Image decoding method using BDPCM and apparatus therefor

Abstract

The present disclosure relates to an image decoding method using BDPCM and an apparatus therefor. An image decoding method performed according to a decoding device of the present document comprises the steps of: obtaining a BDPCM available flag indicating whether block-based incremental pulse code modulation (BDPCM) is available for a chroma block and a luma block; obtaining BDPCM related information for the current luma block and the current chroma block based on the BDPCM available flag; and generating reconstructed samples for the current luma block and the current chroma block on the basis of the BDPCM-related information.

Description

[0001] This application is a divisional application of the patent application with the application number 202080097383.2 (PCT / KR2020 / 015317), the international application date of which is November 4, 2020, and which was filed with the Chinese Patent Office on August 23, 2022, and has the invention title of "Image Decoding Method and Apparatus Using BDPCM". Technical Field

[0002] The present disclosure relates to image coding technology, and more particularly, to an image decoding method and apparatus for performing BDPCM in an image coding system. Background Art

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

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

[0005] Technical Problem

[0006] The present disclosure provides a method and apparatus for improving image coding efficiency.

[0007] Another technical object of the present disclosure is to provide a method and apparatus for increasing BDPCM efficiency.

[0008] Technical Solution

[0009] According to an embodiment of the present disclosure, there is provided an image decoding method performed by a decoding apparatus. The method includes: obtaining a BDPCM enable flag for whether block-based delta pulse code modulation (BDPCM) is enabled for a luminance block and a chrominance block, obtaining BDPCM-related information for a current luminance block and a current chrominance block based on the BDPCM enable flag, and generating reconstructed samples for the current luminance block and the current chrominance block based on the BDPCM-related information.

[0010] According to another embodiment of the present disclosure, a decoding apparatus for performing image decoding is provided. The decoding apparatus includes: an entropy decoder configured to obtain a BDPCM enable flag for whether to enable block-based delta pulse code modulation (BDPCM) for a luminance block and a chrominance block, and obtain BDPCM-related information for a current luminance block and a current chrominance block based on the BDPCM enable flag; and a predictor configured to generate reconstructed samples for the current luminance block and the current chrominance block based on the BDPCM-related information.

[0011] According to still another embodiment of the present disclosure, a video encoding method performed by an encoding apparatus is provided. The method includes: determining whether to enable block-based delta pulse code modulation (BDPCM) for a chrominance block and a luminance block, generating a BDPCM enable flag for whether to enable BDPCM for the chrominance block and the luminance block based on the determined result, generating BDPCM-related information for a current luminance block and a current chrominance block, and encoding image information including the BDPCM enable flag and the BDPCM-related information.

[0012] According to still another embodiment of the present disclosure, a video encoding apparatus is provided. The encoding apparatus includes: a predictor configured to determine whether to enable block-based delta pulse code modulation (BDPCM) for a chrominance block and a luminance block; and an entropy encoder configured to generate a BDPCM enable flag for whether to enable BDPCM for the chrominance block and the luminance block based on the determined result, generate BDPCM-related information for a current luminance block and a current chrominance block, and encode image information including the BDPCM enable flag and the BDPCM-related information.

[0013] According to still another embodiment of the present disclosure, a computer-readable digital storage medium storing a bitstream is provided, the bitstream including image information for causing an image decoding method to be executed. In the computer-readable digital storage medium, the image decoding method includes: obtaining a BDPCM enable flag for whether to enable block-based delta pulse code modulation (BDPCM) for a luminance block and a chrominance block, obtaining BDPCM-related information for a current luminance block and a current chrominance block based on the BDPCM enable flag, and generating reconstructed samples for the current luminance block and the current chrominance block based on the BDPCM-related information.

[0014] Advantageous Effects

[0015] According to the present disclosure, it is possible to determine whether to enable BDPCM for luminance blocks and chrominance blocks in an image by one syntax element, and by doing so, it is possible to reduce the bit amount of BDPCM and improve the overall encoding efficiency.

[0016] According to the present disclosure, a BDPCM enable flag indicating whether to enable BDPCM for luminance blocks and chrominance blocks in an image can be signaled, regardless of the chrominance format of the image, and by doing so, the complexity of BDPCM can be reduced and the overall encoding efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Briefly illustrate an example of a video / image encoding device to which embodiments of the present disclosure can be applied.

[0018] Figure 2 FIG. is a schematic diagram illustrating the configuration of a video / image encoding device to which embodiments of the present disclosure can be applied.

[0019] Figure 3 FIG. is a schematic diagram illustrating the configuration of a video / image decoding device to which embodiments of the present disclosure can be applied.

[0020] Figure 4 Illustrate an example of a video / image encoding method based on intra prediction.

[0021] Figure 5 Illustrate an example of a video / image encoding method based on intra prediction.

[0022] Figure 6 Schematically show the intra prediction process.

[0023] Figure 7 Schematically show an image encoding method by an encoding device according to this document.

[0024] Figure 8 Schematically show an encoding device for performing an image encoding method according to this document.

[0025] Figure 9 Schematically show an image decoding method by a decoding device according to this document.

[0026] Figure 10 Schematically show a decoding device for performing an image decoding method according to this document.

[0027] Figure 11 Illustrate a structural diagram of a content streaming system to which the present disclosure is applied. DETAILED DESCRIPTION

[0028] The present disclosure can be modified in various forms, and specific embodiments thereof will be described and illustrated in the accompanying drawings. However, the embodiments are not intended to limit the present disclosure. The terms used in the following description are only for describing specific embodiments and are not intended to limit the present disclosure. As long as it is clearly understood in a different way, singular expressions include plural expressions. Terms such as "including" and "having" are intended to indicate the presence of the features, numbers, steps, operations, elements, components, or combinations thereof used in the following description, and thus it should be understood that the possibility of the presence or addition of one or more different features, numbers, steps, operations, elements, components, or combinations thereof is not excluded.

[0029] Meanwhile, the elements in the accompanying drawings described in the present disclosure are independently drawn for the convenience of explaining different specific functions, and it does not mean that these elements are embodied by independent hardware or independent software. For example, two or more of the elements can be combined to form a single element, or one element can be divided into multiple elements. Embodiments of combining elements and / or dividing elements belong to the present disclosure without departing from the concept of the present disclosure.

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, throughout the drawings, like reference numerals are used to indicate like elements, and the same description of like elements will be omitted.

[0031] Figure 1 Briefly illustrate an example of a video / image compilation device to which embodiments of the present disclosure can be applied.

[0032] Refer to Figure 1 , a video / image compilation system may include a first device (source device) and a second device (receiving device). The source device may send encoded video / image information or data to the receiving device in the form of a file or a stream via a digital storage medium or a network.

[0033] 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.

[0034] The video source can obtain video / images through processes such as capturing, synthesizing, or generating video / images. The video source can include video / image capture devices and / or video / image generation devices. The video / image capture devices can include, for example, one or more cameras, video / image archives including previously captured video / images, etc. The video / image generation devices can include, for example, computers, tablets, and smart phones, and can (electronically) generate video / images. For example, virtual video / images can be generated by a computer or the like. In this case, the video / image capture process can be replaced by a process of generating relevant data.

[0035] The encoding device can encode the input video / image. The encoding device can perform a series of processes such as prediction, transformation, and quantization to achieve compression and compilation efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0036] The transmitter can send the encoded image / image information or data output in the form of a bitstream to the receiver of the receiving device in the form of a file or a stream via a digital storage medium or a network. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter can include elements for generating a media file in a predetermined file format and can include elements for transmitting via a broadcast / communication network. The receiver can receive / extract the bitstream and send the received bitstream to the decoding device.

[0037] The decoding device can decode the video / image by performing a series of processes such as dequantization, inverse transformation, and prediction corresponding to the operations of the encoding device.

[0038] The renderer can render the decoded video / image. The rendered video / image can be displayed on a display.

[0039] This disclosure relates to video / image compilation. For example, the methods / embodiments disclosed in this disclosure can be applied to the methods disclosed in Versatile Video Coding (VVC), Efficient Video Coding (EVC) standard, AOMedia Video 1 (AV1) standard, Audio Video Coding Standard 2 (AVS2), or the next-generation video / image compilation standards (e.g., H.267, or H.268, etc.).

[0040] This disclosure presents various embodiments of video / image compilation, and unless otherwise mentioned, the embodiments can be executed in combination with each other.

[0041] In the present disclosure, a video may refer to a series of images over time. Generally, a picture refers to a unit representing an image in a specific time zone, and a sub-picture / slice / tile is a unit that is part of a picture being compiled. A sub-picture / slice / tile may include one or more Compilation Tree Units (CTUs). A picture may be composed of one or more sub-pictures / slices / tile. A picture may be composed of one or more tile groups. A tile group may include one or more tiles. A brick may represent a rectangular area of CTU rows within a tile in a picture. A tile may be partitioned into multiple bricks, each brick consisting of one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. Brick scan may sort CTUs in a specific order for the partitioned CTUs of a picture, where CTUs are sorted continuously in raster scan order within a brick, bricks within a tile are sorted continuously in raster scan order of the tiles of the tile, and tiles in a picture are sorted continuously in raster scan order of the tiles of the picture. Additionally, a sub-picture may represent a rectangular area of one or more slices within a picture. That is, a sub-picture contains one or more slices that jointly cover a rectangular area of the picture. A tile is a rectangular area of CTUs within a specific tile column and a specific tile row in a picture. A tile column is a rectangular area of CTUs, the height of which is equal to the height of the picture and the width of which is specified by a syntax element in the picture parameter set. A tile row is a rectangular area of CTUs, the height of which is specified by a syntax element in the picture parameter set and the width of which is equal to the width of the picture. Tile scan is a specific order sorting of CTUs for partitioning a picture, where CTUs may be sorted continuously in raster scan order within a tile, while tiles in a picture may be sorted continuously in raster scan order of the tiles of the picture. A slice includes an integer number of bricks that can be exclusively included in a single NAL unit of a picture. A slice may consist of multiple complete tiles or only of a continuous sequence of complete bricks of one tile. In the present disclosure, tile group and slice may be used interchangeably. For example, in the present disclosure, a tile group / tile group header may be referred to as a slice / slice header.

[0042] A pixel or pel may represent the smallest unit that makes up a picture (or image). Additionally, "sample" may be used as a term corresponding to a pixel. A sample generally may represent a pixel or a pixel value, and may represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chrominance component.

[0043] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of an image and information related to the area. A unit may include a luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit may be used interchangeably with terms such as a block or a region. In general, an M×N block may include a set (or array) of samples (or sample arrays) or transform coefficients having M columns and N rows.

[0044] In this specification, "A or B" may mean "only A", "only B", or "A and B". In other words, in this specification, "A or B" may be interpreted as "A and / or B". For example, "A, B, or C" herein means "only A", "only B", "only C", or "any one and any combination of A, B, and C".

[0045] The slashes ( / ) or commas used in this specification may mean "and / or". For example, "A / B" may mean "A and / or B". Thus, "A / B" may mean "only A", "only B", or "A and B". For example, "A, B, C" may mean "A, B, or C".

[0046] In this specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". Additionally, in this specification, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted the same as "at least one of A and B".

[0047] Additionally, in this specification, "at least one of A, B, and C" means "only A", "only B", "only C", or "any combination of A, B, and C". 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".

[0048] Furthermore, the parentheses used in this specification may mean "for example". Specifically, when indicating "prediction (intra prediction)", "intra prediction" may be presented as an example of "prediction". In other words, "prediction" in this specification is not limited to "intra prediction", and "intra prediction" may be presented as an example of "prediction". Additionally, even when indicating "prediction (i.e., intra prediction)", "intra prediction" may be presented as an example of "prediction".

[0049] In this specification, the technical features separately described in a figure may be implemented separately or may be implemented simultaneously.

[0050] The following drawings are created to explain specific examples of this specification. Since the names of specific devices or the names of specific signals / messages / fields described in the drawings are presented by way of example, the technical features of this specification are not limited to the specific names used in the following drawings.

[0051] Figure 2 is a schematic diagram showing the configuration of a video / image encoding device to which embodiments of the present disclosure can be applied. Hereinafter, the video encoding device may include an image encoding device.

[0052] Referring to Figure 2 , the encoding device 200 includes an image splitter 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter-frame predictor 221 and an intra-frame predictor 222. The residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 may further include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstruction block generator. According to an embodiment, the image splitter 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250, and the filter 260 may be constituted by at least one hardware component (e.g., an encoder chipset or a processor). Additionally, the memory 270 may include a decoded picture buffer (DPB) or may be constituted by a digital storage medium. The hardware component may further include the memory 270 as an internal / external component.

[0053] The image splitter 210 may split an input image (or picture or frame) input to the encoding device 200 into one or more processors. For example, the processors may be referred to as compile units (CUs). In this case, the compile units may be recursively split from the compile tree unit (CTU) or the largest compile unit (LCU) according to the quadtree binary tree ternary tree (QTBTTT) structure. For example, a compile unit may be split into a plurality of deeper compile units based on the quadtree structure, the binary tree structure, and / or the ternary structure. In this case, for example, the quadtree structure may be applied first, and then the binary tree structure and / or the ternary structure may be applied. Alternatively, the binary tree structure may be applied first. The compiling process according to the present disclosure may be performed based on the final compile units that are no longer split. In this case, the largest compile unit may be used as the final compile unit based on the compiling efficiency according to the image characteristics, or if necessary, the compile units may be recursively split into deeper compile units and the compile unit with the optimal size may be used as the final compile unit. Here, the compiling process may include processes of prediction, transformation, and reconstruction, which will be described later. As another example, the processor may further include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may be split or divided from the above-mentioned final compile units. The prediction unit may be a unit for sample prediction, and the transformation unit may be a unit for deriving transformation coefficients and / or a unit for deriving a residual signal from the transformation coefficients.

[0054] In some cases, the unit may be used interchangeably with terms such as block or region. In general, an M×N block may represent a set of samples or transformation coefficients composed of M columns and N rows. Samples may generally represent pixels or pixel values, which may represent only the pixel / pixel values of the luminance component, or only the pixel / pixel values of the chrominance component. Samples may be used as a term corresponding to a picture (or image) of pixels or picture elements.

[0055] In the encoding device 200, a prediction signal (prediction block, prediction sample array) output from the inter-frame predictor 221 or the intra-frame predictor 222 is subtracted from the input image signal (original block, original sample array) to generate a residual signal (residual block, residual sample array), and the generated residual signal is sent to the transformer 232. In this case, as shown in the figure, the unit in the encoder 200 for subtracting the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) may be referred to as the subtractor 231. The predictor may perform prediction on the block to be processed (hereinafter referred to as the current block) and generate a prediction block including the prediction samples of the current block. The predictor can determine whether to apply intra-frame prediction or inter-frame prediction in units of the current block or CU. As described later in the description of each prediction mode, the predictor may generate various information related to the prediction, such as prediction mode information, and send the generated information to the entropy encoder 240. The information about the prediction may be encoded in the entropy encoder 240 and output in the form of a bitstream.

