Avoiding redundant signaling in multi-layer video bitstream

Abstract

To provide a decoding method and an encoding method that eliminate redundancy when signaling parameters corresponding to layers in a multi-layer bitstream.SOLUTION: A decoding method includes receiving a video bitstream that includes a plurality of layers having sub-layers and a video parameter set (VPS) including a first flag having a first value. The first flag specifies that temporal identifiers (IDs) of top-level sub-layer representations for level information, a decoded picture buffer (DPB) parameter, and a hypothetical decoder refresh (HRD) parameter are not present in the VPS and are inferred to be equal to a maximum number of sub-layers present in one of the plurality of layers specified by the VPS. The method also includes obtaining the level information, the HRD parameter, and the DPB parameter corresponding to the temporal ID of the top-level sub-layer representation from the VPS and decoding a picture from one of the plurality of layers.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application US05444806 claims the benefit of U.S. Provisional Patent Application No. 62 / 911,808, entitled "Scalability in Video Coding," filed on October 7, 2019 by Ye-Kui Wang, which is incorporated herein by reference.

[0002] Generally, this disclosure describes techniques for multi-layer video bitstreams in video coding. More specifically, this disclosure describes techniques for eliminating redundancy in signaling parameters corresponding to layers in a multi-layer video bitstream in video coding. [Background technology]

[0003] The amount of video data required to render even a relatively short video can be substantially large, resulting in complications when the data is streamed or otherwise transmitted over a communication network that has limited bandwidth capacity. Thus, in today's telecommunication networks, video data is typically compressed before being transmitted. The size of the video can also be an issue when the video is stored in a storage device, which may also have limited memory resources. Video compression devices often 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 a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. With limited network resources and ever-increasing demands for video quality, improvements in compression and decompression techniques that improve compression ratios with little or no sacrifice in image quality are desirable. Summary of the Invention [Means for solving the problem]

[0004] A first aspect relates to a method of decoding implemented by a video decoder, comprising: receiving, by the video decoder, a video bitstream including a plurality of layers having sub-layers and a video parameter set (VPS) including a first flag having a first value, the first flag having the first value specifying that a temporal identifier (ID) of a top sub-layer representation for level information, a temporal identifier (ID) of the top sub-layer representation for decoded picture buffer (DPB) parameters, and a temporal identifier (ID) of the top sub-layer representation for hypothetical decoder refresh (HRD) parameters are not present in the VPS and are inferred to be equal to a maximum number of sub-layers that may be present in one layer of the plurality of layers specified by the VPS; obtaining, by the video decoder, DPB parameters corresponding to the level information, the HRD parameters, and the temporal ID of the top sub-layer representation from the VPS; and decoding, by the video decoder, a picture from one of the plurality of layers to obtain a decoded picture.

[0005] The method provides a technique to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0006] Optionally, in any of the aforementioned aspects, another implementation of the aspect specifies that the maximum number of sublayers is in the range of 1 to 7, the first value is 1, and the second value is 0.

[0007] Optionally, in any of the aforementioned aspects, another implementation form of the aspect provides that the level information is included in a Profile, Tier, and Level (PTL) parameter.

[0008] Optionally, in any of the aforementioned aspects, another implementation form of the aspect provides that the level information is present in an i-th profile_tier_level() syntax structure in the VPS.

[0009] Optionally, in any of the aforementioned aspects, another implementation form of the aspect provides that the DPB parameters are present in an i-th dpb_parameters() syntax structure in the VPS.

[0010] Optionally, in any of the aforementioned aspects, another implementation form of the aspect specifies that the HRD parameters in the i-th ols_timing_hrd_parameters() syntax structure are in a VPS or a sequence parameter set (SPS).

[0011] Optionally, in any of the aforementioned aspects, another implementation form of the aspect specifies that the picture is decoded using one or both of the level information and the DPB parameters.

[0012] Optionally, in any of the aforementioned aspects, another implementation of the aspect specifies that the picture is decoded without using the HRD parameters.

[0013] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides for displaying the decoded picture on a display of the electronic device.

[0014] A second aspect relates to a method of encoding implemented by a video encoder, the method including generating, by the video encoder, a video parameter set (VPS) including a plurality of layers having sub-layers and a first flag; setting, by the video encoder, the first flag to a first value to specify that a temporal identifier (ID) of a top-level sub-layer representation for level information, a temporal identifier (ID) of a top-level sub-layer representation for decoded picture buffer (DPB) parameters, and a temporal identifier (ID) of a top-level sub-layer representation for hypothetical decoder refresh (HRD) parameters are not present in the VPS and should be inferred to be equal to a maximum number of sub-layers that may be present in one layer of the plurality of layers specified by the VPS; encoding, by the video encoder, the plurality of layers and the VPS into a video bitstream; and storing, by the video encoder, the video bitstream for communication to a video decoder.

[0015] The method provides a technique to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0016] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the maximum number of sublayers is in the range of 1 to 7.

[0017] Optionally, in any of the aforementioned aspects, another implementation form of the aspect provides that the level information is included in a Profile, Tier, and Level (PTL) parameter.

[0018] Optionally, in any of the aforementioned aspects, another implementation of the aspect specifies that the level information is present in an i-th profile_tier_level() syntax structure in the VPS, the DPB parameters are present in an i-th dpb_parameters() syntax structure in the VPS, and the HRD parameters are present in an i-th ols_timing_hrd_parameters() syntax structure in the VPS or a sequence parameter set (SPS).

[0019] Optionally, in any of the aforementioned aspects, another implementation form of the aspect specifies using the HRD parameters to determine whether the encoded video bitstream is conforming.

[0020] A third aspect relates to a decoding device comprising: a receiver configured to receive a video bitstream including a plurality of layers having sub-layers and a video parameter set (VPS) including a first flag having a first value, the first flag having the first value specifying that a temporal identifier (ID) of a top sub-layer representation for level information, a temporal identifier (ID) of the top sub-layer representation for decoded picture buffer (DPB) parameters, and a temporal identifier (ID) of the top sub-layer representation for hypothetical decoder refresh (HRD) parameters are not present in the VPS and are inferred to be equal to a maximum number of sub-layers that may be present in one of the plurality of layers specified by the VPS; and a processor coupled to a memory, the processor configured to execute instructions to cause the decoding device to obtain from the VPS the level information, the HRD parameters, and the DPB parameters corresponding to the temporal ID of the top sub-layer representation, and to decode a picture from one of the plurality of layers to obtain a decoded picture.

[0021] The decoding device provides a technique to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0022] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the maximum number of sublayers is in the range of 1 to 7.

[0023] Optionally, in any of the aforementioned aspects, another implementation form of the aspect provides that the level information is included in a Profile, Tier, and Level (PTL) parameter.

[0024] Optionally, in any of the aforementioned aspects, another implementation of the aspect specifies that the level information is present in an i-th profile_tier_level() syntax structure in the VPS, the DPB parameters are present in an i-th dpb_parameters() syntax structure in the VPS, and the HRD parameters are present in an i-th ols_timing_hrd_parameters() syntax structure in the VPS or a sequence parameter set (SPS).

[0025] Optionally, in any of the aforementioned aspects, another implementation form of the aspect specifies that the picture is decoded using one or both of the level information and the DPB parameters.

[0026] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides for the display being configured to display the decoded picture.

[0027] A fourth aspect relates to an encoding device comprising: a memory containing instructions; a processor coupled to the memory, the processor configured to implement instructions to cause the encoding device to generate a video parameter set (VPS) including a plurality of layers having sub-layers and a first flag, set the first flag to a first value to specify that a temporal identifier (TemporalID) of a top-level sub-layer representation for level information, a decoded picture buffer (DPB) parameter, and a hypothetical decoder refresh (HRD) parameter is not present in the VPS and should be inferred to be equal to a maximum number of sub-layers that may be present in one of the plurality of layers specified by the VPS; and encode the plurality of layers and the VPS into a video bitstream; and a transmitter coupled to the processor, the transmitter configured to transmit the video bitstream toward a video decoder.

[0028] The encoding device provides a technique to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0029] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the maximum number of sublayers is in the range of 1 to 7.

[0030] Optionally, in any of the aforementioned aspects, another implementation form of the aspect provides that the level information is included in a Profile, Tier, and Level (PTL) parameter.

[0031] Optionally, in any of the aforementioned aspects, another implementation of the aspect specifies that the level information is present in an i-th profile_tier_level() syntax structure in the VPS, the DPB parameters are present in an i-th dpb_parameters() syntax structure in the VPS, and the HRD parameters are present in an i-th ols_timing_hrd_parameters() syntax structure in the VPS or a sequence parameter set (SPS).

[0032] A fifth aspect relates to a coding device comprising: a receiver configured to receive a picture to encode or a bitstream to decode, a transmitter coupled to the receiver and configured to transmit the bitstream to a decoder or transmit a decoded image to a display, a memory coupled to at least one of the receiver or the transmitter and configured to store instructions, and a processor coupled to the memory and configured to execute the instructions stored in the memory to perform any of the methods disclosed herein.

[0033] The coding device provides a technique to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0034] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides a display configured to display the decoded picture.

[0035] A sixth aspect relates to a system comprising an encoder and a decoder in communication with the encoder, the encoder or decoder including a decoding device, encoding device, or coding apparatus disclosed herein.

[0036] The system provides techniques to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0037] A seventh aspect relates to a means for coding, comprising: receiving means configured to receive a picture to encode or to receive a bitstream to decode, transmitting means coupled to the receiving means and configured to transmit the bitstream to the decoding means or to transmit the decoded image to the display means, storage means coupled to at least one of the receiving means or the transmitting means and configured to store instructions, and processing means coupled to the storage means and configured to execute the instructions stored in the storage means to perform any of the methods disclosed herein.

[0038] The means for coding provides a technique to ensure that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience to a user when a video is transmitted, received, and / or viewed.

[0039] For the sake of clarity, any one of the above-described embodiments may be combined with any one or more of the other above-described embodiments to form new embodiments within the scope of the present disclosure.

[0040] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

[0041] For a more complete understanding of the present disclosure, reference is now made to the following brief description taken in conjunction with the accompanying drawings and detailed description, in which like numerals represent like parts, and in which: [Brief description of the drawings]

[0042] [Figure 1] 1 is a flowchart of an exemplary method for coding a video signal. [Diagram 2] 1 is a schematic diagram of an example coding and decoding (codec) system for video coding. [Diagram 3] 1 is a schematic diagram illustrating an example video encoder. [Figure 4] 1 is a schematic diagram illustrating an exemplary video decoder. [Diagram 5] FIG. 1 illustrates an example of multi-layer coding for spatial scalability. [Figure 6] FIG. 1 illustrates an example of multi-layer coding using output layer sets (OLS). [Figure 7] FIG. 2 illustrates an example multi-layer video sequence configured for temporal scalability. [Figure 8] FIG. 2 illustrates one embodiment of a video bitstream. [Figure 9] 1 is a diagram of one embodiment of a method for decoding a coded video bitstream. [Figure 10] FIG. 2 is a diagram of one embodiment of a method for encoding a coded video bitstream. [Figure 11] 1 is a schematic diagram of a video coding device. [Figure 12] FIG. 2 is a schematic diagram of an embodiment of a means for coding; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] First, while an exemplary implementation of one or more embodiments is presented below, it should be understood that the disclosed system and / or method may be implemented using any number of currently known or existing technologies. The present disclosure should in no way be limited to the exemplary implementations, drawings, and technologies illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with the full scope of equivalents.

[0044] The following terms are defined as follows unless used in the present specification in a contrary context. Specifically, the following definitions are intended to further clarify the present disclosure. However, terms may be explained differently in different contexts. Therefore, the following definitions should be considered as supplementary and not as limiting any other definitions of the explanations provided for such terms in the present specification.

[0045] A bitstream is a sequence of bits that includes video data that is compressed for transmission between an encoder and a decoder. An encoder is a device configured to compress video data into a bitstream using an encoding process. A decoder is a device configured to reconstruct video data into a bitstream for display using a decoding process. A picture is an array of luma samples and / or an array of chroma samples that make up a frame or a field thereof. A picture being encoded or decoded may be referred to as a current picture for clarity of description. A reference picture is a picture that contains reference samples that can be used when coding other pictures by reference according to inter-prediction and / or inter-layer prediction. A reference picture list is a list of reference pictures used for inter-prediction and / or inter-layer prediction. Some video coding systems utilize two reference picture lists, which may be denoted as reference picture list 1 and reference picture list 0. A reference picture list structure is an addressable syntax structure that includes multiple reference picture lists.

[0046] A profile, tier, and level (PTL) parameter is a syntax structure that provides profile, tier, and / or level information (e.g., the i-th profile_tier_level() syntax structure). The PTL parameter may be specified as a profile_tier_level() syntax structure.

[0047] Inter prediction is a mechanism for coding samples of a current picture by referencing indicated samples in a reference picture different from the current picture when the reference picture and the current picture are in the same layer. A reference picture list structure entry is an addressable location within a reference picture list structure that indicates the reference picture associated with the reference picture list.

[0048] A slice header is a part of a coded slice that contains data elements related to all video data in the tile represented in the slice. A picture parameter set (PPS) is a parameter set that contains data related to an entire picture. More specifically, a PPS is a syntax structure that contains syntax elements that apply to zero or more entire coded pictures as determined by the syntax elements found in each picture header. A sequence parameter set (SPS) is a parameter set that contains data related to a sequence of pictures. An access unit (AU) is a set of one or more coded pictures that are associated with the same display time (e.g., the same picture order count) for output from a decoded picture buffer (DPB) (e.g., for display to a user). An access unit delimiter (AUD) is an indicator or data structure used to indicate the start of an AU or the boundary between AUs. A decoded video sequence is a sequence of pictures reconstructed by a decoder in preparation for display to a user.

[0049] A network abstraction layer (NAL) unit is a syntax structure that contains data in the form of a raw byte sequence payload (RBSP), an indication of the type of data, interspersed with emulation prevention bytes where desired. A video coding layer (VCL) NAL unit is a NAL unit that is coded to contain video data, such as a coded slice of a picture. A non-VCL NAL unit is a NAL unit that contains non-video data, such as syntax and / or parameters that support decoding the video data, performing conformance checks, or other operations. A layer is a set of VCL NAL units and associated non-VCL NAL units that share specified characteristics (e.g., a common resolution, frame rate, picture size, etc.). The VCL NAL units of a layer may share a particular value of the NAL unit header layer identifier (nuh_layer_id). A coded picture is a coded representation of a picture that includes VCL NAL units with a particular value of the NAL unit header layer identifier (nuh_layer_id) in the access unit (AU) and includes all coding tree units (CTUs) of the picture. A decoded picture is a picture produced by applying a decoding process to a coded picture.

[0050] An output layer set (OLS) is a set of layers where one or more layers are designated as output layers. An output layer is a layer designated for output (e.g., to a display). The 0th OLS is an OLS that contains only the lowest layer (the layer with the lowest layer identifier) ​​and therefore only output layers. A video parameter set (VPS) is a data unit that contains parameters related to the entire video. Inter-layer prediction is a mechanism for coding a current picture in a current layer by reference to a reference picture in a reference layer, where the current picture and the reference picture are included in the same AU and the reference layer contains a lower nuh_layer_id than the current layer.

[0051] A profile is a defined set of coding tools used to create a compliant or conforming bitstream. Each profile specifies a subset of algorithmic features and constraints that shall be supported by all decoders conforming to that profile. Tiers and levels are constraints that define a bitstream in terms of maximum bitrate, maximum luma sample rate, maximum luma picture size, minimum compression ratio, maximum number of slices allowed, and maximum number of tiles allowed. Lower tiers are more constrained than higher tiers, and lower levels are more constrained than higher levels. Profile, Tier, and Level (PTL) parameters are syntax structures that provide profile, tier, and / or level information.

[0052] A temporal scalable bitstream is a bitstream coded in multiple layers that provide various temporal resolutions / frame rates (e.g., each layer is coded to support a different frame rate). A sublayer is a temporal scalable layer of a temporal scalable bitstream that includes VCL NAL units and associated non-VCL NAL units with a particular temporal identifier value. For example, a temporal sublayer is a layer that includes video data associated with a specified frame rate. A sublayer representation is a subset of a bitstream that includes NAL units of a particular sublayer and lower sublayer. Thus, one or more temporal sublayers may be combined to achieve a sublayer representation that can be decoded to result in a video sequence with a specified frame rate. An OLS index is an index that uniquely identifies a corresponding OLS. A temporal identifier (TemporalID or TemporalID) is a data element that indicates that the data corresponds to a temporal placement within a video sequence. The value of TemporalId shall be the same for all VCL NAL units of an AU. The value of TemporalId of a coded picture, PU, ​​or AU is the value of TemporalId of the VCL NAL units of the coded picture, PU, ​​or AU. The value of TemporalId of a sub-layer representation is the maximum value of TemporalId of all VCL NAL units in the sub-layer representation.

[0053] The top sublayer representation is the sublayer representation that is furthest from the base sublayer, i.e., there are no other sublayers above, beyond or higher than the top sublayer representation.

[0054] The sub-bitstream extraction process is a process that removes from the bitstream those NAL units that do not belong to a target set as determined by a target OLS index and a target highest temporal ID. The sub-bitstream extraction process results in an output sub-bitstream that contains NAL units from the bitstream that are part of the target set.

[0055] HRD is a decoder model running on an encoder that checks the variability of the bitstream produced by the encoding process to verify its conformance to specified constraints. Bitstream conformance testing is testing to determine whether the encoded bitstream conforms to a standard such as Versatile Video Coding (VVC). HRD parameters are syntax elements that initialize and / or define the operating conditions of the HRD. Sequence-level HRD parameters are HRD parameters that apply to the entire coded video sequence. Maximum HRD temporal ID (hrd_max_tid[i]) specifies the temporal ID of the highest sublayer representation whose HRD parameters are included in the i-th set of OLS HRD parameters. General HRD parameters (general_hrd_parameters) syntax structure is a syntax structure that contains sequence-level HRD parameters. An operation point (OP) is a temporal subset of an OLS identified by an OLS index and a maximum temporal ID. A test target OP (targetOp) is an OP selected for conformance testing in the HRD. The target OLS is the OLS selected to extract from the bitstream. The decoding unit HRD parameters present flag (decoding_unit_hrd_params_present_flag) is a flag indicating whether the corresponding HRD parameters operate at the decoding unit (DU) level or the AU level. The coded picture buffer (CPB) is a first-in, first-out buffer in the HRD that contains coded pictures in decoding order for use during bitstream conformance verification. The decoded picture buffer (DPB) is a buffer for holding decoded pictures for reference, output reordering, and / or output delay.

