Image encoding / decoding method and apparatus for signaling HRD parameters, and computer-readable recording medium for storing bit streams.

Abstract

A method and apparatus for image encoding / decoding using signals to notify HRD parameters, and a method for transmitting a bit stream are provided. The image decoding method according to this disclosure may include the following steps: obtaining first information indicating the number of one or more hypothetical reference decoder (HRD) parameter syntax structures within a video parameter set (VPS); obtaining one or more HRD parameter syntax structures from the VPS based on the first information; obtaining second information from the VPS related to the mapping between one or more multilayer output layer sets (OLS) and one or more HRD parameter syntax structures based on the first information; selecting an HRD parameter syntax structure to apply to the current OLS based on the second information; and processing the current OLS based on the selected HRD parameter syntax structure.

Description

Technical Field

[0001] This disclosure relates to image encoding / decoding methods and apparatus, and more specifically, to an image encoding / decoding method and apparatus that signals relevant parameters of a hypothetical reference decoder (HRD), and a computer-readable recording medium that stores a bitstream generated by the image encoding method / apparatus of this disclosure. Background Technology

[0002] Recently, there has been an increasing demand for high-resolution and high-quality images, such as high-definition (HD) and ultra-high-definition (UHD) images, across various fields. With the improvement in image data resolution and quality, the amount of information or bits transmitted increases relative to existing image data. This increase in the amount of information or bits transmitted leads to increased transmission and storage costs.

[0003] Therefore, efficient image compression techniques are needed to effectively transmit, store, and reproduce information about high-resolution and high-quality images. Summary of the Invention

[0004] Technical issues

[0005] The purpose of this disclosure is to provide an image encoding / decoding method and apparatus with improved encoding / decoding efficiency.

[0006] Another object of this disclosure is to provide an image encoding / decoding method and apparatus that improves encoding / decoding efficiency by efficiently signaling HRD parameters.

[0007] Another object of this disclosure is to provide a method for transmitting a bitstream generated by an image encoding method or device according to this disclosure.

[0008] Another object of this disclosure is to provide a recording medium for storing bitstreams generated by an image encoding method or apparatus according to this disclosure.

[0009] Another object of this disclosure is to provide a recording medium that stores a bitstream received, decoded and used to reconstruct an image by an image decoding device according to this disclosure.

[0010] The technical problems solved by this disclosure are not limited to those described above. Other technical problems not described herein will become clear to those skilled in the art through the following description.

[0011] Technical solution

[0012] An image decoding method performed by an image decoding device according to one aspect of this disclosure may include the following steps: obtaining first information about the number of one or more hypothetical reference decoder (HRD) parameter syntax structures in a specified video parameter set (VPS); obtaining one or more HRD parameter syntax structures from the VPS based on the first information; obtaining second information from the VPS about the mapping between one or more multilayer output layer sets (OLS) and one or more HRD parameter syntax structures based on the first information; selecting an HRD parameter syntax structure to be applied to the current OLS based on the second information; and processing the current OLS based on the selected HRD parameter syntax structure.

[0013] In the image decoding method disclosed herein, the number of one or more HRD parameter syntax structures in the VPS may not exceed the number of one or more multi-layer OLS.

[0014] In the image decoding method disclosed herein, each of one or more HRD parameter syntax structures in a VPS can be mapped to at least one multi-layer OLS in one or more multi-layer OLS.

[0015] In the image decoding method disclosed herein, second information can be obtained from the VPS based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is not equal to the number of one or more multi-layer OLS.

[0016] In the image decoding method disclosed herein, the number of one or more HRD parameter syntax structures based on the VPS is 1, the second information can be obtained from the VPS without obtaining the second information, and the second information can be inferred to be equal to the value 0.

[0017] In the image decoding method disclosed herein, if the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is equal to the number of one or more multi-layer OLS, the second information can be obtained from the VPS, and the second information of the i-th multi-layer OLS can be inferred to be equal to the value i.

[0018] In the image decoding method disclosed herein, since the current OLS contains only a single layer, the HRD parameter syntax structure applied to the current OLS can be obtained from the Sequence Parameter Set (SPS).

[0019] An image decoding apparatus according to another aspect of this disclosure may include a memory and at least one processor. The at least one processor may be configured to: obtain first information about the number of one or more hypothetical reference decoder (HRD) parameter syntax structures in a specified video parameter set (VPS); obtain one or more HRD parameter syntax structures from the VPS based on the first information; obtain second information from the VPS regarding the mapping between one or more multi-layer output layer sets (OLS) and one or more HRD parameter syntax structures based on the first information; select an HRD parameter syntax structure to apply to the current OLS based on the second information; and process the current OLS based on the selected HRD parameter syntax structure.

[0020] An image encoding method performed by an image encoding device according to another aspect of this disclosure may include the following steps: encoding first information about the number of one or more hypothetical reference decoder (HRD) parameter syntax structures in a specified video parameter set (VPS); encoding one or more HRD parameter syntax structures in the VPS based on the first information; encoding second information about the mapping between one or more multilayer output layer sets (OLS) and one or more HRD parameter syntax structures in the VPS based on the first information; and processing the current OLS based on the HRD parameter syntax structure applied to the current OLS.

[0021] In the image encoding method disclosed herein, the number of one or more HRD parameter syntax structures in the VPS may not exceed the number of one or more multi-layer OLS.

[0022] In the image encoding method disclosed herein, each of one or more HRD parameter syntax structures in a VPS can be mapped to at least one multi-layer OLS in one or more multi-layer OLS.

[0023] In the image encoding method disclosed herein, second information can be encoded into the VPS based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is not equal to the number of one or more multi-layer OLS.

[0024] In the image encoding method disclosed herein, the number of syntax structures based on one or more HRD parameters of the VPS is 1, the second information may not be encoded into the VPS, and the second information may be inferred to be equal to the value 0.

[0025] In the image encoding method disclosed herein, if the number of one or more HRD parameter syntax structures based on the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is equal to the number of one or more multi-layer OLS, the second information may not be encoded into the VPS, and the second information of the i-th multi-layer OLS can be inferred to be equal to the value i.

[0026] In the image coding method disclosed herein, since the current OLS contains only a single layer, the HRD parameter syntax structure applied to the current OLS can be encoded into the sequence parameter set (SPS).

[0027] According to another aspect of the transmission method of this disclosure, a bit stream generated by the image encoding device or image encoding method of this disclosure can be transmitted.

[0028] According to another aspect of this disclosure, a computer-readable recording medium may store a bitstream generated by the image encoding device or image encoding method of this disclosure.

[0029] The features described above in this brief overview are merely exemplary aspects of the following detailed description of this disclosure and do not limit the scope of this disclosure.

[0030] Beneficial effects

[0031] According to this disclosure, an image encoding / decoding method and apparatus with improved encoding / decoding efficiency can be provided.

[0032] Furthermore, according to this disclosure, an image encoding / decoding method and apparatus can be provided to improve encoding / decoding efficiency by efficiently notifying HRD parameters with signals.

[0033] Furthermore, according to this disclosure, a method for transmitting a bitstream generated by an image encoding method or device according to this disclosure can be provided.

[0034] Furthermore, according to this disclosure, it is possible to provide a recording medium for storing a bitstream generated by an image encoding method or apparatus according to this disclosure.

[0035] Furthermore, according to this disclosure, a recording medium can be provided that stores a bitstream received, decoded, and used to reconstruct an image by an image decoding device according to this disclosure.

[0036] Those skilled in the art will understand that the effects achievable through this disclosure are not limited to those specifically described above, and that other advantages of this disclosure will become clearer from the detailed description. Attached Figure Description

[0037] Figure 1 This is a view schematically illustrating a video encoding system to which embodiments of this disclosure are applicable.

[0038] Figure 2 This is a schematic view illustrating an image encoding device to which embodiments of the present disclosure are applicable.

[0039] Figure 3 This is a schematic view illustrating an image decoding device to which embodiments of the present disclosure are applicable.

[0040] Figure 4 This is a view illustrating an example of a schematic screen decoding process to which embodiments of this disclosure are applicable.

[0041] Figure 5 This is a view illustrating an example of a schematic screen encoding process to which embodiments of this disclosure are applicable.

[0042] Figure 6 This is a view showing an example of the layered structure of an encoded image / video.

[0043] Figure 7 This is a view illustrating the syntax structure of a VPS according to an embodiment of this disclosure.

[0044] Figure 8 This is a view illustrating the syntax structure of an SPS that signals HRD parameters according to an embodiment of this disclosure.

[0045] Figure 9 This is a view illustrating the general_hrd_parameters() syntax structure according to an embodiment of this disclosure.

[0046] Figure 10 This is a view illustrating the ols_hrd_parameters() syntax structure according to an embodiment of this disclosure.

[0047] Figure 11 This is a view illustrating the sublayer_hrd_parameters() syntax structure according to an embodiment of this disclosure.

[0048] Figure 12 This is a view illustrating an example of an image encoding method to which embodiments of this disclosure are applicable.

[0049] Figure 13 This is a view illustrating an example of an image decoding method to which embodiments of the present disclosure are applicable.

[0050] Figure 14 This is a view illustrating another example of an image decoding method to which embodiments of this disclosure are applicable.

[0051] Figure 15This is a view illustrating the processing of encoding HRD parameters based on num_ols_hrd_params_minus1 according to another embodiment of this disclosure.

[0052] Figure 16 This is a view illustrating the process of decoding HRD parameters based on num_ols_hrd_params_minus1 according to another embodiment of this disclosure.

[0053] Figure 17 This is a view illustrating the content streaming system to which embodiments of this disclosure are applicable. Detailed Implementation

[0054] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings to facilitate implementation by those skilled in the art. However, this disclosure can be implemented in various different forms and is not limited to the embodiments described herein.

[0055] In describing this disclosure, detailed descriptions of relevant known functions or constructions will be omitted if they unnecessarily obscure the scope of this disclosure. In the accompanying drawings, portions irrelevant to the description of this disclosure are omitted, and similar reference numerals are assigned to similar portions.

