Image decoding method and apparatus therefor

Abstract

The invention relates to an image decoding method and an apparatus therefor. An image decoding method performed by a decoding device according to the present document comprises the steps of: obtaining image information through a bitstream; and generating a reconstructed picture based on the image information.

Description

[0001] This application is a divisional application of the patent application with the application number 202080061103.2 (PCT / KR2020 / 008739), the international application date of which is July 3, 2020, and the invention title of which is "Image Decoding Method and Apparatus", and which was filed with the Chinese Patent Office on February 28, 2022. Technical Field

[0002] The present disclosure relates to image encoding technology, and more particularly, to an image decoding method and apparatus that use a chrominance QP mapping table derived based on signaled chrominance quantization parameter data in an image encoding 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 conventional image data. Therefore, when transmitting image data using a medium such as a conventional wired / wireless broadband line or storing image data using an existing storage medium, the transmission cost and storage cost increase.

[0004] Therefore, 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 encoding efficiency.

[0007] Another technical object of the present disclosure is to provide a method and apparatus for improving data encoding 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 apparatus. The method includes: obtaining image information through a bitstream, and generating a reconstructed picture based on the image information.

[0010] According to another embodiment of the present disclosure, there is provided a decoding apparatus that performs image decoding. The decoding apparatus includes: an entropy decoder that obtains image information through a bitstream, and a residual processor that generates a reconstructed picture based on the image information.

[0011] According to still another embodiment of the present disclosure, there is provided a video encoding method performed by an encoding apparatus. The method includes encoding image information, and generating a bitstream including the image information.

[0012] According to another embodiment of the present disclosure, a video encoding apparatus is provided. The encoding apparatus includes: an entropy encoder that encodes image information and generates a bitstream including the image information.

[0013] Advantageous Effects

[0014] According to the present disclosure, when deriving a chrominance quantization parameter for a chrominance component, a chrominance QP mapping table derived based on signaled chrominance quantization parameter data 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, encoding efficiency can be improved by performing encoding based on quantization parameters according to the characteristics of an 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 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 encoding efficiency can be improved by performing encoding based on the chrominance QP mapping table that more specifically reflects the characteristics of an 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 is a schematic diagram illustrating the configuration of a video / image encoding apparatus to which embodiments of the present disclosure can be applied.

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

[0019] Figure 4 Examples of video / image encoding methods based on intra prediction are illustrated.

[0020] Figure 5 Examples of video / image encoding methods based on intra prediction are illustrated.

[0021] Figure 6 The intra prediction process is schematically shown.

[0022] Figure 7 Examples of video / image encoding methods based on inter prediction are illustrated.

[0023] Figure 8 Examples of video / image decoding methods based on inter prediction are illustrated.

[0024] Figure 9 The inter prediction process is schematically shown.

[0025] Figure 10 Schematically shows an image encoding method of an encoding apparatus according to this document.

[0026] Figure 11 Schematically shows an encoding apparatus for performing an image encoding method according to this document.

[0027] Figure 12 Schematically shows an image decoding method of a decoding apparatus according to this document.

[0028] Figure 13 Schematically shows a decoding apparatus for performing an image decoding method according to this document.

[0029] Figure 14 Illustrates a structural diagram of a content stream system to which the present disclosure is applied. Detailed implementation manners

[0030] The present disclosure can be modified in various forms, and specific implementation manners thereof will be described and illustrated in the drawings. However, the implementation manners are not intended to limit the present disclosure. The terms used in the following description are only for describing specific implementation manners 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 the possibility of the presence or addition of one or more different features, numbers, steps, operations, elements, components, or combinations thereof is not excluded.

[0031] In addition, the elements in the drawings described in the present disclosure are independently drawn for conveniently 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 can be combined to form a single element, or one element can 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.

[0032] Hereinafter, implementation manners 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.

[0033] Figure 1 Briefly illustrates an example of a video / image compiling device to which the implementation manners of the present disclosure can be applied.

[0034] Refer 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.

[0035] 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.

[0036] 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 capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, a video / image archive including previously captured video / images, etc. The video / image generation 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 capture process may be replaced by a process of generating relevant data.

[0037] 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 bitstream.

[0038] The transmitter may send the encoded image / video 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 may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter may include elements for generating a media file in a predetermined file format and may include elements for sending via a broadcast / communication network. The receiver may receive / extract the bitstream and send the received bitstream to the decoding device.

[0039] The decoding device may decode the video / images by performing a series of processes such as dequantization, inverse transformation, and prediction corresponding to the operations of the encoding device.

[0040] The renderer may render the decoded video / images. The rendered video / images may be displayed through a display.

[0041] The present disclosure relates to video / image coding. For example, the methods / embodiments disclosed in the present disclosure can be applied to the methods disclosed in Versatile Video Coding (VVC), Efficient Video Coding (EVC) standard, AOMedia Video 1 (AV1) standard, Audio Video Coding Standard 2 (AVS2), or next-generation video / image coding standards (e.g., H.267, or H.268, etc.).

[0042] The present disclosure presents various embodiments of video / image coding, and unless otherwise mentioned, the embodiments can be executed in combination with each other.

[0043] In the present disclosure, 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 in coding. A sub-picture / slice / tile may include one or more coding 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 area 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 can sort the CTUs of a partitioned picture in a specific order, where the CTUs are sorted continuously in raster scan order within a brick, the bricks within a tile are sorted continuously in raster scan order of the tiles, and the tiles in a picture are sorted continuously in raster scan order of the picture tiles. Additionally, a sub-picture may represent a rectangular area of one or more slices within a picture. That is, a sub-picture contains one or more slices that jointly cover a rectangular area of the picture. A tile is a rectangular area of CTUs within a specific tile column and a specific tile row in a picture. A tile column is a rectangular area 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 area 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 the CTUs of a partitioned picture, where the CTUs can be sorted continuously in raster scan order within a tile, while the tiles in a picture can be sorted continuously in raster scan order of the picture tiles. A slice includes an integer number of bricks that can be exclusively included in a single NAL unit of a picture. A slice may consist of multiple complete tiles or only of a continuous sequence of complete bricks of one tile. In the present disclosure, tile group and slice can be used interchangeably. For example, in the present disclosure, a tile group / tile group header may be referred to as a slice / slice header.

[0044] A pixel or pel can represent the smallest unit that makes up a picture (or image). Additionally, the term "sample" can be used as a term corresponding to a pixel. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chrominance component.

[0045] A unit can represent the basic unit of image processing. A unit can include at least one of a specific area of a picture and information related to that area. A unit can include one luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit can be used interchangeably with terms such as a block or a region. Generally, an M×N block can include an array of M columns and N rows of samples (or a set or array of transform coefficients).

[0046] In this specification, "A or B" can mean "only A", "only B", or "A and B". In other words, in this specification, "A or B" can 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".

[0047] The slashes ( / ) or commas used in this specification can mean "and / or". For example, "A / B" can mean "A and / or B". Thus, "A / B" can mean "only A", "only B", or "A and B". For example, "A, B, C" can mean "A, B, or C".

[0048] In this specification, "at least one of A and B" can 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" can be interpreted the same as "at least one of A and B".

[0049] Additionally, 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". Further, "at least one of A, B, or C" or "at least one of A, B, and / or C" can mean "at least one of A, B, and C".

[0050] Furthermore, the parentheses used in this specification can 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" can be presented as an example of "prediction". Additionally, even when indicating "prediction (i.e., intra prediction)", "intra prediction" can also be presented as an example of "prediction".

[0051] In this specification, the technical features described separately in a figure can be implemented separately or can be implemented simultaneously.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 processor may be referred to as a compilation unit (CU). In this case, the compilation unit may be recursively split from a compilation tree unit (CTU) or a largest compilation unit (LCU) according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, a compilation unit may be split into a plurality of compilation units with a deeper depth 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 compilation process according to the present disclosure may be performed based on the final compilation unit that is no longer split. In this case, the largest compilation unit may be used as the final compilation unit based on the compilation efficiency according to the image characteristics, or if necessary, the compilation unit may be recursively split into compilation units with a deeper depth and the compilation unit with the optimal size may be used as the final compilation unit. Here, the compilation 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 split or divided from the above-mentioned final compilation unit. 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.

[0056] In some cases, the 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, may represent only the pixel / pixel value of the luminance component, or may represent only the pixel / pixel value of the chrominance component. A sample may be used as a term corresponding to a picture (or image) of a pixel or a cell.

[0057] 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 in units of 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.

[0058] 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.

[0059] The inter - frame predictor 221 can derive a prediction 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 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. The 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, the residual signal may not be sent. 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.

[0060] 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, e.g., screen content coding (SCC). IBC basically performs prediction in the current picture, but IBC can be performed 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.

[0061] 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 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.

[0062] Quantizer 233 may quantize the transform coefficients and send them to entropy encoder 240, and entropy encoder 240 may encode the quantized signals (information about the quantized transform coefficients) and output a bitstream. The information about the quantized transform coefficients may be referred to as residual information. Quantizer 233 may 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 may be generated. Entropy encoder 240 may 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 may encode the information required for video / image reconstruction other than the quantized transform coefficients (e.g., 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 may 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 may further include general constraint information. In the present disclosure, the information and / or syntax elements sent / signaled from the encoding device to the decoding device may be included in the video / picture information. The video / image information may be encoded through the above encoding process and included in the bitstream. The bitstream may be sent through a network or stored in a digital storage medium. The network may include a broadcast network and / or a communication network, and the digital storage medium may 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 may be included as internal / external elements of encoding device 200. Alternatively, the transmitter may be included in entropy encoder 240.

[0063] 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.

[0064] In addition, during picture encoding and / or reconstruction, luminance mapping and chrominance scaling (LMCS) can be applied.

[0065] 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 the various filtering methods. The information related to filtering can be encoded by the entropy encoder 240 and output in the form of a bitstream.

[0066] 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 mismatch between the encoding device 200 and the decoding device can be avoided, and the encoding efficiency can be improved.

[0067] 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 transfer the reconstructed samples to the intra-frame predictor 222.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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 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. 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 the present 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 bin (binary digit) 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 symbol / bin 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 a symbol corresponding to the value 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 symbol / bin 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 the 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 a 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, the 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 the present 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.

[0072] 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.

[0073] The inverse transformer 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0074] 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 prediction-related information output from the entropy decoder 310, and can determine the specific intra / inter prediction mode.

[0075] The predictor 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, e.g., 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.

[0076] 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 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.

[0077] The inter - frame predictor 332 can derive a prediction block for the 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 regarding the prediction can include information indicating the mode of inter - frame prediction for the current block.

[0078] 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.

[0079] 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.

[0080] In addition, luminance mapping and chrominance scaling (LMCS) can be applied during the picture decoding process.

[0081] 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). The various filtering methods can include, for example, de - blocking filtering, sample - adaptive offset, adaptive loop filter, bilateral filter, etc.

[0082] 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 to be utilized as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 360 can store the reconstructed samples of the reconstructed blocks in the current picture and can transfer the reconstructed samples to the intra - predictor 331.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Meanwhile, as described above, when performing video coding, prediction is performed to improve the compression efficiency. By doing so, a prediction block including prediction samples of the current block can be generated as the block to be coded (i.e., the coding target block). Here, the prediction block includes prediction samples in the spatial domain (or pixel domain). The prediction block is derived in the same way in the encoding device and the decoding device, and the encoding device can signal the information about the residual between the original block and the prediction block (residual information) to the decoding device instead of the original sample values of the original block, thereby improving the image coding 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.

[0087] Residual information can be generated through a transform and quantization process. For example, an encoding device can derive a residual block between an original block and a predicted block, perform a transform process on residual samples (residual sample array) included in the residual block to derive transform coefficients, perform a quantization process on the transform coefficients to derive quantized transform coefficients, and signal relevant residual information (through a bitstream) to a decoding device. Here, the residual information can include value information such as the value information of the quantized transform coefficients, position information, transform technology, 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 predicted block and the residual block. In addition, for reference in inter-prediction of a picture for future reference, the encoding device can dequantize / inverse transform the quantized transform coefficients to derive a residual block and generate a reconstructed picture based on this.

[0088] Intra prediction may refer to prediction that generates prediction samples for a current block based on reference samples in a picture (hereinafter referred to as the current picture) to which the current block belongs. When intra prediction is applied to the current block, adjacent reference samples to be used for intra prediction of the current block can be derived. The adjacent reference samples of the current block can include a total of 2×nH samples adjacent to the left boundary of the current block of size nW×nH and adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2×nW 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 vertically adjacent samples and multiple rows of horizontally adjacent samples. 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 nW×nH, 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.

[0089] However, some of the adjacent reference samples of the current block have not been decoded or may be unavailable. In this case, the decoder can construct adjacent reference samples to be used for prediction by replacing the unavailable samples with available samples. Alternatively, the adjacent reference samples to be used for prediction can be configured by interpolation of available samples.

[0090] When deriving adjacent reference samples, (i) prediction samples can be derived based on the average or interpolation of the adjacent reference samples of the current block, or (ii) prediction samples can be derived based on reference samples existing in a specific (prediction) direction with respect to the prediction samples in the adjacent reference samples of the current block. Case (i) can be referred to as a non-directional mode or a non-angle mode, and case (ii) can be referred to as a directional mode or an angle mode.

[0091] Alternatively, a predicted sample can be generated by interpolating a first neighboring sample in a prediction direction of an intra prediction mode of a current block among neighboring reference samples and a second neighboring sample in a direction opposite to the prediction direction. The above situation can be referred to as linear interpolation intra prediction (LIP). In addition, a chrominance prediction sample can be generated based on luminance samples using a linear model (LM). This situation can be referred to as the LM mode or the chrominance component LM (CCLM) mode.

