OLS for multi-view scalability

Abstract

To provide a video coding mechanism.SOLUTION: A video coding mechanism includes receiving a bitstream comprising an output layer set (OLS) and a video parameter set (VPS). The OLS includes one or more layers of coded pictures and the VPS includes an OLS mode identification code (ols_mode_idc) specifying that for each OLS, all layers in each OLS are output layers. The output layers are determined on the basis of the ols_mode_idc in the VPS. The coded picture from the output layers is decoded to produce a decoded picture. The decoded picture is forwarded for display as a part of a decoded video sequence.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This patent application claims priority to and incorporates by reference U.S. Provisional Patent Application No. 62 / 905,132, entitled "Signalling Of Output Layer Sets For Multiview Scalability", filed Sep. 24, 2019, by Ye - Kui Wang.

[0002] [Technical Field] The present disclosure generally relates to video coding, and more specifically, to constructing output layer sets (OLS) in a multi - layer bitstream to support spatial and signal - to - noise (SNR) scalability for multi - view video.

Background Art

[0003] The amount of video data required to depict even relatively short videos can be quite substantial, which can pose difficulties when the data is streamed or otherwise communicated across a communication network having limited bandwidth capacity. Thus, video data is generally compressed before being communicated across today's telecommunications networks. Since memory resources can be limited, the size of the video can also be a problem 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 prior to transmission or storage, thereby reducing the amount of data required to represent the digital video image. The compressed data is then received at the destination by a video decompression device that decodes the video data. Due to limited network resources and the ever - increasing demand for higher video quality, improved compression and decompression techniques that improve the compression ratio without or with little sacrifice to image quality are desired.

SUMMARY OF THE INVENTION

[0004] In one embodiment, the present disclosure includes a method implemented by a decoder, the method comprising: receiving, by a receiver of the decoder, a bitstream including an output layer set (OLS) and a video parameter set (VPS), wherein the OLS includes one or more layers of coded pictures, and the VPS includes an OLS mode identification code (ols_mode_idc) specifying that all layers within each OLS are output layers; determining, by a processor of the decoder, an output layer based on the ols_mode_idc in the VPS; and decoding, by a processor of the decoder, a coded picture from the output layer and generating a decoded picture.

[0005] Some video coding systems are configured to only decode and output the highest encoded layer, as indicated by a layer ID, along with one or more specified lower layers. This can pose a problem for scalability because the decoder may not want to decode the highest layer. Specifically, the decoder generally requests the highest layer that it can support, but the decoder generally cannot decode a layer higher than the requested layer. As a specific example, the decoder may wish to receive and decode the third layer out of a total of 15 encoded layers. Since layers 4 through 15 are not required to decode the third layer, the third layer can be sent to the decoder without such layers. However, if the highest layer (layer 15) does not exist and the video system is always instructed to decode and display the highest layer, the decoder may not be able to properly decode and display the third layer. This causes an error when video scalability is attempted in such a system. This can be a significant problem because requiring the decoder to always support the highest layer results in a system that cannot scale to intermediate layers based on different hardware and network requirements. This problem becomes more complex when multi-view is used. In multi-view, more than one layer is output for display. For example, the user may use a headset, and different layers may be displayed to each eye to create the impression of a three-dimensional (3D) video. A system that cannot support scalability also cannot support multi-view scalability.

[0006] This example includes a mechanism for supporting multi-view scalability. The layer is included in the OLS. The encoder can transmit the OLS including the layer to scale with respect to specific characteristics such as size or SNR. Further, the encoder may transmit the ols_mode_idc syntax element, for example, in the VPS. The ols_mode_idc syntax element can be set to 1 to indicate the use of multi-view scalability. For example, ols_mode_idc can indicate that the total number of OLSs is equal to the total number of layers specified in the VPS, the i-th OLS includes layers from 0 to i, and all layers for each OLS can be considered output layers. This supports scalability because the decoder can receive and decode all layers within a specific OLS. Since all layers are output layers, the decoder can select the desired output layer for rendering. Thus, the total number of encoded layers may not affect the decoding process and still provide scalable multi-view video while errors can be avoided. Therefore, the disclosed mechanism improves the functions of the encoder and / or decoder. Further, the disclosed mechanism can reduce the bitstream size and thus reduce the processor, memory, and / or network resource utilization in both the encoder and decoder. In certain embodiments, using ols_mode_idc provides bit savings in an encoded bitstream that includes multiple OLSs where much data is shared, thus providing savings in the streaming server and bandwidth savings for transmitting such a bitstream. For example, the advantage of setting ols_mode_idc to 1 is to support use cases such as multi-view applications where two or more views, each represented by one layer, are output and displayed simultaneously.

