Image decoding method and device

Abstract

To provide image decoding method and device for coding image information including chroma quantization parameter data for deriving a chroma quantization parameter table for a chroma component.SOLUTION: An image decoding method includes obtaining a flag indicating whether one chroma quantization parameter table is applied to a chroma component and image information such as chroma quantization parameter data on the basis of the flag, and generating a reconstructed picture on the basis of the image information. When the value of the flag is 0, the chroma quantization parameter data includes first chroma quantization parameter data for a Cb component and second chroma quantization parameter data for a Cr component.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] This document relates to image coding technology, and more particularly, to an image decoding method and apparatus for coding image information including chroma quantization parameter data for deriving a chroma quantization parameter table for a chroma component in an image coding system.

Background Art

[0002] Recently, the demand for high-resolution and high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images has been increasing in various fields. As the image data becomes higher in resolution and quality, the amount of information or bits transmitted relatively increases compared to the existing image data. Therefore, when transmitting image data using a medium such as an existing wired or wireless broadband line, or storing image data using an existing storage medium, the transmission cost and storage cost increase.

[0003] Accordingly, in order to effectively transmit, store, and reproduce information of high-resolution and high-quality images, a highly efficient image compression technology is required.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technical problem of this document is to provide a method and apparatus for increasing image coding efficiency.

[0005] Another technical problem of this document is to provide a method and apparatus for increasing the efficiency of data coding for deriving a quantization parameter for a chroma component.

Means for Solving the Problems

[0006] According to an embodiment of the present document, an image decoding method performed by a decoding device is provided. The method includes a step of acquiring image information and a step of generating a reconstructed picture based on the image information, and includes a step of acquiring a flag indicating whether one chroma quantization parameter table is applied to a chroma component, and a step of acquiring chroma quantization parameter data based on the flag. When the value of the flag is 0, the chroma quantization parameter data includes first chroma quantization parameter data for a Cb component and second chroma quantization parameter data for a Cr component.

[0007] According to another embodiment of the present document, a decoding device for performing image decoding is provided. The decoding device includes an entropy decoding unit that acquires image information and a residual processing unit that generates a reconstructed picture based on the image information. The entropy decoding unit acquires a flag indicating whether one chroma quantization parameter table is applied to a chroma component, acquires chroma quantization parameter data based on the flag, and when the value of the flag is 0, the chroma quantization parameter data includes first chroma quantization parameter data for a Cb component and second chroma quantization parameter data for a Cr component.

[0008] According to still another embodiment of the present document, a video encoding method performed by an encoding device is provided. The method includes a step of encoding image information and a step of generating a bitstream including the image information. The step of encoding the image information includes a step of generating a flag indicating whether one chroma quantization parameter table is applied to a chroma component, a step of generating chroma quantization parameter data for the chroma component based on the flag, and a step of encoding the chroma quantization parameter data and the flag. When the value of the flag is 0, the chroma quantization parameter data includes first chroma quantization parameter data for a Cb component and second chroma quantization parameter data for a Cr component.

[0009] According to still another embodiment of the present document, a video encoding device is provided. The encoding device includes an entropy encoding unit that encodes image information and generates a bitstream including the image information. The entropy encoding unit generates a flag indicating whether one chroma quantization parameter table is applied to a chroma component, generates chroma quantization parameter data for the chroma component based on the flag, encodes the chroma quantization parameter data and the flag, and when the value of the flag is 0, the chroma quantization parameter data includes first chroma quantization parameter data for a Cb component and second chroma quantization parameter data for a Cr component.

Advantages of the Invention

[0010] According to this document, for deriving quantization parameters for chroma components, a chroma quantization parameter table for chroma components can be determined based on a flag indicating whether the same chroma quantization parameter table is used, and coding can be performed based on quantization parameters according to the characteristics of an image to improve coding efficiency.

[0011] According to this document, a chroma quantization parameter table for chroma components can be determined based on chroma quantization data signaled individually or commonly for chroma components, and coding can be performed based on quantization parameters according to the characteristics of an image to improve coding efficiency.

Brief Description of Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] This document can be modified in various ways, can have various embodiments, and specific embodiments are illustrated in the drawings and will be described in detail. However, this is not intended to limit this document to specific embodiments. The terms commonly used in this specification are merely used to describe specific embodiments and are not used with the intention of limiting the technical idea of this document. Singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as "including" or "having" in this specification are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and it should be understood that the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof is not precluded in advance.

[0014] On the other hand, each configuration in the drawings described in this document is independently illustrated for the convenience of explaining different characteristic functions, and it does not mean that each configuration is realized by separate hardware or separate software. For example, among the configurations, two or more configurations can be combined to form one configuration, and one configuration can also be divided into multiple configurations. Embodiments in which each configuration is integrated and / or separated are included in the scope of rights of this document as long as they do not deviate from the essence of this document.

[0015] Hereinafter, with reference to the accompanying drawings, preferred embodiments of this document will be described in more detail. Hereinafter, for the same components on the drawings, the same reference numerals are used, and overlapping descriptions for the same components can be omitted.

[0016] FIG. 1 schematically shows an example of a video / image coding system to which an embodiment of this document can be applied.

[0017] As shown in FIG. 1, the video / image coding system can include a first device (source device) and a second device (receiving device). The source device can transmit encoded video / image information or data in a file or streaming form to the receiving device via a digital storage medium or a network.

[0018] The source device can include a video source, an encoding device, and a transmitting unit. The receiving device can include a receiving unit, a decoding device, and a renderer. The encoding device can be called a video / image encoding device, and the decoding device can be called a video / image decoding device. A transmitter can be included in the encoding device. A receiver can be included in the decoding device. The renderer can include a display unit, and the display unit can also be composed of a separate device or an external component.

[0019] The video source can obtain video / images through processes such as video / image capture, synthesis, or generation. The video source can include a video / image capture device and / or a video / image generation device. The video / image capture device can be equipped with, for example, one or more cameras, a video / image archive containing previously captured video / images, etc. The video / image generation device can be equipped with, for example, a computer, a tablet, and a smartphone, etc., and can (electronically) generate video / images. For example, virtual video / images can be generated via a computer or the like, in which case the video / image capture process can be replaced during the process of generating related data.

[0020] The encoding device can encode the input video / image. The encoding device can execute a series of procedures such as prediction, transformation, quantization, etc. for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0021] The transmitting unit can transmit the encoded video / image information or data output in the form of a bitstream to the receiving unit of the receiving device via a digital storage medium or a network in file or streaming form. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitting unit can include elements for generating a media file via a predetermined file format and can include elements for transmission via a broadcast / communication network. The receiving unit can receive / extract the bitstream and transmit it to the decoding device.

[0022] The decoding device can execute a series of procedures such as inverse quantization, inverse transformation, prediction, etc. corresponding to the operation of the encoding device to decode the video / image.

[0023] The renderer can render the decoded video / image. The rendered video / image can be displayed via the display unit.

[0024] This document relates to video / image coding. For example, the methods / embodiments disclosed in this document can be applied to the methods disclosed in the VVC (versatile video coding) standard, EVC (essential video coding) standard, AV1 (AOMedia Video 1) standard, AVS2 (2nd generation of audio video coding standard), or the next-generation video / image coding standard (e.g., H.267 or H.268, etc.).

[0025] This document presents various embodiments related to video / image coding, and unless otherwise stated, the embodiments can also be executed in combination with each other.

[0026] In this document, video may mean a set of a series of images over time. Picture generally means a unit indicating one image in a specific time period, and subpicture / slice / tile is a unit constituting a part of a picture in coding. A subpicture / slice / tile may include one or more CTUs (coding tree units). One picture may be composed of one or more subpictures / slices / tiles. One picture may be composed of one or more groups of tiles. One tile group may include one or more tiles. A brick represents a rectangular region of CTU rows within a tile in a picture. A tile may be partitioned into multiple bricks, each of which consisting of one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may be also referred to as a brick.A brick scan shows a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a brick, bricks within a tile are ordered consecutively in a raster scan of the bricks of the tile, and tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture. Also, a subpicture may represent a rectangular region of one or more slices within a picture. That is, a subpicture contains one or more slices that collectively cover a rectangular region of a picture. A tile is a rectangular region of CTUs within a particular tile column and a particular tile row in a picture.The tile column is a rectangular region of CTUs having a height equal to the height of the picture and a width specified by syntax elements in the picture parameter set. The tile row is a rectangular region of CTUs having a height specified by syntax elements in the picture parameter set and a width equal to the width of the picture. A tile scan is a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a tile whereas tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture.A slice includes an integer number of bricks of a picture that maybe exclusively contained in a single NAL unit. A slice may consists of either a number of complete tiles or only a consecutive sequence of complete bricks of one tile. In this document, tile group and slice may be used interchangeably. For example, in this document, tile group / tile group header may be called slice / slice header.

[0027] A pixel or pel can mean the smallest unit that makes up a picture (or image). Also, the term "sample" can be used as the term corresponding to a pixel. A sample can generally indicate a pixel or the value of a pixel, and can also indicate only the pixel / pixel value of the luma component, or only the pixel / pixel value of the chroma component.

[0028] A unit can indicate the basic unit of image processing. A unit can include at least one of a specific region of a picture and information related to that region. One unit can include one luma block and two chroma (e.g., cb, cr) blocks. A unit can, in some cases, be used interchangeably with terms such as block or area. In general, an M×N block can include a sample (or sample array) consisting of M columns and N rows, or a set (or array) of transform coefficients.

[0029] In this specification, "A or B" may mean "only A", "only B", or "both A and B". In other words, in this specification, "A or B" may be construed as "A and / or B". For example, in this specification, "A, B, or C" may mean "only A", "only B", "only C", or "any combination of A, B, and C".

[0030] The slashes ( / ) and commas used in this specification may mean "and / or". For example, "A / B" may mean "A and / or B". Thus, "A / B" may mean "only A", "only B", or "both A and B". For example, "A, B, C" may mean "A, B, or C".

[0031] In this specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". Also, in this specification, expressions such as "at least one of A or B" and "at least one of A and / or B" may be construed in the same way as "at least one of A and B".

[0032] Also, in this specification, "at least one of A, B and C" may mean "only A", "only B", "only C", or "any combination of A, B and C". Also, "at least one of A, B or C" and "at least one of A, B and / or C" may mean "at least one of A, B and C".

[0033] Also, the parentheses used in this specification may mean "for example". Specifically, when it is displayed as "prediction (intra prediction)", "intra prediction" may be proposed as an example of "prediction". In other words, the "prediction" in this specification is not limited to "intra prediction", and "intra prediction" may be proposed as an example of "prediction". Also, when it is displayed as "prediction (that is, intra prediction)", "intra prediction" may be proposed as an example of "prediction".

[0034] The technical features separately described within one drawing in this specification may be realized separately or simultaneously.

[0035] The following drawings are created to illustrate a specific example of this specification. Since the names of the specific devices and the names of the specific signals / messages / fields described in the drawings are presented exemplarily, the technical features of this specification are not limited to the specific names used in the following drawings.

[0036] FIG. 2 is a diagram schematically explaining the configuration of a video / image encoding device to which the embodiment of this document can be applied. Hereinafter, the video encoding device can include an image encoding device.

[0037] As shown in FIG. 2, the encoding apparatus 200 can be configured to include an image partitioner 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 can include an inter-predictor 221 and an intra-predictor 222. The residual processor 230 can include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 can further include a subtractor 231. The adder 250 can be referred to as a reconstructor or a reconstructed block generator. The aforementioned image partitioner 210, predictor 220, residual processor 230, entropy encoder 240, adder 250, and filter 260 can be configured by one or more hardware components (e.g., an encoder chipset or a processor) according to an embodiment. Also, the memory 270 can include a DPB (decoded picture buffer) and can also be configured by a digital storage medium. The hardware component can further include the memory 270 as an internal / external component.

[0038] The image segmentation unit 210 can divide an input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, the processing unit can be called a coding unit (CU). In this case, the coding unit can be recursively divided from a coding tree unit (CTU) or a largest coding unit (LCU) by a QTBTTT (Quad-tree binary-tree ternary-tree) structure. For example, one coding unit can be divided into a plurality of coding units with a deeper depth based on a quad-tree structure, a binary-tree structure, and / or a ternary structure. In this case, for example, the quad-tree structure can be applied first, and the binary-tree structure and / or the ternary structure can be applied later. Or, the binary-tree structure can also be applied first. The coding procedure according to this document can be executed based on the final coding unit that cannot be further divided. In this case, based on the coding efficiency according to the image characteristics, etc., the largest coding unit can be immediately used as the final coding unit, or, if necessary, the coding unit can be recursively divided into coding units with a deeper depth, and the coding unit with the optimal size can be used as the final coding unit. Here, the coding procedure can include procedures such as prediction, conversion, and restoration described later. As another example, the processing unit can further include a prediction unit (PU: Prediction Unit) or a transform unit (TU: Transform Unit). In this case, the prediction unit and the transform unit can each be divided or partitioned from the final coding unit described above.The prediction unit is a unit of sample prediction, and the conversion unit is a unit for deriving a conversion coefficient and / or a unit for deriving a residual signal from the conversion coefficient.

[0039] A unit can, in some cases, be used interchangeably with terms such as a block or an area. In general, an M×N block can represent a set of samples or transform coefficients consisting of M columns and N rows. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luma component, or only the pixel / pixel value of the chroma component. A sample can be used as a term corresponding to a pixel or a pel for one picture (or image).

[0040] The encoding device 200 can subtract a prediction signal (predicted block, predicted sample array) output from the inter prediction unit 221 or the intra prediction unit 222 from an input image signal (original block, original sample array) to generate a residual signal (residual signal, residual block, residual sample array), and the generated residual signal is transmitted to the conversion unit 232. In this case, as shown in the figure, the unit that subtracts the prediction signal (predicted block, predicted sample array) from the input image signal (original block, original sample array) in the encoder 200 can be called the subtraction unit 231. The prediction unit can perform a prediction on a processing target block (hereinafter referred to as the current block) and generate a predicted block including predicted samples for the current block. The prediction unit can determine whether intra prediction or inter prediction is applied in units of the current block or CU. The prediction unit can generate various pieces of information related to prediction, such as prediction mode information, and transmit them to the entropy encoding unit 240 as described later in the description of each prediction mode. The information related to prediction can be encoded by the entropy encoding unit 240 and output in the form of a bit stream.

[0041] The intra prediction unit 222 can predict the current block by referring to samples within the current picture. The samples to be referred to can be located in the neighborhood of the current block according to the prediction mode, or can also be located remotely. In intra prediction, the prediction mode can include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes can include, for example, the DC mode and the Planar Mode. The directional modes can include, for example, 33 directional prediction modes or 65 directional prediction modes depending on the degree of fineness of the prediction direction. However, this is only an example, and more or fewer directional prediction modes can be used depending on the setting. The intra prediction unit 222 can also determine the prediction mode to be applied to the current block by using the prediction mode applied to the adjacent blocks.

[0042] The inter prediction unit 221 can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between adjacent blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the adjacent blocks can include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing 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 can be called by names such as a collocated reference block and a collocated CU (colCU), and the reference picture including the temporal neighboring block can also be called a collocated picture (colPic). For example, the inter prediction unit 221 can construct a motion information candidate list based on adjacent blocks and generate information indicating which candidates are used to derive the motion vector and / or reference picture index of the current block. Inter prediction can be performed based on various prediction modes. For example, in the case of the skip mode and the merge mode, the inter prediction unit 221 can use the motion information of adjacent blocks as the motion information of the current block. In the case of the skip mode, a residual signal may not be transmitted, which is different from the merge mode.In the case of the motion information prediction (motion vector prediction, MVP) mode, the motion vector of an adjacent block can be used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling the motion vector difference.

[0043] The prediction unit 220 can generate a prediction signal based on various prediction methods described later. For example, for the prediction of one block, the prediction unit can apply not only intra prediction or inter prediction, but also simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). Also, the prediction unit can be based on the intra block copy (IBC) prediction mode or the palette mode for the prediction of the block. The IBC prediction mode or the palette mode can be used for content image / video coding such as games, for example, like SCC (screen content coding). IBC basically performs prediction within the current picture, but can be executed similarly to inter prediction in terms of deriving a reference block within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in this document. The palette mode can be regarded as an example of intra coding or intra prediction. When the palette mode is applied, the sample values in the picture can be signaled based on the information regarding the palette table and the palette index.

[0044] The prediction signal generated via the prediction unit (including the inter prediction unit 221 and / or the intra prediction unit 222) can be used to generate a restored signal or can be used to generate a residual signal. The conversion unit 232 can apply a conversion technique to the residual signal to generate transform coefficients. For example, the conversion technique can include at least one of DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT (Karhunen-Loeve Transform), GBT (Graph-Based Transform), or CNT (Conditionally Non-linear Transform). Here, GBT means a conversion obtained from a graph when representing the relationship information between pixels as a graph. CNT means a conversion obtained based on generating a prediction signal using all previously reconstructed pixels. Also, the conversion process can be applied to a pixel block having the same size of a square and can also be applied to a non-square, variable-size block.

[0045] The quantization unit 233 quantizes the transform coefficients and transmits them to the entropy encoding unit 240. The entropy encoding unit 240 can encode the quantized signal (information regarding the quantized transform coefficients) and output it as a bitstream. The information regarding the quantized transform coefficients can be referred to as residual information. The quantization unit 233 can reorder the quantized transform coefficients in block form into a one-dimensional vector form based on the coefficient scan order, and can also generate the information regarding the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. The entropy encoding unit 240 can execute various encoding methods such as, for example, exponential Golomb, CAVLC (context-adaptive variable length coding), CABAC (context-adaptive binary arithmetic coding), etc. The entropy encoding unit 240 can encode, together or separately, in addition to the quantized transform coefficients, information necessary for video / image restoration (e.g., values of syntax elements, etc.). The encoded information (e.g., encoded video / image information) can be transmitted or stored in the form of a bitstream in units of NAL (network abstraction layer) units. The video / image information can further include information regarding various parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Also, the video / image information can further include general constraint information. In this document, the information and / or syntax elements transmitted / signaled from the encoding device to the decoding device can be included in the video / image information. The video / image information can be encoded through the above-described encoding procedure and included in the bitstream.The bitstream can be transmitted via a network or stored in a digital storage medium. Here, the network can include a broadcast network and / or a communication network, etc., and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The signal output from the entropy encoding unit 240 can be configured as an internal / external element of the encoding device 200 by a transmission unit (not shown) for transmission and / or a storage unit (not shown) for storage, or the transmission unit can also be included in the entropy encoding unit 240.

[0046] The quantized transform coefficients output from the quantization unit 233 can be used to generate a prediction signal. For example, a residual signal (residual block or residual sample) can be restored by applying inverse quantization and inverse transformation to the quantized transform coefficients via the inverse quantization unit 234 and the inverse transform unit 235. The addition unit 250 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the restored residual signal to the prediction signal output from the inter prediction unit 221 or the intra prediction unit 222. When there is no residual for the block to be processed, as in the case where the skip mode is applied, the predicted block can be used as the reconstructed block. The addition unit 250 can be called a restoration unit or a reconstructed block generation unit. The generated reconstructed signal can be used for intra prediction of the next block to be processed within the current picture, and as will be described later, can also be used for inter prediction of the next picture after passing through filtering.

[0047] On the other hand, LMCS (luma mapping with chroma scaling) can also be applied in the picture encoding and / or restoration process.

[0048] The filtering unit 260 can apply filtering to the restored signal to improve the subjective / objective image quality. For example, the filtering unit 260 can apply various filtering methods to the restored picture to generate a modified restored picture, and can store the modified restored picture in the memory 270, specifically, in the DPB of the memory 270. The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like. The filtering unit 260 can generate various information related to filtering and transmit it to the entropy encoding unit 240 as will be described later in the description of each filtering method. The information related to filtering can be encoded by the entropy encoding unit 240 and output in the form of a bit stream.

[0049] The modified restored picture transmitted to the memory 270 can be used as a reference picture in the inter prediction unit 221. Through this, when inter prediction is applied, the encoding device can avoid prediction mismatches between the encoding device 200 and the decoding device 300, and can also improve the encoding efficiency.

[0050] The memory 270 DPB can store the modified restored picture for use as a reference picture in the inter prediction unit 221. The memory 270 can store the motion information of the blocks for which the motion information in the current picture has been derived (or encoded) and / or the motion information of the blocks in the already restored picture. The stored motion information can be transmitted to the inter prediction unit 221 for utilization as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 270 can store the restored samples of the restored blocks in the current picture and transmit them to the intra prediction unit 222.

[0051] FIG. 3 is a diagram schematically illustrating a configuration of a video / image decoding apparatus to which an embodiment of this document can be applied.

[0052] As shown in FIG. 3, the decoding apparatus 300 can be configured to include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filtering unit 350, and a memory 360. The predictor 330 can include an inter-prediction unit 331 and an intra-prediction unit 332. The residual processor 320 can include a dequantizer 321 and an inverse transformer 322. The entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filtering unit 350 described above can be configured by one hardware component (for example, a decoder chipset or a processor) according to an embodiment. Also, the memory 360 can include a DPB (decoded picture buffer) and can also be configured by a digital storage medium. The hardware component can further include the memory 360 as an internal / external component.

[0053] When a bitstream including video / image information is input, the decoding device 300 can restore an image corresponding to the process in which the video / image information was processed by the encoding device in FIG. 2. For example, the decoding device 300 can derive units / blocks based on the block splitting related information obtained from the bitstream. The decoding device 300 can execute decoding using the processing units applied in the encoding device. Therefore, the processing unit for decoding is, for example, a coding unit, and the coding unit can be split according to a quad tree structure, a binary tree structure, and / or a ternary tree structure from a coding tree unit or a maximum coding unit. One or more transform units can be derived from the coding unit. Then, the restored image signal decoded and output via the decoding device 300 can be played back via a playback device.

