Image decoding method and device

Abstract

An image decoding method performed by a decoding device according to this document includes the following steps: obtaining image information through a bit stream; and generating a reconstructed picture based on the image information.

Description

Technical Field

[0001] The present disclosure relates to an image coding technology, and more particularly, to an image decoding method and an apparatus thereof, which use a chroma QP mapping table derived based on signaled chroma quantization parameter data in an image coding system. Background Art

[0002] Recently, in various fields, the demand for high-resolution, high-quality images such as HD (high definition) images and UHD (ultra high definition) images is growing. Because image data has high resolution and high quality, the amount of information or bits to be transmitted increases relative to conventional image data. Therefore, when image data is transmitted using a medium such as a conventional wired / wireless broadband line or stored using an existing storage medium, its transmission cost and storage cost increase.

[0003] Therefore, there is a need for efficient image compression technology for effectively transmitting, storing and reproducing information of high-resolution and high-quality images. Summary of the invention

[0004] Technical issues

[0005] The technical purpose of the present disclosure is to provide a method and device for improving image coding efficiency.

[0006] Another technical object of the present disclosure is to provide a method and apparatus for improving data coding efficiency for deriving quantization parameters for chroma components.

[0007] Technical Solution

[0008] According to an embodiment of the present disclosure, a method for image decoding performed by a decoding device is provided, wherein the method comprises: obtaining image information through a bit stream, and generating a reconstructed picture based on the image information.

[0009] According to another embodiment of the present disclosure, a decoding device for performing image decoding is provided. The decoding device includes: an entropy decoder that obtains image information through a bit stream, and a residual processor that generates a reconstructed picture based on the image information.

[0010] According to another embodiment of the present disclosure, a video encoding method performed by an encoding device is provided. The method includes encoding image information and generating a bit stream including the image information.

[0011] According to another embodiment of the present disclosure, a video encoding device is provided. The encoding device includes: an entropy encoder that encodes image information and generates a bit stream including the image information.

[0012] Beneficial Effects

[0013] According to the present disclosure, when deriving chroma quantization parameters for chroma components, the chroma quantization parameters for chroma components can be derived using a chroma QP mapping table derived based on signaled chroma quantization parameter data instead of a default chroma QP mapping table, and in this way, coding efficiency can be improved by performing coding based on quantization parameters according to characteristics of an image.

[0014] According to the present disclosure, a chroma QP mapping table may be derived based on a syntax element representing a delta value of input coordinates of a point for deriving the chroma QP mapping table and / or a syntax element representing a delta value of output coordinates of a point for deriving the chroma QP mapping table, and coding efficiency may be improved by performing coding based on the chroma QP mapping table that more specifically reflects characteristics of an image. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An example of a video / image coding device to which embodiments of the present disclosure can be applied is briefly illustrated.

[0016] Figure 2 is a schematic diagram illustrating a configuration of a video / image encoding device to which an embodiment of the present disclosure can be applied.

[0017] Figure 3 is a schematic diagram illustrating a configuration of a video / image decoding device to which an embodiment of the present disclosure can be applied.

[0018] Figure 4 An example of a video / image encoding method based on intra-frame prediction is illustrated.

[0019] Figure 5 An example of a video / image encoding method based on intra-frame prediction is illustrated.

[0020] Figure 6 The intra prediction process is schematically shown.

[0021] Figure 7 An example of a video / image encoding method based on inter-frame prediction is illustrated.

[0022] Figure 8 An example of a video / image decoding method based on inter-frame prediction is illustrated.

[0023] Fig. 9 The inter-frame prediction process is schematically illustrated.

[0024] Fig.10 The image encoding method of the encoding device according to the present document is schematically shown.

[0025] Fig.11 A coding device for performing an image coding method according to the present document is schematically shown.

[0026] Fig.12 The image decoding method of the decoding device according to the present document is schematically shown.

[0027] Fig.13 A decoding device for performing an image decoding method according to the present document is schematically shown.

[0028] Fig.14 A structural diagram of a content streaming system to which the present disclosure is applied is illustrated. DETAILED DESCRIPTION

[0029] The present disclosure can be modified in various forms, and its specific embodiments will be described and illustrated in the accompanying drawings. However, the embodiments are not intended to limit the present disclosure. The terms used in the following description are only used to describe specific embodiments and are not intended to limit the present disclosure. As long as it is clearly understood in different ways, the expression of the singular includes the expression of the plural. 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 therefore 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.

[0030] In addition, the elements in the drawings described in the present disclosure are drawn independently for the convenience of explaining different specific functions, and do not mean that these elements are embodied by independent hardware or independent software. For example, two or more elements in the elements can be combined to form a single element, or an element can be divided into multiple elements. The embodiments of combining elements and / or dividing elements belong to the present disclosure without departing from the concept of the present disclosure.

[0031] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, throughout the accompanying drawings, like reference numerals are used to indicate like elements, and the same description of the like elements will be omitted.

[0032] Figure 1 An example of a video / image coding device to which embodiments of the present disclosure can be applied is briefly illustrated.

[0033] Reference Figure 1 The video / image coding system may include a first device (source device) and a second device (receiving device). The source device may send coded video / image information or data to the receiving device in the form of a file or stream via a digital storage medium or a network.

[0034] 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.

[0035] The video source can obtain the video / image by capturing, synthesizing or generating the process of the video / image. The video source may include a video / image capturing device and / or a video / image generating device. The video / image capturing device may include, for example, one or more cameras, a video / image archive including previously captured videos / images, etc. The video / image generating device may include, for example, a computer, a tablet computer and a smart phone, and may (electronically) generate the video / image. For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capturing process may be replaced by a process that generates relevant data.

[0036] The encoding device can encode the input video / image. The encoding device can perform a series of processes such as prediction, transformation and quantization to achieve compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0037] The transmitter may transmit the encoded image / image information or data output in the form of a bit stream to a receiver of a receiving device in the form of a file or 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 an element for generating a media file in a predetermined file format, and may include an element for transmitting via a broadcast / communication network. The receiver may receive / extract a bit stream and transmit the received bit stream to a decoding device.

[0038] The decoding device may decode the video / image by performing a series of processes such as dequantization, inverse transformation, and prediction corresponding to the operations of the encoding device.

[0039] The renderer may render the decoded video / image. The rendered video / image may be displayed by a display.

[0040] The present disclosure relates to video / image coding. For example, the methods / implementations disclosed in the present disclosure may be applied to methods disclosed in Versatile Video Coding (VVC), EVC (Basic Video Coding) standard, AOMedia Video 1 (AV1) standard, 2nd generation Audio Video Coding standard (AVS2) or next generation video / image coding standard (e.g., H.267, or H.268, etc.).

[0041] The present disclosure presents various embodiments of video / image coding, and unless otherwise mentioned, the embodiments may be performed in combination with each other.

[0042] In the present disclosure, a video may refer to a series of images over time. Generally, a picture refers to a unit representing an image in a specific time zone, and a sub-picture / slice / tile is a unit that constitutes a 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 / tiles. 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 ​​a CTU row within a tile in a picture. A tile may be partitioned into a plurality of tiles, each tile consisting of one or more CTU rows within a tile. Tiles that are not partitioned into a plurality of tiles may also be referred to as tiles. A tile scan may sort the CTUs partitioned in a picture in a specific order, wherein the CTUs are sorted continuously in the tile by a CTU raster scan, the tiles within the tile are sorted continuously by a raster scan of the tile, and the tiles in the picture are sorted continuously by a raster scan of the tile of the picture. In addition, 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 cover a rectangular area of ​​a picture together. A tile is a rectangular area of ​​a CTU within a specific tile column and a specific tile row in a picture. A tile column is a rectangular area of ​​a CTU whose height is equal to the height of the picture and whose width is specified by a syntax element in a picture parameter set. A tile row is a rectangular area of ​​a CTU whose height is specified by a syntax element in a picture parameter set and whose width is equal to the width of the picture. Tile scanning is a specific order sorting of CTUs that partition a picture, wherein CTUs may be sorted continuously in a tile by a CTU raster scan, and tiles in a picture may be sorted continuously by a raster scan of tiles of a picture. A slice includes an integer number of tiles of a picture that may be exclusively contained in a single NAL unit. A slice may consist of multiple complete tiles or only of a complete sequence of tiles of a continuous sequence. In the present disclosure, tile groups and slices may be used interchangeably. For example, in the present disclosure, a tile group / tile group header may be referred to as a slice / slice header.

[0043] A pixel or a picture element (pel) may represent the smallest unit constituting a picture (or image). In addition, a "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel / pixel value of a luminance component or only a pixel / pixel value of a chrominance component.

[0044] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to the area. A unit may include a luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit may be used interchangeably with terms such as a block or an area. In general, an M×N block may include a set (or array) of samples (or sample arrays) or transform coefficients of M columns and N rows.

[0045] In this specification, "A or B" may mean "only A", "only B", or "A and B". In other words, in this specification, "A or B" may be interpreted as "A and / or B". For example, "A, B or C" herein means "only A", "only B", "only C", or "any one and any combination of A, B, and C".

[0046] A slash ( / ) or a comma used in this specification may mean "and / or". For example, "A / B" may mean "A and / or B". Thus, "A / B" may mean "only A", "only B", or "A and B". For example, "A,B,C" may mean "A, B, or C".

[0047] In the present specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in the present specification, the expression "at least one of A or B" or "at least one of A and / or B" may be interpreted as being the same as "at least one of A and B".

[0048] In addition, in the present specification, "at least one of A, B, and C" means "only A", "only B", "only C", or "any combination of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B and / or C" may mean "at least one of A, B, and C".

[0049] In addition, brackets used in this specification may refer to "for example". Specifically, when "prediction (intra-frame prediction)" is indicated, "intra-frame prediction" may be proposed as an example of "prediction". In other words, "prediction" in this specification is not limited to "intra-frame prediction", and "intra-frame prediction" may be proposed as an example of "prediction". In addition, even when "prediction (i.e., intra-frame prediction)" is indicated, "intra-frame prediction" may be proposed as an example of "prediction".

[0050] In this specification, technical features described separately in one figure may be implemented separately or may be implemented simultaneously.

[0051] The following figures 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 figures are presented by way of example, the technical features of this specification are not limited to the specific names used in the following figures.

[0052] Figure 2 is a schematic diagram illustrating a configuration of a video / image encoding device to which an embodiment of the present disclosure can be applied. Hereinafter, a video encoding device may include an image encoding device.

[0053] Reference Figure 2 , the encoding device 200 includes an image segmenter 210, a predictor 220, a residual processor 230 and 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, a dequantizer 234 and an inverse transformer 235. The residual processor 230 may also include a subtractor 231. The adder 250 may be called a reconstructor or a reconstructed block generator. According to an embodiment, the image segmenter 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250 and the filter 260 may be composed of at least one hardware component (e.g., an encoder chipset or processor). In addition, the memory 270 may include a decoded picture buffer (DPB) or may be composed of a digital storage medium. The hardware component may also include a memory 270 as an internal / external component.

[0054] The image divider 210 may divide the 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 coding unit (CU). In this case, the coding unit may be recursively divided from a coding tree unit (CTU) or a maximum coding unit (LCU) according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, a coding unit may be divided into a plurality of coding units with a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary structure. In this case, for example, a quadtree structure may be applied first, and then a binary tree structure and / or a ternary structure may be applied. Alternatively, a binary tree structure may be applied first. The coding process according to the present disclosure may be performed based on a final coding unit that is no longer divided. In this case, the maximum coding unit may be used as the final coding unit based on coding efficiency according to image characteristics, or if necessary, the coding unit may be recursively divided into coding units with a deeper depth and a coding unit with an optimal size may be used as the final coding unit. Here, the coding process may include a process of prediction, transformation, and reconstruction, which will be described later. As another example, the processor may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may be split or partitioned from the above-mentioned final coding unit. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from a transform coefficient.

[0055] In some cases, a unit may be used interchangeably with terms such as a block or region. In general, an M×N block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample may generally represent a pixel or a pixel value, and may represent a pixel / pixel value of only a luminance component, or a pixel / pixel value of only a chrominance component. A sample may be used as a term corresponding to a picture (or image) of a pixel or a pixel element.

[0056] In the encoding device 200, the prediction signal (prediction block, prediction sample array) output from the inter predictor 221 or the intra 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 for subtracting the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) in the encoding device 200 can be called a subtractor 231. The predictor can perform prediction on the 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 can determine whether to apply intra prediction or inter prediction in units of the current block or CU. As described later in the description of each prediction mode, the predictor can 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 can be encoded in the entropy encoder 240 and output in the form of a bit stream.

[0057] The intra-frame predictor 222 can predict the current block by referring to samples in the current picture. Depending on the prediction mode, the referenced sample can be located near the current block, or can be far away from the current block. In intra-frame prediction, the prediction mode may include multiple non-directional modes and multiple directional modes. The non-directional mode may include, for example, a DC mode and a plane mode. Depending on the level of detail of the prediction direction, the directional mode 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 setting. 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.

[0058] The inter-frame predictor 221 may derive a prediction block of the 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 sent in the inter-frame prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may 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 may be the same or different. The temporal neighboring block may be referred to as a collocated reference block, a co-located CU (colCU), etc., and the reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). For example, the inter-frame predictor 221 may configure a motion information candidate list based on the neighboring blocks, and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter-frame prediction may be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter-frame predictor 221 may use the motion information of the neighboring block as the motion information of the current block. In skip mode, unlike merge mode, a residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the neighboring block may be used as a motion vector predictor, and the motion vector of the current block may be indicated by signaling a motion vector difference.

[0059] The predictor 220 may generate a prediction signal based on various prediction methods described below. For example, the predictor may not only apply intra prediction or inter prediction to predict a block, but may also apply both intra prediction and inter prediction at the same time. This may be referred to as inter-frame intra combined prediction (CIIP). In addition, the predictor may predict a block based on an intra-block copy (IBC) prediction mode or a palette mode. The IBC prediction mode or the palette mode may be used for content image / video coding of games, etc., such as screen content coding (SCC). IBC basically performs prediction in the current picture, but may be performed similarly to inter prediction because the reference block is derived in the current picture. That is, IBC may use at least one of the inter prediction techniques described in the present disclosure. The palette mode may be considered as an example of intra coding or intra prediction. When the palette mode is applied, the sample values ​​within the picture may be signaled based on information about the palette table and the palette index.

[0060] The prediction signal generated by the predictor (including the inter-frame predictor 221 and / or the intra-frame predictor 222) can be used to generate a reconstruction signal or to generate a residual signal. The transformer 232 can generate a transform coefficient by applying a transform technique to the residual signal. For example, the transform technique may 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 nonlinear transform (CNT). Here, GBT represents a transform obtained from a graph when the relationship information between pixels is represented by a graph. CNT refers to a transform generated based on a prediction signal generated using all previously reconstructed pixels. In addition, the transform process can be applied to square pixel blocks of the same size, or can be applied to blocks of variable size rather than square.

[0061] The quantizer 233 may quantize the transform coefficients and send them to the entropy encoder 240, and the entropy encoder 240 may encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. Information about the quantized transform coefficients may be referred to as residual information. The quantizer 233 may rearrange the block type quantized transform coefficients into a one-dimensional vector form based on the coefficient scanning 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. The 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. The entropy encoder 240 may encode information required for video / image reconstruction (e.g., values ​​of syntax elements, etc.) other than the quantized transform coefficients together or separately. Encoding information (e.g., encoded video / image information) may be transmitted 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 an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. In the present disclosure, 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 by the above-mentioned encoding process and included in the bitstream. The bitstream may be sent through a network, or may be 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) that sends a signal output from the entropy encoder 240 and / or a storage unit (not shown) that stores the signal may be included as an internal / external element of the encoding device 200, alternatively, the transmitter may be included in the entropy encoder 240.

[0062] 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 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 the case where the skip mode is applied), the prediction block can be used as a reconstructed block. The adder 250 can be called 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 by filtering as described below.

[0063] Furthermore, during picture encoding and / or reconstruction, luma mapping and chroma scaling (LMCS) may be applied.

[0064] 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). Various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filter 260 can generate various information related to filtering, and send the generated information to the entropy encoder 240, as described later in the description of various filtering methods. The information related to filtering can be encoded by the entropy encoder 240 and output in the form of a bit stream.

[0065] The modified reconstructed picture sent to the memory 270 may 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 may be avoided, and coding efficiency may be improved.

[0066] The DPB of the memory 270 may store a modified reconstructed picture used as a reference picture in the inter-frame predictor 221. The memory 270 may store motion information of a block from which motion information in the current picture is derived (or encoded) and / or motion information of a reconstructed block in the picture. The stored motion information may be sent to the inter-frame predictor 221 and used as motion information of a spatially adjacent block or motion information of a temporally adjacent block. The memory 270 may store reconstructed samples of a reconstructed block in the current picture and may transmit the reconstructed samples to the intra-frame predictor 222.

[0067] Figure 3 is a schematic diagram illustrating a configuration of a video / image decoding device to which an embodiment of the present disclosure can be applied.

[0068] Reference 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 composed of hardware components (e.g., a decoder chipset or a processor). In addition, the memory 360 may include a decoded picture buffer (DPB), or may be composed of a digital storage medium. The hardware component may also include a memory 360 as an internal / external component.

[0069] When a bit stream including video / image information is input, the decoding apparatus 300 can be used with Figure 2 The image is reconstructed corresponding to the processing of the video / image information in the encoding device. For example, the decoding device 300 can derive the unit / block based on the block segmentation related information obtained from the bit stream. The decoding device 300 can perform decoding using a processor applied in the encoding device. Therefore, the decoding processor can be, for example, a coding unit, and the coding unit can be divided from the coding tree unit or the maximum coding unit according to a quadtree structure, a binary tree structure and / or a ternary tree structure. One or more transform units can be derived from the coding unit. The reconstructed image signal decoded and output by the decoding device 300 can be reproduced by a reproduction device.

[0070] The decoding device 300 may receive the bit stream from Figure 2The received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can parse the bitstream to derive information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information may also include information about various parameter sets such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The decoding device may also decode the picture based on the information about the parameter set and / or the general constraint information. The signaled / received information and / or syntax elements described later in this disclosure may be decoded by a decoding process and obtained from the bitstream. For example, the entropy decoder 310 decodes the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and outputs syntax elements required for image reconstruction and quantized values ​​of the transform coefficients of the residual. More specifically, the CABAC entropy decoding method can receive a bin (binary bit) 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 arithmetically decode the bin by predicting the probability of occurrence 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 decoded symbol / bin information for the context model of the next symbol / bin. Information related to prediction among the information decoded by the entropy decoder 310 can be provided to the predictor (inter-frame predictor 332 and intra-frame predictor 331), and the residual value (that is, quantized transform coefficients and related parameter information) for which entropy decoding is 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). In addition, information about filtering among the information decoded by the entropy decoder 310 can be provided to the filter 350. In addition, a receiver (not shown) for receiving a signal output from the encoding device may be further configured as an internal / external element of the decoding device 300, or the receiver may be a component of the entropy decoder 310. In addition, the decoding device according to the present disclosure may be referred to as a video / image / picture decoding device, and the decoding device may be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include the entropy decoder 310, and the sample decoder may include at least one of the dequantizer 321, the inverse transformer 322, the adder 340, the filter 350, the memory 360, the inter-frame predictor 332, and the intra-frame predictor 331.

[0071] The dequantizer 321 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 may rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement may be performed based on the coefficient scanning order performed in the encoding device. The dequantizer 321 may dequantize the quantized transform coefficients by using a quantization parameter (e.g., quantization step size information) and obtain the transform coefficients.

[0072] The inverse transformer 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0073] The predictor may perform prediction on the current block and generate a prediction block including prediction samples of the current block. The predictor may determine whether to apply intra prediction or inter prediction to the current block based on information on prediction output from the entropy decoder 310, and may determine a specific intra / inter prediction mode.

