable flag.

[0741] In addition, for example, an encoding device may encode residual information for residual samples. For example, the encoding device may derive transform coefficients based on the residual samples and may generate residual information based on the transform coefficients. For example, the encoding device may derive quantized residual samples by quantizing the residual samples based on chrominance quantization parameters, derive transform coefficients based on the quantized residual samples, and generate and encode residual information based on the transform coefficients. In addition, for example, the encoding device may derive quantized residual samples by quantizing the residual samples based on chrominance quantization parameters, derive transform coefficients by transforming the quantized residual samples, and generate and encode residual information based on the transform coefficients.

[0742] For example, if the value of the flag is 0, the encoding device may derive quantized residual samples for the Cb component by quantizing the residual samples for the Cb component based on a first chrominance quantization parameter for the Cb component, and may derive quantized residual samples for the Cr component by quantizing the residual samples for the Cr component based on a second chrominance quantization parameter for the Cr component. In addition, for example, if the value of the flag is 0, the encoding device may derive quantized residual samples for the Cb component by quantizing the residual samples for the Cb component based on a first chrominance quantization parameter for the Cb component, may derive quantized residual samples for the Cr component by quantizing the residual samples for the Cr component based on a second chrominance quantization parameter for the Cr component, and may derive quantized residual samples for the combined CbCr component by quantizing the residual samples for the combined CbCr component based on a third chrominance quantization parameter for the combined CbCr component. In addition, for example, if the value of the flag is 1, the encoding device may derive quantized residual samples for the chrominance component by quantizing the residual samples for the chrominance component based on chrominance quantization parameters.

[0743] The image information may include residual information. For example, the residual information may include syntax elements for transform coefficients of a current chrominance block. For example, the syntax elements may include syntax elements such as coded_sub_block_flag, sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag, abs_remainder, and / or coeff_sign_flag.

[0744] In addition, for example, the encoding device is capable of encoding and outputting the image information in the form of a bitstream.

[0745] Meanwhile, a bitstream including image information can be sent to a decoding device via a network or a (digital) storage medium. Here, the network can include a broadcast network and / or a communication network, and the digital storage medium can include various types of storage media such as USB drives, SD cards, CDs, DVDs, Blu-ray discs, HDDs, and SSDs.

[0746] Figure 8 Schematically shows an encoding device for performing an image encoding method according to this document. Figure 7 The method disclosed in Figure 8 can be executed by the encoding device disclosed in Figure 8 Specifically, for example, the predictor of the encoding device of

[0747] Figure 9 Schematically shows an image decoding method of a decoding device according to this document. Figure 9 The method disclosed in Figure 3 can be executed by the decoding device disclosed in Figure 9 Specifically, for example, S900 of Figure 9 can be executed by the entropy decoder of the decoding device, Figure 9 S930 of Figure 9 can be executed by the predictor of the decoding device, and

[0748] The decoding device obtains image information, which includes prediction information and residual information for a chrominance component and chrominance quantization parameter data of at least one chrominance quantization parameter (QP) map for the chrominance component (S900). The decoding device can obtain the image information through the bitstream. For example, the image information can include information about the chrominance quantization parameter. The decoding device can obtain the image information through the bitstream.

[0749] For example, the picture information may include chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table. For example, the decoding device may obtain chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for chrominance components. The default chrominance QP mapping table for chrominance components may not be used. That is, if chrominance quantization parameters for chrominance components are used, the decoding device may obtain chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for chrominance components. Further, for example, chrominance components may include a Cb component, a Cr component, and / or a combined CbCr component. Further, for example, the chrominance quantization parameter data may include a syntax element representing the number of points in the chrominance QP mapping table, a syntax element representing an incremental value of an input coordinate for deriving a target point of the chrominance QP mapping table, and / or a syntax element representing an incremental value of an output coordinate for deriving a target point of the chrominance QP mapping table. Further, for example, the value of the syntax element representing the number of points in the chrominance QP mapping table may be in a range from 0 to a specific value. The specific value may be 69 + QpBdOffsetC. Further, for example, the syntax element representing the number of points in the chrominance QP mapping table may be qPi_table_len_idx[i] as described above, and the syntax element representing an incremental value of an input coordinate for deriving a target point of the chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing an incremental value of an output coordinate for deriving a target point of the chrominance QP mapping table may be qp C _qPi_out_idx[i][j].