[0056] In this disclosure, when a component is "connected," "coupled," or "linked" to another component, it may include not only direct connections but also indirect connections where intermediate components exist. Furthermore, when a component "comprises" or "has" other components, unless otherwise stated, it means that other components may be included, not excluded.

[0057] In this disclosure, the terms first, second, etc., are used only for the purpose of distinguishing one component from other components and do not limit the order or importance of the components, unless otherwise stated. Accordingly, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0058] In this disclosure, the components are distinguished from each other to clearly describe each feature, but this does not mean that the components must be separate. That is, multiple components may be integrated into a single hardware or software unit, or a single component may be distributed and implemented across multiple hardware or software units. Therefore, unless otherwise specified, implementations of these integrated or distributed components are included within the scope of this disclosure.

[0059] In this disclosure, the components described in the various embodiments are not necessarily essential components, and some components may be optional. Therefore, embodiments consisting of a subset of the components described in the embodiments are also included within the scope of this disclosure. Furthermore, embodiments that include other components besides those described in the various embodiments are also included within the scope of this disclosure.

[0060] This disclosure relates to the encoding and decoding of images. Unless redefined in this disclosure, the terms used herein may have the general meaning commonly used in the art to which this disclosure pertains.

[0061] In this disclosure, a "picture" generally refers to a unit representing an image within a specific time period, while a slice / tile is a coding unit that constitutes part of a picture. A picture can be composed of one or more slices / tiles. Furthermore, a slice / tile may include one or more coding tree units (CTUs).

[0062] In this disclosure, "pixel" or "pixel" can refer to the smallest unit that constitutes a frame (or image). Furthermore, "sample" can be used as a term corresponding to a pixel. A sample can generally represent a pixel or a pixel value, or it can represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chrominance component.

[0063] In this disclosure, "unit" can refer to a basic unit of image processing. A unit may include at least one of a specific region of a picture and information associated with that region. In some cases, the term "unit" may be used interchangeably with terms such as "sample array," "block," or "region." Generally, an M×N block may include a set (or array) of samples (or transform coefficients) with M columns and N rows.

[0064] In this disclosure, "current block" can mean one of "current coding block," "current coding unit," "coding target block," "decoding target block," or "processing target block." When performing prediction, "current block" can mean "current prediction block" or "prediction target block." When performing transform (inverse transform) / quantization (dequantization), "current block" can mean "current transform block" or "transform target block." When performing filtering, "current block" can mean "filter target block."

[0065] Furthermore, in this disclosure, unless explicitly stated as a chroma block, "current block" may mean a block that includes both luma component blocks and chroma component blocks, or "the luma block of the current block." "The luma block of the current block" can be represented by an explicit description including luma component blocks such as "luma block" or "current luma block." "The chroma block of the current block" can be represented by an explicit description including chroma component blocks such as "chroma block" or "current chroma block."

[0066] In this specification, “A or B” may mean “A only”, “B only”, or “A and B”. In other words, in this disclosure, “A or B” can be interpreted as “A and / or B”. For example, in this disclosure, “A, B or C” may mean “A only”, “B only”, “C only”, or “any combination of A, B and C”.

[0067] As used in this disclosure, a forward slash ( / ) or a comma can mean "and / or". For example, "A / B" can mean "A and / or B". Thus, "A / B" can mean "A only", "B only", or "A and B". For example, "A,B,C" can mean "A, B, or C".

[0068] In this disclosure, "at least one of A and B" may mean "only A", "only B" or "both A and B". Furthermore, in this disclosure, "at least one of A or B" or "at least one of A and / or B" may be interpreted as the same as "at least one of A and B".

[0069] Furthermore, in this 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." Additionally, in this disclosure, "at least one of A, B, or C" or "at least one of A, B, and / or C" may be interpreted as the same as "at least one of A, B, and C."

[0070] Furthermore, the parentheses used in this disclosure may mean "for example". Specifically, when describing "prediction (intra-frame prediction)", "intra-frame prediction" may be cited as an example of "prediction". In other words, the "prediction" in this disclosure is not limited to "intra-frame prediction", and "intra-frame prediction" may be cited as an example of "prediction". In addition, even when describing "prediction (i.e., intra-frame prediction)", "intra-frame prediction" may be cited as an example of "prediction".

[0071] In this disclosure, the technical features described individually in a single figure can be implemented individually or simultaneously.

[0072] Overview of Video Encoding Systems

[0073] Figure 1 This is a view showing a video encoding system according to this disclosure.

[0074] The video encoding system according to the embodiment may include an encoding device 10 and a decoding device 20. The encoding device 10 may deliver encoded video and / or image information or data to the decoding device 20 in the form of a file or stream via a digital storage medium or network.

[0075] The encoding device 10 according to an embodiment may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding device 20 according to an embodiment may include a receiver 21, a decoding unit 22, and a renderer 23. The encoding unit 12 may be referred to as a video / image encoding unit, and the decoding unit 22 may be referred to as a video / image decoding unit. The transmitter 13 may be included in the encoding unit 12. The receiver 21 may be included in the decoding unit 22. The renderer 23 may include a display, and the display may be configured as a separate device or an external component.

[0076] The video source generator 11 can acquire video / images through a process of capturing, compositing, or generating video / images. The video source generator 11 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 video / images, etc. The video / image generation device may include, for example, a computer, tablet computer, and smartphone, and can generate video / images (electronically). For example, virtual video / images can be generated by a computer, etc. In this case, the video / image capture process can be replaced by a process of generating related data.

[0077] The encoding unit 12 can encode the input video / image. For compression and encoding efficiency, the encoding unit 12 can perform a series of processes, such as prediction, transformation, and quantization. The encoding unit 12 can output encoded data (encoded video / image information) in the form of a bitstream.

[0078] Transmitter 13 can transmit encoded video / image information or data, output in bitstream form, to receiver 21 of decoding device 20 in the form of a file or stream via digital storage medium or network. Digital storage medium can include various storage media, such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. Transmitter 13 can include elements for generating media files according to a predetermined file format and may include elements for transmission via broadcast / communication networks. Receiver 21 can extract / receive bitstreams from storage medium or network and transmit the bitstreams to decoding unit 22.

[0079] The decoding unit 22 can decode video / images by performing a series of processes corresponding to the operations of the encoding unit 12, such as dequantization, inverse transform, and prediction.

[0080] Renderer 23 can render decoded video / images. The rendered video / images can be displayed on a monitor.

[0081] Overview of Image Encoding Devices

[0082] Figure 2 This is a schematic view illustrating an image encoding device to which embodiments of this disclosure may be applied.

[0083] like Figure 2 As shown, the image encoding device 100 may include an image segmenter 110, a subtractor 115, a transformer 120, a quantizer 130, a dequantizer 140, an inverse transformer 150, an adder 155, a filter 160, a memory 170, an inter-frame predictor 180, an intra-frame predictor 185, and an entropy encoder 190. The inter-frame predictor 180 and the intra-frame predictor 185 may be collectively referred to as "predictors". The transformer 120, quantizer 130, dequantizer 140, and inverse transformer 150 may be included in a residual processor. The residual processor may also include a subtractor 115.

[0084] In some implementations, all or at least some of the components configuring the image encoding device 100 may be configured by a single hardware component (e.g., an encoder or a processor). Furthermore, the memory 170 may include a decoded screen buffer (DPB) and may be configured by a digital storage medium.

[0085] Image segmenter 110 can segment an input image (or picture or frame) input to image encoding device 100 into one or more processing units. For example, a processing unit may be called an encoding unit (CU). Encoding units can be obtained by recursively segmenting encoding tree units (CTUs) or maximum encoding units (LCUs) according to a quadtree / binary tree / tritree (QT / BT / TT) structure. For example, an encoding unit can be segmented into multiple encoding units of greater depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. For the segmentation of encoding units, a quadtree structure can be applied first, followed by a binary tree structure and / or a ternary tree structure. The encoding process according to this disclosure can be performed based on the final encoding unit that is no longer segmented. The maximum encoding unit can be used as the final encoding unit, or a deeper encoding unit obtained by segmenting the maximum encoding unit can be used as the final encoding unit. Here, the encoding process may include prediction, transformation, and reconstruction processes, which will be described later. As another example, the processing unit of the encoding process may be a prediction unit (PU) or a transformation unit (TU). Prediction units and transform units can be partitioned or segmented from the final coding unit. Prediction units can be sample prediction units, and transform units can be units used to derive transform coefficients and / or units used to derive residual signals from transform coefficients.

[0086] The predictor (inter-frame predictor 180 or intra-frame predictor 185) can perform prediction on the block to be processed (the current block) and generate a prediction block that includes prediction samples of the current block. The predictor can determine whether to apply intra-frame prediction or inter-frame prediction based on the current block or CU. The predictor can generate various information related to the prediction of the current block and transmit the generated information to the entropy encoder 190. The information about the prediction can be encoded in the entropy encoder 190 and output as a bitstream.

[0087] Intra-predictor 185 can predict the current block by referencing samples in the current frame. Depending on the intra-prediction mode and / or intra-prediction technique, the reference samples may be located among the neighbors of the current block or may be placed separately. Intra-prediction modes may include multiple non-directional modes and multiple directional modes. Non-directional modes may include, for example, DC mode and planar mode. Depending on the level of detail in the prediction direction, directional modes may include, for example, 33 or 65 directional prediction modes. However, this is merely an example, and more or fewer directional prediction modes may be used depending on the settings. Intra-predictor 185 can determine the prediction mode to be applied to the current block by using prediction modes applied to neighboring blocks.