[0007] Optionally, in any of the above aspects, another implementation of the aspect provides that ols_mode_idc specifies that the total number of OLSs specified by the VPS is equal to the number of layers specified by the VPS.

[0008] Optionally, in any of the above aspects, another implementation of the aspect provides that ols_mode_idc specifies that the i-th OLS includes layers having layer indices from 0 to i.

[0009] Optionally, in any of the above aspects, another implementation of the aspect provides that ols_mode_idc is equal to 1.

[0010] Optionally, in any of the above aspects, another implementation of the aspect provides that the VPS includes vps_max_layers_minus1, which is the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS and specifies the number of layers specified by the VPS.

[0011] Optionally, in any of the above aspects, another implementation of the aspect provides that the total number of OLSs (TotalNumOlss) is equal to vps_max_layers_minus1 plus 1 when ols_mode_idc is equal to 0 or when ols_mode_idc is equal to 1.

[0012] Optionally, in any of the above aspects, another implementation of the aspect provides that the number of layers (NumLayersInOls[i]) in the i-th OLS and the network abstraction layer (NAL) unit header layer identifier (nuh_layer_id) value (LayerIdInOLS[i][j]) of the j-th layer in the i-th OLS are as follows, that is, NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i = 1; i < TotalNumOlss; i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i]=1 LayerIdInOls[i][0]=vps_layer_id[i] } else if(ols_mode_idc == 0 || ols_mode_idc == 1){ NumLayersInOls[i]=i + 1 for(j = 0; j < NumLayersInOls[i]; j++) LayerIdInOls[i][j]=vps_layer_id[j] is derived as follows, where vps_layer_id[i] is the i-th VPS layer identifier, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a flag indicating that each layer is an OLS, specifying whether at least one OLS contains more than one layer.

[0013] In one embodiment, the present disclosure includes a method implemented by an encoder, the method including encoding, by a processor of the encoder, a bitstream including one or more OLSs including one or more layers of a coded picture; encoding, by the processor, a VPS into the bitstream, the VPS including an ols_mode_idc specifying that all layers within each OLS are output layers for each OLS; and storing, by a memory coupled to the processor, the bitstream for communication to a decoder.

[0014] Some video coding systems are configured to only decode and output the highest coding layer as indicated by a layer ID, along with one or more specified lower layers. This can pose a problem for scalability because the decoder may not want to decode the highest layer. Specifically, the decoder generally requests the highest layer that it can support, but the decoder generally cannot decode a layer higher than the requested layer. As a specific example, the decoder may wish to receive and decode the third layer out of a total of 15 coded layers. Since layers 4-15 are not required to decode the third layer, the third layer can be sent to the decoder without such layers. However, if the highest layer (layer 15) does not exist and the video system is always instructed to decode and display the highest layer, the decoder may not be able to properly decode and display the third layer. This causes an error when video scalability is attempted in such a system. This can be a significant problem because requiring the decoder to always support the highest layer results in a system that cannot scale for intermediate layers based on different hardware and network requirements. The problem becomes more complex when multi-view is used. In multi-view, more than one layer is output for display. For example, the user may use a headset and different layers may be displayed to each eye to create the impression of a three-dimensional (3D) video. A system that cannot support scalability also cannot support multi-view scalability.

[0015] This example includes a mechanism for supporting multi-view scalability. The layer is included in the OLS. The encoder can transmit the OLS including the layer to scale with respect to specific characteristics such as size or SNR. Further, the encoder may transmit the ols_mode_idc syntax element, for example, in the VPS. The ols_mode_idc syntax element can be set to 1 to indicate the use of multi-view scalability. For example, ols_mode_idc can indicate that the total number of OLSs is equal to the total number of layers specified in the VPS, the i-th OLS includes layers from 0 to i, and all layers for each OLS can be considered as output layers. This supports scalability because the decoder can receive and decode all layers within a specific OLS. Since all layers are output layers, the decoder can select and render the desired output layer. Thus, the total number of encoded layers may not affect the decoding process and still provide scalable multi-view video while errors can be avoided. Therefore, the disclosed mechanism improves the functions of the encoder and / or decoder. Further, the disclosed mechanism can reduce the bitstream size and thus reduce the processor, memory, and / or network resource utilization in both the encoder and decoder. In certain embodiments, using ols_mode_idc provides bit savings in an encoded bitstream that includes multiple OLSs where much data is shared, thus providing savings in the streaming server and bandwidth savings for transmitting such a bitstream. For example, the advantage of setting ols_mode_idc to 1 is to support use cases such as multi-view applications where two or more views, each represented by one layer, are output and displayed simultaneously.

