Image decoding / encoding method, image data transmission method, and storage medium

Abstract

The invention provides an image decoding / encoding method, an image data transmission method, and a storage medium. An image decoding method performed by a decoding device according to the present document comprises the steps of: obtaining image information; performing a picture management process on a picture of the decoded picture buffer DPB on the basis of the picture information; and decoding the current picture on the basis of the picture, in which the image information includes an OLS DPB parameter index of a target output layer set OLS, and picture management processing is performed according to DPB parameter information of the target OLS derived on the basis of the OLS DPB parameter index.

Description

[0001] This application is a divisional application of the invention patent application with the original application number 202080097712.3 (international application number: PCT / KR2020 / 019323, application date: December 29, 2020, invention name: Method and device for decoding an image based on image information including OLSDPB parameter index). Technical Field

[0002] The present document relates to an image coding technology, and more particularly, to an image decoding method and apparatus for encoding image information including a decoded picture buffer (DPB) parameter mapped to an output layer set (OLS) in an image coding system. Background Art

[0003] Recently, in various fields, the demand for high-resolution, high-quality images such as HD (high definition) images and UHD (ultra high definition) images is growing. Because image data has high resolution and high quality, the amount of information or bits to be transmitted increases relative to conventional image data. Therefore, when image data is transmitted using a medium such as a conventional wired / wireless broadband line or stored using an existing storage medium, its transmission cost and storage cost increase.

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

[0005] Technical issues

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

[0007] The present disclosure also provides a method and apparatus for deriving decoded picture buffer (DPB) parameters for an output layer set (OLS).

[0008] Technical Solution

[0009] According to an embodiment of the present document, a method for image decoding performed by a decoding device is provided. The method includes: obtaining image information; performing picture management processing on a picture of a decoded picture buffer (DPB) based on the image information; and decoding a current picture based on the picture, wherein the image information includes an output layer set (OLS) DPB parameter index for a target OLS, and wherein the picture management processing is performed according to the DPB parameter information for the target OLS derived based on the OLS DPB parameter index.

[0010] According to another embodiment of the present document, a decoding device for performing image decoding is provided. The decoding device includes: an entropy decoder configured to obtain image information; a decoded picture buffer (DPB) configured to perform picture management processing on a picture of the DPB based on the image information; and a predictor configured to decode a current picture based on the picture, wherein the picture management processing is performed according to the DPB parameter information for the target OLS derived based on the OLS DPB parameter index.

[0011] According to another embodiment of the present document, a video encoding method performed by an encoding device is provided. The method includes: performing picture management processing on a picture of a decoded picture buffer (DPB) based on DPB parameter information for a target output layer set (OLS); decoding a current picture based on the picture; and encoding image information, wherein the image information includes DPB parameter information for a target OLS and an OLSDPB parameter index for the target OLS.

[0012] According to another embodiment of the present document, a video encoding device is provided. The encoding device includes: a decoded picture buffer (DPB), which is configured to perform picture management processing on a picture of the DPB based on DPB parameter information for a target output layer set (OLS); a predictor, which is configured to decode a current picture based on the picture; and an entropy encoder, which is configured to encode image information, wherein the image information includes DPB parameter information for the target OLS and an OLS DPB parameter index for the target OLS.

[0013] According to another embodiment of the present document, a computer-readable digital storage medium storing a bit stream including image information is provided, which enables a decoding device to perform an image decoding method. In the computer-readable digital storage medium, the image decoding method includes: obtaining image information; performing picture management processing on a picture of a decoded picture buffer (DPB) based on the image information; and decoding a current picture based on the picture, wherein the image information includes an output layer set (OLS) DPB parameter index for a target OLS, and wherein the picture management processing is performed according to the DPB parameter information for the target OLS derived based on the OLS DPB parameter index.

[0014] Technical Effects

[0015] According to this document, DPB parameters for OLS can be signaled, and thus, DPB can be adaptively updated for OLS and the overall coding efficiency can be improved.

[0016] According to this document, index information indicating DPB parameters for OLS may be signaled, and thus, DPB parameters may be adaptively derived for OLS, and overall coding efficiency may be improved by updating DPB for OLS based on the derived DPB parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 An example of a video / image encoding device to which an embodiment of the present disclosure can be applied is briefly illustrated.

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

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

[0020] Figure 4 Context-Adaptive Binary Arithmetic Coding (CABAC) for encoding syntax elements is exemplarily shown.

[0021] Figure 5 The encoding process according to the embodiment of this document is exemplified.

[0022] Figure 6 The decoding process according to the embodiment of this document is exemplified.

[0023] Figure 7 The image encoding method performed by the encoding device according to the present disclosure is briefly illustrated.

[0024] Figure 8 An encoding device for performing an image encoding method according to the present disclosure is briefly illustrated.

[0025] Fig. 9 The image decoding method performed by the decoding device according to the present disclosure is briefly illustrated.

[0026] Fig.10 A decoding device for performing an image decoding method according to the present disclosure is briefly illustrated.

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

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

[0029] In addition, the elements in the drawings described in the present disclosure are drawn independently for the convenience of explaining different specific functions, and do not mean that these elements are specifically implemented by independent hardware or independent software. For example, two or more elements in the elements can be combined to form a single element, or an element can be divided into multiple elements. The implementation of combining and / or dividing elements belongs 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 accompanying drawings, like reference numerals are used to indicate like elements, and the same description of the like elements will be omitted.

[0031] Figure 1 An example of a video / image encoding device to which an embodiment of the present disclosure can be applied is briefly illustrated.

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

[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 the video / image by capturing, synthesizing or generating the video / image process. The video source may include a video / image capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, a video / image archive including previously captured videos / images, etc. The video / image generation device may include, for example, a computer, a tablet computer, and a smart phone, and may (electronically) generate the video / image. For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capture process may be replaced by a process that generates 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 coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

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

[0037] The decoding device may decode a 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 may render the decoded video / image. The rendered video / image may be displayed by a display.

[0039] The present disclosure relates to video / image coding. For example, the methods / implementations disclosed in the present disclosure may be applied to methods disclosed in Versatile Video Coding (VVC), EVC (Basic Video Coding) standard, AOMedia Video 1 (AV1) standard, 2nd generation Audio Video Coding standard (AVS2) or next generation video / image coding standard (e.g., H.267, or H.268, etc.).

[0040] The present disclosure presents various embodiments of video / image encoding, and unless otherwise mentioned, the embodiments may be performed in combination with each other.

[0041] In the present disclosure, video may refer to a series of images over time. Generally, a picture refers to a unit representing an image in a specific time region, and a sub-picture / slice / tile is a unit that constitutes a part of a picture in coding. A sub-picture / slice / tile may include one or more coding tree units (CTUs). A picture may be composed of one or more sub-pictures / slices / tiles. A picture may be composed of one or more tile groups. A tile group may include one or more tiles. A tile may represent a rectangular area of ​​a CTU row within a tile in a picture. A tile may be partitioned into a plurality of tiles, each tile consisting of one or more CTU rows within a tile. Tiles that are not partitioned into a plurality of tiles may also be referred to as tiles. Tile scanning is a specific sequential ordering of CTUs that partition a picture, wherein CTUs are continuously ordered in tiles by CTU raster scanning, tiles within tiles are continuously ordered by raster scanning of tiles of tiles, and tiles in a picture are continuously ordered by raster scanning of tiles of tiles of a picture. In addition, a sub-picture may represent a rectangular area of ​​one or more slices within a picture. That is, a sub-picture may contain one or more slices that cover a rectangular area of ​​a picture together. A patch is a rectangular area of ​​a CTU within a specific patch column and a specific patch row in a picture. A patch column is a rectangular area of ​​a CTU whose height is equal to the height of the picture and whose width is specified by a syntax element in a picture parameter set. A patch row is a rectangular area of ​​a CTU whose height is specified by a syntax element in a picture parameter set and whose width is equal to the width of the picture. Patch scanning is a specific sequential ordering of CTUs that partition a picture, wherein CTUs may be continuously ordered in a patch by a CTU raster scan, and patches in a picture may be continuously ordered by a raster scan of patches of a picture. A slice includes an integer number of tiles of a picture that may be exclusively contained in a single NAL unit. A slice may consist of a plurality of complete tiles or only of a continuous sequence of complete tiles of a patch. In the present disclosure, patch groups and slices may be used interchangeably. For example, in this disclosure, a tile group / tile group header may be referred to as a slice / slice header.

