Method and apparatus for encoding / decoding an image based on available slice type information for a gdr picture or irap picture, and recording medium storing a bitstream

Abstract

A method and apparatus for encoding / decoding an image are provided. A method for decoding an image according to the present disclosure can include the steps of determining whether an inter-frame slice type is allowed for a current picture including a current block, determining whether an intra-frame slice type is allowed for the current picture based on the inter-frame slice type being allowed for the current picture, and decoding the current block based on the slice type allowed for the current picture, wherein whether the inter-frame slice type is allowed for the current picture can be determined based on a picture type of the current picture and whether a current layer including the current picture is capable of using inter-layer prediction.

Description

Technical Field

[0001] This disclosure relates to image encoding / decoding methods and apparatus, and more specifically, to image encoding / decoding methods and apparatus based on information about the available slice types for GDR or IRAP frames, and to a recording medium for storing bitstreams generated by the image encoding methods / apparatus of this disclosure. Background Technology

[0002] Recently, there has been an increasing demand across various fields for high-resolution and high-quality images, such as high-definition (HD) and ultra-high-definition (UHD) images. With the increase 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 based on information about the available slice types for GDR or IRAP images.

[0007] Another object of this disclosure is to provide an image encoding / decoding method and apparatus for skipping the step of signaling reference screen list information to an IRAP screen.

[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] 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.

[0011] 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.

[0012] Technical solution

[0013] An image decoding method according to one aspect of this disclosure includes the following steps: determining whether an inter-frame slice type is allowed for a current frame including the current block; determining whether an intra-frame slice type is allowed for the current frame based on the allowed inter-frame slice types for the current frame; and decoding the current block based on the allowed slice types for the current frame. Whether an inter-frame slice type is allowed for the current frame can be determined based on the frame type of the current frame and whether inter-layer prediction can be used for the current layer including the current frame.

[0014] An image decoding apparatus according to one aspect of this disclosure includes a memory and at least one processor. The at least one processor can perform the following steps: determining whether an inter-frame slice type is permitted for a current frame including the current block; determining whether an intra-frame slice type is permitted for the current frame based on the permitted inter-frame slice types for the current frame; and decoding the current block based on the permitted slice types for the current frame. Whether an inter-frame slice type is permitted for the current frame can be determined based on the frame type of the current frame and whether inter-layer prediction can be used for the current layer including the current frame.

[0015] An image coding method according to another aspect of this disclosure includes the following steps: encoding first information regarding whether an inter-frame slice type is allowed for a current frame including the current block; and encoding second information regarding whether an intra-frame slice type is allowed for the current frame, based on the allowable inter-frame slice types for the current frame. Whether an inter-frame slice type is allowed for the current frame can be determined based on the frame type of the current frame and whether inter-layer prediction can be used for the current layer including the current frame.

[0016] Additionally, according to another aspect of this disclosure, a computer-readable recording medium can store a bitstream generated by the image encoding device or image encoding method of this disclosure.

[0017] In another aspect of the transmission method according to this disclosure, a bit stream generated by the image encoding method or image encoding device of this disclosure may be transmitted.

[0018] The features described above in the brief overview of this disclosure are merely exemplary aspects of the following detailed description of this disclosure and do not limit the scope of this disclosure.

[0019] Beneficial effects

[0020] According to this disclosure, an image encoding / decoding method and apparatus with improved encoding / decoding efficiency can be provided.

[0021] According to this disclosure, an image encoding / decoding method and apparatus based on information about the available slice types for GDR or IRAP images can be provided.

[0022] According to this disclosure, an image encoding / decoding method and apparatus can be provided for skipping the step of signaling a reference screen list information to an IRAP screen.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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

[0027] Figure 1 This is a view that schematically illustrates a video coding system to which embodiments of the present disclosure are applicable.

[0028] Figure 2 This is a view schematically illustrating an image encoding device to which embodiments of the present disclosure are applicable.

[0029] Figure 3 This is a view schematically illustrating an image decoding device to which embodiments of the present disclosure are applicable.

[0030] Figure 4 This is a view that illustrates an example of a layered structure for encoding images / videos.

[0031] Figure 5 This is a view that shows an example of the screen header.

[0032] Figure 6 This is a view that shows an example of a slice header.

[0033] Figure 7 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0034] Figures 8 to 9 This is a view illustrating a screen header including idr_pic_flag according to an embodiment of this disclosure.

[0035] Figures 10 to 16 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0036] Figure 17This is a flowchart illustrating an image encoding method according to an embodiment of the present disclosure.

[0037] Figure 18 This is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure.

[0038] Figure 19 A view illustrating the content streaming system to which embodiments of this disclosure are applicable. Detailed Implementation

[0039] 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.

[0040] 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.

[0041] In this disclosure, when a component is "connected," "linked," or "coupled" 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.

[0042] In this disclosure, the terms first, second, etc., are used only to distinguish 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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.

[0049] 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."

[0050] 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 component block of the current block can be represented by an explicit description including terms such as "luma block" or "current luma block." Similarly, "the chroma component block of the current block" can be represented by an explicit description including terms such as "chroma block" or "current chroma block."

[0051] In this disclosure, the terms “ / ” or “,” can be interpreted as indicating “and / or”. For example, “A / B” and “A, B” can mean “A and / or B”. Furthermore, “A / B / C” and “A / B / C” can mean “at least one of A, B and / or C”.

[0052] In this disclosure, the term "or" should be interpreted to indicate "and / or". For example, the expression "A or B" can include 1) only "A", 2) only "B", or 3) both "A and B". In other words, in this disclosure, "or" should be interpreted to indicate "additionally or alternatively".

[0053] Overview of Video Encoding Systems

[0054] Figure 1 This is a view illustrating a video coding system to which embodiments of this disclosure are applicable.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Renderer 23 can render decoded video / images. The rendered video / images can be displayed on a monitor.

[0062] Overview of Image Encoding Devices

[0063] Figure 2 This is a schematic view illustrating an image encoding device to which embodiments of this disclosure may be applied.

[0064] 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 prediction unit 180, an intra-frame prediction unit 185, and an entropy encoder 190. The inter-frame prediction unit 180 and the intra-frame prediction unit 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.

[0065] 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.

[0066] 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.

[0067] The prediction unit (inter-frame prediction unit 180 or intra-frame prediction unit 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 prediction unit can determine whether to apply intra-frame prediction or inter-frame prediction based on the current block or CU. The prediction unit 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.

[0068] Intra-prediction unit 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-prediction unit 185 can determine the prediction mode to be applied to the current block by using prediction modes applied to neighboring blocks.

[0069] The inter-frame prediction unit 180 can deduce the prediction 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 the inter-frame prediction mode, motion information can be predicted on a block, sub-block, or sample basis based on the correlation between 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, the inter-frame prediction unit 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 prediction unit 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.

[0070] The prediction unit can generate a prediction signal based on various prediction methods and techniques described below. For example, the prediction unit 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 Inter-Frame and Intra-Frame Prediction (CIIP). Furthermore, the prediction unit 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.

[0071] The prediction signal generated by the prediction unit can be used to generate a reconstructed signal or a residual signal. Subtractor 115 can generate a residual signal (residual block or residual sample array) by subtracting the prediction signal (prediction block or prediction sample array) output from the prediction unit from the input image signal (original block or original sample array). The generated residual signal can be transmitted to converter 120.

[0072] 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.

[0073] Quantizer 130 can quantize the transform coefficients and transmit them to entropy encoder 190. Entropy encoder 190 can encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. The 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 form based on the coefficient scan order, and generate information about the quantized transform coefficients based on the one-dimensional vector form of the quantized transform coefficients.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Adder 155 adds the reconstructed residual signal to the prediction signal output from inter-frame prediction unit 180 or intra-frame prediction unit 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.

[0078] 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.

