Simulcast Layer for Multiview in Video Coding

Abstract

To provide a video coding mechanism.SOLUTION: A mechanism includes encoding the bitstream which includes one or more layers of coded pictures. A video parameter set (VPS) is also encoded into the bitstream. The VPS includes an "each layer is an output layer set (OLS)" flag (each_layer_is_an_ols_flag) when all layers specified by the VPS are coded independently without inter-layer prediction. Each_layer_is_an_ols_flag specifies whether each OLS contains only one layer. The bitstream is stored for communication towards a decoder.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] FIELD This disclosure relates generally to video coding, and more particularly to constructing output layer sets (OLS) in multi-layer bitstreams for use in multi-view applications. [Background technology]

[0002] The video data required to render even a relatively short video can be substantial, which can pose difficulties when the data is streamed or otherwise communicated over a communication network having limited bandwidth capacity. Thus, video data is generally compressed before being communicated over modern telecommunication networks. Since memory resources may be limited, the size of the video can also be an issue when the video is stored on a storage device. 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 an ever-increasing demand for higher video quality, improved compression and decompression techniques that improve compression ratios without sacrificing much image quality are desirable. Summary of the Invention [Means for solving the problem]

[0003] In one implementation, the present disclosure includes a method performed in a decoder, the method including: receiving, by a receiver of the decoder, a bitstream including coded pictures of one or more layers and a video parameter set (VPS), where when all layers specified by the VPS are independently coded without inter-layer prediction, the VPS includes an "each layer is an output layer set (OLS)" flag (each_layer_is_an_ols_flag), where each_layer_is_an_ols_flag specifies whether each OLS includes only one layer; decoding, by a processor of the decoder, the coded pictures from the output layers of the OLS based on each_layer_is_an_ols_flag in the VPS to generate decoded pictures; and forwarding, by the processor, the decoded pictures for display as part of a decoded video sequence.

[0004] To support scalability, layers of a picture can be used. For example, a video can be coded into multiple layers. A layer can be coded without reference to other layers. Such a layer is called a simulcast layer. Thus, a simulcast layer can be decoded without reference to other layers. As another example, a layer can be coded using inter-layer prediction. This allows a current layer to be coded by including only the difference between the current layer and a reference layer. The layers can be organized into an OLS. An OLS is a set of layers including at least one output layer and any layers that support decoding of the output layer. As a specific example, a first OLS can include a base layer, and a second OLS can include a base layer and further an enhancement layer with increased characteristics. In one example, a first OLS can be sent to a decoder to enable the video to be decoded at a base resolution, or a second OLS can be sent to enable the video to be decoded at a higher enhanced resolution. Thus, the video can be scaled based on user requests. In some cases, scalability is not used and each layer is coded as a simulcast layer. Some systems infer that if all layers are simulcast, then each OLS should contain a single layer (since no reference layers are used). This inference increases coding efficiency since signaling can be omitted from the encoded bitstream. However, such inference does not support multiview. Multiview is also known as stereoscopic video. In multiview, two video sequences of the same scene are recorded by spatially offset cameras. The two video sequences are displayed to the user with different lenses in a headset. In this way, by displaying different spatially offset sequences to each eye, three-dimensional (3D) video and / or the impression of visual depth can be created.Thus, an OLS that implements multiview includes two layers (e.g., one for each eye). However, when the layers are all simulcast, a video decoder may use inference to infer that each OLS includes only one layer. This may result in errors, as the decoder may display only one layer of the multiview or may not be able to continue displaying any of the layers. Thus, when all layers are simulcast, the inference that each OLS includes a single layer may prevent a multiview application from rendering properly at the decoder.

[0005] This example includes a mechanism that allows a video coding system to properly decode multi-view video when all layers in a video are simulcast and do not use inter-layer prediction. An "all independent layers in VPS" flag (vps_all_independent_layers_flag) can be included in the bitstream in the VPS and set to 1 when none of the layers use inter-layer prediction (e.g., all are simulcast). When this flag is set to 1, each_layer_is_an_ols_flag is signaled in the VPS. each_layer_is_an_ols_flag can be set to specify whether each OLS contains a single layer or at least one OLS contains multiple layers (e.g., to support multi-view). Thus, vps_all_independent_layers_flag and each_layer_is_an_ols_flag can be used to support multi-view applications. Additionally, when this occurs, an OLS mode identification code (ols_mode_idc) can be set to 2 in the VPS. This explicitly signals the number of OLSs and the layers associated with the OLSs. The decoder can then use this information to correctly decode the OLSs, including multi-view video. This approach supports coding efficiency while correcting errors. Thus, the disclosed mechanism improves the capabilities of the encoder and / or decoder. Furthermore, the disclosed mechanism may reduce bitstream size and therefore reduce processor, memory, and / or network resource utilization in both the encoder and decoder.

[0006] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, in which each_layer_is_an_ols_flag is set to 1 to specify that each OLS includes only one layer and each layer is the only output layer in each OLS.

[0007] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, in which each_layer_is_an_ols_flag is set to 0 when specifying that at least one OLS includes multiple layers.

[0008] Optionally, in any of the aforementioned aspects, another implementation form of the aspect is provided, where when the OLS mode identification code (ols_mode_idc) is equal to 2, the total number of OLSs is explicitly signaled, the layers associated with the OLSs are explicitly signaled, the “all independent layers of VPS” flag (vps_all_independent_layers_flag) is set to 1, and each_layer_is_an_ols_flag is set to 0, then ols_mode_idc is inferred to be equal to 2.

[0009] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, wherein the VPS includes a vps_all_independent_layers_flag set to 1 to specify that all layers specified by the VPS are independently coded without inter-layer prediction.

[0010] Optionally, in any of the aforementioned aspects, another implementation form of the aspect is provided, wherein the VPS includes a “VPS max layers minus 1” (vps_max_layers_minus1) syntax element that specifies the number of layers specified by the VPS, and when vps_max_layers_minus1 is greater than 0, vps_all_independent_layers_flag is signaled.

[0011] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, wherein the VPS includes a “number of output layer sets minus 1” (num_output_layer_sets_minus1) that specifies the total number of OLSs specified by the VPS when ols_mode_idc is equal to 2.

[0012] In one embodiment, the disclosure includes a method performed in an encoder, the method including the steps of: encoding, by a processor of the encoder, a bitstream including coded pictures of one or more layers; encoding, by the processor, a VPS into the bitstream, where the VPS includes each_layer_is_an_ols_flag when all layers specified by the VPS are independently coded without inter-layer prediction, and each_layer_is_an_ols_flag specifies whether each OLS includes only one layer; and storing, by a memory coupled to the processor, the bitstream for communication to a decoder.

[0013] To support scalability, layers of a picture can be used. For example, a video can be coded into multiple layers. A layer can be coded without reference to other layers. Such a layer is called a simulcast layer. Thus, a simulcast layer can be decoded without reference to other layers. As another example, a layer can be coded using inter-layer prediction. This allows a current layer to be coded by including only the difference between the current layer and a reference layer. The layers can be organized into an OLS. An OLS is a set of layers including at least one output layer and any layers that support decoding of the output layer. As a specific example, a first OLS can include a base layer, and a second OLS can include a base layer and further an enhancement layer with increased characteristics. In one example, a first OLS can be sent to a decoder to enable the video to be decoded at a base resolution, or a second OLS can be sent to enable the video to be decoded at a higher enhanced resolution. Thus, the video can be scaled based on user requests. In some cases, scalability is not used and each layer is coded as a simulcast layer. Some systems infer that if all layers are simulcast, then each OLS should contain a single layer (since no reference layers are used). This inference increases coding efficiency since signaling can be omitted from the encoded bitstream. However, such inference does not support multiview. Multiview is also known as stereoscopic vision. In multiview, two video sequences of the same scene are recorded by spatially offset cameras. The two video sequences are displayed to the user with different lenses in a headset. In this way, by displaying different spatially offset sequences to each eye, a 3D video and / or the impression of visual depth can be created.Thus, an OLS that implements multiview includes two layers (e.g., one for each eye). However, when the layers are all simulcast, a video decoder may use inference to infer that each OLS includes only one layer. This may result in errors, as the decoder may display only one layer of the multiview or may not be able to continue displaying any of the layers. Thus, when all layers are simulcast, the inference that each OLS includes a single layer may prevent a multiview application from rendering properly at the decoder.

[0014] This example includes a mechanism that allows a video coding system to properly decode multi-view video when all layers in a video are simulcast and do not use inter-layer prediction. vps_all_independent_layers_flag is included in the bitstream in the VPS and can be set to 1 when none of the layers use inter-layer prediction (e.g., all are simulcast). When this flag is set to 1, each_layer_is_an_ols_flag is signaled in the VPS. each_layer_is_an_ols_flag can be set to specify whether each OLS contains a single layer or at least one OLS contains multiple layers (e.g., to support multi-view). Thus, vps_all_independent_layers_flag and each_layer_is_an_ols_flag can be used to support multi-view applications. Additionally, when this occurs, ols_mode_idc can be set to 2 in the VPS. This explicitly signals the number of OLSs and the layers associated with the OLS. The decoder can then use this information to correctly decode the OLS including the multi-view video. This approach supports coding efficiency while correcting errors. Thus, the disclosed mechanism improves the performance of the encoder and / or decoder. Furthermore, the disclosed mechanism may reduce bitstream size and thus reduce processor, memory, and / or network resource utilization in both the encoder and the decoder.

[0015] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, in which each_layer_is_an_ols_flag is set to 1 to specify that each OLS includes only one layer and each layer is the only output layer in each OLS.

[0016] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, in which each_layer_is_an_ols_flag is set to 0 when specifying that at least one OLS includes multiple layers.

[0017] Optionally, in any of the aforementioned aspects, another implementation form of the aspect is provided, where when ols_mode_idc is equal to 2, the total number of OLSs is explicitly signaled, the layers associated with the OLSs are explicitly signaled, and when vps_all_independent_layers_flag is set to 1 and each_layer_is_an_ols_flag is set to 0, ols_mode_idc is inferred to be equal to 2.

[0018] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, wherein the VPS includes a vps_all_independent_layers_flag set to 1 to specify that all layers specified by the VPS are independently coded without inter-layer prediction.

[0019] Optionally, in any of the aforementioned aspects, another implementation form of the aspect is provided, wherein the VPS includes a vps_max_layers_minus1 syntax element that specifies the number of layers specified by the VPS, and when vps_max_layers_minus1 is greater than 0, vps_all_independent_layers_flag is signaled.

[0020] Optionally, in any of the aforementioned aspects, another implementation of the aspect is provided, wherein the VPS includes num_output_layer_sets_minus1, which specifies the total number of OLSs specified by the VPS when ols_mode_idc is equal to 2.

[0021] In an embodiment, the present disclosure includes 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, the receiver, the memory, and the transmitter are configured to perform a method according to any of the aforementioned aspects.

[0022] In one embodiment, the present disclosure includes 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 that, when executed by a processor, causes the video coding device to perform a method according to any of the preceding aspects.

[0023] In one embodiment, the present disclosure includes a decoder, the decoder including receiving means for receiving a bitstream including coded pictures of one or more layers and a VPS, where when all layers specified by the VPS are independently coded without inter-layer prediction, the VPS includes each_layer_is_an_ols_flag, which specifies whether each OLS includes only one layer, decoding means for decoding the coded pictures from output layers of the OLS based on each_layer_is_an_ols_flag in the VPS to generate decoded pictures, and forwarding means for forwarding the decoded pictures for display as part of a decoded video sequence.

[0024] To support scalability, layers of a picture can be used. For example, a video can be coded into multiple layers. A layer can be coded without reference to other layers. Such a layer is called a simulcast layer. Thus, a simulcast layer can be decoded without reference to other layers. As another example, a layer can be coded using inter-layer prediction. This allows a current layer to be coded by including only the difference between the current layer and a reference layer. The layers can be organized into an OLS. An OLS is a set of layers including at least one output layer and any layers that support decoding of the output layer. As a specific example, a first OLS can include a base layer, and a second OLS can include a base layer and further an enhancement layer with increased characteristics. In one example, a first OLS can be sent to a decoder to enable the video to be decoded at a base resolution, or a second OLS can be sent to enable the video to be decoded at a higher enhanced resolution. Thus, the video can be scaled based on user requests. In some cases, scalability is not used and each layer is coded as a simulcast layer. Some systems infer that if all layers are simulcast, then each OLS should contain a single layer (since no reference layers are used). This inference increases coding efficiency since signaling can be omitted from the encoded bitstream. However, such inference does not support multiview. Multiview is also known as stereoscopic vision. In multiview, two video sequences of the same scene are recorded by spatially offset cameras. The two video sequences are displayed to the user with different lenses in a headset. In this way, by displaying different spatially offset sequences to each eye, a 3D video and / or the impression of visual depth can be created.Thus, an OLS that implements multiview includes two layers (e.g., one for each eye). However, when the layers are all simulcast, a video decoder may use inference to infer that each OLS includes only one layer. This may result in errors, as the decoder may display only one layer of the multiview or may not be able to continue displaying any of the layers. Thus, when all layers are simulcast, the inference that each OLS includes a single layer may prevent a multiview application from rendering properly at the decoder.