[0750] Further, for example, the chrominance quantization parameter data of the chrominance QP mapping table may be signaled by a high-level syntax. For example, the chrominance quantization parameter data may be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0751] In addition, for example, the decoding device may obtain a flag indicating whether a chrominance QP mapping table is applied to a chrominance component. That is, for example, the decoding device may obtain a flag indicating whether a chrominance QP mapping table is signaled and applied to a chrominance component. The image information may include this flag. Also, for example, the decoding device may obtain a flag indicating whether a chrominance QP mapping table is applied based on the chroma type. Here, the chroma type may mean ChromaArrayType as described above. For example, if the chroma type value is not 0, the decoding device may obtain a flag indicating whether a chrominance QP mapping table is applied. For example, if the chroma type value is 1, the decoding device may obtain a flag indicating whether a chrominance QP mapping table is applied. Here, if the chroma type value is 0, the chroma type may be a monochrome format, and if the chroma type value is 1, the chroma type may be a 4:2:0 format. If the chroma type value is 2, the chroma type may be a 4:2:2 format, and if the chroma type value is 3, the chroma type may be a 4:4:4 format. For example, the syntax element of this flag may be the above-mentioned qp_luma_to_chroma_joint_map_flag, sps_separate_qpc_table_flag, is_separate_chroma_table, or is_same_qp_table_for_cb_cr.

[0752] For example, if the flag value is 1, this flag may indicate that a chrominance QP mapping table is applied to a chrominance component. In addition, for example, if the flag value is 0, this flag may indicate that multiple chrominance QP mapping tables are applied to a chrominance component. That is, for example, if the flag value is 0, this flag may indicate that separate chrominance QP mapping tables are applied to each chrominance component.

[0753] Therefore, for example, if the flag value is 1, the chrominance quantization parameter data for one chrominance QP mapping table for the chrominance component may be signaled, and if the flag value is 0, the chrominance quantization parameter data for multiple chrominance QP mapping tables for the chrominance component may be signaled. That is, for example, if the flag value is 0, the chrominance quantization parameter data for separate chrominance QP mapping tables for each chrominance component may be signaled.

[0754] In addition, for example, the flag may be signaled through the high-level syntax. For example, the flag may be signaled through the Sequence Parameter Set (SPS), Picture Parameter Set (PPS), slice header, or Adaptive Parameter Set (APS).

[0755] In addition, for example, the chrominance quantization parameter data of multiple chrominance QP mapping tables for chrominance components may include the first chrominance quantization parameter data of the first chrominance QP mapping table for the Cb component and the second chrominance quantization parameter data of the second chrominance QP mapping table for the Cr component. In addition, for example, the chrominance quantization parameter data may include the first chrominance quantization parameter data of the first chrominance QP mapping table for the Cb component, the second chrominance quantization parameter data of the second chrominance QP mapping table for the Cr component, and / or the third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component.

[0756] Meanwhile, for example, the decoding device may obtain a combined CbCr enable flag indicating whether there is third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component. For example, the image information may include a combined CbCr enable flag indicating whether there is third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component. In addition, for example, the decoding device may obtain a combined CbCr enable flag indicating whether there is third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component based on the chrominance type. Here, the chrominance type may mean ChromaArrayType as described above. For example, if the chrominance type value is not 0, the decoding device may obtain a combined CbCr enable flag indicating whether there is third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component. For example, if the chrominance type value is 1, the decoding device may obtain a combined CbCr enable flag indicating whether there is third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component. In addition, for example, the combined CbCr enable flag may be signaled through the high-level syntax. For example, the combined CbCr enable flag may be signaled through the sequence parameter set (SPS), the picture parameter set (PPS), the slice header, or the adaptive parameter set (APS).