[0088] Inter-frame predictor 180 can deduce the predicted block of the current block based on a reference block (reference sample array) specified by motion vectors on a reference frame. In this case, to reduce the amount of motion information transmitted in inter-frame prediction mode, motion information can be predicted on a block, sub-block, or sample basis based on the correlation of motion information between neighboring blocks and the current block. Motion information may include motion vectors and reference frame indices. Motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, dual prediction, etc.) information. In the case of inter-frame prediction, neighboring blocks may include spatially neighboring blocks existing in the current frame and temporally neighboring blocks existing in the reference frame. The reference frame including the reference block and the reference frame including the temporally neighboring block may be the same or different. The temporally neighboring block may be referred to as a juxtaposed reference block, a juxtaposed CU (colCU), etc. The reference frame including the temporally neighboring block may be referred to as a juxtaposed frame (colPic). For example, inter-frame predictor 180 can configure a motion information candidate list based on neighboring blocks and generate information indicating which candidate to use to deduce the motion vector and / or reference frame index of the current block. Inter-frame prediction can be performed based on various prediction modes. For example, in skip mode and merge mode, the inter-frame predictor 180 can use motion information from neighboring blocks as motion information for the current block. In skip mode, unlike merge mode, residual signals may not be transmitted. In motion vector prediction (MVP) mode, motion vectors from neighboring blocks can be used as motion vector predictors, and the motion vector of the current block can be signaled by encoding motion vector differences and indicators of the motion vector predictors. The motion vector difference can refer to the difference between the motion vector of the current block and the motion vector predictor.

[0089] The predictor can generate a prediction signal based on various prediction methods and techniques described below. For example, the predictor can apply not only intra-frame prediction or inter-frame prediction, but also both intra-frame prediction and inter-frame prediction simultaneously to predict the current block. A prediction method that simultaneously applies both intra-frame prediction and inter-frame prediction to predict the current block can be called Combined Intra-Frame and Inter-Frame Prediction (CIIP). Furthermore, the predictor can perform Intra-Frame Block Copy (IBC) to predict the current block. Intra-Frame Block Copy can be used for content image / video coding in games, such as Screen Content Coding (SCC). IBC is a method of predicting the current frame using a previously reconstructed reference block in the current frame at a predetermined distance from the current block. When IBC is applied, the position of the reference block in the current frame can be encoded as a vector (block vector) corresponding to the predetermined distance. IBC essentially performs prediction in the current frame, but can be performed similarly to inter-frame prediction because the reference block is derived within the current frame. That is, IBC can use at least one inter-frame prediction technique described in this disclosure.

[0090] The predicted signal generated by the predictor can be used to generate a reconstructed signal or a residual signal. Subtractor 115 generates a residual signal (residual block or residual sample array) by subtracting the predicted signal (predicted block or predicted sample array) output from the predictor from the input image signal (original block or original sample array). The generated residual signal can be transmitted to converter 120.

[0091] Transformer 120 can generate transform coefficients by applying transform techniques to the residual signal. For example, the transform techniques may include at least one of Discrete Cosine Transform (DCT), Discrete Sine Transform (DST), Karhunen-Loève Transform (KLT), Graph-Based Transform (GBT), or Conditional Nonlinear Transform (CNT). Here, GBT refers to a transform obtained from a graph when the relationship information between pixels is represented graphically. CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. Furthermore, the transform processing can be applied to square pixel blocks of the same size or to blocks of variable size instead of square.

[0092] Quantizer 130 quantizes the transform coefficients and transmits them to entropy encoder 190. Entropy encoder 190 encodes the quantized signal (information about the quantized transform coefficients) and outputs a bitstream. This information about the quantized transform coefficients can be referred to as residual information. Quantizer 130 can rearrange the block-type quantized transform coefficients into a one-dimensional vector based on the coefficient scan order and generate information about the quantized transform coefficients based on this one-dimensional vector form.

[0093] The entropy encoder 190 can perform various encoding methods, such as exponential Columbus coding, context-adaptive variable-length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoder 190 can encode, either together or separately, the information required for video / image reconstruction other than the quantization transform coefficients (e.g., values ​​of syntax elements). The encoded information (e.g., encoded video / image information) can be transmitted or stored in bitstream form at the Network Abstraction Layer (NAL) level. The video / image information may also include information about various parameter sets, such as Adaptive Parameter Set (APS), Picture Parameter Set (PPS), Sequence Parameter Set (SPS), or Video Parameter Set (VPS). Furthermore, the video / image information may also include general constraint information. The signaled information, transmitted information, and / or syntax elements described in this disclosure can be encoded and included in the bitstream through the above encoding process.

[0094] The bitstream can be transmitted over a network or stored in a digital storage medium. The network may include broadcast networks and / or communication networks, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. A transmitter (not shown) for transmitting the signal output from the entropy encoder 190 and / or a storage unit (not shown) for storing the signal may be included as internal / external components of the image encoding device 100. Alternatively, a transmitter may be provided as a component of the entropy encoder 190.

[0095] The quantization transform coefficients output from quantizer 130 can be used to generate residual signals. For example, the residual signals (residual blocks or residual samples) can be reconstructed by applying dequantization and inverse transform to the quantization transform coefficients through dequantizer 140 and inverse transformer 150.

[0096] Adder 155 adds the reconstructed residual signal to the prediction signal output from inter-frame predictor 180 or intra-frame predictor 185 to generate a reconstructed signal (reconstructed frame, reconstructed block, reconstructed sample array). If the block to be processed has no residual, such as in the case of applying skip mode, the prediction block can be used as a reconstructed block. Adder 155 can be referred to as a reconstructor or reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current frame, and can be used for inter-frame prediction of the next frame by filtering as described below.

[0097] Filter 160 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, filter 160 can generate a modified reconstructed image by applying various filtering methods to the reconstructed image and store the modified reconstructed image in memory 170, specifically in the DPB of memory 170. Various filtering methods can include, for example, deblocking filtering, sample adaptive offsetting, adaptive loop filtering, bilateral filtering, etc. Filter 160 can generate various filtering-related information and transmit the generated information to entropy encoder 190, as described later in the description of each filtering method. The filtering-related information can be encoded by entropy encoder 190 and output as a bitstream.

[0098] The modified reconstructed frame transmitted to memory 170 can be used as a reference frame in inter-frame predictor 180. When inter-frame prediction is applied by image encoding device 100, prediction mismatch between image encoding device 100 and image decoding device can be avoided and coding efficiency can be improved.

[0099] The DPB of memory 170 can store modified reconstructed frames for use as reference frames in inter-frame predictor 180. Memory 170 can store motion information of blocks from which motion information in the current frame is derived (or encoded) and / or motion information of already reconstructed blocks in the frame. The stored motion information can be transmitted to inter-frame predictor 180 and used as motion information for spatially or temporally neighboring blocks. Memory 170 can store reconstructed samples of reconstructed blocks in the current frame and can transmit the reconstructed samples to intra-frame predictor 185.

[0100] Overview of image decoding devices

[0101] Figure 3 This is a schematic view illustrating an image decoding device to which embodiments of the present disclosure may be applied.

[0102] like Figure 3 As shown, the image decoding device 200 may include an entropy decoder 210, a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame predictor 260, and an intra-frame predictor 265. The inter-frame predictor 260 and the intra-frame predictor 265 may be collectively referred to as "predictors". The dequantizer 220 and the inverse transformer 230 may be included in a residual processor.

[0103] According to an implementation, all or at least some of the components of the image decoding device 200 can be configured by hardware components (e.g., a decoder or a processor). Furthermore, the memory 250 may include a decoded screen buffer (DPB) or may be configured by a digital storage medium.

[0104] The image decoding device 200, having received a bitstream including video / image information, can perform operations related to... Figure 2 The image is reconstructed by processing corresponding to the processing performed by the image encoding device 100. For example, the image decoding device 200 can perform decoding using a processing unit applied in the image encoding device. Therefore, the decoding processing unit can be, for example, an encoding unit. The encoding unit can be obtained by segmenting a coding tree unit or a maximum coding unit. The reconstructed image signal decoded and output by the image decoding device 200 can be reproduced by a reproduction device (not shown).

[0105] Image decoding device 200 can receive data in bitstream form from... Figure 2The signal output by the image encoding device. The received signal can be decoded by the entropy decoder 210. For example, the entropy decoder 210 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 adaptive parameter sets (APS), picture parameter sets (PPS), sequence parameter sets (SPS), or video parameter sets (VPS). In addition, the video / image information may also include general constraint information. The image decoding device can also decode the picture based on the information about the parameter sets and / or general constraint information. The information and / or syntax elements notified / received by signals described in this disclosure can be decoded and obtained from the bitstream through the decoding process. For example, the entropy decoder 210 decodes the information in the bitstream based on encoding methods such as exponential Golomb coding, CAVLC, or CABAC, and outputs the values ​​of the syntax elements required for image reconstruction and the quantized values ​​of the transform coefficients of the residuals. More specifically, the CABAC entropy decoding method can receive bins corresponding to each syntax element in the bitstream, determine the context model using information about the target syntax element, decoding information of neighboring blocks and the target block, or information about symbols / bins decoded in the previous stage, perform arithmetic decoding on the bins based on the determined context model by predicting the occurrence probability of the bins, and generate symbols corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method can update the context model after determining the context model by using the information of the decoded symbols / bins for the context model of the next symbol / bin. The prediction-related information in the information decoded by the entropy decoder 210 can be provided to the predictors (inter-frame predictor 260 and intra-frame predictor 265), and the residual value of entropy decoding performed in the entropy decoder 210, i.e., the quantization transform coefficients and related parameter information, can be input to the dequantizer 220. In addition, the filtering information in the information decoded by the entropy decoder 210 can be provided to the filter 240. Furthermore, the receiver (not shown) for receiving signals output from the image encoding device may be further configured as an internal / external element of the image decoding device 200, or the receiver may be a component of the entropy decoder 210.

[0106] Furthermore, the image decoding apparatus according to this disclosure can be referred to as a video / image / screen decoding apparatus. The image decoding apparatus can be divided into an information decoder (video / image / screen information decoder) and a sample decoder (video / image / screen sample decoder). The information decoder may include an entropy decoder 210. The sample decoder may include at least one of a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame predictor 260, or an intra-frame predictor 265.

[0107] Dequantizer 220 can dequantize the quantized transform coefficients and output transform coefficients. Dequantizer 220 can rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement can be performed based on the coefficient scan order performed in the image encoding device. Dequantizer 220 can obtain transform coefficients by performing dequantization on the quantized transform coefficients using quantization parameters (e.g., quantization step size information).

[0108] The inverse transformer 230 can perform inverse transformation on the transformation coefficients to obtain the residual signal (residual block, residual sample array).

