Encoder, decoder and corresponding signaling method, and semantics within parameter sets

Abstract

To provide improved signaling of syntax elements within a sequence parameter set.SOLUTION: A method for decoding a video bitstream includes the steps of obtaining, from a sequence parameter set (SPS), a value of a first syntax element used to specify whether a Decoded Picture Buffer (DPB) parameter syntax structure is present in the SPS, and obtaining, from the SPS, at least a value of a second syntax element used to specify the presence of a DPB syntax element in the DPB parameter syntax structure when determining that the value of the first syntax element specifies that the DPB parameter syntax structure is present in the SPS. The DPB syntax element applies to a temporal sub-layer except a topmost temporal sub-layer in a video sequence.SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] Embodiments of the present application generally relate to the field of picture processing, and more particularly, to the signaling of syntax elements within a sequence parameter set.

Background Art

[0002] Video coding (video encoding and decoding) is used in a wide range of digital video applications, such as broadcast digital TV, video transmission over the Internet and mobile networks, real-time conversation applications such as video chat, video conferencing, DVDs and Blu-ray discs, video content acquisition and editing systems, and camcorders for security applications.

[0003] The amount of video data required to depict even relatively short videos can be quite large, which can pose difficulties when the data is to be streamed over a communication network having a limited bandwidth capacity or otherwise transmitted. Thus, video data is generally compressed before being transmitted over modern communication networks. The size of the video can also be a problem when the video is stored on a storage device, as memory resources may be limited. In many cases, video compression devices use software and / or hardware at the source to code the video data before transmission or storage, thereby reducing the amount of data required to represent the digital video image. And the compressed data is received at the destination by a video decompression device that decodes the video data. Due to limited network resources and the ever-increasing demand for higher video quality, improved compression and decompression techniques that increase the compression ratio without sacrificing picture quality or sacrificing it at all are desirable.

[0004] In particular, the signaling of syntax elements within a sequence parameter set that is coded in a bitstream used to provide Decoded Picture Buffer information suffers from inefficiencies and even inconsistencies in the art (see the detailed description below). Accordingly, an object of the present application is to provide a technique for signaling such syntax elements with improved coding efficiency. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0005] Embodiments of the present application provide an apparatus and method for encoding and decoding according to independent claims.

[0006] The above and other objects are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the drawings.

[0007] According to a first aspect, the present invention relates to a method of decoding a video bitstream, implemented by a decoding device, wherein a sequence parameter set SPS is coded in the video bitstream and includes syntax elements applied to a video sequence. The method includes obtaining a value of a first syntax element (e.g., a flag) from the SPS, the value of the first syntax element being used to specify whether a decoded picture buffer DPB parameter syntax structure exists within the SPS. The method further includes obtaining a value of a second syntax element (e.g., a flag) from the SPS when it is determined (judged) that the value of the first syntax element specifies that the DPB parameter syntax structure exists within the SPS, the value of the second syntax element being used to specify the existence of DPB syntax elements within the DPB parameter syntax structure, and the DPB syntax elements being applied to temporal sublayers of the video sequence excluding the top temporal sublayer.

[0008] For example, the value of the second syntax structure may be obtained only when it is determined that the value of the first syntax element specifies that the DPB parameter syntax structure exists within the SPS. Here and hereinafter, the first syntax element may be sps_ptl_dpb_hrd_params_present_flag according to the following detailed description, and the second syntax element may be sps_sublayer_dpb_params_flag according to the following detailed description. Here and hereinafter, the DPB syntax element may be one of max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] according to the following detailed description.

[0009] The method thus provided for decoding a video bitstream ensures efficient signaling of DPB syntax elements. In particular, the second syntax element, when present, reliably controls the presence of DPB syntax elements in the DPB parameter syntax structure.

[0010] According to an implementation, the method further includes obtaining a value of a DPB syntax element based on a value of the second syntax element (e.g., when the second syntax element specifies that a DPB syntax element is present within the DPB parameter syntax structure, in particular, only when the second syntax element specifies that a DPB syntax element is present within the DPB parameter syntax structure), and reconstructing a video sequence based on the value of the DPB syntax element. Thus, reconstruction of the video sequence can be realized based on reliable and efficient signaling of DPB information.

[0011] The step of obtaining a value of a DPB syntax element based on a value of the second syntax element includes obtaining the value of the DPB syntax element from the DPB parameter syntax structure when it is determined (judged) that the value of the second syntax element specifies that a DPB syntax element is present within the DPB parameter syntax structure, or setting the value of the DPB syntax element to be equal to the value of another DPB syntax element applied to the topmost temporal sublayer within the DPB parameter syntax structure when it is determined (judged) that the value of the second syntax element specifies that a DPB syntax element is not present within the DPB parameter syntax structure.

[0012] Thereby, a definitive value of the DPB syntax element can be made available in any situation, and it can be ensured that it can be used to reconstruct the video sequence, and there is no need to worry about uncertain behavior in this regard.

[0013] The value thus surely obtained for the DPB syntax element can be used, for example, to configure the DPB to store the reference pictures used for inter prediction processing. Therefore, the step of reconstructing the video sequence based on the value of the DPB syntax element may include configuring the DPB based on the value of the DPB syntax element and reconstructing the video sequence using the DPB.

[0014] Alternatively, the step of reconstructing the video sequence based on the value of the DPB syntax element may include reconstructing the video sequence based on a determination that the DPB used satisfies the requirements specified by the value of the DPB syntax element. Therefore, it can be examined whether the provided DPB is suitable for reconstructing the video sequence.

[0015] According to an implementation, a method of decoding a video bitstream further includes the step of obtaining the value of a third syntax element from the SPS, the value of the third syntax element being used to determine the maximum number of temporal sublayers present in the video sequence. The value of the third syntax element may be 0 if only one temporal sublayer is present. The determination of the maximum number of temporal sublayers present in the video sequence is facilitated simply by signaling the third syntax element, which may be advantageous with respect to coding efficiency.

[0016] Here and below, the third syntax element may be sps_max_sublayers_minus1 according to the following detailed description.

[0017] The step of obtaining the value of a second syntax element from the SPS When it is determined (judged) that the value of the first syntax element specifies that the DPB parameter syntax structure exists within the SPS, based on the value of the third syntax element, determine whether the maximum number of temporal sublayers in the video bitstream is greater than 1, and when it is determined (judged) that the maximum number of temporal sublayers is greater than 1, obtain the value of the second syntax element from the SPS. For example, the value of the second syntax element may be obtained from the SPS only when it is determined that the maximum number of temporal sublayers is greater than 1. Thereby, when the maximum number of temporal layers is 1 or less (i.e., only one temporal sublayer exists), the value of the second syntax element may not be read at all (for example, in this case, if it becomes meaningless), and for a single temporal layer, the DPB syntax element may always be signaled within the SPS, so the coding efficiency may be further enhanced.

[0018] According to a second aspect, there is provided a method of encoding a video bitstream, performed by an encoding device, the method including a syntax element that is encoded in the video bitstream and applied to a video sequence, the method showing the same advantages as those discussed above. The method is determining the existence of a decoded picture buffer DPB parameter syntax structure within the SPS; encoding, in the SPS, the value of a first syntax element (e.g., a flag) based on the determination of the existence of the DPB parameter syntax structure within the SPS, the value of the first syntax element being used to specify whether the DPB parameter syntax structure exists within the SPS; When it is determined that the DPB parameter syntax structure exists within the SPS (when determined, for example, only when determined), a step of determining the existence of DPB syntax elements within the DPB parameter syntax structure, wherein the DPB syntax elements are applied to a temporal sublayer excluding the topmost temporal sublayer within the video sequence, the step and Based on the determination of the existence of DPB syntax elements within the DPB parameter syntax structure, a step of encoding the value of a second syntax element (for example, a flag) into the SPS, wherein the value of the second syntax element is used to indicate the existence of DPB syntax elements within the DPB parameter syntax structure, including the step and

[0019] According to an implementation, the encoding method further includes a step of determining the value of the DPB syntax element when it is determined (determined) that the DPB syntax element exists within the DPB parameter syntax structure, and a step of reconstructing the video sequence based on the value of the DPB syntax element.

[0020] According to an implementation, the encoding method further includes a step of setting the value of the DPB syntax element to be equal to the value of another DPB syntax element applied to the topmost temporal sublayer within the DPB parameter syntax structure, and a step of reconstructing the video sequence based on the value of the DPB syntax element.

[0021] The step of reconstructing the video sequence based on the value of the DPB syntax element may include configuring the DPB to satisfy the value of the DPB syntax element and reconstructing the video sequence using the DPB.

[0022] According to an implementation, when it is determined that the DPB parameter syntax structure exists within the SPS and the maximum number of temporal sublayers within the video bitstream is greater than 1 (for example, only when determined), the existence of DPB syntax elements within the DPB parameter syntax structure is determined.

[0023] Furthermore, there are provided an apparatus for decoding a video bit stream and an apparatus for coding, each of which exhibits the same advantages as those of the methods described above.

[0024] According to a third aspect, there is provided an apparatus for decoding a (coded) video bit stream, the apparatus comprising: an acquisition unit configured to acquire a value of a first syntax element (e.g., a flag) from an SPS, the value of the first syntax element being used to specify whether a DPB parameter syntax structure exists in the SPS coded in the video bit stream; a determination unit configured to determine whether the value of the first syntax element specifies that the DPB parameter syntax structure exists in the SPS; the acquisition unit is further configured to acquire a value of a second syntax element (e.g., a flag) from the SPS at least when it is determined (when determined, e.g., only when determined) that the value of the first syntax element specifies that the DPB parameter syntax structure exists in the SPS, the value of the second syntax element being used to specify the existence of a DPB syntax element within the DPB parameter syntax structure, the DPB syntax element being applied to temporal sub-layers other than the top temporal sub-layer in the video sequence.

[0025] For example, the value of the second syntax structure may be acquired by an acquisition device only when it is determined that the value of the first syntax element specifies that the DPB parameter syntax structure exists in the SPS.

[0026] According to an implementation, the acquisition unit is further configured to acquire a value of a DPB syntax element based on the value of the second syntax element and to reconstruct a video sequence based on the value of the DPB syntax element.

[0027] Obtaining the value of the DPB syntax element based on the value of the second syntax element may include when it is determined (judged) that the value of the second syntax element specifies that the DPB syntax element exists within the DPB parameter syntax structure, obtaining the value of the DPB syntax element from the DPB parameter syntax structure, or when it is determined (judged) that the value of the second syntax element specifies that the DPB syntax element does not exist within the DPB parameter syntax structure, setting the value of the DPB syntax element to be equal to the value of another DPB syntax element applied to the topmost temporal sublayer within the DPB parameter syntax structure.

[0028] Reconstructing a video sequence based on the value of the DPB syntax element may include constructing the DPB based on the value of the DPB syntax element and reconstructing the video sequence using the DPB.

[0029] Here, the DPB is used to store pictures for constructing a reference picture list.

[0030] Alternatively, reconstructing a video sequence based on the value of the DPB syntax element may include reconstructing the video sequence based on a determination that the DPB used satisfies the requirements specified by the value of the DPB syntax element.

[0031] According to an implementation, the obtaining unit is further configured to obtain the value of a third syntax element from the SPS, and the value of the third syntax element is used to determine the maximum number of temporal sublayers existing within the video sequence.

[0032] Obtaining the value of the second syntax element from the SPS may include When it is determined (judged) that the value of the first syntax element specifies that the DPB parameter syntax structure exists within the SPS, based on the value of the third syntax element, determining whether the maximum number of temporal sublayers in the video bitstream is greater than 1, and when it is determined (judged) that the maximum number of temporal sublayers is greater than 1, obtaining the value of the second syntax element from the SPS may be included.

[0033] According to a fourth aspect, an apparatus for encoding a video bitstream is provided, the apparatus comprising a determination unit configured to determine the existence of a decoded picture buffer DPB parameter syntax structure within the SPS, an encoding unit configured to encode the value of a first syntax element (e.g., a flag) into the SPS based on the determination of the existence of the DPB parameter syntax structure within the SPS, the value of the first syntax element being used to specify whether the DPB parameter syntax structure exists within the SPS, The determination unit is further configured to determine the existence of a DPB syntax element within the DPB parameter syntax structure when it is determined (judged) that the DPB parameter syntax structure exists within the SPS (e.g., only when it is determined), the DPB syntax element being applied to temporal sublayers other than the top temporal sublayer in the video sequence, The encoding unit is further configured to encode the value of a second syntax element (e.g., a flag) into the SPS based on the determination of the existence of the DPB syntax element within the DPB parameter syntax structure, the value of the second syntax element being used to specify the existence of the DPB syntax element within the DPB parameter syntax structure.

[0034] According to an implementation, when the determination unit determines (is determined) that the DPB syntax element exists within the DPB parameter syntax structure, the determination unit further determines the value of the DPB syntax element and is further configured to reconstruct the video sequence based on the value of the DPB syntax element.

[0035] According to an implementation, the encoding unit is further configured to set the value of the DPB syntax element to be equal to the value of another DPB syntax element applied to the top temporal sublayer within the DPB parameter syntax structure, and to reconstruct the video sequence based on the value of the DPB syntax element.

[0036] Reconstructing the video sequence based on the value of the DPB syntax element may include configuring the DPB to satisfy the value of the DPB syntax element and reconstructing the video sequence using the DPB.

[0037] According to an implementation, the determination unit is configured to determine that the DPB syntax element exists within the DPB parameter syntax structure when the determination unit determines that the DPB parameter syntax structure exists within the SPS and the maximum number of temporal sublayers within the video bitstream is greater than 1.

[0038] The above methods can be implemented in a decoding device or an encoding device respectively. Therefore, an encoder is provided that includes a processing circuit for implementing a method of encoding a video bitstream according to any one of the above examples. Further, one or more processors and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, wherein the programming configures the encoder to implement a method of encoding a video bitstream according to any one of the above examples when executed by the processor. An encoder is provided that includes a non-transitory computer-readable storage medium. Similarly, a decoder is provided that includes a processing circuit for implementing a method of decoding a video bitstream according to any one of the above examples, and one or more processors and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, wherein the programming configures the decoder to implement a method of decoding a video bitstream according to any one of the above examples when executed by the processor.

[0039] Furthermore, a computer program product is provided that includes program code for executing a method according to any one of the above examples when executed on a computer or a processor. Similarly, a non-transitory computer-readable medium carrying program code for causing a computer device to execute any one of the above methods when executed by the computer device is provided.

[0040] Furthermore, a non-transitory storage medium including an encoded bitstream, wherein the bitstream is generated by dividing a current picture of a video signal or an image signal into a plurality of blocks, includes a plurality of syntax elements, the plurality of syntax elements includes a first syntax element in the SPS, a value of the first syntax element is used to specify whether a decoded picture buffer DPB parameter syntax structure exists in the SPS, and when the value of the first syntax element specifies that the DPB parameter syntax structure exists in the SPS, the bitstream further includes a second syntax element in the SPS, a value of the second syntax element is used to specify the presence of a DPB syntax element in the DPB parameter syntax structure, and the DPB syntax element is applied to a temporal sublayer excluding the top temporal sublayer in the video sequence, and the non-transitory storage medium is provided.

[0041] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0042] Embodiments of the present invention will be described in more detail below with reference to the accompanying figures and drawings.

Brief Description of the Drawings

[0043]

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Best Mode for Carrying Out the Invention

[0044] Hereinafter, the same reference numerals refer to the same or at least functionally equivalent features unless otherwise specified.

[0045] In the following description, reference is made to the accompanying drawings that form a part hereof and which illustrate specific aspects of embodiments of the invention or specific aspects in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other aspects and may include structural or logical changes not shown in the drawings. Accordingly, the following detailed description should not be taken in a limiting sense, and the scope of the invention is defined by the appended claims.

[0046] For example, it is understood that the disclosure related to the described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, if one or more steps of a particular method are described, the corresponding device may include one or more units for performing the one or more steps of the described method, such as functional units (e.g., one unit for performing one or more steps, or multiple units each performing one or more of the multiple steps), even if such one or more units are not explicitly described or shown in the figures. On the other hand, for example, if a particular device is described based on one or more units, such as functional units, the corresponding method may include one step for performing the functions of the one or more units (e.g., one step for performing the functions of one or more units, or multiple steps each performing one or more of the functions of one or more of the multiple units), even if such one or more steps are not explicitly described or shown in the figures. Further, it is understood that the various exemplary embodiments and / or aspects described herein may be combined with each other unless otherwise specified.

[0047] Video coding generally refers to the processing of a sequence of pictures that form a video or video sequence. Instead of the term "picture", the terms "frame" or "image" may be used synonymously in the field of video coding. Video coding (or generally coding) includes two parts, video encoding and video decoding. Video encoding is performed on the source side and generally includes processing the original video pictures (e.g., by compression) to reduce the amount of data required to represent the video pictures (for more efficient storage and / or transmission). Video decoding is performed on the destination side and generally includes the reverse process compared to the encoder to reconstruct the video pictures. Embodiments referring to the "coding" of video pictures (or generally pictures) are understood to relate to the "encoding" or "decoding" of video pictures or respective video sequences. The combination of the encoding part and the decoding part is also called a codec (coding and decoding).

[0048] In the case of reversible video coding, the original video pictures can be reconstructed (assuming no transmission loss or other data loss during storage or transmission), i.e., the reconstructed video pictures have the same quality as the original video pictures. In the case of irreversible video coding, additional compression, e.g., by quantization, is performed to reduce the amount of data representing the video pictures, which cannot be fully reconstructed at the decoder, i.e., the quality of the reconstructed video pictures is lower or worse compared to the quality of the original video pictures.

[0049] Some video coding standards belong to the group of "irreversible hybrid video codecs" (i.e., combining spatial and temporal prediction in the sample domain and 2D transform coding for applying quantization in the transform domain). Each picture of a video sequence is generally partitioned into a set of non-overlapping blocks, and coding is generally performed at the block level. In other words, in the encoder, the video generally generates a prediction block using, for example, spatial (intra-picture) prediction and / or temporal (inter-picture) prediction, subtracts the prediction block from the current block (the block being currently processed / processed), obtains a residual block, transforms the residual block, and quantizes the residual block in the transform domain to reduce the amount of data to be transmitted (compressed), i.e., coded, at the block (video block) level. On the other hand, in the decoder, the inverse process compared to the encoder is applied to the coded or compressed block to reconstruct the current block for presentation. Further, the encoder duplicates the decoder's processing loop so that both generate the same prediction (e.g., intra and inter prediction) and / or reconstruction for processing, i.e., coding, subsequent blocks.

[0050] Hereinafter, embodiments of a video coding system 10, a video encoder 20, and a video decoder 30 will be described based on FIGS. 1 to 3.

[0051] FIG. 1A is a schematic block diagram showing an exemplary coding system 10 that may utilize the technology of the present application, for example, a video coding system 10 (or briefly coding system 10). The video encoder 20 (or briefly encoder 20) and the video decoder 30 (or briefly decoder 30) of the video coding system 10 show examples of devices that may be configured to perform the techniques according to various examples described in the present application.