[0056] The intra-frame predictor 222 may predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the samples referred to may be located near the current block or may be far from the current block. In intra-frame prediction, the prediction mode may include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes may include, for example, the DC mode and the planar mode. Depending on the level of detail of the prediction direction, the directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes may be used depending on the settings. The intra-frame predictor 222 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0057] The inter - frame predictor 221 can derive a prediction block for a current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. Here, in order to reduce the amount of motion information transmitted in the inter - frame prediction mode, the motion information can be predicted in units of blocks, sub - blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include inter - frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter - frame prediction, neighboring blocks can include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block can be the same or different. The temporal neighboring block can be referred to as a collocated reference block, a co - located CU (colCU), etc., and the reference picture including the temporal neighboring block can be referred to as a collocated picture (colPic). For example, the inter - frame predictor 221 can configure a motion information candidate list based on neighboring blocks, and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter - frame prediction can be performed based on various prediction modes. For example, in the skip mode and the merge mode, the inter - frame predictor 221 can use the motion information of neighboring blocks as the motion information of the current block. In the skip mode, different from the merge mode, the residual signal may not be sent. In the case of the motion vector prediction (MVP) mode, the motion vector of a neighboring block can be used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling a motion vector difference.

[0058] The predictor 220 can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra - frame prediction or inter - frame prediction to predict a block, but also apply both intra - frame prediction and inter - frame prediction simultaneously. This can be referred to as combined intra - inter prediction (CIIP). Additionally, the predictor can predict a block based on the intra - block copy (IBC) prediction mode or the palette mode. The IBC prediction mode or the palette mode can be used for content image / video compilation such as games, e.g., screen content coding (SCC). IBC basically performs prediction in the current picture, but can perform IBC similar to inter - frame prediction because the reference block is derived in the current picture. That is, IBC can use at least one of the inter - frame prediction techniques described in this disclosure. The palette mode can be regarded as an example of intra - frame compilation or intra - frame prediction. When the palette mode is applied, the sample values within the picture can be signaled based on information about the palette table and the palette index.

[0059] The prediction signal generated by a predictor (including the inter-frame predictor 221 and / or the intra-frame predictor 222) can be used to generate a reconstructed signal or to generate a residual signal. The transformer 232 can generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique can include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a karhunen-loève transform (KLT), a graph-based transform (GBT), or a conditional non-linear transform (CNT). Here, GBT represents a transform obtained from a graph when the relationship information between pixels is represented by the graph. CNT refers to a transform generated based on a prediction signal generated using all previously reconstructed pixels. Additionally, the transform processing can be applied to a square pixel block of the same size, or can be applied to a block having a variable size rather than a square shape.

[0060] Quantizer 233 may quantize the transform coefficients and send them to entropy encoder 240, and entropy encoder 240 may encode the quantized signals (information regarding the quantized transform coefficients) and output a bitstream. The information regarding the quantized transform coefficients may be referred to as residual information. Quantizer 233 may rearrange the block type quantized transform coefficients into a one-dimensional vector form based on the coefficient scan order, and generate information regarding the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. Information regarding the transform coefficients may be generated. Entropy encoder 240 may perform various encoding methods, such as, for example, exponential Golomb, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), etc. Entropy encoder 240 may encode together or separately the information required for video / image reconstruction other than the quantized transform coefficients (e.g., values of syntax elements, etc.). The encoded information (e.g., encoded video / image information) can be sent or stored in units of NAL (network abstraction layer) in the form of a bitstream. The video / image information may also include information regarding various parameter sets such as adaptive parameter set (APS), picture parameter set (PPS), sequence parameter set (SPS), or video parameter set (VPS). Additionally, the video / image information may further include general constraint information. In the present disclosure, the information and / or syntax elements sent / signaled from the encoding device to the decoding device may be included in the video / picture information. The video / image information may be encoded through the above encoding process and included in the bitstream. The bitstream may be sent through a network or may be stored in a digital storage medium. The network may include a broadcast network and / or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) for sending the signal output from entropy encoder 240 and / or a storage unit (not shown) for storing the signal may be included as internal / external elements of encoding device 200, and alternatively, the transmitter may be included in entropy encoder 240.

[0061] The quantized transform coefficients output from the quantizer 233 can be used to generate a prediction signal. For example, the residual signal (residual block or residual sample) can be reconstructed by applying dequantization and inverse transformation to the quantized transform coefficients by using the dequantizer 234 and the inverse transformer 235. The adder 250 adds the reconstructed residual signal to the prediction signal output from the inter-frame predictor 221 or the intra-frame predictor 222 to generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). If the block to be processed has no residual (such as in the case where the skip mode is applied), the predicted block can be used as the reconstructed block. The adder 250 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture through filtering as described below.

[0062] In addition, during picture encoding and / or reconstruction, luminance mapping and chrominance scaling (LMCS) can be applied.

[0063] The filter 260 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 260 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 270 (specifically, the DPB of the memory 270). The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filter 260 can generate various information related to filtering, and send the generated information to the entropy encoder 240, as described later in the description of various filtering methods. The information related to filtering can be encoded by the entropy encoder 240 and output in the form of a bitstream.

[0064] The modified reconstructed picture sent to the memory 270 can be used as a reference picture in the inter-frame predictor 221. When inter-frame prediction is applied by the encoding device, prediction mismatches between the encoding device 200 and the decoding device can be avoided, and the encoding efficiency can be improved.

[0065] The DPB of the memory 270 can store the modified reconstructed picture used as a reference picture in the inter-frame predictor 221. The memory 270 can store the motion information of the block from which the motion information in the current picture is derived (or encoded) and / or the motion information of the reconstructed blocks in the picture. The stored motion information can be sent to the inter-frame predictor 221 and used as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 270 can store the reconstructed samples of the reconstructed blocks in the current picture, and can transmit the reconstructed samples to the intra-frame predictor 222.

[0066] Figure 3 is a schematic diagram showing the configuration of a video / image decoding device to which embodiments of the present disclosure can be applied.

[0067] Reference Figure 3 Figure 3 , the decoding device 300 may include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-frame predictor 332 and an intra-frame predictor 331. The residual processor 320 may include a dequantizer 321 and an inverse transformer 322. According to an embodiment, the entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 may be constituted by hardware components (e.g., a decoder chipset or a processor). Additionally, the memory 360 may include a decoded picture buffer (DPB), or may be constituted by a digital storage medium. The hardware components may also include the memory 360 as an internal / external component.

[0068] When the input includes a bitstream of video / image information, the decoding device 300 may reconstruct an image corresponding to the processing of the video / image information in the Figure 2 encoding device. For example, the decoding device 300 may derive units / blocks based on the block segmentation-related information obtained from the bitstream. The decoding device 300 may use the processor applied in the encoding device to perform decoding. Therefore, the decoding processor may be, for example, a compilation unit, and may divide the compilation unit from a compilation tree unit or a largest compilation unit according to a quadtree structure, a binary tree structure, and / or a ternary tree structure. One or more transform units may be derived from the compilation unit. The reconstructed image signal decoded and output by the decoding device 300 may be reproduced by a reproduction device.

[0069] The decoding device 300 may receive in the form of a bitstream from Figure 2The signal output by the encoding device, and the received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can parse the bitstream to derive the information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information can also include information about various parameter sets such as adaptive parameter sets (APS), picture parameter sets (PPS), sequence parameter sets (SPS), or video parameter sets (VPS). Additionally, the video / image information can also include general constraint information. The decoding device can also decode the picture based on the information about the parameter sets and / or the general constraint information. The signaled / received information and / or syntax elements described later in this disclosure can be decoded through the decoding process and obtained from the bitstream. For example, the entropy decoder 310 decodes the information in the bitstream based on encoding methods such as exponential Golomb coding, CAVLC, or CABAC, and outputs the syntax elements required for image reconstruction and the quantization values of the transformed coefficients of the residuals. More specifically, the CABAC entropy decoding method can receive the bin (binary digit) corresponding to each syntax element in the bitstream, determine the context model using the information of the syntax element to be decoded, the decoding information of the block to be decoded, or the information of the symbols / bins decoded in the previous stage, and perform arithmetic decoding on the bin by predicting the occurrence probability of the bin according to the determined context model, and generate a symbol corresponding to the value of each syntax element. In this case, after determining the context model, the CABAC entropy decoding method can update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin. The information related to prediction among the information decoded by the entropy decoder 310 can be provided to the predictors (inter-frame predictor 332 and intra-frame predictor 331), and the residual values (i.e., the quantized transform coefficients and related parameter information) for which entropy decoding has been performed in the entropy decoder 310 can be input to the residual processor 320. The residual processor 320 can derive a residual signal (residual block, residual sample, residual sample array). Additionally, the information about filtering among the information decoded by the entropy decoder 310 can be provided to the filter 350. Furthermore, a receiver (not shown) for receiving the signal output by the encoding device can be further configured as an internal / external element of the decoding device 300, or the receiver can be a component of the entropy decoder 310. Additionally, the decoding device according to this disclosure can be referred to as a video / image / picture decoding device, and the decoding device can be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder can include the entropy decoder 310, and the sample decoder can include at least one of a dequantizer 321, an inverse transformer 322, an adder 340, a filter 350, a memory 360, an inter-frame predictor 332, and an intra-frame predictor 331.

[0070] The dequantizer 321 can dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 can rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement can be performed based on the coefficient scan order executed in the encoding device. The dequantizer 321 can perform dequantization on the quantized transform coefficients by using a quantization parameter (e.g., quantization step information) and obtain the transform coefficients.

[0071] The inverse transformer 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0072] The predictor can perform prediction on the current block and generate a prediction block including the prediction samples of the current block. The predictor can determine whether to apply intra prediction or inter prediction to the current block based on the information about prediction output from the entropy decoder 310, and can determine the specific intra / inter prediction mode.

[0073] The predictor 320 can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra prediction or inter prediction to predict a block, but also apply intra prediction and inter prediction simultaneously. This can be referred to as combined intra and inter prediction (CIIP). Additionally, the predictor can predict a block based on the intra block copy (IBC) prediction mode or the palette mode. The IBC prediction mode or the palette mode can be used for content image / video compilation such as games, e.g., screen content compilation (SCC). IBC basically performs prediction in the current picture, but IBC can be performed similar to inter prediction because a reference block is derived in the current picture. That is, IBC can use at least one of the inter prediction techniques described in the present disclosure. The palette mode can be regarded as an example of intra compilation or intra prediction. When the palette mode is applied, the sample values within the picture can be signaled based on the information about the palette table and the palette index.

[0074] The intra predictor 331 can predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the samples referred to can be located near the current block or can be far from the current block. In intra prediction, the prediction mode can include multiple non - directional modes and multiple directional modes. The intra predictor 331 can determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0075] The inter-frame predictor 332 can derive a prediction block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter-frame prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, neighboring blocks can include spatially neighboring blocks present in the current picture and temporally neighboring blocks present in the reference picture. For example, the inter-frame predictor 332 can configure a motion information candidate list based on neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter-frame prediction can be performed based on various prediction modes, and the information regarding the prediction can include information indicating the mode of inter-frame prediction for the current block.

[0076] The adder 340 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to a prediction signal (prediction block, prediction sample array) output from a predictor (including the inter-frame predictor 332 and / or the intra-frame predictor 331). If there is no residual for the block to be processed (e.g., when the skip mode is applied), the prediction block can be used as the reconstructed block.

[0077] The adder 340 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture, can be output through filtering as described below, or can be used for inter-frame prediction of the next picture.

[0078] In addition, luminance mapping and chrominance scaling (LMCS) can be applied during the picture decoding process.

[0079] The filter 350 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 350 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and store the modified reconstructed picture in the memory 360 (specifically, the DPB of the memory 360). The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0080] The (modified) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter - predictor 332. The memory 360 can store the motion information of the blocks from which the motion information in the current picture is derived (or decoded) and / or the motion information of the reconstructed blocks in the picture. The stored motion information can be sent to the inter - predictor 260 to be utilized as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 360 can store the reconstructed samples of the reconstructed blocks in the current picture and can transmit the reconstructed samples to the intra - predictor 331.

[0081] In the present disclosure, the embodiments described in the filter 260, the inter - predictor 221, and the intra - predictor 222 of the encoding device 200 can be the same as or respectively applied to correspond to the filter 350, the inter - predictor 332, and the intra - predictor 331 of the decoding device 300. The same content can also be applied to the inter - predictor 332 and the intra - predictor 331.

[0082] In the present disclosure, at least one of quantization / inverse quantization and / or transform / inverse transform can be omitted. When quantization / inverse quantization is omitted, the quantized transform coefficients can be referred to as transform coefficients. When transform / inverse transform is omitted, the transform coefficients can be referred to as coefficients or residual coefficients, or for the sake of uniformity of expression, can still be referred to as transform coefficients.

[0083] In the present disclosure, the quantized transform coefficients and the transform coefficients can be respectively referred to as transform coefficients and scaled transform coefficients. In this case, the residual information can include information about the transform coefficients, and the information about the transform coefficients can be signaled through the residual coding syntax. The transform coefficients can be derived based on the residual information (or the information about the transform coefficients), and the scaled transform coefficients can be derived by inverse - transforming (scaling) the transform coefficients. The residual samples can be derived based on inverse - transforming (transforming) the scaled transform coefficients. This can also be applied / expressed in other parts of the present disclosure.

[0084] Meanwhile, as described above, when performing video coding, prediction is performed to improve the compression efficiency. By doing so, a prediction block including the prediction samples of the current block can be generated as the block to be coded (i.e., the coding target block). Here, the prediction block includes the prediction samples in the spatial domain (or pixel domain). The prediction block is derived in the same way in both the encoding device and the decoding device, and the encoding device can signal the information about the residual between the original block and the prediction block (residual information) instead of the original sample values of the original block, thereby improving the image coding efficiency. The decoding device can derive a residual block including the residual samples based on the residual information, add the residual block and the prediction block to generate a reconstructed block including the reconstructed samples, and generate a reconstructed picture including the reconstructed block.

[0085] Residual information can be generated through a transform and quantization process. For example, an encoding device can derive a residual block between an original block and a predicted block, perform a transform process on residual samples (residual sample array) included in the residual block to derive transform coefficients, perform a quantization process on the transform coefficients to derive quantized transform coefficients, and signal relevant residual information (through a bitstream) to a decoding device. Here, the residual information can include value information such as the value information of the quantized transform coefficients, position information, transform technique, transform core, and quantization parameters. The decoding device can perform a dequantization / inverse transform process based on the residual information and derive residual samples (or a residual block). The decoding device can generate a reconstructed picture based on the predicted block and the residual block. In addition, for reference in inter-picture prediction of pictures for later reference, the encoding device can dequantize / inverse transform the quantized transform coefficients to derive a residual block, and generate a reconstructed picture based on this.