[0025] This example includes a mechanism that allows a video coding system to properly decode multi-view video when all layers in a video are simulcast and do not use inter-layer prediction. vps_all_independent_layers_flag is included in the bitstream in the VPS and can be set to 1 when none of the layers use inter-layer prediction (e.g., all are simulcast). When this flag is set to 1, each_layer_is_an_ols_flag is signaled in the VPS. each_layer_is_an_ols_flag can be set to specify whether each OLS contains a single layer or at least one OLS contains multiple layers (e.g., to support multi-view). Thus, vps_all_independent_layers_flag and each_layer_is_an_ols_flag can be used to support multi-view applications. Additionally, when this occurs, ols_mode_idc can be set to 2 in the VPS. This explicitly signals the number of OLSs and the layers associated with the OLS. The decoder can then use this information to correctly decode the OLS including the multi-view video. This approach supports coding efficiency while correcting errors. Thus, the disclosed mechanism improves the performance of the encoder and / or decoder. Furthermore, the disclosed mechanism may reduce bitstream size and thus reduce processor, memory, and / or network resource utilization in both the encoder and the decoder.

[0026] Optionally, in any of the preceding aspects, a further implementation of the aspect is provided, wherein the decoder is further configured to perform a method as set forth in any of the preceding aspects.

[0027] In one embodiment, the present disclosure includes an encoder that encodes a bitstream including coded pictures of one or more layers, and includes encoding means for encoding a VPS including each_layer_is_an_ols_flag into a bitstream, where each_layer_is_an_ols_flag specifies whether each OLS includes only one layer, when all layers specified by the VPS are coded independently without inter-layer prediction, and storage means for storing the bitstream for communication to a decoder.

[0028] To support scalability, layers of a picture can be used. For example, a video can be coded into multiple layers. A layer can be coded without reference to other layers. Such a layer is called a simulcast layer. Thus, a simulcast layer can be decoded without reference to other layers. As another example, a layer can be coded using inter-layer prediction. This allows a current layer to be coded by including only the difference between the current layer and a reference layer. The layers can be organized into an OLS. An OLS is a set of layers including at least one output layer and any layers that support decoding of the output layer. As a specific example, a first OLS can include a base layer, and a second OLS can include a base layer and further an enhancement layer with increased characteristics. In one example, a first OLS can be sent to a decoder to enable the video to be decoded at a base resolution, or a second OLS can be sent to enable the video to be decoded at a higher enhanced resolution. Thus, the video can be scaled based on user requests. In some cases, scalability is not used and each layer is coded as a simulcast layer. Some systems infer that if all layers are simulcast, then each OLS should contain a single layer (since no reference layers are used). This inference increases coding efficiency since signaling can be omitted from the encoded bitstream. However, such inference does not support multiview. Multiview is also known as stereoscopic vision. In multiview, two video sequences of the same scene are recorded by spatially offset cameras. The two video sequences are displayed to the user with different lenses in a headset. In this way, by displaying different spatially offset sequences to each eye, a 3D video and / or the impression of visual depth can be created.Thus, an OLS that implements multiview includes two layers (e.g., one for each eye). However, when the layers are all simulcast, a video decoder may use inference to infer that each OLS includes only one layer. This may result in errors, as the decoder may display only one layer of the multiview or may not be able to continue displaying any of the layers. Thus, when all layers are simulcast, the inference that each OLS includes a single layer may prevent a multiview application from rendering properly at the decoder.

[0029] This example includes a mechanism that allows a video coding system to properly decode multi-view video when all layers in a video are simulcast and do not use inter-layer prediction. vps_all_independent_layers_flag is included in the bitstream in the VPS and can be set to 1 when none of the layers use inter-layer prediction (e.g., all are simulcast). When this flag is set to 1, each_layer_is_an_ols_flag is signaled in the VPS. each_layer_is_an_ols_flag can be set to specify whether each OLS contains a single layer or at least one OLS contains multiple layers (e.g., to support multi-view). Thus, vps_all_independent_layers_flag and each_layer_is_an_ols_flag can be used to support multi-view applications. Additionally, when this occurs, ols_mode_idc can be set to 2 in the VPS. This explicitly signals the number of OLSs and the layers associated with the OLS. The decoder can then use this information to correctly decode the OLS including the multi-view video. This approach supports coding efficiency while correcting errors. Thus, the disclosed mechanism improves the performance of the encoder and / or decoder. Furthermore, the disclosed mechanism may reduce bitstream size and thus reduce processor, memory, and / or network resource utilization in both the encoder and the decoder.

[0030] Optionally, in any of the aforementioned aspects, a further implementation of the aspect is provided, wherein the encoder is further configured to perform a method as set forth in any of the aforementioned aspects.

[0031] 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.

[0032] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

[0033] For a more complete understanding of the present disclosure, reference should now be made to the following brief description taken in conjunction with the accompanying drawings and detailed description, in which like reference numerals represent like parts. [Brief description of the drawings]

[0034] [Figure 1] 4 is a flowchart illustrating an exemplary method for coding a video signal. [Diagram 2] 1 is a schematic diagram of an example coding and decoding (codec) system for video coding. [Diagram 3] FIG. 1 is a schematic diagram illustrating an exemplary video encoder. [Figure 4] FIG. 2 is a schematic diagram illustrating an exemplary video decoder. [Diagram 5] 1 is a schematic diagram illustrating an example multi-layer video sequence configured for inter-layer prediction. [Figure 6] FIG. 2 is a schematic diagram illustrating an example multiview sequence including a simulcast layer for use in multiview; [Figure 7] FIG. 1 is a schematic diagram illustrating an example bitstream including an OLS with a simulcast layer for multiview use. [Figure 8] 1 is a schematic diagram illustrating an example video coding device. [Figure 9] 1 is a flowchart illustrating an example method for encoding a video sequence with OLS of a simulcast layer for multiview use. [Figure 10]1 is a flowchart illustrating an example method for decoding a video sequence including OLS of a simulcast layer for multiview use. [Figure 11] 1 is a schematic diagram illustrating an example system for coding a video sequence with OLS of a simulcast layer for multiview use. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Although exemplary implementations of one or more embodiments are provided below, it should be understood at the outset that the disclosed systems and / or methods may be implemented using any number of techniques, whether currently known or in existence. The present disclosure is in no way limited to the exemplary implementations, drawings, and techniques shown below, including the exemplary designs and implementations shown and described herein, and may be modified within the scope of the appended claims, along with their full scope of equivalents.

[0036] The following terms are defined as follows, unless used in the present specification in a contrary context. Specifically, the following definitions are intended to further clarify the present disclosure. However, terms may be described differently in different contexts. Therefore, the following definitions shall be considered as supplementary and shall not be considered as limiting any other definitions of the descriptions provided for such terms herein.

[0037] A bitstream is a sequence of bits that includes video data that is compressed for transmission between an encoder and a decoder. An encoder is a device configured to compress video data into a bitstream using an encoding process. A decoder is a device configured to reconstruct video data from the bitstream for display using a decoding process. A picture is an array of luma samples and / or an array of chroma samples that make up a frame or a field thereof. For clarity of explanation, the picture being encoded or decoded may be referred to as the current picture.

[0038] A network abstraction layer (NAL) unit is a syntax structure that contains data in the form of a raw byte sequence payload (RBSP), an indication of the type of data, and optionally interspersed with emulation prevention bytes. A video coding layer (VCL) NAL unit is a NAL unit that is coded to contain video data, such as a coded slice of a picture. A non-VCL NAL unit is a NAL unit that contains non-video data, such as syntax and / or parameters that support decoding the video data, performing conformance checks, or other operations. A layer is a set of VCL NAL units and associated non-VCL NAL units that share specified characteristics (e.g., a common resolution, frame rate, picture size, etc.). The VCL NAL units of a layer may share a particular value of the NAL unit header layer identifier (nuh_layer_id). A coded picture is a coded representation of a picture that contains VCL NAL units with a particular value of the NAL unit header layer identifier (nuh_layer_id) in the access unit (AU) and contains all coding tree units (CTUs) of the picture. A decoded picture is a picture produced by applying a decoding process to a coded picture.

[0039] An output layer set (OLS) is a set of layers where one or more layers are designated as output layers. An output layer is a layer designated for output (e.g., to a display). The 0th OLS is an OLS that contains only the lowest layer (the layer with the lowest layer identifier) ​​and therefore only output layers. A video parameter set (VPS) is a data unit that contains parameters related to the entire video. Inter-layer prediction is a mechanism for coding a current picture in a current layer by referencing a reference picture in a reference layer, where the current picture and the reference picture are included in the same AU and the reference layer contains a lower nuh_layer_id than the current layer.

[0040] The "each layer is an OLS" flag (each_layer_is_an_ols_flag) is a syntax element that signals whether each OLS in the bitstream contains a single layer. The OLS mode identification code (ols_mode_idc) is a syntax element that indicates information about the number of OLSs, the layers of the OLS, and the output layers of the OLS. The "all independent layers of the VPS" flag (vps_all_independent_layers_flag) is a syntax element that signals whether inter-layer prediction is used to code any of the layers in the bitstream. The "VPS maximum layers minus one" (vps_max_layers_minus1) is a syntax element that signals the number of layers specified by the VPS and thus the maximum number of layers allowed in the corresponding coded video sequence. The "number of output layer sets minus one" (num_output_layer_sets_minus1) is a syntax element that specifies the total number of OLSs specified by the VPS.

[0041] The following acronyms are used in this specification: Coding Tree Block (CTB), Coding Tree Unit (CTU), Coding Unit (CU), Coded Video Sequence (CVS), Joint Video Experts Team (JVET), Motion Constrained Tile Set (MCTS), Maximum Transmission Unit (MTU), Network Abstraction Layer (NAL), Output Layer Set (OLS), Picture Order Count (POC), Raw Byte Sequence Payload (RBSP), Sequence Parameter Set (SPS), Video Parameter Set (VPS), Versatile Video Coding (VVC), and Working Draft (WD).

[0042] Many video compression techniques may be used to reduce the size of video files while minimizing 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. For block-based video coding, video slices (e.g., video pictures, or portions of video pictures) may be partitioned into video blocks, which may also be referred to as tree blocks, coding tree blocks (CTBs), coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are coded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded unidirectionally predictive (P) slice or bidirectionally predictive (B) slice of a picture may be coded by using spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame and / 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 that represents an image block. The 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 that indicates the difference 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. These results 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 be scanned to generate a one-dimensional vector of transform coefficients. To achieve even further compression, entropy coding may be applied.Such video compression techniques are described in further detail below.

[0043] To ensure that the encoded video can be accurately decoded, the video is encoded and decoded according to a corresponding video coding standard, including International Telecommunications 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), as well as three-dimensional (3D) AVC (3D-AVC). HEVC includes extensions such as Scalable HEVC (SHVC), Multiview HEVC (MV-HEVC), and 3D HEVC (3D-HEVC). The joint video experts team (JVET) of ITU-T and ISO / IEC has started developing a video coding standard called Versatile Video Coding (VVC). VVC is included in the Working Drafts, including JVET-O2001-v14.

[0044] Layers of a picture can be used to support scalability. For example, a video can be coded into multiple layers. A layer can be coded without reference to other layers. Such a layer is called a simulcast layer. Thus, a simulcast layer can be decoded without reference to other layers. As another example, a layer can be coded using inter-layer prediction. This allows a current layer to be coded by including only the differences between the current layer and a reference layer. For example, the current layer and the reference layer may include the same video sequence coded by varying characteristics such as signal-to-noise ratio (SNR), picture size, frame rate, etc. The layers can be organized into an output layer set (OLS). An OLS is a set of layers including at least one output layer and any layers that support decoding of the output layer. As a specific example, a first OLS may include a base layer, and a second OLS may include a base layer and further an enhancement layer with increased characteristics. In one example where the characteristic is picture resolution, a first OLS can be transmitted to the decoder to enable the video to be decoded at a base resolution, or a second OLS can be transmitted to enable the video to be decoded at a higher enhanced resolution, so that the video can be scaled based on user requests.