[0052] As shown in FIG. 1A, the coding system 10 includes a source device 12 configured to provide, for example, encoded picture data 21 to a destination device 14 in order to decode the encoded picture data 13.

[0053] The source device 12 includes an encoder 20 and may additionally, i.e., optionally, include a picture source 16, a preprocessor (or preprocessing unit) 18, for example, a picture preprocessor 18, and a communication interface or communication unit 22.

[0054] The picture source 16 may include or be any kind of picture capturing device, for example, a camera for capturing real-world pictures, and / or any kind of picture generating device, for example, a computer graphics processor for generating pictures animated by a computer, or any kind of other device for acquiring and / or providing real-world pictures, pictures generated by a computer (for example, screen content, virtual reality (VR) pictures), and / or any combination thereof (for example, augmented reality (AR) pictures). The picture source may be or be any kind of memory or storage for storing any of the above-described pictures.

[0055] Distinguished from the processing performed by the preprocessor 18 and the preprocessing unit 18, the picture or picture data 17 may also be referred to as raw picture or raw picture data 17.

[0056] The preprocessor 18 is configured to receive the (raw) picture data 17 and perform preprocessing on the picture data 17 to obtain preprocessed picture 19 or preprocessed picture data 19. The preprocessing executed by the preprocessor 18 may include, for example, trimming, color format conversion (e.g., from RGB to YCbCr), color correction, or noise removal. It can be understood that the preprocessing unit 18 may be an optional component.

[0057] The video encoder 20 is configured to receive the preprocessed picture data 19 and provide encoded picture data 21 (further details will be described below, for example, based on FIG. 2).

[0058] The communication interface 22 of the source device 12 is configured to receive the encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) via the communication channel 13 to another device, such as the destination device 14 or any other device, for storage or direct reconstruction.

[0059] The destination device 14 includes a decoder 30 (e.g., a video decoder 30) and may additionally, i.e., optionally, include a communication interface or communication unit 28, a postprocessor 32 (or postprocessing unit 32), and a display device 34.

[0060] The communication interface 28 of the destination device 14 is configured to receive the encoded picture data 21 (or any further processed version thereof), for example, directly from the source device 12 or from any other source, such as a storage device, e.g., a storage device for the encoded picture data, and provide the encoded picture data 21 to the decoder 30.

[0061] Communication interfaces 22 and 28 may be configured to transmit or receive encoded picture data 21 or encoded data 13 between the source device 12 and the destination device 14 via a direct communication link, such as a direct wired or wireless connection, or via any type of network, such as a wired or wireless network or any combination thereof, or any type of private and public network, or any combination of any type thereof.

[0062] Communication interface 22 may be configured to process encoded picture data, for example, by packaging the encoded picture data 21 into an appropriate format, such as a packet, and / or using any type of encoding or processing of the transmission for transmission via a communication link or communication network.

[0063] Communication interface 28, which forms the counterpart of communication interface 22, may be configured to receive the transmitted data and process the transmitted data using any type of corresponding decoding or processing of the transmission and / or unpackaging to obtain the encoded picture data 21.

[0064] Both communication interface 22 and communication interface 28 may be configured as a unidirectional communication interface or a bidirectional communication interface indicated by an arrow regarding communication channel 13 in FIG. 1A pointing from the source device 12 towards the destination device 14, and may be configured to, for example, set up a connection, check and exchange any other information related to the communication link and / or data transmission, such as transmission of encoded picture data, for example, by sending and receiving messages.

[0065] The decoder 30 is configured to receive the encoded picture data 21 and provide the decoded picture data 31 or the decoded picture 31 (further details are described below, for example, based on FIG. 3 or FIG. 5).

[0066] The post-processor 32 of the destination device 14 is configured to post-process the decoded picture data 31 (also referred to as the reconstructed picture data), for example, the decoded picture 31, to obtain the post-processed picture data 33, for example, the post-processed picture 33. The post-processing executed by the post-processing unit 32 may include, for example, color format conversion (e.g., from YCbCr to RGB), color correction, trimming, or resampling, or any other processing for preparing, for example, the decoded picture data 31 for display by the display device 34.

[0067] The display device 34 of the destination device 14 is configured to receive the post-processed picture data 33 for displaying a picture to, for example, a user or viewer. The display device 34 may be any type of display for showing the reconstructed picture, for example, an integrated or external display or monitor, or may include such a display or monitor. The display may include, for example, a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a plasma display, a projector, a micro LED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0068] FIG. 1A shows the source device 12 and the destination device 14 as separate devices, but embodiments of the device may include both or both functions, the source device 12 or corresponding functions and the destination device 14 or corresponding functions. In such embodiments, the source device 12 or corresponding functions and the destination device 14 or corresponding functions may be implemented using the same hardware and / or software or by separate hardware and / or software or any combination thereof.

[0069] As will be apparent to those skilled in the art based on the description, the functions of the different units or the presence and (exact) partitioning of the functions within the source device 12 and / or the destination device 14 shown in FIG. 1A may vary depending on the actual device and application.

[0070] The encoder 20 (e.g., video encoder 20), decoder 30 (e.g., video decoder 30), or both the encoder 20 and decoder 30 may be implemented by a processing circuit as shown in FIG. 1B, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, hardware, or any combination thereof dedicated or otherwise to video coding. The encoder 20 may be implemented by processing circuit 46 to embody various modules considered in relation to the encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. The decoder 30 may be implemented by processing circuit 46 to embody various modules considered in relation to the decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuit may be configured to perform various operations considered later. As shown in FIG. 5, when the technology is implemented partially in software, the device may store instructions for the software on a suitable non-transitory computer-readable storage medium and execute the instructions in hardware using one or more processors to perform the technology of the present disclosure. Either the video encoder 20 or the video decoder 30 may be incorporated, for example, as part of a combined encoder / decoder (codec) within a single device as shown in FIG. 1B.

[0071] The source device 12 and the destination device 14 can include any of a wide range of devices, such as any type of handheld or fixed device, e.g., a notebook or laptop computer, a mobile phone, a smartphone, a tablet or tablet computer, a camera, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (such as a content service server or a content delivery server), a broadcast receiver device, a broadcast transmitter device, etc., and may or may not use an operating system or may use any type of operating system. In some cases, the source device 12 and the destination device 14 may support wireless communication. Thus, the source device 12 and the destination device 14 may be wireless communication devices.

[0072] In some cases, the video coding system 10 shown in FIG. 1A is merely an example, and the techniques of the present disclosure may apply to video coding situations (e.g., video encoding or video decoding) that do not necessarily include any data communication between an encoding device and a decoding device. In other examples, data may be retrieved from local memory or streamed over a network, etc. A video encoding device may encode data and store it in memory and / or a video decoding device may retrieve data from memory and decode it. In some examples, encoding and decoding are performed by devices that do not communicate with each other but simply encode data in memory and / or retrieve and decode data from memory.

[0073] For the sake of convenience in explanation, embodiments of the present invention are described herein by referring to, for example, the reference software of the next-generation video coding standard developed by the Joint Collaboration Team on Video Coding (JCT-VC) of the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Moving Picture Experts Group (MPEG), such as High-Efficiency Video Coding (HEVC) or Versatile Video Coding (VVC). Those skilled in the art will understand that the embodiments of the present invention are not limited to HEVC or VVC.

[0074] Encoder and Encoding Method FIG. 2 shows a schematic block diagram of an exemplary video encoder 20 configured to implement the technology of the present application. In the example of FIG. 2, the video encoder 20 includes an input 201 (or input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy encoding unit 270, and an output 272 (or output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a partitioning unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in FIG. 2 may also be referred to as a hybrid video encoder or a video encoder by a hybrid video codec.

[0075] The residual calculation unit 204, the conversion processing unit 206, the quantization unit 208, and the mode selection unit 260 may be regarded as forming the forward signal path of the encoder 20. On the other hand, the inverse quantization unit 210, the inverse conversion processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may be regarded as forming the reverse signal path of the video encoder 20. The reverse signal path of the video encoder 20 corresponds to the signal path of the decoder (see the video decoder 30 in FIG. 3). The inverse quantization unit 210, the inverse conversion processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 are also regarded as forming the "built-in decoder" of the video encoder 20.

[0076] Picture & Picture Division (Picture & Block) The encoder 20 may be configured to receive, for example, picture 17 (or picture data 17) via input 201, such as a sequence of pictures forming a video or a video sequence. The received picture or picture data may also be the preprocessed picture 19 (or preprocessed picture data 19). For simplicity, the following description refers to picture 17. Picture 17 may also be referred to as the current picture or the picture to be coded (especially in video coding to distinguish the current picture from other pictures, such as the already encoded and / or decoded pictures of the same video sequence, i.e., the video sequence that also includes the current picture).

[0077] (Digital) pictures can be considered or regarded as a two-dimensional array or matrix of samples having intensity values. The samples of the array may also be called pixels (a shortening of picture elements) or pels. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, generally three color components are used, i.e., the picture may be represented or may include three sample arrays. In the RGB format or color space, the picture includes corresponding red, green, and blue sample arrays. However, in video coding, each pixel generally includes a luminance component represented by Y (L may sometimes be used instead) and two chrominance components represented by Cb and Cr, and is represented in YCbCr. The luminance (or short luma) component Y represents brightness or gray-level intensity (similar to, for example, a grayscale picture), while the two chrominance (or short chroma) components Cb and Cr represent chrominance or color information components. Thus, a picture in the YCbCr format includes a luminance sample array of luminance sample values (Y) and two chrominance sample arrays of chrominance values (Cb and Cr). A picture in the RGB format may be converted or transformed to the YCbCr format, and vice versa, and the process is also known as color transformation or conversion. If the picture is monochrome, the picture may include only a luminance sample array. Thus, the picture may be, for example, an array of luma samples in a monochrome format, or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color formats.

[0078] An embodiment of the video encoder 20 may include a picture partitioning unit (not shown in FIG. 2) configured to partition picture 17 into a plurality of (usually non-overlapping) picture blocks 203. These blocks may also be referred to as root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTB) or coding tree units (CTU) (H.265 / HEVC and VVC). The picture partitioning unit may use the same block size with respect to a corresponding grid that defines all pictures and block sizes of the video sequence, or may vary the block size between pictures or subsets or groups of pictures and be configured to partition each picture into corresponding blocks.

[0079] In a further embodiment, the video encoder may be configured to directly receive blocks 203 of picture 17, for example, one, some, or all of the blocks forming picture 17. The picture blocks 203 may also be referred to as current picture blocks or picture blocks to be coded.

[0080] Similar to Picture 17, Picture Block 203 can also be regarded as or can be regarded as a two-dimensional array or matrix of samples that is smaller in size than Picture 17 but has intensity values (sample values). In other words, depending on the applied color format, Block 203 can contain, for example, one sample array (e.g., the luma array in the case of monochrome Picture 17, or the luma or chroma arrays in the case of a color picture), or three sample arrays (e.g., the luma and two chroma arrays in the case of Color Picture 17), or any other number and / or type of arrays. The number of samples in the horizontal and vertical directions (or axes) of Block 203 defines the size of Block 203. Thus, the block can be, for example, an MxN (M columns × N rows) array of samples or an MxN array of transform coefficients.

[0081] The embodiment of video encoder 20 shown in FIG. 2 can be configured to encode Picture 17 block by block. For example, encoding and prediction can be performed for each Block 203.

[0082] The embodiment of video encoder 20 shown in FIG. 2 can be further configured to partition and / or encode a picture by using slices (also called video slices), where the picture can be partitioned into one or more (generally non-overlapping) slices or encoded using one or more (generally non-overlapping) slices, and each slice can contain one or more blocks (e.g., CTUs).

[0083] The embodiment of the video encoder 20 shown in FIG. 2 may be further configured to partition and / or encode a picture by using tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles). A picture may be partitioned into one or more (generally non-overlapping) tile groups or encoded using one or more (generally non-overlapping) tile groups. Each tile group may include, for example, one or more blocks (e.g., CTUs) or one or more tiles. Each tile may, for example, be rectangular in shape and may include one or more blocks (e.g., CTUs), e.g., complete or partial blocks.

[0084] Calculation of Residual The residual calculation unit 204 may be configured to calculate a residual block 205 (also referred to as residual 205) based on a picture block 203 and a prediction block 265 (further details about the prediction block 265 will be given later), for example, by subtracting the sample values of the prediction block 265 from the sample values of the picture block 203 for each sample (per pixel) to obtain the residual block 205 in the sample region.

[0085] Transformation The transformation processing unit 206 may be configured to apply a transformation, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values of the residual block 205 to obtain transformation coefficients 207 in the transformation region. The transformation coefficients 207, also referred to as transformed residual coefficients, may represent the residual block 205 in the transformation region.

[0086] The conversion processing unit 206 may be configured to apply integer approximations of DCT / DST such as the conversion defined for H.265 / HEVC. Compared to the orthogonal DCT transform, such integer approximations are generally scaled at a specific rate. To maintain the norm of the residual blocks processed by the forward and inverse transforms, an additional scaling factor is applied as part of the conversion process. The scaling factor is generally selected based on specific constraints such as the scaling factor being a power of 2 for shift operations, the bit depth of the conversion coefficients, and the trade-off between accuracy and implementation cost. For example, a specific scaling factor may be specified for the inverse transform by, for example, the inverse transform processing unit 212 (and the corresponding inverse transform by, for example, the inverse transform processing unit 312 in the video decoder 30), and the corresponding scaling factor for the forward transform by the conversion processing unit 206 of the encoder 20 may be specified accordingly.

[0087] Embodiments of the video encoder 20 (each, the conversion processing unit 206) may be configured to output conversion parameters, for example, such that the video decoder 30 may receive and use the conversion parameters for decoding, for example, as is or encoded or compressed by the entropy encoding unit 270, for example, a certain one or more conversions.

[0088] Quantization The quantization unit 208 may be configured to obtain the quantized coefficients 209 by quantizing the conversion coefficients 207, for example, by applying scalar quantization or vector quantization. The quantized coefficients 209 may also be referred to as the quantized conversion coefficients 209 or the quantized residual coefficients 209.

[0089] The quantization process may reduce the bit depth associated with some or all of the conversion coefficients 207. For example, an n-bit conversion coefficient may be truncated to an m-bit conversion coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting the quantization parameter (QP). For scalar quantization, for example, different scalings may be applied to achieve finer or coarser quantization. A smaller quantization step size corresponds to finer quantization, while a larger quantization step size corresponds to coarser quantization. The applicable quantization step size may be indicated by the quantization parameter (QP). The quantization parameter may be, for example, an index to a predefined set of applicable quantization step sizes. For example, a small quantization parameter may correspond to fine quantization (small quantization step size), a large quantization parameter may correspond to coarse quantization (large quantization step size), or vice versa. Quantization may involve division by the quantization step size, and for example, the corresponding and / or inverse dequantization by the inverse quantization unit 210 may involve multiplication by the quantization step size. Some standards, such as embodiments according to HEVC, may be configured to determine the quantization step size using the quantization parameter. Generally, the quantization step size may be calculated based on the quantization parameter using a fixed point approximation of an equation involving division. Additional scaling factors may be introduced for quantization and dequantization to restore the norm of the residual block that may be modified due to the scaling used in the fixed point approximation of the equations for the quantization step size and quantization parameter. In one exemplary implementation, the scaling of the inverse transform and dequantization may be combined. Alternatively, a customized quantization table may be used, for example, signaled from the encoder to the decoder within the bitstream.Quantization is an irreversible operation, and the loss increases as the quantization step size increases.

[0090] Embodiments of the video encoder 20 (each, quantization unit 208) may be configured to output, for example, quantization parameters (QP) that are, for example, unchanged or encoded by the entropy encoding unit 270, such that the video decoder 30 may receive and apply the quantization parameters for decoding.

[0091] Inverse quantization The inverse quantization unit 210 is configured to apply inverse quantization of the quantization unit 208 to the quantized coefficients to obtain dequantized coefficients 211 by applying, for example, the inverse of the quantization method applied by the quantization unit 208 based on or using the same quantization step size as the quantization unit 208. The dequantized coefficients 211, also referred to as dequantized residual coefficients 211, may correspond to the transform coefficients 207, although generally not identical to the transform coefficients due to loss by quantization.

[0092] Inverse transformation The inverse transformation processing unit 212 is configured to apply an inverse transformation of the transformation applied by the transformation processing unit 206, such as an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST) or other inverse transformation, to obtain a reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 may also be referred to as a transform block 213.

[0093] Reconstruction The reconstruction unit 214 (e.g., an adder or accumulator 214) is configured to add the reconstructed residual block 213 to the prediction block 265, for example, by adding the sample values of the reconstructed residual block 213 and the prediction block 265 -- sample by sample -- to obtain the reconstructed block 215 in the sample domain.

[0094] Filtering The loop filter unit 220 (or simply "loop filter" 220) is configured to filter the reconstructed block 215 to obtain the filtered block 221, or generally, to filter the reconstructed samples to obtain the filtered samples. The loop filter unit is configured to, for example, smooth pixel transitions or otherwise improve the quality of the video. The loop filter unit 220 may include one or more loop filters such as a deblocking filter, a sample-adaptive offset (SAO) filter, or one or more other filters, for example, a bilateral filter, an adaptive loop filter (ALF), sharpening, a smoothing filter, or a collaborative filter, or any combination thereof. The loop filter unit 220 is shown as an in-loop filter in FIG. 2, but in other configurations, the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as the filtered reconstructed block 221.

[0095] Embodiments of the video encoder 20 (each, loop filter unit 220) may be configured to output loop filter parameters (such as sample adaptive offset information), for example, as is or encoded by the entropy encoding unit 270, such that the decoder 30 may receive the same loop filter parameters or respective loop filters and apply them for decoding.

[0096] Decoded picture buffer The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures or generally reference picture data for encoding video data by the video encoder 20. The DPB 230 may be formed by any of various memory devices such as dynamic random access memory (DRAM) including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may be further configured to store the same current picture or different pictures, such as other already filtered blocks of already reconstructed pictures, such as already reconstructed and filtered block 221, and may provide, for example, for inter prediction, a completely already reconstructed, i.e., decoded picture (and corresponding reference blocks and samples) and / or a partially reconstructed current picture (and corresponding reference blocks and samples). The decoded picture buffer (DPB) 230 may also be configured to store one or more non-filtered reconstructed blocks 215 or generally non-filtered reconstructed samples, or any other further processed version of the reconstructed blocks or samples, if, for example, the reconstructed block 215 is not filtered by the loop filter unit 220.

[0097] Mode Selection (Classification & Prediction) The mode selection unit 260 includes a classification unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original picture data, for example, the original block 203 (the current block 203 of the current picture 17), and reconstructed picture data, for example, from the same (current) picture and / or from one or more already decoded pictures in the decoded picture buffer 230 or other buffers (for example, a line buffer not shown), filtered and / or unfiltered reconstructed samples or blocks. The reconstructed picture data is used as reference picture data for prediction for obtaining the prediction block 265 or predictor 265, for example, inter prediction or intra prediction.

