Scalable nesting SEI message for specified layers

Abstract

To provide a method for efficiently nesting scalable nesting supplemental enhancement information (SEI) messages.SOLUTION: The method includes encoding a bitstream including one or more layers, encoding a scalable nesting supplemental enhancement information (SEI) message into the bitstream at a current SEI network abstraction layer (NAL) unit, and performing a set of bitstream conformance tests on the layers based on the scalable nested SEI message.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] This disclosure relates generally to video coding, and more particularly to scalable nesting supplemental enhancement information (SEI) messages used to support coding layers in multi-layer bitstreams. [Background technology]

[0002] The amount of video data required to depict even a relatively short video is substantial, which can be challenging when the data is streamed or otherwise communicated over communications networks with limited bandwidth capacity. Therefore, video data is typically compressed before being communicated over modern telecommunications networks. Video size can also be an issue when the video is stored on a storage device, as memory resources may be limited. 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 higher video quality, improved compression and decompression techniques that improve compression ratios with little sacrifice in picture quality are desirable. Summary of the Invention

[0003] In one embodiment, the disclosure includes a method implemented in a decoder, the method including: receiving, by a receiver of the decoder, a bitstream including a scalable nesting supplemental enhancement information (SEI) message in one or more layers and a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nesting layer identifiers (Ids) that specify one or more scalable nested SEI messages and layer-Id values ​​of layers to which the scalable nested SEI messages apply, excluding the layer-Id value of the current SEI NAL unit; decoding, by a processor of the decoder, coded pictures from the one or more layers to generate decoded pictures; and forwarding, by the processor, the decoded pictures for display as part of a decoded video sequence.

[0004] Some video coding systems use SEI messages. SEI messages contain information that is not needed by the decoding process to determine the values ​​of samples in a decoded picture. For example, an SEI message may contain parameters used to check the bitstream for conformance with a standard. In some examples, video is coded into a bitstream using multiple layers. A scalable nesting SEI message may be used to contain SEI messages for multiple layers. For example, a scalable nesting SEI message contains a scalable nested SEI message. A problem can arise when a scalable nesting SEI message contains a list of layer IDs to indicate the correspondence between the scalable nested SEI message and the layers. A scalable nesting SEI message is contained in an SEI NAL unit, which may be referred to as the current SEI NAL unit for clarity of discussion. The current SEI NAL unit is associated with a layer ID. A scalable nesting SEI message always pertains to the layer associated with the current SEI NAL unit. This leads to redundant signaling, since the layer-Id of the current SEI NAL unit is included in the current SEI NAL unit, which is also included in the current scalable nesting SEI message.

[0005] This example involves improving the scalable nesting SEI message for use with a specific layer. Specifically, the layer Id is sometimes referred to as the NAL unit header layer Id (nuh_layer_id). The nuh_layer_id of the current SEI NAL unit is excluded from the scalable nesting SEI message. This can be done by using the scalable nesting layer Id (layer_Id[i]) syntax element, which specifies the nuh_layer_id for each layer to which the scalable nesting SEI message applies. The scalable nesting layer_id[i] is constrained to include only nuh_layer_ids that are greater than the nuh_layer_id of the current SEI NAL unit. Therefore, the nuh_layer_id of the current SEI NAL unit is omitted from the scalable nesting SEI message and inferred from the current SEI NAL unit. This improves the scalable nesting SEI message by eliminating redundant Ids. For example, the loop that encodes / decodes scalable nesting layer_id[i] executes once in a shorter time, which reduces processor resources during encoding and / or decoding. Furthermore, this reduces the size of the coded bitstream for each scalable nesting SEI message in the bitstream. As a result, coding efficiency increases, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0006] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies the nuh_layer_id value of the ith layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0.

[0007] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each value of the scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit.

[0008] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the aspect further includes deriving, by the processor, a number of nesting layers (nestingNumLayers) variable that specifies the number of layers to which the scalable nested SEI message applies.

[0009] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the aspect further includes deriving, by the processor, a list of nesting layer Ids (NestingLayerId[i]) that specifies, for i in the range of 0 to nestingNumLayers-1 (inclusive), a list of nuh_layer_id values ​​of layers to which the scalable nested SEI message applies.

[0010] Optionally, in any of the aforementioned aspects, another implementation of the aspect is further characterized in that nestingNumLayers and NestingLayerId[i] are:

number

[0011] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that scalable nesting num_layers_minus1 is in the range of 0 to vps_max_layers_minus1-GeneralLayerIdx[nuh_layer_id] (inclusive), where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit.

[0012] Optionally, in any of the aforementioned aspects, another implementation of the aspect is where the coded picture is decoded based on a scalable nested SEI message.

[0013] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the scalable nesting SEI message includes at least one scalable nested SEI message that applies to a layer of the current SEI NAL unit.

[0014] In one embodiment, the disclosure includes a method implemented in an encoder, the method including: encoding, by a processor of the encoder, a bitstream including one or more layers; encoding, by the processor, a scalable nesting SEI message in a current SEI NAL unit, the scalable nesting SEI message including one or more scalable nesting layer-Ids that specify layer-Id values ​​of layers to which the scalable nested SEI message applies while applying a constraint that omits the one or more scalable nested SEI messages and the layer-Id values ​​of the current SEI NAL unit; performing, by the processor, a set of bitstream conformance tests on the layers based on the scalable nested SEI messages; and storing, by a memory coupled to the processor, the bitstream for communication to a decoder.

[0015] Some video coding systems use SEI messages. SEI messages contain information that is not needed by the decoding process to determine the values ​​of samples in a decoded picture. For example, an SEI message may contain parameters used to check the bitstream for conformance with a standard. In some examples, video is coded into a bitstream using multiple layers. A scalable nesting SEI message may be used to contain SEI messages for multiple layers. For example, a scalable nesting SEI message contains a scalable nested SEI message. A problem can arise when a scalable nesting SEI message contains a list of layer IDs to indicate the correspondence between the scalable nested SEI message and the layers. The scalable nesting SEI message is contained in an SEI NAL unit, which may be referred to as the current SEI NAL unit for clarity of discussion. The current SEI NAL unit is associated with a layer ID. The scalable nesting SEI message always pertains to the layer associated with the current SEI NAL unit. This leads to redundant signaling, since the layer-Id of the current SEI NAL unit is included in the current SEI NAL unit, which is also included in the current scalable nesting SEI message.

[0016] This example involves modifying the scalable nesting SEI message for use with a specific layer. Specifically, the layer Id is sometimes referred to as nuh_layer_id. The nuh_layer_id of the current SEI NAL unit is excluded from the scalable nesting SEI message. This can be done by using the scalable nesting layer_id[i] syntax element, which specifies the nuh_layer_id for each layer to which the scalable nesting SEI message applies. The scalable nesting layer_id[i] is constrained to include only nuh_layer_ids that are greater than the nuh_layer_id of the current SEI NAL unit. Therefore, the nuh_layer_id of the current SEI NAL unit is omitted from the scalable nesting SEI message and is inferred from the current SEI NAL unit. This modifies the scalable nesting SEI message by eliminating redundant Ids. For example, the loop that encodes / decodes scalable nesting layer_id[i] executes once in a shorter time, which reduces processor resources during encoding and / or decoding. Furthermore, this reduces the size of the coded bitstream for each scalable nesting SEI message in the bitstream. As a result, coding efficiency increases, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0017] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the scalable nesting layer_id is a scalable nesting layer_id[i] syntax element that specifies the nuh_layer_id value of the ith layer to which the scalable nesting SEI message applies when the scalable nesting all_layers_flag is equal to 0.

[0018] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each value of the scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit.

[0019] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that performing the set of bitstream conformance tests further includes deriving a number of nesting layers (nestingNumLayers) variable that specifies the number of layers to which the scalable nested SEI message applies.

[0020] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that performing the set of bitstream conformance tests further includes deriving a list of nesting layer Ids (NestingLayerId[i]) that specifies, for i in the range 0 to nestingNumLayers-1 (inclusive), a list of nuh_layer_id values ​​of layers to which the scalable nested SEI message applies.

[0021] Optionally, in any of the aforementioned aspects, another implementation of the aspect is further characterized in that nestingNumLayers and NestingLayerId[i] are:

number

[0022] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that scalable nesting num_layers_minus1 is in the range of 0 to vps_max_layers_minus1-GeneralLayerIdx[nuh_layer_id] (inclusive), where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit.

[0023] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the scalable nesting SEI message includes at least one scalable nested SEI message that applies to a layer of the current SEI NAL unit.

[0024] In one embodiment, the present disclosure comprises a video coding device including a processor, a receiver coupled to the processor, a memory coupled to the processor, and a transmitter coupled to the processor, wherein the processor, receiver, memory, and transmitter are configured to perform the method of any of the preceding aspects.

[0025] In one embodiment, the present disclosure provides a non-transitory computer-readable medium including a computer program product for use by a video coding device, the computer program product including computer-executable instructions stored on the non-transitory computer-readable medium such that, when executed by a processor, the computer program product causes the video coding device to perform a method of any of the preceding aspects.

[0026] In one embodiment, the disclosure includes a decoder including receiving means for receiving a bitstream including a scalable nesting SEI message in one or more layers and a current SEI NAL unit, the scalable nesting SEI message including one or more scalable nesting layer-IDs specifying one or more scalable nested SEI messages and layer-ID values ​​of layers to which the scalable nested SEI messages apply, excluding the layer-ID value of the current SEI NAL unit; decoding means for decoding coded pictures from the one or more layers to generate decoded pictures; and forwarding means for forwarding the decoded pictures for display as part of a decoded video sequence.

[0027] Some video coding systems use SEI messages. SEI messages contain information that is not needed by the decoding process to determine the values ​​of samples in a decoded picture. For example, an SEI message may contain parameters used to check the bitstream for conformance with a standard. In some examples, video is coded into a bitstream using multiple layers. A scalable nesting SEI message may be used to contain SEI messages for multiple layers. For example, a scalable nesting SEI message contains a scalable nested SEI message. A problem can arise when a scalable nesting SEI message contains a list of layer IDs to indicate the correspondence between the scalable nested SEI message and the layers. The scalable nesting SEI message is contained in an SEI NAL unit, which may be referred to as the current SEI NAL unit for clarity of discussion. The current SEI NAL unit is associated with a layer ID. The scalable nesting SEI message always pertains to the layer associated with the current SEI NAL unit. This leads to redundant signaling, since the layer-Id of the current SEI NAL unit is included in the current SEI NAL unit, which is also included in the current scalable nesting SEI message.

[0028] This example involves modifying the scalable nesting SEI message for use with a specific layer. Specifically, the layer Id is sometimes referred to as nuh_layer_id. The nuh_layer_id of the current SEI NAL unit is excluded from the scalable nesting SEI message. This can be done by using the scalable nesting layer_id[i] syntax element, which specifies the nuh_layer_id for each layer to which the scalable nesting SEI message applies. The scalable nesting layer_id[i] is constrained to include only nuh_layer_ids that are greater than the nuh_layer_id of the current SEI NAL unit. Therefore, the nuh_layer_id of the current SEI NAL unit is omitted from the scalable nesting SEI message and is inferred from the current SEI NAL unit. This modifies the scalable nesting SEI message by eliminating redundant Ids. For example, the loop that encodes / decodes scalable nesting layer_id[i] executes once in a shorter time, which reduces processor resources during encoding and / or decoding. Furthermore, this reduces the size of the coded bitstream for each scalable nesting SEI message in the bitstream. As a result, coding efficiency increases, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0029] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the decoder is further configured to perform the method of any of the preceding aspects.

[0030] In one embodiment, the disclosure includes an encoder including: encoding means for encoding a bitstream including one or more layers; and encoding a scalable nesting SEI message in a current SEI NAL unit, the scalable nesting SEI message including one or more scalable nested SEI messages and one or more scalable nesting layer-Ids that specify layer-Id values ​​of layers to which the scalable nested SEI message applies while applying a constraint that omits layer-Id values ​​of the current SEI NAL unit; and HRD means for performing a set of bitstream conformance tests on the layers based on the scalable nested SEI message.

[0031] Some video coding systems use SEI messages. SEI messages contain information that is not needed by the decoding process to determine the values ​​of samples in a decoded picture. For example, an SEI message may contain parameters used to check the bitstream for conformance with a standard. In some examples, video is coded into a bitstream using multiple layers. A scalable nesting SEI message may be used to contain SEI messages for multiple layers. For example, a scalable nesting SEI message contains a scalable nested SEI message. A problem can arise when a scalable nesting SEI message contains a list of layer IDs to indicate the correspondence between the scalable nested SEI message and the layers. The scalable nesting SEI message is contained in an SEI NAL unit, which may be referred to as the current SEI NAL unit for clarity of discussion. The current SEI NAL unit is associated with a layer ID. The scalable nesting SEI message always pertains to the layer associated with the current SEI NAL unit. This leads to redundant signaling, since the layer-Id of the current SEI NAL unit is included in the current SEI NAL unit, which is also included in the current scalable nesting SEI message.