[0092] Alternatively, a temporary predicted sample of a current block is derived based on filtered neighboring reference samples, and a predicted sample of the current block can also be derived by weighted summing the temporary predicted sample and at least one reference sample derived according to an intra prediction mode among existing neighboring reference samples (i.e., unfiltered neighboring reference samples). The above situation can be referred to as position-dependent intra prediction (PDPC).

[0093] Alternatively, a reference sample line with the highest prediction accuracy among a plurality of neighboring reference sample lines of a current block is selected, and a predicted sample is derived using a reference sample in the prediction direction in the selected line. In this case, intra prediction coding can be performed by indicating (signaling) the used reference sample line to a decoding device. The above situation can be referred to as multi-reference line intra prediction or MRL-based intra prediction.

[0094] Alternatively, a current block is divided into vertical or horizontal sub-partitions and intra prediction is performed based on the same intra prediction mode, but 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 neighboring reference samples on a sub-partition basis. This prediction method can be referred to as intra prediction based on intra sub-partition (ISP).

[0095] The above intra prediction methods can be referred to as intra prediction types to distinguish them from intra prediction modes. Intra prediction types can be referred to by various terms, such as intra prediction techniques or additional intra prediction modes. For example, an intra prediction type (or an additional intra prediction mode, etc.) can 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 can be referred to as a normal intra prediction type. When the above specific intra prediction types are not applied, the normal intra prediction type can generally be applied, and prediction can be performed based on the above intra prediction mode. At the same time, if necessary, post-processing filtering can be performed on the derived predicted samples.

[0096] Specifically, the intra prediction process may include an intra prediction mode / type determination step, an adjacent reference sample derivation step, and a predicted sample derivation step based on the intra prediction mode / type. Additionally, if necessary, a post-filtering step may be performed on the derived predicted samples.

[0097] Figure 4 An example of a video / image encoding method based on intra prediction is illustrated.

[0098] Referring to Figure 4 , the encoding device performs intra prediction on the current block (S400). The encoding device derives the intra prediction mode / type of the current block, derives the adjacent reference samples of the current block, and generates predicted samples in the current block based on the intra prediction mode / type and the adjacent reference samples. Here, the intra prediction mode / type determination, adjacent reference sample derivation, and predicted sample generation processes may be performed simultaneously, or one process may be performed before another process. The encoding device may determine the mode / type to be applied to the current block from among multiple intra prediction modes / types. The encoding device may compare the RD costs of the intra prediction modes / types and determine the best intra prediction mode / type for the current block.

[0099] Meanwhile, the encoding device may perform a predicted sample filtering process. Predicted sample filtering may be referred to as post-filtering. Some or all of the predicted samples may be filtered by the predicted sample filtering process. In some cases, the predicted sample filtering process may be omitted.

[0100] The encoding device generates residual samples for the current block based on the (filtered) predicted samples (S410). The encoding device may compare the predicted samples in the original samples of the current block based on phase and derive the residual samples.

[0101] The encoding device may encode the image information including information about intra prediction (prediction information) and residual information about the residual samples (S420). The prediction information may include intra prediction mode information and intra prediction type information. The encoding device is capable of outputting the encoded image information in the form of a bitstream. The output bitstream may be sent to the decoding device via a storage medium or a network.

[0102] The residual information may include a residual compilation syntax described later. The encoding device may transform / quantize the residual samples to derive quantized transform coefficients. The residual information may include information about the quantized transform coefficients.

[0103] Meanwhile, as described above, the encoding device may generate reconstructed pictures (including reconstructed samples and reconstructed blocks). To this end, the encoding device may derive (modified) residual samples by performing inverse quantization / inverse transformation on the quantized transform coefficients again. The reason for performing inverse quantization / inverse transformation again after transforming / quantizing the residual samples in this way is to derive the same residual samples as those derived in the decoding device described above. The encoding device may generate a reconstructed block including reconstructed samples for the current block based on the prediction samples and the (modified) residual samples. A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering process may be further applied to the reconstructed picture.

[0104] Figure 5 FIG. illustrates an example of a video / image encoding method based on intra prediction.

[0105] The decoding device may perform operations corresponding to those performed by the encoding device.

[0106] The prediction information and the residual information may be obtained from the bitstream. The residual samples for the current block may be derived based on the residual information. Specifically, the transform coefficients may be derived by performing inverse quantization on the quantized transform coefficients derived based on the residual information, and the residual samples for the current block may be derived by performing inverse transformation on the transform coefficients.

[0107] Specifically, the decoding device may derive the intra prediction mode / type for the current block (S500) based on the received prediction information (intra prediction mode / type information). The decoding device may derive the neighboring reference samples for the current block (S510). The decoding device generates prediction samples in the current block (S520) based on the intra prediction mode / type and the neighboring reference samples. In this case, the decoding device may perform a prediction sample filtering process. Prediction sample filtering may be referred to as post-filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering process. In some cases, the prediction sample filtering process may be omitted.

[0108] The decoding device generates residual samples for the current block based on the received residual information (S530). The decoding device may generate reconstructed samples for the current block based on the prediction samples and the residual samples, and may derive a reconstructed block including the reconstructed samples (S540). A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering process may be further applied to the reconstructed picture.

[0109] The intra prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) that indicates whether MPM (Most Probable Mode) is applied to the current block or whether a remaining mode is applied. When MPM is applied to the current block, the prediction mode information may further include index information (e.g., intra_luma_mpm_idx) that indicates one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be constituted by an MPM candidate list or an MPM list. Additionally, when MPM is not applied to the current block, the intra prediction mode information includes remaining mode information (e.g., intra_luma_mpm_remainder) that indicates one of the remaining intra prediction modes other than the intra prediction mode candidates (MPM candidates). The decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

[0110] In addition, the intra prediction type information can be implemented in various forms. For example, the intra prediction type information may include intra prediction type index information that indicates one of the intra prediction types. As another example, the intra prediction type information may include at least one of the following: reference sample line information (e.g., intra_luma_ref_idx) that indicates whether MRL is applied to the current block and, if so, which reference sample line is used, ISP flag information (e.g., intra_subpartitions_mode_flag) that indicates whether ISP is applied to the current block, ISP type information (e.g., intra_subpartitions_split_flag) that indicates the split type of the sub - partition when ISP is applied, flag information that indicates whether PDPC is applied, or flag information that indicates whether LIP is applied. In addition, the intra prediction type information may include an MIP flag that indicates whether matrix - based intra prediction (MIP) is applied to the current block.

[0111] The intra prediction mode information and / or the intra prediction type information may be encoded / decoded by the encoding / decoding methods described in the present disclosure. For example, the intra prediction mode information and / or the intra prediction type information may be encoded / decoded by entropy encoding (e.g., CABAC, CAVLC).

[0112] Figure 6 The intra prediction process is schematically illustrated.

[0113] Refer to Figure 6, as described above, the intra prediction process may include steps of determining an intra prediction mode / type, deriving neighboring reference samples, and performing intra prediction (generating prediction samples). The intra prediction process may be performed by the encoding device and the decoding device as described above. In the present disclosure, the compiling device may include an encoding device and / or a decoding device.

[0114] Referring to Figure 6 , the compiling device determines an intra prediction mode / type S600.

[0115] The encoding device may determine an intra prediction mode / type to be applied to a current block from the various intra prediction modes / types described above, and may generate prediction-related information. The prediction-related information may include intra prediction mode information indicating an intra prediction mode applied to the current block and / or intra prediction type information indicating an intra prediction type applied to the current block. The decoding device may determine an intra prediction mode / type to be applied to the current block based on the prediction-related information.

[0116] The intra prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) indicating whether the most probable mode (MPM) is applied to the current block or a remaining mode is applied, and when the MPM is applied to the current block, the prediction mode information may further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be constituted by an MPM candidate list or an MPM list. Additionally, when the MPM is not applied to the current block, the intra prediction mode information may further include remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes other than the intra prediction mode candidates (MPM candidates). The decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

[0117] In addition, the intra prediction type information can be implemented in various forms. For example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information may include at least one of the following: reference sample line information (e.g., intra_luma_ref_idx) indicating whether the MRL is applied to the current block and, if applied, which reference sample line is used, ISP flag information (e.g., intra_subpartitions_mode_flag) indicating whether the ISP is applied to the current block, ISP type information (e.g., intra_subpartitions_split_flag) indicating the split type of the subpartition when the ISP is applied, flag information indicating whether the PDPC is applied, or flag information indicating whether the LIP is applied. In addition, the intra prediction type information may include an MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

[0118] For example, when intra prediction is applied, the intra prediction mode of neighboring blocks can be used to determine the intra prediction mode applied to the current block. For example, the compiling device may select one of the most probable mode (MPM) candidates in the MPM list derived based on additional candidate modes and / or the intra prediction modes of neighboring blocks (e.g., left and / or upper neighboring blocks) of the current block or select one of the remaining intra prediction modes not included in the MPM candidates (and the planar mode) based on the MPM residual information (residual 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 an MPM rather than not an MPM, so the flag (non-planar flag) is signaled first to check whether it is the planar mode.

[0119] 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 of the current block is within the MPM candidates (and the planar mode), while 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 of the current block is the planar mode, and a non-planar flag with a value of 1 can indicate that the intra prediction mode of 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 through an index in the order of the prediction mode numbers. The intra prediction mode can be the intra prediction mode of the luminance component (samples). Hereinafter, the intra prediction mode information can include at least one of 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.

[0120] 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.

[0121] In other words, generally, when performing block segmentation of an image, the current block to be coded and the neighboring blocks have similar image characteristics. 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.

[0122] The encoding device can build a list of the most probable modes (MPMs) for the current block. The MPM list can be referred to as the MPM candidate list. Here, the MPM can refer to a mode that is used to improve the encoding efficiency by considering the similarity between the current block and neighboring blocks during intra prediction mode encoding. As described above, the MPM list can be constructed to include the planar mode, or can 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 can be 6. When the MPM list does not include the planar mode, the number of candidates in the MPM list can be 5.

[0123] The encoding device can perform prediction based on various intra prediction modes, and can determine the best intra prediction mode based on rate distortion optimization (RDO) according to it. In this case, the encoding device can determine the best intra prediction mode by using only the MPM candidates configured in the MPM list and the planar mode, or by further using the remaining intra prediction modes as well as the MPM candidates configured in the MPM list and the planar mode. Specifically, for example, if the intra prediction type of the current block is a specific type other than the normal intra prediction type (such as LIP, MRL, or ISP), the encoding device can determine the best intra prediction mode by considering only the MPM candidates and the planar mode as the intra prediction mode candidates for the current block. That is, in this case, the intra prediction mode of the current block can be determined only from the MPM candidates and the planar mode, and in this case, the encoding / signaling of the mpm flag can be not performed. In this case, the decoding device can infer that the mpm flag is 1 without signaling the mpm flag separately.

[0124] Meanwhile, generally, when the intra prediction mode of the current block is not the planar mode but one of the MPM candidates in the MPM list, the encoding device generates an mpm index (mpm idx) indicating one of the MPM candidates. When the intra prediction mode of the current block is not included in the MPM list, the encoding device generates MPM remainder information (remaining intra prediction mode information) indicating the mode that is the same as the intra prediction mode of the current block among the remaining intra prediction modes not included in the MPM list (and the planar mode). The MPM remainder information can include, for example, the intra_luma_mpm_remainder syntax element.

[0125] The decoding device obtains intra prediction mode information from the bitstream. As described above, the intra prediction mode information may include at least one of an MPM flag, a non - planar flag, an MPM index, and MPM remaining information (remaining intra prediction mode information). The decoding device may construct an MPM list. The construction of the MPM list is the same as that constructed in the encoding device. That is, the MPM list may include the intra prediction modes of neighboring blocks, or may further include specific intra prediction modes according to a predetermined method.

[0126] The decoding device may determine the intra prediction mode of the current block based on the MPM list and the intra prediction mode information. For example, when the value of the MPM flag is 1, the decoding device may (based on the non - planar flag) derive the planar mode as the intra prediction mode of the current block, or derive the candidate indicated by the MPM index among the MPM candidates in the MPM list as the intra prediction mode of the current block. Here, the MPM candidates may only represent the candidates included in the MPM list, or may include not only the candidates included in the MPM list but also the planar mode applicable when the value of the MPM flag is 1.

[0127] For another example, when the value of the MPM flag is 0, the decoding device may derive the intra prediction mode indicated by the remaining intra prediction mode information (which may be referred to as mpm remaining information) among the remaining intra prediction modes not included in the MPM list and the planar mode as the intra prediction mode of the current block. Meanwhile, as another example, when the intra prediction type of the current block is a specific type (such as LIP, MRL, or ISP, etc.), the decoding device may derive the candidate indicated by the planar mode or the MPM flag in the MPM list as the intra prediction mode of the current block without parsing / decoding / checking the MPM flag.

[0128] The compiling device derives adjacent reference samples of the current block (S610). When intra prediction is applied to the current block, adjacent reference samples to be used for intra prediction of the current block may be derived. The adjacent reference samples of the current block may include a total of 2×nH samples adjacent to the left boundary of the current block of size nW×nH and adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2×nW 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 may include multiple columns of vertically adjacent samples and multiple rows of horizontally adjacent samples. In addition, the adjacent reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of size nW×nH, 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.

[0129] On the other hand, when applying MRL (i.e., when the value of the MRL index is greater than 0), the adjacent reference samples may be located on lines 1 to 2 instead of line 0 adjacent to the current block on the left / upper side, and in this case, the number of adjacent reference samples can be further increased. Meanwhile, when applying ISP, the adjacent reference samples can be derived in units of sub-partitions.