[0074] 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 at the same time. This can be called inter-frame and intra-frame combined prediction (CIIP). In addition, the predictor can predict blocks based on intra-frame block copy (IBC) prediction mode or palette mode. IBC prediction mode or palette mode can be used for content image / video coding of games, etc., such as screen content coding (SCC). IBC basically performs prediction in the current picture, but IBC can be performed similarly 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 this disclosure. The palette mode can be regarded as an example of intra coding or intra prediction. When the palette mode is applied, the sample value within the picture can be signaled based on information about the palette table and the palette index.

[0075] The intra-frame predictor 331 can predict the current block by referring to samples in the current picture. Depending on the prediction mode, the referenced sample can be located near the current block, or can be far away from the current block. In intra-frame prediction, the prediction mode can include multiple non-directional modes and multiple directional modes. The intra-frame predictor 331 can determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

[0076] The inter-frame predictor 332 may derive a prediction block of 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 sent in the inter-frame prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may 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 may configure a motion information candidate list based on the neighboring blocks, and derive a motion vector and / or a reference picture index of the current block based on the received candidate selection information. Inter-frame prediction may be performed based on various prediction modes, and information about the prediction may include information indicating a mode of inter-frame prediction for the current block.

[0077] The adder 340 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the predictor (including the inter-frame predictor 332 and / or the intra-frame predictor 331). If the block to be processed has no residual (for example, when the skip mode is applied), the prediction block can be used as the reconstructed block.

[0078] The adder 340 may be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal may be used for intra prediction of the next block to be processed in the current picture, may be output through filtering as described below, or may be used for inter prediction of the next picture.

[0079] In addition, luma mapping and chroma scaling (LMCS) can be applied during picture decoding.

[0080] The filter 350 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 350 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 360 (specifically, the DPB of the memory 360). Various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0081] The (modified) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter-frame predictor 332. The memory 360 can store the motion information of the block from which the motion information in the current picture is derived (or decoded) and / or the motion information of the reconstructed block in the picture. The stored motion information can be sent to the inter-frame predictor 332 to be used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 360 can store the reconstructed samples of the reconstructed block in the current picture, and can transmit the reconstructed samples to the intra-frame predictor 331.

[0082] In the present disclosure, the embodiments described in the filter 260, the inter-frame predictor 221, and the intra-frame predictor 222 of the encoding device 200 may be the same as the filter 350, the inter-frame predictor 332, and the intra-frame predictor 331 of the decoding device 300 or may be respectively applied to correspond to the filter 350, the inter-frame predictor 332, and the intra-frame predictor 331 of the decoding device 300. The same contents may also be applied to the inter-frame predictor 332 and the intra-frame predictor 331.

[0083] In the present disclosure, at least one of quantization / inverse quantization and / or transform / inverse transform may be omitted. When quantization / inverse quantization is omitted, the quantized transform coefficient may be referred to as a transform coefficient. When transform / inverse transform is omitted, the transform coefficient may be referred to as a coefficient or a residual coefficient, or may still be referred to as a transform coefficient for the sake of uniformity of expression.

[0084] In the present disclosure, the quantized transform coefficient and the transform coefficient may be referred to as a transform coefficient and a scaled transform coefficient, respectively. In this case, the residual information may include information about the transform coefficient, and the information about the transform coefficient may be signaled by the residual coding syntax. The transform coefficient may be derived based on the residual information (or information about the transform coefficient), and the scaled transform coefficient may be derived by inversely transforming (scaling) the transform coefficient. The residual sample may be derived based on inversely transforming (transforming) the scaled transform coefficient. This may also be applied / expressed in other parts of the present disclosure.

[0085] At the same time, as described above, when performing video coding, prediction is performed to improve compression efficiency. In this way, a prediction block including prediction samples of the current block can be generated as a block to be coded (ie, a 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 manner in the encoding device and the decoding device, and the encoding device can signal the decoding device with information about the residual between the original block and the prediction block (residual information) instead of the original sample value of the original block, thereby improving 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.

[0086] The residual information may be generated by a transformation and quantization process. For example, the encoding device may derive a residual block between the original block and the prediction block, may perform a transformation process on the residual samples (residual sample array) included in the residual block to derive a transformation coefficient, may perform a quantization process on the transformation coefficient to derive a quantized transformation coefficient, and may signal the relevant residual information (through a bitstream) to the decoding device. Here, the residual information may include value information, position information, transformation technology, transformation core, and value information of quantization parameters, etc. of the quantized transformation coefficient. The decoding device may perform a dequantization / inverse transformation process based on the residual information and derive residual samples (or residual blocks). The decoding device may generate a reconstructed picture based on the prediction block and the residual block. In addition, for reference for inter-frame prediction of a reference picture later, the encoding device may dequantize / inverse transform the quantized transformation coefficient to derive a residual block, and generate a reconstructed picture based on this.

[0087] Intra-frame prediction may refer to generating a prediction of a prediction sample for a current block based on a reference sample in a picture to which the current block belongs (hereinafter referred to as the current picture). When intra-frame prediction is applied to the current block, the neighboring reference samples to be used for intra-frame prediction of the current block may be derived. The neighboring reference samples of the current block may include samples adjacent to the left boundary of the current block of size nWxnH and a total of 2xnH samples adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2xnW samples adjacent to the upper right, and samples adjacent to the upper left of the current block. Alternatively, the neighboring reference samples of the current block may include multiple columns of upper adjacent samples and multiple rows of left adjacent samples. In addition, the neighboring reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the lower boundary of the current block, and samples adjacent to the lower right of the current block.

[0088] However, some neighboring reference samples of the current block have not been decoded or may not be available. In this case, the decoder can construct neighboring reference samples to be used for prediction by replacing unavailable samples with available samples. Alternatively, the neighboring reference samples to be used for prediction can be configured by interpolation of available samples.

[0089] When deriving the neighboring reference samples, (i) the prediction samples may be derived based on an average or interpolation of the neighboring reference samples of the current block, or (ii) the prediction samples may be derived based on reference samples existing in a specific (prediction) direction relative to the prediction samples in the neighboring reference samples of the current block. Case (i) may be referred to as a non-directional mode or a non-angular mode, and case (ii) may be referred to as a directional mode or an angular mode.

[0090] In addition, the prediction sample can be generated by interpolating the first neighboring sample located in the prediction direction of the intra prediction mode of the current block based on the prediction sample of the current block among the adjacent reference samples and the second neighboring sample located in the direction opposite to the prediction direction. The above situation can be called linear interpolation intra prediction (LIP). In addition, a linear model (LM) can be used to generate chrominance prediction samples based on luma samples. This situation can be called LM mode or chrominance component LM (CCLM) mode.

[0091] In addition, a temporary prediction sample of the current block is derived based on the filtered adjacent reference sample, and the prediction sample of the current block can also be derived by weighted summing the temporary prediction sample with at least one reference sample derived according to the intra prediction mode in the existing adjacent reference sample (i.e., the unfiltered adjacent reference sample). The above situation can be called position-dependent intra prediction (PDPC).

[0092] In addition, a reference sample line with the highest prediction accuracy among multiple adjacent reference sample lines of the current block is selected, and a prediction sample is derived using a reference sample located in the prediction direction in the selected line. In this case, intra-frame prediction encoding can be performed by indicating (signaling) the reference sample line used to the decoding device. The above situation can be referred to as multi-reference line intra-frame prediction or MRL-based intra-frame prediction.

[0093] In addition, the current block is divided into vertical or horizontal sub-partitions and performs intra prediction based on the same intra prediction mode, but it is possible to derive and use adjacent reference samples in units of sub-partitions. That is, in this case, the intra prediction mode of the current block is also applicable to the sub-partitions, but in some cases, the intra prediction performance can be improved by deriving and using adjacent reference samples in units of sub-partitions. This prediction method can be called intra prediction based on intra sub-partition (ISP).

[0094] The above-mentioned intra-frame prediction method may be referred to as an intra-frame prediction type to distinguish it from an intra-frame prediction mode. The intra-frame prediction type may be referred to by various terms, such as an intra-frame prediction technique or an additional intra-frame prediction mode. For example, the intra-frame prediction type (or additional intra-frame prediction mode, etc.) may include at least one of the above-mentioned LIP, PDPC, MRL, and ISP. A general intra-frame prediction method excluding specific intra-frame prediction types such as LIP, PDPC, MRL, and ISP may be referred to as a normal intra-frame prediction type. When the above-mentioned specific intra-frame prediction type is not applied, a normal intra-frame prediction type may generally be applied, and prediction may be performed based on the above-mentioned intra-frame prediction mode. At the same time, if necessary, post-processing filtering may be performed on the derived prediction samples.

[0095] Specifically, the intra prediction process may include an intra prediction mode / type determination step, an adjacent reference sample derivation step, and a prediction sample derivation step based on the intra prediction mode / type. In addition, if necessary, a post-filtering step may be performed on the derived prediction samples.

[0096] Figure 4 An example of a video / image encoding method based on intra-frame prediction is illustrated.

[0097] Reference 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 prediction 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 prediction sample generation processes may be performed simultaneously, or one process may be performed before the other. The encoding device may determine a mode / type applied to the current block from a plurality of intra prediction modes / types. The encoding device may compare the RD costs of the intra prediction modes / types and determine the optimal intra prediction mode / type for the current block.

[0098] At the same time, the encoding device may perform a prediction sample filtering process. Prediction sample filtering may be referred to as post-filtering. Some or all prediction samples may be filtered by the prediction sample filtering process. In some cases, the prediction sample filtering process may be omitted.

[0099] The encoding apparatus generates residual samples of the current block based on the (filtered) prediction samples (S410). The encoding apparatus may compare the prediction samples among the original samples of the current block based on a phase and derive the residual samples.

[0100] The encoding device may encode image information including information about intra prediction (prediction information) and residual information about residual samples (S420). The prediction information may include intra prediction mode information and intra prediction type information. The encoding device may output the encoded image information in the form of a bit stream. The output bit stream may be sent to a decoding device via a storage medium or a network.

[0101] The residual information may include a residual coding 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.

[0102] At the same time, as described above, the encoding device can generate a reconstructed picture (including reconstructed samples and reconstructed blocks). To this end, the encoding device can 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 the residual samples derived in the above-mentioned decoding device. The encoding device can generate a reconstructed block including reconstructed samples for the current block based on the predicted samples and the (modified) residual samples. A reconstructed picture for the current picture can be generated based on the reconstructed block. As described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0103] Figure 5 An example of a video / image encoding method based on intra-frame prediction is illustrated.

[0104] The decoding device may perform operations corresponding to those performed by the encoding device.

[0105] Prediction information and residual information may be obtained from a bitstream. Residual samples of a current block may be derived based on the residual information. Specifically, transform coefficients may be derived by performing inverse quantization based on quantized transform coefficients derived from the residual information, and residual samples of the current block may be derived by performing inverse transformation on the transform coefficients.

[0106] Specifically, the decoding device may derive the intra prediction mode / type of the current block based on the received prediction information (intra prediction mode / type information) (S500). The decoding device may derive the adjacent reference samples of the current block (S510). The decoding device generates the prediction samples in the current block based on the intra prediction mode / type and the adjacent reference samples (S520). 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 prediction samples may be filtered by the prediction sample filtering process. In some cases, the prediction sample filtering process may be omitted.

[0107] The decoding device generates a residual sample for the current block based on the received residual information (S530). The decoding device can generate a reconstructed sample of the current block based on the predicted sample and the residual sample, and can derive a reconstructed block including the reconstructed sample (S540). A reconstructed picture of the current picture can be generated based on the reconstructed block. As described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0108] The intra-frame prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) indicating whether MPM (most probable mode) is applied to the current block or whether the residual mode is applied, and when 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-frame prediction mode candidates (MPM candidates). The intra-frame prediction mode candidates (MPM candidates) may be composed of an MPM candidate list or an MPM list. In addition, when MPM is not applied to the current block, the intra-frame prediction mode information includes residual mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra-frame prediction modes other than the intra-frame prediction mode candidates (MPM candidates). The decoding device may determine the intra-frame prediction mode of the current block based on the intra-frame prediction mode information.

[0109] 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 indicating whether MRL is applied to the current block, and if applied, which reference sample line is used (e.g., intra_luma_ref_idx), ISP flag information indicating whether ISP is applied to the current block (e.g., intra_subpartitions_mode_flag), ISP type information indicating the split type of the sub-partition when ISP is applied (e.g., intra_subpartitions_split_flag), flag information indicating whether PDPC is applied, or flag information indicating whether LIP is applied. In addition, the intra prediction type information may include a MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

[0110] The intra-frame prediction mode information and / or the intra-frame prediction type information may be encoded / decoded by the coding method described in the present disclosure. For example, the intra-frame prediction mode information and / or the intra-frame prediction type information may be encoded / decoded by entropy coding (e.g., CABAC, CAVLC).

[0111] Figure 6 The intra prediction process is schematically shown.

[0112] Reference Figure 6As described above, the intra prediction process may include a step of determining an intra prediction mode / type, a step of deriving adjacent reference samples, and a step of performing intra prediction (generating prediction samples). The intra prediction process may be performed by an encoding device and a decoding device as described above. In the present disclosure, a coding device may include an encoding device and / or a decoding device.

[0113] Reference Figure 6 , the coding device determines the intra prediction mode / type S600.

[0114] The encoding device may determine the intra-prediction mode / type applied to the 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 the intra-prediction mode applied to the current block and / or intra-prediction type information indicating the intra-prediction type applied to the current block. The decoding device may determine the intra-prediction mode / type applied to the current block based on the prediction related information.

[0115] The intra-frame 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 the residual 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-frame prediction mode candidates (MPM candidates). The intra-frame prediction mode candidates (MPM candidates) may be composed of an MPM candidate list or an MPM list. In addition, when the MPM is not applied to the current block, the intra-frame prediction mode information may further include residual mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra-frame prediction modes other than the intra-frame prediction mode candidates (MPM candidates). The decoding device may determine the intra-frame prediction mode of the current block based on the intra-frame prediction mode information.

[0116] 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 indicating whether MRL is applied to the current block, and if applied, which reference sample line is used (e.g., intra_luma_ref_idx), ISP flag information indicating whether ISP is applied to the current block (e.g., intra_subpartitions_mode_flag), ISP type information indicating the split type of the sub-partition when ISP is applied (e.g., intra_subpartitions_split_flag), flag information indicating whether PDPC is applied, or flag information indicating whether LIP is applied. In addition, the intra prediction type information may include a MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

[0117] For example, when intra prediction is applied, the intra prediction mode of the neighboring block may be used to determine the intra prediction mode applied to the current block. For example, the coding device may select one of the most likely mode (MPM) candidates in the MPM list derived based on the intra prediction mode of the neighboring blocks (e.g., left and / or upper neighboring blocks) of the additional candidate mode and / or the current block, or select one of the remaining intra prediction modes not included in the MPM candidates (and the plane mode) based on the MPM residual information (remaining intra prediction mode information). The MPM list may be configured to include or exclude the plane mode as a candidate. For example, when the MPM list includes the plane mode as a candidate, the MPM list may have 6 candidates, and when the MPM list does not include the plane mode as a candidate, the MPM list may have 5 candidates. When the MPM list does not include the plane 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 a plane 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 is that the planar mode is always considered to be the MPM rather than considering that the planar mode is not the MPM, and therefore, the flag (non-planar flag) is signaled first to check whether it is the planar mode.

[0118] For example, it can be indicated based on an MPM flag (e.g., intra_luma_mpm_flag) whether the intra prediction mode applied to the current block is among the MPM candidates (and 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 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 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 a 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 a planar mode. The MPM index can be signaled in the form of an mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information can be signaled in the form of a rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information may indicate one of the remaining intra prediction modes that is not included in the MPM candidates (and planar mode) among all intra prediction modes by indexing in order of the prediction mode number. The intra prediction mode may be an intra prediction mode of a luminance component (sample). Hereinafter, the intra prediction mode information may 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 may be referred to by a variety of terms, such as an MPM candidate list and candModeList.

[0119] When a MIP is applied to a current block, a separate mpm flag (eg, intra_mip_mpm_flag), an mpm index (eg, intra_mip_mpm_idx), and remaining intra prediction mode information (eg, intra_mip_mpm_remainder) for the MIP may be signaled, and a non-planar flag may not be signaled.

[0120] In other words, in general, when performing block segmentation of an image, the current block to be coded and the neighboring blocks have similar image features. Therefore, the possibility that the current block and the neighboring blocks have the same or similar intra-frame prediction mode is high. Therefore, the encoder can use the intra-frame prediction mode of the neighboring block to encode the intra-frame prediction mode of the current block.

[0121] The coding device may construct a most probable mode (MPM) list for the current block. The MPM list may be referred to as an MPM candidate list. Here, MPM may refer to a mode for improving coding efficiency by considering the similarity between the current block and the neighboring blocks during intra-frame prediction mode coding. As described above, the MPM list may be constructed to include a planar mode, or may be constructed to exclude a planar mode. For example, when the MPM list includes a planar mode, the number of candidates in the MPM list may be 6. And when the MPM list does not include a planar mode, the number of candidates in the MPM list may be 5.

[0122] The encoding device may perform prediction based on various intra prediction modes, and may determine the best intra prediction mode based on rate distortion optimization (RDO) therefrom. In this case, the encoding device may determine the best intra prediction mode by using only the MPM candidates and plane modes configured in the MPM list, or by further using the remaining intra prediction modes and the MPM candidates and plane modes configured in the MPM list. Specifically, for example, if the intra prediction type of the current block is a specific type other than the normal intra prediction type (e.g., LIP, MRL, or ISP), the encoding device may determine the best intra prediction mode by considering only the MPM candidates and plane modes as intra prediction mode candidates for the current block. That is, in this case, the intra prediction mode of the current block may be determined only from the MPM candidates and plane modes, and in this case, encoding / signaling of the mpm flag may not be performed. In this case, the decoding device may infer that the mpm flag is 1 without separately signaling the mpm flag.

[0123] 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 residual information (remaining intra prediction mode information) indicating the same mode 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 residual information may include, for example, an intra_luma_mpm_remainder syntax element.

[0124] 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 residual information (residual intra prediction mode information). The decoding device may construct an MPM list. The construction of the MPM list is the same as the MPM list constructed in the encoding device. That is, the MPM list may include the intra prediction mode of the neighboring block, or may further include a specific intra prediction mode according to a predetermined method.

[0125] The decoding device can determine the intra-frame prediction mode of the current block based on the MPM list and the intra-frame prediction mode information. For example, when the value of the MPM flag is 1, the decoding device can (based on the non-planar flag) derive the plane mode as the intra-frame 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-frame prediction mode of the current block. Here, the MPM candidate 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 plane mode applicable when the value of the MPM flag is 1.

[0126] 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 plane mode as the intra prediction mode of the current block. At the same time, 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 MPM flag in the plane mode or the MPM list as the intra prediction mode of the current block without parsing / decoding / checking the MPM flag.

[0127] The coding device derives neighboring reference samples of the current block (S610). When intra prediction is applied to the current block, neighboring reference samples to be used for intra prediction of the current block may be derived. The neighboring reference samples of the current block may include samples adjacent to the left boundary of the current block of size nWxnH and a total of 2xnH samples adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2xnW samples adjacent to the upper right, and samples adjacent to the upper left of the current block. Alternatively, the neighboring reference samples of the current block may include multiple columns of upper adjacent samples and multiple rows of left adjacent samples. In addition, the neighboring reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the lower boundary of the current block, and samples adjacent to the lower right of the current block.

[0128] On the other hand, when MRL is applied (ie, when the value of the MRL index is greater than 0), the neighboring reference sample may be located on line 1 to 2 instead of line 0 adjacent to the current block on the left / upper side, and in this case, the number of neighboring reference samples can be further increased. Meanwhile, when ISP is applied, the neighboring reference sample can be derived in units of sub-partitions.

[0129] The coding device derives a prediction sample by performing intra prediction on the current block (S620). The coding device may derive the prediction sample based on the intra prediction mode / type and the neighboring samples. The coding device may derive the reference sample according to the intra prediction mode of the current block among the neighboring reference samples of the current block, and may derive the prediction sample of the current block based on the reference sample.