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

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

[0044] In the present disclosure, "A or B" may mean "only A", "only B", or "A and B". In other words, in the present disclosure, "A or B" may be interpreted as "A and / or B". For example, in the present disclosure, "A, B or C" may mean "only A", "only B", "only C", or "any combination of A, B, and C".

[0045] A slash ( / ) or a comma used in the present disclosure 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 the present disclosure, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in the present disclosure, the expression "at least one of A or B" or "at least one of A and / or B" may be interpreted as being the same as "at least one of A and B".

[0047] In addition, in the present disclosure, "at least one of A, B, and C" may mean "only A", "only B", "only C", or "any combination of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B and / or C" may mean "at least one of A, B, and C".

[0048] In addition, brackets used in the present disclosure may refer to "for example". Specifically, when "prediction (intra-frame prediction)" is indicated, "intra-frame prediction" may be proposed as an example of "prediction". In other words, "prediction" in the present disclosure may not be limited to "intra-frame prediction", and "intra-frame prediction" may be proposed as an example of "prediction". In addition, even when "prediction (i.e., intra-frame prediction)" is indicated, "intra-frame prediction" may be proposed as an example of "prediction".

[0049] Technical features described separately in one figure in the present disclosure may be implemented separately or may be implemented simultaneously.

[0050] The following figures are created to explain specific examples of the present disclosure. Since the names of specific devices or the names of specific signals / messages / fields described in the figures are presented as examples, the technical features of the present disclosure are not limited to the specific names used in the following figures.

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

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

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

[0054] In some cases, a unit may be used interchangeably with terms such as a block or region. In general, an M×N block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample may generally represent a pixel or a pixel value, may represent a pixel / pixel value of a luminance component only, or may represent a pixel / pixel value of a chrominance component only. A sample may be used as a term corresponding to a picture (or image) of a pixel or a picture element.

[0055] In the encoding device 200, the 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 for subtracting the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) in the encoding device 200 can be called a subtractor 231. The predictor can perform prediction on the block to be processed (hereinafter referred to as the current block) and generate a prediction block including the prediction sample 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 can generate various information related to the prediction (such as prediction mode information) and send the generated information to the entropy encoder 240. The information about the prediction can be encoded in the entropy encoder 240 and output in the form of a bit stream.

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

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

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

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

[0060] The quantizer 233 may quantize the transform coefficients and send them to the entropy encoder 240, and the entropy encoder 240 may encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. Information about the quantized transform coefficients may be referred to as residual information. The quantizer 233 may rearrange the block type quantized transform coefficients into a one-dimensional vector form based on the coefficient scanning order, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. Information about the transform coefficients may be generated. The entropy encoder 240 may perform various encoding methods, such as, for example, exponential Golomb, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 240 may encode information required for video / image reconstruction (e.g., values ​​of syntax elements, etc.) other than the quantized transform coefficients together or separately. Encoded information (e.g., encoded video / image information) may be transmitted or stored in units of NAL (network abstraction layer) in the form of a bitstream. The video / image information may also include information about various parameter sets such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. In the present disclosure, information and / or syntax elements sent / signaled from an encoding device to a decoding device may be included in the video / picture information. The video / image information may be encoded and included in a bitstream through the above-mentioned encoding process. 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 a signal output from the entropy encoder 240 and / or a storage unit (not shown) for storing the signal may be included as an internal / external element of the encoding device 200, alternatively, the transmitter may be included in the entropy encoder 240.

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

[0062] Furthermore, during picture encoding and / or reconstruction, luma mapping and chroma scaling (LMCS) may 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). Various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filter 260 can generate various information related to filtering, and send the generated information to the entropy encoder 240, as described later in the description of various filtering methods. The information related to filtering can be encoded by the entropy encoder 240 and output in the form of a bit stream.

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

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

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

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

[0068] When a bit stream including video / image information is input, the decoding device 300 can be used with Figure 2 The image is reconstructed correspondingly to the processing of the video / image information in the encoding device. For example, the decoding device 300 can derive the unit / block based on the block segmentation related information obtained from the bit stream. The decoding device 300 can perform decoding using a processor applied in the encoding device. Therefore, the decoding processor can be, for example, a coding unit, and the coding unit can be segmented from the coding tree unit or the maximum coding unit according to a quadtree structure, a binary tree structure and / or a ternary tree structure. One or more transform units can be derived from the coding unit. The reconstructed image signal decoded and output by the decoding device 300 can be reproduced by a reproduction device.

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

[0070] The dequantizer 321 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 may rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement may be performed based on the coefficient scanning order performed in the encoding device. The dequantizer 321 may perform dequantization on the quantized transform coefficients by using a quantization parameter (e.g., quantization step size 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 may perform prediction on the current block and generate a prediction block including prediction samples of the current block. The predictor may determine whether to apply intra prediction or inter prediction to the current block based on information on prediction output from the entropy decoder 310, and may determine a specific intra / inter prediction mode.

[0073] The predictor 330 can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra prediction or inter prediction to predict a block, but also apply intra prediction and inter prediction at the same time. This can be called inter-frame intra combined prediction (CIIP). In addition, the predictor can predict the 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 encoding of games, etc., for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but IBC can be performed similarly to inter prediction because the 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 coding or intra prediction. When the palette mode is applied, the sample value within the picture can be signaled based on information about the palette table and the palette index.

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

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

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

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

[0078] In addition, luma mapping and chroma scaling (LMCS) can be applied during picture decoding.

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

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

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

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

[0084] As described above, the encoding device can perform various encoding methods such as exponential Golomb coding, context adaptive variable length coding (CAVLC) and context adaptive binary arithmetic coding (CABAC). In addition, the decoding device can decode the information in the bit stream based on the encoding method such as exponential Golomb coding, CAVLC or CABAC, and output the value of the syntax element required for image reconstruction and the quantized value of the transform coefficient related to the residual.

[0085] For example, the above encoding method may be performed as follows.

[0086] Figure 4Context-Adaptive Binary Arithmetic Coding (CABAC) for encoding syntax elements is exemplarily shown. For example, in the CABAC encoding process, when the input signal is a syntax element rather than a binary value, the encoding device can convert the input signal into a binary value by binarizing the value of the input signal. In addition, when the input signal is already a binary value (that is, when the value of the input signal is a binary value), the binarization may not be performed and may be bypassed. Here, each binary number 0 or 1 constituting a binary value may be referred to as a bin. For example, if the binary string after binarization is 110, each of 1, 1, and 0 is referred to as a bin. The bin for a syntax element may indicate the value of the syntax element.

[0087] Thereafter, the binarized bins of the syntax elements may be input to a conventional coding engine or a bypass coding engine. The conventional coding engine of the coding device may assign a context model reflecting a probability value to the corresponding bin, and may encode the corresponding bin based on the assigned context model. The conventional coding engine of the coding device may update the context model of each bin after encoding each bin. The bin encoded as described above may be referred to as a context-encoded bin.

[0088] In addition, when the bins of the grammatical elements are input to the bypass coding engine, they can be encoded as follows. For example, the bypass coding engine of the coding device omits the process of estimating the probability relative to the input bin and the process of updating the probability model applied to the bin after coding. When bypass coding is applied, the coding device can encode the input bin by applying a uniform probability distribution instead of assigning a context model, thereby improving the coding rate. The bin encoded as described above can be referred to as a bypass bin.

[0089] Entropy decoding may mean a process of performing the same process as the above-described entropy encoding in reverse order.

[0090] For example, when a syntax element is decoded based on a context model, the decoding device may receive a bin corresponding to the syntax element through a bitstream, determine a context model using the syntax element and decoding information of a decoding target block or a neighboring block or information of a symbol / bin decoded at a previous stage, predict the occurrence probability of the received bin according to the determined context model, and perform arithmetic decoding on the bin to derive the value of the syntax element. Thereafter, the context model of the next decoded bin may be updated using the determined context model.