[0054] The decoding device 300 can receive the signal output from the encoding device of FIG. 2 in the form of a bitstream, and the received signal can be decoded via the entropy decoding unit 310. For example, the entropy decoding unit 310 can parse the bitstream to derive information (e.g., video / image information) necessary for image restoration (or picture restoration). The video / image information can further include information regarding various parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Also, the video / image information can further include general constraint information. The decoding device can further decode the picture based on the information regarding the parameter set and / or the general constraint information. The signaling / received information and / or syntax elements described later in this document can be decoded via the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 can decode the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output values of syntax elements necessary for image restoration, quantized values of transform coefficients regarding the residual, etc. More specifically, the CABAC entropy decoding method receives bins corresponding to each syntax element in the bitstream, determines a context model using the syntax element information to be decoded, the information of the surrounding and decoded blocks of the decoding target, or the information of the symbols / bins decoded in the previous step, predicts the occurrence probability of the bin based on the determined context model, and executes arithmetic decoding of the bin to generate a symbol corresponding to the value of each syntax element. At this time, the CABAC entropy decoding method can update the context model using the information of the symbols / bins decoded for the context model of the next symbol / bin after determining the context model.Of the information decoded by the entropy decoding unit 310, the information related to prediction is provided to the prediction unit (inter prediction unit 332 and intra prediction unit 331), and the residual value for which entropy decoding is performed by the entropy decoding unit 310, that is, the quantized transform coefficient and related parameter information can be input to the residual processing unit 320. The residual processing unit 320 can derive a residual signal (residual block, residual sample, residual sample array). Also, among the information decoded by the entropy decoding unit 310, the information related to filtering can be provided to the filtering unit 350. On the other hand, a receiving unit (not shown) that receives the signal output from the encoding device can be further configured as an internal / external element of the decoding device 300, or the receiving unit is a component of the entropy decoding unit 310. On the other hand, the decoding device according to the present document can be called a video / image / picture decoding device, and the decoding device can be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder can include the entropy decoding unit 310, and the sample decoder can include at least one of the inverse quantization unit 321, inverse transform unit 322, addition unit 340, filtering unit 350, memory 360, inter prediction unit 332, and intra prediction unit 331.

[0055] In the inverse quantization unit 321, the quantized transform coefficient can be inverse quantized to output a transform coefficient. The inverse quantization unit 321 can reorder the quantized transform coefficients in a two-dimensional block form. In this case, the reordering can be performed based on the coefficient scan order executed by the encoding device. The inverse quantization unit 321 can perform inverse quantization on the quantized transform coefficient using a quantization parameter (for example, quantization step size information) to obtain a transform coefficient.

[0056] In the inverse conversion unit 322, the conversion coefficient is inversely converted to obtain a residual signal (residual block, residual sample array).

[0057] The prediction unit can perform prediction on the current block and generate a predicted block including prediction samples for the current block. The prediction unit can determine whether intra prediction or inter prediction is applied to the current block based on the information regarding the prediction output from the entropy decoding unit 310, and can determine a specific intra / inter prediction mode.

[0058] The prediction unit 320 can generate a prediction signal based on various prediction methods described later. For example, the prediction unit can not only apply intra prediction or inter prediction for predicting one block, but also apply intra prediction and inter prediction simultaneously. This can be called combined inter and intra prediction (CIIP). Also, the prediction unit can be based on the intra block copy (IBC) prediction mode or the palette mode for predicting a block. The IBC prediction mode or the palette mode can be used for content image / video coding such as games, for example, like SCC (screen content coding). IBC basically performs prediction within the current picture, but can be executed similarly to inter prediction in terms of deriving a reference block within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in this document. The palette mode can be regarded as an example of intra coding or intra prediction. When the palette mode is applied, information regarding the palette table and the palette index can be included in and signaled in the video / image information.

[0059] The intra prediction unit 331 can predict the current block by referring to samples within the current picture. The samples to be referred can be located in the neighborhood of the current block or at a distance therefrom, depending on the prediction mode. In intra prediction, the prediction mode can include a plurality of non - directional modes and a plurality of directional modes. The intra prediction unit 331 can also determine the prediction mode to be applied to the current block using the prediction mode applied to an adjacent block.

[0060] The inter prediction unit 332 can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted from the inter prediction mode, the motion information can be predicted in units of blocks, sub - blocks, or samples based on the correlation of motion information between an adjacent block and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the adjacent blocks can include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter prediction unit 332 can construct a motion information candidate list based on adjacent blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter prediction can be executed based on various prediction modes, and the information regarding the prediction can include information indicating the mode of inter prediction for the current block.

[0061] The adder 340 can generate a restored signal (restored picture, restored block, restored sample array) by adding the obtained residual signal to the predicted signal (predicted block, predicted sample array) output from the prediction unit (including the inter prediction unit 332 and / or the intra prediction unit 331). When there is no residual for the block to be processed, as in the case where the skip mode is applied, the predicted block can be used as the restored block.

[0062] The adder 340 can be referred to as a restoration unit or a restored block generation unit. The generated restored signal can be used for intra prediction of the next block to be processed in the current picture, and as will be described later, can be output after passing through filtering, or can also be used for inter prediction of the next picture.

[0063] On the other hand, LMCS (luma mapping with chroma scaling) can also be applied in the picture decoding process.

[0064] The filtering unit 350 can apply filtering to the restored signal to improve the subjective / objective image quality. For example, the filtering unit 350 can apply various filtering methods to the restored picture to generate a modified restored picture, and can transmit the modified restored picture to the memory 360, specifically, to the DPB of the memory 360. The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0065] The (corrected) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter prediction unit 332. The memory 360 can store the motion information of the block for which the motion information in the current picture has been derived (or decoded) and / or the motion information of the blocks in the already reconstructed picture. The stored motion information can be transmitted to the inter prediction unit 260 for utilization as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 360 can store the reconstructed samples of the reconstructed blocks in the current picture and can transmit them to the intra prediction unit 331.

[0066] In this specification, the embodiments described in the filtering unit 260, the inter prediction unit 221, and the intra prediction unit 222 of the encoding device 200 can also be applied to the filtering unit 350, the inter prediction unit 332, and the intra prediction unit 331 of the decoding device 300 so as to be identical or corresponding.

[0067] In this document, at least one of quantization / inverse quantization and / or transform / inverse transform can be omitted. When the quantization / inverse quantization is omitted, the quantized transform coefficients can be called transform coefficients. When the transform / inverse transform is omitted, the transform coefficients can be called coefficients or residual coefficients, or can still be called transform coefficients for the sake of uniformity of expression.

[0068] In this document, the quantized transform coefficients and the transform coefficients can be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, the residual information can include information regarding the transform coefficients (etc.), and the information regarding the transform coefficients (etc.) can be signaled via a residual coding syntax. The transform coefficients can be derived based on the residual information (or the information regarding the transform coefficients (etc.)), and the scaled transform coefficients can be derived via an inverse transform (scaling) for the transform coefficients. The residual samples can be derived based on an inverse transform (transformation) for the scaled transform coefficients. This can be applied / expressed similarly in other parts of this document.

[0069] As described above, in performing video coding, prediction is performed to increase the compression efficiency. Through this, a predicted block including prediction samples for the current block, which is the block to be coded, can be generated. Here, the predicted block includes prediction samples in the spatial domain (or pixel domain). The predicted block is derived identically in the encoding device and the decoding device, and the encoding device can increase the image coding efficiency by signaling to the decoding device information regarding the residual (residual information) between the original block, which is not the original sample value of the original block itself, and the predicted block. The decoding device can derive a residual block including residual samples based on the residual information, and can generate a restored block including restored samples by combining the residual block and the predicted block, and can generate a restored picture including the restored block.

[0070] The residual information can be generated through the conversion and quantization procedures. For example, an encoding device can derive a residual block between the original block and the predicted block, perform a conversion procedure on the residual samples (residual sample array) included in the residual block to derive conversion coefficients, perform a quantization procedure on the conversion coefficients to derive quantized conversion coefficients, and signal the related residual information (via a bitstream) to a decoding device. Here, the residual information can include information such as the value information, position information, conversion technique, conversion kernel, quantization parameter, etc. of the quantized conversion coefficients. The decoding device can perform an inverse quantization / inverse conversion procedure based on the residual information to derive residual samples (or a residual block). The decoding device can generate a restored picture based on the predicted block and the residual block. The encoding device can further inverse quantize / inverse convert the quantized conversion coefficients to derive a residual block for reference in the inter prediction of subsequent pictures, and generate a restored picture based on this.

[0071] Intra prediction can represent a prediction that generates prediction samples for a current block based on reference samples within a picture to which the current block belongs (hereinafter, the current picture). When intra prediction is applied to the current block, peripheral reference samples to be used for intra prediction of the current block can be derived. The peripheral reference samples of the current block can include a total of 2×nH samples adjacent to the left boundary of the current block of size nW×nH and adjacent to the bottom-left, samples adjacent to the top boundary of the current block and a total of 2×nW samples adjacent to the top-right, and 1 sample adjacent to the top-left of the current block. Alternatively, the peripheral reference samples of the current block can also include a plurality of columns of upper peripheral samples and a plurality of rows of left peripheral samples. Further, the peripheral reference samples of the current block can include a total of nH samples adjacent to the right boundary of the current block of size nW×nH, a total of nW samples adjacent to the bottom boundary of the current block, and 1 sample adjacent to the bottom-right of the current block.

[0072] However, some of the peripheral reference samples of the current block may not have been decoded yet or may not be available. In this case, the decoder can substitute unavailable samples with available samples to form peripheral reference samples to be used for prediction. Alternatively, peripheral reference samples to be used for prediction can be formed through interpolation of available samples.

[0073] When a neighboring reference sample is derived, (i) a predicted sample can be derived based on the average or interpolation of the neighboring reference samples of the current block, and (ii) the predicted sample can also be derived based on the reference samples among the neighboring reference samples of the current block that exist in a specific (predicted) direction with respect to the predicted sample. In the case of (i), it can be called a non-directional mode or a non-angular mode, and in the case of (ii), it can be called a directional mode or an angular mode.

[0074] Also, among the neighboring reference samples, the predicted sample can be generated by interpolation between a first neighboring sample located in the prediction direction of the intra prediction mode of the current block and a second neighboring sample located in the direction opposite to the prediction direction with respect to the predicted sample of the current block. In the case described above, it can be called linear interpolation intra prediction (LIP). Also, a chroma predicted sample can be generated based on luma samples using a linear model (LM). In this case, it can be called the LM mode or the CCLM (chroma component LM) mode.

[0075] Also, a temporary predicted sample of the current block can be derived based on the filtered neighboring reference samples, and at least one reference sample derived by the intra prediction mode among the existing neighboring reference samples, that is, the neighboring reference samples that have not been filtered, and the temporary predicted sample are weighted-summed to derive the predicted sample of the current block. In the case described above, it can be called PDPC (Position dependent intra prediction).

[0076] Also, among the surrounding multiple-reference sample lines of the current block, the reference sample line with the highest prediction accuracy is selected, and a prediction sample is derived using the reference sample located in the prediction direction on this line. At this time, intra prediction coding can be performed by a method of instructing (signaling) the used reference sample line to the decoding device. In the case described above, it can be called multi-reference line intra prediction or MRL-based intra prediction.

[0077] Also, although the current block is divided into vertical or horizontal sub-partitions and intra prediction is performed based on the same intra prediction mode, peripheral reference samples can be derived and used in units of the sub-partitions. That is, in this case, although the intra prediction mode for the current block is similarly applied to the sub-partitions, by deriving and using peripheral reference samples in units of the sub-partitions, the intra prediction performance can be improved in some cases. Such a prediction method can be called ISP (intra sub-partitions)-based intra prediction.

[0078] The intra prediction methods described above can be called intra prediction types, distinguished from the intra prediction mode. The intra prediction type can be called by various terms such as intra prediction techniques or additional intra prediction modes. For example, the intra prediction type (or additional intra prediction mode, etc.) can include at least one of LIP, PDPC, MRL, and ISP described above. The general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP can be called the normal intra prediction type. The normal intra prediction type can be generally applied when the above specific intra prediction types are not applicable, and prediction can be performed based on the intra prediction mode described above. On the other hand, post-processing filtering can also be performed on the prediction sample derived as needed.

[0079] Specifically, the intra prediction procedure can include an intra prediction mode / type determination step, a neighboring reference sample derivation step, and an intra prediction mode / type-based prediction sample derivation step. Additionally, if necessary, a post-filtering step for the derived prediction samples can also be performed.

[0080] FIG. 4 shows an example of a video / image encoding method based on intra prediction.

[0081] As shown in FIG. 4, the encoding device performs intra prediction on the current block (S400). The encoding device can derive an intra prediction mode / type for the current block, derive neighboring reference samples of the current block, and generate prediction samples within the current block based on the intra prediction mode / type and the neighboring reference samples. Here, the intra prediction mode / type determination, neighboring reference sample derivation, and prediction sample generation procedures can be performed simultaneously, or any one of the procedures can be performed prior to the other procedures. The encoding device can determine the mode / type applied to the current block among a plurality of intra prediction modes / types. The encoding device can compare the RD cost for the intra prediction mode / type and determine the optimal intra prediction mode / type for the current block.

[0082] On the other hand, the encoding device can also perform a prediction sample filtering procedure. The prediction sample filtering can be referred to as post-filtering. Some or all of the prediction samples can be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure can be omitted.

[0083] The encoding device generates residual samples for the current block based on (filtered) prediction samples (S410). The encoding device can compare the prediction samples with the original samples of the current block on a phase basis and derive the residual samples.

[0084] The encoding device can encode image information including the information related to the intra prediction (prediction information) and the residual information related to the residual samples (S420). The prediction information can include the intra prediction mode information and the intra prediction type information. The encoding device can output the encoded image information in the form of a bitstream. The output bitstream can be transmitted to the decoding device via a storage medium or a network.

[0085] The residual information can include a residual coding syntax described later. The encoding device can convert / quantize the residual samples to derive quantized transform coefficients. The residual information can include information related to the quantized transform coefficients.

[0086] On the other hand, as described above, the encoding device can generate a restored picture (including restored samples and restored blocks). For this purpose, the encoding device can perform inverse quantization / inverse transformation processing on the quantized transform coefficients again to derive (corrected) residual samples. The reason for performing inverse quantization / inverse transformation again after converting / quantizing the residual samples is to derive the same residual samples as the residual samples derived from the decoding device, as described above. The encoding device can generate a restored block including restored samples for the current block based on the prediction samples and the (corrected) residual samples. A restored picture for the current picture can be generated based on the restored block. As described above, an in-loop filtering procedure or the like can be further applied to the restored picture.

[0087] FIG. 5 shows an example of a video / image encoding method based on an intra prediction basis.

[0088] The decoding device can perform operations corresponding to the operations performed by the encoding device.

[0089] Prediction information and residual information can be obtained from the bitstream. Residual samples for the current block can be derived based on the residual information. Specifically, based on the quantized transform coefficients derived based on the residual information, inverse quantization is performed to derive the transform coefficients, inverse transform is performed on the transform coefficients, and residual samples for the current block can be derived.

[0090] Specifically, the decoding device can derive the intra prediction mode / type for the current block based on the received prediction information (intra prediction mode / type information) (S500). The decoding device can derive the surrounding reference samples of the current block (S510). The decoding device generates prediction samples within the current block based on the intra prediction mode / type and the surrounding reference samples (S520). In this case, the decoding device can perform a prediction sample filtering procedure. Prediction sample filtering can be referred to as post-filtering. Some or all of the prediction samples can be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure can be omitted.

[0091] The decoding device generates residual samples for the current block based on the received residual information (S530). The decoding device can generate restored samples for the current block based on the prediction samples and the residual samples, and derive a restored block including the restored samples (S540). A restored picture for the current picture can be generated based on the restored block. As described above, an in-loop filtering procedure or the like can be further applied to the restored picture.

[0092] The intra prediction mode information can 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 whether the remaining mode is applied. When the MPM is applied to the current block, the prediction mode information can further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) can be composed of an MPM candidate list or an MPM list. When the MPM is not applied to the current block, the intra prediction mode information can further include remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes excluding the intra prediction mode candidates (MPM candidates). The decoding device can determine the intra prediction mode of the current block based on the intra prediction mode information.

[0093] Also, the intra prediction type information can be realized in various forms. As an example, the intra prediction type information includes intra prediction type index information indicating any one of the intra prediction types. As another example, the intra prediction type information includes reference sample line information (e.g., intra_luma_ref_idx) indicating whether the MRL is applied to the current block and which reference sample line is used if it is applied, ISP flag information (e.g., intra_subpartitions_mode_flag) indicating whether the ISP is applied to the block, ISP type information (e.g., intra_subpartitions_split_flag) indicating the split type of the subpartition if the ISP is applied, flag information indicating whether PDCP is applicable or flag information indicating whether LIP is applicable, at least one of which. Also, the intra prediction type information includes an MIP flag indicating whether MIP (matrix-based intra prediction) is applied to the current block.

[0094] The intra prediction mode information and / or the intra prediction type information can be encoded / decoded by the coding method described in this document. For example, the intra prediction mode information and / or the intra prediction type information can be encoded / decoded via entropy coding (e.g., CABAC, CAVLC).

[0095] FIG. 6 exemplarily shows the intra prediction procedure.

[0096] Referring to FIG. 6, as described above, the intra prediction procedure can include an intra prediction mode / type determination step, a peripheral reference sample derivation step, and an intra prediction execution (prediction sample generation) step. The intra prediction procedure can be performed by an encoding device and a decoding device as described above. In this document, the coding device can include an encoding device and / or a decoding device.

[0097] As shown in FIG. 6, the coding device determines an intra prediction mode / type (S600).

[0098] The encoding device can determine the intra prediction mode / type applied to the current block among the various intra prediction modes / types described above, and can generate prediction-related information. The prediction-related information can include intra prediction mode information representing the intra prediction mode applied to the current block and / or intra prediction type information representing the intra prediction type applied to the current block. The decoding device can determine the intra prediction mode / type applied to the current block based on the prediction-related information.

[0099] The intra prediction mode information can 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 remaining mode is applied. When the MPM is applied to the current block, the prediction mode information can further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) can be composed of an MPM candidate list or an MPM list. Also, when the MPM is not applied to the current block, the intra prediction mode information can further include remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes excluding the intra prediction mode candidates (MPM candidates). The decoding device can determine the intra prediction mode of the current block based on the intra prediction mode information.

[0100] In addition, the intra prediction type information can be realized in various forms. As an example, the intra prediction type information includes intra prediction type index information indicating any one of the intra prediction types. As another example, the intra prediction type information includes reference sample line information (e.g., intra_luma_ref_idx) indicating whether the MRL is applied to the current block and which reference sample line is used if it is applied, ISP flag information (e.g., intra_subpartitions_mode_flag) indicating whether the ISP is applied to the current block, ISP type information (e.g., intra_subpartitions_split_flag) indicating the split type of the subpartition if the ISP is applied, flag information indicating whether PDCP is applicable or flag information indicating whether LIP is applicable, and at least one of them. Further, the intra prediction type information includes an MIP flag indicating whether MIP (matrix-based intra prediction) is applied to the current block.

[0101] For example, when intra prediction is applied, the intra prediction mode applied to the current block can be determined using the intra prediction modes of neighboring blocks. For example, the coding device can select one of the MPM (most probable mode) candidates in the MPM list derived based on the intra prediction modes of the neighboring blocks (e.g., left and / or upper neighboring blocks) of the current block and / or additional candidate modes based on the received MPM index, or can select one of the remaining intra prediction modes not included in the MPM candidates (and the planar mode) based on the MPM reminder information (remaining intra prediction mode information). The MPM list can be configured to include or not include the planar mode as a candidate. For example, when the MPM list includes the planar mode as a candidate, the MPM list can have 6 candidates, and when the MPM list does not include the planar mode as a candidate, the MPM list can have 5 candidates. When the MPM list does not include the planar mode as a candidate, a not planar flag (e.g., intra_luma_not_planar_flag) indicating whether the intra prediction mode of the current block is not the planar mode can be signaled. For example, the MPM flag can be signaled first, and the MPM index and the not planar flag can be signaled when the value of the MPM flag is 1. Also, the MPM index can be signaled when the value of the not planar flag is 1. Here, the reason for configuring the MPM list not to include the planar mode as a candidate is to signal the flag (not planar flag) first to check whether it is the planar mode first because the planar mode is always considered as an MPM rather than not being an MPM.

[0102] For example, whether the intra prediction mode currently applied to a block is among the MPM candidates (and the planar mode) or among the remaining modes can be indicated based on the MPM flag (e.g., intra_luma_mpm_flag). A value of 1 for the MPM flag can indicate that the intra prediction mode for the current block is within the MPM candidates (and the planar mode), and a value of 0 for the MPM flag can indicate that the intra prediction mode for the current block is not within the MPM candidates (and the planar mode). A value of 0 for the not planar flag (e.g., intra_luma_not_planar_flag) can indicate that the intra prediction mode for the current block is the planar mode, and a value of 1 for the not planar flag can indicate that the intra prediction mode for the current block is not the planar mode. The MPM index can be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information can be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information can index the remaining intra prediction modes not included in the MPM candidates (and the planar mode) among all the intra prediction modes in the order of prediction mode numbers and point to one of them. The intra prediction mode can be the intra prediction mode for the luma component (samples). Hereinafter, the intra prediction mode information can include at least one of the MPM flag (e.g., intra_luma_mpm_flag), the not planar flag (e.g., intra_luma_not_planar_flag), the MPM index (e.g., mpm_idx or intra_luma_mpm_idx), and the remaining intra prediction mode information (rem_intra_luma_pred_mode or intra_luma_mpm_remainder).In this document, the MPM list can be referred to by various terms such as the MPM candidate list, candModeList, etc.