[0130] Meanwhile, when inter-frame prediction is applied, the predictor of the encoding device / decoding device may derive prediction samples by performing inter-frame prediction in units of blocks. When prediction is performed on the current block, inter-frame prediction may be applied. That is, the predictor of the encoding / decoding device (more specifically, the inter-frame predictor) may derive prediction samples by performing inter-frame prediction in units of blocks. Inter-frame prediction may refer to a prediction derived by a method depending on data elements (e.g., sample values ​​or motion information) of (one or more) pictures other than the current picture. When inter-frame prediction is applied to the current block, a prediction block (prediction sample array) for the current block may 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 sent in the inter-frame prediction mode, the motion information of the current block may 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 may include a motion vector and a reference picture index. The motion information may further include inter-frame prediction type (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of applying inter-frame prediction, the neighboring blocks may 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 may be the same as or different from each other. The temporal neighboring block may be referred to as a name such as a collocated reference block, a collocated CU (ColCU), etc., and the reference picture including the temporal neighboring block may be referred to as a collocated picture (ColPic). For example, a motion information candidate list may be configured based on the neighboring blocks of the current block, and a flag or index information indicating which candidate is selected (used) may be signaled to derive the motion vector and / or reference picture index of the current block. Inter-frame prediction may be performed based on various prediction modes, and, for example, in the case of a skip mode and a merge mode, the motion information of the current block may be the same as the motion information of the selected neighboring block. In the case of the skip mode, unlike the merge mode, a residual signal may not be sent. In the case of a motion vector prediction (MVP) mode, the motion vector of the selected neighboring block may be used as a motion vector predictor, and the motion vector difference may be signaled. In this case, the motion vector of the current block may be derived by using the sum of the motion vector predictor and the motion vector difference.

[0131] According to the inter 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. Prediction based on the L0 motion vector may be referred to as the L0 prediction, prediction based on the L1 motion vector may be referred to as the L1 prediction, and prediction based on both the L0 motion vector and the L1 motion vector may be referred to as 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 a picture before the current picture in output order, and the reference picture list L1 may include a picture after the current picture in output order as a reference picture. The previous picture may be referred to as a forward (reference) picture, and the subsequent picture may be referred to as a backward (reference) picture. The reference picture list L0 may further include a picture after the current picture in output order as a reference picture. In this case, the previous picture may be indexed first in the reference picture list L0, and then the subsequent picture may be indexed. The reference picture list L1 may further include a picture before the current picture in the output order as a reference picture. In this case, the subsequent picture may be indexed first in the reference picture list L1, and then the previous picture may be indexed. Here, the output order may correspond to a picture sequence count (POC) order.

[0132] The video / image encoding process based on inter-frame prediction may schematically include, for example, the following contents.

[0133] Figure 7 An example of a video / image encoding method based on inter-frame prediction is illustrated.

[0134] The encoding device performs inter prediction on the current block (S700). The encoding device may derive the inter prediction mode and motion information of the current block, and generate a prediction sample of the current block. Here, the inter prediction mode determination process, the motion information derivation process, and the prediction sample generation process may be performed simultaneously, and any one process 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 with the smallest difference from the current block or equal to or less than a predetermined criterion. A reference picture index indicating the reference picture where the reference block is located may be derived based on this, and a motion vector may be derived based on the position difference between the reference block and the current block. The encoding device may determine a mode applied to the current block among various prediction modes. The encoding apparatus may compare the RD costs of various prediction modes and determine an optimal prediction mode for the current block.

[0135] For example, when the skip mode or 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 with the current block or being 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.

[0136] As another example, when the (A)MVP mode is applied to the current block, the encoding device may configure the (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. In this case, for example, the motion vector indicating the reference block derived by motion estimation may be used as the motion vector of the current block, and the MVP candidate having the motion vector with the minimum difference from the motion vector of the current block among the MVP candidates may become the selected MVP candidate. A motion vector difference (MVD) may be derived, which is the difference obtained by subtracting the MVP from the motion vector of the current block. 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.

[0137] The encoding apparatus may derive residual samples based on the prediction samples (S710). The encoding apparatus may derive residual samples by comparing original samples and prediction samples of the current block.

[0138] The encoding device encodes the 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., a skip flag, a merge flag, or a mode index, etc.) and information about motion information as information related to the prediction process. The information about the motion information may include candidate selection information (e.g., a merge index, an mvp flag, or an mvp index), which is information for deriving a motion vector. In addition, the information about the motion information may include information about the MVD and / or reference picture index information. In addition, the information about the motion information may include information indicating whether L0 prediction, L1 prediction, or dual prediction is applied. The residual information is information about the residual sample. The residual information may include information about the quantized transform coefficients used for the residual sample.

[0139] The output bitstream may be stored in a (digital) storage medium and transmitted to a decoding device, or transmitted to a decoding device via a network.

[0140] At the same time, as described above, the encoding device can generate a reconstructed picture (including a reconstructed sample and a reconstructed block) based on the reference sample and the residual sample. This is to derive the same prediction result as the prediction result performed by the decoding device, and as a result, the coding efficiency can be improved. Therefore, the encoding device can store the reconstructed picture (or reconstructed sample or reconstructed block) in a memory and use the reconstructed picture as a reference picture. As described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0141] The video / image decoding process based on inter-frame prediction may schematically include, for example, the following contents.

[0142] Figure 8 An example of a video / image decoding method based on inter-frame prediction is illustrated.

[0143] Reference Figure 8 The decoding device may perform an operation corresponding to the operation performed by the encoding device. The decoding device may perform prediction on the current block based on the received prediction information and derive a prediction sample.

[0144] Specifically, the decoding apparatus may determine a prediction mode of the current block based on the received prediction information (S800). The decoding apparatus may determine which inter prediction mode to apply to the current block based on prediction mode information in the prediction information.

[0145] For example, it may be determined whether to apply the merge mode or (A)MVP mode to the current block based on the merge flag. Alternatively, one of various inter-frame prediction mode candidates may be selected based on the mode index. The inter-frame prediction mode candidate may include a skip mode, a merge mode, and / or an (A)MVP mode, or may include various inter-frame prediction modes described below.

[0146] The decoding device derives motion information of the current block based on the determined inter-frame prediction mode (S810). For example, when the skip mode or merge mode is applied to the current block, the decoding device may configure a merge candidate list to be described below, and select a merge candidate from among the merge candidates included in the merge candidate list. Here, the selection may be performed based on the 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.

[0147] As another example, when the (A)MVP mode is applied to the current block, the decoding device 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 the selection information (MVP flag or MVP index). In this case, the MVD of the current block may be derived based on the information about the MVD, and the motion vector of the current block may be derived based on the MVP and 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 referenced by the inter-frame prediction of the current block.

[0148] Meanwhile, as described below, the motion information of the current block may be derived without the candidate list configuration, 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.

[0149] The decoding device may generate a prediction sample for the current block based on the motion information of the current block (S820). In this case, a reference picture may be derived based on a reference picture index of the current block, and a prediction sample of the current block may be derived by using a sample of the reference block indicated by a motion vector of the current block on the reference picture. In this case, in some cases, a prediction sample filtering process for all or some prediction samples of the current block may be further performed.

[0150] For example, the inter-frame prediction unit of the decoding device may include a prediction mode determination unit, a motion information export unit and a prediction sample export unit, and the prediction mode determination unit can determine the prediction mode of the current block based on the received prediction mode information, the motion information export unit can export the motion information (motion vector and / or reference picture index) of the current block based on the information about the received motion information, and the prediction sample export unit can export the prediction sample of the current block.

[0151] The decoding device generates residual samples of the current block based on the received residual information (S830). The decoding device can generate reconstructed samples of the current block based on the predicted samples and the residual samples, and generate a reconstructed picture based on the generated reconstructed samples (S840). Thereafter, as described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0152] Fig. 9 The inter-frame prediction process is schematically illustrated.

[0153] refer to Fig. 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 processing (prediction sample generation) step based on the derived motion information. The inter-frame prediction process may be performed by the encoding device and the decoding device as described above. In this article, the coding device may include an encoding device and / or a decoding device.

[0154] Reference Fig. 9 , the coding device determines the inter prediction mode of the current block (S900). Various inter prediction modes can be used for the prediction of the current block in the picture. For example, various modes such as merge mode, skip mode, motion vector prediction (MVP) mode, affine mode, sub-block merge mode, merge with MVD (MMVD) mode and historical motion vector prediction (HMVP) mode can be used. Decoder-side motion vector refinement (DMVR) mode, adaptive motion vector resolution (AMVR) mode, dual prediction with CU-level weights (BCW) and bidirectional optical flow (BDOF) can be further used as additional modes. Affine mode can also be referred to as affine motion prediction mode. MVP mode can also be referred to as advanced motion vector prediction (AMVP) mode. In this article, some modes and / or motion information candidates derived from some modes can also be included in one of the motion information related candidates in other modes. For example, an HMVP candidate can be added to the merge candidate of the merge / skip mode, or to the MVP candidate of the MVP mode. If the HMVP candidate is used as a motion information candidate for a merge mode or a skip mode, the HMVP candidate may be referred to as an HMVP merge candidate.

[0155] Prediction mode information indicating the inter-frame prediction mode of the current block can be signaled from the encoding device to the decoding device. In this case, the prediction mode information can be included in the 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-frame 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 the skip mode is applied can be indicated by signaling a skip flag, when the skip mode is not applied, whether the merge mode is applied can be indicated by signaling a merge flag, and when the merge mode is not applied, the MVP mode is indicated to be applied or a flag for additional distinction can be further signaled. The affine mode can be signaled as an independent mode, or signaled as a subordinate mode with respect to the merge mode or the MVP mode. For example, the affine mode may include an affine merge mode and an affine MVP mode.

[0156] The coding apparatus derives motion information of a current block (S910). The motion information may be derived based on an inter prediction mode.

[0157] The coding device may use the motion information of the current block to perform inter-frame prediction. The coding device may derive the best motion information of the current block through a motion estimation process. For example, the coding device may search for a similar reference block with high correlation in units of fractional pixels within a predetermined search range in a reference picture by using an original block in an original picture of the current block, and derive motion information through the searched reference block. The similarity of the blocks may be derived based on the difference in sample values ​​based on the phase. For example, the similarity of the blocks may be calculated based on the sum of absolute differences (SAD) between the current block (or a template of the current block) and the reference block (or a template of the reference block). In this case, the motion information may be derived based on the reference block with the smallest SAD in the search area. The derived motion information may be signaled to the decoding device according to various methods based on the inter-frame prediction mode.

[0158] The coding apparatus performs inter prediction based on the motion information of the current block (S920). The coding apparatus may derive (one or more) prediction samples of the current block based on the motion information. The current block including the prediction samples may be referred to as a prediction block.

[0159] Meanwhile, as described above, the quantizer of the encoding device may derive quantized transform coefficients by applying quantization to the transform coefficients. The dequantizer of the encoding device or the dequantizer of the decoding device may derive transform coefficients by applying dequantization to the quantized transform coefficients.

[0160] Generally, in video / image coding, the quantization ratio can be changed, and the compression rate can be adjusted using the changed quantization ratio. In terms of implementation, a quantization parameter (QP) can be used by considering complexity instead of directly using the quantization ratio. For example, a quantization parameter having an integer value of 0 to 63 can be used, and each quantization parameter value can correspond to an actual quantization ratio. In addition, for example, the quantization parameter QP for the luminance component Y and the quantization parameter QP for the chroma components C Can be configured differently.

[0161] In the quantization process, the transform coefficient C can be input, and 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 multiplying the quantization ratio by the scale in consideration of computational complexity, the quantization ratio can be generated in an integer form, and the shift operation can be performed by 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 the 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 result of the application.

[0162] 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 transformation and / or quantization process, the reconstructed transform coefficient C`` may be slightly different from the first transform coefficient C. Therefore, dequantization is performed in the encoding device as in the decoding device.

[0163] At the same time, an adaptive frequency weighted quantization technique for adjusting the quantization strength according to the frequency may be applied. The adaptive frequency weighted quantization technique is a method of applying the quantization strength differently to each frequency. In the adaptive frequency weighted quantization, the quantization strength for each frequency may be applied differently using a predefined quantization scaling matrix. That is, the above-mentioned quantization / dequantization process may be performed based on the quantization scaling matrix. For example, in order to generate the size of the current block and / or the residual signal of the current block, different quantization scaling matrices may be used depending on whether the prediction mode applied to the current block is inter-frame prediction or intra-frame prediction. The quantization scaling matrix may be referred to as a quantization matrix or a scaling matrix. The quantization scaling matrix may be predefined. In addition, for frequency adaptive scaling, quantization scale information for each frequency of the quantization scaling matrix may be constructed / encoded in the encoding device, and signaled to the decoding device. The quantization scale information for each frequency may be referred to as quantization scaling information. The quantization scale information for each frequency may include scaling list data (scaling_list_data). The (modified) quantization scaling matrix may be derived based on the scaling list data. In addition, the quantization scale information for each frequency may include presence flag information indicating whether the scaling list data exists. Alternatively, if the scaling list data is signaled in a higher level (e.g., SPS), information indicating whether the scaling list data is modified in a lower level in the higher level (e.g., PPS or tile group header, etc.) may also be included.

[0164] As in the foregoing, quantization / dequantization may be applied to luma components and chroma components based on quantization parameters.

[0165] The quantization parameter for the coding unit may be determined based on information signaled in the picture and / or slice level. For example, the quantization parameter may be derived as described later.

[0166] For example, information related to the derivation of quantization parameters may be signaled through a sequence parameter set (SPS) as in the following table.

[0167] [Table 1]

[0168]

[0169] The semantics of the syntax elements in Table 1 may be the same as in the following table.

[0170] [Table 2]

[0171]

[0172] For example, the syntax element bit_depth_luma_minus8 can represent BitDepth YThat is, the bit depth of the samples in the brightness array, and QpBdOffset Y That is, the brightness quantization parameter range offset. That is, for example, the BitDepth can be derived based on the syntax element bit_depth_luma_minus8 Y and QpBdOffset Y For example, BitDepth Y It can be derived as the value obtained by adding 8 to the value of the syntax element bit_depth_luma_minus8. QpBdOffset Y It may be derived as a value obtained by multiplying the value of the syntax element bit_depth_luma_minus8 by 6. Furthermore, bit_depth_luma_minus8 may be in the range of 0 to 8.

[0173] In addition, for example, the syntax element bit_depth_chroma_minus8 can indicate BitDepth C That is, the bit depth of the samples of the chroma array, and QpBdOffset C That is, the chroma quantization parameter range offset. That is, for example, the 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 It can be derived as a value obtained by multiplying the value of the syntax element bit_depth_chroma_minus8 by 6. In addition, bit_depth_chroma_minus8 can be in the range of 0 to 8.

[0174] In addition, information related to the derivation of the quantization parameter may be signaled, for example, through a picture parameter set (PPS) as in the following table. The information may include chroma Cb offset, chroma Cr offset, joint chroma offset, and initial quantization parameter. That is, the information may include syntax elements for chroma Cb offset, chroma Cr offset, joint chroma offset, and initial quantization parameter.

[0175] [Table 3]

[0176]

[0177] The semantics of the syntax elements in Table 3 may be the same as in the following table.

[0178] [Table 4]

[0179]

[0180] For example, a value obtained by adding 26 to the syntax element init_qp_minus26 may represent the SliceQp value for each slice of the reference PPS. Y If a non-zero value of slice_qp_delta is decoded, SliceQp Y The initial value of can be modified in the slice layer. init_qp_minus26 0 can be in -(26+QpBdOffset Y ) to +37.

[0181] In addition, for example, the syntax elements pps_cb_qp_offset and pps_cr_qp_offset may indicate the syntax elements used to derive Qp′, respectively. Cb and Qp' Cr The brightness 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, pps_cb_qp_offset and pps_cr_qp_offset may not be used during decoding, and the decoding device may ignore the value of this syntax element.

[0182] In addition, for example, the syntax element pps_joint_cbcr_qp_offset may indicate the offset used to derive Qp' CbCr The brightness quantization parameter Qp' Y pps_joint_cbcr_qp_offset may be in the range of -12 to +12. In addition, when ChromaArrayType is 0, pps_joint_cbcr_qp_offset may not be used during decoding, and the decoding device may ignore the value of this syntax element.

[0183] Furthermore, for example, the syntax element pps_slice_chroma_qp_offsets_present_flag may 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, pps_slice_chroma_qp_offsets_present_flag having a value of 1 may 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. Furthermore, for example, pps_slice_chroma_qp_offsets_present_flag having a value of 0 may indicate that the syntax elements slice_cb_qp_offset and slice_cr_qp_offset do not exist in the slice header associated with the syntax elements slice_cb_qp_offset and slice_cr_qp_offset. Furthermore, when ChromaArrayType is 0, pps_slice_chroma_qp_offsets_present_flag may be the same as 0 during decoding.

[0184] As in the foregoing, the syntax elements parsed in the PPS may 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 may indicate the SliceQp for each slice of the referenced PPS. Y In addition, the syntax elements pps_cb_qp_offset, pps_cr_qp_offset, and pps_joint_cbcr_qp_offset may indicate the initial value of the quantization parameter Qp' for the brightness. Y In addition, the syntax element pps_slice_chroma_qp_offsets_present_flag may indicate whether the offset parameter is present in the slice header.

[0185] Furthermore, information related to the derivation of quantization parameters may be signaled through a slice header as in the following table, for example.

[0186] [Table 5]

[0187]

[0188] The semantics of the syntax elements in Table 5 may be the same as in the following table.

[0189] [Table 6]

[0190]

[0191]

[0192] For example, slice_qp_delta can represent the Qp to be used in the compilation block within the slice. Y The initial value of until it is modified by the value of CuQpDeltaVal at the compilation unit level. For example, Qp for a slice Y The initial value of SliceQp Y Can be exported as 26+init_qp_minus26+slice_qp_delta. The value of SliceQpY can be set in -QpBdOffset Y to a range of +63.

[0193] In addition, for example, slice_cb_qp_offset may indicate when determining the quantization parameter Qp' Cb The value of slice_cb_qp_offset is the difference to be added to the value of pps_cb_qp_offset. The value of slice_cb_qp_offset may be in the range of -12 to +12. Furthermore, for example, if slice_cb_qp_offset does not exist, slice_cb_qp_offset may be inferred to be 0. The value of pps_cb_qp_offset+slice_cb_qp_offset may be in the range of 12 to +12.

[0194] In addition, for example, slice_cr_qp_offset may indicate when determining the quantization parameter Qp' Cr The value of slice_cr_qp_offset is the difference to be added to the value of pps_cr_qp_offset. The value of slice_cr_qp_offset may be in the range of -12 to +12. Furthermore, for example, if slice_cr_qp_offset does not exist, slice_cr_qp_offset may be inferred to be 0. The value of pps_cr_qp_offset+slice_cr_qp_offset may be in the range of 12 to +12.

[0195] In addition, for example, slice_cbcr_qp_offset may indicate when determining the quantization parameter Qp' CbCr The value of slice_cbcr_qp_offset is the difference to be added to the value of pps_cbcr_qp_offset. The value of slice_cbcr_qp_offset may be in the range of -12 to +12. Also, for example, if slice_cbcr_qp_offset does not exist, slice_cbcr_qp_offset may be inferred to be 0. The value of pps_cbcr_qp_offset+slice_cbcr_qp_offset may be in the range of 12 to +12.

[0196] The derivation process for luma and chroma quantization parameters can be started based on the fact that the input of the process is the luma position, the parameters for specifying the width and height of the current coding block, and the parameters for specifying a single tree or a dual tree. Meanwhile, as in the foregoing, the luma quantization parameter, the chroma quantization parameter, and the joint chroma quantization parameter can be represented as Qp' Y , Qp' Cb , Qp' Cr and Qp' CbCr .

[0197] Meanwhile, for example, the syntax element cu_qp_delta_sign_flag indicating the sign of CuQpDeltaVal may be parsed. For example, cu_qp_delta_sign_flag may indicate the sign of CuQpDeltaVal as follows.