[0098] The mode selection unit 260 may be configured to determine or select a classification and a prediction mode (for example, an intra or inter prediction mode) for the prediction mode of the current block (without classification), and generate a corresponding prediction block 265 used for the calculation of the residual block 205 and the reconstruction of the reconstructed block 215.

[0099] Embodiments of the mode selection unit 260 may be configured to select a partitioning and prediction mode that provides the best match, or in other words the minimum residual (the minimum residual means better compression for transmission or storage) or the minimum signaling overhead (the minimum signaling overhead means better compression for transmission or storage), or to take into account or balance both, from among, for example, the partitioning and prediction modes supported by the mode selection unit 260 or available to the mode selection unit 260. The mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate distortion optimization (RDO), i.e., to select the prediction mode that provides the minimum rate distortion. Terms such as "best," "minimum," "optimal," etc. in this context do not necessarily refer to the overall "best," "minimum," "optimal," etc., but may also refer to a termination or selection criterion such as a value exceeding or falling below a threshold, or to other constraints that potentially lead to a "quasi-optimal selection" while satisfying complexity and processing time reduction.

[0100] In other words, the partitioning unit 262 may be configured to repeatedly use, for example, quad-tree partitioning (QT), binary partitioning (BT), or ternary-tree partitioning (TT), or any combination thereof, to partition the block 203 into smaller block partitions or sub-blocks (which also form blocks), and for example, to perform prediction for each of the block partitions or sub-blocks. The mode selection may include the selection of the tree structure of the partitioned block 203, and the prediction mode is applied to each of the block partitions or sub-blocks.

[0101] The partitioning and prediction processing (e.g., by the partitioning unit 260) and prediction processing (by the inter prediction unit 244 and the intra prediction unit 254) performed by the exemplary video encoder 20 are described in more detail below.

[0102] Partitioning The partitioning unit 262 may partition (or divide) the current block 203 into smaller partitions, for example, smaller blocks of square or rectangular size. These smaller blocks (which may also be referred to as sub-blocks) may be further partitioned into even smaller partitions. This is also called a tree partition or a hierarchical tree partition. For example, a root block at the root tree level 0 (hierarchical level 0, depth 0) may be recursively partitioned into, for example, two or more blocks at the next lower tree level, for example, nodes at tree level 1 (hierarchical level 1, depth 1), and these blocks may be further partitioned into two or more blocks at the next lower level, for example, tree level 2 (hierarchical level 2, depth 2), and so on until a termination criterion is met, for example, the maximum tree depth or the minimum block size is reached and the partitioning ends. Blocks that are not further partitioned are also called leaf blocks or leaf nodes of the tree. A tree using a partition into two partitions is called a binary tree (BT), a tree using a partition into three partitions is called a ternary tree (TT), and a tree using a partition into four partitions is called a quadtree (QT).

[0103] As described above, the term "block" as used herein may be a portion of a picture, particularly, a portion of a square or rectangle. For example, in relation to HEVC and VVC, a block may be a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU), and a transform unit (TU), and / or a corresponding block, for example, a coding tree block (CTB), a coding block (CB), a transform block (TB), or a prediction block (PB) or may correspond to them.

[0104] For example, a coding tree unit (CTU) may be or may contain the CTB of luma samples, two corresponding CTBs of chroma samples of a picture having three sample arrays, or the CTB of samples of a picture coded using three separate colour planes and syntax structures for coding monochrome pictures or samples. Correspondingly, a coding tree block (CTB) may be an NxN block of samples for some value of N such that the division of the constituent CTBs is a partition. A coding unit (CU) may be or may contain the coding block of luma samples, two corresponding coding blocks of chroma samples of a picture having three sample arrays, or the coding block of samples of a picture coded using three separate colour planes and syntax structures for coding monochrome pictures or samples. Correspondingly, a coding block (CB) may be an MxN block of samples for some values of M and N such that the division of the CTB into coding blocks is a partition.

[0105] For example, in an embodiment according to HEVC, a coding tree unit (CTU) may be divided into CUs by using a quadtree structure represented as a coding tree. The determination of whether to code a picture area using inter-picture (temporal) prediction or to code a picture area using intra-picture (spatial) prediction is made at the CU level. Each CU may be further divided into one, two, or four PUs according to the PU partition type. Within one PU, the same prediction process is applied and the relevant information is sent to the decoder based on the PU. After obtaining a residual block by applying a prediction process based on the PU partition type, the CU may be partitioned into transform units (TUs) by another quadtree structure similar to the coding tree for the CU.

[0106] For example, in an embodiment according to the currently developed latest video coding standard called Versatile Video Coding (VVC), a combined quadtree and binary tree (QTBT) partitioning is used, for example, to partition coding blocks. In the QTBT block structure, a CU can have a shape that is either square or rectangular. For example, a coding tree unit (CTU) is first partitioned by a quadtree structure. The leaf nodes of the quadtree are further partitioned by a binary tree or a ternary (or triple) tree structure. The leaf nodes of the partitioning tree are called coding units (CUs), and their segmentation is used for prediction and transformation processing without any further partitioning. This means that CUs, PUs, and TUs have the same block size in the QTBT coding block structure. In parallel, multi-partitions, for example, ternary partitions, may be used together with the QTBT block structure.

[0107] In one example, the mode selection unit 260 of the video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0108] As described above, the video encoder 20 is configured to determine or select the best or optimal prediction mode from a set of (e.g., pre-determined) prediction modes. The set of prediction modes may include, for example, an intra prediction mode and / or an inter prediction mode.

[0109] Intra Prediction A set of intra prediction modes may include, for example, 35 different intra prediction modes defined in HEVC, such as non-directional modes like DC (or average) mode and planar mode, or directional modes, or alternatively, 67 different intra prediction modes defined for VVC, such as non-directional modes like DC (or average) mode and planar mode, or directional modes.

[0110] The intra prediction unit 254 is configured to generate an intra prediction block 265 using the reconstructed samples of neighboring blocks of the same current picture according to an intra prediction mode among a set of intra prediction modes.

[0111] The intra prediction unit 254 (or generally the mode selection unit 260) is further configured to output an intra prediction parameter (or generally information indicating the selected intra prediction mode for a block) to the entropy encoding unit 270 in the form of a syntax element 266 for inclusion in the encoded picture data 21 so that, for example, the video decoder 30 can receive the prediction parameter and potentially use it for decoding.

[0112] Inter prediction A set of (or possible) inter prediction modes depends on available reference pictures (i.e., for example, at least partially decoded previous pictures stored in the DBP 230) and other inter prediction parameters, for example, whether the entire reference picture is used to search for the most matching reference block or only a part of the reference picture, for example, only the search window area around the area of the current block, and / or for example, whether pixel interpolation, for example, half / semi-pel and / or quarter-pel interpolation, is applied.

[0113] In addition to the prediction modes described above, a skip mode and / or a direct mode may be applied.

[0114] The inter-prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (neither of which is shown in FIG. 2). The motion estimation unit is configured to receive or obtain, for motion estimation, the picture block 203 (the current picture block 203 of the current picture 17) and the decoded picture 231, or at least one or a plurality of already reconstructed blocks, for example, the reconstructed blocks of one or a plurality of other / different already decoded pictures 231. For example, the video sequence may include the current picture and the already decoded picture 231, or in other words, the current picture and the already decoded picture 231 may be part of a sequence of pictures forming the video sequence or may form such a sequence of pictures.

[0115] The encoder 20 may be configured to select, for example, reference blocks from a plurality of reference blocks of the same or different pictures among a plurality of other pictures, and provide the motion estimation unit with the reference picture (or reference picture index) and / or the offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as inter-prediction parameters. This offset is also referred to as a motion vector (MV).

[0116] The motion compensation unit is configured to obtain, for example receive, an inter prediction parameter and perform an inter prediction based on or using the inter prediction parameter to obtain an inter prediction block 265. The motion compensation performed by the motion compensation unit may include fetching or generating a prediction block based on a motion / block vector determined by motion estimation that perhaps performs interpolation with sub-pixel accuracy. Interpolation filtering may generate additional pixel samples from known pixel samples and thus potentially increase the number of candidate prediction blocks that may be used to code a picture block. When receiving a motion vector for a PU of a current picture block, the motion compensation unit may find a prediction block pointed to by the motion vector in one of the reference picture lists.

[0117] The motion compensation unit may also generate blocks for use by the video decoder 30 when decoding a picture block of a video slice and syntax elements associated with the video slice. In addition to or instead of the slice and its respective syntax elements, tile groups and / or tiles and their respective syntax elements may be generated or used.

[0118] Entropy coding The entropy encoding unit 270 is configured to apply, for example, an entropy encoding algorithm or method (e.g., variable length coding (VLC) method, context adaptive VLC (CAVLC), arithmetic coding method, binarization, context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy encoding method or technique) or bypass (non-compression) to the quantized coefficients 209, inter prediction parameters, intra prediction parameters, loop filter parameters, and / or other syntax elements, so as to obtain, for example, the encoded picture data 21 that can be output via output 272 in the form of an encoded bitstream 21 such that, for example, the video decoder 30 can receive the parameters and may use them for decoding. The encoded bitstream 21 may be transmitted to the video decoder 30 or stored in a memory for later transmission or retrieval by the video decoder 30.

[0119] Variations in the structure of the video encoder 20 and others can be used to encode the video stream. For example, a non-transform-based encoder 20 can directly quantize the residual signal without the transform processing unit 206 for a particular block or frame. In another implementation, the encoder 20 can have a quantization unit 208 and an inverse quantization unit 210 combined in a single unit.

[0120] Decoder and Decoding Method FIG. 3 shows an example of a video decoder 30 configured to implement the technology of the present application. The video decoder 30 is configured to receive, for example, encoded picture data 21 (e.g., an encoded bitstream 21) encoded by the encoder 20 in order to obtain a decoded picture 331. The encoded picture data or bitstream includes information for decoding data representing encoded picture blocks of an encoded video slice (and / or tile group or tile) and related syntax elements, for example.

[0121] In the example of FIG. 3, the decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., an adder 314), a loop filter 320, a decoded picture buffer (DBP) 330, a mode application unit 360, an inter prediction unit 344, and an intra prediction unit 354. The inter prediction unit 344 may be a motion compensation unit or may include a motion compensation unit. The video decoder 30 may, in some examples, execute a decoding path that is generally inverse to the encoding path described in relation to the video encoder 100 of FIG. 2.

[0122] As described in relation to the encoder 20, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 344, and the intra prediction unit 354 are also considered to form the "built-in decoder" of the video encoder 20. Therefore, the inverse quantization unit 310 may be functionally identical to the inverse quantization unit 110, the inverse transform processing unit 312 may be functionally identical to the inverse transform processing unit 212, the reconstruction unit 314 may be functionally identical to the reconstruction unit 214, the loop filter 320 may be functionally identical to the loop filter 220, and the decoded picture buffer 330 may be functionally identical to the decoded picture buffer 230. Therefore, the descriptions given for each unit and function of the video 20 encoder apply mutatis mutandis to each unit and function of the video decoder 30.

[0123] Entropy decoding The entropy decoding unit 304 analyzes the bitstream 21 (or generally the encoded picture data 21), for example, performs entropy decoding on the encoded picture data 21 to obtain, for example, the quantized coefficients 309 and / or the decoded coding parameters (not shown in FIG. 3), such as inter prediction parameters (e.g., reference picture index and motion vector), intra prediction parameters (e.g., intra prediction mode or index), transform parameters, quantization parameters, loop filter parameters, and / or any or all of other syntax elements. The entropy decoding unit 304 may be configured to apply a decoding algorithm or method corresponding to the encoding method described in relation to the entropy encoding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter prediction parameters, intra prediction parameters, and / or other syntax elements to the mode application unit 360 and other parameters to other units of the decoder 30. The video decoder 30 may receive syntax elements at the video slice level and / or at the video block level. In addition to or instead of the slice and each syntax element, tile groups and / or tiles and each syntax element may be received and / or used.

[0124] Inverse quantization The inverse quantization unit 310 receives the quantization parameter (QP) (or generally information related to inverse quantization) and the quantized coefficients from the encoded picture data 21 (e.g., by the entropy decoding unit 304, e.g., by parsing and / or decoding), and is configured to apply inverse quantization based on the quantization parameter to the decoded quantized coefficients 309 to obtain the dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include using the quantization parameter determined by the video encoder 20 for each video block within a video slice (or tile or tile group) to determine the degree of quantization and, similarly, the degree of inverse quantization to be applied.

[0125] Inverse transformation The inverse transform processing unit 312 receives the dequantized coefficients 311, which may also be referred to as transform coefficients 311, and is configured to apply a transform to the dequantized coefficients 311 to obtain the reconstructed residual block 213 in the sample region. The reconstructed residual block 213 may also be referred to as a transform block 313. The transform may be an inverse transform, e.g., inverse DCT, inverse DST, inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may be further configured to receive transform parameters or corresponding information from the encoded picture data 21 (e.g., by the entropy decoding unit 304, e.g., by parsing and / or decoding) to determine the transform to be applied to the dequantized coefficients 311.

[0126] Reconstruction The reconstruction unit 314 (e.g., adder or summer 314) may be configured to add the reconstructed residual block 313 to the prediction block 365, e.g., by adding the sample values of the reconstructed residual block 313 and the sample values of the prediction block 365, to obtain the reconstructed block 315 in the sample region.

[0127] Filtering (Either within or after the coding loop) The loop filter unit 320 is configured to filter the reconstructed block 315 to obtain a filtered block 321, for example, to smooth pixel transitions or otherwise improve the quality of the video. The loop filter unit 320 may include one or more loop filters such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, for example, a bilateral filter, an adaptive loop filter (ALF), sharpening, a smoothing filter, or a joint filter, or any combination thereof. The loop filter unit 320 is shown as an in-loop filter in FIG. 3, but in other configurations, the loop filter unit 320 may be implemented as a post-loop filter.

[0128] Decoded Picture Buffer Then, the decoded video block 321 of the picture is stored in a decoded picture buffer 330 that stores the decoded picture 331 for subsequent motion compensation with respect to other pictures and / or for outputting respectively on a display as a reference picture.

[0129] The decoder 30 is configured to output the decoded picture 311, for example, via output 312, for presentation or viewing by a user.

[0130] Prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (especially the motion compensation unit), and the intra prediction unit 354 may be functionally identical to the inter prediction unit 254, and performs determination and prediction of division or segmentation based on the segmentation and / or prediction parameters or respective information received from the encoded picture data 21 (for example, by the entropy decoding unit 304, for example, by analyzing and / or decoding). The mode application unit 360 may be configured to perform prediction (intra or inter prediction) for each block based on the reconstructed picture, block, or respective samples (filtered or unfiltered) to obtain the prediction block 365.

[0131] When a video slice is coded as an intra-coded (I) slice, the intra prediction unit 354 of the mode application unit 360 is configured to generate a prediction block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from already decoded blocks of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, the inter prediction unit 344 (e.g., a motion compensation unit) of the mode application unit 360 is configured to generate a prediction block 365 for a video block of the current video slice based on the motion vector and other syntax elements received from the entropy decoding unit 304. For inter prediction, the prediction block may be generated from one of the reference pictures in one of the reference picture lists. The video decoder 30 may construct the reference frame lists, List 0 and List 1, using a default construction technique based on the reference pictures stored in the DPB 330. The same or similar may apply for embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or as an alternative to slices (e.g., video slices), e.g., the video may be coded using I, P, or B tile groups and / or tiles.

[0132] The mode application unit 360 is configured to determine prediction information regarding a video block of a current video slice by analyzing a motion vector or related information and other syntax elements, and use the prediction information to generate a prediction block regarding the currently decoded video block. For example, the mode application unit 360 uses a part of the received syntax elements to determine a prediction mode (e.g., intra or inter prediction) used to code a video block of a video slice, a slice type of inter prediction (e.g., B slice, P slice, or GPB slice), construction information regarding one or more of the reference picture lists for the slice, a motion vector regarding each inter-coded video block of the slice, a status of inter prediction regarding each inter-coded video block of the slice, and other information for decoding a video block within the current video slice. The same or similar things may apply to or be applied by embodiments that use a tile group (e.g., video tile group) and / or a tile (e.g., video tile) in addition to or as an alternative to a slice (e.g., video slice), for example, a video may be coded using I, P, or B tile groups and / or tiles.

[0133] An embodiment of the video decoder 30 shown in FIG. 3 may be configured to partition and / or decode a picture by using slices (also called video slices), and the picture may be partitioned into one or more (generally non-overlapping) slices or decoded using one or more (generally non-overlapping) slices, and each slice may include one or more blocks (e.g., CTUs).

[0134] The embodiment of video decoder 30 shown in FIG. 3 may be configured to partition and / or decode a picture by using tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into one or more (generally non-overlapping) tile groups or decoded using one or more (generally non-overlapping) tile groups, each tile group may include, for example, one or more blocks (e.g., CTUs) or one or more tiles, each tile may, for example, be rectangular in shape and may include one or more blocks (e.g., CTUs), e.g., complete or partial blocks.

[0135] Other variations of video decoder 30 may be used to decode the encoded picture data 21. For example, decoder 30 may generate an output video stream without loop filtering unit 320. For example, a transform-free decoder 30 may directly inverse quantize the residual signal without inverse transform processing unit 312 for a particular block or frame. In another implementation, video decoder 30 may have an inverse quantization unit 310 and an inverse transform processing unit 312 combined in a single unit.

[0136] It should be understood that in encoder 20 and decoder 30, the processing result of the current step may be further processed and then output to the next step. For example, additional operations such as Clip or Shift may be performed on the processing results of interpolation filtering, motion vector derivation, or loop filtering after interpolation filtering, motion vector derivation, or loop filtering.

[0137] Note that further operations may be applied to the derived motion vectors of the current block (including, but not limited to, the control point motion vector in affine mode, affine, plane, sub-block motion vectors in ATMVP mode, temporal motion vector, etc.). For example, the value of the motion vector is constrained to a predetermined range according to its representation bits. When the representation bits of the motion vector are bitDepth, the range is -2^(bitDepth - 1) to 2^(bitDepth - 1) - 1, where "^" means exponentiation. For example, when bitDepth is set to be equal to 16, the range is -32768 to 32767, and when bitDepth is set to be equal to 18, the range is -131072 to 131071. For example, the value of the derived motion vector (e.g., the MV of four 4×4 sub-blocks within one 8×8 block) is constrained such that the maximum difference between the integer parts of the MVs of the four 4×4 sub-blocks is no more than N pixels, such as 1 pixel. Here, two methods for constraining the motion vector according to bitDepth are provided.

[0138] Method 1: Delete the overflow MSB (Most Significant Bit) by the flowing operation ux = (mvx + 2 bitDepth ) % 2 bitDepth (1) mvx = (ux >= 2 bitDepth-1 )? (ux - 2 bitDepth ) : ux (2) uy = (mvy + 2 bitDepth ) % 2 bitDepth (3) mvy = (uy >= 2 bitDepth-1 )? (uy - 2 bitDepth ) : uy (4) Wherein, mvx is the horizontal component of the motion vector of the image block or sub-block, mvy is the vertical component of the motion vector of the image block or sub-block, and ux and uy represent intermediate values.