[0757] In this case, if the flag value is 0 (i.e., the flag indicates that multiple chrominance QP mapping tables are applied to the chrominance component) and the combined CbCr enable flag value is 1 (i.e., the combined CbCr enable flag indicates that there is third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component), the chrominance quantization parameter data may include the first chrominance quantization parameter data of the first chrominance QP mapping table for the Cb component, the second chrominance quantization parameter data of the second chrominance QP mapping table for the Cr component, and the third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component.

[0758] In addition, for example, the first chrominance quantization parameter data may include a syntax element representing the number of points of a first chrominance QP mapping table for the Cb component, a syntax element representing an incremental value of an input coordinate for deriving a target point of the first chrominance QP mapping table, and / or a syntax element representing an incremental value of an output coordinate for deriving a target point of the first chrominance QP mapping table. The syntax element representing the number of points of the first chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element representing the incremental value of the input coordinate for deriving the target point of the first chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinate for deriving the target point of the first chrominance QP mapping table may be qp C _qPi_out_idx[i][j]. In addition, for example, the first chrominance quantization parameter data may be signaled by high-level syntax. For example, the first chrominance quantization parameter data may be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0759] In addition, for example, the second chrominance quantization parameter data may include a syntax element representing the number of points of a second chrominance QP mapping table for the Cr component, a syntax element representing an incremental value of an input coordinate for deriving a target point of the second chrominance QP mapping table, and / or a syntax element representing an incremental value of an output coordinate for deriving a target point of the second chrominance QP mapping table. The syntax element representing the number of points of the second chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element representing the incremental value of the input coordinate for deriving the target point of the second chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinate for deriving the target point of the second chrominance QP mapping table may be qp C _qPi_out_idx[i][j]. In addition, for example, the second chrominance quantization parameter data may be signaled by high-level syntax. For example, the second chrominance quantization parameter data may be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0760] In addition, for example, the third chrominance quantization parameter data may include a syntax element representing the number of points of a third chrominance QP mapping table for the combined CbCr components, a syntax element representing an incremental value of the input coordinates of a target point for deriving the third chrominance QP mapping table, and / or a syntax element representing an incremental value of the output coordinates of a target point for deriving the third chrominance QP mapping table. The syntax element representing the number of points of the third chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element representing the incremental value of the input coordinates of a target point for deriving the third chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element representing the incremental value of the output coordinates of a target point for deriving the third chrominance QP mapping table may be qp C _qPi_out_idx[i][j]. In addition, for example, the third chrominance quantization parameter data may be signaled by high-level syntax. For example, the third chrominance quantization parameter data may be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0761] In addition, for example, if the flag value is 1 (i.e., the flag indicates that a chrominance QP mapping table is applied to the chrominance components), the chrominance quantization parameter data may include the chrominance quantization parameter data of (a) chrominance QP mapping table for the Cb component, the CbCr component, and the combined CbCr components.

[0762] In addition, for example, the image information may include prediction information and / or residual information for the chrominance components. For example, the image information may include prediction information for the chrominance components, and the prediction information may include prediction mode information. The prediction mode information may indicate whether inter prediction or intra prediction is applied to the current block for the chrominance components. In addition, for example, the residual information may include syntax elements of transform coefficients of the current block for the chrominance components. For example, the syntax elements may include syntax elements such as coded_sub_block_flag, sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag, abs_remainder, and / or coeff_sign_flag.

[0763] The decoding device derives a chrominance QP mapping table based on the chrominance quantization parameter data (S910). The decoding device may derive a chrominance QP mapping table based on the chrominance quantization parameter data. The chrominance QP mapping table may be referred to as a chrominance quantization parameter table, or a user-defined quantization parameter mapping table.