[0056] The decoded picture buffer (DPB) parameters are syntax structures that provide the DPB size and, optionally, the maximum picture reorder number and maximum latency information, which may be collectively referred to by the acronym MRML.

[0057] Acronyms used in this specification are: coding tree block (CTB), coding tree unit (CTU), coding unit (CU), coded video sequence (CVS), joint video experts team (JVET), motion constrained tile set (MCTS), maximum transmission unit (MTU), network abstraction layer (NAL), picture order count (POC), picture parameter set (PPS), raw byte sequence payload (RBSP), sequence parameter set (SPS), versatile video coding (VVC), and working draft (WD).

[0058] 1 is a flow chart of an exemplary operational method 100 of coding a video signal. Specifically, the video signal is encoded at an encoder. The encoding process compresses the video signal by using various mechanisms to reduce the video file size. The smaller file size allows the compressed video file to be transmitted to a user while reducing the associated bandwidth overhead. A decoder then decodes the compressed video file and reconstructs the original video signal for display to an end user. The decoding process generally mirrors the encoding process to allow the decoder to consistently reconstruct the video signal.

[0059] At step 101, a video signal is input to an encoder. For example, the video signal may be an uncompressed video file stored in memory. As another example, the video file may be captured by a video capture device, such as a video camera, and encoded to support live streaming of the video. The video file may include both audio and video components. The video component includes a series of image frames that, when viewed in sequence, give the visual impression of motion. The frames include pixels that are represented in terms of light, referred to herein as luma components (or luma samples), and color, referred to as chroma components (or color samples). In some examples, the frames may also include depth values ​​to support three-dimensional displays.

[0060] At step 103, the video is partitioned into several blocks. Partitioning involves subdividing pixels in each frame into square and / or rectangular blocks for compression. For example, in High Efficiency Video Coding (HEVC) (also known as H.265 and MPEG-H Part 2), a frame may first be partitioned into coding tree units (CTUs), which are blocks of a predefined size (e.g., 64 pixels by 64 pixels). A CTU contains both luma and chroma samples. A coding tree may be employed to partition a CTU into several blocks and then recursively subdivide the blocks until a configuration that supports further encoding is achieved. For example, the luma component of a frame may be subdivided until each block contains relatively homogenous illumination values. Furthermore, the chroma component of a frame may be subdivided until each block contains relatively homogenous color values. Thus, the partitioning mechanism differs depending on the content of the video frame.

[0061] At step 105, various compression mechanisms are employed to compress the image blocks partitioned at step 103. For example, inter prediction and / or intra prediction may be employed. Inter prediction is designed to take advantage of the fact that objects in a common scene tend to appear in successive frames. Thus, a block depicting an object in a reference frame need not be repeatedly described in adjacent frames. Specifically, an object such as a table may remain in a constant position across multiple frames. Thus, once a table is described, adjacent frames may refer back to the reference frame. Pattern matching mechanisms may be employed to match objects across multiple frames. Additionally, objects may be represented that move across multiple frames, such as due to object movement or camera movement. As a particular example, a video may show a car moving across the screen across multiple frames. Motion vectors may be used to describe such movement. A motion vector is a two-dimensional vector that provides an offset from the coordinates of the object in the frame to the coordinates of the object in the reference frame. As such, inter prediction may encode image blocks in a current frame as a set of motion vectors that indicate an offset from a corresponding block in the reference frame.

[0062] Intra prediction encodes blocks within a common frame. Intra prediction exploits the fact that luma and chroma components tend to cluster within a frame. For example, a green patch in a part of a tree tends to be positioned adjacent to a similar patch of green. Intra prediction uses multiple directional prediction modes (e.g., 33 types in HEVC), planar mode, and direct current (DC) mode. These directional modes indicate that the current block is similar / same as the samples of neighboring blocks in the corresponding direction. Planar mode indicates that a series of blocks along a row / column (e.g., a plane) may be interpolated based on the neighboring blocks at the end of the row. Planar mode actually indicates a smooth transition of light / color across the row / column by using a relatively constant gradient in the changing values. DC mode is used for boundary smoothing and indicates that the block is similar / same as the average value associated with the samples of all neighboring blocks related to the angular direction of the directional prediction mode. Thus, intra prediction blocks can represent image blocks as various related prediction mode values ​​rather than actual values. Furthermore, inter prediction blocks can represent image blocks as motion vector values ​​rather than actual values. In either case, the prediction block may not exactly represent the image block in some cases. Any differences are contained within a residual block. To further compress the file, a transform may be applied to the residual block.

[0063] In step 107, various filtering techniques may be applied. In HEVC, filters are applied according to an in-loop filtering scheme. Block-based prediction, as described above, may result in blocky images at the decoder. Furthermore, the block-based prediction scheme may encode a block and then reconstruct the encoded block for later use as a reference block. The in-loop filtering scheme iteratively applies a noise suppression filter, a deblocking filter, an adaptive loop filter, and a sample adaptive offset (SAO) filter to the block / frame. These filters reduce such blocking artifacts, so that the encoded file can be accurately reconstructed. Furthermore, these filters reduce artifacts in the reconstructed reference block, so that the artifacts are less likely to cause further artifacts in subsequent blocks that are encoded based on the reconstructed reference block.

[0064] After the video signal has been partitioned, compressed, and filtered, the resulting data is encoded into a bitstream at step 109. The bitstream includes the data described above, as well as any signaling data desired to support proper video signal reconstruction at the decoder. For example, such data may include partition data, prediction data, residual blocks, and various flags that send coding instructions to the decoder. The bitstream may be stored in memory for transmission to the decoder upon request. The bitstream may also be broadcast and / or multicast to multiple decoders. Creation of the bitstream is an iterative process. Thus, steps 101, 103, 105, 107, and 109 may be performed sequentially and / or simultaneously across multiple frames and blocks. The order depicted in FIG. 1 is presented for clarity and ease of explanation and is not intended to limit the video coding process to a particular order.

[0065] The decoder receives the bitstream and begins the decoding process at step 111. Specifically, the decoder uses an entropy decoding scheme to convert the bitstream into corresponding syntax and video data. The decoder uses syntax data from the bitstream to determine the partition for the frame at step 111. The partition should match the result of the block partitioning at step 103. We now describe entropy encoding / decoding as employed at step 111. The encoder makes many choices in the compression process, such as selecting a block partitioning scheme from several possible choices based on the spatial positioning of values ​​in the input image. In signaling the exact choice, multiple bins may be used. As used herein, a bin is a binary value (e.g., a bit value that can change depending on the context) that is treated as a variable. Entropy coding allows the encoder to discard any options that are clearly infeasible for a particular case, leaving a set of acceptable options. Each acceptable option is then assigned a codeword. The length of the codeword is based on the number of allowable options (e.g., one bin for two options, two bins for three to four options, etc.). The encoder then encodes a codeword for the selected option. This scheme reduces the size of the codeword since it is desirable to uniquely indicate a selection from a small subset of allowable options, as opposed to uniquely indicating a selection from a potentially large set of all possible options. The decoder then decodes the selection by determining the set of allowable options in a manner similar to the encoder. By determining the set of allowable options, the decoder can read the codeword and determine the selection made by the encoder.

[0066] In step 113, the decoder performs block decoding. Specifically, the decoder employs an inverse transform to generate a residual block. The decoder then uses the residual block and a corresponding prediction block to reconstruct an image block according to the partitioning. The prediction block may include both intra-prediction blocks and inter-prediction blocks as generated in the encoder in step 105. The reconstructed image block is then positioned within a frame of the reconstructed video signal according to the partitioning data determined in step 111. The syntax for step 113 may also be signaled in the bitstream via entropy coding as described above.

[0067] At step 115, filtering is performed on the frames of the reconstructed video signal in a manner similar to step 107 at the encoder. For example, a noise suppression filter, a deblocking filter, an adaptive loop filter, and an SAO filter may be applied to the frames to remove blocking artifacts. After the frames are filtered, the video signal may be output to a display at step 117 for viewing by an end user.

[0068] FIG. 2 is a schematic diagram of an exemplary coding and decoding (codec) system 200 for video coding. Specifically, the codec system 200 provides functionality to support implementation of the operational method 100. The codec system 200 is generalized to depict components employed in both an encoder and a decoder. The codec system 200 receives and segments a video signal as described with respect to steps 101 and 103 of the operational method 100, resulting in a segmented video signal 201. The codec system 200 then compresses the segmented video signal 201 into a coded bitstream when operating as an encoder as described with respect to steps 105, 107, and 109 in the method 100. The codec system 200 generates an output video signal from the bitstream when operating as a decoder as described with respect to steps 111, 113, 115, and 117 of the operational method 100. Codec system 200 includes a general coder control component 211, a transform scaling and quantization component 213, an intra picture estimation component 215, an intra picture prediction component 217, a motion compensation component 219, a motion estimation component 221, a scaling and inverse transform component 229, a filter control analysis component 227, an in-loop filter component 225, a decoded picture buffer component 223, and a header formatting and context adaptive binary arithmetic coding (CABAC) component 231. Such components are coupled as shown. In FIG. 2, the black lines indicate the movement of data to be encoded / decoded, and the dashed lines indicate the movement of control data that controls the operation of the other components. The components of codec system 200 may all be present in an encoder. A decoder may include a subset of the components of codec system 200.For example, the decoder may include an intra-picture prediction component 217, a motion compensation component 219, a scaling and inverse transform component 229, an in-loop filter component 225, and a decoded picture buffer component 223. These components are now described.

[0069] The partitioned video signal 201 is a captured video sequence partitioned into several blocks of pixels by a coding tree. The coding tree employs various partitioning modes to subdivide the blocks of pixels into smaller blocks of pixels. These blocks may then be further subdivided into smaller blocks. The blocks may be referred to as nodes of the coding tree. Larger parent nodes are partitioned into smaller child nodes. The number of times a node is subdivided is referred to as the depth of the node / coding tree. The partitioned blocks may be included in a coding unit (CU) in some cases. For example, a CU may be a sub-part of a CTU that includes a luma block, a red-difference chroma (Cr) block, and a blue-difference chroma (Cb) block, along with corresponding syntax instructions for the CU. The partitioning modes may include a binary tree (BT), a ternary tree (TT), and a quad tree (QT), which are employed to partition a node into two, three, or four child nodes of various shapes, respectively, depending on the partitioning mode employed. The segmented video signal 201 is forwarded to a general coder control component 211, a transform scaling and quantization component 213, an intra-picture estimation component 215, a filter control analysis component 227, and a motion estimation component 221 for compression.

[0070] The general coder control component 211 is configured to make decisions related to the coding of images of a video sequence into a bitstream according to application constraints. For example, the general coder control component 211 manages the optimization of bitrate / bitstream size versus reconstruction quality. Such decisions may be based on storage space / bandwidth availability and image resolution requirements. The general coder control component 211 also manages buffer utilization in light of transmission rate to mitigate buffer under-run and over-run issues. To manage these issues, the general coder control component 211 manages segmentation, prediction, and filtering by other components. For example, the general coder control component 211 may dynamically increase compression complexity to increase resolution and bandwidth usage, or decrease compression complexity to decrease resolution and bandwidth usage. Thus, the general coder control component 211 controls other components of the codec system 200 to balance video signal reconstruction quality and bitrate considerations. The general coder control component 211 creates control data that controls the operation of other components. The control data is also forwarded to the header formatting and CABAC component 231 and encoded into the bitstream to signal parameters for decoding at the decoder.

[0071] The partitioned video signal 201 is also sent to a motion estimation component 221 and a motion compensation component 219 for inter prediction. A frame or slice of the partitioned video signal 201 may be divided into multiple video blocks. The motion estimation component 221 and the motion compensation component 219 perform inter predictive coding of the received video blocks with respect to one or more blocks in one or more reference frames to perform temporal prediction. The codec system 200 may perform multiple coding passes to, for example, select an appropriate coding mode for each block of video data.

[0072] The motion estimation component 221 and the motion compensation component 219 may be highly integrated, but are illustrated separately for conceptual purposes. Motion estimation performed by the motion estimation component 221 is a process of generating motion vectors, which estimate motion with respect to a video block. A motion vector may indicate, for example, the displacement of a coded object with respect to a predictive block. A predictive block is a block that is found to match well with a block to be coded with respect to pixel differences. A predictive block may also be referred to as a reference block. Such pixel differences may be determined by sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metrics. HEVC employs several coded objects, including CTUs, coding tree blocks (CTBs), and CUs. For example, a CTU may be divided into CTBs, which may then be divided into CBs to be included in a CU. A CU may be encoded as a prediction unit (PU) that includes prediction data and / or a transform unit (TU) that includes transformed residual data for the CU. The motion estimation component 221 generates the motion vectors, PUs, and TUs by using a rate-distortion analysis as part of a rate-distortion optimization process. For example, the motion estimation component 221 may determine multiple reference blocks, multiple motion vectors, etc. for a current block / frame and select the reference block, motion vector, etc. with the best rate-distortion characteristics. The best rate-distortion characteristics balance both the quality of the video reconstruction (e.g., the amount of data lost due to compression) and the coding efficiency (e.g., the size of the final encoding).

[0073] In some examples, the codec system 200 may calculate values ​​for sub-integer pixel positions of reference pictures stored in the decoded picture buffer component 223. For example, the video codec system 200 may interpolate values ​​for quarter-pixel positions, eighth-pixel positions, or other fractional pixel positions of the reference pictures. Thus, the motion estimation component 221 may perform motion searches for full-pixel positions and fractional pixel positions and output motion vectors with fractional pixel accuracy. The motion estimation component 221 calculates motion vectors for PUs of video blocks in inter-coded slices by comparing the positions of the PUs with the positions of predictive blocks of the reference pictures. The motion estimation component 221 outputs the calculated motion vectors as header formatting for encoding and motion to the motion compensation component 219 and motion data to the CABAC component 231.

[0074] The motion compensation performed by the motion compensation component 219 may involve fetching or generating a predictive block based on a motion vector determined by the motion estimation component 221. Again, the motion estimation component 221 and the motion compensation component 219 may be functionally integrated in some examples. Upon receiving a motion vector for the PU of the current video block, the motion compensation component 219 may locate the predictive block to which the motion vector points. A residual video block is then formed by subtracting pixel values ​​of the predictive block from pixel values ​​of the current video block being coded to form pixel difference values. In general, the motion estimation component 221 performs motion estimation with respect to the luma component, and the motion compensation component 219 uses the motion vector calculated based on the luma component for both the chroma and luma components. The predictive block and the residual block are forwarded to the transform scaling and quantization component 213.

[0075] The partitioned video signal 201 is also sent to an intra-picture estimation component 215 and an intra-picture prediction component 217. As with the motion estimation component 221 and the motion compensation component 219, the intra-picture estimation component 215 and the intra-picture prediction component 217 may be highly integrated, but are illustrated separately for conceptual purposes. The intra-picture estimation component 215 and the intra-picture prediction component 217 intra-predict a current block with respect to blocks in a current frame, as an alternative to the inter-prediction performed by the motion estimation component 221 and the motion compensation component 219 between frames, as described above. In particular, the intra-picture estimation component 215 determines an intra-prediction mode to use to encode the current block. In some examples, the intra-picture estimation component 215 selects an appropriate intra-prediction mode to encode the current block from a plurality of tested intra-prediction modes. The selected intra-prediction mode is then forwarded to the header formatting and CABAC component 231 for encoding.

[0076] For example, the intra picture estimation component 215 calculates rate-distortion values ​​using a rate-distortion analysis for various tested intra prediction modes and selects an intra prediction mode with the best rate-distortion characteristics from among the tested modes. The rate-distortion analysis generally determines the amount of distortion (or error) between an encoded block and an original unencoded block that was encoded to generate the encoded block, as well as the bit rate (e.g., number of bits) used to generate the encoded block. The intra picture estimation component 215 calculates ratios from the distortion and rate for various encoded blocks to determine which intra prediction mode exhibits the best rate-distortion value for the block. In addition, the intra picture estimation component 215 may be configured to code a depth block of a depth map using a depth modeling mode (DMM) based on a rate-distortion optimization (RDO).

[0077] The intra picture prediction component 217 may generate a residual block from the prediction block based on a selected intra prediction mode determined by the intra picture estimation component 215 when implemented in an encoder, or may read the residual block from a bitstream when implemented in a decoder. The residual block includes value differences between the prediction block and the original block, represented as a matrix. The residual block is then forwarded to the transform scaling and quantization component 213. The intra picture estimation component 215 and the intra picture prediction component 217 may operate on both the luma and chroma components.

[0078] The transform scaling and quantization component 213 is configured to further compress the residual block. The transform scaling and quantization component 213 applies a transform, such as a discrete cosine transform (DCT), a discrete sine transform (DST), or a conceptually similar transform, to the residual block to generate a video block including residual transform coefficient values. A wavelet transform, an integer transform, a subband transform, or other types of transforms could also be used. The transform may convert the residual information from the pixel value domain to a transform domain, such as the frequency domain. The transform scaling and quantization component 213 is also configured to scale the transformed residual information, for example based on frequency. Such scaling involves applying a scale factor to the residual information such that different frequency information is quantized with different granularity, which may affect the final visual quality of the reconstructed video. The transform scaling and quantization component 213 is also configured to quantize the transform coefficients to further reduce the bit rate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be changed by adjusting a quantization parameter. In some examples, the transform scaling and quantization component 213 may then perform a scan of a matrix containing the quantized transform coefficients, which are forwarded to the header formatting and CABAC component 231 and encoded into the bitstream.

[0079] The scaling and inverse transform component 229 applies the inverse operations of the transform scaling and quantization component 213 to support motion estimation. The scaling and inverse transform component 229 applies inverse scaling, transformation, and / or quantization to reconstruct a residual block in the pixel domain, for example, for later use as a reference block that may become a predictive block for another current block. The motion estimation component 221 and / or the motion compensation component 219 may calculate a reference block by adding the residual block back to the corresponding predictive block for use in motion estimation of a later block / frame. A filter is applied to the reconstructed reference block, thereby mitigating artifacts created during scaling, quantization, and transformation. Such artifacts may otherwise cause inaccurate predictions (and create additional artifacts) when subsequent blocks are predicted.

[0080] The filter control analysis component 227 and the in-loop filter component 225 apply filters to the residual block and / or the reconstructed image block. For example, the transformed residual block from the scaling and inverse transform component 229 may be combined with a corresponding prediction block from the intra-picture prediction component 217 and / or the motion compensation component 219 to reconstruct the original image block. A filter may then be applied to the reconstructed image block. In some examples, the filter may be applied to the residual block instead. As with the other components of FIG. 2, the filter control analysis component 227 and the in-loop filter component 225 are highly integrated and may be implemented together, but are depicted separately for conceptual purposes. The filters applied to the reconstructed reference block are applied to a particular spatial region and include multiple parameters to adjust how such filters are applied. The filter control analysis component 227 analyzes the reconstructed reference block to determine where such filters should be applied and sets the corresponding parameters. Such data is forwarded to the header formatting and CABAC component 231 as filter control data for encoding. The in-loop filter component 225 applies such filters based on the filter control data. The filters may include deblocking filters, noise suppression filters, SAO filters, and adaptive loop filters. Such filters may be applied in the spatial / pixel domain (e.g., on reconstructed pixel blocks) or in the frequency domain, depending on the example.