[0139] For example, when the value of mvx is -32769, after applying equations (1) and (2), the resulting value is 32767. In a computer system, decimal numbers are stored as two's complements. The two's complement of -32769 is 1,0111,1111,1111,1111 (17 bits), and at that time, the MSB is discarded. Therefore, the resulting two's complement is 0111,1111,1111,1111 (decimal 32767), which is the same as the output by applying equations (1) and (2). ux = (mvpx + mvdx + 2 bitDepth ) % 2 bitDepth (5) mvx = (ux >= 2 bitDepth-1 )? (ux - 2 bitDepth ) : ux (6) uy = (mvpy + mvdy + 2 bitDepth ) % 2 bitDepth (7) mvy = (uy >= 2 bitDepth-1 )? (uy - 2 bitDepth ) : uy (8)

[0140] The operation may be applied in the sum of mvp and mvd as shown in equations (5) to (8).

[0141] Method 2: Remove the overflow MSB by clipping the value vx = Clip3(-2 bitDepth-1 , 2 bitDepth-1 -1, vx) vy = Clip3(-2 bitDepth-1 , 2 bitDepth-1 -1, vy) Where vx is the horizontal component of the motion vector of the image block or sub-block, vy is the vertical component of the motion vector of the image block or sub-block, x, y, and z respectively correspond to the three input values of the MV clipping process, and the definition of the function Clip3 is as follows.

Number

[0142] Figure 4 is a schematic diagram of a video coding device 400 according to an embodiment of the present disclosure. The video coding device 400 is suitable for implementing the disclosed embodiments as described herein. In an embodiment, the video coding device 400 may be a decoder such as the video decoder 30 of FIG. 1A or an encoder such as the video encoder 20 of FIG. 1A.

[0143] The video coding device 400 includes an incoming port 410 (or input port 410) and a receiver unit (Rx) 420 for receiving data, a processor, logic unit, or central processing unit (CPU) 430 for processing data, a transmitter unit (Tx) 440 and an outgoing port 450 (or output port 450) for transmitting data, and a memory 460 for storing data. The video coding device 400 may also include opto-electrical (OE) components and electro-optical (EO) components coupled to the incoming port 410, the receiver unit 420, the transmitter unit 440, and the outgoing port 450 for the transmission or reception of optical or electrical signals.

[0144] Processor 430 is implemented by hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGA, ASIC, and DSP. Processor 430 communicates with incoming port 410, receiver unit 420, transmitter unit 440, outgoing port 450, and memory 460. Processor 430 includes coding module 470. Coding module 470 implements the disclosed embodiments described above. For example, coding module 470 implements, processes, prepares, or provides various coding operations. Thus, including coding module 470 significantly improves the function of video coding device 400 and results in the conversion of video coding device 400 to different states. Alternatively, coding module 470 is implemented as instructions stored in memory 460 and executed by processor 430.

[0145] Memory 460 may include one or more disks, tape drives, and solid state drives and may be used as an over-flow data storage device for storing such programs when selected for program execution and for storing instructions and data read during program execution. Memory 460 may be, for example, volatile and / or non-volatile and may be read-only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random access memory (SRAM).

[0146] FIG. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of the source device 12 and the destination device 14 of FIG. 1 according to an exemplary embodiment.

[0147] The processor 502 of the device 500 can be a central processing unit. Alternatively, the processor 502 can be any other type of one or more devices, existing or to be developed in the future, capable of manipulating or processing information. The disclosed implementation can be carried out by a single processor, such as the processor 502, as shown, but advantages in terms of speed and efficiency can be realized by using two or more processors.

[0148] The memory 504 of the device 500 can be a read-only memory (ROM) device or a random access memory (RAM) device in an implementation. Any other suitable type of storage device can be used as the memory 504. The memory 504 can include code and data 506 accessed by the processor 502 using the bus 512. The memory 504 can further include an operating system 508 and an application program 510, and the application program 510 includes at least one program that enables the processor 502 to execute the methods described herein. For example, the application program 510 can include applications 1 to N that further include a video coding application that executes the methods described herein.

[0149] The device 500 can also include one or more output devices, such as a display 518. In one example, the display 518 can be a touch display combined with a touch sensing element operable to sense touch input on the display. The display 518 can be coupled to the processor 502 via the bus 512.

[0150] Although shown here as a single bus, the bus 512 of the apparatus 500 can be composed of a plurality of buses. Further, the secondary storage 514 can be directly coupled to other components of the apparatus 500 or can be accessed via a network and can include a single integrated unit such as a memory card or a plurality of units such as a plurality of memory cards. Thus, the apparatus 500 can be implemented in a wide variety of configurations.

[0151] Parameter set The parameter sets are basically similar and share the same basic design goals - namely, bitrate efficiency, error resilience, and provision of a system layer interface. HEVC (H.265) has a hierarchy of parameter sets that includes video parameter sets (VPSs), sequence parameter sets (SPSs), and picture parameter sets (PPSs) that are similar to their counterparts in AVC and VVC. Each slice refers to a single active PPS, SPS, and VPS to access the information used to decode the slice. The PPS contains information that applies to all slices within a picture, and thus all slices within a picture must refer to the same PPS. Slices of different pictures are also permitted to refer to the same PPS. Similarly, the SPS contains information that applies to all pictures within the same coded video sequence.

[0152] The PPS may be different for separate pictures, but often many or all pictures in a coded video sequence refer to the same PPS. Reusing parameter sets is bitrate efficient as it avoids the need to transmit shared information multiple times. Also, reusing parameter sets is robust to loss as it enables the content of the parameter sets to be carried over some more reliable external communication link or to be frequently repeated within the bitstream to ensure that the content of the parameter sets is not lost.

[0153] Scalable Video Coding, Layers, and Video Parameter Set (VPS) Scalable video coding provides a mechanism for coding video into multiple layers, where each layer represents a rendition of the quality of the same video scene. The base layer (BL) is the lowest quality rendition. One or more enhancement layers (EL) are coded with reference to the lower layer(s) and may provide improved video quality. Decoding a subset of the layers of a scalable coded video bitstream results in a lower but acceptable quality video. This generally allows for a more graceful degradation compared to non-scalable video bitstreams where a reduction in bitrate generally results in a more severe degradation of video quality.

[0154] Scalable video sequences have multiple types of scalability including temporal scalability, spatial scalability, and quality scalability. FIG. 11 provides an example showing both spatial and temporal scalability. In FIG. 11, two layers are coded at different resolutions. The BL has a lower resolution and the EL has a higher resolution, and spatial scalability is achieved by providing a decoder for decoding either the BL, the EL, or both.

[0155] In addition to spatial scalability, temporal scalability is realized within the coding layer. In this example, each coding layer is divided into two temporal sub-layers, which are labeled with temporal ID 0 and IID 1 respectively. Temporal scalability is realized by providing the ability to decode either temporal sub-layer 0 (where the temporal ID is equal to 0) or both sub-layers 0 and 1.

[0156] Each layer's picture is assigned a layer ID, for example, the syntax element nuh_layer_id. A coded layer video sequence (CLVS) is a sequence of pictures with the same value of nuh_layer_id that includes, in decoding order, a special coding layer video sequence starting coding picture (CLVSS, for example, an intra picture), and zero or more subsequent pictures that are not CLVSS pictures, but that follow the CLVSS picture and precede any subsequent picture that is a CLVSS picture.

[0157] A coded video sequence (CVS) includes one or more coded layer video sequences (CLVS). In the example of Figure 11, assuming that the first pictures of the BL and EL are CLVSS pictures and all other pictures are not CLVSS pictures, this CVS includes two CLVS.

[0158] Sequence Parameter Set (SPS) The SPS is applied to one layer of the coded video sequence and includes parameters that do not change picture by picture within the coded video sequence.

[0159] In some extreme cases, the SPS may not be used by any picture in the CLVS.

[0160] The SPS may also be shared by different CLVSs.

[0161] In the latest VVC specification draft (i.e., http: / / phenix.it-sudparis.eu / jvet / doc_end_user / documents / 19_Teleconference / wg11 / JVET-S0152-v5.zip, hereinafter referred to as the VVC draft for simplicity in the following sections), the definition of the SPS is as follows. Sequence Parameter Set (SPS): A syntax structure containing syntax elements applicable to zero or more entire CLVSs, determined by the content of the syntax elements found in the PPS, which are referred to by the syntax elements found in each picture header.

[0162] For the definitions of PPS and picture header, please refer to the VVC draft.

[0163] In particular, the SPS contains information regarding the signaling of the decoded picture buffer (i.e., dpb).

[0164] Some parts of the following table show some snapshots of the signaling of the dpb in the SPS in VVC.

[0165] Signaling of Decoded Picture Buffer (DPB) Information Decoded Picture Buffer The decoded picture buffer (DPB) is a buffer used to store decoded pictures for reference, for example, as reference pictures for inter prediction. In the examples disclosed in the VVC draft, the relevant syntax elements of the parameters regarding the DBP in the Sequence Parameter Set (SPS) are emphasized.

[0166]

Table 1

[0167] The sps_ptl_dpb_hrd_params_present_flag equal to 1 specifies that the profile_tier_level( ) syntax structure and the dpb_parameters( ) syntax structure may exist in the SPS, and the general_hrd_parameters( ) syntax structure and the ols_hrd_parameters( ) syntax structure may also exist in the SPS. The sps_ptl_dpb_hrd_params_present_flag equal to 0 specifies that none of these four syntax structures exist in the SPS.

[0168] When there is an OLS that contains exactly one layer with an sps_video_parameter_set_id greater than 0 and equal to the nuh_layer_id of the SPS, or when the sps_video_parameter_set_id is equal to 0, the value of the sps_ptl_dpb_hrd_params_present_flag is equal to 1.

[0169] An OLS (output layer set) is a set of layers in which one or more layers are specified as output layers. An output layer is a layer of the output layer set that is output.

[0170] Syntax tables for the syntax structures profile_tier_level( ), dpb_parameters( ), general_hrd_parameters( ), ols_hrd_parameters( ) can be found in the VVC draft.

[0171] The syntax element sps_max_sublayers_minus1 indicates the number of available temporal sublayers. When the number of available temporal sublayers is greater than 1 (e.g., the value of the syntax element sps_max_sublayers_minus1 is greater than 0), the value of the syntax element sps_sublayer_dpb_params_flag is signaled in the bitstream. The syntax element sps_sublayer_dpb_params_flag indicates whether the decoded picture information should be signaled for each available sublayer (when its value is equal to 1) or only for the topmost temporal sublayer (when its value is equal to 0). When the value of sps_sublayer_dpb_params_flag does not exist, e.g., when there is only one temporal sublayer (the value of sps_max_sublayers_minus1 == 0), the value of sps_max_sublayers_minus1 is assumed to be 0.

[0172] In some examples, the value of the syntax element sps_ptl_dpb_hrd_params_present_flag indicates whether the signaling structure dpb_parameter( ) is signaled within the SPS. When the value of the syntax element sps_ptl_dpb_hrd_params_present_flag is equal to 1, the signaled data structure dpb_parameter( ) is called with the value obtained by subtracting 1 from the number of available temporal sublayers (sps_max_sublayers_minus1) and the flag sps_sublayer_dpb_params_flag as the first and second parameters, respectively.

[0173] In an example, the signaling structure of dpb_parameter( ) in the VVC draft is defined as follows.

[0174] [Table 2]

[0175] The dpb_parameters( ) syntax structure provides the DPB size of one or more OLSs, the maximum picture reorder number, and the maximum latency information.

[0176] When the dpb_parameters( ) syntax structure is included in the VPS, the OLS to which the dpb_parameters( ) syntax structure is applied is specified by the VPS. When the dpb_parameters( ) syntax structure is included in the SPS, the dpb_parameters( ) syntax structure is applied only to the OLS that includes only the lowest layer among the layers that refer to the SPS, and this lowest layer is an independent layer.

[0177] The value obtained by adding 1 to max_dec_pic_buffering_minus1[ i ] specifies the maximum required size of the DPB in units of the picture storage buffer when Htid is equal to i. The value of max_dec_pic_buffering_minus1[ i ] is in the range from 0 to MaxDpbSize - 1, including 0 and MaxDpbSize - 1, where MaxDpbSize is as defined in Clause A.4.2. When i is greater than 0, max_dec_pic_buffering_minus1[ i ] is greater than or equal to max_dec_pic_buffering_minus1[ i - 1 ]. Since subLayerInfoFlag is equal to 0, when max_dec_pic_buffering_minus1[ i ] does not exist for i in the range from 0 to maxSubLayersMinus1 - 1, including 0 and maxSubLayersMinus1 - 1, max_dec_pic_buffering_minus1[ i ] is presumed to be equal to max_dec_pic_buffering_minus1[ maxSubLayersMinus1 ].

[0178] max_num_reorder_pics[ i ] specifies the maximum allowable number of pictures in the OLS that can be before any picture in the OLS in decode order and after that picture in output order when Htid is equal to i. The value of max_num_reorder_pics[ i ] is in the range from 0 to max_dec_pic_buffering_minus1[ i ] inclusive of 0 and max_dec_pic_buffering_minus1[ i ]. When i is greater than 0, max_num_reorder_pics[ i ] is greater than or equal to max_num_reorder_pics[ i - 1 ]. Since subLayerInfoFlag is equal to 0, when max_num_reorder_pics[ i ] does not exist for i in the range from 0 to maxSubLayersMinus1 - 1 inclusive of 0 and maxSubLayersMinus1 - 1, max_num_reorder_pics[ i ] is presumed to be equal to max_num_reorder_pics[ maxSubLayersMinus1 ].

[0179] max_latency_increase_plus1[ i ] not equal to 0 is used to calculate the value of MaxLatencyPictures[ i ] that specifies the maximum number of pictures in the OLS that can be before any picture in the OLS in output order and after that picture in decode order when Htid is equal to i.

[0180] When max_latency_increase_plus1[ i ] is not equal to 0, the value of MaxLatencyPictures[ i ] is specified as follows. MaxLatencyPictures[ i ] = max_num_reorder_pics[ i ] + max_latency_increase_plus1[ i ] - 1 (112) When max_latency_increase_plus1[ i ] is equal to 0, the corresponding restriction is not shown. The value of max_latency_increase_plus1[ i ] is between 0 and 2 32 - including -2, from 0 to 2 32 - up to -2. Since subLayerInfoFlag is equal to 0, when max_latency_increase_plus1[ i ] does not exist for i in the range from 0 to maxSubLayersMinus1 - 1, including 0 and maxSubLayersMinus1 - 1, max_latency_increase_plus1[ i ] is assumed to be equal to max_latency_increase_plus1[ maxSubLayersMinus1 ].

[0181] For more details on the syntax elements and variables used to describe the dpb parameters (max_dec_pic_buffering_minus1[i], max_num_reorder_pics[i], and max_latency_increase_plus1[i]), refer to the VVC draft.

[0182] The dpb_parameters signaling structure is controlled by the value of subLayerInfoFlag and signals either the decoded picture buffer information of one sublayer or the decoded picture information of each sublayer. When the value of subLayerInfoFlag is 0, the decoded picture buffer information of the top - most sublayer among the available temporal sublayers is signaled (i = maxSubLayersMinus1). When the value of subLayerInfoFlag is 1, the decoded picture buffer information of each sublayer among the available temporal sublayers is signaled (the value of i is in the range from 0 to maxSubLayersMinus1, including 0 and maxSubLayersMinus1).

[0183] Questions about the semantics of the syntax element sps_sublayer_dpb_params_flag In the VVC draft, the semantics of sps_sublayer_dpb_params_flag are defined as follows. sps_sublayer_dpb_params_flag is used to control the existence of the max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] syntax elements within the dpb_parameters( ) syntax structure in the SPS. When it does not exist, the value of sps_sub_dpb_params_info_present_flag is presumed to be equal to 0.

[0184] The above semantics have two problems. First, the last sentence When it does not exist, the value of sps_sub_dpb_params_info_present_flag is presumed to be equal to 0 has a misprint. sps_sub_dpb_params_info_present_flag is not defined anywhere else, and the last sentence is corrected as follows. When it does not exist, the value of sps_sublayer_dpb_params_flag is presumed to be equal to 0

[0185] Second, the semantics of sps_sublayer_dpb_params_flag are not strict enough, because the range of i in max_dec_pic_buffering_minus1[i], max_num_reorder_pics[i], and max_latency_increase_plus1[i] is not defined. When i is equal to maxSubLayersMinus1 (corresponding to sps_max_sublayers_minus1 in Table 1), it can be seen from Table 2 that the syntax elements max_dec_pic_buffering_minus1[i], max_num_reorder_pics[i], and max_latency_increase_plus1[i] are always signaled, whether sps_sublayer_dpb_params_flag is equal to 0 or 1. In this case, sps_sublayer_dpb_params_flag does not control the existence of max_dec_pic_buffering_minus1[i], max_num_reorder_pics[i], and max_latency_increase_plus1[i], which is inconsistent with the current definition.

[0186] In some examples, the syntax element sps_sublayer_dpb_params_flag is used only as the second parameter of dpb_parameters.

[0187] Regarding the following embodiments, we assume that the misdescription (the first problem) has already been corrected, and the proposed embodiments focus on addressing the second problem, the inaccurate semantics of sps_sublayer_dpb_params_flag.

[0188] Embodiment 1 According to the first embodiment, the semantics of sps_sublayer_dpb_params_flag are corrected as follows. When sps_max_sublayers_minus1 is greater than 0, sps_sublayer_dpb_params_flag is used to control the presence of the max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] syntax elements within the dpb_parameters( ) syntax structure in the SPS for i in the range from 0 to sps_max_sublayers_minus1 - 1, inclusive of 0 and sps_max_sublayers_minus1 - 1. When sps_max_sublayers_minus1 is equal to 0, the value of sps_sublayer_dpb_params_flag is assumed to be 0, and max_dec_pic_buffering_minus1

[0000] , max_num_reorder_pics

[0000] , and max_latency_increase_plus1

[0000] are always signaled for the only sublayer that references the SPS.

[0189] In this way, the semantics of sps_sublayer_dpb_params_flag are clarified. Only when there are two or more sublayers (sps_max_sublayers_minus1 is greater than 0), sps_sublayer_dpb_params_flag controls the existence of minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] within the dpb_parameters( ) syntax structure for i in the range from 0 to sps_max_sublayers_minus1 - 1. Otherwise (sps_max_sublayers_minus1 is equal to 0), regardless of the value of sps_sublayer_dpb_params_flag, the signaling of max_dec_pic_buffering_minus1

[0000] , max_num_reorder_pics

[0000] , and max_latency_increase_plus1

[0000] is always signaled. Therefore, the semantics may be changed as follows in Embodiment 2.