[0016] Optionally, in any of the above aspects, another implementation of the aspect provides that ols_mode_idc specifies that the total number of OLSs specified by the VPS is equal to the number of layers specified by the VPS.

[0017] Optionally, in any of the above aspects, another implementation of the aspect provides that ols_mode_idc specifies that the i-th OLS includes layers having layer indices from 0 to i.

[0018] Optionally, in any of the above aspects, another implementation of the aspect provides that ols_mode_idc is equal to 1.

[0019] Optionally, in any of the above aspects, another implementation of the aspect provides that the VPS includes vps_max_layers_minus1 that specifies the number of layers specified by the VPS, where vps_max_layers_minus1 is the maximum allowable number of layers in each CVS that refers to the VPS.

[0020] Optionally, in any of the above aspects, another implementation of the aspect provides that TotalNumOlss is equal to vps_max_layers_minus1 plus 1 when ols_mode_idc is equal to 0 or when ols_mode_idc is equal to 1.

[0021] Optionally, in any of the above aspects, another implementation of the aspect provides that NumLayersInOls[i] and LayerIdInOLS[i][j] are as follows, that is, NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1,i<TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i]=1 LayerIdInOls[i][0] = vps_layer_id[i] } else if (ols_mode_idc == 0 || ols_mode_idc == 1) { NumLayersInOls[i] = i + 1 for (j = 0; j < NumLayersInOls[i]; j++) LayerIdInOls[i][j] = vps_layer_id[j] is derived as such, where vps_layer_id[i] is the i-th VPS layer identifier, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a flag indicating that each layer is an OLS, specifying whether at least one OLS contains more than one layer.

[0022] In one 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 execute the method according to any of the above aspects.

[0023] In one embodiment, the present disclosure includes a non-transitory computer-readable medium including a computer program product used 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, cause the video coding device to execute the method according to any of the above aspects.

[0024] In one embodiment, the present disclosure includes a receiver for receiving a bitstream including OLS and VPS, where the OLS includes one or more layers of a coded picture, and the VPS includes an ols_mode_idc that specifies that all layers within each OLS are output layers for each OLS, a determination means for determining an output layer based on the ols_mode_idc within the VPS, a decoding means for decoding the coded picture from the output layer and generating a decoded picture, and a transfer means for transferring the decoded picture for display as part of a decoded video sequence. The decoder includes these components.

[0025] Some video coding systems are configured to only decode and output the highest coding layer as indicated by a layer ID, along with one or more specified lower layers. This can pose a problem for scalability because there may be cases where the decoder does not want to decode the highest layer. Specifically, the decoder generally requests the highest layer that it can support, but the decoder generally cannot decode a layer higher than the requested layer. As a specific example, the decoder may wish to receive and decode the third layer out of a total of 15 coded layers. Since layers 4 - 15 are not required to decode the third layer, the third layer can be sent to the decoder without such layers. However, if the highest layer (layer 15) does not exist and the video system is always instructed to decode and display the highest layer, the decoder may not be able to properly decode and display the third layer. This causes an error when video scalability is attempted in such a system. This can be a significant problem because requiring the decoder to always support the highest layer results in a system that cannot scale intermediate layers based on different hardware and network requirements. The problem becomes more complex when multi-view is used. In multi-view, more than one layer is output for display. For example, the user may use a headset and different layers may be displayed to each eye to create the impression of a three-dimensional (3D) video. A system that cannot support scalability also cannot support multi-view scalability.

[0026] This example includes a mechanism for supporting multi-view scalability. The layer is included in the OLS. The encoder can transmit the OLS including the layer to scale for specific characteristics such as size or SNR. Further, the encoder may transmit the ols_mode_idc syntax element, for example, in the VPS. The ols_mode_idc syntax element can be set to 1 to indicate the use of multi-view scalability. For example, ols_mode_idc can indicate that the total number of OLSs is equal to the total number of layers specified in the VPS, the i-th OLS includes layers from 0 to i, and all layers for each OLS can be considered output layers. This supports scalability because the decoder can receive and decode all layers within a specific OLS. Since all layers are output layers, the decoder can select the desired output layer for rendering. Thus, the total number of encoded layers may not affect the decoding process and still provide scalable multi-view video while errors can be avoided. Therefore, the disclosed mechanism improves the functions of the encoder and / or decoder. Further, the disclosed mechanism can reduce the bitstream size and thus reduce the processor, memory, and / or network resource utilization in both the encoder and decoder. In certain embodiments, using ols_mode_idc provides bit savings in an encoded bitstream including multiple OLSs where much data is shared, thus providing savings in the streaming server and bandwidth savings for transmitting such a bitstream. For example, the advantage of setting ols_mode_idc to 1 is to support use cases such as multi-view applications where two or more views, each represented by one layer, are output and displayed simultaneously.