[0045] In some cases, scalability is not used and each layer is coded as a simulcast layer. Some systems infer that if all layers are simulcast, then each OLS should contain a single layer (since no reference layers are used). This inference increases coding efficiency since signaling can be omitted from the encoded bitstream. However, such inference does not support multiview. Multiview is also known as stereoscopic vision. In multiview, two video sequences of the same scene are recorded by spatially offset cameras. The two video sequences are displayed to the user with different lenses in a headset. In this way, by displaying different spatially offset sequences for each eye, the impression of three-dimensional (3D) video and / or visual depth can be created. Thus, an OLS that implements multiview contains two layers (e.g., one for each eye). However, when the layers are all simulcast, a video decoder may use inference to infer that each OLS contains only one layer. This may result in errors, since the decoder may only display one layer of the multiview, or may not be able to continue displaying any layers. Thus, the inference that each OLS contains a single layer when all layers are simulcast may prevent multiview applications from rendering properly at the decoder.

[0046] Disclosed herein is a mechanism that enables a video coding system to properly decode a multiview video when all layers in the video are simulcast and do not use inter-layer prediction. An "all independent layers in VPS" flag (vps_all_independent_layers_flag) can be included in the bitstream in the VPS and set to 1 when none of the layers use inter-layer prediction (e.g., all are simulcast). When this flag is set to 1, an "each layer is an output layer set (OLS)" flag (each_layer_is_an_ols_flag) is signaled in the VPS. each_layer_is_an_ols_flag can be set to specify whether each OLS contains a single layer or at least one OLS contains multiple layers (e.g., to support multiview). Thus, vps_all_independent_layers_flag and each_layer_is_an_ols_flag can be used to support multiview applications. Furthermore, when this occurs, the OLS mode identification code (ols_mode_idc) can be set to 2 in the VPS. This explicitly signals the number of OLSs and the layers associated with the OLS. The decoder can then use this information to correctly decode the OLS, including multi-view video. This approach supports coding efficiency while correcting errors. Thus, the disclosed mechanism improves the functionality of the encoder and / or decoder. Furthermore, the disclosed mechanism may reduce bitstream size and therefore reduce processor, memory, and / or network resource utilization in both the encoder and decoder.

[0047] 1 is a flow chart illustrating an exemplary operational method 100 of coding a video signal. Specifically, a video signal is encoded in an encoder. The encoding process compresses the video signal 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 an end user. The decoding process generally mirrors the encoding process to allow the decoder to consistently reconstruct the video signal.

[0048] 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 audio and video components. The video component includes a series of image frames that, when viewed in sequence, give the visual impression of motion. The frames include pixels represented by light, referred to herein as luma components (or luma samples), and colors, referred to herein as chroma components (or color samples). In some examples, the frames may also include depth values ​​to support three-dimensional viewing.

[0049] In step 103, the video is partitioned into blocks. Partitioning involves subdividing pixels in each frame into square and / or rectangular blocks for compression. For example, in High Efficiency Video Coding (HEVC) (also known as H.265 and MPEG-H Part 2), a frame may first be divided into coding tree units (CTUs), which are blocks of a predefined size (e.g., 64 pixels by 64 pixels). CTUs include both luma and chroma samples. A coding tree may be used to divide the CTUs into blocks, which may then be recursively subdivided until a configuration is achieved that supports further encoding. For example, the luma component of a frame may be subdivided until each block contains a relatively uniform illumination value. Additionally, the chroma component of a frame may be subdivided until each block contains a relatively uniform color value. Thus, the partitioning mechanism varies depending on the content of the video frame.

[0050] In step 105, various compression mechanisms are used 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 does not need to be described repeatedly in adjacent frames. Specifically, an object such as a table may remain in a constant position across multiple frames. Thus, the table may be described once and adjacent frames may refer to the reference frame. For matching of objects across multiple frames, a pattern matching mechanism may be used. Furthermore, a moving object may be represented across multiple frames, for example, by object motion or camera motion. As a specific example, a video may show a car moving across the screen across multiple frames. To describe such motion, a motion vector may be used. A motion vector is a two-dimensional vector that provides an offset from the coordinates of the object in the frame to the coordinates of the object in the reference frame. Thus, inter-prediction may encode an image block in a current frame as a set of motion vectors indicating an offset from a corresponding block in a reference frame.

[0051] Intra prediction encodes blocks within a common frame. Intra prediction exploits the fact that luma and chroma components tend to cluster within a frame. For example, some green patches of a tree tend to be located adjacent to similar patches of green. Intra prediction uses multiple directional prediction modes (e.g., 33 in HEVC), planar mode, and direct current (DC) mode. The directional mode indicates that the current block is similar / same as samples of neighboring blocks in the corresponding direction. The planar mode indicates that a series of blocks along a row / column (e.g., a plane) may be interpolated based on neighboring blocks at the edge of the row. The planar mode effectively indicates a smooth transition of light / color across the row / column by using a relatively constant slope for the change in value. The DC mode is used for boundary smoothing and indicates that the block is similar / same as the average value associated with the samples of all neighboring blocks associated with the angular direction of the directional prediction mode. Thus, intra prediction blocks can represent image blocks as various relational prediction mode values ​​instead of actual values. Additionally, inter prediction blocks can represent image blocks as motion vector values ​​instead of actual values. In either case, the prediction block may in some cases not exactly represent the image block. Any differences are stored in a residual block. To further compress the file, a transform may be applied to the residual block.

[0052] In step 107, various filtering techniques may be applied. In HEVC, filters are applied according to an in-loop filtering scheme. The block-based prediction described above may create a blocky image at the decoder. Furthermore, the block-based prediction scheme may encode a block and then reconstruct the encoded block for later use as a reference block. The in-loop filtering scheme iteratively applies a noise suppression filter, a deblocking filter, an adaptive loop filter, and a sample adaptive offset (SAO) filter to the block / frame. These filters mitigate such blocking artifacts so that the encoded file can be accurately reconstructed. Furthermore, these filters mitigate artifacts in the reconstructed reference block so that the artifacts are less likely to create additional artifacts in subsequent blocks that are encoded based on the reconstructed reference block.

[0053] 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 described above, as well as any signaling data desired to support proper video signal reconstruction at the decoder. For example, such data may include partition data, prediction data, residual blocks, and various flags that provide coding instructions to the decoder. The bitstream may be stored in a memory for transmission to a decoder on demand. The bitstream may be broadcast and / or multicast to multiple decoders. Creation of the bitstream is an iterative process. Thus, steps 101, 103, 105, 107, and 109 may occur sequentially and / or simultaneously across multiple frames and blocks. The order depicted in FIG. 1 is presented for clarity and ease of explanation, and is not intended to limit the video coding process to any particular order.

[0054] The decoder receives the bitstream and starts the decoding process in step 111. Specifically, the decoder uses an entropy decoding scheme to convert the bitstream into corresponding syntax and video data. The decoder uses syntax data from the bitstream in step 111 to determine the partition of the frame. The partitioning should match the result of the block partitioning in step 103. Next, the entropy encoding / decoding used in step 111 is 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 positioning of values ​​in the input image. Signaling the exact selection may use a number of bins. As used herein, a bin is a binary value that is treated as a variable (e.g., a bit value that can change depending on the context). Entropy coding allows the encoder to discard any options that are clearly not viable in a particular case, leaving a set of acceptable options. A codeword is then assigned to each acceptable option. The length of the codeword is based on the number of allowable options (e.g., one bin for two options, two bins for three to four options, etc.). The encoder then encodes a codeword for the selected option. This scheme reduces the size of the codeword because the codeword is only as large as necessary to uniquely indicate a selection from a small subset of allowable options, as opposed to uniquely indicating a selection from a potentially large set of all possible options. The decoder then decodes the selection by determining the set of allowable options in a similar manner as the encoder. By determining the set of allowable options, the decoder can read the codeword and determine the selection made by the encoder.

[0055] In step 113, the decoder performs block decoding. Specifically, the decoder generates a residual block using an inverse transform. 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-prediction blocks and inter-prediction blocks as generated in the encoder in step 105. The reconstructed image block is then placed into a frame of the reconstructed video signal according to the partitioning data determined in step 111. The syntax in step 113 may also be signaled in the bitstream via entropy coding as described above.

[0056] In 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, in step 117 the video signal may be output to a display for viewing by an end user.

[0057] FIG. 2 is a schematic diagram of an exemplary coding and decoding (codec) system 200 for video coding. Specifically, the codec system 200 provides functionality to support the implementation of the operating method 100. The codec system 200 is generalized to show components used in both the encoder and the decoder. The codec system 200 receives and partitions a video signal, as described for steps 101 and 103 of the operating method 100, resulting in a partitioned video signal 201. The codec system 200 then compresses the partitioned video signal 201 into a coded bitstream when operating as an encoder, as described for steps 105, 107, and 109 of the method 100. When operating as a decoder, the codec system 200 generates an output video signal from the bitstream, as described for steps 111, 113, 115, and 117 of the operating 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 be present in an encoder. A decoder may include a subset of the components of codec system 200.For example, the decoder may include an intra-picture prediction component 217, a motion compensation component 219, a scaling and inverse transform component 229, an in-loop filter component 225, and a decoded picture buffer component 223. These components are now described.

[0058] The partitioned video signal 201 is a captured video sequence that has been partitioned 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. The blocks may be 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 referred to as 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 CTU that includes a luma block, a red-difference chroma (Cr) block, and a blue-difference chroma (Cb) block, along with corresponding syntax instructions for the CU. The partitioning modes may include a binary tree (BT), a ternary tree (TT), and a quad tree (QT), which are used to partition a node into two, three, or four child nodes, respectively, of various 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.

[0059] The general coder control component 211 is configured to make decisions related to coding the images of the video sequence into a bitstream according to application constraints. For example, the general coder control component 211 manages the optimization of bitrate / bitstream size versus reconstruction quality. Such decisions may be made based on storage space / bandwidth availability and image resolution requirements. The general coder control component 211 also manages buffer utilization in light of transmission rate to mitigate buffer under-run and over-run issues. To manage these issues, the general coder control component 211 manages partitioning, prediction, and filtering by other components. For example, the general coder control component 211 may dynamically increase compression complexity to increase resolution and increase bandwidth usage, or decrease compression complexity to decrease resolution and bandwidth usage. Thus, the general coder control component 211 controls other components of the codec system 200 to balance video signal reconstruction quality with respect to bitrate. The general coder control component 211 creates control data that controls the operation of other components. Control data is also forwarded to the header formatting and CABAC component 231 and encoded into the bitstream for signaling parameters for decoding at the decoder.

[0060] The partitioned video signal 201 is also sent to a motion estimation component 221 and a motion compensation component 219 for inter prediction. A frame or slice of the partitioned video signal 201 may be divided into multiple video blocks. The motion estimation component 221 and the motion compensation component 219 perform inter predictive coding of the received video blocks with respect to one or more blocks in one or more reference frames to 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.

[0061] 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 a process of generating motion vectors that estimate the motion of a video block. 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 block to be coded in terms of pixel difference. A predictive block may also be referred to as a reference block. Such pixel difference may be determined by sum of absolute difference (SAD), sum of squared difference (SSD), or other difference metric. HEVC uses several coded objects including CTUs, coding tree blocks (CTBs), and CUs. For example, a CTU may be divided into CTBs, which may be divided into CBs for inclusion in a CU. A CU may be coded as a prediction unit (PU) that includes prediction data and / or a transform unit (TU) that includes transformed residual data for the CU. The motion estimation component 221 generates the motion vectors, PUs, and TUs by using a rate-distortion analysis as part of a rate-distortion optimization process. For example, the motion estimation component 221 may determine multiple reference blocks, multiple motion vectors, etc. for the current block / frame and may 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).

[0062] In some examples, the codec system 200 may calculate values ​​of sub-integer pixel positions of the reference picture stored in the decoded picture buffer component 223. For example, the video codec system 200 may interpolate values ​​of quarter-pixel positions, eighth-pixel positions, or other fractional pixel positions of the reference picture. Thus, the motion estimation component 221 may perform motion search for full-pixel positions and fractional pixel positions and output motion vectors with fractional pixel accuracy. The motion estimation component 221 calculates the motion vector of the PU of the video block in the inter-coded slice by comparing the position of the PU with the position of the predictive block of 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 outputs the motion to the motion compensation component 219.