[0103] When MIP is currently applied to a block, a separate MPM flag (e.g., intra_mip_mpm_flag) for MIP, an MPM index (e.g., intra_mip_mpm_idx), and remaining intra prediction mode information (e.g., intra_mip_mpm_remainder) can be signaled, and the not planar flag can be not signaled.

[0104] In other words, generally when block partitioning is performed on an image, the current block to be coded and neighboring blocks tend to have similar image characteristics. Therefore, the current block and neighboring blocks are likely to be identical to each other or have similar intra prediction modes. Thus, the encoder can use the intra prediction mode of neighboring blocks to encode the intra prediction mode of the current block.

[0105] The coding device can construct an MPM (most probable modes) list for the current block. The MPM list can also be referred to as the MPM candidate list. Here, MPM can mean a mode used to improve coding efficiency by considering the similarity between the current block and neighboring blocks during intra prediction mode coding. As described above, the MPM list can be configured to include the planar mode or can be configured excluding the planar mode. For example, when the MPM list includes the planar mode, the number of candidates in the MPM list can be six. And when the MPM list does not include the planar mode, the number of candidates in the MPM list can be five.

[0106] The encoding device can perform prediction based on various intra prediction modes, and can determine the optimal intra prediction mode based on RDO (rate - distortion optimization) based on this. In this case, the encoding device can determine the optimal intra prediction mode using only the MPM candidates and the planar mode configured in the MPM list, or can also determine the optimal intra prediction mode using not only the MPM candidates and the planar mode configured in the MPM list but also the remaining intra prediction modes. Specifically, for example, if the intra prediction type of the current block is a specific type (e.g., LIP, MRL, or ISP) that is not the normal intra prediction type, the encoding device can determine the optimal intra prediction mode by considering only the MPM candidates and the planar mode as intra prediction mode candidates for the current block. That is, in this case, the intra prediction mode for the current block can be determined among the MPM candidates and the planar mode, and in this case, the MPM flag cannot be encoded / signaled. The decoding device can, in this case, presume that the MPM flag is 1 even if the MPM flag is not signaled separately.

[0107] On the other hand, generally, when the intra prediction mode of the current block is not the planar mode and is one of the MPM candidates within the MPM list, the encoding device generates an MPM index (mpm idx) that points to one of the MPM candidates. If the intra prediction mode of the current block is not within the MPM list, MPM remainder information (remaining intra prediction mode information) that points to the same mode as the intra prediction mode of the current block is generated from among the remaining intra prediction modes not included in the MPM list (and the planar mode). The MPM remainder information can include, for example, the intra_luma_mpm_remainder syntax element.

[0108] The decoding device acquires intra prediction mode information from the bitstream. As described above, the intra prediction mode information can include at least one of an MPM flag, a not planar flag, an MPM index, and MPM remainder information (remaining intra prediction mode information). The decoding device can construct an MPM list. The MPM list is configured in the same manner as the MPM list configured by the encoding device. That is, the MPM list can include the intra prediction modes of peripheral blocks and can further include a specific intra prediction mode by a predetermined method.

[0109] The decoding device can determine the intra prediction mode of the current block based on the MPM list and the intra prediction mode information. As an example, when the value of the MPM flag is 1, the decoding device can derive the planar mode as the intra prediction mode of the current block (based on the not planar flag), or can derive the candidate pointed to by the MPM index among the MPM candidates in the MPM list as the intra prediction mode of the current block. Here, the MPM candidate can represent only the candidates included in the MPM list, or can also include the planar mode that can be applied when the value of the MPM flag is 1 in addition to the candidates included in the MPM list.

[0110] As another example, when the value of the MPM flag is 0, the decoding device can derive, as the intra prediction mode of the current block, the intra prediction mode pointed to by the remaining intra prediction mode information (which can be called mpm remainder information) that is not included in the MPM list and the planner mode, from among the remaining intra prediction modes. On the other hand, as yet another example, when the intra prediction type of the current block is a specific type (e.g., LIP, MRL, or ISP, etc.), the decoding device can derive, as the intra prediction mode of the current block, the candidate pointed to by the MPM flag in the planner mode or the MPM list, even without parsing / decoding / verifying the MPM flag.

[0111] The coding device derives the surrounding reference samples of the current block (S610). When intra prediction is applied to the current block, the surrounding reference samples used for intra prediction of the current block can be derived. The surrounding reference samples of the current block can include a total of 2×nH samples adjacent to the left boundary and the bottom - left of the current block of size nW×nH, samples adjacent to the top boundary of the current block and a total of 2×nW samples adjacent to the top - right, and 1 sample adjacent to the top - left of the current block. Or, the surrounding reference samples of the current block can also include a plurality of columns of upper - surrounding samples and a plurality of rows of left - surrounding samples. Also, the surrounding reference samples of the current block can include a total of nH samples adjacent to the right boundary of the current block of size nW×nH, a total of nW samples adjacent to the bottom boundary of the current block, and 1 sample adjacent to the bottom - right of the current block.

[0112] On the one hand, when the MRL is applied (i.e., when the value of the MRL index is greater than 0), the peripheral reference samples can be located on lines 1 or 2, not line 0, adjacent to the current block on the left side / upper side. In this case, the number of peripheral reference samples can be further increased. On the other hand, when the ISP is applied, the peripheral reference samples can be derived in sub-partition units.

[0113] The coding device performs intra prediction on the current block to derive prediction samples (S620). The coding device can derive the prediction samples based on the intra prediction mode / type and the peripheral samples. The coding device can derive the reference samples according to the intra prediction mode of the current block among the peripheral reference samples of the current block, and can derive the prediction samples of the current block based on the reference samples.

[0114] On the one hand, when inter prediction is applied, the prediction unit of the encoding / decoding device can perform inter prediction in block units to derive prediction samples. Inter prediction can represent a prediction derived in a manner that is dependent on data elements (e.g., sample values or motion information) of pictures (etc.) other than the current picture (Inter prediction can be a prediction derived in a manner that is dependent on data elements (ex. sample values or motion information) of picture(s) other than the current picture). When inter prediction is applied to the current block, a predicted block (prediction sample array) for the current block can be derived based on a reference block (reference sample array) specified by a motion vector on the reference picture pointed to by the reference picture index. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information of the current block can be predicted in block, sub-block, or sample units based on the correlation of the motion information between the surrounding blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.) information. When inter prediction is applied, the surrounding blocks can include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block can be the same or different. The temporal neighboring block can be called by names such as a collocated reference block and a collocated CU (colCU), and the reference picture including the temporal neighboring block can also be called a collocated picture (colPic).For example, a motion information candidate list can be configured based on neighboring blocks of a current block, and in order to derive a motion vector and / or a reference picture index of the current block, flag or index information indicating which candidate is selected (used) can be signaled. Inter prediction can be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the motion information of the current block can be the same as that of the selected neighboring block. In the case of skip mode, unlike merge mode, a residual signal can be not transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the selected neighboring block is used as a motion vector predictor, and a motion vector difference can be signaled. In this case, the motion vector of the current block can be derived using the sum of the motion vector predictor and the motion vector difference.

[0115] The motion information can include L0 motion information and / or L1 motion information depending on the inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). The motion vector in the L0 direction can be called the L0 motion vector or MVL0, and the motion vector in the L1 direction can be called the L1 motion vector or MVL1. The prediction based on the L0 motion vector can be called L0 prediction, the prediction based on the L1 motion vector can be called L1 prediction, and the prediction based on both the L0 motion vector and the L1 motion vector can be called bi (Bi) prediction. Here, the L0 motion vector can represent a motion vector associated with the reference picture list L0 (L0), and the L1 motion vector can represent a motion vector associated with the reference picture list L1 (L1). The reference picture list L0 can include previous pictures as reference pictures in terms of output order from the current picture, and the reference picture list L1 can include subsequent pictures. The previous picture can be called a forward (reference) picture, and the subsequent picture can be called a backward (reference) picture. The reference picture list L0 can further include subsequent pictures as reference pictures in terms of output order from the current picture. In this case, the previous picture can be indexed first within the reference picture list L0, and the subsequent picture can be indexed next. The reference picture list L1 can further include previous pictures as reference pictures in terms of output order from the current picture. In this case, the subsequent picture can be indexed first within the reference picture list 1, and the previous picture can be indexed next. Here, the output order can correspond to the POC (picture order count) order (order).

[0116] The video / image encoding procedure based on inter prediction can generally include, for example, the following.

[0117] FIG. 7 shows an example of a video / image encoding method based on inter prediction.

[0118] The encoding device performs inter prediction on the current block (S700). The encoding device can derive the inter prediction mode and motion information of the current block and generate a predicted sample of the current block. Here, the inter prediction mode determination, motion information derivation, and predicted sample generation procedures can be performed simultaneously, or any one of the procedures can be performed prior to the other procedures. For example, the inter prediction unit of the encoding device can include a prediction mode determination unit, a motion information derivation unit, and a predicted sample derivation unit. The prediction mode determination unit determines the prediction mode for the current block, the motion information derivation unit derives the motion information of the current block, and the predicted sample derivation unit can derive the predicted sample of the current block. For example, the inter prediction unit of the encoding device searches for a block similar to the current block within a certain region (search region) of the reference picture via motion estimation, and can derive a reference block whose difference from the current block is the smallest or below a certain criterion. Based on this, a reference picture index indicating the reference picture where the reference block is located can be derived, and a motion vector can be derived based on the positional difference between the reference block and the current block. The encoding device can determine the mode to be applied to the current block among various prediction modes. The encoding device can compare the RD costs for the various prediction modes and determine the optimal prediction mode for the current block.

[0119] For example, when the skip mode or merge mode is applied to the current block, the encoding device constructs a merge candidate list described later, and among the reference blocks pointed to by the merge candidates included in the merge candidate list, it can derive the current block and a reference block whose difference from the current block is the smallest or below a certain criterion. In this case, a merge candidate associated with the derived reference block can be selected, and merge index information indicating the selected merge candidate can be generated and signaled to the decoding device. The motion information of the current block can be derived using the motion information of the selected merge candidate.

[0120] As another example, when the (A)MVP mode is applied to the current block, the encoding device configures an (A)MVP candidate list described later, and among the mvp (motion vector predictor) candidates included in the (A)MVP candidate list, the motion vector of the selected mvp candidate can be used as the mvp of the current block. In this case, for example, the motion vector indicating the reference block derived by the above-described motion estimation can be used as the motion vector of the current block, and among the mvp candidates, the mvp candidate having the motion vector with the smallest difference from the motion vector of the current block can be the selected mvp candidate. An MVD (motion vector difference), which is the difference obtained by subtracting the mvp from the motion vector of the current block, can be derived. In this case, information regarding the MVD can be signaled to the decoding device. Further, when the (A)MVP mode is applied, the value of the reference picture index can be configured with reference picture index information and separately signaled to the decoding device.

[0121] The encoding device can derive a residual sample based on the prediction sample (S710). The encoding device can derive the residual sample by comparing the original sample of the current block with the prediction sample.

[0122] The encoding device encodes image information including prediction information and residual information (S720). The encoding device can output the encoded image information in the form of a bitstream. The prediction information can include prediction mode information (e.g., skip flag, merge flag, or mode index, etc.) and information related to motion information as information related to the prediction procedure. The information related to the motion information can include candidate selection information (e.g., merge index, mvp flag, or mvp index) which is information for deriving a motion vector. Also, the information related to the motion information can include information related to the aforementioned MVD and / or reference picture index information. Also, the information related to the motion information can include information indicating whether L0 prediction, L1 prediction, or bi-prediction is applied. The residual information is information related to the residual samples. The residual information can include information related to the quantized transform coefficients for the residual samples.

[0123] The output bitstream can be stored in a (digital) storage medium and transmitted to the decoding device, or can also be transmitted to the decoding device via a network.

[0124] On the other hand, as described above, the encoding device can generate a reconstructed picture (including reconstructed samples and reconstructed blocks) based on the reference samples and the residual samples. This is to derive the same prediction result in the encoding device as that performed in the decoding device, and through this, the coding efficiency can be improved. Therefore, the encoding device can store the reconstructed picture (or reconstructed samples, reconstructed blocks) in the memory and utilize it as a reference picture for inter prediction. As described above, an in-loop filtering procedure or the like can be further applied to the reconstructed picture.

[0125] The video / image decoding procedure based on inter prediction can generally include, for example, the following.

[0126] FIG. 8 shows an example of a video / image decoding method based on an inter prediction basis.

[0127] As shown in FIG. 8, the decoding device can perform operations corresponding to the operations performed by the encoding device. The decoding device can perform prediction on the current block based on the received prediction information and derive a prediction sample.

[0128] Specifically, the decoding device can determine a prediction mode for the current block based on the received prediction information (S800). The decoding device can determine which inter prediction mode is applied to the current block based on the prediction mode information in the prediction information.

[0129] For example, based on the merge flag, it can be determined whether the merge mode is applied to the current block or whether the (A)MVP mode is determined. Or, based on the mode index, one of various inter prediction mode candidates can be selected. The inter prediction mode candidates can include a skip mode, a merge mode, and / or an (A)MVP mode, or can include various inter prediction modes described later.

[0130] The decoding device derives motion information of the current block based on the determined inter prediction mode (S810). For example, when the skip mode or the merge mode is applied to the current block, the decoding device constructs a merge candidate list described later and can select one merge candidate from the merge candidates included in the merge candidate list. The selection can be performed based on the selection information (merge index) described above. The motion information of the selected merge candidate can be used to derive the motion information of the current block. The motion information of the selected merge candidate can be used as the motion information of the current block.

[0131] As another example, when the (A)MVP mode is applied to the current block, the decoding device configures an (A)MVP candidate list described later, and among the mvp (motion vector predictor) candidates included in the (A)MVP candidate list, the motion vector of the selected mvp candidate can be used as the mvp of the current block. The selection can be performed based on the selection information (mvp flag or mvp index) described above. In this case, the MVD of the current block can be derived based on the information regarding the MVD, and the motion vector of the current block can be derived based on the mvp of the current block and the MVD. Also, the reference picture index of the current block can be derived based on the reference picture index information. The picture pointed to by the reference picture index within the reference picture list regarding the current block can be derived as the reference picture to be referred to for the inter prediction of the current block.

[0132] On the other hand, as will be described later, the motion information of the current block can be derived without configuring a candidate list, and in this case, the motion information of the current block can be derived by the procedure disclosed in the prediction mode described later. In this case, the candidate list configuration as described above can be omitted.

[0133] The decoding device can generate a prediction sample for the current block based on the motion information of the current block (S820). In this case, the reference picture can be derived based on the reference picture index of the current block, and the prediction sample of the current block can be derived using the sample of the reference block pointed to by the motion vector of the current block on the reference picture. In this case, as will be described later, in some cases, a prediction sample filtering procedure can be further performed on all or part of the prediction samples of the current block.

[0134] For example, the inter prediction unit of the decoding device can include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit. The prediction mode for the current block is determined based on the prediction mode information received by the prediction mode determination unit, the motion information (motion vector and / or reference picture index) of the current block is derived based on the information related to the motion information received by the motion information derivation unit, and the prediction sample of the current block can be derived by the prediction sample derivation unit.

[0135] The decoding device generates a residual sample for the current block based on the received residual information (S830). The decoding device can generate a restored sample for the current block based on the prediction sample and the residual sample, and generate a restored picture based on this (S840). As described above, an in-loop filtering procedure or the like can be further applied to the restored picture.

[0136] FIG. 9 exemplarily shows an inter prediction procedure.

[0137] Referring to FIG. 9, as described above, the inter prediction procedure can include an inter prediction mode determination step, a motion information derivation step according to the determined prediction mode, and a prediction execution (prediction sample generation) step based on the derived motion information. The inter prediction procedure can be performed by the encoding device and the decoding device as described above. In this document, the coding device can include the encoding device and / or the decoding device.

[0138] As shown in FIG. 9, the coding device determines an inter prediction mode for the current block (S900). For the prediction of the current block in the picture, various inter prediction modes can be used. For example, various modes such as a merge mode, a skip mode, an MVP (motion vector prediction) mode, an Affine mode, a sub-block merge mode, an MMVD (merge with MVD) mode, etc. can be used. A DMVR (Decoder side motion vector refinement) mode, an AMVR (adaptive motion vector resolution) mode, a Bi-prediction with CU-level weight (BCW), a Bi-directional optical flow (BDOF), etc. can be further or alternatively used as accompanying modes. The Affine mode can also be called an affine motion prediction mode. The MVP mode can also be called an AMVP (advanced motion vector prediction) mode. In this document, some modes and / or motion information candidates derived by some modes can be included as one of the motion information related candidates of other modes. For example, the HMVP candidate can be added as a merge candidate of the merge / skip mode, or can be added as an mvp candidate of the MVP mode. When the HMVP candidate is used as a motion information candidate of the merge mode or the skip mode, the HMVP candidate can be called an HMVP merge candidate.

[0139] Prediction mode information indicating the inter prediction mode of the current block can be signaled from an encoding device to a decoding device. The prediction mode information can be included in a bitstream and received by the decoding device. The prediction mode information can include index information indicating one of a plurality of candidate modes. Alternatively, the inter prediction mode can also be indicated via hierarchical signaling of flag information. In this case, the prediction mode information can include one or more flags. For example, a skip flag is signaled to indicate whether the skip mode can be applied. When the skip mode is not applied, a merge flag is signaled to indicate whether the merge mode can be applied. When the merge mode is not applied, it can be indicated that the MVP mode is applied, or a flag for additional classification can be further signaled. The affine mode can be signaled as an independent mode, or can also be signaled as a mode subordinate to a merge mode or an MVP mode, etc. For example, the affine mode can include an affine merge mode and an affine MVP mode.

[0140] The coding device derives motion information for the current block (S910). The motion information derivation can be derived based on the inter prediction mode.

[0141] The coding device can perform inter prediction using the motion information of the current block. The encoding device can derive the optimal motion information for the current block through a motion estimation procedure. For example, the encoding device can search for a highly correlated similar reference block within a determined search range in the reference picture in units of fractional pixels using the original block in the original picture for the current block, and derive the motion information through this. The similarity of the blocks can be derived based on the difference in sample values on a phase basis. For example, the similarity of the blocks can be calculated based on the SAD between the current block (or a template of the current block) and the reference block (or a template of the reference block). In this case, the motion information can be derived based on the reference block with the smallest SAD within the search area. The derived motion information can be signaled to the decoding device in various ways based on the inter prediction mode.

[0142] The coding device performs inter prediction based on the motion information for the current block (S920). The coding device can derive prediction samples (etc.) for the current block based on the motion information. The current block including the prediction samples can be called a predicted block.

[0143] On the other hand, as described above, the quantization unit of the encoding device applies quantization to the transform coefficients to derive quantized transform coefficients, and the inverse quantization unit of the encoding device or the inverse quantization unit of the decoding device can apply inverse quantization to the quantized transform coefficients to derive the transform coefficients.

[0144] Generally, in video / image coding, the quantization rate can be changed, and the compression rate can be adjusted using the changed quantization rate. From the perspective of implementation, instead of directly using the quantization rate considering complexity, a quantization parameter (QP) is used. For example, quantization parameters with integer values from 0 to 63 are used, and each quantization parameter value can correspond to an actual quantization rate. Also, for example, the quantization parameter (QP Y ) for the luma component (luma samples) and the quantization parameter (QP C ) for the chroma component (chroma samples) can be set differently.

[0145] The quantization process takes the transform coefficient (C) as input, divides it by the quantization rate (Q step ), and based on this, the quantized transform coefficient (C') can be obtained. In this case, considering the computational complexity, the quantization rate is multiplied by a scale to make it in integer form, and a shift operation can be performed by the value corresponding to the scale value. A quantization scale can be derived based on the product of the quantization rate and the scale value. That is, the quantization scale can be derived by the QP. For example, the quantization scale can be applied to the transform coefficient (C), and based on this, the quantized transform coefficient (C') can also be derived.

[0146] The inverse quantization process is the reverse process of the quantization process. By multiplying the quantized transform coefficient (C') by the quantization rate (Q step ), the restored transform coefficient (C'') can be obtained based on this. In this case, a level scale is derived by the quantization parameter, and the level scale is applied to the quantized transform coefficient (C'), and based on this, the restored transform coefficient (C'') is derived. The restored transform coefficient (C'') may have a slight difference from the original transform coefficient (C) due to the loss in the transform and / or quantization process. Therefore, the inverse quantization is also performed in the encoding device in the same way as in the decoding device.

[0147] On the one hand, an adaptive frequency weighting quantization technique for adjusting quantization intensity according to frequency can be applied. The adaptive frequency weighting quantization technique is a method of applying different quantization intensities for different frequencies. The adaptive frequency weighting quantization can apply different quantization intensities for different frequencies using a predefined quantization scaling metric. That is, the above quantization / inverse quantization process can be performed based on the quantization scaling metric. For example, different quantization scaling metrics are used depending on whether the prediction mode applied to the current block is inter prediction or intra prediction in order to generate the size of the current block and / or the residual signal of the current block. The quantization scaling metric may be referred to as a quantization metric or a scaling metric. The quantization scaling metric may be predefined. Also, for frequency adaptive scaling, frequency-specific quantization scale information for the quantization scaling metric is configured / encoded in the encoding device and signaled to the decoding device. The frequency-specific quantization scale information may be referred to as quantization scaling information. The frequency-specific quantization scale information includes scaling_list_data. The (modified) quantization scaling metric is derived based on the scaling_list_data. Also, the frequency-specific quantization scale information includes present flag information indicating the presence or absence of the scaling_list_data. Alternatively, when the scaling_list_data is signaled at a higher level (e.g., SPS), information indicating whether the scaling_list_data is modified at a lower level of the higher level (e.g., PPS or tile group header, etc.) is further included.