[0027] Optionally, in any of the above aspects, other implementations of the aspect provide that the decoder is further configured to execute any of the methods of the above aspects.

[0028] In one embodiment, the present disclosure is an encoding means for encoding a bitstream including one or more OLSs including one or more layers of a coded picture, and encoding a VPS into the bitstream, the VPS including an ols_mode_idc specifying that all layers within each OLS are output layers for each OLS, and an encoder including a storage means for storing the bitstream for communication to a decoder.

[0029] Some video coding systems are configured to only decode and output the highest encoded layer, as indicated by a layer ID, along with one or more specified lower layers. This can pose a problem for scalability because there may be situations where the decoder does not want to decode the highest layer. Specifically, the decoder generally requests the highest layer that it can support, but it is generally not possible for the decoder to decode a layer higher than the requested layer. As a specific example, the decoder may wish to receive and decode the third layer out of a total of 15 encoded layers. Since layers 4 through 15 are not required to decode the third layer, the third layer can be sent to the decoder without such layers. However, if the highest layer (layer 15) does not exist and the video system is always instructed to decode and display the highest layer, the decoder may not be able to properly decode and display the third layer. This causes an error when video scalability is attempted in such a system. This can be a significant problem because requiring the decoder to always support the highest layer results in a system that cannot scale intermediate layers based on different hardware and network requirements. This problem becomes more complex when multi-view is used. In multi-view, more than one layer is output for display. For example, the user may use a headset and different layers may be displayed to each eye to create the impression of a three-dimensional (3D) video. A system that cannot support scalability also cannot support multi-view scalability.

[0030] This example includes a mechanism for supporting multi-view scalability. The layer is included in the OLS. The encoder can transmit the OLS including the layer to scale for specific characteristics such as size or SNR. Further, the encoder may transmit the ols_mode_idc syntax element, for example, in the VPS. The ols_mode_idc syntax element can be set to 1 to indicate the use of multi-view scalability. For example, ols_mode_idc can indicate that the total number of OLSs is equal to the total number of layers specified in the VPS, the i-th OLS includes layers from 0 to i, and all layers for each OLS can be considered as output layers. This supports scalability because the decoder can receive and decode all layers within a specific OLS. Since all layers are output layers, the decoder can select the desired output layer for rendering. Thus, the total number of encoded layers may not affect the decoding process and still provide scalable multi-view video while errors can be avoided. Therefore, the disclosed mechanism improves the functions of the encoder and / or decoder. Further, the disclosed mechanism can reduce the bitstream size and thus reduce the processor, memory, and / or network resource utilization in both the encoder and decoder. In a particular embodiment, using ols_mode_idc provides bit savings in an encoded bitstream including multiple OLSs where much data is shared, thus providing savings in the streaming server and bandwidth savings for transmitting such a bitstream. For example, the advantage of setting ols_mode_idc to 1 is to support use cases such as multi-view applications where two or more views, each represented by one layer, are output and displayed simultaneously.

[0031] Optionally, in any of the above aspects, another implementation of the aspect provides that the encoder is further configured to execute any of the methods of the above aspects.

[0032] For the purpose of clarification, any one of the above embodiments may be combined with any one or more of the other above embodiments to create new embodiments within the scope of the present disclosure.

[0033] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and the claims.

Brief Description of the Drawings

[0034] For a more complete understanding of the present disclosure, reference is now made to the following brief description taken in conjunction with the accompanying drawings and detailed description, in which like reference numerals represent like parts.

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[0035] First, exemplary implementations of one or more embodiments are provided below. However, it should be understood that the disclosed system and / or method can be implemented using any number of technologies, whether currently known or existing. The present disclosure should in no way be limited to the exemplary implementations, drawings, and technologies shown below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims, together with the full scope of their exact equivalents.