[0190] Embodiment 2 When sps_max_sublayers_minus1 is greater than 0, sps_sublayer_dpb_params_flag is used to control the presence of the max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] syntax elements within the dpb_parameters( ) syntax structure in the SPS for i in the range from 0 to sps_max_sublayers_minus1 - 1, inclusive of 0 and sps_max_sublayers_minus1 - 1. When sps_max_sublayers_minus1 is equal to 0, the value of sps_sublayer_dpb_params_flag is presumed to be equal to 1, and max_dec_pic_buffering_minus1

[0000] , max_num_reorder_pics

[0000] , and max_latency_increase_plus1

[0000] are always signaled for the only sublayer that refers to the SPS.

[0191] Or, as shown in Embodiment 3, even delete the inference rule for the value of sps_sublayer_dpb_params_flag.

[0192] Embodiment 3 The sps_sublayer_dpb_params_flag is used to control the presence of the max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] syntax elements within the dpb_parameters( ) syntax structure in the SPS for i in the range from 0 to sps_max_sublayers_minus1 - 1, inclusive of 0 and sps_max_sublayers_minus1 - 1 when sps_max_sublayers_minus1 is greater than 0. When sps_max_sublayers_minus1 is equal to 0, for the only sublayer that refers to the SPS, max_dec_pic_buffering_minus1

[0000] , max_num_reorder_pics

[0000] , and max_latency_increase_plus1

[0000] are always signaled.

[0193] Or, as shown in Embodiment 4, provide some explanation when sps_max_sublayers_minus1 is equal to 0.

[0194] Embodiment 4 The sps_sublayer_dpb_params_flag is used to control the presence of the max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] syntax elements within the dpb_parameters( ) syntax structure in the SPS for i in the range from 0 to sps_max_sublayers_minus1 - 1, inclusive of 0 and sps_max_sublayers_minus1 - 1 when sps_max_sublayers_minus1 is greater than 0. When sps_max_sublayers_minus1 is equal to 0, the value of sps_sublayer_dpb_params_flag has no meaning, and max_dec_pic_buffering_minus1

[0000] , max_num_reorder_pics

[0000] , and max_latency_increase_plus1

[0000] are always signaled for the only sublayer that references the SPS.

[0195] Correction of Idea 1 using Embodiments 1 to 4 The data structure dpb_parameter( ) may be called not only in the SPS but also in the VPS. The following is a snapshot of the VPS where dpb_parameter( ) is called.

[0196]

Table 3

[0197] Specify the number of dpb_parameters( ) syntax structures within the VPS.

[0198] The vps_default_ptl_dpb_hrd_max_tid_flag equal to 1 specifies that the syntax elements vps_ptl_max_tid[i], vps_dpb_max_tid[i], and vps_hrd_max_tid[i] do not exist and are assumed to be equal to the default value vps_max_sublayers_minus1. The vps_default_ptl_dpb_hrd_max_tid_flag equal to 0 specifies that the syntax elements vps_ptl_max_tid[i], vps_dpb_max_tid[i], and vps_ptl_max_tid[i] exist. When they do not exist, the value of vps_default_ptl_dpb_hrd_max_tid_flag is assumed to be equal to 1.

[0199] For the detailed description of vps_ptl_max_tid[i] and vps_hrd_max_tid[i], please refer to the VVC draft.

[0200] vps_dpb_max_tid[i] specifies the TemporalId of the representation of the topmost sublayer where DPB parameters may exist within the i-th dpb_parameters( ) syntax structure in the VPS. The value of vps_dpb_max_tid[i] is in the range from 0 to vps_max_sublayers_minus1, including 0 and vps_max_sublayers_minus1. When it does not exist, the value of vps_dpb_max_tid[i] is assumed to be equal to vps_max_sublayers_minus1. and The vps_sublayer_dpb_params_flag is used to control the presence of the max_dec_pic_buffering_minus1[], max_num_reorder_pics[], and max_latency_increase_plus1[] syntax elements within the dpb_parameters( ) syntax structure in the VPS. When it is not present, the vps_sub_dpb_params_info_present_flag is assumed to be equal to 0.

[0201] The semantics of the vps_sublayer_dpb_params_present_flag have the same problem as the semantics of the aforementioned sps_sublayer_dpb_params_flag.

[0202] The sizes of the syntax element arrays max_dec_pic_buffering_minus1[], max_num_reorder_pics[], and max_latency_increase_plus1[] are not defined semantically. (Corresponding to vps_dpb_max_tid[ i ] in Table 4 (Table 4) equal to 0) When there is only one sublayer, it can be observed from Table 2 (Table 2) that the syntax elements max_dec_pic_buffering_minus1[], max_num_reorder_pics[], and max_latency_increase_plus1[] are always signaled regardless of whether the vps_sublayer_dpb_params_present_flag is equal to 0 or 1. In this case, the vps_sublayer_dpb_params_present_flag does not control the presence of max_dec_pic_buffering_minus1[], max_num_reorder_pics[], and max_latency_increase_plus1[], which is inconsistent with the current definition.

[0203] Embodiment 9 In one example, the semantics of vps_sublayer_dpb_params_present_flag are modified as follows. vps_sublayer_dpb_params_present_flag is used to control the presence of the max_dec_pic_buffering_minus1[j], max_num_reorder_pics[j], and max_latency_increase_plus1[j] syntax elements within the dpb_parameters( ) syntax structure in the VPS, for j in the range from 0 to vps_dpb_max_tid[i] - 1, inclusive of 0 and vps_dpb_max_tid[i] - 1, when vps_dpb_max_tid[i] within the VPS is greater than 0. When not present, vps_sub_dpb_params_info_present_flag is assumed to be equal to 0. It is noted that j is used instead of i to specify the range of the syntax element arrays max_dec_pic_buffering_minus1[], max_num_reorder_pics[], and max_latency_increase_plus1[] in order to avoid confusion with i of vps_dpb_max_tid[i].

[0204] Remark, problem 2 and corresponding solutions, dependentFlag, etc. When inter prediction is performed, the reference picture can be a decoded picture from the same layer or a reference picture from a lower layer. In the latter case, the reference picture of the lower layer is called an inter-layer reference picture (ILRP), and the lower layer containing one or more ILRPs is called the reference (or dependent) layer.

[0205] To support inter-layer prediction, several intermediate variables are used according to the syntax elements signaled by the VPS. For example, in Equation (37) of the VVC draft, the derivation processes of the variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] are defined as follows. The variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] are derived as follows. for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0; j <= vps_max_layers_minus1; j++ ) { dependencyFlag[ i ][ j ] = vps_direct_ref_layer_flag[ i ][ j ] for( k = 0; k < i; k++ ) if( vps_direct_ref_layer_flag[ i ][ k ] && dependencyFlag[ k ][ j ] ) dependencyFlag[ i ][ j ] = 1 } LayerUsedAsRefLayerFlag[ i ] = 0 } for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0, d = 0, r = 0; j <= vps_max_layers_minus1; j++ ) { (37) if (vps_direct_ref_layer_flag[i][j]) { DirectRefLayerIdx[i][d++] = j LayerUsedAsRefLayerFlag[j] = 1 } if (dependencyFlag[i][j]) RefLayerIdx[i][r++] = j } NumDirectRefLayers[i] = d NumRefLayers[i] = r }

[0206] A dependencyFlag[i][j] equal to 1 specifies that the layer with index j is a reference layer of the layer with index i. A dependencyFlag[i][j] equal to 0 specifies that the layer with index j is not a reference layer of the layer with index i.

[0207] The dependency between the layer with index i and its reference layer j can be direct or indirect. If the j-th layer is a direct dependent layer of the i-th layer, the dependency is signaled using the syntax element vps_direct_ref_layer_flag[i][j] for ranges i from 0 to and j from 0 to i - 1 within the VPS. As shown in Table 4, syntax elements unrelated to the present invention are removed so that

[0208]

Table 4

[0209] The above syntax table shows how the VPS signals dependencies between layers when some layers are not independent layers.

[0210] vps_max_layers_minus1 represents the maximum allowable number of layers within each CVS that refers to the VPS. Information on layer dependencies is signaled only from the second lowest layer (i.e., i = 1), and when some layers are not independent layers, it is indicated by the syntax element vps_all_independent_layers_flag.

[0211] A vps_all_independent_layers_flag equal to 1 specifies that all layers specified by the VPS are coded independently without using inter-layer prediction. A vps_all_independent_layers_flag equal to 0 specifies that one or more of the layers specified by the VPS may use inter-layer prediction. When it does not exist, the value of vps_all_independent_layers_flag is presumed to be equal to 1.

[0212] In VVC, the lowest layer (i.e., corresponding to vps_independent_layer_flag

[0000] ) is always an independent layer. Therefore, the syntax element vps_independent_layer_flag[ i ] is signaled from the second lowest layer (i.e., vps_independent_layer_flag

[0001] ), and its semantics are extremely simple and straightforward.

[0213] A vps_independent_layer_flag[ i ] equal to 1 specifies that the layer with index i does not use inter-layer prediction. A vps_independent_layer_flag[ i ] equal to 0 specifies that the layer with index i may use inter-layer prediction and that for j in the range from 0 to i - 1, inclusive of 0 and i - 1, the syntax element vps_direct_ref_layer_flag[ i ][ j ] exists within the VPS. When it does not exist, the value of vps_independent_layer_flag[ i ] is assumed to be equal to 1.

[0214] The direct dependency layer of a layer is signaled only when the layer is not an independent layer (i.e., vps_independent_layer_flag[ i ] is 0) and is indicated by vps_direct_ref_layer_flag[ i ][ j ] for j in the range from 0 to i - 1.

[0215] The semantics of vps_direct_ref_layer_flag[ i ][ j ] are defined as follows. A vps_direct_ref_layer_flag[ i ][ j ] equal to 0 specifies that the layer with index j is not a direct reference layer of the layer with index i. A vps_direct_ref_layer_flag[ i ][ j ] equal to 1 specifies that the layer with index j is a direct reference layer of the layer with index i. When vps_direct_ref_layer_flag[ i ][ j ] does not exist for i and j in the range from 0 to vps_max_layers_minus1, including 0 and vps_max_layers_minus1, vps_direct_ref_layer_flag[ i ][ j ] is presumed to be equal to 0. When vps_independent_layer_flag[ i ] is equal to 0, there exists at least one value of j in the range from 0 to i - 1, including 0 and i - 1, such that the value of vps_direct_ref_layer_flag[ i ][ j ] is equal to 1.

[0216] When a layer is a dependent layer (i.e., its vps_independent_layer_flag[ i ] is equal to 0), the constraint in the semantics of vps_direct_ref_layer_flag[ i ][ j ] specifies that at least one of its lower layers j in the range from 0 to i - 1, including 0 and i - 1, is a reference layer for layer i.

[0217] In the case of an indirect dependency, it can occur when layer i directly depends on layer k (k < i), and further, layer k depends on layer j (j < k). In such a case, the layer with index i depends on layer j, and the corresponding dependencyFlag[ i ][ j ] is equal to 1.

[0218] Problems in the derivation process. Since a certain layer can only depend on lower layers, the loop for finding the dependent lower layer j in the derivation process can be simplified. It is not necessary for the loop for all layers in the VPS, but only for the loop for layers lower than the current layer i.

[0219] Embodiment 5 In one example, the derivation process of the variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] is modified as follows. The variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] are derived as follows. for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0; j < i; j++ ) { dependencyFlag[ i ][ j ] = vps_direct_ref_layer_flag[ i ][ j ] for( k = 0; k < i; k++ ) if( vps_direct_ref_layer_flag[ i ][ k ] && dependencyFlag[ k ][ j ] ) dependencyFlag[ i ][ j ] = 1 } LayerUsedAsRefLayerFlag[ i ] = 0 } for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0, d = 0, r = 0; j <i; j++ ) { (37) if( vps_direct_ref_layer_flag[ i ][ j ] ) { DirectRefLayerIdx[ i ][ d++ ] = j LayerUsedAsRefLayerFlag[ j ] = 1 } if( dependencyFlag[ i ][ j ] ) RefLayerIdx[ i ][ r++ ] = j } NumDirectRefLayers[ i ] = d NumRefLayers[ i ] = r }

[0220] Embodiment 6 In another example, the derivation process of the variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] is modified as follows. The variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] are derived as follows. for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0; j < i; j++ ) { dependencyFlag[ i ][ j ] = vps_direct_ref_layer_flag[ i ][ j ] for( k = j+1; k < i; k++ ) if( vps_direct_ref_layer_flag[ i ][ k ] && dependencyFlag[ k ][ j ] ) dependencyFlag[ i ][ j ] = 1 } LayerUsedAsRefLayerFlag[ i ] = 0 } for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0, d = 0, r = 0; j < i; j++ ) { (37) if( vps_direct_ref_layer_flag[ i ][ j ] ) { DirectRefLayerIdx[ i ][ d++ ] = j LayerUsedAsRefLayerFlag[ j ] = 1 } if( dependencyFlag[ i ][ j ] ) RefLayerIdx[ i ][ r++ ] = j } NumDirectRefLayers[ i ] = d NumRefLayers[ i ] = r }

[0221] Embodiment 7 In another example, the derivation process of the variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] is modified as follows. The variables dependencyFlag[ i ][ j ], NumDirectRefLayers[ i ], DirectRefLayerIdx[ i ][ d ], NumRefLayers[ i ], RefLayerIdx[ i ][ r ], and LayerUsedAsRefLayerFlag[ j ] are derived as follows. for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0; j <= vps_max_layers_minus1; j++ ) { dependencyFlag[ i ][ j ] = vps_direct_ref_layer_flag[ i ][ j ] for( k = j+1; k < i; k++ ) if( vps_direct_ref_layer_flag[ i ][ k ] && dependencyFlag[ k ][ j ] ) dependencyFlag[ i ][ j ] = 1 } LayerUsedAsRefLayerFlag[ i ] = 0 } for( i = 0; i <= vps_max_layers_minus1; i++ ) { for( j = 0, d = 0, r = 0; j <= vps_max_layers_minus1; j++ ) { (37) if( vps_direct_ref_layer_flag[ i ][ j ] ) { DirectRefLayerIdx[ i ][ d++ ] = j LayerUsedAsRefLayerFlag[ j ] = 1 } if( dependencyFlag[ i ][ j ] ) RefLayerIdx[ i ][ r++ ] = j }} NumDirectRefLayers[ i ] = d NumRefLayers[ i ] = r }}

[0222] Only the loop for( k = 0; k < i; k++ ) is modified to for( k = j+1; k < i; k++ ).

[0223] Embodiment 8 Correspondingly, the semantics of vps_direct_ref_layer_flag[ i ][ j ] are changed as follows. vps_direct_ref_layer_flag[ i ][ j ] equal to 0 specifies that the layer with index j is not a direct reference layer of the layer with index i. vps_direct_ref_layer_flag[ i ][ j ] equal to 1 specifies that the layer with index j is a direct reference layer of the layer with index i. When vps_direct_ref_layer_flag[ i ][ j ] does not exist for i in the range from 1 to vps_max_layers_minus1 including 1 and vps_max_layers_minus1 and jj in the range from 0 to i-1 including 0 and i-1, vps_direct_ref_layer_flag[ i ][ j ] is presumed to be equal to 0. When vps_independent_layer_flag[ i ] is equal to 0, there exists at least one value of j in the range from 0 to i - 1 including 0 and i - 1 such that the value of vps_direct_ref_layer_flag[ i ][ j ] is equal to 1. There are several other variable syntax elements representing dependencies similar to vps_direct_ref_layer_flag[i][j], and their ranges are changed in the same way.

[0224] According to the above description, a method for decoding a video bitstream and a method for encoding a video bitstream are provided herein. Correspondingly, an apparatus for decoding a (coded) video bitstream and an apparatus for decoding a video bitstream are provided herein.

[0225] FIG. 14 shows a method for decoding a video bitstream, implemented by a decoding device, in which a sequence parameter set SPS is coded in the video bitstream and includes syntax elements applied to the video sequence. This method includes step 1410 of obtaining (e.g., by parsing the bitstream) the value of a first syntax element (e.g., sps_ptl_dpb_hrd_params_present_flag according to the above description) from the SPS, where the value of the first syntax element is used to specify whether a decoded picture buffer DPB parameter syntax structure exists within the SPS. The method further includes step 1420 of obtaining (e.g., by parsing the bitstream) the value of a second syntax element (e.g., sps_sublayer_dpb_params_flag according to the above description) from the SPS when it is determined (judged) that the value of the first syntax element specifies that the DPB parameter syntax structure exists within the SPS, where the value of the second syntax element is used to specify the presence of a DPB syntax element (e.g., one of max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] according to the above detailed description) within the DPB parameter syntax structure, and the DPB syntax element is applied to a temporal sublayer other than the top temporal sublayer within the video sequence.

[0226] It should be noted that the bitstream may be obtained by a wireless network or a wired network. The bitstream may be transmitted from a website, a server, or other remote sources using a coaxial cable, an optical fiber cable, a twisted pair, a digital subscriber line (DSL), or a wireless technology such as infrared, radio, microwave, WIFI, Bluetooth, LTE, or 5G.

[0227] The bitstream may be a sequence of bits in the form of a network abstraction layer (NAL) unit stream or a byte stream that forms a representation of a sequence of access units (AUs) that form one or more coded video sequences (CVSs).

[0228] In certain examples, the format of the bitstream specifies the relationship between the network abstraction layer (NAL) unit stream and the byte stream, and either the network abstraction layer (NAL) unit stream or the byte stream is referred to as the bitstream.

[0229] The bitstream can be in one of two formats, namely, the NAL unit stream format or the byte stream format. The NAL unit stream format is conceptually a more "basic" type. The NAL unit stream format includes a sequence of syntax structures called NAL units. This sequence is ordered in decoding order. There are constraints imposed on the decoding order (and content) of the NAL units of the NAL unit stream.

[0230] The format of the byte stream can be constructed from the format of the NAL unit stream by ordering the NAL units in decoding order and prefixing each NAL unit with a start code prefix and zero or more zero-value bytes to form a byte stream. The format of the NAL unit stream can be extracted from the format of the byte stream by searching for the positions of the unique start code prefix patterns within this byte stream.

[0231] FIG. 15 shows a method of encoding a video bitstream, implemented by an encoding device, in which a sequence parameter set (SPS) includes syntax elements that are encoded in the video bitstream and applied to a video sequence. The method includes step 1510 of determining the presence of a decoded picture buffer (DPB) parameter syntax structure within the SPS. Based on the determination of the presence of the DPB parameter syntax structure within the SPS, the value of a first syntax element (e.g., sps_ptl_dpb_hrd_params_present_flag according to the above description) is encoded in the SPS (1520), and the value of the first syntax element is used to indicate whether the DPB parameter syntax structure is present within the SPS. Further, the method shown in FIG. 15 includes step 1530 of determining the presence of a DPB syntax element (e.g., one of max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] according to the above detailed description) within the DPB parameter syntax structure when it is determined (judged) in step 1510 that the DPB parameter syntax structure is present within the SPS (e.g., only when judged), the DPB syntax element being applied to a temporal sublayer other than the top temporal sublayer within the video sequence. Based on the determination of the presence of the DPB syntax element within the DPB parameter syntax structure, the value of a second syntax element (e.g., sps_sublayer_dpb_params_flag according to the above description) is encoded in the SPS (1540), and the value of the second syntax element is used to indicate the presence of the DPB syntax element within the DPB parameter syntax structure.