[0079] The modified reconstructed frame transmitted to memory 170 can be used as a reference frame in inter-frame prediction unit 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.

[0080] The DPB of memory 170 can store modified reconstructed frames for use as reference frames in inter-frame prediction unit 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 prediction unit 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 prediction unit 185.

[0081] Overview of image decoding devices

[0082] Figure 3 This is a schematic view illustrating an image decoding device to which embodiments of the present disclosure may be applied.

[0083] 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 prediction unit 260, and an intra-frame prediction unit 265. The inter-frame prediction unit 260 and the intra-frame prediction unit 265 may be collectively referred to as "predictors". The dequantizer 220 and the inverse transformer 230 may be included in a residual processor.

[0084] 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.

[0085] 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).

[0086] 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 prediction units (inter-frame prediction unit 260 and intra-frame prediction unit 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.

[0087] 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 prediction unit 260, or an intra-frame prediction unit 265.

[0088] 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).

[0089] The inverse transformer 230 can perform inverse transformation on the transformation coefficients to obtain the residual signal (residual block, residual sample array).

[0090] The prediction unit can perform prediction on the current block and generate a prediction block that includes prediction samples of the current block. The prediction unit 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).

[0091] Similar to that described in the prediction unit of the image coding device 100, the prediction unit can generate a prediction signal based on various prediction methods (techniques) described later.

[0092] Intra-prediction unit 265 can predict the current block by referring to samples in the current frame. The description of intra-prediction unit 185 also applies to intra-prediction unit 265.

[0093] The inter-frame prediction unit 260 can deduce the prediction 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, the inter-frame prediction unit 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.

[0094] 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 prediction unit (including inter-frame prediction unit 260 and / or intra-frame prediction unit 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.

[0095] 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.

[0096] The (modified) reconstructed frame stored in the DPB of memory 250 can be used as a reference frame in inter-frame prediction unit 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 prediction unit 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 prediction unit 265.

[0097] In this disclosure, the embodiments described in the filter 160, inter-frame prediction unit 180 and intra-frame prediction unit 185 of the image encoding device 100 can be equally or correspondingly applied to the filter 240, inter-frame prediction unit 260 and intra-frame prediction unit 265 of the image decoding device 200.

[0098] Example of encoding layer structure

[0099] The encoded video / images according to this disclosure can be processed, for example, according to the coding layers and structures described below.

[0100] Figure 4 This is a view that illustrates an example of a layered structure for encoding images / videos.

[0101] Encoded images / videos are classified into a Video Coding Layer (VCL) for image / video 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.

[0102] 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.

[0103] In NAL, header information (NAL unit header) can be added to the raw byte sequence payload (RBSP) generated in VCL to generate NAL units. In this case, RBSP refers to the slice data, parameter set, and SEI message generated in VCL. The NAL unit header may include NAL unit type information specified according to the RBSP data included in the corresponding NAL unit.

[0104] like Figure 4 As shown, NAL units can be classified into VCL NAL units and non-VCL NAL units based on the type of 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).

[0105] 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 have a data format with a predetermined standard (e.g., H.266 / VVC file format, RTP (Real-Time Transport Protocol), or TS (Transport Stream)) and sent over various networks.

[0106] 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.

[0107] Below are examples of NAL cell types specified based on the type of parameter set / information included in non-VCL NAL cell types.

[0108] - DCI (Decoding Capability Information) NAL Unit Type (NUT): Includes the NAL unit type of DCI.

[0109] -VPS (Video Parameter Set) NUT: Includes the NAL unit type of the VPS.

[0110] -SPS (Sequence Parameter Set) NUT: NAL unit type including SPS

[0111] -PPS (Picture Parameter Set) NUT: Includes the NAL unit type of PPS.

[0112] -APS (Adaptive Parameter Set) NUT: Includes NAL unit types of APS.

[0113] -PH (Picture Header) NUT: NAL unit type including the picture header.

[0114] 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.

[0115] Furthermore, 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.

[0116] 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.

[0117] 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.

[0118] NAL unit type

[0119] Typically, a single NAL unit type can be assigned to a screen. As mentioned above, the syntax information indicating the NAL unit type can be stored in the NAL unit header of the NAL unit 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. Table 1 below shows examples of NAL unit types.

[0120] [Table 1]

[0121]

[0122]

[0123] Referring to Table 1, VCL NAL unit types can be categorized into NAL unit types #0 to #12 based on the scene type. Additionally, non-VCL NAL unit types can be categorized into NAL unit types #13 to #31 based on the parameter type. The VCL NAL unit types are summarized by scene type as follows.

[0124] (1) IRAP (Intra-Frame Random Access Point) screen

[0125] An IRAP frame is a randomly accessible frame and can refer to a frame with the same NAL unit type in the range IDR_W_RADL to CRA_NUT. IRAP frames can include Instantaneous Decode Refresh (IDR) frames and Clean Random Access (CRA) frames. IRAP frames may not use inter-frame prediction based on a reference frame in the same layer during decoding processing. The first frame in the bitstream in decoding order can be an IRAP frame or a Progressive Decode Refresh (GDR) frame. For a single-layer bitstream, when the required set of reference parameters is available, the IRAP frame and all non-random access skip leader (RASL) frames in the Coding Layer Video Sequence (CLVS) that follow the IRAP frame in decoding order can be correctly decoded, even if no frames have been decoded before the IRAP frame in decoding order.

[0126] (2) CRA (Clean Random Access) screen

[0127] A CRA frame refers to an IRAP frame in which each VCL NAL unit has a NAL unit type such as CRA_NUT. CRA frames may not use inter-frame prediction during decoding. A CRA frame can be the first frame in the bitstream in decoding order or a frame following the first frame. A CRA frame can be associated with a RADL or RASL frame. When NoOutputBeforeRecoveryFlag has a first value (e.g., 1) for a CRA frame, the RASL frame associated with the CRA frame may not be decoded because a reference frame not present in the bitstream is referenced, and therefore may not be output by the image decoding device. Here, NoOutputBeforeRecoveryFlag can specify whether a frame preceding the recovery point frame in decoding order is output before the recovery point frame. For example, a NoOutputBeforeRecoveryFlag with a first value (e.g., 1) can specify that a frame preceding the recovery point frame in decoding order is not output before the recovery point frame. In this case, the CRA frame can be the first frame in the bitstream or the first frame following the End of Sequence (EOS) NAL unit in decoding order, which can indicate that random access has occurred. In contrast, a NoOutputBeforeRecoveryFlag with a second value (e.g., 0) can specify that a frame before the recovery point frame in the decoding order can be output before the recovery point frame. In this case, the CRA frame may not be the first frame in the bitstream or the first frame after the End of Sequence (EOS) NAL unit in the decoding order, which can mean that random access does not occur.

[0128] (3) IDR (Instant Decoding Refresh) screen

[0129] An IDR frame can refer to an IRAP frame in which each VCL NAL unit has a NAL unit type such as IDR_W_RADL or IDR_N_LP. IDR frames may not use inter-frame prediction during decoding. An IDR frame can be the first frame in the bitstream in decoding order, or it can be a frame following the first frame. Each IDR frame can be the first frame in the CVS (Coded Video Sequence) in decoding order. When each VCL NAL unit for an IDR frame has a NAL unit type such as IDR_W_RADL, the IDR frame can have an associated RADL frame. In contrast, when each VCL NAL unit for an IDR frame has a NAL unit type such as IDR_N_LP, the IDR frame may not have an associated leading frame. Furthermore, an IDR frame may not have an associated RASL frame.

[0130] (4) RADL (Random Access Decodeable Pilot) screen

[0131] A RADL screen can refer to a screen in which each VCL NAL unit has a NAL unit type such as RADL_NUT. All RADL screens can be lead screens.