[0086] Intra prediction can refer to a prediction that generates prediction samples for a current block based on reference samples in a picture (hereinafter referred to as the current picture) to which the current block belongs. When intra prediction is applied to the current block, adjacent reference samples to be used for intra prediction of the current block can be derived. The adjacent reference samples of the current block can include a total of 2×nH samples adjacent to the left boundary of the current block of size nW×nH and adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2×nW samples adjacent to the upper right, and samples adjacent to the upper left of the current block. Alternatively, the adjacent reference samples of the current block can include multiple columns of vertically adjacent samples and multiple rows of horizontally adjacent samples. In addition, the adjacent reference samples of the current block can include a total of nH samples adjacent to the right boundary of the current block of size nW×nH, a total of nW samples adjacent to the lower boundary of the current block, and samples adjacent to the lower right of the current block.

[0087] However, some of the adjacent reference samples of the current block have not been decoded or may be unavailable. In this case, the decoder can construct adjacent reference samples to be used for prediction by replacing the unavailable samples with available samples. Alternatively, the adjacent reference samples to be used for prediction can be configured by interpolation of available samples.

[0088] When deriving adjacent reference samples, (i) prediction samples can be derived based on the average or interpolation of the adjacent reference samples of the current block, or (ii) prediction samples can be derived based on reference samples existing in a specific (prediction) direction with respect to the prediction samples in the adjacent reference samples of the current block. Case (i) can be referred to as a non-directional mode or non-angle mode, and case (ii) can be referred to as a directional mode or angle mode.

[0089] Alternatively, a predicted sample for a current block may be generated by interpolating between a first neighboring sample among neighboring reference samples that is in a prediction direction of an intra prediction mode for the current block and a second neighboring sample in a direction opposite to the prediction direction. The above may be referred to as linear interpolation intra prediction (LIP). In addition, a chrominance prediction sample may be generated based on luma samples using a linear model (LM). This may be referred to as the LM mode or the chrominance component LM (CCLM) mode.

[0090] Alternatively, a temporary predicted sample for a current block may be derived based on filtered neighboring reference samples, and a predicted sample for the current block may also be derived by weighted summing the temporary predicted sample and at least one reference sample derived according to an intra prediction mode among existing neighboring reference samples (i.e., unfiltered neighboring reference samples). The above may be referred to as position-dependent intra prediction (PDPC).

[0091] Alternatively, a reference sample line having the highest prediction accuracy among a plurality of neighboring reference sample lines of a current block is selected, and a predicted sample is derived using a reference sample in the prediction direction in the selected line. In this case, intra prediction coding may be performed by indicating (signaling) the reference sample line used to a decoding device. The above may be referred to as multi-reference line intra prediction or MRL-based intra prediction.

[0092] Alternatively, a current block is divided into vertical or horizontal sub-partitions and intra prediction is performed based on the same intra prediction mode, but neighboring reference samples may be derived and used on a sub-partition basis. That is, in this case, the intra prediction mode of the current block also applies to the sub-partitions, but in some cases, the intra prediction performance may be improved by deriving and using neighboring reference samples on a sub-partition basis. This prediction method may be referred to as intra prediction based on intra sub-partition (ISP).

[0093] The above intra prediction methods may be referred to as intra prediction types to distinguish them from intra prediction modes. Intra prediction types may be referred to by various terms, such as intra prediction techniques or additional intra prediction modes. For example, an intra prediction type (or an additional intra prediction mode, etc.) may include at least one of the above LIP, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP may be referred to as a normal intra prediction type. When the above specific intra prediction types are not applied, the normal intra prediction type may generally be applied, and prediction may be performed based on the above intra prediction mode. Meanwhile, if necessary, post-processing filtering may be performed on the derived predicted samples.

[0094] Specifically, the intra prediction process may include an intra prediction mode / type determination step, an adjacent reference sample derivation step, and a predicted sample derivation step based on the intra prediction mode / type. Additionally, if necessary, a post-filtering step may be performed on the derived predicted samples.

[0095] Figure 4 An example of a video / image encoding method based on intra prediction is illustrated.

[0096] Reference Figure 4 , the encoding device performs intra prediction S400 on the current block. The encoding device derives the intra prediction mode / type of the current block, derives the adjacent reference samples of the current block, and generates predicted samples in the current block based on the intra prediction mode / type and the adjacent reference samples. Here, the intra prediction mode / type determination, adjacent reference sample derivation, and predicted sample generation processes may be performed simultaneously, or one process may be performed before another process. The encoding device may determine the mode / type to be applied to the current block from among multiple intra prediction modes / types. The encoding device may compare the RD costs of the intra prediction modes / types and determine the best intra prediction mode / type for the current block.

[0097] Meanwhile, the encoding device may perform a predicted sample filtering process. Predicted sample filtering may be referred to as post-filtering. Some or all of the predicted samples may be filtered by the predicted sample filtering process. In some cases, the predicted sample filtering process may be omitted.

[0098] The encoding device generates residual samples for the current block based on the (filtered) predicted samples S410. The encoding device may compare the predicted samples in the original samples of the current block based on phase and derive the residual samples.

[0099] The encoding device may encode the image information including information about intra prediction (prediction information) and residual information about the residual samples S420. The prediction information may include intra prediction mode information and intra prediction type information. The encoding device is capable of outputting the encoded image information in the form of a bitstream. The output bitstream may be sent to the decoding device via a storage medium or a network.

[0100] The residual information may include a residual compilation syntax described later. The encoding device may transform / quantize the residual samples to derive quantized transform coefficients. The residual information may include information about the quantized transform coefficients.

[0101] Meanwhile, as described above, the encoding device may generate reconstructed pictures (including reconstructed samples and reconstructed blocks). To this end, the encoding device may derive (modified) residual samples by performing inverse quantization / inverse transformation on the quantized transform coefficients again. The reason for performing inverse quantization / inverse transformation again after transforming / quantizing the residual samples in this way is to derive the same residual samples as those derived in the decoding device described above. The encoding device may generate a reconstructed block including the reconstructed samples for the current block based on the prediction samples and the (modified) residual samples. A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, the in-loop filtering process may be further applied to the reconstructed picture.

[0102] Figure 5 FIG. illustrates an example of a video / image encoding method based on intra prediction.

[0103] The decoding device may perform operations corresponding to those performed by the encoding device.

[0104] The prediction information and the residual information may be obtained from the bitstream. The residual samples for the current block may be derived based on the residual information. Specifically, the transform coefficients may be derived by performing inverse quantization on the quantized transform coefficients derived based on the residual information, and the residual samples for the current block may be derived by performing inverse transformation on the transform coefficients.

[0105] Specifically, the decoding device may derive the intra prediction mode / type S500 of the current block based on the received prediction information (intra prediction mode / type information). The decoding device may derive the neighboring reference samples S510 of the current block. The decoding device generates the prediction samples S520 in the current block based on the intra prediction mode / type and the neighboring reference samples. In this case, the decoding device may perform a prediction sample filtering process. Prediction sample filtering may be referred to as post-filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering process. In some cases, the prediction sample filtering process may be omitted.

[0106] The decoding device generates the residual samples S530 for the current block based on the received residual information. The decoding device may generate the reconstructed samples for the current block based on the prediction samples and the residual samples, and may derive a reconstructed block S540 including the reconstructed samples. A reconstructed picture of the current picture may be generated based on the reconstructed block. As described above, the in-loop filtering process may be further applied to the reconstructed picture.

[0107] The intra prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) indicating whether the MPM (Most Probable Mode) is applied to the current block or whether the remaining mode is applied, and when the MPM is applied to the current block, the prediction mode information may further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be constituted by an MPM candidate list or an MPM list. In addition, when the MPM is not applied to the current block, the intra prediction mode information includes remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes other than the intra prediction mode candidates (MPM candidates). The decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

[0108] In addition, the intra prediction type information can be implemented in various forms. For example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information may include at least one of the following: reference sample line information (e.g., intra_luma_ref_idx), the reference sample line information indicating whether the MRL is applied to the current block and, if applied, which reference sample line is used; ISP flag information (e.g., intra_subpartitions_mode_flag), the ISP flag information indicating whether the ISP is applied to the current block; or ISP type information (e.g., intra_subpartitions_split_flag), the ISP type information indicating the split type of the subpartitions when the ISP is applied. In addition, the intra prediction type information may include an MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

[0109] The intra prediction mode information and / or the intra prediction type information may be encoded / decoded by the encoding / decoding methods described in the present disclosure. For example, the intra prediction mode information and / or the intra prediction type information may be encoded / decoded by entropy encoding (e.g., CABAC, CAVLC).

[0110] Figure 6 The intra prediction process is schematically illustrated.

[0111] Refer to Figure 6, as described above, the intra prediction process may include steps of determining an intra prediction mode / type, deriving adjacent reference samples, and performing intra prediction (generating prediction samples). The intra prediction process may be performed by the encoding device and the decoding device as described above. In the present disclosure, the compiling device may include an encoding device and / or a decoding device.

[0112] Reference Figure 6 , the compiling device determines the intra prediction mode / type S600.

[0113] The encoding device may determine an intra prediction mode / type to be applied to a current block from among the various intra prediction modes / types described above, and may generate prediction-related information. The prediction-related information may include intra prediction mode information indicating the intra prediction mode applied to the current block and / or intra prediction type information indicating the intra prediction type applied to the current block. The decoding device may determine the intra prediction mode / type to be applied to the current block based on the prediction-related information.

[0114] The intra prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) indicating whether the most probable mode (MPM) is applied to the current block or the remaining mode is applied, and when the MPM is applied to the current block, the prediction mode information may further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be constituted by an MPM candidate list or an MPM list. Additionally, when the MPM is not applied to the current block, the intra prediction mode information may further include remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes other than the intra prediction mode candidates (MPM candidates). The decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

[0115] In addition, the intra prediction type information can be implemented in various forms. For example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information may include at least one of the following: reference sample line information (e.g., intra_luma_ref_idx), which represents whether the MRL is applied to the current block and, if so, which reference sample line is used; ISP flag information (e.g., intra_subpartitions_mode_flag), which represents whether the ISP is applied to the current block; or ISP type information (e.g., intra_subpartitions_split_flag), which indicates the split type of the subpartition when the ISP is applied. In addition, the intra prediction type information may include an MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

[0116] For example, when intra prediction is applied, the intra prediction mode of neighboring blocks can be used to determine the intra prediction mode applied to the current block. For example, the compiling device can select one of the most probable mode (MPM) candidates in the MPM list derived based on additional candidate modes and / or the intra prediction modes of neighboring blocks (e.g., left and / or upper neighboring blocks) of the current block or select one of the remaining intra prediction modes not included in the MPM candidates (and the planar mode) based on the MPM residual information (residual intra prediction mode information). The MPM list can be configured to include or not include the planar mode as a candidate. For example, when the MPM list includes the planar mode as a candidate, the MPM list can have 6 candidates, and when the MPM list does not include the planar mode as a candidate, the MPM list can have 5 candidates. When the MPM list does not include the planar mode as a candidate, a non-planar flag (e.g., intra_luma_not_planar_flag) indicating whether the intra prediction mode of the current block is not the planar mode can be signaled. For example, the MPM flag can be signaled first, and when the value of the MPM flag is 1, the MPM index and the non-planar flag can be signaled. In addition, when the value of the non-planar flag is 1, the MPM index can be signaled. Here, the fact that the MPM list is configured not to include the planar mode as a candidate means that the planar mode is always considered an MPM rather than not considering the planar mode an MPM. Therefore, the flag (non-planar flag) is signaled first to check whether it is the planar mode.

[0117] For example, based on an MPM flag (e.g., intra_luma_mpm_flag), it can be indicated whether the intra prediction mode applied to the current block is among the MPM candidates (and the planar mode) or among the remaining modes. An MPM flag with a value of 1 can indicate that the intra prediction mode of the current block is within the MPM candidates (and the planar mode), while an MPM flag with a value of 0 can indicate that the intra prediction mode of the current block is not within the MPM candidates (and the planar mode). A non-planar flag with a value of 0 (e.g., intra_luma_not_planar_flag) can indicate that the intra prediction mode of the current block is the planar mode, and a non-planar flag with a value of 1 can indicate that the intra prediction mode of the current block is not the planar mode. The MPM index can be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information can be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information can indicate one of the remaining intra prediction modes not included in the MPM candidates (and the planar mode) among all the intra prediction modes by indexing in the order of the prediction mode numbers. The intra prediction mode can be the intra prediction mode of the luminance component (samples). Hereinafter, the intra prediction mode information can include at least one of an MPM flag (e.g., intra_luma_mpm_flag), a non-planar flag (e.g., intra_luma_not_planar_flag), an MPM index (e.g., mpm_idx or intra_luma_mpm_idx), or the remaining intra prediction mode information (rem_intra_luma_luma_mpm_mode or intra_luma_mpminder). In the present disclosure, the MPM list can be referred to by various terms, such as the MPM candidate list and candModeList.

[0118] When applying MIP to the current block, a separate MPM flag (e.g., intra_mip_mpm_flag), an MPM index (e.g., intra_mip_mpm_idx), and the remaining intra prediction mode information (e.g., intra_mip_mpm_remainder) for MIP can be signaled, and the non-planar flag can not be signaled.

[0119] In other words, generally, when performing block segmentation of an image, the current block to be coded and the neighboring blocks have similar image characteristics. Therefore, it is highly likely that the current block and the neighboring blocks have the same or similar intra prediction modes. Thus, the encoder can use the intra prediction mode of the neighboring blocks to code the intra prediction mode of the current block.

[0120] The encoding device can build a list of the most probable modes (MPMs) for the current block. The MPM list can be referred to as the MPM candidate list. Here, the MPM can refer to a mode that is used to improve the encoding efficiency by considering the similarity between the current block and neighboring blocks during intra prediction mode encoding. As described above, the MPM list can be built to include the planar mode, or can be built to exclude the planar mode. For example, when the MPM list includes the planar mode, the number of candidates in the MPM list can be 6. When the MPM list does not include the planar mode, the number of candidates in the MPM list can be 5.

[0121] The encoding device can perform prediction based on various intra prediction modes and can determine the optimal intra prediction mode based on rate distortion optimization (RDO) according to it. In this case, the encoding device can determine the optimal intra prediction mode by using only the MPM candidates configured in the MPM list and the planar mode, or by further using the remaining intra prediction modes as well as the MPM candidates and the planar mode configured in the MPM list. Specifically, for example, if the intra prediction type of the current block is a specific type other than the normal intra prediction type (e.g., LIP, MRL, or ISP), the encoding device can determine the optimal intra prediction mode by considering only the MPM candidates and the planar mode as the intra prediction mode candidates for the current block. That is, in this case, the intra prediction mode of the current block can be determined only from the MPM candidates and the planar mode, and in this case, the encoding / signaling of the MPM flag can be not performed. In this case, the decoding device can infer that the MPM flag is 1 without signaling the MPM flag separately.

[0122] Meanwhile, generally, when the intra prediction mode of the current block is not the planar mode but one of the MPM candidates in the MPM list, the encoding device generates an MPM index (mpm idx) indicating one of the MPM candidates. When the intra prediction mode of the current block is not included in the MPM list, the encoding device generates MPM remainder information (remaining intra prediction mode information) indicating the mode that is the same as the intra prediction mode of the current block among the remaining intra prediction modes not included in the MPM list (and the planar mode). The MPM remainder information can include, for example, the intra_luma_mpm_remainder syntax element.