[0232] The method described above may be embedded in a video decoding device or a video encoding device (generating a bitstream), respectively, as described below.

[0233] As shown in FIG. 16, the video decoding apparatus 1600 provided in this specification according to the embodiment includes an acquisition unit 1610 (including, for example, a parser) and a determination unit 1620. As shown in FIG. 17, the video encoding apparatus 1700 provided in this specification according to the embodiment includes a determination unit 1710 and an encoding unit 1720.

[0234] The acquisition unit 1610 included in the video decoding apparatus 1600 shown in FIG. 16 is configured to obtain the value of a first syntax element (for example, sps_ptl_dpb_hrd_params_present_flag according to the above description) from the SPS, and the value of the first syntax element is used to specify whether the decoding picture buffer DPB parameter syntax structure exists in the SPS coded in the video bitstream. The determination unit 1620 included in the video decoding apparatus 1600 shown in FIG. 16 is configured to determine whether the value of the first syntax element specifies that the DPB parameter syntax structure exists in the SPS. Further, the acquisition unit 1610 is configured to obtain the value of a second syntax element (for example, sps_sublayer_dpb_params_flag according to the above description) from the SPS at least when it is determined (judged) that the value of the first syntax element specifies that the DPB parameter syntax structure exists in the SPS, and the value of the second syntax element is used to specify the existence of a DPB syntax element (for example, one of max_dec_pic_buffering_minus1[i], max_num_reorder_pics[i], and max_latency_increase_plus1[i] according to the above detailed description) in the DPB parameter syntax structure, and the DPB syntax element is applied to a temporal sublayer other than the topmost temporal sublayer in the video sequence.

[0235] The determination unit 1710 included in the video encoding device 1700 shown in FIG. 17 is configured to determine the presence of a decoded picture buffer (DPB) parameter syntax structure in the SPS. The encoding unit 1720 included in the video encoding device 1700 shown in FIG. 17 is configured to encode the value of a first syntax element (e.g., sps_ptl_dpb_hrd_params_present_flag according to the above description) into the SPS based on the determination of the presence of the DPB parameter syntax structure in the SPS, and the value of the first syntax element is used to specify whether the DPB parameter syntax structure exists in the SPS. Further, when the determination unit 1710 determines (is determined) that the DPB parameter syntax structure exists in the SPS (e.g., only when determined), the determination unit 1710 is configured to determine the presence of a DPB syntax element (e.g., one of max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] according to the above detailed description) in the DPB parameter syntax structure, and the DPB syntax element is applied to a temporal sublayer excluding the top temporal sublayer in the video sequence. Further, the encoding unit 1720 is configured to encode the value of a second syntax (e.g., sps_sublayer_dpb_params_flag according to the above description) element into the SPS based on the determination of the presence of the DPB syntax element in the DPB parameter syntax structure, and the value of the second syntax element is used to specify the presence of the DPB syntax element in the DPB parameter syntax structure.

[0236] The video decoder 1600 shown in FIG. 16 may be, or may be included by, the decoder 30 shown in FIGS. 1A, 1B, and 3 and the video decoder 3206 shown in FIG. 9. Further, the decoding device 1700 may be included by the video coding device 400 shown in FIG. 4, the device 500 shown in FIG. 5, and the terminal device 3106 shown in FIG. 8. The encoding device 1700 shown in FIG. 17 may be, or may be included by, the encoder 20 shown in FIGS. 1A, 1B, and 3. Further, the encoding device 1700 may be included by the video coding device 400 shown in FIG. 4, the device 500 shown in FIG. 5, and the capture device 3102 shown in FIG. 8.

[0237] In particular, the SPS includes information regarding sub-picture signaling.

[0238] Some parts of the following table are download links as follows, namely, http: / / phenix.it-sudparis.eu / jvet / doc_end_user / documents / 17_Brussels / wg11 / JVET-Q2001-v13.zip which shows a snapshot of a part of the sub-picture signaling within the SPS in ITU JVET-Q2001-v13. In the remainder of this application, this document is referred to as VVC Draft 8 for simplicity.

[0239]

Table 5A

Table 5B

[0240] Some syntax elements of the SPS signal the position information and control flags of each sub-picture. The position information of the i-th sub-picture includes the following. · subpic_ctu_top_left_x[ i ], which indicates the horizontal component of the top-left coordinate of sub-picture i within the picture, or · subpic_ctu_top_left_y[ i ], which indicates the vertical component of the top-left coordinate of sub-picture i within the picture, or · subpic_width_minus1[ i ], which indicates the width of sub-picture i within the picture, or · subpic_height_minus1[ i ], which indicates the height of sub-picture i within the picture

[0241] Some syntax elements, for example, sps_num_subpics_minus1, indicate the number of sub-pictures within the picture.

[0242] Partitioning of a picture into CTUs, slices, tiles, and sub-pictures Partitioning of a picture into CTUs A picture is divided into a sequence of coding tree units (CTUs). The term CTU may be used interchangeably with CTB (coding tree block). In the example, the term CTU is the same as the definition of CTU in ITU-T H.265. For a picture with three sample arrays, a CTU includes an N×N block of luma samples and two corresponding blocks of chroma samples. Figure 6 shows an example of a picture divided into CTUs. The size of CTUs must be the same except for the CTUs at the boundaries of the picture (where incomplete CTUs may exist).

[0243] Partitioning of a picture into tiles In some examples, when tiles are enabled, a picture is divided into rectangular groups of CTUs separated by vertical and / or horizontal boundaries. The vertical and horizontal tile boundaries intersect the picture from the top and bottom and from the left picture boundary to the right picture boundary, respectively. Indication information related to the positions of the horizontal and vertical tile boundaries is coded in the bitstream.

[0244] Figure 7 illustrates the partitioning of a picture into nine tiles. In this example, the boundaries of the tiles are indicated by thick dashed lines.

[0245] When there are two or more tiles that divide the picture vertically, the scan order of the CTUs is changed based on the raster scan order of the CTUs within the picture. The CTUs are scanned according to the following rules. 1. The tiles are scanned in raster scan order from left to right and top to bottom, which is called the tile scan order. This means starting from the top - left tile, first all the tiles within the same tile row are scanned from left to right. Then, starting from the first tile in the second tile row (the tile row one below), all the tiles in the second tile row are scanned from left to right. This process is repeated until all tiles are scanned. 2. For a tile, the CTUs within this tile are scanned in raster scan order. For each CTU row, the CTUs are scanned from left to right and the CTU rows are scanned from top to bottom. Figure 7 illustrates the scan order of the CTUs within a tile, and the numbers corresponding to the CTUs indicate the scan order.

[0246] Tiles provide a partitioning of a picture in such a way that each tile is independently decodable from the other tiles of the same picture. Decoding refers to entropy, residual, and predictive decoding. Further, tiles can divide a picture into regions of similar size. Thus, it is possible to process the tiles of a picture in parallel with each other, which is preferable in a multi - core processing environment where each processing core is identical to the others.

[0247] The terms processing order and scan order are used in this application as follows. The processing refers to the encoding or decoding of CTUs in an encoder or decoder. The scan order is related to the indexing of specific sections within a picture. CTUs are indexed in ascending order within a picture according to a specified scan order. The CTU scan order within a tile means how the CTUs within the tile are indexed, which may not be the same as the order in which the CTUs are processed (i.e., the processing order).

[0248] Partitioning of a picture into slices The concept of a slice provides a partitioning of a picture in such a way that each slice is decodable independently of the other slices of the same picture, and decoding refers to entropy, residual, and predictive decoding. The difference from a tile is that a slice can have an arbitrary shape that is not necessarily rectangular (more flexible in terms of partitioning possibilities), and the purpose of slice partitioning is not parallel processing but packet size matching and error resilience in a transmission environment.

[0249] A slice may contain a complete picture or a part of a picture. In ITU-T H.265, a slice contains consecutive CTUs of a picture in processing order. A slice is identified by a start CTU address, which is signaled within a slice header or a picture parameter set or other unit. In an example, when a slice is required to contain an integer number of tiles, the slice may be identified by a start tile address.

[0250] In draft 8 of VVC, a slice contains an integer number of tiles or an integer number of consecutive CTU rows within a tile of a picture. As a result, the vertical slice boundaries are also the vertical tile boundaries. The horizontal slice boundaries may not be the tile boundaries, and the horizontal CTU boundaries may be included within a tile. For example, when a tile is divided into multiple rectangular slices, each slice contains an integer number of consecutive complete CTU rows within the tile.

[0251] In some examples, there are two slice modes, the raster scan slice mode and the rectangle slice mode. In the raster scan slice mode, a slice comprises a sequence of tiles of a raster scan of tiles of a picture. In the rectangle slice mode, a slice comprises several tiles that collectively form a rectangular region of the picture, or a slice comprises several consecutive rows of CTUs of one tile that collectively form a rectangular region of the picture. Tiles within a rectangular slice are scanned in raster scan order of the tiles within the rectangular region corresponding to that slice.

[0252] All slices of a picture collectively form the complete picture, i.e., all CTUs of the picture are included in one of the slices of the picture. Similar rules apply to tiles and subpictures.

[0253] Partitioning of a picture into subpictures A subpicture may be a rectangular partition of a picture. A subpicture may be the whole picture or a part of the picture. A subpicture is a partitioning of a picture in such a way that each subpicture is decodable independently of the other subpictures of the entire video sequence. In VVC draft 8, for subpicture i, when the indication of subpic_treated_as_pic_flag[i] is true (e.g., the value of subpic_treated_as_pic_flag[i] is 1), that subpicture i is decodable independently of the other subpictures of the entire video sequence.

[0254] The difference between a subpicture and a tile or a slice is that a subpicture produces a video sequence that is decodable independently. For tiles and slices, independent decoding is performed within a single picture of the video sequence.

[0255] In VVC Draft 8, a subpicture includes one or more slices that collectively enclose a rectangular region of a picture. Thus, the boundary of each subpicture is always the boundary of a slice, and the boundary of each vertical subpicture is always the boundary of a vertical tile.

[0256] Figure 10 provides examples of tiles, slices, and subpictures.

[0257] In an example shown in Figure 8, a picture is partitioned into 216 CTUs, 4 tiles, 4 slices, and 3 subpictures. The value of sps_num_subpics_minus1 is 2, and the syntax elements related to the position have the following values. For subpicture 0, · subpic_ctu_top_left_x

[0000] is not signaled and is inferred to be 0. · subpic_ctu_top_left_y

[0000] is not signaled and is inferred to be 0. · subpic_width_minus1

[0000] , the value is 8. · subpic_height_minus1

[0000] , the value is 11. For subpicture 1, · subpic_ctu_top_left_x

[0001] , the value is 9. · subpic_ctu_top_left_y

[0001] , the value is 0. · subpic_width_minus1

[0001] , the value is 8. · subpic_height_minus1

[0001] , the value is 5. For subpicture 2, · subpic_ctu_top_left_x

[0002] , the value is 9. · subpic_ctu_top_left_y

[0002] , the value is 6. · subpic_width_minus1

[0002] is not signaled and is inferred to be 8. ·subpic_height_minus1

[0002] is not signaled and is assumed to be 5.

[0258] Signaling of Decoded Picture Buffer (DPB) Information Decoded Picture Buffer The decoded picture buffer (DPB) is a buffer used to store decoded pictures for reference, for example, as reference pictures for inter prediction. In an example disclosed in the VVC draft (e.g., ITU JVET-Q2001-v13), the relevant syntax elements of the parameters related to the DBP in the sequence parameter set (SPS) are emphasized.

[0259]

Table 6

[0260] The value obtained by adding 1 to sps_max_sublayers_minus1 specifies the maximum number of temporal sublayers that may exist in each CLVS that refers to the SPS. The value of sps_max_sublayers_minus1 is in the range from 0 to vps_max_sublayers_minus1, inclusive of 0 and vps_max_sublayers_minus1.

[0261] sps_sublayer_dpb_params_flag is used to control the presence of the max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and max_latency_increase_plus1[ i ] syntax elements in the dpb_parameters( ) syntax structure within the SPS. When it does not exist, the value of sps_sub_dpb_params_info_present_flag is assumed to be equal to 0.

[0262] The sps_ptl_dpb_hrd_params_present_flag equal to 1 specifies that the profile_tier_level( ) syntax structure and the dpb_parameters( ) syntax structure may be present in the SPS, and the general_hrd_parameters( ) syntax structure and the ols_hrd_parameters( ) syntax structure may also be present in the SPS. The sps_ptl_dpb_hrd_params_present_flag equal to 0 specifies that none of these four syntax structures are present in the SPS. The value of the sps_ptl_dpb_hrd_params_present_flag shall be equal to vps_independent_layer_flag[ GeneralLayerIdx[ nuh_layer_id ] ].

[0263] The syntax element sps_max_sublayers_minus1 indicates the number of available temporal sublayers. When the number of available temporal sublayers is greater than 1 (e.g., the value of the syntax element sps_max_sublayers_minus1 is greater than 0), the value of the syntax element sps_sublayer_dpb_params_flag is signaled in the bitstream. The syntax element sps_sublayer_dpb_params_flag indicates whether the decoded picture information should be signaled for each available sublayer (when its value is equal to 1) or only for the topmost temporal sublayer (when its value is equal to 0). If the value of sps_sublayer_dpb_params_flag does not exist, e.g., when there is only one temporal sublayer (the value of sps_max_sublayers_minus1 == 0), the value of sps_max_sublayers_minus1 is inferred to be 0.

[0264] In some examples, the value of the syntax element sps_ptl_dpb_hrd_params_present_flag indicates whether the signaling structure dpb_parameter( ) is signaled within the SPS. When the value of the syntax element sps_ptl_dpb_hrd_params_present_flag is equal to 1, the signaled data structure dpb_parameter( ) is called with the value obtained by subtracting 1 from the number of available temporal sublayers (sps_max_sublayers_minus1) and the flag sps_sublayer_dpb_params_flag as the first and second parameters, respectively.

[0265] In an example, the signaling structure of dpb_parameter( ) in the VVC draft (e.g., ITU JVET-Q2001-v13) is defined as follows.

[0266] [Table 7]

[0267] The dpb_parameters( ) syntax structure provides information on the DPB size, maximum picture reordering number, and maximum latency of one or more OLSs. (Output Layer Set (OLS): A set of layers consisting of a specified set of layers, where one or more layers within the set of layers are designated as output layers.)

[0268] When the dpb_parameters( ) syntax structure is included in the VPS, the OLS to which the dpb_parameters( ) syntax structure applies is specified by the VPS. When the dpb_parameters( ) syntax structure is included in the SPS, the dpb_parameters( ) syntax structure applies only to the OLS that includes only the lowest layer among the layers that reference the SPS, and this lowest layer is an independent layer.

[0269] The value obtained by adding 1 to max_dec_pic_buffering_minus1[ i ] specifies the maximum required size of the DPB in units of the picture memory buffer when Htid is equal to i. The value of max_dec_pic_buffering_minus1[ i ] is in the range from 0 to MaxDpbSize - 1, including 0 and MaxDpbSize - 1, where MaxDpbSize is as defined in Clause A.4.2. When i is greater than 0, max_dec_pic_buffering_minus1[ i ] is greater than or equal to max_dec_pic_buffering_minus1[ i - 1 ]. Since subLayerInfoFlag is equal to 0, when max_dec_pic_buffering_minus1[ i ] does not exist for i in the range from 0 to maxSubLayersMinus1 - 1, including 0 and maxSubLayersMinus1 - 1, max_dec_pic_buffering_minus1[ i ] is presumed to be equal to max_dec_pic_buffering_minus1[ maxSubLayersMinus1 ].

[0270] max_num_reorder_pics[ i ] specifies the maximum number of pictures in the OLS that can be before any picture in the OLS in decoding order and after that picture in output order when Htid is equal to i. The value of max_num_reorder_pics[ i ] is in the range from 0 to max_dec_pic_buffering_minus1[ i ] inclusive of 0 and max_dec_pic_buffering_minus1[ i ]. When i is greater than 0, max_num_reorder_pics[ i ] is greater than or equal to max_num_reorder_pics[ i - 1 ]. Since subLayerInfoFlag is equal to 0, when max_num_reorder_pics[ i ] does not exist for i in the range from 0 to maxSubLayersMinus1 - 1 inclusive of 0 and maxSubLayersMinus1 - 1, max_num_reorder_pics[ i ] is assumed to be equal to max_num_reorder_pics[ maxSubLayersMinus1 ].

[0271] max_latency_increase_plus1[ i ] not equal to 0 is used to calculate the value of MaxLatencyPictures[ i ] which specifies the maximum number of pictures in the OLS that can be before any picture in the OLS in output order and after that picture in decoding order when Htid is equal to i.

[0272] When max_latency_increase_plus1[ i ] is not equal to 0, the value of MaxLatencyPictures[ i ] is specified as follows. MaxLatencyPictures[ i ] = max_num_reorder_pics[ i ] + max_latency_increase_plus1[ i ] - 1 (7-111) When max_latency_increase_plus1[ i ] is equal to 0, the corresponding restriction is not shown. The value of max_latency_increase_plus1[ i ] is 0 and 2 32 - including - 2 and ranging from 0 to 2 32 - up to - 2. Since subLayerInfoFlag is equal to 0, when max_latency_increase_plus1[ i ] does not exist for i in the range from 0 to maxSubLayersMinus1 - 1 including 0 and maxSubLayersMinus1 - 1, max_latency_increase_plus1[ i ] is presumed to be equal to max_latency_increase_plus1[ maxSubLayersMinus1 ].

[0273] The dpb_parameters signaling structure is controlled by the value of subLayerInfoFlag and signals either the decoded picture buffer information of one sublayer or the decoded picture information of each sublayer. When the value of subLayerInfoFlag is 0, the decoded picture buffer information of the top - most sublayer among the available temporal sublayers is signaled (i = maxSubLayersMinus1). When the value of subLayerInfoFlag is 1, the decoded picture buffer information of each sublayer among the available temporal sublayers is signaled (the value of i is in the range from 0 to maxSubLayersMinus1 including 0 and maxSubLayersMinus1).

[0274] In some examples, the syntax element sps_sublayer_dpb_params_flag is used only as the second parameter of dpb_parameters.

[0275] Embodiment 10 According to the 10th embodiment, the value of the syntax element sps_sublayer_dpb_params_flag is coded in the bitstream as follows based on the value of the syntax element sps_ptl_dpb_hrd_params_present_flag.

[0276]

Table 8

[0277] In this embodiment, when the value of sps_max_sublayers_minus1 is greater than 0 and the value of sps_ptl_dpb_hrd_params_present_flag is equal to 0, the value of the syntax element sps_sublayer_dpb_params_flag need not be coded in the bitstream.