[0032] This example involves modifying the scalable nesting SEI message for use with a specific layer. Specifically, the layer Id is sometimes referred to as nuh_layer_id. The nuh_layer_id of the current SEI NAL unit is excluded from the scalable nesting SEI message. This can be done by using the scalable nesting layer_id[i] syntax element, which specifies the nuh_layer_id for each layer to which the scalable nesting SEI message applies. The scalable nesting layer_id[i] is constrained to include only nuh_layer_ids that are greater than the nuh_layer_id of the current SEI NAL unit. Therefore, the nuh_layer_id of the current SEI NAL unit is omitted from the scalable nesting SEI message and is inferred from the current SEI NAL unit. This modifies the scalable nesting SEI message by eliminating redundant Ids. For example, the loop that encodes / decodes scalable nesting layer_id[i] executes once in a shorter time, which reduces processor resources during encoding and / or decoding. Furthermore, this reduces the size of the coded bitstream for each scalable nesting SEI message in the bitstream. As a result, coding efficiency increases, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0033] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the encoder is further configured to perform the method of any of the preceding aspects.

[0034] For clarity, any one of the above-described embodiments may be combined with any one or more of the other above-described embodiments to create new embodiments within the scope of the present disclosure.

[0035] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. [Brief explanation of the drawings]

[0036] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in conjunction with the accompanying drawings and detailed description, in which like reference numerals represent like parts.

[0037] [Figure 1] 1 is a flowchart of an exemplary method for coding a video signal.

[0038] [Figure 2] 1 is a schematic diagram of an exemplary coding and decoding (codec) system for video coding.

[0039] [Figure 3] 1 is a schematic diagram illustrating an example video encoder;

[0040] [Figure 4] 1 is a schematic diagram illustrating an exemplary video decoder.

[0041] [Figure 5] 1 is a schematic diagram illustrating an exemplary hypothetical reference decoder (HRD).

[0042] [Figure 6] FIG. 1 is a schematic diagram illustrating an example multi-layer video sequence configured for inter-layer prediction.

[0043] [Figure 7] FIG. 2 is a schematic diagram illustrating an exemplary bitstream.

[0044] [Figure 8] 1 is a schematic diagram of an exemplary video coding device.

[0045] [Figure 9] 1 is a flowchart of an exemplary method for encoding a video sequence into a bitstream that includes scalable nesting SEI messages applied to layers.

[0046] [Figure 10] 10 is a flowchart of an example method for decoding a video sequence from a bitstream that includes a scalable nesting SEI message applied to a layer.

[0047] [Figure 11] FIG. 1 is a schematic diagram of an example system for encoding a video sequence using a bitstream including scalable nesting SEI messages applied to layers. DETAILED DESCRIPTION OF THE INVENTION

[0048] First, while exemplary implementations of one or more embodiments are provided below, it should be understood that the disclosed systems and / or methods may be implemented using any number of technologies, whether currently known or in existence. The present disclosure is in no way limited to the exemplary implementations, drawings, and technologies shown below, including the exemplary designs and implementations shown and described herein, but may be modified within the scope of the appended claims to the full range of equivalents thereof.

[0049] The following terms are defined as follows, unless used herein in a contrary context. Specifically, the following definitions are intended to provide further clarity to the present disclosure. However, in different contexts, terms may be explained differently. Therefore, the following definitions should be considered supplemental and not limiting of any other definitions provided for such terms herein.

[0050] A bitstream may be a sequence of bits containing video data to be compressed for transmission between an encoder and a decoder. An encoder may be a device configured to use an encoding process to compress video data into a bitstream. A decoder may be a device configured to use a decoding process to reconstruct video data from the bitstream for display. A picture may be an array of luma and / or chroma samples that generate a frame or its fields. A picture being coded or decoded may be referred to as the current picture for clarity of discussion. A coded picture may be a coded representation of a picture containing Video Coding Layer (VCL) Network Abstraction Layer (NAL) units that have a particular value of the NAL unit header layer identifier (nuh_layer_id) within an access unit (AU) and include all coding tree units (CTUs) of the picture. A decoded picture may be a picture generated by applying a decoding process to a coded picture. An AU may be a set of coded pictures contained in different layers and related to the same time for output from the decoded picture buffer (DPB). A NAL unit contains data in the form of a Raw Byte Sequence Payload (RBSP), an indication of the type of data, and may optionally be a syntactic structure interspersed with emulation prevention bytes. A VCL NAL unit may be a NAL unit coded to contain video data, such as a coded slice of a picture. A non-VCL NAL unit may be a NAL unit containing non-video data, such as syntax and / or parameters, that support decoding, conformance checking, or other operations on the video data. A layer may be a set of VCL NAL units that share certain characteristics (e.g., a common resolution, frame rate, picture size, etc.), as indicated by a layerId (identifier) ​​and the associated non-VCL NAL units.A NAL unit header layer identifier (nuh_layer_id) may be a syntax element that specifies the identifier of the layer that contains the NAL unit. A video parameter set (VPS) may be a data unit that contains parameters related to the entire video. A coded video sequence may be a set of one or more coded pictures. A decoded video sequence may be a set of one or more decoded pictures.

[0051] A hypothetical reference decoder (HRD) may be a decoder model operating in an encoder that examines the variability of the bitstream generated by the encoding process to verify conformance with specified constraints. A bitstream conformance test may be a test to determine whether the encoded bitstream conforms to a standard such as Generic Video Coding (VVC). HRD parameters are syntax elements that initialize and / or define the operating conditions of the HRD. HRD parameters may be included in supplemental enhancement information (SEI) messages. SEI messages may be syntax structures with specified semantics that carry information not required by the decoding process to determine the values ​​of samples in the decoded picture. An SEI NAL unit may be a NAL unit that contains one or more SEI messages. A particular SEI NAL unit may be referred to as the current SEI NAL unit. A scalable nesting SEI message may be a message that contains multiple SEI messages corresponding to one or more output layer sets (OLSs) or one or more layers. The buffer period (BP) SEI message may be an SEI message containing HRD parameters for initializing the HRD and managing the coded picture buffer (CPB). The picture timing (PT) SEI message may be an SEI message containing HRD parameters for managing delivery information for access units (AUs) in the CPB and / or decoded picture buffer (DPB). The decoding unit information (DUI) SEI message may be an SEI message containing HRD parameters for managing delivery information for DUs in the CPB and / or DPB.

[0052] A scalable nesting SEI message may be a set of scalable nested SEI messages. A scalable nested SEI message may be an SEI message nested within a scalable nesting SEI message. A scalable nesting layer Id (layer_Id[i]) may be a syntax element in a scalable nesting SEI message that specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies. A scalable nesting all layers flag (all_layers_flag) may be a syntax element in a scalable nesting SEI message that specifies whether the scalable nested SEI messages in the scalable nesting SEI message apply to all layers. A scalable nesting number of layers minus 1 (num_layers_minus1) may be a syntax element in a scalable nesting SEI message that specifies the number of layers to which the scalable nested SEI message applies. VPS max layers - 1 (vps_max_layers_minus1) may be a syntax element in the VPS that specifies the number of layers specified by the VPS. VPS layer Id (vps_layer_id[i]) may be a syntax element in the VPS that specifies the nuh_layer_id value of the i-th layer. Nesting number of layers (nestingNumLayers) may be a variable that is set to the number of layers to which the scalable nested SEI message applies based on the data in the bitstream. Nesting layer Id list (NestingLayerId[i]) may be a variable that is set to specify a list of nuh_layer_id values ​​of layers to which the scalable nested SEI message applies for each layer i based on the data in the bitstream.The general layer index (GeneralLayerIdx) may be a variable that is set to specify the layer index of each layer with nuh_layer_id based on the data in the bitstream.

[0053] The following acronyms are used herein: Access Unit (AU), Coding Tree Block (CTB), Coding Tree Unit (CTU), Coding Unit (CU), Coded Layer Video Sequence (CLVS), Coded Layer Video Sequence Start (CLVSS), Coded Video Sequence (CVS), Coded Video Sequence Supervision (CVSS), Joint Video Experts Team (JVET), Motion Constrained Tile Set (MCTS), Maximum Transmission Unit (MTU), Network Abstraction Layer (NAL), Output Layer Set (OLS), Picture Order Count (POC), Random Access Point (RAP), Raw Byte Sequence Payload (RBSP), Sequence Parameter Set (SPS), Video Parameter Set (VPS), and Generic Video Coding (VVC).

[0054] Many video compression techniques may be used to reduce the size of video files with minimal data loss. For example, video compression techniques may include performing spatial (e.g., intra-picture) prediction and / or temporal (e.g., inter-picture) prediction to reduce or remove data redundancy in a video sequence. In block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may be referred to as 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 coded using spatial prediction with respect to reference samples in neighboring blocks within the same picture. Video blocks in an inter-coded unidirectionally predicted (P) or bidirectionally predicted (B) slice of a picture may be coded using spatial prediction with respect to reference samples in neighboring blocks within 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 / or an image, and a reference picture may be referred to as a reference frame and / or a reference image. Spatial or temporal prediction results in a prediction block, which represents an image block. Residual data represents pixel differences between the original image block and the prediction block. Thus, inter-coded blocks are coded according to a motion vector that points to a block of reference samples that form the prediction block, and the residual data indicates the differences between the coded block and the prediction block. Intra-coded blocks are coded 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, resulting in residual transform coefficients, which may be quantized. The quantized transform coefficients may be initially arranged in a two-dimensional array. The quantized transform coefficients may then be scanned to generate a one-dimensional vector of transform coefficients.Entropy coding may be applied to achieve even greater compression. Such video compression techniques are discussed in more detail below.

[0055] To ensure that the coded video can be decoded accurately, the video is coded and decoded according to corresponding video coding standards, including International Telecommunication Union (ITU) Standardization Sector (ITU-T) H.261, International Organization for Standardization / International Electrotechnical Commission (ISO / IEC) Motion Picture Experts Group (MPEG)-1 Part 2, Advanced Video Coding (AVC), also known as 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) and Multiview Video Coding plus Depth (MVC+D), and three-dimensional (3D) AVC (3D-AVC). HEVC includes extensions such as Scalable HEVC (SHVC), Multiview HEVC (MV-HEVC), and 3D HEVC (3D-HEVC). The ITU-T and ISO / IEC Joint Video Experts Team (JVET) has begun development of a video coding standard called Versatile Video Coding. VVC is included in working drafts (WDs) including JVET-N1001-v14.

[0056] Some video coding systems use supplemental enhancement information (SEI) messages. SEI messages contain information that is not needed by the decoding process to determine the values ​​of samples in a decoded picture. For example, an SEI message may contain parameters used to test a bitstream for conformance with a standard. In some examples, video is coded into a bitstream using multiple layers. A scalable nesting SEI message may be used to contain SEI messages for multiple layers. For example, a scalable nesting SEI message contains a scalable nested SEI message.

[0057] The first problem can occur when a scalable nesting SEI message includes a list of layer identifiers (Ids) to indicate the correspondence between the scalable nesting SEI message and the layers. The scalable nesting SEI message is included in an SEI Network Abstraction Layer (NAL) unit, which may be denoted the current SEI NAL unit for clarity of discussion. The current SEI NAL unit is associated with a layer Id. The scalable nesting SEI message always pertains to the layer associated with the current SEI NAL unit. This leads to redundant signaling, because the layer Id of the current SEI NAL unit is included in the current SEI NAL unit, which is included in the current NAL unit, which is also included in the current scalable nesting SEI message.

[0058] In a first example, disclosed herein is an enhancement to a scalable nesting SEI message for use in conjunction with a particular layer. Specifically, the layer Id may be referred to as the NAL unit header layer Id (nuh_layer_id). The nuh_layer_id of the current SEI NAL unit is excluded from the scalable nesting SEI message. This can be done by using a scalable nesting layer Id (layer_Id[i]) syntax element, which specifies the nuh_layer_id for each layer to which the scalable nesting SEI message applies. The scalable nesting layer_id[i] is constrained to include only nuh_layer_ids that are greater than the nuh_layer_id of the current SEI NAL unit. Therefore, the nuh_layer_id of the current SEI NAL unit is omitted from the scalable nesting SEI message and inferred from the current SEI NAL unit. This enhances the scalable nesting SEI message by eliminating redundant Ids. For example, the loop that encodes / decodes scalable nesting layer_id[i] executes once in a shorter time, which reduces processor resources during encoding and / or decoding. Furthermore, this reduces the size of the coded bitstream for each scalable nesting SEI message in the bitstream. As a result, coding efficiency increases, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0059] The second problem occurs when a flag in a scalable nesting SEI message is used to indicate that the scalable nesting SEI message applies to all layers in an access unit (AU). An AU is a set of coded pictures contained in different layers and associated with the same output time. This approach works when all AUs contain pictures for all layers. However, in some cases, pictures may be present for the output time in some layers and omitted in other layers. For example, a high-frame-rate layer may contain pictures in each AU, while a low-frame-rate layer omits pictures in many AUs occupied by the high-frame-rate layer. As a result, the flag ensures that the SEI message applies only to layers that contain pictures in the current AU. This can cause a conformance test error because a hypothetical reference decoder (HRD) may not be able to associate the scalable nesting SEI message with a layer that omits a picture in the current AU. For example, such a layer may contain pictures in an AU after the current AU. In such cases, the HRD will not recognize the scalable nesting SEI message as applying to such layers when the later AU is tested for conformance, and therefore the HRD may not be able to correctly test such layers for conformance in later AUs when flags for all layers are used in the incomplete AU.