[0091] In addition, for example, when a syntax element is bypass-decoded, the decoding device may receive a bin corresponding to the syntax element through a bitstream and decode the input bin by applying a uniform probability distribution. In this case, the process of deriving a context model of the syntax element by the decoding device and the process of updating the context model applied to the bin after decoding may be omitted.

[0092] As described above, the residual samples can be derived into quantized transform coefficients through transform processing and quantization processing. Quantized transform coefficients may also be referred to as transform coefficients. In this case, the transform coefficients in the block may be signaled in the form of residual information. The residual information may include residual coding syntax. That is, the encoding device may configure the residual coding syntax using the residual information, encode it, and output it in the form of a bitstream, and the decoding device may decode the residual coding syntax from the bitstream and derive the residual (quantized) transform coefficients. The residual coding syntax may include syntax elements indicating whether a transform is applied to the corresponding block, the position of the last valid transform coefficient in the block, whether there are valid transform coefficients in the sub-block, the size / sign of the valid transform coefficient, etc., as will be described later.

[0093] In addition, the above-mentioned decoded picture buffer (DPB) can be conceptually constructed from sub-DPBs, and the sub-DPB can include a picture storage buffer for storing a decoded picture of a layer. The picture storage buffer can include decoded pictures marked as "for reference" or reserved for future output.

[0094] In addition, for multi-layer bitstreams, instead of allocating to each output layer set (OLS), DPB parameters can be allocated to each layer. For example, up to two PB parameters can be allocated to each layer. One can be allocated when the layer is an output layer (i.e., for example, when the layer can be used for reference and future output), and another can be allocated when the layer is not an output layer but is used as a reference layer (e.g., when there is no layer switching, and when the layer can only be used as a reference for a picture / slice / block of an output layer). This is considered to be simpler than the DPB parameters of the multi-layer bitstream of the HEVC layered extension (where each layer of the OLS has its own DPB parameters).

[0095] For example, the signaling of DPB parameters may be as follows in terms of syntax and semantics.

[0096] [Table 1]

[0097]

[0098] For example, Table 1 above may represent a video parameter set (VPS) including syntax elements of signaled DPB parameters. The semantics of the syntax elements shown in Table 1 above may be as follows.

[0099] [Table 2]

[0100]

[0101]

[0102] For example, the syntax element vps_num_dpb_params may indicate the number of dpb_parameters() syntax structures in the VPS. For example, the value of vps_num_dpb_params may be in the range of 0 to 16. In addition, when the syntax element vps_num_dpb_params is not present, the value of the syntax element vps_num_dpb_params may be inferred to be equal to 0.

[0103] For example, the syntax element same_dpb_size_output_or_nonoutput_flag may also indicate whether the syntax element layer_nonoutput_dpb_params_idx[i] may be present in the VPS. For example, when the value of the syntax element same_dpb_size_output_or_nonoutput_flag is 1, the syntax element same_dpb_size_output_or_nonoutput_flag may indicate that the syntax element layer_nonoutput_dpb_params_idx[i] is not present in the VPS, and when the value of the syntax element same_dpb_size_output_or_nonoutput_flag is 0, the syntax element same_dpb_size_output_or_nonoutput_flag may indicate that the syntax element layer_nonoutput_dpb_params_idx[i] may be present in the VPS.

[0104] For example, the syntax element vps_sublayer_dpb_params_present_flag may also be used to control the presence of the syntax elements max_dec_pic_buffering_minus1[], max_num_reorder_pics[], and max_latency_increase_plus1[] in the dpb_parameters() syntax structure of the VPS. In addition, when the syntax element vps_sublayer_dpb_params_present_flag is not present, the value of the syntax element vps_sublayer_dpb_params_present_flag may be inferred to be equal to 0.

[0105] For example, the syntax element dpb_size_only_flag[i] may also indicate whether the syntax elements max_num_reorder_pics[] and max_latency_increase_plus1[] may be present in the ith dpb_parameters() syntax structure of the VPS. For example, when the value of the syntax element dpb_size_only_flag[i] is 1, the syntax element dpb_size_only_flag[i] may indicate that the syntax elements max_num_reorder_pics[] and max_latency_increase_plus1[] are not present in the ith dpb_parameters() syntax structure of the VPS, and when the value of the syntax element dpb_size_only_flag[i] is 0, the syntax element dpb_size_only_flag[i] may indicate that the syntax elements max_num_reorder_pics[] and max_latency_increase_plus1[] may be present in the ith dpb_parameters() syntax structure of the VPS.

[0106] For example, the syntax element dpb_max_temporal_id[i] may also indicate the TemporalId of the highest sublayer representation of the DPB parameter that may be present in the ith dpb_parameters() syntax structure in the VPS. Additionally, the value of dpb_max_temporal_id[i] may be in the range of 0 to vps_max_sublayers_minus1. Additionally, for example, when the value of vps_max_sublayers_minus1 is 0, the value of dpb_max_temporal_id[i] may be inferred to be 0. Additionally, for example, when the value of vps_max_sublayers_minus1 is greater than 0 and vps_all_layers_same_num_sublayers_flag is 1, the value of dpb_max_temporal_id[i] may be inferred to be equal to vps_max_sublayers_minus1.

[0107] In addition, for example, the syntax element layer_output_dpb_params_idx[i] may specify an index into the dpb_parameters() syntax structure list of the VPS for the dpb_parameters() syntax structure applied to the i-th layer as the output layer of the OLS. When the syntax element layer_output_dpb_params_idx[i] is present, the value of the syntax element layer_output_dpb_params_idx[i] may be in the range of 0 to vps_num_dpb_params-1.

[0108] For example, when vps_independent_layer_flag[i] is 1, the dpb_parameters() syntax structure applied to the i-th layer as the output layer may be a dpb_parameters() syntax structure present in the SPS referenced by the layer.

[0109] Alternatively, for example, when vps_independent_layer_flag[i] is 0, the following may apply.

[0110] -When vps_num_dpb_params is 1, the value of layer_output_dpb_params_idx[i] can be inferred to be equal to 0.

[0111] - A bitstream conformance requirement may be that the value of layer_output_dpb_params_idx[i] is such that the value of dpb_size_only_flag[layer_output_dpb_params_idx[i]] is equal to 0.

[0112] In addition, for example, the syntax element layer_nonoutput_dpb_params_idx[i] may specify an index into the dpb_parameters() syntax structure list of the VPS for the dpb_parameters() syntax structure applied to the i-th layer as a non-output layer of the OLS. When the syntax element layer_nonoutput_dpb_params_idx[i] is present, the value of the syntax element layer_nonoutput_dpb_params_idx[i] may be in the range of 0 to vps_num_dpb_params-1.

[0113] For example, when same_dpb_size_output_or_nonoutput_flag is 1, the following may apply.

[0114] - When vps_independent_layer_flag[i] is 1, the dpb_parameters() syntax structure applied to the i-th layer as a non-output layer may be the dpb_parameters() syntax structure present in the SPS referenced by the layer.

[0115] - When vps_independent_layer_flag[i] is 0, the value of layer_nonoutput_dpb_params_idx[i] may be inferred to be equal to layer_output_dpb_params_idx[i].

[0116] Alternatively, for example, when same_dpb_size_output_or_nonoutput_flag is 0, and when vps_num_dpb_params is 1, the value of layer_output_dpb_params_idx[i] may be inferred to be 0.

[0117] In addition, for example, the syntax and semantics of dpb_parameters() may be as follows.

[0118] [Table 3]

[0119]

[0120] Referring to Table 3, the dpb_parameters() syntax structure may provide information on the DPB size, the maximum picture reordering number, and the maximum delay of each CLVS of the CVS. The dpb_parameters() syntax structure may be represented as information on DPB parameters or DPB parameter information.

[0121] When the VPS includes a dpb_parameters() syntax structure, the OLS to which the dpb_parameters() syntax structure is applied may be specified by the VPS. In addition, when the dpb_parameters() syntax structure is included in the SPS, the dpb_parameters() syntax structure may be applied to the OLS including only the lowest layer among the layers that reference the SPS, wherein the lowest layer may be an independent layer.