[0130] The encoding device derives prediction samples by performing intra prediction on the current block (S620). The encoding device can derive prediction samples based on the intra prediction mode / type and adjacent samples. The encoding device can derive reference samples according to the intra prediction mode of the current block among the adjacent reference samples of the current block, and can derive the prediction samples of the current block based on the reference samples.

[0131] Meanwhile, when inter-frame prediction is applied, the predictor of the encoding / decoding device can derive predicted samples 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 predicted samples by performing inter-frame prediction on a block-by-block basis. Inter-frame prediction can represent 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 a 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, the 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 the 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.

[0132] 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 picture may be called a forward (reference) picture, and the subsequent picture may be called a backward (reference) picture. 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.

[0133] The video / image encoding process based on inter - frame prediction may schematically include, for example, the following.

[0134] Figure 7 Examples of a video / image encoding method based on inter - frame prediction are illustrated.

[0135] The encoding device performs inter prediction on the current block (S700). The encoding device may derive an inter prediction mode and motion information of the current block, and generate a prediction sample of the current block. Herein, the inter prediction mode determination process, the motion information derivation process, and the prediction sample generation process may be performed simultaneously, and any one of the processes may be performed earlier than the other processes. For example, the inter prediction unit of the encoding device may include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit, and the prediction mode determination unit may determine the prediction mode of the current block, the motion information derivation unit may derive the motion information of the current block, and the prediction sample derivation unit may derive the prediction sample of the current block. For example, the inter prediction unit of the encoding device may search for a block similar to the current block in a predetermined area (search area) of a reference picture through motion estimation, and derive a reference block having the smallest difference from the current block or equal to or less than a predetermined criterion. A reference picture index indicating the reference picture in which the reference block is located may be derived based on this, and a motion vector may be derived based on the positional difference between the reference block and the current block. The encoding device may determine a mode to be applied to the current block among various prediction modes. The encoding device may compare the RD costs of various prediction modes, and determine the best prediction mode of the current block.

[0136] For example, when the skip mode or the merge mode is applied to the current block, the encoding device may configure a merge candidate list to be described below, and derive a reference block having 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, a merge candidate associated with the derived reference block may be selected, and merge index information indicating the selected merge candidate may be generated and signaled to the decoding device. The motion information of the current block may be derived by using the motion information of the selected merge candidate.

[0137] As another example, when the (A)MVP mode is applied to the current block, the encoding device may configure an (A)MVP candidate list to be described below, and use the motion vector of a 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 indicating the reference block derived through motion estimation may be used as the motion vector of the current block, and the mvp candidate having the smallest difference from the motion vector of the current block among the mvp candidates may become the selected mvp candidate. A motion vector difference (MVD), which is a difference obtained by subtracting the mvp from the motion vector of the current block, may be derived. In this case, information about the MVD may be signaled to the decoding device. In addition, when the (A)MVP mode is applied, the value of the reference picture index may be configured as reference picture index information and signaled to the decoding device separately.

[0138] The encoding device may derive a residual sample based on a prediction sample (S710). The encoding device may derive a residual sample by comparing an original sample of a current block with the prediction sample.

[0139] The encoding device encodes image information including prediction information and residual information (S720). 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., skip flag, merge flag, or 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., merge index, mvp flag, or mvp index), which is information for deriving a motion vector. In addition, the information about motion information may include information about MVD and / or reference picture index information. In addition, the information about motion information may include information indicating whether L0 prediction, L1 prediction, or bi-prediction is applied. The residual information is information about the residual sample. The residual information may include information about quantization transform coefficients for the residual sample.

[0140] 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.

[0141] Meanwhile, as described above, the encoding device may generate a reconstructed picture (including reconstructed samples and reconstructed blocks) based on the reference sample and the residual sample. This is to derive the same prediction result as the prediction result executed by the decoding device, and as a result, the encoding efficiency can be improved. Therefore, the encoding device may store the reconstructed picture (or reconstructed samples or reconstructed blocks) in the memory and use the reconstructed picture as a reference picture. As described above, the in-loop filtering process may be further applied to the reconstructed picture.

[0142] The video / image decoding process based on inter prediction may schematically include, for example, the following.

[0143] Figure 8 An example of a video / image decoding method based on inter prediction is illustrated.

[0144] Referring to Figure 8 , the decoding device may perform operations corresponding to the operations 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.

[0145] Specifically, the decoding device may determine a prediction mode of a current block based on the received prediction information (S800). The decoding device may determine which inter prediction mode to apply to the current block based on the prediction mode information in the prediction information.

[0146] For example, it is possible to determine whether to apply the merge mode or the (A)MVP mode to the current block based on a merge flag. Alternatively, one of various inter prediction mode candidates can be selected based on a mode index. The inter prediction mode candidates can include a skip mode, a merge mode, and / or the (A)MVP mode, or can include various inter prediction modes to be described below.

[0147] The decoding apparatus derives motion information for the current block based on the determined inter prediction mode (S810). For example, when the skip mode or the merge mode is applied to the current block, the decoding apparatus may 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 may be performed based on selection information (merge index). The motion information of the current block may be derived by using the motion information of the selected merge candidate. The motion information of the selected merge candidate may be used as the motion information of the current block.

[0148] As another example, when the (A)MVP mode is applied to the current block, the decoding apparatus may 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 may be performed based on selection information (mvp flag or mvp index). In this case, the MVD of the current block may be derived based on information about the MVD, and the motion vector of the current block may be derived based on the mvp and the MVD of the current block. In addition, the reference picture index of the current block may be derived based on the reference picture index information. The picture indicated by the reference picture index in the reference picture list of the current block may be derived as the reference picture referred to for the inter prediction of the current block.

[0149] Meanwhile, as described below, it is possible to derive the motion information of the current block without configuring a candidate list, and in this case, the motion information of the current block may be derived according to the process disclosed in the prediction mode. In this case, the candidate list configuration may be omitted.

[0150] The decoding apparatus may generate a prediction sample for the current block based on the motion information of the current block (S820). In this case, the reference picture may be derived based on the reference picture index of the current block, and the prediction sample of the current block may be derived by using the sample 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 may be further performed for all or some of the prediction samples of the current block.

[0151] 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 the prediction mode of the 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 sample of the current block.

[0152] The decoding device generates the residual sample of the current block based on the received residual information (S830). The decoding device may generate the reconstructed sample of the current block based on the prediction sample and the residual sample, and generate the reconstructed picture based on the generated reconstructed sample (S840). Thereafter, as described above, the in-loop filtering process may be further applied to the reconstructed picture.

[0153] Figure 9 The inter-frame prediction process is schematically shown.

[0154] Reference Figure 9 , 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.

[0155] Refer to Figure 9 , the compiling device determines the inter-frame prediction mode of the current block (S900). Various inter-frame prediction modes may be used for the prediction of the current block in the picture. For example, various modes such as the merge mode, the skip mode, the motion vector prediction (MVP) mode, the affine mode, the sub-block merge mode, the merge with MVD (MMVD) mode, and the historical motion vector prediction (HMVP) mode may be used. The decoder-side motion vector refinement (DMVR) mode, the adaptive motion vector resolution (AMVR) mode, the bi-prediction with CU-level weight (BCW), and the bi-directional optical flow (BDOF), etc. may be further used as additional modes. The affine mode may also be referred to as the affine motion prediction mode. The MVP mode may also be referred to as the 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 the motion information candidate of the merge mode or the skip mode, the HMVP candidate may be referred to as the HMVP merge candidate.

[0156] Prediction mode information indicating an inter prediction mode of a current block may be signaled from an encoding device to a decoding device. In this case, the prediction mode information may be included in a bitstream and received by the decoding device. The prediction mode information may include index information indicating one of a plurality of candidate modes. Alternatively, the inter prediction mode may be indicated by hierarchical signaling of flag information. In this case, the prediction mode information may include one or more flags. For example, whether to apply a skip mode may be indicated by signaling a skip flag, and when the skip mode is not applied, whether to apply a merge mode may be indicated by signaling a merge flag, and when the merge mode is not applied, indicating to apply an MVP mode or additional flags for further discrimination may be signaled. An affine mode may be signaled as an independent mode, or signaled as a dependent mode with respect to a merge mode or an MVP mode. For example, the affine mode may include an affine merge mode and an affine MVP mode.

[0157] An encoding device derives motion information of a current block (S910). Motion information derivation may be based on an inter prediction mode.

[0158] An encoding device may perform inter prediction using the motion information of the current block. The encoding device may derive optimal motion information of the current block through a motion estimation process. For example, the encoding device may search for a similar reference block with high correlation in a predetermined search range in a reference picture by using an original block in an original picture of the current block in units of fractional pixels, and derive motion information through the searched reference block. Similarity of a block may be derived based on a difference in sample values based on a phase. For example, similarity of a block may be calculated based on a 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, motion information may be derived based on a reference block having the minimum SAD in a search area. The derived motion information may be signaled to the decoding device according to various methods based on the inter prediction mode.

[0159] An encoding device performs inter prediction based on the motion information of the current block (S920). The encoding device may derive (one or more) predicted samples of the current block based on the motion information. The current block including the predicted samples may be referred to as a prediction block.

[0160] Meanwhile, as described above, a quantizer of the encoding device may derive quantized transform coefficients by applying quantization to transform coefficients. A dequantizer of the encoding device or a dequantizer of the decoding device may derive transform coefficients by applying dequantization to the quantized transform coefficients.

[0161] 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 instead of directly using the quantization ratio by considering complexity. 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.

[0162] During 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 generate 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.

[0163] 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 losses 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.

[0164] Meanwhile, an adaptive frequency weighted quantization technique for adjusting the quantization strength according to frequency can be applied. The adaptive frequency weighted quantization technique is a method of applying the quantization strength differently for each frequency. In adaptive frequency weighted quantization, a predefined quantization scaling matrix can be used to apply the quantization strength for each frequency differently. That is, the above quantization / dequantization process can be performed based on the quantization scaling matrix. For example, 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.

[0165] As described above, quantization / dequantization can be applied to the luminance component and the chrominance component based on the quantization parameter.

[0166] The quantization parameter for the coding unit can be determined based on the information signaled at the picture and / or slice level. For example, the quantization parameter can be derived as described later.

[0167] For example, information related to the derivation of the quantization parameter can be signaled through a sequence parameter set (SPS) as shown in the following table.

[0168] [Table 1]

[0169]

[0170] The semantics of the syntax elements in Table 1 can be the same as those in the following table.

[0171] [Table 2]

[0172]

[0173] For example, the syntax element bit_depth_luma_minus8 can represent BitDepth Yi.e., the bit depth of the samples of the luminance array, and QpBdOffset Y i.e., the luminance quantization parameter range offset. That is, for example, BitDepth can be derived based on the syntax element bit_depth_luma_minus8 Y and QpBdOffset Y . 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. Additionally, bit_depth_luma_minus8 can be in the range of 0 to 8.

[0174] 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 chrominance array, and QpBdOffset C i.e., the chrominance quantization parameter range offset. That is, for example, BitDepth can be derived based on the syntax element bit_depth_chroma_minus8 C and QpBdOffset C . 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, and additionally, bit_depth_chroma_minus8 can be in the range of 0 to 8.

[0175] In addition, information related to the derivation of quantization parameters can be signaled, for example, via a picture parameter set (PPS) as shown in the following table. This information can include the chrominance Cb offset, chrominance Cr offset, combined chrominance offset, and initial quantization parameter. That is, this information can include the syntax elements for the chrominance Cb offset, chrominance Cr offset, combined chrominance offset, and initial quantization parameter.

[0176] [Table 3]

[0177]

[0178] The semantics of the syntax elements in Table 3 can be the same as the following table.

[0179] [Table 4]

[0180]

[0181] For example, the value obtained by adding 26 to the syntax element init_qp_minus26 may 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 may be modified in the slice layer. init_qp_minus26 0 may be in the range of -(26 + QpBdOffset Y ).

[0182] In addition, for example, the syntax elements pps_cb_qp_offset and pps_cr_qp_offset may represent the offsets for deriving Qp’ Cb and Qp’ Cr for the luma quantization parameter Qp’ Y . pps_cb_qp_offset and pps_cr_qp_offset may 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 may ignore the values of these syntax elements.

[0183] In addition, for example, the syntax element pps_joint_cbcr_qp_offset may represent the offset for deriving Qp’ CbCr for the luma quantization parameter Qp’ Y . pps_joint_cbcr_qp_offset may 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 may ignore the value of this syntax element.

[0184] 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.

[0185] 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 indicate 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 indicate 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.

[0186] 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.

[0187] [Table 5]

[0188]

[0189] The semantics of the syntax elements in Table 5 can be the same as those in the following table.

[0190] [Table 6]

[0191]

[0192]

[0193] 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 Y can be exported as 26 + init_qp_minus26 + slice_qp_delta. The value of SliceQpY can be in the range of -QpBdOffset Y to +63. Y

[0194] 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'. 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. Cb

[0195] 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'. 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. Cr

[0196] ​​​In addition, for example, slice_cbcr_qp_offset can represent the difference to be added to the value of pps_cbcr_qp_offset when determining the value of quantization parameter Qp'. CbCr The value of slice_cbcr_qp_offset can be in the range of -12 to +12. In addition, for example, if slice_cbcr_qp_offset does not exist, slice_cbcr_qp_offse can be inferred as 0.

[0197] The value of pps_cbcr_qp_offset + slice_cbcr_qp_offset can be in the range of 12 to +12.

[0198] The derivation process for the luminance and chrominance quantization parameters can be started based on the following facts:

[0199] The input to this process is the luminance position, parameters for specifying the width and height of the current coding block,

[0200] and parameters for specifying a single tree or a double tree. At the same time, as in the foregoing, the luminance quantization parameter, chrominance quantization parameter, and joint chrominance quantization parameter can be represented as Qp' Y 、Qp' Cb 、Qp' Cr and Qp' CbCr .