[0036] The following terms are defined as follows, unless used in the contrary context herein. Specifically, the following definitions are intended to provide further clarity to the present disclosure. However, in different contexts, terms may be described differently. Accordingly, the following definitions should be considered supplementary and should not be considered to limit any other definitions provided herein for such terms.

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

[0038] A network abstraction layer (NAL) unit is a syntax structure that includes data in the form of a Raw Byte Sequence Payload (RBSP) and an indication of the data type, with emulation prevention bytes scattered as desired. A video coding layer (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 to support video data decoding, compliance checking, or other operations. A layer is a set of VCL NAL units that share specified characteristics (e.g., common resolution, frame rate, image size, etc.) and related non-VCL NAL units. The VCL NAL units of a layer may share a specific value of the NAL unit header layer identifier (nuh_layer_id). A coded picture is a coded representation of a picture that includes VCL NAL units having a specific value of the NAL unit header layer identifier (nuh_layer_id) within an access unit (AU) and includes all coding tree units (CTUs) of the picture. A decoded picture is a picture generated by applying a decoding process to the coded picture. A coded video sequence (CVS) is a sequence of AUs that includes, in decoding order, one or more coded video sequence start (CVSS) AUs and optionally one or more AUs that are not CVSS AUs.The CVSS AU is an AU that includes prediction units (PUs) for each layer specified by a video parameter set (VPS), and the coded picture within each PU is the start picture of the CVS / coded layer video sequence (CLVS).

[0039] The output layer set (OLS) is a set of layers in which one or more layers are specified as output layers. The output layer is the layer specified for output (e.g., to a display). The top layer is the layer within the OLS that has the largest layer identifier (ID) among all the layers within the OLS. In some exemplary OLS modes, the top layer may always be the output layer. In other modes, the indicated layer and / or all layers are output layers. A video parameter set (VPS) is a data unit that contains parameters related to the overall video. Inter-layer prediction is a mechanism for coding the current picture in the current layer by referring to a reference picture in a reference layer, where the current picture and the reference picture are included in the same AU, and the reference layer has a lower nuh_layer_id than the current layer.

[0040] The OLS mode identification code (ols_mode_idc) is a syntax element indicating information about the number of OLSs, the layer of the OLS, and the output layer within the OLS. The VPS maximum layer minus 1 (vps_max_layers_minus1) is a syntax element that conveys the number of layers specified by the VPS, and thus the maximum number of layers allowed in the corresponding CVS. The flag that each layer is an OLS (each_layer_is_an_ols_flag) is a syntax element that conveys whether each OLS in the bitstream contains a single layer. The total number of OLSs (TotalNumOLss) is a variable that specifies the total number of OLSs specified by the VPS. The number of layers in the i-th OLS (NumLayersInOLS[i]) is a variable that specifies the number of layers within a particular OLS indicated by the OLS index value of i. The layer ID within the OLS (LayerIdInOLS[i][j]) is a variable that specifies the nuh_layer_id value of the j-th layer within the i-th OLS indicated by the layer index j and the OLS index i. The vps_layer_id[i] is a syntax element that indicates the layer ID of the i-th layer.

[0041] The following abbreviations, namely, 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 Transfer 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), and Versatile Video Coding (VVC) are used herein.

[0042] Many video compression techniques can be used to reduce the size of video files with minimal data loss. For example, video compression techniques can include performing spatial (e.g., intra-picture) prediction and / or temporal (e.g., inter-picture) prediction to reduce or remove data redundancy in a video sequence. In block-based video coding, a video slice (e.g., a video picture or a part of a video picture) may be partitioned into video blocks that 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 within an intra-coded (I) slice of a picture are coded using spatial prediction with respect to reference samples in adjacent blocks within the same picture. Video blocks within an inter-coded unidirectional prediction (P) or bidirectional prediction (B) slice of a picture may be coded by using spatial prediction with respect to reference samples in adjacent blocks within the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may also be referred to as a frame and / or an image, and a reference picture may also be referred to as a reference frame and / or a reference image. Spatial or temporal prediction results in a prediction block that represents the image block. Residual data represents the pixel difference between the original image block and the prediction block. Thus, an inter-coded block is coded according to a motion vector that points to a block of reference samples forming the prediction block and residual data that indicates the difference between the coded block and the prediction block. An intra-coded block is coded according to an intra-coding mode and residual data. For further compression, the residual data may be transformed from the pixel domain to the transform domain. These result in residual transform coefficients, which may be quantized. The quantized transform coefficients may first be arranged in a two-dimensional array. The quantized transform coefficients may be scanned to generate a one-dimensional vector of the transform coefficients.To achieve more compression, entropy coding may be applied. Such video compression techniques will be described in more detail below.