[0122] The semantics of the syntax elements shown in Table 3 above may be as follows.

[0123] [Table 4]

[0124]

[0125]

[0126] For example, the syntax element max_dec_pic_buffering_minus1[i] plus 1 may specify, for each CLVS of the CVS, the maximum required size of the DPB in units of picture storage buffers when Htid is equal to i. For example, max_dec_pic_buffering_minus1[i] may be information about the size of the DPB. For example, the value of the syntax element max_dec_pic_buffering_minus1[i] may be in the range of 0 to MaxDpbSize-1. Additionally, for example, when i is greater than 0, max_dec_pic_buffering_minus1[i] may be greater than or equal to max_dec_pic_buffering_minus1[i-1]. Additionally, for example, if max_dec_pic_buffering_minus1[i] does not exist for i in the range of 0 to maxSubLayersMinus1-1, then due to subLayerInfoFlag being equal to 0, the value of the syntax element max_dec_pic_buffering_minus1[i] may be inferred to be equal to max_dec_pic_buffering_minus1[maxSubLayersMinus1].

[0127] In addition, for example, the syntax element max_num_reorder_pics[i] may specify, for each CLVS of the CVS, the maximum allowed number of CLVSs that may precede all pictures of the CLVS in decoding order and follow the corresponding picture in output order when Htid is equal to i. For example, max_num_reorder_pics[i] may be information about the maximum picture reordering number of the DPB. The value of max_num_reorder_pics[i] may be in the range of 0 to max_dec_pic_buffering_minus1[i]. In addition, for example, when i is greater than 0, max_num_reorder_pics[i] may be greater than or equal to max_num_reorder_pics[i-1]. In addition, for example, if max_num_reorder_pics[i] does not exist for i in the range of 0 to maxSubLayersMinus1-1, then since subLayerInfoFlag is equal to 0, the syntax element max_num_reorder_pics[i] may be inferred to be equal to max_num_reorder_pics[maxSubLayersMinus1].

[0128] In addition, for example, a syntax element max_latency_increase_plus1[i] having a value other than 0 may be used to calculate the value of MaxLatencyPictures[i]. MaxLatencyPictures[i] may specify, for each CLVS of a CVS, the maximum number of pictures of the CLVS that may precede all pictures of the CLVS in output order and follow the corresponding picture in decoding order when Htid is equal to i. For example, max_latency_increase_plus1[i] may be information about the maximum delay of the DPB.

[0129] For example, when max_latency_increase_plus1[i] is not 0, the value of MaxLatencyPictures[i] can be derived as follows.

[0130] [Formula 1]

[0131] MaxLatencyPictures[i]=max_num_reorder_pics[i]+max_latency_increase_plus1[i]-1

[0132] In addition, for example, if max_latency_increase_plus1[i] is 0, the corresponding limit may not be expressed. The value of max_latency_increase_plus1[i] can be between 0 and 2. 32 Additionally, for example, if max_latency_increase_plus1[i] does not exist for i in the range of 0 to maxSubLayersMinus1-1, then due to subLayerInfoFlag being equal to 0, the syntax element max_latency_increase_plus1[i] may be inferred to be equal to max_latency_increase_plus1[maxSubLayersMinus1].

[0133] In addition, DPB parameters can be used for output and removal of picture processing as shown in the following table.

[0134] [Table 5]

[0135]

[0136]

[0137] In addition, the DPB parameter signaling design in the conventional VVC standard may have at least the following problems.

[0138] First, the VVC draft considers the concept of sub-DPB, but the physical decoding device may only have one DPB for decoding a multi-layer bitstream. Therefore, the decoding device needs to know the DPB size requirement before decoding the OLS in a given multi-layer bitstream, but the traditional VVC draft does not clearly disclose how to know this information.

[0139] For example, the DPB size required for the OLS in the bitstream cannot be simply derived from the sub-DPB size of each layer of the OLS. That is, the DPB size required for the OLS cannot be simply derived as the sum of the max_dec_pic_buffering_minus1[]+1 values ​​of the layers in the OLS. For example, the sum of the max_dec_pic_buffering_minus1[]+1 of the layers in the OLS may be larger than the actual DPB size. For example, in a specific access unit, since the layers in the DPB may have different reference picture list structures, the number of reconstructed pictures of the layers in the DPB may not be the maximum, and therefore, the DPB size required for the OLS cannot be simply derived from the sum of the max_dec_pic_buffering_minus1[]+1 values ​​of the layers in the OLS.

[0140] For example, the following table exemplarily shows the pictures required for each sub-DPB to exist for a bitstream with two spatial scalability layers, a group of pictures (GOP) size of 16, and no temporal sub-layers.

[0141] [Table 6]

[0142]

[0143] Referring to Table 6, the base layer (ie, layer 0) may have a more complex RPL structure than layer 1, and considering the picture size between the two layers, the size of sub-DPB 0 may include more reference pictures than sub-DPB 1. In addition, for example, as shown in Table 6, the maximum number of reference pictures of the two layers (ie, 12) may be greater than the actual number of total pictures of the DPB (ie, 11).

[0144] Secondly, the bump processing may not be called when it is actually needed. When using the above example, the number of pictures of sub-DPB 1 does not reach the maximum sub-DPB size after the first slice header of the picture with the picture order count (POC) 37 of the second layer has been decoded, so the bump processing may not be called. That is, if a picture with POC 37 is included, the number of pictures of sub-DPB 1 can be 4, and the maximum number of pictures of sub-DPB 1 can be increased to 5. However, since the maximum number of pictures of DPB has been reached, the bump processing must be called at the corresponding time. This problem may occur because only the DPB parameters of the current layer are checked under the condition of calling the bump processing. Here, for example, the bump processing may refer to the process of deriving the desired pictures from the pictures in the DPB and removing the pictures that are not used as references from the DPB.

[0145] Therefore, this document proposes a solution to the above problems. The proposed embodiments can be applied individually or in combination.

[0146] As an example, a method of signaling DPB parameters mapped to the OLS in addition to signaling DPB parameters mapped to each layer is proposed.

[0147] In addition, as an example, a method may be proposed by which the value of max_dec_pic_buffering_minus1[i] is derived so that when there is no DPB parameter mapped to the OLS because the signaling of the DPB parameter mapped to the OLS may be optional, it is equal to a value obtained by subtracting 1 from the sum of the values ​​obtained by adding 1 to max_dec_pic_buffering_minus1[i] for all layers in the OLS. The method proposed in the present embodiment may be performed based on a flag indicating whether there is a DPB parameter mapped to the OLS. For example, when the value of the flag is 1, the flag may indicate that there are DPB parameter indexes for all OLSs including at least one or more layers, otherwise, that is, when the value of the flag is 0, the flag may indicate that there is no DPB parameter mapped to the OLS (that is, the DPB parameter index of the OLS). In addition, for example, the flag may exist for each OLS.

[0148] In addition, as an example, a method may be provided by which the value of max_dec_pic_buffering_minus1[highest temporal sublayer] of each OLS is not greater than a value obtained by subtracting 1 from the sum of a value obtained by subtracting 1 from MaxDpbSize and a value obtained by adding 1 to max_dec_pic_buffering_minus1[highest temporal sublayer] of a layer within the OLS, minus 1.

[0149] In addition, as an example, a method may be proposed in which the DPB parameters allocated to the OLS include only the DPB size.

[0150] In addition, as an example, a method of updating the condition for calling the bumping process in consideration of the number of pictures in the DPB and the value of max_dec_pic_buffering_minus1[i] of the OLS being processed by the decoding device may be proposed.

[0151] Furthermore, for example, the embodiment can be applied according to the following process.

[0152] Figure 5 The encoding process according to the embodiment of this document is exemplified.

[0153] Reference Figure 5 , the encoding device can decode the (reconstructed) picture (S500). The encoding device can update the DPB based on the DPB parameters (S510). For example, the decoded picture can be basically inserted into the DPB, and the decoded picture can be used as a reference picture for inter-frame prediction. In addition, the decoded picture in the DPB can be deleted based on the DPB parameters. In addition, the encoding device can encode the image information including the DPB parameters (S520). In addition, although not shown, the encoding device can further decode the current picture based on the DPB updated after step S510. In addition, the decoded current picture can be inserted into the DPB, and the DPB including the decoded current picture can be further updated based on the DPB parameters before the next picture is decoded in the decoding order.