[0201] At the same time, for example, the syntax element cu_qp_delta_sign_flag representing the sign of CuQpDeltaVal can be parsed. For example, cu_qp_delta_sign_flag can represent the sign of CuQpDeltaVal as follows.

[0202] For example, when cu_qp_delta_sign_flag is 0, the CuQpDeltaVal corresponding to cu_qp_delta_sign_flag can have a positive value. Alternatively, for example, when cu_qp_delta_sign_flag is 1, the CuQpDeltaVal corresponding to cu_qp_delta_sign_flag can have a negative value. In addition, if cu_qp_delta_sign_flag does not exist, cu_qp_delta_sign_flag can be inferred as 0.

[0203] In addition, for example, if cu_qp_delta_abs exists, the parameter IsCuQpDeltaCoded

[0204] can be exported as 1. The parameter CuQpDeltaVal can be exported as cu_qp_delta_abs

[0205] *(1 - 2 * cu_qp_delta_sign_flag). CuQpDeltaVal can be in the range of -(32 +

[0206] QpBdOffsetY / 2) to +(31 + QpBdOffsetY / 2).

[0207] Thereafter, for example, the luminance quantization parameter Qp’ Y can be derived as in the following equation.

[0208] [Equation 1]

[0209] Qp Y = ((qP Y_PRED + CuQpDeltaVal + 64 + 2 * QpBdOffset Y ) % (64 + QpBdOffset Y )) - QpBdOffset Y

[0210] In addition, if ChromaArrayType is not 0 and treeType is SINGLE_TREE or DUAL_TREE_CHROMA, the following can be applied.

[0211] - When treeType is equal to DUAL_TREE_CHROMA, the parameter Qp Y can be set the same as the luminance quantization parameter Qp of the luminance coding unit including the luminance position QpY(xCb + cbWidth / 2, yCb + cbHeight / 2). Y identically.

[0212] - The parameters qP Cb 、qP Cr and qP CbCr can be derived as follows.

[0213] [Equation 2]

[0214] qPi Cb = Clip3(-QpBdOffset C , 69, Qp Y + pps_cb_qp_offset + slice_cb_qp_offset)

[0215] qPi Cr = Clip3(-QpBdOffset C,69,Qp Y +(pps_cr_qp_offset + slice_cr_qp_offset)

[0216] qPi CbCr = Clip3(-QpBdOffsct C ,69,Qp Y +(pps_joint_cbcr_qp_offset + slice_joint_cbcr_qp_offset)

[0217] 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.

[0218] [Table 7]

[0219] 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

[0220] 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.

[0221] - 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.

[0222] [Equation 3]

[0223] Qp′ CB = qP Cb + QpBdOffset C

[0224] Qp′ Cr = qP Cr + QpBdOffset C

[0225] Qp′ CbCr = qPCbCr +QpBdOffset C

[0226] Meanwhile, this document proposes a solution for improving the compilation efficiency in quantization / dequantization processing.

[0227] 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 chroma quantization mapping table predefined 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 predefined 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 values of predefined syntax elements, and the user defines the chroma quantization table mapping based on the sent values. 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, for example, Table 7.

[0228] 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.

[0229] [Table 8]

[0230]

[0231] 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.

[0232] The semantics of the syntax elements in Table 8 can be the same as those in the following table.

[0233] [Table 9]

[0234]

[0235] For example, the syntax element adaptation_parameter_set_id may provide an identifier of the APS that is referenced by other syntax elements.

[0236] 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, a 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. A 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.

[0237] 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 that follows this version of the standard may ignore all syntax elements aps_extension_data_flag.

[0238] 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.

[0239] [Table 10]

[0240]

[0241] 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.

[0242] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0243] For example, the present embodiment proposes a scheme for signaling user - defined Qp in an Image Parameter Set (PPS). C As an example for implementing the scheme proposed in the present 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 the present 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.

[0244] A flag indicating whether the PPS includes user - defined data can be signaled as shown in the following table.

[0245] [Table 11]

[0246]

[0247] 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.

[0248] In addition, the user - defined data signaled in the PPS according to the present embodiment can be the same as the following table.

[0249] [Table 12]

[0250]

[0251] Meanwhile, for example, Qpc_data() can include information required for chroma quantization derivation when ChromaArrayType is 1.

[0252] In addition, this document proposes another embodiment in which information for quantization parameters is signaled.

[0253] For example, this embodiment proposes a flexible structure for chrominance quantization parameter (QP) derivation and combined chrominance QP derivation. This embodiment proposes a scheme for signaling an initial flag that indicates whether there is a user-defined mode in which parameters representing functions for deriving chrominance quantization parameters (QP) in the SPS and / or PPS can be used.

[0254] For example, the flag information signaled in the high-level syntax proposed in this embodiment can be the same as the table described later.

[0255] [Table 13]

[0256]

[0257] For example, the Qpc_data_present_flag can indicate whether parameters for deriving chrominance quantization parameters exist in the high-level syntax RBSP syntax structure. For example, a Qpc_data_present_flag with a value of 0 can indicate that chrominance quantization parameters do not exist in the high-level syntax RBSP syntax structure. Additionally, for example, a Qpc_data_present_flag with a value of 1 can indicate that chrominance quantization parameters exist in the high-level syntax RBSP syntax structure.

[0258] Alternatively, the syntax element Qpc_data_present_flag can be used in the bitstream to indicate the scheme for using chrominance quantization derivation. For example, the syntax element Qpc_data_present_flag can represent a tool for chrominance quantization derivation or the use of the following user-defined mode.

[0259] For example, the Qpc_data_present_flag in the bitstream can indicate whether user-defined chrominance quantization is used. For example, a Qpc_data_present_flag with a value of 0 can indicate that user-defined chrominance quantization is not used in the bitstream. Additionally, for example, a Qpc_data_present_flag with a value of 1 can indicate that user-defined chrominance quantization is used alone or in combination with another flag.

[0260] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0261] For example, this embodiment proposes how user-defined information signaled in a function can be used to derive chrominance quantization parameters (QP) (i.e., Qp` Cb 、Qp` Cr and Qp` CbCrExample of (). For example, according to this embodiment, data representing a function for deriving 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 user-defined QP mapping table) can be signaled as in the following table.

[0262] [Table 14]

[0263]

[0264] The semantics of the syntax elements in Table 14 can be the same as the following table.

[0265] [Table 15]

[0266]

[0267] For example, the syntax element qPi_min_idx can represent the minimum qPi index used in chrominance quantization.

[0268] 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. For example, Qp c The maximum index qPiMaxIdx used in derivation can be derived as in the following equation.

[0269] [Equation 4]

[0270] qPiMaxIdx = qPi_min_idx + qPi_delta_max_idx

[0271] In addition, for example, the syntax element Qp C _qPi_val[i] can represent the Qp value for the i-th index C .

[0272] In addition, for example, the syntax element QpOffset C can represent the offset value for deriving Qp C .

[0273] In addition, for example, the parameter Qp for qPi C Idx[qPi] can be derived as follows. In this case, qPi can be from 0 to qPiMaxIdx.

[0274] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set to be the same as qPi.

[0275] - When qPi = qPi_min_idx... qPiMaxIdx, Qp C Idx[qPi] can be associated with Qp C _qPi_val[qPi] is set in the same way.

[0276] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - QpOffset C .

[0277] Thereafter, the value of Qp C can be derived as Qp C Idx[qPi].

[0278] 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.

[0279] [Table 16]

[0280]

[0281]

[0282]

[0283] Referring to Table 16, the process for deriving luminance and chrominance quantization parameters can be started based on the following facts: The input for this process is the luminance position (xCb, yCb), the parameters cbWidth and cbHeight specifying the width and height of the current coding block, and the parameter treeType specifying a single tree or a double tree. Meanwhile, as described above, the luminance quantization parameter and the chrominance quantization parameter can be represented as Qp’ Y , Qp’ Cb and Qp’ Cr .

[0284] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0285] For example, this embodiment presents an example in which, as a flag within the SPS, there is a user-defined mode or a default mode, thus using 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 the following table. Meanwhile, the structure of the syntax elements is not limited to, for example, the structure illustrated in the following table.

[0286] [Table 17]

[0287]

[0288] [Table 18]

[0289]

[0290] [Table 19]

[0291]

[0292] For example, the syntax element Qpc_data_default_flag can indicate whether a user - defined mode is used to export quantization parameters. For example, a Qpc_data_default_flag with a value of 0 can indicate that the user - defined mode is used to export quantization parameters. Additionally, for example, a Qpc_data_default_flag with a value of 1 can indicate that the default table is used to export chrominance quantization parameters. In this case, the default table can 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 can be inferred as 1.

[0293] Meanwhile, if the user - defined mode is used, the corresponding slice header, tile group / header, or another appropriate header can be used to signal the APS ID. For example, as shown in Table 18, a syntax element representing the APS ID can be signaled through the slice header.

[0294] For example, the syntax element slice_Qp c _aps_id can represent the adaptation_parameter_set_id of the Qp c APS referenced 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 can 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 referenced by two or more slices of the same image, then multiple Qp c APSs with an adaptation_parameter_set_id including the same value can have the same content.

[0295] In addition, the APS structure for transmitting chrominance quantization data proposed in this embodiment can be the same as Table 19.

[0296] For example, the syntax element adaptation_parameter_set_id may provide an identifier for the APS that is referenced by other syntax elements.

[0297] 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, a 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. A 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.

[0298] In addition, for example, the syntax element aps_extension_data_flag may have any value. The presence (presence 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 that follows this version of the standard may ignore all syntax elements aps_extension_data_flag.

[0299] 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.

[0300] The Qpc_data() disclosed in Table 19 may be signaled as shown in the following table.

[0301] [Table 20]

[0302]

[0303] For example, the syntax element qPi_min_idx may indicate the minimum qPi index used in chrominance quantization.

[0304] 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 chrominance Qp c derivation. The value of qPiMaxIdx may be greater than or equal to qPi_min_idx. For example, the maximum index qPiMaxIdx used in Qp c derivation may be derived as shown in Equation 4.

[0305] In addition, for example, by adding 1 to the syntax element Qp cThe value obtained by _prec_minus1 can represent the number of bits used to represent the syntax lmcs_delta_abs_cw[i]. Qp c The value of _prec_minus1 can be in the range of 0 to BitDepth Y - 2.

[0306] In addition, for example, the syntax element Qp c _init_val can represent the Qp corresponding to qPi_min_idx C value.

[0307] 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.

[0308] In addition, for example, the syntax element QpOffset C can represent the offset value used to derive Qp c value.

[0309] 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.

[0310] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set to be the same as qPi.

[0311] - 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].

[0312] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - QpOffset C .

[0313] Thereafter, the value of Qp C can be derived as Qp C Idx[qPi].

[0314] As in the foregoing embodiments, the chroma quantization parameter, i.e., Qp’ Cb and Qp’ Crand Qp’ CbCr 。

[0315] For example, in this embodiment, if the process of exporting quantization parameters is written in a standard format, the process can be represented as in the following table.

[0316] [Table 21]

[0317]

[0318]

[0319]

[0320]

[0321] 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 user - defined information signaled as 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.

[0322] In addition, this document presents another embodiment in which information for quantizing parameters is signaled.

[0323] For example, this embodiment proposes a syntax element that can be used to control the export 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.

[0324] [Table 22]

[0325]

[0326] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization.

[0327] In addition, for example, the syntax element qPi_delta_max_idx may represent the delta value between Qpi_min_idx and the maximum qPi index used in the derivation of the chroma 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.

[0328] In addition, for example, the syntax element Qp C _qPi_delta_val[i] may represent the delta of the Qp value for the i-th index. C

[0329] In addition, for example, the syntax element QpOffset C may represent an offset value used in the derivation of Qp c such as the foregoing.

[0330] As in the foregoing embodiments, chroma quantization parameters, i.e., Qp' Cb 、Qp' Cr and Qp' CbCr may be derived using the signaling user-defined information or the default values used in a default table such as Table 7.

[0331] For example, in this embodiment, if the process of deriving quantization parameters is written in a standard format, the process may be represented as in the following table.

[0332] [Table 23]

[0333]

[0334]

[0335]

[0336]

[0337] 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 ​It can be derived based on the signaling user - defined information as proposed in this embodiment. For example, 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 identically based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively, with the value Qp C as follows.

[0338] For example, the parameter Qp C Idx[i] can be derived as follows.

[0339] - When i < qPi_min_idx, Qp C Idx[qPi] can be set identically to qPi.

[0340] - 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].

[0341] - When i > qPiMaxIdx, Qp C Idx[i] can be set to qPi - QpOffset C .

[0342] Thereafter, Qp C can be set to Qp C Idx[i].

[0343] 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 parameters qP Cb 、qP Cr and qP CbCr can be derived from the default table based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively.

[0344] In addition, this document presents another embodiment in which information for quantized parameters is signaled.

[0345] For example, this embodiment proposes syntax elements for chrominance quantization (Qp C ) derived parameters in an Adaptive Parameter Set (APS). For example, the APS ID can be signaled in the slice header. In addition, for example, a flag can be proposed within the Picture Parameter Set (PPS) that indicates whether to use the default table or a table derived from the information signaled in the APS. In addition, 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.

[0346] 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.

[0347] This embodiment proposes adding a function for signaling the chrominance quantization parameter Qp C as a function of the index qPi. The APS can be used to integrate the signaling scheme for Qp C values.

[0348] For example, the APS according to this embodiment can be the same as the following table.

[0349] [Table 24]

[0350]

[0351] For example, the syntax element adaptation_parameter_set_id can provide an identifier for the APS referenced by other syntax elements.