[0060] In a second example, disclosed herein is a scalable nesting all layers flag (all_layers_flag) for correcting the above-mentioned error. The scalable nesting all_layers_flag can be set to indicate that a scalable nesting SEI message in a scalable nesting SEI message applies to all layers specified in the video parameter set (VPS). The VPS lists all layers. Therefore, this approach allows an encoder to clearly indicate when a scalable nesting SEI message applies globally to all layers. The HRD conformance test process can test a bitstream for conformance without returning unpredictable errors in AUs following an incomplete AU associated with a scalable nesting SEI message. Therefore, the scalable nesting all_layers_flag increases the functionality of an encoder and / or decoder by allowing a bitstream to be correctly tested for conformance when incomplete AUs are present. Furthermore, the scalable nesting all_layers_flag reduces the size of the coded bitstream by eliminating explicit layer signaling for scalable nesting SEI messages when such messages apply to all layers, resulting in increased coding efficiency, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0061] FIG. 1 is a flowchart of an exemplary method 100 for coding a video signal. Specifically, a video signal is encoded by 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 to reconstruct the original video signal for display to the end user. The decoding process generally mirrors the encoding process, allowing the decoder to consistently reconstruct the video signal.

[0062] In 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 an audio component and a video component. The video component includes a series of image frames that, when viewed in sequence, create the impression of visual movement. The frames include pixels represented in terms of light, referred to herein as luma components (or luma samples), and color, referred to herein as chroma components (or color samples). In some examples, the frames may also include depth values ​​to support three-dimensional viewing.

[0063] In step 103, the video is partitioned into blocks. Partitioning involves subdividing pixels within 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 divided into coding tree units (CTUs), which are blocks of a predetermined size (e.g., 64 pixels by 64 pixels). CTUs contain both luma and chroma samples. A coding tree may be used to divide the CTUs into blocks, and then the blocks may be recursively subdivided 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 uniform light values. Furthermore, the chroma component of a frame may be subdivided until each block contains relatively uniform color values. Thus, the partitioning mechanism varies depending on the content of the video frame.

[0064] In step 105, various compression mechanisms are employed to compress the image blocks partitioned in step 103. For example, inter-prediction and / or intra-prediction may be used. Inter-prediction is designed to take advantage of the fact that objects in a common scene tend to appear in consecutive frames. Thus, a block representing 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. Therefore, the table may be described once, and adjacent frames may reference back to the reference frame. A pattern matching mechanism may be used to match objects across multiple frames. Furthermore, moving objects may be represented across multiple frames, for example, due to object motion or camera motion. As a specific example, a video may show a car moving across the screen over multiple frames. Such motion can be described using motion vectors. A motion vector is a two-dimensional vector that provides an offset from the object's coordinates in a frame to the object's coordinates in a reference frame. In this manner, inter-prediction can encode an image block in a current frame as a set of motion vectors that indicate an offset from a corresponding block in a reference frame.

[0065] Intra prediction encodes blocks within a common frame. It takes advantage of the fact that luma and chroma components tend to cluster within a frame. For example, a green patch in a tree section tends to be located adjacent to similar green patches. Intra prediction uses multi-directional prediction modes (e.g., 33 in HEVC), planar mode, and direct current (DC) mode. Directional mode indicates that the current block is similar / identical to samples from neighboring blocks in the corresponding direction. Planar mode indicates that a series of blocks (e.g., a plane) along a row / column can be interpolated based on neighboring blocks at the end of the row. Planar mode effectively indicates a smooth transition of light / color across a row / column by using a relatively constant slope in changing values. DC mode is used for boundary smoothing, indicating that the block is similar / identical to the average value associated with samples from all neighboring blocks associated with the angular direction of the directional prediction mode. Therefore, intra-predicted blocks can represent image blocks as various related prediction mode values ​​instead of their actual values. Furthermore, inter-predicted blocks can represent image blocks as motion vector values ​​instead of actual values. In either case, the predicted block may not accurately represent the image block in some cases. Any differences are stored in the residual block. A transform may be applied to the residual block to further compress the file.

[0066] Various filtering techniques may be applied in step 107. In HEVC, filters are applied according to an in-loop filtering scheme. The block-based prediction discussed above can result in the generation of blocky images at the decoder. Furthermore, block-based prediction schemes may encode blocks and then reconstruct the encoded blocks for later use as reference blocks. In-loop filtering schemes sequentially apply noise suppression filters, deblocking filters, adaptive loop filters, and sample adaptive offset (SAO) filters to blocks / frames. These filters mitigate such blocking artifacts so that the encoded file can be accurately reconstructed. Furthermore, these filters mitigate artifacts in the reconstructed reference blocks, making the artifacts less likely to generate additional artifacts in subsequent blocks that are coded based on the reconstructed reference blocks.

[0067] Once the video signal has been partitioned, compressed, and filtered, the resulting data is coded into a bitstream in step 109. The bitstream includes the data discussed above, as well as any signal 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 provide 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. Generating the bitstream is an iterative process. Thus, steps 101, 103, 105, 107, and 109 may occur sequentially and / or simultaneously across many frames and blocks. The order depicted in FIG. 1 is presented for clarity and ease of discussion and is not intended to limit the video coding process to any particular order.

[0068] The decoder receives the bitstream and begins the decoding process in step 111. Specifically, the decoder uses an entropy decoding scheme to convert the bitstream into corresponding syntax data and video data. The decoder uses the syntax data from the bitstream to determine the frame partitions in step 111. The partitioning matches the results of the block partitioning in step 103. The entropy encoding / decoding used in step 111 is now described. The encoder makes many choices during the compression process, such as selecting a block partitioning scheme from several possible choices based on the spatial location of values ​​in the input image. Signaling the exact selection may use multiple bins. 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 retain a set of acceptable options and discard any options that are clearly infeasible for a particular case. Each acceptable option is assigned a codeword. The length of the code word 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 code word for the selected option. This scheme reduces the size of the code word because it is desirable for the code word to be large enough to uniquely indicate a selection from a small subset of allowable options, as opposed to uniquely indicating a selection from a larger possible set of all possible options. The decoder then decodes the selection by determining the set of allowable options in a similar manner to the encoder. By determining the set of allowable options, the decoder can read the code word and determine the selection made by the encoder.

[0069] In step 113, the decoder performs block decoding. Specifically, the decoder uses an inverse transform to generate a residual block. The decoder then uses the residual block and the corresponding prediction block to reconstruct an image block according to the partitioning. The prediction block may include both intra-predicted and inter-predicted blocks, as generated by 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 by entropy coding, as discussed above.

[0070] At step 115, filtering is performed on the frames of the reconstructed video signal in a manner similar to step 107 in 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. Once the frames have been filtered, the video signal may be output to a display at step 117 for viewing by an end user.

[0071] FIG. 2 is a schematic diagram of an exemplary coding and decoding (codec) system 200 for video coding. Specifically, codec system 200 provides functionality to support the implementation of operational method 100. Codec system 200 is generalized to illustrate components used in both an encoder and a decoder. Codec system 200 receives and partitions a video signal, as discussed with respect to steps 101 and 103 in operational method 100, resulting in partitioned video signal 201. When acting as an encoder, codec system 200 then compresses partitioned video signal 201 into a coded bitstream, as discussed with respect to steps 105, 107, and 109 in method 100. When acting as a decoder, codec system 200 generates an output video signal from the bitstream, as discussed with respect to steps 111, 113, 115, and 117 in 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, black lines indicate the movement of data to be coded / decoded, and dashed lines indicate the movement of control data that controls the operation of other components. All of the components of codec system 200 may reside within 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 described herein.

[0072] The partitioned video signal 201 is a captured video sequence that has been divided into blocks of pixels by a coding tree. The coding tree uses various partitioning modes to subdivide the blocks of pixels into smaller blocks of pixels. These blocks can then be further subdivided into smaller blocks. Blocks are sometimes referred to as nodes on the coding tree. Larger parent nodes are divided into smaller child nodes. The number of times a node is subdivided is called the depth of the node / coding tree. In some cases, the partitioned blocks may be included in a coding unit (CU). For example, a CU may be a subpart of a coding unit (CTU), which includes a luma block, a red-difference chroma (Cr) block, and a blue-difference chroma (Cb) block, along with the corresponding syntax instructions for the CU. Partitioning modes may include binary trees (BT), triple trees (TT), and quad trees (QT), which are used to partition a node into two, three, or four child nodes of varying shapes, depending on the partitioning mode used. The partitioned 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.

[0073] The generic coder control component 211 is configured to make decisions related to coding images of a video sequence into a bitstream according to application constraints. For example, the generic coder control component 211 manages the optimization of bitrate / bitstream size versus reconstruction quality. Such decisions may be made based on storage space / bandwidth availability and image resolution requirements. The generic coder control component 211 also manages buffer utilization in relation to transmission rate to mitigate buffer underrun and overrun issues. To manage these issues, the generic coder control component 211 manages partitioning, prediction, and filtering by other components. For example, the generic coder control component 211 can dynamically increase compression complexity to increase resolution and bandwidth usage, or decrease compression complexity to decrease resolution and bandwidth usage. Therefore, the generic coder control component 211 controls other components of the codec system 200 to balance bitrate concerns with video signal reconstruction quality. The generic coder control component 211 generates control data that controls the operation of other components. The control data is also forwarded to the header format and CABAC component 231 to be encoded in the bitstream into signal parameters for decoding at the decoder.

[0074] 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 relative to one or more blocks in one or more reference frames to provide temporal prediction. The codec system 200 may perform multiple coding passes, for example, to select an appropriate coding mode for each block of video data.

[0075] The motion estimation component 221 and the motion compensation component 219 may be highly integrated but are shown separately for conceptual purposes. Motion estimation, performed by the motion estimation component 221, is the process of generating motion vectors, which estimate the motion of video blocks. A motion vector may indicate, for example, the displacement of a coded object relative to a predictive block. A predictive block is a block that is found to closely match a coded block in terms of pixel differences. A predictive block is sometimes 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 uses several coded objects, including CTUs, coding tree blocks (CTBs), and CUs. For example, a CTU can be divided into CTBs, which are then divided into CBs for inclusion in CUs. A CU can be coded as a prediction unit (PU), which contains prediction data, and / or a transform unit (TU), which contains the transform residual data of the CU. The motion estimation component 221 generates the motion vectors, PUs, and TUs by using 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).

[0076] In some examples, the codec system 200 may calculate values ​​for sub-integer pixel positions of a reference picture 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 picture. Accordingly, the motion estimation component 221 may perform motion search for whole-pixel and fractional pixel positions and output fractional-pixel precision motion vectors. The motion estimation component 221 calculates the motion vector for a PU of a video block in an inter-coded slice by comparing the position of the PU with the position of a predictive block in the reference picture. The motion estimation component 221 outputs the calculated motion vector as motion data to the header formatting and CABAC component 231 for encoding and the motion compensation component 219.

[0077] The motion compensation performed by motion compensation component 219 may involve fetching or generating a predictive block based on the motion vector determined by motion estimation component 221. Again, in some examples, motion estimation component 221 and motion compensation component 219 may be functionally integrated. Upon receiving the motion vector for the PU of the current video block, motion compensation unit 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. Generally, motion estimation component 221 performs motion estimation on the luma component, and 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 residual block are forwarded to scaling and quantization component 213 for transformation.

[0078] The partitioned video signal 201 is also sent to an intra-picture estimation component 215 and an intra-picture prediction component 217. Like 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 shown separately for conceptual purposes. The intra-picture estimation component 215 and the intra-picture prediction component 217 intra-predict the current block relative to blocks within the current frame as an alternative to the inter-prediction performed by the inter-frame motion estimation component 221 and the motion compensation component 219, as described above. In particular, the intra-picture estimation component 215 determines the 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 multiple tested intra-picture prediction modes. The selected intra-prediction mode is then forwarded to the header formatting and CABAC component 231 for encoding.

[0079] For example, the intra picture estimation component 215 may use a rate-distortion analysis to calculate rate-distortion values ​​for various tested intra picture prediction modes and select the 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 a coded block and the original uncoded block coded to generate the coded block, as well as the bitrate (e.g., number of bits) used to generate the coded block. The intra picture estimation component 215 may calculate a ratio from the distortion and rate for various coded blocks to determine which intra prediction mode exhibits the best rate-distortion value for the block. Additionally, the intra picture estimation component 215 may be configured to code depth blocks of a depth map using a rate-distortion optimization (RDO)-based depth modeling mode (DMM).