[0198] For example, when cu_qp_delta_sign_flag is 0, CuQpDeltaVal corresponding to cu_qp_delta_sign_flag may have a positive value. Alternatively, for example, when cu_qp_delta_sign_flag is 1, CuQpDeltaVal corresponding to cu_qp_delta_sign_flag may have a negative value. Furthermore, if cu_qp_delta_sign_flag is not present, cu_qp_delta_sign_flag may be inferred to be 0.

[0199] Furthermore, for example, if cu_qp_delta_abs is present, the parameter IsCuQpDeltaCoded may be derived as 1. The parameter CuQpDeltaVal may be derived as cu_qp_delta_abs*(1-2*cu_qp_delta_sign_flag). CuQpDeltaVal may be in the range of -(32+QpBdOffsetY / 2) to +(31+QpBdOffsetY / 2).

[0200] Thereafter, for example, the luminance quantization parameter Qp' Y It can be derived as follows.

[0201] [Equation 1]

[0202] Q Y =((qP Y_PRED +CuQpDeltaVal+64+2*QpBdOffset Y )%(64+QpBdOffset Y ))-QpBdOffset Y

[0203] Additionally, if ChromaArrayType is not 0 and treeType is SINGLE_TREE or DUAL_TREE_CHROMA, the following may apply.

[0204] -When treeType is equal to DUAL_TREE_CHROMA, parameter Qp Y The luma quantization parameter Qp of the luma coding unit including the luma position QpY(xCb+cbWidth / 2, yCb+cbHeight / 2) may be Y are set identically.

[0205] -Parameter qP Cb ,qP Cr and qP CbCr It can be exported as follows.

[0206] [Equation 2]

[0207] Q Cb =Clip3(-QpBdOffset C , 69, Qp Y +pps_cb_qp_offset+slice_cb_qp_offset)

[0208] Q Cr =Clip3(-QpBdOffset C , 69, QpY +pps_cr_qp_offset+slice_cr_qp_offset)

[0209] Q CbCr =Clip3(-QpBdOffsct C , 69, Qp Y +pps_joint_cbcr_qp_offsct+slicc_joint_cbcr_qp_offsct)

[0210] For example, when ChromaArrayType is 1, the parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is set identically to the QpC value specified in Table 7.

[0211] [Table 7]

[0212] Q ＜30 30 31 32 33 34 35 36 37 38 39 40 41 42 43 ＞43 <![CDATA[Qp C ]]> =aPi 29 30 31 32 33 33 34 34 35 35 36 36 37 37 =aPi-6

[0213] Alternatively, when ChromaArrayType is not 1, the parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbC The same index qPi is set identically to Min(qPi, 63).

[0214] The chromaticity quantization parameter Qp' for the Cb component and the Cr component can be derived as follows Cb and Qp' Cr , and the chrominance quantization parameter Qp' for joint Cb-Cr coding CbCr .

[0215] [Equation 3]

[0216] Qp′ Cb =qP Cb +QpBdOffset C

[0217] Qp′ Cr =qP Cr +QpBdOffset C

[0218] QP′ CbCr =qP CbCr+QpBdOffset C

[0219] At the same time, the document proposes a solution for improving the coding efficiency in the quantization / dequantization process.

[0220] In an embodiment, the present document proposes a method of defining and using a user-defined chrominance quantization mapping table, instead of a method of obtaining a chrominance quantization parameter value from a luma quantization parameter value through a chrominance quantization mapping table predefined in the existing VVCDraft5 v.7 when ChromaArrayType is not 0 (for example, when ChromaArrayType is 1). In the VVC specification text (for example, VVC Draft5 v.7), when qPi (luma quantization parameter value) is given, Qpc (chrominance quantization parameter value) is derived through a predefined chrominance quantization table (for example, Table 7), but the document proposes a method of deriving Qpc from qPi based on a user-defined chrominance quantization mapping table. According to an embodiment of the present document, a method is proposed in which a Qpc value can be derived through a function relationship of a qPi value, the function can be signaled as a syntax such as APS, SPS, or PPS through a user-defined function method, the function relationship sends a value of a predefined syntax element, and the user defines a chrominance quantization table mapping based on the sent value. For example, since the Qpc value can be derived through a functional relationship of the qPi value, if a syntax element value representing the corresponding function is sent, the user-defined chrominance quantization mapping table can be derived in a form such as Table 7.

[0221] In an embodiment, a scheme for signaling information about a syntax element (Qpc_data) in an adaptive parameter set (APS) representing a function related to chrominance quantization mapping as in the following table to be described later is proposed.

[0222] [Table 8]

[0223]

[0224] Referring to Table 8, if aps_params_type indicates Qpc_APS, for example, when the value of aps_params_type is 2, Qpc_data() may be signaled.

[0225] The semantics of the syntax elements in Table 8 may be the same as in the following table.

[0226] [Table 9]

[0227]

[0228] For example, the syntax element adaptation_parameter_set_id may provide an identifier of an APS referenced by other syntax elements.

[0229] 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 having 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 having a value of 0 may indicate that the aps_extension_data_flag syntax element is not present in the APS RBSP syntax structure.

[0230] Furthermore, 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 suitability of the profile specified in the version of this standard. For example, a decoding device conforming to the version of this standard may ignore all syntax elements aps_extension_data_flag.

[0231] 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.

[0232] [Table 10]

[0233]

[0234] 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 the 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 the 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 the APS parameter is a Qpc data parameter. The Qpc data parameter may indicate a chroma quantization data parameter.

[0235] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0236] For example, this embodiment proposes a method for signaling a user-defined Qp in a picture parameter set (PPS). C As an example for executing the scheme proposed in the present embodiment, a flag indicating whether the PPS includes the user-defined data in the SPS may be introduced. That is, a flag indicating whether the PPS includes the user-defined data in the SPS may be signaled. In addition, according to the present embodiment, the user-defined data may be signaled in the PPS. Alternatively, the user-defined data may be signaled in a slice header and / or another header set.

[0237] A flag indicating whether the PPS includes user-defined data may be signaled as shown in the following table.

[0238] [Table 11]

[0239]

[0240] For example, the syntax element Qpc_data_default_flag may be a syntax element of the aforementioned flag. The syntax element Qpc_data_default_flag may indicate whether the Qpc_data() parameter is present in the PPS RBSP syntax structure. For example, Qpc_data_default_flag being 0 may indicate that the Qpc_data() parameter is not present in the PPS RBSP syntax structure, and the default table is used to assist in the determination of the chrominance quantization. In this case, the default table may be the same as Table 7, and further, for example, Qpc_data_default_flag being 1 may indicate that the Qpc_data() parameter may be present in the PPS RBSP syntax structure.

[0241] Furthermore, user-defined data signaled in the PPS according to the present embodiment may be the same as the following table.

[0242] [Table 12]

[0243]

[0244] Meanwhile, for example, Qpc_data() may include information required for chroma quantization derivation when ChromaArrayType is 1.

[0245] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0246] For example, the present embodiment proposes a flexible structure for chroma quantization parameter (QP) derivation and combined chroma QP derivation. The present embodiment proposes a scheme for signaling an initial flag indicating whether there is a user-defined mode in which parameters representing a function for deriving chroma quantization parameters (QP) in SPS and / or PPS can be used.

[0247] For example, the flag information signaled in the high-level syntax proposed in the present embodiment may be the same as a table described later.

[0248] [Table 13]

[0249]

[0250] For example, Qpc_data_present_flag may indicate whether the parameters for deriving the chrominance quantization parameters are present in the high-level syntax RBSP syntax structure. For example, Qpc_data_present_flag having a value of 0 may indicate that the chrominance quantization parameters are not present in the high-level syntax RBSP syntax structure. In addition, for example, Qpc_data_present_flag having a value of 1 may indicate that the chrominance quantization parameters are present in the high-level syntax RBSP syntax structure.

[0251] Alternatively, the syntax element Qpc_data_present_flag may be used in the bitstream to indicate the scheme of using chroma quantization derivation.For example, the syntax element Qpc_data_present_flag may indicate the tool used for chroma quantization derivation or the use of a user-defined mode as follows.

[0252] For example, Qpc_data_present_flag may indicate whether user-defined chroma quantization is used in the bitstream. For example, Qpc_data_present_flag with a value of 0 may indicate that user-defined chroma quantization is not used in the bitstream. In addition, for example, Qpc_data_present_flag with a value of 1 may indicate that user-defined chroma quantization is used alone or in conjunction with another flag.

[0253] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0254] For example, this embodiment proposes how to derive the chrominance quantization parameter (QP) (i.e., Qp`) using user-defined information signaled in a function Cb , Qp` Cr and Qp` CbCr) embodiment. For example, according to the present embodiment, data representing a function for deriving a chromaticity quantization parameter (QP) may be signaled, and the chromaticity quantization parameter may be derived based on the chromaticity quantization data. The data for chromaticity quantization parameter derivation (or a user-defined QP mapping table) may be signaled as in the following table.

[0255] [Table 14]

[0256]

[0257] The semantics of the syntax elements in Table 14 may be the same as in the following table.

[0258] [Table 15]

[0259]

[0260] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization.

[0261] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx. c The increment value between the maximum qPi indices used in the export. The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. For example, QPi c The maximum index qPiMaxIdx used in the derivation can be derived as in the following equation.

[0262] [Equation 4]

[0263] qPiMaxIdx=qPi_min_idx+qPi_delta_max_idx

[0264] Furthermore, for example, the syntax element Qp C _qPi_val[i] can represent the Qp for the i-th index C value.

[0265] Furthermore, for example, the syntax element QpOffset C It can be expressed as the value used to derive Qp C The offset value of .

[0266] Furthermore, for example, the parameter Qp for qPi C Idx[qPi] can be derived as follows. In this case, qPi can be 0 to qPiMaxIdx.

[0267] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set to be the same as qPi.

[0268] - When qPi = qPi_min_idx ... qPiMaxIdx, Qp C Idx[qPi] can be combined with Qp C _qPi_val[qPi] is set identically.

[0269] -When qPi>qPiMaxIdx, Qp C Idx[qPi] can be set to qPi-QpOffset C .

[0270] After that, Qp C The value of Qp can be derived as C Idx[qPi].

[0271] For example, according to the present embodiment, if the process of deriving the quantization parameter is described in a standard format, the process may be as shown in the following table.

[0272] [Table 16]

[0273]

[0274]

[0275]

[0276]

[0277]

[0278]

[0279] Referring to Table 16, the derivation process for luma and chroma quantization parameters can be started based on the fact that the input for the process is the luma 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 in the foregoing, the luma quantization parameter and the chroma quantization parameter can be expressed as Qp' Y , Qp' Cb and Qp' Cr .

[0280] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0281] For example, the present embodiment proposes an example in which a user-defined mode or a default mode is provided as a flag within the SPS, thereby using an example of a syntax element that can be used to control the derivation of a quantization parameter. An example of a syntax element that can be used to derive a quantization parameter can be the same as the following table. At the same time, the structure of the syntax element is not limited to the structure illustrated in the following table, for example.

[0282] [Table 17]

[0283]

[0284] [Table 18]

[0285]

[0286] [Table 19]

[0287]

[0288] For example, the syntax element Qpc_data_default_flag may indicate whether a user-defined mode is used to derive a quantization parameter. For example, a Qpc_data_default_flag having a value of 0 may indicate that a user-defined mode is used to derive a quantization parameter. In addition, for example, a Qpc_data_default_flag having a value of 1 may indicate that a default table is used to derive a chrominance quantization parameter. In this case, the default table may be the same as Table 7. In addition, if the syntax element Qpc_data_default_flag does not exist, the syntax element Qpc_data_default_flag may be inferred to be 1.

[0289] Meanwhile, if the user-defined mode is used, the corresponding slice header, tile group / header or another appropriate header may be used to signal the APS ID. For example, as shown in Table 18, the syntax element representing the APS ID may be signaled through the slice header.

[0290] For example, the syntax element slice_Qp c _aps_id can indicate the Qp referenced by the slice c APS adaptation_parameter_set_id. c _aps_id) c The TemporalId of the APS NAL unit may be less than or equal to the TemporalId of the coded slice NAL unit. cIf an APS is referenced by two or more slices of the same picture, multiple Qp c APS may have the same content.

[0291] In addition, the APS structure for transmitting chromaticity quantization data proposed in this embodiment can be the same as Table 19.

[0292] For example, the syntax element adaptation_parameter_set_id may provide an identifier of an APS referenced by other syntax elements.

[0293] 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 having 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 having a value of 0 may indicate that the aps_extension_data_flag syntax element is not present in the APS RBSP syntax structure.

[0294] Furthermore, 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 suitability of the profile specified in the version of this standard. For example, a decoding device conforming to the version of this standard may ignore all syntax elements aps_extension_data_flag.

[0295] 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.

[0296] Qpc_data() disclosed in Table 19 may be signaled as shown below.

[0297] [Table 20]

[0298]

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

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

[0301] Furthermore, for example, by adding 1 to the syntax element Qp c The value obtained by _prec_minus1 can represent the number of bits used to represent the syntax lmcs_delta_abs_cw[i]. c _prec_minus1 can have a value between 0 and BitDepth Y In the range of -2.

[0302] Furthermore, for example, the syntax element Qp c _init_val can represent the Qp corresponding to qPi_min_idx C value.

[0303] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th index C The increment of the value.

[0304] Furthermore, for example, the syntax element QpOffset C It can be expressed as the value used to derive Qp c The offset value of .

[0305] For example, the parameter Qp for qPi C Idx[qPi] can be derived as follows. In this case, qPi can be 0 to qPiMaxIdx.

[0306] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set to be the same as qPi.

[0307] - 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].

[0308] -When qPi>qPiMaxIdx, Qp CIdx[qPi] can be set to qPi-QpOffset C .

[0309] After that, Qp C The value of Qp can be derived as C Idx[qPi].

[0310] As in the aforementioned embodiments, the chromaticity quantization parameters, ie, Qp′, may be derived using signaled user-defined information or default values ​​illustrated in a default table such as Table 7. Cb , Qp' Cr and Qp' CbCr .

[0311] For example, in this embodiment, if the process of deriving the quantization parameter is written in a standard format, the process can be expressed as in the following table.

[0312] [Table 21]

[0313]

[0314]

[0315]

[0316]

[0317]

[0318]

[0319]

[0320] 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), parameter qP Cb ,qP Cr and qP CbCr It can be derived based on the signaled user-defined information as proposed in this embodiment. c _data_default_flag indicates true (i.e., for example, when Qp c _data_default_flag is 1), parameter qP Cb ,qP Cr and qP CbCr can be based on the same index qPiCb ,qPi Cr and qPi CbCr Exported from the default table.

[0321] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0322] For example, the present embodiment proposes a syntax element that can be used to control the derivation of a quantization parameter by indicating a user-defined mode or a default mode via a flag of an SPS. Specifically, the present embodiment proposes a scheme for signaling a syntax element of 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.

[0323] [Table 22]

[0324]

[0325] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization.

[0326] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx. c The increment value between the maximum qPi indices used in the export. The value of qPiMaxIdx can be greater than or equal to qPi_min_idx. For example, QPi c The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0327] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th index C The increment of the value.

[0328] Furthermore, for example, the syntax element QpOffset C It can be expressed in Qp c The offset value used in the derivation of , such as the aforementioned.

[0329] As in the previous embodiments, the chromaticity quantization parameters, i.e., Qp′, may be derived using signaled user-defined information or default values ​​used in a default table such as Table 7. Cb , Qp' Cr and Qp' CbCr .

[0330] For example, in this embodiment, if the process of deriving quantization parameters is written in a standard format, the process can be expressed as in the following table.

[0331] [Table 23]

[0332]

[0333]

[0334]

[0335]

[0336]

[0337]

[0338]

[0339]

[0340] Refer 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), parameter qP Cb ,qP Cr and qP CbCr It can be derived based on the user-defined information signaled 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi and value Qp C Export the same as below.

[0341] For example, the parameter Qp C Idx[i] can be derived as follows.

[0342] -When i<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0343] - 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].

[0344] -When i>qPiMaxIdx, Qp C Idx[i] can be set to qPi-QpOffset C .

[0345] After that, Qp C Can be set to Qp C Idx[i].

[0346] 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is derived by the default table.

[0347] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0348] For example, this embodiment proposes a chromaticity quantization (Qp C ) syntax elements for deriving parameters. For example, the APS ID may be signaled in the slice header. In addition, for example, a flag may be raised in the picture parameter set (PPS) indicating whether to use a default table or a table derived from information signaled in the APS. In addition, for example, if the default table is not used, the syntax element for supporting Qp C An additional control scheme for access of APS data is added to the slice header.

[0349] Meanwhile, according to existing video / image standards, chroma QP can be derived from luma QP and can be updated by additionally signaling a chroma QP offset. C The table may be a default table such as Table 7.

[0350] This embodiment proposes to add a chromaticity quantization parameter Qp for signaling as a function of the index qPi C APS can be used to integrate Qp C The signaling scheme of the value.

[0351] For example, the APS according to the present embodiment may be the same as the following table.

[0352] [Table 24]

[0353]

[0354] For example, the syntax element adaptation_parameter_set_id may provide an identifier of an APS referenced by other syntax elements.

[0355] 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.

[0356] 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 having 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 having a value of 0 may indicate that the aps_extension_data_flag syntax element is not present in the APS RBSP syntax structure.

[0357] Furthermore, 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 suitability of the profile specified in the version of this standard. For example, a decoding device conforming to the version of this standard may ignore all syntax elements aps_extension_data_flag.

[0358] Qp disclosed in Table 24 c _data() can signal as shown in the following table.

[0359] [Table 25]

[0360]

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

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

[0363] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th index C The difference between the values. This difference can also be called the delta.

[0364] Furthermore, for example, the syntax element Qp C Offset C _present_flag can indicate QpOffset C Is present in the bitstream? For example, a Qp with a value of 1 C Offset C _present_flag can indicate QpOffset C is present in the bitstream. In addition, for example, Qp with a value of 0 C Offset C _present_flag can indicate QpOffset C does not exist in the bitstream. C Offset C When _present_flag does not exist, Qp C Offset C _present_flag can be inferred to be 0.

[0365] Furthermore, for example, the syntax element QpOffset C It can be expressed as Qp c The offset value used in the export of .

[0366] For example, the parameter Qp of qPi C Idx[qPi] can be derived as follows. In this case, qPi can be 0 to 63.

[0367] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0368] - 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].

[0369] - If qPi>qPiMaxIdx, then when Qp C Offset C When _present_flag is 1, Qp C Idx[qPi] can be set to qPi-QpOffset C If Qp C Offset C _present_flag is not 1, that is, if Qp C Offset C _present_flag is 0, then Qp C Idx[qPi] can be set to qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0370] After that, Qp C The value of Qp can be derived as C Idx[qPi].

[0371] In addition, this embodiment proposes signaling as shown in the following table as a sign of PPS.

[0372] [Table 26]

[0373]

[0374] For example, the syntax element Qp c _data_default_flag may indicate whether a user-defined mode is used for quantization parameter derivation. For example, Qp with a value of 0 c _data_default_flag may indicate a user-defined mode for quantization parameter derivation. In addition, for example, Qp with a value of 1 c _data_default_flag may indicate that the above default table is used for quantization parameter derivation. The default table may be the same as Table 7. If Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred to be 1.

[0375] In addition, this embodiment proposes signaling as a syntax element of a slice header as shown in the following table.

[0376] [Table 27]

[0377]

[0378] For example, the syntax element slice_Qp c _aps_id can represent the Qp referenced by the slice c APS adaptation_parameter_set_id. c _aps_id) c The TemporalId of the APS NAL unit may be less than or the same as the TemporalId of the coded slice NAL unit. c If an APS is referenced by two or more slices of the same picture, multiple Qp c APS may have the same content.

[0379] For example, in this embodiment, if the process of deriving the quantization parameter is written in a standard format, the process can be expressed as in the following table.

[0380] [Table 28]

[0381]

[0382]

[0383]

[0384]

[0385]

[0386]

[0387]

[0388] 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), parameter qP Cb ,qP Cr and qP CbCrIt 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is exported via the default table.