[0352] In addition, for example, the syntax element aps_params_type can indicate the type of APS parameters included in the APS, as shown in Table 10.

[0353] 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.

[0354] 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 that follows this version of the standard may ignore all syntax elements aps_extension_data_flag.

[0355] The Qp c _data() disclosed in Table 24 may be signaled as shown in the following table.

[0356] [Table 25]

[0357]

[0358] For example, the syntax element qPi_min_idx may indicate the minimum qPi index used in chroma quantization. The value of qPi_min_idx may be in the range of 0 to 63.

[0359] 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 chroma Qp c derivation. The value of qPiMaxIdx may be greater than or equal to qPi_min_idx. In addition, for example, the value of qPi_delta_max_idx may be in the range of 0 to 63. For example, the maximum index qPiMaxIdx used in Qp c derivation may be derived as shown in Equation 4.

[0360] In addition, for example, the syntax element Qp C _qPi_delta_val[i] may indicate the difference between the Qp C values of the i-th index. This difference may also be referred to as the increment.

[0361] In addition, for example, the syntax element Qp C Offset C _present_flag can indicate whether QpOffset C exists in the bitstream. For example, Qp with a value of 1 C Offset C _present_flag can indicate that QpOffset C exists in the bitstream. In addition, for example, Qp with a value of 0 C Offset C _present_flag can indicate that QpOffset C 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.

[0362] In addition, for example, the syntax element QpOffset C can represent the offset value used in the derivation of Qp c .

[0363] For example, the parameter Qp of qPi C Idx[qPi] can be derived as follows. In this case, qPi can be from 0 to 63.

[0364] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0365] - 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].

[0366] - 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 COffset C If _present_flag is 0, then Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0367] After that, Qp C value can be derived as Qp C Idx[qPi].

[0368] In addition, this embodiment proposes signaling in the following table as a flag for PPS.

[0369] [Table 26]

[0370]

[0371] 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, 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, 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 Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred as 1.

[0372] In addition, this embodiment proposes signaling in the following table as a syntax element of the slice header.

[0373] [Table 27]

[0374]

[0375] For example, the syntax element slice_Qp c _aps_id can indicate the adaptation_parameter_set_id of the Qp c referred to by the slice. Qp with an adaptation_parameter_set_id (such as slice_Qp c _aps_id) cThe TemporalId 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 Qps with the same adaptation_parameter_set_id c APS is referenced by two or more slices of the same picture, then there are multiple Qps with the same adaptation_parameter_set_id c APS may have the same content.

[0376] 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.

[0377] [Table 28]

[0378]

[0379]

[0380]

[0381]

[0382] 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 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 respectively based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr through the default table.

[0383] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0384] For example, in this embodiment, a user - defined derivation for signaling chrominance quantization in SPS is proposed as follows. For example, this embodiment proposes a user - defined chrominance quantization (Qp C ). For example, the flag in the SPS can indicate whether the default table is used for chrominance quantization derivation or the content of the table used for chrominance quantization derivation is derived in the information signaled in the SPS.

[0385] For example, this embodiment proposes a scheme for performing chrominance quantization according to the index qPi by using the syntax elements shown in the following table.

[0386] [Table 29]

[0387]

[0388] 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.

[0389] 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.

[0390] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the increment of the Qp C value of the i - th index.

[0391] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0392] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi

[0393] - 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].

[0394] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0395] Thereafter, Qp C can be set to Qp C Idx[qPi].

[0396] In addition, in the present embodiment, the flag of the SPS indicating whether the default table is used for chroma quantization derivation or whether the signaling information is used for chroma quantization derivation can be the same as the following table.

[0397] [Table 30]

[0398]

[0399] 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. In addition, for example, Qp with a value of 1 c _data_default_flag 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.

[0400] For example, according to the present 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.

[0401] [Table 31]

[0402]

[0403]

[0404]

[0405]

[0406] Referring to Table 31, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp cWhen _data_default_flag is 0, the parameter qP Cb 、qP Cr and qP CbCr can be derived based on the signaling 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 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 through the default table respectively.

[0407] In addition, this document presents another embodiment in which information for signaling quantization parameters is provided.

[0408] For example, this embodiment proposes adding a function for signaling the chroma quantization parameter Qp C as a function of the index qPi. For example, a scheme for signaling the syntax elements of a user - defined table for quantization 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.

[0409] The syntax elements of the user - defined table for signaling in the PPS proposed in this embodiment can be the same as the following table.

[0410] [Table 32]

[0411]

[0412] 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.

[0413] 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 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.

[0414] 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 increment.

[0415] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0416] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0417] - 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].

[0418] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0419] Thereafter, Qp C can be set to Qp C Idx[qPi].

[0420] In addition, the flag in the SPS that indicates whether the default table is used for chroma quantization derivation or whether the signaling information is used for chroma quantization derivation proposed in this embodiment can be the same as the following table.

[0421] [Table 33]

[0422]

[0423] 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 with a value of 0 c _data_default_flag can 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 can indicate the use of the chroma quantization parameter data Qp c _data(). When Qp cWhen _data_default_flag is 0, a signal can be sent to notify the chroma quantization parameter data Qp c _data(). In addition, for example, Qp with a value of 1 c _data_default_flag can indicate the use of a default table to derive the 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.

[0424] 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.

[0425] [Table 34]

[0426]

[0427]

[0428]

[0429]

[0430] 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 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 from the default table based on the indices qPi Cb 、qPi Cr and qPi CbCr which are the same as qPi respectively.

[0431] In addition, this document presents another embodiment in which information for quantizing parameters is signaled.

[0432] For example, the present embodiment proposes a normal mode in which chroma quantization parameter Qp is derived and signaled. C

[0433] The chroma quantization parameter data Qp_data() for the chroma quantization parameter proposed in the present embodiment c can be signaled as shown in the following table.

[0434] [Table 35]

[0435]

[0436] 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.

[0437] 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 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.

[0438] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the increment of the Qp C value at the i-th index.

[0439] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0440] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0441] - 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].

[0442] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C ​Idx[qPiMaxIdx]).

[0443] After that, Qp C can be set to Qp C Idx[qPi].

[0444] 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 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 following table.

[0445] [Table 36]

[0446]

[0447] 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 a 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 using chroma quantization parameter data Qp c _data(). When Qp c _data_default_flag is 0, 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 a default table is used for deriving 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 to be 1.

[0448] 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.

[0449] [Table 37]

[0450]

[0451]

[0452]

[0453]

[0454] 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 parameter qP Cb 、qP Cr and qP CbCr can be derived based on the signaling 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 parameter qP Cb 、qP Cr and qP CbCr can be derived based on the qPi Cb 、qPi Cr and qPi CbCr with the same index qPi through the default table respectively.

[0455] In addition, this document presents another embodiment in which the information for quantizing parameters is signaled.

[0456] 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.

[0457] [Table 38]

[0458]

[0459] 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.

[0460] 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 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, in Qpc The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0461] In addition, for example, the syntax element Qp C _qPi_delta_val[i] can represent the difference between the Qp values of the i-th index. C This difference can also be referred to as the increment.

[0462] For example, the parameter Qp C Idx[qPi] can be derived as follows. In this case, qPi can be from 0 to 63.

[0463] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0464] - 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].

[0465] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0466] Thereafter, Qp C can be set to Qp C Idx[qPi].

[0467] In addition, this document presents another embodiment in which information for quantization parameters is signaled.

[0468] For example, this embodiment presents a scheme in which the increment (or difference) between consecutive Qp values is limited to 1 as an example. C For example, this embodiment presents a scheme in which user-defined chroma quantization (Qp

[0469] ) is additionally included in the existing image / video standard. 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 the user-defined chroma quantization, and the encoding efficiency can be improved. C

[0470] For example, this embodiment proposes to add chroma quantization Qp for signaling a function of index qPi by using the syntax elements in the following table C function.

[0471] [Table 39]

[0472]

[0473] 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 1 to 63.

[0474] 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 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 1 to 63. For example, the maximum index qPiMaxIdx used in Qp c derivation can be derived as in Equation 4.

[0475] In addition, for example, the syntax element QpC_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 the i-th Qp C value compared with the (i - 1)-th Qp C value whether it increases by 1. For example, QpC_qPi_flag[i] with a value of 1 can represent that the Qp C value increases by 1. QpC_qPi_flag[i] with a value of 0 can represent that the Qp C value does not increase.

[0476] For example, the parameter Qp C Idx[qPi] can be derived as follows. In this case, qPi can be 0 to 63.

[0477] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0478] - When qPi = qPi_min_idx... qPiMaxIdx, Qp C Idx[qPi] can be set to Qp C _qPi_flag[qPi]+Qp CIdx[qPi - 1].

[0479] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0480] After that, Qp C can be set to Qp C Idx[qPi].

[0481] 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. 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 following table.

[0482] [Table 40]

[0483]

[0484] 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 that chrominance quantization parameter data Qp c _data() is used. When Qp c _data_default_flag is 0, 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 a 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 to be 1.

[0485] 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.

[0486] [Table 41]

[0487]

[0488]

[0489]

[0490]

[0491] 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 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 through the default table based on the same index qPi Cb 、qPi Cr and qPi CbCr respectively.

[0492] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters.

[0493] 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. Further, for example, if the chroma_qp_mapping_flag value is 1, the syntax elements for signaling the chroma QP mapping table can be signaled as shown in the following table.

[0494] [Table 42]

[0495]

[0496] For example, the syntax element Qp C_data_default_flag can indicate whether the user-defined mode is used to export quantization parameters. For example, Qp with a value of 0 C _data_default_flag can indicate that the user-defined mode is used to export 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 from the chroma quantization parameter data shown in Table 42 as described above is used to export chroma quantization parameters. If Qp C _data_default_flag is 0, the chroma 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 export 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.

[0497] 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.

[0498] 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.

[0499] 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.

[0500] The chroma QP mapping table can be derived as follows based on the chroma quantization parameter data shown in Table 42.

[0501] For example, the variable cQpFatSize can be derived as in the following equation.

[0502] [Equation 5]

[0503] cQpFlatSize = qPi_delta_max_idx_minus1 + 1

[0504] In addition, for example, the variable cQpFlat[] can be derived as in the following table.

[0505] [Table 43]

[0506]

[0507] Thereafter, based on the variable cQpFlatSize and the variable cQpFlat[], the chroma QP mapping table can be derived as shown in the following table.

[0508] [Table 44]

[0509]

[0510] In addition, the present disclosure proposes another embodiment for signaling information regarding quantization parameters.

[0511] For example, this embodiment proposes a scheme for adding chroma_qp_mapping_flag as a new syntax element in the SPS. For example, if the value of chroma_qp_mapping_flag is 0, the default chroma QP mapping table can be used to derive the chroma quantization parameters. In addition, for example, if the value of chroma_qp_mapping_flag is 1, the syntax elements for deriving the chroma QP mapping table can be signaled as shown in the following table.

[0512] [Table 45]

[0513]

[0514] 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 C _data_default_flag with a value of 0 can indicate that the user-defined mode is used to derive the quantization parameters. That is, for example, Qp C _data_default_flag with a value of 0 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 C _data_default_flag with a value of 1 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, Qp C _data_default_flag can be inferred to be 1.

[0515] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can represent the number of points where the mapping function does not increase.

[0516] 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.

[0517] In addition, for example, by adding 1 to the syntax element Qp C _qPi_idx_minus1[i], the value obtained 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.

[0518] The chrominance QP mapping table can be derived as follows based on the chrominance quantization parameter data shown in Table 45.

[0519] For example, the variable cQpFlatSize can be derived as in Equation 5 as described above.

[0520] In addition, for example, the variable cQpFlat[] can be derived as in the following table.

[0521] [Table 46]

[0522]

[0523] 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.

[0524] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters.

[0525] 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.

[0526] 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.

[0527] [Table 47]

[0528]

[0529] For example, the syntax element qp_luma_to_chroma_joint_map_flag can indicate whether a common luma-chroma quantization parameter mapping table is used for 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 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.

[0530] 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.

[0531] 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.

[0532] [Equation 6]

[0533] for(i = 0; i < 3; i++){

[0534] qPiMaxIdx[i] = qPi_min_idx_minus1[i] + 1 + qPi_delta_max_idx_minus1[i] + 1

[0535] 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 jth Qp of the ith chroma component C value and the (j - 1)th QpC whether the value is increased by 1 compared to the value. For example, QpC_qPi_flag[j] equal to 1 can indicate that Qp C the value is increased by 1, and QpC_qPi_flag[j] equal to 0 can indicate that Qp C the value is not increased.

[0536] For example, the variable Qp C Idx[i][qPi] can be derived as follows. Here, when the value is 0, qPi can be maxQp.

[0537] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0538] - 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].

[0539] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0540] Thereafter, the Qp C value can be derived as QpCIdx[i][qPi].

[0541] Meanwhile, according to this embodiment, a flag indicating whether to signal a syntax element for deriving a chrominance QP mapping table in the SPS or to use a default table can be signaled. For example, the flag can be signaled as shown in the following table.

[0542] [Table 48]

[0543]

[0544] 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 can indicate that the chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 47 as described 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 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 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.

[0545] For example, according to this embodiment, through the description in the standard format, the process of deriving the quantization parameters can be represented as shown in the following table.

[0546] [Table 49]

[0547]

[0548]

[0549]

[0550]

[0551] 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 same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively.

[0552] 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 chroma Qp C and the maximum qPi index can be signaled.

[0553] 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().

[0554] [Table 50]

[0555]

[0556] For example, the syntax element qPi_min_idx can represent the minimum qPi index for chroma quantization. The qPi_min_idx value can be in the range of 0 to 63.

[0557] 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 chroma 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.