[0764] For example, as described above, the chrominance QP mapping table can be derived based on a syntax element representing the number of points of the chrominance QP mapping table, a syntax element representing an incremental value of an input coordinate for deriving a target point of the chrominance QP mapping table, and / or a syntax element representing an incremental value of an output coordinate for deriving a target point of the chrominance QP mapping table. That is, for example, the chrominance QP mapping table for the chrominance component can be derived based on quantization parameter data. For example, as shown in Table 72 above, the chrominance QP mapping table for the chrominance component can be derived based on quantization parameter data.

[0765] For example, if the flag value is 0 (i.e., the flag indicates that multiple chrominance QP mapping tables are applied to the chrominance component), the first chrominance QP mapping table for the chrominance Cb component can be derived based on the first chrominance quantization parameter data of the first chrominance QP mapping table for the chrominance Cb component. In addition, for example, if the flag value is 0, the second chrominance QP mapping table for the chrominance Cb component can be derived based on the second chrominance quantization parameter data of the second chrominance QP mapping table for the Cr component. In addition, for example, if the flag value is 0, the first chrominance QP mapping table for the chrominance CbCr component can be derived based on the third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component.

[0766] In addition, for example, if the flag value is 1 (i.e., the flag indicates that one chrominance QP mapping table is applied to the chrominance component), the chrominance quantization parameter table for the chrominance component can be derived based on the chrominance quantization parameter data of the chrominance QP mapping table for the chrominance component. The chrominance component can include a Cb component, a Cr component, and / or a combined CbCr component.

[0767] The decoding device derives the chrominance quantization parameter for the chrominance component based on the chrominance QP mapping table (S920). The decoding device can derive the chrominance quantization parameter for the chrominance component based on the chrominance QP mapping table.

[0768] For example, if the flag value is 0, the first chrominance quantization parameter for the Cb component can be derived based on the first chrominance QP mapping table, and the second chrominance quantization parameter for the Cr component can be derived based on the second chrominance QP mapping table. In addition, for example, if the flag value is 0, the first chrominance quantization parameter for the Cb component can be derived based on the first chrominance QP mapping table, the second chrominance quantization parameter for the Cr component can be derived based on the second chrominance QP mapping table, and the third chrominance quantization parameter for the combined CbCr component can be derived based on the third chrominance QP mapping table. Here, the quantization parameter for the Cb component can represent QP` as described above Cb , the quantization parameter for the Cr component can represent QP` as described above Cr , and the quantization parameter for the combined CbCr component can represent QP` as described aboveCbCr 。

[0769] For example, an index for a chrominance component (Cb component, Cr component, or combined CbCr component) can be derived based on a quantization parameter for a luminance component, and a chrominance quantization parameter for the chrominance component can be derived based on the chrominance quantization parameter of a point of the index of the chrominance QP mapping table for the chrominance component. That is, for example, the chrominance quantization parameter for the chrominance component can be derived based on the chrominance quantization parameter of a point with the same index as the quantization parameter of the luminance component in the chrominance QP mapping table.

[0770] In addition, for example, the chrominance quantization parameter for the chrominance component (Cb component, Cr component, or combined CbCr component) can be derived by adding an offset to the chrominance quantization parameter of a point of the index of the chrominance QP mapping table for the chrominance component (e.g., QP Cb 、QP CR or QP CbCr ). The chrominance quantization parameter for the chrominance component (e.g., QP` Cb 、QP` Cr or QP` CbCr ) can be derived based on a syntax element representing the offset for deriving the quantization parameter of the chrominance component.

[0771] In addition, for example, if the flag value is 1, the chrominance quantization parameter for the chrominance component can be derived based on the chrominance quantization parameter table for the chrominance component. Therefore, the chrominance quantization parameter can be similarly applied to the chrominance component.