[0154] Figure 6 The decoding process according to the embodiment of this document is exemplified.

[0155] Reference Figure 6 , the decoding device can obtain image information including information about DPB parameters from the bitstream (S600). The decoding device can output a picture decoded from DPB based on the information about DPB parameters (S605). In addition, when the layer related to DPB (or DPB parameters) is not an output layer but a reference layer, step S605 can be skipped.

[0156] In addition, the decoding device can update the DPB based on the information about the DPB parameters (S610). The decoded picture can be basically inserted into the DPB. Then, the DPB can be updated before decoding the current picture. For example, the decoded picture in the DPB can be deleted based on the information of the DPB parameters. Here, the DPB update can be referred to as DPB management.

[0157] The information about the DPB parameters may include the information / syntax elements disclosed in the above Tables 1 and 3. In addition, for example, different DPB parameters may be signaled depending on whether the current layer is an output layer or a reference layer, or different DPB parameters may be signaled depending on whether the DPB (or DPB parameters) is used for OLS (mapped to OLS) as in the embodiment proposed in this document.

[0158] In addition, the decoding device can decode the current picture based on the DPB (S620). For example, the decoding device can decode the current picture based on inter-frame prediction of blocks / slices of the current picture using a decoded picture of the DPB (before the current picture) as a reference picture.

[0159] In addition, although not shown, the encoding device can decode the current picture based on the DPB updated after the above step S510. In addition, the decoded current picture can be inserted into the DPB, and the DPB including the decoded current picture can be further updated based on the DPB parameters before decoding the next picture.

[0160] The syntax and DPB management process to which the embodiments proposed in this document are applied will be described below.

[0161] As an implementation, the signaled video parameter set (VPS) syntax may be as follows.

[0162] [Table 7]

[0163]

[0164] Referring to Table 7, the VPS may include syntax elements vps_num_dpb_params, same_dpb_size_output_or_nonoutput_flag, vps_sublayer_dpb_params_present_flag, dpb_size_only_flag[i], dpb_max_temporal_id[i], layer_output_dpb_params_idx[i], and / or layer_nonoutput_dpb_params_idx[i].

[0165] In addition, referring to Table 7, the VPS may further include syntax elements vps_ols_dpb_params_present_flag and / or ols_dpb_params_idx[i].

[0166] For example, the syntax element vps_ols_dpb_params_present_flag may indicate whether ols_dpb_params_idx[] may be present. For example, when the value of vps_ols_dpb_params_present_flag is 1, vps_ols_dpb_params_present_flag may indicate that ols_dpb_params_idx[] may be present, and when the value of vps_ols_dpb_params_present_flag is 0, vps_ols_dpb_params_present_flag may indicate that ols_dpb_params_idx[] does not exist. In addition, when vps_ols_dpb_params_present_flag does not exist, the value of vps_ols_dpb_params_present_flag may be inferred to be 0.

[0167] Additionally, for example, when i is less than TotalNumOlss, and when vps_ols_dpb_params_present_flag is 1, and when vps_num_dpb_params is greater than 1, and if NumLayersInOls[i] is greater than 1, the syntax element ols_dpb_params_idx[i] may be signaled. ols_dpb_params_idx[i] may be denoted as vps_ols_dpb_params_idx[i].

[0168] For example, when NumLayersInOls[i] is greater than 1, the syntax element ols_dpb_params_idx[i] may specify the index of the dpb_parameters() syntax structure applied to the i-th OLS in the dpb_parameters() syntax structure list of the VPS. That is, for example, the syntax element ols_dpb_params_idx[i] may indicate the dpb_parameters() syntax structure of the VPS for the target OLS (i.e., the i-th OLS). When ols_dpb_params_idx[i] exists, the value of ols_dpb_params_idx[i] may be in the range of 0 to vps_num_dpb_params-1.

[0169] In addition, for example, when NumLayersInOls[i] is equal to 1, a dpb_parameters( ) syntax structure applied to the i th OLS may exist in an SPS referenced by a layer in the i th OLS.

[0170] Furthermore, according to the present embodiment, OlsMaxDecPicBufferingMinus1[Htid] may be defined as follows.

[0171] [Table 8]

[0172]

[0173] For example, referring to Table 8, the value of OlsMaxDecPicBufferingMinus1[Htid] of the target OLS can be derived as follows.

[0174] For example, when the value of vps_ols_dpb_params_present_flag is 1, OlsMaxDecPicBufferingMinus1[Htid] may be derived such that it is equal to the value of max_dec_pic_buffering_minus1[Htid] in ols_dpb_params_idx[opOlsIdx].

[0175] In addition, for example, in other cases, that is, when the value of vps_ols_dpb_params_present_flag is 0, OlsMaxDecPicBufferingMinus1[Htid] may be derived such that it is equal to a value obtained by subtracting 1 from the sum of max_dec_pic_buffering_minus1[Htid]+1 of each layer in the target OLS.

[0176] In addition, according to the present embodiment, the screen output and removal process (ie, the DPB management process) can be defined as follows.

[0177] [Table 9]

[0178]

[0179]

[0180] For example, referring to Table 9, the number of pictures of the sub-DPB may be greater than or equal to max_dec_pic_buffering_minus1[Htid] + 1. In addition, for example, the number of pictures of the DPB may be greater than or equal to OlsMaxDecPicBufferingMinus1[Htid] + 1.

[0181] In addition, according to the present embodiment, the constraint on the maximum picture of the DPB (ie, the maximum number of pictures of the DPB) may be updated as follows: Here, the maximum number of pictures of the DPB may be expressed as a maximum DPB size.

[0182] [Table 10]

[0183]

[0184]

[0185] For example, referring to Table 10, when the level is not level 8.5, the value of OlsMaxDecPicBufferingMinus1[Htid]+1 may be less than or equal to MaxDpbSize.

[0186] Alternatively, as an embodiment, the signaled video parameter set (VPS) syntax may be as follows.

[0187] [Table 11]

[0188]

[0189] Referring to Table 11, the VPS may include syntax elements vps_num_dpb_params, same_dpb_size_output_or_nonoutput_flag, vps_sublayer_dpb_params_present_flag, dpb_size_only_flag[i], dpb_max_temporal_id[i], layer_output_dpb_params_idx[i], and / or layer_nonoutput_dpb_params_idx[i].

[0190] In addition, referring to Table 11, the VPS may further include syntax elements vps_ols_dpb_params_present_flag and / or ols_dpb_params_idx[i].

[0191] For example, the syntax element vps_ols_dpb_params_present_flag may be signaled when i is less than TotalNumOlss, and when vps_num_dpb_params is greater than 1, and if NumLayersInOls[i] is greater than 1. Unlike the implementation shown in Table 7 above where vps_ols_dpb_params_present_flag is signaled without a separate condition, vps_ols_dpb_params_present_flag may be signaled only when i is less than TotalNumOlss and vps_num_dpb_params is greater than 1.

[0192] For example, the syntax element vps_ols_dpb_params_present_flag may indicate whether ols_dpb_params_idx[] may be present. For example, when the value of vps_ols_dpb_params_present_flag is 1, vps_ols_dpb_params_present_flag may indicate that ols_dpb_params_idx[] may be present, and when the value of vps_ols_dpb_params_present_flag is 0, vps_ols_dpb_params_present_flag may indicate that ols_dpb_params_idx[] does not exist. In addition, when vps_ols_dpb_params_present_flag does not exist, the value of vps_ols_dpb_params_present_flag may be inferred to be 0.

[0193] Additionally, for example, when vps_ols_dpb_params_present_flag is 1, the syntax element ols_dpb_params_idx[i] may be signaled.

[0194] For example, when NumLayersInOls[i] is greater than 1, the syntax element ols_dpb_params_idx[i] may specify the index of the dpb_parameters() syntax structure applied to the i-th OLS in the dpb_parameters() syntax structure list of the VPS. That is, for example, the syntax element ols_dpb_params_idx[i] may indicate the dpb_parameters() syntax structure of the VPS for the target OLS (i.e., the i-th OLS). When ols_dpb_params_idx[i] exists, the value of ols_dpb_params_idx[i] may be in the range of 0 to vps_num_dpb_params-1.