[0558] [Equation 7]

[0559] qPiMaxIdx = maxQp - qPi_delta_max_idx

[0560] 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.

[0561] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to 63.

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

[0563] - When qPi = qPi_min_idx…qPiMaxIdx, Qp C Idx[qPi] can be configured as QpC_qPi_flag[qPi] + Qp C Idx[qPi - 1].

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

[0565] After that, Qp C can be configured as 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 chroma quantization or signaling information used to derive chroma quantization. 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 51]

[0568]

[0569] 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, a 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, a Qp C _data_default_flag with a value of 0 can indicate the use of chroma quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then chroma 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 for exporting quantization parameters. The default table may be like that in Table 7 as described above. Additionally, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag may be inferred as 1.

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

[0571] [Table 52]

[0572]

[0573]

[0574]

[0575]

[0576] Referring to Table 52 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. 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 from the default table based on the same index qPi Cb , qPi Cr and qPi CbCr respectively.

[0577] Furthermore, the present disclosure proposes 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 of the maximum QP or as the difference between the starting point and the value obtained by adding the increment to the starting point.

[0578] 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.

[0579] [Table 53]

[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 indicate whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, is_delta_maxQp with a value of 1 can indicate that qPiMaxIdx is derived from the maxQp value. In addition, for example, is_delta_maxQp with a value of 0 can indicate 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 increment 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.

[0584] [Table 54]

[0585]

[0586] In addition, for example, the syntax element Qp C _qPi_flag[i] can indicate whether the Qp C value is incremented by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate 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 indicate that the Qp C value is incremented by 1, and QpC_qPi_flag[i] with a value of 0 can indicate that the QpC The value is not increased.

[0587] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to maxQp.

[0588] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0589] - When qPi = qPi_min_idx_minus1…qPiMaxIdx, Qp C Idx[qPi] can be configured to Qp C _qPi_flag[qPi] + QpCIdx[qPi - 1].

[0590] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0591] After that, Qp C can be configured to Qp C Idx[qPi].

[0592] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for deriving chrominance quantization or signaling information used for deriving chrominance quantization. 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.

[0593] [Table 55]

[0594]

[0595] 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 using the chrominance quantization parameter data Qp C _data(). If Qp CIf _data_default_flag is 0, a signal can be sent to notify the chroma 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 export the 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.

[0596] For example, according to this embodiment, through the description in the standard format, the process of exporting the quantization parameters can be represented as shown in the following table.

[0597] [Table 56]

[0598]

[0599]

[0600]

[0601]

[0602] 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.

[0603] 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.

[0604] 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.

[0605] [Table 57]

[0606]

[0607] 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 from 1 to maxQp.

[0608] 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.

[0609] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can represent the increment 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 from 1 to 63. The maximum index qPiMaxIdx for deriving Qp C can be derived as described above as shown in Table 54.

[0610] 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 represent Qp C The value is not incremented.

[0611] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to maxQp.

[0612] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0613] - 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].

[0614] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0615] After that, Qp C can be configured as Qp C Idx[qPi].

[0616] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for deriving chroma quantization or signaling information used for deriving chroma quantization. The flag can be signaled through high-level syntax such as a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS). The flag signaled through high-level syntax can be the same as those in the following table.

[0617] [Table 58]

[0618]

[0619] For example, the syntax element Qp C _data_default_flag can represent whether a user-defined mode is used for deriving quantization parameters. For example, Qp C _data_default_flag with a value of 0 can represent that a user-defined mode is used for deriving quantization parameters. That is, for example, Qp C_data_default_flag can indicate the use of chroma quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chroma quantization parameter data Qp C _data() can be signaled. Additionally, 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. Additionally, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be considered as 1.

[0620] 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.

[0621] [Table 59]

[0622]

[0623]

[0624]

[0625] 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. 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 through the default table based on the same index qPi as qPi Cb 、qPi Cr and qPi CbCr respectively.

[0626] In addition, the present disclosure presents another embodiment for signaling information about quantization parameters. This embodiment presents a scheme for signaling the index of a chrominance QP mapping table by using the minus1 nomenclature instead of real values.

[0627] The chrominance quantization parameter data Qp for chrominance quantization parameters proposed in this embodiment C _data() can be signaled as shown in the following table.

[0628] [Table 60]

[0629]

[0630] 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.

[0631] In addition, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 can represent the increment 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.

[0632] [Equation 8]

[0633] qPiMaxIdx = qPi_min_idx_minus1 + 1 + qPi_delta_max_idx_minus1 + 1

[0634] 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.

[0635] For example, the variable Qp CIdx[qPi] can be derived as follows. Here, qPi can be from 0 to 63.

[0636] - When qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0637] - When qPi = qPi_min_idx_minus1 + 1…qPiMaxIdx, Qp C Idx[qPi] can be configured to Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0638] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0639] After that, Qp C can be configured to Qp C Idx[qPi].

[0640] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for deriving chroma quantization or signaling information used for deriving chroma quantization. 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.

[0641] [Table 61]

[0642]

[0643] 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 using chroma quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then chroma quantization parameter data Qp C_data(). In addition, for example, Qp with a value of 1 C _data_default_flag may indicate that the default table is used to export quantization parameters. The default table may 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 may be considered as 1.

[0644] For example, according to this embodiment, through the description in the standard format, the process of exporting quantization parameters can be represented as in the following table.

[0645] [Table 62]

[0646]

[0647]

[0648]

[0649]

[0650] 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 same index qPi as that of qPi Cb 、qPi Cr and qPi CbCr respectively.

[0651] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. This embodiment proposes a scheme in which a separate chroma quantization table is used for each chroma component.

[0652] The chrominance quantization parameter data for the chrominance quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0653] [Table 63]

[0654]

[0655] 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 parameters. 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 parameters. 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 parameters is used.

[0656] 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 Cb samples and Cr samples.

[0657] Meanwhile, for example, the variable Qp Cb [i] can represent the Qp C table for Cb samples. In addition,

[0658] 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.

[0659] 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.

[0660] The value of qPi_Cb_min_idx_minus1 may be in the range of 1 to 69.

[0661] 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 to derive 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.

[0662] [Equation 9]

[0663] 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] and the (i - 1)-th Qp C value Qp Cb [i - 1].

[0664] Qp C The value of _cb_qPi_flag[i] may be in the range of 0 to 1.

[0665] For example, the variable Qp Cb [i] may be derived as follows. Here, i may be from 0 to 69.

[0666] - When i = 0...qPiMaxIdxCb, Qp Cb [i] may be configured to be the same as i.

[0667] - When i = qPi_cb_min_idx_minus1 + 1 + 1...qPiMaxIdxCb, Qp Cb[i] can be configured as Qp Cb [i - 1]+Qp C _cb_qPi_flag[i].

[0668] - In the case of i = qPiMaxIdxCb + 1...69, Qp Cb [i] can be configured as i - deltaEnd, and deltaEnd can be derived as qPiMaxIdxCb - Qp Cb [qPiMaxIdxCb].

[0669] In addition, for example, qPi_cr_min_idx_minus1, qPiMaxIdxCr, and Qp as syntax elements of the Cr component C _cr_qPi_flag[i] can have the same meaning as the syntax elements of the Cb component.

[0670] 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 above-described embodiments. That is, for example, the embodiments of the present disclosure can be applied jointly.

[0671] Specifically, for example, this embodiment proposes including user - defined chroma quantization parameters (Qp C ) in the VVC specification text. For example, according to this embodiment, a 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 signaled information in the SPS. Thus, user - defined chroma quantization parameters can be used in image coding considering the content characteristics of the image, and the coding 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.

[0672] For example, the chroma quantization parameter data Qp C _data() for the chroma quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0673] [Table 64]

[0674]

[0675] 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.

[0676] 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.

[0677] 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, while QpC_qPi_flag[i] with a value of 0 can represent that the Qp C value is not incremented.

[0678] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, qPi can be from 0 to 69.

[0679] - When qPi < qPi_min_idx, Qp C Idx[qPi] can be configured to be the same as qPi.

[0680] - When qPi = qPi_min_idx...qPiMaxIdx, Qp C Idx[qPi] can be configured as Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0681] - When qPi > qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0682] Thereafter, Qp C can be configured as Qp C Idx[qPi].

[0683] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive a chroma quantization or a chroma QP mapping table derived based on the signaled information 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.

[0684] [Table 65]

[0685]

[0686] 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, a 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, a 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 the chroma quantization parameter data Qp C _data() can be signaled. In addition, for example, a 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 as in Table 7 described above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred to be 1.

[0687] For example, according to this embodiment, through a description in a standard format, the process of deriving quantization parameters can be represented as shown in the following table.

[0688] [Table 66]

[0689]

[0690]

[0691]

[0692]

[0693] Referring to Table 66 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 from the default table based on the same index qPi Cb 、qPi Cr and qPi CbCr respectively.

[0694] Furthermore, for example, the chrominance quantization parameter data Qp C _data() in the case of using separate user - defined tables for respective chrominance components as proposed in this embodiment can be signaled as shown in the following table.

[0695] [Table 67]

[0696]

[0697] For example, the syntax element is_separate_chroma_table can indicate whether separate chrominance quantization table - related parameters 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 chrominance 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 - chrominance 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 chrominance 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 chrominance 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]. Additionally, for example, if the is_separate_chroma_table value is 0, qPi_min_idx_minus1[i], qPi_delta_max_idx[i], and Qp for the Cb component, Cr component, and combined CbCr component can be signaled C _qPi_flag[i][j].

[0698] Additionally, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1[i] can represent the minimum qPi index for chroma 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].

[0699] Additionally, for example, the syntax element qPi_delta_max_idx can represent the incremental value between qPi_min_idx[i] and the maximum qPi index used to derive the chroma 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] used to derive Qp C can be derived as in the following equation.

[0700] [Equation 10]

[0701] qPiMaxldx[i] = qPi_min_idx[i] + qPi_delta_max_idx_minus1[i] + 1

[0702] The qPiMaxIdx[i] value can be equal to or greater than qPi_min_idx_minus1[i].

[0703] Additionally, for example, the syntax element Qp C _qPi_flag[i][j] can represent whether the j-th Qp C value of the i-th chroma 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 chroma component and the (j - 1)-th QpC whether the value is incremented by 1 compared to the previous value. For example, QpC_qPi_flag[j] with a value of 1 can indicate that the Qp of the j-th position in the i-th chrominance component C has its value incremented by 1, while QpC_qPi_flag[j] with a value of 0 can indicate that the Qp of the j-th position in the i-th chrominance component C has not had its value incremented.

[0704] 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.

[0705] [Table 68]

[0706]

[0707] 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.

[0708] Furthermore, 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, Cr component, and combined CbCr component. That is, one chrominance quantization parameter mapping table can be used for the chrominance components.

[0709] Furthermore, referring to Table 68, Qp C Idx[i][qPi] can be derived as follows.

[0710] - When qPi < qPi_min_idx[i], Qp C Idx[i][qPi] can be configured to be the same as qPi.

[0711] - 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].

[0712] - When qPi > qPiMaxIdx, Qp C Idx[i][qPi] can be configured as qPi - (qPiMaxIdx[i] - Qp C Idx[i][qPiMaxIdx]).

[0713] Thereafter, Qp C value can be derived as Qp C Idx[i][qPi].

[0714] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chroma quantization or the information used for chroma quantization is signaled. 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 flags in the following table.

[0715] [Table 69]

[0716]

[0717] 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 using the chroma quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the 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 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.

[0718] 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.

[0719] [Table 70]

[0720]

[0721]

[0722]

[0723]

[0724] 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 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 (e.g., 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 Cb 、qPi Cr and qPi CbCr respectively.

[0725] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. For example, this embodiment proposes a scheme for signaling parameters for the chroma QP table without default configuration. In addition, 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.

[0726] The chroma quantization parameter data of the chroma quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0727] [Table 71]

[0728]

[0729] 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. Further, 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 3 chrominance QP mapping tables are signaled and applied for the Cb component, the Cr component, and the combined CbCr component.

[0730] Further, 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 + QpBdOffset C inclusive.

[0731] Further, for example, the syntax element qp C _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.

[0732] Further, for example, the syntax element qp C_qPi_out_idx[i][j] may represent an increment value for deriving the output coordinates of the j-th pivot point of the i-th chrominance QP mapping table.

[0733] Based on the above 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, then i can be 0, and if same_qp_table_for_cb_cr is not 1, then i can be one of 0 to 2.

[0734] [Table 72]

[0735]

[0736] Referring to Table 72 as described above, the input coordinates of the j-th pivot point of the i-th chrominance 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 may 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 chrominance 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 may represent the output coordinates of the j-th pivot point.

[0737] In addition, according to this embodiment, the following changes can be made to derive the chrominance QP. For example, the limitations in the following table can be added.

[0738] [Table 73]

[0739]

[0740] 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].

[0741] In addition, if the chroma type is not 0, for example, if the chroma type is 1, then when chroma_qp_table_present_flag is equal to 1, the variables qP Cb and qP Cr can be configured to be the same as ChromaQpTable[0][qPiCb], ChromaQpTable[1][qPiCr], and ChromaQpTable[1][qPiCbCr], respectively.

[0742] 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 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.

[0743] 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.

[0744] 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.

[0745] Figure 10 An image encoding method of an encoding device according to this document is schematically shown. Figure 10 The method disclosed in Figure 2 can be executed by the encoding device disclosed in Figure 10 Specifically, for example,

[0746] The encoding device encodes the image information (S1000).

[0747] The encoding device can encode the image information. For example, the image information can include prediction information for a chrominance component, residual information for a chrominance component, and / or chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for a chrominance component. The chrominance component can include a Cb component, a Cr component, and / or a combined CbCr component.