[0043] To ensure that the encoded video can be accurately decoded, the video is encoded and decoded according to the corresponding video coding standard. The video coding standards include International Telecommunication Union (ITU) Standardization Sector (ITU-T) H.261, International Organization for Standardization / International Electrotechnical Commission (ISO / IEC) Moving Picture Experts Group (MPEG)-1 Part 2, ITU-T H.262 or ISO / IEC MPEG-2 Part 2, ITU-T H.263, ISO / IEC MPEG-4 Part 2, ITU-T H.264 or Advanced Video Coding (AVC), also known as ISO / IEC MPEG-4 Part 10, and High Efficiency Video Coding (HEVC), also known as ITU-T H.265 or MPEG-H Part 2. AVC includes extensions such as Scalable Video Coding (SVC), Multiview Video Coding (MVC) and Multiview Video Coding plus Depth (MVC+D), and three dimensional (3D) AVC (3D-AVC). HEVC includes extensions such as Scalable HEVC (SHVC), Multiview HEVC (MV-HEVC) and 3D HEVC (3D-HEVC).The ITU-T and ISO / IEC joint video experts team (JVET) has started developing a video coding standard called Versatile Video Coding (VVC). VVC is included in the WD, including JVET-O2001-v14.

[0044] To support scalability, picture layers can be used. For example, a video can be coded into multiple layers. A layer may be coded without referring to other layers. Such a layer is called a simulcast layer. Thus, a simulcast layer can be decoded without referring to other layers. As another example, a layer can be coded using inter-layer prediction. This enables the current layer to be coded by including only the difference between the current layer and the 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.

[0045] Some video coding systems are configured to only decode and output the highest coding layer, as indicated by a layer identifier (ID), along with one or more specified lower layers. This can pose a problem for scalability because the decoder may not want to decode the highest layer. Specifically, the decoder generally requests the highest layer that it can support, but the decoder generally cannot decode a layer higher than the requested layer. As a specific example, the decoder may wish to receive and decode the third layer out of a total of 15 coded layers. Since layers 4-15 are not required to decode the third layer, the third layer can be sent to the decoder without such layers. However, if the highest layer (layer 15) does not exist and the video system is always instructed to decode and display the highest layer, the decoder may not be able to properly decode and display the third layer. This causes an error when video scalability is attempted in such a system. This can be a significant problem because requiring the decoder to always support the highest layer results in a system that cannot scale intermediate layers based on different hardware and network requirements. The problem becomes more complex when multi-view is used. In multi-view, more than one layer is output for display. For example, the user may use a headset, and different layers may be displayed to each eye to create the impression of a three-dimensional (3D) video. A system that cannot support scalability also cannot support multi-view scalability.

[0046] Disclosed herein is a mechanism for supporting multi-view scalability. Layers are included in an output layer set (OLS). The encoder can send an OLS including layers to scale with respect to specific characteristics such as size or SNR. Spatial scalability enables a video sequence to be coded into layers such that the layers are arranged in the OLS so that each OLS contains sufficient data to decode the video sequence to the corresponding output screen size. Therefore, spatial scalability may include a set of layers for decoding video for a smartphone screen, a set of layers for decoding video for a large TV screen, and a set of layers for an intermediate screen size. SNR scalability enables a video sequence to be coded into layers such that the layers are arranged in the OLS so that each OLS contains sufficient data to decode the video sequence at a different SNR. Therefore, SNR scalability may include a set of layers that can be decoded for low-quality video, high-quality video, and various intermediate video qualities based on network conditions. Further, the encoder may transmit an ols_mode_idc syntax element, for example, in a video parameter set (VPS). The ols_mode_idc syntax element can be set to 1 to indicate the use of multi-view scalability. For example, the ols_mode_idc can indicate that the total number of OLSs is equal to the total number of layers specified in the VPS, the i-th OLS contains layers from 0 to i, and all layers for each OLS are considered output layers. This supports scalability because the decoder can receive and decode all layers within a specific OLS. Since all layers are output layers, the decoder can select the desired output layer for rendering. Thus, the total number of coded layers may not affect the decoding process and still provide scalable multi-view video while errors can be avoided.Accordingly, the disclosed mechanism improves the functionality of the encoder and / or decoder. Further, the disclosed mechanism reduces the bitstream size and thus may reduce the processor, memory, and / or network resource utilization in both the encoder and decoder.