[0081] When operating as an encoder, the filtered reconstructed image blocks, residual blocks, and / or predictive blocks are stored in the decoded picture buffer component 223 for later use in motion estimation as described above. When operating as a decoder, the decoded picture buffer component 223 stores the reconstructed and filtered blocks and forwards them to a display as part of the output video signal. The decoded picture buffer component 223 may be any memory device capable of storing predictive blocks, residual blocks, and / or reconstructed image blocks.

[0082] The header formatting and CABAC component 231 receives data from various components of the codec system 200 and encodes such data into a coded bitstream for transmission towards a decoder. In particular, the header formatting and CABAC component 231 generates various headers to encode control data, such as general control data and filter control data. In addition, prediction data, including intra prediction data and motion data, as well as residual data in the form of quantized transform coefficient data, are all encoded into the bitstream. The final bitstream contains all the information desired for a decoder to reconstruct the original partitioned video signal 201. Such information may also include an intra prediction mode index table (also referred to as a codeword mapping table), definitions of encoding contexts for various blocks, indications of the most likely intra prediction modes, indications of partition information, etc. Such data may be encoded by employing entropy coding. For example, the information may be encoded by employing Context-Adaptive Variable Length Coding (CAVLC), CABAC, Syntax-Based Context-Adaptive Binary Arithmetic Coding (SBAC), Probability Interval Partitioning Entropy (PIPE) coding, or another entropy coding technique. Following entropy coding, the coded bitstream may be transmitted to another device (e.g., a video decoder) or archived for later transmission or removal.

[0083] 3 is a block diagram illustrating an example video encoder 300. The video encoder 300 may be employed to implement the encoding functionality of the codec system 200 and / or to implement steps 101, 103, 105, 107, and / or 109 of the method of operation 100. The encoder 300 segments an input video signal, resulting in a segmented video signal 301, which is substantially similar to the segmented video signal 201. The segmented video signal 301 is then compressed and encoded into a bitstream by components of the encoder 300.

[0084] Specifically, the partitioned video signal 301 is forwarded to an intra-picture prediction component 317 for intra prediction. The intra-picture prediction component 317 may be substantially similar to the intra-picture estimation component 215 and the intra-picture prediction component 217. The partitioned video signal 301 is also forwarded to a motion compensation component 321 for inter prediction based on a reference block in a decoded picture buffer component 323. The motion compensation component 321 may be substantially similar to the motion estimation component 221 and the motion compensation component 219. The prediction block and the residual block from the intra-picture prediction component 317 and the motion compensation component 321 are forwarded to a transform and quantization component 313 for transforming and quantizing the residual block. The transform and quantization component 313 may be substantially similar to the transform scaling and quantization component 213. The transformed and quantized residual blocks and the corresponding prediction blocks (along with associated control data) are forwarded to an entropy coding component 331 for coding into the bitstream. The entropy coding component 331 may be substantially similar to the header formatting and CABAC component 231.

[0085] The transformed and quantized residual block and / or the corresponding prediction block are transferred from the transform and quantization component 313 to the inverse transform and quantization component 329 for reconstructing into a reference block and for use by the motion compensation component 321. The inverse transform and quantization component 329 may be substantially similar to the scaling and inverse transform component 229. An in-loop filter in the in-loop filter component 325 is also applied to the residual block and / or the reconstructed reference block, depending on the example. The in-loop filter component 325 may be substantially similar to the filter control analysis component 227 and the in-loop filter component 225. The in-loop filter component 325 may comprise multiple filters as described with respect to the in-loop filter component 225. The filtered block is then stored in the decoded picture buffer component 323 for use as a reference block by the motion compensation component 321. The decoded picture buffer component 323 may be substantially similar to the decoded picture buffer component 223.

[0086] 4 is a block diagram illustrating an example video decoder 400. The video decoder 400 may be employed to implement the decoding functionality of the codec system 200 and / or to implement steps 111, 113, 115, and / or 117 of the method of operation 100. The decoder 400 receives a bitstream, for example, from the encoder 300, and generates a reconstructed output video signal based on the bitstream for display to an end user.

[0087] The bitstream is received by the entropy decoding component 433. The entropy decoding component 433 is configured to implement an entropy decoding scheme, such as CAVLC, CABAC, SBAC, PIPE coding, or other entropy coding techniques. For example, the entropy decoding component 433 may employ header information to provide a context for interpreting additional data encoded as codewords in the bitstream. The decoded information includes any desired information for decoding a video signal, such as general control data, filter control data, partition information, motion data, prediction data, and quantized transform coefficients from the residual block. The quantized transform coefficients are forwarded to the inverse transform and quantization component 429 for reconstruction into the residual block. The inverse transform and quantization component 429 may be similar to the inverse transform and quantization component 329.

[0088] The reconstructed residual block and / or predictive block are forwarded to the intra-picture prediction component 417 for reconstructing into an image block based on an intra-prediction operation. The intra-picture prediction component 417 may be similar to the intra-picture estimation component 215 and the intra-picture prediction component 217. Specifically, the intra-picture prediction component 417 employs a prediction mode to identify the location of a reference block in a frame and applies the residual block to the result to reconstruct an intra-predictive image block. The reconstructed intra-predictive image block and / or residual block and the corresponding inter-predictive data are forwarded to the decoded picture buffer component 423 via the in-loop filter component 425, which may be substantially similar to the decoded picture buffer component 223 and the in-loop filter component 225, respectively. The in-loop filter component 425 filters the reconstructed image block, the residual block and / or the predictive block, and such information is stored in the decoded picture buffer component 423. The reconstructed image block from the decoded picture buffer component 423 is forwarded to the motion compensation component 421 for inter prediction. The motion compensation component 421 may be substantially similar to the motion estimation component 221 and / or the motion compensation component 219. Specifically, the motion compensation component 421 employs a motion vector from a reference block to generate a prediction block and applies a residual block to the result to reconstruct an image block. The resulting reconstructed block may also be forwarded to the decoded picture buffer component 423 via the in-loop filter component 425. The decoded picture buffer component 423 continues to store additional reconstructed image blocks, which may be reconstructed into a frame via the partition information. Such frames may be placed into a sequence. The sequence is output to a display as a reconstructed output video signal.

[0089] With the above in mind, video compression techniques perform spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (i.e., a video picture, or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as tree blocks, coding tree blocks (CTBs), coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture, or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. A POC is a variable associated with each picture that uniquely identifies the associated picture among all pictures in a pre-coded layer video sequence (CLVS), indicates when the associated picture should be output from the DPB, and indicates the position of the associated picture in output order relative to the output order positions of other pictures in the same CLVS that should be output from the DPB. A flag is a variable or 1-bit syntax element that can take one of two possible values, 0 and 1.

[0090] The spatial or temporal prediction results in a predictive block for the block to be coded. The residual data represents pixel differences between the original block to be coded and the predictive block. The inter-coded block is encoded according to a motion vector pointing to a block of reference samples forming the predictive block, and the residual data indicating the difference between the coded block and the predictive block. The intra-coded block is encoded according to an intra-coding mode and the residual data. For further compression, the residual data may be transformed from the pixel domain to a transform domain to obtain residual transform coefficients, which may then be quantized. The quantized transform coefficients, which are initially arranged in a two-dimensional array, may be scanned to generate a one-dimensional vector of transform coefficients, and entropy coding may be applied to achieve even more compression.

[0091] Image and video compression has undergone rapid growth, resulting in a variety of coding standards. Such video coding standards include Advanced Video Coding (AVC), also known as ITU-T H.261, International Organization for Standardization / International Electrotechnical Commission (ISO / IEC) MPEG-1 Part 2, ITU-T H.262 or ISO / IEC MPEG-2 Part 2, ITU-T H.263, ISO / IEC MPEG-4 Part 2, ITU-T H.264 or ISO / IEC MPEG-4 Part 10, and High Efficiency Video Coding (HEVC), also known as ITU-T H.265 or MPEG-H Part 2. AVC includes extensions such as Scalable Video Coding (SVC), Multiview Video Coding (MVC), Multiview Video Coding plus Depth (MVC+D), and 3D AVC (3D-AVC). HEVC includes extensions such as Scalable HEVC (SHVC), Multiview HEVC (MV-HEVC), and 3D HEVC (3D-HEVC).

[0092] There is also a new video coding standard named Versatile Video Coding (VVC) being developed by the ITU-T and ISO / IEC Joint Video Experts Team (JVET). The VVC standard has several working drafts, but one working draft (WD) of VVC in particular is referenced herein: B. Bross, J. Chen, and S. Liu, "Versatile Video Coding (Draft 5)," JVET-N1001-v3, 13th JVET Meeting, March 27, 2019 (VVC Draft 5).

[0093] Scalability in video coding is usually supported by using multi-layer coding techniques. A multi-layer bitstream includes a base layer (BL) and one or more enhancement layers (EL). Examples of scalability include spatial scalability, quality / signal-to-noise ratio (SNR) scalability, multiview scalability, etc. When a multi-layer coding technique is used, a picture or a portion thereof may be coded (1) without using a reference picture, i.e., using intra prediction, (2) by referencing a reference picture that is in the same layer, i.e., using inter prediction, or (3) by referencing a reference picture that is in another layer, i.e., using inter-layer prediction. A reference picture used for inter-layer prediction of a current picture is referred to as an inter-layer reference picture (ILRP).

[0094] 5 is a schematic diagram illustrating an example of layer-based prediction 500 as performed to determine motion vectors (MVs), for example, in the block compression step 105, the block decoding step 113, the motion estimation component 221, the motion compensation component 219, the motion compensation component 321, and / or the motion compensation component 421. The layer-based prediction 500 is compatible with unidirectional inter prediction and / or bidirectional inter prediction, but also performed between pictures in different layers.

[0095] Layer-based prediction 500 is applied between pictures 511, 512, 513, and 514 and pictures 515, 516, 517, and 518 in different layers. In the illustrated example, pictures 511, 512, 513, and 514 are part of layer N+1 532 and pictures 515, 516, 517, and 518 are part of layer N 531. A layer, such as layer N 531 and / or layer N+1 532, is a group of pictures that are all associated with similar values ​​of characteristics such as similar size, quality, resolution, signal-to-noise ratio, capacity, etc. In the illustrated example, layer N+1 532 is associated with a larger image size than layer N 531. Thus, pictures 511, 512, 513, and 514 of layer N+1 532 have a larger picture size (e.g., larger height and width, and therefore more samples) than pictures 515, 516, 517, and 518 of layer N 531 in this example. However, such pictures may be separated between layer N+1 532 and layer N 531 by other characteristics. Although only two layers, layer N+1 532 and layer N 531, are shown, a set of pictures may be separated into any number of layers based on relevant characteristics. Layer N+1 532 and layer N 531 may be indicated by a layer ID. A layer ID is an item of data associated with a picture and indicates that the picture is part of the indicated layer. Thus, each picture 511-518 may be associated with a corresponding layer ID, which may indicate which layer N+1 532 or layer N 531 contains the corresponding picture.

[0096] The pictures 511-518 in the different layers 531-532 are configured to be displayed in alternative ways. As such, the pictures 511-518 in the different layers 531-532 may share the same temporal identifier (ID) and may be included in the same AU. As used herein, an AU is a set of one or more coded pictures that are associated with the same display time for output from the DPB. For example, a decoder may decode and display picture 515 at the current display time if a smaller picture is desired, or the decoder may decode and display picture 511 at the current display time if a larger picture is desired. As such, the pictures 511-514 in the upper layer N+1 532 include substantially the same image data as the corresponding pictures 515-518 in the lower layer N 531 (regardless of differences in picture size). Specifically, picture 511 contains substantially the same image data as picture 515, picture 512 contains substantially the same image data as picture 516, and so on.

[0097] Pictures 511-518 may be coded with reference to other pictures 511-518 in the same layer N 531 or N+1 532. Coding a picture with reference to another picture in the same layer results in inter prediction 523, which is compatible with unidirectional inter prediction and / or bidirectional inter prediction. Inter prediction 523 is shown with a solid arrow. For example, picture 513 may be coded by employing inter prediction 523 using one or two of pictures 511, 512, and / or 514 of layer N+1 532 as references, one picture referenced for unidirectional inter prediction and / or two pictures referenced for bidirectional inter prediction. Furthermore, picture 517 may be coded by employing inter prediction 523 using one or two of pictures 515, 516, and / or 518 in layer N 531 as references, one picture being referenced for unidirectional inter prediction and / or two pictures being referenced for bidirectional inter prediction. When a picture is used as a reference for another picture in the same layer when performing inter prediction 523, the picture may be referred to as a reference picture. For example, picture 512 may be a reference picture used to code picture 513 according to inter prediction 523. Inter prediction 523 may also be referred to as intra-layer prediction in a multi-layer context. As such, inter prediction 523 is a mechanism for coding samples of a current picture by referencing indicated samples in a reference picture different from the current picture when the reference picture and the current picture are in the same layer.

[0098] Pictures 511-518 may also be coded by referencing other pictures 511-518 in different layers. This process is known as inter-layer prediction 521 and is indicated by dashed arrows. Inter-layer prediction 521 is a mechanism for coding samples of a current picture by referencing indicated samples in reference pictures where the current picture and the reference picture are in different layers and therefore have different layer IDs. For example, a picture of a lower layer N 531 may be used as a reference picture for coding a corresponding picture of an upper layer N+1 532. As a specific example, picture 511 may be coded by referencing picture 515 according to inter-layer prediction 521. In such a case, picture 515 is used as an inter-layer reference picture. An inter-layer reference picture is a reference picture used for inter-layer prediction 521. In most cases, inter-layer prediction 521 is constrained such that a current picture, such as picture 511, can only use inter-layer reference pictures that are included in the same AU and are in a lower layer, such as picture 515. When multiple layers (eg, more than two) are available, inter-layer prediction 521 can encode / decode the current picture based on multiple inter-layer reference pictures at a lower level than the current picture.

[0099] A video encoder may employ layer-based prediction 500 to encode pictures 511-518 via many different combinations and / or permutations of inter-prediction 523 and inter-layer prediction 521. For example, picture 515 may be coded according to intra prediction. Pictures 516-518 may then be coded according to inter-prediction 523 by using picture 515 as a reference picture. Furthermore, picture 511 may be coded according to inter-layer prediction 521 by using picture 515 as an inter-layer reference picture. Pictures 512-514 may then be coded according to inter-prediction 523 by using picture 511 as a reference picture. As such, a reference picture may serve as both a single layer reference picture and an inter-layer reference picture for different coding mechanisms. By coding the upper layer N+1 532 picture based on the lower layer N 531 picture, the upper layer N+1 532 can avoid employing intra prediction, which has significantly lower coding efficiency than inter prediction 523 and inter-layer prediction 521. As such, the coding inefficiency of intra prediction can be limited to the smallest / lowest quality pictures and thus limited to coding a minimum amount of video data. Pictures used as reference pictures and / or inter-layer reference pictures can be indicated in entries of a reference picture list included in a reference picture list structure.

[0100] Each AU 506 in FIG. 5 may include multiple pictures. For example, one AU 506 may include pictures 511 and 515. Another AU 506 may include pictures 512 and 516. In effect, each AU 506 is a set of one or more coded pictures associated with the same display time (e.g., the same temporal ID) for output from a decoded picture buffer (DPB) (e.g., for display to a user). Each AUD 508 is an indicator or data structure used to indicate the start of an AU (e.g., AU 508) or a boundary between AUs.

[0101] Previous H.26x video coding families have provided support for scalability in profiles other than those for single-layer coding. Scalable video coding (SVC) is a scalable extension of AVC / H.264 that provides support for spatial, temporal, and quality scalability. For SVC, a flag is signaled in each macroblock (MB) in an EL picture to indicate whether the EL MB is predicted using co-located blocks from lower layers. Predictions from co-located blocks may include texture, motion vectors, and / or coding modes. An SVC implementation cannot directly reuse unmodified H.264 / AVC implementations in its design. The SVC EL macroblock syntax and decoding process are different from the H.264 / AVC syntax and decoding process.

[0102] Scalable HEVC (SHVC) is an extension of the HEVC / H.265 standard that provides support for spatial and quality scalability, Multiview HEVC (MV-HEVC) is an extension of HEVC / H.265 that provides support for multiview scalability, and 3D HEVC (3D-HEVC) is an extension of HEVC / H.264 that provides support for three-dimensional (3D) video coding that is more advanced and efficient than MV-HEVC. It is noted that temporal scalability is included as an integral part of the single-layer HEVC codec. The design of the multi-layer extension of HEVC employs the idea that decoded pictures used for inter-layer prediction come only from the same access unit (AU), are treated as long-term reference pictures (LTRPs), and are assigned a reference index in a reference picture list together with other temporal reference pictures in the current layer. Inter-layer prediction (ILP) is achieved at the prediction unit (PU) level by setting the value of the reference index to refer to an inter-layer reference picture in the reference picture list.

[0103] In particular, both reference picture resampling and spatial scalability functions require resampling of a reference picture or a part thereof. Reference picture resampling (RPR) can be realized either at the picture level or at the coding block level. However, when RPR is referred to as a coding function, it is a function for single-layer coding. Nevertheless, it is possible, or even preferable from a codec design point of view, to use the same resampling filter for both the RPR function for single-layer coding and the spatial scalability function for multi-layer coding.

[0104] Figure 6 illustrates an example of layer-based prediction 600 utilizing an output layer set (OLS) as performed, for example, in block compression step 105, block decoding step 113, motion estimation component 221, motion compensation component 219, motion compensation component 321, and / or motion compensation component 421 to determine MV. The layer-based prediction 600 is compatible with unidirectional inter prediction and / or bidirectional inter prediction, but is also performed between pictures in different layers. The layer-based prediction of Figure 6 is similar to that of Figure 5. Therefore, for the sake of brevity, a full description of the layer-based prediction will not be repeated.

[0105] Some of the layers in the coded video sequence (CVS) 690 of FIG. 6 are included in an OLS. An OLS is a set of layers where one or more layers are designated as output layers. An output layer is a layer of the OLS that is output. FIG. 6 shows three different OLSs, namely, OLS1, OLS2, and OLS3. As shown, OLS1 includes layer N 631 and layer N+1 632. OLS2 includes layer N 631, layer N+1 632, layer N+2 633, and layer N+3 634. OLS3 includes layer N 631, layer N+1 632, and layer N+2 633. Although three OLSs are shown, a different number of OLSs may be used in an actual application. Other layers, such as layer N+4 635, are not included in the illustrated OLSs (e.g., OLS1, 2, and 3), but are available for inclusion in other OLSs.