[0748] For example, the encoding device can derive prediction samples for a chrominance component based on a prediction mode. That is, for example, the encoding device can derive prediction samples for the current block of a chrominance component based on a 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.

[0749] For example, the encoding device may determine whether to perform inter prediction or intra prediction with respect to the current block for the chrominance component, and may determine a specific inter prediction mode or a specific intra prediction mode based on the RD cost. According to the determined mode, the encoding device may derive prediction samples for the current block.

[0750] Thereafter, for example, the encoding device may generate and encode prediction information for the current block. The prediction information may include prediction mode information indicating the prediction mode of the current block for the chrominance component. The image information may include the prediction information.

[0751] In addition, for example, the encoding device may derive residual samples by subtracting the prediction samples from the original samples of the current block for the chrominance component in the current picture.

[0752] Thereafter, for example, the encoding device may encode the residual information of the 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 the chrominance quantization parameter, 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 the chrominance quantization parameter, derive transform coefficients by transforming the quantized residual samples, and generate and encode residual information based on the transform coefficients.

[0753] For example, the residual information may include syntax elements for the transform coefficients of the 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.

[0754] In addition, for example, the encoding device may generate and encode chrominance quantization parameter data for at least one chrominance quantization parameter (QP) map for chrominance components. The default chrominance QP map for chrominance components may not be used. That is, if chrominance quantization parameters for chrominance components are used, the encoding device may generate chrominance quantization parameter data for at least one chrominance quantization parameter (QP) map for chrominance components. The image information may include chrominance quantization parameter data for at least one chrominance QP map for chrominance components. In addition, for example, the chrominance components 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 map, a syntax element representing an incremental value of the input coordinates of the target point for deriving the chrominance QP map, and / or a syntax element representing an incremental value of the output coordinates of the target point for deriving the chrominance QP map. In addition, for example, the value of the syntax element representing the number of points in the chrominance QP map 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 map may be qPi_table_len_idx[i] as described above, and the syntax element representing the incremental value of the input coordinates of the target point for deriving the chrominance QP map 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 chrominance QP map may be qp C _qPi_out_idx[i][j].

[0755] In addition, for example, the encoding device may determine whether a chrominance QP map is applied to a chrominance component, and may generate a flag indicating whether a chrominance QP map is applied to a chrominance component. The image information may include a flag indicating whether a chrominance QP map is applied to a chrominance component.

[0756] For example, the encoding device may generate a flag indicating whether a chrominance QP mapping table is applied to a chrominance 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 chrominance QP mapping table is applied to the chrominance component. For example, if the chroma type value is 1, the encoding device may generate a flag indicating whether a chrominance QP mapping table is applied to the chrominance 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.

[0757] For example, if the flag value is 1, the flag may indicate that a chrominance QP mapping table is applied to the chrominance component. In addition, for example, if the flag value is 0, the flag may indicate that multiple chrominance QP mapping tables are applied to the chrominance component. That is, for example, if the flag value is 0, the flag may indicate that separate chrominance QP mapping tables are applied to each chrominance component.

[0758] 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.

[0759] In addition, for example, the flag may be signaled through the high-level syntax. For example, the flag may be signaled through 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 encoding device may generate chrominance quantization parameter data for the chrominance component based on the flag.

[0761] 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. Additionally, 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.

[0762] 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. Additionally, 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. Additionally, for example, the combined CbCr enable flag may be signaled through high-level syntax. For example, the combined CbCr enable flag may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0763] 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.

[0764] In addition, for example, the first chrominance quantization parameter data may include a syntax element representing the number of points in the first chrominance QP mapping table for the Cb component, a syntax element representing the incremental value of the input coordinates of the target point for deriving the first chrominance QP mapping table, and / or a syntax element representing the 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 in 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 a 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).

[0765] In addition, for example, the second chrominance quantization parameter data may include a syntax element representing the number of points in the second chrominance QP mapping table for the Cr component, a syntax element representing the incremental value of the input coordinates of the target point for deriving the second chrominance QP mapping table, and / or a syntax element representing the 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 in 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 a 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).

[0766] In addition, for example, the third chrominance quantization parameter data may include a syntax element indicating the number of points of the third chrominance QP mapping table for the combined CbCr components, a syntax element indicating the incremental value of the input coordinates of the target point for deriving the third chrominance QP mapping table, and / or a syntax element indicating the incremental value of the output coordinates of the target point for deriving the third chrominance QP mapping table. The syntax element indicating the number of points of the third chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element indicating the incremental value of the input coordinates of the target point for deriving the third chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element indicating the incremental value of the output coordinates of the 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 a 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).

[0767] 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 the chrominance quantization parameter data of one chrominance QP mapping table for the Cb component, the Cr component, and the combined CbCr components.

[0768] The encoding device generates a bitstream including image information (S1010).

[0769] For example, the encoding device may output a bitstream including image information, which includes prediction information about chrominance components, residual information about chrominance components, and / or chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for chrominance components. The bitstream may include prediction information, residual information, and / or chrominance quantization parameter data of at least one chrominance quantization parameter (QP) mapping table for chrominance components. In addition, the image information may further include a flag indicating whether one chrominance QP mapping table is applied to the chrominance components and / or a combined CbCr enable flag.

[0770] The encoding device is capable of encoding and outputting image information in the form of a bitstream.

[0771] Meanwhile, the bitstream including image information may be sent to the decoding device via a network or a (digital) storage medium. Here, the network may include a broadcast network and / or a communication network, and the digital storage medium may include various types of storage media such as a USB flash drive, SD, CD, DVD, Blu-ray disc, HDD, and SSD.

[0772] Figure 11 Schematically shows an encoding apparatus for performing an image encoding method according to this document. Figure 10 The method disclosed in Figure 11 can be executed by the encoding apparatus disclosed in Figure 11 Specifically, for example, the entropy encoder of the encoding apparatus of

[0773] Figure 12 Schematically shows an image decoding method of a decoding apparatus according to this document. Figure 12 The method disclosed in Figure 3 can be executed by the decoding apparatus disclosed in Figure 12 Specifically, for example, S1200 of Figure 12 can be executed by the entropy decoder of the decoding apparatus, and

[0774] The decoding apparatus obtains image information through a bitstream (S1200).

[0775] For example, the image information may include information about chroma quantization parameters.

[0776] For example, the image information may include chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table. For example, the decoding apparatus may obtain chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for chroma components. The default chroma QP mapping table for chroma components may not be used. That is, if chroma quantization parameters for chroma components are used, the decoding apparatus may obtain chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for chroma components. In addition, for example, the chroma components may include Cb component, Cr component, and / or combined CbCr component. In addition, for example, the chroma quantization parameter data may include a syntax element representing the number of points in the chroma QP mapping table, a syntax element representing an increment value of the input coordinates of the target point for deriving the chroma QP mapping table, and / or a syntax element representing an increment value of the output coordinates of the target point for deriving the chroma QP mapping table. In addition, for example, the value of the syntax element representing the number of points in the chroma QP mapping table may be in the range of 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 chroma QP mapping table may be qPi_table_len_idx[i] as described above, and the syntax element representing the increment value of the input coordinates of the target point for deriving the chroma QP mapping table may be qp as described aboveC _qPi_in_idx[i][j], and the syntax element representing the increment value of the output coordinates of the target point for deriving the chrominance QP mapping table can be qp as described above C _qPi_out_idx[i][j].

[0777] In addition, for example, the chrominance quantization parameter data of the chrominance QP mapping table can be signaled by a high-level syntax. For example, the chrominance quantization parameter data can be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0778] In addition, for example, the decoding device can obtain a flag indicating whether a chrominance QP mapping table is applied to the chrominance component. That is, for example, the decoding device can obtain a flag indicating whether a chrominance QP mapping table is signaled and applied to the chrominance component. The image information can include this flag. At the same time, for example, the decoding device can obtain a flag indicating whether a chrominance QP mapping table is applied based on the chrominance type. Here, the chrominance type can mean ChromaArrayType as described above. For example, if the chrominance type value is not 0, the decoding device can obtain a flag indicating whether a chrominance QP mapping table is applied. For example, if the chrominance type value is 1, the decoding device can obtain a flag indicating whether a chrominance QP mapping table is applied. Here, if the chrominance type value is 0, the chrominance type can be a monochrome format, and if the chrominance type value is 1, the chrominance type can be a 4:2:0 format. If the chrominance type value is 2, the chrominance type can be a 4:2:2 format, and if the chrominance type value is 3, the chrominance type can be a 4:4:4 format. For example, the syntax element of this flag can 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.

[0779] For example, if the flag value is 1, this flag can indicate that a chrominance QP mapping table is applied to the chrominance component. In addition, for example, if the flag value is 0, this flag can indicate that multiple chrominance QP mapping tables are applied to the chrominance component. That is, for example, if the flag value is 0, this flag can indicate that separate chrominance QP mapping tables are applied to each chrominance component.

[0780] Thus, for example, if the flag value is 1, the chroma quantization parameter data of one chroma QP mapping table for the chroma component can be signaled, and if the flag value is 0, the chroma quantization parameter data of multiple chroma QP mapping tables for the chroma component can be signaled. That is, for example, if the flag value is 0, the chroma quantization parameter data of a separate chroma QP mapping table for each chroma component can be signaled.

[0781] In addition, for example, the flag can be signaled through high-level syntax. For example, the flag can be signaled through a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, or an Adaptive Parameter Set (APS).

[0782] In addition, for example, the chroma quantization parameter data of multiple chroma QP mapping tables for the chroma component can 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. In addition, for example, the chroma quantization parameter data can 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.

[0783] Meanwhile, for example, the decoding device can obtain a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of a third chroma QP mapping table for the combined CbCr component. For example, the image information can include a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of a third chroma QP mapping table for the combined CbCr component. In addition, for example, the decoding device can obtain a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of a third chroma QP mapping table for the combined CbCr component based on the chroma type. Here, the chroma type can mean ChromaArrayType as described above. For example, if the chroma type value is not 0, the decoding device can obtain a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of a third chroma QP mapping table for the combined CbCr component. For example, if the chroma type value is 1, the decoding device can obtain a combined CbCr enable flag indicating whether there is third chroma quantization parameter data of a third chroma QP mapping table for the combined CbCr component. In addition, for example, the combined CbCr enable flag can be signaled through high-level syntax. For example, the combined CbCr enable flag can be signaled through a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, or an Adaptive Parameter Set (APS).

[0784] 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 the existence of third chrominance quantization parameter data for the third chrominance QP mapping table of the combined CbCr component), then the chrominance quantization parameter data may include first chrominance quantization parameter data for the Cb component of the first chrominance QP mapping table, second chrominance quantization parameter data for the Cr component of the second chrominance QP mapping table, and third chrominance quantization parameter data for the combined CbCr component of the third chrominance QP mapping table.

[0785] In addition, for example, the first chrominance quantization parameter data may include a syntax element indicating the number of points of the first chrominance QP mapping table for the Cb component, a syntax element indicating an incremental value of the input coordinates for deriving the target points of the first chrominance QP mapping table, and / or a syntax element indicating an incremental value of the output coordinates for deriving the target points of the first chrominance QP mapping table. The syntax element indicating the number of points of the first chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element indicating an incremental value of the input coordinates for deriving the target points of the first chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element indicating an incremental value of the output coordinates for deriving the target points 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 a 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).

[0786] In addition, for example, the second chrominance quantization parameter data may include a syntax element indicating the number of points of the second chrominance QP mapping table for the Cr component, a syntax element indicating an incremental value of the input coordinates for deriving the target points of the second chrominance QP mapping table, and / or a syntax element indicating an incremental value of the output coordinates for deriving the target points of the second chrominance QP mapping table. The syntax element indicating the number of points of the second chrominance QP mapping table may be qPi_table_len_idx[i], the syntax element indicating an incremental value of the input coordinates for deriving the target points of the second chrominance QP mapping table may be qp C _qPi_in_idx[i][j], and the syntax element indicating an incremental value of the output coordinates for deriving the target points of the second chrominance QP mapping table may be qp C_qPi_out_idx[i][j]. Additionally, for example, the second chrominance quantization parameter data can be signaled by high-level syntax. For example, the second chrominance quantization parameter data can be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0787] Additionally, for example, the third chrominance quantization parameter data can include a syntax element representing the number of points of a third chrominance QP mapping table for the combined CbCr component, 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 can 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 can 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 can be qp C _qPi_out_idx[i][j]. Additionally, for example, the third chrominance quantization parameter data can be signaled by high-level syntax. For example, the third chrominance quantization parameter data can be signaled by a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptive parameter set (APS).

[0788] Additionally, 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 data can include the chrominance quantization parameter data of (one) chrominance QP mapping table for the Cb component, the Cr component, and the combined CbCr component.

[0789] Meanwhile, for example, the image information can include prediction information and / or residual information for the chrominance component. For example, the image information can include prediction information for the chrominance component, and the prediction information can include prediction mode information. The prediction mode information can indicate whether inter prediction or intra prediction is applied to the current block for the chrominance component. Additionally, for example, the residual information can include syntax elements of transform coefficients of the current block for the chrominance component. For example, the syntax elements can 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.

[0790] The decoding device generates a reconstructed picture based on the image information (S1210).

[0791] For example, the decoding device may derive a chrominance QP mapping table based on chrominance quantization parameter data, derive chrominance quantization parameters for chrominance components based on the chrominance QP mapping table, derive residual samples for chrominance components based on the chrominance quantization parameters, and generate a reconstructed picture based on the residual samples.

[0792] Specifically, for example, the decoding device may derive a chrominance QP mapping table based on 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.