[0047] FIG. 1 is a flowchart of an exemplary operational method 100 for coding a video signal. Specifically, the video signal is encoded by an encoder. The encoding process compresses the video signal by using various mechanisms for reducing the video file size. The smaller file size enables the compressed video file to be transmitted to the user while reducing the associated bandwidth overhead. The decoder then decodes the compressed video file and reconstructs the original video signal for display to the end user. The decoding process generally reflects the encoding process and enables the decoder to consistently reconstruct the video signal.

[0048] In step 101, a video signal is input to the encoder. For example, the video signal may be an uncompressed video file stored in memory. As another example, the video file may be captured by a video capture device such as a video camera and encoded to support live streaming of the video. The video file may include both an audio component and a video component. The video component includes a series of image frames that give a visual impression of movement when viewed in sequence. The frames include pixels represented in terms of brightness, herein called the luma component (or luma samples), and color, herein called the chroma component (or color samples). In some examples, the frames may also include depth values to support three-dimensional displays.

[0049] In step 103, the video is partitioned into blocks. Partitioning includes subdividing the pixels within each frame into square and / or rectangular blocks for compression. For example, in High Efficiency Video Coding (HEVC), also known as H.265 and MPEG-H Part 2, a frame can first be divided into coding tree units (CTUs), which are blocks of a predetermined size (e.g., 64 pixels × 64 pixels). A CTU contains both luma samples and chroma samples. Coding trees may be used to divide a CTU into blocks and then recursively subdivide the blocks until a configuration that supports further encoding is achieved. For example, the luma component of a frame may be subdivided until the individual blocks contain relatively uniform brightness values. Further, the chroma component of a frame may be subdivided until the individual blocks contain relatively uniform color values. 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 utilize the fact that objects within a common scene tend to appear in consecutive frames. Therefore, blocks depicting objects within a reference frame need not be repeatedly described in adjacent frames. Specifically, an object such as a table may remain in a fixed position over multiple frames. Thus, the table is described once, and adjacent frames can refer back to the reference frame. A pattern matching mechanism may be used to match objects over multiple frames. Further, a moving object may be represented over multiple frames, for example, due to the movement of the object or the camera. As a specific example, a video may show a car moving between screens over multiple frames. To describe such movement, motion vectors can be used. A motion vector is a two-dimensional vector that provides an offset from the coordinates of an object in one frame to the coordinates of the corresponding object in a reference frame. Therefore, inter prediction can encode an image block in the current frame as a set of motion vectors indicating the offsets from the corresponding blocks in the reference frame.

[0051] Intra prediction encodes blocks within a common frame. Intra prediction utilizes the fact that luma and chroma components tend to group within a frame. For example, a green patch of a part of a tree tends to be located adjacent to similar green patches. Intra prediction uses multiple direction prediction modes (e.g., 33 in HEVC), a planar mode, and a direct current (DC) mode. The direction mode indicates that the current block is similar / identical to the samples of adjacent blocks in the corresponding direction. The planar mode indicates that a series of blocks along a row / column (e.g., a plane) can be interpolated based on adjacent blocks at the end of the row. The planar mode effectively indicates a smooth transition of brightness / color across the row / column by using a relatively constant slope when changing values. The DC mode is used for boundary smoothing and indicates that the block is similar / identical to the average value related to the samples of all adjacent blocks related to the angular direction of the direction prediction mode. Thus, an intra prediction block can represent an image block as various relationship prediction mode values instead of actual values. Furthermore, an inter prediction block can represent an image block as a motion vector value instead of actual values. In either case, the prediction block may not accurately represent the image block in some cases. Any difference is stored in the 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 the in-loop filtering method. The above block-based prediction may result in the creation of an image with block noise in the decoder. Further, the block-based prediction method may encode a block and then reconstruct the encoded block for later use as a reference block. The in-loop filtering method repeatedly applies a noise reduction filter, a deblocking filter, an adaptive loop filter, and a sample adaptive offset (SAO) filter to blocks / frames. These filters reduce such blocking artifacts so that the encoded file can be accurately reconstructed. Further, these filters reduce artifacts in the reconstructed reference block so that artifacts are less likely to create further artifacts in subsequent blocks encoded based on the reconstructed reference block.