[0389] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0390] For example, in this embodiment, it is proposed to signal a user-defined derivation of the chromaticity quantization in the SPS as follows. C ). For example, a flag of the SPS may indicate whether a default table is used for colorimetric quantization derivation or the contents of a table used for colorimetric quantization derivation are derived in information signaled in the SPS.

[0391] For example, this embodiment proposes a scheme for performing chroma quantization according to the index qPi by using the syntax elements shown in the following table.

[0392] [Table 29]

[0393]

[0394] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx may be in the range of 0 to 63.

[0395] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx. c The delta value between the maximum qPi indices used in the 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 Qp c The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0396] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th indexC The increment of the value.

[0397] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0398] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi

[0399] - 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].

[0400] -When qPi>qPiMaxIdx, Qp C Idx[qPi] can be set to qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0401] After that, Qp C Can be set to Qp C Idx[qPi].

[0402] In addition, the flag of the SPS indicating whether the default table is used for chromaticity quantization derivation or whether the signaled information is used for chromaticity quantization derivation proposed in the present embodiment may be the same as the following table.

[0403] [Table 30]

[0404]

[0405] For example, the syntax element Qp c _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, Qp with a value of 0 c _data_default_flag may indicate that a user-defined mode is used to derive quantization parameters. In addition, for example, a Qp with a value of 1 c _data_default_flag may indicate that the default table is used to derive the quantization parameters. The default table may be the same as Table 7, except that if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred to be 1.

[0406] For example, according to the present embodiment, if the process of deriving the quantization parameter is written in a standard format, the process can be represented as in the following table.

[0407] [Table 31]

[0408]

[0409]

[0410]

[0411]

[0412]

[0413]

[0414]

[0415]

[0416] Referring to Table 31, when ChromaArrayType is 1 and Qp c _data_default_flag indicates false (i.e., for example, when Qp c _data_default_flag is 0), parameter qP Cb ,qP Cr and qP CbCr It 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is exported via the default table.

[0417] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0418] For example, this embodiment proposes to add a chrominance quantization parameter Qp for signaling as a function of the index qPi CFor example, a scheme for signaling a syntax element of a user-defined table for quantization parameter derivation in a PPS may be proposed. Thus, flexibility may be provided with respect to changing the user-defined table and the default table in each picture of the reference PPS.

[0419] The syntax elements of the user-defined table used for signaling in the PPS proposed in this embodiment may be the same as the following table.

[0420] [Table 32]

[0421]

[0422] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx may be in the range of 0 to 63.

[0423] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx. c The delta value between the maximum qPi indices used in the 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 Qp c The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0424] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th index C The increment of the value.

[0425] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0426] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0427] - 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].

[0428] -When qPi>qPiMaxIdx, Qp C Idx[qPi] can be set to qPi-(qPiMaxIdx-QpC Idx[qPiMaxIdx]).

[0429] After that, Qp C Can be set to Qp C Idx[qPi].

[0430] In addition, the flag of the SPS indicating whether the default table is used for chromaticity quantization derivation or whether the signaled information is used for chromaticity quantization derivation proposed in the present embodiment may be the same as the following table.

[0431] [Table 33]

[0432]

[0433] For example, the syntax element Qp c _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, Qp with a value of 0 c _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp with a value of 0 c _data_default_flag can indicate the use of chrominance quantization parameter data Qp c _data(). When Qp c When _data_default_flag is 0, the chrominance quantization parameter data Qp can be signaled c _data(). In addition, for example, Qp with value 1 c _data_default_flag may indicate that the default table is used to derive the quantization parameter. The default table may be the same as Table 7. In addition, if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred to be 1.

[0434] For example, in this embodiment, if the process of deriving the quantization parameter is written in a standard format, the process can be expressed as in the following table.

[0435] [Table 34]

[0436]

[0437]

[0438]

[0439]

[0440]

[0441]

[0442]

[0443] 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), parameter 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is derived from the default table.

[0444] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0445] For example, this embodiment proposes a method in which the chrominance quantization parameter Qp is derived and signaled. C Normal mode.

[0446] The chromaticity quantization parameter data Qp for the chromaticity quantization parameter proposed in this embodiment is c _data() can signal as shown in the following table.

[0447] [Table 35]

[0448]

[0449] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx may be in the range of 0 to 63.

[0450] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx.c The delta value between the maximum qPi indices used in the 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 Qp c The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0451] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th index C The increment of the value.

[0452] For example, the parameter Qp C Idx[qPi] can be derived as follows.

[0453] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0454] - 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].

[0455] -When qPi>qPiMaxIdx, Qp C Idx[qPi] can be set to qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0456] After that, Qp C Can be set to Qp C Idx[qPi].

[0457] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chroma quantization derivation or whether the signaled information is used for chroma quantization derivation. The flag may be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax may be the same as the following table.

[0458] [Table 36]

[0459]

[0460] For example, the syntax element Qp c_data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, Qp with a value of 0 c _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp with a value of 0 c _data_default_flag can indicate the use of chrominance quantization parameter data Qp c _data(). When Qp c When _data_default_flag is 0, the chrominance quantization parameter data Qp can be signaled c _data(). In addition, for example, Qp with value 1 c _data_default_flag may indicate that the default table is used to derive the quantization parameters. The default table may be the same as Table 7, except that if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred to be 1.

[0461] For example, in this embodiment, if the process of deriving the quantization parameter is written in a standard format, the process can be expressed as in the following table.

[0462] [Table 37]

[0463]

[0464]

[0465]

[0466]

[0467]

[0468]

[0469]

[0470] Refer 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), parameter qP Cb ,qP Cr and qP CbCrIt 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is exported by the default table.

[0471] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0472] For example, this embodiment proposes a method for deriving a color quantization parameter Qp without offset. C The scheme of the table. This embodiment can be proposed to be used with APS or used independently. For example, the syntax structure of APS integrated with colorimetric quantization data can be the same as the following table.

[0473] [Table 38]

[0474]

[0475] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx may be in the range of 0 to 63.

[0476] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx. c The delta value between the maximum qPi indices used in the 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 Qp c The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0477] Furthermore, for example, the syntax element Qp C _qPi_delta_val[i] can represent the Qp of the i-th index C The difference between the values. This difference can also be called the delta.

[0478] For example, the parameter Qp CIdx[qPi] can be derived as follows. In this case, qPi can be 0 to 63.

[0479] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0480] - 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].

[0481] -When qPi>qPiMaxIdx, Qp C Idx[qPi] can be set to qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0482] After that, Qp C Can be set to Qp C Idx[qPi].

[0483] Furthermore, this document proposes another embodiment in which information for quantization parameters is signaled.

[0484] For example, this embodiment proposes a method in which the continuous Qp C A scheme in which the increment (or difference) between values ​​is limited to 1 is taken as an example.

[0485] For example, this embodiment proposes a method in which the user defines the chromaticity quantization (Qp C ) is additionally included in the existing image / video standard. For example, a flag of a sequence parameter set (SPS) proposed in this embodiment can indicate whether an existing default table is used for chroma quantization parameter derivation or whether the content of the table is derived based on information signaled in the SPS. According to this embodiment, a scheme suitable for coding an image can be selected by adapting to user-defined chroma quantization, and coding efficiency can be improved.

[0486] For example, this embodiment proposes to add a chrominance quantization Qp for signaling as a function of the index qPi by using the syntax elements in the following table: C function.

[0487] [Table 39]

[0488]

[0489] For example, the syntax element qPi_min_idx may represent the minimum qPi index used in chroma quantization. The value of qPi_min_idx may be in the range of 1 to 63.

[0490] In addition, for example, the syntax element qPi_delta_max_idx can represent Qpi_min_idx and chroma Qpi_delta_max_idx. c The delta value between the maximum qPi indices used in the 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, in Qp c The maximum index qPiMaxIdx used in the derivation can be derived as in Equation 4.

[0491] In addition, for example, the syntax element QpC_qPi_flag[i] may indicate Qp C Whether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate the i-th Qp C Value and (i-1)th Qp C The value is increased by 1. For example, QpC_qPi_flag[i] with a value of 1 can indicate that Qp C The value increases by 1. QpC_qPi_flag[i] with a value of 0 may indicate that Qp C The value does not increase.

[0492] For example, the parameter Qp C Idx[qPi] can be derived as follows. In this case, qPi can be 0 to 63.

[0493] -When qPi<qPi_min_idx, Qp C Idx[qPi] can be set the same as qPi.

[0494] - When qPi = qPi_min_idx ... qPiMaxIdx, Qp C Idx[qPi] can be set to Qp C _qPi_flag[qPi]+Qp C Idx[qPi-1].

[0495] -When qPi>qPiMaxIdx, Qp C Idx[qPi] can be set to qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0496] After that, Qp C Can be set to QpC Idx[qPi].

[0497] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chroma quantization derivation or whether the signaled information is used for chroma quantization derivation. The flag may be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax may be the same as the following table.

[0498] [Table 40]

[0499]

[0500] For example, the syntax element Qp c _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, Qp with a value of 0 c _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp with a value of 0 c _data_default_flag can indicate the use of chrominance quantization parameter data Qp c _data(). When Qp c When _data_default_flag is 0, the chrominance quantization parameter data Qp can be signaled c _data(). In addition, for example, Qp with value 1 c _data_default_flag may indicate that the default table is used to derive the quantization parameters. The default table may be the same as Table 7. In addition, if Qp c _data_default_flag does not exist, then Qp c _data_default_flag can be inferred to be 1.

[0501] For example, in this embodiment, if the process of deriving quantization parameters is written in a standard format, the process can be expressed as in the following table.

[0502] [Table 41]

[0503]

[0504]

[0505]

[0506]

[0507]

[0508]

[0509]

[0510]

[0511] 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), parameter qP Cb ,qP Cr and qP CbCr It 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), parameter qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is exported via the default table.

[0512] Furthermore, the present disclosure proposes another embodiment for signaling information about a quantization parameter.

[0513] 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 SPS. For example, if the chroma_qp_mapping_flag value is 0, the default chroma QP mapping table can be used to derive the chroma quantization parameters. In addition, for example, if the chroma_qp_mapping_flag value is 1, the syntax element for deriving the chroma QP mapping table can be signaled as in the following table.

[0514] [Table 42]

[0515]

[0516] 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 value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag may indicate that the chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 42 as described above is used to derive the chroma quantization parameters. C _data_default_flag is 0, the chrominance quantization parameter data shown in Table 42 as described above may be signaled. In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be the same as the default table 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.

[0517] Furthermore, for example, a value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 may represent the number of points to which the mapping function does not increase.

[0518] Furthermore, for example, the syntax element qPi_min_idx_minus1 may represent the first element of a set of points for which the mapping function is not increased.

[0519] Furthermore, for example, the syntax element Qp C _qPi_flag[i] may represent the incremental value between the i-th element and the (i-1)-th element of the point set that is not added by the mapping function.

[0520] The chroma QP mapping table can be derived based on the chroma quantization parameter data shown in Table 42 as follows.

[0521] For example, the variable cQpFatSize may be derived as in the following equation.

[0522] [Equation 5]

[0523] cQpFlatSize=qPi_delta_max_idx_minus1+1

[0524] In addition, for example, the variable cQpFlat[] can be derived as shown in the following table.

[0525] [Table 43]

[0526]

[0527] Thereafter, based on the variable cQpFlatSize and the variable cQpFlat[], the chroma QP mapping table can be derived as shown in the following table.

[0528] [Table 44]

[0529]

[0530] Furthermore, the present disclosure proposes another embodiment for signaling information about a quantization parameter.

[0531] For example, this embodiment proposes a scheme for adding chroma_qp_mapping_flag as a new syntax element in SPS. For example, if the chroma_qp_mapping_flag value is 0, the default chroma QP mapping table can be used to derive the chroma quantization parameters. In addition, for example, if the chroma_qp_mapping_flag value is 1, the syntax element for deriving the chroma QP mapping table can be signaled as in the following table.

[0532] [Table 45]

[0533]

[0534] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag may indicate that the chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 42 as described above is used to derive the chroma quantization parameters. C _data_default_flag is 0, the chrominance quantization parameter data shown in Table 42 as described above may be signaled. In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as shown in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred to be 1.

[0535] Furthermore, for example, a value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 may represent the number of points to which the mapping function does not increase.

[0536] Furthermore, for example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1 may represent the first element of a point set to which the mapping table is not added.

[0537] Furthermore, for example, by adding 1 to the syntax element Qp C The value obtained by _qPi_idx_minus1[i] can represent the incremental value between the i-th element and the (i-1)-th element of the point set that is not increased by the mapping function.

[0538] The chroma QP mapping table can be derived based on the chroma quantization parameter data shown in Table 45 as follows.

[0539] For example, the variable cQpFlatSize may be derived as in Equation 5 as described above.

[0540] In addition, for example, the variable cQpFlat[] can be derived as shown in the following table.

[0541] [Table 46]

[0542]

[0543] Thereafter, based on the variable cQpFlatSize and the variable cQpFlat[], the chroma QP mapping table may be derived. For example, the chroma QP mapping table may be derived as in Table 44 as described above.

[0544] Furthermore, the present disclosure proposes another embodiment for signaling information about a quantization parameter.

[0545] For example, the present embodiment proposes a scheme for signaling a separate table for each chroma component. That is, for example, the present embodiment proposes a scheme for signaling a syntax element for deriving a chroma QP mapping table for a corresponding chroma component.

[0546] For example, a chroma QP mapping table for corresponding chroma components may be derived, and syntax elements for the corresponding chroma components may be signaled as in the following table.

[0547] [Table 47]

[0548]

[0549] For example, the syntax element qp_luma_to_chroma_joint_map_flag may indicate whether a common luminance-chrominance quantization parameter mapping table is used for the chrominance components Cb, Cr, and CbCr. That is, for example, the syntax element qp_luma_to_chroma_joint_map_flag may indicate whether one luminance-chrominance quantization parameter mapping table is applied to the Cb residual, the Cr residual, and the CbCr residual. For example, if the value of qp_luma_to_chroma_joint_map_flag is 1, a common luminance-chrominance quantization parameter mapping table may be used for the chrominance components Cb, Cr, and CbCr, and if the value of qp_luma_to_chroma_joint_map_flag is 0, a separate luminance-chrominance quantization parameter mapping table may be used for each of the chrominance components Cb, Cr, and CbCr.

[0550] In addition, for example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1 may represent the minimum qPi index used for chroma quantization. The qPi_min_idx_minus1 value may be in the range of 1 to 63.

[0551] In addition, for example, a value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 may indicate that Qpi_min_idx is equal to the value for chroma Qpi_delta_max_idx_minus1. C The delta value between the derived maximum qPi indices. 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. C The derived maximum index qPiMaxIdx may be derived as in the following equation.

[0552] [Equation 6]

[0553] for(i=0;i<3;i++){

[0554] qPiMaxIdx[i]=qPi_min_idx_minus1[i]+1+qPi_delta_max_idx_minus1[i]+1 In addition, for example, the syntax element Qp C _qPi_flag[j] can represent Qp C Whether the value is increased by 1, that is, for example, the syntax element QpC_qPi_flag[i][j] can indicate the jth Qp value of the i-th chrominance component. C Value and (j-1)th Qp CThe value is increased by 1. For example, QpC_qPi_flag[j] equal to 1 can indicate that Qp C The value increases by 1, and QpC_qPi_flag[j] equal to 0 can indicate that Qp C The value does not increase.

[0555] For example, the variable Qp C Idx[i][qPi] can be derived as follows: Here, in the case where the value is 0, qPi can be maxQp.

[0556] - In the case of qPi<qPi_min_idx_minus1+1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0557] - In the case of qPi = qPi_min_idx_minus1+1…qPiMaxIdx, Qp C Idx[qPi] can be configured as QpC_qPi_flag[qPi]+Qp C Idx[qPi-1].

[0558] - In the case of qPi>qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0559] After that, Qp C The value can be derived as QpCIdx[i][qPi].

[0560] Meanwhile, according to the present embodiment, a flag indicating whether to signal a syntax element for deriving a chroma QP mapping table in an SPS or to use a default table may be signaled. For example, the flag may be signaled as shown in the following table.

[0561] [Table 48]

[0562]

[0563] Syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C_data_default_flag may 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. C _data_default_flag is 0, the chrominance quantization parameter data shown in Table 47 as described above may be signaled. In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be the same as the default table 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.

[0564] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0565] [Table 49]

[0566]

[0567]

[0568]

[0569]

[0570]

[0571]

[0572]

[0573]

[0574] 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 variable qP Cb ,qP Cr and qP CbCr can be derived based on the signaled user-defined information as proposed in this embodiment. In addition, for example, if ChromaArrayType is 1 and Qp C _data_default_flag indicates true (for example, if QpC _data_default_flag is 1), then the variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi, exported by the default table.

[0575] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. This embodiment proposes a scheme for signaling the maximum difference between the start point and the end point by signaling the end point as an increment for the maximum QP. That is, for example, according to this embodiment, it is possible to signal the maximum difference between the start point and the end point for deriving the chrominance QP. C The syntax element that contains the delta value between maxQp and the maximum qPi index.

[0576] The chromaticity quantization parameter data Qp for the chromaticity quantization parameter proposed in this embodiment may be signaled as in the following table: C _data().

[0577] [Table 50]

[0578]

[0579] For example, the syntax element qPi_min_idx may represent the minimum qPi index for chroma quantization. The qPi_min_idx value may be in the range of 0 to 63.

[0580] In addition, for example, the syntax element qPi_delta_max_idx may indicate the difference between maxQp and the value used to derive chroma Qp. C The delta value between the maximum qPi index of the qPiMaxIdx value. The qPi_delta_max_idx 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, to derive Qp C The maximum index qPiMaxIdx can be derived as in the following equation.

[0581] [Equation 7]

[0582] qPiMaxIdx=maxQp-qPi_delta_max_idx

[0583] Furthermore, for example, the syntax element Qp C _qPi_flag[i] can represent Qp CWhether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate the i-th Qp C Value and (i-1)th Qp C The value is increased by 1. For example, a QpC_qPi_flag[i] value of 1 can indicate that Qp C The value of QpC_qPi_flag[i] increases by 1, and the value of 0 can indicate that Qp C The value of has not increased.

[0584] For example, the variable Qp C Idx[qPi] can be derived as follows: Here, qPi can be 0 to 63.

[0585] - In the case of qPi<qPi_min_idx, Qp C Idx[qPi] can be configured to be the same as qPi.

[0586] - In the case of qPi = qPi_min_idx ... qPiMaxIdx, Qp C Idx[qPi] can be configured as QpC_qPi_flag[qPi]+Qp C Idx[qPi-1].

[0587] - In the case of qPi>qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0588] After that, Qp C Can be configured as Qp C Idx[qPi].

[0589] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or signaling that information for deriving chrominance quantization is used. The flag may be signaled by a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled by the high-level syntax may be as shown in the following table.

[0590] [Table 51]

[0591]

[0592] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C_data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp can be signaled C _data(). In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as described in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred to be 1.

[0593] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0594] [Table 52]

[0595]

[0596]

[0597]

[0598]

[0599]

[0600]

[0601]

[0602] 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 variable qP Cb ,qP Cr and qP CbCr It can be derived based on the signaled user-defined information 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 variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is exported by the default table.

[0603] In addition, the present disclosure proposes another embodiment for signaling information about a quantization parameter. This embodiment proposes 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 a difference between a start point and a value obtained by adding the increment to the start point.

[0604] The chromaticity quantization parameter data Qp for the chromaticity quantization parameter proposed in this embodiment is C _data() can signal as shown in the following table.

[0605] [Table 53]

[0606]

[0607] For example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1 may represent the minimum qPi index for chroma quantization. The qPi_min_idx value may be in the range of 1 to maxQp.

[0608] In addition, for example, the syntax element is_delta_maxQp may indicate whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, a is_delta_maxQp value of 1 may indicate that qPiMaxIdx is derived from the maxQp value. In addition, for example, a is_delta_maxQp value of 0 may indicate that qPiMaxIdx is derived from the syntax element qPi_min_idx_minus1.