[0109] The predictor can perform prediction on the current block and generate a prediction block that includes prediction samples of the current block. The predictor can determine whether to apply intra-frame prediction or inter-frame prediction to the current block based on the prediction information output from the entropy decoder 210, and can determine a specific intra-frame / inter-frame prediction mode (prediction technique).

[0110] Similar to that described in the predictor of the image coding device 100, the predictor can generate a predictive signal based on various prediction methods (techniques) described later.

[0111] Intra-predictor 265 can predict the current block by referring to samples in the current frame. The description of intra-predictor 185 also applies to intra-predictor 265.

[0112] Inter-frame predictor 260 can deduce the predicted block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference frame. In this case, to reduce the amount of motion information transmitted in the inter-frame prediction mode, motion information can be predicted on a block, sub-block, or sample basis based on the correlation of motion information between neighboring blocks and the current block. Motion information may include motion vectors and reference frame indices. Motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, dual prediction, etc.) information. In the case of inter-frame prediction, neighboring blocks may include spatially neighboring blocks existing in the current frame and temporally neighboring blocks existing in the reference frame. For example, inter-frame predictor 260 can configure a motion information candidate list based on neighboring blocks and deduce the motion vector and / or reference frame index of the current block based on the received candidate selection information. Inter-frame prediction can be performed based on various prediction modes, and the information about the prediction may include information indicating the inter-frame prediction mode of the current block.

[0113] Adder 235 generates a reconstruction signal (reconstructed frame, reconstruction block, reconstruction sample array) by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the predictor (including inter-frame predictor 260 and / or intra-frame predictor 265). If the block to be processed has no residual (e.g., in the case of applying skip mode), the prediction block can be used as a reconstruction block. The description of adder 155 also applies to adder 235. Adder 235 may be referred to as a reconstructor or reconstruction block generator. The generated reconstruction signal can be used for intra-frame prediction of the next block to be processed in the current frame, and can be used for inter-frame prediction of the next frame by filtering as described below.

[0114] Filter 240 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, filter 240 can generate a modified reconstructed image by applying various filtering methods to the reconstructed image and store the modified reconstructed image in memory 250, specifically in the DPB of memory 250. Various filtering methods may include, for example, deblocking filtering, adaptive sample shifting, adaptive loop filtering, bilateral filtering, etc.

[0115] The (modified) reconstructed frame stored in the DPB of memory 250 can be used as a reference frame in inter-frame predictor 260. Memory 250 can store motion information of blocks from which motion information in the current frame is derived (or decoded) and / or motion information of already reconstructed blocks in the frame. The stored motion information can be transmitted to inter-frame predictor 260 to be used as motion information for spatially or temporally neighboring blocks. Memory 250 can store reconstructed samples of reconstructed blocks in the current frame and transmit the reconstructed samples to intra-frame predictor 265.

[0116] In this disclosure, the embodiments described in the filter 160, inter-frame predictor 180 and intra-frame predictor 185 of the image encoding device 100 can be applied equally or correspondingly to the filter 240, inter-frame predictor 260 and intra-frame predictor 265 of the image decoding device 200.

[0117] General image / video encoding process

[0118] In image / video coding, the frames of an image / video can be encoded / decoded according to the decoding order. The output order of the decoded frames can be set differently from the decoding order, and based on this, not only forward prediction but also backward prediction can be performed during inter-frame prediction.

[0119] Figure 4 An example of an illustrative screen decoding process to which embodiments of this disclosure apply is shown.

[0120] Figure 4The processes shown can be derived from Figure 3 The image decoding device performs the following steps: For example, step S410 can be performed by entropy decoder 210, step S420 can be performed by a predictor including predictors 265 and 260, step S430 can be performed by residual processors 220 and 230, step S440 can be performed by adder 235, and step S450 can be performed by filter 240. Step S410 may include the information decoding process described in this disclosure, step S420 may include the inter-frame / intra-frame prediction process described in this disclosure, step S430 may include the residual processing process described in this disclosure, step S440 may include the block / frame reconstruction process described in this disclosure, and step S450 may include the in-loop filtering process described in this disclosure.

[0121] Reference Figure 4 The image decoding process can schematically include a process for obtaining image / video information from the bitstream (through decoding) (S410), an image reconstruction process (S420 to S440), and an in-loop filtering process for the reconstructed image (S450). The image reconstruction process can be performed based on prediction samples and residual samples obtained through inter-frame / intra-frame prediction (S420) and residual processing (S430) (dequantization and inverse transform of quantization transform coefficients) described in this disclosure. A modified reconstructed image can be generated by an in-loop filtering process for the reconstructed image generated by the image reconstruction process. In this case, the modified reconstructed image can be stored as a decoded image output in the decoded image buffer (DPB) of memory 250 and used as a reference image in the inter-frame prediction process when the image is decoded later. The in-loop filtering process (S450) can be omitted. In this case, the reconstructed image can be stored as a decoded image output in the DPB of memory 250 and used as a reference image in the inter-frame prediction process when the image is decoded later. As described above, the in-loop filtering process (S450) may include a deblocking filtering process, a sample adaptive offset (SAO) process, an adaptive loop filter (ALF) process, and / or a bilateral filter process, some or all of which may be omitted. Furthermore, one or more of the deblocking filtering process, the sample adaptive offset (SAO) process, the adaptive loop filter (ALF) process, and / or the bilateral filter process may be applied sequentially, or all of them may be applied sequentially. For example, the SAO process may be performed after applying the deblocking filtering process to the reconstructed image. Alternatively, the ALF process may be performed after applying the deblocking filtering process to the reconstructed image. This can even be performed similarly in an encoding device.

[0122] Figure 5 An example of an illustrative screen encoding process to which embodiments of this disclosure are applicable is shown.

[0123] Figure 5 The processes shown can be derived from Figure 2 The image encoding device performs the operation. For example, step S510 can be performed by predictors 185 and 180, step S520 can be performed by residual processors 115, 120 and 130, and step S530 can be performed in entropy encoder 190. Step S510 may include the inter-frame / intra-frame prediction process described in this disclosure, step S520 may include the residual processing process described in this disclosure, and step S530 may include the information encoding process described in this disclosure.

[0124] Reference Figure 5 The image encoding process can be schematically described as including not only the process of encoding information used for image reconstruction (e.g., prediction information, residual information, segmentation information, etc.) and outputting it in the form of a bitstream, but also the process of generating a reconstructed image for the current image and the process of applying in-loop filtering to the reconstructed image (optional), as shown in the reference. Figure 2 The encoding device can derive (modified) residual samples from the quantization transform coefficients using dequantizer 140 and inverse transformer 150, and generate a reconstructed frame based on the predicted samples and (modified) residual samples as the output of step S510. The reconstructed frame thus generated can be equal to the reconstructed frame generated in the decoding device. A modified reconstructed frame can be generated by an in-loop filtering process on the reconstructed frame. In this case, the modified reconstructed frame can be stored in the decoding frame buffer or memory 170, and similar to the decoding device, can be used as a reference frame during inter-frame prediction when the frame is encoded later. As described above, in some cases, some or all of the in-loop filtering process can be omitted. When the in-loop filtering process is performed, the (in-loop) filtering-related information (parameters) can be encoded in the entropy encoder 190 and output as a bitstream, and the decoding device can perform the in-loop filtering process using the same method as the encoding device based on the filtering-related information.

[0125] This in-loop filtering process reduces noise (e.g., block artifacts and ringing artifacts) that occurs during image / video encoding, and improves subjective / objective visual quality. Furthermore, by performing the in-loop filtering process in both the encoding and decoding devices, the encoding and decoding devices can derive the same prediction results, increasing the reliability of image encoding and reducing the amount of data that needs to be sent for image encoding.

[0126] As described above, the image reconstruction process can be performed not only in an image decoding device but also in an image encoding device. Reconstruction blocks can be generated on a block-by-block basis based on intra-frame prediction / inter-frame prediction, and a reconstructed image including these blocks can be generated. When the current image / slice / patch group is an I-frame / slice / patch group, the blocks included in the current image / slice / patch group can be reconstructed based solely on intra-frame prediction. On the other hand, when the current image / slice / patch group is a P-frame / slice / patch group or a B-frame / slice / patch group, the blocks included in the current image / slice / patch group can be reconstructed based on either intra-frame prediction or inter-frame prediction. In this case, inter-frame prediction can be applied to some blocks in the current image / slice / patch group, and intra-frame prediction can be applied to the remaining blocks. The color components of the image can include luminance components and chrominance components, and unless explicitly limited in this disclosure, the methods and implementations of this disclosure are applicable to both luminance and chrominance components.

[0127] Example of coding layer structure

[0128] For example, the encoded video / image according to this disclosure can be processed according to the following coding layers and structure.

[0129] Figure 6 This is a view showing the layer structure of the encoded image.

[0130] Encoded images are classified into a Video Coding Layer (VCL) for image decoding and processing, a lower layer system for sending and storing encoded information, and a Network Abstraction Layer (NAL) that exists between the VCL and the lower layer system and is responsible for network adaptation functions.

[0131] In VCL, VCL data that includes compressed image data (slice data) can be generated, or additional enhancement information (SEI) messages required for image decoding processing or parameter sets that include information such as picture parameter set (PPS), sequence parameter set (SPS), or video parameter set (VPS) can be generated.

[0132] In NAL, header information (NAL cell header) can be added to the raw byte sequence payload (RBSP) generated in VCL to generate NAL cells. In this case, RBSP refers to the slice data, parameter set, and SEI message generated in VCL. The NAL cell header may include NAL cell type information specified according to the RBSP data included in the corresponding NAL cell.

[0133] like Figure 6As shown, NAL units can be classified into VCL NAL units and non-VCL NAL units based on the RBSP generated in the VCL. A VCL NAL unit can refer to a NAL unit that includes information about the image (slice data), while a non-VCL NAL unit can refer to a NAL unit that includes information required for decoding the image (parameter set or SEI message).

[0134] VCL NAL units and non-VCL NAL units can be appended with header information and sent over the network according to the data standard of the underlying system. For example, NAL units can be modified to a predetermined standard (e.g., H.266 / VVC file format, RTP (Real-Time Transport Protocol), or TS (Transport Stream)) data format and sent over various networks.

