Video or image coding based on signaling of zoom list data

Abstract

The invention provides video or image coding based on signaling of zoom list data. According to the disclosure of this document, zoom list data and zoom list related information may be signaled hierarchically, and by this, the amount of data that must be signaled for video / image coding may be reduced, and coding efficiency may be increased.

Description

[0001] This application is a divisional application of the patent application with application number 202080028623.3 (PCT / KR2020 / 004693) filed on October 13, 2021, application date on April 7, 2020, and titled "Video or image compilation based on signaling of zoom list data". Technical Field

[0002] The present disclosure relates to image or video coding, for example, to coding techniques based on signaling of scaling list data. Background Art

[0003] Recently, there is an increasing demand for high-resolution and high-quality images and videos such as ultra-high-definition (HUD) images and 4K or 8K or larger videos in various fields. As image and video data become high-resolution and high-quality, the amount of information or the number of bits transmitted relative to existing image and video data increases. Therefore, if a medium such as an existing wired or wireless broadband line is used to transmit image data or an existing storage medium is used to store image and video data, the transmission cost and storage cost increase.

[0004] In addition, recently, interest and demand for immersive media such as virtual reality (VR), artificial reality (AR) content or holograms are increasing. Broadcasting of images and videos whose image characteristics are different from those of real images, such as game images, is increasing.

[0005] Therefore, in order to effectively compress and transmit or store and play back information of high-resolution and high-quality images and videos having such various characteristics, efficient image and video compression technology is required.

[0006] Furthermore, there are discussions on adaptive frequency weighted quantization techniques in the scaling process in order to improve compression efficiency and increase subjective / objective visual quality. In order to effectively apply this technique, a method for signaling relevant information is required. Summary of the invention

[0007] Technical issues

[0008] A technical aspect of the present disclosure is to provide a method and apparatus for increasing image coding efficiency.

[0009] Another technical aspect of the present disclosure is to provide a method and apparatus for increasing coding efficiency during a scaling process.

[0010] Yet another technical aspect of the present disclosure is to provide a method and apparatus for efficiently constructing a zoom list used in a zooming process.

[0011] Yet another technical aspect of the present disclosure is to provide a method and apparatus for hierarchically signaling zoom list related information used in a zooming process.

[0012] Yet another technical aspect of the present disclosure is to provide a method and apparatus for efficiently applying a zooming process based on a zooming list.

[0013] Technical Solution

[0014] According to an embodiment of this document, scaling list data may be signaled via an adaptive parameter set (APS), and APS identification information (APS ID) indicating the ID of the APS referenced by the scaling list data may be signaled via header information (picture header / slice header / tile group header, etc.).

[0015] According to an embodiment of this document, type information of an APS parameter may be signaled through an APS, and whether a corresponding APS is a zoom list data (zoom list parameter) APS may be indicated based on the type information of the APS parameter.

[0016] According to an embodiment of this document, available flag information indicating whether scaling list data is available can be signaled hierarchically, and based on the available flag information signaled in a higher level syntax (e.g., SPS), available flag information in a lower level syntax (e.g., picture header / slice header / type group header, etc.) can be signaled.

[0017] According to an embodiment of this document, constraint flag information may be signaled through a general constraint information syntax, and whether available flag information of scaling list data is used may be indicated based on the constraint flag information.

[0018] According to an embodiment of this document, APS ID number information indicating the number of IDs of APSs associated with zoom list data may be signaled through header information, and identification information syntax elements of as many APSs associated with zoom list data as the number of APS IDs may be signaled.

[0019] According to an embodiment of this document, a video / image decoding method performed by a decoding device is provided. The video / image decoding method may include the method disclosed in the embodiment of this document.

[0020] According to an embodiment of this document, a decoding device for performing video / image decoding is provided. The decoding device can perform the method disclosed in the embodiment of this document.

[0021] According to an embodiment of this document, a video / image encoding method performed by an encoding device is provided. The video / image encoding method may include the method disclosed in the embodiment of this document.

[0022] According to an embodiment of this document, a coding device for performing video / image coding is provided. The coding device can perform the method disclosed in the embodiment of this document.

[0023] According to an embodiment of this document, there is provided a computer-readable digital storage medium storing encoded video / image information generated according to the video / image encoding method disclosed in at least one embodiment of this document.

[0024] According to an embodiment of this document, there is provided a computer-readable digital storage medium storing encoding information or encoded video / image information that enables a decoding device to perform a video / image decoding method disclosed in at least one embodiment of this document.

[0025] Beneficial Effects

[0026] This document may have various effects. For example, according to an embodiment of this document, the overall image / video compression efficiency can be increased. In addition, according to an embodiment of this document, by applying an effective scaling process, the coding efficiency can be increased and the subjective / objective visual quality can be improved. In addition, according to an embodiment of this document, a scaling list used in the scaling process can be effectively configured, and through this, scaling list related information can be signaled hierarchically. In addition, according to an embodiment of this document, the coding efficiency can be increased by effectively applying a scaling process based on a scaling list.

[0027] The effects that can be obtained through the specific embodiments of this document are not limited to the effects listed above. For example, there may be various technical effects that can be understood or derived from this document by ordinary technicians in the relevant field. Therefore, the specific effects of this document are not limited to those explicitly described in this document, and may include various effects that can be understood or derived from the technical features of this document. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 An example of a video / image coding system to which embodiments of the present disclosure can be applied is schematically shown.

[0029] Figure 2 is a diagram schematically describing a configuration of a video / image encoding device to which an embodiment of the present disclosure can be applied.

[0030] Figure 3 is a diagram schematically describing a configuration of a video / image decoding device to which an embodiment of the present disclosure can be applied.

[0031] Figure 4An example of an exemplary video / image encoding method to which the embodiments of the present disclosure can be applied is shown.

[0032] Figure 5 An example of an exemplary video / image decoding method to which the embodiments of the present disclosure can be applied is shown.

[0033] Figure 6 The hierarchical structure of the compiled image / video is shown exemplarily.

[0034] Figure 7 is a flowchart schematically illustrating an example of a video / image encoding method according to an embodiment of this document.

[0035] Figure 8 is a flowchart schematically illustrating an example of a video / image decoding method according to an embodiment of this document.

[0036] Fig. 9 The structure of a content streaming transmission system to which the present disclosure is applied is schematically shown. DETAILED DESCRIPTION

[0037] This document can be modified in various ways and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit this document to specific embodiments. The terms commonly used in this specification are used to describe specific embodiments rather than to limit the technical spirit of this document. Unless otherwise clearly indicated in the context, singular expressions include plural expressions. Terms such as "including" or "having" in this specification should be understood to indicate the presence of characteristics, numbers, steps, operations, elements, components, or combinations thereof described in this specification, without excluding the possibility of the presence or addition of one or more characteristics, numbers, steps, operations, elements, components, or combinations thereof.

[0038] In addition, in order to facilitate the description related to different feature functions, the elements in the drawings described in this document are illustrated independently. This does not mean that each element is implemented as separate hardware or separate software. For example, at least two elements can be combined to form a single element, or a single element can be divided into multiple elements. Embodiments in which elements are combined and / or separated are also included in the scope of the rights of this document, unless it deviates from the essence of this document.

[0039] In this document, the term "A or B" may mean "only A", "only B", or "both A and B". In other words, in this document, the term "A or B" may be interpreted as indicating "A and / or B". For example, in this document, the term "A, B, or C" may mean "only A", "only B", "only C", or "any combination of A, B, and C".

[0040] A slash “ / ” or a comma used in this document 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”.

[0041] In this document, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in this document, the expression "at least one of A or B" or "at least one of A and / or B" may be interpreted as "at least one of A and B".

[0042] Furthermore, in this document, “at least one of A, B, and C” may mean “only A,” “only B,” “only C,” or “any combination of A, B, and C.” Furthermore, “at least one of A, B, or C” or “at least one of A, B and / or C” may mean “at least one of A, B, and C.”

[0043] In addition, brackets used in this document may mean "for example". Specifically, in the case of expressing "prediction (intra-frame prediction)", it may indicate that "intra-frame prediction" is proposed as an example of "prediction". In other words, the term "prediction" in this document is not limited to "intra-frame prediction", and it may indicate that "intra-frame prediction" is proposed as an example of "prediction". In addition, even in the case of expressing "prediction (i.e., intra-frame prediction)", it may indicate that "intra-frame prediction" is proposed as an example of "prediction".

[0044] This document relates to video / image coding. For example, the methods / embodiments disclosed in this document can be applied to methods disclosed in Versatile Video Coding (VVC). In addition, the methods / embodiments disclosed in this document can be applied to methods disclosed in the Basic Video Coding (EVC) standard, the AOMedia Video 1 (AV1) standard, the second generation audio video coding standard (AVS2), or the next generation video / image coding standard (e.g., H.267 or H.268, etc.).

[0045] This document proposes various embodiments of video / image coding, and unless mentioned to the contrary, these embodiments may be performed in combination with each other.

[0046] In this document, video may mean a collection of a series of images according to the passage of time. A picture generally means a unit representing an image of a specific time period, and a slice / tile is a unit that constitutes a part of a picture in coding. A slice / tile may include one or more coding tree units (CTUs). A tile is a rectangular area of ​​a CTU within a specific tile column and a specific tile row in a picture. A tile column is a rectangular area in which the height of a CTU is equal to the height of a picture and the width is specified by a syntax element in a picture parameter set. A tile row is a rectangular area in which the height of a CTU is specified by a syntax element in a picture parameter set and the width is equal to the width of a picture. Tile scanning is a specific order sorting of CTUs of the following partitioned pictures: CTUs can be sorted continuously in tiles by CTU raster scanning, and tiles in a picture can be sorted continuously by raster scanning of tiles of a picture. A slice includes an integer number of complete tiles or an integer number of continuous complete CTU rows within a tile of a picture that can be exclusively contained in a single NAL unit.

[0047] At the same time, a picture can be divided into two or more sub-pictures. A sub-picture can be a rectangular area of ​​one or more slices within a picture.

[0048] A pixel or a picture element (pel) may refer to the smallest unit constituting a picture (or image). In addition, a "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a value of a pixel, and may represent only a pixel / pixel value of a luminance component, or only a pixel / pixel value of a chrominance component.

[0049] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to the area. A unit may include a luminance block and two chrominance (e.g., cb, cr) blocks. Depending on the situation, terms such as unit, block, area, etc. may be used interchangeably. In general, an M×N block may include a set (or array) of samples (or sample arrays) or transform coefficients consisting of M columns and N rows.

[0050] In addition, in this document, at least one of quantization / dequantization and / or transform / inverse transform may be omitted. When quantization / dequantization is omitted, the quantized transform coefficient may be referred to as a transform coefficient. When transform / inverse transform is omitted, the transform coefficient may be referred to as a coefficient or a residual coefficient, or may still be referred to as a transform coefficient for the sake of uniformity of expression.

[0051] In this document, quantized transform coefficients and transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, the residual information may include information about the transform coefficients, and the information about the transform coefficients may be signaled through residual coding syntax. The transform coefficients may be derived based on the residual information (or information about the transform coefficients), and the scaled transform coefficients may be derived by inversely transforming (scaling) the transform coefficients. The residual samples may be derived based on the inverse transform of the scaled transform coefficients. This may also be applied / expressed in other parts of this document.

[0052] In this document, technical features explained separately in one drawing may be implemented separately, or may be implemented at the same time.

[0053] Hereinafter, preferred embodiments of the present document will be described in more detail with reference to the accompanying drawings. Hereinafter, in the accompanying drawings, the same reference numerals are used in the same elements, and repeated description of the same elements may be omitted.

[0054] Figure 1 An example of a video / image coding system to which embodiments of this document may be applied is schematically illustrated.

[0055] refer to Figure 1 The video / image coding system may include a first device (source device) and a second device (receiving device). The source device may transmit the encoded video / image information or data to the receiving device in the form of a file or stream transmission via a digital storage medium or a network.

[0056] The source device may include a video source, an encoding device, and a transmitter. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be referred to as a video / image encoding device, and the decoding device may be referred to as a video / image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display, and the display may be configured as a separate device or an external component.

[0057] The video source can obtain the video / image by capturing, synthesizing or generating the process of the video / image. The video source may include a video / image capturing device and / or a video / image generating device. The video / image capturing device may include, for example, one or more cameras, a video / image archive including previously captured videos / images, etc. The video / image generating device may include, for example, a computer, a tablet computer and a smart phone, and may (electronically) generate the video / image. For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capturing process may be replaced by the process of generating the relevant data.

[0058] The encoding device can encode the input video / image. The encoding device can perform a series of processes such as prediction, transformation and quantization for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bit stream.

[0059] The transmitter may transmit the encoded video / image information or data output in the form of a bit stream to a receiver of a receiving device in the form of a file or stream transmission through a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter may include an element for generating a media file in a predetermined file format, and may include an element for transmitting through a broadcast / communication network. The receiver may receive / extract a bit stream and transmit the received / extracted bit stream to a decoding device.

[0060] The decoding device can decode the video / image by performing a series of processes such as dequantization, inverse transformation, prediction, etc. corresponding to the operation of the encoding device.

[0061] The renderer can render the decoded video / image, and the rendered video / image can be displayed through a display.

[0062] Figure 2 is a diagram schematically describing a configuration of a video / image encoding device to which the present document can be applied. Hereinafter, the encoding device may include an image encoding device and / or a video encoding device.

[0063] refer to Figure 2 , the encoding device 200 may include an image segmenter 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter-frame predictor 221 and an intra-frame predictor 222. The residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 may also include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstructed block generator. According to an embodiment, the image segmenter 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250, and the filter 260 described above may be composed of one or more hardware components (e.g., an encoder chipset or processor). In addition, the memory 270 may include a decoded picture buffer (DPB) and may be composed of a digital storage medium. The hardware component may also include a memory 270 as an internal / external component.