[0123] The decoding device obtains intra prediction mode information from the bitstream. As described above, the intra prediction mode information may include at least one of an MPM flag, a non-planar flag, an MPM index, and MPM residual information (residual intra prediction mode information). The decoding device may construct an MPM list. The construction of the MPM list is the same as that constructed in the encoding device. That is, the MPM list may include the intra prediction modes of neighboring blocks, or may further include specific intra prediction modes according to a predetermined method.

[0124] The decoding device may determine the intra prediction mode of the current block based on the MPM list and the intra prediction mode information. For example, when the value of the MPM flag is 1, the decoding device may derive the planar mode as the intra prediction mode of the current block (based on the non-planar flag), or may derive the candidate indicated by the MPM index among the MPM candidates in the MPM list as the intra prediction mode of the current block. Here, the MPM candidates may only represent the candidates included in the MPM list, or may include not only the candidates included in the MPM list, but also the planar mode applicable when the value of the MPM flag is 1.

[0125] As another example, when the value of the MPM flag is 0, the decoding device may derive the intra prediction mode indicated by the residual intra prediction mode information (which may be referred to as mpm residual information) among the residual intra prediction modes not included in the MPM list and the planar mode as the intra prediction mode of the current block. Meanwhile, as another example, when the intra prediction type of the current block is a specific type (such as LIP, MRL, or ISP, etc.), the decoding device may derive the candidate indicated by the planar mode or the MPM flag in the MPM list as the intra prediction mode of the current block without parsing / decoding / checking the MPM flag.

[0126] The compiling device derives adjacent reference samples of the current block (S610). When intra prediction is applied to the current block, adjacent reference samples to be used for the intra prediction of the current block may be derived. The adjacent reference samples of the current block may include samples adjacent to the left boundary of the current block with a size of nW x nH and a total of 2 x nH samples adjacent to the lower left of the current block, samples adjacent to the upper boundary of the current block and a total of 2 x nW samples adjacent to the upper right, and samples adjacent to the upper left of the current block. Alternatively, the adjacent reference samples of the current block may include multiple columns of adjacent samples above and multiple rows of adjacent samples to the left. In addition, the adjacent reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block with a size of nW x nH, a total of nW samples adjacent to the lower boundary of the current block, and samples adjacent to the lower right of the current block.

[0127] On the other hand, when applying MRL (i.e., when the value of the MRL index is greater than 0), the adjacent reference samples may be located on lines 1 to 2 instead of line 0 adjacent to the current block on the left / upper side, and in this case, the number of adjacent reference samples can be further increased. Meanwhile, when applying ISP, the adjacent reference samples can be derived in units of sub-partitions.

[0128] The encoding device derives a predicted sample S620 by performing intra-frame prediction on the current block. The encoding device can derive the predicted sample based on the intra-frame prediction mode / type and adjacent samples. The encoding device can derive reference samples according to the intra-frame prediction mode of the current block in the adjacent reference samples of the current block, and can derive the predicted sample of the current block based on the reference samples.

[0129] In addition, according to an embodiment, the block differential pulse code modulation (BDPCM) technique can be used. BDPCM can also be referred to as RDPCM (residual difference pulse code modulation based on a quantized residual block).

[0130] When predicting a block by applying BDPCM, the reconstructed samples can be used to predict the rows or columns of the block line by line. In this case, the reference samples used can be unfiltered samples. The BDPCM direction can indicate whether to use the vertical direction or the horizontal direction for prediction. That is, when applying BDPCM, the vertical direction or the horizontal direction can be selected as the BDPCM direction, and prediction can be performed in the BDPCM direction. The prediction error can be quantized in the spatial domain, and the samples can be reconstructed by adding the inverse-quantized prediction error to the prediction (i.e., the predicted sample). The prediction error can refer to the residual. As an alternative to this BDPCM, a quantized residual domain BDPCM can be proposed, and the prediction direction or signaling can be the same as that of the BDPCM applied to the spatial domain. That is, the quantization coefficients themselves can be accumulated like DPCM (Delta Pulse Code Modulation) through the quantized residual domain BDPCM, and then the residual is reconstructed through inverse quantization. Therefore, in the sense of applying DPCM in the residual encoding state, the quantized residual domain BDPCM can be used. The quantized residual domain used below is a domain in which the residual derived from the prediction is quantized without being transformed, which means a domain for quantizing residual samples. For example, the quantized residual domain can include quantized residuals (or quantized residual coefficients) to which transform skip is applied, that is, the transform is skipped but quantization is applied to the residual samples. Or, for example, the quantized residual domain can include quantized transform coefficients.

[0131] For a block of size M×N, it can be assumed that the residual r(i,j) (0 ≤ i ≤ M−1, 0 ≤ j ≤ N−1) is derived by performing intra prediction in the horizontal direction (copying the left adjacent sample line to the prediction block line by line) using the unfiltered samples in the left or upper boundary samples (i.e., the left adjacent samples or the upper adjacent samples), or obtained by performing intra prediction in the vertical direction (copying the upper adjacent sample line to the prediction block line by line). Here, M can represent the row or height, and N can represent the column or width. Also, it can be assumed that the quantized value of the residual r(i,j) is Q(r(i,j)) (0 ≤ i ≤ M−1, 0 ≤ j ≤ N−1). Here, the residual refers to the difference between the original block and the prediction block values.

[0132] Then, if BDPCM is applied to the quantized residual samples, a modified array of M×N with the following configuration can be derived as the configuration of M×N

[0133] For example, when vertically BDPCM is signaled (i.e., when vertical BDPCM is applied), it can be derived as in the following equation

[0134] [Equation 1]

[0135]

[0136] That is, for example, when vertical BDPCM is applied, the encoding device can perform vertical intra prediction based on the upper adjacent samples, and can derive the quantized residual samples for the current block as in the above Equation 1. Referring to Equation 1 above, the quantized residual samples of the rows other than the first row of the current block can be derived as the difference between the quantized value at the corresponding position and the quantized value at the position of the previous row of the corresponding position (i.e., the upper adjacent position of the corresponding position).

[0137] In addition, when similarly applied to horizontal prediction (i.e., when BDPCM in the horizontal direction is applied), the residual quantization samples can be derived as in the following equation.

[0138] [Equation 2]

[0139]

[0140] That is, for example, when horizontal BDPCM is applied, the encoding device can perform horizontal intra prediction based on the left adjacent samples, and can derive the quantized residual samples for the current block as in the above Equation 2. Referring to Equation 2 above, the quantized residual samples of the columns other than the first column of the current block can be derived as the difference between the quantized value at the corresponding position and the quantized value at the position of the previous column of the corresponding position (i.e., the left adjacent position of the corresponding position).

[0141] Quantized residual samples can be sent to a decoding device.

[0142] In the decoding device, the above operations can be performed in reverse to derive Q(r(i,j)) (0 ≤ i ≤ M - 1, 0 ≤ j ≤ N - 1).

[0143] The following formula can be applied to vertical prediction.

[0144] [Equation 3]

[0145]

[0146] In addition, the following formula can be applied to horizontal prediction.

[0147] [Equation 4]

[0148]

[0149] The dequantized quantization residual (Q -1 (Q(r i，j ))) is added to the intra - prediction value within the block to derive the reconstructed sample value.

[0150] The main advantage of this technique is that inverse BDPCM can be performed by simply adding predictors even during or after parsing the coefficients.

[0151] As described above, BDPCM can be applied to the quantization residual domain, and the quantization residual domain can include quantization residuals (or quantization residual coefficients), in which case transform skip is applied to the residuals. That is, when BDPCM is applied, the transform can be skipped and quantization can be applied to the residual samples. Alternatively, the quantization residual domain can include quantized transform coefficients. A flag indicating whether BDPCM is available can be signaled at the sequence level (SPS), and this flag can be signaled only when the transform skip mode is enabled in the SPS. This flag can be referred to as the BDPCM enable flag or the SPS BDPCM enable flag.

[0152] When BDPCM is applied, intra - prediction for the entire block can be performed by sample replication according to a prediction direction similar to the intra - prediction direction (e.g., vertical prediction or horizontal prediction). The residual, which is the difference between the original block and the predicted block, is quantized by skipping the transform, and the delta value can be compiled, i.e., the difference between the quantized residual and the predictor in the horizontal or vertical direction (i.e., the quantized residual in the horizontal or vertical direction).

[0153] If BDPCM is applicable, when the CU size is less than or equal to the MaxTsSize (maximum transform skip block size) of the luma samples and the CU is compiled using intra prediction, the flag information can be sent at the CU level. The flag information can be referred to as the BDPCM flag. Here, the MaxTsSize can refer to the maximum block size that allows the transform skip mode. The flag information can indicate whether traditional intra compilation or BDPCM is applied. When BDPCM is applied, the BDPCM prediction direction flag indicating whether the prediction direction is horizontal or vertical can be sent. The BDPCM prediction direction flag can be referred to as the BDPCM direction flag. Thereafter, the unfiltered reference samples can be used to predict the block through the traditional horizontal or vertical intra prediction process. In addition, the residuals can be quantized, and the difference between each quantized residual and its predictor (e.g., between the residuals quantized in the horizontal or vertical direction according to the BDPCM prediction direction) can be compiled.

[0154] Meanwhile, as described later, the above BDPCM is described in the standard document format.

[0155] For example, as shown in the following table, the syntax elements for the above BDPCM enable flag and the semantics for the syntax elements are shown.

[0156] [Table 1]

[0157]

[0158] [Table 2]

[0159]

[0160] Table 1 signals the sps_bdpcm_enabled_flag and sps_bdpcm_chroma_enabled_flag in the Sequence Parameter Set (SPS). When the syntax element sps_bdpcm_enabled_flag is 1, it can indicate the existence of flag information in the coded luma unit that represents whether BDPCM is applied to the coded luma unit where intra prediction is performed, namely "intra_bdpcm_luma_flag". When the syntax element sps_bdpcm_chroma_enabled_flag is 1, it can indicate the existence of flag information in the coded chroma unit that represents whether BDPCM is applied to the coded chroma unit where intra prediction is performed, namely "intra_bdpcm_chroma_flag". The syntax elements sps_bdpcm_enabled_flag and sps_bdpcm_chroma_enabled_flag can be syntax elements for BDPCM enable flags. In addition, when the syntax element "sps_bdpcm_enabled_flag" does not exist, its value can be regarded as 0. In addition, when the syntax element "sps_bdpcm_chroma_enabled_flag" does not exist, its value can be regarded as 0.

[0161] In addition, for example, the syntax elements for BDPCM flags and BDPCM direction flags as described above can be signaled separately for the luma component and the chroma component. For example, the coded unit syntax including the syntax elements and the semantics for the syntax elements can be represented as in the following table.

[0162] [Table 3]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170]

[0171] [Table 4]

[0172]

[0173] As described above, the syntax element intra_bdpcm_luma_flag in Table 3 can indicate whether BDPCM is applied to the current luma block, and intra_bdpcm_chroma_flag can indicate whether BDPCM is applied to the current luma block or the current chroma block. For example, when the value of intra_bdpcm_luma_flag or intra_bdpcm_chroma_flag is 1, the transform for the corresponding coded block can be skipped, and the prediction mode for the coded block can be set in the horizontal or vertical direction by intra_bdpcm_luma_dir_flag or intra_bdpcm_chroma_dir_flag indicating the prediction direction. When intra_bdpcm_luma_flag or intra_bdpcm_chroma_flag does not exist, it can be inferred that the value of intra_bdpcm_luma_flag or intra_bdpcm_chroma_flag is equal to 0.

[0174] In addition, for example, when the value of intra_bdpcm_luma_dir_flag or intra_bdpcm_chroma_dir_flag indicating the prediction direction is 0, intra_bdpcm_luma_dir_flag or intra_bdpcm_chroma_dir_flag can indicate that the BDPCM prediction direction is the horizontal direction, and when the value of intra_bdpcm_luma_dir_flag or intra_bdpcm_chroma_dir_flag is 1, intra_bdpcm_luma_dir_flag or intra_bdpcm_chroma_dir_flag can indicate that the BDPCM prediction direction is the vertical direction.

[0175] Meanwhile, intra_bdpcm_luma_flag can indicate the syntax element of the BDPCM luma flag for the current luma block, intra_bdpcm_chroma_flag can indicate the syntax element of the BDPCM chroma flag for the current chroma block, intra_bdpcm_luma_dir_flag can indicate the syntax element of the BDPCM luma direction flag for the current luma block, and intra_bdpcm_chroma_dir_flag can indicate the syntax element of the BDPCM chroma direction flag for the current chroma block.

[0176] In addition, in the case of applying BDPCM, an example of the dequantization process can be represented as shown in the following table.

[0177] [Table 5]

[0178]

[0179]

[0180] In addition, in the case of applying BDPCM, an example of the dequantization process can be represented as shown in the following table.

[0181] [Table 6]

[0182]

[0183]

[0184]

[0185]

[0186] Referring to Table 5 or Table 6, when the value of bdpcm_flag is 1, the inverse quantization residual value d[x][y] can be derived based on the intermediate variable dz[x][y]. Here, x is the horizontal coordinate that increases from left to right, y is the vertical coordinate that increases from top to bottom, and the position in the two-dimensional block can be represented as (x, y). In addition, when the upper left position of the block is set to (0, 0), the position in the two-dimensional block indicates the (x, y) position.

[0187] For example, when the value of bdpcm_dir_flag is 0, that is, when horizontal BDPCM is applied, when x is 0, the variable dz[x][y] can be TransCoeffLevel[xTby][yTby][cIdx][x][y], and when x is not 0, dz[x][y] can be derived based on dz[x - 1][y] + dz[x][y]. That is, when horizontal BDPCM (the value of bdpcm_dir_flag is 0) is applied, the variable dz[x][y] of the sample located in the first column (where x is 0) is derived as TransCoeffLevel[xTby][yTby][cIdx][x][y] derived based on the residual information of the sample, and the variable dz[x][y] of the sample located in the columns other than the first column (where x is not 0) is derived as the sum of dz[x - 1][y] of the left adjacent sample of the sample and dz[x][y] of the sample. Here, dz[x][y] of the sample added to dz[x - 1][y] can be derived based on the residual information for the sample sent by the signal.

[0188] In addition, for example, when the value of bdpcm_dir_flag is 1, that is, when vertical BDPCM is applied, the variable dz[x][y] is derived based on dz[x][y - 1]+dz[x][y]. That is, when vertical BDPCM (the value of bdpcm_dir_flag is 1) is applied, the variable dz[x][y] of the samples in the first row where y is 0 is derived as TransCoeffLevel[xTby][yTby][cIdx][x][y] derived based on the residual information of the samples, and the variable dz[x][y] of the samples in the rows other than the first row where y is not 0 is derived as the sum of dz[x][y - 1] of the upper adjacent sample of the sample and dz[x][y] of the sample. Here, the dz[x][y] of the sample added to dz[x][y - 1] can be derived based on the residual information of the sample signaled.