[0135] As described above, within a NAL unit, the NAL unit type can be specified based on the RBSP data structure included in the corresponding NAL unit, and information about the NAL unit type can be stored in the NAL unit header and signaled. For example, this can be broadly categorized into VCL NAL unit types and non-VCL NAL unit types based on whether the NAL unit includes information about the image (slice data). VCL NAL unit types can be categorized based on the nature and type of the image included in the VCL NAL unit, while non-VCL NAL unit types can be categorized based on the type of parameter set.

[0136] Below are examples of NAL cell types specified based on the type of parameter set / information included in non-VCL NAL cell types.

[0137] - DCI (Decoding Capability Information) NAL Unit Type (NUT): Includes the NAL unit type of DCI.

[0138] -VPS (Video Parameter Set) NUT: Includes the NAL unit type of the VPS.

[0139] -SPS (Sequence Parameter Set) NUT: NAL unit type including SPS

[0140] -PPS (Picture Parameter Set) NUT: Includes the NAL unit type of PPS.

[0141] -APS (Adaptive Parameter Set) NUT: Includes NAL unit types of APS.

[0142] -PH (Header) NUT: Includes the NAL unit type of PH.

[0143] The aforementioned NAL unit type can have syntax information for the NAL unit type, and this syntax information can be stored in the NAL unit header and signaled. For example, this syntax information can be nal_unit_type, and the NAL unit type can be specified using the nal_unit_type value.

[0144] Furthermore, as mentioned above, a frame can include multiple slices, and a slice can include a slice header and slice data. In this case, a frame header can be further added to the multiple slices (slice headers and slice data sets) within a frame. The frame header (frame header syntax) can include information / parameters common to the frame. The slice header (slice header syntax) can include information / parameters common to the slice. APS (APS syntax) or PPS (PPS syntax) can include information / parameters common to one or more slices or frames. SPS (SPS syntax) can include information / parameters common to one or more sequences. VPS (VPS syntax) can be information / parameters common to multiple layers. DCI (DCI syntax) can include information / parameters related to decoding capabilities.

[0145] In this disclosure, the high-level syntax (HLS) may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DCI syntax, picture header syntax, or slice header syntax. Additionally, in this disclosure, the low-level syntax (LLS) may include, for example, slice data syntax, CTU syntax, coding unit syntax, transform unit syntax, etc.

[0146] Furthermore, in this disclosure, the image / video information encoded in the encoding device and signaled to the decoding device in the form of a bitstream may include not only intra-frame segmentation related information, intra / inter-frame prediction information, residual information, and intra-loop filtering information, but also information about slice headers, frame headers, APS, PPS, SPS, VPS, and / or DCI. Additionally, the image / video information may also include general constraint information and / or information about NAL unit headers.

[0147] High-level syntax signaling and semantics

[0148] As described above, the image / video information according to this disclosure may include High-Level Syntax (HLS). Image encoding methods and / or image decoding methods may be performed based on the image / video information.

[0149] Video Parameter Set Signaling

[0150] A Video Parameter Set (VPS) is a set of parameters used to carry layer information. For example, layer information may include information about the Output Layer Set (OLS), information about the profile layer level, information about the relationship between the OLS and the hypothetical reference decoder, and information about the relationship between the OLS and the Decoder Picture Buffer (DPB). A VPS may not be necessary for decoding the bitstream.

[0151] The VPS raw byte sequence payload (RBSP) should be available for decoding processing and then referenced, either in at least one access unit (AU) with TemporalId equal to 0 or provided by external means.

[0152] All VPSNAL units in an encoded video sequence (CVS) with a specific value for vps_video_parameter_set_id should have the same content.

[0153] Figure 7 This is a view illustrating the syntax structure of a VPS according to an embodiment of this disclosure.

[0154] Figure 7 The syntax structure of the VPS shown includes only the syntax elements relevant to this disclosure. Figure 7 Various other syntax elements not shown in the diagram can be included in the VPS.

[0155] exist Figure 7 In the example shown, `vps_video_parameter_set_id` provides an identifier for the VPS. Other syntax elements can use `vps_video_parameter_set_id` to reference the VPS. The value of `vps_video_parameter_set_id` should be greater than 0.

[0156] Increasing `vps_max_layers_minus1` by 1 specifies the maximum allowed number of layers in each CVS of the reference VPS.

[0157] Increasing `vps_max_sublayers_minus1` by 1 specifies the maximum number of time-limited sublayers that can exist in the layers of each CVS of the reference VPS. `vps_max_sublayers_minus1` can be in the range of 0 to 6 (inclusive).

[0158] When both `vps_max_layers_minus1` and `vps_max_sublayers_minus1` are greater than 0, `vps_all_layers_same_num_sublayers_flag` can be signaled. `vps_all_layers_same_num_sublayers_flag` equaling the first value (e.g., 1) specifies that all layers in the various CVSs of the reference VPS have the same number of time sublayers. `vps_all_layers_same_num_sublayers_flag` equaling the second value (e.g., 0) specifies that layers in the various CVSs of the reference VPS may not have the same number of time sublayers. When `vps_all_layers_same_num_sublayers_flag` is not present, its value can be inferred to be equal to the first value (e.g., 1).

[0159] When `vps_max_layers_minus1` is greater than 0, `vps_all_independent_layers_flag` can be signaled. `vps_all_independent_layers_flag` equal to the first value (e.g., 1) specifies that all layers in the CVS are encoded independently without using inter-layer prediction. `vps_all_independent_layers_flag` equal to the second value (e.g., 0) specifies that one or more layers in the CVS can use inter-layer prediction. When `vps_all_independent_layers_flag` does not exist, its value can be inferred to be equal to the first value (e.g., 1).

[0160] When `vps_max_layers_minus1` is greater than 0, `each_layer_is_an_ols_flag` can be signaled. Additionally, when `vps_all_independent_layers_flag` equals the first value, `each_layer_is_an_ols_flag` can be signaled. `each_layer_is_an_ols_flag` equal to the first value (e.g., 1) specifies that each OLS contains only one layer. Furthermore, `each_layer_is_an_ols_flag` equal to the first value (e.g., 1) specifies that each layer in the reference VPS's CVS is itself an OLS (i.e., one layer contained in the OLS is an output-only layer). Additionally, `each_layer_is_an_ols_flag` equal to the second value (e.g., 0) specifies that at least one OLS can contain more than one layer. If `vps_max_layers_minus1` equals 0, the value of `each_layer_is_an_ols_flag` can be inferred to be equal to 1. Otherwise, when vps_all_independent_layers_flag equals 0, the value of each_layer_is_an_ols_flag can be inferred to be equal to 0.

[0161] When each_layer_is_an_ols_flag equals the second value (e.g., 0) and vps_all_independent_layers_flag equals the second value (e.g., 0), ols_mode_idc can be notified by a signal.

[0162] Setting `ols_mode_idc` to the first value (e.g., 0) allows you to specify that the total number of OLSs specified by the VPS is equal to `vps_max_layers_minus1+1`. In this case, the i-th OLS can contain layers with layer indices from 0 to i (inclusive). Additionally, for each OLS, only the layer with the highest layer index in the OLS (the highest layer) can be output.

[0163] Setting `ols_mode_idc` to the second value (e.g., 1) allows you to specify that the total number of OLSs specified by the VPS is equal to `vps_max_layers_minus1+1`. In this case, the i-th OLS can contain layers with layer indices from 0 to i (inclusive). Additionally, for each OLS, all layers in the OLS can be output.

[0164] The `ols_mode_idc` parameter, when set to a third value (e.g., 2), can explicitly signal the total number of OLS specified by the VPS. Additionally, for each OLS, the output layer is explicitly signaled. Other layers that are not output layers are layers that serve as direct or indirect reference layers to the output layers of the OLS.

[0165] When vps_all_independent_layers_flag equals 1 and each_layer_is_an_ols_flag equals 0, the value of ols_mode_idc can be inferred to be equal to the third value (e.g., 2).

[0166] When ols_mode_idc is 2, num_output_layer_sets_minus1 and ols_output_layer_flag[i][j] can be explicitly signaled.

[0167] Increasing 1 to num_output_layer_sets_minus1 specifies the total number of OLS specified for the VPS.

[0168] When ols_mode_idc is 2, ols_output_layer_flag[i][j] can specify whether the j-th layer of the i-th OLS is an output layer. ols_output_layer_flag[i][j] equal to the first value (e.g., 1) can specify that the layer whose layer identifier nuh_layer_id equals vps_layer_id[j] is an output layer of the i-th OLS. ols_output_layer_flag[i][j] equal to the second value (e.g., 0) can specify that the layer whose layer identifier nuh_layer_i equals vps_layer_id[j] is not an output layer of the i-th OLS.

[0169] The following describes the HRD parameters that are signaled in a VPS.

[0170] When `each_layer_is_an_ols_flag` equals the second value (e.g., 0), `vps_general_hrd_params_present_flag` can be signaled. `vps_general_hrd_params_present_flag` equaling the first value (e.g., 1) specifies that the `general_hrd_parameters()` syntax and other HRD parameters exist in the VPS. `vps_general_hrd_params_present_flag` equaling the second value (e.g., 0) specifies that the `general_hrd_parameters()` syntax and other HRD parameters do not exist in the VPS. When `vps_general_hrd_params_present_flag` does not exist, its value can be inferred to be equal to the second value (e.g., 0).

[0171] When the i-th OLS contains a layer (NumLayersInOls[i] equals 1), the general_hrd_parameters() syntax structure applied to the i-th OLS can exist in the sequence parameter set (SPS) referenced by the layer in the i-th OLS.

[0172] When `vps_max_sublayers_minus1` is greater than 0, `vps_sublayer_cpb_params_present_flag` can be signaled. `vps_sublayer_cpb_params_present_flag` equal to the first value (e.g., 1) specifies that the `i`th `ols_hrd_parameters()` syntax structure in the VPS contains HRD parameters for sublayers whose temporal identifier `TemporalId` is in the range of 0 to `hrd_max_tid[i]` (inclusive). `vps_sublayer_cpb_params_present_flag` equal to the second value (e.g., 0) specifies that the `i`th `ols_hrd_parameters()` syntax structure in the VPS contains only HRD parameters for sublayers whose temporal identifier `TemporalId` is equal to `hrd_max_tid[i]`. When `vps_max_sublayers_minus1` equals 0, `vps_sublayer_cpb_params_present_flag` can be inferred to be equal to the second value (e.g., 0).