[0063] The motion compensation performed by the motion compensation component 219 may involve fetching or generating a predictive block based on a motion vector determined by the motion estimation component 221. Again, in some examples, the motion estimation component 221 and the motion compensation component 219 may be functionally integrated. Upon receiving a motion vector for the PU of the current video block, the motion compensation component 219 may find a 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, and pixel difference values ​​are formed. In general, the motion estimation component 221 performs motion estimation on the luma component, and the motion compensation component 219 uses the motion vector calculated based on the luma component for both the chroma and luma components. The predictive block and the residual block are forwarded to the transform scaling and quantization component 213.

[0064] The partitioned video signal 201 is also sent to an intra picture estimation component 215 and an intra picture prediction component 217. As with the motion estimation component 221 and the motion compensation component 219, the intra picture estimation component 215 and the intra picture prediction component 217 may be highly integrated, but are shown separately for conceptual purposes. The intra picture estimation component 215 and the intra picture prediction component 217 intra predict a current block relative to blocks in a 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 an intra prediction mode to use to encode the current block. In some examples, the intra picture estimation component 215 selects an appropriate intra prediction mode to encode the current block from a plurality of tested intra prediction modes. The selected intra prediction mode is then forwarded to the header formatting and CABAC component 231 for encoding.

[0065] For example, the intra picture estimation component 215 calculates a rate distortion value using a rate distortion analysis of various tested intra prediction modes and selects an intra prediction mode with the best rate distortion characteristics among the tested modes. The rate distortion analysis generally determines the amount of distortion (or error) between a coding block and an original uncoded block that was coded to generate the coding block, as well as the bit rate (e.g., number of bits) used to generate the coding block. The intra picture estimation component 215 calculates a ratio from the distortion and rate of various coding blocks to determine which intra prediction mode exhibits the best rate distortion value for the block. In addition, the intra picture estimation component 215 may be configured to code the depth block of the depth map using a depth modeling mode (DMM) based on rate distortion optimization (RDO).

[0066] The intra picture prediction component 217 may generate a residual block from the prediction block based on a selected intra prediction mode determined by the intra picture estimation component 215 when implemented in an encoder, or may read the residual block from a bitstream when implemented in a decoder. The residual block includes value differences between the prediction block and the original block, represented as a matrix. The residual block is then forwarded to the transform scaling and quantization component 213. The intra picture estimation component 215 and the intra picture prediction component 217 may operate on both luma and chroma components.

[0067] 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, resulting in a video block that includes residual transform coefficient values. A wavelet transform, an integer transform, a subband transform, or other types of transforms may also be used. The transform may convert the residual information from a pixel value domain to a transform domain, such as a frequency domain. The transform scaling and quantization component 213 is also configured to scale the transformed residual information, for example based on frequency. Such scaling involves applying a scale factor to the residual information such that different frequency information is quantized with different granularity, which may affect the final visual quality of the reconstructed video. The transform scaling and quantization component 213 is also configured to quantize the transform coefficients to further reduce the bit rate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be 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 for encoding into a bitstream.

[0068] The scaling and inverse transform component 229 applies the inverse operations of the transform scaling and quantization component 213 to support motion estimation. The scaling and inverse transform component 229 applies inverse scaling, transformation, and / or quantization to reconstruct residual blocks in the pixel domain for later use as reference blocks that may become predictive blocks for other current blocks, for example. The motion estimation component 221 and / or the motion compensation component 219 may calculate reference blocks by adding the residual blocks back to the corresponding predictive blocks for use in motion estimation of later blocks / frames. A filter is applied to the reconstructed reference blocks to mitigate artifacts created during the scaling, quantization, and transformation. Such artifacts may otherwise cause inaccurate predictions (and create additional artifacts) when subsequent blocks are predicted.

[0069] The filter control analysis component 227 and the in-loop filter component 225 apply filters to the residual block and / or the reconstructed image block. For example, the transformed residual block from the scaling and inverse transform component 229 may be combined with the corresponding prediction block from the intra-picture prediction component 217 and / or the motion compensation component 219 to reconstruct the original image block. The filter may then be applied to the reconstructed image block. In some examples, the filter may be applied to the residual block instead. As with the other components of FIG. 2, the filter control analysis component 227 and the in-loop filter component 225 may be highly integrated and implemented together, but are shown separately for conceptual purposes. The filters applied to the reconstructed reference block are applied to a particular spatial region and include multiple parameters to adjust how such filters are applied. The filter control analysis component 227 analyzes the reconstructed reference block to determine where such filters should be applied and sets the corresponding parameters. Such data is forwarded to the header formatting and CABAC component 231 as filter control data for encoding. The in-loop filter component 225 applies such filters based on the filter control data. The filters may include deblocking filters, noise suppression filters, SAO filters, and adaptive loop filters. Such filters may be applied in the spatial / pixel domain (e.g., reconstructed pixel blocks) or in the frequency domain, depending on the example.

[0070] When operating as an encoder, the filtered reconstructed image blocks, residual blocks, and / or predictive blocks are stored in the decoded picture buffer component 223 for later use in motion estimation, as described above. When operating as a decoder, the decoded picture buffer component 223 stores the reconstructed and filtered blocks and forwards them towards the display as part of the output video signal. The decoded picture buffer component 223 may be any memory device capable of storing predictive blocks, residual blocks, and / or reconstructed image blocks.

[0071] The header formatting and CABAC component 231 receives data from various components of the codec system 200 and encodes such data into a coded bitstream for transmission towards a decoder. Specifically, the header formatting and CABAC component 231 generates various headers for encoding control data, such as general control data and filter control data. In addition, prediction data, including intra prediction and motion data, as well as residual data in the form of quantized transform coefficient data, are all encoded into the bitstream. The final bitstream contains all information desired by the decoder to reconstruct the original partitioned video signal 201. Such information may also include an intra prediction mode index table (also called a codeword mapping table), definitions of coding contexts for various blocks, indications of the most probable intra prediction mode, indications of partition information, etc. Such data may be encoded by using entropy coding. For example, the information may be encoded by using Context-Adaptive Variable Length Coding (CAVLC), CABAC, Syntax-Based Context-Adaptive Binary Arithmetic Coding (SBAC), Probability Interval Partitioned Entropy (PIPE) coding, or other entropy coding techniques. Following entropy coding, the coded bitstream may be transmitted to other devices (e.g., a video decoder) or archived for later transmission or retrieval.

[0072] 3 is a block diagram illustrating an example video encoder 300. The video encoder 300 may be used to implement the encoding functionality of the codec system 200 and / or to implement steps 101, 103, 105, 107, and / or 109 of the operating method 100. The encoder 300 partitions an input video signal, resulting in a partitioned video signal 301 that is substantially similar to the partitioned video signal 201. The partitioned video signal 301 is then compressed and encoded into a bitstream by components of the encoder 300.

[0073] Specifically, the partitioned video signal 301 is forwarded to an intra-picture prediction component 317 for intra prediction. The intra-picture prediction component 317 may be substantially similar to the intra-picture estimation component 215 and the intra-picture prediction component 217. The partitioned video signal 301 is also forwarded to a motion compensation component 321 for inter prediction based on a reference block in a decoded picture buffer component 323. The motion compensation component 321 may be substantially similar to the motion estimation component 221 and the motion compensation component 219. The prediction block and the residual block from the intra-picture prediction component 317 and the motion compensation component 321 are forwarded to a transform and quantization component 313 for transform and quantization of 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 .

[0074] The transformed and quantized residual block and / or the corresponding prediction block are also transferred from the transform and quantization component 313 to the inverse transform and quantization component 329 and reconstructed 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 described for 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.

[0075] 4 is a block diagram illustrating an example video decoder 400. The video decoder 400 may be used to implement the decoding functionality of the codec system 200 and / or to implement steps 111, 113, 115, and / or 117 of the method of operation 100. The decoder 400 receives a bitstream, for example, from the encoder 300, and generates a reconstructed output video signal based on the bitstream for display to an end user.

[0076] The bitstream is received by the entropy decoding component 433. The entropy decoding component 433 is configured to implement an entropy decoding scheme, such as CAVLC, CABAC, SBAC, PIPE coding, or other entropy coding techniques. For example, the entropy decoding component 433 may use header information to provide a context for interpreting additional data encoded as codewords in the bitstream. The decoded information includes any desired information for decoding 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 may be similar to the inverse transform and quantization component 329.

[0077] The reconstructed residual block and / or predictive block are forwarded to the intra picture prediction component 417 for reconstructing into an image block based on an intra prediction operation. The intra picture prediction component 417 may be similar to the intra picture estimation component 215 and the intra picture prediction component 217. Specifically, the intra picture prediction component 417 uses the prediction mode to find the location of a reference block in 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 the corresponding inter prediction data are forwarded to the decoded picture buffer component 423 via the in-loop filter component 425, which may be substantially similar to the decoded picture buffer component 223 and the in-loop filter component 225, respectively. The in-loop filter component 425 filters the reconstructed image block, the residual block, and / or the predictive block, and such information is stored in the decoded picture buffer component 423. The reconstructed image block from the decoded picture buffer component 423 is forwarded to the motion compensation component 421 for inter prediction. The motion compensation component 421 may be substantially similar to the motion estimation component 221 and / or the motion compensation component 219. Specifically, the motion compensation component 421 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 transferred to the decoded picture buffer component 423 via the in-loop filter component 425. The decoded picture buffer component 423 subsequently stores additional reconstructed image blocks that may be reconstructed into frames via the partition information. Such frames may be arranged in a sequence. The sequence is output to a display as a reconstructed output video signal.

[0078] 5 is a schematic diagram illustrating an example multi-layer video sequence 500 configured for inter-layer prediction 521. The multi-layer video sequence 500 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, for example, according to method 100. The multi-layer video sequence 500 is included to illustrate an example application for layers in a coded video sequence. The multi-layer video sequence 500 is any video sequence that uses multiple layers, such as layer N 531 and layer N+1 532.

[0079] In one example, the multi-layer video sequence 500 may use inter-layer prediction 521. Inter-layer prediction 521 is applied between pictures 511, 512, 513, and 514 and pictures 515, 516, 517, and 518 of different layers. In the illustrated example, pictures 511, 512, 513, and 514 are part of layer N+1 532, and pictures 515, 516, 517, and 518 are part of layer N 531. A layer, such as layer N 531 and / or layer N+1 532, is a group of pictures that are all associated with similar values ​​of characteristics such as similar size, quality, resolution, signal-to-noise ratio, capacity, etc. A layer may be formally defined as a set of VCL NAL units and associated non-VCL NAL units that share the same nuh_layer_id. A VCL NAL unit is 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 video data, performing conformance checks, or other operations.

[0080] In the illustrated example, layer N+1 532 is associated with a larger image size than layer N 531. Thus, pictures 511, 512, 513, and 514 in layer N+1 532 have a larger picture size (e.g., larger height and width, and therefore more samples) than pictures 515, 516, 517, and 518 in layer N 531 in this example. However, such pictures may be divided between layer N+1 532 and layer N 531 by other characteristics. Although only two layers, layer N+1 532 and layer N 531, are shown, a set of pictures may be divided into any number of layers based on associated characteristics. Layer N+1 532 and layer N 531 may also be indicated by a layer identifier (ID). A layer ID is an item of data associated with a picture and indicates that the picture is part of the indicated layer. Thus, each picture 511-518 may be associated with a corresponding layer ID to indicate which layer N+1 532 or layer N 531 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 an identifier of a layer that contains a NAL unit (e.g., containing slices and / or parameters of a picture within a layer). A layer associated with a lower quality / bitstream size, such as layer N 531, 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+1 532, is generally assigned a higher layer ID and is referred to as a higher layer.

[0081] Pictures 511-518 in different layers 531-532 are configured to be displayed as alternatives. As a particular example, a decoder may decode and display picture 515 at the current display time if a smaller picture is desired, or the decoder may decode and display picture 511 at the current display time if a larger picture is desired. Thus, pictures 511-514 in higher layer N+1 532 contain substantially the same image data as corresponding pictures 515-518 in lower layer N 531 (despite the difference in picture size). Specifically, picture 511 contains substantially the same image data as picture 515, picture 512 contains substantially the same image data as picture 516, and so on.