[0148] As described above, quantization / inverse quantization is applied to the luma component and the chroma component based on the quantization parameter.

[0149] The quantization parameter for a coding unit is determined based on information signaled at the picture and / or slice level. For example, the quantization parameter can be derived as described below.

[0150] For example, information regarding the derivation of the quantization parameter is signaled via the SPS (sequence parameter set) as shown in the following table.

[0151]

Table 1

[0152] The semantics for the syntax elements in Table 1 above are as shown in the following table.

[0153]

Table 2

[0154] For example, the syntax element bit_depth_luma_minus8 indicates the bit depth BitDepth of the samples in the luma array Y and the luma quantization parameter range offset QpBdOffset Y That is, for example, based on the syntax element bit_depth_luma_minus8, the BitDepth Y and the QpBdOffset Y can be derived. For example, the BitDepth Y is derived as the value obtained by adding 8 to the value of the syntax element bit_depth_luma_minus8, and the QpBdOffset YIt is derived as a value obtained by multiplying the value of the syntax element bit_depth_luma_minus8 by 6. Also, the bit_depth_luma_minus8 can be in the range of 0 to 8.

[0155] Also, for example, the syntax element bit_depth_chroma_minus8 is the bit depth BitDepth of the samples of the chroma array c and the chroma quantization parameter range offset QpBdOffset. c That is, for example, the BitDepth c and the QpBdOffset c can be derived based on the syntax element bit_depth_chroma_minus8. For example, the BitDepth c is derived as a value obtained by adding 8 to the value of the syntax element bit_depth_chroma_minus8, and the QpBdOffset c is derived as a value obtained by multiplying the value of the syntax element bit_depth_chroma_minus8 by 6. Also, the bit_depth_chroma_minus8 can be in the range of 0 to 8.

[0156] Also, for example, information regarding the derivation of quantization parameters is signaled via the PPS (picture parameter set) as shown in the following table. The information includes the Chroma Cb offset, Chroma Cr offset, joint chroma offset, and initial quantization parameter. That is, the information includes syntax elements for the Chroma Cb offset, Chroma Cr offset, joint chroma offset, and initial quantization parameter.

[0157]

Table 3

[0158] The semantics for the syntax elements in the aforementioned Table 3 are as shown in the following table.

[0159]

Table 4

[0160] For example, the value obtained by adding 26 to the syntax element init_qp_minus26 indicates the initial value of SliceQp for each slice that refers to the PPS. When a non-zero value of slice_qp_delta is decoded, the initial value of the SliceQp Y can be modified in the slice layer. The init_qp_minus26 0 can be in the range of -(26 + QpBdOffset Y ) to +37. Y

[0161] Also, for example, the syntax elements pps_cb_qp_offset and pps_cr_qp_offset indicate the offsets for the luma quantization parameter Qp’ Cb and Qp’ Cr used for the derivation of Qp’ Y . The pps_cb_qp_offset and pps_cr_qp_offset can be in the range of -12 to +12. Also, when ChromaArrayType is 0, the pps_cb_qp_offset and pps_cr_qp_offset may not be used in the decoding process, and the decoding device can ignore the values of the syntax elements.

[0162] Also, for example, the syntax element pps_joint_cbcr_qp_offset indicates an offset for the luma quantization parameter Qp’ CbCr used in the derivation of Qp’ Y . The pps_joint_cbcr_qp_offset can be in the range of -12 to +12. Also, when ChromaArrayType is 0, the pps_joint_cbcr_qp_offset may not be used in the decoding process, and the decoding device can ignore the value of the syntax element.

[0163] Also, for example, the syntax element pps_slice_chroma_qp_offsets_present_flag indicates whether the syntax elements slice_cb_qp_offset and slice_cr_qp_offset are present in the relevant slice header. For example, a pps_slice_chroma_qp_offsets_present_flag with a value of 1 indicates that slice_cb_qp_offset and slice_cr_qp_offset are present in the relevant slice header. Also, for example, a pps_slice_chroma_qp_offsets_present_flag with a value of 0 indicates that slice_cb_qp_offset and slice_cr_qp_offset are not present in the relevant slice header. Also, when ChromaArrayType is 0, the pps_slice_chroma_qp_offsets_present_flag seems to be 0 in the decoding process.

[0164] As described above, the syntax elements parsed in PPS can be init_qp_minus26, pps_cb_qp_offset_pps_cr_qp_offset, pps_joint_cbcr_qp_offset, and pps_slice_chroma_qp_offsets_present_flag. The syntax element init_qp_minus26 indicates the initial value of SliceQpY for each slice that refers to the PPS. Also, the syntax elements pps_cb_qp_offset, pps_cr_qp_offset, and pps_joint_cbcr_qp_offset indicate the offsets for the luma quantization parameter Qp’ Y . Also, the syntax element pps_slice_chroma_qp_offsets_present_flag indicates whether the offset parameter is present in the slice header.

[0165] Also, for example, information regarding the derivation of the quantization parameter can be signaled as shown in the following table via a slice header.

[0166]

Table 5

[0167] The semantics for the syntax elements in Table 5 above are as shown in the following table.

[0168]

Table 6-1

[0169]

Table 6-2

[0170] For example, slice_qp_delta is the Qp used for coding blocks within a slice until it is modified by the value of CuQpDeltaVal in the coding unit layer. Y It indicates the initial value. For example, the initial value of Qp Y for a slice, SliceQp Y is derived as 26 + init_qp_minus26 + slice_qp_delta. The value of SliceQp Y can be in the range of -QpBdOffset Y to +63.

[0171] Also, for example, slice_cb_qp_offset indicates the difference added to the value of pps_cb_qp_offset when determining the value of quantization parameter Qp'. Cb The value of slice_cb_qp_offset can be in the range of -12 to +12. Also, for example, if slice_cb_qp_offset does not exist, the slice_cb_qp_offset is inferred to be 0. The value of pps_cb_qp_offset + slice_cb_qp_offset can be in the range of -12 to +12.

[0172] Also, for example, slice_cr_qp_offset indicates the difference added to the value of pps_cr_qp_offset when determining the value of quantization parameter Qp'. Cr The value of slice_cr_qp_offset can be in the range of -12 to +12. Also, for example, if slice_cr_qp_offset does not exist, the slice_cr_qp_offset is inferred to be 0. The value of pps_cr_qp_offset + slice_cr_qp_offset can be in the range of -12 to +12.

[0173] Also, for example, slice_cbcr_qp_offset indicates the difference added to the value of pps_cbcr_qp_offset when determining the value of quantization parameter Qp'. CbCrThe slice_cbcr_qp_offset value may range from -12 to +12. For example, if slice_cbcr_qp_offset does not exist, slice_cbcr_qp_offset is inferred to be 0. The pps_cbcr_qp_offset+slice_cbcr_qp_offset value may range from 12 to +12.

[0174] The derivation process for the luma and chroma quantization parameters begins with the inputs to the process being variables specifying the luma location, the width and height of the current coding block, and a variable specifying whether it is a single tree or a dual tree. Meanwhile, as mentioned above, the luma quantization parameter, chroma quantization parameter, and joint chroma quantization parameter are Qp' Y , Qp' Cb , Qp' Cr and Qp' CbCr It can be shown that:

[0175] Meanwhile, for example, a syntax element cu_qp_delta_sign_flag indicating the sign of CuQpDeltaVal is parsed. For example, the cu_qp_delta_sign_flag may indicate the sign of CuQpDeltaVal as follows:

[0176] For example, when the cu_qp_delta_sign_flag is 0, the CuQpDeltaVal corresponding to the cu_qp_delta_sign_flag has a positive value. Or, for example, when the cu_qp_delta_sign_flag is 1, the CuQpDeltaVal corresponding to the cu_qp_delta_sign_flag has a negative value. Also, when the cu_qp_delta_sign_flag does not exist, the cu_qp_delta_sign_flag is regarded as 0.

[0177] Also, for example, when cu_qp_delta_abs exists, the variable IsCuQpDeltaCoded is derived as 1, and the variable CuQpDeltaVal is derived as cu_qp_delta_abs*(1 - 2*cu_qp_delta_sign_flag). The CuQpDeltaVal can be in the range of -(32 + QpBdOffsetY / 2) to +(31 + QpBdOffsetY / 2).

[0178] After that, for example, the luma quantization parameter Qp’ Y is derived as follows.

[0179]

Equation

[0180] Also, when ChromaArrayType is not 0 and treeType is SINGLE_TREE or DUAL_TREE_CHROMA, the following applies.

[0181] - When treeType is like DUAL_TREE_CHROMA, the variable Qp Y can be set the same as the luma quantization parameter Qp Y of the luma coding unit including the luma position (xCb + cbWidth / 2, yCb + cbHeight / 2).

[0182] - The variable qP Cb 、qP Cr and qP CbCr are derived as follows.

[0183]

Equation

[0184] For example, when ChromaArrayType is 1, the variables qP Cb 、qP Cr and qP CbCr can be set to be the same as the QpC values specified in Table 7 below based on the same index qPi Cb 、qPi Cr and qPi CbCr respectively.

[0185]

Table 7

[0186] Or, when ChromaArrayType is not 1, the variables qP Cb 、qP Cr and qP CbCr can be set to be the same as Min(qPi, 63) based on the same index qPi Cb 、qPi Cr and qPi CbCr respectively.

[0187] - Chroma quantization parameters for the Cb and Cr components, Qp’ Cb and Qp’ Cr 、The chroma quantization parameter Qp’CbCr for joint Cb-Cr coding is derived as follows.

[0188]

Equation

[0189] On the one hand, this document proposes a solution for improving the coding efficiency in the quantization / inverse quantization process.

[0190] As one embodiment, when ChromaArrayType is not 0 (for example, when ChromaArrayType is 1), instead of obtaining the chroma quantization parameter value from the luma quantization parameter value through the chroma quantization mapping table predefined in the existing VVC draft 5v.7, this document proposes a method in which the user defines a chroma quantization mapping table (user defined Chroma Quantization Table) and uses it. In the VVC specification text (for example, VVC draft 5v.7), when qPi (luma quantization parameter value) is given, Qpc (chroma quantization parameter value) is derived through the predefined chroma quantization table (for example, the aforementioned Table 7), but this document proposes a method of deriving Qpc from qPi based on the newly defined chroma quantization mapping table by the user. According to the embodiment of this document, the Qpc value is derived from the functional relationship of the qPi value, and the function can be signaled in the syntax such as APS, SPS, or PPS by the user defined functionality method. The functional relationship proposes a method of transmitting the values of the predefined syntax elements and defining the chroma quantization table mapping by the user based on the transmitted values. As an example, since the Qpc value can be derived from the functional relationship of the qPi value, when the syntax element value indicating the function is transmitted, the chroma quantization mapping table (a user defined Chroma Quantization Table) defined by the user can be derived in the form of Table 7.

[0191] As an embodiment, a scheme for signaling information regarding a syntax element (Qpc_data) indicating a chroma quantization mapping related function as shown in the table described later in an APS (adaptation parameter set) is proposed.

[0192]

Table 8

[0193] Referring to the above Table 8, when the aps_params_type indicates Qpc_APS, for example, when the value of the aps_params_type is 2, Qpc_data() is signaled.

[0194] The semantics for the syntax elements in the above Table 8 are as shown in the following table.

[0195]

Table 9

[0196] For example, the syntax element adaptation_parameter_set_id provides an identifier of the APS that is referenced by other syntax elements.

[0197] Also, for example, the syntax element aps_extension_flag indicates whether the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure. For example, the syntax element aps_extension_flag with a value of 1 indicates that the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure, and the syntax element aps_extension_flag with a value of 0 indicates that the aps_extension_data_flag syntax element does not exist in the APS RBSP syntax structure.

[0198] Also, for example, the syntax element aps_extension_data_flag can have any value. The presence and value of the aps_extension_data_flag may not affect the decoder compliance with the profile specified in this version of the standard. For example, a decoding device compliant with this version of the standard can ignore all syntax elements aps_extension_data_flag.

[0199] Also, for example, the syntax element aps_params_type indicates the type of APS parameters included in the APS, as shown in Table 10 below.

[0200]

Table 10

[0201] For example, referring to Table 10, when the value of the syntax element aps_params_type is 0, the syntax element aps_params_type indicates that the type of the APS parameter is the ALF parameter; when the value of the syntax element aps_params_type is 1, the syntax element aps_params_type indicates that the type of the APS parameter is the LMCS parameter; when the value of the syntax element aps_params_type is 2, the syntax element aps_params_type indicates that the type of the APS parameter is the Qpc parameter. The Qpc data parameter can indicate the chroma quantization data parameter.

[0202] In addition, this document proposes another embodiment for signaling information related to quantization parameters.

[0203] For example, in this embodiment, a scheme for signaling user-defined Qp C data (user defined Qp C data) in the PPS (picture parameter set) is proposed. As an example for implementing the scheme proposed in this embodiment, a flag indicating whether the PPS in the SPS contains user-defined data may be introduced. That is, a flag indicating whether the PPS in the SPS contains user-defined data is signaled. Also, according to this embodiment, the user-defined data is signaled in the PPS. Alternatively, the user-defined data may also be signaled in the slice header and / or other header sets.

[0204] The flag indicating whether the PPS contains user-defined data is signaled as shown in the following table.

[0205]

Table 11

[0206] For example, the syntax element Qpc_data_default_flag can be the syntax element of the aforementioned flag. The syntax element Qpc_data_default_flag indicates whether the Qpc_data() parameter exists in the PPS RBSP syntax structure. For example, a Qpc_data_default_flag of 0 indicates that the Qpc_data() parameter does not exist in the PPS RBSP syntax structure, and that the default table is used to assist in the determination of chroma quantization. Here, the default table is as shown in Table 7 above. Also, for example, a Qpc_data_default_flag of 1 indicates that the Qpc_data() parameter exists in the PPS RBSP syntax structure.

[0207] Also, the user - defined data signaled in the PPS according to this embodiment is as follows.

[0208]

Table 12

[0209] On the other hand, for example, Qpc_data() contains information necessary for chroma quantization derivation when ChromaArrayType is 1.

[0210] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0211] For example, in this embodiment, a flexible structure for chroma quantization parameter (QP) derivation and combined chroma QP derivation is proposed. This embodiment proposes a scheme for signaling an initial flag indicating the presence or absence of a user defined mode in which parameters used to derive the chroma quantization parameter (QP) in the SPS and / or PPS can be used.

[0212] For example, the flag information signaled in the high level syntax proposed in this embodiment is as shown in the table described later.

[0213]

Table 13

[0214] For example, Qpc_data_present_flag indicates whether there are parameters for deriving the chroma quantization coefficient in the high level syntax RBSP syntax structure. For example, a Qpc_data_present_flag of 0 indicates that there are no chroma quantization parameters in the high level syntax RBSP syntax structure. Also, for example, a Qpc_data_present_flag of 1 indicates that there are chroma quantization parameters in the high level syntax RBSP syntax structure.

[0215] Alternatively, the syntax element Qpc_data_present_flag may also be used to indicate the usage scheme of chroma quantization derivation in the bitstream. For example, Qpc_data_present_flag can indicate the use of tools or user defined modes used for chroma quantization derivation as follows.

[0216] For example, the Qpc_data_present_flag indicates whether user defined chroma quantization is used in the bitstream. For example, a Qpc_data_present_flag of 0 indicates that user defined chroma quantization is not used in the bitstream. Also, for example, a Qpc_data_present_flag of 1 indicates that user defined chroma quantization is used alone or together with other flags.

[0217] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0218] For example, in this embodiment, a user defined Information signaled in one function is used to derive chroma quantization parameters (QP), i.e., Qp‘ Cb Qp‘ Cr and Qp‘ CbCr and proposes an embodiment of how they are derived. For example, according to this embodiment, data indicating a function for deriving chroma quantization parameters (QP) is signaled, and chroma quantization parameters are derived based on the chroma quantization data. The data for deriving the chroma quantization coefficient (or, user defined QP mapping table) is signaled as shown in the following table.

[0219]

Table 14

[0220] The semantics for the syntax elements in Table 14 above are as shown in the following table.

[0221]

Table 15

[0222] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization.

[0223] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between the Qpi_min_idx and the maximum qPi index used for Qp C derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. For example, Qp C The maximum index qPiMaxIdx used for derivation can be derived as follows.

[0224]

Equation

[0225] Also, for example, the syntax element QpC_qPi_val[i] indicates the Qp value for the i-th index. C value.

[0226] Also, for example, the syntax element QpOffset C indicates the offset value used for the derivation of Qp C value.

[0227] Also, for example, the variable Qp for qPi C Idx[qPi] can be derived as follows. Here, the qPi can be from 0 to qPiMaxIdx.

[0228] When -qPi < qPi_min_idx, Qp C Idx[qPi] is set to be the same as qPi.

[0229] When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp CIdx[qPi] is set to be the same as QpC_qPi_val[qPi].

[0230] - If -qPi > qPiMaxIdx, then Qp C Idx[qPi] is qPi - QpOffset C is set to it.

[0231] After that, the value of Qp C is derived as Qp C Idx[qPi].

[0232] For example, when the process of deriving quantization parameters according to this embodiment is described in a standard format, it is as shown in the following table.

[0233]

Table 16 - 1

[0234]

Table 16 - 2

[0235]

Table 16 - 3

[0236]

Table 16 - 4

[0237] Referring to Table 16 above, the derivation process for luma and chroma quantization parameters starts from the fact that the input to the process is the luma position (xCb, yCb), the variables cbWidth and cbHeight that specify the width and height of the current coding block, and the variable treeType that specifies whether it is a single tree or a dual tree. On the other hand, as described above, the luma quantization parameter and the chroma quantization parameter are Qp’ Y , Qp’Cb and Qp’ Cr are shown as follows.

[0238] In addition, this document proposes another embodiment for signaling information regarding quantization parameters.

[0239] For example, this embodiment proposes an example of using a syntax element that can be used to control the derivation of quantization parameters by having a flag in the SPS in a user defined mode or a default mode. An example of a syntax element that can be used to derive quantization parameters is as follows. On the other hand, the structure of the said syntax element is an example, and the said structure is not limited to the structure shown in the following table.

[0240] [Table 17]

[0241] [Table 18]

[0242] [Table 19]

[0243] For example, the syntax element Qpc_data_default_flag indicates whether a user-defined mode is used for the derivation of quantization parameters. For example, a Qpc_data_default_flag of 0 indicates that the user-defined mode is used for the derivation of quantization parameters. Also, for example, a Qpc_data_default_flag of 1 indicates that the default table is used to derive the chroma quantization parameters. Here, the default table is as shown in Table 7 above. Also, when the syntax element Qpc_data_default_flag does not exist, the syntax element Qpc_data_default_flag is regarded as 1.

[0244] On the other hand, when the user-defined mode is used, the corresponding slice header, tile group / header, or other appropriate header is used for the signaling of the APS ID. For example, a syntax element indicating the APS ID can be signaled via the slice header as shown in Table 18 above.

[0245] For example, the syntax element slice_Qp C _aps_id indicates the Qp C adaptation_parameter_set_id of the APS to which the slice refers. A Qp having an adaptation_parameter_set_id such as slice_Qp C _aps_id C The TemporalId of the APS NAL unit is less than or equal to the TemporalId of the coded slice NAL unit. Multiple Qps having the same value of adaptation_parameter_set_id C When the APS is referred to by two or more slices of the same picture, multiple Qps having the same value of adaptation_parameter_set_id C The APS can have the same content.

[0246] Also, the APS structure for transmitting the chroma quantization data proposed in this embodiment is as shown in Table 19 above.

[0247] For example, the syntax element adaptation_parameter_set_id can provide an identifier of the APS that is referenced by other syntax elements.

[0248] Also, for example, the syntax element aps_extension_flag indicates whether the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure. For example, the syntax element aps_extension_flag with a value of 1 indicates that the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure, and the syntax element aps_extension_flag with a value of 0 indicates that the aps_extension_data_flag syntax element does not exist in the APS RBSP syntax structure.

[0249] Also, for example, the syntax element aps_extension_data_flag can have any value. The presence and value of the aps_extension_data_flag may not affect the decoder compliance for the profile specified in this version of the standard. For example, a decoding device compliant with this version of the standard can ignore all syntax elements aps_extension_data_flag.

[0250] Also, for example, the syntax element aps_params_type indicates the type of APS parameters included in the APS, as shown in Table 10 above.

[0251] Qp disclosed in Table 19 above C_data() is signaled as shown in the following table.

[0252]

Table 20

[0253] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization.

[0254] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between the Qpi_min_idx and the maximum qPi index used for Qp C derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. For example, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in Equation 4 above.

[0255] Also, for example, the syntax element Qp C The value obtained by adding 1 to _prec_minus1 indicates the number of bits used for the representation of the syntax lmcs_delta_abs_cw[i]. Qp C The value of _prec_minus1 can be in the range of 0 to BitDepthY - 2.

[0256] Also, for example, the syntax element Qp C _init_val indicates the Qp C value corresponding to qPi_min_idx.

[0257] Also, for example, the syntax element Qp C _qPi_delta_val[i] indicates the delta of the Qp C value for the i-th index.

[0258] Also, for example, the syntax element QpOffsetC represents the offset value used for the derivation of Qp C For example, the variable Qp for qPi

[0259] Idx[qPi] is derived as follows. Here, the qPi can range from 0 to qPiMaxIdx C When -qPi < qPi_min_idx, Qp

[0260] Idx[qPi] is set to be the same as qPi C When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp

[0261] Idx[qPi] is set to Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1] C When -qPi > qPiMaxIdx, Qp

[0262] Idx[qPi] is set to qPi - QpOffset C When -qPi > qPiMaxIdx, Qp C Idx[qPi] is set to qPi - QpOffset

[0263] After that, the value of Qp C can be derived from Qp C Idx[qPi]

[0264] As in the foregoing embodiments, the chroma quantization parameters, namely, Qp‘Cb, Qp‘Cr, and Qp‘CbCr can be derived using user - defined information that is signaled or using default values shown in a default table such as Table 7 above

[0265] For example, when the process of deriving the quantization parameter according to this embodiment is described in a standard format, it is as shown in the following table

[0266]

Table 21 - 1

[0267]

Table 21-2

[0268]

Table 21-3

[0269]

Table 21-4

[0270]

Table 21-5

[0271] Referring to Table 21 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb qP Cr and qP CbCr are derived based on the user-defined information signaled as proposed in this embodiment. When ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb qP Cr and qP CbCr are derived from the default table based on the same index qPi Cb qPi Cr and qPi CbCr respectively.