[0609] In addition, for example, a value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 may represent the difference between maxQp and the value used to derive chroma Qp. C The delta value between the maximum qPi indices of the qPiMaxIdx. The qPi_delta_max_idx_minus1 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. CThe derived maximum index qPiMaxIdx may be derived as shown in the following table.

[0610] [Table 54]

[0611]

[0612] Furthermore, for example, the syntax element Qp C _qPi_flag[i] can represent Qp C Whether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate the i-th Qp C Value and (i-1)th Qp C The value is increased by 1. For example, a QpC_qPi_flag[i] value of 1 can indicate that Qp C The value of QpC_qPi_flag[i] increases by 1, and the value of 0 can indicate that Qp C The value of has not increased.

[0613] For example, the variable Qp C Idx[qPi] can be derived as follows: Here, qPi can be 0 to maxQp.

[0614] - In the case of qPi<qPi_min_idx_minus1+1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0615] - In the case of qPi = qPi_min_idx_minus1 ... qPiMaxIdx, Qp C Idx[qPi] can be configured as Qp C _qPi_flag[qPi]+QpCIdx[qPi-1].

[0616] - In the case of qPi>qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0617] After that, Qp C Can be configured as Qp C Idx[qPi].

[0618] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or signaling that information for deriving chrominance quantization is used. The flag may be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax may be as shown in the following table.

[0619] [Table 55]

[0620]

[0621] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp can be signaled C _data(). In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as described in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred to be 1.

[0622] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0623] [Table 56]

[0624]

[0625]

[0626]

[0627]

[0628]

[0629]

[0630]

[0631]

[0632] 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 variable qP Cb ,qP Cr and qP CbCr It can be derived based on the signaled user-defined information 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 variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi, exported by the default table.

[0633] In addition, the present disclosure proposes another embodiment for signaling information about a quantization parameter. This embodiment proposes 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 a difference between a start point and a value obtained by adding the increment to the start point.

[0634] The chromaticity quantization parameter data Qp for the chromaticity quantization parameter proposed in this embodiment is C _data() can signal as shown in the following table.

[0635] [Table 57]

[0636]

[0637] For example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1 may represent the minimum qPi index for chroma quantization. The qPi_min_idx value may be in the range of 1 to maxQp.

[0638] In addition, for example, the syntax element is_delta_maxQp may indicate whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, a is_delta_maxQp value of 1 may indicate that qPiMaxIdx is derived from the maxQp value. In addition, for example, a is_delta_maxQp value of 0 may indicate that qPiMaxIdx is derived from the syntax element qPi_min_idx_minus1.

[0639] In addition, for example, a value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 may represent the difference between maxQp and the value used to derive chroma Qp. C The delta value between the maximum qPi indices. 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. C The maximum index qPiMaxIdx can be derived as described above as in Table 54.

[0640] Furthermore, for example, the syntax element Qp C _qPi_flag[i] can represent Qp C Whether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate the i-th Qp C Value and (i-1)th Qp C The value is increased by 1. For example, a QpC_qPi_flag[i] value of 1 can indicate that Qp C The value of QpC_qPi_flag[i] increases by 1, and the value of 0 can indicate that Qp C The value of has not increased.

[0641] For example, the variable Qp C Idx[qPi] can be derived as follows: Here, qPi can be 0 to maxQp.

[0642] - In the case of qPi<qPi_min_idx_minus1+1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0643] - In the case of qPi = qPi_min_idx_minus1 ... qPiMaxIdx, Qp C Idx[qPi] can be configured as Qp C _qPi_flag[qPi]+Qp C Idx[qPi-1].

[0644] - In the case of qPi>qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0645] After that, Qp C Can be configured as Qp C Idx[qPi].

[0646] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or signaling that information for deriving chrominance quantization is used. The flag may be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax may be the same as in the following table.

[0647] [Table 58]

[0648]

[0649] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp can be signaled C _data(). In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as described in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be considered as 1.

[0650] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0651] [Table 59]

[0652]

[0653]

[0654]

[0655]

[0656]

[0657]

[0658]

[0659] 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 variable qP Cb ,qP Cr and qP CbCr It can be derived based on the signaled user-defined information 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 variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi, exported by the default table.

[0660] Furthermore, the present disclosure proposes another embodiment for signaling information about quantization parameters. The present embodiment proposes a scheme for signaling an index of a chroma QP mapping table by using minus1 notation instead of a real value.

[0661] The chromaticity quantization parameter data Qp for the chromaticity quantization parameter proposed in this embodiment is C _data() can signal as shown in the following table.

[0662] [Table 60]

[0663]

[0664] For example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1 may represent the minimum qPi index for chroma quantization. The qPi_min_idx value may be in the range of 1 to 63.

[0665] In addition, for example, a value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 may indicate that qPi_min_idx is equal to the value used to derive the chrominance Qp C The delta value between the maximum qPi index of 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, to derive the Qp C The maximum index qPiMaxIdx can be derived as in the following equation.

[0666] [Equation 8]

[0667] qPiMaxIdx=qPi_min_idx_minus1+1+qPi_delta_max_idx_minus1+1

[0668] Furthermore, for example, the syntax element Qp C _qPi_flag[i] can represent Qp C Whether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate the i-th Qp C Value and (i-1)th Qp C The value is increased by 1. For example, a QpC_qPi_flag[i] value of 1 can indicate that Qp C The value of QpC_qPi_flag[i] increases by 1, and the value of 0 can indicate that Qp C The value of has not increased.

[0669] For example, the variable Qp C Idx[qPi] can be derived as follows: Here, qPi can be 0 to 63.

[0670] - In the case of qPi<qPi_min_idx_minus1+1, Qp C Idx[qPi] can be configured to be the same as qPi.

[0671] - In the case of qPi = qPi_min_idx_minus1+1…qPiMaxIdx, Qp C Idx[qPi] can be configured as Qp C _qPi_flag[qPi]+Qp CIdx[qPi-1].

[0672] - In the case of qPi>qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0673] After that, Qp C Can be configured as Qp C Idx[qPi].

[0674] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or signaling that information for deriving chrominance quantization is used. The flag may be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax may be as shown in the following table.

[0675] [Table 61]

[0676]

[0677] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp can be signaled C _data(). In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as shown in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be considered as 1.

[0678] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0679] [Table 62]

[0680]

[0681]

[0682]

[0683]

[0684]

[0685]

[0686] 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 variable qP Cb ,qP Cr and qP CbCr It 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 variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi, exported by the default table.

[0687] Furthermore, the present disclosure proposes another embodiment for signaling information about quantization parameters.The present embodiment proposes a scheme in which a separate chrominance quantization table is used for each chrominance component.

[0688] The chromaticity quantization parameter data for the chromaticity quantization parameters proposed in this embodiment may be signaled as in the following table.

[0689] [Table 63]

[0690]

[0691] For example, the syntax element Qp C _data_default_flag can indicate whether to use the default chrominance quantization parameter table. For example, a Qp value of 1C _data_default_flag may indicate that a default chromaticity quantization parameter table is used to derive chromaticity quantization parameters. The default table may be as described in Table 7 above. In addition, for example, a Qp value of 0 C _data_default_flag may indicate that the default chrominance quantization parameter table is not used to derive the chrominance quantization parameters. That is, for example, a Qp value of 0 C _data_default_flag may indicate that a chromaticity quantization parameter table derived based on the signaled chromaticity quantization parameter data for deriving the chromaticity quantization parameter is used.

[0692] In addition, for example, the syntax element sps_separate_qpc_table_flag may indicate two separate Qpc tables. C Whether the table is used for Cb samples and Cr samples. That is, for example, the syntax element sps_separate_qpc_table_flag can indicate whether separate luma-chroma quantization parameter mapping tables are used for Cb residual and Cr residual, respectively. For example, a sps_separate_qpc_table_flag with a value of 1 can indicate whether separate Qp C The tables are used for Cb samples and Cr samples respectively, and the sps_separate_qpc_table_flag with a value of 0 can indicate a Qp C The table is used for Cb samples and Cr samples.

[0693] At the same time, for example, the variable Qp Cb [i] can represent Qp for Cb samples C In addition, for example, the variable Qp Cr [i] can represent Qp for Cr samples C In addition, for example, if the sps_separate_qpc_table_flag value is 0, then Qp Cr [i] can be compared with Qp Cb Here, i can be from 0 to 69.

[0694] In addition, for example, a value obtained by adding 1 to the syntax element qPi_Cb_min_idx_minus1 may represent the minimum qPi index for the Cb chrominance component. The qPi_Cb_min_idx_minus1 value may be in the range of 1 to 69.

[0695] In addition, for example, a value obtained by adding 1 to the syntax element qPi_Cb_delta_max_idx_minus1 may indicate that qPi_Cb_min_idx_minus1 is equal to the value used to derive the Cb chrominance Qp C The value of qPiMaxIdx can be equal to or greater than qPi_min_idx. The value of qPi_Cb_delta_max_idx_minus1 can be in the range of 1 to 69. For example, the Qp used to derive the Cb component C The maximum index qPiMaxIdxcb can be derived as in the following equation.

[0696] [Equation 9]

[0697] 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] can represent the i-th Qp of the Cb component C Value Qp Cb [i] and (i-1)th Qp C Value Qp Cb The incremental value between [i-1]. Qp C _cb_qPi_flag[i] value can be in the range of 0 to 1.

[0698] For example, the variable Qp Cb [i] can be derived as follows. Here, i can be from 0 to 69.

[0699] - In the case of i = 0...qPiMaxIdxCb, Qp Cb [i] can be configured to be the same as i.

[0700] - In the case of 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].

[0701] - 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].

[0702] In addition, for example, qPi_cr_min_idx_minus1, qPiMaxIdxCr, and Qpi_cr_min_idx_minus1 as syntax elements of the Cr component C _cr_qPi_flag[i] may have the same meaning as the syntax element of the Cb component.

[0703] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. For example, the present embodiment proposes a scheme for signaling parameters of multiple chroma QP tables. In addition, the present embodiment can be connected to at least one of the embodiments described above. That is, for example, the embodiments of the present disclosure can be applied together.

[0704] Specifically, for example, this embodiment proposes to include a user-defined chromaticity quantization parameter (Qp C ). For example, according to the present embodiment, a flag of a sequence parameter set (SPS) may indicate whether a default table is used to derive chroma quantization parameters or a chroma QP mapping table is derived based on signaled information in the SPS. Thus, user-defined chroma quantization parameters may be used in image coding in consideration of content characteristics of an image, and coding efficiency may be improved. In addition, the present embodiment may provide flexibility through an option in which one user-defined table is used for chroma components and an option in which separate user-defined tables are used for Cb components and Cr components.

[0705] For example, the chromaticity quantization parameter data Qp for the chromaticity quantization parameter proposed in this embodiment may be signaled as in the following table: C _data().

[0706] [Table 64]

[0707]

[0708] For example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1 may represent the minimum qPi index for chroma quantization. The qPi_min_idx value may be in the range of 1 to 69.

[0709] In addition, for example, the syntax element qPi_delta_max_idx can represent qPi_min_idx and is used to derive the chrominance Qp C The delta value between the maximum qPi index of the qPiMaxIdx value. The qPi_delta_max_idx 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, to derive Qp CThe maximum index qPiMaxIdx of can be derived as in Equation 4 as described above.

[0710] Furthermore, for example, the syntax element Qp C _qPi_flag[i] can represent Qp C Whether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i] can indicate the i-th Qp C Value and (i-1)th Qp C The value is increased by 1. For example, a QpC_qPi_flag[i] value of 1 can indicate that Qp C The value of QpC_qPi_flag[i] increases by 1, and the value of 0 can indicate that Qp C The value of has not increased.

[0711] For example, the variable Qp C Idx[qPi] can be derived as follows: Here, qPi can be 0 to 69.

[0712] - In the case of qPi<qPi_min_idx, Qp C Idx[qPi] can be configured to be the same as qPi.

[0713] - In the case of qPi = qPi_min_idx ... qPiMaxIdx, Qp C Idx[qPi] can be configured as Qp C _qPi_flag[qPi]+Qp C Idx[qPi-1].

[0714] - In the case of qPi>qPiMaxIdx, Qp C Idx[qPi] can be configured as qPi-(qPiMaxIdx-Qp C Idx[qPiMaxIdx]).

[0715] After that, Qp C Can be configured as Qp C Idx[qPi].

[0716] In addition, the present embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chroma quantization or a chroma QP mapping table derived based on the signaled information is used. The flag may be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax may be as shown in the following table.

[0717] [Table 65]

[0718]

[0719] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp can be signaled C _data(). In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as shown in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred to be 1.

[0720] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0721] [Table 66]

[0722]

[0723]

[0724]

[0725]

[0726]

[0727]

[0728] Referring to Table 66 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 variable qP Cb ,qP Cr and qP CbCrIt can be derived based on the signaled user-defined information 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 variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi is exported by the default table.

[0729] In addition, for example, the chromaticity quantization parameter data Qp in the case of using separate user-defined tables for the respective chromaticity components proposed in the present embodiment is C _data() can be signaled as in the following table.

[0730] [Table 67]

[0731]

[0732] For example, the syntax element is_separate_chroma_table may indicate whether separate chroma 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 may indicate whether two separate chroma quantization parameter mapping tables are used for the Cb component and the Cr component. For example, the syntax element is_separate_chroma_table may indicate whether separate luminance-chroma quantization parameter mapping tables are used for the Cb residual and the Cr residual, respectively. For example, an is_separate_chroma_table value of 1 may indicate that separate chroma quantization parameter mapping tables are signaled for the Cb component and the Cr component, and an is_separate_chroma_table value of 0 may indicate that one chroma quantization parameter mapping table is used for the Cb element, the Cr element, and the joint CbCr element. For example, if the is_separate_chroma_table value is 1, Pi_min_idx_minus1[i], qPi_delta_max_idx[i], and Qp[i] for the Cb component may be signaled. C _qPi_flag[i][j] and qPi_min_idx_minus1[i], qPi_delta_max_idx[i], and Qp for Cr components C_qPi_flag[i][j]. In addition, for example, if the is_separate_chroma_table value is 0, qPi_min_idx_minus1[i], qPi_delta_max_idx[i], and QPi_delta_max_idx[i] for the Cb component, the Cr component, and the joint CbCr component may be signaled. C _qPi_flag[i][j].

[0733] In addition, for example, a value obtained by adding 1 to the syntax element qPi_min_idx_minus1[i] may represent the minimum qPi index for chrominance quantization. The qPi_min_idx value may be in the range of 1 to 69. The variable qPi_min_idx[i] may be configured to be the same as a value obtained by adding 1 to qPi_min_idx_minus1[i].

[0734] In addition, for example, the syntax element qPi_delta_max_idx may indicate the difference between qPi_min_idx[i] and qPi_delta_max_idx[i] used to derive the chrominance Qp C The delta value between the maximum qPi index of the qPiMaxIdx[i] 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, to derive Qp C The maximum index qPiMaxIdx[i] can be derived as in the following equation.

[0735] [Equation 10]

[0736] qPiMaxIdx[i]=qPi_min_idx[i]+qPi_delta_max_idx_minus1[i]+1

[0737] The qPiMaxIdx[i] value may be equal to or greater than qPi_min_idx_minus1[i].

[0738] Furthermore, for example, the syntax element Qp C _qPi_flag[i][j] can represent the jth Qp of the i-th chroma component C Whether the value is increased by 1. That is, for example, the syntax element QpC_qPi_flag[i][j] can indicate the jth Qp value of the i-th chrominance component. C The value is the same as the (j-1)th Qp C The value is increased by 1. For example, a QpC_qPi_flag[j] value of 1 can indicate the jth Qp of the i-th chrominance component. CThe value increases by 1, and the QpC_qPi_flag[j] with a value of 0 can indicate the jth Qp of the i-th chrominance component. C The value did not increase.

[0739] For example, the variable Qp C Idx[i][qPi] can be derived as shown in the following table: Here, qPi can be 0 to 69.

[0740] [Table 68]

[0741]

[0742] Referring to Table 68, if the value of is_separate_chroma_table is 1, the 0th (i=0) chromaticity quantization parameter data and the 1st (i=1) chromaticity quantization parameter data may be signaled. Here, for example, the 0th (i=0) chromaticity quantization parameter data may be chromaticity quantization parameter data for deriving a chromaticity quantization parameter mapping table for a Cb component, and the 1st (i=0) chromaticity quantization parameter data may be chromaticity quantization parameter data for deriving a chromaticity quantization parameter mapping table for a Cr component.

[0743] In addition, referring to Table 68, if the value of is_separate_chroma_table is 0, only the 0th (i=0) chroma quantization parameter data may be signaled. Here, for example, the 0th (i=0) chroma quantization parameter data may be chroma quantization parameter data used to derive chroma quantization parameter mapping tables for Cb components, Cr components, and joint CbCr components. That is, one chroma quantization parameter mapping table may be used for chroma components.

[0744] In addition, referring to Table 68, Qp C Idx[i][qPi] can be derived as follows.

[0745] - In the case of qPi<qPi_min_idx[i], Qp C Idx[i][qPi] may be configured to be the same as qPi.

[0746] - In the case of qPi = qPi_min_idx[i] ... qPiMaxIdx[i], Qp C Idx[qPi] can be configured as Qp C _qPi_flag[i][qPi]+Qp C Idx[i][qPi-1].

[0747] - In the case of qPi>qPiMaxIdx, Qp CIdx[i][qPi] can be configured as qPi-(qPiMaxIdx[i]-Qp C Idx[i][qPiMaxIdx]).

[0748] After that, Qp C The value can be derived as Qp C Idx[i][qPi].

[0749] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used to derive chrominance quantization or signaling information used to derive chrominance quantization is used. The flag can be signaled through a high-level syntax such as a sequence parameter set (SPS) or a picture parameter set (PPS). The flag signaled through the high-level syntax can be the same as the flag in the following table.

[0750] [Table 69]

[0751]

[0752] For example, the syntax element Qp C _data_default_flag may indicate whether a user-defined mode is used to derive quantization parameters. For example, a Qp value of 0 C _data_default_flag may indicate that a user-defined mode is used to derive the quantization parameter. That is, for example, a Qp value of 0 C _data_default_flag can indicate the use of chrominance quantization parameter data Qp C _data(). If Qp C _data_default_flag is 0, then the chrominance quantization parameter data Qp can be signaled C _data(). In addition, for example, a Qp value of 1 C _data_default_flag may indicate that a default table is used to derive quantization parameters. The default table may be as shown in Table 7 above. In addition, if Qp C _data_default_flag does not exist, then Qp C _data_default_flag can be inferred to be 1.

[0753] For example, according to this embodiment, through the description of the standard format, the process of deriving the quantization parameter can be expressed as shown in the following table.

[0754] [Table 70]

[0755]

[0756]

[0757]

[0758]

[0759]

[0760]

[0761]

[0762] Referring to Table 70 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 variable qP Cb ,qP Cr and qP CbCr It 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 variable qP Cb ,qP Cr and qP CbCr Can be based on qPi Cb ,qPi Cr and qPi CbCr The same index qPi, exported by the default table.

[0763] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. For example, the present embodiment proposes a scheme for signaling parameters for a chroma QP table without a default configuration. In addition, the present 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 collectively.

[0764] The chromaticity quantization parameter data of the chromaticity quantization parameters proposed in this embodiment may be signaled as shown in the following table.