[0132] (5) RASL (Random Access Skip Preview) screen

[0133] A RASL screen can refer to a screen in which at least one VCL NAL unit has a NAL unit type such as RASL_NUT and the remaining VCL NAL units have a NAL unit type such as RASL_NUT or RADL_NUT. All RASL screens can be leading screens for associated CRA screens.

[0134] (6) Ending screen

[0135] The end screen can refer to a screen where each VCL NAL unit has a NAL unit type such as TRAIL_NUT. The end screen associated with an IRAP screen or GDR screen can be after the IRAP screen or GDR screen in decoding order. A screen that is not allowed to be after the associated IRAP screen in output order and before the associated IRAP screen in decoding order is also not allowed.

[0136] (7) GDR (Progressive Decoding Refresh) screen

[0137] A GDR screen is a screen that can be accessed randomly, and can refer to a screen in which each VCL NAL unit has a NAL unit type such as GDR_NUT.

[0138] GDR (Gross Decoding) features can refer to decoding starting from a frame where all parts of the reconstructed frame may not have been correctly decoded, but the correctly decoded parts of the reconstructed frames in subsequent frames (subsequence frames) are gradually increased until the entire frame is correctly decoded. In this case, the frame where the decoding process can begin with GDR features is called a GDR frame, and the first frame after the GDR frame where the entire frame is correctly decoded is called the recovery point frame.

[0139] (8) STSA (Step-by-Step Time Sublayer Access) screen

[0140] STSA screens are randomly accessible screens and can refer to screens where each VCL NAL unit has a NAL unit type such as STSA_NUT.

[0141] Advanced Syntax

[0142] As described above, for image / video coding, a High-Level Syntax (HLS) can be encoded / signaled. Image / video information can include the HLS, and image / video coding methods can be performed based on the image / video information.

[0143] As an example of image / video information, reference picture list information (e.g., ref_pic_lists) can be signaled in the picture header or slice header based on the rpl_info_in_ph_flag syntax signaled in the picture parameter set. For example, an rpl_info_in_ph_flag with a first value (e.g., 1) can specify that the reference picture list information exists in the picture header but not in the slice header. In contrast, an rpl_info_in_ph_flag with a second value (e.g., 0) can specify that the reference picture list information does not exist in the picture header but may exist in the slice header.

[0144] Figure 5 This is a view that shows an example of the screen header.

[0145] Reference Figure 5 The frame header can include the syntax element `gdr_or_irap_pic_flag`. `gdr_or_irap_pic_flag` can specify whether the current frame is a GDR (Progressive Decoding Refresh) frame or an IRAP (Intra-Frame Random Access Point) frame. For example, a first value (e.g., 1) of `gdr_or_irap_pic_flag` can specify that the current frame is either a GDR or IRAP frame. In contrast, a second value (e.g., 0) of `gdr_or_irap_pic_flag` can specify that the current frame is not a GDR frame but can be an IRAP frame.

[0146] Additionally, the frame header may include the syntax element `gdr_pic_flag`. `gdr_pic_flag` can specify whether the current frame is a GDR frame. For example, a `gdr_pic_flag` with a first value (e.g., 1) can specify that the current frame is a GDR frame. In contrast, a `gdr_pic_flag` with a second value (e.g., 0) can specify that the current frame is not a GDR frame. When `gdr_pic_flag` is not present (i.e., no signal is given), its value can be inferred to be the second value (e.g., 0). When a GDR frame is unavailable and does not exist in the CLVS (Coding Layer Video Sequence) (e.g., `sps_gdr_enabled_flag == 0`), the value of `gdr_pic_flag` can be limited to the second value (e.g., 0). Furthermore, when `gdr_or_irap_pic_flag` has a first value (e.g., 1) and `gdr_pic_flag` has a second value (e.g., 0), the current frame can be determined to be an IRAP frame.

[0147] Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag`. `ph_inter_slice_allowed_flag` can specify whether one or more slices in the current frame can have an inter-slice type (e.g., B-slice type or P-slice type). For example, a first value (e.g., 1) of `ph_inter_slice_allowed_flag` can specify that one or more coded slices with a B-slice type (i.e., `sh_slice_type = 0`) or a P-slice type (i.e., `sh_slice_type = 1`) can exist in the current frame. In contrast, a second value (e.g., 0) of `ph_inter_slice_allowed_flag` can specify that all coded slices in the current frame have an I-slice type (i.e., `sh_slice_type = 2`).

[0148] Additionally, the frame header may include the syntax element `ph_intra_slice_allowed_flag`. `ph_intra_slice_allowed_flag` can specify whether one or more slices in the current frame can have an intra-slice type (e.g., I-slice type). For example, a first value (e.g., 1) of `ph_intra_slice_allowed_flag` can specify that one or more coded slices with I-slice type (i.e., `sh_slice_type = 2`) can exist in the current frame. In contrast, a second value (e.g., 0) of `ph_intra_slice_allowed_flag` can specify that all coded slices in the current frame have B-slice type (i.e., `sh_slice_type = 0`) or P-slice type (i.e., `sh_slice_type = 1`). `ph_intra_slice_allowed_flag` can be signaled only if it has a first value (e.g., 1). When ph_intra_slice_allowed_flag does not exist, the value of ph_intra_slice_allowed_flag can be inferred to be the first value (e.g., 1).

[0149] In addition, when the above rpl_info_in_ph_flag has a first value (e.g., 1), the reference picture list information ref_pic_lists can be signaled in the picture header.

[0150] As described above, the picture header can include two syntax elements (e.g., ph_inter_slice_allowed_flag and ph_intra_slice_allowed_flag) that specify whether signaling is allowed for inter-slice and intra-slice prediction slices in the picture header. However, since GDR pictures include one or more slices of the inter-slice type due to picture attributes, signaling for ph_inter_slice_allowed_flag is not required for GDR pictures. However, in Figure 5 In the video header, because ph_inter_slice_allowed_flag is unconditionally signaled, there is an unnecessary increase in signaling overhead.

[0151] Figure 6 This is a view that shows an example of a slice header.

[0152] Reference Figure 6When `rpl_info_in_ph_flag` has a second value (e.g., 0), the reference picture list information `ref_pic_lists` can be signaled in the slice header under predetermined conditions. Specifically, `ref_pic_lists` can be signaled when `rpl_info_in_ph_flag` has a second value (e.g., 0), the NAL unit type is not `IDR_W_RADL` or `IDR_N_LP` (i.e., `nal_unit_type != IDR_W_RADL && nal_unit_type != IDR_N_LP`), or when `sps_idr_rpl_present_flag` has a first value (e.g., 1). Here, the first value (e.g., 1) of `sps_idr_rpl_present_flag` can specify that syntax elements regarding the reference picture list can exist in the slice header of slices with NAL unit types such as `IDR_W_RADL` or `IDR_N_LP`.

[0153] Typically, when an IDR frame has a NAL unit type such as IDR_W_RADL or IDR_N_LP, reference frame list information is unnecessary due to frame attributes. Therefore, to signal the reference frame list information `ref_pic_list`, it's necessary to check the `nal_unit_type` value, which contains information about the NAL unit type signaled in the NAL unit header. Furthermore, even if `nal_unit_type` has a value related to the IDR frame, reference frame list information may still be needed in bitstream extraction and merging scenarios. Therefore, to signal the reference frame list information `ref_pic_list`, it's necessary to check if the syntax element specifying the reference frame list exists in the slice header `sps_idr_rpl_present_flag`.

[0154] However, the reference picture list information is signaled in the picture header without considering the aforementioned additional signaling. That is, the reference picture list information `ref_pic_list` is signaled in the picture header solely based on `rpl_info_in_ph_flag`. Therefore, even for IDR pictures that do not involve bitstream extraction and merging, there is still a problem of potentially unnecessary signaling of the reference picture list information `ref_pic_list`.

[0155] To address the aforementioned issues, signaling conditions for a reference screen list can be added, or a flag designating the current screen as an IDR screen can be added to the screen header. Alternatively, signaling conditions for syntax elements related to inter-frame slices can be added to the screen header. Embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.