[0189] As described above, the residual at a specific position can be derived based on the sum of the residual at a previous position (i.e., left or up) in the horizontal or vertical direction and the received value as the residual information of the specific position. This is because, when BDPCM is applied, the difference between the residual sample value at a specific position (x, y) and the residual sample value at a previous position (i.e., (x - 1, y) or (x, y - 1)) in the horizontal or vertical direction is signaled as the residual information.

[0190] As described above, information about BDPCM can be signaled, but in the present disclosure, other embodiments for signaling information about BDPCM are proposed. For example, according to the existing video standard, since BDPCM for only luminance blocks can be performed in YUV 420 and BDPCM for both luminance blocks and chrominance blocks can be performed in YUV 444, as shown in the table above, the sps_bdpcm_enabled_flag as a syntax element for the BDPCM enable flag for luminance blocks and the sps_bdpcm_chroma_enabled_flag as a syntax element for the BDPCM enable flag for chrominance blocks can be signaled respectively in the sequence parameter set (SPS) syntax. Specifically, the BDPCM enable flag for chrominance blocks can be signaled only when BDPCM is enabled for luminance blocks and the chroma format of the image is YUV 444 (i.e., when chroma_format_idc = 3).

[0191] Different from the above, the present disclosure presents embodiments for controlling whether to enable BDPCM for both luminance blocks and chrominance blocks based on a flag. For example, in the proposed embodiments, as shown in Table 7 to be described later, only one syntax element sps_bdpcm_enabled_flag for whether to enable BDPCM can be sent in the SPS syntax, and by doing so, it can be derived whether BDPCM is enabled / disabled for both luminance blocks and chrominance blocks. According to this embodiment, it is possible to determine whether to enable BDPCM for luminance blocks and chrominance blocks in an image through one syntax element, and by doing so, the bit amount for BDPCM can be reduced, and the overall encoding efficiency can be improved.

[0192] [Table 7]

[0193]

[0194] [Table 8]

[0195]

[0196] For example, referring to Table 8, when sps_bdpcm_enabled_flag is 1, it can mean that BDPCM is enabled for both luminance blocks and chrominance blocks, while when sps_bdpcm_enabled_flag is 0, it can mean that BDPCM is not enabled for both luminance blocks and chrominance blocks. That is to say, for example, when the syntax element sps_bdpcm_enabled_flag is 1, it can indicate that BDPCM is enabled in the coding unit (including the luminance component and the chrominance component) where intra prediction is performed, while when the syntax element sps_bdpcm_enabled_flag is 0, it can indicate that BDPCM is not enabled in the coding unit where intra prediction is performed. That is to say, for example, when the syntax element sps_bdpcm_enabled_flag is 1, it can indicate that intra_bdpcm_luma_flag and intra_bdpcm_chroma_flag exist in the coding unit, while when the syntax element sps_bdpcm_enabled_flag is 0, it can indicate that intra_bdpcm_luma_flag and intra_bdpcm_chroma_flag do not exist in the coding unit. intra_bdpcm_luma_flag and intra_bdpcm_chroma_flag can be represented as intra_bdpcm_flag.

[0197] Meanwhile, the flag for enabling BDPCM can be sent not only from the SPS syntax exemplified above, but also from the Adaptive Parameter Set (APS) syntax, Picture Parameter Set (PPS) syntax, Video Parameter Set (VPS) syntax, Decoding Parameter Set (DPS) syntax, Picture Header syntax, or Slice Header syntax.

[0198] In addition, in the proposed embodiment, the semantics of the syntax element sps_bdpcm_enabled_flag can be changed as shown in Table 8.

[0199] In addition, in this embodiment, since the enabling of BDPCM for luma blocks and chroma blocks is controlled at once by the syntax element sps_bdpcm_enabled_flag, the compilation unit syntax according to this embodiment can be as shown in the following table.

[0200] [Table 9]

[0201]

[0202]

[0203]

[0204]

[0205]

[0206]

[0207]

[0208]

[0209] In addition, the present disclosure proposes another embodiment for signaling information about BDPCM. For example, the present disclosure proposes an embodiment for controlling the enabling of BDPCM for both luma blocks and chroma blocks regardless of the chroma format of the image. According to this embodiment, information about whether to enable BDPCM for luma blocks and information about whether to enable BDPCM for chroma blocks can be sent separately, regardless of the chroma format of the image. According to this embodiment, regardless of the chroma format of the image, a BDPCM chroma enable flag indicating whether to enable BDPCM for chroma blocks in the image can be signaled, and by doing so, the complexity of BDPCM can be reduced and the overall compilation efficiency can be improved.

[0210] For example, in the proposed embodiment, if the transform skip mode is enabled (i.e., if sps_transform_skip_enabled_flag is 1), as shown in Table 10 which will be described later, the syntax elements sps_bdpcm_enabled_flag for whether BDPCM for luma blocks is enabled and sps_bdpcm_chroma_enabled_flag for whether BDPCM for chroma blocks is enabled can be sent from the SPS syntax.

[0211] [Table 10]

[0212]

[0213] [Table 11]

[0214]

[0215] For example, if sps_bdpcm_enabled_flag is 1, it can mean that BDPCM is enabled for luma blocks, while if sps_bdpcm_enabled_flag is 0, it can mean that BDPCM is not enabled for luma blocks. That is to say, for example, if the syntax element sps_bdpcm_enabled_flag is 1, it can indicate that BDPCM is enabled in the luma coding unit where intra prediction is performed, and if the syntax element sps_bdpcm_enabled_flag is 0, it can indicate that BDPCM is not enabled in the luma coding unit where intra prediction is performed. That is to say, for example, if the syntax element sps_bdpcm_enabled_flag is 1, it can indicate that intra_bdpcm_luma_flag exists in the coding unit, while if the syntax element sps_bdpcm_enabled_flag is 0, it can indicate that intra_bdpcm_luma_flag does not exist in the coding unit.

[0216] In addition, for example, if the sps_bdpcm_chroma_enabled_flag is 1, it may mean that BDPCM is enabled for chroma blocks, and if the sps_bdpcm_chroma_enabled_flag is 0, it may mean that BDPCM is not enabled for chroma blocks. That is to say, for example, if the syntax element sps_bdpcm_chroma_enabled_flag is 1, it may indicate that BDPCM is enabled in the chroma coding unit where intra prediction is performed, and if the syntax element sps_bdpcm_chroma_enabled_flag is 0, it may indicate that BDPCM is not enabled in the chroma coding unit where intra prediction is performed. That is to say, for example, if the syntax element sps_bdpcm_chroma_enabled_flag is 1, it may indicate that intra_bdpcm_chroma_flag exists in the coding unit, and if the syntax element sps_bdpcm_enabled_flag is 0, it may indicate that intra_bdpcm_chroma_flag does not exist in the coding unit.

[0217] Meanwhile, the flag for whether to enable BDPCM can be sent not only from the SPS syntax exemplified above, but also from the Adaptive Parameter Set (APS) syntax, the Picture Parameter Set (PPS) syntax, the Video Parameter Set (VPS) syntax, the Decoding Parameter Set (DPS) syntax, the Picture Header syntax, or the Slice Header syntax.

[0218] In addition, in the proposed embodiment, the semantics for the syntax element sps_bdpcm_enabled_flag and the syntax element sps_bdpcm_chroma_enabled_flag may be changed as shown in Table 11.

[0219] In addition, the present disclosure proposes another embodiment for signaling information about BDPCM. For example, the present disclosure proposes an embodiment for controlling whether to enable BDPCM for both luma blocks and chroma blocks regardless of the chroma format of the image. According to this embodiment, information about whether to enable BDPCM for luma blocks and information about whether to enable BDPCM for chroma blocks can be sent separately regardless of the chroma format of the image, and information about whether to enable BDPCM for chroma blocks can be sent only when BDPCM is enabled for luma blocks. According to this embodiment, regardless of the chroma format of the image, a BDPCM enable flag indicating whether to enable BDPCM for luma blocks and chroma blocks in the image can be signaled, and by doing so, the complexity of BDPCM can be reduced, and the overall coding efficiency can be improved.

[0220] For example, in the proposed embodiment, if the transform skip mode is enabled (i.e., if sps_transform_skip_enabled_flag is 1), as shown in Table 12 which will be described later, the syntax element sps_bdpcm_enabled_flag indicating whether BDPCM for luma blocks is enabled can be sent, and if BDPCM is enabled for luma blocks (i.e., if sps_bdpcm_enabled_flag is 1), the syntax element sps_bdpcm_chroma_enabled_flag indicating whether BDPCM for chroma blocks is enabled can be sent from the SPS syntax.

[0221] [Table 12]

[0222]

[0223] [Table 13]

[0224]

[0225]

[0226] For example, if sps_bdpcm_enabled_flag is 1, it can mean that BDPCM is enabled for luma blocks, and if sps_bdpcm_enabled_flag is 0, it can mean that BDPCM is not enabled for luma blocks. That is, for example, if the syntax element sps_bdpcm_enabled_flag is 1, it can indicate that BDPCM is enabled in the luma coding unit where intra prediction is performed, and if the syntax element sps_bdpcm_enabled_flag is 0, it can indicate that BDPCM is not enabled in the luma coding unit where intra prediction is performed. That is, for example, if the syntax element sps_bdpcm_enabled_flag is 1, it can indicate that intra_bdpcm_luma_flag exists in the coding unit, and if the syntax element sps_bdpcm_enabled_flag is 0, it can indicate that intra_bdpcm_luma_flag does not exist in the coding unit.

[0227] In addition, for example, if the sps_bdpcm_chroma_enabled_flag is 1, it may mean that BDPCM is enabled for chroma blocks, and if the sps_bdpcm_chroma_enabled_flag is 0, it may mean that BDPCM is not enabled for chroma blocks. That is to say, for example, if the syntax element sps_bdpcm_chroma_enabled_flag is 1, it may indicate that BDPCM is enabled in the chroma coding unit where intra prediction is performed, and if the syntax element sps_bdpcm_chroma_enabled_flag is 0, it may indicate that BDPCM is not enabled in the chroma coding unit where intra prediction is performed. That is to say, for example, if the syntax element sps_bdpcm_chroma_enabled_flag is 1, it may indicate that intra_bdpcm_chroma_flag exists in the coding unit, and if the syntax element sps_bdpcm_enabled_flag is 0, it may indicate that intra_bdpcm_chroma_flag does not exist in the coding unit.

[0228] Meanwhile, the flag for whether to enable BDPCM can be sent not only from the SPS syntax exemplified above, but also from the Adaptive Parameter Set (APS) syntax, Picture Parameter Set (PPS) syntax, Video Parameter Set (VPS) syntax, Decoding Parameter Set (DPS) syntax, Picture Header syntax, or Slice Header syntax.

[0229] In addition, the present disclosure presents another embodiment for signaling information about BDPCM. For example, in addition to the above embodiments, the present disclosure also presents an embodiment for performing the processes to be described later. For example, according to this embodiment, BDPCM can be enabled for both luma blocks and chroma blocks in the SPS syntax, VPS syntax, DPS syntax, picture header syntax, or slice header syntax, and if a specific condition for performing BDPCM is satisfied, intra_bdpcm_chroma_flag and intra_bdpcm_chroma_dir_flag are not sent in the CU syntax or TU syntax, and the value of intra_bdpcm_chroma_flag can be derived as the value of infra_bdpcm_luma_flag, and the value of intra_bdpcm_chroma_dir_flag can be derived as the value of intra_bdpcm_luma_dir_flag. Here, for example, the specific condition can be a case where the tree type is a binary tree and / or the width and height of the current block are all less than the maximum size of the defined transform skip block (i.e., in the case of cbWidth <= MaxTsSize && cbHeight <= MaxTsSize).

[0230] In addition, for example, according to this embodiment, if a specific condition for performing BDPCM is satisfied, intra_bdpcm_chroma_flag may not be sent, and the value of intra_bdpcm_chroma_flag can be derived as the value of intra_bdpcm_luma_flag. This means that in the case of coding the luma block of the current block in BDPCM mode, the chroma block of the current block is coded in BDPCM mode without sending an additional syntax element (i.e., intra_bdpcm_chroma_flag). However, in the above embodiment, intra_bdpcm_chroma_dir_flag can have a different value independent of intra_bdpcm_luma_dir_flag. That is, in the above embodiment, intra_bdpcm_chroma_dir_flag for the current block can be sent.

[0231] As another example, if both intra_bdpcm_luma_flag and intdra_bdpcm_chroma_flag for the current block are 1 when specific conditions for enabling BDPCM are met, intra_bdpcm_chroma_dir_flag may not be sent, and the value of intra_bdpcm_chroma_dir_flag may be derived as the value of intra_bdpcm_luma_dir_flag.

[0232] In addition, the present disclosure presents another embodiment for signaling information regarding BDPCM. For example, in addition to one of the above-described embodiments in the present disclosure, the present disclosure also presents an embodiment for performing the processes described later.

[0233] For example, according to this embodiment, when BDPCM for chroma blocks is enabled based on intra_bdpcm_enabled_flag or intra_bdpcm_chroma_enabled_flag in the high-level syntax (e.g., SPS syntax, VPS syntax, DPS syntax, picture header syntax, or slice header syntax) and the tree type is a single tree, intra_bdpcm_chroma_flag and intra_bdpcm_chroma_dir_flag for each chroma block (Cb chroma block and Cr chroma block) are not separately sent in the CU syntax or TU syntax, and intra_bdpcm_chroma_flag and intra_bdpcm_chroma_dir_flag for the Cb chroma block and Cr chroma block may be sent. That is, if the value of the sent intra_bdpcm_chroma_flag is 1, it means that both the Cb chroma block and Cr chroma block of the current block are coded in BDPCM mode, and if the value of the sent intra_bdpcm_chroma_flag is 0, it means that neither the Cb chroma block nor the Cr chroma block of the current block is coded in BDPCM mode. Further, if the value of intra_bdpcm_chroma_dir_flag is 0, it means that the BDPCM prediction direction for the Cb chroma block and Cr chroma block of the current block is the horizontal direction, and if the value of intra_bdpcm_chroma_dir_flag is 1, it means that the BDPCM prediction direction for the Cb chroma block and Cr chroma block of the current block is the vertical direction.

[0234] Alternatively, for example, according to this embodiment, when BDPCM for chroma blocks is enabled based on intra_bdpcm_enabled_flag or intra_bdpcm_chroma_enabled_flag in high-level syntax (such as SPS syntax, VPS syntax, DPS syntax, picture header syntax, or slice header syntax) and the tree type is a single tree, the intra_bdpcm_chroma_flag for each chroma block (Cb chroma block and Cr chroma block) may not be sent separately in the CU syntax or TU syntax, and the intra_bdpcm_chroma_flag for the Cb chroma block and Cr chroma block may be sent. That is, if the value of the sent intra_bdpcm_chroma_flag is 1, it means that both the Cb chroma block and Cr chroma block of the current block are coded in the BDPCM mode, and if the value of the sent intra_bdpcm_chroma_flag is 0, it means that neither the Cb chroma block nor the Cr chroma block of the current block is coded in the BDPCM mode. Here, the intra_bdpcm_chroma_dir_flag for each chroma block may be sent, and the intra_bdpcm_chroma_dir_flag for each chroma block may have different values.