[0080] The intra-picture prediction component 217 may generate a residual block from the prediction block based on the selected intra-picture prediction mode determined by the intra-picture prediction component 215 when implemented in an encoder, or may read the residual block from the bitstream when implemented in a decoder. The residual block contains the 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.

[0081] 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 containing residual transform coefficient values. Wavelet transforms, integer transforms, subband transforms, or other types of transforms may 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 so that different frequency information is quantized with different granularities, 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 bitrate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, the transform scaling and quantization component 213 may then perform a scan of the matrix containing the quantized transform coefficients, which are forwarded to the header formatting and CABAC component 231 to be encoded in the bitstream.

[0082] 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, transform, and / or quantization to reconstruct a residual block in the pixel domain, for example, for use as a reference block that may later become a predictive block for another current block. The motion estimation component 221 and / or motion compensation component 219 may calculate a reference block by adding the residual block to the corresponding predictive block for use in motion estimation for a later block / frame. A filter is applied to the reconstructed reference block to mitigate artifacts generated during scaling, quantization, and transform. Otherwise, such artifacts may cause inaccurate predictions (and create additional artifacts) when subsequent blocks are predicted.

[0083] The filter control analysis component 227 and the in-loop filter component 225 apply filters to residual blocks and / or reconstructed image blocks. For example, a 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 motion compensation component 219 to reconstruct an original image block. The filter may then be applied to the reconstructed image block. In some examples, the filter may instead be applied to the residual block. Like the other components in 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 shown separately for conceptual purposes. The filters applied to reconstructed reference blocks are applied to specific spatial regions and include multiple parameters to adjust how such filters are applied. The filter control analysis component 227 analyzes the reconstructed reference blocks 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., reconstructed pixel blocks) or the frequency domain, depending on the example.

[0084] When operating as an encoder, the filtered reconstructed picture blocks, residual blocks, and / or prediction blocks are stored in the decoded picture buffer component 223 for later use in motion estimation as discussed above. When operating as a decoder, the decoded picture buffer component 223 stores the reconstructed and filtered blocks and forwards them to the display as part of the output video signal. The decoded picture buffer component 223 may be any memory device capable of storing prediction blocks, residual blocks, and / or reconstructed picture blocks.

[0085] 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 to the decoder. Specifically, the Header Formatting and CABAC component 231 generates various headers for encoding control data, such as general control data and filter control data. Additionally, prediction data, including intra-prediction and motion data, as well as residual data in the form of quantized transform coefficient data, are all encoded in the bitstream. The final bitstream contains all information required by the decoder to reconstruct the original partitioned video signal 201. Such information may also include an intra-prediction mode index table (also known as a codeword mapping table), definitions of coding contexts for various blocks, indications of the most likely intra-prediction modes, indications of partition information, etc. Such data may be encoded using entropy coding. For example, the information may be encoded using 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. After entropy coding, the coded bitstream may be transmitted to another device (e.g., a video decoder) or archived for later transmission or retrieval.

[0086] 3 is a block diagram illustrating an exemplary video encoder 300. Video encoder 300 may be used to implement the encoding functionality of codec system 200 and / or to implement steps 101, 103, 105, 107, and / or 109 of operating method 100. Encoder 300 partitions an input video signal, resulting in a partitioned video signal 301 that is substantially similar to partitioned video signal 201. Partitioned video signal 301 is then compressed and encoded into a bitstream by components of encoder 300.

[0087] 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 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 block and the corresponding prediction block (along with associated control data) are forwarded to an entropy coding component 331 for coding into a bitstream. The entropy coding component 331 may be substantially similar to the header formatting and CABAC component 231.

[0088] The transformed and quantized residual block and / or the corresponding prediction block are also forwarded from the transform and quantization component 313 to the inverse transform and quantization component 329 for reconstruction into a reference block 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 include multiple filters, as discussed 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.

[0089] 4 is a block diagram illustrating an exemplary video decoder 400. Video decoder 400 may be used to implement the decoding functionality of codec system 200 and / or to implement steps 111, 113, 115, and / or 117 of operating method 100. Decoder 400 receives a bitstream from, for example, encoder 300, and generates a reconstructed output video signal based on the bitstream for display to an end user.

[0090] 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 can use header information to provide context for interpreting additional data encoded as codewords in the bitstream. The decoded information includes any desired information for decoding the 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 can be similar to the inverse transform and quantization component 329.

[0091] 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 substantially similar to the intra-picture estimation component 215 and the intra-picture prediction component 217. Specifically, the intra-picture prediction component 417 uses a prediction mode to locate a reference block within a frame and applies the residual block to the result to reconstruct an intra-predicted image block. The reconstructed intra-predicted image block and / or residual block and corresponding inter-predicted 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, residual block, and / or predictive block, and such information is stored in the decoded picture buffer component 423. The reconstructed picture blocks from the decoded picture buffer component 423 are 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 generates a prediction block using a motion vector from a reference block and applies a residual block to the result to reconstruct an image block. The resulting reconstructed block may be forwarded to the decoded picture buffer component 423 via an in-loop filter component 425. The decoded picture buffer component 423 continues to store additional reconstructed image blocks, which may be reconstructed into frames via partition information. Such frames may be arranged in a sequence. The sequence is output to a display as a reconstructed output video signal.

[0092] 5 is a schematic diagram illustrating an exemplary HRD 500. The HRD 500 may be used in codec system 200 and / or an encoder, such as encoder 30. The HRD 500 may inspect the bitstream generated in step 109 of method 100 before the bitstream is forwarded to a decoder, such as decoder 400. In some examples, the bitstream may be continuously forwarded through the HRD 500 as it is encoded. If a portion of the bitstream does not conform to an associated constraint, the HRD 500 can indicate such incompatibility to the encoder so that the encoder re-encodes the corresponding section of the bitstream using a different mechanism.

[0093] The HRD 500 includes a virtual stream scheduler (HSS) 541. The HSS 541 is a component configured to implement a virtual delivery mechanism. The virtual delivery mechanism is used to check the conformance of a bitstream or decoder with respect to the timing and data flow of a bitstream 551 input to the HRD 500. For example, the HSS 541 may receive the bitstream 551 output from an encoder and manage a conformance testing process on the bitstream 551. In a particular example, the HSS 541 may control the rate at which coded pictures move through the HRD 500 and verify that the bitstream 551 does not contain non-conforming data.

[0094] The HSS 541 may transfer the bitstream 551 to the CPB 543 at a predetermined rate. The HRD 500 may manage data in a decoding unit (DU) 553. A DU 553 is an access unit (AU) or a subset of an AU, and is associated with a non-video coding layer (VCL) network abstraction layer (NAL) unit. Specifically, an AU includes one or more pictures related to output time. For example, an AU may include a single picture in a single-layer bitstream or a picture for each layer in a multi-layer bitstream. Each picture in an AU may be divided into slices, each of which is included in a corresponding VCL NAL unit. Therefore, a DU 553 may include one or more pictures, one or more slices of a picture, or a combination thereof. Additionally, parameters used to decode AUs, pictures, and / or slices may be included in non-VCL NAL units. Therefore, a DU 553 includes non-VCL NAL units that include data necessary to support the decoding of the VCL NAL units in the DU 553. The CPB 543 is a first-in, first-out buffer in the HRD 500. The CPB 543 contains the DU 553, which contains video data in decoding order. The CPB 543 stores video data for use during bitstream conformance verification.

[0095] The CPB 543 forwards the DU 553 to a decoding process component 545. The decoding process component 545 is a component that conforms to the VVC standard. For example, the decoding process component 545 may emulate the decoder 400 used by an end user. The decoding process component 545 decodes the DU 553 at a rate that can be achieved by an exemplary end user decoder. If the decoding process component 545 cannot decode the DU 553 fast enough to prevent overflow of the CPB 543, the bitstream 551 does not conform to the standard and should be re-encoded.

[0096] The decoding process component 545 decodes the DU 553, generating a decoded DU 555. The decoded DU 555 contains the decoded picture. The decoded DU 555 is forwarded to the DPB 547. The DPB 547 may be substantially similar to the decoded picture buffer components 223, 323, and / or 423. To support inter-prediction, pictures marked for use as reference pictures 556 obtained from the decoded DU 555 are returned to the decoding process component 545 to support further decoding. The DPB 547 outputs the decoded video sequence as a series of pictures 557. The pictures 557 are reconstructed pictures, typically mirror pictures, that were coded into the bitstream 551 by the encoder.

[0097] Picture 557 is forwarded to output cropping component 549, which is configured to apply an adaptive cropping window to picture 557, resulting in output cropped picture 559. Output cropped picture 559 is a perfectly reconstructed picture. Thus, output cropped picture 559 mimics what an end user would see when decoding bitstream 551. Therefore, the encoder can review output cropped picture 559 to ensure that the encoding is satisfactory.

[0098] The HRD 500 is initialized based on HRD parameters in the bitstream 551. For example, the HRD 500 may read the HRD parameters from a VPS, SPS, and / or SEI message. The HRD 500 may then perform conformance testing operations on the bitstream 551 based on the information in such HRD parameters. As a specific example, the HRD 500 may determine one or more CPB delivery schedules from the HRD parameters. The delivery schedules specify the timing of delivery of video data to and / or from memory locations, such as the CPB and / or DPB. Thus, the CPB delivery schedule specifies the timing of delivery of AUs, DUs 553, and / or pictures to and from the CPB 543. Note that the HRD 500 may use a DPB delivery schedule for the DPB 547 that is similar to the CPB delivery schedule.

[0099] Video may be coded into different layers and / or OLSs for use by decoders with varying levels of hardware capabilities and for varying network conditions. CPB delivery schedules are selected to reflect these considerations. Thus, upper layer sub-bitstreams are designated for optimal hardware and network conditions; therefore, upper layers may receive one or more CPB delivery schedules that use large amounts of memory in CPB 543 and short delays for transferring DUs 553 toward DPB 547. Similarly, lower layer sub-bitstreams are designated for limited decoder hardware capabilities and / or poor network conditions; therefore, lower layers may receive one or more CPB delivery schedules that use small amounts of memory in CPB 543 and longer delays for transferring DUs 553 toward DPB 547. OLSs, layers, sub-layers, or combinations thereof may then be tested according to the corresponding delivery schedules to ensure that the resulting sub-bitstreams can be accurately decoded under the conditions expected for the sub-bitstreams. Thus, the HRD parameters in the bitstream 551 may indicate a CPB delivery schedule and may include sufficient data to enable the HRD 500 to determine the CPB delivery schedule and correlate the CPB delivery schedule to the corresponding OLS, layer, and / or ablayer.

[0100] 6 is a schematic diagram illustrating an example multi-layer video sequence 600 configured for inter-layer prediction 621. The multi-layer video sequence 600 may be encoded by an encoder, such as codec system 200 and / or encoder 300, and decoded by a decoder, such as codec system 200 and / or decoder 400, according to method 100, for example. Furthermore, the multi-layer video sequence 600 may be checked for standards conformance by an HRD, such as HRD 500. The multi-layer video sequence 600 is included to illustrate an example application for layers in a coded video sequence. The multi-layer video sequence 600 is any video sequence that employs multiple layers, such as layer N 631 and layer N+1 632.

[0101] In one embodiment, the multi-layer video sequence 600 may use inter-layer prediction 621. Inter-layer prediction 621 is applied to different layers between pictures 611, 612, 613, and 614 and pictures 615, 616, 617, and 618. In the illustrated example, pictures 611, 612, 613, and 614 are part of layer N+1 632, and pictures 615, 616, 617, and 618 are part of layer N 631. A layer, such as layer N 631 and / or layer N+1 632, is a group of pictures that all relate to similar values ​​of a characteristic, such as similar size, quality, resolution, signal-to-noise ratio, capacity, etc. A layer may be formally defined as a set of VCL NAL units and associated non-VCL NAL units. A VCL NAL unit may be a NAL unit 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, conformance checking, or other operations on the video data.

[0102] In the illustrated example, layer N+1 632 is associated with a larger image size than layer N 631. Thus, pictures 611, 612, 613, and 614 in layer N+1 632 have a larger picture size (e.g., larger height and width, and therefore more samples) than pictures 615, 616, 617, and 618 in layer N 631 in this example. However, such pictures may be separated by other characteristics between layer N+1 632 and layer N 631. Although only two layers, layer N+1 632 and layer N 631, are shown, a set of pictures may be separated into any number of layers based on associated characteristics. Layer N+1 632 and layer N 631 may also 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 611-618 can be associated with a corresponding layer Id to indicate which layer N+1 632 or layer N 631 contains the corresponding picture. For example, the layer Id may include a NAL unit header layer identifier (nuh_layer_id), which is a syntax element that specifies the identifier of the layer containing the NAL unit (e.g., containing slices and / or parameters of the picture in the layer). A layer associated with a lower quality / bitstream size, such as layer N 631, is generally assigned a lower layer Id and is referred to as a lower layer. Furthermore, a layer associated with a higher quality / bitstream size, such as layer N+1 632, is generally assigned a higher layer Id and is referred to as a higher layer.