[0793] For example, as described above, the chrominance QP mapping table may be derived based on a syntax element representing the number of points of the chrominance QP mapping table, a syntax element representing an increment value of the input coordinates of the target point for deriving the chrominance QP mapping table, and / or a syntax element representing an increment value of the output coordinates of the target point for deriving the chrominance QP mapping table. That is, for example, the chrominance QP mapping table for chrominance components may be derived based on quantization parameter data. For example, as shown in Table 72 above, the chrominance QP mapping table for chrominance components may be derived based on quantization parameter data.

[0794] 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 may be derived based on the first chrominance quantization parameter data of the first chrominance QP mapping table for the Cb component. In addition, for example, if the flag value is 0, the second chrominance QP mapping table for the chrominance Cb component may 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 may be derived based on the third chrominance quantization parameter data of the third chrominance QP mapping table for the combined CbCr component.

[0795] 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 may be derived based on the chrominance quantization parameter data of the chrominance QP mapping table for the chrominance component. The chrominance component may include a Cb component, a Cr component, and / or a combined CbCr component.

[0796] In addition, for example, the decoding device may derive chrominance quantization parameters for chrominance components based on the chrominance QP mapping table.

[0797] 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. Additionally, 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 the QP` as described above. Cb The quantization parameter for the Cr component can represent the QP` as described above. Cr The quantization parameter for the combined CbCr component can represent the QP` as described above. CbCr .

[0798] For example, an index for the chrominance component (Cb component, Cr component, or combined CbCr component) can be derived based on the quantization parameter for the luminance component, and the chrominance quantization parameter for the chrominance component can be derived based on the chrominance quantization parameter at the 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 at the point of the same index as the quantization parameter for the luminance component in the chrominance QP mapping table.

[0799] Additionally, 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 at the point of the index of the chrominance QP mapping table for the chrominance component (e.g., QP Cb , QP CR or QP CbCr ). The offset can be derived based on the syntax element representing the offset for deriving the quantization parameter for the chrominance component. Cb The chrominance quantization parameter for the chrominance component (e.g., QP` Cr , QP` CbCr ) can be derived.

[0800] Furthermore, for example, if the flag value is 1, the chrominance quantization parameter for the chrominance component can be derived based on one chrominance QP mapping table for the chrominance component. Thus, the chrominance quantization parameter can be equally applied to the chrominance component.

[0801] 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 a chrominance quantization parameter for a chrominance component can be derived based on a chrominance quantization parameter of a point of an index of a chrominance QP mapping table for the chrominance component. That is, for example, a chrominance quantization parameter for a chrominance component can be derived based on a chrominance quantization parameter of a point in the chrominance QP mapping table having the same index as the quantization parameter of the luminance component.

[0802] In addition, for example, a chrominance quantization parameter for a chrominance component can be derived by adding an offset to a chrominance quantization parameter of a point of an index of a 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.

[0803] Thereafter, for example, a decoding device can derive residual samples for a chrominance component based on the chrominance quantization parameter.

[0804] For example, a decoding device can derive transform coefficients for a chrominance component based on received residual information. The image information can include the residual information. In addition, for example, a decoding device can derive transform coefficients based on the received residual information, and can derive inverse transform coefficients by performing an inverse transform on the transform coefficients. The transform coefficients can include transform coefficients for the Cb component, transform coefficients for the Cr component, and / or transform coefficients for the combined CbCr component.

[0805] Thereafter, the decoding device can derive residual samples by dequantizing the transform coefficients based on the chrominance quantization parameter.

[0806] For example, if a flag value is 0, the decoding device can derive residual samples for the Cb component by dequantizing the transform coefficients for the Cb component based on a first chrominance quantization parameter for the Cb component, and can derive residual samples for the Cr component by dequantizing the transform coefficients for the Cr component based on a second chrominance quantization parameter for the Cr component. In addition, for example, if the flag value is 0, the decoding device can derive residual samples for the Cb component by dequantizing the transform coefficients for the Cb component based on a first chrominance quantization parameter for the Cb component, derive residual samples for the Cr component by dequantizing the transform coefficients for the Cr component based on a second chrominance quantization parameter for the Cr component, and derive residual samples for the combined CbCr component by dequantizing the transform coefficients for the combined CbCr component based on a third chrominance quantization parameter for the combined CbCr component. In addition, for example, if the flag value is 1, the decoding device can derive residual samples for a chrominance component by dequantizing the transform coefficients for the chrominance component based on the chrominance quantization parameter.

[0807] In addition, if the flag value is 0, the decoding device may dequantize the transform coefficients of the inverse transform for the Cb component based on the first chrominance quantization parameter for the Cb component to derive the residual samples for the Cb component, and may dequantize the transform coefficients of the inverse transform for the Cr component based on the second chrominance quantization parameter for the Cr component to derive the residual samples for the Cr component. In addition, for example, if the flag value is 0, the decoding device may dequantize the transform coefficients of the inverse transform for the Cb component based on the first chrominance quantization parameter for the Cb component to derive the residual samples for the Cb component, dequantize the transform coefficients of the inverse transform for the Cr component based on the second chrominance quantization parameter for the Cr component to derive the residual samples for the Cr component, and dequantize the transform coefficients of the inverse transform for the combined CbCr component based on the third chrominance quantization parameter for the combined CbCr component to derive the residual samples for the combined CbCr component. In addition, for example, if the flag value is 1, the decoding device may dequantize the transform coefficients of the inverse transform for the chrominance component based on the chrominance quantization parameter to derive the residual samples for the chrominance component.

[0808] Thereafter, for example, the decoding device may generate a reconstructed picture based on the residual samples.

[0809] Meanwhile, for example, the decoding device may derive prediction samples for the chrominance component based on the received prediction information. The picture information may include the prediction information. The decoding device may determine whether inter prediction or intra prediction is applied to the chrominance component based on the received prediction information, and may perform prediction based thereon. That is, the decoding device may determine whether inter prediction or intra prediction is applied to the current block of the chrominance component based on the prediction information, and may perform prediction based thereon.

[0810] For example, the decoding device may derive a prediction mode applied to a current block for a chrominance component based on prediction information, and may derive prediction samples for the current block based on the prediction mode. For example, if inter prediction is applied to the current block, the decoding device may derive motion information of 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, if 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 reference samples of the current block and the intra prediction mode. The reference samples may include a top reference sample and a left reference sample of the current block. For example, if 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 respectively, 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].

[0811] Thereafter, for example, the decoding device may generate a reconstructed picture based on the prediction samples and the residual samples. For example, the decoding device may generate reconstructed samples and / or a reconstructed picture by adding the prediction samples and the residual samples together.

[0812] After that, as needed, in order to improve the subjective / objective image quality, an in-loop filtering process such as a deblocking filter and SAO and / or ALF process may be applied to the reconstructed samples as described above.

[0813] Figure 13 A decoding device for performing the image decoding method according to this document is schematically illustrated. Figure 12 The method disclosed in Figure 13 may be performed by the decoding device disclosed in Figure 13 Specifically, for example, the entropy decoder of the decoding device of Figure 12 may perform S1200 of Figure 13 and the residual processor of the decoding device of Figure 12 may perform S1210 of

[0814] 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 the signaled chrominance quantization parameter data may be used instead of the default chrominance QP mapping table to derive the chrominance quantization parameter for the chrominance component, and by doing so, the encoding efficiency may be improved by performing encoding based on the quantization parameter according to the characteristics of the image.

[0815] In addition, according to the present disclosure, a chroma QP mapping table can be derived based on a syntax element representing an increment value of an input coordinate of a point for deriving the chroma QP mapping table and / or a syntax element representing an increment value of an output coordinate of a point for deriving the chroma QP mapping table, and compilation efficiency can be improved by performing compilation based on the chroma QP mapping table that more specifically reflects characteristics of an image.

[0816] 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 an order different 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 can further include other steps, or one or more steps in the flowchart can be deleted without affecting the scope of the present disclosure.

[0817] The embodiments described in this specification can be executed by being implemented 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, information for implementation (e.g., information about instructions) or algorithms can be stored in a digital storage medium.

[0818] In addition, a decoding device and an 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, a digital video recorder (DVR), etc.

[0819] In addition, the processing method of the present disclosure can be generated in the form of a computer-executable program and can be stored in a computer-readable recording medium. 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, BD, Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. 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.

[0820] In addition, 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 embodiments of the present disclosure. The program code can be stored on a computer-readable carrier.

[0821] Figure 14 The structural diagram of a content stream system to which the present disclosure is applied is illustrated.

[0822] The content stream system applying embodiments of the present disclosure may mainly include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0823] The encoding server compresses the content input from a multimedia input device such as a smartphone, 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 smartphone, a camera, or a camcorder directly generates a bitstream, the encoding server can be omitted.

[0824] The bitstream can be generated by an encoding method or a bitstream generation method applying embodiments of the present disclosure, and the streaming server can temporarily store the bitstream during the process of sending or receiving the bitstream.

[0825] The streaming server sends multimedia data to the user device via 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.

[0826] The streaming server may receive content from a media storage and / or an 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.

[0827] Examples of user devices may include mobile phones, smartphones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigators, touchscreen PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, and head-mounted displays), digital TVs, desktop computers, and digital signage, etc. Each server within the content streaming system may operate as a distributed server, and in this case, the data received from each server may be distributed.

[0828] The claims described in this disclosure can be combined in various ways. For example, the technical features of the method claims of this disclosure can be combined to be implemented as a device, and the technical features of the device claims of this disclosure can be combined to be implemented as a method. In addition, the technical features of the method claims of this disclosure and the technical features of the device claims of this disclosure can be combined to be implemented as a device, and the technical features of the method claims of this disclosure and the technical features of the device claims of this 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, the at least one processor being connected to the memory, the at least one processor being configured to: Obtain image information from a bitstream; and Generate a reconstructed picture based on the image information, Wherein, in the obtained image information, the at least one processor is further configured to: Obtain (i) a flag indicating whether a chrominance quantization parameter (QP) mapping table is signaled and applied to chrominance components, and (ii) a combined CbCr enable flag, wherein the chrominance components include a Cb component, a Cr component, and a combined CbCr component; and Based on (i) the flag and (ii) the combined CbCr enable flag, obtain chrominance quantization parameter data for at least one chrominance QP mapping table for the chrominance components, 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, Wherein, based on the value of the flag being equal to 1, the one chrominance QP mapping table is signaled and applied to the Cb component, the Cr component, and the combined CbCr component, and wherein chrominance quantization parameters for the Cb component, the Cr component, and the combined CbCr component are derived based on the one chrominance QP mapping table, 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 mapping tables each including a chrominance QP mapping table for each of the Cb component, the Cr component, and the combined CbCr component are signaled, and wherein chrominance quantization parameters for the Cb component, the Cr component, and the combined CbCr component are derived based on each chrominance QP mapping table 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, the at least one processor being connected to the memory, the at least one processor being configured to: Encode image information; and Generate a bitstream including the image information, Wherein, in encoding the image information, the at least one processor is further configured to: Generate (i) a flag indicating whether a chrominance quantization parameter (QP) mapping table is signaled and applied to chrominance components, and (ii) a combined CbCr enable flag, wherein the chrominance components include a Cb component, a Cr component, and a combined CbCr component; and Based on (i) the flag and (ii) the combined CbCr enable flag, generate chrominance quantization parameter data for at least one chrominance QP mapping table for the chrominance components, Among them, the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP mapping table, a syntax element for the increment value of the input coordinates of the target point used to derive the chrominance QP mapping table, and a syntax element for the increment value of the output coordinates of the target point used to derive the chrominance QP mapping table. Among them, based on the value of the flag being equal to 1, the one chrominance QP mapping table is signaled and applied to the Cb component, the Cr component, and the combined CbCr component, and among them, the chrominance quantization parameters for the Cb component, the Cr component, and the combined CbCr component are derived based on the one chrominance QP mapping table, and Among them, 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 including each chrominance QP mapping table for each of the Cb component, the Cr component, and the combined CbCr component are signaled, and among them, the chrominance quantization parameters for the Cb component, the Cr component, and the combined CbCr component are derived based on each chrominance QP mapping table for each of the Cb component, the Cr component, and the combined CbCr component.

3. A device for transmitting data of an image, the device includes: At least one processor configured to obtain a bitstream of image information, where the bitstream is generated based on generating (i) a flag for whether one chrominance quantization parameter (QP) mapping table is signaled and applied to chrominance components, and (ii) a combined CbCr enable flag, where the chrominance components include a Cb component, a Cr component, and a combined CbCr component, generating chrominance quantization parameter data for at least one chrominance QP mapping table for the chrominance components based on (i) the flag and (ii) the combined CbCr enable flag, and encoding the image information including the flag, the combined CbCr enable flag, and the chrominance quantization parameter data; and A transmitter configured to transmit the data including the bitstream of the image information, Among them, the chrominance quantization parameter data includes a syntax element for the number of points in the chrominance QP mapping table, a syntax element for the increment value of the input coordinates of the target point used to derive the chrominance QP mapping table, and a syntax element for the increment value of the output coordinates of the target point used to derive the chrominance QP mapping table. Among them, based on the value of the flag being equal to 1, the one chrominance QP mapping table is signaled and applied to the Cb component, the Cr component, and the combined CbCr component, and among them, the chrominance quantization parameters for the Cb component, the Cr component, and the combined CbCr component are derived based on the one chrominance QP mapping table, and Among them, based on the value of the flag being equal to 0 and the value of the combined CbCr enable flag being equal to 1, a plurality of chroma QP mapping tables for each of the chroma QP mapping tables for each of the Cb component, the Cr component, and the combined CbCr component are signaled, and wherein the chroma quantization parameters for the Cb component, the Cr component, and the combined CbCr component are derived based on each of the chroma QP mapping tables for each of the Cb component, the Cr component, and the combined CbCr component.

Images