[0082] Pictures 511-518 may be coded by referencing other pictures 511-518 in the same layer N 531 or N+1 532. Coding a picture with reference to other pictures in the same layer results in inter prediction 523. Inter prediction 523 is indicated by a solid arrow. For example, picture 513 may be coded by using inter prediction 523 using one or two of pictures 511, 512, and / or 514 in layer N+1 532 as references, one picture being referenced for unidirectional inter prediction and / or two pictures being referenced for bidirectional inter prediction. Furthermore, picture 517 may be coded by using inter prediction 523 using one or two of pictures 515, 516, and / or 518 in layer N 531 as references, one picture being referenced for unidirectional inter prediction and / or two pictures being referenced for bidirectional inter prediction. When performing inter prediction 523, a picture may be referred to as a reference picture when it is used as a reference for other pictures in the same layer. For example, picture 512 may be a reference picture used to code picture 513 according to inter prediction 523. Inter prediction 523 may also be referred to as intra-layer prediction in a multi-layer context. Thus, inter prediction 523 is a mechanism for coding samples of a current picture by referring to indicated samples in a reference picture different from the current picture when the reference picture and the current picture are in the same layer.

[0083] Pictures 511-518 can also be coded by referencing other pictures 511-518 in different layers. This process is known as inter-layer prediction 521 and is indicated by dashed arrows. Inter-layer prediction 521 is a mechanism for coding samples of a current picture by referencing indicated samples in a reference picture when the current picture and the reference picture are in different layers and therefore have different layer IDs. For example, a picture in a lower layer N 531 can be used as a reference picture for coding a corresponding picture in an upper layer N+1 532. As a specific example, picture 511 can be coded by referencing picture 515 according to inter-layer prediction 521. In such a case, picture 515 is used as an inter-layer reference picture. An inter-layer reference picture is a reference picture used for inter-layer prediction 521. In most cases, inter-layer prediction 521 is constrained so that a current picture, such as picture 511, can only use inter-layer reference pictures that are included in the same AU and are in a lower layer, such as picture 515. An AU is a set of pictures associated with a particular output time in a video sequence, and thus an AU may contain one picture per layer. If multiple layers (e.g., three or more) are available, inter-layer prediction 521 can encode / decode the current picture based on multiple inter-layer reference pictures at a lower level than the current picture.

[0084] A video encoder can use the multi-layer video sequence 500 to encode pictures 511-518 through many different combinations and / or permutations of inter-prediction 523 and inter-layer prediction 521. For example, picture 515 may be coded according to intra-prediction. Pictures 516-518 can then be coded according to inter-prediction 523 by using picture 515 as a reference picture. Furthermore, picture 511 may be coded according to inter-layer prediction 521 by using picture 515 as an inter-layer reference picture. Pictures 512-514 can then be coded according to inter-prediction 523 by using picture 511 as a reference picture. Thus, a reference picture can function as both a single-layer reference picture and an inter-layer reference picture of different coding mechanisms. By coding the upper layer N+1 532 picture based on the lower layer N 531 picture, the upper layer N+1 532 can avoid using intra prediction, which has much lower coding efficiency than inter prediction 523 and inter-layer prediction 521. Thus, the poor coding efficiency of intra prediction can be limited to the smallest / lowest quality pictures and thus to coding a minimum amount of video data. Pictures used as reference pictures and / or inter-layer reference pictures can be indicated in entries of a reference picture list included in a reference picture list structure.

[0085] To perform such operations, layers such as layer N 531 and layer N+1 532 may be included in OLS 525. OLS 525 is a set of layers where one or more layers are designated as output layers. An output layer is a layer that is designated for output (e.g., to a display). For example, layer N 531 may be included only to support inter-layer prediction 521 and may never be output. In such a case, layer N+1 532 is decoded and output based on layer N 531. In such a case, OLS 525 includes layer N+1 532 as an output layer. OLS 525 may include many layers in different combinations. For example, an output layer in OLS 525 may be coded according to inter-layer prediction 521 based on one, two, or many lower layers. Furthermore, OLS 525 may include more than one output layer. Thus, OLS 525 may include one or more output layers and any supporting layers necessary to reconstruct the output layer. A multi-layer video sequence 500 can be coded by using many different OLSs 525, each using a different combination of layers.

[0086] As a particular example, inter-layer prediction 521 may be used to support scalability. For example, a video may be coded into a base layer, such as layer N 531, and several enhancement layers, such as layer N+1 532, layer N+2, layer N+3, which are coded according to inter-layer prediction 521. A video sequence may be coded for several scalable characteristics, such as resolution, frame rate, picture size, etc. An OLS 525 may then be created for each allowable characteristic. For example, an OLS 525 for a first resolution may include only layer N 531, an OLS 525 for a second resolution may include layer N 531 and layer N+1 532, an OLS for a third resolution may include layer N 531, layer N+1 532, layer N+2, etc. In this manner, the OLS 525 can be transmitted to allow a decoder to decode which version of the multi-layer video sequence 500 is desired based on network conditions, hardware constraints, etc.

[0087] 6 is a schematic diagram illustrating an example multiview sequence 600 including simulcast layers 631, 632, 633, and 634 for use in multiview. The multiview sequence 600 is a type of multilayer video sequence 500. Thus, the multiview 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, e.g., according to method 100.

[0088] Multi-view video is also referred to as stereoscopic video. In multi-view, a video sequence is simultaneously captured from multiple camera angles into a single video stream. For example, a pair of spatially offset cameras can be used to capture the video. Each camera captures the video from a different angle. This results in a pair of views of the same subject. A first view can be presented to the user's right eye and a second view can be presented to the user's left eye. For example, this can be achieved by using a head-mounted display (HMD) that includes a left-eye display and a separate right-eye display. Displaying a pair of streams of the same subject from different angles creates an impression of visual depth and therefore a 3D viewing experience.

[0089] To implement multi-view, video may be coded into multiple OLSs, such as OLS 625 and OLS 626, which are similar to OLS 525. Each view is coded into a layer, such as layers 631, 632, 633, and 634, which may be similar to layer N 531. As a specific example, the right eye view may be coded into layer 631, and the left eye view may be coded into layer 632. Layers 631 and 632 may then be included in OLS 625. In this manner, OLS 625 may be transmitted to a decoder, with layers 631 and 632 marked as output layers. The decoder may then decode and display both layers 631 and 632. Thus, OLS 625 provides sufficient data to enable a representation of the multi-view video. As with other types of video, multi-view video may be coded into several representations to enable different display devices, different network conditions, and the like. Thus, OLS 626 includes video that is substantially similar to OLS 625, but coded to achieve different characteristics. For example, layer 633 may be substantially similar to layer 631, and layer 634 may be substantially similar to layer 632. However, layers 633 and 634 may have different characteristics than layers 631 and 632. As a specific example, layers 633 and 634 may be encoded at a different resolution, frame rate, screen size, etc. than layers 631 and 632. As a specific example, if a first picture resolution is desired, OLS 625 may be transmitted to the decoder, and if a second picture resolution is desired, OLS 626 may be transmitted to the decoder.

[0090] In some cases, scalability is not used. A layer that does not use inter-layer prediction is called a simulcast layer. A simulcast layer can be fully decoded without reference to other layers. For example, layers 631-634 shown are all simulcast layers because they do not depend on any reference layers. This configuration may cause errors in some video coding systems.

[0091] For example, some video coding systems may be configured to infer that each OLS contains a single layer when all layers are simulcast. In some cases, such inference is valid. For example, when scalability is not used for standard video, the system may assume that each simulcast layer can be displayed without any other layers, and therefore the OLS shall contain only one layer. This inference may prevent multiview from working properly. As shown, OLS 625 and 626 each contain two layers 631 and 632, and layers 633 and 634, respectively. In such a case, the decoder may decode and not display both layers because it is uncertain which layer to decode and only one layer is expected.

[0092] This disclosure addresses this issue by using each_layer_is_an_ols_flag in the bitstream. Specifically, each_layer_is_an_ols_flag is signaled once all layers 631-634 are simulcast, as indicated by vps_all_independent_layers_flag. each_layer_is_an_ols_flag indicates whether each OLS includes a single layer or whether any OLS, such as OLS 625 and 626, includes two or more layers. This allows the multiview sequence 600 to be properly decoded. Additionally, ols_mode_idc may be set to indicate that the number of OLSs 625-626 as well as information related to layers 631-634 should be explicitly signaled (e.g., an indication of which layers 631-634 are output layers). These flags provide sufficient information for a decoder to correctly decode and display OLSs 625 and / or 626 using multiview. Note that each_layer_is_an_ols_flag, vps_all_independent_layers_flag, and ols_mode_idc are named based on the nomenclature used by the VVC standard. Such names are included herein for consistency and clarity of description. However, such syntax elements may be called by other names without departing from the scope of this disclosure.

[0093] 7 is a schematic diagram illustrating an example bitstream 700 including an OLS with a simulcast layer for use in multiview. 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 according to the method 100. Additionally, the bitstream 700 may include the coded multi-layer video sequence 500 and / or the multiview sequence 600.

[0094] Bitstream 700 includes a VPS 711, one or more sequence parameter sets (SPS) 713, a plurality of picture parameter sets (PPS) 715, a plurality of slice headers 717, and image data 720. VPS 711 includes data related to the entire bitstream 700. For example, VPS 711 may include data related OLS, layers, and / or sublayers used in bitstream 700. SPS 713 includes sequence data common to all pictures in a coded video sequence included in bitstream 700. For example, each layer may include one or more coded video sequences, and each coded video sequence may reference SPS 713 for corresponding parameters. Parameters in SPS 713 may include picture sizing, bit depth, coding tool parameters, bit rate limits, etc. Note that while each sequence points to an SPS 713, in some examples, a single SPS 713 may include data for multiple sequences. PPS 715 includes parameters that apply to the entire picture. Thus, each picture in a video sequence may reference a PPS 715. Note that while each picture references a PPS 715, in some examples, a single PPS 715 may contain data for multiple pictures. For example, multiple similar pictures may be coded according to similar parameters. In such a case, a single PPS 715 may contain data for such similar pictures. The PPS 715 may indicate coding tools available for slices, quantization parameters, offsets, etc. within the corresponding picture.

[0095] The slice header 717 includes parameters specific to each slice 727 in the picture 725. Thus, there may be one slice header 717 per slice 727 in a video sequence. The slice header 717 may include slice type information, POC, 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 includes parameters that apply to all slices 727 in a single picture. For this reason, picture header and slice header 717 may be used interchangeably in some contexts. For example, some parameters may be moved between slice header 717 and picture header depending on whether such parameters are common to all slices 727 in a picture 725.

[0096] Image data 720 includes video data encoded according to inter prediction and / or intra prediction, as well as corresponding transformed and quantized residual data. For example, image data 720 may include layers 723 of a picture 725. The layers 723 may be organized into OLSs 721. The OLSs 721 may be substantially similar to the OLSs 525, 625, and / or 626. Specifically, an OLS 721 is a set of layers 723 where one or more layers 723 are designated as output layers. For example, a bitstream 700 may be coded to include several OLSs 721 having video coded at different resolutions, frame rates, picture 725 sizes, etc. Upon request by the decoder, a sub-bitstream extraction process can remove all but the requested OLSs 721 from the bitstream 700. The encoder can then send a bitstream 700 to the decoder that includes only the requested OLSs 721, and thus only video that meets the requested criteria.

[0097] Layer 723 may be substantially similar to layer N 531, layer N+1 532, and / or layers 631, 632, 633, and / or 634. Layer 723 is generally a set of coded pictures 725. Layer 723 may be formally defined as a set of VCL NAL units that, when decoded, share specified characteristics (e.g., a common resolution, frame rate, picture size, etc.). Layer 723 also includes associated non-VCL NAL units to support decoding of VCL NAL units. The VCL NAL units of layer 723 may share a particular value of nuh_layer_id. Layer 723 may be a simulcast layer coded without inter-layer prediction, or layer 723 coded according to inter-layer prediction, as described for Figures 6 and 5, respectively.

[0098] A picture 725 is an array of luma samples and / or array of chroma samples that make up a frame or a field thereof. For example, a picture 725 may be a coded image that may be output for display or used to support coding of other pictures 725 for output. A picture 725 may include a set of VCL NAL units. A picture 725 includes one or more slices 727. A slice 727 may be defined as an integer number of complete tiles of a picture 725 that are exclusively contained in a single NAL unit, in particular a VCL NAL unit, or an integer number of contiguous complete coding tree unit (CTU) rows (e.g., within a tile). 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 a coding tree. A CTB is a subset of a CTU and includes the luma or chroma components of the CTU. The CTU / CTB is further divided into coding blocks based on the coding tree. The coding block can then be encoded / decoded according to the prediction mechanism.