[0272] Furthermore, this document proposes another embodiment for signaling information regarding quantization parameters.

[0273] For example, this embodiment proposes a syntax element that can be used to control the derivation of quantization parameters by indicating that the flag of the SPS is in the user-defined mode or the default mode. Specifically, this embodiment proposes a scheme for signaling a syntax element with the following syntax structure. On the other hand, the structure of the syntax element is an example, and the structure is not limited to the structure shown in the following table.

[0274]

Table 22

[0275] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization.

[0276] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between Qpi_min_idx and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. For example, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in Equation 4 above.

[0277] Also, for example, the syntax element Qp C _qPi_delta_val[i] indicates the delta of the Qp C value for the i-th index.

[0278] Also, for example, the syntax element QpOffset C indicates the offset value used for the derivation of Qp C as described above.

[0279] As in the foregoing embodiments, the chroma quantization parameters, i.e., Qp‘Cb, Qp‘Cr, and Qp‘CbCr, can be derived using user - defined information that is signaled or using default values shown in a default table such as Table 7 above.

[0280] For example, when describing the process of deriving quantization parameters according to this embodiment in a standard format, it is as shown in the following table.

[0281] [Table 23 - 1]

[0282] [Table 23 - 2]

[0283] [Table 23 - 3]

[0284] [Table 23 - 4]

[0285] [Table 23 - 5]

[0286] Referring to Table 23 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates false (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb qP Cr and qP CbCrcan be derived based on user-defined information signaled as proposed in this embodiment. For example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr can be derived to be the same as the values of qPi Cb , qPi Cr and qPi CbCr respectively, based on the same index qPi as that of Qp C .

[0287] For example, the variable Qp C Idx[i] is derived as follows.

[0288] - If i < qPi_min_idx, Qp C Idx[qPi] is set to be the same as qPi.

[0289] - If i = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[i] is set to Qp C _qPi_delta_val[i] + Qp C Idx[i - 1].[[]END]

[0290] - If i > qPiMaxIdx, Qp C Idx[i] is set to qPi - QpOffset C .

[0291] Then, the said Qp C can be set to the said Qp C Idx[i].[[]END]

[0292] Also, referring to Table 23, when ChromaArrayType is 1 and Qp CWhen the _data_default_flag indicates positive (TRUE) (i.e., for example, Qp C when the _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr are derived from the default table based on the same index qPi Cb , qPi Cr , qPi CbCr respectively.

[0293] In addition, this document proposes another embodiment for signaling information regarding quantization parameters.

[0294] For example, this embodiment proposes a syntax element for the chroma quantization (Qp C ) derivation parameter in the APS (Adaptation Parameter Set). For example, the APS ID can be signaled in the slice header. Also, for example, a flag in the PPS (picture parameter set) is proposed to indicate whether a default table is used or a table derived from the information signaled in the APS is used. Also, for example, when the default table is not used, an additional control scheme for supporting access to the APS including Qp C data is added.

[0295] On the other hand, according to existing video / image standards, the chroma QP is derived from the luma QP and can be additionally updated by the signaled chroma QP offset. The existing chroma quantization parameter QpC table can be a default table such as Table 7 described above.

[0296] This embodiment proposes to add a function for signaling the chroma quantization parameter Qp C as a function of the index qPi. The APS is used for the integration of the signaling scheme of the Qp C value.

[0297] For example, the APS according to this embodiment is as shown in the following table.

[0298]

Table 24

[0299] For example, the syntax element adaptation_parameter_set_id provides an identifier of the APS that is referenced by other syntax elements.

[0300] Also, for example, the syntax element aps_params_type indicates the type of APS parameters included in the APS, as shown in Table 10 above.

[0301] Also, for example, the syntax element aps_extension_flag indicates whether the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure. For example, the syntax element aps_extension_flag with a value of 1 indicates that the aps_extension_data_flag syntax element exists in the APS RBSP syntax structure, and the syntax element aps_extension_flag with a value of 0 indicates that the aps_extension_data_flag syntax element does not exist in the APS RBSP syntax structure.

[0302] Also, for example, the syntax element aps_extension_data_flag has an arbitrary value. The presence and value of the aps_extension_data_flag may not affect the decoder compliance with the profile specified in this version of the standard. For example, a decoding device compliant with this version of the standard can ignore all syntax elements aps_extension_data_flag.

[0303] Qp disclosed in Table 24 above C _data() is signaled as shown in the following table.

[0304]

Table 25

[0305] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0306] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between Qpi_min_idx and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. Also, for example, the value of qPi_delta_max_idx can be in the range of 0 to 63. For example, Qp C The maximum index qPiMaxIdx used for derivation is derived as shown in Equation 4 above.

[0307] Also, for example, the syntax element Qp C _qPi_delta_val[i] indicates the difference in Qp C value for the i-th index. The difference may also be called a delta.

[0308] Also, for example, the syntax element Qp C Offset C _present_flag indicates whether QpOffset C exists in the bit stream. For example, a Qp of 1 C Offset C _present_flag indicates that QpOffset C exists in the bit stream. Also, for example, a Qp of 0 C Offset C _present_flag indicates that QpOffset C does not exist in the bit stream. When the Qp C Offset C _present_flag does not exist, the Qp C Offset C _present_flag is considered to be 0.

[0309] Also, for example, the syntax element QpOffset C represents the offset value used for the derivation of Qp C .

[0310] For example, the variable Qp for qPi C Idx[qPi] is derived as follows. Here, the qPi can be from 0 to 63.

[0311] - When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0312] - When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is set to Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0313] - When -qPi > qPiMaxIdx, Qp COffset C If _present_flag is 1, then Qp C Idx[qPi] is set to qPi - QpOffset C and Qp C Offset C If _present_flag is not 1, that is, if Qp C Offset C _present_flag is 0, then Qp C Idx[qPi] is set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0314] After that, the value of Qp C is derived from Qp C Idx[qPi].

[0315] In addition, this embodiment proposes a flag signaled in the PPS as shown in the following table.

[0316]

Table 26

[0317] For example, the syntax element Qp C _data_default_flag indicates whether the user defined mode is used for the derivation of the quantization parameter. For example, Qp C _data_default_flag of 0 indicates that the user defined mode is used for deriving the quantization parameter. Also, for example, Qp C _data_default_flag of 1 indicates that the aforementioned default table is used for deriving the quantization parameter. The default table is as shown in Table 7 above. Qp C If Qp C _data_default_flag does not exist, then Qp

[0318] Furthermore, this embodiment proposes syntax elements signaled by a slice header as shown in the following table.

[0319]

Table 27

[0320] For example, the syntax element slice_Qp C _aps_id refers to the Qp C indicated by the adaptation_parameter_set_id of the APS. slice_Qp C A Qp with an adaptation_parameter_set_id such as slice_Qp C _aps_id. The TemporalId of the APS NAL unit is less than or equal to the TemporalId of the coded slice NAL unit. Multiple Qps with the same value of adaptation_parameter_set_id C If the APS is referenced by two or more slices of the same picture, multiple Qps with the same value of adaptation_parameter_set_id C The APS can have the same content.

[0321] For example, when describing the process of deriving the quantization parameter according to this embodiment in a standard format, it can be shown as in the following table.

[0322]

Table 28-1

[0323]

Table 28-2

[0324]

Table 28-3

[0325]

Table 28-4

[0326] Referring to Table 28 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr are derived based on user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived from the default table based on the same index qPi Cb , qPi Cr and qPi CbCr respectively.

[0327] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0328] For example, in this embodiment, it is proposed to signal user-defined derivation of chroma quantization in the SPS as follows. For example, this embodiment proposes user-defined chroma quantization (Qp C ). For example, the SPS flag can indicate whether to use the default table for chroma quantization derivation or to derive the content of the table for chroma quantization derivation from the information signaled in the SPS.

[0329] For example, the present embodiment proposes a scheme for performing chroma quantization as a function of the index qPi using the syntax elements shown in the following table.

[0330]

Table 29

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

[0332] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between Qpi_min_idx and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in Equation 4 above.

[0333] Also, for example, the syntax element Qp C _qPi_delta_val[i] indicates the delta of the Qp value for the i-th index. C

[0334] For example, the variable Qp C Idx[qPi] is derived as follows.

[0335] - When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0336] - When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is Qp C_qPi_delta_val[qPi] + Qp C It is set to Idx[qPi - 1].

[0337] When -qPi > qPiMaxIdx, Qp C Idx[qPi] is qPi - (qPiMaxIdx - Qp C It is set to Idx[qPiMaxIdx]).

[0338] After that, the said Qp C is the said Qp C It is set to Idx[qPi].

[0339] Also, the flag of the SPS indicating whether to use the default table for chroma quantization derivation proposed in this embodiment or the information signaled for chroma quantization derivation is as shown in the following table.

[0340]

Table 30

[0341] For example, the syntax element Qp C _data_default_flag indicates whether the user - defined mode is used for the derivation of quantization parameters. For example, Qp C _data_default_flag of 0 indicates that the user - defined mode is used for the derivation of quantization parameters. Also, for example, Qp C _data_default_flag of 1 indicates that the default table is used for the derivation of quantization parameters. The said default table is as shown in Table 7 above. Also, when Qp C _data_default_flag does not exist, the said Qp C _data_default_flag is regarded as 1.

[0342] For example, when describing the process of deriving quantization parameters according to this embodiment in standard form, it is as shown in the following table.

[0343]

Table 31-1

[0344]

Table 31-2

[0345]

Table 31-3

[0346]

Table 31-4

[0347]

Table 31-5

[0348] Referring to Table 31 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb qP Cr and qP CbCr can be derived based on the user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb qP Cr and qP CbCr are respectively qPi Cb qPi Cr qPi CbCrIt can be derived by the default table based on the same index qPi.

[0349] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0350] For example, this embodiment proposes adding a function for signaling the chroma quantization parameter Qp as a function of the index qPi. C For example, a scheme is proposed for signaling syntax elements for a user defined table for deriving quantization parameters in the PPS, thereby providing the flexibility to switch between the user defined table and the default table for each picture that refers to the PPS.

[0351] The syntax elements for the user defined table signaled in the PPS proposed in this embodiment are as follows in the following table.

[0352]

Table 32

[0353] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0354] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between Qpi_min_idx and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx is 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, Qp CThe maximum index qPiMaxIdx used for derivation can be derived as in the above-mentioned Equation 4.

[0355] Also, for example, the syntax element QpC_qPi_delta_val[i] represents the delta of the Qp value for the i-th index. C indicates the delta of the Qp value for the i-th index.

[0356] For example, the variable Qp C Idx[qPi] can be derived as follows.

[0357] When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0358] When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1].

[0359] When -qPi > qPiMaxIdx, Qp C Idx[qPi] is set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0360] After that, the said Qp C is set to the said Qp C Idx[qPi].

[0361] Also, the SPS flag indicating whether to use the default table for chroma quantization derivation proposed in this embodiment or the information signaled for chroma quantization derivation is as shown in the following table.

[0362]

Table 33

[0363] For example, the syntax element Qp C _data_default_flag indicates whether the user-defined mode is used for deriving quantization parameters. For example, for Qp of 0 C _data_default_flag indicates that the user-defined mode is used for deriving quantization parameters. That is, for example, for Qp of 0 C _data_default_flag indicates the chroma quantization parameter data Qp C _data() is used. The Qp C When _data_default_flag is 0, the chroma quantization parameter data Qp C _data() can be signaled. Also, for example, for Qp of 1 C _data_default_flag indicates that the default table is used for deriving quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0364] For example, when the process of deriving quantization parameters according to this embodiment is described in a standard format, it is as shown in the following table.

[0365]

Table 34-1

[0366]

Table 34-2

[0367]

Table 34-3

[0368]

Table 34-4

[0369]

Table 34-5

[0370] Referring to Table 34 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr can be derived based on the user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived from the default table based on the same index qPi Cb , qPi Cr , qPi CbCr respectively.

[0371] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0372] For example, this embodiment proposes a general mode for deriving and signaling the chroma quantization parameter Qp C .

[0373] For the chroma quantization parameter data for the chroma quantization parameter proposed in this embodiment, Qp C_data() is signaled as shown in the following table.

[0374]

Table 35

[0375] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0376] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between Qpi_min_idx and the maximum qPi index used for Qp C derivation. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in Equation 4 above.

[0377] Also, for example, the syntax element QpC_qPi_delta_val[i] indicates the delta of the Qp C value for the i-th index.

[0378] For example, the variable Qp C Idx[qPi] can be derived as follows.

[0379] - When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0380] - When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1] is set.

[0381] When -qPi > qPiMaxIdx, Qp C Idx[qPi] is qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]) is set.

[0382] Then, the said Qp C is the said Qp C is set to Idx[qPi].

[0383] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chroma quantization derivation or information signaled for chroma quantization derivation is used. The said flag can be signaled via a high - level syntax such as an SPS (sequence parameter set) or a PPS (picture parameter set). The said flag signaled via the high - level syntax is as follows in the following table.

[0384]

Table 36

[0385] For example, the syntax element Qp C _data_default_flag indicates whether a user - defined mode is used for the derivation of quantization parameters. For example, a Qp C _data_default_flag of 0 indicates that a user - defined mode is used for the derivation of quantization parameters. That is, for example, a Qp C _data_default_flag of 0 indicates that the above - mentioned chroma quantization parameter data Qp C _data() is used. When the said Qp C _data_default_flag is 0, the said chroma quantization parameter data Qp C_data() can be signaled. Also, for example, a Qp of 1 C _data_default_flag indicates that the default table is used for the derivation of quantization parameters. The aforementioned default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0386] For example, when describing the process of deriving quantization parameters according to this embodiment in a standard format, it is as shown in the following table.

[0387]

Table 37-1

[0388]

Table 37-2

[0389]

Table 37-3

[0390]

Table 37-4

[0391]

Table 37-5

[0392] Referring to Table 37 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (that is, for example, when Qp C _data_default_flag is 0), the variable qP Cb , qPCr and qP CbCr is derived based on user - defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variable qP Cb qP Cr and qP CbCr can be derived from a default table based on the same index qPi Cb qPi Cr and qPi CbCr respectively.

[0393] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0394] For example, this embodiment proposes a scheme for deriving a chroma quantization parameter Qp C table without an offset. This embodiment can be used together with APS or can also be proposed to be used independently. For example, the syntax structure of APS integrated with chroma quantization data is as follows.

[0395]

Table 38

[0396] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range from 0 to 63.

[0397] Also, for example, the syntax element qPi_delta_max_idx is between Qpi_min_idx and chroma Qp CIndicates the delta value between the maximum qPi indices used for derivation. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in the aforementioned Equation 4.

[0398] Also, for example, the syntax element QpC_qPi_delta_val[i] indicates the difference in the Qp value for the i-th index. The said difference may be referred to as delta. C Indicates the difference in value. The said difference may be called delta.

[0399] For example, the variable Qp C Idx[qPi] is derived as follows. Here, the said qPi can be from 0 to 63.

[0400] When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0401] When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is Qp C _qPi_delta_val[qPi] + Qp C Idx[qPi - 1] is set.

[0402] When -qPi > qPiMaxIdx, Qp C Idx[qPi] is set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0403] After that, the said Qp C is set to the said Qp C Idx[qPi].

[0404] Furthermore, this document proposes another embodiment for signaling information regarding quantization parameters.

[0405] For example, this embodiment presents, as an example, a scheme where the delta (or difference) between consecutive Qp C values is limited to 1.

[0406] For example, this embodiment proposes a scheme of adding user - defined chroma quantization (Qp C ) to existing image / video standards. For example, the flag in the SPS (sequence parameter set) proposed in this embodiment indicates whether to use the existing default table for chroma quantization parameter derivation or to derive the content of the table based on the information signaled in the SPS. According to this embodiment, a scheme suitable for the image coded with the acceptance of user - defined chroma quantization can be selected, and the coding efficiency can be improved.

[0407] For example, this embodiment proposes to add a function of signaling chroma quantization (Chroma Quantization) Qp C as a function of the index qPi using syntax elements as shown in the following table.

[0408]

Table 39

[0409] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 1 to 63.

[0410] Also, for example, the syntax element qPi_delta_max_idx is between Qpi_min_idx and chroma Qp CIndicates the delta value between the maximum qPi indices used for derivation. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in Equation 4 above.

[0411] Also, for example, the syntax element Qp C _qPi_flag[i] indicates whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i] can indicate whether the value of the i-th Qp C is 1 greater than the value of the (i - 1)-th Qp C value. For example, a Qp C _qPi_flag[i] of 1 indicates that the Qp C value increases by 1, and a Qp C _qPi_flag[i] of 0 indicates that the Qp C value has not increased.

[0412] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, the qPi can be from 0 to 63.

[0413] - When qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0414] - When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is set to Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0415] - When -qPi > qPiMaxIdx, Qp C Idx[qPi] is qPi - (qPiMaxIdx - QpC It is set to Idx[qPiMaxIdx].

[0416] After that, the Qp C is the Qp C It is set to Idx[qPi].

[0417] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chroma quantization derivation or information signaled for chroma quantization derivation is used. The flag can be signaled via a high-level syntax such as an SPS (sequence parameter set) or a PPS (picture parameter set). The flag signaled via the high-level syntax is as follows in the following table.

[0418]

Table 40

[0419] For example, the syntax element Qp C _data_default_flag indicates whether a user-defined mode is used for the derivation of quantization parameters. For example, a Qp of 0 C _data_default_flag indicates that a user-defined mode is used for the derivation of quantization parameters. That is, for example, a Qp of 0 C _data_default_flag indicates that the chroma quantization parameter data Qp C _data() is used. The Qp C _data_default_flag is 0, the chroma quantization parameter data Qp C _data() can be signaled. Also, for example, a Qp of 1 C_data_default_flag indicates that the default table is used for deriving quantization parameters. The default table is as shown in Table 7 above. Also, Qp C if _data_default_flag does not exist, the Qp C _data_default_flag is considered to be 1.

[0420] For example, when describing the process of deriving quantization parameters according to this embodiment in standard form, it is as shown in the following table.

[0421]

Table 41-1

[0422]

Table 41-2

[0423]

Table 41-3

[0424]

Table 41-4

[0425]

Table 41-5

[0426] Referring to Table 41 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (that is, for example, when Qp C _data_default_flag is 0), qP Cb , the variable qP Cr and qP CbCrcan be derived based on user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates affirmative (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived from the default table based on the same index qPi as qPi Cb , qPi Cr , qPi CbCr .

[0427] This document also proposes another embodiment for signaling information regarding quantization parameters.

[0428] For example, this embodiment proposes an example of a data signaling structure for chroma QP derivation. Specifically, this embodiment proposes a scheme of adding a chroma_qp_mapping_flag, which is a new syntax element in the SPS. For example, when the value of the chroma_qp_mapping_flag is 0, a default chroma QP mapping table can be used for deriving the chroma quantization parameter. Also, for example, when the value of the chroma_qp_mapping_flag is 1, the syntax elements used for deriving the chroma QP mapping table can be signaled as shown in the following table.

[0429]

Table 42

[0430] For example, the syntax element Qp C_data_default_flag indicates whether the user-defined mode is used for deriving quantization parameters. For example, Qp of 0 C _data_default_flag indicates that the user-defined mode is used for deriving quantization parameters. That is, for example, Qp of 0 C _data_default_flag indicates that the chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 42 above is used for deriving the chroma quantization parameters. The Qp C When _data_default_flag is 0, the chroma quantization parameter data shown in Table 42 above can be signaled. Also, for example, Qp of 1 C _data_default_flag indicates that the default table is used for deriving quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0431] Also, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 indicates the number of points where the mapping function does not increase.

[0432] Also, for example, the syntax element qPi_min_idx_minus1 indicates the first element of the set of points where the mapping function does not increase.

[0433] Also, for example, the syntax element Qp C _qPi_flag[i] indicates the delta value between the i-th element and the (i - 1)-th element of the set of points where the mapping function does not increase.

[0434] The chroma QP mapping table can be derived as follows based on the chroma quantization parameter data shown in Table 42.

[0435] For example, the variable cQpFlatSize can be derived as in the following formula.

[0436]

Equation

[0437] Also, for example, the variable cQpFlat[] can be derived as in the following table.

[0438]

Table 43

[0439] After that, the chroma QP mapping table can be derived as in the following table based on the variable cQpFlatSize and the variable cQpFlat[].

[0440]

Table 44

[0441] In addition, this document proposes another embodiment for signaling information regarding quantization parameters.

[0442] For example, this embodiment proposes adding a chroma_qp_mapping_flag, which is a new syntax element in the SPS. For example, when the value of the chroma_qp_mapping_flag is 0, the default chroma QP mapping table is used for deriving the chroma quantization parameter. Also, for example, when the value of the chroma_qp_mapping_flag is 1, the syntax elements used for deriving the chroma QP mapping table are signaled as in the following table.