[0772] For example, an index for a chrominance component (Cb component, Cr component, and combined CbCr component) can be derived based on a quantization parameter for a luminance component, and the chrominance quantization parameter for the chrominance component can be derived based on the chrominance quantization parameter of the index of the chrominance QP mapping table for the chrominance component. That is to say, for example, the chrominance quantization parameter for the chrominance component can be derived based on the chrominance quantization parameter of a point with the same index as the quantization parameter of the luminance component in the chrominance QP mapping table.

[0773] In addition, for example, the chrominance quantization parameter for the chrominance component can be derived by adding an offset to the chrominance quantization parameter of a point of the index of the chrominance QP mapping table for the chrominance component. The offset can be derived based on a syntax element representing the offset for deriving the chrominance quantization parameter of the chrominance component.

[0774] The decoding device derives a predicted sample for the chrominance component based on prediction information (S930). The decoding device can determine whether inter prediction or intra prediction is applied to the chrominance component based on the prediction information, and can perform prediction based on this. That is, for example, the decoding device can determine whether inter prediction or intra prediction is applied to the current block of the chrominance component based on the prediction information, and can perform prediction based on this.

[0775] For example, the decoding device may derive a prediction mode of a current block applied to a chrominance component based on prediction information, and may derive prediction samples of the current block based on the prediction mode. For example, when inter prediction is applied to the current block, the decoding device may derive motion information regarding the current block based on the prediction information included in the picture information, and may derive prediction samples of the current block based on the motion information. Further, for example, when intra prediction is applied to the current block, the decoding device may derive reference samples based on neighboring samples of the current block, and may derive prediction samples of the current block based on the intra prediction mode of the current block and the reference samples. The reference samples may include a top reference sample and a left reference sample of the current block. For example, when the size of the current block is NxN and the x and y components of the top left sample position of the current block are 0, the left reference samples may be p[-1][0] to p[-1][2N-1], and the top reference samples may be p[0][-1] to p[2N-1][-1].

[0776] The decoding device derives transform coefficients for the chrominance component based on residual information (S940). For example, the decoding device may derive transform coefficients for the chrominance component based on the received residual information. Alternatively, for example, the decoding device may derive transform coefficients based on the residual information, and may derive inverse transform coefficients by performing an inverse transform on the transform coefficients. The transform coefficients may include transform coefficients for the Cb component, transform coefficients for the Cr component, and / or transform coefficients for the combined CbCr component.

[0777] The decoding device derives residual samples by dequantizing the transform coefficients based on a chrominance quantization parameter (S950). The decoding device may derive residual samples based on the chrominance quantization parameter.

[0778] For example, if the value of the flag is 0, the decoding device may derive the residual samples for the Cb component by dequantizing the transform coefficients for the Cb component based on the first chrominance quantization parameter for the Cb component, and may derive the residual samples for the Cr component by dequantizing the transform coefficients for the Cr component based on the second chrominance quantization parameter for the Cr component. Further, for example, if the value of the flag is 0, the decoding device may derive the residual samples for the Cb component by dequantizing the transform coefficients for the Cb component based on the first chrominance quantization parameter for the Cb component, and may derive the residual samples for the Cr component by dequantizing the transform coefficients for the Cr component based on the second chrominance quantization parameter for the Cr component, and may derive the residual samples for the combined CbCr component by dequantizing the transform coefficients for the combined CbCr component based on the third chrominance quantization parameter for the combined CbCr component. Further, for example, if the value of the flag is 1, the decoding device may derive the residual samples for the chrominance component by dequantizing the transform coefficients for the chrominance component based on the chrominance quantization parameter.