[0099] This disclosure includes mechanisms that enable a video coding system to properly decode a multiview video, such as multiview sequence 600, when all layers 723 in a video are simulcast and do not use inter-layer prediction. For example, VPS 711 may include various data to indicate to a decoder that the layers 723 are all simulcast and that OLS 721 includes two or more layers 723. vps_all_independent_layers_flag 731 may be included in bitstream 700 within VPS 711. vps_all_independent_layers_flag 731 is a syntax element that signals whether inter-layer prediction is used to code any of the layers 723 in bitstream 700. For example, vps_all_independent_layers_flag 731 may be set to 1 when none of the layers 723 use inter-layer prediction and therefore are all simulcast. In another example, vps_all_independent_layers_flag 731 can be set to 0 to indicate that at least one of the layers 723 uses inter-layer prediction. When vps_all_independent_layers_flag 731 is set to 1 to indicate that all layers 723 are simulcast, each_layer_is_an_ols_flag 733 is signaled in the VPS 711. Each_layer_is_an_ols_flag 733 is a syntax element that signals whether each OLS 721 in the bitstream 700 includes a single layer 723. For example, each OLS 721 may include a single simulcast layer in most cases. However, when a multiview video is encoded into the bitstream 700, one or more OLSs 721 may include two simulcast layers.Thus, each_layer_is_an_ols_flag 733 may be set (e.g., to 1) to specify that each OLS 721 includes a single layer 723, or may be set (e.g., to 0) to specify that at least one OLS 721 includes two or more layers 723 to support multi-view. Thus, vps_all_independent_layers_flag 731 and each_layer_is_an_ols_flag 733 may be used to support multi-view applications.

[0100] Additionally, the VPS 711 may include ols_mode_idc 735. The ols_mode_idc 735 is a syntax element that indicates information regarding the number of OLSs 721, the layers 723 of the OLSs 721, and the output layers of the OLSs 721. An output layer 723 is any layer that is specified for output by a decoder, as opposed to being used only for reference-based coding. The ols_mode_idc 735 may be set to 0 or 1 for coding other types of video. The ols_mode_idc 735 can be set to 2 to support multiview. For example, the ols_mode_idc 735 can be set to 2 when the vps_all_independent_layers_flag 731 is set to 1 (indicating a simulcast layer) and each_layer_is_an_ols_flag 733 is set to 0, indicating that at least one OLS 721 includes two or more layers 723. When ols_mode_idc735 is set to 2, the number of OLS721 and information regarding the number of layers 723 and / or output layers each OLS721 contains are explicitly signaled.

[0101] The VPS 711 may also include vps_max_layers_minus1 737, which is a syntax element that signals the number of layers 723 specified by the VPS 711 and thus the maximum number of layers 723 allowed in the corresponding coded video sequence in the bitstream 700. The VPS 711 may also include num_output_layer_sets_minus1 739, which is a syntax element that specifies the total number of OLSs 721 specified by the VPS 711. In one example, vps_max_layers_minus1 737 and num_output_layer_sets_minus1 739 may be signaled in the VPS 711 when ols_mode_idc 735 is set to 2. This signals the number of OLSs 721 and the number of layers 723 when the video includes multiview. Specifically, vps_max_layers_minus1 737 and num_output_layer_sets_minus1 739 may be signaled when vps_all_independent_layers_flag 731 is set to 1 (indicating simulcast layers) and each_layer_is_an_ols_flag 733 is set to 0, indicating that at least one OLS 721 includes two or more layers 723. The decoder can then use this information to correctly decode the OLSs 721 that include multiview video. This approach supports coding efficiency while correcting errors. In particular, multiview is supported. However, when multiview is not used, the number of OLSs 721 and / or layers 723 may still be inferred from the bitstream 700 and omitted. Thus, the disclosed mechanisms improve the capabilities of encoders and / or decoders by enabling such devices to properly code multi-view video.Furthermore, the disclosed mechanisms may maintain reduced bitstream size, thus reducing processor, memory, and / or network resource utilization in both the encoder and decoder.

[0102] The aforementioned information will now be described in more detail below. Layered video coding is also referred to as scalable video coding or video coding with scalability. Scalability in video coding may be supported by using a multi-layer coding technique. 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, multi-view scalability, frame rate scalability, etc. When a multi-layer coding technique is used, a picture or a part thereof may be coded without using a reference picture (intra prediction), may be coded by referencing a reference picture in the same layer (inter prediction), and / or may be coded by referencing a reference picture in another layer (inter-layer prediction). A reference picture used for inter-layer prediction of a current picture is called an inter-layer reference picture (ILRP). Figure 5 shows an example of multi-layer coding for spatial scalability where pictures of different layers have different resolutions.

[0103] Some video coding families provide support for scalability in separate 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. For SVC, at each macroblock (MB) in an EL picture, a flag is signaled to indicate whether the EL MB is predicted using a collocated block from the lower layer. Predictions from the collocated block may include texture, motion vectors, and / or coding mode. SVC implementations cannot directly reuse unmodified AVC implementations in their design. The SVC EL macroblock syntax and decoding process are different from the AVC syntax and decoding process.

[0104] Scalable HEVC (SHVC) is an extension of HEVC that supports 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 more advanced and efficient 3D video coding than MV-HEVC. Temporal scalability may be included as an integral part of a single-layer HEVC codec. In multi-layer extensions of HEVC, decoded pictures used for inter-layer prediction are only from the same AU and are treated as long-term reference pictures (LTRPs). Such pictures are assigned a reference index in a 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 resamples a reference picture or a part of it when the ILRP has a different spatial resolution than the current picture being coded or decoded. Reference picture resampling can be achieved either at the picture level or at the coding block level.

[0105] VVC may also support layered video coding. A VVC bitstream may include multiple layers. The layers may all be independent of each other. For example, each layer may be coded without using inter-layer prediction. In this case, the layers may also be referred to as simulcast layers. In some cases, some of the layers are coded using ILP. A flag in the VPS may indicate whether the layers are simulcast layers 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 may not specify an OLS. An OLS includes a specified set of layers, and one or more layers in the set of layers are specified to be output layers. An output layer is a layer of the OLS that is output. In some implementations of VVC, when a layer is a simulcast layer, only one layer may be selected for decoding and output. In some implementations of VVC, the entire bitstream including all layers is specified to be decoded when any layer uses ILP. Additionally, some of the layers are designated as output layers, which may be indicated to be only the top layer, all layers, or the top layer plus the set of indicated lower layers.

[0106] The above-mentioned aspect includes some problems. For example, when a layer is a simulcast layer, only one layer may be selected for decoding and output. However, this approach does not support the case where two or more layers can be decoded and output, such as in a multi-view application.

[0107] In general, this disclosure describes an approach to support operation points with multiple output layers of a simulcast layer. The description of the technique is based on VVC by JVET of ITU-T and ISO / IEC. However, the technique also applies to layered video coding based on other video codec specifications.

[0108] One or more of the above problems may be solved as follows. Specifically, the present disclosure includes a simple and efficient method for supporting the decoding and output of multiple layers of a bitstream, including a simulcast layer, as summarized below. The VPS may include an indication of whether each layer is an OLS. When each layer is an OLS, only one layer may be decoded and output. In this case, the number of OLSs is inferred to be equal to the number of layers. Furthermore, each OLS includes one layer, and that layer is an output layer. Otherwise, the number of OLSs is explicitly signaled. For each OLS except the 0th OLS, the layers included in the OLS may be explicitly signaled. Furthermore, each layer within each OLS may be inferred to be an output layer. The 0th OLS includes only the lowest layer, which is an output layer.

[0109] An exemplary implementation of the aforementioned mechanism is as follows: An exemplary video parameter set syntax is as follows:

[0110] [Table 1A] [Table 1B]

[0111] Exemplary video parameter set semantics are as follows: A VPS RBSP is available to the decoding process before being referenced and is included in at least one access unit with a TemporalId equal to 0 or provided via an external mechanism, and a VPS NAL unit containing a VPS RBSP should have a nuh_layer_id equal to vps_layer_id[0]. All VPS NAL units with a particular value of vps_video_parameter_set_id in a CVS should have the same content. vps_video_parameter_set_id provides an identifier for the VPS for reference by other syntax elements. vps_max_layers_minus1 plus 1 specifies the maximum allowed number of layers in each CVS that references the VPS. vps_max_sub_layers_minus1 plus 1 specifies the maximum number of temporal sublayers that may be present in each CVS that references the VPS. The value of vps_max_sub_layers_minus1 should be in the range from 0 to 6 (inclusive).

[0112] vps_all_independent_layers_flag may be set equal to 1 to specify that all layers in the CVS are independently coded, without inter-layer prediction. vps_all_independent_layers_flag may be set equal to 0 to specify that one or more of the layers in the CVS may use inter-layer prediction. When not present, the value of vps_all_independent_layers_flag is inferred to be equal to 0. When vps_all_independent_layers_flag is equal to 1, the value of vps_independent_layer_flag[i] is inferred to be equal to 1. When vps_all_independent_layers_flag is equal to 0, the value of vps_independent_layer_flag[0] is inferred to be equal to 0. vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer. For any two non-negative integer values ​​of m and n, when m is less than n, the value of vps_layer_id[m] should be less than vps_layer_id[n]. vps_independent_layer_flag[i] may be set equal to 1 to specify that the layer with index i does not use inter-layer prediction. vps_independent_layer_flag[i] may be set equal to 0 to specify that the layer with index i uses inter-layer prediction and vps_layer_dependency_flag[i] is present in the VPS. When not present, the value of vps_independent_layer_flag[i] is inferred to be equal to 1.

[0113] vps_direct_dependency_flag[i][j] may be set equal to 0 to specify that the layer with index j is not a direct reference layer of the layer with index i. vps_direct_dependency_flag[i][j] may be set equal to 1 to specify that the layer with index j is a direct reference layer of the layer with index i. When vps_direct_dependency_flag[i][j] is not present for i and j in the range from 0 to vps_max_layers_minus1 (inclusive), vps_direct_dependency_flag[i][j] is inferred to be equal to 0. The variable DirectDependentLayerIdx[i][j], which specifies the jth direct dependent layer of the ith layer, is derived as follows: for( i = 1; i < vps_max_layers_minus1; i++ ) if( !vps_independent_layer_flag[ i ] ) for( j = i, k = 0; j >= 0; j-- ) if( vps_direct_dependency_flag[ i ][ j ] ) DirectDependentLayerIdx[ i ][ k++ ] = j

[0114] The variable GeneralLayerIdx[i], which specifies the layer index of the layer with nuh_layer_id equal to vps_layer_id[i], is derived as follows: for( i = 0; i <= vps_max_layers_minus1; i++ ) GeneralLayerIdx[ vps_layer_id[ i ] ] = i

[0115] each_layer_is_an_ols_flag may be set equal to 1 to specify that each output layer set contains only one layer, and each layer in the bitstream is itself an output layer set where the single contained layer is the only output layer. each_layer_is_an_ols_flag may be set equal to 0 to specify that the output layer set may contain two or more layers. When vps_max_layers_minus1 is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 1. Otherwise, when vps_all_independent_layers_flag is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 0.

[0116] ols_mode_idc may be set equal to 0 to specify that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i (inclusive), and for each OLS, only the top layer in the OLS is output. ols_mode_idc may be set equal to 1 to specify that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i (inclusive), and for each OLS, all layers within the OLS are output. ols_mode_idc may be set equal to 2 to specify that the total number of OLSs specified by the VPS are explicitly signaled, and for each OLS, the top layer in the OLS and the set of explicitly signaled lower layers are output. The value of ols_mode_idc should range from 0 to 2 (inclusive). The value 3 for ols_mode_idc is reserved. When vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, a value of ols_mode_idc equal to 2 is inferred.