[0443]

Table 45

[0444] For example, the syntax element Qp C _data_default_flag indicates whether the user-defined mode is used for the derivation of quantization parameters. For example, for Qp of 0 C _data_default_flag indicates that the user-defined mode is used for the derivation of quantization parameters. That is, for example, for Qp of 0 C _data_default_flag indicates that the chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 42 above is used for the derivation of chroma quantization parameters. The aforementioned Qp C When the Qp C _data_default_flag is 0, the chroma quantization parameter data shown in Table 42 above is signaled. Also, for example, for Qp of 1 C _data_default_flag indicates that the default table is used for the derivation of quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When the Qp

[0445] Also, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 indicates the number of points at which the mapping function does not increase.

[0446] Also, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 indicates the first element of the set of points at which the mapping function does not increase.

[0447] Also, for example, syntax element Qp C The value obtained by adding 1 to _qPi_idx_minus1[i] indicates the delta value between the i-th element and the (i-1)-th element of the set of points where the mapping function does not increase.

[0448] Based on the chroma quantization parameter data shown in Table 45, the chroma QP mapping table can be derived as follows.

[0449] For example, the variable cQpFlatSize can be derived as shown in Equation 5 above.

[0450] Also, for example, the variable cQpFlat[] can be derived as shown in the following table.

[0451] [Table 46]

[0452] Then, based on the variable cQpFlatSize and the variable cQpFlat[], the chroma QP mapping table can be derived. For example, the chroma QP mapping table is derived as shown in Table 44 above.

[0453] This document also proposes another embodiment for signaling information related to quantization parameters.

[0454] For example, this embodiment proposes a scheme for signaling an individual table for each chroma component. That is, for example, this embodiment proposes a scheme for signaling the syntax elements used to derive the chroma QP mapping table for each chroma component.

[0455] For example, the chroma QP mapping table for each chroma component is derived, and the syntax elements for each chroma component can be signaled as shown in the following table.

[0456]

Table 47

[0457] For example, the syntax element qp_luma_to_chroma_joint_map_flag indicates whether a common luma-chroma quantization parameter mapping table is used for the chroma components Cb, Cr, and CbCr. That is, for example, the syntax element qp_luma_to_chroma_joint_map_flag indicates whether one luma-chroma quantization parameter mapping table is applied to the Cb residual, Cr residual, and CbCr residual. For example, when the value of qp_luma_to_chroma_joint_map_flag is 1, a common luma-chroma quantization parameter mapping table is used for the chroma components Cb, Cr, and CbCr, and when the value of qp_luma_to_chroma_joint_map_flag is 0, individual luma-chroma quantization parameter mapping tables are used for each of the chroma components Cb, Cr, and CbCr.

[0458] Also, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx_minus1 can be in the range of 1 to 63.

[0459] Also, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 is the Qpi_min_idx and the chroma Qp CIndicates the delta value between the maximum qPi indices used in the derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. For example, the value of qPi_delta_max_idx_minus1 can be in the range of 1 to 63. Qp C The maximum index qPiMaxIdx used in the derivation is derived as follows in the following formula.

[0460]

Equation

[0461] Also, for example, the syntax element Qp C _qPi_flag[j] indicates whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i][j] indicates whether the j-th Qp of the i-th chroma component C value increases by 1 from the (j - 1)-th Qp C value. For example, QpC_qPi_flag[j] of 1 indicates that the Qp C value increases by 1, and QpC_qPi_flag[j] of 0 indicates that the Qp C value has not increased.

[0462] For example, the variable Qp C Idx[i][qPi] can be derived as follows. Here, the qPi can be from 0 to maxQp.

[0463] - When -qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] is set to be the same as qPi.

[0464] - When -qPi = qPi_min_idx_minus1 + 1 ··· qPiMaxIdx, Qp C Idx[qPi] is set to QpC_qPi_flag[qPi] + Qp C Idx[qPi - 1].

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

[0466] Then, the Qp C value can be derived from the Qp C Idx[i][qPi].

[0467] On the other hand, according to this embodiment, a flag indicating whether a syntax element used to derive a chroma QP mapping table by SPS is signaled or a default table is used can be signaled. For example, the flag is signaled as shown in the following table.

[0468]

Table 48

[0469] The syntax element Qp C _data_default_flag indicates whether a user - defined mode is used for the derivation of quantization parameters. For example, a Qp C _data_default_flag of 0 indicates that a user - defined mode is used for the derivation of quantization parameters. That is, for example, a Qp C _data_default_flag of 0 indicates that a chroma QP mapping table derived based on the chroma quantization parameter data shown in Table 47 above is used for the derivation of chroma quantization parameters. The Qp C _data_default_flag is 0, the chroma quantization parameter data shown in Table 47 above is signaled. Also, for example, a Qp C_data_default_flag indicates that the default table is used for deriving quantization parameters. The default table is as shown in Table 7 above. Also, Qp C if _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0470] For example, when describing the process of deriving quantization parameters according to this embodiment in a standard format, it can be shown as in the following table.

[0471]

Table 49-1

[0472]

Table 49-2

[0473]

Table 49-3

[0474]

Table 49-4

[0475]

Table 49-5

[0476] Referring to Table 49 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (that is, for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCrIt is derived based on the user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates affirmative (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr are derived from the default table based on the same index qPi Cb as qPi Cr and qPi CbCr respectively.

[0477] Also, this document proposes another embodiment for signaling information regarding quantization parameters. This embodiment proposes a scheme for signaling the maximum difference between the starting point and the end point by signaling the end point as a delta with respect to the maximum QP. That is, for example, according to this embodiment, a syntax element indicating the delta value between the maxQp used for chroma QpC derivation and the maximum qPi index is signaled.

[0478] The chroma quantization parameter data for the chroma quantization parameter proposed in this embodiment, Qp C _data() is signaled as shown in the following table.

[0479]

Table 50

[0480] For example, the syntax element qPi_min_idx indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 0 to 63.

[0481] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between the maximum qPi index used for deriving maxQp and the chroma Qp. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for deriving Qp can be derived as follows. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in the following formula.

[0482]

Equation

[0483] Also, for example, the syntax element Qp C _qPi_flag[i] indicates whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i] indicates whether the i-th Qp C value is 1 greater than the (i - 1)-th Qp C value. For example, a Qp C _qPi_flag[i] of 1 indicates that the Qp C value increases by 1, and a Qp C _qPi_flag[i] of 0 indicates that the Qp C value has not increased.

[0484] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, the qPi can be from 0 to 63.

[0485] When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0486] When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is QpC_qPi_flag[qPi] + QpC It is set to Idx[qPi - 1].

[0487] - If -qPi > qPiMaxIdx, then Qp C Idx[qPi] is qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]) is set.

[0488] Then, the said Qp C is the said Qp C is set to Idx[qPi].

[0489] Also, this embodiment proposes a scheme for signaling a flag indicating whether to use a default table for chroma quantization derivation or whether information signaled for chroma quantization derivation is used. The said flag can be signaled via a high - level syntax such as an SPS (sequence parameter set) or a PPS (picture parameter set). The said flag signaled via the high - level syntax is as follows in the following table.

[0490]

Table 51

[0491] For example, the syntax element Qp C _data_default_flag indicates whether a user - defined mode is used for the derivation of quantization parameters. For example, a Qp C _data_default_flag of 0 indicates that a user - defined mode is used for the derivation of quantization parameters. That is, for example, a Qp C _data_default_flag of 0 indicates that the above - mentioned chroma quantization parameter data Qp C _data() is used. When the said Qp C _data_default_flag is 0, the said chroma quantization parameter data QpC _data() can be signaled. Also, for example, a Qp of 1 C _data_default_flag indicates that the default table is used for the derivation of quantization parameters. The default table is as shown in Table 7 above. Also, Qp C when _data_default_flag does not exist, the Qp C _data_default_flag is considered to be 1.

[0492] For example, when describing the process of deriving quantization parameters according to this embodiment in a standard format, it can be shown as in the following table.

[0493]

Table 52-1

[0494]

Table 52-2

[0495]

Table 52-3

[0496]

Table 52-4

[0497]

Table 52-5

[0498] Referring to Table 52 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (that is, for example, when Qp C _data_default_flag is 0), the variable qPCb and qP Cr and qP CbCr can be derived based on user - defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates affirmative (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb and qP Cr and qP CbCr can each be derived by a default table based on the same index qPi Cb as qPi Cr and qPi CbCr respectively.

[0499] Also, this document proposes another embodiment for signaling information regarding quantization parameters. This embodiment proposes signaling the maximum difference between a starting point and an end point by signaling the end point as a delta with respect to the maximum QP or as the difference between the value obtained by adding a delta to the starting point and the starting point.

[0500] The chroma quantization parameter data, Qp C _data() for the chroma quantization parameter proposed in this embodiment is signaled as follows in the following table.

[0501]

Table 53

[0502] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range from 1 to maxQp.

[0503] Also, for example, the syntax element is_delta_maxQp indicates whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, an is_delta_maxQp of 1 indicates that qPiMaxIdx is derived from the maxQp value. Also, for example, an is_delta_maxQp of 0 indicates that qPiMaxIdx is derived from the syntax element qPi_min_idx_minus1.

[0504] Also, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 indicates the delta value between maxQp and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. For example, the value of qPi_delta_max_idx_minus1 can be in the range of 1 to 63. The maximum index qPiMaxIdx used for Qp C derivation can be derived as shown in the following table.

[0505]

Table 54

[0506] Also, for example, the syntax element Qp C _qPi_flag[i] indicates whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i] indicates whether the i-th Qp C value increases by 1 from the (i - 1)-th Qp C value. For example, a Qp C _qPi_flag[i] of 1 indicates that the Qp C value increases by 1, and a Qp C _qPi_flag[i] of 0 indicates that the Qp C value does not increase.

[0507] For example, the variable Qp CIdx[qPi] is derived as follows. Here, the qPi can be from 0 to maxQp.

[0508] - When -qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] is set to be the same as qPi.

[0509] - When -qPi = qPi_min_idx_minus1 ··· qPiMaxIdx, Qp C Idx[qPi] is Qp C _qPi_flag[qPi] + Qp C and is set to Idx[qPi - 1].

[0510] - When -qPi > qPiMaxIdx, Qp C Idx[qPi] is qPi - (qPiMaxIdx - Qp C and is set to Idx[qPiMaxIdx]).

[0511] After that, the Qp C is the Qp C and is set to Idx[qPi].

[0512] Also, this embodiment proposes a scheme for signaling a flag indicating whether to use a default table for chroma quantization derivation or information signaled for chroma quantization derivation. The flag can be signaled via a high level syntax such as SPS (sequence parameter set) or PPS (picture parameter set). The flag signaled via the high level syntax is as shown in the following table.

[0513]

Table 55

[0514] For example, the syntax element Qp C_data_default_flag indicates whether the user-defined mode is used for deriving quantization parameters. For example, Qp of 0 C _data_default_flag indicates that the user-defined mode is used for deriving quantization parameters. That is, for example, Qp of 0 C _data_default_flag refers to the chroma quantization parameter data Qp C _data() is used. The Qp C When _data_default_flag is 0, the chroma quantization parameter data Qp C _data() is signaled. Also, for example, Qp of 1 C _data_default_flag indicates that the default table is used for deriving quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0515] For example, when the process of deriving quantization parameters according to this embodiment is described in standard form, it is as shown in the following table.

[0516]

Table 56-1

[0517]

Table 56-2

[0518]

Table 56-3

[0519]

Table 56-4

[0520]

Table 56-5

[0521] Referring to the aforementioned Table 56, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived from the default table based on the same index qPi Cb , qPi Cr and qPi CbCr respectively.

[0522] Also, this document proposes another embodiment for signaling information regarding quantization parameters. This embodiment proposes signaling the maximum difference between the starting point and the ending point by signaling the ending point as the delta with respect to the maximum QP or the difference between the value obtained by adding the delta to the starting point and the starting point.

[0523] The chroma quantization parameter data Qp C _data() for the chroma quantization parameters proposed in this embodiment is signaled as follows in the following table.

[0524]

Table 57

[0525] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 1 to maxQp.

[0526] Also, for example, the syntax element is_delta_maxQp indicates whether the maximum index qPiMaxIdx is derived from the maxQp value. For example, an is_delta_maxQp of 1 indicates that qPiMaxIdx is derived from the maxQp value. Also, for example, an is_delta_maxQp of 0 indicates that qPiMaxIdx is derived from the syntax element qPi_min_idx_minus1.

[0527] Also, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 C indicates the delta value between maxQp and the maximum qPi index used for chroma Qp derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. For example, the value of qPi_delta_max_idx_minus1 can be in the range of 1 to 63. Qp C The maximum index qPiMaxIdx used for Qp derivation can be derived as described in Table 54 above.

[0528] Also, for example, the syntax element Qp C _qPi_flag[i] indicates whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i] indicates that the i-th Qp C value is the (i - 1)-th Qp CIndicates whether it increases by 1 from the value. For example, QpC_qPi_flag[i] of 1 indicates that Qp C increases by 1, and QpC_qPi_flag[i] of 0 indicates that Qp C does not increase in value.

[0529] For example, variable Qp C Idx[qPi] is derived as follows. Here, the qPi can be from 0 to maxQp.

[0530] When -qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] is set to be the same as qPi.

[0531] When -qPi = qPi_min_idx_minus1 ··· qPiMaxIdx, Qp C Idx[qPi] is QpC_qPi_flag[qPi] + Qp C set to Idx[qPi - 1].

[0532] When -qPi > qPiMaxIdx, Qp C Idx[qPi] is qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0533] After that, the Qp C can be set to the Qp C Idx[qPi].

[0534] Also, this embodiment proposes a scheme for signaling a flag indicating whether to use a default table for chroma quantization derivation or whether information signaled for chroma quantization derivation is used. The flag is signaled via a high level syntax such as SPS (sequence parameter set) or PPS (picture parameter set). The flag signaled via the high level syntax is as shown in the following table.

[0535]

Table 58

[0536] For example, the syntax element Qp C _data_default_flag indicates whether the user - defined mode is used for deriving quantization parameters. For example, Qp of 0 C _data_default_flag indicates that the user - defined mode is used for deriving quantization parameters. That is, for example, Qp of 0 C _data_default_flag indicates the chroma quantization parameter data Qp C _data() is used. The Qp C When _data_default_flag is 0, the chroma quantization parameter data Qp C _data() is signaled. Also, for example, Qp of 1 C _data_default_flag indicates that the default table is used for deriving quantization parameters. The aforementioned default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0537] For example, when the process of deriving quantization parameters according to this embodiment is described in standard form, it can be shown as in the following table.

[0538]

Table 59 - 1

[0539]

Table 59 - 2

[0540]

Table 59-3

[0541]

Table 59-4

[0542]

Table 59-5

[0543] Referring to Table 59 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr are derived based on the user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived from the default table based on the same index qPi Cb , qPi Cr and qPi CbCr respectively.

[0544] In addition, this document proposes another embodiment for signaling information related to quantization parameters. This embodiment proposes a scheme for signaling the index for the chroma QP mapping table using the minus1 nomenclature instead of the actual value.

[0545] For the chroma quantization parameter data, Qp, for the chroma quantization parameter proposed in this embodiment C _data() is signaled as shown in the following table.

[0546]

Table 60

[0547] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 1 to 63.

[0548] Also, for example, the value obtained by adding 1 to the syntax element qPi_delta_max_idx_minus1 indicates the delta value between qPi_min_idx and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx is 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, Qp C The maximum index qPiMaxIdx used for derivation can be derived as shown in the following mathematical formula.

[0549]

Equation

[0550] Also, for example, the syntax element Qp C _qPi_flag[i] indicates whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i] indicates whether the i-th Qp C value increases by 1 compared to the (i - 1)-th Qp C value. For example, a Qp of 1 C _qPi_flag[i] is the Qp CIndicates that the value increases by 1 and Qp of 0 C _qPi_flag[i] is Qp C Indicates that the value has not increased.

[0551] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, the qPi can be from 0 to 63.

[0552] When -qPi < qPi_min_idx_minus1 + 1, Qp C Idx[qPi] is set to be the same as qPi.

[0553] When -qPi = qPi_min_idx_minus1 + 1 ··· qPiMaxIdx, Qp C Idx[qPi] is Qp C _qPi_flag[qPi] + Qp C Is set to Idx[qPi - 1].

[0554] When -qPi > qPiMaxIdx, Qp C Idx[qPi] is qPi - (qPiMaxIdx - Qp C Is set to Idx[qPiMaxIdx]).

[0555] After that, the QpC can be set to the Qp C Idx[qPi].

[0556] In addition, this embodiment proposes a scheme for signaling a flag indicating whether to use a default table for chroma quantization derivation or whether information signaled for chroma quantization derivation is used. The flag can be signaled via a high level syntax such as an SPS (sequence parameter set) or a PPS (picture parameter set). The flag signaled via the high level syntax is as shown in the following table.

[0557]

Table 61

[0558] For example, the syntax element Qp C _data_default_flag indicates whether the user - defined mode is used for the derivation of quantization parameters. For example, Qp of 0 C _data_default_flag indicates that the user - defined mode is used for the derivation of quantization parameters. That is, for example, Qp of 0 C _data_default_flag is for the chroma quantization parameter data Qp C _data() being used. The aforementioned Qp C When _data_default_flag is 0, the chroma quantization parameter data Qp C _data() can be signaled. Also, for example, Qp of 1 C _data_default_flag indicates that the default table is used for the derivation of quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the aforementioned Qp C _data_default_flag is regarded as 1.

[0559] For example, when describing the process of deriving quantization parameters according to this embodiment in standard form, it can be shown as in the following table.

[0560]

Table 62 - 1

[0561]

Table 62 - 2

[0562]

Table 62-3

[0563]

Table 62-4

[0564]

Table 62-5

[0565] Referring to Table 62 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr can be derived based on the user-defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived by a default table based on the same index qPi Cb , qPi Cr , qPi CbCr respectively.

[0566] Also, this document proposes another embodiment for signaling information regarding quantization parameters. This embodiment proposes a scheme where individual chroma quantization tables are used for respective chroma components.

[0567] The chroma quantization parameter data for the chroma quantization parameters proposed in this embodiment can be signaled as shown in the following table.

[0568]

Table 63

[0569] For example, the syntax element Qp C _data_default_flag indicates whether the default chroma quantization parameter table is used. For example, a Qp of 1 C _data_default_flag indicates that the default chroma quantization parameter table is used for the derivation of the chroma quantization parameters. The default table is as shown in Table 7 above. Also, for example, a Qp of 0 C _data_default_flag indicates that the default chroma quantization parameter table is not used for the derivation of the chroma quantization parameters. That is, for example, a Qp of 0 C _data_default_flag indicates that the chroma quantization parameter table derived based on the chroma quantization parameter data signaled for the derivation of the chroma quantization parameters is used.

[0570] Also, for example, the syntax element sps_separate_qpc_table_flag indicates whether two separate Qp C tables are used for Cb samples and Cr samples. That is, for example, the syntax element sps_separate_qpc_table_flag can indicate whether an individual luma-chroma quantization parameter mapping table is used for each of the Cb residual and the Cr residual. For example, a sps_separate_qpc_table_flag of 1 means a separate Qp for each of the Cb samples and the Cr samples CIndicates that a table is used, and a sps_separate_qpc_table_flag of 0 means one Qp for Cb samples and Cr samples C Indicates that a table is used.

[0571] On the other hand, for example, variable Qp Cb [i] is the Qp table used for Cb samples C Indicates the table. Also, for example, variable Qp Cr [i] is the Qp table used for Cr samples C Indicates the table. Also, for example, when the value of sps_separate_qpc_table_flag is 0, Qp Cr [i] can be the same as Qp Cb [i]. Here, i can be from 0 to 69.

[0572] Also, for example, the value obtained by adding 1 to the syntax element qPi_cb_min_idx_minus1 indicates the minimum qPi index used for the Cb chroma component. The value of qPi_cb_min_idx_minus1 can be in the range of 1 to 69.

[0573] Also, for example, the value obtained by adding 1 to the syntax element qPi_cb_delta_max_idx_minus1 indicates the delta value between qPi_cb_min_idx_minus1 and the maximum qPi_cb_delta_idx_minus1 used for Cb chroma Qp C derivation. The value of qPiMaxIdx is greater than or equal to qPi_min_idx. The value of qPi_cb_delta_max_idx_minus1 can be in the range of 1 to 69. For example, the maximum index qPiMaxIdxcb used for Qp derivation for the Cb component can be derived as follows C in the following formula.

[0574]

Equation

[0575] Also, for example, the syntax element Qp C _cb_qPi_flag[i] is the Qp for the i-th C value Qp Cb [i] and the Qp of the (i - 1)-th C value Qp Cb [i - 1] indicates the delta values between them. Qp C The value of _cb_qPi_flag[i] can be in the range of 0 to 1.

[0576] For example, the variable Qp Cb [i] is derived as follows. Here, the said i can be from 0 to 69.

[0577] - When i = 0..qPiMaxIdxCb, qP Cb [i] is set to be the same as i.

[0578] - When i = qPi_cb_min_idx_minus1 + 1 + 1..qPiMaxIdxCb, Qp Cb [i] is Qp Cb [i - 1]+Qp C _cb_qPi_flag[i].

[0579] - When i = qPiMaxIdxCb + 1...69, Qp Cb [i] is set to i - deltaEnd, and deltaEnd can be derived as qPiMaxIdxCb - qP Cb [qPiMaxIdxCb].

[0580] Also, for example, the syntax elements qPi_cr_min_idx_minus1, qPiMaxIdxCr, and Qp for the Cr component C _cr_qPi_flag[i] have the same meaning as the syntax elements for the Cb component.

[0581] Furthermore, this document proposes another embodiment for signaling information regarding quantization parameters. For example, this embodiment proposes a scheme for signaling parameters for multiple chroma QP tables. Also, this embodiment can be connected to at least one of the aforementioned embodiments. That is, for example, the embodiments of this document can be commonly applied.