[0779] Further, for example, if the value of the flag is 0, the decoding device may derive the residual samples for the Cb component by dequantizing the transform coefficients for the inverse transform of the Cb component based on the first chrominance quantization parameter for the Cb component, and may derive the residual samples for the Cr component by dequantizing the transform coefficients for the inverse transform of the Cr component based on the second chrominance quantization parameter for the Cr component. Further, for example, if the value of the flag is 0, the decoding device may derive the residual samples for the Cb component by dequantizing the transform coefficients for the inverse transform of the Cb component based on the first chrominance quantization parameter for the Cb component, and may derive the residual samples for the Cr component by dequantizing the transform coefficients for the inverse transform of the Cr component based on the second chrominance quantization parameter for the Cr component, and may derive the residual samples for the combined CbCr component by dequantizing the transform coefficients for the inverse transform of the combined CbCr component based on the third chrominance quantization parameter for the combined CbCr component. Further, for example, if the value of the flag is 1, the decoding device may derive the residual samples for the chrominance component by dequantizing the transform coefficients for the inverse transform of the chrominance component based on the chrominance quantization parameter.

[0780] The decoding device generates a reconstructed picture based on the prediction samples and the residual samples (S960). For example, the decoding device may generate a reconstructed picture based on the residual samples.

[0781] Meanwhile, for example, the decoding device may derive prediction samples by performing an inter prediction mode or an intra prediction mode for a current block based on prediction information received through a bitstream, and may generate reconstructed samples and / or a reconstructed picture by adding the prediction samples and residual samples.

[0782] After that, as needed, in order to improve subjective / objective image quality, an in-loop filtering process such as a deblocking filter and SAO and / or ALF processes may be applied to the reconstructed samples as described above.

[0783] Figure 10 A decoding device for performing an image decoding method according to this document is schematically shown. Figure 9 The method disclosed in Figure 10 may be performed by a decoding device disclosed in Figure 10 Specifically, for example, the entropy decoder of the decoding device of Figure 9 may perform S900 of Figure 10 the predictor of the decoding device of Figure 9 may perform S930 of Figure 10 the residual processor of the decoding device of Figure 9 may perform S910 to S920 and S940 to S950 of Figure 10 and the adder of the decoding device of Figure 9 may perform S960 of

[0784] According to the present disclosure as described above, in order to derive a chrominance quantization parameter for a chrominance component, a chrominance QP mapping table derived based on signaled chrominance quantization parameter data may be used instead of a default chrominance QP mapping table to derive the chrominance quantization parameter for the chrominance component, and by doing so, the compilation efficiency may be improved by performing compilation based on quantization parameters according to the characteristics of the image.

[0785] In addition, according to the present disclosure, a chrominance QP mapping table may be derived based on a syntax element representing an increment value of an input coordinate of a point for deriving the chrominance QP mapping table and / or a syntax element representing an increment value of an output coordinate of a point for deriving the chrominance QP mapping table, and the compilation efficiency may be improved by performing compilation based on the chrominance QP mapping table that more specifically reflects the characteristics of the image.

[0786] In the above embodiments, the method is described based on a flowchart having a series of steps or blocks. The present disclosure is not limited to the order of the above steps or blocks. Some steps or blocks can be executed in a different order from other steps or blocks described above or simultaneously. In addition, those skilled in the art will understand that the steps shown in the flowchart are not exclusive and may further include other steps, or one or more steps in the flowchart may be deleted without affecting the scope of the present disclosure.

[0787] The embodiments described in this specification can be implemented by being executed on a processor, a microprocessor, a controller, or a chip. For example, each functional unit shown in each figure can be executed by being implemented on a computer, a processor, a microprocessor, a controller, or a chip. In this case, the information for implementation (e.g., information about instructions) or algorithms can be stored in a digital storage medium.