[0156] Implementation Method 1

[0157] According to Embodiment 1 of this disclosure, in the screen header, reference screen list information can be signaled based on whether a syntax element for a reference screen list of IDR screens exists in the slice header (i.e., sps_idr_rpl_present_flag).

[0158] Figure 7 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0159] Reference Figure 7 The frame header may include the syntax element `gdr_or_irap_pic_flag` specifying whether the current frame is a GDR (Progressive Decoding Refresh) frame or an IRAP (Intra-Frame Random Access Point) frame, and the syntax element `gdr_pic_flag` specifying whether the current frame is a GDR frame. Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag` specifying whether one or more slices in the current frame can have inter-slice types (e.g., B-slice type or P-slice type), and the syntax element `ph_intra_slice_allowed_flag` specifying whether one or more slices in the current frame can have intra-slice types (e.g., I-slice type). (Refer to the above.) Figure 5 It describes the semantics of each of the grammatical elements.

[0160] In the picture header, the reference picture list information ref_pic_lists (710) can be signaled based on a predetermined first condition. Specifically, ref_pic_lists can only be signaled if the reference picture list information is in the picture header (i.e., rpl_info_in_ph_flag == 1) and the syntax elements concerning the reference picture list exist in the slice header of a slice with a NAL unit type such as IDR_N_LP or IDR_W_RADL. Here, IDR_N_LP can refer to the NAL unit type of an IDR picture that does not have an associated leading picture (e.g., a RASL picture and a RADL picture) in the bitstream. In addition, IDR_W_RADL can refer to the NAL unit type of an IDR picture that does not have an associated RASL picture in the bitstream but may have an associated RADL picture.

[0161] Figure 7 The situation can be compared with Figure 5The screen header differs because the reference screen list information `ref_pic_list` is signaled based on whether `sps_idr_rpl_present_flag` has a first value (e.g., 1). That is, when the syntax element regarding the reference screen list is not present in the slice header (i.e., `sps_idr_rpl_present_flag == 0`), it is not necessary to signal `ref_pic_list` in the screen header. Therefore, the problem of unnecessarily signaling the reference screen list information of the IDR screen in the screen header can be solved.

[0162] Implementation Method 2

[0163] According to Embodiment 2 of this disclosure, a new syntax element can be added to the screen header to specify whether the current screen is an IDR screen.

[0164] Figure 8 This is a view illustrating a screen header including idr_pic_flag according to an embodiment of this disclosure.

[0165] Reference Figure 8 The frame header may include the syntax element `gdr_or_irap_pic_flag` specifying whether the current frame is a GDR or IRAP frame, and the syntax element `gdr_pic_flag` specifying whether the current frame is a GDR frame. Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag` specifying whether one or more slices in the current frame can have inter-slice types (e.g., B-slice or P-slice types), and the syntax element `ph_intra_slice_allowed_flag` specifying whether one or more slices in the current frame can have intra-slice types (e.g., I-slice types). (Refer to the above.) Figure 5 It describes the semantics of each of the grammatical elements.

[0166] Additionally, the screen header may include the syntax element `idr_pic_flag` (810). `idr_pic_flag` can specify whether the current screen is an IDR screen. For example, an `idr_pic_flag` with a first value (e.g., 1) can specify that the current screen is an IDR screen. In contrast, an `idr_pic_flag` with a second value (e.g., 0) can specify that the current screen is not an IDR screen. When `idr_pic_flag` is not present, it can be inferred to be the second value (e.g., 0).

[0167] The `idr_pic_flag` can be conditionally signaled based on `gdr_or_irap_pic_flag`. For example, when `gdr_or_irap_pic_flag` has a first value (e.g., 1) specifying that the current frame is a GDR frame or an IRAP frame, the `idr_pic_flag` can be signaled. Conversely, when `gdr_or_irap_pic_flag` has a second value (e.g., 0) specifying that the current frame is not a GDR frame but can be an IRAP frame, the `idr_pic_flag` can be signaled without signaling. In this way, the `idr_pic_flag` can be signaled under the same conditions as `gdr_pic_flag` (i.e., `gdr_or_irap_pic_flag == 1`).

[0168] In another implementation, idr_pic_flag can be conditionally notified by signaling based on gdr_or_irap_pic_flag and gdr_pic_flag.

[0169] Figure 9 This is a view illustrating a screen header including idr_pic_flag according to another embodiment of this disclosure.

[0170] Reference Figure 9 The frame header may include the syntax element `gdr_or_irap_pic_flag` specifying whether the current frame is a GDR or IRAP frame, and the syntax element `gdr_pic_flag` specifying whether the current frame is a GDR frame. Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag` specifying whether one or more slices in the current frame can have inter-slice types (e.g., B-slice or P-slice types), and the syntax element `ph_intra_slice_allowed_flag` specifying whether one or more slices in the current frame can have intra-slice types (e.g., I-slice types). (Refer to the above.) Figure 5 It describes the semantics of each of the grammatical elements.

[0171] Additionally, the screen header can also include the syntax element `idr_pic_flag(910)`, which specifies whether the current screen is an IDR screen. (See above for reference.) Figure 8 The semantics of idr_pic_flag are described.

[0172] The `idr_pic_flag` can be conditionally notified based on `gdr_or_irap_pic_flag` and `gdr_pic_flag`. For example, `idr_pic_flag` can be notified by signaling when `gdr_or_irap_pic_flag` has a first value (e.g., 1) specifying that the current frame is a GDR frame or an IRAP frame, and `gdr_pic_flag` has a second value (e.g., 0) specifying that the current frame is not a GDR frame. In contrast, `idr_pic_flag` can be notified without signaling when `gdr_or_irap_pic_flag` has a second value (e.g., 0) specifying that the current frame is not a GDR frame but can be an IRAP frame, or when `gdr_or_irap_pic_flag` has a first value (e.g., 1) specifying that the current frame is a GDR frame. Therefore, `idr_pic_flag` can only be notified by signaling when the current frame is an IRAP frame.

[0173] Therefore, since the idr_pic_flag, which specifies the current screen as an IDR screen, is explicitly signaled, the signaling conditions for various syntax elements can be simplified when the current screen is an IDR screen.

[0174] Implementation Method 3

[0175] According to Embodiment 3 of this disclosure, the reference screen list information can be signaled in the screen header based on whether the current screen is an IDR screen.

[0176] Figure 10 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0177] Reference Figure 10 The frame header may include the syntax element `gdr_or_irap_pic_flag` specifying whether the current frame is a GDR or IRAP frame, and the syntax element `gdr_pic_flag` specifying whether the current frame is a GDR frame. Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag` specifying whether one or more slices in the current frame can have inter-slice types (e.g., B-slice or P-slice types), and the syntax element `ph_intra_slice_allowed_flag` specifying whether one or more slices in the current frame can have intra-slice types (e.g., I-slice types). (Refer to the above.) Figure 5 It describes the semantics of each of the grammatical elements.

[0178] In one implementation, when `gdr_or_irap_pic_flag` has a first value (e.g., 1), `gdr_pic_flag` has a second value (e.g., 0) (that is, the current frame is an IRAP frame), and `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` has a first value (e.g., 1), the value of `ph_inter_slice_allowed_flag` can be set to the second value (e.g., 0). Here, the first value (e.g., 1) of `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` can specify that the layer with index `GeneralLayerIdx[nuh_layer_id]` does not use inter-layer prediction.

[0179] Additionally, the screen header can also include the syntax element `idr_pic_flag`, which specifies whether the current screen is an IDR screen. (See above for reference.) Figure 8 The semantics and signaling conditions of idr_pic_flag are described.