[0765] [Table 71]

[0766]

[0767] For example, the syntax element is_same_qp_table_for_cb_cr may indicate whether only one chroma QP mapping table is signaled and applied for the Cb component, the Cr component, and the joint CbCr component. That is, for example, the syntax element is_same_qp_table_for_cb_cr may indicate whether parameters related to only one chroma QP mapping table are signaled for the Cb component, the Cr component, and the joint CbCr component, and one chroma QP mapping table is applied. For example, is_same_qp_table_for_cb_cr having a value of 1 may indicate that only one chroma QP mapping table is signaled and applied for the Cb component, the Cr component, and the joint CbCr component. That is, for example, is_same_qp_table_for_cb_cr having a value of 1 may indicate that parameters related to only one chroma QP mapping table are signaled for the Cb component, the Cr component, and the joint CbCr component, and one chroma QP mapping table is applied. In addition, for example, is_same_qp_table_for_cb_cr having a value of 0 may indicate that multiple chroma QP mapping tables are signaled and applied for the Cb component, the Cr component, and the joint CbCr component. That is, for example, is_same_qp_table_for_cb_cr having a value of 0 may indicate that parameters related to multiple chroma QP mapping tables are signaled for the Cb component, the Cr component, and the joint CbCr component, and multiple chroma QP mapping tables are applied. For example, is_same_qp_table_for_cb_cr having a value of 0 may indicate that 3 chroma QP mapping tables are signaled and applied for the Cb component, the Cr component, and the joint CbCr component.

[0768] In addition, for example, the syntax element qPi_table_len_idx[i] may indicate the number of points used to interpret the i-th chroma QP mapping table. That is, for example, qPi_table_len_idx[i] may indicate the number of indices of the i-th chroma QP mapping table. The qPi_table_len_idx[i] value may be between 0 and 69+QpBdOffset C within the range.

[0769] Furthermore, for example, the syntax element qp C _qPi_in_idx[i][j] may represent the incremental value of the input coordinates of the j-th pivot point used to derive the i-th chroma QP mapping table.

[0770] Furthermore, for example, the syntax element qp C_qPi_out_idx[i][j] may represent the incremental value of the output coordinates of the j-th pivot point used to derive the i-th chroma QP mapping table.

[0771] Based on the above syntax elements, the i-th QP mapping table cQPTable[i] may be derived as shown in the following table: Here, if same_qp_table_for_cb_cr is 1, i may be 0, and if same_qp_table_for_cb_cr is not 1, i may be one of 0 to 2.

[0772] [Table 72]

[0773]

[0774] Referring to Table 72 as described above, it is possible to C _qPi_in_idx[i][j] is used to derive the input coordinates of the jth pivot point of the i-th chroma QP mapping table. qpVal[i][j] illustrated in Table 72 as described above may represent the input coordinates of the jth pivot point. In addition, referring to Table 72 as described above, qp may be used to derive the input coordinates of the jth pivot point of the i-th chroma QP mapping table. C _qPi_out_idx[i][j] is used to derive the output coordinates of the j-th pivot point of the i-th chroma QP mapping table. cQPTable[i][j] illustrated in Table 72 as described above may represent the output coordinates of the j-th pivot point.

[0775] Furthermore, according to the present embodiment, the following changes may be made to derive the chroma QP. For example, the restrictions in the following table may be added.

[0776] [Table 73]

[0777]

[0778] Referring to Table 73 as described above, the qpVal[i][j] value may be greater than the value qpVal[i][j-1]. Here, j may be any one of 1 to qPi_table_len_idx[i].

[0779] In addition, if the chroma type is not 0, for example, if the chroma type is 1, then in the case where chroma_qp_table_present_flag is equal to 1, the variable qP Cb and qP Cr They may be configured to be the same as ChromaQpTable[0][qPiCb], ChromaQpTable[1][qPiCr], and ChromaQpTable[1][qPiCbCr], respectively.

[0780] In addition, the present disclosure proposes another embodiment for signaling information about quantization parameters. This embodiment may be connected to at least one of the above-mentioned embodiments. For example, this embodiment proposes a scheme for limiting the range of the signaled qp index. As an example, this embodiment may propose to signal the syntax element qPi_table_len_idx in the previous example described above, as follows.

[0781] For example, the syntax element qPi_table_len_idx[i] may indicate the number of points used to interpret the chroma QP map. Furthermore, the value of the syntax element qPi_table_len_idx[i] may be in the range of 0 to 69+QpBdOffsetC.

[0782] As described above, the present embodiment may propose a scheme for limiting a parameter (eg, the number of points of the chroma QP mapping table represented by qPi_table_len_idx[i]) to a minimum range that can be signaled or inferred in another manner.

[0783] Fig.10 The image encoding method of the encoding device according to this document is schematically shown. Fig.10 The method disclosed in can be Figure 2 Specifically, for example, Fig.10 S1000 to S1010 of the encoding device may be performed by an entropy encoder. In addition, although not shown, the process of deriving the prediction sample for the chrominance component may be performed by a predictor of the encoding device, and the process of generating the reconstructed sample and the reconstructed picture based on the residual sample and the prediction sample of the chrominance component may be performed by an adder of the encoding device.

[0784] The encoding device encodes image information (S1000).

[0785] The encoding device may encode the image information. For example, the image information may 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 the chrominance component. The chrominance component may include a Cb component, a Cr component, and / or a joint CbCr component.

[0786] For example, the encoding device may derive prediction samples for the chrominance component based on the prediction mode. That is, for example, the encoding device may derive prediction samples for the current block of the chrominance component based on the prediction mode. In this case, various prediction methods disclosed in the present disclosure, such as inter-frame prediction or intra-frame prediction, may be applied.

[0787] 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 a prediction sample for the current block.

[0788] 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 a prediction mode for the current block of the chrominance component. The image information may include the prediction information.

[0789] Furthermore, for example, the encoding apparatus may derive residual samples by subtracting original samples and predicted samples of the current block for the chrominance component in the current picture.

[0790] Thereafter, for example, the encoding device may encode the residual information of the residual sample. For example, the encoding device may derive a transform coefficient based on the residual sample, and may generate the residual information based on the transform coefficient. For example, the encoding device may derive a quantized residual sample by quantizing the residual sample based on the chroma quantization parameter, derive the transform coefficient based on the quantized residual sample, and generate and encode the residual information based on the transform coefficient. In addition, for example, the encoding device may derive a quantized residual sample by quantizing the residual sample based on the chroma quantization parameter, derive the transform coefficient by transforming the quantized residual sample, and generate and encode the residual information based on the transform coefficient.

[0791] For example, the residual information may include syntax elements for transform coefficients of the current chroma 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.

[0792] In addition, for example, the encoding device may generate and encode chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for the chroma component. The default chroma QP mapping table for the chroma component may not be used. That is, if the chroma quantization parameter for the chroma component is used, the encoding device may generate chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for the chroma component. The image information may include chroma quantization parameter data of at least one chroma QP mapping table for the chroma component. In addition, for example, the chroma component may include a Cb component, a Cr component, and / or a joint CbCr component. In addition, for example, the chroma quantization parameter data may include a syntax element indicating the number of points in the chroma QP mapping table, a syntax element indicating an incremental value of the input coordinates of the target point for deriving the chroma QP mapping table, and / or a syntax element indicating an incremental 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 indicating the number of points of 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 indicating the number of points of the chroma QP mapping table may be qPi_table_len_idx[i] as described above, and the syntax element indicating the delta value of the input coordinates of the target point for deriving the chroma QP mapping table may be qPi_table_len_idx[i] as described above. C _qPi_in_idx[i][j], and the syntax element representing the delta value of the output coordinates of the target point for deriving the chroma QP mapping table may be qp as described above C _qPi_out_idx[i][j].

[0793] Furthermore, for example, the encoding apparatus may determine whether a chroma QP mapping table is applied to the chroma component, and may generate a flag indicating whether a chroma QP mapping table is applied to the chroma component.The image information may include a flag indicating whether a chroma QP mapping table is applied to the chroma component.

[0794] For example, the encoding device may generate a flag indicating whether a chroma QP mapping table is applied to the chroma component based on the chroma type. Here, the chroma type may mean the ChromaArrayType as described above. For example, if the chroma type value is not 0, the encoding device may generate a flag indicating whether a chroma QP mapping table is applied to the chroma component. For example, if the chroma type value is 1, the encoding device may generate a flag indicating whether a chroma QP mapping table is applied to the chroma component. Here, if the chroma type value is 0, the chroma type may be a monochrome format, and if the chroma type value is 1, the chroma type may be a 4:2:0 format. If the chroma type value is 2, the chroma type may be a 4:2:2 format, and if the chroma type value is 3, the chroma type may be a 4:4:4 format. For example, the syntax element of the flag may be the above-mentioned qp_luma_to_chroma_joint_map_flag flag, sps_separate_qpc_table_flag, is_separate_chroma_table, or is_same_qp_table_for_cb_cr.

[0795] For example, if the flag value is 1, the flag may indicate that one chroma QP mapping table is applied to the chroma component. Also, for example, if the flag value is 0, the flag may indicate that multiple chroma QP mapping tables are applied to the chroma component. That is, for example, if the flag value is 0, the flag may indicate that a separate chroma QP mapping table is applied to each chroma component.

[0796] Thus, for example, if the flag value is 1, chroma quantization parameter data for one chroma QP mapping table for a chroma component may be signaled, and if the flag value is 0, chroma quantization parameter data for multiple chroma QP mapping tables for chroma components may be signaled. That is, for example, if the flag value is 0, chroma quantization parameter data for a separate chroma QP mapping table for each chroma component may be signaled.

[0797] In addition, for example, the flag can be signaled through a 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 adaptation parameter set (APS).

[0798] Furthermore, for example, the encoding device may generate chroma quantization parameter data of the chroma component based on the flag.

[0799] For example, the chroma quantization parameter data of the plurality of chroma QP mapping tables for chroma components may include first chroma quantization parameter data of a first chroma QP mapping table for a Cb component and second chroma quantization parameter data of a second chroma QP mapping table for a Cr component. In addition, for example, the chroma quantization parameter data may include first chroma quantization parameter data of a first chroma QP mapping table for a Cb component, second chroma quantization parameter data of a second chroma QP mapping table for a Cr component, and / or third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component.

[0800] Meanwhile, for example, the encoding device may generate a joint CbCr enable flag indicating whether there is a third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component. That is, for example, the encoding device may determine whether there is a third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component, and may generate a joint CbCr enable flag. In addition, for example, the encoding device may generate a joint CbCr enable flag indicating whether there is a third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component based on a chroma type. Here, the chroma type may mean a ChromaArrayType as described above. For example, if the chroma type value is not 0, the encoding device may generate a joint CbCr enable flag indicating whether there is a third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component. For example, if the chroma type value is 1, the encoding device may generate a joint CbCr enable flag indicating whether there is a third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component. In addition, for example, the joint CbCr enable flag may be signaled by a high-level syntax. For example, the joint-CbCr enabling flag may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0801] In this case, if the flag value is 0 (i.e., it is determined that multiple chroma QP mapping tables are applied to chroma components) and the value of the joint-CbCr enable flag is 1 (i.e., it is determined that there is third chroma quantization parameter data of a third chroma QP mapping table for joint-CbCr components), the chroma quantization parameter data may include first chroma quantization parameter data of a first chroma QP mapping table for Cb components, second chroma quantization parameter data of a second chroma QP mapping table for Cr components, and third chroma quantization parameter data of a third chroma QP mapping table for joint-CbCr components.

[0802] In addition, for example, the first chroma quantization parameter data may include a syntax element indicating the number of points of the first chroma QP mapping table for the Cb component, a syntax element indicating an incremental value of input coordinates of a target point for deriving the first chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the first chroma QP mapping table. The syntax element indicating the number of points of the first chroma QP mapping table may be qPi_table_len_idx[i], the syntax element indicating the incremental value of input coordinates of a target point for deriving the first chroma QP mapping table may be qpC_qPi_in_idx[i][j], and the syntax element indicating the incremental value of output coordinates of a target point for deriving the first chroma 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 through a high-level syntax. For example, the first chrominance quantization parameter data may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0803] In addition, for example, the second chroma quantization parameter data may include a syntax element indicating the number of points of the second chroma QP mapping table for the Cr component, a syntax element indicating an incremental value of input coordinates of a target point for deriving the second chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the second chroma QP mapping table. The syntax element indicating the number of points of the second chroma QP mapping table may be qPi_table_len_idx[i], the syntax element indicating the incremental value of input coordinates of a target point for deriving the second chroma QP mapping table may be qPi_table_len_idx[i]. C _qPi_in_idx[i][j], and a syntax element representing the delta value of the output coordinates of the target point for deriving the second chroma 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 adaptation parameter set (APS).

[0804] In addition, for example, the third chroma quantization parameter data may include a syntax element indicating the number of points of the third chroma QP mapping table for the joint CbCr component, a syntax element indicating an incremental value of input coordinates of a target point for deriving the third chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the third chroma QP mapping table. The syntax element indicating the number of points of the third chroma QP mapping table may be qPi_table_len_idx[i], and the syntax element indicating the incremental value of input coordinates of a target point for deriving the third chroma QP mapping table may be qp_table_len_idx[i]. C _qPi_in_idx[i][j], and a syntax element representing the delta value of the output coordinates of the target point for deriving the third chroma 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 through a high-level syntax. For example, the third chrominance quantization parameter data may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0805] Furthermore, for example, if the flag value is 1 (ie, determining that one chroma QP mapping table is applied to the chroma component), the chroma quantization parameter data may include chroma quantization parameter data of one chroma QP mapping table for the Cb component, the Cr component, and the joint CbCr component.

[0806] The encoding apparatus generates a bitstream including image information (S1010).

[0807] For example, the encoding device may output a bitstream including image information, the image information including prediction information about the chroma component, residual information about the chroma component, and / or chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for the chroma component. The bitstream may include prediction information, residual information, and / or chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for the chroma component. In addition, the image information may also include a flag indicating whether a chroma QP mapping table is applied to the chroma component and / or a joint CbCr enable flag.

[0808] The encoding device is capable of encoding and outputting image information in the form of a bit stream.

[0809] At the same time, the bit stream including the image information can 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 disk, SD, CD, DVD, Blu-ray disc, HDD, and SSD.

[0810] Fig.11 A coding device for performing the image coding method according to the present document is schematically shown. Fig.10 The method disclosed in can be Fig.11 Specifically, for example, Fig.11 The entropy encoder of the encoding device may perform S1000 to S1010. In addition, although not shown, the process of deriving the prediction sample for the chrominance component may be performed by the predictor of the encoding device, and the process of generating the reconstructed sample and the reconstructed picture based on the residual sample and the prediction sample for the chrominance component may be performed by the adder of the encoding device.

[0811] Fig.12 The image decoding method of the decoding device according to the document is schematically shown. Fig.12 The method disclosed in can be Figure 3 Specifically, for example, Fig.12 S1200 may be performed by an entropy decoder of a decoding device, and Fig.12 S1210 may be performed by a residual processor of the decoding device.

[0812] The decoding apparatus obtains image information through a bit stream (S1200).

[0813] For example, the image information may include information about colorimetric quantization parameters.

[0814] 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 device may obtain chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for the chroma component. The default chroma QP mapping table for the chroma component may not be used. That is, if the chroma quantization parameter for the chroma component is used, the decoding device may obtain chroma quantization parameter data of at least one chroma quantization parameter (QP) mapping table for the chroma component. In addition, for example, the chroma component may include a Cb component, a Cr component, and / or a joint CbCr component. In addition, for example, the chroma quantization parameter data may include a syntax element indicating the number of points in the chroma QP mapping table, a syntax element indicating an incremental value of the input coordinates of the target point for deriving the chroma QP mapping table, and / or a syntax element indicating an incremental 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 indicating the number of points of 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 indicating the number of points of the chroma QP mapping table may be qPi_table_len_idx[i] as described above, and the syntax element indicating the delta value of the input coordinates of the target point for deriving the chroma QP mapping table may be qPi_table_len_idx[i] as described above.C _qPi_in_idx[i][j], and the syntax element representing the delta value of the output coordinates of the target point for deriving the chroma QP mapping table may be qp as described above C _qPi_out_idx[i][j].

[0815] In addition, for example, the chroma quantization parameter data of the chroma QP mapping table can be signaled through a high-level syntax. For example, the chroma quantization parameter data can be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0816] In addition, for example, the decoding device may obtain a flag indicating whether a chroma QP mapping table is applied to the chroma component. That is, for example, the decoding device may obtain a flag indicating whether a chroma QP mapping table is signaled and applied to the chroma component. The image information may include the flag. At the same time, for example, the decoding device may obtain a flag indicating whether a chroma QP mapping table is applied based on the chroma type. Here, the chroma type may mean the ChromaArrayType as described above. For example, if the chroma type value is not 0, the decoding device may obtain a flag indicating whether a chroma QP mapping table is applied. For example, if the chroma type value is 1, the decoding device may obtain a flag indicating whether a chroma QP mapping table is applied. Here, if the chroma type value is 0, the chroma type may be a monochrome format, and if the chroma type value is 1, the chroma type may be a 4:2:0 format. If the chroma type value is 2, the chroma type may be a 4:2:2 format, and if the chroma type value is 3, the chroma type may be a 4:4:4 format. For example, the syntax element of 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.

[0817] For example, if the flag value is 1, the flag may indicate that one chroma QP mapping table is applied to the chroma component. Also, for example, if the flag value is 0, the flag may indicate that multiple chroma QP mapping tables are applied to the chroma component. That is, for example, if the flag value is 0, the flag may indicate that a separate chroma QP mapping table is applied to each chroma component.

[0818] Thus, for example, if the flag value is 1, chroma quantization parameter data for one chroma QP mapping table for a chroma component may be signaled, and if the flag value is 0, chroma quantization parameter data for multiple chroma QP mapping tables for chroma components may be signaled. That is, for example, if the flag value is 0, chroma quantization parameter data for a separate chroma QP mapping table for each chroma component may be signaled.

[0819] In addition, for example, the flag can be signaled through a 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 adaptation parameter set (APS).

[0820] In addition, for example, the chroma quantization parameter data of the plurality of chroma QP mapping tables for the chroma components may include first chroma quantization parameter data of a first chroma QP mapping table for a Cb component and second chroma quantization parameter data of a second chroma QP mapping table for a Cr component. In addition, for example, the chroma quantization parameter data may include first chroma quantization parameter data of a first chroma QP mapping table for a Cb component, second chroma quantization parameter data of a second chroma QP mapping table for a Cr component, and / or third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component.

[0821] Meanwhile, for example, the decoding device may obtain a joint CbCr enable flag indicating whether the third chroma quantization parameter data of the third chroma QP mapping table for the joint CbCr component exists. For example, the image information may include a joint CbCr enable flag indicating whether the third chroma quantization parameter data of the third chroma QP mapping table for the joint CbCr component exists. In addition, for example, the decoding device may obtain a joint CbCr enable flag indicating whether the third chroma quantization parameter data of the third chroma QP mapping table for the joint CbCr component exists based on the chroma type. Here, the chroma type may mean the ChromaArrayType as described above. For example, if the chroma type value is not 0, the decoding device may obtain a joint CbCr enable flag indicating whether the third chroma quantization parameter data of the third chroma QP mapping table for the joint CbCr component exists. For example, if the chroma type value is 1, the decoding device may obtain a joint CbCr enable flag indicating whether the third chroma quantization parameter data of the third chroma QP mapping table for the joint CbCr component exists. In addition, for example, the joint CbCr enable flag may be signaled by a high-level syntax. For example, the joint-CbCr enabling flag may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0822] In this case, if the flag value is 0 (i.e., the flag indicates that multiple chroma QP mapping tables are applied to chroma components) and the joint-CbCr enable flag value is 1 (i.e., the joint-CbCr enable flag indicates that there is third chroma quantization parameter data of a third chroma QP mapping table for joint-CbCr components), the chroma quantization parameter data may include first chroma quantization parameter data of a first chroma QP mapping table for Cb components, second chroma quantization parameter data of a second chroma QP mapping table for Cr components, and third chroma quantization parameter data of a third chroma QP mapping table for joint-CbCr components.