[0103] Pictures 611-618 in different layers 631-632 are configured to be displayed alternatively. As a particular example, if a smaller picture is desired, the decoder may decode and display picture 615 at the current display time, and if a larger picture is desired, the decoder may decode and display picture 611 at the current display time. Thus, pictures 611-614 in higher layer N+1 632 contain substantially the same image data as corresponding pictures 615-618 in lower layer N 631 (despite differences in picture size). Specifically, picture 611 contains substantially the same image data as picture 615, picture 612 contains substantially the same image data as picture 616, and so on.

[0104] Pictures 611-618 may be coded by referencing other pictures 611-618 in the same layer N 631 or N+1 632. Coding a picture with reference to another picture in the same layer results in inter-prediction 623. Inter-prediction 623 is indicated by a solid arrow. For example, picture 613 may be coded by using one or two of pictures 611, 612, and / or 614 in layer N+1 632 as references, one picture referenced for unidirectional inter-prediction and / or two pictures referenced for bidirectional inter-prediction. Furthermore, picture 617 may be coded by using one or two of pictures 615, 616, and / or 618 in layer N 631 as references, one picture referenced for unidirectional inter-prediction and / or two pictures referenced for bidirectional inter-prediction. When a picture is used as a reference for another picture in the same layer when performing inter prediction 623, the picture may be called a reference picture. For example, picture 612 may be a reference picture used to code picture 613 according to inter prediction 623. Inter prediction 623 may also be called intra-layer prediction in a multi-layer context. Thus, inter prediction 623 is a mechanism for coding samples of a current picture by referencing indicated samples in a reference picture different from the current picture, where the reference picture and the current picture are in the same layer.

[0105] Pictures 611-618 may also be coded by referencing other pictures 611-618 in different layers. This process is known as inter-layer prediction 621 and is indicated by the dashed arrows. Inter-layer prediction 621 is a mechanism for coding samples of a current picture by referencing indicated samples in a reference picture, where the current picture and the reference picture are in different layers and therefore have different layer IDs. For example, a picture in lower layer N 631 may be used as a reference picture to code a corresponding picture in upper layer N+1 631. As a specific example, picture 611 may be coded by referencing picture 615 according to inter-layer prediction 621. In such a case, picture 615 is used as an inter-layer reference picture. An inter-layer reference picture is a reference picture used for inter-layer prediction 621. In most cases, inter-layer prediction 621 is constrained so that a current picture, such as picture 611, can only use inter-layer reference pictures that are contained in the same AU and that are in a lower layer, such as picture 615. When multiple layers (e.g., two or more) are available, inter-layer prediction 621 can encode / decode the current picture based on multiple inter-layer reference pictures at a lower level than the current picture.

[0106] Using the multi-layer video sequence 600, a video encoder can encode pictures 611-618 via many different combinations and / or permutations of inter-prediction 623 and inter-layer prediction 621. For example, picture 615 may be coded according to intra-prediction. Pictures 616-618 may then be coded according to inter-prediction 623 by using picture 615 as a reference picture. Furthermore, picture 611 may be coded according to inter-layer prediction 621 by using picture 615 as an inter-layer reference picture. Pictures 612-614 may then be coded according to inter-prediction 623 by using picture 611 as a reference picture. In this manner, reference pictures can function as both single-layer reference pictures and inter-layer reference pictures for different coding mechanisms. By coding the upper layer N+1 632 picture based on the lower layer N 631 picture, the upper layer N+1 632 can avoid using intra prediction, which has much lower coding efficiency than inter prediction 623 and inter-layer prediction 621. Thus, the poor coding efficiency of intra prediction can be limited to pictures with the smallest / lowest quality and therefore to coding a minimum amount of video data. Pictures used as reference pictures and / or inter-layer reference pictures can be indicated in reference picture list entries included in a reference picture list structure.

[0107] Pictures 611-618 may also be included in access units 627 and 628. AUs 627-628 are a set of coded pictures included in different layers and associated with the same output time during decoding. Thus, pictures coded in the same AUs 627-628 are scheduled for output from the DPB at the same time at the decoder. For example, pictures 614 and 618 are in the same AU 628. Pictures 613 and 617 are in a different AU 627 from pictures 614 and 618. Pictures 614 and 618 in the same AU 628 may be displayed alternatively. For example, picture 618 may be displayed when a small picture size is desired, and picture 614 may be displayed when a large picture size is desired. When a large picture size is desired, picture 614 is output, and picture 618 is used only for inter-layer prediction 621. In this case, the picture 618 is discarded without being output when the inter-layer prediction 621 is completed. An AU 627 that includes pictures at all layers may be referred to as a complete AU 627. An AU 628 that does not include pictures at all layers may be referred to as an incomplete AU 628.

[0108] Layer N-1 633 is included to illustrate a scenario in which AU 628 is incomplete. Layer N-1 633 includes pictures 625 and 626, which are substantially identical to pictures 615 and 617, respectively. However, layer N-1 633 does not include pictures corresponding to pictures 616 and 618. Thus, layer N-1 633 is substantially similar to layer N 631, but includes a lower frame rate. Therefore, AU 627, which includes pictures 611, 615, and 625, is complete. However, AU 628, which includes pictures 612 and 616, is incomplete AU 628 because AU 628 is missing pictures in the N-1 633 layer.

[0109] Encoding an incomplete AU 628 can be useful because it allows the multi-layer video sequence 600 to be transmitted at different frame rates to different users. However, the incomplete AU 628 can create difficulties when inspecting the encoded video sequence for conformance. For example, an SEI message may be used to transmit parameters used by an HRD, such as the HRD 500, when inspecting the multi-layer video sequence 600 for conformance with a standard. Some video coding systems allow an SEI message to apply to all layers in AUs 627-628. The problem is that such an SEI message may be persistent across multiple AUs 627-628. When an SEI message applies to all layers in an incomplete AU 628, the SEI message does not apply to layer N-1 633 because layer N-1 633 is not included in the incomplete AU 628. Therefore, the SEI message does not apply to layer N-1 633 in the complete AU 627 that follows the incomplete AU 628. This can lead to unpredictable errors because the SEI message is properly applied to layer N-1 633 when such a message occurs associated with a complete AU 627, but is not applied to layer N-1 633 when such a message occurs associated with an incomplete AU 628. This and other issues are addressed by the signaling scheme described below.

[0110] 7 is a schematic diagram illustrating an exemplary bitstream 700. For example, the bitstream 700 may be generated by the codec system 200 and / or the encoder 300 for decoding by the codec system 200 and / or the decoder 400 in accordance with the method 100. Furthermore, the bitstream 700 may include the multi-layer video sequence 600. Additionally, the bitstream 700 may include various parameters for controlling the operation of an HRD, such as the HRD 500. Based on such parameters, the HRD 500 may check the bitstream 700 for conformance with the standard before sending it to the decoder for decoding.

[0111] The bitstream 700 includes a VPS 711, one or more SPSs 713, multiple picture parameter sets (PPSs) 715, multiple slice headers 717, image data 720, and an SEI message 719. The VPS 711 includes data related to the entire bitstream 700. For example, the VPS 711 may include data related to the layers, layers, and / or sublayers used in the bitstream 700. The SPS 713 includes sequence data common to all pictures in a coded video sequence included in the bitstream 700. For example, each layer may include one or more coded video sequences, and each coded video sequence may reference the SPS 713 for corresponding parameters. Parameters in the SPS 713 may include picture size, bit depth, coding tool parameters, bitrate limits, etc. Note that while each sequence references an SPS 713, a single SPS 713 may include data for multiple sequences in some instances. PPS 715 contains parameters that apply to the entire picture. Therefore, each picture in a video sequence may reference PPS 715. Note that while each picture references PPS 715, a single PPS 715 can contain data for multiple pictures in some instances. For example, multiple similar pictures may be coded according to similar parameters. In such cases, a single PPS 715 may contain data for such similar pictures. PPS 715 may indicate coding tools available for slices in the corresponding picture, quantization parameters, offsets, etc.

[0112] The slice header 717 contains parameters specific to each slice in a picture. Therefore, there may be one slice header 717 per slice in a video sequence. The slice header 717 may include slice type information, POC, a reference picture list, prediction weights, tile entry points, deblocking parameters, etc. Note that in some examples, the bitstream 700 may also include a picture header, which is a syntax structure that contains parameters that apply to all slices in a single picture. For this reason, the picture header and slice header 717 may be used interchangeably in some contexts. For example, certain parameters may be moved between the slice header 717 and the picture header depending on whether such parameters are common to all slices in a picture.

[0113] Image data 720 includes video data coded according to inter-prediction and / or intra-prediction, as well as corresponding transformed and quantized residual data. For example, image data 720 may include layer 723, picture 725, and / or slice 727. Layer 723 is a set of VCL NAL units and associated non-VCL NAL units that share certain characteristics (e.g., a common resolution, frame rate, picture size, etc.), as indicated by a layer ID such as nuh_layer_id 729. For example, layer 723 may include a set of pictures 725 that share the same nuh_layer_id. Layer 723 may be substantially similar to layers 631, 632, and / or 633. nuh_layer_id 729 is a syntax element that specifies an identifier for layer 723, which contains at least one NAL unit. For example, the lowest quality layer 723, known as the base layer, may include the lowest value of nuh_layer_id 729, increasing the values ​​of nuh_layer_id 729 for higher quality layers 723. Thus, lower layers are layers 723 with smaller values ​​of nuh_layer_id 729, and higher layers are layers 723 with larger values ​​of nuh_layer_id 729.

[0114] A picture 725 is an array of luma samples and / or chroma samples that generate a frame or a field thereof. For example, a picture 725 is a coded image that can be output for display or used to support coding of other pictures 725 for output. A picture 725 includes one or more slices 727. A slice 727 may be defined as an integer number of complete tiles or an integer number of contiguous complete coding tree unit (CTU) rows (e.g., within a tile) of a picture 725 that are exclusively contained in a single NAL unit. A slice 727 is further divided into CTUs and / or coding tree blocks (CTBs). A CTU is a group of samples of a predefined size that can be partitioned by the coding tree. A CTB is a subset of a CTU and contains the luma or chroma component of the CTU. CTUs / CTBs are further divided into coding blocks based on the coding tree. The coding blocks may then be encoded / decoded according to a prediction mechanism.

[0115] The bitstream 700 may be coded as a sequence of NAL units. NAL units are containers for video data and / or supporting syntax. The NAL units may be VCL NAL units or non-VCL NAL units. VCL NAL units are NAL units coded to contain video data, such as image data 720 and associated slice headers 717. Non-VCL NAL units are NAL units containing non-video data, such as syntax and / or parameters, that support decoding, conformance checking, or other operations on the video data. For example, non-VCL NAL units may contain a VPS 711, an SPS 713, a PPS 715, an SEI message 719, or other supporting syntax.

[0116] An SEI message 719 may be a syntactic structure with a specified semantics that carries information not required by the decoding process to determine the values ​​of samples in a decoded picture. For example, an SEI message 719 may include data supporting the HRD process or other support data not directly related to decoding the bitstream 700 at the decoder. A set of SEI messages 719 may be implemented as a scalable nesting SEI message 741. The scalable nesting SEI message 741 provides a mechanism for associating an SEI message 719 with a particular layer 723. A scalable nesting SEI message 741 is a message that contains multiple scalable nested SEI messages 742. A scalable nesting SEI message 742 is an SEI message 719 that corresponds to one or more OLSs or one or more layers 723. An OLS is a set of layers 723, at least one of which is an output layer. Thus, depending on the context, the scalable nesting SEI message 741 can be said to include a set of scalable nested SEI messages 742 or a set of SEI messages 719. Furthermore, the scalable nesting SEI message 741 includes a set of scalable nested SEI messages 742 of the same type. The SEI message 719 may include a BP SEI message including HRD parameters for initializing the HRD and managing the CPB to test the corresponding OLS and / or layer 723. The SEI message 719 may also include a PT SEI message including HRD parameters for managing delivery information for AUs in the CPB and / or DPB to test the corresponding OLS and / or layer 723. The SEI message 719 may also include a DUI SEI message including HRD parameters for managing delivery information for DUs in the CPB and / or DPB to test the corresponding OLS and / or layer 723.

[0117] As mentioned above, the SEI message 719 may be included in a non-VCL NAL unit. For example, the scalable nesting SEI message 741 may be included in an SEI NAL unit 743. The SEI NAL unit 743 is an NAL unit having type data indicating that the SEI NAL unit 743 contains SEI data. One advantage of the scalable nesting SEI message 741 is that it allows a set of scalable nesting SEI messages 742 to be included in a single SEI NAL unit 743. When the scalable nesting SEI message 741 is not used, each SEI message 719 is included in a separate SEI NAL unit 743. For clarity of discussion, a particular SEI NAL unit 743 may be referred to as the current SEI NAL unit 743.