[0064] The image divider 210 divides the input image (or picture or frame) input to the encoding device 200 into one or more processing units. As an example, the processing unit may be referred to as a coding unit (CU). In this case, starting from a coding tree unit (CTU) or a maximum coding unit (LCU), the coding unit may be recursively divided according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, a coding unit may be divided into a plurality of coding units with a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. In this case, for example, a quadtree structure may be applied first, and then a binary tree structure and / or a ternary tree structure may be applied. Alternatively, a binary tree structure may be applied first. The coding process according to this document may be performed based on a final coding unit that is not further divided. In this case, based on the coding efficiency according to image characteristics, the maximum coding unit may be directly used as the final coding unit. Alternatively, the coding unit may be recursively divided into coding units with a further deeper depth as needed, so that a coding unit of an optimal size may be used as the final coding unit. Here, the coding process may include processes such as prediction, transformation, and reconstruction, which will be described later. As another example, the processing unit may also include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may be divided or partitioned from the above-mentioned final coding unit. The prediction unit may be a unit for sample prediction, and the transformation unit may be a unit for deriving a transformation coefficient and / or a unit for deriving a residual signal based on the transformation coefficient.

[0065] Depending on the situation, the unit and terms such as block, region, etc. may be used interchangeably. In general, an M×N block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample may generally represent a pixel or a value of a pixel, and may represent only a pixel / pixel value of a luminance component, or only a pixel / pixel value of a chrominance component. A sample may be used as a term corresponding to a pixel or a pel of a picture (or image).

[0066] In the encoding device 200, a prediction signal (prediction block, prediction sample array) output from the inter predictor 221 or the intra predictor 222 is subtracted from the input image signal (original block, original sample array) to generate a residual signal (residual block, residual sample array), and the generated residual signal is sent to the transformer 232. In this case, as shown, the unit that subtracts the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) in the encoder 200 may be referred to as a subtractor 231. The predictor may perform prediction on a processing target block (hereinafter, referred to as a "current block"), and may generate a prediction block including prediction samples for the current block. The predictor may determine whether intra prediction or inter prediction is applied on a current block or CU basis. As discussed later in the description of each prediction mode, the predictor may generate various information related to prediction such as prediction mode information, and send the generated information to the entropy encoder 240. Information about the prediction may be encoded in the entropy encoder 240 and output in the form of a bitstream.

[0067] The intra-frame predictor 222 can predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the reference sample can be located near the current block or separated from the current block. In intra-frame prediction, the prediction mode may include a variety of non-directional modes and a variety of directional modes. The non-directional mode may include, for example, a DC mode and a plane mode. Depending on the level of detail of the prediction direction, the directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes may be used depending on the setting. The intra-frame predictor 222 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0068] The inter-frame predictor 221 may derive a prediction block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information may be predicted based on a block, a sub-block, or a sample based on the correlation of the motion information between the neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may include spatial neighboring blocks 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 as or different from each other. The temporal neighboring block may be referred to as a collocated reference block, a collocated CU (colCU), etc., and the reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). For example, the inter-frame predictor 221 may configure a motion information candidate list based on the neighboring blocks, and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter-frame prediction may be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter-frame predictor 221 can use the motion information of the neighboring block as the motion information of the current block. In skip mode, unlike merge mode, the residual signal cannot be sent. In the case of motion information prediction (motion vector prediction, MVP) mode, the motion vector of the neighboring 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.

[0069] The predictor 220 may generate a prediction signal based on various prediction methods. For example, the predictor may apply intra prediction or inter prediction to the prediction of a block, and may also apply intra prediction and inter prediction at the same time. This may be referred to as combined inter and intra prediction (CIIP). In addition, the predictor may be based on an intra block copy (IBC) prediction mode or a palette mode to perform prediction on a block. The IBC prediction mode or the palette mode may be used for content image / video coding of games such as screen content coding (SCC). Although IBC basically performs prediction in the current picture, its execution is similar to inter prediction in that it derives a reference block in the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document. The palette mode may be considered as an example of intra coding or intra prediction. When the palette mode is applied, the sample values ​​in the picture may be signaled based on information about the palette index and the palette table.

[0070] The prediction signal generated by the predictor (including the inter-frame predictor 221 and / or the intra-frame predictor 222) can be used to generate a reconstruction signal or to generate a residual signal. The transformer 232 can generate a transform coefficient by applying a transform technique to the residual signal. For example, the transform technique may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loève transform (KLT), a graph-based transform (GBT), or a conditional nonlinear transform (CNT). Here, GBT means a transform obtained from a curve graph when the relationship information between pixels is represented by a curve graph. CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. In addition, the transform process can be applied to square pixel blocks of the same size, or can be applied to blocks of variable size rather than square blocks.

[0071] The quantizer 233 may quantize the transform coefficients and send them to the entropy encoder 240, and the entropy encoder 240 may encode the quantized signal (information about the quantized transform coefficients) and output the encoded signal in the bitstream. The information about the quantized transform coefficients may be referred to as residual information. The quantizer 233 may rearrange the quantized transform coefficients of the block type into a one-dimensional vector form based on the coefficient scanning order, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. The entropy encoder 240 may perform various encoding methods such as, for example, exponential Golomb, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 240 may encode the information required for video / image reconstruction other than the quantized transform coefficients (e.g., the value of the syntax element, etc.) together or separately. The encoded information (e.g., the encoded video / image information) may be transmitted or stored on a unit basis of a network abstraction layer (NAL) in the form of a bitstream. The video / image information may also include information about various parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), a video parameter set (VPS), etc. In addition, the video / image information may also include conventional constraint information. In this document, information and / or syntax elements sent from an encoding device to a decoding device with a signal may be included in the video / image information. The video / image information may be encoded by the above-mentioned encoding process and included in a bitstream. The bitstream may be transmitted over a network or stored in a digital storage medium. Here, the network may include a broadcast network, a communication network, and / or the like, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) that transmits a signal output from the entropy encoder 240 or a memory (not shown) that stores it may be configured as an internal / external element of the encoding device 200, or the transmitter may be included in the entropy encoder 240.

[0072] The quantized transform coefficients output from the quantizer 233 can be used to generate a prediction signal. For example, by applying dequantization and inverse transform using the transform coefficients vectorized by the dequantizer 234 and the inverse transformer 235, the residual signal (residual block or residual sample) can be reconstructed. The adder 155 adds the reconstructed residual signal to the prediction signal output from the inter-frame predictor 221 or the intra-frame predictor 222, so that a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) can be generated. When there is no residual for the processing target block as in the case of applying the skip mode, the prediction block can be used as a reconstructed block. The adder 250 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next processing target block in the current picture, and as described later, can be used for inter-frame prediction of the next picture performed by filtering.

[0073] Furthermore, during the picture encoding and / or reconstruction process, luminance mapping and chrominance scaling (LMCS) may be applied.

[0074] The filter 260 can improve the subjective / objective video quality by applying filtering to the reconstructed signal. For example, the filter 260 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and the modified reconstructed picture can be stored in the memory 270, especially in the DPB of the memory 270. Various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive ring filtering, bilateral filtering, etc. As discussed later in the description of each filtering method, the filter 260 can generate various information related to filtering and send the generated information to the entropy encoder 240. Information about filtering can be encoded in the entropy encoder 240 and output in the form of a bitstream.

[0075] The modified reconstructed picture transmitted to the memory 270 may be used as a reference picture in the inter-frame predictor 221. Accordingly, the encoding apparatus can avoid prediction mismatch in the encoding apparatus 100 and the decoding apparatus when applying inter-frame prediction, and can also improve encoding efficiency.

[0076] The memory 270DPB can store the modified reconstructed picture so that it can be used as a reference picture in the inter-frame predictor 221. The memory 270 can store the motion information of the block in the current picture from which the motion information has been derived (or encoded) and / or the motion information of the block in the reconstructed picture. The stored motion information can be sent to the inter-frame predictor 221 to be used as the motion information of the neighboring block or the motion information of the temporal neighboring block. The memory 270 can store the reconstructed samples of the reconstructed block in the current picture and send them to the intra-frame predictor 222.

[0077] Figure 3is a diagram schematically describing a configuration of a video / image decoding device to which the present document can be applied. Hereinafter, a decoding device may include an image decoding device and / or a video decoding device.

[0078] refer to Figure 3 , the video decoding device 300 may include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-frame predictor 331 and an intra-frame predictor 332. The residual processor 320 may include a dequantizer 321 and an inverse transformer 322. According to an embodiment, the entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 described above may be composed of one or more hardware components (e.g., a decoder chipset or a processor). In addition, the memory 360 may include a decoded picture buffer (DPB) and may be composed of a digital storage medium. The hardware component may also include a memory 360 as an internal / external component.

[0079] When a bit stream including video / image information is input, the decoding device 300 can be used in conjunction with the bit stream already in the Figure 2 The image is reconstructed correspondingly to the processing of the video / image information in the encoding device. For example, the decoding device 300 can derive the unit / block based on the information related to the block segmentation obtained from the bit stream. The decoding device 300 can perform decoding by using the processing unit applied in the encoding device. Therefore, the decoding processing unit can be, for example, a coding unit, which can be divided from a coding tree unit or a maximum coding unit along a quadtree structure, a binary tree structure and / or a ternary tree structure. One or more transform units can be derived from the coding unit. And, the reconstructed image signal decoded and output by the decoding device 300 can be reproduced by a reproduction device.

[0080] The decoding device 300 may receive the Figure 2The signal output by the encoding device of the encoding device, and the received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can parse the bitstream to derive information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information may also include information about various parameter sets such as adaptive parameter set (APS), picture parameter set (PPS), sequence parameter set (SPS), video parameter set (VPS), etc. In addition, the video / image information may also include conventional constraint information. The decoding device may further decode the picture based on the information about the parameter set and / or the conventional constraint information. In this document, the information and / or syntax elements sent / received with the signal described later can be decoded and obtained from the bitstream through the decoding process. For example, the entropy decoder 310 can decode the information in the bitstream based on coding methods such as exponential Golomb coding, CAVLC, CABAC, etc., and can output the values ​​of the syntax elements required for image reconstruction and the quantized values ​​of the transform coefficients of the residual. More specifically, the CABAC entropy decoding method can receive the bin corresponding to each syntax element in the bitstream, use the decoding target syntax element information and the decoding information of the neighboring and decoding target blocks or the information of the symbol / bin decoded in the previous step to determine the context model, predict the bin generation probability according to the determined context model and perform arithmetic decoding on the bin to generate the symbol corresponding to each syntax element value. Here, the CABAC entropy decoding method can update the context model using the information of the symbol / bin decoded by the context model for the next symbol / bin after determining the context model. The information about prediction among the information decoded in the entropy decoder 310 can be provided to the predictor (inter-frame predictor 332 and intra-frame predictor 331), and the residual value (ie, quantized transform coefficient) and the associated parameter information that have been entropy decoded in the entropy decoder 310 can be input to the residual processor 320. The residual processor 320 can derive a residual signal (residual block, residual sample, residual sample array). In addition, the information about filtering among the information decoded in the entropy decoder 310 can be provided to the filter 350. In addition, a receiver (not shown) receiving a signal output from the encoding device may also constitute the decoding device 300 as an internal / external element, and the receiver may be a component of the entropy decoder 310. In addition, the decoding device according to the present document may be referred to as a video / image / picture decoding device, and the decoding device may be divided into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include the entropy decoder 310, and the sample decoder may include at least one of the dequantizer 321, the inverse transformer 322, the adder 340, the filter 350, the memory 360, the inter-frame predictor 332, and the intra-frame predictor 331.

[0081] The dequantizer 321 may output the transform coefficient by dequantizing the quantized transform coefficient. The dequantizer 321 may rearrange the quantized transform coefficient into the form of a two-dimensional block. In this case, the rearrangement may be performed based on the order of coefficient scanning that has been performed in the encoding device. The dequantizer 321 may perform dequantization on the quantized transform coefficient using a quantization parameter (e.g., quantization step size information) and obtain the transform coefficient.

[0082] The inverse transformer 322 obtains a residual signal (residual block, residual sample array) by performing inverse transformation on the transformation coefficients.

[0083] The predictor may perform prediction on the current block and generate a prediction block including prediction samples for the current block. The predictor may determine whether to apply intra prediction or inter prediction to the current block based on information on prediction output from the entropy decoder 310, and may specifically determine an intra / inter prediction mode.

[0084] The predictor 320 can generate a prediction signal based on various prediction methods. For example, the predictor can apply intra prediction or inter prediction to the prediction of a block, and can also apply intra prediction and inter prediction at the same time. This can be called combined inter and intra prediction (CIIP). In addition, the predictor can be based on an intra block copy (IBC) prediction mode or a palette mode to perform prediction on the block. The IBC prediction mode or the palette mode can be used for content image / video coding such as games such as screen content coding (SCC). Although IBC basically performs prediction in the current picture, its execution mode is similar to inter prediction in that it derives a reference block in the current picture. That is, IBC can use 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 about the palette table and the palette index can be included in the video / image information and sent with a signal.

[0085] The intra-frame predictor 331 can predict the current block by referring to samples in the current picture. Depending on the prediction mode, the reference sample can be located near the current block or separated from the current block. In intra-frame prediction, the prediction mode can include multiple non-directional modes and multiple directional modes. The intra-frame predictor 331 can determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

[0086] The inter-frame predictor 332 can derive a prediction block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information can be predicted based on a block, a sub-block, or a sample based on the correlation of the motion information between the neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter-frame predictor 332 may configure a motion information candidate list based on neighboring blocks, and derive a motion vector and / or a reference picture index of the current block based on the received candidate selection information. Inter-frame prediction may be performed based on various prediction modes, and information about the prediction may include information indicating a mode of inter-frame prediction for the current block.

[0087] The adder 340 adds the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the predictor (inter-frame predictor 332 or intra-frame predictor 331), so that a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) can be generated. When there is no residual for the processing target block as in the case of applying the skip mode, the prediction block can be used as the reconstructed block.