[0823] In addition, for example, the first chroma quantization parameter data may include a syntax element indicating the number of points of the first chroma QP mapping table for the Cb component, a syntax element indicating an incremental value of input coordinates of a target point for deriving the first chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the first chroma QP mapping table. The syntax element indicating the number of points of the first chroma QP mapping table may be qPi_table_len_idx[i], the syntax element indicating the incremental value of input coordinates of a target point for deriving the first chroma QP mapping table may be qp_table_len_idx[i]. C _qPi_in_idx[i][j], and a syntax element representing the delta value of the output coordinates of the target point for deriving the first chroma 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 through a high-level syntax. For example, the first chrominance quantization parameter data may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0824] In addition, for example, the second chroma quantization parameter data may include a syntax element indicating the number of points of the second chroma QP mapping table for the Cr component, a syntax element indicating an incremental value of input coordinates of a target point for deriving the second chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the second chroma QP mapping table. The syntax element indicating the number of points of the second chroma QP mapping table may be qPi_table_len_idx[i], the syntax element indicating the incremental value of input coordinates of a target point for deriving the second chroma QP mapping table may be qPi_table_len_idx[i]. C _qPi_in_idx[i][j], and a syntax element representing the delta value of the output coordinates of the target point for deriving the second chroma 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 adaptation parameter set (APS).

[0825] In addition, for example, the third chroma quantization parameter data may include a syntax element indicating the number of points of the third chroma QP mapping table for the joint CbCr component, a syntax element indicating an incremental value of input coordinates of a target point for deriving the third chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the third chroma QP mapping table. The syntax element indicating the number of points of the third chroma QP mapping table may be qPi_table_len_idx[i], and the syntax element indicating the incremental value of input coordinates of a target point for deriving the third chroma QP mapping table may be qp_table_len_idx[i]. C _qPi_in_idx[i][j], and a syntax element representing the delta value of the output coordinates of the target point for deriving the third chroma 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 through a high-level syntax. For example, the third chrominance quantization parameter data may be signaled through a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0826] Furthermore, for example, if the flag value is 1 (ie, the flag indicates that one chroma QP mapping table is applied to the chroma component), the chroma quantization parameter data may include chroma quantization parameter data of (one) chroma QP mapping table for the Cb component, the Cr component, and the joint CbCr component.

[0827] At the same time, for example, the image information may include prediction information and / or residual information for the chrominance component. For example, the image information may include prediction information for the chrominance component, and the prediction information may include prediction mode information. The prediction mode information may indicate whether inter-frame prediction or intra-frame prediction is applied to the current block for the chrominance component. In addition, for example, the residual information may include syntax elements of transform coefficients of the current block for the chrominance component. 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.

[0828] The decoding apparatus generates a reconstructed picture based on the image information ( S1210 ).

[0829] For example, the decoding device may derive a chroma QP mapping table based on the chroma quantization parameter data, derive chroma quantization parameters for chroma components based on the chroma QP mapping table, derive residual samples for chroma components based on the chroma quantization parameters, and generate a reconstructed picture based on the residual samples.

[0830] Specifically, for example, the decoding device may derive a chroma QP mapping table based on the chroma quantization parameter data. The chroma QP mapping table may be referred to as a chroma quantization parameter table or a user-defined quantization parameter mapping table.

[0831] For example, as described above, the chroma QP mapping table may be derived based on a syntax element indicating the number of points of the chroma QP mapping table, a syntax element indicating an incremental value of input coordinates of a target point for deriving the chroma QP mapping table, and / or a syntax element indicating an incremental value of output coordinates of a target point for deriving the chroma QP mapping table. That is, for example, the chroma QP mapping table for the chroma component may be derived based on the quantization parameter data. For example, as shown in Table 72 above, the chroma QP mapping table for the chroma component may be derived based on the quantization parameter data.

[0832] For example, if the flag value is 0 (i.e., the flag indicates that multiple chroma QP mapping tables are applied to chroma components), a first chroma QP mapping table for a chroma Cb component may be derived based on first chroma quantization parameter data of a first chroma QP mapping table for a Cb component. Also, for example, if the flag value is 0, a second chroma QP mapping table for a chroma Cb component may be derived based on second chroma quantization parameter data of a second chroma QP mapping table for a Cr component. Also, for example, if the flag value is 0, a first chroma QP mapping table for a chroma CbCr component may be derived based on third chroma quantization parameter data of a third chroma QP mapping table for a joint CbCr component.

[0833] In addition, for example, if the flag value is 1 (i.e., the flag indicates that a chroma QP mapping table is applied to the chroma component), the chroma quantization parameter table for the chroma component can be derived based on the chroma quantization parameter data of the chroma QP mapping table for the chroma component. The chroma component can include a Cb component, a Cr component, and / or a joint CbCr component.

[0834] Furthermore, for example, the decoding apparatus may derive chroma quantization parameters for chroma components based on the chroma QP mapping table.

[0835] For example, if the flag value is 0, a first chroma quantization parameter for a Cb component may be derived based on a first chroma QP mapping table, and a second chroma quantization parameter for a Cr component may be derived based on a second chroma QP mapping table. Also, for example, if the flag value is 0, a first chroma quantization parameter for a Cb component may be derived based on a first chroma QP mapping table, a second chroma quantization parameter for a Cr component may be derived based on a second chroma QP mapping table, and a third chroma quantization parameter for a joint CbCr component may be derived based on a third chroma QP mapping table. Here, the quantization parameter for the Cb component may represent the QP as described above. Cb , the quantization parameter for the Cr component can be expressed as QP` as described above Cr , and the quantization parameter for the joint CbCr component can represent QP` as described above CbCr .

[0836] For example, an index for a chroma component (Cb component, Cr component, or joint CbCr component) may be derived based on a quantization parameter for a luma component, and the chroma quantization parameter for the chroma component may be derived based on a chroma quantization parameter of a point of an index of a chroma QP mapping table for the chroma component. That is, for example, the chroma quantization parameter for the chroma component may be derived based on a chroma quantization parameter of a point of an index that is the same as the quantization parameter of the luma component in the chroma QP mapping table.

[0837] In addition, for example, the chroma quantization parameter (eg, QP) of a point indexed into a chroma QP mapping table for a chroma component (Cb component, Cr component, or joint CbCr component) may be set. Cb , QP CR or QP CbCr ) adds offsets to derive chroma quantization parameters (e.g., QP`) for chroma components Cb ,QP` Cr or QP` CbCr ). The offset may be derived based on a syntax element representing an offset for deriving a quantization parameter for a chroma component.

[0838] In addition, for example, if the flag value is 1, the chroma quantization parameters for the chroma components may be derived based on one chroma QP mapping table for the chroma components. Therefore, the chroma quantization parameters may be applied to the chroma components in the same manner.

[0839] For example, the index for the chroma component (Cb component, Cr component, and joint CbCr component) may be derived based on the quantization parameter for the luma component, and the chroma quantization parameter for the chroma component may be derived based on the chroma quantization parameter of the point of the index of the chroma QP mapping table for the chroma component. That is, for example, the chroma quantization parameter for the chroma component may be derived based on the chroma quantization parameter of the point of the same index as the quantization parameter of the luma component in the chroma QP mapping table.

[0840] Furthermore, for example, chroma quantization parameters for chroma components may be derived by adding an offset to the chroma quantization parameters for points indexed into the chroma QP mapping table for the chroma components. The offset may be derived based on a syntax element representing an offset for deriving the chroma quantization parameters for the chroma components.

[0841] Thereafter, for example, the decoding apparatus may derive residual samples for the chroma components based on the chroma quantization parameters.

[0842] For example, the decoding device may derive transform coefficients for chrominance components based on the received residual information. The image information may include residual information. In addition, for example, the decoding device may derive transform coefficients based on the received residual information, and may derive inversely transformed transform coefficients by inversely transforming the transform coefficients. The transform coefficients may include transform coefficients for Cb components, transform coefficients for Cr components, and / or transform coefficients for joint CbCr components.

[0843] Thereafter, the decoding apparatus may derive residual samples by dequantizing the transform coefficients based on the chrominance quantization parameters.

[0844] For example, if the flag value is 0, the decoding device may derive residual samples for the Cb component by dequantizing the transform coefficient for the Cb component based on the first chrominance quantization parameter for the Cb component, and may derive residual samples for the Cr component by dequantizing the transform coefficient for the Cr component based on the second chrominance quantization parameter for the Cr component. In addition, for example, if the flag value is 0, the decoding device may derive residual samples for the Cb component by dequantizing the transform coefficient for the Cb component based on the first chrominance quantization parameter for the Cb component, derive residual samples for the Cr component by dequantizing the transform coefficient for the Cr component based on the second chrominance quantization parameter for the Cr component, and derive residual samples for the joint CbCr component by dequantizing the transform coefficient for the joint CbCr component based on the third chrominance quantization parameter for the joint CbCr component. In addition, for example, if the flag value is 1, the decoding device may derive residual samples for the chrominance component by dequantizing the transform coefficient for the chrominance component based on the chrominance quantization parameter.

[0845] In addition, if the flag value is 0, the decoding device may derive residual samples for the Cb component by dequantizing the transform coefficient for the inverse transform of the Cb component based on the first chrominance quantization parameter for the Cb component, and may derive residual samples for the Cr component by dequantizing the transform coefficient for the inverse transform of the Cr component based on the second chrominance quantization parameter for the Cr component. In addition, for example, if the flag value is 0, the decoding device may derive residual samples for the Cb component by dequantizing the transform coefficient for the inverse transform of the Cb component based on the first chrominance quantization parameter for the Cb component, derive residual samples for the Cr component by dequantizing the transform coefficient for the inverse transform of the Cr component based on the second chrominance quantization parameter for the Cr component, and derive residual samples for the joint CbCr component by dequantizing the transform coefficient for the inverse transform of the joint CbCr component based on the third chrominance quantization parameter for the joint CbCr component. Furthermore, for example, if the flag value is 1, the decoding apparatus may derive residual samples for the chroma components by dequantizing transform coefficients for inverse transformation of the chroma components based on the chroma quantization parameters.

[0846] Thereafter, for example, the decoding device may generate a reconstructed picture based on the residual samples.

[0847] Meanwhile, for example, the decoding device may derive a prediction sample for a chroma component based on the received prediction information. The image information may include the prediction information. The decoding device may determine whether inter-frame prediction or intra-frame prediction is applied to the chroma component based on the received prediction information, and may perform prediction based on this. That is, the decoding device may determine whether inter-frame prediction or intra-frame prediction is applied to the current block of the chroma component based on the prediction information, and may perform prediction based on this.

[0848] For example, the decoding device may derive a prediction mode applied to the current block for the chrominance component based on the prediction information, and may derive a prediction sample 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 image information, and may derive a prediction sample of the current block based on the motion information. In addition, for example, if intra prediction is applied to the current block, the decoding device may derive a reference sample based on adjacent samples of the current block, and may derive a prediction sample of the current block based on the reference sample of the current block and the intra prediction mode. The reference sample 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 component and the y component of the upper left sample position of the current block are 0, respectively, the left reference sample may be p[-1][0] to p[-1][2N-1], and the upper reference sample may be p[0][-1] to p[2N-1][-1].

[0849] Thereafter, for example, the decoding device may generate a reconstructed picture based on the prediction sample and the residual sample. For example, the decoding device may generate a reconstructed sample and / or a reconstructed picture by adding the prediction sample and the residual sample.

[0850] Thereafter, as desired, in order to improve subjective / objective image quality, in-loop filtering processes such as deblocking filtering and SAO and / or ALF processes may be applied to the reconstructed samples as described above.

[0851] Fig.13 A decoding device for executing the image decoding method according to the document is schematically shown. Fig.12 The method disclosed in can be Fig.13 Specifically, for example, Fig.13 The entropy decoder of the decoding device can perform Fig.12 S1200, and Fig.13 The residual processor of the decoding device may perform Fig.12 S1210.

[0852] According to the present disclosure as described above, in order to derive chroma quantization parameters for chroma components, a chroma QP mapping table derived based on signaled chroma quantization parameter data can be used instead of a default chroma QP mapping table to derive chroma quantization parameters for chroma components, and by doing so, coding efficiency can be improved by performing coding based on quantization parameters according to characteristics of an image.

[0853] In addition, according to the present disclosure, a chroma QP mapping table may be derived based on a syntax element representing a delta value of input coordinates of a point for deriving the chroma QP mapping table and / or a syntax element representing a delta value of output coordinates of a point for deriving the chroma QP mapping table, and coding efficiency may be improved by performing coding based on the chroma QP mapping table that more specifically reflects characteristics of an image.

[0854] In the above embodiments, methods are described based on a flow chart with a series of steps or boxes. The present disclosure is not limited to the order of the above steps or boxes. Some steps or boxes can be performed in an order different from other steps or boxes mentioned above or performed simultaneously. In addition, it will be understood by those skilled in the art that the steps shown in the flow chart are not exclusive, and other steps may also be included, or one or more steps in the flow chart may be deleted without affecting the scope of the present disclosure.

[0855] The embodiments described in this specification may be implemented on a processor, a microprocessor, a controller or a chip. For example, the functional units shown in each figure may be implemented on a computer, a processor, a microprocessor, a controller or a chip. In this case, information (e.g., information about instructions) or algorithms for implementation may be stored in a digital storage medium.

[0856] In addition, the decoding device and encoding device of the present disclosure can be included in the following devices: multimedia broadcast sending / receiving devices, mobile communication terminals, home theater video devices, digital theater video devices, surveillance cameras, video chat devices, real-time communication devices such as video communication, mobile streaming devices, storage media, portable cameras, VoD service providers, over-the-top (OTT) video devices, Internet streaming service providers, three-dimensional (3D) video devices, teleconferencing video devices, transportation user devices (e.g., vehicle user devices, aircraft user devices, and ship user devices) and medical video equipment; and the decoding device and encoding device of the present disclosure can be used to process video signals or data signals. For example, over-the-top (OTT) video devices may include game consoles, Blu-ray players, Internet access televisions, home theater systems, smart phones, tablet computers, digital video recorders (DVRs), etc.

[0857] In addition, the processing method of the present invention can be generated in the form of a program executed by a computer, and can be stored in a computer-readable recording medium. The multimedia data with a data structure according to the present invention 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 may include, for example, BD, universal serial bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage device. In addition, the computer-readable recording medium includes a medium implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, the bit stream generated by the encoding method can be stored in a computer-readable recording medium or transmitted via a wired / wireless communication network.

[0858] In addition, the embodiments of the present disclosure may be implemented using a computer program product according to a program code, and the program code may be executed in a computer through the embodiments of the present disclosure. The program code may be stored on a computer readable carrier.

[0859] Fig.14 A structural diagram of a content streaming system to which the present disclosure is applied is illustrated.

[0860] The content streaming system to which the embodiments of the present disclosure are applied may mainly include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0861] 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.

[0862] A bitstream may be generated by an encoding method or a bitstream generating method to which an embodiment of the present disclosure is applied, and a streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0863] The streaming server sends multimedia data to the user device through the network server based on the user request, and the network server is used as a medium to notify the user of the service. When the user requests the required service from the network server, the network server delivers the request to the streaming server, and the streaming server sends the multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server is used to control the command / response between the devices within the content streaming system.

[0864] The streaming server can receive content from a media storage and / or encoding server. For example, when receiving content from an encoding server, the content can be received in real time. In this case, in order to provide a stable streaming service, the streaming server can store the bitstream for a predetermined period of time.

[0865] Examples of user devices may include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigators, touch screen PCs, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, 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, in which case data received from each server may be distributed.

[0866] 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 implement as a device, and the technical features of the device claims of this disclosure can be combined to implement as a method. In addition, the technical features of the method claims of this disclosure and the technical features of the device claims can be combined to implement as a device, and the technical features of the method claims of this disclosure and the technical features of the device claims can be combined to implement as a method.

Claims

1. A method for decoding an image performed by a decoding device, the method comprising: Obtain image information through bit stream; as well as Based on the image information, a reconstructed image is generated, Wherein, obtaining the image information includes: Obtaining (i) a flag indicating whether a chroma quantization parameter (QP) map is signaled and applied to a chroma component, and (ii) a joint CbCr enable flag, wherein the chroma component includes a Cb component, a Cr component, and a joint CbCr component; and obtaining chroma quantization parameter data for at least one chroma QP mapping table for the chroma component based on (i) the flag and (ii) the joint CbCr enabled flag, The chroma quantization parameter data includes a syntax element for the number of points in the chroma QP mapping table, a syntax element for a delta value used to derive an input coordinate of a target point of the chroma QP mapping table, and a syntax element for a delta value used to derive an output coordinate of a target point of the chroma QP mapping table, wherein, based on the value of the flag being equal to 1, one chroma QP mapping table is signaled and applied to the Cb component, the Cr component, and the joint CbCr component, and wherein chroma quantization parameters for the Cb component, the Cr component, and the joint CbCr component are derived based on the one chroma QP mapping table, and wherein, based on the value of the flag being equal to 0 and the value of the joint-CbCr enable flag being equal to 1, a plurality of chroma QP mapping tables including each chroma QP mapping table for each of the Cb component, the Cr component, and the joint-CbCr component are signaled, and wherein chroma quantization parameters for the Cb component, the Cr component, and the joint-CbCr component are derived based on each chroma QP mapping table for each of the Cb component, the Cr component, and the joint-CbCr component.

2. A method for encoding an image performed by an encoding device, the method comprising: Encode image information; as well as generating a bit stream including the image information, Wherein, encoding the image information comprises: Obtaining (i) a flag indicating whether a chroma quantization parameter (QP) map is signaled and applied to a chroma component, and (ii) a joint CbCr enable flag, wherein the chroma component includes a Cb component, a Cr component, and a joint CbCr component; and generating chroma quantization parameter data for at least one chroma QP mapping table for a chroma component based on (i) the flag and (ii) the joint CbCr enabled flag, The chroma quantization parameter data includes a syntax element for the number of points in the chroma QP mapping table, a syntax element for a delta value used to derive an input coordinate of a target point of the chroma QP mapping table, and a syntax element for a delta value used to derive an output coordinate of a target point of the chroma QP mapping table, wherein, based on the value of the flag being equal to 1, one chroma QP mapping table is signaled and applied to the Cb component, the Cr component, and the joint CbCr component, and wherein chroma quantization parameters for the Cb component, the Cr component, and the joint CbCr component are derived based on the one chroma QP mapping table, and wherein, based on the value of the flag being equal to 0 and the value of the joint-CbCr enable flag being equal to 1, a plurality of chroma QP mapping tables including each chroma QP mapping table for each of the Cb component, the Cr component, and the joint-CbCr component are signaled, and wherein chroma quantization parameters for the Cb component, the Cr component, and the joint-CbCr component are derived based on each chroma QP mapping table for each of the Cb component, the Cr component, and the joint-CbCr component.

3. A method for transmitting image data, the method comprising: Obtaining a bitstream of image information, the bitstream being generated based on (i) generating a flag indicating whether a chroma quantization parameter (QP) mapping table is signaled and applied to a chroma component, and (ii) a joint CbCr enable flag, wherein the chroma component includes a Cb component, a Cr component, and a joint CbCr component, generating chroma quantization parameter data of at least one chroma QP mapping table for the chroma component based on (i) the flag and (ii) the joint CbCr enable flag, and encoding image information including the flag, the joint CbCr enable flag, and the chroma quantization parameter data; and sending data of the bit stream including the image information, The chroma quantization parameter data includes a syntax element for the number of points in the chroma QP mapping table, a syntax element for a delta value of an input coordinate used to derive a target point of the chroma QP mapping table, and a syntax element for a delta value of an output coordinate used to derive the target point of the chroma QP mapping table. wherein, based on the value of the flag being equal to 1, one chroma QP mapping table is signaled and applied to the Cb component, the Cr component, and the joint CbCr component, and wherein chroma quantization parameters for the Cb component, the Cr component, and the joint CbCr component are derived based on the one chroma QP mapping table, and wherein, based on the value of the flag being equal to 0 and the value of the joint-CbCr enable flag being equal to 1, a plurality of chroma QP mapping tables including each chroma QP mapping table for each of the Cb component, the Cr component, and the joint-CbCr component are signaled, and wherein chroma quantization parameters for the Cb component, the Cr component, and the joint-CbCr component are derived based on each chroma QP mapping table for each of the Cb component, the Cr component, and the joint-CbCr component.

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