[0582] Specifically, for example, this embodiment proposes including user-defined chroma quantization parameters (Qp C ) in the VVC Specification Text. For example, according to this embodiment, the flag in the SPS (sequence parameter set) indicates whether to use the default table for deriving the chroma quantization parameters or to derive the chroma QP mapping table based on the information signaled in the SPS. Thereby, user-defined chroma quantization parameters can be used considering the content characteristics of the image in image coding, and the coding efficiency can be improved. Also, this embodiment can provide flexibility as an option where one user-defined table is used for the chroma component and as an option where separate user-defined tables are used for the Cb component and the Cr component.

[0583] For example, the chroma quantization parameter data Qp C _data() for the chroma quantization parameters proposed in this embodiment is signaled as shown in the following table.

[0584]

Table 64

[0585] For example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1 indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 1 to 69.

[0586] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between the minimum qPi index qPi_min_idx and the maximum qPi index used in the derivation of chroma Qp C The value of qPiMaxIdx is greater than or equal to qPi_min_idx. The value of qPi_delta_max_idx can be in the range of 0 to 69. For example, the maximum index qPiMaxIdx used in the derivation of Qp C can be derived as shown in Equation 4 above.

[0587] Also, for example, the syntax element Qp C _qPi_flag[i] can indicate whether the Qp C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i] indicates whether the i-th Qp C value increases by 1 compared to the (i - 1)-th Qp C value. For example, a Qp C _qPi_flag[i] of 1 indicates that the Qp C value increases by 1, and a Qp C _qPi_flag[i] of 0 indicates that the Qp C value does not increase.

[0588] For example, the variable Qp C Idx[qPi] can be derived as follows. Here, the qPi can be from 0 to 69.

[0589] - When -qPi < qPi_min_Idx, Qp C Idx[qPi] is set to be the same as qPi.

[0590] - When -qPi = qPi_min_idx ··· qPiMaxIdx, Qp C Idx[qPi] is set to Qp C _qPi_flag[qPi] + Qp C Idx[qPi - 1].

[0591] - When qPi > qPiMaxIdx, Qp C Idx[qPi] is set to qPi - (qPiMaxIdx - Qp C Idx[qPiMaxIdx]).

[0592] Then, the said Qp C is set to the said Qp C Idx[qPi].

[0593] Also, this embodiment proposes a scheme of signaling a flag indicating whether a default table is used for chroma quantization derivation or a chroma QP mapping table derived based on the signaled information is used. The said flag can be signaled via a high level syntax such as SPS (sequence parameter set) or PPS (picture parameter set). The said flag signaled via the high level syntax is as follows in the following table.

[0594]

Table 65

[0595] For example, the syntax element Qp C _data_default_flag indicates whether a user - defined mode is used for the derivation of quantization parameters. For example, a Qp C _data_default_flag of 0 indicates that a user - defined mode is used for the derivation of quantization parameters. That is, for example, a Qp C _data_default_flag of 0 indicates that the chroma quantization parameter data Qp C _data() is used. When the said Qp C _data_default_flag is 0, the chroma quantization parameter data Qp C_data() can be signaled. Also, for example, a Qp of 1 C _data_default_flag indicates that the default table is used for the derivation of quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0596] For example, when describing the process of deriving quantization parameters according to this embodiment in a standard format, it can be shown as in the following table.

[0597]

Table 66-1

[0598]

Table 66-2

[0599]

Table 66-3

[0600]

Table 66-4

[0601]

Table 66-5

[0602] Referring to Table 66 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (that is, for example, when Qp C _data_default_flag is 0), the variable qP Cb 、qPCr and qP CbCr can be derived based on user - defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variable qP Cb qP Cr and qP CbCr can each be derived from a default table based on the same index qPi Cb qPi Cr qPi CbCr as that of qPi.

[0603] Also, for example, when a separate user - defined table is used for each of the chroma components proposed in this embodiment, the chroma quantization parameter data Qp C _data() can be signaled as shown in the following table.

[0604]

Table 67

[0605] For example, the syntax element is_separate_chroma_table indicates 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 can indicate whether two separate chroma quantization parameter mapping tables are used for the Cb component and the Cr component. For example, the syntax element is_separate_chroma_table can indicate whether individual luma-chroma quantization parameter mapping tables are used for each of the Cb residual and the Cr residual. For example, an is_separate_chroma_table of 1 indicates that separate chroma quantization parameter mapping tables are signaled for the Cb component and the Cr component, and an is_separate_chroma_table of 0 indicates that one chroma quantization parameter mapping table is used for the Cb element, the Cr element, and the joint CbCr element. For example, when the value of is_separate_chroma_table is 1, qPi_min_idx_minus1[i], qPi_delta_max_Idx[i], and Qp C _qPi_flag[i][j] for the Cb component and qPi_min_idx_minus1[i], qPi_delta_max_Idx[i], and Qp C _qPi_flag[i][j] for the Cr component can be signaled. Also, for example, when the value of is_separate_chroma_table is 0, qPi_min_idx_minus1[i], qPi_delta_max_Idx[i], and Qp C _qPi_flag[i][j] for the Cb component, the Cr component, and the joint CbCr component can be signaled.

[0606] Also, for example, the value obtained by adding 1 to the syntax element qPi_min_idx_minus1[i] indicates the minimum qPi index used for chroma quantization. The value of qPi_min_idx can be in the range of 1 to 69. The variable qPi_min_Idx[i] is set to the same value as the value obtained by adding 1 to qPi_min_idx_minus1[i].

[0607] Also, for example, the syntax element qPi_delta_max_idx indicates the delta value between qPi_min_Idx[i] and the maximum qPi index used for chroma Qp C derivation. The value of qPiMaxIdx[i] is greater than or equal to qPi_min_Idx[i]. The value of qPi_delta_max_idx can be in the range of 0 to 69. For example, Qp C The maximum index qPiMaxIdx[i] used for derivation can be derived as follows.

[0608]

Equation

[0609] The value of qPiMaxIdx[i] is greater than or equal to qPi_min_idx_minus1[i].

[0610] Also, for example, the syntax element Qp C _qPi_flag[i][j] indicates whether the j-th Qp of the i-th chroma component C value increases by 1. That is, for example, the syntax element Qp C _qPi_flag[i][j] indicates whether the j-th Qp of the i-th chroma component C value increases by 1 from the (j - 1)-th Qp C value. For example, QpC_qPi_flag[j] of 1 indicates that the j-th Qp of the i-th chroma component C value increases by 1, and QpC_qPi_flag[j] of 0 indicates that the j-th Qp of the i-th chroma component CIndicates that the value does not increase.

[0611] For example, the variable Qp C Idx[i][qPi] can be derived as shown in the following table. Here, the qPi can be from 0 to 69.

[0612]

Table 68

[0613] Referring to Table 68, when the value of is_separate_chroma_table is 1, the 0th (i = 0) chroma quantization parameter data and the 1st (i = 1) chroma quantization parameter data can be signaled. Here, for example, the 0th (i = 0) chroma quantization parameter data is the chroma quantization parameter data for deriving the chroma quantization parameter mapping table for the Cb component, and the 1st (i = 0) chroma quantization parameter data can be the chroma quantization parameter data for deriving the chroma quantization parameter mapping table for the Cr component.

[0614] Also, referring to Table 68, when the value of is_separate_chroma_table is 0, only the 0th (i = 0) chroma quantization parameter data can be signaled. Here, for example, the 0th (i = 0) chroma quantization parameter data can be the chroma quantization parameter data for deriving the chroma quantization parameter mapping tables for the Cb component, the Cr component, and the joint CbCr component. That is, one chroma quantization parameter mapping table is used for the chroma components.

[0615] Also, referring to Table 68, Qp C Idx[i][qPi] is derived as follows.

[0616] When -qPi < qPi_min_Idx[i], Qp CIdx[i][qPi] is set to be the same as qPi.

[0617] - When qPi = qPi_min_Idx[i] ··· qPiMaxIdx[i], Qp C Idx[qPi] is Qp C _qPi_flag[i][qPi]+Qp C is set to Idx[i][qPi - 1].

[0618] - When qPi > qPiMaxIdx, Qp C Idx[i][qPi] is qPi - (qPiMaxIdx[i] - Qp C is set to Idx[i][qPiMaxIdx]).

[0619] Then, the value of the said Qp C can be derived from the said Qp C and Idx[i][qPi].

[0620] In addition, this embodiment proposes a scheme for signaling a flag indicating whether a default table is used for chroma quantization derivation or information signaled for chroma quantization derivation is used. The said flag can be signaled via a high level syntax such as SPS (sequence parameter set) or PPS (picture parameter set). The said flag signaled via the high level syntax is as follows in the following table.

[0621]

Table 69

[0622] For example, the syntax element Qp C _data_default_flag indicates whether a user - defined mode is used for the derivation of quantization parameters. For example, a Qp of 0 C_data_default_flag indicates that the user-defined mode is used for deriving quantization parameters. That is, for example, Qp of 0 C _data_default_flag indicates the chroma quantization parameter data Qp C _data() is used. The Qp C When _data_default_flag is 0, the chroma quantization parameter data Qp C _data() can be signaled. Also, for example, Qp of 1 C _data_default_flag indicates that the default table is used for deriving quantization parameters. The default table is as shown in Table 7 above. Also, Qp C When _data_default_flag does not exist, the Qp C _data_default_flag is regarded as 1.

[0623] For example, when describing the process of deriving quantization parameters according to this embodiment in a standard format, it can be shown as in the following table.

[0624]

Table 70-1

[0625]

Table 70-2

[0626]

Table 70-3

[0627]

Table 70-4

[0628]

Table 70-5

[0629] Referring to Table 70 above, when ChromaArrayType is 1 and Qp C _data_default_flag indicates negative (FALSE) (i.e., for example, when Qp C _data_default_flag is 0), the variables qP Cb , qP Cr and qP CbCr can be derived based on the user - defined information signaled as proposed in this embodiment. Also, for example, when ChromaArrayType is 1 and Qp C _data_default_flag indicates positive (TRUE) (i.e., for example, when Qp C _data_default_flag is 1), the variables qP Cb , qP Cr and qP CbCr can be derived by a default table based on the same index qPi as qPi Cb , qPi Cr and qPi CbCr respectively.

[0630] FIG. 10 schematically shows an image encoding method by an encoding device based on this document. The method disclosed in FIG. 10 is performed by the encoding device disclosed in FIG. 2. Specifically, for example, S1000 to S1010 in FIG. 10 are performed by the entropy encoding unit of the encoding device. Also, although not shown, the process of deriving prediction samples for chroma components is performed by the prediction unit of the encoding device, and the process of generating restored samples and a restored picture based on the residual samples and prediction samples for chroma components is performed by the addition unit of the encoding device.

[0631] The encoding device encodes image information (S1000).

[0632] The encoding device can encode the image information. For example, the image information can include prediction information for the chroma component, residual information for the chroma component, chroma quantization parameter data for the chroma component, and / or a flag indicating whether one chroma quantization parameter table is applied to the chroma component. The chroma component can include a Cb component, a Cr component, and / or a joint CbCr component.

[0633] For example, the encoding device derives prediction samples for the chroma component based on a prediction mode. That is, for example, the encoding device derives prediction samples for the current block of the chroma component based on the prediction mode. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, are applied.

[0634] For example, the encoding device can determine whether to perform inter prediction or intra prediction on the current block of the chroma component, and can 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 derives prediction samples for the current block.

[0635] Thereafter, for example, the encoding device can generate and encode prediction information for the current block. The prediction information includes prediction mode information indicating the prediction mode of the current block for the chroma component. The image information includes the prediction information.

[0636] Also, for example, the encoding device can derive residual samples for the chroma component based on the prediction samples. For example, the encoding device can derive the residual samples by subtracting the prediction samples from the original samples of the current block for the chroma component within the current picture.

[0637] Thereafter, for example, the encoding device encodes residual information for the residual samples. For example, the encoding device can derive a conversion coefficient based on the residual samples and generate the residual information based on the conversion coefficient. For example, the encoding device quantizes the residual samples based on a chroma quantization parameter to derive quantized residual samples, derives a conversion coefficient based on the quantized residual samples, and can generate and encode the residual information based on the conversion coefficient. Or, for example, the encoding device quantizes the residual samples based on a chroma quantization parameter to derive quantized residual samples, converts the quantized residual samples to derive a conversion coefficient, and can generate and encode the residual information based on the conversion coefficient.

[0638] For example, the residual information includes syntax elements for the conversion coefficients of the current chroma block. For example, the syntax elements 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.

[0639] Also, for example, the encoding device can generate and encode a flag indicating whether one chroma quantization parameter table is applied to the chroma component. The encoding device can determine whether one chroma quantization parameter table is applied to the chroma component and can generate and encode the flag.

[0640] For example, the encoding device can generate and encode a flag indicating whether one chroma quantization parameter table is applied to the chroma component based on the chroma type. Here, the chroma type can mean the ChromaArrayType described above. For example, when the value of the chroma type is not 0, the encoding device can generate a flag indicating whether one chroma quantization parameter table is applied to the chroma component. For example, when the value of the chroma type is 1, the encoding device can generate a flag indicating whether one chroma quantization parameter table is applied to the chroma component. Here, when the value of the chroma type is 0, the chroma type can be a Monochrome format, when the value of the chroma type is 1, the chroma type can be a 4:2:0 format, when the value of the chroma type is 2, the chroma type can be a 4:2:2 format, and when the value of the chroma type is 3, the chroma type can be a 4:4:4 format. For example, the syntax element for the flag can be the qp_luma_to_chroma_joint_map_flag flag, sps_separate_qpc_table_flag, or is_separate_chroma_table described above.

[0641] For example, when the value of the flag is 1, the flag can indicate that one chroma quantization parameter table is applied to the chroma component. Also, for example, when the value of the flag is 0, the flag can indicate that multiple chroma quantization parameter tables are applied to the chroma component. That is, for example, when the value of the flag is 0, the flag can indicate that an individual chroma quantization parameter table is applied to each of the chroma components.

[0642] Also, for example, the flag can be signaled via high level syntax. For example, the flag can be signaled via SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set), etc.

[0643] Also, for example, the encoding device can generate and encode chroma quantization parameter data for the chroma component based on the flag.

[0644] For example, when the value of the flag is 0 (i.e., when it is determined that a plurality of chroma quantization parameter tables are applied to the chroma component), the chroma quantization parameter data can include first chroma quantization parameter data for the Cb component and second chroma quantization parameter data for the Cr component. Or, for example, when the value of the flag is 0 (i.e., when it is determined that a plurality of chroma quantization parameter tables are applied to the chroma component), the chroma quantization parameter data can include first chroma quantization parameter data for the Cb component, second chroma quantization parameter data for the Cr component, and / or third chroma quantization parameter data for the joint CbCr component.

[0645] On one hand, for example, an encoding device can generate and encode a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. That is, for example, the encoding device can determine whether there is third chroma quantization parameter data for the joint CbCr component, and can generate and encode the joint CbCr available flag. Also, for example, the encoding device can generate and encode a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component based on the chroma type. Here, the chroma type can mean the ChromaArrayType described above. For example, when the value of the chroma type is not 0, the encoding device can generate a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. For example, when the value of the chroma type is 1, the encoding device can generate a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. Also, for example, the joint CbCr available flag can be signaled via high level syntax. For example, the joint CbCr available flag can be signaled via a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS), etc.

[0646] In this case, when the value of the flag is 0 (i.e., it is determined that a plurality of chroma quantization parameter tables are applied to the chroma component), and when the value of the joint CbCr available flag is 1 (i.e., it is determined that there is third chroma quantization parameter data for the joint CbCr component), the chroma quantization parameter data can include first chroma quantization parameter data for the Cb component, second chroma quantization parameter data for the Cr component, and third chroma quantization parameter data for the joint CbCr component.

[0647] Also, for example, the first chroma quantization parameter data can include a syntax element representing the start index of the first chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the first chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to the index of the first chroma quantization parameter table. That is, for example, the first chroma quantization parameter data can include a syntax element representing the start index of the first chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the first chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to each index of the first chroma quantization parameter table. The syntax element representing the start index can be qPi_min_idx, qPi_min_idx_minus1[i], or qPi_cb_min_idx_minus1 as described above. Also, the syntax element representing the difference between the start index and the last index can be qPi_delta_max_idx, qPi_cb_delta_max_idx_minus1, or qPi_delta_max_idx[i]. Also, the syntax element for the quantization parameter value corresponding to the index can be QpC_qPi_val[i], QpC_cb_qPi_flag[i], or QpC_qPi_flag[i][j] as described above. Also, for example, the first chroma quantization parameter data can be signaled via high level syntax.For example, the first chroma quantization parameter data can be signaled via an SPS (sequence parameter set), a PPS (picture parameter set), a slice header, or an APS (adaptation parameter set), etc.

[0648] Also, for example, the second chroma quantization parameter data can include a syntax element representing the start index of the second chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the second chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to the index of the second chroma quantization parameter table. That is, for example, the second chroma quantization parameter data can include a syntax element representing the start index of the second chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the second chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to each index of the second chroma quantization parameter table. The syntax element representing the start index can be qPi_min_idx, qPi_min_idx_minus1[i], or qPi_cr_min_idx_minus1 as described above. Also, the syntax element representing the difference between the start index and the last index can be qPi_delta_max_idx, qPi_cr_delta_max_idx_minus1, or qPi_delta_max_idx[i]. Also, the syntax element for the quantization parameter value corresponding to the index can be QpC_qPi_val[i], QpC_cr_qPi_flag[i], or QpC_qPi_flag[i][j] as described above. Also, for example, the second chroma quantization parameter data can be signaled via high level syntax.For example, the second chroma quantization parameter data can be signaled via SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set), etc.

[0649] Also, for example, the third chroma quantization parameter data can include a syntax element representing the start index of the third chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the third chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to the index of the third chroma quantization parameter table. That is, for example, the third chroma quantization parameter data can include a syntax element representing the start index of the third chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the third chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to each index of the third chroma quantization parameter table. The syntax element representing the start index can be the above-mentioned qPi_min_idx or qPi_min_idx_minus1[i]. Also, the syntax element representing the difference between the start index and the last index can be qPi_delta_max_idx or qPi_delta_max_idx[i]. Also, the syntax element for the quantization parameter value corresponding to the index can be the above-mentioned QpC_qPi_val[i] or QpC_qPi_flag[i][j]. Also, for example, the third chroma quantization parameter data can be signaled via high level syntax. For example, the third chroma quantization parameter data can be signaled via SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set), etc.

[0650] Also, for example, when the value of the flag is 1 (i.e., when it is determined that one chroma quantization parameter table is applied to the chroma component), the chroma quantization parameter data can include chroma quantization parameter data for the Cb component, the Cr component, and the joint CbCr component.

[0651] The encoding device generates a bitstream including the image information (S1010).

[0652] For example, the encoding device can output, in a bitstream, image information including prediction information for the chroma component, residual information for the chroma component, chroma quantization parameter data for the chroma component, and / or a flag indicating whether one chroma quantization parameter table is applied to the chroma component. The bitstream can include the prediction information, the residual information, the quantization parameter data, and / or the flag. Also, the image information can further include the joint CbCr available flag.

[0653] The encoding device encodes the image information and outputs it in the form of a bitstream.

[0654] On the other hand, the bitstream including the image information can be transmitted to a decoding device via a network or a (digital) storage medium. Here, the network can include a broadcast network and / or a communication network, etc., and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc.

[0655] FIG. 11 schematically shows an encoding apparatus that performs an image encoding method according to this document. The method disclosed in FIG. 10 is performed by the encoding apparatus disclosed in FIG. 11. Specifically, for example, the entropy encoding unit of the encoding apparatus in FIG. 11 can perform S1000 to S1010. Although not shown, the process of deriving a prediction sample for a chroma component is performed by the prediction unit of the encoding apparatus, and the process of generating a restored sample and a restored picture based on the residual sample and the prediction sample for the chroma component is performed by the addition unit of the encoding apparatus.

[0656] FIG. 12 schematically shows an image decoding method by a decoding apparatus according to this document. The method disclosed in FIG. 12 can be performed by the decoding apparatus disclosed in FIG. 3. Specifically, for example, S1200 in FIG. 12 is performed by the entropy decoding unit of the decoding apparatus, and S1210 in FIG. 12 is performed by the residual processing unit of the decoding apparatus.

[0657] The decoding apparatus acquires image information (S1200). The decoding apparatus can acquire image information via a bitstream.

[0658] For example, the image information can include information regarding a chroma quantization parameter.

[0659] For example, the decoding device can obtain a flag indicating whether one chroma quantization parameter table is applied to the chroma component. That is, for example, the image information can include a flag indicating whether one chroma quantization parameter table is applied. For example, the decoding device can obtain a flag indicating whether one chroma quantization parameter table is applied based on the chroma type. Here, the chroma type can mean the ChromaArrayType described above. For example, when the value of the chroma type is not 0, the decoding device can obtain a flag indicating whether one chroma quantization parameter table is applied. For example, when the value of the chroma type is 1, the decoding device can obtain a flag indicating whether one chroma quantization parameter table is applied. Here, when the value of the chroma type is 0, the chroma type can be the Monochrome format, and when the value of the chroma type is 1, the chroma type can be the 4:2:0 format, when the value of the chroma type is 2, the chroma type can be the 4:2:2 format, and when the value of the chroma type is 3, the chroma type can be the 4:4:4 format. Also, for example, the chroma component can include a Cb component, a Cr component, and / or a joint CbCr component. For example, the syntax element for the flag can be the qp_luma_to_chroma_joint_map_flag flag, the sps_separate_qpc_table_flag, or the is_separate_chroma_table described above.

[0660] For example, when the value of the flag is 1, the flag can indicate that one chroma quantization parameter table is applied to the chroma component. Also, for example, when the value of the flag is 0, the flag can indicate that a plurality of chroma quantization parameter tables are applied to the chroma component. That is, for example, when the value of the flag is 0, the flag can indicate that an individual chroma quantization parameter table is applied to each of the chroma components.