[0788] In addition, the decoding device and the encoding device applying the present disclosure can be included in the following devices: a multimedia broadcast transmission / reception device, a mobile communication terminal, a home theater video device, a digital cinema video device, a surveillance camera, a video chat device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a portable camera, a VoD service providing device, an over-the-top (OTT) video device, an Internet streaming service providing device, a three-dimensional (3D) video device, a videoconference video device, a transportation user device (e.g., a vehicle user device, an aircraft user device, and a ship user device), and a medical video device; and the decoding device and the encoding device applying the present disclosure can be used to process video signals or data signals. For example, an over-the-top (OTT) video device can include a game console, a Blu-ray player, an Internet-connected television, a home theater system, a smart phone, a tablet computer, a digital video recorder (DVR), etc.

[0789] In addition, the processing method applying the present disclosure can be generated in the form of a computer-executable program and can be stored in a computer-readable recording medium. The multimedia data having a data structure according to the present disclosure can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices in which computer-readable data is stored. The computer-readable recording medium can include, for example, a BD, a universal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. In addition, the computer-readable recording medium includes a medium implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, the bitstream generated by the encoding method can be stored in a computer-readable recording medium or transmitted through a wired / wireless communication network.

[0790] In addition, the embodiments of the present disclosure can be implemented using a computer program product according to program code, and the program code can be executed in a computer by the embodiments of the present disclosure. The program code can be stored on a computer-readable carrier.

[0791] Figure 11 The structural diagram of a content stream system to which the present disclosure is applied is illustrated.

[0792] The content stream system applying the embodiments of the present disclosure may mainly include an encoding server, a streaming server, a web server, a media storage, user equipment, and a multimedia input device.

[0793] The encoding server compresses the content input from a multimedia input device such as a smart phone, a camera, or a camcorder into digital data to generate a bitstream and sends the bitstream to the streaming server. As another example, when a multimedia input device such as a smart phone, a camera, or a camcorder directly generates a bitstream, the encoding server may be omitted.

[0794] The bitstream may be generated by applying the encoding method or the bitstream generation method of the embodiments of the present disclosure, and the streaming server may temporarily store the bitstream during the process of sending or receiving the bitstream.

[0795] The streaming server sends multimedia data to the user equipment through the web server based on a user request, and the web server serves as a medium for notifying the user of the service. When the user requests a required service from the web server, the web server delivers the request to the streaming server, and the streaming server sends the multimedia data to the user. In this case, the content stream system may include a separate control server. In this case, the control server is used to control commands / responses between devices within the content stream system.

[0796] The streaming server may receive content from the media storage and / or the encoding server. For example, when receiving content from the encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined period of time.

[0797] Examples of the user equipment may include a mobile phone, a smart phone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigator, a touch screen PC, a tablet PC, a superbook, wearable devices (such as smart watches, smart glasses, and head-mounted displays), a digital TV, a desktop computer, and a digital signage, etc. Each server within the content stream system may operate as a distributed server, and in this case, the data received from each server may be distributed.

[0798] The claims described in the present disclosure can be combined in various ways. For example, the technical features of the method claims of the present disclosure can be combined to be implemented as a device, and the technical features of the device claims of the present disclosure can be combined to be implemented as a method. In addition, the technical features of the method claims of the present disclosure and the technical features of the device claims of the present disclosure can be combined to be implemented as a device, and the technical features of the method claims of the present disclosure and the technical features of the device claims of the present disclosure can be combined to be implemented as a method.