[0278] Embodiment 11 According to the 11th embodiment, the value of the syntax element sps_sublayer_dpb_params_flag is coded in the bitstream as follows based on the value of the syntax element sps_ptl_dpb_hrd_params_present_flag.

[0279]

Table 9

[0280] In this embodiment, when the value of sps_max_sublayers_minus1 is greater than 0 and the value of sps_ptl_dpb_hrd_params_present_flag is equal to 0, the value of the syntax element sps_sublayer_dpb_params_flag need not be coded in the bitstream. Further, the syntax element is reconstructed with a clearer design. The syntax element sps_ptl_dpb_hrd_params_present_flag is raised in level to command the signaling of both the syntax element sps_sublayer_dpb_params_flag and the signaling structure dpb_parameters().

[0281] Embodiment 12 According to the 12th embodiment, the value of the syntax element sps_sublayer_dpb_params_flag is coded in the bitstream as follows based on the value of the syntax element sps_ptl_dpb_hrd_params_present_flag.

[0282] [Table 10]

[0283] Correspondingly, the signaling structure of dpb_parameters is modified as follows.

[0284] [Table 11]

[0285] In this embodiment, when the value of sps_max_sublayers_minus1 is greater than 0 and the value of sps_ptl_dpb_hrd_params_present_flag is equal to 0, the value of the syntax element sps_sublayer_dpb_params_flag need not be coded in the bitstream. Compared with Embodiment 11, the signaling structure of dpb_parameter( ) is signaled from the first sublayer indicated by the parameters firstSubLayer and maxSubLayersMinus1 to the topmost sublayer. The selection of the first sublayer is removed from dpb_parameter( ). The semantics of sps_sublayer_dpb_params_flag are thus clearer.

[0286] In the example, as disclosed in the VVC draft (e.g., ITU JVET-Q2001-v13), there are two modes for a slice, the raster scan slice mode and the rectangle slice mode. However, according to the current definition, a slice can be either in the raster scan mode or the rectangle mode.

[0287] The definition of a slice is described as follows. A slice consists of an integer number of complete tiles or an integer number of consecutive complete CTU rows within a tile of a picture. As a result, the boundaries of each vertical slice are always also the boundaries of the vertical tiles. The horizontal boundaries of a slice are not the boundaries of the tiles, but can consist of the horizontal CTU boundaries within the tile, which occurs when a tile is divided into a plurality of rectangle slices and each of the rectangle slices consists of an integer number of consecutive complete CTU rows within the tile.

[0288] Two modes of slicing, namely, raster scan slice mode and rectangular slice mode, are supported. In the raster scan slice mode, a slice contains a complete sequence of tiles of a raster scan of tiles of a picture. In the rectangular slice mode, a slice contains either several complete tiles that collectively form a rectangular region of a picture or several consecutive complete CTU rows of one tile that collectively form a rectangular region of a picture. Tiles within a rectangular slice are scanned in raster scan order of the tiles within the rectangular region corresponding to that slice.

[0289] The only constraint regarding a raster scan slice is that it "contains a complete sequence of tiles of a raster scan of tiles of a picture". For example, as shown in FIG. 12, there are only two tiles and one slice within a picture. This slice can be either in the raster scan slice mode or the rectangular slice mode. This may cause confusion between the two modes of slicing.

[0290] Embodiment 13 It is proposed to further restrict the definition of a raster scan slice as follows. In the raster scan slice mode, a slice contains a complete sequence of tiles of a raster scan of tiles of a picture, and this picture contains at least one slice that forms a non-rectangular shape.

[0291] For example, with this definition of a raster scan slice, the picture shown in FIG. 13 is a raster scan slice, while the picture shown in FIG. 12 can only use the rectangular slice mode.

[0292] Correspondingly, the signaling regarding the tile structure is modified.

[0293] In one example, the signaling of tile information becomes as follows within the PPS.

[0294]

Table 12

[0295] A no_pic_partition_flag equal to 1 specifies that picture partitioning does not apply to each picture that refers to the PPS. A no_pic_partition_flag equal to 0 specifies that each picture that refers to the PPS may be partitioned into two or more tiles or slices.

[0296] It is a requirement for bitstream conformance that the value of no_pic_partition_flag be the same for all PPSs referred to by the coded pictures within the CLVS.

[0297] When the value of sps_num_subpics_minus1 + 1 is greater than 1, it is a requirement for bitstream conformance that the value of no_pic_partition_flag not be equal to 1.

[0298] The value obtained by adding 5 to pps_log2_ctu_size_minus5 specifies the luma coding tree block size of each CTU. pps_log2_ctu_size_minus5 is equal to sps_log2_ctu_size_minus5.

[0299] The value obtained by adding 1 to num_exp_tile_columns_minus1 specifies the number of widths of the explicitly provided tile columns. The value of num_exp_tile_columns_minus1 is in the range from 0 to PicWidthInCtbsY - 1, including 0 and PicWidthInCtbsY - 1. When no_pic_partition_flag is equal to 1, the value of num_exp_tile_columns_minus1 is presumed to be equal to 0.

[0300] The value obtained by adding 1 to num_exp_tile_rows_minus1 specifies the number of explicitly provided tile row heights. The value of num_exp_tile_rows_minus1 is within the range from 0 to PicHeightInCtbsY - 1, inclusive of 0 and PicHeightInCtbsY - 1. When no_pic_partition_flag is equal to 1, the value of num_tile_rows_minus1 is presumed to be equal to 0.

[0301] The value obtained by adding 1 to tile_column_width_minus1[ i ] specifies the width of the i-th tile column in units of CTB for i within the range from 0 to num_exp_tile_columns_minus1, inclusive of 0 and num_exp_tile_columns_minus1 - 1. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns having indices greater than or equal to num_exp_tile_columns_minus1 as defined in Clause 6.5.1. The value of tile_column_width_minus1[ i ] is within the range from 0 to PicWidthInCtbsY - 1, inclusive of 0 and PicWidthInCtbsY - 1. When it does not exist, the value of tile_column_width_minus1

[0000] is presumed to be equal to PicWidthInCtbsY - 1.

[0302] The value obtained by adding 1 to tile_row_height_minus1[ i ] specifies the height of the i-th tile row in units of CTB for i within the range from 0 to num_exp_tile_rows_minus1 inclusive of 0 and num_exp_tile_rows_minus1 - 1. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows having indices greater than or equal to num_exp_tile_rows_minus1 as specified in clause 6.5.1. The value of tile_row_height_minus1[ i ] is within the range from 0 to PicHeightInCtbsY - 1 inclusive of 0 and PicHeightInCtbsY - 1. When it does not exist, the value of tile_row_height_minus1

[0000] is presumed to be equal to PicHeightInCtbsY - 1.

[0303] A rect_slice_flag equal to 0 specifies that the tiles within each slice are in raster scan order and the slice information is not signaled in the PPS. A rect_slice_flag equal to 1 specifies that the tiles within each slice cover a rectangular region of the picture and the slice information is signaled in the PPS. When it does not exist, the rect_slice_flag is presumed to be equal to 1. When subpic_info_present_flag is equal to 1, the value of rect_slice_flag is equal to 1.

[0304] The single_slice_per_subpic_flag equal to 1 specifies that each subpicture consists of only one rectangular slice. The single_slice_per_subpic_flag equal to 0 specifies that each subpicture may consist of one or more rectangular slices. When single_slice_per_subpic_flag is equal to 1, num_slices_in_pic_minus1 is assumed to be equal to sps_num_subpics_minus1. When it does not exist, the value of single_slice_per_subpic_flag is assumed to be equal to 0. [Editor (Ed.) (GJS): Consider renaming this flag or clarifying it in another way to avoid the interpretation that this flag is only relevant when there are more than two subpictures within each picture.]

[0305] When the number of tiles in the picture is greater than 1, the flag rect_slice_flag is parsed from the bitstream, and the value of rect_slice_flag indicates whether the rectangular slice mode (when the value is equal to 1) or the raster scan slice mode (when the value is equal to 0) is used for the picture.

[0306] Correspondingly, in the slice header

[0307] [Table 13]

[0308] The picture_header_in_slice_header_flag equal to 1 specifies that the PH syntax structure exists within the slice header. The picture_header_in_slice_header_flag equal to 0 specifies that the PH syntax structure does not exist within the slice header.

[0309] It is a requirement for bitstream compliance that the value of picture_header_in_slice_header_flag be the same for all coded slices within the CLVS.

[0310] For a coded slice for which picture_header_in_slice_header_flag is equal to 1, it is a requirement for bitstream compliance that there be no VCL NAL unit with nal_unit_type equal to PH_NUT within the CLVS.

[0311] When picture_header_in_slice_header_flag is equal to 0, all coded slices within the current picture have a picture_header_in_slice_header_flag equal to 0, and the current PU has a PH NAL unit.

[0312] slice_subpic_id specifies the subpicture ID of the subpicture containing the slice. If slice_subpic_id is present, the value of the variable CurrSubpicIdx is derived such that SubpicIdVal[ CurrSubpicIdx ] is equal to slice_subpic_id. Otherwise (if slice_subpic_id is not present), CurrSubpicIdx is derived to be equal to 0. The length of Slice_subpic_id is sps_subpic_id_len_minus1 + 1 bits.

[0313] slice_address specifies the slice address of the slice. When not present, the value of slice_address is assumed to be equal to 0. When rect_slice_flag is equal to 1 and NumSlicesInSubpic[ CurrSubpicIdx ] is equal to 1, the value of slice_address is assumed to be equal to 0.

[0314] When rect_slice_flag is equal to 0, the following applies. - The slice address is the raster scan tile index. - The length of slice_address is Ceil( Log2( NumTilesInPic ) ) bits. - The value of slice_address is in the range from 0 to NumTilesInPic - 1, inclusive of 0 and NumTilesInPic - 1.

[0315] Otherwise (when rect_slice_flag is equal to 1), the following applies. - The slice address is the sub-picture level slice index of the slice. - The length of slice_address is Ceil( Log2( NumSlicesInSubpic[ CurrSubpicIdx ] ) ) bits. - The value of slice_address is in the range from 0 to NumSlicesInSubpic[ CurrSubpicIdx ] - 1, inclusive of 0 and NumSlicesInSubpic[ CurrSubpicIdx ] - 1.

[0316] The following constraints apply, which are requirements for bitstream compliance. - When rect_slice_flag is equal to 0 or subpic_info_present_flag is equal to 0, the value of slice_address is not equal to the value of slice_address of any other coded slice of the same coded picture in the NAL unit. - Otherwise, the pair of the value of slice_subpic_id and the value of slice_address is not equal to the pair of the value of slice_subpic_id and the value of slice_address of any other coded slice of the same coded picture in the NAL unit. - The shape of the slice of the picture is such that each CTU, when decoded, has the entire left boundary and the entire upper boundary consisting of the boundary of the picture or the boundary of the already decoded CTUs.

[0317] sh_extra_bit[ i ] may be equal to 1 or 0. A decoder compliant with this version of this specification ignores the value of sh_extra_bit[ i ]. Its value does not affect the decoder's compliance with the profile defined in this version of the specification.

[0318] The value obtained by adding 1 to num_tiles_in_slice_minus1 specifies the number of tiles in the slice when it exists. The value of num_tiles_in_slice_minus1 is in the range from 0 to NumTilesInPic - 1, including 0 and NumTilesInPic - 1.

[0319] It is proposed to modify the above signaling mechanism in the PPS and slice headers as follows.

[0320]

Table 14

[0321]

Table 15

[0322] In particular, the following embodiments are also provided herein (in the new enumeration).

[0323] 1. A coding method implemented by a decoding device or an encoding device, a step of obtaining a bitstream, wherein a sequence parameter set SPS is coded in the bitstream, A step of obtaining a value of a first syntax element sps_max_sublayers_minus1 according to a bitstream, wherein the value of the first syntax element sps_max_sublayers_minus1 is used to indicate the maximum number of temporal sublayers present within a coded layer video sequence CLVS that references the SPS. A step of obtaining a value of a second syntax element sps_ptl_dpb_hrd_params_present_flag according to a bitstream, wherein the value of the second syntax element sps_ptl_dpb_hrd_params_present_flag is used to indicate whether a decoded picture buffer DPB parameter syntax structure (e.g., dpb_prameters) is present within the SPS. When the value of the first syntax element sps_max_sublayers_minus1 is greater than a first default value (e.g., the first default value is equal to 0), and when the value of the second syntax element sps_ptl_dpb_hrd_params_present_flag is equal to a second default value (e.g., the second default value is equal to 1), a method comprising a step of parsing a value of a third syntax element sps_sublayer_dpb_params_flag from the bitstream, wherein the value of the third syntax element sps_sublayer_dpb_params_flag is used to control the presence of syntax elements (e.g., when sps_max_sublayers_minus1 is greater than 0, max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and / or max_latency_increase_plus1[ i ] for i in the range from 0 to sps_max_sublayers_minus1 - 1 including 0 and sps_max_sublayers_minus1 - 1) within a DPB parameter syntax structure (e.g., dpb_prameters) within the SPS.

[0324] 2. A method according to Embodiment 1, further comprising the step of setting a value of a third syntax element sps_sublayer_dpb_params_flag to a third default value (for example, the third default value is equal to 0 or 1) when a value of a first syntax element sps_max_sublayers_minus1 is less than or equal to a first default value, or when a value of a second syntax element sps_ptl_dpb_hrd_params_present_flag is not equal to a second default value.

[0325] 3. A method according to Embodiment 1 or 2, in which a value of a third syntax element sps_sublayer_dpb_params_flag is coded in the SPS.

[0326] 4. A coding method implemented by a decoding device or an encoding device, comprising: a step of obtaining a bitstream, wherein a sequence parameter set SPS is coded in the bitstream; a step of obtaining a value of a first syntax element sps_max_sublayers_minus1 according to the bitstream, wherein the value of the first syntax element sps_max_sublayers_minus1 is used to specify a maximum number of temporal sublayers existing in a coded layer video sequence CLVS referring to the SPS; a step of obtaining a value of a second syntax element sps_ptl_dpb_hrd_params_present_flag according to the bitstream, wherein the value of the second syntax element sps_ptl_dpb_hrd_params_present_flag is used to specify whether a decoded picture buffer DPB parameter syntax structure (for example, dpb_prameters) exists in the SPS; Determining whether the value of the second syntax element sps_ptl_dpb_hrd_params_present_flag is equal to a second default value (for example, the second default value is equal to 1). When it is determined that the value of the second syntax element sps_ptl_dpb_hrd_params_present_flag is equal to the second default value, determining whether the value of the first syntax element sps_max_sublayers_minus1 is greater than a first default value (for example, the first default value is equal to 0). When it is determined that the value of the first syntax element sps_max_sublayers_minus1 is greater than the first default value (for example, the first default value is equal to 0), a method including the step of parsing the value of the third syntax element sps_sublayer_dpb_params_flag from the bitstream, where the value of the third syntax element sps_sublayer_dpb_params_flag is used to control the presence of syntax elements (for example, when sps_max_sublayers_minus1 is greater than 0, max_dec_pic_buffering_minus1[ i ], max_num_reorder_pics[ i ], and / or max_latency_increase_plus1[ i ] for i in the range from 0 to sps_max_sublayers_minus1 - 1 including 0 and sps_max_sublayers_minus1 - 1) within the DPB parameter syntax structure (for example, dpb_prameters) within the SPS.

[0327] 5. A method according to Embodiment 4 further comprising the step of setting the value of a third syntax element sps_sublayer_dpb_params_flag to a third default value (e.g., the third default value is equal to 0 or 1) when it is determined that the value of a first syntax element sps_max_sublayers_minus1 is less than or equal to a first default value, or when it is determined that the value of a second syntax element sps_ptl_dpb_hrd_params_present_flag is not equal to a second default value.

[0328] 6. A method according to Embodiment 4 or 5, wherein the value of a third syntax element sps_sublayer_dpb_params_flag is coded in the SPS (in other examples, the value of the third syntax element sps_sublayer_dpb_params_flag is coded in the picture parameter set PPS, or the value of the third syntax element sps_sublayer_dpb_params_flag is coded in the video parameter set VPS).

[0329] 7. A method according to any one of Embodiments 1 to 6, wherein the value of a first syntax element is coded in the picture parameter set PPS, or the value of a first syntax element is coded in the video parameter set VPS (in another example, the value of a second syntax element is coded in the picture parameter set PPS, or the value of a second syntax element is coded in the video parameter set VPS).

[0330] 8. A method according to any one of Embodiments 1 to 7, wherein when sps_max_sublayers_minus1 is equal to 0, max_dec_pic_buffering_minus1

[0000] , max_num_reorder_pics

[0000] , and max_latency_increase_plus1

[0000] are always signaled for the only sublayer that references the SPS.

[0331] 9. A coding method implemented by a decoding device or an encoding device, comprising: determining an indirect reference layer having index j of a layer having index i from only at least one layer having an index less than i; when inter-layer prediction is enabled for the current picture, obtaining a reference picture of the current picture within the indirect reference layer having index j; predicting the current picture using the reference picture from the indirect reference layer having index j.

[0332] 10. The method according to embodiment 9, wherein the step of determining the indirect reference layer of the layer having index i comprises determining that there exists a layer having index k which is a direct reference of the layer having index i only among at least one layer having an index smaller than i and larger than j, and determining that the indirect reference layer having index j is a reference layer of the direct reference layer having index k.

[0333] 11. The method according to embodiment 9, wherein the step of determining the indirect and direct reference layer of the layer having index i comprises determining that there exists a layer having index k which is a direct reference of the layer having index i only among at least one layer having an index smaller than i, and determining that the indirect reference layer having index j is a reference layer of the direct reference layer having index k.

[0334] 12. A coding method implemented by a decoding device or an encoding device, comprising: Determining an indirect reference layer having index j of a layer having index i, when it is determined that there exists a layer having index k which is a direct reference layer of the layer having index i, only among at least one layer having an index smaller than i and larger than j, wherein the layer having index j is a reference layer of the direct reference layer having index k, When inter-layer prediction is enabled for the current picture, obtaining a reference picture of the current picture within the indirect reference layer having index j, A method comprising predicting the current picture using a reference picture from the indirect reference layer having index j.

[0335] 13. A coding method performed by a decoding device or an encoding device, Obtaining a bitstream, wherein a picture parameter set PPS is coded in the bitstream, Obtaining the number NumTileColumns of tile columns of the current picture according to the bitstream (for example, the current picture includes at least one slice forming a non-rectangular shape), Obtaining the number NumTileRows of tile rows of the current picture according to the bitstream, Obtaining the value of a variable NumTilesInPic according to the number NumTileColumns of tile columns and the number NumTileRows of tile rows, When the value of the variable NumTilesInPic is larger than a preset value (for example, the preset value is 3), parsing the value of a syntax element rect_slice_flag from the bitstream, wherein the value of the syntax element rect_slice_flag is used to specify whether slice information is signaled within the PPS, the method comprising the step.

[0336] 14. An embodiment 13 method further including a step of setting the value of the syntax element rect_slice_flag to a fourth default value (for example, the fourth default value is equal to 1) when the value of the variable NumTilesInPic is less than or equal to a preset value.