[0195] Figure 7 The image encoding method performed by the encoding device according to the present disclosure is briefly illustrated. Figure 7 The method disclosed in can be Figure 2 Specifically, for example, Figure 7 S700 may be executed by a DPB of an encoding device, Figure 7 S710 may be performed by a predictor and a residual processor of an encoding device, Figure 7 S720 may be performed by an entropy encoder of the encoding device.

[0196] The encoding device performs picture management processing (S700) on the picture of the decoded picture buffer (DPB) based on the DPB parameter information of the target output layer set (OLS). For example, the encoding device may perform picture management processing on the picture of the DPB based on the DPB parameter information of the target OLS. For example, the encoding device may generate and encode the DPB parameter information of the OLS including the DPB parameter information of the target OLS. The image information may include the DPB parameter information of the OLS. For example, the video parameter set (VPS) syntax may include the DPB parameter information of the OLS.

[0197] For example, the DPB parameter information of the target OLS may include information about the DPB size of the target OLS, information about the maximum picture reordering number of the DBP of the target OLS, and / or information about the maximum delay of the DBP of the target OLS. Here, the DPB size may indicate the maximum number of pictures that the DPB may include.

[0198] The syntax element of the information on the DPB size of the target OLS may be the above-mentioned max_dec_pic_buffering_minus1[i], the syntax element of the information on the maximum picture reordering number of the DBP of the target OLS may be the above-mentioned max_num_reorder_pics[i], and the syntax element of the information on the maximum delay of the DBP of the target OLS may be the above-mentioned max_latency_increase_plus1[i].

[0199] In addition, for example, it may be determined whether to perform bump processing on the pictures in the DPB based on the number of pictures in the DPB and the information about the DPB size of the target OLS. For example, when the number of pictures in the DPB is greater than or equal to the value derived based on the information about the DPB size, the bump processing may be performed, and when the number of pictures in the DPB is less than the value derived based on the information about the DPB size, the bump processing may not be performed. Here, for example, the value derived based on the information about the DPB size may be a value obtained by adding 1 to the value of the information about the DPB size.

[0200] The encoding device decodes the current picture based on the picture (S710). For example, the encoding device can decode the current picture based on the picture of the DPB that performs the picture management process. That is, the encoding device can decode the current picture based on the picture of the updated DPB. For example, the encoding device can derive the prediction sample by performing inter-frame prediction on the block in the current picture based on the reference picture of the updated DPB, and can generate a reconstructed sample and / or a reconstructed picture for the current picture based on the prediction sample. In addition, for example, the encoding device can derive the residual sample of the block in the current picture, and can generate a reconstructed sample and / or a reconstructed picture by adding the prediction sample and the residual sample.

[0201] In addition, for example, the encoding device may generate and encode prediction information for a block of the current picture. In this case, various prediction methods disclosed in this document (e.g., inter-frame prediction or intra-frame prediction) may be applied. For example, the encoding device may determine whether to perform inter-frame prediction or intra-frame prediction on a block, and may determine a specific inter-frame prediction mode or a specific intra-frame prediction mode based on an RD cost. Based on the determined mode, the encoding device may derive a prediction sample for the current chroma block. The prediction information may include prediction mode information for the current chroma block. The image information may include prediction information.

[0202] In addition, for example, the encoding apparatus may encode residual information of a block of a picture.

[0203] For example, the encoding device may derive residual samples by subtracting original samples and predicted samples of the block.

[0204] Thereafter, for example, the encoding device may derive quantized residual samples by quantizing the residual samples, and may derive transform coefficients based on the quantized residual samples, and may generate and encode residual information based on the transform coefficients. Alternatively, for example, the encoding device may derive quantized residual samples by quantizing the residual samples, and may derive transform coefficients by transforming the quantized residual samples, and may generate and encode residual information based on the transform coefficients. The image information may include residual information. In addition, for example, the encoding device may encode the image information and output the encoded image information in the form of a bitstream.

[0205] The encoding device can generate a reconstructed sample and / or a reconstructed picture by adding the predicted sample and the residual sample. Thereafter, as described above, an in-loop filtering process such as ALF processing, SAO and / or deblocking filtering can be applied to the reconstructed sample as needed to improve the subjective / objective video quality.

[0206] The encoding device encodes the image information (S720). The encoding device may encode the image information. For example, the image information may include DPB parameter information of the target OLS and an OLSDPB parameter index of the target OLS.

[0207] For example, the encoding device may generate and encode DPB parameter information of an OLS, and the DPB parameter information of the OLS may include the DPB parameter information of the target OLS. The image information may include the DPB parameter information of the OLS. For example, a video parameter set (VPS) syntax may include the DPB parameter information of the OLS.

[0208] For example, the DPB parameter information of the target OLS may include information about the DPB size of the target OLS, information about the maximum picture reordering number of the DBP of the target OLS, and / or information about the maximum delay of the DBP of the target OLS. Here, the DPB size may indicate the maximum number of pictures that the DPB may include. The syntax element of the information about the DPB size of the target OLS may be the above-mentioned max_dec_pic_buffering_minus1[i], the syntax element of the information about the maximum picture reordering number of the DBP of the target OLS may be the above-mentioned max_num_reorder_pics[i], and the syntax element of the information about the maximum delay of the DBP of the target OLS may be the above-mentioned max_latency_increase_plus1[i].

[0209] In addition, for example, the encoding device may generate and encode the OLSDPB parameter index of the DPB parameter information of the target OLS. The image information may include the OLSDPB parameter index of the DPB parameter information of the target OLS. For example, the VPS syntax may include the OLSDPB parameter index.

[0210] For example, the OLSDPB parameter index of the target OLS may indicate the DPB parameter information of the target OLS. For example, the OLSDPB parameter index of the target OLS may indicate the DPB parameter information of the target OLS among the DPB parameter information of the OLS. The syntax element of the OLSDPB parameter index may be the above-mentioned vps_ols_dpb_params_idx[i] or ols_dpb_params_idx[i].

[0211] In addition, for example, the encoding device may generate and encode an OLSDPB parameter flag for whether there is DPB parameter information of OLS. For example, the image information may include the OLSDPB parameter flag. In addition, for example, the VPS syntax may include the OLSDPB parameter flag. For example, the OLSDPB parameter flag may indicate whether there is DPB parameter information of OLS. For example, when the value of the OLSDPB parameter flag is 1, the OLSDPB parameter flag may indicate that there may be DPB parameter information of OLS, and when the value of the OLSDPB parameter flag is 0, the OLSDPB parameter flag may indicate that the DPB parameter information of OLS does not exist. In addition, for example, the OLSDPB parameter index may be generated and encoded based on the OLSDPB parameter flag. For example, when the value of the OLSDPB parameter flag is 1, the OLSDPB parameter index may be generated / encoded / signaled, and when the value of the OLSDPB parameter flag is 0, the OLSDPB parameter index may not be generated / encoded / signaled. The syntax element of the OLSDPB parameter flag may be the above-mentioned vps_ols_dpb_params_present_flag.

[0212] In addition, for example, the encoding apparatus may encode prediction information and residual information of a block in the current picture.

[0213] For example, the encoding device may determine whether to perform inter-frame prediction or intra-frame prediction on the block, and may determine a specific inter-frame prediction mode or a specific intra-frame prediction mode based on the RD cost. According to the determined mode, the encoding device may derive the prediction sample of the block. The prediction information may include prediction mode information of the block.

[0214] In addition, the encoding device may generate and encode a reference picture index indicating a reference picture of the block. For example, the prediction information may include the reference picture index. In addition, the encoding device may derive motion information of the block, and may generate and encode information about the motion information. For example, the prediction information may include information about the motion information and the reference picture index.

[0215] In addition, for example, the encoding device may encode residual information of a block of the picture. For example, the encoding device may derive residual samples by subtracting original samples and predicted samples of the block.