[0118] One issue with scalable nesting SEI message 741 is that the entire set of scalable nested SEI messages 742 is contained in a single SEI NAL unit 743. However, a set of scalable nested SEI messages 742 can relate to corresponding layers 723 in many ways. For example, each of the scalable nested SEI messages 742 in the set can relate to all layers 723. In another example, each of the scalable nested SEI messages 742 in the set can relate to one or more of the layers 723. Various flags can be used to indicate the correlation between the scalable nesting SEI message 742 and the layers 723. As mentioned above, one issue with scalable nested SEI message 742 flags is that the flags indicating scalable nested SEI messages 742 apply to all layers in an AU, which can cause errors when a video sequence contains incomplete AUs. Another problem is that the SEI NAL unit 743 containing the scalable nesting SEI message 741 is always associated with a layer 723, e.g., the layer 723 with the lowest nuh_layer_id 729. When the scalable nesting SEI message 742 applies to the layer 723 associated with the SEI NAL unit 743, the association is signaled in both the SEI NAL unit 743 and the scalable nesting SEI message 741. This is redundant and wastes bits.

[0119] The bitstream 700 includes various flags for signaling the configuration of the SEI message 719 while addressing the above-mentioned issues. For example, the scalable nesting SEI message 741 may include a scalable nesting all layers flag (all_layers_flag) 735. The scalable nesting all_layers_flag 735 syntax element specifies whether the scalable nested SEI message 742 in the scalable nesting SEI message 741 applies to all layers 723, for example, as specified in the VPS 711. By using the scalable nesting all_layers_flag 735, which does not address AUs, the incomplete AU problem is avoided. Thus, when scalable nesting all_layers_flag 735 is set, the scalable nested SEI message 742 contained in the scalable nesting SEI message 741 applies to all layers 723, regardless of the number of layers 723 contained in the AU to which the scalable nesting SEI message 741 applies. In a particular example, scalable nesting all_layers_flag 735 is set equal to 1 to specify that the scalable nested SEI message 742 applies to all layers 723 with a nuh_layer_id 729 greater than or equal to the nuh_layer_id 729 of the current SEI NAL unit 743. Additionally, scalable nesting all_layers_flag 735 may be set equal to 0 to specify that the scalable nested SEI message 742 may or may not apply to all layers 723 with nuh_layer_id 729 greater than or equal to the nuh_layer_id 729 of the current SEI NAL unit 743.Therefore, scalable nesting all_layers_flag 735 increases the functionality of the encoder and / or decoder by ensuring that the bitstream 700 is properly checked for conformance when incomplete AUs are present. Furthermore, scalable nesting all_layers_flag 735 reduces the size of the coded bitstream 700 by eliminating explicit layer signaling for scalable nested SEI messages 742 when such messages apply to all layers 723. As a result, coding efficiency is increased, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0120] To address the redundant signaling issue, the scalable nesting SEI message 741 may include a scalable nesting layer id (layer_id[i]) 739. The scalable nesting layer_id[i] 739 is a syntax element that specifies the nuh_layer_id 729 value of the i-th layer to which the scalable nested SEI message 742 applies. The scalable nesting layer_id[i] 739 may be used when the scalable nesting all_layers_flag 735 is set to 0. In this way, the layer_Id[i] 739 can be used to correlate each of the scalable nested SEI messages 742 with the corresponding layer 723. Further, scalable nesting layer_id[i] 739 is configured to signal all nuh_layer_id 729 of the layer 723 corresponding to the scalable nested SEI message 742, except for the nuh_layer_id 729 of the layer 723 corresponding to the SEI NAL unit 743. When the scalable nested SEI message 742 is not associated with a nuh_layer_id 729 value in scalable nesting layer_id[i] 739, it can be inferred that the scalable nested SEI message 742 pertains to the layer 723 associated with the SEI NAL unit 743. For example, the SEI NAL unit 743 may be associated with the lowest value of nuh_layer_id 729. Therefore, scalable nesting layer_id[i] 739 may be constrained such that scalable nesting layer_id[i] 739 for each layer i must be greater than nuh_layer_id 729 of the current SEI NAL unit 743 .This ensures that the nuh_layer_id 729 of the current SEI NAL unit 743 is signaled in the current SEI NAL unit yunitto 743 but is not repeated in the scalable nesting layer_id[i] 739 in the scalable nesting SEI message 741 . This improves the scalable nesting SEI message 741 by eliminating redundant Ids. For example, the loop that encodes / decodes the scalable nesting layer_id[i] 739 runs once in less time, which reduces processor resources during encoding and / or decoding. Furthermore, this reduces the size of the coded bitstream 700 for each scalable nesting SEI message 741 in the bitstream 700. As a result, coding efficiency is increased, which reduces the usage of processor, memory, and / or network signaling resources in both the encoder and decoder.

[0121] The HRD and / or decoder can use scalable nesting layer_id[i] 739 and scalable nesting all_layers_flag 735 to correlate the scalable nested SEI message 742 to layers 723, e.g., based on other syntax elements in the bitstream 700. For example, the HRD and / or decoder can use the number of nesting layers (nestingNumLayers) variable and the list of nesting layer IDs (NestingLayerId[i]) variable. As a matter of nomenclature, syntax elements with an underscore may be signaled in the bitstream 700 by the encoder, while syntax elements without an underscore or space may be variables determined (e.g., by the HRD and / or decoder) when reading data from the bitstream 700. The nestingNumLayers variable specifies the number of layers 723 to which the scalable nesting SEI message 742 applies based on the data in the bitstream 700. The NestingLayerId[i] variable is a variable that is set to specify a list of nuh_layer_id values ​​of layers 723 to which scalable nested SEI message 742 applies, for i in the range 0 to nestingNumLayers-1 (inclusive), based on the data in bitstream 700. nestingNumLayers and NestingLayerId[i] may be determined as follows:

number

[0122] The preceding code relies on the VPS maximum layers minus one (vps_max_layers_minus1) 731. vps_max_layers_minus1 731 is a syntax element carried in the VPS 711 that specifies the multiple layers 723 in the bitstream 700. The preceding code also relies on the VPS Layer Id (vps_layer_id[i]) 733. The vps_layer_id[i] 733 is a syntax element carried in the VPS 733 that specifies the nuh_layer_id 729 value of the i-th layer. Therefore, vps_layer_id[i] 733 specifies the nuh_layer_id 729 for each layer 723 such that the nuh_layer_id 729 can be accessed by layer index i.

[0123] The preceding code also relies on the general layer index (GeneralLayerIdx) variable. GeneralLayerIdx is a variable determined by the HRD and / or decoder that specifies the layer index of layer 723 with nuh_layer_id equal to vps_layer_id[i] 733. The preceding code also relies on the scalable nesting number of layers minus one (num_layers_minus1) 737 syntax element. scalable nesting num_layers_minus1 737 is a syntax element carried in the scalable nesting SEI message 741 that specifies the number of layers 723 to which the scalable nested SEI message 742 applies in the scalable nesting SEI message 741. scalable nesting num_layers_minus1 737 uses minus-1 format and therefore contains one less than the actual value. For example, if scalable nesting SEI message 741 includes scalable nesting SEI message 742 related to five layers 723, scalable nesting num_layers_minus1 737 is set to a value of 4. In some examples, scalable nesting num_layers_minus1 737 is constrained to be in the range 0 to vps_max_layers_minus1 731 - GeneralLayerIdx[nuh_layer_id] (inclusive), where nuh_layer_id 729 is the nuh_layer_id 729 of the current SEI NAL unit 743.

[0124] The foregoing information is described in more detail below in this specification. Layered video coding is also referred to as scalable video coding or scalable video coding. Scalability in video coding may be 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, frame rate scalability, etc. When multi-layer coding techniques are used, a picture or a portion thereof may be coded without using a reference picture (intra-prediction), coded by referencing a reference picture in the same layer (inter-prediction), or coded by referencing a reference picture in another layer (inter-layer prediction). A reference picture used for inter-layer prediction of the current picture is called an inter-layer reference picture (ILRP). Figure 6 shows an example of multi-layer coding for spatial scalability, where pictures in different layers have different resolutions.

[0125] Some video coding families provide support for scalability in profiles separate from profiles for single-layer coding. Scalable Video Coding (SVC) is a scalable extension of Advanced Video Coding (AVC) that provides support for spatial, temporal, and quality scalability. In SVC, a flag is signaled in each macroblock (MB) in an EL picture to indicate whether the EL MB is predicted using collocated blocks from the lower layer. Predictions from collocated blocks may include texture, motion vectors, and / or coding modes. An SVC implementation may not directly reuse an unmodified AVC implementation in its design. The SVC EL macroblock syntax and decoding process differ from the AVC syntax and decoding process.

[0126] Scalable HEVC (SHVC) is an extension of HEVC that provides support for spatial and quality scalability. Multiview HEVC (MV-HEVC) is an extension of HEVC that supports multiview scalability. 3D HEVC (3D-HEVC) is an extension of HEVC that provides support for 3D video coding, which is more advanced and efficient than MV-HEVC. Temporal scalability may be included as an integral part of a single-layer HEVC codec. In the multi-layer extension of HEVC, decoded pictures used for inter-layer prediction originate only from the same AU and are treated as long-term reference pictures (LTRPs). Such pictures are assigned reference indices in the reference picture list along 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. Spatial scalability involves resampling a reference picture or part of it when the ILRP has a different spatial resolution than the current picture being coded or decoded. The resampling of the reference picture can be achieved either at the picture level or at the coding block level.

[0127] VVC may also support layered video coding. A VVC bitstream can contain multiple layers. Each layer may be independent of the others. For example, each layer may be coded without using inter-layer prediction. In this case, the layers are also referred to as co-cast layers. In some cases, some of the layers are coded using ILP. A flag in the VPS can indicate whether a layer is a co-cast layer or whether some layers use ILP. When some layers use ILP, layer dependencies between layers are also signaled in the VPS. Unlike SHVC and MV-HEVC, VVC does not require an OLS to be specified. An OLS contains a specified set of layers, and one or more layers in the set of layers are designated as output layers. An output layer is a layer in the OLS that is output. In some implementations of VVC, only one layer may be selected for decoding and output when a layer is a co-cast layer. In some implementations of VVC, the entire bitstream, including all layers, is designated to be decoded when any layer uses ILP. Furthermore, certain layers among the layers are designated as output layers. The output layer may be indicated to be the top layer, all layers, or just the top layer plus the set of indicated lower layers.

[0128] The aforementioned aspects involve certain problems. Some video coding systems specify that scalable nesting SEI messages for associating SEI messages with bitstream subsets correspond to various operation points with specific layers and / or sublayers. The first problem occurs when nesting an SEI message for a specific layer using a scalable nesting SEI message included in an SEI NAL unit with a specific nuh_layer_id value of nuh_LayerId. In this case, when the nested SEI message does not apply to all layers, applicable layers with nuh_layer_id equal to nuh_LayerId are also explicitly signaled. However, applicable layers with nuh_layer_id equal to nuh_LayerId are always applicable layers. Therefore, signaling nuh_layer_id in the SEI NAL unit is unnecessary (e.g., redundant) and is a waste of bits.

[0129] The second problem occurs when a nested SEI message applies to all layers. The semantics may indicate that all_layer_flag is set equal to 1 to specify that the list nestingLayerIdList[0] contains all values ​​of nuh_layer_id present in the current access unit that are equal to or greater than the nuh_layer_id of the current SEI NAL unit, in ascending order of value. However, the current AU may be an incomplete AU. This may occur when the AU does not have pictures present for all layers. The persistent scope of the nested SEI message may include other AUs that contain pictures for more layers than the current AU. As a result, layers missing from the current AU (the AU containing the scalable nesting SEI message) are not specified as applicable. When other AUs in the persistent scope of the nested SEI message contain pictures for layers missing from the current AU, the information carried in the nested SEI message is interpreted as not applicable to those pictures. As a result, an error may occur. For example, if a nested SEI message contains a frame packaging SEI message, the rendered picture may contain artifacts that result in a poor user experience.

[0130] In general, this disclosure describes an approach for scalable nesting of SEI messages for layers in a multi-layer video bitstream. The description of the technique is based on VVC. However, the technique also applies to layered video coding based on other video codec specifications.

[0131] One or more of the above-described problems may be solved as follows. Specifically, the present disclosure includes a method for efficiently nesting SEI messages for use with layers in conjunction with incomplete AUs, as described above. First, the layer with a layer Id equal to that of the SEI NAL unit containing the scalable nesting SEI message is inferred to be the layer to which the nested SEI message applies, rather than being explicitly signaled. Second, when the nested SEI message applies to all layers, the nested SEI message applies to all layers specified by the VPS, which are all layers that may be present in the bitstream, rather than all layers present in the current AU.

[0132] An example implementation of the aforementioned mechanism is as follows: An example scalable nesting SEI message syntax is as follows: [Table 1]

[0133] In an alternative example, the syntax element nesting_layer_id[i] is a ue(v) coding of the layer index between layers specified by the VPS. In another alternative example, the syntax element nesting_layer_id[i] is a ue(v) coding of the delta of the layer index between layers specified by the VPS. In another alternative example, the syntax element nesting_layer_id[i] is a ue(v) coding of the delta of nuh_layer_id.