[0337] 15. The method according to embodiment 13 or 14, wherein the value of the variable NumTilesInPic is equal to NumTileColumns * NumTileRows.

[0338] 16. A method according to any one of embodiments 13 to 15, further including a step of parsing the value of the slice address slice_address of the current slice from the bitstream when the value of the syntax element rect_slice_flag is equal to a fifth default value (for example, the fifth default value is equal to 0) and the value of the variable NumTilesInPic is greater than a preset value, and the current slice is included in the current picture.

[0339] 17. The method according to embodiment 16, wherein the value of the slice address is coded in the slice header of the current slice.

[0340] 18. A method according to any one of embodiments 13 to 17, further including a step of obtaining the number of tiles num_tiles_in_slice_minus1 included in the current slice when the value of the syntax element rect_slice_flag is equal to a fifth default value and the value of the variable NumTilesInPic is greater than a preset value.

[0341] 19. The method according to embodiment 18, wherein the number of tiles num_tiles_in_slice_minus1 is coded in the slice header of the current slice.

[0342] 20. A decoder (30) including a processing circuit for implementing the method according to any one of embodiments 1 to 19.

[0343] 21. A computer program product including program code for executing the method according to any one of Embodiments 1 to 19 when executed on a computer or a processor.

[0344] 22. One or more processors and A non - transitory computer - readable storage medium coupled to the processor and storing programming for execution by the processor, the programming configuring a decoder to implement the method according to any one of Embodiments 1 to 19 when executed by the processor, a decoder including the non - transitory computer - readable storage medium.

[0345] 23. A non - transitory computer - readable medium carrying program code that, when executed by a computer device, causes the computer device to execute the method according to any one of Embodiments 1 to 19.

[0346] The following is an explanation of the encoding method, decoding method, their applications, and the systems using them shown in the above - mentioned embodiments.

[0347] FIG. 8 is a block diagram showing a content supply system 3100 for realizing a content delivery service. This content supply system 3100 includes a capture device 3102, a terminal device 3106, and optionally includes a display 3126. The capture device 3102 communicates with the terminal device 3106 via a communication link 3104. The communication link may include the communication channel 13 described above. The communication link 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any combination of these types.

[0348] The capture device 3102 can generate data and encode the data by the encoding method shown in the above embodiments. Alternatively, the capture device 3102 can deliver the data to a streaming server (not shown), and the server encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 includes, but is not limited to, a camera, a smartphone or a smart pad, a computer or a laptop, a video conferencing system, a PDA, an in-vehicle device, or any combination thereof. For example, the capture device 3102 can include the above-described source device 12. When the data includes video, the video encoder 20 included in the capture device 3102 can actually perform video encoding processing. When the data includes audio (i.e., voice), the audio encoder included in the capture device 3102 can actually perform audio encoding processing. For some actual scenarios, the capture device 3102 distributes the encoded video and audio data by multiplexing them together. For other actual scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed. The capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

[0349] In content supply system 3100, terminal device 310 receives and plays back encoded data. Terminal device 3106 can be a smartphone or smart pad 3108, computer or laptop 3110, network video recorder (NVR) / digital video recorder (DVR) 3112, TV 3114, set-top box (STB) 3116, video conferencing system 3118, video surveillance system 3120, personal digital assistant (PDA) 3122, in-vehicle device 3124, or a combination of any of these, which are devices having data reception and restoration capabilities. For example, terminal device 3106 may include the above-described destination device 14. When the encoded data includes video, video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, the audio decoder included in the terminal device is prioritized to perform audio decoding processing.

[0350] Regarding a terminal device having a display, such as smartphone or smart pad 3108, computer or laptop 3110, network video recorder (NVR) / digital video recorder (DVR) 3112, TV 3114, personal digital assistant (PDA), or in-vehicle device 3124, the terminal device can supply the decoded data to the display of the terminal device. Regarding a terminal device without a display, such as STB 3116, video conferencing system 3118, or video surveillance system 3120, it communicates with external display 3126, and the decoded data is received and shown.

[0351] When each device of this system performs encoding or decoding, the picture encoding device or picture decoding device shown in the above-described embodiments may be used.

[0352] FIG. 9 is a diagram showing the structure of an example of the terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, the protocol progress unit 3202 analyzes the transmission protocol of the stream. The protocol includes, but is not limited to, the Real-Time Streaming Protocol (RTSP), the Hypertext Transfer Protocol (HTTP), the HTTP Live Streaming Protocol (HLS), MPEG-DASH, the Real-Time Transport Protocol (RTP), the Real-Time Messaging Protocol (RTMP), or any combination of these types.

[0353] After the protocol progress unit 3202 processes the stream, a stream file is generated. The file is output to the demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. As described above, for some actual scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed. In this situation, the encoded data is sent to the video decoder 3206 and the audio decoder 3208 without passing through the demultiplexing unit 3204.

[0354] Through multiplex separation processing, a video elementary stream (ES), an audio ES, and optionally subtitles are generated. A video decoder 3206 including the video decoder 30 described in the above embodiment decodes the video ES by the decoding method shown in the above embodiment to generate video frames, and supplies this data to the synchronization unit 3212. The audio decoder 3208 decodes the audio ES to generate audio frames, and supplies this data to the synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in FIG. 9) before supplying the video frames to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in FIG. 9) before supplying the audio frames to the synchronization unit 3212.

[0355] The synchronization unit 3212 synchronizes the video frames and the audio frames, and supplies the video / audio to the video / audio display 3214. For example, the synchronization unit 3212 synchronizes the presentation of the video information and the audio information. The information may be coded in a syntax that uses time stamps related to the presentation of the coded audio data and the visual data as well as time stamps related to the delivery of the data stream itself.

[0356] When subtitles are included in the stream, the subtitle decoder 3210 decodes the subtitles, synchronizes the subtitles with the video frames and the audio frames, and supplies the video / audio / subtitle to the video / audio / subtitle display 3216.

[0357] The present invention is not limited to the above-described system, and either the picture encoding device or the picture decoding device of the above-described embodiment may be incorporated into other systems, for example, an automotive system.

[0358] Mathematical operator The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are more precisely defined, and additional operations such as exponentiation and division of real values are defined. The rules for numbering and counting generally start from 0. For example, "the first" is equivalent to number 0, "the second" is equivalent to number 1, and so on.

[0359] Arithmetic Operators The following arithmetic operators are defined as follows. + Addition - Subtraction (as a two-argument operator) or negation (as a unary prefix operator) * Multiplication including matrix multiplication x y Exponentiation. Defines y to the power of x. In other contexts, such notation is used for superscript writing that is not intended to be interpreted as exponentiation. / Integer division that truncates the result towards zero. For example, 7 / 4 and -7 / -4 are truncated to 1, and -7 / 4 and 7 / -4 are truncated to -1. ÷ Used to represent division in mathematical equations where truncation or rounding is not intended.

Number

Number

[0360] Logical Operators The following logical operators are defined as follows. x && y Boolean logical "product" of x and y x || y Boolean logical "sum" of x and y ! Boolean logic "negation" x ? y : z If x is true or not equal to 0, it is evaluated to the value y, otherwise it is evaluated to the value z.

[0361] Relational operators The following relational operators are defined as follows. > Greater than >= Greater than or equal to < Less than <= Less than or equal to == Equal to != Not equal to

[0362] When a relational operator is applied to a syntax element or variable to which the value "na" (not applicable) is assigned, the value "na" is treated as a different value with respect to the syntax element or variable. The value "na" is considered not equal to any other value.

[0363] Bitwise operators The following bitwise operators are defined as follows. & Bitwise "logical product". When operating on integer arguments, it acts on the two's complement representation of the integer value. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding leading bits equal to 0. | Bitwise "logical sum". When operating on integer arguments, it acts on the two's complement representation of the integer value. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding leading bits equal to 0. ^ Bitwise "exclusive logical sum". When operating on integer arguments, it acts on the two's complement representation of the integer value. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding leading bits equal to 0. x >> y Arithmetic right shift by y bits of the two's complement representation of the integer x. This function is defined only for non-negative integer values of y. The bit shifted into the most significant bit (MSB) as a result of the right shift has a value equal to the MSB of x before the shift operation. x << y Arithmetic left shift by y bits of the two's complement representation of the integer x. This function is defined only for non-negative integer values of y. The bit shifted into the least significant bit (LSB) as a result of the left shift has a value equal to 0.

[0364] Assignment operator The following arithmetic operators are defined as follows. = Assignment operator ++ Increment, i.e., x++ is equivalent to x = x + 1, and when used as an array index, the value of the variable is evaluated before the increment operation. -- Decrement, i.e., x-- is equivalent to x = x - 1, and when used as an array index, the value of the variable is evaluated before the decrement operation. += Increment by the specified amount, i.e., x += 3 is equivalent to x = x + 3, and x += (-3) is equivalent to x = x + (-3). -= Decrement by the specified amount, i.e., x -= 3 is equivalent to x = x - 3, and x -= (-3) is equivalent to x = x - (-3).

[0365] Range notation The following notations are used to specify a range of values. x = y..z x takes integer values from y to z, inclusive, where x, y, and z are integer values and z is greater than y.

[0366] Mathematical functions The following mathematical functions are defined.

Number

Mathematics

Mathematics

Mathematics

Mathematics

Mathematics

[0367] Operator precedence When the precedence in the expression is not explicitly indicated using parentheses, the following rules apply. - Operations with higher precedence are evaluated before any operations with lower precedence. - Operations with the same precedence are evaluated in order from left to right.

[0368] The following table shows the operator precedence from the highest to the lowest, and the higher the position in the table, the higher the precedence.

[0369] Regarding the operators also used in the C programming language, the precedence used in this specification is the same as that used in the C programming language.

[0370] [Table 16]

[0371] Text description of logical operations In the text, in the following form, that is, if(condition 0) Statement 0 else if(condition 1) Statement 1 ... else / * Comment conveying information about the remaining conditions * / Statement n Logical operation statements mathematically described in the form of As follows... / ... The following applies. - If condition 0, statement 0 - Otherwise, if condition 1, statement 1 -... - Otherwise (a comment conveying information about the remaining conditions), statement n

[0372] Each "if... then..., else if... then..., otherwise..." statement in the text is introduced by "As follows..." or "... The following applies." immediately following "if... then...". The last condition of "if... then..., else if... then..., otherwise..." is always "otherwise...". The alternatingly inserted "if... then..., else if... then..., otherwise..." statements can be identified by matching "As follows..." or "... The following applies." with the ending "otherwise...".

[0373] In the text, in the following form, that is, if( condition 0a && condition 0b ) statement 0 else if( condition 1a || condition 1b ) statement 1 ... else statement n The logical operation statements described mathematically in the form of can be described as follows. As follows... / ... The following applies. - If all of the following conditions are true, statement 0 - condition 0a - condition 0b - Otherwise, if one or more of the following conditions are true, statement 1 - condition 1a - condition 1b -... - Otherwise, statement n

[0374] In the present document, in the following form, namely, if (condition 0) Statement 0 if (condition 1) Statement 1 A statement of a logical operation mathematically described in the form of may be described as follows. When condition 0, statement 0 When condition 1, statement 1

[0375] Although embodiments of the present invention have been mainly described based on video coding, embodiments of the coding system 10, the encoder 20, and the decoder 30 (and the corresponding system 10), as well as other embodiments described herein, may be configured for the processing or coding of still pictures, i.e., individual pictures independent of any preceding or consecutive pictures similar to video coding. Note that generally, when the processing coding of a picture is limited to a single picture 17, only the inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other functions (also called tools or technologies) of the video encoder 20 and the video decoder 30, for example, residual calculation 204 / 304, transformation 206, quantization 208, inverse quantization 210 / 310, (inverse) transformation 212 / 312, segmentation 262 / 362, intra prediction 254 / 354, and / or loop filters 220, 320, and entropy coding 270, and entropy decoding 304 may be equally used for the processing of still pictures.

[0376] For example, the encoder 20 and decoder 30, and embodiments of the functions described herein in connection with, for example, the encoder 20 and decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on a computer-readable medium as one or more instructions or code or transmitted over a communication medium and may be executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium, or a communication medium including any medium that facilitates transfer of a computer program from one place to another, for example, by a communication protocol. In this way, generally, the computer-readable medium may correspond to (1) a tangible computer-readable storage medium that is non-transitory or (2) a communication medium such as a signal or carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0377] By way of example and not limitation, such computer-readable storage media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store the desired program code in the form of instructions or data structures and that is accessible by a computer. Also, any connection can be properly termed a computer-readable medium. For example, if the instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but instead are directed to non-transient, tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray (registered trademark) disc, where disk typically magnetically reproduces data, while disc optically reproduces data using a laser. Combinations of the above should also be included within the scope of computer-readable media.

[0378] The commands may be executed by one or more processors such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, the term "processor" as used herein may refer to either the foregoing structures or any other structure suitable for implementation of the techniques described herein. Additionally, in some aspects, the functions described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Also, the techniques may be implemented entirely in one or more circuits or logic elements.

[0379] The techniques of the present disclosure may be implemented in a variety of devices or apparatuses including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize aspects of the functionality of a device configured to execute the disclosed techniques, but implementation by different hardware units is not necessarily required. Rather, as described above, the various units may be provided by a combination in a codec hardware unit or by a set of interoperable hardware units including one or more of the foregoing processors in conjunction with suitable software and / or firmware.

Explanation of Signs

[0380] 1 subpicture 10 video coding system, coding system 12 source device 13 encoded picture data, communication channel 14 destination device 16 picture source 17 Pictures, picture data, raw picture, raw picture data, monochrome picture, color picture, current picture 18 Preprocessor, preprocessing unit, picture preprocessor 19 Preprocessed picture, preprocessed picture data 20 Video encoder, encoder 21 Encoded picture data, encoded bitstream 22 Communication interface, communication unit 28 Communication interface, communication unit 30 Decoder, video decoder 31 Decoded picture data, decoded picture 32 Postprocessor, postprocessing unit 33 Postprocessed picture data, postprocessed picture 34 Display device 46 Processing circuit 100 Video encoder 201 Input, input interface 203 Picture block, original block, current block, segmented block, current picture block 204 Residual calculation unit, residual calculation 205 Residual block, residual 206 Transformation processing unit, transformation 207 Transformation coefficient 208 Quantization unit, quantization 209 Quantized coefficient, quantized transformation coefficient, quantized residual coefficient 210 Inverse quantization unit, inverse quantization 211 Dequantized coefficient, dequantized residual coefficient 212 Inverse transformation processing unit, (inverse) transformation 213 Reconstructed residual block, inverse quantized coefficient, transformation block 214 Reconstruction unit, adder, summer 215 Reconstructed block 216 Buffer 220 Loop Filter Unit, Loop Filter 221 Filtered Block, Filtered Reconstructed Block 230 Decoded Picture Buffer (DPB) 231 Decoded Picture 244 Inter Prediction Unit 254 Intra Prediction Unit, Inter Prediction Unit, Intra Prediction 260 Mode Selection Unit 262 Partitioning Unit, Partitioning 265 Prediction Block, Predictor 266 Syntax Element 270 Entropy Coding Unit, Entropy Coding 272 Output, Output Interface 304 Entropy Decoding Unit, Residual Calculation, Entropy Decoding 309 Quantized Coefficient 310 Inverse Quantization Unit, Inverse Quantization 311 Dequantized Coefficient, Transform Coefficient 312 Inverse Transform Processing Unit, (Inverse) Transform, Output 313 Reconstructed Residual Block 314 Reconstruction Unit, Adder, Adder 315 Reconstructed Block 320 Loop Filter, Loop Filter Unit, Loop Filtering Unit 321 Filtered Block, Decoded Video Block 330 Decoded Picture Buffer (DPB), Decoded Picture Buffer (DBP) 331 Decoded Picture 344 Inter Prediction Unit 354 Intra Prediction Unit, Intra Prediction 360 Mode Application Unit 362 Partitioning 365 Prediction Block 400 Video Coding Device 410 Incoming Port, Input Port 420 Receiver Unit (Rx) 430 Processor, Logic Unit, Central Processing Unit (CPU) 440 Transmitter Unit (Tx) 450 Transmission Port, Output Port 460 Memory 470 Coding Module 500 Device 502 Processor 504 Memory 506 Data 508 Operating System 510 Application Program 512 Bus 514 Secondary Storage 518 Display 1600 Video Decoder 1610 Acquisition Unit 1620 Determination Unit 1700 Video Encoder 1710 Determination Unit 1720 Encoding Unit 3100 Content Supply System 3102 Capture Device 3104 Communication Link 3106 Terminal Device 3108 Smartphone, Smart Pad 3110 Computer, Laptop 3112 Network Video Recorder (NVR) / Digital Video Recorder (DVR) 3114 TV 3116 Set - Top Box (STB) 3118 Video Conference System 3120 Video Surveillance System 3122 Personal Digital Assistant (PDA) 3124 In - Vehicle Device 3126 Display 3202 Protocol Progress Unit 3204 Multiplexing Separation Unit 3206 Video Decoder 3208 Audio Decoder 3210 Subtitle Decoder 3212 Synchronization Unit 3214 Video / Audio Display 3216 Video / Audio / Subtitle Display

Claims

1. 1. A device for storing a bitstream, comprising: A communication interface, a processor, and a storage medium; the communication interface is configured to receive and / or transmit the bitstream; the storage medium is configured to store the bitstream; the bitstream is generated by dividing a current picture of a video or image signal into a number of blocks, and includes a sequence parameter set (SPS) and a number of syntax elements to be applied to the video sequence; the plurality of syntax elements includes a third syntax element in the SPS, a value of the third syntax element being used to specify to a decoding device a maximum number of temporal sub-layers present in the video sequence; the plurality of syntax elements further includes a first syntax element in the SPS, a value of the first syntax element being used to specify to the decoding device whether a Decoded Picture Buffer (DPB) parameters syntax structure is present in the SPS; A device, wherein if the value of the first syntax element specifies that the DPB parameter syntax structure is present in the SPS and the maximum number of temporal sublayers is greater than one, the plurality of syntax elements further includes a second syntax element in the SPS, the value of the second syntax element is used to specify to the decoding device the presence of a DPB syntax element in the DPB parameter syntax structure, and the second syntax element is applied by the decoding device to each temporal sublayer except for a topmost temporal sublayer in the video sequence.

2. The device of claim 1 , wherein the DPB syntax elements are used to reconstruct the video sequence.

3. The device of claim 1, wherein if the value of the second syntax element specifies that the DPB syntax element is not present in the DPB parameter syntax structure, the value of the DPB syntax element is set to a value equal to the value of another DPB syntax element that applies to the top-level temporal sublayer in the DPB parameter syntax structure.

4. The device of claim 1 , wherein the DPB syntax elements are used to configure a DPB at a decoder side.

5. The DPB syntax elements are used to configure a DPB at a decoder side, The device of claim 1 , wherein the video sequence is reconstructed when the DPB satisfies the values ​​of the DPB syntax elements.

Images