[0173] When vps_sublayer_cpb_params_present_flag is equal to the second value (e.g., 0), the HRD parameters of sublayers with TemporalId in the range of 0 to hrd_max_tid[i]-1 (inclusive) are inferred to be the same as those of sublayers with TemporalId equal to hrd_max_tid[i].

[0174] Increasing `num_ols_hrd_params_minus1` by 1 specifies the number of `ols_hrd_parameters()` syntax structures in the VPS. `num_ols_hrd_params_minus1` can range from 0 to `TotalNumOlss-1`. `TotalNumOlss` specifies the total number of OLS specified by the VPS. In this disclosure, the `HRD` parameter can refer to `ols_hrd_parameters()`. Therefore, the number of `HRD` parameter syntax structures can refer to the number of `ols_hrd_parameters()` syntax structures.

[0175] When vps_max_sublayers_minus1 is greater than 0 and vps_all_layers_same_num_sublayers_flag is equal to the second value (e.g., 0), hrd_max_tid[i] can be signaled. hrd_max_tid[i] can specify the temporalId of the highest sublayer whose relevant HRD parameters are contained in the i-th ols_hrd_parameters() syntax structure.

[0176] hrd_max_tid[i] can be in the range of 0 to vps_max_sublayers_minus1 (inclusive). When vps_max_sublayers_minus1 equals 0, the value of hrd_max_tid[i] can be inferred to be equal to 0. When vps_max_sublayers_minus1 is greater than 0 and vps_all_layers_same_num_sublayers_flag equals 1, the value of hrd_max_tid[i] can be inferred to be equal to vps_max_sublayers_minus1.

[0177] like Figure 7As shown, the variable `firstSubLayer`, which specifies the temporal identifier `TemporalId` of the first sublayer, can be inferred to be 0 or `hrd_max_tid[i]` based on `vps_sublayer_cpb_params_present_flag`. Specifically, when `vps_sublayer_cpb_params_present_flag` equals 1, `firstSubLayer` can be inferred to be 0; otherwise, `firstSubLayer` can be inferred to be `hrd_max_tid[i]`. Based on the inferred `firstSubLayer` and `hrd_max_tid[i]`, the `ols_hrd_parameters()` syntax structure can be signaled.

[0178] When num_ols_hrd_params_minus1 plus 1 is not equal to TotalNumOlss and num_ols_hrd_params_minus1 is greater than 0, ols_hrd_idx[i] can be signaled. In this case, when the number of layers contained in the i-th OLS (NumLayersInOls[i]) is greater than 1, ols_hrd_idx[i] can be signaled for the i-th OLS. ols_hrd_idx[i] specifies the index of the ols_hrd_parameters() syntax structure applied to the i-th OLS in the list of ols_hrd_parameters() syntax structures in the VPS. The value of ols_hrd_idx[[i]] can be in the range from 0 to num_ols_hrd_params_minus1 (inclusive). When the number of layers contained in the i-th OLS (NumLayersInOls[i]) is equal to 1, the ols_hrd_parameters() syntax structure applied to the i-th OLS can exist in the SPS referenced by the layer in the i-th OLS.

[0179] In this disclosure, ols_hrd_idx[i] is the index of ols_hrd_parameters() applied to the i-th OLS or the i-th multi-level OLS, and can be referred to as the mapping information (information about the mapping) between the (multi-level) OLS and the HRD parameter syntax structure (ols_hrd_parameters()).

[0180] When num_ols_hrd_param_minus1 plus 1 equals TotalNumOlss, the value of ols_hrd_idx[i] can be inferred to be equal to i. Otherwise, when NumLayersInOls[i] is greater than 1 and num_ols_hrd_params_minus1 equals 0, the value of ols_hrd_idx[i] can be inferred to be equal to 0.

[0181] HRD Signaling in VPS and SPS

[0182] The signaling of the HRD parameters according to this disclosure will be described in more detail below. The HRD parameters can be signaled for each Output Layer Set (OLS). It is assumed that the reference decoder (HRD) is a hypothetical decoder model that specifies constraints on the variability of the consistent NAL unit stream or consistent byte stream that the encoding process can generate.

[0183] HRD parameters can be referenced as follows. Figure 7 The notification may be included in the VPS and signaled, or it may be included in the SPS and signaled.

[0184] Figure 8 This is a view illustrating the syntax structure of an SPS that signals HRD parameters according to an embodiment of this disclosure.

[0185] exist Figure 8In the example shown, `sps_ptl_dpb_hrd_params_present_flag` equal to the first value (e.g., 1) specifies that the `profile_tier_level()` and `dpb_parameters()` syntax structures exist in SPS. `profile_tier_level()` can be a syntax structure used to send parameters at the profile tier level, and `dpb_parameters()` can be a syntax structure used to send parameters for the decoded picture buffer (DPB). Alternatively, `sps_ptl_dpb_hrd_params_present_flag` equal to the first value (e.g., 1) specifies that the `general_hrd_parameters()` and `ols_hrd_parameters()` syntax structures exist in SPS. `sps_ptl_dpb_hrd_params_present_flag` equal to the second value (e.g., 0) specifies that the above four syntax structures do not exist in SPS. The value of sps_ptl_dpb_hrd_params_present_flag can be equal to the value of vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]. That is, the value of sps_ptl_dpb_hrd_params_present_flag can be encoded as the value of vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]].

[0186] In the above text, `vps_independent_layer_flag[i]` can be a syntax element included in and sent to the VPS. `vps_independent_layer_flag[i]` equal to the first value (e.g., 1) specifies that the layer at index i is an independent layer that does not use inter-layer prediction. `vps_independent_layer_flag[i]` equal to the second value (e.g., 0) specifies that the layer at index i can use inter-layer prediction. When `vps_independent_layer_flag[i]` does not exist, its value is inferred to be equal to the first value (e.g., 1).

[0187] When sps_ptl_dpb_hrd_params_present_flag equals 1, sps_general_hrd_params_present_flag can be notified via a signal.

[0188] A `sps_general_hrd_params_present_flag` equal to the first value (e.g., 1) specifies that SPS includes both the `general_hrd_parameters()` and `ols_hrd_parameters()` syntax structures. A `sps_general_hrd_params_present_flag` equal to the second value (e.g., 0) specifies that SPS does not include either the `general_hrd_parameters()` or `ols_hrd_parameters()` syntax structures.

[0189] like Figure 8 As shown, when `sps_max_sublayers_minus1` is greater than 0, `sps_sublayer_cpb_params_present_flag` can be signaled. In this case, adding 1 to `sps_max_sublayers_minus1` specifies the maximum number of temporal sublayers that can exist in each coding layer video sequence (CLVS) of the reference SPS. `sps_sublayer_cpb_params_present_flag` equal to the first value (e.g., 1) specifies that the `ols_hrd_parameters()` syntax structure in the SPS includes the HRD parameters of sublayers whose temporal layer identifier `TemporalId` is in the range of 0 to `sps_max_sublayers_minus1` (inclusive). `sps_sublayer_cpb_params_present_flag` equal to the second value (e.g., 0) specifies that the `ols_hrd_parameters()` syntax structure in the SPS only includes the HRD parameters of sublayers whose temporal layer identifier `TemporalId` is equal to `sps_max_sublayers_minus1`. When sps_max_sublayers_minus1 equals 0, the value of sps_sublayer_cpb_params_present_flag is inferred to be equal to the second value (e.g., 0).

[0190] When sps_sublayer_cpb_params_present_flag is equal to the second value (e.g., 0), the HRD parameters of sublayers whose temporal identifier TemporalId is in the range of 0 to sps_max_sublayers_minus1-1 (inclusive) are inferred to be the same as those of sublayers whose temporal identifier TemporalId is equal to sps_max_sublayers_minus1.

[0191] Figure 9This is a view illustrating the general_hrd_parameters() syntax structure according to an embodiment of this disclosure.

[0192] like Figure 9 As shown, the general_hrd_parameters() syntax structure can include some sequence-level HRD parameters used in HRD operations. The requirement for bitstream consistency is that the contents of general_hrd_parameters() in any VPS or SPS within the bitstream should be identical.

[0193] When the `general_hrd_parameters()` syntax is included in a VPS, it can be applied to all OLSs specified by the VPS. When the `general_hrd_parameters()` syntax is included in an SPS, it can be applied to the lowest-level OLS within a layer that only references the SPS. In this case, the lowest-level layer is an independent layer.

[0194] like Figure 9 As shown, the general_hrd_parameters() syntax structure is HRD parameters and can include syntax elements such as num_units_in_tick, time_scale, and general_nal_hrd_params_present_flag. Figure 9 The HRD parameters shown can have the same meaning as traditional HRD parameters. Therefore, detailed descriptions of HRD parameters that are not particularly relevant to this disclosure will be omitted.

[0195] Figure 10 This is a view illustrating the ols_hrd_parameters() syntax structure according to an embodiment of this disclosure.

[0196] When the ols_hrd_parameters() syntax structure is included in the VPS, the OLS applying the ols_hrd_parameters() syntax structure can be specified by the VPS. When the ols_hrd_parameters() syntax structure is included in the SPS, the ols_hrd_parameters() syntax structure can be applied to the OLS of the lowest layer in the layers containing the reference SPS. In this case, the lowest layer is an independent layer.

[0197] like Figure 10As shown, the ols_hrd_parameters() syntax structure is an HRD parameter and can include syntax elements such as fixed_pic_rate_general_flag, fixed_pic_rate_within_cvs_flag, and elemental_duration_in_tc_minus1. Figure 10 The HRD parameters shown can have the same meaning as traditional HRD parameters. Therefore, detailed descriptions of HRD parameters that are not particularly relevant to this disclosure will be omitted.

[0198] Figure 11 This is a view illustrating the sublayer_hrd_parameters() syntax structure according to an embodiment of this disclosure.