[0117] num_output_layer_sets_minus1 plus 1 specifies the total number of OLSs specified by the VPS when ols_mode_idc is equal to 2. The variable TotalNumOlss, which specifies the total number of OLSs specified by the VPS, is derived as follows: if( vps_max_layers_minus1 = = 0 ) TotalNumOlss = 1 else if( each_layer_is_an_ols_flag | | ols_mode_idc = = 0 | | ols_mode_idc = = 1 ) TotalNumOlss = vps_max_layers_minus1 + 1 else if( ols_mode_idc == 2 ) TotalNumOlss = num_output_layer_sets_minus1 + 1

[0118] layer_included_flag[i][j] specifies whether the jth layer (e.g., the layer with nuh_layer_id equal to vps_layer_id[j]) is included in the ith OLS when ols_mode_idc is equal to 2. layer_included_flag[i][j] may be set equal to 1 to specify that the jth layer is included in the ith OLS. layer_included_flag[i][j] may be set equal to 0 to specify that the jth layer is not included in the ith OLS.

[0119] The variable NumLayersInOls[i], which specifies the number of layers in the i-th OLS, and the variable NumLayersInOls[i], which specifies the nuh_layer_id value of the j-th layer in the i-th OLS, may be derived as follows: NumLayersInOls

[0000] = 1 LayerIdInOls

[0000]

[0000] = vps_layer_id

[0000] for( i = 1, i < TotalNumOlss; i++ ) { if( each_layer_is_an_ols_flag ) { NumLayersInOls[ i ] = 1 LayerIdInOls[ i ]

[0000] = vps_layer_id[ i ] } else if( ols_mode_idc = = 0 | | ols_mode_idc = = 1 ) { NumLayersInOls[ i ] = i + 1 for( j = 0; j < NumLayersInOls[ i ]; j++ ) LayerIdInOls[ i ][ j ] = vps_layer_id[ j ] } else if( ols_mode_idc = = 2 ) { for( k = 0, j = 0; k <= vps_max_layers_minus1; k++ ) if( layer_included_flag[ i ][ k ] ) LayerIdInOls[ i ][ j++ ] = vps_layer_id[ k ] NumLayersInOls[ i ] = j } }

[0120] The variable OlsLayeIdx[i][j], which specifies the OLS layer index of the layer with nuh_layer_id equal to LayerIdInOls[i][j], is derived as follows: for( i = 0, i < TotalNumOlss; i++ ) for j = 0; j < NumLayersInOls[ i ]; j++ ) OlsLayeIdx[ i ][ LayerIdInOls[ i ][ j ] ] = j

[0121] The lowest layer in each OLS should be an independent layer. In other words, for each i in the range from 0 to TotalNumOlss-1 (inclusive), the value of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]] should be equal to 1. The top layer, e.g., the layer with nuh_layer_id equal to vps_layer_id[vps_max_layers_minus1], should be included in at least one OLS specified by the VPS. In other words, for at least one i in the range from 0 to TotalNumOlss-1 (inclusive), the value of LayerIdInOls[i][NumLayersInOls[i]-1] should be equal to vps_layer_id[vps_max_layers_minus1].

[0122] vps_output_layer_flag[i][j] specifies whether the jth layer of the ith OLS is output when ols_mode_idc is 2. vps_output_layer_flag[i] may be set equal to 1 to specify that the jth layer of the ith OLS is output. vps_output_layer_flag[i] may be set equal to 0 to specify that the jth layer of the ith OLS is not output. It can be inferred that the value of vps_output_layer_flag[i] is equal to 1 when vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0.

[0123] The variable OutputLayerFlag[i][j], where a value of 1 specifies that the jth layer of the ith OLS is output and a value of 0 specifies that the jth layer of the ith OLS is not output, may be derived as follows: for( i = 0, i < TotalNumOlss; i++ ) { OutputLayerFlag[ i ][ NumLayersInOls[ i ] - 1 ] = 1 for( j = 0; j < NumLayersInOls[ i ] - 1; j++ ) if( ols_mode_idc[ i ] == 0 ) OutputLayerFlag[ i ][ j ] = 0 else if( ols_mode_idc[ i ] = = 1 ) OutputLayerFlag[ i ][ j ] = 1 else if( ols_mode_idc[ i ] = = 2 ) OutputLayerFlag[ i ][ j ] = vps_output_layer_flag[ i ][ j ] }

[0124] Any layer in the OLS should be an output layer of the OLS or a reference layer (direct or indirect) of an output layer of the OLS. The 0th OLS includes only the lowest layer (e.g., the layer with nuh_layer_id equal to vps_layer_id[0]), and for the 0th OLS, the only included layer is output. vps_constraint_info_present_flag may be set equal to 1 to specify that the general_constraint_info() syntax structure is present in the VPS. vps_constraint_info_present_flag may be set equal to 0 to specify that the general_constraint_info() syntax structure is not present in the VPS. In a conforming bitstream, vps_reserved_zero_7bits should be equal to 0. Other values ​​of vps_reserved_zero_7bits are reserved. Decoders should ignore the value of vps_reserved_zero_7bits.

[0125] general_hrd_params_present_flag may be set equal to 1 to specify that the syntax elements num_units_in_tick and time_scale and the syntax structure general_hrd_parameters() are present in the SPS RBSP syntax structure. general_hrd_params_present_flag may be set equal to 0 to specify that the syntax elements num_units_in_tick and time_scale and the syntax structure general_hrd_parameters() are not present in the SPS RBSP syntax structure. num_units_in_tick is the number of time units of a clock running at a frequency time_scale Hertz (Hz) that corresponds to one increment (called a clock tick) of the clock tick counter. num_units_in_tick should be greater than 0. Clock ticks in seconds are equal to num_units_in_tick divided by time_scale. For example, when the picture rate of a video signal is 25 Hz, time_scale may be equal to 27000000 and num_units_in_tick may be equal to 1080000, so that a clock tick is equal to 0.04 seconds.

[0126] time_scale is the number of time units that pass per second. For example, a time coordinate system that measures time using a 27 megahertz (MHz) clock has a time_scale of 27,000,000. The value of time_scale should be greater than 0. vps_extension_flag may be set equal to 0 to specify that the vps_extension_data_flag syntax element is not present in the VPS RBSP syntax structure. vps_extension_flag may be set equal to 1 to specify that there is a vps_extension_data_flag syntax element present in the VPS RBSP syntax structure. vps_extension_data_flag may have any value. The presence and value of vps_extension_data_flag does not affect a decoder's conformance to the profile. Conforming decoders should ignore all vps_extension_data_flag syntax elements.

[0127] FIG. 8 is a schematic diagram illustrating an example 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 (Tx / Rx) 810 including a transmitter and / or a 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 a central processing unit (CPU) for processing data and a memory 832 for storing data. The video coding device 800 may also include electrical, optical-electrical (OE) components, electrical-optical (EO) components, and / or wireless communication components coupled to the upstream port 850 and / or the 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.

[0128] The processor 830 is realized by hardware and software. The processor 830 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), and digital signal processors (DSPs). The processor 830 communicates 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 disclosed embodiments described herein, such as the methods 100, 900, and 1000, which may use the multi-layer video sequence 500, the multiview 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, and / or the decoder 400. For example, the coding module 814 may be used to code each_layer_is_an_ols_flag to indicate whether each OLS includes a single layer or at least one OLS includes multiple layers to support multiview when simulcast layers are used. Thus, the coding module 814 allows the video coding device 800 to provide additional functionality and / or coding efficiency when coding video data. Thus, the coding module 814 not only improves the functionality of the video coding device 800 but also addresses problems specific to the video coding field. Furthermore, the coding module 814 transforms the video coding device 800 into a different state. 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 in a non-transitory medium).

[0129] The memory 832 includes one or more memory types such as a disk, a tape drive, a solid state drive, a read only memory (ROM), a random access memory (RAM), a flash memory, a ternary content addressable memory (TCAM), a static random access memory (SRAM), etc. The memory 832 may be used as an overflow data storage device, storing programs when such programs are selected for execution and storing instructions and data read during program execution.

[0130] 9 is a flow chart illustrating an example method 900 for encoding a video sequence, e.g., in bitstream 700, with OLS of a simulcast layer for use in a multiview, such as multiview sequence 600. 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.

[0131] The method 900 may begin when an encoder receives a video sequence and determines, for example, based on user input, to encode the video sequence into a set of simulcast layers for use in multiview. At step 901, the encoder encodes a bitstream including coded pictures of one or more layers. For example, the layers may be simulcast layers and may not be coded according to inter-layer prediction. Additionally, the layers may be coded to support multiview video. Thus, the layers may be organized into one or more OLSs including two layers (e.g., one layer for display to each eye of an end user).

[0132] In step 903, the encoder may encode the VPS into a bitstream. The VPS may include various syntax elements to indicate the layer / OLS configuration to the decoder for proper multiview decoding and display. For example, the VPS may include vps_all_independent_layers_flag, which may be set to 1 to specify that all layers specified by the VPS are independently coded without inter-layer prediction. When vps_all_independent_layers_flag is set to 1, and thus all layers specified by the VPS are independently coded without inter-layer prediction, the VPS may also include each_layer_is_an_ols_flag. each_layer_is_an_ols_flag may specify whether each OLS includes only one layer or at least one OLS includes multiple layers. For example, each_layer_is_an_ols_flag may be set to 1 when each OLS includes only one layer and / or each layer specifies that the single included layer is an OLS that is the only output layer. Thus, when multiview is not being used, each_layer_is_an_ols_flag may be set to 1. As another example, when at least one OLS includes two or more layers, thus specifying that the bitstream coded in step 901 includes multiview video, each_layer_is_an_ols_flag may be set to 0.

[0133] The VPS may also include an ols_mode_idc syntax element. For example, when each_layer_is_an_ols_flag is set to 0 and vps_all_independent_layers_flag is set to 1, ols_mode_idc may be set to 2. When ols_mode_idc is set / equal to 2, the total number of OLSs is explicitly signaled in the VPS. Additionally, when ols_mode_idc is set / equal to 2, the number of layers and / or the number of output layers associated with each OLS is explicitly signaled in the VPS. In certain examples, a vps_max_layers_minus1 syntax element may be included in the VPS to explicitly specify the number of layers specified by the VPS and thus the number of layers that may be included in an OLS. In some examples, vps_all_independent_layers_flag may be signaled when vps_max_layers_minus1 is greater than 0. In another particular example, num_output_layer_sets_minus1 may be included in the VPS when ols_mode_idc is equal to 2. num_output_layer_sets_minus1 may specify the total number of OLSs specified by the VPS. Thus, vps_max_layers_minus1 and num_output_layer_sets_minus1 may be signaled in the VPS to indicate the number of layers and the number of OLSs, respectively, when such data is explicitly signaled (e.g., when each_layer_is_an_ols_flag is set to 0, vps_all_independent_layers_flag is set to 1, and ols_mode_idc is set to 2 and / or inferred to be equal to 2). As a particular example, ols_mode_idc may be inferred to be equal to 2 when vps_all_independent_layers_flag is set to 1 and each_layer_is_an_ols_flag is set to 0.

[0134] In step 905, the bitstream is stored for communication to a decoder.

[0135] 10 is a flow chart illustrating an example method 1000 of decoding a video sequence, e.g., from bitstream 700, that includes an OLS of a simulcast layer for use in a multiview, such as multiview sequence 600. 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.

[0136] Method 1000 may begin when a decoder begins to receive a bitstream including an OLS for a simulcast multiview layer, for example as a result of method 900. In step 1001, the decoder receives a bitstream. The bitstream may include one or more OLSs and one or more layers. For example, a layer may be a simulcast layer and may not be coded according to inter-layer prediction. Additionally, a layer may be coded to support multiview video. Thus, the layers may be organized into an OLS where one or more OLSs include two layers (e.g., one layer for display to each eye of an end user).

[0137] The bitstream may also include a VPS. The VPS may include various syntax elements to indicate the layer / OLS configuration to the decoder for proper multiview decoding and display. For example, the VPS may include vps_all_independent_layers_flag, which may be set to 1 to specify that all layers specified by the VPS are independently coded without inter-layer prediction. When vps_all_independent_layers_flag is set to 1, and thus all layers specified by the VPS are independently coded without inter-layer prediction, the VPS may also include each_layer_is_an_ols_flag. each_layer_is_an_ols_flag may specify whether the OLS includes multiple layers. For example, each_layer_is_an_ols_flag may be set to 1 when each OLS includes only one layer and / or when each layer specifies that the single included layer is an OLS that is the only output layer. Thus, when multiview is not being used, each_layer_is_an_ols_flag may be set to 1. As another example, when at least one OLS contains two or more layers, thus specifying that the bitstream contains multiview video, each_layer_is_an_ols_flag may be set to 0.