[0088] The adder 340 may be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal may be used for intra prediction of the next block to be processed in the current picture, may be output through filtering as described below, or may be used for inter prediction of the next picture.

[0089] In addition, luma mapping and chroma scaling (LMCS) can be applied to the picture decoding process.

[0090] The filter 350 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 350 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 360, specifically, in the DPB of the memory 360. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0091] The (modified) reconstructed picture stored in the DPB of the memory 360 may be used as a reference picture in the inter-frame predictor 332. The memory 360 may store the motion information of the block from which the motion information in the current picture is derived (or decoded) and / or the motion information of the block in the reconstructed picture. The stored motion information may be sent to the inter-frame predictor 332 so as to be used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 360 may store the reconstructed samples of the reconstructed blocks in the current picture and transmit the reconstructed samples to the intra-frame predictor 331.

[0092] In the present disclosure, the implementation described in the filter 260, the inter-frame predictor 221 and the intra-frame predictor 222 of the encoding device 200 may be the same as the filter 350, the inter-frame predictor 332 and the intra-frame predictor 331 of the decoding device 300 or may be applied corresponding to the filter 350, the inter-frame predictor 332 and the intra-frame predictor 331 of the decoding device 300, respectively.

[0093] As described above, when performing video coding, prediction is performed to improve compression efficiency. A prediction block including prediction samples of a current block, that is, a target coding block, can be generated by prediction. In this case, the prediction block includes prediction samples in the spatial domain (or pixel domain). The prediction block is derived similarly in the encoding device and the decoding device. The encoding device can improve image coding efficiency by signaling information (residual information) about the residual between the original block rather than the original sample value of the original block itself and the prediction block to the decoding device. The decoding device can derive a residual block including residual samples based on the residual information, can generate a reconstructed block including reconstructed samples by adding the residual block to the prediction block, and can generate a reconstructed picture including the reconstructed block.

[0094] Residual information can be generated through a transformation and quantization process. For example, the encoding device can derive a residual block between the original block and the prediction block, can derive a transform coefficient by performing a transformation process on the residual samples (residual sample array) included in the residual block, can derive a quantized transform coefficient by performing a quantization process on the transform coefficient, and can send the relevant residual information to the decoding device (through a bitstream) with a signal. In this case, the residual information may include information such as value information, position information, a transformation scheme, a transform kernel, and a quantization parameter of the quantized transform coefficient. The decoding device can perform a dequantization / inverse transformation process based on the residual information, and can derive residual samples (or residual blocks). The decoding device can generate a reconstructed picture based on the prediction block and the residual block. In addition, the encoding device can derive a residual block for inter-frame prediction reference of a subsequent picture by dequantizing / inverse transforming the quantized transform coefficient, and can generate a reconstructed picture.

[0095] Intra prediction may indicate that a prediction for a current block prediction sample is generated based on a reference sample in a picture to which the current block belongs (hereinafter referred to as the current picture). When intra prediction is applied to the current block, neighboring reference samples to be used for intra prediction of the current block may be derived. The neighboring reference samples of the current block may include a total of 2xnH samples as samples adjacent to the left boundary of the current block of size nWxnH and samples adjacent to the upper left corner of the current block of size nWxnH, a total of 2xnH samples as samples adjacent to the upper boundary of the current block and samples adjacent to the upper right corner of the current block, and a sample adjacent to the upper left corner of the current block. Alternatively, the neighboring reference samples of the current block may include multiple columns of upper neighboring samples and multiple rows of left neighboring samples. In addition, the neighboring reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the lower boundary of the current block, and a sample adjacent to the lower right corner of the current block.

[0096] However, some of the neighboring reference samples of the current block have not been decoded or may not be available. In this case, the decoding device can construct the neighboring reference samples to be used for prediction by replacing the unavailable samples with available samples. Alternatively, the neighboring reference samples to be used for prediction can be configured by interpolation of available samples.

[0097] If the neighboring reference samples are derived, (i) the prediction samples may be derived based on an average or interpolation of the neighboring reference samples of the current block, and (ii) the prediction samples may be derived based on reference samples existing in a specific (prediction) direction with respect to the prediction samples among the neighboring reference samples of the current block. The case of (i) may be referred to as a non-directional mode or a non-angular mode, and the case of (ii) may be referred to as a directional mode or an angular mode.

[0098] In addition, the prediction sample can be generated by interpolating the first neighboring sample located in the prediction direction of the intra prediction mode of the current block based on the prediction sample of the current block among the neighboring reference samples and the second neighboring sample located in the direction opposite to the prediction direction. The above situation can be called linear interpolation intra prediction (LIP). In addition, the chrominance prediction sample can be generated based on the luma sample using a linear model. This situation can be called LM mode or CCLM (chrominance component LM) mode.

[0099] In addition, a temporary prediction sample of the current block may be derived based on the filtered neighboring reference sample, and the prediction sample of the current block may also be derived by weighted summing at least one reference sample derived from among the normal neighboring reference samples (i.e., the unfiltered neighboring reference samples) according to the intra prediction mode and the temporary prediction sample. The foregoing may be referred to as position-dependent intra prediction (PDPC).

[0100] In addition, a prediction sample can be derived using a reference sample in a prediction direction located in a corresponding line by selecting a reference sample line with the highest prediction accuracy among neighboring multiple reference sample lines of the current block, and intra-frame prediction encoding can be performed by a method for indicating (signaling) the reference sample line used at this time to a decoding device. The foregoing case may be referred to as multi-reference line (MRL) intra-frame prediction or MRL-based intra-frame prediction.

[0101] In addition, intra prediction can be performed based on the same intra prediction mode by dividing the current block into vertical or horizontal sub-partitions, and neighboring reference samples can be derived and used in units of sub-partitions. That is, in this case, the intra prediction mode of the current block is equally applied to the sub-partitions, and neighboring reference samples can be derived and used in units of sub-partitions, thereby enhancing intra prediction performance in some cases. This prediction method may be referred to as intra sub-partition (ISP) intra prediction or ISP-based intra prediction.

[0102] The aforementioned intra prediction method may be referred to as an intra prediction type separate from the intra prediction mode. The intra prediction type may be referred to as various terms such as an intra prediction technique or an additional intra prediction mode. For example, the intra prediction type (or additional intra prediction mode, etc.) may include at least one of the aforementioned LIP, PDPC, MRL, and ISP. A general intra prediction method different from a specific intra prediction type such as LIP, PDPC, MRL, and ISP may be referred to as a normal intra prediction type. If a specific intra prediction type is not applied, a normal intra prediction type may generally be applied, and prediction may be performed based on the aforementioned intra prediction mode. In addition, if necessary, post-processing filtering may also be performed on the derived prediction samples.

[0103] Specifically, the intra prediction process may include an intra prediction mode / type determination step, a neighboring reference sample derivation step, and a prediction sample derivation step based on the intra prediction mode / type. In addition, if necessary, a post-filtering step may be performed on the derived prediction samples.

[0104] When intra prediction is applied, the intra prediction mode applied to the current block can be determined by using the intra prediction mode of the neighboring block. For example, the encoding device can select one of the MPM candidates in the MPM (most likely mode) list based on the received MPM index, and the MPM (most likely mode) list is derived based on the intra prediction mode of the neighboring block (e.g., the left and / or upper neighboring block) of the current block and the additional candidate mode, or can select one of the remaining intra prediction modes not included in the MPM candidate (and the plane mode) based on the remaining intra prediction mode information. The MPM list can be configured to include or exclude the plane mode as a candidate. For example, when the MPM list includes the plane mode as a candidate, the MPM list can have 6 candidates, and when the MPM list does not include the plane mode as a candidate, the MPM list can have 5 candidates. When the MPM list does not include the plane mode as a candidate, a non-planar flag (e.g., intra_luma_not_planar_flag) indicating whether the intra prediction mode of the current block is not a plane mode can be sent with a signal. For example, the MPM flag may be signaled first, and the MPM index and the non-planar flag may be signaled when the value of the MPM flag is 1. Furthermore, the MPM index may be signaled when the value of the non-planar flag is 1. Here, the reason why the MPM list is configured not to include the planar mode as a candidate is that the planar mode is always regarded as the MPM, so it is first checked whether the MPM is in the planar mode by first signaling the flag (non-planar flag), rather than saying that the planar mode is not the MPM.

[0105] For example, it can be indicated based on an MPM flag (e.g., intra_luma_mpm_flag) whether the intra prediction mode applied to the current block is among the MPM candidates (and planar mode) or among the remaining modes. An MPM flag value of 1 can indicate that the intra prediction mode of the current block is within the MPM candidates (and planar mode), while an MPM flag value of 0 can indicate that the intra prediction mode of the current block is not within the MPM candidates (and planar mode). A non-planar flag (e.g., intra_luma_not_planar_flag) value of 0 can indicate that the intra prediction mode of the current block is a planar mode, and a non-planar flag value of 1 can indicate that the intra prediction mode of the current block is not a planar mode. The MPM index can be signaled in the form of an mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information can be signaled in the form of a rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information may indicate one of the remaining intra prediction modes that is not included in the MPM candidates (and planar mode) among all intra prediction modes by indexing in order of the prediction mode number. The intra prediction mode may be an intra prediction mode of a luminance component (sample). In the following, the intra prediction mode information may include at least one of an MPM flag (e.g., intra_luma_mpm_flag), a non-planar flag (e.g., intra_luma_not_planar_flag), an MPM index (e.g., mpm_idx or intra_luma_mpm_idx), and remaining intra prediction mode information (rem_intra_luma_pred_mode or intra_luma_mpm_remainder). In this document, the MPM list may be referred to by a variety of terms such as MPM candidate list and candModeList. When a MIP is applied to the current block, a separate MPM flag (eg, intra_mip_mpm_flag), an mpm index (eg, intra_mip_mpm_idx), and remaining intra prediction mode information (eg, intra_mip_mpm_remainder) for the MIP may be separately signaled, and the non-planar flag may not be signaled.

[0106] In other words, generally, when an image is divided into blocks, the current block to be coded and the neighboring blocks have similar image characteristics. Therefore, the possibility that the current block and the neighboring blocks have the same or similar intra-frame prediction mode is high. Therefore, the encoding device can use the intra-frame prediction mode of the neighboring block to encode the intra-frame prediction mode of the current block.

[0107] For example, the encoder / decoder may configure a most probable mode (MPM) list for the current block. The MPM list may be referred to as an MPM candidate list. Here, MPM may refer to a mode for improving coding efficiency by considering the similarity between the current block and the neighboring blocks during intra prediction mode coding. As described above, the MPM list may be configured to include a planar mode, or may be configured to exclude a planar mode. For example, when the MPM list includes a planar mode, the number of candidates in the MPM list may be six. And, when the MPM list does not include a planar mode, the number of candidates in the MPM list may be five. The encoder / decoder may configure an MPM list including 5 or 6 MPMs.

[0108] To configure the MPM list, three modes may be considered: default intra mode, neighboring intra mode, and derived intra mode. In this case, for the neighboring intra mode, two neighboring blocks may be considered, ie, the left neighboring block and the upper neighboring block.

[0109] As described above, if the MPM list is configured not to include the planar mode, the planar mode is excluded from the list, and the number of MPM list candidates may be set to five.

[0110] Furthermore, among the intra prediction modes, the non-directional mode (or non-angular mode) is a DC mode based on an average value of neighboring reference samples of a current block or an interpolation-based planar mode of neighboring reference samples.

[0111] When inter-frame prediction is applied, the predictor of the encoding device / decoding device can derive prediction samples by performing inter-frame prediction in units of blocks. Inter-frame prediction can be applied when prediction is performed on the current block. That is, the predictor of the encoding / decoding device (more specifically, the inter-frame predictor) can derive prediction samples by performing inter-frame prediction in units of blocks. Inter-frame prediction may refer to a prediction derived by a method that depends on data elements (e.g., sample values ​​or motion information) of a picture other than the current picture. When inter-frame prediction is applied to the current block, a prediction block (prediction sample array) for the current block may be derived based on a reference block (reference sample array) specified by a motion vector on a reference picture indicated by a reference picture index. In this case, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information of the current block may be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter-frame prediction type (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of applying inter-frame prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same as or different from each other. The temporal neighboring block may be referred to as a name such as a collocated reference block, a collocated CU (colCU), etc., and the reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). For example, a motion information candidate list may be configured based on the neighboring blocks of the current block, and a flag or index information indicating which candidate is selected (used) may be signaled to derive the motion vector and / or reference picture index of the current block. Inter-frame prediction may be performed based on various prediction modes, and, for example, in the case of a skip mode and a merge mode, the motion information of the current block may be the same as the motion information of the selected neighboring block. In the case of the skip mode, unlike the merge mode, a residual signal may not be sent. In the case of a motion vector prediction (MVP) mode, the motion vector of the selected neighboring block may be used as a motion vector predictor and the motion vector difference may be signaled. In this case, the motion vector of the current block may be derived by using the sum of the motion vector predictor and the motion vector difference.

[0112] The motion information may further include L0 motion information and / or L1 motion information according to the inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). The L0 direction motion vector may be referred to as the L0 motion vector or MVL0, and the L1 direction motion vector may be referred to as the L1 motion vector or MVL1. Prediction based on the L0 motion vector may be referred to as the L0 prediction, prediction based on the L1 motion vector may be referred to as the L1 prediction, and prediction based on both the L0 motion vector and the L1 motion vector may be referred to as bidirectional prediction. Here, the L0 motion vector may indicate a motion vector associated with the reference picture list L0, and the L1 motion vector may indicate a motion vector associated with the reference picture list L1. The reference picture list L0 may include pictures before the current picture in output order, and the reference picture list L1 may include pictures after the current picture in output order as reference pictures. The previous picture may be referred to as a forward (reference) picture and the subsequent picture may be referred to as a backward (reference) picture. The reference picture list L0 may further include pictures after the current picture in output order as reference pictures. In this case, the previous picture may be indexed first in the reference picture list L0, and then the subsequent picture may be indexed. The reference picture list L1 may further include a picture preceding the current picture in the output order as a reference picture. In this case, the subsequent picture may be indexed first in the reference picture list L1, and then the previous picture may be indexed. Here, the output order may correspond to a picture order count (POC) order.