[0106] Each of the different OLSs may include any number of layers. The different OLSs are generated in an effort to accommodate the coding capabilities of a variety of different devices with various coding capabilities. For example, an OLS1 including only two layers may be generated to accommodate a mobile phone having a relatively limited coding capability. Meanwhile, an OLS2 including four layers may be generated to accommodate a large screen television that can decode higher layers than a mobile phone. An OLS3 including three layers may be generated to accommodate a personal computer, laptop computer, or tablet computer that may be able to decode higher layers than a mobile phone, but cannot decode the top layer such as a large screen television.

[0107] The layers in FIG. 6 may all be independent of each other. That is, each layer may be coded without using inter-layer prediction (ILP). In this case, the layer is referred to as a simulcast layer. One or more of the layers in FIG. 6 may be coded using ILP. Whether a layer is a simulcast layer or whether some of the layers are coded using ILP is signaled by a flag in a video parameter set (VPS), which will be described in more detail below. When some layers use ILP, layer dependencies between layers are also signaled in the VPS.

[0108] In one embodiment, when a layer is a simulcast layer, only one layer is selected for decoding and output. In one embodiment, when several layers use ILP, all of the layers (e.g., the entire bitstream) are designated to be decoded and certain of the layers are designated to be output layers. The output layer or layers may be, for example, 1) only the top layer, 2) all layers, or 3) the top layer + a set of indicated lower layers. For example, layer N+3 634 (which is the top layer) and layers N 631 and N+1 632 (which are lower layers) from OLS2 are output when the top layer + a set of indicated lower layers is specified for output by a flag in the VPS.

[0109] As shown in Figure 6, each layer may consist of any number of pictures. For example, layer N 631 includes pictures 615-618, layer N+1 632 includes pictures 611-614, layer N+2 633 includes pictures 641-644, layer N+3 634 includes pictures 651-654, and layer N+4 635 includes pictures 661-664.

[0110] 7 is a schematic diagram illustrating an example multi-layer video sequence 700 configured for temporal scalability. The multi-layer video sequence 700 may be encoded by an encoder, such as the codec system 200 and / or the encoder 300, and decoded by a decoder, such as the codec system 200 and / or the decoder 400, for example, according to the method 100. The multi-layer video sequence 700 is included to illustrate another example application for layers in a coded video sequence. For example, the multi-layer video sequence 700 may be employed as a separate embodiment or may be combined with techniques described with respect to the layer-based prediction 500 or 600.

[0111] The multi-layer video sequence 700 includes sublayers 710, 720, and 730. Sublayers are temporal scalable layers of a temporal scalable bitstream that include VCL NAL units (e.g., pictures) with specific temporal identifier values ​​as well as associated non-VCL NAL units (e.g., supporting parameters). Sublayer 710 may be referred to as a base layer, and sublayers 720 and 730 may be referred to as enhancement layers. As shown, sublayer 710 includes pictures 711 at a first frame rate, such as 30 frames per second. Sublayer 710 is a base layer because it includes a base / lowest frame rate. Sublayer 720 includes pictures 721 that are temporally offset from pictures 711 of sublayer 710. Sublayer 710 and sublayer 720 can then be combined to result in a higher total frame rate compared to the frame rate of sublayer 710 alone. For example, sublayer 710 and sublayer 720 may have a combined frame rate of 60 frames per second. Thus, sublayer 720 enhances the frame rate of sublayer 710. Additionally, sublayer 730 includes picture 731 that is also temporally offset from pictures 721 and 711 of sublayers 720 and 710. As such, sublayer 730 can be combined with sublayers 720 and 710 to further enhance sublayer 710. For example, sublayers 710, 720, and 730 may have a combined frame rate of 90 frames per second.

[0112] The sublayer representation 740 can be dynamically created by combining the sublayers 710, 720, and / or 730. The sublayer representation 740 is a subset of the bitstream that includes NAL units of a particular sublayer and lower sublayers. In the illustrated example, the sublayer representation 740 includes picture 741, which is a combined picture 711, 721, and 731 of the sublayers 710, 720, and 730. Thus, the multi-layer video sequence 700 can be temporally scaled to a desired frame rate by selecting a sublayer representation 740 that includes a desired set of sublayers 710, 720, and / or 730. The sublayer representation 740 can be created by employing an OLS that includes the sublayers 710, 720, and / or 730 as layers. In such a case, the sublayer representation 740 is selected as an output layer. Thus, temporal scalability is one of several mechanisms that can be achieved using the multi-layer mechanism.

[0113] In one embodiment, each of the sublayers 710, 720, and 730 is also associated with a temporal identifier (ID), which may be designated as a TemporalID. For example, sublayer 710 may have TemporalID 755, sublayer 720 may have TemporalID 757, and sublayer 730 may have TemporalID 759. TemporalIDs 755, 757, and 759 may be used to uniquely identify each of the sublayers.

[0114] In one embodiment, a syntax element designated vps_max_sublayers_minus1+1 specifies the maximum number of temporal sublayers (e.g., sublayers 710, 720, 730, etc.) that may be present in a layer designated by the VPS (e.g., layers 631, 632, etc.). In one embodiment, the value of vps_max_sublayers_minus1 shall be in the range of 0 to 6. Thus, the multi-layer video sequence 700 includes a maximum number of sublayers in the range of 1 to 7.

[0115] In the example shown in Figure 7, sublayer 730 is the sublayer furthest from sublayer 710, which is the base sublayer. That is, none of the sublayers in Figure 7 are above, beyond, or higher than sublayer 730. Thus, sublayer 730 in Figure 7 may be referred to as a top sublayer representation.

[0116] Video coding standards such as HEVC, SHVC, MV-HEVC, and VVC specify and signal profiles, tiers, and levels. Profiles, tiers, and levels specify limitations on a bitstream and therefore on the capabilities required to decode the bitstream. Profiles, tiers, and levels may be used to indicate interoperability points between individual decoder implementations. A profile is a defined set of coding tools used to create a compliant or conforming bitstream. Each profile specifies a subset of algorithmic features and limitations that shall be supported by all decoders conforming to that profile.

[0117] A level is a set of constraints on a bitstream (e.g., maximum luma sample rate, maximum bitrate for a resolution, etc.) That is, a level is a set of constraints that indicate the required decoder capabilities to play a bitstream of a specified profile.

[0118] The levels are divided into two tiers: primary and upper. The primary tier is the tier below the upper tier. The tiers are made to handle different applications in terms of their maximum bitrates. The primary tier is designed for most applications and the upper tier is designed for very demanding applications. The set of constraints and / or tiers corresponding to a level may be referred to herein as level information.

[0119] Each level of a tier specifies a set of restrictions on the values ​​that may be taken by syntax elements of a particular standard (e.g., HEVC, VVC). The same set of tier and level definitions is used in all profiles, but individual implementations may support different tiers for each supported profile, and within a tier, different levels. For any given profile, the level of a tier generally corresponds to a particular decoder processing load and memory capability.

[0120] Representative examples of levels and tiers for different profiles using the HEVC standard are shown in Table 1 below. [Table 1]

[0121] The profile, tier, and level (PTL) parameters are syntax structures (e.g., the i-th profile_tier_level() syntax structure) that provide the profile, tier, and / or level as noted in the table above. The decoded picture buffer (DPB) parameters are syntax structures (e.g., the i-th dpb_parameters() syntax structure) that provide the DPB size and, optionally, the maximum picture reorder number and the maximum latency information. The maximum picture reorder number and the maximum latency information may be collectively referred to by the acronym MRML. The HRD parameters are syntax structures (e.g., the i-th ols_timing_hrd_parameters() syntax structure) that initialize and / or define the operating conditions of the HRD. Further details and specifications regarding one or more of the PTL parameters, the DPB parameters, and the HRD parameters are provided below.

[0122] In one embodiment, the maximum picture reordering number is specified as dpb_max_num_reorder_pics[i], which specifies the maximum allowed number of pictures in the OLS that can precede any picture in the OLS in decoding order and follow it in output order when Htid is equal to i. The value of dpb_max_num_reorder_pics[i] shall be in the range from 0 to dpb_max_dec_pic_buffering_minus1[i]. When i is greater than 0, dpb_max_num_reorder_pics[i] shall be greater than or equal to dpb_max_num_reorder_pics[i-1]. It is inferred to be equal to dpb_max_num_reorder_pics[MaxSubLayersMinus1] when dpb_max_num_reorder_pics[i] is not present for i in the range from 0 to MaxSubLayersMinus1-1 due to subLayerInfoFlag equal to 0. Htid is a variable that identifies the highest temporal sub-layer to be decoded.

[0123] dpb_max_dec_pic_buffering_minus1[i]+1 specifies the maximum required size of the DPB in units of the picture storage buffer when Htid is equal to i. The value of dpb_max_dec_pic_buffering_minus1[i] shall be in the range from 0 to MaxDpbSize-1, where MaxDpbSize is as specified in subclause A.4.2 of the VVC Standard. When i is greater than 0, dpb_max_dec_pic_buffering_minus1[i] shall be greater than or equal to dpb_max_dec_pic_buffering_minus1[i-1]. When dpb_max_dec_pic_buffering_minus1[i] does not exist for i in the range from 0 to MaxSubLayersMinus1-1 due to subLayerInfoFlag equal to 0, it is inferred to be equal to dpb_max_dec_pic_buffering_minus1[MaxSubLayersMinus1].

[0124] In one embodiment, the maximum latency information is specified as dpb_max_latency_increase_plus1[i]. dpb_max_latency_increase_plus1[i] not equal to 0 is used to calculate a value of MaxLatencyPictures[i], which specifies the maximum number of pictures of the OLS that can precede any picture in the OLS in output order and follow that picture in decoding order when Htid is equal to i.

[0125] MaxLatencyPictures[i]=dpb_max_num_reorder_pics[i]+dpb_max_latency_increase_plus1[i]-1 It is.

[0126] Unfortunately, level information (and possibly other PTL parameters), HRD parameters, and DPB parameters are signaled for each of the layers (e.g., layers 631, 632, etc.) in the multi-layer bitstream, even when the PTL parameters, HRD parameters, and / or DPB parameters are the same for one or more of the layers (e.g., when all layers have the same number of sub-layers). Thus, the same parameters are signaled repeatedly within the multi-layer bitstream, which causes redundancy and inefficiencies in the coding process.

[0127] Disclosed herein is a technique for ensuring that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0128] FIG. 8 illustrates an embodiment of a video bitstream 800. As used herein, the video bitstream 800 may also be referred to as a coded video bitstream, a bitstream, or variations thereof. As shown in FIG. 8, the bitstream 800 includes at least one picture unit (PU) 801. Although three of the PUs 801 are shown in FIG. 8, in a practical application, a different number of PUs 801 may be present in the bitstream 800. Each PU 801 is a set of NAL units that are associated with each other according to a specified classification rule, are consecutive in decoding order, and contain exactly one coded picture (e.g., picture 814).

[0129] In one embodiment, each PU 801 includes one or more of a decoding capability information (DCI) 802, a video parameter set (VPS) 804, a sequence parameter set (SPS) 806, a picture parameter set (PPS) 808, a picture header (PH) 812, and a picture 814. Each of the DCI 802, VPS 804, SPS 806, and PPS 808 may be generally referred to as a parameter set. In one embodiment, other parameter sets not shown in FIG. 8 may also be included in the bitstream 800, such as, for example, an adaptation parameter set (APS), which is a syntax structure that includes syntax elements that apply to zero or more slices as determined by zero or more syntax elements found in a slice header.

[0130] The DCI 802, which may also be referred to as a Decoding Parameter Set (DPS) or Decoder Parameter Set, is a syntax structure that contains syntax elements that apply to the entire bitstream. The DCI 802 contains parameters that remain constant for the lifetime of a video bitstream (e.g., bitstream 800), which may translate to the lifetime of a session. The DCI 802 may contain profile, level, and subprofile information to determine a maximum complexity interconnection point that is guaranteed never to be exceeded even if splicing of a video sequence occurs within a session. It may further optionally contain constraint flags, which indicate that the video bitstream is constrained in the use of certain features as indicated by the values ​​of those flags. This allows the bitstream to be labeled as not using certain tools, which allows resource allocation in decoder implementations, among other things. As with all parameter sets, the DCI 802 is present when first referenced and is referenced by the very first picture in a video sequence, which means that it must be transmitted between the first NAL units in the bitstream 800. Multiple DCIs 802 may be present in the bitstream 800, but the values ​​of the syntax elements therein may not be contradictory when referenced.

[0131] The VPS 804 contains decoding dependencies or information for enhancement layer reference picture set construction. The VPS 804 provides an overall perspective or view of the scalable sequence, including what types of operation points are provided, the profile, tier, and level of the operation points, as well as several other high-level properties of the bitstream 800 that can be used as the basis for session negotiation, content selection, etc.

[0132] In one embodiment, the VPS 804 includes a flag 850. In one embodiment, the flag 850 is designated as vps_default_ptl_dpb_hrd_max_tid_flag. The flag 850 may be set to or have a first value (e.g., 1) or a second value (e.g., 0). When not present, the value of the flag 850 is inferred to be equal to 1. The flag 850 having a first value specifies that the syntax elements vps_ptl_max_tid[i], vps_dpb_max_tid[i], and vps_hrd_max_tid[i] are not present in the VPS 804 and are inferred to be equal to the default value vps_max_sublayers_minus1. That is, the temporal identifier (tid) of the highest sub-layer representation (e.g., sub-layer 730) corresponding to the profile tier level (PTL) parameters, decoded picture buffer (DPB) parameters, and hypothetical reference decoder (HRD) parameters is not present in the VPS 804.

[0133] vps_ptl_max_tid[i] specifies the TemporalId of the highest sublayer representation (e.g., sublayer 730) whose level information exists in the i-th profile_tier_level() syntax structure in VPS804, and the TemporalId of the highest sublayer representation exists in the OLS with OLS index olsIdx such that vps_ols_ptl_idx[olsIdx] is equal to i.

[0134] vps_dpb_max_tid[i] specifies the TemporalId of the highest sublayer representation (e.g., sublayer 730) whose DPB parameters may be present in the i-th dpb_parameters() syntax structure in VPS 804. The value of vps_dpb_max_tid[i] shall be in the range of 0 to vps_max_sublayers_minus1. When not present, the value of vps_dpb_max_tid[i] is inferred to be equal to vps_max_sublayers_minus1.

[0135] vps_hrd_max_tid[i] specifies the TemporalId of the top-level sublayer representation (e.g., sublayer 730) whose HRD parameters are included in the i-th ols_timing_hrd_parameters() syntax structure. In one embodiment, it is present in the i-th ols_timing_hrd_parameters() syntax structure, VPS 804 or sequence parameter set (SPS) 806. The value of vps_hrd_max_tid[i] shall be in the range from 0 to vps_max_sublayers_minus1. When not present, the value of vps_hrd_max_tid[i] is inferred to be equal to vps_max_sublayers_minus1.

[0136] vps_max_sublayers_minus1+1 specifies the maximum number of temporal sublayers (e.g., sublayers 710, 720, 730) that may be present in a layer (e.g., layers 631, 632, 633, etc.) specified by VPS 804. In one embodiment, the value of vps_max_sublayers_minus1 is in the range of 0 to 6. Thus, the maximum number of sublayers is in the range of 1 to 7. That is, there may be anywhere from 1 to 7 sublayers in the multi-layer bitstream depending on the value of vps_max_sublayers_minus1.

[0137] A flag 850 having a second value specifies that the syntax elements vps_ptl_max_tid[i], vps_dpb_max_tid[i], and vps_hrd_max_tid[i] are present in the VPS 804. That is, the temporal identifiers (tids) of the top-level sub-layer representations (e.g., sub-layer 730) corresponding to the profile tier level (PTL) parameters, the decoded picture buffer (DPB) parameters, and the hypothetical reference decoder (HRD) parameters are present in the VPS 804.

[0138] In one embodiment, the flag 850 is specified as vps_all_layers_same_num_sublayers_flag. The flag 850 may be set to or have a first value (e.g., 1) or a second value (e.g., 0). The flag 850 with a first value specifies that the number of temporal sublayers is the same for all layers in each pre-coded video sequence (CVS) 816 that references the VPS 804. The flag 850 with a second value specifies that the layers in each CVS 816 that references the VPS 804 may or may not have the same number of temporal sublayers. When not present, the value of the flag 850 is inferred to be equal to 1. In one embodiment, the name and semantics of flag 850 is changed from vps_all_layers_same_num_sublayers_flag to vps_default_ptl_dpb_hrd_max_tid_flag, thereby controlling only the VPS syntax without requiring the number of sublayers to be the same for all layers.

[0139] The SPS 806 contains data common to all pictures in a sequence of pictures (SOP). The SPS 806 is a syntax structure that contains syntax elements that apply across zero or more CLVSs as determined by the content of syntax elements found in the PPSs referenced by syntax elements found in each picture header. In contrast, the PPS 808 contains data common to an entire picture. The PPS 808 is a syntax structure that contains syntax elements that apply across zero or more coded pictures as determined by syntax elements found in each picture header (e.g., PH 812).

[0140] In one embodiment, the VPS 804 and / or SPS 806 include the following SPS syntax and semantics to implement one or more of the embodiments disclosed herein.

[0141] The VPS syntax includes the following: [Table 2A] [Table 2B]

[0142] The SPS Raw Byte Sequence Payload (RBSP) syntax includes the following: [Table 3]

[0143] The DPB syntax includes the following: [Table 4]

[0144] The HRD parameter syntax includes a general HRD parameter syntax, an OLS HRD parameter syntax, and a sub-layer HRD parameter syntax.

[0145] The general HRD parameter syntax includes the following: [Table 5]

[0146] The OLS HRD parameter syntax includes the following: [Table 6]

[0147] The sublayer HRD parameter syntax includes the following: [Table 7]

[0148] The VPS semantics are as follows:

[0149] vps_max_layers_minus1+1 specifies the maximum number of layers allowed in each CVS that references the VPS.

[0150] vps_max_sub_layers_minus1+1 specifies the maximum number of temporal sublayers that may be present in each CVS that references a VPS. The value of vps_max_sub_layers_minus1 shall be in the range 0 to 6 inclusive.