[0199] The sublayer_hrd_parameters() syntax structure can be included in Figure 10 The ols_hrd_parameters() syntax structure is used with signal notification.

[0200] like Figure 11 As shown, the sublayer_hrd_parameters() syntax structure is an HRD parameter and can include syntax elements such as bit_rate_value_minus1, cpb_size_value_minus1, and cpb_size_du_value_minus1. Figure 11 The HRD parameters shown can have the same meaning as traditional HRD parameters. Therefore, detailed descriptions of HRD parameters that are not particularly relevant to this disclosure will be omitted.

[0201] For reference, the output time can be the time when the reconstructed image is output from the DPB. The output time can be specified by the HRD based on the output timing DPB operation.

[0202] Two sets of HRD parameters can be used, such as NAL HRD parameters and VCL HRD parameters. HRD parameters can be signaled using the general_hrd_parameters() and ols_hrd_parameters() syntax structures. The general_hrd_parameters() and ols_hrd_parameters() syntax structures can be included in the VPS and signaled, or they can be included in the SPS and signaled.

[0203] For example, DPB management can be performed based on HRD parameters. As an example, removing a frame from the DPB before decoding and / or outputting the current frame can be performed based on HRD parameters.

[0204] Reference Figures 7 to 11 The signaling method for describing HRD parameters has at least the following problems.

[0205] As mentioned above, num_ols_hrd_params_minus1 can be constrained to the range of 0 to TotalNumOlss-1 (inclusive). However, there is no constraint that each HRD parameter signaled in the VPS must be associated with at least one OLS. Therefore, signaling efficiency may be degraded because the VPS may include unused HRD parameters.

[0206] As mentioned above, `num_ols_hrd_params_minus1` can be constrained to the range of 0 to `TotalNumOlss-1` (inclusive). However, since there may be one or more OLSs containing only one layer, this constraint allows unused HRD structures to be included in the VPS and signaled. These OLSs containing only one layer are not associated with signaled HRD parameter structures in the VPS.

[0207] The signaling of HRD parameters associated with OLS includes the aforementioned issues, and also includes disadvantages not described in this disclosure.

[0208] Implementations of this disclosure for solving at least one problem may include at least one of the following configurations. These configurations may be applied individually or in combination.

[0209] Configuration 1: Allows you to constrain the structure of each HRD parameter in the VPS that is notified by signals to be associated with at least one OLS.

[0210] Configuration 2: The number of HRD parameter structures signaled in the VPS (i.e., num_ols_hrd_params_minus1) should not exceed the number of OLSs containing more than one layer. In other words, the number of HRD parameter structures signaled in the VPS should not exceed the total number of OLSs minus the number of OLSs containing only one layer.

[0211] Figure 12 This is a view illustrating an example of an image encoding method to which embodiments of this disclosure are applicable.

[0212] The image encoding device can derive the HRD parameters (S1210) and encode the image / video information (S1220). In this case, the image / video information may include information related to the derived HRD parameters.

[0213] although Figure 12 As not shown in the figure, the image encoding device can perform DPB management based on the HRD parameters derived in step S1210.

[0214] Figure 13 This is a view illustrating an example of an image decoding method to which embodiments of the present disclosure are applicable.

[0215] The image decoding device can obtain image / video information (S1310). In this case, the image / video information may include information related to the HRD parameters.

[0216] The image decoding device can decode the image based on the obtained HRD parameters (S1320).

[0217] Figure 14 This is a view illustrating another example of an image decoding method to which embodiments of this disclosure are applicable.

[0218] The image decoding device can obtain image / video information from the bitstream (S1410). In this case, the image / video information may include information related to the HRD parameters.

[0219] The image decoding device can perform DPB management based on the obtained HRD parameters (S1420).

[0220] The image decoding device can decode the image based on the DPB (S1430). For example, a block / slice in the current image can be decoded based on inter-frame prediction using an image that has already been reconstructed in the DPB as a reference image.

[0221] In reference Figures 12 to 14 In the described examples, the information related to the HRD parameters may include at least one information / syntax element described in conjunction with at least one embodiment of this disclosure. Additionally, as described above, DPB management can be performed based on the HRD parameters. For example, removing a screen from the DPB before decoding and / or (decoding) screen output of the current screen can be performed based on the HRD parameters.

[0222] According to the embodiments of this disclosure for solving at least some of the above-mentioned problems, the individual HRD parameter structures that are signaled in the VPS can be constrained to be associated with at least one OLS.

[0223] As described above, the ols_hrd_parameters() applied to the i-th OLS can be specified by ols_hrd_idx[i]. According to this embodiment, each of all ols_hrd_parameters() notified by signals in the VPS can be constrained to apply to at least one OLS. That is, each ols_hrd_parameters() in the VPS can be specified by at least one ols_hrd_idx[i].

[0224] According to this embodiment, each ols_hrd_parameters() in the VPS is used at least once. That is, no signal is used to notify unused ols_hrd_parameters(). Therefore, according to this embodiment, the signaling of ols_hrd_parameters() can be executed efficiently.

[0225] According to another embodiment of this disclosure for solving at least some of the above-mentioned problems, the number of HRD parameter structures notified by signals in the VPS (i.e., num_ols_hrd_params_minus1) can be constrained to be no greater than the number of OLS containing more than one layer.

[0226] According to reference Figure 7 As described in the example, adding 1 to num_ols_hrd_params_minus1 can specify the number of ols_hrd_parameters() syntax structures in the VPS, and num_ols_hrd_params_minus1 can be in the range of 0 to TotalNumOlss-1 (inclusive).

[0227] However, as mentioned above, there may be an OLS that contains only one layer, and an OLS that contains only one layer is not associated with the HRD parameter structure that is signaled in the VPS. Figure 7 The range of values ​​for num_ols_hrd_params_minus1 in the example may lead to inaccurate signaling. Therefore, accurate signaling can be performed by specifying the number of ols_hrd_parameters() syntax structures by the number of OLSs containing multiple layers (NumMultiLayerOlss) rather than the total number of OLSs (TotalNumOlss).

[0228] According to this implementation, incrementing 1 by num_ols_hrd_params_minus1 specifies the number of ols_hrd_parameters() syntax structures in the VPS, and num_ols_hrd_params_minus1 can be in the range of 0 to NumMultiLayerOlss-1 (inclusive). In this case, the number of OLS containing multiple layers (NumMultiLayerOlss) can be equal to the total number of OLS (TotalNumOlss) minus the number of OLS containing only one layer (NumSingleLayerOlss).

[0229] As described above, each HRD parameter signaled in the VPS can be constrained to be associated (mapped) with at least one OLS. Furthermore, the number of HRD parameters signaled in the VPS (i.e., num_ols_hrd_params_minus1) can be constrained to be no greater than the number of OLSs containing multiple layers (multi-layer OLSs). These two implementations can be combined as follows to construct another implementation.

[0230] Figure 15 This is a view illustrating the processing of encoding HRD parameters based on num_ols_hrd_params_minus1 according to another embodiment of this disclosure.

[0231] The image encoding device can encode num_ols_hrd_params_minus1 into the VPS (S1510). Increasing 1 to num_ols_hrd_params_minus1 specifies the number of ols_hrd_parameters() syntax structures in the VPS, and num_ols_hrd_params_minus1 can be in the range of 0 to NumMultiLayerOlss-1 (inclusive).

[0232] The image encoding device can encode the syntax structure num_ols_hrd_params_minus1 + one ols_hrd_parameters() into the VPS (S1520).

[0233] The image encoding device can determine the following condition 1 (S1530).

[0234] Condition 1: (num_ols_hrd_params_minus1+1!=NumMultiLayerOlss&&num_ols_hrd_params_minus1>0)?

[0235] Condition 1 is the condition for encoding ols_hrd_idx into the bitstream. When condition 1 is met (S1530: Yes), the image encoding device can encode ols_hrd_idx into the VPS (S1540). (Refer to reference...) Figure 15 In the described implementation, ols_hrd_idx[i] is an index in the ols_hrd_parameters() list in the VPS, and can be an index of ols_hrd_parameters() applied to an OLS containing multiple i-th layers (multi-layer OLS). That is, ols_hrd_idx[i] in the VPS can be signaled for multi-layer OLS, and can be in the range of 0 to num_ols_hrd_params_minus1 (inclusive).

[0236] When condition 1 is not met (S1530: No), the image encoding device can infer ols_hrd_idx instead of encoding ols_hrd_idx into the VPS (S1550). Specifically, when num_ols_hrd_params_minus1 equals 0, the value of ols_hrd_idx[i] can be inferred to be equal to 0. Otherwise, when num_ols_hrd_param_minus1 plus 1 equals NumMultiLayerOlss, the value of ols_hrd_idx[i] can be inferred to be equal to i.

[0237] Additionally, the ols_hrd_parameters() syntax structure applied to an OLS containing only a single layer may not be encoded into the VPS, but may be encoded into the SPS referenced by the layer in the OLS.

[0238] Additionally, each ols_hrd_parameters() in the VPS can be referenced by at least one ols_hrd_idx[i] (i is in the range of 0 to NumMultiLayerOlss-1 (inclusive)).

[0239] The image encoding device can encode the image based on the HRD parameters (S1560). In this case, the HRD parameters can be ols_hrd_parameters() in the VPS referenced by ols_hrd_idx[i] obtained in step S1540 or inferred in step S1550. Alternatively, in the case of an OLS containing only a single layer, the HRD parameters can be ols_hrd_parameters() in the SPS referenced by that single layer.

[0240] Figure 16This is a view illustrating the process of decoding HRD parameters based on num_ols_hrd_params_minus1 according to another embodiment of this disclosure.

[0241] The image decoding device can obtain num_ols_hrd_params_minus1 (S1610) from the VPS. Increasing 1 to num_ols_hrd_params_minus1 specifies the number of ols_hrd_parameters() syntax structures in the VPS, and num_ols_hrd_params_minus1 can be in the range of 0 to NumMultiLayerOlss-1 (inclusive).

[0242] The image decoding device can obtain a num_ols_hrd_params_minus1 + one ols_hrd_parameters() syntax structure from the VPS (S1620).