[0180] In the screen header, the reference screen list information ref_pic_lists (1010) can be signaled based on a predetermined second condition. Specifically, ref_pic_lists can only be signaled if the reference screen list information exists in the screen header (i.e., rpl_info_in_ph_flag == 1) and the current screen is not an IDR screen (i.e., idr_pic_flag == 0).

[0181] Figure 10 The situation can be compared with Figure 5 The screen header differs because the reference screen list information (ref_pic_list) is signaled based on whether the current screen is an IDR screen. In other words, when the current screen is an IDR screen (i.e., idr_pic_flag == 1), it's unnecessary to signal ref_pic_lists in the screen header. Therefore, the problem of unnecessarily signaling the reference screen list information for IDR screens in the screen header can be solved.

[0182] Implementation Method 4

[0183] According to Embodiment 4 of this disclosure, in the screen header, reference screen list information can be signaled based on whether the current screen is an IDR screen and whether the syntax element of the reference screen list for the IDR screen exists in the slice header.

[0184] Figure 11 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0185] Reference Figure 11 The frame header may include the syntax element `gdr_or_irap_pic_flag` specifying whether the current frame is a GDR or IRAP frame, and the syntax element `gdr_pic_flag` specifying whether the current frame is a GDR frame. Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag` specifying whether one or more slices in the current frame can have inter-slice types (e.g., B-slice or P-slice types), and the syntax element `ph_intra_slice_allowed_flag` specifying whether one or more slices in the current frame can have intra-slice types (e.g., I-slice types). (Refer to the above.) Figure 5 It describes the semantics of each of the grammatical elements.

[0186] In one implementation, when `gdr_or_irap_pic_flag` has a first value (e.g., 1), `gdr_pic_flag` has a second value (e.g., 0) (that is, the current frame is an IRAP frame), and `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` has a first value (e.g., 1), the value of `ph_inter_slice_allowed_flag` can be set to the second value (e.g., 0). Here, the first value (e.g., 1) of `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` can specify that the layer with index `GeneralLayerIdx[nuh_layer_id]` does not use inter-layer prediction.

[0187] Additionally, the screen header can also include the syntax element `idr_pic_flag`, which specifies whether the current screen is an IDR screen. (See above for reference.) Figure 8 The semantics and signaling conditions of idr_pic_flag are described.

[0188] In the screen header, the reference screen list information ref_pic_lists (1110) can be signaled based on a predetermined third condition. Specifically, ref_pic_lists can only be signaled if the reference screen list information exists in the screen header (i.e., rpl_info_in_ph_flag == 1), the syntax elements of the reference screen list exist in the slice header of a slice with a NAL unit type such as IDR_N_LP or IDR_W_RADL, or the current screen is not an IDR screen (i.e., sps_idr_rpl_present_flag == 1 or idr_pic_flag == 0).

[0189] Figure 11 The situation can be compared with Figure 5 The screen header differs because the reference screen list information `ref_pic_lists` is signaled based on whether `sps_idr_rpl_present_flag` has a first value (e.g., 1) or whether `idr_pic_flag` has a second value (e.g., 0). That is, when the syntax element for the reference screen list of an IDR screen does not exist in the slice header (i.e., `sps_idr_rpl_present_flag == 0`), and the current screen is an IDR screen (i.e., `idr_pic_flag == 1`), the `ref_pic_list` does not need to be signaled in the screen header. Therefore, the problem of unnecessarily signaling the reference screen list information of an IDR screen in the screen header can be solved.

[0190] Implementation Method 5

[0191] According to Embodiment 5 of this disclosure, in the screen header, reference screen list information can be signaled based on whether the current screen is an IDR screen and whether the syntax element of the reference screen list for the IDR screen exists in the slice header.

[0192] Figure 12 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0193] Reference Figure 12The frame header may include the syntax element `gdr_or_irap_pic_flag` specifying whether the current frame is a GDR or IRAP frame, and the syntax element `gdr_pic_flag` specifying whether the current frame is a GDR frame. Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag` specifying whether one or more slices in the current frame can have inter-slice types (e.g., B-slice or P-slice types), and the syntax element `ph_intra_slice_allowed_flag` specifying whether one or more slices in the current frame can have intra-slice types (e.g., I-slice types). (Refer to the above.) Figure 5 It describes the semantics of each of the grammatical elements.

[0194] Additionally, the screen header can include the syntax element `idr_pic_flag`, which specifies whether the current screen is an IDR screen. `idr_pic_flag` can be combined with... Figure 11 The `idr_pic_flag` flag differs from `gdr_pic_flag` because it only signals when the current frame is not a GDR frame (i.e., `gdr_pic_flag == 0`). In other words, when `gdr_pic_flag` has a first value (e.g., 1), `idr_pic_flag` does not need to be signaled. Furthermore, even if `gdr_pic_flag` is not signaled, it can still be signaled when it is set to a second value (e.g., 0).

[0195] In the screen header, the reference screen list information ref_pic_lists (1210) can be signaled based on a predetermined third condition. Specifically, ref_pic_lists can only be signaled if the reference screen list information exists in the screen header (i.e., rpl_info_in_ph_flag == 1), the syntax elements of the reference screen list exist in the slice header of a slice with a NAL unit type such as IDR_N_LP or IDR_W_RADL, or the current screen is not an IDR screen (i.e., sps_idr_rpl_present_flag == 1 or idr_pic_flag == 0).

[0196] Figure 12 The situation can be compared with Figure 5The screen header differs because the reference screen list information `ref_pic_lists` is signaled based on whether `sps_idr_rpl_present_flag` has a first value (e.g., 1) or whether `idr_pic_flag` has a second value (e.g., 0). That is, when the syntax element for the reference screen list of an IDR screen does not exist in the slice header (i.e., `sps_idr_rpl_present_flag == 0`), and the current screen is an IDR screen (i.e., `idr_pic_flag == 1`), it is not necessary to signal `ref_pic_list` in the screen header. Therefore, the problem of unnecessarily signaling the reference screen list information of an IDR screen in the screen header can be solved.

[0197] Implementation Method 6

[0198] According to Embodiment 6 of this disclosure, the frame header can be used to signal whether inter-frame slicing is allowed in the current frame based on whether the current frame is a GDR frame.

[0199] Figure 13 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0200] Reference Figure 13 The screen header can include the syntax element `gdr_or_irap_pic_flag` specifying whether the current screen is a GDR screen or an IRAP screen, and the syntax element `gdr_pic_flag` specifying whether the current screen is a GDR screen. (See above for reference.) Figure 5 It describes the semantics of each of the grammatical elements.

[0201] Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag`. `ph_inter_slice_allowed_flag` can specify whether one or more slices in the current frame can have an inter-slice type (e.g., B-slice type or P-slice type). For example, a first value (e.g., 1) of `ph_inter_slice_allowed_flag` can specify that one or more coded slices with B-slice type (i.e., slice_type = 0) or P-slice type (i.e., slice_type = 1) can exist in the current frame. In contrast, a second value (e.g., 0) of `ph_inter_slice_allowed_flag` can specify that all coded slices in the current frame have I-slice type (i.e., slice_type = 2).

[0202] The `ph_inter_slice_allowed_flag` (1310) can only be signaled when the current frame is not a GDR frame. For example, when `gdr_pic_flag` has a second value (e.g., 0) indicating that the current frame is not a GDR frame, `ph_inter_slice_allowed_flag` can be signaled. In contrast, when `gdr_pic_flag` has a first value (e.g., 1) indicating that the current frame is a GDR frame, `ph_inter_slice_allowed_flag` can be left unsigned. When `ph_inter_slice_allowed_flag` is left unsigned, the value of `ph_inter_slice_allowed_flag` can be inferred to be the first value (e.g., 1).