[0151] vps_all_layers_same_num_sub_layers_flag equal to 1 specifies that the number of temporal sublayers is the same for all layers in each CVS that references the VPS. vps_all_layers_same_num_sub_layers_flag equal to 0 specifies that layers in each CVS that references the VPS may or may not have the same number of temporal sublayers. When not present, the value of vps_all_layers_same_num_sub_layers_flag is inferred to be equal to 1.

[0152] vps_all_independent_layers_flag equal to 1 specifies that all layers in the CVS are coded independently without using inter-layer prediction. vps_all_independent_layers_flag equal to 0 specifies that one or more of the layers in the CVS may use inter-layer prediction. When not present, the value of vps_all_independent_layers_flag is inferred to be equal to 1. When vps_all_independent_layers_flag is equal to 1, the value of vps_independent_layer_flag[i] is inferred to be equal to 1. When vps_all_independent_layers_flag is equal to 0, the value of vps_independent_layer_flag[0] is inferred to be equal to 1.

[0153] vps_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. When vps_direct_dependency_flag[i][j] is not present for i and j in the range from 0 to vps_max_layers_minus1, it is inferred to be equal to 0.

[0154] The variables DirectDependentLayerIdx[i][j], which specifies the jth direct dependent layer of the ith layer, and LayerUsedAsRefLayerFlag[j], which specifies whether the layer with layer index j is used as a reference layer by any other layer, are derived as follows: for(i=0; i<=vps_max_layers_minus1; i++) LayerUsedAsRefLayerFlag[j]=0 for(i=1; i <vps_max_layers_minus1; i++) if(!vps_independent_layer_flag[i]) for(j=i-1, k=0; j>=0; j--) if(vps_direct_dependency_flag[i][j]) { DirectDependentLayerIdx[i][k++]=j LayerUsedAsRefLayerFlag[j]=1 }

[0155] The variable GeneralLayerIdx[i], which specifies the layer index of the layer whose nuh_layer_id is equal to vps_layer_id[i], is derived as follows: for(i=0; i<=vps_max_layers_minus1; i++) GeneralLayerIdx[vps_layer_id[i]]=i

[0156] each_layer_is_an_ols_flag equal to 1 specifies that each output layer set contains only one layer, and each layer in the bitstream is itself an output layer set where the single contained layer is the only output layer. each_layer_is_an_ols_flag equal to 0 specifies that an output layer set may contain multiple layers. If vps_max_layers_minus1 is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 1. Otherwise, when vps_all_independent_layers_flag is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 0.

[0157] ols_mode_idc equal to 0 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i, and for each OLS, only the top layer in the OLS is output. ols_mode_idc equal to 1 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i, and for each OLS, all layers in the OLS are output. ols_mode_idc equal to 2 specifies that the total number of OLSs specified by the VPS is explicitly signaled, and for each OLS, an explicitly signaled set of top and bottom layers in the OLS are output. The value of ols_mode_idc shall be in the range from 0 to 2. The value 3 of ols_mode_idc is reserved for future use in ITU-T|ISO / IEC. When vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, the value of ols_mode_idc is inferred to be equal to 2.

[0158] num_output_layer_sets_minus1+1 specifies the total number of OLS specified by the VPS when ols_mode_idc is equal to 2.

[0159] The variable TotalNumOlss, which specifies the total number of OLSs specified by the VPS, is derived as follows: if(vps_max_layers_minus1==0) TotalNumOlss=1 else if(each_layer_is_an_ols_flag || ols_mode_idc==0 || ols_mode_idc==1) TotalNumOlss=vps_max_layers_minus1+1 else if(ols_mode_idc==2) TotalNumOlss=num_output_layer_sets_minus1+1

[0160] layer_included_flag[i][j] specifies that the jth layer (i.e., the layer with nuh_layer_id equal to vps_layer_id[j]) is included in the ith OLS when ols_mode_idc is equal to 2. layer_included_flag[i][j] equal to 1 specifies that the jth layer is included in the ith OLS. layer_included_flag[i][j] equal to 0 specifies that the jth layer is not included in the ith OLS.

[0161] The variable NumLayersInOls[i], which specifies the number of layers in the ith OLS, and the variable LayerIdInOls[i][j], which specifies the nuh_layer_id value of the jth layer in the ith OLS, are derived as follows: NumLayersInOls[0] = 1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1, i <TotalNumOlss; i++) { if(each_layer_is_an_ols_flag) { NumLayersInOls[i] = 1 LayerIdInOls[i][0]=vps_layer_id[i] } else if(ols_mode_idc==0 | | ols_mode_idc==1) { NumLayersInOls[i]=i+1 for(j=0; j <NumLayersInOls[i]; j++) LayerIdInOls[i][j]=vps_layer_id[j] } else if(ols_mode_idc==2) { for(k=0, j=0; k<=vps_max_layers_minus1; k++) if(layer_included_flag[i][k]) LayerIdInOls[i][j++]=vps_layer_id[k] NumLayersInOls[i] = j } }

[0162] The variable OlsLayeIdx[i][j], which specifies the OLS layer index of the layer whose nuh_layer_id is equal to LayerIdInOls[i][j], is derived as follows: for(i=0, i <TotalNumOlss; i++) for j=0; j <NumLayersInOls[i]; j++) OlsLayeIdx[i][LayerIdInOls[i][j]]=j

[0163] The bottom layer in each OLS shall be an independent layer, i.e. for each i in the range 0 to TotalNumOlss-1, the value of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]] shall be equal to 1.

[0164] Each layer shall be contained within at least one OLS specified by the VPS. In other words, for each layer with a particular value of nuh_layer_id nuhLayerId equal to one of vps_layer_id[k] for k in the range from 0 to vps_max_layers_minus1, there shall be at least one pair of values ​​of i and j, where i is in the range from 0 to TotalNumOlss-1 and j is in the range NumLayersInOls[i]-1, and the value of LayerIdInOls[i][j] is equal to nuhLayerId.

[0165] Any layer in the OLS may be either an output layer of the OLS or a reference layer (direct or indirect) of an output layer of the OLS.

[0166] vps_output_layer_flag[i][j] specifies whether the jth layer in the ith OLS is output when ols_mode_idc is equal to 2. vps_output_layer_flag[i] equal to 1 specifies that the jth layer in the ith OLS is output. vps_output_layer_flag[i] equal to 0 specifies that the jth layer in the ith OLS is not output. The value of vps_output_layer_flag[i] is inferred to be equal to 1 when vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0.

[0167] The variable OutputLayerFlag[i][j], where a value of 1 specifies that the jth layer in the ith OLS is output and a value of 0 specifies that the jth layer in the ith OLS is not output, is derived as follows: for(i=0, i <TotalNumOlss; i++) { OutputLayerFlag[i][NumLayersInOls[i]-1]=1 for(j=0; j <NumLayersInOls[i]-1; j++) if(ols_mode_idc[i]==0) OutputLayerFlag[i][j]=0 else if(ols_mode_idc[i]==1) OutputLayerFlag[i][j]=1 else if(ols_mode_idc[i]==2) OutputLayerFlag[i][j]=vps_output_layer_flag[i][j] }

[0168] NOTE - The 0th OLS only includes the lowest layers (i.e. layers whose nuh_layer_id is equal to vps_layer_id[0]) and for the 0th OLS, only the included layers are output.

[0169] vps_num_ptls specifies the number of profile_tier_level() syntax structures for the VPS.

[0170] A pt_present_flag[i] equal to 1 specifies that profile, tier, and general constraint information is present in the i-th profile_tier_level() syntax structure in the VPS. A pt_present_flag[i] equal to 0 specifies that profile, tier, and general constraint information is not present in the i-th profile_tier_level() syntax structure in the VPS. The value of pt_present_flag[0] is inferred to be equal to 0. When pt_present_flag[i] is equal to 0, the profile, tier, and general constraint information for the i-th profile_tier_level() syntax structure in the VPS is inferred to be identical to that of the (i-1)-th profile_tier_level() syntax structure in the VPS.

[0171] ptl_max_temporal_id[i] specifies the TemporalId of the highest sublayer representation whose level information is present in the i-th profile_tier_level() syntax structure in the VPS. The value of ptl_max_temporal_id[i] shall be in the range of 0 to vps_max_sub_layers_minus1. When vps_max_sub_layers_minus1 is equal to 0, the value of ptl_max_temporal_id[i] is inferred to be equal to 0. When vps_max_sub_layers_minus1 is greater than 0 and vps_all_layers_same_num_sub_layers_flag is equal to 1, the value of ptl_max_temporal_id[i] is inferred to be equal to vps_max_sub_layers_minus1.

[0172] vps_ptl_byte_alignment_zero_bit shall be equal to 0.

[0173] ols_ptl_idx[i] specifies an index into the list of profile_tier_level() syntax structures in the VPS for the profile_tier_level() syntax structure that applies to the i-th OLS. When present, the value of ols_ptl_idx[i] shall be in the range from 0 to vps_num_ptls-1.

[0174] The profile_tier_level() syntax structure that applies to the i-th OLS when NumLayersInOls[i] is equal to 1, is in the SPS referenced by the layer in the i-th OLS.

[0175] vps_num_dpb_params specifies the number of dpb_parameters() syntax structures in the VPS. The value of vps_num_dpb_params shall be in the range of 0 to 16. When not present, the value of vps_num_dpb_params is inferred to be equal to 0.

[0176] same_dpb_size_output_or_nonoutput_flag equal to 1 specifies that the layer_nonoutput_dpb_params_idx[i] syntax element is not present in the VPS. same_dpb_size_output_or_nonoutput_flag equal to 0 specifies that the layer_nonoutput_dpb_params_idx[i] syntax element may or may not be present in the VPS.

[0177] The vps_sub_layer_dpb_params_present_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 in the dpb_parameters() syntax structure in the VPS. When not present, vps_sub_dpb_params_info_present_flag is inferred to be equal to 0.

[0178] dpb_size_only_flag[i] equal to 1 specifies that the max_num_reorder_pics[ ] and max_latency_increase_plus1[ ] syntax elements are not present in that VPS of the i-th dpb_parameters() syntax structure. dpb_size_only_flag[i] equal to 1 specifies that the max_num_reorder_pics[ ] and max_latency_increase_plus1[ ] syntax elements may be present in that VPS of the i-th dpb_parameters() syntax structure.

[0179] dpb_max_temporal_id[i] specifies the TemporalId of the highest sublayer representation for which a DPB parameter may be present in the i-th dpb_parameters() syntax structure in the VPS. The value of dpb_max_temporal_id[i] shall be in the range of 0 to vps_max_sub_layers_minus1. When vps_max_sub_layers_minus1 is equal to 0, the value of dpb_max_temporal_id[i] is inferred to be equal to 0. When vps_max_sub_layers_minus1 is greater than 0 and vps_all_layers_same_num_sub_layers_flag is equal to 1, the value of dpb_max_temporal_id[i] is inferred to be equal to vps_max_sub_layers_minus1.

[0180] layer_output_dpb_params_idx[i] specifies an index into the list of dpb_parameters() syntax structures in the VPS for the dpb_parameters() syntax structure that applies to the i-th layer when it is an output layer in OLS. When present, the value of layer_output_dpb_params_idx[i] shall be in the range from 0 to vps_num_dpb_params-1.

[0181] If vps_independent_layer_flag[i] is equal to 1, the dpb_parameters() syntax structure that applies to the i-th layer when it is an output layer is the dpb_parameters() syntax structure that exists in the SPS referenced by the layer.

[0182] Otherwise (vps_independent_layer_flag[i] is equal to 0), the following applies:

[0183] When vps_num_dpb_params is equal to 1, the value of layer_output_dpb_params_idx[i] is inferred to be equal to 0.

[0184] It is a bitstream conformance requirement that the value of layer_output_dpb_params_idx[i] shall be such that dpb_size_only_flag[layer_output_dpb_params_idx[i]] is equal to 0.

[0185] layer_nonoutput_dpb_params_idx[i] specifies an index into the list of dpb_parameters() syntax structures in the VPS for the dpb_parameters() syntax structures that apply to the i-th layer when it is a non-output layer in OLS. When present, the value of layer_nonoutput_dpb_params_idx[i] shall be in the range from 0 to vps_num_dpb_params-1.

[0186] If same_dpb_size_output_or_nonoutput_flag is equal to 1, the following applies:

[0187] If vps_independent_layer_flag[i] is equal to 1, the dpb_parameters() syntax structure that applies to the i-th layer when it is a non-output layer is the dpb_parameters() syntax structure that exists in the SPS referenced by the layer.

[0188] Otherwise (if vps_independent_layer_flag[i] is equal to 0), the value of layer_nonoutput_dpb_params_idx[i] is inferred to be equal to layer_output_dpb_params_idx[i].

[0189] Otherwise (when same_dpb_size_output_or_nonoutput_flag is equal to 0), when vps_num_dpb_params is equal to 1, the value of layer_output_dpb_params_idx[i] is inferred to be equal to 0.

[0190] vps_extension_flag equal to 0 specifies that the vps_extension_data_flag syntax element is not present in the VPS RBSP syntax structure. vps_extension_flag equal to 1 specifies that the vps_extension_data_flag syntax element is present in the VPS RBSP syntax structure.

[0191] vps_extension_data_flag may have any value. Its presence and value have no effect on decoder conformance to the profile specified in this version of this specification. Decoders conforming to this version of this specification shall ignore all vps_extension_data_flag syntax elements.

[0192] The SPS RBSP semantics are as follows:

[0193] The SPS RBSP shall be available to the decoding process before being referenced, either contained in at least one access unit with TemporalId equal to 0 or provided through external means, and the SPS NAL unit containing the SPS RBSP shall have a nuh_layer_id equal to the lowest nuh_layer_id value of the PPS NAL units that reference it.

[0194] All SPS NAL units with a particular value of sps_seq_parameter_set_id in the CVS shall have the same content.

[0195] sps_decoding_parameter_set_id, when greater than 0, specifies the value of dps_decoding_parameter_set_id for the DPS referenced by the SPS. When sps_decoding_parameter_set_id is equal to 0, the SPS does not reference a DPS, and the DPS is not referenced when decoding each CLVS that references the SPS. The value of sps_decoding_parameter_set_id shall be the same for all SPSs referenced by coded pictures in the bitstream.

[0196] When sps_video_parameter_set_id is greater than 0, it specifies the value of vps_video_parameter_set_id for the VPS referenced by the SPS. When sps_video_parameter_set_id is equal to 0, the SPS does not reference a VPS, the VPS is not referenced when decoding each CLVS that references the SPS, the value of GeneralLayerIdx[nuh_layer_id] is inferred to be equal to 0, and the value of vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is inferred to be equal to 1.

[0197] When vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equal to 1, an SPS referenced by a CLVS with a particular nuh_layer_id value nuhLayerId shall have nuh_layer_id equal to nuhLayerId.

[0198] sps_max_sub_layers_minus1+1 specifies the maximum number of temporal sub-layers that may be present in each CLVS that references an SPS. The value of sps_max_sub_layers_minus1 shall be in the range from 0 to vps_max_sub_layers_minus1 inclusive.

[0199] sps_reserved_zero_4bits shall be equal to 0 in bitstreams conforming to this version of this specification. Other values ​​for sps_reserved_zero_4bits are reserved for future use by ITU-T|ISO / IEC.

[0200] sps_ptl_dpb_present_flag equal to 1 specifies that the profile_tier_level() and dpb_parameters() syntax structures are present in the SPS. sps_ptl_dpb_present_flag equal to 0 specifies that neither the profile_tier_level() nor the dpb_parameters() syntax structures are present in the SPS. The value of sps_ptl_dpb_present_flag shall be equal to vps_independent_layer_flag[nuh_layer_id].

[0201] If vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equal to 1, then the variable MaxDecPicBuffMinus1 is set equal to max_dec_pic_buffering_minus1[sps_max_sub_layers_minus1] in the dpb_parameters() syntax structure in the SPS. Otherwise, MaxDecPicBuffMinus1 is set equal to max_dec_pic_buffering_minus1[sps_max_sub_layers_minus1] in the layer_nonoutput_dpb_params_idx[GeneralLayerIdx[nuh_layer_id]]th dpb_parameters() syntax structure in the VPS.

[0202] A gdr_enabled_flag equal to 1 specifies that progressive decoding refresh (GDR) pictures may be present in the CLVS that references the SPS. A gdr_enabled_flag equal to 0 specifies that no GDR pictures are present in the CLVS that references the SPS.

[0203] sps_sub_layer_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 in the SPS. When not present, sps_sub_dpb_params_info_present_flag is inferred to be equal to 0.

[0204] long_term_ref_pics_flag equal to 0 specifies that LTRP is not used for inter prediction of any coded picture in CLVS. long_term_ref_pics_flag equal to 1 specifies that LTRP may be used for inter prediction of one or more coded pictures in CLVS.

[0205] General profile, tier, and level semantics are as follows:

[0206] The profile_tier_level() syntax structure provides level information, and optionally profile, tier, subprofile, and general constraint information (denoted as PT information).

[0207] When the profile_tier_level() syntax structure is included in a DPS, OlsInScope is an OLS that includes all layers in the entire bitstream that references the DPS. When the profile_tier_level() syntax structure is included in a VPS, OlsInScope is one or more OLSs specified by the VPS. When the profile_tier_level() syntax structure is included in an SPS, OlsInScope is an OLS that includes only the layers that are the lowest layer among the layers that reference the SPS, which shall be independent layers.

[0208] general_profile_idc indicates the profile to which OlsInScope conforms as specified in Annex A of the VVC standard. Bitstreams shall not contain values ​​of general_profile_idc other than those specified in Annex A. Other values ​​of general_profile_idc are reserved for future use by ITU-T|ISO / IEC.

[0209] general_tier_flag specifies the tier context for the interpretation of general_level_idc as specified in Appendix A.

[0210] num_sub_profiles specifies the number of general_sub_profile_idc[i] syntax elements.

[0211] general_sub_profile_idc[i] indicates the ith interoperability metadata registered as specified by Recommendation ITU-T T.35, the content of which is not specified by the VVC standard.

[0212] general_level_idc indicates the level at which OlsInScope conforms as specified in Annex A. Bitstreams shall not contain values ​​of general_level_idc other than those specified in Annex A. Other values ​​of general_level_idc are reserved for future use by ITU-T|ISO / IEC.

[0213] NOTE 1 - A higher value of general_level_idc indicates a higher level. The maximum level signaled in a DPS for an OlsInScope may be higher than the level signaled in an SPS for a CVS contained within the OlsInScope.

[0214] NOTE 2 - When OlsInScope conforms to multiple profiles, general_profile_idc should indicate the profile that provides the preferred decoded result or the preferred bitstream identification, as determined by the encoder (in a manner not specified herein).

[0215] NOTE 3 - When the profile_tier_level() syntax structure contained in the DPS and the CVS of OlsInScope conform to different profiles, the general_profile_idc and level_idc should indicate the profile and level of the decoder that can decode OlsInScope.