[0138] The VPS may also include an ols_mode_idc syntax element. For example, when each_layer_is_an_ols_flag is set to 0 and vps_all_independent_layers_flag is set to 1, ols_mode_idc may be set equal to 2. When ols_mode_idc is set equal to 2, the total number of OLSs is explicitly signaled in the VPS. Additionally, when ols_mode_idc is set / equal to 2, the number of layers associated with each OLS and / or the number of output layers is explicitly signaled in the VPS. In certain examples, a vps_max_layers_minus1 syntax element may be included in the VPS to explicitly specify the number of layers specified by the VPS and thus the number of layers that may be included in an OLS. In some examples, vps_all_independent_layers_flag may be signaled when vps_max_layers_minus1 is greater than 0. In another particular example, num_output_layer_sets_minus1 may be included in the VPS when ols_mode_idc is equal to 2. num_output_layer_sets_minus1 may specify the total number of OLSs specified by the VPS. Thus, vps_max_layers_minus1 and num_output_layer_sets_minus1 may be signaled in the VPS to indicate the number of layers and the number of OLSs, respectively, when such data is explicitly signaled (e.g., when each_layer_is_an_ols_flag is set to 0, vps_all_independent_layers_flag is set to 1, and ols_mode_idc is set to 2 and / or inferred to be equal to 2). As a particular example, ols_mode_idc may be inferred to be equal to 2 when vps_all_independent_layers_flag is set to 1 and each_layer_is_an_ols_flag is set to 0.

[0139] In step 1003, the coded picture is decoded from the output layer of the OLS based on each_layer_is_an_ols_flag in the VPS to generate a decoded picture. For example, the decoder may read vps_all_independent_layers_flag to determine that all layers are simulcast. The decoder may also read each_layer_is_an_ols_flag to determine that at least one OLS includes two or more layers. The decoder may also read ols_mode_idc to determine that the number of OLSs and the number of layers are explicitly signaled. The decoder may then determine the number of OLSs and the number of layers by reading num_output_layer_sets_minus1 and vps_max_layers_minus1, respectively. The decoder may then use this information to locate the correct multiview layer in the bitstream. The decoder may also locate the correct coded picture from the layer. The decoder may then decode the picture to generate a decoded picture.

[0140] In step 1005, the decoder can forward the decoded pictures for display as part of the decoded video sequence.

[0141] 11 is a schematic diagram illustrating an example system 1100 for coding a video sequence, e.g., in bitstream 700, with OLS of a simulcast layer for use in a multiview, such as multiview sequence 600. System 1100 may be implemented by an encoder and a decoder, such as codec system 200, encoder 300, decoder 400, and / or video coding device 800. Furthermore, system 1100 may use multi-layer video sequence 500. In addition, system 1100 may be used when implementing methods 100, 900, and / or 1000.

[0142] The system 1100 includes a video encoder 1102. The video encoder 1102 includes an encoding module 1105 for encoding a bitstream including one or more layers of a coded picture. The encoding module 1105 is further for encoding a VPS including each_layer_is_an_ols_flag into a bitstream, where each_layer_is_an_ols_flag specifies whether each OLS includes only one layer when all layers specified by the VPS are coded independently without inter-layer prediction. The video encoder 1102 further includes a storage module 1106 for storing the bitstream for communication toward a decoder. The video encoder 1102 further includes a transmission module 1107 for transmitting the bitstream toward a video decoder 1110. The video encoder 1102 may be further configured to perform any of the steps of the method 900.

[0143] The system 1100 also includes a video decoder 1110. The video decoder 1110 includes a receiving module 1111 for receiving a bitstream including coded pictures of one or more layers and a VPS, where the VPS includes an each_layer_is_an_ols_flag, which specifies whether each OLS includes only one layer when all layers specified by the VPS are coded independently without inter-layer prediction. The video decoder 1110 further includes a decoding module 1113 for decoding the coded pictures from the output layers of the OLS based on the each_layer_is_an_ols_flag in the VPS to generate a decoded picture. The video decoder 1110 further includes a transport module 1115 for transporting the decoded picture 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.

[0144] A first component is directly bonded 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 bonded 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 "bonded" and variants thereof include both directly bonded and indirectly bonded. Use of the term "about" means a range including ±10% of the succeeding number unless otherwise specified.

[0145] It should also be understood that the steps of the exemplary methods described herein do not necessarily have to be performed in the order described, and the ordering of steps in such methods is understood to be merely exemplary. Similarly, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the present disclosure.

[0146] Although several embodiments have been 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 to be considered as illustrative rather than limiting, and the invention is not limited to the details set forth herein. For example, the various elements or components may be combined or integrated into other systems, or certain features may be omitted or not implemented.

[0147] In addition, the techniques, systems, subsystems, and methods described and illustrated in various embodiments as separate or distinct 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 of ordinary skill in the art and could be made without departing from the spirit and scope disclosed herein. [Explanation of symbols]

[0148] 100 ways 200 Codec System 201 Partitioned Video Signal 211 General Coder Control Component 213 Transform Scaling and Quantization Components 215 In-Picture Estimation Component 217 Intra-Picture Prediction Component 219 Motion Compensation Component 221 Motion Estimation Component 223 Decoded Picture Buffer Component 225 In-Loop Filter Components 227 Filter Control Analysis Component 229 Scaling and Inverse Transformation Components 231 Header Formatting and Context-Adaptive Binary Arithmetic Coding (CABAC) Components 300 Video Encoder 301 Partitioned Video Signal 313 Transform and Quantize Components 317 Intra-Picture Prediction Component 321 Motion Compensation Component 323 Decoded Picture Buffer Component 325 In-Loop Filter Components 329 Inverse Transform and Quantization Components 331 Entropy Coding Component 400 Video Decoder 417 In-Picture Prediction Component 421 Motion Compensation Component 423 Decoded Picture Buffer Component 425 In-Loop Filter Components 429 Inverse Transform and Quantization Components 433 Entropy Decoding Component 500 Multi-layer Video Sequences 511 Pictures 512 Pictures 513 Pictures 514 Pictures 515 Pictures 516 Pictures 517 Pictures 518 Pictures 521 Inter-layer Prediction 523 Inter Prediction 525 OLS 531 Layer N 532 Layer N+1 600 multiview sequences 625 OLS 626 OLS 631 Simulcast Layer 632 Simulcast Layer 633 Simulcast Layer 634 Simulcast Layer 700 bitstream 711 VPS 713 Sequence Parameter Set (SPS) 715 Picture Parameter Set (PPS) 717 Slice Header 720 Image data 721 OLS 723 Layer 725 Pictures 727 Slice 731 vps_all_independent_layers_flag 733 each_layer_is_an_ols_flag 735 ols_mode_idc 737 vps_max_layers_minus1 739 num_output_layer_sets_minus1 800 Video Coding Device 810 Transceiver Unit (Tx / Rx) 814 Coding Module 820 downstream ports 830 Processor 832 Memory 850 Upstream Ports 860 I / O Devices 900 ways 1000 ways 1100 System 1102 Video Encoder 1105 Encoding Module 1106 Memory Module 1107 Transmitting Module 1110 Video Decoder 1111 Receiver Module 1113 Decryption module 1115 Transfer Module

Claims

1. A method performed in a decoder, the method comprising the steps of: receiving a bitstream including one or more layers of coded pictures and a video parameter set (VPS), wherein the VPS includes a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus one specifies the maximum number of layers allowed in each coded video sequence (CVS) that references the VPS, and when vps_max_layers_minus1 is equal to 0, vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer, and each layer is the only output layer in each OLS; decoding the coded picture from the output layer of the OLS based on the vps_max_layers_minus1 to generate a decoded picture; The method includes:

2. The method of claim 1 , wherein if vps_max_layers_minus1 is equal to 0, then the value of each_layer_is_an_ols_flag is inferred to be equal to 1.

3. A method according to any one of claims 1 to 2, wherein vps_all_independent_layers_flag is signaled when vps_max_layers_minus1 is greater than 0.

4. 1. A method performed in an encoder, the method comprising: encoding a bitstream including coded pictures of one or more layers; encoding into the bitstream a video parameter set (VPS), the VPS including a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus one specifies a maximum number of layers allowed in each coded video sequence (CVS) that references the VPS, and where if vps_max_layers_minus1 is equal to 0, then vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer, and that each layer is the only output layer in each OLS; The method includes:

5. The method of claim 4, wherein if vps_max_layers_minus1 is equal to 0, then the value of each_layer_is_an_ols_flag is inferred to be equal to 1, and each_layer_is_an_ols_flag specifies whether each OLS contains a single layer or at least one OLS contains two or more layers.

6. A method according to any one of claims 4 to 5, wherein vps_all_independent_layers_flag is signaled when vps_max_layers_minus1 is greater than 0.

7. A non-transitory computer readable medium comprising a computer program for use by a video coding device, the computer program comprising computer executable instructions stored on the non-transitory computer readable medium which, when executed by a processor, causes the video coding device to perform the method of any one of claims 1 to 6.

8. A decoder comprising: receiving means for receiving a bitstream including one or more layers of coded pictures and a video parameter set (VPS), wherein the VPS includes a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus one specifies the maximum number of layers allowed in each coded video sequence (CVS) that references the VPS, and when vps_max_layers_minus1 is equal to 0, vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer and that each layer is the only output layer in each OLS; decoding means for decoding a coded picture from an output layer of the OLS based on the vps_max_layers_minus1 to generate a decoded picture; A decoder including:

9. The decoder of claim 8, wherein the decoder is further configured to perform the method of any one of claims 2-3.

10. 1. An encoder comprising: Encoding a bitstream including coded pictures of one or more layers; encoding means for encoding a video parameter set (VPS) including a parameter vps_max_layers_minus1 into the bitstream, where vps_max_layers_minus1 plus one specifies a maximum allowed number of layers in each coded video sequence (CVS) that references the VPS, and when vps_max_layers_minus1 is equal to 0, vps_max_layers_minus1 specifies that each output layer set (OLS) contains only one layer, and each layer is the only output layer in each OLS; Including the encoder.

11. The encoder of claim 10, further configured to perform the method of any one of claims 5 to 6.

12. A method for storing a bitstream, comprising the steps of: receiving or transmitting a bitstream over a communications interface; and storing the bitstream on one or more storage media, the bitstream comprising:

1. A method comprising: a coded picture of one or more layers; and a video parameter set (VPS), wherein the VPS includes a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus 1 specifies the maximum number of layers allowed in each coded video sequence (CVS) that references the VPS; if vps_max_layers_minus1 is equal to 0, vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer and each layer is the only output layer in each OLS; and a value of each_layer_is_an_ols_flag in the VPS is used to decode the coded picture from the output layers of the OLS to generate a decoded picture.

13. A device for storing a bitstream, said device comprising at least one storage medium and at least one communication interface; the at least one communication interface is configured to receive or transmit the bitstream; the at least one storage medium is configured to store the bitstream; A device, wherein the bitstream includes a coded picture of one or more layers and a video parameter set (VPS), wherein the VPS includes a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus 1 specifies the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS, and when vps_max_layers_minus1 is equal to 0, vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer and each layer is the only output layer in each OLS, and the value of each_layer_is_an_ols_flag in the VPS is used to decode the coded picture from the output layers of the OLS to generate a decoded picture.

14. A device for transmitting a bitstream, comprising: at least one storage medium configured to store at least one bitstream, the bitstream including a coded picture of one or more layers and a video parameter set (VPS), the VPS including a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus 1 specifies the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS, and if vps_max_layers_minus1 is equal to 0, the vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer and each layer is the only output layer in each OLS, and a value of each_layer_is_an_ols_flag in the VPS is used to decode the coded picture from an output layer of an OLS to generate a decoded picture; at least one processor configured to retrieve one or more bitstreams from one of the at least one storage medium and transmit the one or more bitstreams to a destination device; 16. A device comprising:

15. A method for transmitting a bitstream, comprising the steps of: storing at least one bitstream on at least one storage medium, the bitstream including coded pictures of one or more layers and a video parameter set (VPS), the VPS including a parameter vps_max_layers_minus1, where vps_max_layers_minus1 plus 1 specifies the maximum allowed number of layers in each coded video sequence (CVS) that references the VPS, and if vps_max_layers_minus1 is equal to 0, the vps_max_layers_minus1 specifies that each output layer set (OLS) includes only one layer and each layer is the only output layer in each OLS, and a value of each_layer_is_an_ols_flag in the VPS is used to decode coded pictures from output layers of an OLS to generate a decoded picture; obtaining one or more bitstreams from one of the at least one storage medium; transmitting the one or more bitstreams to a destination device; The method includes:

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