Claims

1. A decoding apparatus for image decoding, the decoding apparatus comprising: a memory; and at least one processor connected to the memory, the at least one processor being configured to: obtain image information, the image information including prediction information and residual information for a chrominance component and chrominance quantization parameter data of at least one chrominance quantization parameter (QP) map for the chrominance component; derive a chrominance QP map based on the chrominance quantization parameter data; derive chrominance quantization parameters for the chrominance component based on the chrominance QP map; derive prediction samples for the chrominance component by performing inter prediction or intra prediction based on the prediction information; derive transform coefficients for the chrominance component based on the residual information; derive residual samples by dequantizing the transform coefficients based on the chrominance quantization parameters; and generate a reconstructed picture based on the prediction samples and the residual samples, wherein the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP map, a syntax element for an increment value of an input coordinate of a target point used to derive the chrominance QP map, and a syntax element for an increment value of an output coordinate of the target point used to derive the chrominance QP map, wherein the chrominance quantization parameter data is signaled via a sequence parameter set (SPS), wherein a chrominance QP map for the chrominance component is derived based on (i) a flag related to whether one chrominance QP map is signaled and applied for the Cb component, Cr component, and combined CbCr component and (ii) a combined CbCr enable flag, wherein, based on the value of the flag being equal to 1, one chrominance QP map is signaled and applied for the Cb component, the Cr component, and the combined CbCr component, and wherein, based on the value of the flag being equal to 0 and the value of the combined CbCr enable flag being equal to 1, multiple chrominance QP maps are signaled, the multiple chrominance QP maps including each chrominance QP map for each of the Cb component, the Cr component, and the combined CbCr component.

2. An encoding apparatus for image encoding, the encoding apparatus comprising: a memory; and at least one processor connected to the memory, the at least one processor being configured to: derive prediction samples for a chrominance component based on inter prediction or intra prediction; derive residual samples for the chrominance component based on the prediction samples; generate chrominance quantization parameter data of at least one chrominance quantization parameter (QP) map for the chrominance component; and encode prediction information for the chrominance component, residual information for the chrominance component, and the chrominance quantization parameter data, Wherein, the chrominance quantization parameter data includes a syntax element for the number of points in a chrominance QP mapping table, a syntax element for an incremental value of an input coordinate of a target point used to derive the chrominance QP mapping table, and a syntax element for an incremental value of an output coordinate of the target point used to derive the chrominance QP mapping table. Wherein, the chrominance quantization parameter data is signaled through a sequence parameter set (SPS). Wherein, a chrominance QP mapping table for the chrominance component is derived based on (i) a flag related to whether to signal and apply one chrominance QP mapping table for the Cb component, the Cr component, and the combined CbCr component, and (ii) a combined CbCr enable flag. Wherein, based on the value of the flag being equal to 1, the one chrominance QP mapping table is signaled and applied for the Cb component, the Cr component, and the combined CbCr component. Wherein, based on the value of the flag being equal to 0 and the value of the combined CbCr enable flag being equal to 1, multiple chrominance QP mapping tables are signaled, and the multiple chrominance QP mapping tables include each chrominance QP mapping table for each of the Cb component, the Cr component, and the combined CbCr component.

3. An apparatus for transmitting data for an image, the apparatus comprising: at least one processor configured to obtain a bitstream of image information, the image information including prediction information for a chrominance component, residual information for the chrominance component, and chrominance quantization parameter data for at least one chrominance quantization parameter (QP) mapping table for the chrominance component; and a transmitter configured to transmit data including the bitstream of the image information, the image information including the prediction information, the residual information, and the chrominance quantization parameter data, Wherein, the chrominance quantization parameter data includes a syntax element for the number of points in a chrominance QP mapping table, a syntax element for an incremental value of an input coordinate of a target point used to derive the chrominance QP mapping table, and a syntax element for an incremental value of an output coordinate of the target point used to derive the chrominance QP mapping table. Wherein, the chrominance quantization parameter data is signaled through a sequence parameter set (SPS). Wherein, a chrominance QP mapping table for the chrominance component is derived based on (i) a flag related to whether to signal and apply one chrominance QP mapping table for the Cb component, the Cr component, and the combined CbCr component, and (ii) a combined CbCr enable flag. Wherein, based on the value of the flag being equal to 1, the one chrominance QP mapping table is signaled and applied for the Cb component, the Cr component, and the combined CbCr component. Wherein, based on the value of the flag being equal to 0 and the value of the combined CbCr enable flag being equal to 1, multiple chrominance QP mapping tables are signaled, and the multiple chrominance QP mapping tables include each chrominance QP mapping table for each of the Cb component, the Cr component, and the combined CbCr component.

Images