[0243] The image decoding device can determine the following condition 2 (S1630).

[0244] Condition 2: (num_ols_hrd_params_minus1+1!=NumMultiLayerOlss&&num_ols_hrd_params_minus1>0)?

[0245] Condition 2 is the condition for obtaining ols_hrd_idx from the bitstream, and when condition 2 is met (S1630: Yes), the image decoding device can obtain ols_hrd_idx from the VPS (S1640). (Refer to...) Figure 16 In the described implementation, ols_hrd_idx[i] is an index in the list of ols_hrd_parameters() in the VPS, and can be an index applied to ols_hrd_parameters() that contains multiple i-th layers of OLS (multi-layer OLS).

[0246] That is, ols_hrd_idx[i] in the VPS can be signaled for multi-level OLS and can be in the range of 0 to num_ols_hrd_params_minus1 (inclusive).

[0247] When condition 2 is not met (S1630: No), the image decoding device can infer ols_hrd_idx instead of obtaining it from the VPS (S1650). Specifically, when num_ols_hrd_params_minus1 equals 0, the value of ols_hrd_idx[i] can be inferred to be equal to 0. Otherwise, when num_ols_hrd_param_minus1 plus 1 equals NumMultiLayerOlss, the value of ols_hrd_idx[i] can be inferred to be equal to i.

[0248] Additionally, the ols_hrd_parameters() syntax structure applied to an OLS containing only a single layer can be obtained from the SPS referenced by the layer in the OLS, rather than from the VPS.

[0249] Additionally, each ols_hrd_parameters() in the VPS can be referenced by at least one ols_hrd_idx[i] (i is in the range of 0 to NumMultiLayerOlss-1 (inclusive)).

[0250] The image decoding device can decode the image based on the HRD parameters (S1660). In this case, the HRD parameters can be ols_hrd_parameters() in the VPS referenced by ols_hrd_idx[i] obtained in step S1640 or inferred in step S1650. Alternatively, in the case of an OLS containing only a single layer, the HRD parameters can be ols_hrd_parameters() in the SPS referenced by that single layer.

[0251] According to reference Figures 15 to 16 The described implementation, by signaling the ols_hrd_parameters() syntax structure of the OLS containing a single layer only via the SPS, prevents unnecessary signaling of the unreferenced ols_hrd_parameters() syntax structure in the VPS, and performs HRD parameter signaling more accurately and efficiently.

[0252] In reference Figure 15 and Figure 16 In the described method, some steps can be omitted or their order can be changed. Additionally, steps can be added at any point. Figure 15 and Figure 16 The steps are not shown in the diagram.

[0253] Although the exemplary methods of this disclosure described above are represented as a series of operations for clarity of description, they are not intended to limit the order in which the steps are performed, and these steps may be performed simultaneously or in different orders if necessary. To implement the method according to the invention, the described steps may further include other steps, including steps in addition to some steps, or may include additional steps in addition to some steps.

[0254] In this disclosure, the image encoding device or image decoding device that performs a predetermined operation (step) can perform an operation (step) that confirms the execution conditions or circumstances of the corresponding operation (step). For example, if it is described that a predetermined operation is performed when predetermined conditions are met, the image encoding device or image decoding device can perform the predetermined operation after determining whether the predetermined conditions are met.

[0255] The various embodiments of this disclosure are not a list of all possible combinations and are intended to describe representative aspects of this disclosure; the matters described in the various embodiments may be applied independently or in combination of two or more.

[0256] Various embodiments of this disclosure can be implemented in hardware, firmware, software, or a combination thereof. When this disclosure is implemented in hardware, it can be implemented using application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), general-purpose processors, controllers, microcontrollers, microprocessors, etc.

[0257] Furthermore, the image decoding and image encoding devices applying the embodiments of this disclosure can be included in multimedia broadcasting transmission and receiving devices, mobile communication terminals, home theater video devices, digital cinema video devices, surveillance cameras, video chat devices, real-time communication devices such as video communication, mobile streaming devices, storage media, cameras, video-on-demand (VoD) service providers, OTT (over-the-top) video devices, internet streaming service providers, three-dimensional (3D) video devices, video telephony devices, medical video devices, etc., and can be used to process video signals or data signals. For example, OTT video devices can include game consoles, Blu-ray players, internet access televisions, home theater systems, smartphones, tablet PCs, digital video recorders (DVRs), etc.

[0258] Figure 17 This is a view illustrating a content streaming system to which embodiments of the present disclosure can be applied.

[0259] like Figure 17As shown, the content streaming system applying the embodiments of this disclosure may mainly include an encoding server, a streaming server, a network server, a media storage device, a user device, and a multimedia input device.

[0260] The encoding server compresses content input from multimedia input devices such as smartphones, cameras, and camcorders into digital data to generate a bitstream and then sends the bitstream to the streaming server. As another example, when multimedia input devices such as smartphones, cameras, and camcorders directly generate bitstreams, the encoding server can be omitted.

[0261] The bitstream can be generated by an image encoding method or image encoding device applying the embodiments of this disclosure, and the stream server can temporarily store the bitstream during the sending or receiving of the bitstream.

[0262] A streaming server sends multimedia data to a user's device based on a request from a web server, and the web server acts as a medium for informing the user of the service. When a user requests a service from the web server, the web server can deliver it to the streaming server, and the streaming server can send the multimedia data to the user. In this scenario, the content streaming system may include a separate control server. In this case, the control server is used to control the commands / responses between devices in the content streaming system.

[0263] A streaming server can receive content from media storage devices and / or encoding servers. For example, when receiving content from an encoding server, the content can be received in real time. In this case, to provide a smooth streaming service, the streaming server can store the bitstream for a predetermined period of time.

[0264] Examples of user devices may include mobile phones, smartphones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, head-mounted displays), digital televisions, desktop computers, digital signage, etc.

[0265] In a content streaming system, each server can operate as a distributed server, in which case the data received from each server can be distributed.

[0266] The scope of this disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) for enabling the operation of methods according to various embodiments to be executed on a device or computer, and non-transitory computer-readable media having such software or commands stored thereon and executable on a device or computer.

[0267] Industrial applicability

[0268] The embodiments disclosed herein can be used to encode or decode images.

Claims

1. An image decoding method performed by an image decoding device, the image decoding method comprising the following steps: Obtain first information about the number of HRD parameter syntax structures used for one or more assumed reference decoders in a specified video parameter set VPS; Based on the first information, obtain the syntax structure of one or more HRD parameters from the VPS; Based on the first information, obtain second information from the VPS regarding the mapping between one or more multi-layer output layer sets (OLS) and the one or more HRD parameter syntax structures; The HRD parameter syntax structure to be applied to the current OLS is selected based on the second information; as well as The current OLS is processed based on the selected HRD parameter syntax structure. Wherein, each of the one or more HRD parameter syntax structures in the VPS is mapped to at least one of the one or more multi-tier OLS, and Specifically, the second information is obtained from the VPS based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is not equal to the number of one or more multi-layer OLS.

2. The image decoding method according to claim 1, wherein, The number of one or more HRD parameter syntax structures in the VPS is no greater than the number of one or more multi-tier OLS.

3. The image decoding method according to claim 1, wherein, Based on the fact that the number of one or more HRD parameter syntax structures in the VPS is 1, the second information is not obtained from the VPS, and the second information is inferred to be equal to the value 0.

4. The image decoding method according to claim 1, wherein, Based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is equal to the number of one or more multi-level OLS, the second information is not obtained from the VPS, and the second information of the i-th multi-level OLS is inferred to be equal to the value i.

5. The image decoding method according to claim 1, wherein, Given that the current OLS contains only a single layer, the HRD parameter syntax structure applied to the current OLS is obtained from the sequence parameter set SPS.

6. An image encoding method performed by an image encoding device, the image encoding method comprising the following steps: The first information used to specify the number of HRD parameter syntax structures for one or more assumed reference decoders is encoded in the video parameter set VPS; Based on the first information, the syntax structure of one or more HRD parameters is encoded in the VPS; Based on the first information, second information regarding the mapping between one or more multi-layer output layer sets (OLS) and the one or more HRD parameter syntax structures is encoded in the VPS; as well as Based on the HRD parameter syntax structure applied to the current OLS, the current OLS is processed. Wherein, each of the one or more HRD parameter syntax structures in the VPS is mapped to at least one of the one or more multi-tier OLS, and Wherein, the second information is encoded into the VPS based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is not equal to the number of one or more multi-layer OLS.

7. The image encoding method according to claim 6, wherein, The number of one or more HRD parameter syntax structures in the VPS is no greater than the number of one or more multi-tier OLS.

8. The image encoding method according to claim 6, wherein, Since the number of one or more HRD parameter syntax structures in the VPS is 1, the second information is not encoded into the VPS, and the second information is inferred to be equal to the value 0.

9. The image encoding method according to claim 6, wherein, Based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is equal to the number of multi-level OLS, the second information is not encoded into the VPS, and the second information of the i-th multi-level OLS is inferred to be equal to the value i.

10. The image encoding method according to claim 6, wherein, Since the current OLS contains only a single layer, the HRD parameter syntax structure applied to the current OLS is encoded in the sequence parameter set SPS.

11. A method for transmitting a bit stream, the method comprising the following steps: Generate the bit stream; as well as Send the bit stream, The bitstream is generated through the following steps: The first information used to specify the number of HRD parameter syntax structures for one or more assumed reference decoders is encoded in the video parameter set VPS; Based on the first information, the syntax structure of one or more HRD parameters is encoded in the VPS; Based on the first information, second information regarding the mapping between one or more multi-layer output layer sets (OLS) and the one or more HRD parameter syntax structures is encoded in the VPS; and Based on the HRD parameter syntax structure applied to the current OLS, the current OLS is processed. Wherein, each of the one or more HRD parameter syntax structures in the VPS is mapped to at least one of the one or more multi-tier OLS, and Wherein, the second information is encoded into the VPS based on the fact that the number of one or more HRD parameter syntax structures in the VPS is greater than 1 and the number of one or more HRD parameter syntax structures in the VPS is not equal to the number of one or more multi-layer OLS.

Images