[0216] A sub_layer_level_present_flag[i] equal to 1 specifies that the level information is present in the profile_tier_level() syntax structure for the sub-layer representation with TemporalId equal to i. A sub_layer_level_present_flag[i] equal to 0 specifies that the level information is not present in the profile_tier_level() syntax structure for the sub-layer representation with TemporalId equal to i.

[0217] ptl_alignment_zero_bits shall be equal to 0.

[0218] The semantics of the syntax element sub_layer_level_idc[i] is the same as the syntax element general_level_idc, apart from specifying the inference of non-existent values, but it applies to the sub-layer representation with TemporalId equal to i.

[0219] The DPB semantics are as follows:

[0220] The dpb_parameters(maxSubLayersMinus1, subLayerInfoFlag) syntax structure provides information on the DPB size, the maximum number of picture reorders, and the maximum latency for each CLVS in the CVS.

[0221] When the dpb_parameters() syntax structure is included in a 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 an SPS, it applies to the OLS that includes only layers that are the lowest layer among the layers that reference the SPS, which shall be independent layers.

[0222] max_dec_pic_buffering_minus1[i]+1 specifies, for each CLVS of the CVS, the maximum required size of the decoded picture buffer in units of the picture storage buffer when Htid is equal to i. The value of max_dec_pic_buffering_minus1[i] shall be in the range from 0 to MaxDpbSize-1, where MaxDpbSize is as specified elsewhere. When i is greater than 0, max_dec_pic_buffering_minus1[i] shall be greater than or equal to max_dec_pic_buffering_minus1[i-1]. When max_dec_pic_buffering_minus1[i] is not present for i in the range from 0 to maxSubLayersMinus1-1 due to subLayerInfoFlag equal to 0, it is inferred to be equal to max_dec_pic_buffering_minus1[maxSubLayersMinus1].

[0223] max_num_reorder_pics[i] specifies, for each CLVS in the CVS, the maximum allowable number of pictures in the CLVS that can precede any picture in the CLVS in decoding order and follow it in output order when Htid is equal to i. The value of max_num_reorder_pics[i] shall be in the range from 0 to max_dec_pic_buffering_minus1[i]. When i is greater than 0, max_num_reorder_pics[i] shall be greater than or equal to max_num_reorder_pics[i-1]. When max_num_reorder_pics[i] is not present for i in the range from 0 to maxSubLayersMinus1-1 due to subLayerInfoFlag equal to 0, it is inferred to be equal to max_num_reorder_pics[maxSubLayersMinus1].

[0224] max_latency_increase_plus1[i] not equal to 0 is used to calculate a value of MaxLatencyPictures[i], which specifies, for each CLVS in the CVS, the maximum number of pictures in the CLVS that can precede in output order and follow in decoding order any picture in the CLVS when Htid is equal to i.

[0225] 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

[0226] When max_latency_increase_plus1[i] is equal to 0, the corresponding limit is not expressed.

[0227] The value of max_latency_increase_plus1[i] shall be in the range of 0 to 2-2. When max_latency_increase_plus1[i] is not present for i in the range of 0 to maxSubLayersMinus1-1 due to subLayerInfoFlag equal to 0, it is inferred to be equal to max_latency_increase_plus1[maxSubLayersMinus1].

[0228] The HRD parameter semantics include the general HRD parameter semantics.

[0229] The general HDR parameter semantics are as follows:

[0230] The general_hrd_parameters() syntax structure specifies the HRD parameters used in HRD calculations.

[0231] num_ols_hrd_params_minus1+1 specifies the number of ols_hrd_parameters() syntax structures present in the general_hrd_parameters() syntax structure. The value of num_ols_hrd_params_minus1 shall be in the range of 0 to 63. When TotalNumOlss is greater than 1, the value of num_ols_hrd_params_minus1 is inferred to be equal to 0.

[0232] hrd_cpb_cnt_minus1+1 specifies the number of alternative CPBs in the CVS bitstream. The value of hrd_cpb_cnt_minus1 must be in the range of 0 to 31.

[0233] hrd_max_temporal_id[i] specifies the TemporalId of the top-level sublayer representation whose HRD parameters are included in the i-th layer_level_hrd_parameters() syntax structure. The value of hrd_max_temporal_id[i] shall be in the range from 0 to vps_max_sub_layers_minus1. When vps_max_sub_layers_minus1 is equal to 0, the value of hrd_max_temporal_id[i] is inferred to be equal to 0.

[0234] ols_hrd_idx[i] specifies the index of the ols_hrd_parameters() syntax structure that applies to the i-th OLS. The value of ols_hrd_idx[[i] shall be in the range from 0 to num_ols_hrd_params_minus1. When not present, the value of ols_hrd_idx[[i] is inferred to be equal to 0.

[0235] The reference picture list structure semantics are as follows:

[0236] The ref_pic_list_struct(listIdx, rplsIdx) syntax structure may be present in the SPS or in the slice header. Depending on whether the syntax structure is included in the slice header or the SPS, the following applies:

[0237] - If present in the slice header, the ref_pic_list_struct(listIdx, rplsIdx) syntax structure specifies the reference picture list listIdx of the current picture (the picture that contains the slice).

[0238] - Otherwise (if present in the SPS), the ref_pic_list_struct(listIdx, rplsIdx) syntax structure specifies candidates for the reference picture list listIdx, and the term "current picture" in the semantics specified in the remainder of this section refers to each picture that 1) has one or more slices with ref_pic_list_idx[listIdx] equal to an index into the list of ref_pic_list_struct(listIdx, rplsIdx) syntax structures contained in the SPS, and 2) is in a CVS that references the SPS.

[0239] num_ref_entries[listIdx][rplsIdx] specifies the number of entries in the ref_pic_list_struct(listIdx, rplsIdx) syntax structure. The value of num_ref_entries[listIdx][rplsIdx] shall be in the range of 0 to MaxDecPicBuffMinus1+14.

[0240] DCI 802, VPS 804, SPS 806, and PPS 808 are included in different types of network abstraction layer (NAL) units. NAL units are syntax structures that contain an indication of the type of data that follows (e.g., coded video data). NAL units are classified into video coding layer (VCL) NAL units and non-VCL NAL units. VCL NAL units contain data that represent values ​​of samples in a video picture, and non-VCL NAL units contain any relevant additional information such as parameter sets (important data that is applicable to many VCL NAL units) and additive enhancement information (timing information and other supplementary data that may enhance the usability of the decoded video signal but are not necessary to decode values ​​of samples in a video picture).

[0241] In one embodiment, DCI 802 is included in a non-VCL NAL unit designated as a DCI NAL unit or a DPS NAL unit. That is, DCI NAL units have a DCI NAL unit type (NUT) and DPS NAL units have a DPS NUT. In one embodiment, VPS 804 is included in a non-VCL NAL unit designated as a VPS NAL unit. Thus, the VPS NAL unit has a VPS NUT. In one embodiment, SPS 806 is a non-VCL NAL unit designated as an SPS NAL unit. Thus, the SPS NAL unit has an SPS NUT. In one embodiment, PPS 808 is included in a non-VCL NAL unit designated as a PPS NAL unit. Thus, the PPS NAL unit has a PPS NUT.

[0242] PH 812 is a syntax structure that includes syntax elements that apply to all slices (e.g., slice 818) of a coded picture (e.g., picture 814). In one embodiment, PH 812 is in a new type of non-VCL NAL unit designated as a PH NAL unit. Thus, a PH NAL unit has a PH NUT (e.g., PH_NUT). In one embodiment, each PU 801 contains only one PH 812. That is, a PU 801 contains a single, or isolated, PH 812. In one embodiment, exactly one PH NAL unit exists for each picture 814 in the bitstream 800.

[0243] A picture 814 is an array of luma samples in 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. In one embodiment, each PU 801 contains only one picture 814. As such, there is only one PH 812 and only one picture 814 corresponding to that PH 812 in each PU 801. That is, a PU 801 contains a single, or isolated, picture 814.

[0244] Pictures 814 may be either frames or fields. However, in one CVS 816, either all pictures 814 are frames or all pictures 814 are fields. CVS 816 is a coded video sequence for all coded layered video sequences (CLVS) in video bitstream 800. In particular, CVS 816 and CLVS are the same when video bitstream 800 contains a single layer. CVS 816 and CLVS are different only when video bitstream 800 contains multiple layers (e.g., as shown in Figures 5 and 6).

[0245] Each picture 814 includes one or more slices 818. A slice 818 is an integer number of complete tiles or an integer number of contiguous complete CTU rows within a tile of a picture (e.g., picture 814). Each slice 818 is exclusively contained within a single NAL unit (e.g., a VCL NAL unit). A tile (not shown) is a rectangular region of CTUs within a particular tile column and a particular tile row within a picture (e.g., picture 814). A CTU (not shown) is a CTB of luma samples, two corresponding CTBs of chroma samples for a picture with a three sample array, or a CTB of samples for a monochrome picture or a picture coded using three separate color planes and syntax structures used to code the samples. A CTB (not shown) is an N×N block of samples for some value of N such that dividing the components into CTBs is a partitioning. A block (not shown) is an M×N (M columns×N rows) array of samples (e.g., pixels), or an M×N array of transform coefficients.

[0246] In one embodiment, each slice 818 includes a slice header 820. The slice header 820 is a portion of a coded slice 818 that contains data elements related to all tiles or CTU rows within the tile represented by the slice 818. That is, the slice header 820 includes information about the slice 818, such as, for example, the slice type, which of the reference pictures are used, etc.

[0247] The picture 814 and its slices 818 contain data associated with the image or video being encoded or decoded. Thus, the picture 814 and its slices 818 may simply be referred to as the payload or data carried in the bitstream 800.

[0248] Those skilled in the art will appreciate that the bitstream 800 may include other parameters and information in practical applications.

[0249] FIG. 9 is an embodiment of a method 900 of decoding implemented by a video decoder (e.g., video decoder 400). The method 900 may be executed after a bitstream is received directly or indirectly from a video encoder (e.g., video encoder 300). The method 900 improves the decoding process by ensuring that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (aka "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience to users when videos are transmitted, received, and / or viewed.

[0250] In block 902, a video decoder receives a video bitstream. The video bitstream includes a plurality of layers (e.g., layers 531, 532) having sublayers (e.g., sublayers 710, 720, 730) and a VPS (e.g., VPS 804). The VPS includes a first flag (e.g., flag 850) having a first value (e.g., 1). The first flag having the first value specifies that a temporal identifier (TemporalID) of a top sublayer representation (e.g., sublayer 730) for level information, decoded picture buffer (DPB) parameters, and hypothetical decoder refresh (HRD) parameters is not present in the VPS and is inferred to be equal to the maximum number of sublayers that may be present in one layer of the plurality of layers specified by the VPS.

[0251] In one embodiment, the maximum number of sublayers is in the range of 1 to 7. In one embodiment, the level information is included in the profile, tier, and level (PTL) parameters. In one embodiment, the level information is present in the i-th profile_tier_level() syntax structure in the VPS. In one embodiment, the DPB parameters are present in the i-th dpb_parameters() syntax structure in the VPS. In one embodiment, the HRD parameters are in the i-th ols_timing_hrd_parameters() syntax structure in the VPS or Sequence Parameter Set (SPS).

[0252] In block 904, level information corresponding to the temporal ID of the top sub-layer representation, the HRD parameters, and the DPB parameters are obtained from the VPS.

[0253] In block 906, the video decoder decodes a picture from one of the layers to obtain a decoded picture. In one embodiment, the picture is decoded without using the HRD parameters, i.e., the HRD parameters are used to test the conformance of the bitstream and are not used to decode the pictures contained therein.

[0254] After the pictures are decoded, they may be used to generate or form an image or video sequence for display to a user on a display or screen of an electronic device (e.g., a smartphone, tablet, laptop, personal computer, etc.).

[0255] FIG. 10 is an embodiment of a method 1000 for encoding a video bitstream implemented by a video encoder (e.g., video encoder 300). The method 1000 may be executed when pictures (e.g., from a video) are encoded into a video bitstream and then transmitted toward a video decoder (e.g., video decoder 400). The method 1000 improves the encoding process by ensuring that the same profile, tier, and level (PTL) parameters, hypothetical reference decoder (HRD) parameters, and decoded picture buffer (DPB) parameters are not repeatedly signaled for layers in a multi-layer bitstream. Signaling the same PTL parameters, HRD parameters, and DPB parameters only once reduces redundancy for a multi-layer video bitstream and increases coding efficiency. Thus, the coder / decoder (a.k.a. "codec") in video coding is improved compared to current codecs. In practical terms, the improved video coding process provides a better user experience to users when videos are transmitted, received, and / or viewed.

[0256] In block 1002, a video encoder generates a number of layers (e.g., layers 531, 532) having sublayers (e.g., sublayers 710, 720, 730) and a VPS (e.g., VPS 804) including a first flag (e.g., flag 850).

[0257] In block 1004, the video encoder sets a first flag to a first value to specify that a temporal identifier (TemporalID) of the top-level sub-layer representation (e.g., sub-layer 730) for level information, decoded picture buffer (DPB) parameters, and hypothetical decoder refresh (HRD) parameters is not present in the VPS and should be inferred to be equal to the maximum number of sub-layers that may be present in one of the multiple layers specified by the VPS.

[0258] In one embodiment, the maximum number of sublayers is in the range of 1 to 7. In one embodiment, the level information is included in the profile, tier, and level (PTL) parameters. In one embodiment, the level information is present in the i-th profile_tier_level() syntax structure in the VPS. In one embodiment, the DPB parameters are present in the i-th dpb_parameters() syntax structure in the VPS. In one embodiment, the HRD parameters are in the i-th ols_timing_hrd_parameters() syntax structure in the VPS or Sequence Parameter Set (SPS).

[0259] In one embodiment, the method 1000 further includes using the HRD parameters to determine whether the encoded video bitstream is compliant, i.e., whether the bitstream conforms to a standard (e.g., the VVC standard) when it was encoded.

[0260] At block 1006, the video encoder encodes the multiple layers and the VPS into a video bitstream. At block 1008, the video encoder stores the video bitstream for communication to the video decoder. The video bitstream may be stored in a memory until the video bitstream is transmitted to the video decoder. Once received by the video decoder, the encoded video bitstream may be decoded (e.g., as described above) to generate or form images or video sequences for display to a user on a display or screen of an electronic device (e.g., a smartphone, tablet, laptop, personal computer, etc.).

[0261] Additional and / or supplemental details are provided below.

[0262] The general decoding process is as follows:

[0263] The input to this process is a bitstream BitstreamToDecode. The output of this process is a list of decoded pictures.

[0264] The decoding process is specified such that all decoders conforming to a specified profile and level will produce numerically identical cropped decoded output pictures when invoking the decoding process associated with that profile on a bitstream conforming to that profile and level. Any decoding process that produces cropped decoded output pictures identical to those produced by the process described herein (with the correct output order or output timing, as specified) conforms to the decoding process requirements of the VVC standard.

[0265] For each IRAP AU in the bitstream the following applies:

[0266] - The variable NoIncorrectPicOutputFlag is set equal to 1 if the AU is the first AU in decoding order in the bitstream, or the respective picture is an Instantaneous Decoding Refresh (IDR) picture, or the respective picture is the first picture of the layer that follows the end of the sequence NAL unit in decoding order.

[0267] - Otherwise, if some external means not specified herein is available to set the variable HandleCraAsCvsStartFlag to a value for the AU, then HandleCraAsCvsStartFlag is set equal to the value provided by the external means and NoIncorrectPicOutputFlag is set equal to HandleCraAsCvsStartFlag.

[0268] - Otherwise, HandleCraAsCvsStartFlag and NoIncorrectPicOutputFlag are both set equal to 0.

[0269] For each GDR AU in the bitstream the following applies:

[0270] The variable NoIncorrectPicOutputFlag is set equal to 1 if the AU is the first AU in the bitstream in decoding order or if the respective picture is the first picture of the layer following the end of the sequence NAL unit in decoding order.

[0271] - Otherwise, if some external means not specified in this specification are available to set the variable HandleGdrAsCvsStartFlag to a value for the AU, HandleGdrAsCvsStartFlag is set equal to the value provided by the external means and NoIncorrectPicOutputFlag is set equal to HandleGdrAsCvsStartFlag.

[0272] - Otherwise, HandleGdrAsCvsStartFlag and NoIncorrectPicOutputFlag are both set equal to 0.

[0273] NOTE – For both IRAP and GDR pictures, the above operations are necessary to identify the CVS in the bitstream.

[0274] Section 8.1.2 is called repeatedly for each coded picture in BitstreamToDecode, in decoding order.

[0275] The decoding process for constructing a reference picture list is as follows.

[0276] This process is invoked at the beginning of the decoding process for each slice of a non-IDR picture.

[0277] A reference picture is addressed through a reference index, which is an index into a reference picture list. When decoding an I slice, no reference picture list is used in decoding the slice data. When decoding a P slice, only reference picture list 0 (i.e., RefPicList[0]) is used in decoding the slice data. When decoding a B slice, both reference picture list 0 and reference picture list 1 (i.e., RefPicList[1]) are used in decoding the slice data.

[0278] It is a requirement of bitstream conformance that the following constraints apply:

[0279] - For each i equal to 0 or 1, num_ref_entries[i][RplsIdx[i]] shall not be less than NumRefIdxActive[i].

[0280] - The picture referenced by each active entry in RefPicList[0] or RefPicList[1] shall be present in the DPB and shall have a TemporalId less than or equal to the TemporalId of the current picture.

[0281] - The picture referenced by each entry in RefPicList[0] or RefPicList[1] shall not be the current picture and shall have non_reference_picture_flag equal to 0.

[0282] - A short-term reference picture (STRP) entry in RefPicList[0] or RefPicList[1] of a slice of a picture and an LTRP entry in RefPicList[0] or RefPicList[1] of the same slice or a different slice of the same picture shall not reference the same picture.

[0283] - There shall be no LTRP entries in RefPicList[0] or RefPicList[1] such that the difference between the PicOrderCntVal of the current picture and the PicOrderCntVal of the picture referenced by that entry is 224 or more.

[0284] - Let setOfRefPics be the set of unique pictures referenced by all entries in RefPicList[0] with the same nuh_layer_id as the current picture and all entries in RefPicList[1] with the same nuh_layer_id as the current picture. The number of pictures in setOfRefPics shall be less than or equal to MaxDecPicBuffMinus1, and setOfRefPics shall be the same for all slices of a picture.

[0285] - When the current picture is a Progressive Temporal Sub-layer Access (STSA) picture, there shall be no active entry in RefPicList[0] or RefPicList[1] with TemporalId equal to the TemporalId of the current picture.