[0203] Additionally, the frame header may include the syntax element `ph_intra_slice_allowed_flag`. `ph_intra_slice_allowed_flag` can specify that one or more slices in the current frame can have an intra-slice type (e.g., I-slice type). For example, a first value (e.g., 1) of `ph_intra_slice_allowed_flag` can specify that one or more coded slices with I-slice type (i.e., slice_type = 2) can exist in the current frame. In contrast, a second value (e.g., 0) of `ph_intra_slice_allowed_flag` can specify that all coded slices in the current frame have B-slice type (i.e., slice_type = 0) or P-slice type (i.e., slice_type = 1).

[0204] The `ph_intra_slice_allowed_flag` (1320) can only be signaled if inter-slicing is permitted for the current frame. For example, `ph_intra_slice_allowed_flag` can be signaled when `ph_inter_slice_allowed_flag` has a first value (e.g., 1) specifying that one or more coded slices of type B or P can exist in the current frame. Conversely, `ph_intra_slice_allowed_flag` can be left unsigned when `ph_inter_slice_allowed_flag` has a second value (e.g., 0) specifying that all coded slices in the current frame are of type I. When `ph_intra_slice_allowed_flag` is left unsigned, the value of `ph_intra_slice_allowed_flag` can be inferred to be the first value (e.g., 1).

[0205] In another implementation, the ph_intra_slice_allowed_flag can only be signaled if the current frame is not a GDR frame and inter-frame slices are available for the current frame.

[0206] Figure 14 This is a schematic diagram illustrating a screen header according to another embodiment of this disclosure. Besides the signaling condition ph_intra_slice_allowed_flag, Figure 14 The image header can have the same Figure 13 The image header has the same structure and semantics. Therefore, its repeated description will be omitted.

[0207] Reference Figure 14In the frame header, the `ph_intra_slice_allowed_flag` (1410) can only be signaled if the current frame is not a GDR frame and inter-frame slicing is allowed for the current frame. For example, the `ph_intra_slice_allowed_flag` can be signaled when `gdr_pic_flag` has a second value (e.g., 0) indicating that the current frame is not a GDR frame, and `ph_inter_slice_allowed_flag` has a first value (e.g., 1) indicating that one or more coded slices of type B or P slice can exist in the current frame. In contrast, the `ph_intra_slice_allowed_flag` can be signaled without being signaled when `gdr_pic_flag` has a first value (e.g., 1) indicating that the current frame is a GDR frame, or when `ph_inter_slice_allowed_flag` has a second value (e.g., 0) indicating that all coded slices in the current frame are of type I slice. When ph_intra_slice_allowed_flag is not signaled, the value of ph_intra_slice_allowed_flag can be inferred to be the first value (e.g., 1).

[0208] As mentioned above Figure 13 and Figure 14 As described, the ph_inter_slice_allowed_flag can only be signaled when the current frame is not a GDR frame. Therefore, for GDR frames that may include inter-frame slices due to frame attributes, the problem of unnecessarily signaling ph_inter_slice_allowed_flag can be solved.

[0209] Implementation Method 7

[0210] According to embodiment 7 of this disclosure, in the frame header, information indicating whether inter-frame slicing is allowed in the current frame can be signaled based on whether the current layer of the current frame can use inter-layer prediction and whether the current frame is an IRAP frame.

[0211] Figure 15 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0212] Reference Figure 15 The screen header can include the syntax element `gdr_or_irap_pic_flag` specifying whether the current screen is a GDR screen or an IRAP screen, and the syntax element `gdr_pic_flag` specifying whether the current screen is a GDR screen. (See above for reference.) Figure 5It describes the semantics of each of the grammatical elements.

[0213] Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag`, which specifies whether inter-frame slicing (e.g., B-slices or P-slices) is allowed for the current frame. (See above for reference.) Figure 13 The semantics of ph_inter_slice_allowed_flag are described.

[0214] The ph_inter_slice_allowed_flag (1510) can be signaled based on a predetermined fourth condition. Specifically, the ph_inter_slice_allowed_flag can be signaled when vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] has a second value (e.g., 0) indicating that the current layer, including the current image, can use inter-layer prediction; or gdr_or_irap_pic_flag has a second value (e.g., 0) indicating that the current image is not a GDR image but can be an IRAP image; or gdr_pic_flag has a first value (e.g., 1) indicating that the current image is a GDR image (i.e., !(vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]&&gdr_or_irap_pic_flag&&!gdr_pic_flag)==1). In contrast, when vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] has a first value (e.g., 1) specifying that the current layer, including the current frame, cannot use inter-layer prediction, gdr_or_irap_pic_flag has a first value (e.g., 1) specifying that the current frame is a GDR frame or an IRAP frame, and gdr_pic_flag has a second value (e.g., 0) specifying that the current frame is not a GDR frame (i.e., !(vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]&&gdr_or_irap_pic_flag&&!gdr_pic_flag)==0), ph_inter_slice_allowed_flag may not be signaled and can be inferred to be a second value (e.g., 0) specifying that inter-slicing is not allowed for the current frame. In other words, when the current frame is an IRAP frame that is included in an independent layer that does not use inter-layer prediction, ph_inter_slice_allowed_flag may not be signaled and may be inferred to be a second value (e.g., 0) that specifies that inter-slicing is not allowed for the current frame.

[0215] In another implementation, without signaling ph_inter_slice_allowed_flag, when the current frame is a GDR frame (i.e., gdr_or_irap_pic_flag == 1 && gdr_pic_flag == 1), ph_inter_slice_allowed_flag can be inferred to be a first value (e.g., 1) specifying that inter-frame slicing is allowed for the current block. In contrast, when the current frame is not a GDR frame (e.g., the current frame is an IRAP frame included in an independent layer (i.e., gdr_or_irap_pic_flag == 1 && gdr_pic_flag == 0 && vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] == 1)), ph_inter_slice_allowed_flag can be inferred to be a second value (e.g., 0) specifying that inter-frame slicing is not allowed for the current frame.

[0216] Furthermore, in one implementation, when `gdr_or_irap_pic_flag` has a first value (e.g., 1), `gdr_pic_flag` has a second value (e.g., 0) (that is, the current frame is an IRAP frame), and `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` has a first value (e.g., 1), the value of `ph_inter_slice_allowed_flag` can be set to the second value (e.g., 0). Here, the first value (e.g., 1) of `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` can specify that the layer with index `GeneralLayerIdx[nuh_layer_id]` does not use inter-layer prediction.

[0217] As mentioned above Figure 15As described, when the current frame belongs to an independent layer that does not use inter-layer prediction and is only an IRAP frame (i.e., !(vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]&&gdr_or_irap_pic_flag&&!gdr_pic_flag)==0), it is not necessary to signal ph_inter_slice_allowed_flag. Therefore, for IRAP frames that may include intra-frame slices due to frame attributes, the problem of unnecessarily signaling ph_inter_slice_allowed_flag can be solved.

[0218] Implementation Method 8

[0219] According to Embodiment 8 of this disclosure, in the frame header, information indicating whether inter-frame slicing is allowed in the current frame can be signaled based on whether the current frame is a GDR frame, whether the current layer of the current frame can use inter-layer prediction, and whether the current frame is an IRAP frame.

[0220] Figure 16 This is a view illustrating a screen header according to an embodiment of the present disclosure.

[0221] Reference Figure 16 The screen header can include the syntax element `gdr_or_irap_pic_flag` specifying whether the current screen is a GDR screen or an IRAP screen, and the syntax element `gdr_pic_flag` specifying whether the current screen is a GDR screen. (See above for reference.) Figure 5 It describes the semantics of each of the grammatical elements.

[0222] Additionally, the frame header may include the syntax element `ph_inter_slice_allowed_flag`, which specifies whether inter-frame slicing (e.g., B-slicing or P-slicing) is allowed for the current frame. (See above for reference.) Figure 13 The semantics of ph_inter_slice_allowed_flag are described.