[0134] An example scalable nesting SEI message semantics is as follows: A scalable nesting SEI message provides a mechanism to associate an SEI message with a specific layer in the context of a specific OLS or with a specific layer not in the context of an OLS. A scalable nesting SEI message contains one or more SEI messages. An SEI message contained in a scalable nesting SEI message is also called a scalable nested SEI message. Bitstream conformance may require that the following restrictions apply when an SEI message is included in a scalable nesting SEI message:

[0135] An SEI message with payloadType equal to 132 (decoded picture hash) or 133 (scalable nesting) SHOULD NOT be included in a scalable nesting SEI message. When a scalable nesting SEI message contains a buffer duration, picture timing, or decoding unit information SEI message, the scalable nesting SEI message SHOULD NOT contain any other SEI message with payloadType not equal to 0 (buffer duration), 1 (picture timing), or 130 (decoding unit information).

[0136] Bitstream conformance MAY need to apply the following restrictions on the value of nal_unit_type of SEI NAL units that contain scalable nesting SEI messages: When a scalable nesting SEI message contains an SEI message with payloadType equal to 0 (buffer duration), 1 (picture timing), 130 (decoded unit information), 145 (dependent RAP indication), or 168 (frame field information), the SEI NAL unit that contains the scalable nesting SEI message SHOULD have nal_unit_type set equal to PREFIX_SEI_NUT. When a scalable nesting SEI message contains an SEI message with payloadType equal to 132 (decoded picture hash), the SEI NAL unit that contains the scalable nesting SEI message SHOULD have nal_unit_type set equal to SUFFIX_SEI_NUT.

[0137] nesting_ols_flag may be set equal to 1 to specify that the scalable nesting SEI message applies to a particular layer in the context of a particular OLS. nesting_ols_flag may be set equal to 0 to specify that the scalable nesting SEI message applies to a particular layer in general (e.g., not in the context of an OLS).

[0138] Bitstream conformance may require that the following constraints apply to the value of nesting_ols_flag: When a scalable nesting SEI message contains an SEI message with payloadType equal to 0 (buffer duration), 1 (picture timing), or 130 (decoding unit information), the value of nesting_ols_flag shall be equal to 1. 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.

[0139] 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 of 0 to TotalNumOlss-1. nesting_ols_Idx_delta_minus1[i] is used to derive the variable NestingOlsIdx[i], which specifies the OLS index of the ith 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 of 0 to TotalNumOls-2, inclusive. The variable NestingOlsIdx[i] may be derived as follows:

number

[0140] nesting_num_ols_layers_minus1[i]+1 specifies the number of layers to which the scalable nested SEI message applies in the context of the NestingOlsIdx[i]th OLS. The value of nesting_num_ols_layers_minus1[i] should be in the range 0 to NumLayersInOls[NestingOlsIdx[i]]-1, inclusive.

[0141] nesting_ols_layer_idx_delta_minus1[i][j] is used to derive the variable NestingOlsLayerIdx[i][j] that specifies the OLS layer index of the jth layer to which the scalable nested SEI message applies in the context of the NestingOlsLayerIdx[i][j]th OLS when nesting_ols_flag is equal to 1. The value of nesting_ols_layer_idx_delta_minus1[i] should be in the range 0 to NumLayersInOls[nestingOlsIdx[i]]-2, inclusive.

[0142] The variable NestingOlsLayerIdx[i][j] may be derived as follows:

number

[0143] LayerIdInOls[NestingOlsIdx[i]][NestingOlsIdx[i][NestingOlsLayerIdx[i][0]], for i in the range 0 to nesting_num_olss_minus1 (inclusive), SHALL be equal to the nuh_layer_id of the current SEI NAL unit (e.g., the SEI NAL unit containing the scalable nesting SEI message). nesting_all_layers_flag MAY be set equal to 1 to specify that the scalable nesting SEI message applies generically to all layers with a nuh_layer_id greater than or equal to the nuh_layer_id of the current SEI NAL unit. nesting_all_layers_flag MAY be set equal to 0 to specify that the scalable nesting SEI message may or may not apply generically to all layers with a nuh_layer_id greater than or equal to the nuh_layer_id of the current SEI NAL unit.

[0144] nesting_num_layers_minus1+1 specifies the number of layers to which a scalable nested SEI message generally applies. The value of nesting_num_layers_minus1 SHALL be in the range from 0 to vps_max_layers_minus1-GeneralLayerIdx[nuh_layer_id] (inclusive), where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit. nesting_layer_id[i] specifies the nuh_layer_id value of the ith layer to which a scalable nested SEI message generally 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.

[0145] The variables NestingNumLayer[i], which specifies the number of layers to which the scalable nested SEI message generally applies when nesting_ols_flag is equal to 1, and NestingLayerId[i], which specifies the list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to NestingNumLayer-1 (inclusive), are derived as follows, where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit:

number

[0146] nesting_num_seis_minus1+1 specifies the number of scalable nested SEI messages. The value of nesting_num_seis_minus1 should be in the range of 0 to 63 (inclusive). nesting_zero_bit should be set equal to zero.

[0147] FIG. 8 is a schematic diagram of an exemplary video coding device 800. The video coding device 800 is suitable for implementing the disclosed examples / embodiments described herein. The video coding device 800 includes a downstream port 820, an upstream port 850, and / or a transceiver unit 810 including a transmitter and / or receiver for communicating data upstream and / or downstream over a network. The video coding device 800 also includes a processor 830 including a logic unit and / or central processing unit (CPU) for processing data and a memory 832 for storing data. The video coding device 800 may also include electrical components, optical-to-electrical (OE) components, electrical-to-optical (EO) components, and / or wireless communication components coupled to the upstream port 850 and / or downstream port 820 for communicating data over an electrical, optical, or wireless communication network. The video coding device 800 may also include input and / or output (I / O) devices 860 for communicating data to and from a user. The I / O devices 860 may include output devices such as a display for displaying video data, speakers for outputting audio data, etc. The I / O devices 860 may also include input devices such as a keyboard, mouse, trackball, etc., and / or corresponding interfaces for interacting with such output devices.

[0148] The processor 830 is implemented in hardware and software. The processor 830 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and digital signal processors (DSPs). The processor 830 is in communication with the downstream port 820, the Tx / Rx 810, the upstream port 850, and the memory 832. The processor 830 includes a coding module 814. The coding module 814 implements the embodiments described and disclosed herein, such as methods 100, 900, and 1000, which may use the multi-layer video sequence 600 and / or the bitstream 700. The coding module 814 may also implement any other method / mechanism described herein. Additionally, the coding module 814 may implement the codec system 200, the encoder 300, the decoder 400, and / or the HRD 500. For example, coding module 814 may be used to implement an HRD. Furthermore, coding module 814 may be used to encode a scalable nesting SEI message with a corresponding flag to support clear and concise signaling of the correlation between the scalable nested SEI message and the corresponding layer in the scalable nesting SEI message. Thus, coding module 814 may be configured to implement a mechanism to address one or more of the problems described above. Therefore, coding module 814 may cause video coding device 800 to provide additional functionality and / or coding efficiency when coding video data. In this manner, coding module 814 improves the functionality of video coding device 800 while addressing problems inherent in video coding techniques. Furthermore, coding module 814 may perform transformations of video coding device 800 into different states.Alternatively, the coding module 814 may be implemented as instructions stored in the memory 832 and executed by the processor 830 (e.g., as a computer program product stored on a non-transitory medium).

[0149] Memory 832 may include one or more memory types such as a disk, tape drive, solid state drive, read-only memory (ROM), random access memory (RAM), flash memory, ternary content addressable memory (TCAM), static random access memory (SRAM), etc. Memory 832 is 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 program execution.

[0150] 9 is a flowchart of an example method 900 for encoding a video sequence into a bitstream, such as bitstream 700, that includes scalable nesting SEI messages applied to layers. Method 900 may be used by an encoder, such as codec system 200, encoder 300, and / or video coding device 800, when performing method 100. Additionally, method 900 may operate on HRD 500 and, therefore, may perform conformance testing on multi-layer video sequence 600.

[0151] Method 900 may begin when an encoder receives a video sequence and decides, for example, based on user input, to encode the video sequence into a multi-layer bitstream. In step 901, the encoder encodes the video sequence into one or more layers and encodes the layers into a multi-layer bitstream. Thus, the bitstream includes one or more layers. A layer may include a set of VCL NAL units and non-VCL NAL units with the same layer ID. For example, a layer may include a set of VCL NAL units containing video data of a coded picture as well as any parameter sets used to code such a picture. One or more of the layers may be output layers. Layers that are not output layers are coded to support reconstruction of output layers, but such support layers are not intended for output at a decoder. In this way, the encoder can encode various combinations of layers for transmission to a decoder upon request. Layers may be transmitted as needed to enable the decoder to obtain different representations of the video sequence depending on network conditions, hardware capabilities, and / or user settings.

[0152] In step 903, the encoder encodes one or more scalable nesting SEI messages into the bitstream in the current SEI NAL unit. An SEI message is a syntax structure that contains data not used for decoding. For example, an SEI message may contain data to support conformance testing to ensure that the bitstream conforms to a standard. To support simplified signaling when used in conjunction with a multi-layer bitstream, the SEI message is encoded as a scalable nesting SEI message. The scalable nesting SEI message contains one or more scalable nested SEI messages. The scalable nested SEI messages may each apply to one or more OLSs and / or one or more layers. To support simplified signaling, the scalable nesting SEI message includes one or more scalable nesting layer-IDs that specify the layer-ID values ​​of the layers to which the scalable nesting SEI message applies, excluding the layer-ID value of the current SEI NAL unit. This exception prevents redundant signaling of the layer Id of the current SEI NAL unit because the current SEI NAL unit also includes the corresponding layer Id. Note that a scalable nesting SEI message omits the layer Id of the current SEI NAL unit even when the scalable nesting SEI message contains at least one scalable nested SEI message that applies to the layer of the current SEI NAL unit.

[0153] In some examples, the scalable nesting layer_id is a scalable nesting layer_id[i] syntax element that specifies the nuh_layer_id value of the ith layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag is equal to 0. In some examples, each value of scalable nesting layer_id[i] is constrained to be greater than the nuh_layer_id value of the current SEI NAL unit. Note that syntax elements described herein as including an underscore may be included in the bitstream, but syntax elements without spaces may also be derived. The foregoing constraints and / or requirements ensure that the bitstream complies, for example, with VVC as modified as set forth herein or some other standard. However, the encoder may also be able to operate in other modes that are not subject to the constraints, for example, when operating with a different standard or a different version of the same standard.

[0154] In step 905, an HRD operating in the encoder may perform a set of bitstream conformance tests on the layers based on the scalable nesting SEI message. For example, the HRD may read a flag in the scalable nesting SEI message to determine how to interpret the scalable nested SEI message included in the scalable nesting SEI message. The HRD may then read the scalable nested SEI message to determine how to test the layers for conformance to the standard. The HRD may then perform conformance tests on the layers based on corresponding flags in the scalable nested SEI message and / or the scalable nesting SEI message.

[0155] In some examples, the HRD can determine the correlation between a scalable nested SEI message and a layer using the nestingNumLayers and NestingLayerId[i] variables. The nestingNumLayers variable specifies the number of layers to which the scalable nested SEI message applies. NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive). nestingNumLayers and NestingLayerId[i] can be derived by the HRD based on data from the bitstream. The HRD can then use the nestingNumLayers and NestingLayerId[i] variables as needed to support conformance testing. In some examples, nestingNumLayers and NestingLayerId[i] are derived as follows:

number

[0156] In step 907, the encoder can store the bitstream for communication to the decoder upon request. The encoder can also transmit the bitstream to the encoder as needed.

[0157] 10 is a flowchart of an example method 1000 of decoding a video sequence from a bitstream, such as bitstream 700, that includes scalable nesting SEI messages applied to layers. Method 1000 may be used by a decoder, such as codec system 200, decoder 400, and / or video coding device 800, when performing method 100. Additionally, method 1000 may be used with a multi-layer video sequence 600 that has been checked for conformance by an HRD, such as HRD 500.

[0158] Method 1000 can begin when a decoder begins receiving a bitstream of coded data representing a multi-layer video sequence, e.g., as a result of method 900. In step 1001, the decoder receives a bitstream including one or more layers. A layer may include a set of VCL NAL units and non-VCL NAL units with the same layer ID. For example, a layer may include a set of VCL NAL units containing video data of a coded picture as well as any parameter sets used to encode such picture. One or more of the layers may be output layers. Layers that are not output layers are decoded to support decoding of the output layer, but such supporting layers are not output.