[0113] Figure 4 An example of an exemplary video / image encoding method to which an embodiment of the present invention is applicable is illustrated.

[0114] Figure 4 The method disclosed in the above Figure 2 Specifically, S400 may be performed by the inter-frame predictor 221 or the intra-frame predictor 222 of the encoding device 200, and each of S410, S420, S430, and S440 may be performed by the subtractor 231, the transformer 232, the quantizer 233, and the entropy encoder 240 of the encoding device 200.

[0115] refer to Figure 4 , the encoding device may derive a prediction sample by predicting the current block (S400). The encoding device may determine whether to perform inter-frame prediction or intra-frame prediction on the current block, and may determine a specific inter-frame prediction mode or a specific intra-frame prediction mode based on the RD cost. According to the determined mode, the encoding device may derive a prediction sample of the current block.

[0116] The encoding apparatus may derive residual samples by comparing original samples and predicted samples of the current block ( S410 ).

[0117] The encoding apparatus may derive a transform coefficient through a transform process for the residual sample ( S420 ), and derive a quantized transform coefficient by quantizing the derived transform coefficient ( S430 ).

[0118] The encoding device may encode the image information including the prediction information and the residual information, and may output the encoded image information in the form of a bitstream (S440). The prediction information is information related to the prediction process and may include prediction mode information and motion information (for example, when inter-frame prediction is applied). The residual information may include information about the quantized transform coefficients. The residual information may be entropy coded.

[0119] The output bitstream may be stored in a storage medium or transmitted to a decoding device via a network.

[0120] Figure 5 An example of an illustrative video / image decoding method to which embodiments of this document may be applied is shown.

[0121] exist Figure 5 The method disclosed in the above Figure 3 The decoding device 500 of the decoding device 300 is performed. Specifically, S500 can be performed by the inter-frame predictor 332 or the intra-frame predictor 331 of the decoding device 300. The process of deriving the value of the relevant syntax element by decoding the prediction information included in the bitstream in S500 can be performed by the entropy decoder 310 of the decoding device 300. S510, S520, S530 and S540 can be performed by the entropy decoder 310, the dequantizer 321, the inverse transformer 322 and the adder 340 of the decoding device 300, respectively.

[0122] refer to Figure 5 The decoding device may perform an operation corresponding to the operation performed by the encoding device. The decoding device may perform inter-frame prediction or intra-frame prediction on the current block based on the received prediction information and derive a prediction sample (S500).

[0123] The decoding apparatus may derive a quantized transform coefficient of the current block based on the received residual information (S510). The decoding apparatus may derive the quantized transform coefficient from the residual information through entropy decoding.

[0124] The decoding apparatus may dequantize the quantized transform coefficient to derive a transform coefficient ( S520 ).

[0125] The decoding apparatus derives residual samples through an inverse transform process for the transform coefficients (S530).

[0126] The decoding apparatus may generate reconstructed samples for the current block based on the prediction samples and the residual samples, and generate a reconstructed picture based on the generated reconstructed samples (S540). Thereafter, the in-loop filtering process may be further applied to the reconstructed picture as described above.

[0127] Meanwhile, as described above, the quantizer of the encoding device may apply quantization to the transform coefficient to derive the quantized transform coefficient, and the dequantizer of the encoding device or the dequantizer of the decoding device may derive the transform coefficient by applying dequantization to the quantized transform coefficient.

[0128] Typically, in video / image coding, the quantization rate can be changed, and compression can be adjusted using the changed quantization rate. From an implementation perspective, a quantization parameter (QP) can be used instead of directly using the quantization rate, taking into account complexity. For example, a quantization parameter with an integer value of 0 to 63 can be used, and each quantization parameter value can correspond to an actual quantization rate. The quantization parameter (QP) for the luminance component (luminance samples) is the value of the quantization parameter. Y ) and the quantization parameter (QP) for the chroma components (chroma samples) C ) can be set differently.

[0129] The quantization process takes the transform coefficient (C) as input and divides it by the quantization rate (Qstep) to obtain a quantized transform coefficient (C') based thereon. In this case, considering the computational complexity, the quantization rate is multiplied by the scaling to form an integer, and the shift operation can be performed by a value corresponding to the scaling value. The quantization scaling (quantization scale) can be derived based on the product of the quantization rate and the scaling value. That is, the quantization scaling can be derived according to the QP. The quantization scaling can be applied to the transform coefficient (C) to derive the quantized transform coefficient (C') based thereon.

[0130] The dequantization process is the inverse process of the quantization process, and the quantized transform coefficient (C') is multiplied by the quantization rate (Qstep), and the reconstructed transform coefficient (C") can be obtained based on this. In this case, the level scaling can be derived according to the quantization parameter, and the level scaling can be applied to the quantized transform coefficient (C') to derive the reconstructed transform coefficient (C") based on this. Due to losses in the transformation and / or quantization process, the reconstructed transform coefficient (C") may be slightly different from the original transform coefficient (C). Therefore, the encoding device performs dequantization in the same manner as the decoding device.

[0131] In addition, an adaptive frequency weighted quantization technique that adjusts the quantization strength according to the frequency can be applied. The adaptive frequency weighted quantization technique is a method of applying different quantization strengths to each frequency. Adaptive frequency weighted quantization can use a predefined quantization scaling matrix to apply quantization strengths differently for each frequency. That is, the above-mentioned quantization / dequantization process can be further performed based on the quantization scaling matrix. For example, different quantization scaling matrices can be used to generate a residual signal of the current block according to the size of the current block and / or whether the prediction mode applied to the current block is inter-frame prediction or intra-frame prediction. The quantization scaling matrix can be referred to as a quantization matrix or a scaling matrix. The quantization scaling matrix can be predefined. In addition, for frequency adaptive scaling, frequency quantization scaling information about the quantization scaling matrix can be configured / encoded in the encoding device and sent to the decoding device with a signal. The frequency quantization scaling information can be referred to as quantization scaling information. The frequency quantization scaling information may include scaling list data (scaling_list_data). The (modified) quantization scaling matrix can be derived based on the scaling list data. In addition, the frequency quantization scaling information may include existence flag information indicating whether the scaling list data exists. Alternatively, when the scaling list data is signaled at a higher level (eg, SPS), information indicating whether the scaling list data is modified at a lower level (eg, PPS or tile group header, etc.) may be further included.

[0132] As described above, scaling list data may be signaled to indicate a (frequency-based quantization) scaling matrix to use for quantization / dequantization.

[0133] Signaling support for default and user-defined scaling matrices exists in the HEVC standard and is currently adopted in the VVC standard. However, for the VVC standard, additional support for signaling of the following functions has been incorporated.

[0134] -Three modes of scaling matrix: OFF, DEFAULT, USER_DEFINED

[0135] - Larger block size range (4x4 to 64x64 for luma, 2x2 to 32x32 for chroma)

[0136] - Rectangular Transform Block (TB)

[0137] - Related Quantification

[0138] -Multiple Transform Selection (MTS)

[0139] - Large transforms that zero out high frequency coefficients

[0140] -Intra-frame sub-block partitioning (ISP)

[0141] - Intra Block Copy (IBC) (also known as Current Picture Reference (CPR))

[0142] - Default scaling matrix for all TB sizes, default value is 16

[0143] It should be noted that the scaling matrix should not be applied to all sizes of Transform Skip (TS) and Secondary Transform (ST).

[0144] In the following, the high-level syntax (HSL) structure for supporting scaling lists in the VVC standard will be described in detail. First, a flag can be signaled through a sequence parameter set (SPS) to indicate that a scaling list is available for the currently coded video sequence (CVS) being decoded. Then, if the flag is available, an additional flag can be parsed to indicate whether specific data is present in the scaling list of the SPS. This can be shown in Table 1.

[0145] Table 1 is an excerpt from the SPS to describe the scaling list of CVS.

[0146] [Table 1]

[0147]

[0148] The semantics of the syntax elements included in the SPS syntax of Table 1 can be shown in Table 2 below.

[0149] [Table 2]

[0150]

[0151] Referring to Tables 1 and 2 above, scaling_list_enabled_flag may be signaled from the SPS. For example, if the value of scaling_list_enabled_flag is 1, it may indicate that a scaling list is used in the scaling process of the transform coefficients, and if the value of scaling_list_enabled_flag is 0, it may indicate that a scaling list is not used in the scaling process of the transform coefficients. In this case, when the value of scaling_list_enabled_flag is 1, sps_scaling_list_data_present_flag may be further signaled from the SPS. For example, when the value of sps_scaling_list_data_present_flag is 1, it may indicate that a scaling_list_data() syntax structure exists in the SPS, and when the value of sps_scaling_list_data_present_flag is 0, it may indicate that a scaling_list_data() syntax structure does not exist in the SPS. If sps_scaling_list_data_present_flag is not present, the value of sps_scaling_list_data_present_flag may be inferred to be 0.

[0152] In addition, a flag (e.g., pps_scaling_list_data_present_flag) may be parsed first in the picture parameter set (PPS). If this flag is available, scaling_list_data() may be parsed in the PPS. If scaling_list_data() is initially present in the SPS and later parsed in the PPS, the data in the PPS may take precedence over the data in the SPS. Table 3 below is an excerpt from the PPS to describe the scaling list data.

[0153] [Table 3]

[0154]

[0155] The semantics of the syntax elements included in the PPS syntax of Table 3 can be shown in Table 4 below.

[0156] [Table 4]

[0157]

[0158] Referring to Tables 3 and 4, pps_scaling_list_data_present_flag may be signaled from the PPS. For example, when the value of pps_scaling_list_data_present_flag is 1, it may indicate that the scaling list data used for the picture of the reference PPS is derived based on the scaling list specified by the active SPS and the scaling list specified by the PPS. When the value of pps_scaling_list_data_present_flag is 0, it may indicate that the scaling list data for the picture of the reference PPS is inferred to be the same as the scaling list specified by the active SPS. At this time, when the value of scaling_list_enabled_flag is 0, the value of pps_scaling_list_data_present_flag should be 0. When the value of scaling_list_enabled_flag is 1, the value of sps_scaling_list_data_present_flag is 0, and the value of pps_scaling_list_data_present_flag is 0, the default scaling list data may be used to derive the scan factor as described in the scaling list data semantics.

[0159] A scaling list may be defined in the VVC standard for the following quantization matrix sizes. This may be shown in Table 5 below. The supported range of quantization matrices has been extended to include 2x2 and 64x64 in the HEVC standard as well as 4x4, 8x8, 16x16, and 32x32.

[0160] [Table 5]

[0161] The size of the quantization matrix sizeId 1x1 0 2x2 1 4x4 2 8x8 3 16x16 4 32x32 5 64x64 6

[0162] Table 5 defines the sizeId of all used quantization matrix sizes. The matrixId can be assigned to different combinations of sizeId, prediction mode (CuPredMode) of the coding unit and color components using the above combination. The CuPredMode that can be considered here can be inter-frame, intra-frame and IBC (intra-frame block copy). Intra-frame mode and IBC mode can be treated equally. Therefore, the same matrixId can be shared for a given color component. Here, the color components that can be considered can be brightness (Luma (Y)) and two color components (Cb and Cr). The allocated matrixId can be represented as shown in Table 6 below.

[0163] Table 6 shows matrixId according to sizeId, prediction mode, and color component.

[0164] [Table 6]

[0165]

[0166] Table 7 below shows an example of a syntax structure for scaling list data (eg, scaling_list_data()).

[0167] [Table 7]

[0168]

[0169] The semantics of the syntax elements included in the syntax of Table 7 can be shown in Table 8 below.

[0170] [Table 8]

[0171]

[0172]

[0173] Referring to Tables 7 and 8, in order to extract scaling list data (e.g., scaling_list_data()), for all sizeIds from 1 to 6 and matrixIds from 0 to 5, the scaling list data can be applied to 2x2 chroma components and 64x64 luma components. Then, a flag (e.g., scaling_list_pred_mode_flag) can be parsed to indicate whether the value of the scaling list is the same as that of the reference scaling list. The reference scaling list can be represented by scaling_list_pred_matrix_id_delta[sizeId][matrixId]. However, when scaling_list_pred_mode_flag[sizeId][matrixId] is 1, the scaling list data can be explicitly signaled. When scaling_list_pred_matrix_id_delta is 0, the DEFAULT mode with default values ​​can be used, as shown in Tables 9 to 12. For other values ​​of scaling_list_pred_matrix_id_delta, as shown in the semantics of Table 8, refMatrixId may be determined first.

[0174] In explicit signaling, i.e., in USER_DEFINED mode, the maximum number of coefficients to be signaled may be determined first. In the case of quantization block sizes of 2x2, 4x4, and 8x8, all coefficients may be signaled. For sizes larger than 8x8, i.e., 16x16, 32x32, and 64x64, only 64 coefficients may be signaled. That is, an 8x8 base matrix may be signaled and the remaining coefficients may be upsampled from the base matrix.

[0175] Table 9 below is an example, which shows the default values ​​of ScalingList[1][matrixId][i] (i=0..3).

[0176] [Table 9]

[0177] i 0 1 2 3 ScalingList[1][1,2,4,5][i] 16 16 16 16

[0178] Table 10 below is an example showing the default values ​​of ScalingList[2][matrixId][i] (i=0..15).

[0179] [Table 10]

[0180] i 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[2][0..5][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

[0181] Table 11 below is an example showing the default values ​​of ScalingList[3..5][matrixId][i] (i=0..63).

[0182] [Table 11]

[0183] i 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[3..5][0..5][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 i-16 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[3..5][0..5][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 i-32 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[3..5][0..5][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 i-48 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[3..5][0..5][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

[0184] Table 12 below is an example showing the default values ​​of ScalingList[6][matrixId][i] (i=0..63).