[0216] Thereafter, for example, the encoding device may derive quantized residual samples by quantizing the residual samples, and may derive transform coefficients based on the quantized residual samples, and may generate and encode residual information based on the transform coefficients. Alternatively, for example, the encoding device may derive quantized residual samples by quantizing the residual samples, and may derive transform coefficients by transforming the quantized residual samples, and may generate and encode residual information based on the transform coefficients. The image information may include residual information. In addition, for example, the encoding device may encode the image information and output the encoded image information in the form of a bitstream.

[0217] In addition, the bit stream including the image information may be sent to the decoding device via a network or a (digital) storage medium. Here, the network may include a broadcast network, a communication network, etc., and the digital storage medium may include various storage media such as a universal serial bus (USB), a secure digital (SD), a compact disc (CD), a digital video disc (DVD), a Blu-ray, a hard disk drive (HDD), a solid state drive (SSD), etc.

[0218] Figure 8 An encoding device for performing an image encoding method according to the present disclosure is briefly illustrated. Figure 7 The method disclosed in can be Figure 8 Specifically, for example, Figure 8 The DPB of the encoding device may execute S700, Figure 8 The predictor and residual processor of the encoding device may perform S710, Figure 8 The entropy encoder of the encoding device may perform S720.

[0219] Fig. 9 The image decoding method performed by the decoding device according to the present disclosure is briefly illustrated. Fig. 9 The method disclosed in can be Figure 3 Specifically, for example, Fig. 9 S900 may be performed by an entropy encoder of an encoding device, Fig. 9 S910 may be executed by the DPB of the encoding device, Fig. 9 S920 may be performed by a predictor of the decoding device.

[0220] The decoding device obtains image information (S900). The decoding device may obtain the image information from a bitstream. For example, the image information may include an OLSDPB parameter index of a target output layer set (OLS).

[0221] For example, the decoding device may obtain a video parameter set (VPS) syntax from a bitstream. The image information may include the VPS syntax. The image information may be received in the bitstream. The VPS syntax may include an OLSDPB parameter index of a target OLS. That is, for example, the decoding device may obtain an OLSDPB parameter index of a target OLS using the VPS syntax.

[0222] For example, the OLSDPB parameter index of the target OLS may indicate the DPB parameter information of the target OLS. In addition, for example, the image information may include the DPB parameter information of the OLS. The VPS syntax may include the DPB parameter information of the OLS. That is, for example, the decoding device may obtain the DPB parameter information of the OLS using the VPS syntax. For example, the DPB parameter information of the OLS may include the DPB parameter information of the target OLS, and the OLSDPB parameter index of the target OLS may indicate the DPB parameter information of the target OLS in the DPB parameter information of the OLS. The syntax element of the OLSDPB parameter index may be the above-mentioned vps_ols_dpb_params_idx[i] or ols_dpb_params_idx[i].

[0223] For example, the DPB parameter information of the target OLS may include information about the DPB size of the target OLS, information about the maximum picture reordering number of the DBP of the target OLS, and / or information about the maximum delay of the DBP of the target OLS. Here, the DPB size may indicate the maximum number of pictures that the DPB may include. The syntax element of the information about the DPB size of the target OLS may be the above-mentioned max_dec_pic_buffering_minus1[i], the syntax element of the information about the maximum picture reordering number of the DBP of the target OLS may be the above-mentioned max_num_reorder_pics[i], and the syntax element of the information about the maximum delay of the DBP of the target OLS may be the above-mentioned max_latency_increase_plus1[i].

[0224] In addition, for example, the decoding device may obtain an OLSDPB parameter flag for whether there is DPB parameter information of OLS. For example, the image information may include the OLSDPB parameter flag. In addition, for example, the VPS syntax may include the OLSDPB parameter flag. For example, the OLSDPB parameter flag may indicate whether there is DPB parameter information of OLS. For example, when the value of the OLSDPB parameter flag is 1, the OLSDPB parameter flag may indicate that DPB parameter information of OLS may exist, and when the value of the OLSDPB parameter flag is 0, the OLSDPB parameter flag may indicate that DPB parameter information of OLS does not exist. In addition, for example, the OLSDPB parameter index may be obtained based on the OLSDPB parameter flag. For example, when the value of the OLSDPB parameter flag is 1, the OLSDPB parameter index may be signaled / obtained, and when the value of the OLSDPB parameter flag is 0, the OLSDPB parameter index may not be signaled / obtained. The syntax element of the OLSDPB parameter flag may be the above-mentioned vps_ols_dpb_params_present_flag.

[0225] The decoding device performs picture management processing on the picture of the decoded picture buffer (DPB) based on the image information (S910). For example, the decoding device may perform picture management processing on the picture of the decoded picture buffer (DPB) based on the image information. For example, the picture management processing may be performed according to the DPB parameter information of the target OLS derived based on the OLS DPB parameter index.

[0226] For example, the decoding device may derive the DPB parameter information of the target OLS among the DPB parameter information of the OLS based on the OLS DPB parameter index.For example, the decoding device may derive the DPB parameter information of the target OLS indicated by the OLS DPB parameter index among the DPB parameter information of the OLS.

[0227] In addition, for example, the decoding device may perform picture management processing on the picture of the DPB based on the DPB parameter information of the target OLS. The decoding device may update the DPB based on the DPB parameter information. For example, the decoding device may perform picture management processing on the (decoded) picture of the DPB based on the DPB parameter information. For example, the decoding device may add a decoded picture to the DPB, or may remove a decoded picture in the DPB. For example, a decoded picture in the DPB may be used as a reference picture for inter-frame prediction of the current picture, or a decoded picture in the DPB may be used as an output picture. A decoded picture may refer to a picture decoded before the current picture in the decoding order in the target OLS.

[0228] For example, the decoding device may determine whether to perform impact processing on the pictures in the DPB based on the information about the DPB size of the target OLS and the number of pictures in the DPB, and may perform impact processing on the pictures in the DPB based on the determination result. For example, when the number of pictures in the DPB is greater than or equal to the value derived based on the information about the DPB size, the impact processing may be performed, and when the number of pictures in the DPB is less than the value derived based on the information about the DPB size, the impact processing may not be performed. Here, for example, the value derived based on the information about the DPB size may be a value obtained by adding 1 to the value of the information about the DPB size.

[0229] The decoding device decodes the current picture based on the picture (S920). The decoding device can decode the current picture based on the picture of the DPB that performs the picture management process. That is, the decoding device can decode the current picture based on the picture of the updated DPB. For example, the decoding device can derive the prediction sample by performing inter-frame prediction on the block in the current picture based on the reference picture of the DPB, and can generate the reconstructed sample and / or reconstructed picture of the current picture based on the prediction sample. In addition, for example, the decoding device can derive the residual sample of the block in the current picture based on the residual information received through the bitstream, and can generate the reconstructed picture and / or reconstructed sample by adding the prediction sample and the residual sample.

[0230] In addition, for example, the decoding device may obtain prediction information and residual information of a block of the current picture. The image information may include prediction information and residual information. For example, the prediction information may include a reference picture index indicating a reference picture of the block. In addition, for example, the prediction information may include information about motion information of the block.

[0231] In addition, for example, the residual information may include information such as value information of (quantized) transform coefficients of the block, position information, transform technology, transform kernel and quantization parameter. In addition, for example, the residual information may include a transform skip flag. The transform skip flag may indicate whether a transform is applied to the block.

[0232] Thereafter, as described above, in-loop filtering processing such as ALF processing, SAO and / or deblocking filtering may be applied to the reconstructed samples as needed in order to improve the subjective / objective video quality.

[0233] Fig.10 A decoding device for performing an image decoding method according to the present disclosure is briefly illustrated. Fig. 9 The method disclosed in can be Fig.10 Specifically, for example, Fig.10 The entropy decoder of the decoding device can perform Fig. 9 S900, Fig.10The DPB of the decoding device can perform Fig. 9 S910, Fig.10 The predictor of the decoding device can perform Fig. 9 S920.

[0234] According to the above-mentioned document, the DPB parameters of the OLS can be signaled, and thus, the DPB can be adaptively updated for the OLS, and the overall coding efficiency can be improved.