[0223] The signal ph_inter_slice_allowed_flag (1610) can be used to notify the user based on a predetermined fifth condition. In this case, the fifth condition may include conditions (5-1) and (5-2). Specifically, condition (5-1) may mean that gdr_pic_flag has a second value (e.g., 0) indicating that the current frame is not a GDR frame (i.e., !(gdr_pic_flag) == 1). Additionally, condition (5-2) can mean that `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` has a second value (e.g., 0) specifying that the current layer, including the current image, can use inter-layer prediction, or that `gdr_or_irap_pic_flag` has a second value (e.g., 0) specifying that the current image is not a GDR image and can be an IRAP image, or that `gdr_pic_flag` has a first value (e.g., 1) specifying that the current image is a GDR image (i.e., !(vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]&&gdr_or_irap_pic_flag&&!gdr_pic_flag)==1). When both conditions (5-1) and (5-2) are true, `ph_inter_slice_allowed_flag` can be signaled. In contrast, when at least one of condition (5-1) or condition (5-2) is false, ph_inter_slice_allowed_flag can be used without signaling and can be inferred to be a second value (e.g., 0) that specifies that inter-slicing is not allowed for the current frame. That is, when the current frame is a GDR frame or an IRAP frame included in an independent layer that does not use inter-layer prediction, ph_inter_slice_allowed_flag can be used without signaling and can be inferred to be a second value (e.g., 0) that specifies that inter-slicing is not allowed for the current frame.

[0224] In another implementation, without signaling ph_inter_slice_allowed_flag, when the current frame is a GDR frame (i.e., gdr_or_irap_pic_flag == 1 && gdr_pic_flag == 1), ph_inter_slice_allowed_flag can be inferred to be a first value (e.g., 1) specifying that inter-frame slicing is allowed for the current block. In contrast, when the current frame is not a GDR frame (e.g., the current frame is an IRAP frame included in an independent layer (i.e., gdr_or_irap_pic_flag == 1 && gdr_pic_flag == 0 && vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] == 1)), ph_inter_slice_allowed_flag can be inferred to be a second value (e.g., 0) specifying that inter-frame slicing is not allowed for the current frame.

[0225] Furthermore, in one implementation, when `gdr_or_irap_pic_flag` has a first value (e.g., 1), `gdr_pic_flag` has a second value (e.g., 0) (that is, the current frame is an IRAP frame), and `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` has a first value (e.g., 1), the value of `ph_inter_slice_allowed_flag` can be set to the second value (e.g., 0). Here, the first value (e.g., 1) of `vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]` can specify that the layer with index `GeneralLayerIdx[nuh_layer_id]` does not use inter-layer prediction.

[0226] As mentioned above Figure 16As described, when the current frame is a GDR frame (i.e., !(gdr_pic_flag) == 0) or the current frame belongs to an independent layer that does not use inter-layer prediction, and the current frame is only an IRAP frame (i.e., !(vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]&&gdr_or_irap_pic_flag&&!gdr_pic_flag) == 0), it is not necessary to signal ph_inter_slice_allowed_flag. Therefore, for IRAP frames that may include intra-frame slices and GDR frames that may include inter-frame slices due to frame attributes, the problem of unnecessarily signaling ph_inter_slice_allowed_flag can be solved.

[0227] In the following text, reference will be made to Figure 17 and Figure 18 A detailed description of an image encoding / decoding method according to embodiments of the present disclosure is provided.

[0228] Figure 17 This is a flowchart illustrating an image encoding method according to an embodiment of the present disclosure. Figure 17 Image encoding methods can be derived from Figure 2 The image encoding device performs the operation.

[0229] Reference Figure 17 The image encoding device can encode first information regarding whether an inter-frame slice type is allowed for the current frame, including the current block (S1710). The first information may be, for example, as described above. Figures 7 to 16 The `ph_inter_slice_allowed_flag` is described. In one example, the first information can be determined based on the slice type of the slices in the current frame. For example, when one or more slices in the current frame have a B slice type or a P slice type, the first information can have a first value (e.g., 1) specifying the allowed inter-slice types for the current frame. In contrast, when all slices in the current frame have an I slice type, the first information can have a second value (e.g., 0) specifying the disallowed inter-slice types for the current frame.

[0230] In one implementation, whether inter-frame slice types are allowed for the current frame can be determined based on the frame type of the current frame and whether the current layer including the current frame can use inter-layer prediction. For example, when the current frame has the same frame type as an IRAP (Intra-IRAP Random Access Point) frame and the current layer including the current frame does not use inter-layer prediction, inter-frame slice types may not be allowed for the current frame. Alternatively, when the current frame has the same frame type as a GDR (Progressive Decoding Refresh) frame, inter-frame slice types may be allowed for the current frame. Additionally, in this case, the encoding of the first information can be skipped.

[0231] Information about the current frame type can be encoded in the frame header. This information may include third information regarding whether the current frame has the same frame type as a GDR (Progressive Decoding Refresh) frame or an IRAP (Intra-Frame Random Access Point) frame, and fourth information regarding whether the current frame has the same frame type as a GDR frame. The third and fourth information may be, for example, as described above. Figures 7 to 16 The description includes `gdr_or_irap_pic_flag` and `gdr_pic_flag`. When the current frame has the same frame type as the IRAP frame, the third information may have a first value (e.g., 1) specifying that the current frame has the same frame type as the GDR or IRAP frame. Additionally, the fourth information may have a second value (e.g., 0) specifying that the current frame has a different frame type than the GDR frame.

[0232] Furthermore, a fifth piece of information (e.g., vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]]) regarding whether the current layer can use inter-layer prediction (i.e., whether the current layer is an independent layer in a multi-layer structure) can be encoded in the video parameter set. When the fifth piece of information has a first value (e.g., 1), the current layer cannot use inter-layer prediction. In contrast, when the fifth piece of information has a second value (e.g., 0), the current layer can use inter-layer prediction.

[0233] Based on the permissible inter-frame slice types for the current frame, the image encoding device can encode second information regarding whether intra-frame slice types are permissible for the current frame (S1720). The second information can be, for example, as described above. Figures 7 to 16The described `ph_intra_slice_allowed_flag`. Similar to the first information, the second information can be determined based on the slice type of the slice in the current frame. For example, when one or more slices in the current frame have an I slice type, the second information can have a first value (e.g., 1) specifying the allowed intra-slice types for the current frame. In contrast, when all slices in the current frame have a B slice type or a P slice type, the second information can have a second value (e.g., 0) specifying the disallowed intra-slice types for the current frame. The second information can be encoded / signed in the frame header along with the first information. Furthermore, in this disclosure, the first and second information can be referred to as available slice type information.

[0234] Figure 18 This is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure. Figure 18 Image decoding methods can be derived from Figure 3 The image decoding device performs the operation.

[0235] Reference Figure 18 The image decoding device can determine whether an inter-frame slice type is allowed for the current frame, including the current block (S1810).

[0236] Whether an inter-slice type is allowed for the current frame can be determined based on first information obtained from the frame header (e.g., ph_inter_slice_allowed_flag). For example, when the first information has a first value (e.g., 1), the inter-slice type is allowed for the current frame. In contrast, when the first information has a second value (e.g., 0), the inter-slice type is not allowed for the current frame.

[0237] In one implementation, whether inter-frame slice types are allowed for the current frame can be determined based on the frame type of the current frame and whether the current layer including the current frame can use inter-layer prediction. For example, if the current frame has the same frame type as an IRAP (Intra-IRAP Random Access Point) frame and the current layer does not use inter-layer prediction, inter-frame slice types may not be allowed for the current frame. Alternatively, when the current frame has the same frame type as a GDR (Progressive Decoding Refresh) frame, inter-frame slice types may be allowed for the current frame. Furthermore, in this case, the parsing of the first information can be skipped.