[0185] [Table 12]

[0186] i 0 1 3 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[6][0,3][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 i-16 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[6][0,3][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 i-32 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[6][0,3][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 i-48 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ScalingList[6][0,3][i] 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

[0187] As described above, the default scaling list data may be used to derive a scaling factor (ScalingFactor).

[0188] The 5-dimensional array scaling factor ScalingFactor[sizeId][sizeId][matrixId][x][y] (where x, y = 0..(1<<sizeId)-1) can represent an array of scaling factors based on the variable sizeId shown in Table 5 and the variable matrixId shown in Table 6 above.

[0189] Table 13 below shows an example of deriving a scaling factor according to the size of a quantization matrix based on the above-mentioned default scaling list.

[0190] [Table 13]

[0191]

[0192]

[0193] For a quantization matrix of rectangular size, the scaling factors of the 5D array ScalingFactor[sizeIdW][sizeIdH][matrixId][x][y] (where x = 0..(1<<sizeIdW)-1, y = 0..(1<<sizeIdH)-1, sizeIdW != sizeIdH) can represent the scaling factor array according to the variables sizeIdW and sizeIdH shown in Table 15 below, and can be derived as shown in Table 14 below.

[0194] [Table 14]

[0195]

[0196] For samples that meet the following conditions, the quantization matrix of square size shall be zeroed.

[0197] -x > 32

[0198] -y > 32

[0199] - The decoded TU is not compiled using the default transform mode, (1<<sizeIdW) == 32 and x > 16

[0200] - The decoded TU is not compiled using the default transform mode, (1<<sizeIdH) == 32 and y > 16

[0201] Table 15 below shows examples of sizeIdW and sizeIdH according to the size of the quantization matrix.

[0202] [Table 15]

[0203] The size of the quantization matrix sizeIdW sizeIdH 1 0 0 2 1 1 4 2 2 8 3 3 16 4 4 32 5 5 64 6 6

[0204] In the following, this document presents a method for efficiently signaling scaling list data when applying the adaptive frequency weighted quantization technique during the quantization / dequantization process.

[0205] Figure 6 Exemplarily shows the hierarchical structure of the compiled image / video.

[0206] Reference Figure 6 , the compiled image / video is divided into a subsystem that processes the image / video decoding process and its own VCL (Video Coding Layer), sends and stores the compiled information, and a Network Abstraction Layer (NAL) that exists between both the VCL and the subsystem and is responsible for network adaptation functions.

[0207] VCL can generate VCL data including compressed image data (slice data), or generate parameter sets including picture parameter sets (Picture Parameter Set: PPS), sequence parameter sets (Sequence Parameter Set: SPS), video parameter sets (Video Parameter Set: VPS), etc., or additional supplementary enhancement information (SEI) messages necessary for the image decoding process.

[0208] In NAL, a NAL unit may be generated by adding header information (NAL unit header) to a raw byte sequence payload (RBSP) generated in the VCL. In this case, the RBSP refers to slice data, parameter sets, SEI messages, etc. generated in the VCL. The NAL unit header may include NAL unit type information specified according to the RBSP data included in the corresponding NAL unit.

[0209] In addition, the NAL unit can be divided into a VCL NAL unit and a non-VCL NAL unit according to the RBSP generated in the VCL. The VCL NAL unit may refer to a NAL unit including information about the image (slice data), and the non-VCL NAL unit may refer to a NAL unit containing information necessary for decoding the image (parameter set or SEI message).

[0210] The above-mentioned VCL NAL unit and non-VCL NAL unit can be sent through the network by adding header information according to the data standard of the subsystem. For example, the NAL unit can be converted into a data form of a predetermined standard such as H.266 / VVC file format, real-time transport protocol (RTP), transport stream (TS), etc., and sent through various networks.

[0211] As described above, in a NAL unit, a NAL unit type may be specified according to an RBSP data structure included in a corresponding NAL unit, and information on the NAL unit type may be stored and signaled in a NAL unit header.

[0212] For example, depending on whether the NAL unit includes information about an image (slice data), the NAL unit can be roughly classified into a VCL NAL unit type and a non-VCL NAL unit type. The VCL NAL unit type can be classified according to the attributes and types of the pictures included in the VCL NAL unit, and the non-VCL NAL unit type can be classified according to the type of parameter set.

[0213] The following are examples of NAL unit types specified according to the type of parameter sets included in a non-VCL NAL unit type.

[0214] -APS (Adaptation Parameter Set) NAL unit: type used for NAL units that include APS

[0215] -DPS (Decoding Parameter Set) NAL unit: type used for NAL units that include DPS

[0216] - VPS (Video Parameter Set) NAL unit: Type used for NAL units that include VPS

[0217] - SPS (Sequence Parameter Set) NAL unit: type used for NAL units that include SPS

[0218] -PPS (Picture Parameter Set) NAL unit: Type used for NAL units that include PPS

[0219] - PH (Picture Header) NAL unit: type used for NAL units including PH

[0220] The above-mentioned NAL unit type has syntax information for the NAL unit type, and the syntax information may be stored in the NAL unit header and transmitted with a signal. For example, the syntax information may be nal_unit_type, and the NAL unit type may be specified by the nal_unit_type value.

[0221] Meanwhile, as described above, a picture may include multiple slices, and a slice may include a slice header and slice data. In this case, a picture header may be further added to multiple slices (slice headers and slice data sets) in a picture. The picture header (picture header syntax) may include information / parameters generally applicable to pictures. In this document, slices may be mixed with or replaced by tile groups. In addition, in this document, slice headers may be mixed with or replaced by type group headers.

[0222] A slice header (slice header syntax) may include information / parameters that are generally applicable to slices. APS (APS syntax) or PPS (PPS syntax) may include information / parameters that are generally applicable to one or more slices or pictures. SPS (SPS syntax) may include information / parameters that are generally applicable to one or more sequences. VPS (VPS syntax) may include information / parameters that are generally applicable to multiple layers. DPS (DPS syntax) may include information / parameters that are generally applicable to the entire video. DPS may include information / parameters related to the concatenation of a coded video sequence (CVS). In this document, a high-level syntax (HLS) may include at least one of an APS syntax, a PPS syntax, an SPS syntax, a VPS syntax, a DPS syntax, a picture header syntax, and a slice header syntax.

[0223] In this document, the image / video information encoded in the encoding device and transmitted to the decoding device in the form of a bitstream may include information included in a slice header, information included in a picture header, information included in an APS, information included in a PPS, information included in an SPS, information included in a VPS, and / or information included in a DPS, as well as picture partition related information in a picture, intra / inter prediction information, residual information, in-loop filtering information, etc. In addition, the image / video information may further include information of a NAL unit header.

[0224] On the other hand, APS (Adaptive Parameter Set) is used in the VVC standard to transmit information for ALF (Adaptive Loop Filter) and LMCS (Chroma Scaling and Luma Mapping) processes. In addition, APS has an extensible structure so that it can be used to transmit other data structures (i.e., different syntax structures). Therefore, this document proposes a method of parsing / signaling scaling list data for frequency-weighted quantization through APS.

[0225] The scaling list data is quantization scaling information for frequency-weighted quantization that may be applied in the quantization / dequantization process as described above, and may be a list associating a scaling factor with each frequency index.

[0226] As an embodiment, the following Table 16 shows an example of an adaptive parameter set (APS) structure for sending scaling list data.

[0227] [Table 16]

[0228]

[0229]

[0230] The semantics of the syntax elements included in the APS syntax of Table 16 can be shown in the following Table 17.

[0231] [Table 17]

[0232]

[0233] Referring to Tables 16 and 17, the adaptation_parameter_set_id syntax element may be parsed / signaled in the APS. The adaptation_parameter_set_id provides an identifier for the APS for reference by other syntax elements. That is, the APS may be identified based on the adaptation_parameter_set_id syntax element. The adaptation_parameter_set_id syntax element may be referred to as APS ID information. The APS may be shared between pictures and may be different in different tile groups within a picture.

[0234] In addition, an aps_params_type syntax element may be parsed / signaled in APS. aps_params_type may indicate the type of APS parameters transmitted from APS, as shown in the following Table 18. The aps_params_type syntax element may be referred to as APS parameter type information or APS type information.

[0235] For example, the following Table 18 is an example showing types of APS parameters that can be transmitted through APS, and each APS parameter type can be indicated corresponding to the value of aps_params_type.

[0236] [Table 18]

[0237]

[0238] Referring to Table 18, aps_params_type may be a syntax element for classifying the type of the corresponding APS. When the value of aps_params_type is 0, the corresponding APS type may be ALF_APS, the corresponding APS may carry ALF data, and the ALF data may include ALF parameters for deriving filters / filter coefficients. When the value of aps_params_type is 1, the corresponding APS type may be LMCS_APS, the corresponding APS may carry LMCS data, and the LMCS data may include LMCS parameters for deriving LMCS models / bins / mapping indexes. When the value of aps_params_type is 2, the corresponding APS type may be SCALING_APS, the corresponding APS may carry SCALING list data, and the SCALING list data may include scaling list data parameters for deriving values ​​of frequency-based quantization scaling matrices / scaling factors / scaling lists.

[0239] For example, as shown in Table 16 above, the aps_params_type syntax element may be parsed / signaled in APS, and in this case, when the aps_params_type indication value is 0 (i.e., aps_params_type indicates ALF_APS), ALF data (i.e., alf_data()) may be parsed / signaled. Alternatively, when the value of aps_params_type is 1 (i.e., aps_params_type indicates LMCS_APS), LMCS data (i.e., lmcs_data()) may be parsed / signaled. Alternatively, when the value of aps_params_type is 2 (i.e., aps_params_type indicates SCALING_APS), scaling list data (i.e., scaling_list_data()) may be parsed / signaled.

[0240] In addition, referring to Tables 16 and 17, the aps_extension_flag syntax element can be parsed / signaled in APS. aps_extension_flag can indicate whether an APS extension data flag (aps_extension_data_flag) syntax element is present. For example, aps_extension_flag can be used to provide extension points for higher versions of the VVC standard. The aps_extension_flag syntax element may be referred to as an APS extension flag. For example, when the value of aps_extension_flag is 0, it may indicate that the APS extension data flag (aps_extension_data_flag) is not present in the APS RBSP syntax structure. Alternatively, when the value of aps_extension_flag is 1, it may indicate that the APS extension data flag (aps_extension_data_flag) is present in the APS RBSP syntax structure.

[0241] The aps_extension_data_flag syntax element may be parsed / signaled based on the aps_extension_flag syntax element. The aps_extension_data_flag syntax element may be referred to as an APS extension data flag. For example, when the value of aps_extension_flag is 1, aps_extension_data_flag may be parsed / signaled, and in this case, aps_extension_data_flag may have any value.

[0242] As described above, according to an embodiment of the present document, valid scaling list data can be carried by allocating a data type (e.g., SCALING_APS) for indicating scaling list data and parsing / signaling a syntax element (e.g., aps_params_type) indicating the data type. That is, according to an embodiment of the present document, the structure of the APS in which scaling list data is integrated can be used.

[0243] On the other hand, in the current VVC standard, the use of scaling list data (i.e., scaling_list_data()) can be indicated based on indicating whether the scaling list data is available in the SPS (sequence parameter set). If a flag (i.e., sps_scaling_list_enabled_flag) is enabled (i.e., 1 or true as a case of indicating that scaling list data is available), another flag (i.e., sps_scaling_list_data_present_flag) can be parsed. In addition, when sps_scaling_list_data_present_flag is enabled (i.e., when it indicates that scaling list data is present in the SPS and is 1 or true), scaling list data (i.e., scaling_list_data()) can be parsed. That is, in the current VVC standard, the SPS signals the scaling list data. In this case, because the SPS enables session negotiation and is typically sent out-of-band, the scaling list data does not need to be sent as information related to determining the scaling factor of the transform block, and can be used in the decoding process. If the encoder sends the scaling list data in the SPS, the decoder needs to keep a lot of memory to store the information obtained from the scaling list data, and also needs to keep the information until it is used for transform block decoding. Therefore, this process may be unnecessary at the SPS level, and it may be more efficient to parse / signal at a lower level. Therefore, this document proposes a hierarchical structure to efficiently parse / signal scaling list data.

[0244] In one embodiment, the scaling list data is not parsed / signaled from the higher level syntax SPS, but is parsed / signaled from the lower level syntax PPS, tile group header, slice header and / or other suitable headers.

[0245] For example, the SPS syntax may be modified as shown in the following Table 19. The following Table 19 shows an SPS syntax example for describing a zoom list for a CVS.

[0246] [Table 19]

[0247]

[0248] The semantics of the syntax elements included in the SPS syntax of Table 19 can be shown in the following Table 20.

[0249] [Table 20]

[0250]

[0251] Referring to Tables 19 and 20, a scaling_list_enabled_flag syntax element may be parsed / signaled in the SPS. The scaling_list_enabled_flag syntax element may indicate whether a scaling list is available based on whether its value is 0 or 1. For example, when the value of scaling_list_enabled_flag is 1, it indicates that the scaling list is used for the scaling process of the transform coefficients, and when the value of scaling_list_enabled_flag is 0, it may indicate that the scaling list is not used in the scaling process of the transform coefficients.

[0252] That is, the scaling_list_enabled_flag syntax element may be referred to as a scaling list available flag and may be signaled at the SPS (or SPS level). In other words, based on the value of the scaling_list_enabled_flag signaled at the SPS level, it may be determined that the scaling list is substantially available for the picture in the CVS that references the corresponding SPS. In addition, the scaling list may be obtained by signaling an additional available flag at a level lower than the SPS (e.g., a PPS, a tile group header, a slice header, and / or other appropriate headers).