[0235] For example, according to this embodiment, when BDPCM for chroma blocks is enabled based on intra_bdpcm_enabled_flag or intra_bdpcm_chroma_enabled_flag in high-level syntax (such as SPS syntax, VPS syntax, DPS syntax, picture header syntax, or slice header syntax) and the tree type is a single tree, the intra_bdpcm_chroma_flag for each chroma block (Cb chroma block and Cr chroma block) is sent in the CU syntax or TU syntax, and the intra_bdpcm_chroma_dir_flag for the Cb chroma block and Cr chroma block may be sent.

[0236] That is to say, if the intra_bdpcm_chroma_flag values sent for chrominance blocks are all 1, then the intra_bdpcm_chroma_dir_flag of the chrominance block to be encoded later between two chrominance blocks may not be encoded, and the intra_bdpcm_chroma_dir_flag for the chrominance color difference block encoded earlier between two chrominance blocks may be exported as the intra_bdpcm_chroma_dir_flag for the chrominance block to be encoded later. For example, if the value of intra_bdpcm_chroma_dir_flag is 0, it may mean that the BDPCM prediction directions for the Cb chrominance block and the Cr chrominance block of the current block are horizontal directions, and if the value of intra_bdpcm_chroma_dir_flag is 1, it may mean that the BDPCM prediction directions for the Cb chrominance block and the Cr chrominance block of the current block are vertical directions.

[0237] Figure 7 Schematically shows an image encoding method performed by an encoding device according to the present disclosure. Figure 7 The method disclosed in Figure 2 can be executed by the encoding device disclosed in Figure 7 S700 of Figure 7 can be executed by the predictor of the encoding device, and

[0238] The encoding device determines whether to enable block-based differential pulse code modulation (BDPCM) for chrominance blocks and luminance blocks (S700). For example, the encoding device may determine whether to enable block-based differential pulse code modulation (BDPCM) for chrominance blocks and luminance blocks in the image.

[0239] The encoding device generates a BDPCM enable flag for whether to enable BDPCM for chrominance blocks and luminance blocks based on the determined result (S710). The encoding device may generate a BDPCM enable flag for whether to enable BDPCM for chrominance blocks and luminance blocks based on the determined result. For example, the image information may include a BDPCM enable flag for whether to enable BDPCM for chrominance blocks and luminance blocks. For example, the BDPCM enable flag may indicate whether to enable block-based differential pulse code modulation (BDPCM) for chrominance blocks and luminance blocks. For example, if the value of the BDPCM enable flag is 1, the BDPCM enable flag may indicate that block-based differential pulse code modulation (BDPCM) is enabled for chrominance blocks and luminance blocks, and if the value of the BDPCM enable flag is 0, the BDPCM enable flag may indicate that block-based differential pulse code modulation (BDPCM) is not enabled for chrominance blocks and luminance blocks. That is, for example, the BDPCM enable flag may indicate whether there is a BDPCM flag for chrominance blocks and luminance blocks. For example, if the value of the BDPCM enable flag is 1, the BDPCM enable flag may indicate that the BDPCM flag for chrominance blocks and luminance blocks exists, and if the value of the BDPCM enable flag is 0, the BDPCM enable flag may indicate that the BDPCM flag for chrominance blocks and luminance blocks does not exist. In addition, for example, the chrominance blocks may include blocks of the chrominance Cb component (chrominance Cb blocks) and / or blocks of the chrominance Cr component (chrominance Cr blocks).

[0240] In addition, for example, the BDPCM enable flag may be signaled regardless of the chrominance format of the image. For example, in the case where the chrominance format of the image is YUV 444, YUV 420, or YUV 422, the BDPCM enable flag may be signaled. That is, for example, even in the case where the chrominance format of the image is YUV 444, the BDPCM enable flag may be signaled.

[0241] In addition, for example, the BDPCM enable flag may be signaled through the high-level syntax. For example, the BDPCM enable flag may be signaled through the sequence parameter set (SPS). In addition, for example, the BDPCM enable flag may be signaled through the adaptive parameter set (APS) syntax, the picture parameter set (PPS) syntax, the video parameter set (VPS) syntax, the decoding parameter set (DPS) syntax, the picture header syntax (PH syntax), or the slice header syntax. For example, the syntax element of the BDPCM enable flag may be sps_bdpcm_enabled_flag as described above.

[0242] The encoding device generates BDPCM-related information for the current luminance block and the current chrominance block (S720). For example, if the value of the BDPCM enable flag is 1 (i.e., if it is determined that BDPCM is enabled for the chrominance block and the luminance block), the encoding device may generate BDPCM-related information for the current luminance block and BDPCM-related information for the current chrominance block. The image information may include BDPCM-related information.

[0243] For example, the encoding device may determine whether to apply BDPCM to the current luminance block and may generate a BDPCM luminance flag for whether to apply BDPCM to the current luminance block.

[0244] For example, the BDPCM luminance flag may indicate whether BDPCM is applied to the current luminance block and whether there is a BDPCM luminance direction flag for the current luminance block. For example, if the value of the BDPCM luminance flag is 1, the BDPCM luminance flag may indicate that BDPCM is applied to the current luminance block and there is a BDPCM luminance direction flag for the current luminance block, while if the value of the BDPCM luminance flag is 0, the BDPCM luminance flag may indicate that BDPCM is not applied to the current luminance block and there is no BDPCM luminance direction flag for the current luminance block. For example, the syntax element of the BDPCM luminance flag may be bdpcm_flag or intra_bdpcm_luma_flag as described above. In addition, for example, the BDPCM luminance flag can be signaled on a coding unit (CU) basis.

[0245] In addition, for example, the encoding device may determine whether to apply BDPCM to the current luminance block and may determine the direction in which BDPCM is performed. For example, if the BDPCM luminance flag indicates that BDPCM is applied to the current luminance block, the encoding device may generate and encode a BDPCM luminance direction flag. For example, the BDPCM luminance direction flag may indicate the vertical direction or the horizontal direction as the prediction direction for the current luminance block. For example, if the value of the BDPCM luminance direction flag is 0, the BDPCM luminance direction flag may indicate that the prediction direction for the current luminance block is the horizontal direction, while if the value of the BDPCM luminance direction flag is 1, the BDPCM luminance direction flag may indicate that the prediction direction for the current luminance block is the vertical direction. For example, the syntax element of the BDPCM luminance direction flag may be bdpcm_dir_flag or intra_bdpcm_luma_dir_flag as described above. In addition, for example, the BDPCM luminance direction flag can be signaled on a coding unit (CU) basis.

[0246] For example, the BDPCM related information for the current luminance block may include the BDPCM luminance flag and / or the BDPCM luminance direction flag of the current luminance block.

[0247] In addition, for example, the encoding device may determine whether to apply BDPCM to the current chrominance block, and may generate a BDPCM chrominance flag for whether to apply block-based differential pulse code modulation (BDPCM) to the current chrominance block. For example, the BDPCM chrominance flag may indicate whether BDPCM is applied to the current chrominance block and whether there is a BDPCM chrominance direction flag for the current chrominance block. For example, if the value of the BDPCM chrominance flag is 1, the BDPCM chrominance flag may indicate that BDPCM is applied to the current chrominance block and there is a BDPCM chrominance direction flag for the current chrominance block, while if the value of the BDPCM chrominance flag is 0, the BDPCM chrominance flag may indicate that BDPCM is not applied to the current chrominance block and there is no BDPCM chrominance direction flag for the current chrominance block. That is, for example, if the value of the BDPCM chrominance flag is 1, the BDPCM chrominance flag may indicate that BDPCM is applied to all current chrominance blocks and there is a BDPCM chrominance direction flag for all current chrominance blocks, while if the value of the BDPCM chrominance flag is 0, the BDPCM chrominance flag may indicate that BDPCM is not applied to all current chrominance blocks and there is no BDPCM chrominance direction flag for all current chrominance blocks. Here, for example, the current chrominance block may include the current chrominance Cb block and the current chrominance Cr block. For example, the syntax element of the BDPCM chrominance flag may be the bdpcm_flag or intra_bdpcm_chroma_flag as described above. In addition, for example, the BDPCM chrominance flag can be signaled in units of coding units (CUs).

[0248] In addition, for example, an encoding device may determine whether to apply BDPCM to a current chroma block and may determine the direction in which BDPCM is to be performed. For example, if a BDPCM chroma flag indicates that BDPCM is to be applied to a current chroma block, the encoding device may generate and encode a BDPCM chroma direction flag. For example, the BDPCM chroma direction flag may indicate a vertical direction or a horizontal direction as the prediction direction for the current chroma block. For example, if the value of the BDPCM chroma direction flag is 0, the BDPCM chroma direction flag may indicate that the prediction direction for the current chroma block is the horizontal direction, and if the value of the BDPCM chroma direction flag is 1, the BDPCM chroma direction flag may indicate that the prediction direction for the current chroma block is the vertical direction. For example, the syntax element of the BDPCM chroma direction flag may be bdpcm_dir_flag or intra_bdpcm_chroma_dir_flag as described above. In addition, for example, the BDPCM chroma direction flag can be signaled on a coding unit (CU) basis.

[0249] For example, the BDPCM-related information for a current chroma block may include a BDPCM chroma flag and / or a BDPCM chroma direction flag for the current chroma block. In addition, for example, in the case where the tree type of an image is a single tree and the value of the BDPCM enable flag is 1, the BDPCM-related information for the current chroma block (i.e., for all current chroma blocks) may be signaled. That is, for example, in the case where the tree type of an image is a single tree and BDPCM is enabled for the current chroma block, the BDPCM-related information for the current chroma block (i.e., for all current chroma blocks) may be signaled. Meanwhile, depending on whether the current chroma block corresponding to the current luma block has a separate partitioning structure, the tree type of the current block may be divided into a single tree (SINGLE_TREE) or a dual tree (DUAL_TREE). For example, if the partitioning structure of the current chroma block is the same as that of the current luma block, it may be represented as a single tree, and if the partitioning structure of the current chroma block is different from that of the current luma block, it may be represented as a dual tree.

[0250] Meanwhile, for example, the encoding device may derive prediction samples by performing intra prediction for the current luma block based on the prediction direction in which BDPCM for the current luma block is performed. For example, the prediction direction may be a vertical direction or a horizontal direction, and prediction samples for the current luma block may be generated according to the resulting intra prediction mode.

[0251] For example, if the value of the BDPCM luminance direction flag is 0, that is, for example, if the prediction direction of the current chrominance block is derived as the horizontal direction, the encoding device may derive the current luminance block based on the horizontal intra prediction mode. In other words, for example, if the value of the BDPCM luminance direction flag is 0, that is, for example, if the prediction direction for the current luminance block is derived as the horizontal direction, the encoding device may derive the predicted samples of the current luminance block by performing intra prediction based on the left adjacent samples of the current luminance block. For example, if the prediction direction of the current luminance block is derived as the horizontal direction, the encoding device may derive the sample value of the left adjacent sample in the same row as the row of the predicted samples as the sample value of the predicted samples.

[0252] In addition, for example, if the value of the BDPCM luminance direction flag is 1, that is, for example, if the prediction direction for the current luminance block is derived as the vertical direction, the encoding device may derive the predicted samples of the current luminance block based on the vertical intra prediction mode. In other words, for example, if the value of the BDPCM luminance direction flag is 1, that is, for example, if the prediction direction for the current luminance block is derived as the vertical direction, the encoding device may derive the predicted samples of the current luminance block based on the upper adjacent samples of the current luminance block. For example, if the prediction direction for the current luminance block is derived as the vertical direction, the encoding device may derive the sample value of the upper adjacent sample in the same column as the column of the predicted samples as the sample value of the predicted samples.

[0253] In addition, for example, the encoding device may derive the predicted samples of the current chrominance block based on the intra prediction mode derived based on the BDPCM chrominance direction flag.

[0254] For example, if the value of the BDPCM chrominance direction flag is 0, that is, for example, the prediction direction for the current chrominance block is derived as the horizontal direction, the encoding device may derive the predicted samples of the current chrominance block based on the horizontal intra prediction mode. In other words, for example, if the value of the BDPCM chrominance direction flag is 0, that is, for example, the prediction direction for the current chrominance block is derived as the horizontal direction, the encoding device may derive the predicted samples of the current chrominance block by performing intra prediction based on the left adjacent samples of the current chrominance block. For example, if the prediction direction for the current chrominance block is derived as the horizontal direction, the encoding device may derive the sample value of the left adjacent sample in the same row as the row of the predicted samples as the sample value of the predicted samples.

[0255] In addition, for example, if the value of the BDPCM chrominance direction flag is 1, that is, for example, the prediction direction of the current chrominance block is derived as the vertical direction, the encoding device may derive the prediction samples of the current chrominance block based on the intra-frame prediction mode in the vertical direction. In other words, for example, if the value of the BDPCM chrominance direction flag is 1, that is, for example, the prediction direction for the current chrominance block is derived as the vertical direction, the encoding device may derive the prediction samples of the current chrominance block by performing intra-frame prediction based on the upper adjacent samples of the current chrominance block. For example, if the prediction direction for the current chrominance block is derived as the vertical direction, the encoding device may derive the sample values of the upper adjacent samples in the same column as the column of the prediction samples as the sample values of the prediction samples.

[0256] Meanwhile, for example, the encoding device may derive the residual samples of the current luminance block based on the prediction samples of the current luminance block. For example, the encoding device may derive the residual samples by subtracting the prediction samples from the original samples for the current luminance block. In addition, for example, the encoding device may derive the residual samples of the current chrominance block based on the prediction samples of the current chrominance block. For example, the encoding device may derive the residual samples by subtracting the prediction samples from the original samples of each current chrominance block.

[0257] The encoding device encodes the image information including the BDPCM enable flag and BDPCM-related information (S730). The encoding device may encode the image information including the BDPCM enable flag and BDPCM-related information. For example, the BDPCM-related information may include a BDPCM luminance flag for whether to apply BDPCM to the current luminance block, a BDPCM chrominance flag for whether to apply BDPCM to the current chrominance block, a BDPCM luminance direction flag for the prediction direction of the current luminance block, and / or a BDPCM chrominance direction flag for the prediction direction of the current chrominance block.

[0258] Meanwhile, for example, the image information may include residual information. For example, the encoding device may derive the residual coefficients of the current luminance block or the current chrominance block based on the residual samples of the current luminance block or the current chrominance block. For example, if BDPCM is applied to the current luminance block or the current chrominance block, the encoding device may determine not to apply a transform to the current luminance block or the current chrominance block. In this case, for example, the encoding device may derive the residual coefficients by performing quantization on the current luminance block or the current chrominance block. Here, for example, the block to which no transform is applied may be represented as a transform skip block. That is, for example, the current luminance block or the current chrominance block may be a transform skip block.

[0259] Thereafter, for example, the encoding device may encode the residual information for the residual coefficients. For example, the residual information may include the residual information for the residual coefficients of the residual samples.