[0159] The bitstream also includes one or more scalable nesting SEI messages. An SEI message is a syntactic structure that contains data not used for decoding. For example, an SEI message may contain data to support conformance testing to ensure that the bitstream conforms to a standard. To support simplified signaling when used in conjunction with a multi-layer bitstream, an SEI message is coded in a scalable nesting SEI message. A scalable nesting SEI message contains one or more scalable nested SEI messages. A specified scalable nesting SEI message may be contained in the current SEI NAL unit, which is a non-VCL NAL unit that contains the SEI message. A scalable nested SEI message may each apply to one or more OLSs and / or one or more layers. To support simplified signaling, a scalable nesting SEI message includes one or more scalable nesting layer-Ids that specify the layer-Id values ​​of the layers to which the scalable nesting SEI message applies, excluding the layer-Id value of the current SEI NAL unit. This exception prevents redundant signaling of the layer-Id of the current SEI NAL unit, because the current SEI NAL unit also includes the corresponding layer-Id. Note that a scalable nesting SEI message omits the layer-Id of the current SEI NAL unit even when the scalable nesting SEI message includes at least one scalable nested SEI message that applies to the layer of the current SEI NAL unit.

[0160] In some examples, the scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies the nuh_layer_id value of the ith layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag is equal to 0. In some examples, each value of scalable nesting layer_id[i] is constrained to be greater than the nuh_layer_id value of the current SEI NAL unit.

[0161] In some examples, the decoder can determine the correlation between a scalable nested SEI message and a layer using the nestingNumLayers and NestingLayerId[i] variables. The nestingNumLayers variable specifies the number of layers to which the scalable nested SEI message applies. NestingLayerId[i], for i in the range 0 to nestingNumLayers-1 (inclusive), specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies. nestingNumLayers and NestingLayerId[i] may be derived by a decoder based on data from the bitstream. The decoder can then use the nestingNumLayers and NestingLayerId[i] variables as needed to support decoding and / or display. In some examples, nestingNumLayers and NestingLayerId[i] are derived as follows:

number

[0162] In an embodiment, the video decoder expects the scalable nesting SEI message to omit the layer-Id of the current SEI NAL unit, as described above based on VVC or some other standard. However, if the decoder determines that this condition is not true, the decoder may detect an error, signal an error, request that a corrected bitstream (or a portion thereof) be retransmitted, or take some other corrective action to ensure that a conforming bitstream is received.

[0163] In step 1003, the decoder may decode coded pictures from one or more layers to generate decoded pictures. For example, the presence of a scalable nesting SEI message may indicate that the bitstream has been inspected by the HRD at the encoder and therefore conforms to the standard. Thus, the presence of the scalable nesting SEI message indicates that the bitstream can be decoded. In step 1005, the decoder may forward the decoded video for display as part of a decoded video sequence. For example, the decoded pictures and / or video sequence may be displayed to a user on a display or screen of an electronic device (e.g., a smartphone, tablet, laptop, personal computer, etc.).

[0164] 11 is a schematic diagram of an example system 1100 for coding a video sequence using a bitstream including scalable nesting SEI messages applied to layers. System 1100 may be implemented by an encoder and decoder, such as codec system 200, encoder 300, decoder 400, and / or video coding device 800. Furthermore, system 1100 may use HRD 500 to perform conformance testing on multi-layer video sequence 600 and / or bitstream 700. Additionally, system 1100 may be used when implementing methods 100, 900, and / or 1000.

[0165] The system 1100 includes a video encoder 1102. The video encoder 1102 includes a coding module 1103 for encoding a bitstream including one or more layers. The coding module 1103 is further for encoding a scalable nesting SEI message in a current SEI NAL unit into the bitstream, the scalable nesting SEI message including one or more scalable nesting layer-IDs specifying one or more scalable nested SEI messages and layer-ID values ​​of layers to which the scalable nested SEI messages apply, excluding the layer-ID value of the current SEI NAL unit. The video encoder 1102 further includes an HRD module 1105 for performing a set of bitstream conformance tests on the layers based on the scalable nested SEI messages. The video encoder 1102 further includes a storage module 1106 for storing the bitstream for communication to a decoder. The video encoder 1102 further includes a transmission module 1107 for transmitting the bitstream towards the video decoder 1110. The video encoder 1102 may be further configured to perform any of the steps of the method 900.

[0166] The system 1100 also includes a video decoder 1110. The video decoder 1110 includes a receiving module 1111 for receiving a bitstream including one or more layers and a scalable nesting supplemental enhancement information (SEI) message in a current SEI network abstraction layer (NAL) unit, the scalable nesting SEI message including one or more scalable nesting layer identifiers (Ids) specifying layer Id values ​​of layers to which the scalable nesting SEI messages apply, excluding the layer Id value of the current SEI NAL unit. The video decoder 1110 further includes a decoding module 1113 for decoding coded pictures from the one or more layers to generate decoded pictures. The video decoder 1110 further includes a transport module 1115 for transporting the decoded pictures for display as part of a decoded video sequence. The video decoder 1110 may be further configured to perform any of the steps of the method 1000 .

[0167] A first component is directly coupled to a second component when there are no intervening components other than a line, trace, or other medium between the first and second components. A first component is indirectly coupled to a second component when there are intervening components other than a line, trace, or other medium between the first and second components. The term "coupled" and variations thereof include both directly coupled and indirectly coupled. The use of the term "about," unless otherwise specified, means a range that includes ±10% of the subsequent number.

[0168] 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 that the order of steps of such methods is 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.

[0169] While multiple embodiments are provided in this disclosure, it will 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 are considered to be illustrative and not limiting, and the intention is not to be limited to the details provided herein. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted, or not implemented.

[0170] Additionally, the techniques, systems, subsystems, and methods described and illustrated individually or separately in various embodiments may be combined or integrated with other systems, components, techniques, or methods without departing from the scope of the present disclosure. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and may be made without departing from the spirit and scope disclosed herein.

Claims

1. 1. A method implemented in a decoder, comprising: receiving, by a receiver of a decoder, a bitstream including scalable nesting supplemental enhancement information (SEI) messages in one or more layers and a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI messages including one or more scalable nested SEI messages and one or more scalable nesting layer Ids that specify layer Id values ​​of the layers to which the scalable nested SEI messages apply, excluding a layer identifier (Id) value of the current SEI NAL unit; The scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; and deriving, by a processor of the decoder, a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), where nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies and NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and where nestingNumLayers and NestingLayerId[i] [Equation 1] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], where vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which said scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which said scalable nested SEI message applies; decoding, by the processor, coded pictures from the one or more layers to generate decoded pictures.

2. 2. The method of claim 1, wherein scalable nesting num_layers_minus1 is in the range of 0 to vps_max_layers_minus1-GeneralLayerIdx[nuh_layer_id], inclusive, where nuh_layer_id is the nuh_layer_id of the current SEI NAL unit.

3. 1. A method implemented in an encoder, comprising: encoding, by a processor of the encoder, a bitstream comprising one or more layers; encoding, by the processor, a scalable nesting supplemental enhancement information (SEI) message in a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nesting layer Ids specifying layer Id values ​​of the layers to which the scalable nested SEI messages apply, while applying a constraint of omitting layer Id values ​​of one or more scalable nested SEI messages and the current SEI NAL unit; The scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; and deriving by the processor a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), wherein the nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies, and the NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and wherein the nestingNumLayers and the NestingLayerId[i] [Equation 2] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], where vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which said scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which said scalable nested SEI message applies; A method comprising:

4. 1. A decoder comprising:

1. A receiving means for receiving a bitstream including scalable nesting supplemental enhancement information (SEI) messages in one or more layer and current SEI Network Abstraction Layer (NAL) units, the scalable nesting SEI messages including one or more scalable nested SEI messages and one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply, the receiving means comprising: receiving means, wherein the scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when a scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; 1. A derivation means for deriving a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), wherein said nestingNumLayers specifies the number of layers to which said scalable nested SEI message applies, and said NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which said scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and wherein said nestingNumLayers and said NestingLayerId[i] [Equation 3] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which the scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies; decoding means for decoding coded pictures from the one or more layers to generate decoded pictures.

5. 1. A video encoder comprising: encoding a bitstream including one or more layers; 1. An encoding means for encoding a scalable nesting supplemental enhancement information (SEI) message in a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply, while applying a constraint of omitting layer identifier (Id) values ​​of the current SEI NAL unit, encoding means, wherein the scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when a scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; 1. A derivation means for deriving a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), wherein said nestingNumLayers specifies the number of layers to which said scalable nested SEI message applies, and said NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which said scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and wherein said nestingNumLayers and said NestingLayerId[i] [Equation 4] where vps_max_layers_minus1+1 specifies the number of layers specified by the video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which the scalable nested SEI message applies, and scalable nesting and a deriving means, wherein layer_id[i] specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies.

6. 1. A method for storing a bitstream, comprising: receiving or transmitting a bitstream over a communications interface; storing the bitstream on one or more storage media, the bitstream including one or more layers and a scalable nesting supplemental enhancement information (SEI) message in a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nested SEI messages and one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply; The scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; and deriving a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), where nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies and NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and where nestingNumLayers and NestingLayerId[i] satisfy: [Equation 5] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], where vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which said scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which said scalable nested SEI message applies; A method comprising:

7. 1. A method for transmitting a bitstream, comprising: storing at least one bitstream on at least one storage medium, the bitstream including one or more layers and a scalable nesting supplemental enhancement information (SEI) message in a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nested SEI messages and one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply; The scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; and deriving a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), where nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies and NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and where nestingNumLayers and NestingLayerId[i] satisfy: [Equation 6] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], where vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which said scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which said scalable nested SEI message applies; obtaining one or more bitstreams from one of the at least one storage medium; transmitting the one or more bitstreams to a destination device.

8. 1. A system for processing a bitstream, comprising: an encoding device; one or more storage devices; and a decoding device; the encoding device is configured to obtain a video signal and encode the video signal to obtain one or more bitstreams, the bitstream including one or more layers and a scalable nesting supplemental enhancement information (SEI) message in a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nested SEI messages and one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply; The scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; The encoding device is further configured to derive a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), wherein the nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies and the NestingLayerId[i] specifies, for i in the range 0 to nestingNumLayers-1 (inclusive), a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, and wherein the nestingNumLayers and the NestingLayerId[i] satisfy [Equation 7] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], where vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which the scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies, the one or more storage devices are used to store the one or more bitstreams; The decoding device is used to decode the one or more bitstreams.

9. A computer-readable storage medium storing a computer program executable by a processor, the computer program causing the processor to perform the method of any one of claims 1 to 3 and 6 to 7 when executed by the processor.

10. A program comprising program code for carrying out the method according to any one of claims 1 to 3, 6 to 7 when the program is run on a computer or processor.

11. A coder including processing circuitry for implementing the method of any one of claims 1 to 3, 6 to 7.

12. 1. A device for storing and decoding video or image bitstreams, comprising: a communication interface, a processor, and a storage medium; the communication interface is configured to receive and / or transmit a bitstream, and the storage medium is configured to store the bitstream, the bitstream including one or more layers and scalable nesting supplemental enhancement information (SEI) messages in a current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI messages including one or more scalable nested SEI messages and one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply; The scalable nesting layer Id is a scalable nesting layer_id[i] syntax element that specifies a NAL unit header layer Id (nuh_layer_id) value of the i-th layer to which the scalable nested SEI message applies when scalable nesting all_layers_flag (all_layers_flag) is equal to 0, where nuh_layer_id is a syntax element that specifies a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; The processor is configured to derive a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), where nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies and NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and where nestingNumLayers and NestingLayerId[i] satisfy: [Equation 8] where vps_max_layers_minus1+1 specifies the number of layers specified by a video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which the scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies.

13. A data structure of a bitstream, the data structure comprising: one or more layers; a scalable nesting supplemental enhancement information (SEI) message in the current SEI Network Abstraction Layer (NAL) unit, the scalable nesting SEI message including one or more scalable nested SEI messages and one or more scalable nesting layer Ids specifying layer identifier (Id) values ​​of the layers to which the scalable nested SEI messages apply, the scalable nesting layer Ids specifying a NAL unit header layer Id (nuh_layer_id) value of the ith layer to which the scalable nested SEI messages apply when a scalable nesting all_layers_flag (all_layers_flag) is equal to 0. layer_id[i] syntax element, nuh_layer_id is a syntax element specifying a layer identifier, and each value of scalable nesting layer_id[i] is greater than the nuh_layer_id value of the current SEI NAL unit; The data structure comprises: parsing the one or more layers from the bitstream; Parsing the scalable nesting supplemental enhancement information (SEI) message in a current SEI Network Abstraction Layer (NAL) unit from the bitstream; deriving a number of nesting layers (nestingNumLayers) and a list of nesting layer Ids (NestingLayerId[i]), where nestingNumLayers specifies the number of layers to which the scalable nested SEI message applies and NestingLayerId[i] specifies a list of nuh_layer_id values ​​of the layers to which the scalable nested SEI message applies, for i in the range 0 to nestingNumLayers-1 (inclusive), and where nestingNumLayers and NestingLayerId[i] satisfy: [Equation 9] where vps_max_layers_minus1+1 specifies the number of layers specified by the video parameter set (VPS), GeneralLayerIdx is a variable that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i], vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer, scalable nesting num_layers_minus1+1 specifies the number of layers to which the scalable nested SEI message applies, and scalable nesting layer_id[i] specifies the nuh_layer_id value of the i-th layer to which the scalable nested SEI message applies.

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