[0253] As described above, according to an embodiment of the present document, the scaling list (scaling_list_data()) is not directly signaled at the SPS level, and only the scaling list available flag (scaling_list_enabled_flag) can be configured to be explicitly signaled. Thereafter, the scaling list (scaling_list_data()) can be parsed separately in a lower-level syntax based on the available flag (scaling_list_enabled_flag) in the SPS. Therefore, according to an embodiment of the present document, since the scaling list data can be parsed / signaled according to the hierarchical structure, the coding efficiency can be further improved.

[0254] On the other hand, the presence or absence of scaling list data and the use of scaling list data are conditional on the presence of a tool enable flag. Here, the tool enable flag may be information indicating whether the corresponding tool is enabled, and may include, for example, a scaling_list_enabled_flag syntax element. That is, the scaling_list_enabled_flag syntax element may be used to indicate whether the scaling list is enabled by indicating whether scaling list data is available. However, this tool should have syntactic restrictions on the decoder. That is, a constraint flag must be present to inform the decoder that this tool is not currently used to decode a coded video sequence (CVS). Therefore, this document proposes a method in which a constraint flag for scaling list data is applied.

[0255] As an embodiment, the following Table 21 shows an example of a syntax (eg, general constraint information syntax) for signaling scaling list data using a constraint flag.

[0256] [Table 21]

[0257]

[0258] The semantics of the syntax elements included in the syntax of Table 21 can be shown in the following Table 22.

[0259] [Table 22]

[0260]

[0261] Referring to Tables 21 and 22, the constraint flag can be parsed / signaled through general_constraint_info(). general_constraint_info() can be referred to as information about the general constraint information field or constraint flag. For example, the no_scaling_list_constraint_flag syntax element can be used as a constraint flag. Here, the constraint flag can be used to specify a consistent bitstream attribute. For example, when the value of the no_scaling_list_constraint_flag syntax element is 1, the scaling_list_enabled_flag indicates a bitstream consistency requirement that must be specified as 0, and when the value of the no_scaling_list_constraint_flag syntax element is 0, it can indicate that there is no restriction.

[0262] Meanwhile, as described above, according to an embodiment of the present document, scaling list data may be delivered through a hierarchical structure. Therefore, the present document proposes a structure of scaling list data that may be parsed / signaled through a slice header. Here, the slice header may be referred to as a tile group header, or may be mixed with a picture header or replaced with a picture header.

[0263] As an embodiment, Table 23 below shows an example of a slice header syntax for signaling scaling list data.

[0264] [Table 23]

[0265]

[0266] The semantics of the syntax elements included in the slice header syntax of Table 23 can be expressed as shown in Table 24 below.

[0267] [Table 24]

[0268]

[0269]

[0270] Referring to Tables 23 and 24, the slice_pic_parameter_set_id syntax element may be parsed / signaled in the slice header. The slice_pic_parameter_set_id syntax element may indicate an identifier of the PPS being used. That is, the slice_pic_parameter_set_id syntax element is information for identifying a PPS referenced in a corresponding slice, and may indicate a value of pps_pic_parameter_set_id. The value of slice_pic_parameter_set_id must be in the range of 0 to 63. The slice_pic_parameter_set_id syntax element may be referred to as PPS identification information or PPS ID information referenced by a slice.

[0271] In addition, the slice_scaling_list_enabled_flag syntax element can be parsed / signaled in the slice header. The slice_scaling_list_enabled_flag syntax element can indicate whether the scaling list is available in the current slice. For example, when the value of slice_scaling_list_enabled_flag is 1, it can indicate that the scaling list is available in the current slice, and when the value of slice_scaling_list_enabled_flag is 0, it can indicate that the scaling list is not available in the current slice. Alternatively, if slice_scaling_list_enabled_flag is not present in the slice header, its value can be inferred to be 0.

[0272] In this case, whether to parse the slice_scaling_list_enabled_flag syntax element may be determined based on the scaling_list_enabled_flag syntax element signaled in a higher level syntax (i.e., SPS). For example, when the value of scaling_list_enabled_flag signaled from the SPS is 1 (i.e., when it is determined that scaling list data is available at a higher level), the slice_scaling_list_enabled_flag is parsed from the slice header, and it is determined whether to perform the scaling process using the scaling list in the corresponding slice.

[0273] In addition, the slice_scaling_list_aps_id syntax element may be parsed / signaled in the slice header. The slice_scaling_list_aps_id syntax element may indicate an identifier of the APS referenced in the corresponding slice. That is, the slice_scaling_list_aps_id syntax element may indicate the ID information (adaptation_parameter_set_id) of the APS including the scaling list data referenced by the corresponding slice. On the other hand, the TemporalId (i.e., temporary ID) of the APS NAL unit having the same APS ID information (adaptation_parameter_set_id) as the slice_scaling_list_aps_id (i.e., the APS NAL unit including the scaling list data) must be less than or equal to the TemporalId (i.e., temporary ID) of the slice NAL unit to be coded.

[0274] In addition, whether to parse the slice_scaling_list_aps_id syntax element may be determined based on the slice_scaling_list_enabled_flag syntax element. For example, when the value of slice_scaling_list_aps_id is 1 (i.e., when it is determined that the scaling list is available in the slice header), slice_scaling_list_aps_id may be parsed. Thereafter, the scaling list data may be obtained from the APS indicated by the parsed slice_scaling_list_aps_id.

[0275] Furthermore, when multiple scaling data APSs (including multiple APSs of scaling list data) having the same value of APS ID information (adaptation_parameter_set_id) are referenced by two or more slices in the same picture, the multiple scaling data APSs having the same value of APS ID information (adaptation_parameter_set_id) must include the same content.

[0276] Furthermore, when the above-mentioned syntax elements are present, the value of each of the slice header syntax elements slice_pic_parameter_set_id, slice_pic_order_cnt_lsb, and slice_temporal_mvp_enabled_flag must be the same in all slice headers of a coded picture.

[0277] As described above, according to an embodiment of the present document, a hierarchical structure can be used to efficiently signal scaling list data. That is, it is possible to determine whether scaling list data is used at each lower level by first signaling an enable flag (e.g., scaling_list_enabled_flag) indicating whether scaling list data is available at a higher level (SPS syntax), and then signaling an additional available flag (e.g., slice_scaling_list_enabled_flag) at a lower level (e.g., slice header, picture header, etc.). In addition, APS ID information (e.g., slice_scaling_list_aps_id) referenced by a corresponding slice or tile group is signaled through a lower level (e.g., slice header, picture header, etc.), and scaling list data can be derived from the APS identified by the APS ID information.

[0278] In addition, the present document may apply methods such as those proposed in Tables 23 and 24 above in signaling scaling list data according to a hierarchical structure, and the scaling list data may be delivered through the structure of a slice header as shown in Table 25 below.

[0279] As an embodiment, the following Table 25 shows an example of a slice header syntax for signaling scaling list data. Here, the slice header may be referred to as a tile group header, or may be mixed with a picture header or replaced with a picture header.

[0280] [Table 25]

[0281]

[0282] The semantics of the syntax elements included in the slice header syntax of Table 25 can be shown in the following Table 26.

[0283] [Table 26]

[0284]

[0285] Referring to Tables 25 and 26 above, the slice_pic_parameter_set_id syntax element may be parsed / signaled in the slice header. The slice_pic_parameter_set_id syntax element may indicate an identifier of the PPS being used. That is, the slice_pic_parameter_set_id syntax element is information for identifying a PPS referenced in a corresponding slice, and may indicate a value of pps_pic_parameter_set_id. The value of slice_pic_parameter_set_id must be in the range of 0 to 63. The slice_pic_parameter_set_id syntax element may be referred to as PPS identification information or PPS ID information referenced by a slice.

[0286] In addition, the slice_scaling_list_aps_id syntax element may be parsed / signaled in the slice header. The slice_scaling_list_aps_id syntax element may indicate an identifier of the APS referenced in the corresponding slice. That is, the slice_scaling_list_aps_id syntax element may indicate the ID information (adaptation_parameter_set_id) of the APS including the scaling list data referenced by the corresponding slice. For example, the TemporalId (i.e., temporary ID) of the APS NAL unit having the same APS ID information (adaptation_parameter_set_id) as the slice_scaling_list_aps_id (i.e., the APS NAL unit including the scaling list data) must be less than or equal to the TemporalId (i.e., temporary ID) of the slice NAL unit to be coded.

[0287] In this case, whether to parse the slice_scaling_list_aps_id syntax element may be determined based on the scaling_list_enabled_flag syntax element signaled in the higher-level syntax (i.e., SPS). For example, when the value of scaling_list_enabled_flag signaled by the SPS is 1 (i.e., when it is determined that scaling list data is available at a higher level), slice_scaling_list_aps_id may be parsed from the slice header. Thereafter, scaling list data may be acquired from the APS indicated by the parsed slice_scaling_list_aps_id.

[0288] That is, according to the present embodiment, because the APS ID including scaling list data can be parsed when the corresponding flag (e.g., scaling_list_enabled_flag) in the SPS is enabled, as shown in the above Table 25, based on the scaling_list_enabled_flag syntax element sent by a signal in a higher-level syntax (i.e., SPS), the APS ID (e.g., slice_scaling_list_aps_id) information including scaling list data to be referenced in a lower level (e.g., a slice header or a picture header) can be parsed.

[0289] In addition, the document proposes a method for signaling scaling list data using multiple APSs. Hereinafter, a method for effectively signaling multiple APS IDs including scaling list data according to an embodiment of the present document will be described. This method is useful during bitstream merging.

[0290] As an embodiment, the following Table 27 shows an example of a slice header syntax for signaling scaling list data using multiple APSs. Here, the slice header may be referred to as a tile group header, or may be mixed with a picture header or replaced with a picture header.

[0291] [Table 27]

[0292]

[0293] The semantics of the syntax elements included in the slice header syntax of Table 27 can be expressed as shown in the following Table 28.

[0294] [Table 28]

[0295]

[0296]

[0297] Referring to Tables 27 and 28 above, the slice_pic_parameter_set_id syntax element may be parsed / signaled in a slice header. The slice_pic_parameter_set_id syntax element may indicate an identifier of a PPS used in the slice_pic_parameter_set_id syntax element. That is, the slice_pic_parameter_set_id syntax element is information for identifying a PPS referenced in a corresponding slice, and may indicate a value of pps_pic_parameter_set_id. The value of slice_pic_parameter_set_id must be in the range of 0 to 63. The slice_pic_parameter_set_id syntax element may be referred to as PPS identification information or PPS ID information referenced by a slice.

[0298] In addition, the slice_scaling_list_enabled_flag syntax element can be parsed / signaled in the slice header. The slice_scaling_list_enabled_flag syntax element can indicate whether the scaling list is available in the current slice. For example, when the value of slice_scaling_list_enabled_flag is 1, it can indicate that the scaling list is available in the current slice, and when the value of slice_scaling_list_enabled_flag is 0, it can indicate that the scaling list is not available in the current slice. Alternatively, when slice_scaling_list_enabled_flag is not present in the slice header, its value can be inferred to be 0.

[0299] In this case, whether to parse the slice_scaling_list_enabled_flag syntax element may be determined based on the scaling_list_enabled_flag syntax element signaled in a higher-level syntax (ie, SPS). For example, when the value of scaling_list_enabled_flag signaled from the SPS is 1 (ie, when it is determined that scaling list data is available at a higher layer), the slice_scaling_list_enabled_flag is parsed from the slice header, and it may be determined whether to perform the scaling process using the scaling list in the corresponding slice.

[0300] In addition, the num_scaling_list_aps_ids_minus1 syntax element may be parsed / signaled in the slice header. The num_scaling_list_aps_ids_minus1 syntax element may be information for indicating the number of APSs including scaling list data referenced by the corresponding slice. For example, a value obtained by adding 1 to the value of the num_scaling_list_aps_ids_minus1 syntax element may be the number of APSs. The value of num_scaling_list_aps_ids_minus1 must be in the range of 0 to 7.

[0301] Here, whether to parse the num_scaling_list_aps_ids_minus1 syntax element may be determined based on the slice_scaling_list_enabled_flag syntax element. For example, when the value of slice_scaling_list_enabled_flag is 1 (i.e., when it is determined that scaling list data is available in the corresponding slice), num_scaling_list_aps_ids_minus1 may be parsed. In this case, the slice_scaling_list_aps_id[i] syntax element may be parsed / signaled based on the value of num_scaling_list_aps_ids_minus1.

[0302] That is, slice_scaling_list_aps_id[i] may indicate an identifier (adaptation_parameter_set_id) of an APS including the i-th scaling list data (i.e., the i-th scaling data APS). In other words, APS ID information may be signaled as many as the number of APSs indicated by the num_scaling_list_aps_ids_minus1 syntax element. On the other hand, the TemporalId (i.e., temporary ID) of an APS NAL unit having the same APS ID information (adaptation_parameter_set_id) as slice_scaling_list_aps_id[i] (i.e., an APS NAL unit including scaling list data) must be less than or equal to the TemporalId (i.e., temporary ID) of the slice NAL unit to be coded.

[0303] Furthermore, when multiple scaling data APSs (including multiple APSs of scaling list data) having the same value of APS ID information (adaptation_parameter_set_id) are referenced by two or more slices in the same picture, the multiple scaling data APSs having the same value (adaptation_parameter_set_id) must include the same content.

[0304] The following figures are created to explain specific examples of this document. The names of specific devices or specific terms or names (e.g., names of syntax / syntax elements, etc.) described in the figures are provided only as examples, so that the technical features of this document are not limited to the specific names used in the following figures.

[0305] Figure 7 is a flowchart schematically illustrating an example of a video / image encoding method according to an embodiment of this document.

[0306] Figure 7 The method disclosed in can be Figure 2 Specifically, Figure 7 Step S700 may be performed by Figure 2 The subtractor 231 shown in FIG. 1 performs, and Figure 7 Step S710 may be performed by Figure 2 The converter 232 shown in FIG. Figure 7 Steps S720 and S730 may be performed by Figure 2 The illustrated quantizer 233 performs, and Figure 7 Step S740 may be performed by Figure 2 The entropy encoder 240 shown in FIG. 1 is executed. In addition, Figure 7 The method disclosed in includes the above embodiments in this document. Figure 7 In the embodiment, the detailed description of the contents overlapping with the above-mentioned embodiments will be omitted or simplified.