[0238] The frame type of the current frame can be determined based on third information regarding whether the current frame has the same frame type as a GDR (Progressive Decoding Refresh) frame or an IRAP (Intra-Frame Random Access Point) frame, and fourth information regarding whether the current frame has the same frame type as a GDR frame. The third and fourth information can be, for example, as described above. Figures 7 to 16The descriptions of gdr_or_irap_pic_flag and gdr_pic_flag. When the third information specifies that the current frame has the same frame type as the GDR frame or IRAP frame and the fourth information specifies that the current frame has a different frame type than the GDR frame, the frame type of the current frame can be determined to be the same as the IRAP frame.

[0239] Furthermore, a fifth piece of information obtained from the video parameter set can be used to determine whether the current layer can use inter-layer prediction (i.e., whether the current layer is an independent layer in a multi-layer structure). For example, when the fifth piece of information has a first value (e.g., 1), the current layer cannot use inter-layer prediction. In contrast, when the fifth piece of information has a second value (e.g., 0), the current layer can use inter-layer prediction.

[0240] Based on the permissible inter-frame slice types for the current frame, the image decoding device can determine whether the intra-frame slice type is permissible for the current frame (S1820).

[0241] Whether an intra-slice type is allowed for the current frame can be determined based on second information obtained from the frame header (e.g., ph_intra_slice_allowed_flag). For example, when the second information has a first value (e.g., 1), the intra-slice type is allowed for the current frame. Conversely, when the second information has a second value (e.g., 0), the intra-slice type is not allowed for the current frame. Furthermore, in this disclosure, the first and second information may be referred to as available slice type information.

[0242] Furthermore, the image decoding device can decode the current block based on the allowed slice types for the current frame (S1830). For example, the image decoding device can determine the slice type of the slice in the current frame based on the allowed slice types for the current frame. When the current block is included in a slice with an inter-frame slice type, the image decoding device can decode the current block by performing inter-frame prediction. In contrast, when the current block is included in a slice with an intra-frame slice type, the image decoding device can decode the current block by performing intra-frame prediction.

[0243] According to the image encoding / decoding method of this disclosure, when the current frame belongs to an independent layer that does not use inter-layer prediction and the current frame is only an IRAP frame, inter-slice types may not be allowed for the current frame. Therefore, in the encoding stage, since it is not necessary to signal information specifying whether inter-slice types are allowed for the current block (e.g., ph_inter_slice_allowed_flag), signaling overhead can be reduced and encoding efficiency can be improved. Furthermore, in the decoding stage, since it is not necessary to parse information specifying whether inter-slice types are allowed for the current block (e.g., ph_inter_slice_allowed_flag), computational complexity can be reduced and decoding efficiency can be improved.

[0244] The names of the syntax elements described in this disclosure may include information about the location of the corresponding syntax element being signaled. For example, a syntax element beginning with "sps_" may indicate that the corresponding syntax element is signaled in the Sequence Parameter Set (SPS). Additionally, syntax elements beginning with "pps_", "ph_", or "sh_" may indicate that the corresponding syntax element is signaled in the Picture Parameter Set (PPS), Picture Header, and Slice Header, respectively.

[0245] 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 methods according to this disclosure, 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.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] Figure 19 This is a view illustrating a content streaming system to which embodiments of the present disclosure can be applied.

[0251] like Figure 19 As 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.

[0252] 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.

[0253] 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.

[0254] 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.

[0255] 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.

[0256] Examples of user devices may include mobile phones, smartphones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, board PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, head-mounted displays), digital televisions, desktop computers, digital signage, etc.

[0257] 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.

[0258] 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.

[0259] Industrial applicability

[0260] The embodiments disclosed herein can be used to encode or decode images.

Claims

1. An image decoding method performed by an image decoding device, wherein, The image decoding method includes the following steps: Determine whether inter-frame slices are allowed for the current frame, including the current block; Based on whether the inter-frame slice type is allowed for the current frame, determine whether the intra-frame slice type is allowed for the current frame; and The current block is decoded based on the allowed slice types for the current frame. Specifically, the determination of whether the inter-frame slice type is allowed for the current frame is based on the frame type of the current frame and whether the current layer including the current frame is an independent layer that will be decoded without referring to other layers. Wherein, based on the current frame's frame type being an Intra-Frame Random Access Point (IRAP) frame and the current layer being the independent layer, the inter-frame slice type is not allowed for the current frame. The frame type of the current frame is determined based on third information regarding whether the frame type of the current frame is a Progressive Decoding Refresh (GDR) frame or an Intra-Frame Random Access Point (IRAP) frame, and fourth information regarding whether the frame type of the current frame is a GDR frame. Specifically, the fifth piece of information is used to determine whether the current layer is the independent layer.

2. The image decoding method according to claim 1, in, Based on the first information obtained from the frame header, it is determined whether the inter-frame slice type is allowed for the current frame, and Specifically, the intra-frame slice type is determined based on the second information obtained from the frame header.

3. The image decoding method according to claim 1, in, Based on the third information specifying that the current frame has the same frame type as the GDR frame or IRAP frame, and the fourth information specifying that the current frame has a different frame type than the GDR frame, It is determined that the current screen type is the same as the IRAP screen type.

4. The image decoding method according to claim 1, wherein, The fifth piece of information is obtained from the video parameter set.

5. An image encoding method performed by an image encoding device, wherein, The image encoding method includes the following steps: Encode the first information regarding whether inter-frame slice types are allowed for the current frame, including the current block; and Based on whether the inter-frame slice type is allowed for the current frame, second information regarding whether the intra-frame slice type is allowed for the current frame is encoded. Specifically, the determination of whether the inter-frame slice type is allowed for the current frame is based on the frame type of the current frame and whether the current layer including the current frame is an independent layer that will be decoded without referring to other layers. Wherein, based on the current frame's frame type being an Intra-Frame Random Access Point (IRAP) frame and the current layer being the independent layer, the inter-frame slice type is not allowed for the current frame. The information regarding the frame type of the current frame includes third information about whether the frame type of the current frame is a Progressive Decoding Refresh (GDR) frame or an Intra-Frame Random Access Point (IRAP) frame, and fourth information about whether the frame type of the current frame is a GDR frame. Specifically, the fifth piece of information regarding whether the current layer is the independent layer is encoded.

6. The image encoding method according to claim 5, wherein, Since the current frame has the same frame type as the progressively decoded refreshed GDR frame, the inter-frame slice type is allowed for the current frame and the step of encoding the first information is skipped.

7. The image encoding method according to claim 5, wherein, The information regarding the screen type of the current screen is encoded in the screen header.

8. The image encoding method according to claim 5, wherein, Based on the fact that the current screen has the same screen type as the IRAP screen, the third information has a first value indicating that the current screen has the same screen type as the GDR screen or the IRAP screen, and the fourth information has a second value indicating that the current screen has a different screen type than the GDR screen.

9. The image encoding method according to claim 5, wherein, The fifth piece of information is encoded in the video parameter set.

10. A method for transmitting a bit stream, the method comprising the following steps: Encode the first information regarding whether inter-frame slice types are allowed for the current frame, including the current block; Based on whether the inter-frame slice type is allowed for the current frame, second information regarding whether the intra-frame slice type is allowed for the current frame is encoded. Generate the bitstream comprising encoded first information and encoded second information; as well as Send data including the bit stream. Specifically, the determination of whether the inter-frame slice type is allowed for the current frame is based on the frame type of the current frame and whether the current layer including the current frame is an independent layer that will be decoded without referring to other layers. Wherein, based on the current frame's frame type being an Intra-Frame Random Access Point (IRAP) frame and the current layer being the independent layer, the inter-frame slice type is not allowed for the current frame. The information regarding the frame type of the current frame includes third information about whether the frame type of the current frame is a Progressive Decoding Refresh (GDR) frame or an Intra-Frame Random Access Point (IRAP) frame, and fourth information about whether the frame type of the current frame is a GDR frame. Specifically, the fifth piece of information regarding whether the current layer is the independent layer is encoded.

Images