[0286] When the current picture is a picture that follows, in decoding order, an STSA picture with a TemporalId equal to the TemporalId of the current picture, there shall be no picture with a TemporalId equal to the TemporalId of the current picture included as an active entry in RefPicList[0] or RefPicList[1] that precedes the STSA picture in decoding order.

[0287] - The pictures referenced by each ILRP entry in RefPicList[0] or RefPicList[1] of a slice of the current picture shall be in the same access unit as the current picture.

[0288] - The picture referenced by each ILRP entry in RefPicList[0] or RefPicList[1] of a slice of the current picture shall be present in the DPB and shall have a nuh_layer_id less than the nuh_layer_id of the current picture.

[0289] - Each ILRP entry in RefPicList[0] or RefPicList[1] of a slice shall be an active entry.

[0290] The HRD general aspects of Section C.1 of the VVC standard include:

[0291] This appendix specifies the Hypothetical Reference Decoder (HRD) and its use for checking the conformance of bitstreams and decoders.

[0292] A set of bitstream conformance tests is required to check the conformance of the entire bitstream, denoted as the entireBitstream. The set of bitstream conformance tests is to test the conformance of each OP of each OLS specified by the VPS.

[0293] For each test, the following sequence of steps are applied in the order listed, followed by the process described after those steps in this section.

[0294] 1. An operation point to be tested, denoted targetOp, is selected by selecting the target OLS with OLS index opOlsIdx and highest TemporalId value opTid. The value of opOlsIdx lies in the range from 0 to TotalNumOlss-1. The value of opTid lies in the range from 0 to vps_max_sub_layers_minus1. Each pair of selected values ​​of opOlsIdx and opTid shall be such that the sub-bitstream output by invoking the sub-bitstream extraction process specified in section C.6 with inputs entireBitstream, opOlsIdx, and opTid satisfies the following condition:

[0295] - There is at least one VCL NAL unit with nuh_layer_id value equal to nuh_layer_id in LayerIdInOls[opOlsIdx] in BitstreamToDecode.

[0296] - There is at least one VCL NAL unit in BitstreamToDecode with TemporalId equal to opTid.

[0297] 2. If the layers in targetOp include all layers in the entireBitstream and opTid is greater than or equal to the highest TemporalId value among all NAL units in the entireBitstream, then BitstreamToDecode is set to be identical to the entireBitstream. Otherwise, BitstreamToDecode is set to be output by invoking the sub-bitstream extraction process as specified in Section C.6 with the entireBitstream, opOlsIdx, and opTid as input.

[0298] 3. The values ​​of TargetOlsIdx and Htid are set equal to the opOlsIdx and opTid of targetOp, respectively.

[0299] 4. A value for ScIdx is selected. The selected ScIdx shall be in the range from 0 to hrd_cpb_cnt_minus1.

[0300] 5. The access unit in BitstreamToDecode associated with the buffering period SEI message applicable to TargetOlsIdx (present in TargetLayerBitstream or available through external means not specified herein) is selected as the HRD initialization point and is referenced as access unit 0 for each layer of the target OLS.

[0301] 6. The ols_hrd_parameters() syntax structure and sub_layer_hrd_parameters() syntax structure applicable to BitstreamToDecode are selected as follows:

[0302] - The ols_hrd_idx[TargetOlsIdx]th ols_hrd_parameters() syntax structure in the VPS (or provided through external means not specified here) is selected.

[0303] - within the selected ols_hrd_parameters() syntax structure, if BitstreamToDecode is a type I bitstream, then the sub_layer_hrd_parameters(Htid) syntax structure that comes immediately after the condition "if(general_vcl_hrd_params_present_flag)" is selected and the variable NalHrdModeFlag is set equal to 0, otherwise (if BitstreamToDecode is a type II bitstream), then the sub_layer_hrd_parameters(Htid) syntax structure that comes immediately after either the condition "if(general_vcl_hrd_params_present_flag)" (in this case the variable NalHrdModeFlag is set equal to 0) or the condition "if(general_nal_hrd_params_present_flag)" (in this case the variable NalHrdModeFlag is set equal to 1) is selected. When BitstreamToDecode is a Type II bitstream and NalHrdModeFlag is equal to 0, all non-VCL NAL units except filler data NAL units, as well as all leading_zero_8bits, zero_byte, start_code_prefix_one_3bytes, and trailing_zero_8bits syntax elements that form a byte stream from the NAL unit stream (as specified in Appendix B), when present, are discarded from BitstreamToDecode and the remaining bitstream is assigned to BitstreamToDecode.

[0304] 7. When decoding_unit_hrd_params_present_flag is equal to 1, the CPB is scheduled to operate either at the access unit level (in this case the variable DecodingUnitHrdFlag is set equal to 0) or at the decoding unit level (in this case the variable DecodingUnitHrdFlag is set equal to 1). Otherwise, DecodingUnitHrdFlag is set equal to 0 and the CPB is scheduled to operate at the access unit level.

[0305] 8. For each access unit in BitstreamToDecode starting with access unit 0, a buffering period SEI message (present in BitstreamToDecode or available through external means not specified herein) associated with the access unit and applied to TargetOlsIdx is selected, a picture timing period SEI message (present in BitstreamToDecode or available through external means not specified herein) associated with the access unit and applied to TargetOlsIdx is selected, and when DecodingUnitHrdFlag is equal to 1 and decoding_unit_cpb_params_in_pic_timing_sei_flag is equal to 0, a decoding unit information SEI message (present in BitstreamToDecode or available through external means not specified herein) associated with a decoding unit in the access unit and applied to TargetOlsIdx is selected.

[0306] Each conformance test consists of a combination of one option in each of the steps above. When there are multiple options for a step, only one option is selected for any particular conformance test. All possible combinations of all steps form the entire set of conformance tests. For each operational point to be tested, the number of bitstream conformance tests to be performed is equal to n0*n1*n2*n3, where the values ​​of n0, n1, n2, and n3 are specified as follows:

[0307] - n1 is equal to hrd_cpb_cnt_minus1+1.

[0308] - n1 is the number of access units in BitstreamToDecode associated with the buffering period SEI message.

[0309] - n2 is derived as follows:

[0310] - If BitstreamToDecode is a Type I bitstream, n0 is equal to 1.

[0311] - Otherwise (if BitstreamToDecode is a Type II bitstream), n0 is equal to 2.

[0312] - n3 is derived as follows:

[0313] - If decoding_unit_hrd_params_present_flag is equal to 0, n3 is equal to 1.

[0314] - Otherwise, n3 is equal to 2.

[0315] The HRD includes a bitstream extractor (optionally present), a coded picture buffer (CPB), an instantaneous decoding process, a decoded picture buffer (DPB) that conceptually contains sub-DPBs for each layer, and output cropping.

[0316] For each bitstream conformance test, the CPB size (in bits) is CpbSize[Htid][ScIdx] as specified in Section 7.4.5.2, where ScIdx and the HRD parameters are specified above in this section, and the DPB parameters max_dec_pic_buffering_minus1[Htid], max_num_reorder_pics[Htid], and MaxLatencyPictures[Htid] for each layer are found in or derived from the dpb_pameters() syntax structure that applies to that layer depending on whether the layer is an independent layer and whether the layer is an output layer of the target OLS.

[0317] HRD works as follows:

[0318] - The HDR is initialized with decoding unit 0, and both the CPB and each sub-DPB of the DPB are set to empty (the sub-DPB fill amount for each sub-DPB is set to be equal to 0).

[0319] NOTE – After initialization, the HRD is not reinitialized by any subsequent buffering period SEI messages.

[0320] - Data associated with the decoding units that flow into each CPB according to a specified arrival schedule is delivered by the Virtual Stream Scheduler (HSS).

[0321] - Data associated with each decoding unit is removed and instantaneously decoded by the instantaneous decoding process at the CPB removal time of the decoding unit.

[0322] - Each decoded picture is placed in the DPB.

[0323] - A decoded picture is removed from the DPB when it is no longer needed for inter prediction reference and no longer needed for output.

[0324] A decoded picture buffer operation is provided.

[0325] The specifications in this section apply independently to each set of Decoded Picture Buffer (DPB) parameters selected as specified in Section C.1.

[0326] The decoded picture buffer is conceptually composed of sub-DPBs, each of which contains a picture storage buffer for storing decoded pictures of one layer. Each of the picture storage buffers may contain decoded pictures that are marked as "used for reference" or are kept for future output. The processes specified in sections C3.2, C3.3, and C3.4 are applied sequentially as specified below, and are applied independently for each layer starting with the lowest layer in the OLS, in order of increasing nuh_layer_id values ​​of the layers in the OLS. When these processes are applied for a particular layer, only the sub-DPB for that particular layer is affected. In the description of these processes, DPB refers to the sub-DPB for a particular layer, and that particular layer is referred to as the current layer.

[0327] NOTE – In the operation of the Output Timing DPB, decoded pictures with PicOutputFlag equal to 1 in the same access unit are output consecutively in ascending order of the nuh_layer_id values ​​of the decoded pictures.

[0328] Let picture n and the current picture be the coded or decoded pictures of access unit n for a particular value of nuh_layer_id, where n is a non-negative integer value.

[0329] Removing a picture from the DPB before decoding the current picture is described.

[0330] Removal of a picture from the DPB before decoding of the current picture (but after parsing the slice header of the first slice of the current picture) occurs instantaneously at the CPB removal time of the first decoding unit of access unit n (containing the current picture) and proceeds as follows:

[0331] - The decoding process for reference picture list construction is invoked as specified in subclause 8.3.2, and the decoding process for reference picture marking is invoked as specified in subclause 8.3.3.

[0332] - When the current AU is a CVSS AU that is not AU 0, the following ordered steps are applied:

[0333] 1. The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows:

[0334] - The values ​​of pic_width_max_in_luma_samples, pic_height_max_in_luma_samples, chroma_format_idc, separate_colour_plane_flag, bit_depth_luma_minus8, bit_depth_chroma_minus8 or max_dec_pic_buffering_minus1[Htid] derived for any picture in the current AU are greater than or equal to the pic_width_in_luma_samples derived for the preceding picture in the same CLVS, respectively. If the value of no_output_of_prior_pics_flag is different from the values ​​of es, pic_height_in_luma_samples, chroma_format_idc, separate_colour_plane_flag, bit_depth_luma_minus8, bit_depth_chroma_minus8, or max_dec_pic_buffering_minus1[Htid], NoOutputOfPriorPicsFlag may (and should not be) set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.

[0335] NOTE - Although setting NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is permitted to set NoOutputOfPriorPicsFlag to 1 in this case.

[0336] - Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag.

[0337] 2. The derived value of NoOutputOfPriorPicsFlag for the decoder under test is applied to the HRD so that when the value of NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB are emptied without output of the pictures they contain and the DPB fullness is set equal to 0.

[0338] - Every picture k in the DPB is removed from the DPB when both of the following conditions are true for that picture k in the DPB:

[0339] - Picture k is marked as "unused for reference".

[0340] - Picture k has PictureOutputFlag equal to 0 or its DPB output time is less than or equal to the CPB removal time of the first decoding unit of the current picture n (denoted as decoding unit m), i.e., DpbOutputTime[k] is less than or equal to DuCpbRemovalTime[m].

[0341] - For each picture removed from the DPB, the DPB fullness is decremented by one.

[0342] The operation of the output order DPB will now be described.

[0343] The specifications in this section apply independently to each set of Decoded Picture Buffer (DPB) parameters selected as specified in Section C.1.

[0344] The decoded picture buffer is conceptually composed of sub-DPBs, each of which contains a picture storage buffer for storing the decoded pictures of one layer. Each of the picture storage buffers contains decoded pictures that are marked as "used for reference" or are retained for future output.

[0345] The process for outputting and removing a picture from the DPB before decoding the current picture as specified in clause C.5.2.2 is invoked, followed by the process for marking and storing the current decoded picture as specified in clause C.3.4, followed finally by the process for additional bumping as specified in clause C.5.2.3. The "bumping" process is specified in clause C.5.2.4 and is invoked as specified in clauses C.5.2.2 and C.5.2.3.

[0346] These processes are applied independently for each layer in the order of increasing nuh_layer_id values ​​of layers in the OLS, starting from the lowest layer in the OLS. When these processes are applied for a particular layer, only the sub-DPBs for that particular layer are affected.

[0347] NOTE – In the Output Order DPB operation, like the Output Timing DPB operation, decoded pictures with PicOutputFlag equal to 1 within the same access unit are also output consecutively in ascending order of the nuh_layer_id values ​​of the decoded pictures.

[0348] Let picture n and the current picture be the coded or decoded pictures of access unit n for a particular value of nuh_layer_id, where n is a non-negative integer value.

[0349] Outputting and removing pictures from the DPB is described.

[0350] The output and removal of a picture from the DPB before decoding of the current picture (but after parsing the slice header of the first slice of the current picture) occurs the instantaneously when the first decoding unit of the access unit containing the current picture is removed from the CPB, and proceeds as follows:

[0351] - The decoding process for reference picture list construction is invoked as specified in subclause 8.3.2, and the decoding process for reference picture marking is invoked as specified in subclause 8.3.3.

[0352] - If the current AU is a CVSS AU that is not AU0, the following ordered steps are applied:

[0353] 1. The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows:

[0354] - The values ​​of pic_width_max_in_luma_samples, pic_height_max_in_luma_samples, chroma_format_idc, separate_colour_plane_flag, bit_depth_luma_minus8, bit_depth_chroma_minus8 or max_dec_pic_buffering_minus1[Htid] derived for any picture in the current AU are greater than or equal to the pic_width_in_luma_samples derived for the preceding picture in the same CLVS, respectively. If the value of no_output_of_prior_pics_flag is different from the values ​​of s, pic_height_in_luma_samples, chroma_format_idc, separate_colour_plane_flag, bit_depth_luma_minus8, bit_depth_chroma_minus8, or max_dec_pic_buffering_minus1[Htid], NoOutputOfPriorPicsFlag may (and should not be) set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.

[0355] NOTE - Although setting NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is permitted to set NoOutputOfPriorPicsFlag to 1 in this case.

[0356] - Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag.

[0357] 2. The value of the variable NoOutputOfPriorPicsFlag derived for the decoder under test is applied for HRD as follows:

[0358] - If NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB are emptied without output of the pictures they contain and the DPB fullness is set equal to 0.

[0359] - Otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing pictures marked as "not needed for output" and "unused for reference" are emptied (without output), all non-empty picture storage buffers in the DPB are emptied by repeatedly invoking the "bumping" process specified in clause C.5.2.4, and the DPB fullness is set equal to 0.

[0360] - Otherwise (if the current picture is not a CLVSS picture), all Picture Storage Buffers containing pictures marked as "not needed for output" and "unused for reference" are emptied (without output). For each Picture Storage Buffer emptied, the DPB fullness is decremented by 1. When one or more of the following conditions are true, the "bumping" process specified in clause C.5.2.4 is repeatedly invoked, further decrementing the DPB fullness by 1 for each additional Picture Storage Buffer emptied, until none of the following conditions are true:

[0361] The number of pictures in the DPB marked as "required for output" is greater than max_num_reorder_pics[Htid].

[0362] max_latency_increase_plus1[Htid] is not equal to 0 and there is at least one picture in the DPB marked as "needed for output" whose associated variable PicLatencyCount is greater than or equal to MaxLatencyPictures[Htid].

[0363] The number of pictures in the DPB is greater than or equal to max_dec_pic_buffering_minus1[Htid]+1.

[0364] Additional bumping is described.

[0365] The process specified in this section occurs the instant that the last decoding unit of access unit n, which contains the current picture, is removed from the CPB.

[0366] When the current picture has PictureOutputFlag equal to 1, for each picture in the DPB that is marked as "required for output" and follows the current picture in output order, the associated variable PicLatencyCount is set equal to PicLatencyCount+1.

[0367] The following applies:

[0368] - If the current decoded picture has PictureOutputFlag equal to 1, it is marked as "needed for output" and its associated variable PicLatencyCount is set equal to 0.

[0369] - Otherwise (the current decoded picture has PictureOutputFlag equal to 0), it is marked as "not needed for output".

[0370] When one or more of the following conditions are true, the "bumping" process specified in Section C.5.2.4 is repeatedly invoked until none of the following conditions are true:

[0371] - The number of pictures in the DPB that are marked as "required for output" is greater than max_num_reorder_pics[Htid].

[0372] - max_latency_increase_plus1[Htid] is not equal to 0 and there is at least one picture in the DPB marked as "needed for output" whose associated variable PicLatencyCount is greater than or equal to MaxLatencyPictures[Htid].

[0373] A bumping process is described.

[0374] The "bumping" process consists of the following ordered steps:

[0375] The picture or pictures that are first for output are selected as those with the minimum value of PicOrderCntVal of all pictures in the DPB marked as "required for output".

[0376] Each of these pictures is cropped using the adaptive cropping window for the picture, in ascending nuh_layer_id order, the cropped picture is output, and the picture is marked as "not needed for output".

[0377] Each picture storage buffer, including a picture marked as "unused for reference" and which was one of the cropped and output pictures, is emptied and the fullness of the associated sub-DPB is decremented by one.

[0378] NOTE - For any two pictures picA and picB that belong to the same CVS and are output by the "bumping process", when picA is output earlier than picB, the value of PicOrderCntVal of picA is less than the value of PicOrderCntVal of picB.

[0379] A sub-bitstream extraction process is described.

[0380] The inputs to this process are the bitstream inBitstream, the target OLS index targetOlsIdx, and the target highest TemporalId value tIdTarget.

[0381] The output of this process is the sub-bitstream outBitstream.

[0382] Given a bitstream, targetOlsIdx equal to an index into the list of OLSs specified in the VPS, and tIdTarget equal to any value in the range from 0 to 6, it is a bitstream conformance requirement for an input bitstream that any output sub-bitstream that is the output of a process specified in this section that satisfies the following conditions is a conforming bitstream:

[0383] - The output sub-bitstream contains at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​in LayerIdInOls[targetOlsIdx].

[0384] - The output sub-bitstream contains at least one VCL NAL unit with TemporalId equal to tIdTarget.

[0385] NOTE - A conforming bitstream contains one or more coded slice NAL units with TemporalId equal to 0, but it does not have to contain any coded slice NAL units with nuh_layer_id equal to 0.

[0386] The output sub-bitstream OutBitstream is derived as follows.

[0387] The bitstream outBitstream is set to be identical to the bitstream inBitstream.

[0388] - Remove all NAL units with TemporalId greater than tIdTarget from outBitstream.

[0389] - Remove all NAL units with nuh_layer_id that are not included in the list LayerIdInOls[targetOlsIdx] from outBitstream.