[0307] refer to Figure 7 , the encoding apparatus may derive residual samples of the current block (S700).

[0308] As an embodiment, first, the encoding device may determine the prediction mode of the current block and derive the prediction sample. For example, the encoding device may determine whether to perform inter-frame prediction or intra-frame prediction on the current block, or may determine a specific inter-frame prediction mode or a specific intra-frame prediction mode based on the RD cost. The encoding device may derive the prediction sample of the current block by performing prediction according to the determined prediction mode. In this case, various prediction methods disclosed in this document, such as inter-frame prediction or intra-frame prediction, may be applied. In addition, the encoding device may generate and encode information related to the prediction applied to the current block (e.g., prediction mode information).

[0309] Also, the encoding apparatus may derive residual samples by comparing original samples and predicted samples of the current block.

[0310] The encoding apparatus may generate a transform coefficient based on the residual sample ( S710 ).

[0311] In an embodiment, the encoding device may derive the transform coefficients by a transform process on the residual samples. In this case, the encoding device may determine whether to apply the transform to the current block in consideration of coding efficiency. That is, the encoding device may determine whether to apply the transform to the residual samples. For example, when the transform is not applied to the residual samples, the encoding device may derive the residual samples as transform coefficients. Alternatively, when the transform is applied to the residual samples, the encoding device may derive the transform coefficients by performing the transform on the residual samples. In this case, the encoding device may generate and encode the transform skip flag information based on whether the transform is applied to the current block. The transform skip flag information may be information indicating whether the transform is applied or skipped relative to the current block.

[0312] The encoding apparatus may derive a quantized transform coefficient based on the transform coefficient ( S720 ).

[0313] As an embodiment, the encoding device may derive quantized transform coefficients by applying a quantization process to the transform coefficients. In this case, the encoding device may apply frequency-weighted quantization that adjusts the quantization strength according to the frequency. In this case, the quantization process may be further performed based on the quantization scale value for each frequency. The quantization scaling value for frequency-weighted quantization may be derived using a scaling matrix. For example, the encoding device / decoding device may use a predefined scaling matrix, and the encoding device may configure and encode frequency quantization scaling information about the scaling matrix, and may send it to the decoding device with a signal. The frequency quantization scaling information may include scaling list data. The (modified) scaling matrix may be derived based on the scaling list data.

[0314] In addition, the encoding device may perform a dequantization process in the same manner as the decoding device. In this case, the encoding device may derive a (modified) scaling matrix based on the scaling list data, and may derive a reconstructed transform coefficient by applying dequantization to the quantized transform coefficient based thereon. In this case, the reconstructed transform coefficient may be different from the original transform coefficient due to losses in the transform / quantization process.

[0315] Here, the scaling matrix may refer to the above-mentioned frequency-based quantization scaling matrix, and for ease of description may be used interchangeably or replaced with quantization scaling matrix, quantization matrix, scaling matrix, scaling list, etc., and is not limited to the specific names used in this document.

[0316] That is, the encoding device may further apply frequency weighted quantization when performing the quantization process, and in this case, the scaling list data may be generated as information about the scaling matrix. Since this process has been described in detail using Tables 5 to 15 as an example, redundant content or detailed description will be omitted in this embodiment.

[0317] The encoding apparatus may generate residual information including information about the quantized transform coefficient (S730).

[0318] Here, the residual information may include information on the value of the quantized transform coefficient, position information, a transform technique, a transform kernel, a quantization parameter, and the like.

[0319] The encoding device may encode the image information (or video information) (S740). Here, the image information may include residual information. In addition, the image information may include prediction related information (e.g., prediction mode information). In addition, the image information may include information about scaling list data. That is, the image information may include various information derived from the encoding process, and may be encoded by including such various information.

[0320] As an embodiment, the image information may include various information according to the above-described embodiments in this document, and may include information disclosed in at least one of the above-described Tables 1 to 28.

[0321] For example, the image information may include an adaptive parameter set (APS). The APS may include APS identification information (APS ID information) and type information of the APS parameters. In addition, the APS may include scaling list data based on the type information of the APS parameters. The scaling list data may include scaling list parameters for deriving a scaling list / scaling matrix / scaling factor used in the quantization / dequantization process as described above. In other words, the scaling list data may include syntax elements for constructing a scaling list.

[0322] As an example, the APS may be configured as shown in Table 16 above. The APS identification information may be the adaptation_parameter_set_id described in Tables 16 and 17 above. The type information of the APS parameter may be the aps_params_type described in Tables 16 to 18 above. For example, when the type information (e.g., aps_params_type) of the APS parameter is a SCALING_APS type associated with an indication that it is an APS including scaling list data (or when the value of the type information (e.g., aps_params_type) of the APS parameter is equal to 2), the APS may include scaling list data (e.g., scaling_list_data()). That is, the encoding device may signal the scaling list data (e.g., scaling_list_data()) through the APS based on the SCALING_APS type information indicating that it is an APS including scaling list data.

[0323] In addition, for example, the image information may include header information. The header information may be header information related to a picture or a slice including the current block, and may include, for example, a picture header or a slice header. The header information may include APS identification information related to the scaling list data. The APS identification information related to the scaling list data included in the header information may indicate identification information of the APS including the scaling list data. For example, the APS identification information related to the scaling list data included in the header information may be the slice_scaling_list_aps_id described in Tables 23 to 26 above, and may be identification information of the APS (including the scaling list data) referenced by the slice / picture including the current block. That is, the APS including the scaling list data can be identified based on the APS identification information related to the scaling list data.

[0324] In addition, for example, the image information may include a sequence parameter set (SPS). The SPS may include first available flag information related to indicating whether scaling list data is available. For example, the SPS may be configured as shown in Table 19, and the first available flag information may be scaling_list_enabled_flag described in Tables 19 and 20 above.

[0325] At this time, based on the first available flag information (e.g., scaling_list_enabled_flag) related to indicating that the scaling list data is available (e.g., when the value of the first available flag information (e.g., scaling_list_enabled_flag) is equal to 1 or true), the header information may include APS identification information (e.g., slice_scaling_list_aps_id) related to the scaling list data. As an example, the encoding device may signal the identification information (e.g., slice_scaling_list_aps_id) of the APS including the scaling list data through the header information based on the first available flag information (e.g., scaling_list_enabled_flag) as shown in Tables 23 and 25 above.

[0326] The header information may include second available flag information related to indicating whether the scaling list data is available in the picture or slice. For example, the second available flag information may be slice_scaling_list_enabled_flag described in Tables 23 and 24 above.

[0327] At this time, based on the first available flag information (e.g., scaling_list_enabled_flag) related to indicating that the scaling list data is available (e.g., when the value of the first available flag information (e.g., scaling_list_enabled_flag) is equal to 1 or true), the header information may include the second available flag information (e.g., slice_scaling_list_enabled_flag). And, based on the second available flag information (e.g., slice_scaling_list_enabled_flag) (e.g., when the value of the second available flag information (e.g., slice_scaling_list_enabled_flag) is equal to 1 or true), the header information may include APS identification information related to the scaling list data (e.g., slice_scaling_list_aps_id). As an example, the encoding device may signal second available flag information (e.g., slice_scaling_list_enabled_flag) through header information based on first available flag information (e.g., scaling_list_enabled_flag) signaled from the SPS shown in Table 23 above, and may then signal APS identification information related to scaling list data (e.g., slice_scaling_list_aps_id) through header information based on the second available flag information (e.g., slice_scaling_list_enabled_flag).

[0328] In addition, for example, the image information may include constraint flag information about the use of the first available flag information. For example, the constraint flag information may be the no_scaling_list_constraint_flag described in Tables 21 and 22 above. The constraint flag information (e.g., no_scaling_list_constraint_flag) may be signaled by being included in a general constraint information syntax (e.g., general_constraint_info()). For example, when the value of the constraint flag information (e.g., no_scaling_list_constraint_flag) is equal to 1, the general constraint information syntax (e.g., general_constraint_info()) is restricted so that the value of the first available flag information (e.g., scaling_list_enabled_flag) is set to 0. Alternatively, when the value of the constraint flag information (e.g., no_scaling_list_constraint_flag) is equal to 0, it may be indicated that there is no constraint on the first available flag information (e.g., scaling_list_enabled_flag).

[0329] In addition, for example, the image information may include header information related to a picture or a slice including the current block. For example, the header information may include a picture header or a slice header. The header information may include APS quantity information indicating the number of APS identification information related to the scaling list data. In this case, the header information may include as much APS identification information related to the scaling list data as the number of APS identification information derived based on the APS quantity information.

[0330] As an example, the APS number information may be num_scaling_list_aps_ids_minus1 described in the above Tables 27 and 28. As described in Table 27, a value obtained by adding 1 to the value of num_scaling_list_aps_ids_minus1 may be the number of APS identification information. Therefore, as many slice_scaling_list_aps_ids as the number of APS identification information (the value of num_scaling_list_aps_ids_minus1 plus 1) may be included in the header information.

[0331] The image information including various information as described above can be encoded and output in the form of a bit stream. The bit stream can be sent to a decoding device via a network or a (digital) storage medium. Here, the network can include a broadcast network and / or a communication network, and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD and SSD.

[0332] Figure 8 is a flowchart schematically illustrating an example of a video / image decoding method according to an embodiment of this document.

[0333] Figure 8 The method disclosed in can be Figure 3 The illustrated decoding device 300 performs. Specifically, Figure 8 Steps S800 and S810 may be performed by Figure 3 The entropy decoder 310 shown in FIG. Figure 8 Step S820 may be performed by Figure 3 The dequantizer 321 shown in FIG. Figure 8 Step S830 can be performed by Figure 3 The inverse converter 322 shown in FIG. 1 is executed, and Figure 8 Step 840 may be performed by Figure 3 The adder 340 shown in the figure performs. In addition, it is possible to perform Figure 8 The method disclosed in, including the above embodiments in this document. Figure 8 In the embodiment, the detailed description of the contents overlapping with the above-mentioned embodiments will be omitted or simplified.

[0334] refer to Figure 8 , the decoding apparatus may receive image information (or video information) from a bit stream (S800).

[0335] As an embodiment, the decoding device can derive information necessary for image reconstruction (or picture reconstruction) (e.g., video / image information) by parsing the bitstream. In this case, the image information may include residual information, and the residual information may include information such as information about the value of the quantized transform coefficient, position information, transform technology, transform kernel, and quantization parameter. In addition, the image information may include information related to prediction (e.g., prediction mode information). In addition, the image information may include information about scaling list data. That is, the image information may include various information required in the decoding process, and may be decoded based on coding methods such as exponential Golomb coding, CAVLC, CABAC, etc.

[0336] As an embodiment, the image information may include various information according to the above-described embodiments in this document, and may include information disclosed in at least one of the above-described Tables 1 to 28.

[0337] For example, the image information may include an adaptive parameter set (APS). The APS may include APS identification information and type information of the APS parameters. In addition, the APS may include scaling list data based on the type information of the APS parameters. The scaling list data may include scaling list parameters for deriving a scaling list / scaling matrix / scaling factor used in the quantization / dequantization process as described above. In other words, the scaling list data may include syntax elements for constructing a scaling list.

[0338] As an example, the APS may be configured as shown in Table 16 above. The APS identification information may be the adaptation_parameter_set_id described in Tables 16 and 17 above. The type information of the APS parameter may be the aps_params_type described in Tables 16 to 18 above. For example, when the type information (e.g., aps_params_type) of the APS parameter is a SCALING_APS type associated with an indication that it is an APS including scaling list data (or when the value of the type information (e.g., aps_params_type) of the APS parameter is equal to 2), the APS may include scaling list data (e.g., scaling_list_data()). That is, the decoding device may obtain and parse the scaling list data (e.g., scaling_list_data()) through the APS based on the SCALING_APS type information indicating that it is an APS including scaling list data.

[0339] In addition, for example, the image information may include header information. The header information may be header information related to a picture or a slice including the current block, and may include, for example, a picture header or a slice header. In addition, the header information may include APS identification information related to the scaling list data. The APS identification information related to the scaling list data included in the header information may indicate identification information of the APS including the scaling list data. For example, the APS identification information related to the scaling list data included in the header information may be the slice_scaling_list_aps_id described in Tables 23 to 26 above, and may be identification information of the APS (including the scaling list data) referenced by the slice / picture including the current block. That is, the decoding device may identify the APS based on the APS identification information (e.g., slice_scaling_list_aps_id) in the header information, and may obtain scaling list data from the APS.

[0340] In addition, for example, the image information may include a sequence parameter set (SPS). The SPS may include first available flag information related to indicating whether the scaling list data is available. For example, the SPS may be configured as shown in Table 19, and the first available flag information may be the scaling_list_enabled_flag described in Tables 19 and 20 above.

[0341] At this time, based on the first available flag information (e.g., scaling_list_enabled_flag) related to indicating that the scaling list data is available (e.g., when the value of the first available flag information (e.g., scaling_list_enabled_flag) is equal to 1 or true), the header information may include APS identification information (e.g., slice_scaling_list_aps_id) related to the scaling list data. As an example, the decoding device may obtain the identification information (e.g., slice_scaling_list_aps_id) of the APS including the scaling list data through the header information based on the first available flag information (e.g., scaling_list_enabled_flag) as shown in Tables 23 and 25 above.

[0342] In addition, for example, the header information may include second available flag information related to indicating whether the scaling list data is available in the picture or the slice. For example, the second available flag information may be slice_scaling_list_enabled_flag described in Tables 23 and 24 above.