[0260] For example, the residual information may include syntax elements for the residual samples of the current block, and based on the syntax elements for the target residual sample, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample or the upper adjacent residual sample of the target residual sample may be derived. For example, if the prediction direction of the current luminance block or the current chrominance block is horizontal, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual sample. That is, for example, if the prediction direction of the current luminance block or the current chrominance block is horizontal, the syntax elements for the target residual sample may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample. In addition, for example, if the prediction direction of the current luminance block or the current chrominance block is vertical, the syntax elements for the target residual sample may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample. That is, for example, if the prediction direction of the current luminance block or the current chrominance block is vertical, the syntax elements for the target residual sample may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample. In addition, if the target residual sample is located in the first row or the first column of the current luminance block or the current chrominance block, the residual coefficient value of the target residual sample may be derived based on the syntax elements for the target residual sample. That is, if the target residual sample is located in the first row or the first column of the current luminance block or the current chrominance block, the syntax elements for the target residual sample may represent the residual coefficient value of the target residual sample.

[0261] Meanwhile, a bitstream including image information may be sent to a decoding device via a network or a (digital) storage medium. Here, the network may include a broadcast network and / or a communication network, and the digital storage medium may include various types of storage media such as a USB drive, SD, CD, DVD, Blu-ray disc, HDD, and SSD.

[0262] Figure 8 Schematically shown is an encoding device for performing an image encoding method according to the present disclosure. Figure 7 The method disclosed in Figure 8 may be executed by the encoding device disclosed in Figure 8 Specifically, for example, Figure 7 the predictor of the encoding device of

[0263] Figure 9 An image decoding method of a decoding apparatus according to the present disclosure is schematically illustrated. Figure 9 The method disclosed in Figure 3 can be executed by the decoding apparatus disclosed in Figure 9 Specifically, for example, S900 to S910 of Figure 9 can be executed by the entropy decoder of the decoding apparatus, and

[0264] The decoding apparatus obtains a BDPCM enable flag for whether to enable block-based differential pulse code modulation (BDPCM) for a luminance block and a chrominance block (S900). The decoding apparatus may obtain a BDPCM enable flag for whether to enable BDPCM for a luminance block and a chrominance block. The decoding apparatus may obtain image information through a bitstream. For example, the image information may include a BDPCM enable flag for whether to enable BDPCM for a luminance block and a chrominance block. For example, the BDPCM enable flag may indicate whether to enable block-based differential pulse code modulation (BDPCM) for a chrominance block and a luminance block. For example, if the value of the BDPCM enable flag is 1, the BDPCM enable flag may indicate that block-based differential pulse code modulation (BDPCM) is enabled for a chrominance block and a luminance block, and if the value of the BDPCM enable flag is 0, the BDPCM enable flag may indicate that block-based differential pulse code modulation (BDPCM) is not enabled for a chrominance block and a luminance block. That is, for example, the BDPCM enable flag may indicate whether there is a BDPCM flag for a chrominance block and a luminance block. For example, if the value of the BDPCM enable flag is 1, the BDPCM enable flag may indicate that there is a BDPCM flag for a chrominance block and a luminance block, and if the value of the BDPCM enable flag is 0, the BDPCM enable flag may indicate that there is no BDPCM flag for a chrominance block and a luminance block. In addition, for example, a chrominance block may include a block of a chrominance Cb component (chrominance Cb block) and / or a block of a chrominance Cr component (chrominance Cr block).

[0265] In addition, for example, regardless of the chrominance format of the image, the BDPCM enable flag can be signaled. For example, in the case where the chrominance format of the image is YUV 444, YUV 420, or YUV 422, the BDPCM enable flag can be signaled. That is, for example, even in the case where the chrominance format of the image is YUV 444, the BDPCM enable flag can be signaled.

[0266] In addition, for example, the BDPCM enable flag can be signaled using high-level syntax. For example, the BDPCM enable flag can be signaled using a sequence parameter set (SPS). In addition, for example, the BDPCM enable flag can be signaled using adaptive parameter set (APS) syntax, picture parameter set (PPS) syntax, video parameter set (VPS) syntax, decoding parameter set (DPS) syntax, picture header syntax (PH syntax), or slice header syntax. For example, the syntax element of the BDPCM enable flag can be sps_bdpcm_enabled_flag as described above.

[0267] The decoding device obtains BDPCM-related information for the current luminance block and the current chrominance block based on the BDPCM enable flag (S910). The decoding device can obtain BDPCM-related information for the current luminance block and the current chrominance block based on the BDPCM enable flag.

[0268] For example, the BDPCM-related information for the current luminance block may include a BDPCM luminance flag and / or a BDPCM luminance direction flag for the current luminance block. For example, if the value of the BDPCM enable flag is 1 (i.e., if BDPCM is indicated to be enabled for chrominance blocks and luminance blocks), the decoding device can obtain a BDPCM luminance flag for whether BDPCM is applied to the current luminance block and a BDPCM chrominance flag for whether BDPCM is applied to the current chrominance block. For example, the BDPCM luminance flag can indicate whether BDPCM is applied to the current luminance block and whether there is a BDPCM luminance direction flag for the current luminance block. For example, if the value of the BDPCM luminance flag is 1, the BDPCM luminance flag can indicate that BDPCM is applied to the current luminance block and there is a BDPCM luminance direction flag for the current luminance block, while if the value of the BDPCM luminance flag is 0, the BDPCM luminance flag can indicate that BDPCM is not applied to the current luminance block and there is no BDPCM luminance direction flag for the current luminance block. For example, the syntax element of the BDPCM luminance flag can be bdpcm_flag or intra_bdpcm_luma_flag as described above. In addition, for example, the BDPCM luminance flag can be signaled on a coding unit (CU) basis.

[0269] For example, the decoding device may obtain a BDPCM luma direction flag for the prediction direction of the current luma block based on the BDPCM luma flag. For example, if the BDPCM luma flag indicates that BDPCM is applied to the current luma block, the decoding device may obtain the BDPCM luma direction flag. That is, for example, if the value of the BDPCM luma flag is 1, the decoding device may obtain the BDPCM luma direction flag. For example, the BDPCM luma direction flag may indicate the vertical direction or the horizontal direction as the prediction direction for the current luma block. For example, if the value of the BDPCM luma direction flag is 0, the BDPCM luma direction flag may indicate that the prediction direction for the current luma block is the horizontal direction, and if the value of the BDPCM luma direction flag is 1, the BDPCM luma direction flag may indicate that the prediction direction for the current luma block is the vertical direction. For example, the syntax element of the BDPCM luma direction flag may be bdpcm_dir_flag or intra_bdpcm_luma_dir_flag as described above. In addition, for example, the BDPCM luma direction flag can be signaled on a coding unit (CU) basis.

[0270] In addition, for example, the BDPCM-related information may include a BDPCM chroma flag and / or a BDPCM chroma direction flag for the current chroma block. In addition, for example, in the case where the tree type of the image is a single tree and the value of the BDPCM enable flag is 1, the BDPCM-related information for the current chroma block (i.e., for all current chroma blocks) can be signaled. That is, for example, in the case where the tree type of the image is a single tree and BDPCM is enabled for the current chroma block, the BDPCM-related information for the current chroma block (i.e., for all current chroma blocks) can be signaled. At the same time, depending on whether the current chroma block corresponding to the current luma block has a separate partitioning structure, the tree type of the current block can be divided into a single tree (SINGLE_TREE) or a dual tree (DUAL_TREE). For example, if the current chroma block has the same partitioning structure as the partitioning structure of the current luma block, it can be represented as a single tree, and if the current chroma block has a different partitioning structure from the partitioning structure of the current luma block, it can be represented as a dual tree.

[0271] For example, the BDPCM luma flag may indicate whether BDPCM is applied to the current luma block and whether there is a BDPCM luma direction flag for the current luma block. For example, if the value of the BDPCM luma flag is 1, the BDPCM luma flag may indicate that BDPCM is applied to the current luma block and there is a BDPCM luma direction flag for the current luma block, while if the value of the BDPCM luma flag is 0, the BDPCM luma flag may indicate that BDPCM is not applied to the current luma block and there is no BDPCM luma direction flag for the current luma block. For example, the syntax element of the BDPCM luma flag may be bdpcm_flag or intra_bdpcm_luma_flag as described above. In addition, for example, the BDPCM luma flag can be signaled on a coding unit (CU) basis.

[0272] For example, the decoding device may obtain the BDPCM chroma direction flag for the prediction direction of the current chroma block based on the BDPCM chroma flag. For example, if the BDPCM chroma flag indicates that BDPCM is applied to the current chroma block, the decoding device may obtain the BDPCM chroma direction flag. That is, for example, if the value of the BDPCM chroma flag is 1, the decoding device may obtain the BDPCM chroma direction flag. For example, the BDPCM chroma direction flag may indicate the vertical direction or the horizontal direction as the prediction direction for the current chroma block. For example, if the value of the BDPCM chroma direction flag is 0, the BDPCM chroma direction flag may indicate that the prediction direction for the current chroma block is the horizontal direction, while if the value of the BDPCM chroma direction flag is 1, the BDPCM chroma direction flag may indicate that the prediction direction for the current chroma block is the vertical direction. For example, the syntax element of the BDPCM chroma direction flag may be bdpcm_dir_flag or intra_bdpcm_chroma_dir_flag as described above. In addition, for example, the BDPCM chroma direction flag can be signaled on a coding unit (CU) basis.

[0273] The decoding device generates reconstructed samples for the current luma block and the current chroma block based on the BDPCM-related information (S920).

[0274] For example, the decoding device may derive the prediction samples of the current luma block based on the intra prediction mode derived based on the BDPCM luma direction flag.

[0275] For example, if the value of the BDPCM luminance direction flag is 0, that is, for example, if the BDPCM luminance direction flag indicates that the prediction direction for the current luminance block is the horizontal direction, the decoding device may derive the prediction samples of the current luminance block based on the horizontal intra prediction mode. In other words, for example, if the value of the BDPCM luminance direction flag is 0, that is, for example, if the BDPCM luminance direction flag indicates that the prediction direction for the current luminance block is the horizontal direction, the decoding device may derive the prediction samples of the current luminance block by performing intra prediction based on the left neighboring samples of the current luminance block. For example, if the prediction direction for the current luminance block is derived as the horizontal direction, the decoding device may derive the sample value of the left neighboring sample in the same row as the row of the prediction samples as the sample value of the prediction samples.

[0276] In addition, for example, if the value of the BDPCM luminance direction flag is 1, that is, for example, if the BDPCM luminance direction flag indicates that the prediction direction for the current luminance block is the vertical direction, the decoding device may derive the prediction samples of the current luminance block based on the vertical intra prediction mode. In other words, for example, if the value of the BDPCM luminance direction flag is 1, that is, for example, if the BDPCM luminance direction flag indicates that the prediction direction for the current luminance block is the vertical direction, the decoding device may derive the prediction samples of the current luminance block by performing intra prediction based on the upper neighboring samples of the current luminance block. For example, if the prediction direction of the current luminance block is derived as the vertical direction, the decoding device may derive the sample value of the upper neighboring sample in the same column as the column of the prediction samples as the sample value of the prediction samples.

[0277] In addition, for example, the decoding device derives the prediction samples of the current chrominance block based on the intra prediction mode derived based on the BDPCM chrominance direction flag.

[0278] For example, if the value of the BDPCM chrominance direction flag is 0, that is, for example, if the BDPCM chrominance direction flag indicates that the prediction direction for the current chrominance block is the horizontal direction, the decoding device may derive the prediction samples of the current chrominance block based on the horizontal intra prediction mode. In other words, for example, if the value of the BDPCM chrominance direction flag is 0, that is, for example, if the BDPCM chrominance direction flag indicates that the prediction direction for the current chrominance block is the horizontal direction, the decoding device may derive the prediction samples of the current chrominance block by performing intra prediction based on the left neighboring samples of the current chrominance block. For example, if the prediction direction for the current chrominance block is derived as the horizontal direction, the decoding device may derive the sample value of the left neighboring sample in the same row as the row of the prediction samples as the sample value of the prediction samples.

[0279] In addition, for example, if the value of the BDPCM chrominance direction flag is 1, that is, for example, if the BDPCM chrominance direction flag indicates that the prediction direction for the current chrominance block is the vertical direction, the decoding device may derive the prediction samples of the current chrominance block based on the vertical intra prediction mode. In other words, for example, if the value of the BDPCM chrominance direction flag is 1, that is, for example, if the BDPCM chrominance direction flag indicates that the prediction direction for the current chrominance block is the vertical direction, the decoding device may derive the prediction samples of the current chrominance block by performing intra prediction based on the upper adjacent samples of the current chrominance block. For example, if the prediction direction of the current chrominance block is derived as the vertical direction, the decoding device may derive the sample values of the upper adjacent samples in the same column as the column of the prediction samples as the sample values of the prediction samples.

[0280] The decoding device may derive the reconstructed samples and / or the reconstructed picture for the current luma block and the current chrominance block based on the prediction samples of the current luma block and the prediction samples of the current chrominance block. For example, the decoding device may derive the reconstructed samples of the current luma block by adding the prediction samples of the current luma block to the residual samples of the current luma block. In addition, for example, the decoding device may derive the reconstructed samples of the current chrominance block by adding the prediction samples of the current chrominance block to the residual samples of the current chrominance block.

[0281] Meanwhile, for example, the decoding device may derive the residual samples of the current luma block based on the received residual information, and may derive the residual samples of the current chrominance block based on the received residual information.

[0282] For example, if BDPCM is applied to the current luma block, the residual information may include syntax elements for the residual samples of the current luma block (that is, if BDPCM is applied to the current luma block, the residual information may include syntax elements for the target residual samples of the current luma block), and the syntax elements for the target residual samples may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample or the upper adjacent residual sample of the target residual sample. That is, for example, if BDPCM is applied to the current luma block, the residual information may include syntax elements for the target residual samples of the current luma block, and the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample or the upper adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual samples.

[0283] For example, if BDPCM is applied to a current luminance block and the prediction direction for the current luminance block is horizontal, the syntax element for a target residual sample may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample. That is, for example, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample can be derived based on the syntax element for the target residual sample. Thereafter, the residual coefficient of the target residual sample can be derived by the sum of the residual coefficient value of the left adjacent residual sample of the target residual sample and the difference. Here, the target residual sample may be a residual sample in a column excluding the first column of the current luminance block. For example, the residual coefficient of the target residual sample can be derived based on Equation 4 as described above. At the same time, for example, if the target residual sample is a residual sample in the first column of the current luminance block, the residual coefficient of the target residual sample can be derived based on the syntax element of the target residual sample.

[0284] In addition, for example, if BDPCM is applied to a current luminance block and the prediction direction for the current luminance block is vertical, the syntax element for a target residual sample may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample. That is, for example, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample can be derived based on the syntax element for the target residual sample. Thereafter, the residual coefficient of the target residual sample can be derived by the sum of the residual coefficient value of the upper adjacent residual sample of the target residual sample and the difference. Here, the target residual sample may be a residual sample in a row excluding the first row of the current luminance block. For example, the residual coefficient of the target residual sample can be derived based on Equation 3 as described above. At the same time, for example, if the target residual sample is a residual sample in the first row of the current luminance block, the residual coefficient of the target residual sample can be derived based on the syntax element of the target residual sample.