[0661] Also, for example, the flag can be signaled via high level syntax. For example, the flag can be signaled via SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set).

[0662] Also, the decoding device can obtain chroma quantization parameter data based on the flag. For example, the image information can include the chroma quantization parameter data.

[0663] For example, when the value of the flag is 0 (i.e., when the flag indicates that a plurality of chroma quantization parameter tables are applied to the chroma component), the chroma quantization parameter data can include first chroma quantization parameter data for the Cb component and second chroma quantization parameter data for the Cr component. Or, for example, when the value of the flag is 0 (i.e., when the flag indicates that a plurality of chroma quantization parameter tables are applied to the chroma component), the chroma quantization parameter data can include first chroma quantization parameter data for the Cb component, second chroma quantization parameter data for the Cr component, and / or third chroma quantization parameter data for the joint CbCr component.

[0664] On the other hand, for example, the decoding device can obtain a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. For example, the image information can include a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. Also, for example, the decoding device can obtain a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component based on the chroma type. Here, the chroma type can mean the ChromaArrayType described above. For example, when the value of the chroma type is not 0, the decoding device can obtain a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. For example, when the value of the chroma type is 1, the decoding device can obtain a joint CbCr available flag indicating whether there is third chroma quantization parameter data for the joint CbCr component. Also, for example, the joint CbCr available flag can be signaled via high level syntax. For example, the joint CbCr available flag can be signaled via a sequence parameter set (SPS), a picture parameter set (PPS), a slice header, or an adaptation parameter set (APS).

[0665] In this case, when the value of the flag is 0 (i.e., the flag indicates that a plurality of chroma quantization parameter tables are applied to the chroma component), and when the value of the joint CbCr available flag is 1 (i.e., the joint CbCr available flag indicates the existence of third chroma quantization parameter data for the joint CbCr component), the chroma quantization parameter data can include first chroma quantization parameter data for the Cb component, second chroma quantization parameter data for the Cr component, and third chroma quantization parameter data for the joint CbCr component.

[0666] Also, for example, the first chroma quantization parameter data can include a syntax element representing the start index of the first chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the first chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to the index of the first chroma quantization parameter table. That is, for example, the first chroma quantization parameter data can include a syntax element representing the start index of the first chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the first chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to each index of the first chroma quantization parameter table. The syntax element representing the start index can be qPi_min_idx, qPi_min_idx_minus1[i], or qPi_cb_min_idx_minus1 as described above. Also, the syntax element representing the difference between the start index and the last index can be qPi_delta_max_idx, qPi_cb_delta_max_idx_minus1, or qPi_delta_max_idx[i]. Also, the syntax element for the quantization parameter value corresponding to the index can be QpC_qPi_val[i], QpC_cb_qPi_flag[i], or QpC_qPi_flag[i][j] as described above. Also, for example, the first chroma quantization parameter data can be signaled via high level syntax.For example, the first chroma quantization parameter data can be signaled via an SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set), etc.

[0667] Also, for example, the second chroma quantization parameter data can include a syntax element representing the start index of the second chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the second chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to the index of the second chroma quantization parameter table. That is, for example, the second chroma quantization parameter data can include a syntax element representing the start index of the second chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the second chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to each index of the second chroma quantization parameter table. The syntax element representing the start index can be qPi_min_idx, qPi_min_idx_minus1[i], or qPi_cr_min_idx_minus1 as described above. Also, the syntax element representing the difference between the start index and the last index can be qPi_delta_max_idx, qPi_cr_delta_max_idx_minus1, or qPi_delta_max_idx[i]. Also, the syntax element for the quantization parameter value corresponding to the index can be QpC_qPi_val[i], QpC_cr_qPi_flag[i], or QpC_qPi_flag[i][j] as described above. Also, for example, the second chroma quantization parameter data can be signaled via high level syntax.For example, the second chroma quantization parameter data can be signaled via an SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set), etc.

[0668] Also, for example, the third chroma quantization parameter data can include a syntax element representing the start index of the third chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the third chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to the index of the third chroma quantization parameter table. That is, for example, the third chroma quantization parameter data can include a syntax element representing the start index of the third chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the third chroma quantization parameter table, and / or a syntax element for the chroma quantization parameter value corresponding to each index of the third chroma quantization parameter table. The syntax element representing the start index can be the above-mentioned qPi_min_idx or qPi_min_idx_minus1[i]. Also, the syntax element representing the difference between the start index and the last index can be qPi_delta_max_idx or qPi_delta_max_idx[i]. Also, the syntax element for the quantization parameter value corresponding to the index can be the above-mentioned QpC_qPi_val[i] or QpC_qPi_flag[i][j]. Also, for example, the third chroma quantization parameter data can be signaled via high level syntax. For example, the third chroma quantization parameter data can be signaled via SPS (sequence parameter set), PPS (picture parameter set), slice header, or APS (adaptation parameter set), etc.

[0669] Also, for example, when the value of the flag is 1 (i.e., when the flag indicates that one chroma quantization parameter table is applied to the chroma component), the chroma quantization parameter data can include chroma quantization parameter data for the Cb component, the Cr component, and the joint CbCr component.

[0670] Also, for example, the image information can include prediction information and / or residual information for the chroma component. For example, the image information can include prediction information for the chroma component, and the prediction information can include the prediction mode information. The prediction mode information can indicate whether inter prediction or intra prediction is applied to the current block for the chroma component. Also, for example, the residual information can include syntax elements for the transform coefficients of the current block for the chroma component. For example, the syntax elements can include syntax elements such as coded_sub_block_flag, sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag, abs_remainder, and / or coeff_sign_flag.

[0671] The decoding device generates a restored picture based on the image information (S1210).

[0672] For example, the decoding device can derive the chroma quantization parameter table based on the chroma quantization parameter data, can derive the chroma quantization parameter for the chroma component based on the chroma quantization parameter table, can derive the residual samples for the chroma component based on the chroma quantization parameter, and can generate a restored picture based on the residual samples.

[0673] Specifically, for example, the decoding device can derive the chroma quantization parameter table based on the chroma quantization parameter data. The chroma quantization parameter table can also be referred to as a chroma quantization parameter mapping table or a user defined quantization parameter mapping table.

[0674] For example, as described above, the chroma quantization parameter table can be derived based on a syntax element representing the start index of the chroma quantization parameter table, a syntax element representing the difference between the start index and the last index of the chroma quantization parameter table, and / or a syntax element for the quantization parameter value of the index of the chroma quantization parameter table. That is, for example, a chroma quantization parameter table for chroma components can be derived based on the quantization parameter data.

[0675] For example, when the value of the flag is 0 (i.e., when the flag indicates that a plurality of chroma quantization parameter tables are applied to the chroma component), the first chroma quantization parameter table for the chroma Cb component can be derived based on the first chroma quantization parameter data for the Cb component. Also, for example, when the value of the flag is 0, the second chroma quantization parameter table for the chroma Cr component can be derived based on the second chroma quantization parameter data for the Cr component. Also, for example, when the value of the flag is 0, the third chroma quantization parameter table for the chroma joint CbCr component can be derived based on the third chroma quantization parameter data for the joint CbCr component.

[0676] Also, for example, when the value of the flag is 1 (i.e., when the flag indicates that one chroma quantization parameter table is applied to the chroma component), the first chroma quantization parameter table for the chroma component can be derived based on the chroma quantization parameter data for the chroma component. The chroma component can include a Cb component, a Cr component, and a joint CbCr component.

[0677] Also, for example, a decoding device can derive a chroma quantization parameter for the chroma component based on the chroma quantization parameter table.

[0678] For example, when the value of the flag is 0, the first chroma quantization parameter for the Cb component can be derived based on the first chroma quantization parameter table, and the second chroma quantization parameter for the Cr component can be derived based on the second chroma quantization parameter table. Also, for example, when the value of the flag is 0, the first chroma quantization parameter for the Cb component can be derived based on the first chroma quantization parameter table, and the second chroma quantization parameter for the Cr component can be derived based on the second chroma quantization parameter table, and the third chroma quantization parameter for the joint CbCr component can be derived based on the third chroma quantization parameter table. Here, the quantization parameter for the Cb component can represent QP’ Cb as described above, the quantization parameter for the Cr component can represent QP’ Cr as described above, and the quantization parameter for the joint CbCr component can represent QP’ CbCr as described above.

[0679] For example, an index for a chroma component (Cb component, Cr component, or joint CbCr component) can be derived based on quantization parameters for a luma component, and chroma quantization parameters for the chroma component can be derived based on the chroma quantization parameters for the index in the chroma quantization parameter table for the chroma component. That is, for example, the chroma quantization parameters for the chroma component can be derived based on the chroma quantization parameters for the same index as the quantization parameters of the luma component in the chroma quantization parameter table.

[0680] Also, for example, an offset is added to the chroma quantization parameters (e.g., QP cb , QP cr , or QP cbCr ) for the index in the chroma quantization parameter table for the chroma component (Cb component, Cr component, or joint CbCr component) to derive the chroma quantization parameters (e.g., QP’ Cb , QP’ Cr , or QP’ CbCr ) for the chroma component. The offset can be derived based on a syntax element representing an offset for deriving quantization parameters for the chroma component.

[0681] Or, for example, when the value of the flag is 1, chroma quantization parameters for the chroma component can be derived based on the chroma quantization parameter table for the chroma component. That is, for example, when the value of the flag is 1, chroma quantization parameters for the chroma component can be derived based on one chroma quantization parameter table for the chroma component. Therefore, the chroma quantization parameters can be applied identically to the chroma component.

[0682] For example, an index for a chroma component (Cb component, Cr component, and joint CbCr component) can be derived based on quantization parameters for a luma component, and a chroma quantization parameter for the chroma component can be derived based on the chroma quantization parameter in the chroma quantization parameter table for the index of the chroma component. That is, for example, the chroma quantization parameter for the chroma component can be derived based on the chroma quantization parameter for the same index as the quantization parameter of the luma component in the chroma quantization parameter table.

[0683] Also, for example, an offset can be added to the chroma quantization parameter for the index of the chroma quantization parameter table for the chroma component to derive the chroma quantization parameter for the chroma component. The offset can be derived based on a syntax element representing an offset for deriving quantization parameters for the chroma component.

[0684] Thereafter, for example, the decoding device can derive a residual sample for the chroma component based on the chroma quantization parameter.

[0685] For example, the decoding device can derive a conversion coefficient for a chroma component based on the received residual information. The image information includes the residual information. Or, for example, the decoding device can derive a conversion coefficient based on the received residual information, and inverse-transform the conversion coefficient to derive an inverse-transformed conversion coefficient. The conversion coefficient includes a conversion coefficient for the Cb component, a conversion coefficient for the Cr component, and / or a conversion coefficient for the joint CbCr component.

[0686] Thereafter, the decoding device can inverse-quantize the conversion coefficient based on the chroma quantization parameter to derive a residual sample.

[0687] For example, when the value of the flag is 0, the decoding device can inverse-quantize the transform coefficient for the Cb component based on the first chroma quantization parameter for the Cb component to derive the residual sample for the Cb component, and inverse-quantize the transform coefficient for the Cr component based on the second chroma quantization parameter for the Cr component to derive the residual for the Cr component. Or, for example, when the value of the flag is 0, the decoding device inverse-quantizes the transform coefficient for the Cb component based on the first chroma quantization parameter for the Cb component to derive the residual sample for the Cb component, inverse-quantizes the transform coefficient for the Cr component based on the second chroma quantization parameter for the Cr component to derive the residual for the Cr component, and inverse-quantizes the transform coefficient for the joint CbCr component based on the third chroma quantization parameter for the joint CbCr component to derive the residual sample for the joint CbCr component. Or, for example, when the value of the flag is 1, the decoding device can inverse-quantize the transform coefficient for the chroma component based on the chroma quantization parameter to derive the residual sample for the chroma component.

[0688] Alternatively, when the value of the flag is 0, the decoding device can inverse quantize the inverse-transformed transform coefficients for the Cb component based on the first chroma quantization parameter for the Cb component to derive the residual samples for the Cb component, and inverse quantize the inverse-transformed transform coefficients for the Cr component based on the second chroma quantization parameter for the Cr component to derive the residual samples for the Cr component. Alternatively, for example, when the value of the flag is 0, the decoding device can inverse quantize the inverse-transformed transform coefficients for the Cb component based on the first chroma quantization parameter for the Cb component to derive the residual samples for the Cb component, inverse quantize the inverse-transformed transform coefficients for the Cr component based on the second chroma quantization parameter for the Cr component to derive the residual samples for the Cr component, and inverse quantize the inverse-transformed transform coefficients for the joint CbCr component based on the third chroma quantization parameter for the joint CbCr component to derive the residual samples for the joint CbCr component. Alternatively, for example, when the value of the flag is 1, the decoding device can inverse quantize the inverse-transformed transform coefficients for the chroma component based on the chroma quantization parameter to derive the residual samples for the chroma component.

[0689] Thereafter, for example, the decoding device can generate a restored picture based on the residual samples.

[0690] On the other hand, for example, the decoding device can derive prediction samples for the chroma component based on the received prediction information. The image information includes the prediction information. The decoding device can determine whether inter prediction or intra prediction is applied to the chroma component based on the prediction information, and perform prediction based on this. That is, for example, the decoding device can determine whether inter prediction or intra prediction is applied to the current block for the chroma component based on the prediction information, and perform prediction based on this.

[0691] For example, the decoding device can derive the prediction mode applied to the current block for the chroma component based on the prediction information, and derive the prediction samples of the current block based on the prediction mode. For example, when inter prediction is applied to the current block, the decoding device can derive the motion information of the current block based on the prediction information included in the image information, and derive the prediction samples of the current block based on the motion information. Also, for example, when intra prediction is applied to the current block, the decoding device can derive reference samples based on the surrounding samples of the current block, and derive the prediction samples in the current block based on the reference samples and the intra prediction mode of the current block. The reference samples include the upper reference sample and the left reference sample of the current block. For example, when the size of the current block is N×N and the x component and y component of the top-left sample position of the current block are 0, the left reference sample can be p[-1][0] to p[-1][2N-1], and the upper reference sample can be p[0][-1] to p[2N-1][-1].

[0692] Thereafter, for example, the decoding device can generate a reconstructed picture based on the prediction samples and the residual samples. For example, the decoding device can generate reconstructed samples and / or a reconstructed picture by adding the prediction samples and the residual samples.

[0693] Thereafter, as described above, in-loop filtering procedures such as deblocking filtering, SAO, and / or ALF procedures can be applied to the reconstructed samples in order to improve subjective / objective picture quality as necessary.

[0694] FIG. 13 schematically shows a decoding apparatus that performs an image decoding method according to this document. The method disclosed in FIG. 12 is performed by the decoding apparatus disclosed in FIG. 13. Specifically, for example, the entropy decoding unit of the decoding apparatus in FIG. 13 can perform S1200 in FIG. 12, and the residual processing unit of the decoding apparatus in FIG. 13 can perform S1210 in FIG. 12.

[0695] According to the above-described document, for deriving quantization parameters for chroma components, a chroma quantization parameter table for chroma components can be determined based on a flag indicating whether the same chroma quantization parameter table is used, and coding can be performed based on quantization parameters according to the characteristics of the image to improve coding efficiency.

[0696] Also, according to this document, a chroma quantization parameter table for chroma components can be determined based on chroma quantization data signaled individually or commonly for chroma components, and coding can be performed based on quantization parameters according to the characteristics of the image to improve coding efficiency.

[0697] In the foregoing embodiments, the method has been described based on a flowchart in a series of steps or blocks, but this document is not limited to the order of the steps, and a certain step can occur in a different order or simultaneously with steps different from the foregoing. Also, those skilled in the art can understand that the steps shown in the flowchart are not exclusive, other steps are included, or one or more steps of the flowchart can be deleted without affecting the scope of this document.

[0698] The embodiments described in this document can be implemented and executed on a processor, microprocessor, controller, or chip. For example, the functional units illustrated in each drawing can be implemented and executed on a computer, processor, microprocessor, controller, or chip. In this case, information for implementation (e.g., information on instructions) or algorithms can be stored in a digital storage medium.

[0699] In addition, the decoding device and encoding device to which the embodiments of this document are applied can be included in a multimedia broadcast transceiver, mobile communication terminal, home cinema video device, digital cinema video device, surveillance camera, video conferencing device, real-time communication device such as video communication, mobile streaming device, storage medium, camcorder, video-on-demand (VoD) service providing device, over-the-top (OTT) video device, Internet streaming service providing device, three-dimensional (3D) video device, picture phone video device, transportation means terminal (e.g., vehicle terminal, airplane terminal, ship terminal, etc.), and medical video device, etc., and can be used to process video signals or data signals. For example, as an over-the-top (OTT) video device, it can be equipped with a game console, Blu-ray player, Internet-connected TV, home theater system, smartphone, tablet PC, digital video recorder (DVR), etc.

[0700] In addition, the processing method to which the embodiments of this document are applied can be produced in the form of a program executed by a computer and can be stored in a computer-readable recording medium. Multimedia data having the data structure according to this document can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices in which data that can be read by a computer is stored. The computer-readable recording medium can include, for example, Blu-ray Disc (BD), Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. Further, the computer-readable recording medium includes a medium realized in the form of a carrier wave (for example, transmission via the Internet). Also, a bitstream generated by an encoding method can be stored in a computer-readable recording medium or transmitted via a wired or wireless communication network.

[0701] In addition, the embodiments of this document can be realized by a computer program product with program code, and the program code can be executed by a computer according to the embodiments of this document. The program code can be stored on a carrier readable by a computer.

[0702] FIG. 14 exemplarily shows a structural diagram of a content streaming system to which the embodiments of this document are applied.

[0703] The content streaming system to which the embodiments of this document are applied can generally include an encoding server, a streaming server, a web server, a media repository, a user device, and a multimedia input device.

[0704] The encoding server compresses the content input from multimedia input devices such as smartphones, cameras, and camcorders into digital data to generate a bitstream, and plays the role of transmitting this to the streaming server. As another example, when multimedia input devices such as smartphones, cameras, and camcorders directly generate a bitstream, the encoding server can be omitted.

[0705] The bitstream can be generated by an encoding method or a bitstream generation method to which the embodiments of this document are applied, and the streaming server can temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0706] The streaming server transmits multimedia data to the user device based on a user request via a web server, and the web server plays the role of a medium for informing the user of what services are available. When the user requests a desired service from the web server, the web server transmits this to the streaming server, and the streaming server transmits multimedia data to the user. At this time, the content streaming system can include another control server, and in this case, the control server plays the role of controlling commands / responses between each device in the content streaming system.

[0707] The streaming server can receive content from a media repository and / or an encoding server. For example, when it comes to receiving content from the encoding server, the content can be received in real time. In this case, in order to provide a smooth streaming service, the streaming server can store the bitstream for a certain period of time.

[0708] Examples of the user device include a mobile phone, smartphone, laptop computer, digital broadcast terminal, PDA (personal digital assistants), PMP (portable multimedia player), navigation device, slate PC, tablet PC, ultrabook, wearable device (e.g., smartwatch, smart glass, head mounted display (HMD)), digital TV, desktop computer, digital signage, etc. Each server in the content streaming system can be operated as a distributed server, and in this case, the data received by each server can be processed distributively.

[0709] The claims described in this specification can be combined in various ways. For example, the technical features of the method claims in this specification can be combined and realized as a device, and the technical features of the device claims in this specification can be combined and realized as a method. Also, the technical features of the method claims in this specification and the technical features of the device claims can be combined and realized as a device, and the technical features of the method claims in this specification and the technical features of the device claims can be combined and realized as a method.

Claims

1. An image decoding method performed by a decoding device, obtaining image information including prediction information and residual information for a current block; deriving a prediction sample based on the prediction information; deriving transformation coefficients based on the residual information; dequantizing the transform coefficients to derive residual samples; generating a reconstructed picture based on the prediction samples and the residual samples; Including, The step of acquiring image information includes: obtaining a flag indicating whether one chroma quantization parameter table is applied; obtaining at least one chroma quantization parameter table based on the flag; Including, The flag equal to 0 indicates that a first chroma quantization parameter table for a Cb component, a second chroma quantization parameter table for a Cr component, and a third chroma quantization parameter table for a joint CbCr component are signaled.

2. An image encoding method performed by an encoding device, comprising: deriving a predicted sample for the current block; deriving prediction information relating to the prediction samples; deriving a residual sample based on the prediction sample; deriving residual information associated with the residual samples; encoding image information including the prediction information and the residual information; generating a bitstream containing said image information; Including, The step of encoding the image information includes: generating a flag indicating whether one chroma quantization parameter table is applied; generating at least one chroma quantization parameter table based on the flag; encoding the at least one chroma quantization parameter table and the flag; Including, The method for encoding an image, wherein the flag equal to 0 indicates that a first chroma quantization parameter table for a Cb component, a second chroma quantization parameter table for a Cr component, and a third chroma quantization parameter table for a joint CbCr component are signaled.

3. A method for transmitting data for an image, comprising: obtaining a bitstream of image information including a flag and at least one chroma quantization parameter table, the bitstream being generated based on: deriving a prediction sample for a current block, deriving prediction information related to the prediction sample, deriving a residual sample based on the prediction sample, deriving residual information related to the residual sample, and encoding image information including the prediction information and the residual information; transmitting said data including said bitstream of image information including said flag and said at least one chroma quantization parameter table; Including, The flag indicates whether one chroma quantization parameter table is applied or not, the at least one chroma quantization parameter table is generated based on the flag; The data transmission method, wherein the flag equal to 0 indicates that a first chroma quantization parameter table for a Cb component, a second chroma quantization parameter table for a Cr component, and a third chroma quantization parameter table for a joint CbCr component are signaled.

Images