[0343] At this time, based on the first available flag information (e.g., scaling_list_enabled_flag) related to indicating that the scaling list data is available (e.g., when the value of the first available flag information (e.g., scaling_list_enabled_flag) is equal to 1 or true), the header information may include the second available flag information (e.g., slice_scaling_list_enabled_flag). And, based on the second available flag information (e.g., slice_scaling_list_enabled_flag) (e.g., when the value of the second available flag information (e.g., slice_scaling_list_enabled_flag) is equal to 1 or true), the header information may include APS identification information related to the scaling list data (e.g., slice_scaling_list_aps_id). For example, the decoding device can obtain second available flag information (e.g., slice_scaling_list_enabled_flag) through header information based on first available flag information (e.g., scaling_list_enabled_flag) sent by an SPS signal as shown in Table 23 above, and can then obtain APS identification information related to scaling list data (e.g., slice_scaling_list_aps_id) through header information based on the second available flag information (e.g., slice_scaling_list_enabled_flag).

[0344] In addition, for example, the image information may include constraint flag information about the use of the first available flag information. For example, the constraint flag information may be the no_scaling_list_constraint_flag described in Tables 21 and 22 above. The constraint flag information (e.g., no_scaling_list_constraint_flag) may be signaled by being included in a general constraint information syntax (e.g., general_constraint_info()). For example, when the value of the constraint flag information (e.g., no_scaling_list_constraint_flag) is equal to 1, the general constraint information syntax (e.g., general_constraint_info()) is restricted so that the value of the first available flag information (e.g., scaling_list_enabled_flag) is set to 0. Alternatively, when the value of the constraint flag information (e.g., no_scaling_list_constraint_flag) is equal to 0, it may be indicated that there is no constraint on the first available flag information (e.g., scaling_list_enabled_flag).

[0345] In addition, for example, the image information may include header information related to a picture or a slice including the current block. For example, the header information may include a picture header or a slice header. In addition, the header information may include APS quantity information indicating the number of APS identification information related to the scaling list data. In this case, the header information may include as much APS identification information related to the scaling list data as the number of APS identification information derived based on the APS quantity information.

[0346] As an example, the APS number information may be num_scaling_list_aps_ids_minus1 described in the above Tables 27 and 28. As described in Table 27, a value obtained by adding 1 to the value of num_scaling_list_aps_ids_minus1 may be the number of APS identification information. Therefore, as many slice_scaling_list_aps_ids as the number of APS identification information (the value of num_scaling_list_aps_ids_minus1 plus 1) may be included in the header information.

[0347] The decoding apparatus may derive a quantized transform coefficient of a current block ( S810 ).

[0348] As an embodiment, the decoding device may obtain residual information included in the image information. The residual information may include information such as information about the value of the quantized transform coefficient as described above, position information, transform technology, transform kernel, and quantization parameter. The decoding device may derive the quantized transform coefficient of the current block based on the quantized transform coefficient information included in the residual information.

[0349] The decoding apparatus may derive a transform coefficient based on the quantized transform coefficient (S820).

[0350] As an example, the decoding device may derive the transform coefficients by applying a dequantization process to the quantized transform coefficients. In this case, the decoding device may apply frequency-weighted quantization that adjusts the quantization strength according to the frequency. In this case, the dequantization process may be further performed based on the quantization scaling value for each frequency. The quantization scaling value for frequency-weighted quantization may be derived using a scaling matrix. For example, the decoding device may use a predefined scaling matrix, or may use frequency quantization scaling information about the scaling matrix signaled from the encoding device. The frequency quantization scaling information may include scaling list data. The (modified) scaling matrix may be derived based on the scaling list data.

[0351] That is, the decoding device may further apply frequency-weighted quantization in performing the dequantization process. In this case, the decoding device may derive the transform coefficient by applying the dequantization process to the quantized transform coefficient based on the scaling list data.

[0352] As an embodiment, the decoding device may obtain the APS included in the image information, and may obtain the scaling list data based on the type information of the APS parameters included in the APS. For example, the decoding device may obtain the scaling list data included in the APS based on the SCALING_APS type information associated with the APS indicating that it is an APS including the scaling list data. In this case, the decoding device may derive a scaling matrix based on the scaling list data, may derive a scaling factor based on the scaling matrix, and may derive a transform coefficient by applying dequantization based on the scaling factor. Because the process of performing scaling based on the scaling list data has been described in detail with reference to Tables 5 to 15 as an example, redundant content or detailed description will be omitted in this embodiment.

[0353] In addition, the decoding device can determine whether to apply frequency-weighted quantization during the dequantization process (that is, whether to use a (frequency-based quantization) scaling list to derive transform coefficients during the dequantization process). For example, the decoding device determines whether to use scaling list data based on a first available flag obtained from an SPS included in the image information and / or second available flag information obtained from header information included in the image information. If it is determined based on the first available flag and / or the second available flag information to use scaling list data, the decoding device can identify the corresponding APS based on the APS identification information related to the scaling list data included in the header information, and can obtain the scaling list data from the identified APS.

[0354] The decoding apparatus may derive residual samples based on the transform coefficients ( S830 ).

[0355] As an embodiment, the decoding device may derive the residual samples of the current block by performing an inverse transform on the transform coefficients of the current block. In this case, the decoding device may obtain information indicating whether an inverse transform is applied to the current block (i.e., transform skip flag information), and derive the residual samples based on this information (i.e., transform skip flag information).

[0356] For example, when the inverse transform is not applied to the transform coefficient (when the value of the transform skip flag information of the current block is equal to 1), the decoding device may derive the transform coefficient as the residual sample of the current block. Alternatively, when the inverse transform is applied to the transform coefficient (when the value of the transform skip flag information of the current block is equal to 0), the decoding device may perform inverse transform on the transform coefficient to derive the residual sample of the current block.

[0357] The decoding apparatus may generate reconstructed samples based on the residual samples ( S840 ).

[0358] As an embodiment, the decoding device may determine whether to perform inter-frame prediction or intra-frame prediction on the current block based on the prediction information (e.g., prediction mode information) included in the image information, and derive the prediction sample of the current block by performing the prediction according to the determination. In addition, the decoding device may generate a reconstructed sample based on the prediction sample and the residual sample. At this time, the decoding device may directly use the prediction sample as the reconstructed sample according to the prediction mode, or may generate the reconstructed sample by adding the residual sample to the prediction sample. In addition, a reconstructed block or a reconstructed picture may be derived based on the reconstructed sample. Thereafter, as described above, if necessary, the decoding device may apply an in-loop filtering process such as a deblocking filter and / or an SAO process to the reconstructed picture in order to improve the subjective / objective picture quality.

[0359] In the above-mentioned embodiments, although the methods have been described based on flowcharts in the form of a series of steps or units, the embodiments of this document are not limited to the order of these steps, and some of these steps may be performed in an order different from the order of other steps or may be performed simultaneously with other steps. In addition, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive, and without affecting the scope of rights of this document, these steps may include additional steps or one or more steps in the flowcharts may be deleted.

[0360] The above-mentioned method according to the present document may be implemented in software form, and the encoding device and / or decoding device according to the present document may be included in an apparatus for performing image processing, such as a TV, a computer, a smart phone, a set-top box, or a display device.

[0361] In this document, when the implementation is implemented in software form, the above-mentioned method can be implemented as a module (program, function, etc.) for performing the above-mentioned functions. The module can be stored in a memory and executed by a processor. The memory can be arranged inside or outside the processor and connected to the processor by various well-known means. The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits and / or data processing devices. The memory may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium and / or other storage devices. That is, the implementation described in this document can be implemented and executed on a processor, a microprocessor, a controller or a chip. For example, the functional unit illustrated in the accompanying drawings can be implemented and executed on a computer, a processor, a microprocessor, a controller or a chip. In this case, information (e.g., information about instructions) or an algorithm for such implementation can be stored in a digital storage medium.

[0362] In addition, the decoding device and the encoding device to which this document is applied may be included in multimedia broadcast sending and receiving devices, mobile communication terminals, home theater video devices, digital theater video devices, surveillance cameras, video chat devices, real-time communication devices such as video communication, mobile streaming devices, storage media, cameras, video on demand (VoD) service providing devices, over-the-top (OTT) video devices, Internet streaming service providing devices, three-dimensional (3D) video devices, virtual reality (VR) devices, augmented reality (AR) devices, video phone video devices, transportation means terminals (e.g., vehicle (including autonomous vehicle) terminals, aircraft terminals, and ship terminals) and medical video devices, and may be used to process video signals or data signals. For example, over-the-top (OTT) video devices may include game consoles, Blueray players, Internet access TVs, home theater systems, smart phones, tablet PCs, and digital video recorders (DVRs).

[0363] In addition, the processing method of the application of this document can be generated in the form of a program executed by a computer, and can be stored in a computer-readable recording medium. The multimedia data with a data structure according to this document can also be stored in a computer-readable recording medium. Computer-readable recording media include all kinds of storage devices storing computer-readable data. Computer-readable recording media may include, for example, Blueray discs (BD), universal serial buses (USB), ROMs, PROMs, EPROMs, EEPROMs, RAMs, CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. In addition, computer-readable recording media include media implemented in the form of carrier waves (e.g., transmitted over the Internet). In addition, the bit stream generated using the encoding method can be stored in a computer-readable recording medium, or can be transmitted over wired and wireless communication networks.

[0364] In addition, the embodiments of this document may be implemented as a computer program product using program code. The program code may be executed by a computer according to the embodiments of this document. The program code may be stored on a carrier that can be read by a computer.

[0365] Fig. 9 An example of a content streaming system to which the embodiments disclosed in this document can be applied is illustrated.

[0366] refer to Fig. 9 The content streaming media system to which the embodiment of the present invention is applied may basically include an encoding server, a streaming server, a web server, a media storage, a user device and a multimedia input device.

[0367] The encoding server compresses the content input from a multimedia input device such as a smart phone, a camera, a camcorder, etc. into digital data to generate a bit stream, and transmits the bit stream to the streaming server. As another example, when a multimedia input device such as a smart phone, a camera, a camcorder, etc. directly generates a bit stream, the encoding server can be omitted.

[0368] A bitstream may be generated by applying the encoding method or the bitstream generating method of the embodiment of this document, and the streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0369] The streaming server sends multimedia data to the user device through the web server based on the user's request, and the web server is used as a medium to inform the user of the service. When the user requests the desired service from the web server, the web server transmits it to the streaming server, and the streaming server sends the multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server is used to control the command / response between the devices in the content streaming system.

[0370] The streaming server can receive content from a media storage device and / or an encoding server. For example, when receiving content from an encoding server, the content can be received in real time. In this case, in order to provide a stable streaming service, the streaming server can store the bit stream for a predetermined time.

[0371] Examples of user devices may include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigators, touch-screen PCs, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage, etc.

[0372] The various servers in the content streaming system may operate as distributed servers, in which case data received from the various servers may be distributed.

[0373] The claims described herein may be combined in various ways. For example, the technical features of the method claims of this specification may be combined and implemented as a device, and the technical features of the device claims of this specification may be combined and implemented as a method. In addition, the technical features of the method claims of this specification and the technical features of the device claims may be combined and implemented as a device, and the technical features of the method claims of this specification and the technical features of the device claims may be combined and implemented as a method.

Claims

1. A method for decoding an image performed by a decoding device, the method comprising: Obtaining image information including residual information from a bitstream; Based on the residual information, deriving quantized transform coefficients for the current block; deriving transform coefficients based on the quantized transform coefficients; deriving residual samples based on the transform coefficients; as well as generating a reconstructed sample based on the residual sample, The image information includes an adaptive parameter set (APS), The APS includes APS identification information and type information of APS parameters. wherein the type information specifies which information among information related to adaptive loop filter (ALF) parameters, information about luma mapping and chroma scaling (LMCS) parameters, and information related to scaling list data is included in the APS, wherein based on the type information, only one of the information related to the ALF parameters, the information related to the LMCS parameters, and the information related to the scaling list data is included in the APS, wherein the APS includes scaling list data based on the type information, wherein the scaling list data comprises scaling list parameters used in a dequantization process for the quantized transform coefficients, and The derivation of the transform coefficients includes: Based on the type information included in the APS, obtaining the zoom list data; and The transform coefficients are derived by applying the dequantization process to the quantized transform coefficients based on the scaling list data.

2. An image encoding method performed by an image encoding device, the method comprising: deriving residual samples for the current block; deriving transform coefficients based on the residual samples; deriving quantized transform coefficients by applying a quantization process to the transform coefficients; generating residual information including information about the quantized transform coefficients; as well as encoding image information including the residual information, The image information includes an adaptive parameter set (APS), Wherein, the APS includes zoom list data, and the zoom list data includes zoom list parameters, The APS includes APS identification information and type information of APS parameters. wherein the type information specifies which information among information related to adaptive loop filter (ALF) parameters, information about luma mapping and chroma scaling (LMCS) parameters, and information related to the scaling list data is included in the APS, wherein, based on the type information, only one of the information related to the ALF parameters, the information related to the LMCS parameters, and the information related to the scaling list data is configured to be included in the APS, and Wherein, the APS includes the scaling list data based on the type information.

3. A method for transmitting data for image information, the method comprising: obtaining a bitstream of the image information including residual information, wherein the bitstream is generated based on: deriving residual samples for a current block, deriving transform coefficients based on the residual samples, deriving quantized transform coefficients by applying a quantization process to the transform coefficients, generating residual information including information about the quantized transform coefficients, and encoding the image information including the residual information; as well as sending the data, the data comprising a bit stream of the image information including the residual information, The image information includes an adaptive parameter set (APS), Wherein, the APS includes zoom list data, and the zoom list data includes zoom list parameters, The APS includes APS identification information and type information of APS parameters. wherein the type information specifies which information among information related to adaptive loop filter (ALF) parameters, information about luma mapping and chroma scaling (LMCS) parameters, and information related to the scaling list data is included in the APS, wherein, based on the type information, only one of the information related to the ALF parameters, the information related to the LMCS parameters, and the information related to the scaling list data is configured to be included in the APS, and Wherein, the APS includes the scaling list data based on the type information.

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