[0390] - Remove from outBitstream all SEI NAL units, including scalable nesting SEI messages, with nesting_ols_flag equal to 1, no value of i in the range from 0 to nesting_num_olss_minus1, and NestingOlsIdx[i] equal to targetOlsIdx.

[0391] - Remove all SEI NAL units, including non-scalable nested SEI messages, with payloadType equal to 0 (buffering duration), 1 (picture timing), or 130 (decoding unit information) from outBitstream when targetOlsIdx is greater than 0.

[0392] A scalable nesting SEI message syntax is presented. [Table 8]

[0393] General SEI payload semantics are presented.

[0394] On the applicable layer or OLS of a non-scalable nested SEI message, the following applies:

[0395] - For non-scalable nested SEI messages, when payloadType is equal to 0 (buffering duration), 1 (picture timing), or 130 (decoding unit information), the non-scalable nested SEI message applies only to the 0th OLS.

[0396] - For non-scalable nested SEI messages, when payloadType is equal to any value in VclAssociatedSeiList, the non-scalable nested SEI message applies only to the layer with nuh_layer_id equal to the nuh_layer_id of the SEI NAL unit up to which the VCL NAL unit containing the SEI message belongs.

[0397] …

[0398] It is a bitstream conformance requirement that the following restrictions apply to values ​​of nuh_layer_id in SEI NAL units:

[0399] - When a non-scalable nested SEI message has payloadType equal to 0 (buffering duration), 1 (picture timing), or 130 (decoding unit information), the SEI NAL unit containing the non-scalable nested SEI message shall have nuh_layer_id equal to vps_layer_id[0].

[0400] - When a non-scalable nested SEI message has payloadType equal to any value in VclAssociatedSeiList, the SEI NAL unit that contains the non-scalable nested SEI message shall have nuh_layer_id equal to the value of nuh_layer_id of the VCL NAL unit associated with the SEI NAL unit.

[0401] - An SEI NAL unit containing a scalable nesting SEI message shall have nuh_layer_id equal to the minimum of nuh_layer_id of all layers to which the scalable nesting SEI message applies (when nesting_ols_flag in the scalable nesting SEI message is equal to 0) or the minimum of nuh_layer_id of all layers in the OLS to which the scalable nesting SEI message applies (when nesting_ols_flag in the scalable nesting SEI message is equal to 1).

[0402] Scalable nesting SEI message semantics are presented.

[0403] Scalable nesting SEI messages provide a mechanism to associate an SEI message with a particular OLS or with a particular layer.

[0404] The scalable nesting SEI message includes one or more SEI messages. An SEI message included in the scalable nesting SEI message is also referred to as a scalable nest SEI message.

[0405] It is a bitstream conformance requirement that the following restrictions apply to the inclusion of SEI messages within a scalable nesting SEI message:

[0406] - SEI messages with payloadType equal to 132 (decoded picture hash) or 133 (scalable nesting) shall not be included in a scalable nesting SEI message.

[0407] - When a scalable nesting SEI message contains a buffering period, picture timing, or decoding unit information SEI message, the scalable nesting SEI message shall not contain any other SEI message with payloadType not equal to 0 (buffering period), 1 (picture timing), or 130 (decoding unit information).

[0408] It is a bitstream conformance requirement that the following restrictions apply to values ​​of nal_unit_type of SEI NAL units that contain scalable nesting SEI messages:

[0409] - When a scalable nesting SEI message contains an SEI message with payloadType equal to 0 (buffering period), 1 (picture timing), 130 (decoding unit information), 145 (dependent RAP indication), or 168 (frame field information), the SEI NAL unit containing the scalable nesting SEI message shall have nal_unit_type equal to PREFIX_SEI_NUT.

[0410] nesting_ols_flag equal to 1 specifies that the scalable nested SEI message applies to a specific OLS. nesting_ols_flag equal to 0 specifies that the scalable nested SEI message applies to a specific layer.

[0411] It is a bitstream conformance requirement that the following restrictions apply to the value of nesting_ols_flag:

[0412] - The value of nesting_ols_flag shall be equal to 1 when the scalable nesting SEI message contains an SEI message with payloadType equal to 0 (buffering period), 1 (picture timing), or 130 (decoding unit information).

[0413] - When a scalable nesting SEI message contains an SEI message with payloadType equal to a value in VclAssociatedSeiList, the value of nesting_ols_flag shall be equal to 0.

[0414] nesting_num_olss_minus1+1 specifies the number of OLSs to which the scalable nesting SEI message applies. The value of nesting_num_olss_minus1 shall be in the range from 0 to TotalNumOlss-1.

[0415] nesting_ols_idx_delta_minus1[i] is used to derive the variable NestingOlsIdx[i], which specifies the OLS index of the i-th OLS to which the scalable nesting SEI message applies when nesting_ols_flag is equal to 1. The value of nesting_ols_idx_delta_minus1[i] shall be in the range from 0 to TotalNumOlss-2.

[0416] The variable NestingOlsIdx[i] is derived as follows: if(i==0) NestingOlsIdx[i]=nesting_ols_idx_delta_minus1[i] else NestingOlsIdx[i]=NestingOlsIdx[i-1]+nesting_ols_idx_delta_minus1[i]+1

[0417] nesting_all_layers_flag equal to 1 specifies that the scalable nested SEI message applies to all layers with nuh_layer_id greater than or equal to the nuh_layer_id of the current SEI NAL unit. nesting_all_layers_flag equal to 0 specifies that the scalable nested SEI message may or may not apply to all layers with nuh_layer_id greater than or equal to the nuh_layer_id of the current SEI NAL unit.

[0418] nesting_num_layers_minus1+1 specifies the number of layers to which the scalable nested SEI message applies. The value of nesting_num_layers_minus1 shall be in the range from 0 to vps_max_layers_minus1-GeneralLayerIdx[nuh_layer_id], where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit.

[0419] nesting_layer_id[i] specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies when nesting_all_layers_flag is equal to 0. The value of nesting_layer_id[i] shall be greater than nuh_layer_id, where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit.

[0420] The variable NestingNumLayers, which specifies the number of layers to which the scalable nesting SEI message applies when nesting_ols_flag is equal to 0, and the list NestingLayerId[i], for i in the range from 0 to NestingNumLayers-1, which specifies the list of layer nuh_layer_id values ​​to which the scalable nesting SEI message applies, are derived as follows, where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit: if(nesting_all_layers_flag) { NestingNumLayers= ps_max_layers_minus1+1-GeneralLayerIdx[nuh_layer_id] for(i=0; i <NestingNumLayers; i++) NestingLayerId[i]=vps_layer_id[GeneralLayerIdx[nuh_layer_id]+i] } else { NestingNumLayers=nesting_num_layers_minus1+1 for(i=0; i <NestingNumLayers; i++) NestingLayerId[i]=(i==0) ? nuh_layer_id: nesting_layer_id[i] }

[0421] nesting_num_seis_minus1+1 specifies the number of scalable nested SEI messages. The value of nesting_num_seis_minus1 shall be in the range of 0 to 63.

[0422] nesting_zero_bit shall be equal to 0.

[0423] FIG. 11 is a schematic diagram of a video coding device 1100 (e.g., video encoder 300 or video decoder 400) according to one embodiment of the disclosure. The video coding device 1100 is suitable for implementing the disclosed embodiments as described herein. The video coding device 1100 comprises a receiving port 1110 and a receiver unit (Rx) 1120 for receiving data, a processor, logic unit, or central processing unit (CPU) 1130 for processing data, a transmitter unit (Tx) 1140 and a transmitting port 1150 for transmitting data, and a memory 1160 for storing data. The video coding device 1100 may also comprise optical-electrical (OE) and electrical-optical (EO) components coupled to the receiving port 1110, the receiver unit 1120, the transmitter unit 1140, and the transmitting port 1150 for transmitting or receiving optical or electrical signals.

[0424] The processor 1130 is implemented by hardware and software. The processor 1130 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), and digital signal processors (DSPs). The processor 1130 communicates with the receiving port 1110, the receiver unit 1120, the transmitter unit 1140, the transmitting port 1150, and the memory 1160. The processor 1130 comprises a coding module 1170. The coding module 1170 implements the disclosed embodiments described above. For example, the coding module 1170 implements, processes, prepares, or provides various codec functions. Thus, the inclusion of the coding module 1170 brings substantial improvement to the functionality of the video coding device 1100 and brings about the transformation of the video coding device 1100 into different states. Alternatively, the coding module 1170 is implemented as instructions stored in the memory 1160 and executed by the processor 1130 .

[0425] Video coding device 1100 may also include input and / or output (I / O) devices 1180 for communicating data to and receiving data from a user. I / O devices 1180 may include output devices such as a display for displaying video data, speakers for outputting audio data, etc. I / O devices 1180 may also include input devices such as a keyboard, mouse, trackball, etc., and / or corresponding interfaces for interactively manipulating such output devices.

[0426] The memory 1160 may include one or more disks, tape drives, and solid state drives, and may be used as an overflow data storage device to store programs when such programs are selected for execution and to store instructions and data read during the execution of the programs. The memory 1160 may be 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).

[0427] 12 is a schematic diagram of one embodiment of a means for coding 1200. In one embodiment, the means for coding 1200 is implemented in a video coding device 1202 (e.g., video encoder 300 or video decoder 400). The video coding device 1202 includes a means for receiving 1201. The means for receiving 1201 is configured to receive a picture to encode or to receive a bitstream to decode. The video coding device 1202 includes a means for transmitting 1207 coupled to the means for receiving 1201. The means for transmitting 1207 is configured to transmit the bitstream to a decoder or transmit the decoded image to a display means (e.g., one of the I / O devices 1180).

[0428] The video coding device 1202 includes a storage means 1203. The storage means 1203 is coupled to at least one of the receiving means 1201 or the transmitting means 1207. The storage means 1203 is configured to store instructions. The video coding device 1202 also includes a processing means 1205. The processing means 1205 is coupled to the storage means 1203. The processing means 1205 is configured to execute the instructions stored in the storage means 1203 to perform the methods disclosed herein.

[0429] It should also be understood that the steps of the exemplary methods described herein do not necessarily have to be performed in the order described, and the order of steps of such methods should be understood to be merely exemplary. Similarly, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the present disclosure.

[0430] Although several embodiments are provided in this disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the disclosure. The examples should be considered illustrative and not restrictive, and the invention should not be limited to the details set forth in the specification. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0431] In addition, techniques, systems, subsystems, and methods described and illustrated in various embodiments as being discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items illustrated or described as being coupled or directly coupled or in communication with one another may be indirectly coupled or in communication through some interface, device, or intermediate component, whether electrical, mechanical, or otherwise. Other examples of changes, substitutions, and alterations can be ascertained by one of ordinary skill in the art and may be made without departing from the spirit and scope disclosed herein. [Explanation of symbols]

[0432] 1. OLS 2. OLS 3. OLS 100 How it works 200 Coding and Decoding (Codec) Systems 201 Segmented Video Signal 211 General Coder Control Component 213 Transform Scaling and Quantization Components 215 In-Picture Estimation Component 217 Intra-Picture Prediction Component 219 Motion Compensation Component 221 Motion Estimation Component 223 Decoded Picture Buffer Component 225 In-Loop Filter Components 227 Filter Control Analysis Component 229 Scaling and Inverse Transformation Components 231 Header Formatting and Context-Adaptive Binary Arithmetic Coding (CABAC) Components 300 Video Encoder 301 Segmented Video Signal 313 Transform and Quantize Components 317 Intra-Picture Prediction Component 321 Motion Compensation Component 323 Decoded Picture Buffer Component 325 In-Loop Filter Components 329 Inverse Transform and Quantization Components 331 Entropy Coding Component 400 Video Decoder 417 In-Picture Prediction Component 421 Motion Compensation Component 423 Decoded Picture Buffer Component 425 In-Loop Filter Components 429 Inverse Transform and Quantization Components 433 Entropy Decoding Component 500 Layer-based Prediction 506AU 508 AUD 511, 512, 513, 514 Pictures 515, 516, 517, 518 Pictures 521 Inter-layer Prediction 523 Inter Prediction 531 Layer N 532 Layer N+1 600 Layer-based Prediction 611~614 Pictures 615~618 Pictures 631 Layer N 632 Layer N+1 633 Layer N+2 634 Layer N+3 635 Layer N+4 641~644 Pictures 651~654 Pictures 661~664 Pictures 690 Coded Video Sequence (CVS) 700 Multi-layer Video Sequences 710, 720, 730 Sublayers 711 Pictures 721 Pictures 731 Pictures 740 Sublayer Representation 741 Pictures 755 TemporalID 757 TemporalID 759 TemporalID 800 Video Bitstream 801 Picture Unit (PU) 802 Decoding Capability Information (DCI) 804 Video Parameter Set (VPS) 806 Sequence Parameter Set (SPS) 808 Picture Parameter Set (PPS) 812 Picture Header (PH) 814 Pictures 816 Video Sequence (CVS) 818 slices 820 slice header 850 Flag 900 ways 1000 ways 1100 Video Coding Device 1110 inbound port 1120 Receiver Unit (Rx) 1130 Processor, Logic Unit, or Central Processing Unit (CPU) 1140 Transmitter Unit (Tx) 1150 outgoing port 1160 Memory 1170 Coding Module 1180 Input and / or Output (I / O) Devices 1200 A tool for coding 1201 Receiving means 1202 Video Coding Device 1203 Memory means 1205 Processing means 1207 Means of transmission

Claims

1. A method of decoding, comprising: receiving a video bitstream including a plurality of layers having sub-layers and a video parameter set (VPS), the VPS including a flag that, when having a first value, specifies that syntax elements including a first syntax element specifying a first temporal identifier (ID) of a highest sub-layer representation for level information and a second syntax element specifying a second temporal identifier (ID) of a highest sub-layer representation for decoded picture buffer (DPB) parameters are not present in the VPS, and that each syntax element should be inferred to be equal to a value of a third syntax element, the value of the third syntax element + 1 specifying the maximum number of the sub-layers that may be present in one layer of the plurality of layers specified by the VPS; decoding one of the plurality of layers by using the level information corresponding to the first temporal ID and / or the DPB parameters corresponding to the second temporal ID to obtain a decoded picture; A method comprising:

2. obtaining the level information corresponding to the first temporal ID as inferred according to the flag; and / or obtaining the DPB parameters corresponding to the second temporal ID as inferred according to the flag; The method of claim 1 further comprising:

3. A method of encoding, comprising: generating a video parameter set (VPS) including a plurality of layers including sub-layers, and a flag that, when having a first value, specifies that syntax elements including a first syntax element specifying a first temporal identifier (ID) of a highest sub-layer representation for level information and a second syntax element specifying a second temporal identifier (ID) of a highest sub-layer representation for decoded picture buffer (DPB) parameters are not present in the VPS, and that each syntax element should be inferred to be equal to a value of a third syntax element, the value of the third syntax element + 1 specifying the maximum number of sub-layers that may be present in one layer of the plurality of layers specified by the VPS; encoding the plurality of layers and the VPS into a video bitstream; A method comprising:

4. A method as described in claim 1 or 3, wherein the first value is 1 and the value of the third syntax element is in the range of 0 to 6.

5. A method as described in claim 1 or 3, wherein the flag, when having a second value, specifies that the syntax element is present in the VPS, and the second value is 0.

6. A method as described in claim 1 or 3, wherein the flag is present in the VPS when the value of the fourth syntax element is greater than 0 and the value of the third syntax element is greater than 0, and the value of the fourth syntax element +1 specifies the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS.

7. The method described in claim 6, wherein the first syntax element is specified as vps_ptl_max_tid[i], the second syntax element is specified as vps_dpb_max_tid[i], the third syntax element is specified as vps_max_sublayers_minus1, and the fourth syntax element is specified as vps_max_layers_minus1.

8. The method of claim 7, further comprising: storing the video bitstream for communication with a video decoder; or transmitting the video bitstream to the video decoder.

4. The method of claim 3, further comprising:

9. A decoding device configured to perform the method of any one of claims 1, 2, and 4 to 7.

10. An encoding device configured to perform the method of any one of claims 3 to 8.

11. A video bitstream for use by a computer, comprising: a plurality of layers including sub-layers, and a video parameter set (VPS), the VPS including a flag that, when having a first value, specifies that syntax elements including a first syntax element specifying a first temporal identifier (ID) of a highest sub-layer representation for level information and a second syntax element specifying a second temporal identifier (ID) of a highest sub-layer representation for decoded picture buffer (DPB) parameters are not present in the VPS, and that each syntax element should be inferred to be equal to a value of a third syntax element, the value of the third syntax element +1 specifying the maximum number of the sub-layers that may be present in one layer of the plurality of layers specified by the VPS; If the flag has the first value, the processor of the computer inferring the first temporal ID as the value of the third syntax element and obtaining the level information corresponding to the inferred first temporal ID from the VPS, and / or inferring the second temporal ID as the value of the third syntax element and obtaining the DPB parameters corresponding to the inferred second temporal ID from the VPS; and decoding one of the plurality of layers by using the level information corresponding to the first temporal ID and / or the DPB parameters corresponding to the second temporal ID to obtain a decoded picture; Making it possible to Video bitstream.

12. A video bitstream as described in Claim 11, wherein the first value is 1 and the value of the third syntax element is in the range of 0 to 6.

13. The flag, when having a second value, specifies that the syntax element is present in the VPS, the second value being 0; If the flag has the second value, the processor of the computer: Obtaining, from the VPS, the level information corresponding to the first temporal ID specified by the first syntax element present in the VPS, and / or obtaining, from the VPS, the DPB parameters corresponding to the second temporal ID specified by the second syntax element present in the VPS. The video bitstream of claim 11, wherein the bitstream enables:

14. A video bitstream as described in claim 11, wherein the flag is present in the VPS when the value of the fourth syntax element is greater than 0 and the value of the third syntax element is greater than 0, and the value of the fourth syntax element +1 specifies the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS.

15. A method for obtaining a video bitstream according to any one of claims 11 to 14, storing said video bitstream on at least one storage medium; A method of memorization, including:

16. The step of obtaining the video bitstream comprising:

16. The method of claim 15, comprising receiving the video bitstream from an encoding device of claim 10 via a communications interface.

17. A storage device configured to perform the storage method of claim 15 or 16.

18. A method for obtaining a video bitstream according to any one of claims 11 to 14, transmitting the video bitstream to a destination device via a communication interface; a transmission method, 19. The step of obtaining the video bitstream comprising:

19. The transmission method of claim 18, comprising receiving the video bitstream from the encoding device of claim 10 via the communication interface.

20. A transmitting device configured to perform the transmitting method of claim 18 or 19.

21. An encoding device according to claim 10; A transmitting device according to claim 20 Including, the system.

22. The system of claim 21, further comprising a storage device of claim 17 or a decoding device of claim 9.

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