[0285] Thereafter, for example, the decoding device can derive the target residual sample by dequantizing the residual coefficient. That is, for example, the target residual sample can be derived by dequantizing the residual coefficient.

[0286] In addition, for example, if BDPCM is applied to the current chrominance block, the residual information may include syntax elements for the residual samples of the current chrominance block (i.e., if BDPCM is applied to the current chrominance block, the residual information may include syntax elements for the target residual samples of the current chrominance block), and the syntax elements for the target residual samples may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample or the upper adjacent residual sample of the target residual sample. That is, for example, if BDPCM is applied to the current chrominance block, the residual information may include syntax elements for the target residual samples of the current chrominance block, and the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample or the upper adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual samples.

[0287] For example, if BDPCM is applied to the current chrominance block and the prediction direction for the current chrominance block is the horizontal direction, the syntax elements for the target residual samples may represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample. That is, for example, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual samples. Thereafter, the residual coefficient of the target residual sample may be derived by the sum of the residual coefficient value of the left adjacent residual sample of the target residual sample and the difference. Here, the target residual sample may be a residual sample in the column excluding the first column of the current chrominance block. For example, the residual coefficient of the target residual sample may be derived based on Equation 4 as described above. At the same time, for example, if the target residual sample is a residual sample in the first column of the current chrominance block, the residual coefficient of the target residual sample may be derived based on the syntax elements of the target residual sample.

[0288] In addition, for example, if BDPCM is applied to the current chrominance block and the prediction direction for the current chrominance block is the vertical direction, the syntax element for the target residual sample can represent the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample. That is, for example, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample can be derived based on the syntax element for the target residual sample. Thereafter, the residual coefficient of the target residual sample can be derived by the sum of the residual coefficient value of the upper adjacent residual sample of the target residual sample and the difference. Here, the target residual sample can be a residual sample in a row excluding the first row of the current chrominance block. For example, the residual coefficient of the target residual sample can be derived based on Equation 3 as described above. At the same time, for example, if the target residual sample is a residual sample in the first row of the current chrominance block, the residual coefficient of the target residual sample can be derived based on the syntax element of the target residual sample.

[0289] Thereafter, for example, the decoding device can derive the target residual sample by dequantizing the residual coefficient. That is, for example, the target residual sample can be derived by dequantizing the residual coefficient.

[0290] At the same time, although not shown in the drawings, for example, the decoding device can obtain the residual information for the current luminance block based on the BDPCM luminance flag. For example, if the BDPCM luminance flag indicates that BDPCM is applied to the current luminance block, that is, if BDPCM is applied to the current luminance block, the residual information can include the syntax element for the residual sample of the current luminance block, and the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample or the upper adjacent residual sample of the target residual sample can be derived based on the syntax element for the target residual sample. For example, if the prediction direction of the current luminance block is the horizontal direction, that is, if the prediction direction of the current luminance block is derived as the horizontal direction based on the BDPCM luminance direction flag, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the left adjacent residual sample of the target residual sample can be derived based on the syntax element for the target residual sample. In addition, for example, if the prediction direction of the current luminance block is the vertical direction, that is, if the prediction direction of the current luminance block is derived as the vertical direction based on the BDPCM luminance direction flag, the difference between the residual coefficient value of the target residual sample and the residual coefficient value of the upper adjacent residual sample of the target residual sample can be derived based on the syntax element of the target residual sample. In addition, if the target residual sample is located in the first row or the first column of the current block, the residual coefficient value of the target residual sample can be derived based on the syntax element for the target residual sample.

[0291] In addition, for example, the decoding device may obtain residual information for a current chrominance block based on the BDPCM chrominance flag. For example, if the BDPCM chrominance flag indicates that BDPCM is applied to the current chrominance block, i.e., if BDPCM is applied to the current chrominance block, the residual information may include syntax elements for residual samples of the current chrominance block, and a difference between a residual coefficient value of a target residual sample and a residual coefficient value of a left adjacent residual sample or an upper adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual sample. For example, if the prediction direction of the current chrominance block is a horizontal direction, i.e., if the prediction direction of the current chrominance block is derived as the horizontal direction based on the BDPCM chrominance direction flag, a difference between a residual coefficient value of a target residual sample and a residual coefficient value of a left adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual sample. In addition, for example, if the prediction direction of the current chrominance block is a vertical direction, i.e., if the prediction direction of the current chrominance block is derived as the vertical direction based on the BDPCM chrominance direction flag, a difference between a residual coefficient value of a target residual sample and a residual coefficient value of an upper adjacent residual sample of the target residual sample may be derived based on the syntax elements for the target residual sample. In addition, if the target residual sample is located in the first row or the first column of the current chrominance block, a residual coefficient value of the target residual sample may be derived based on the syntax elements for the target residual sample.

[0292] The decoding device may derive a reconstructed sample by adding a predicted sample and a residual sample. Thereafter, if necessary, in order to improve subjective / objective image quality, an in-loop filtering process (such as a deblocking filtering, SAO, and / or ALF process) may be applied to the reconstructed sample as described above.

[0293] Figure 10 A decoding device for performing an image decoding method according to the present disclosure is schematically illustrated. Figure 9 The method disclosed in Figure 10 may be performed by the decoding device disclosed in Figure 10 Specifically, for example, Figure 9 the entropy decoder of the decoding device of Figure 10 may perform Figure 9 S900 to S910 of

[0294] According to the present invention as described above, in order to derive a chrominance quantization parameter for a chrominance component, it may be determined whether BDPCM for a luma block and a chrominance block in an image is enabled by one syntax element, and by doing so, the amount of bits for BDPCM may be reduced, and the overall encoding efficiency may be improved.

[0295] In addition, according to the present disclosure, regardless of the chrominance format of an image, a BDPCM enable flag indicating whether BDPCM of a luminance block and a chrominance block in the image is enabled can be signaled, and by doing so, the complexity for BDPCM can be reduced and the overall encoding efficiency can be improved.

[0296] In the above embodiments, the method has been described based on a flowchart having a series of steps or blocks. The present disclosure is not limited to the order of the above steps or blocks. Some steps or blocks can be executed in a different order from other steps or blocks described above or executed simultaneously. In addition, those skilled in the art will understand that the steps shown in the flowchart are not exclusive and can further include other steps, or one or more steps in the flowchart can be deleted without affecting the scope of the present disclosure.

[0297] The embodiments described in this specification can be executed by being implemented on a processor, a microprocessor, a controller, or a chip. For example, each functional unit shown in each figure can be executed by being implemented on a computer, a processor, a microprocessor, a controller, or a chip. In this case, the information for implementation (e.g., information about instructions) or algorithms can be stored in a digital storage medium.

[0298] In addition, the decoding device and the encoding device applying the present disclosure can be included in the following devices: a multimedia broadcast transmission / reception device, a mobile communication terminal, a home theater video device, a digital cinema video device, a surveillance camera, a video chat device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a portable camera, a VoD service providing device, an over-the-top (OTT) video device, an Internet streaming service providing device, a three-dimensional (3D) video device, a videoconference video device, a transportation user device (e.g., a vehicle user device, an aircraft user device, and a ship user device), and a medical video device; and the decoding device and the encoding device applying the present disclosure can be used to process video signals or data signals. For example, an over-the-top (OTT) video device can include a game console, a Blu-ray player, an Internet-connected television, a home theater system, a smart phone, a tablet computer, a digital video recorder (DVR), etc.

[0299] In addition, the processing method of the present disclosure can be generated in the form of a computer-executable program and can be stored in a computer-readable recording medium. The multimedia data having a data structure according to the present disclosure can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices in which computer-readable data is stored. The computer-readable recording medium can include, for example, BD, Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. In addition, the computer-readable recording medium includes a medium implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, the bitstream generated by the encoding method can be stored in a computer-readable recording medium or transmitted through a wired / wireless communication network.

[0300] In addition, embodiments of the present disclosure can be implemented using a computer program product according to program code, and the program code can be executed in a computer by embodiments of the present disclosure. The program code can be stored on a computer-readable carrier.

[0301] Figure 11 The structural diagram of a content stream system to which the content of the present disclosure is applied is illustrated.

[0302] The content stream system applying the embodiments of this document may mainly include an encoding server, a streaming server, a network server, a media storage, a user device, and a multimedia input device.

[0303] The encoding server compresses the content input from a multimedia input device such as a smartphone, a camera, or a portable video camera into digital data to generate a bitstream and sends the bitstream to the streaming server. As another example, when a multimedia input device such as a smartphone, a camera, or a video camera directly generates a bitstream, the encoding server can be omitted.

[0304] The bitstream can be generated by an encoding method or a bitstream generation method applying the embodiments of the present disclosure, and the streaming server can temporarily store the bitstream during the process of sending or receiving the bitstream.

[0305] The streaming server sends multimedia data to the user device through the network server based on a user request, and the network server serves as a medium for notifying the user of the service. When the user requests a required service from the network server, the network server delivers the request to the streaming server, and the streaming server sends the multimedia data to the user. In this case, the content stream system can include a separate control server. In this case, the control server is used to control commands / responses between devices within the content stream system.

[0306] The streaming server may receive content from a media storage and / or an encoding server. For example, when receiving content from the encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined period of time.

[0307] Examples of user devices may include mobile phones, smartphones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigators, touchscreen PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, and head-mounted displays), digital TVs, desktop computers, and digital signage, etc. Each server within the content streaming system may operate as a distributed server, in which case the data received from each server may be distributed.

[0308] The claims described in this disclosure can be combined in various ways. For example, the technical features of the method claims of this disclosure can be combined to be implemented as a device, and the technical features of the device claims of this disclosure can be combined to be implemented as a method. In addition, the technical features of the method claims of this disclosure and the technical features of the device claims of this disclosure can be combined to be implemented as a device, and the technical features of the method claims of this disclosure and the technical features of the device claims of this disclosure can be combined to be implemented as a method.

Claims

1. A decoding device for image decoding, the decoding device comprises: a memory; and at least one processor, the processor being coupled to the memory, wherein the at least one processor is configured to: obtain a BDPCM enable flag indicating whether block - based differential pulse - code modulation (BDPCM) is enabled for both a luminance block and a chrominance block; obtain BDPCM - related information for a current luminance block and a current chrominance block based on the BDPCM enable flag; and generate reconstructed samples for the current luminance block and the current chrominance block based on the BDPCM - related information, wherein, based on the value of the BDPCM enable flag, determining whether the BDPCM is enabled for the luminance block is determined to be the same as determining whether the BDPCM is enabled for the chrominance block, wherein a value of the BDPCM enable flag equal to 0 indicates that the BDPCM is not enabled for both the luminance block and the chrominance block, and a value of the BDPCM enable flag equal to 1 indicates that the BDPCM is enabled for both the luminance block and the chrominance block, and wherein, in response to a case where a tree type of a current block including the current luminance block and the current chrominance block is a single tree and the value of the BDPCM enable flag is 1, obtain a BDPCM chrominance flag indicating whether to apply the BDPCM to the current chrominance block and a BDPCM chrominance direction flag indicating a prediction direction of the current chrominance block from a bitstream.

2. An encoding device for image encoding, the encoding device comprises: a memory; and at least one processor, the processor being coupled to the memory, wherein the at least one processor is configured to: determine whether block - based differential pulse - code modulation (BDPCM) is enabled for a chrominance block and a luminance block; generate a BDPCM enable flag indicating whether the BDPCM is enabled for both the chrominance block and the luminance block based on a determined result; generate BDPCM - related information for a current luminance block and a current chrominance block; and encode image information including the BDPCM enable flag and the BDPCM - related information, wherein, based on the value of the BDPCM enable flag, determining whether the BDPCM is enabled for the luminance block is determined to be the same as determining whether the BDPCM is enabled for the chrominance block, wherein a value of the BDPCM enable flag equal to 0 indicates that the BDPCM is not enabled for both the luminance block and the chrominance block, and a value of the BDPCM enable flag equal to 1 indicates that the BDPCM is enabled for both the luminance block and the chrominance block, and wherein, in response to a case where a tree type of a current block including the current luminance block and the current chrominance block is a single tree and the value of the BDPCM enable flag is 1, obtain a BDPCM chrominance flag indicating whether to apply the BDPCM to the current chrominance block and a BDPCM chrominance direction flag indicating a prediction direction of the current chrominance block from a bitstream.

3. A device for transmitting image data, the device comprises: At least one processor configured to: obtain a bitstream of image information including a block-based differential pulse code modulation (BDPCM) enable flag and BDPCM-related information for a current luminance block and a current chrominance block; and A transmitter configured to: transmit the data of the bitstream including the image information, the image information including the BDPCM enable flag and the BDPCM-related information, wherein it is determined whether BDPCM is enabled for the chrominance block and the luminance block, and based on the determination result, the BDPCM enable flag indicating whether BDPCM is enabled for both the chrominance block and the luminance block is generated, wherein based on the value of the BDPCM enable flag, it is determined that whether BDPCM is enabled for the luminance block is the same as whether BDPCM is enabled for the chrominance block, wherein a value of the BDPCM enable flag equal to 0 indicates that BDPCM is not enabled for both the luminance block and the chrominance block, and a value of the BDPCM enable flag equal to 1 indicates that BDPCM is enabled for both the luminance block and the chrominance block, and wherein in response to a case where the tree type of a current block including the current luminance block and the current chrominance block is a single tree and the value of the BDPCM enable flag is 1, a BDPCM chrominance flag indicating whether BDPCM is applied to the current chrominance block and a BDPCM chrominance direction flag indicating a prediction direction of the current chrominance block are obtained from the bitstream.

4. A non-transitory computer-readable storage medium storing a bitstream generated by a method, the method comprising: determining whether block-based differential pulse code modulation (BDPCM) is enabled for a chrominance block and a luminance block; based on the determination result, generating a BDPCM enable flag indicating whether BDPCM is enabled for the chrominance block and the luminance block; generating BDPCM-related information for a current luminance block and a current chrominance block; and encoding image information including the BDPCM enable flag and the BDPCM-related information, and generating the bitstream including the image information, wherein based on the value of the BDPCM enable flag, it is determined that whether BDPCM is enabled for the luminance block is the same as whether BDPCM is enabled for the chrominance block, wherein a value of the BDPCM enable flag equal to 0 indicates that BDPCM is not enabled for both the luminance block and the chrominance block, and a value of the BDPCM enable flag equal to 1 indicates that BDPCM is enabled for both the luminance block and the chrominance block, and wherein in response to a case where the tree type of a current block including the current luminance block and the current chrominance block is a single tree and the value of the BDPCM enable flag is 1, a BDPCM chrominance flag indicating whether BDPCM is applied to the current chrominance block and a BDPCM chrominance direction flag indicating a prediction direction of the current chrominance block are obtained from the bitstream.

Images