[0235] In addition, according to the present document, index information indicating the DPB parameters of the OLS may be signaled, and thus, the DPB parameters may be adaptively derived for the OLS, and the overall encoding efficiency may be improved by updating the DPB of the OLS based on the derived DPB parameters.

[0236] In the above-mentioned embodiment, method is described based on the flow chart with a series of steps or square frames. The present disclosure is not limited to the order of the above steps or square frames. Some steps or square frames can be performed in an order different from other steps or square frames mentioned above or performed simultaneously. In addition, it will be appreciated by those skilled in the art that the steps shown in the flow chart are not exclusive, and other steps may also be included, or one or more steps in the flow chart may be deleted without affecting the scope of the present disclosure.

[0237] The embodiments described in this specification may be implemented on a processor, a microprocessor, a controller or a chip. For example, the functional units shown in each figure may be implemented on a computer, a processor, a microprocessor, a controller or a chip. In this case, information (e.g., information about instructions) or algorithms for implementation may be stored in a digital storage medium.

[0238] In addition, the decoding device and encoding device of the present disclosure can be included in the following devices: multimedia broadcast sending / receiving devices, mobile communication terminals, home theater video devices, digital theater video devices, surveillance cameras, video chat devices, real-time communication devices such as video communication, mobile streaming devices, storage media, portable cameras, VoD service providing devices, over-the-top (OTT) video devices, Internet streaming service providing devices, three-dimensional (3D) video devices, teleconferencing video devices, transportation user devices (e.g., vehicle user devices, aircraft user devices, and ship user devices) and medical video devices; and the decoding device and encoding device of the present disclosure can be used to process video signals or data signals. For example, over-the-top (OTT) video devices can include game consoles, Blu-ray players, Internet access televisions, home theater systems, smart phones, tablet computers, digital video recorders (DVRs), etc.

[0239] In addition, the processing method of the present invention can be generated in the form of a program executed by a computer and can be stored in a computer-readable recording medium. The multimedia data with a data structure according to the present invention can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices in which computer-readable data is stored. The computer-readable recording medium may include, for example, a BD, a universal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. In addition, the computer-readable recording medium includes a medium implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, the bit stream generated by the encoding method can be stored in a computer-readable recording medium or transmitted via a wired / wireless communication network.

[0240] In addition, the embodiments of the present disclosure may be implemented using a computer program product according to a program code, and the program code may be executed in a computer through the embodiments of the present disclosure. The program code may be stored on a computer readable carrier.

[0241] Fig.11 A structural diagram of a content streaming system to which the present disclosure is applied is illustrated.

[0242] The content streaming system to which the embodiments of the present disclosure are applied may mainly include an encoding server, a streaming server, a network server, a media storage, a user device, and a multimedia input device.

[0243] The encoding server compresses the content input from a multimedia input device such as a smartphone, a camera, or a camcorder into digital data to generate a bitstream and transmits the bitstream to the streaming server. As another example, when a multimedia input device such as a smartphone, a camera, or a camcorder directly generates a bitstream, the encoding server may be omitted.

[0244] A bitstream may be generated by an encoding method or a bitstream generating method to which an embodiment of the present disclosure is applied, and a streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0245] The streaming server sends multimedia data to the user device through the network server based on the user request, and the network server is used as a medium to notify the user of the service. When the user requests the required service from the network server, the network server transmits the request to the streaming server, and the streaming server sends the multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server is used to control the command / response between the devices within the content streaming system.

[0246] The streaming server can receive content from a media storage and / or encoding server. For example, when receiving content from an encoding server, the content can be received in real time. In this case, in order to provide a stable streaming service, the streaming server can store the bitstream for a predetermined time.

[0247] Examples of user devices may include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigators, touch screen PCs, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, smart glasses, and head mounted displays), digital TVs, desktop computers, and digital signage, etc. Each server within the content streaming system may operate as a distributed server, in which case data received from each server may be distributed.

[0248] The claims described in this disclosure may be combined in various ways. For example, the technical features of the method claims of this disclosure may be combined to be implemented as a device, and the technical features of the device claims of this disclosure may 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 may 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 may be combined to be implemented as a method.

Claims

1. An image decoding method performed by a decoding device, the image decoding method comprising the following steps: Obtain image information; Performing picture management processing on pictures of the decoded picture buffer DPB based on the image information; as well as decoding a current picture based on the picture, wherein the image information includes an OLSDPB parameter index for a target output layer set OLS, and wherein the picture management process is performed according to the DPB parameter information for the target output layer set OLS derived based on the OLSDPB parameter index, The DPB parameter information for the target output layer set OLS includes information about the DPB size, information about the maximum picture reordering number of the DPB for the target output layer set OLS, and information about the maximum delay of the DPB. The picture management process includes collision processing.

2. The image decoding method according to claim 1, wherein: The image information includes an OLSDPB parameter flag indicating whether there is DPB parameter information for OLS.

3. The image decoding method according to claim 2, wherein: When the value of the OLSDPB parameter flag is 1, the OLSDPB parameter flag indicates that the DPB parameter information for the OLS exists, and When the value of the OLSDPB parameter flag is 0, the OLSDPB parameter flag indicates that the DPB parameter information for the OLS does not exist.

4. The image decoding method according to claim 3, wherein: The OLS DPB parameter index is obtained based on the OLS DPB parameter flag.

5. The image decoding method according to claim 4, wherein: When the value of the OLSDPB parameter flag is 1, the OLSDPB parameter index is obtained.

6. The image decoding method according to claim 2, wherein: The OLSDPB parameter index and the OLSDPB parameter flag are included in the video parameter set VPS syntax.

7. The image decoding method according to claim 1, wherein: The DPB parameter information for the target output layer set OLS is included in a video parameter set VPS syntax.

8. An image encoding method performed by an encoding device, the image encoding method comprising the following steps: Performing picture management processing on pictures of the DPB based on decoded picture buffer DPB parameter information for the target output layer set OLS; decoding a current picture based on the picture; as well as Encode the image information. The image information includes the DPB parameter information for the target output layer set OLS and the OLSDPB parameter index for the target output layer set OLS. The DPB parameter information for the target output layer set OLS includes information about the DPB size, information about the maximum picture reordering number of the DPB for the target output layer set OLS, and information about the maximum delay of the DPB. The picture management process includes collision processing.

9. The image encoding method according to claim 8, wherein: The image information includes an OLSDPB parameter flag indicating whether there is DPB parameter information for OLS.

10. The image encoding method according to claim 9, wherein: When the value of the OLSDPB parameter flag is 1, the OLSDPB parameter flag indicates that the DPB parameter information for the OLS exists, and When the value of the OLSDPB parameter flag is 0, the OLSDPB parameter flag indicates that the DPB parameter information for the OLS does not exist.

11. The image encoding method according to claim 10, wherein: The OLS DPB parameter index is encoded based on the OLS DPB parameter flag.

12. The image encoding method according to claim 11, wherein: When the value of the OLSDPB parameter flag is 1, the OLSDPB parameter index is encoded.

13. A non-transitory computer-readable storage medium storing a program, which, when executed by a processor, causes the following operations to be performed: Performing picture management processing on pictures of the DPB based on decoded picture buffer DPB parameter information for the target output layer set OLS; decoding a current picture based on the picture; Encode image information; as well as generating a bit stream including the image information, The image information includes the DPB parameter information for the target output layer set OLS and the OLSDPB parameter index for the target output layer set OLS. The DPB parameter information for the target output layer set OLS includes information about the DPB size, information about the maximum picture reordering number of the DPB for the target output layer set OLS, and information about the maximum delay of the DPB. The picture management process includes collision processing.

14. A method for transmitting image data, the method comprising the following steps: Obtain a bitstream of image information, wherein the image information includes decoded picture buffer DPB parameter information and OLSDPB parameter index for a target output layer set OLS; as well as sending the data of the bitstream including the image information, the image information including the DPB parameter information and the OLS DPB parameter index for the target output layer set OLS, wherein, based on the DPB parameter information for the target output layer set OLS, picture management processing of the DPB picture is performed, The DPB parameter information for the target output layer set OLS includes information about the DPB size, information about the maximum picture reordering number of the DPB for the target output layer set OLS, and information about the maximum delay of the DPB. The picture management process includes collision processing.

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