[0053] When the video signal is partitioned, compressed, and filtered, in step 109, the resulting data is encoded into a bitstream. The bitstream includes the above data and any signaling data desired to support proper video signal reconstruction in the decoder. For example, such data may include partition data, prediction data, residual blocks, and various flags that provide coding instructions to the decoder. The bitstream may be stored in memory for transmission to the decoder upon request. The bitstream may also be broadcast and / or multicast to multiple decoders. The creation of the bitstream is an iterative process. Thus, steps 101, 103, 105, 107, and 109 may occur continuously and / or simultaneously over many frames and blocks. The order shown in FIG. 1 is presented for clarity and ease of explanation and is not intended to limit the video coding process to a particular order.

[0054] In step 111, the decoder receives the bitstream and starts the decoding process. Specifically, the decoder uses an entropy decoding method to convert the bitstream into the corresponding syntax and video data. The decoder uses the syntax data from the bitstream to determine the partition for the frame in step 111. The partition splitting should be consistent with the result of the block partition splitting in step 103. The entropy coding / decoding used in step 111 will be described here. The encoder makes many selections, such as selecting a block partition splitting method from several possible options based on the spatial position of the values in the input image during the compression process. Communicating exact options may involve using a large number of bins. When used here, a bin is a binary value treated as a variable (e.g., a bit value that can vary depending on the context). Entropy coding allows the encoder to discard any option that is clearly not executable in a particular case and leave the acceptable options. Then, a codeword is assigned to each acceptable option. The length of the codeword is based on the number of acceptable options (e.g., 1 bin for 2 options, 2 bins for 3 to 4 options, etc.). Then, the encoder encodes the codeword for the selected option. This method reduces the size of the codeword because the codeword uniquely indicates a selection from a small subset of acceptable options rather than from a potentially large set of all possible options. Then, the decoder decodes the selection by determining the set of acceptable options in a manner similar to the encoder. By determining the set of acceptable 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 uses inverse transformation to generate residual blocks. Then, the decoder uses the residual blocks and corresponding prediction blocks to reconstruct the image blocks according to the partition splitting. The prediction blocks may include both intra prediction blocks and inter prediction blocks generated by the encoder in step 105. Then, the reconstructed image blocks are positioned in the frame of the reconstructed video signal according to the partition splitting data determined in step 111. The syntax for step 113 may also be transmitted in the bitstream via entropy coding as described above.

[0056] In step 115, filtering is performed on the frame 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 frame to remove blocking artifacts. When the frame is filtered, in step 117, the video signal can be output to the display for viewing by the end user.

[0057] Figure 2 is a schematic diagram of an exemplary coding and decoding (codec) system 200 for video coding. Specifically, the codec system 200 provides functions to support the implementation of the operation method 100. The codec system 200 is generalized to show components used in both the encoder and the decoder. As described with respect to steps 101 and 103 in the operation method 100, the codec system 200 receives and partitions a video signal, which results in a partitioned video signal 201. Next, when acting as an encoder, the codec system 200 compresses the partitioned video signal 201 into a coded bitstream as described with respect to steps 105, 107, and 109 in method 100. When acting as a decoder, the codec system 200 generates an output video signal from the bitstream as described with respect to steps 111, 113, 115, and 117 in the operation method 100. The codec system 200 includes an overall encoder 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 format and context adaptive binary arithmetic coding (CABAC) component 231. Such components are coupled as shown. In Figure 2, the solid lines indicate the movement of data to be encoded / decoded, and the dashed lines indicate the movement of control data that controls the operation of other components. All components of the codec system 200 may be present in the encoder. The decoder may include a subset of the components of the 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 will be described herein.

[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 even 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. The partitioned blocks can, in some cases, be included in coding units (CUs). For example, a CU can be a part of a CTU that includes a luma block, a red difference chroma (Cr) block, and a blue difference chroma (Cb) block, along with the corresponding syntax instructions for that CU. The partitioning modes may include a binary tree (BT), a triple tree (TT), and a quad tree (QT) that 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 transferred for compression to the overall coder control component 201, the transform scaling and quantization component 213, the intra-picture estimation component 215, the filter control analysis component 227, and the motion estimation component 221.

[0059] The overall coder control component 211 is configured to make determinations related to the coding of the images of the video sequence into a bitstream according to the application constraints. For example, the overall coder control component 211 manages the optimization of the bitrate / bitstream size with respect to the reconstructed quality. Such determinations may be made based on the availability of memory space / bandwidth and the image resolution requirements. The overall coder control component 211 also manages the buffer utilization in light of the transmission speed in order to mitigate the problems of buffer underrun and overrun. To manage these problems, the overall coder control component 211 manages the partitioning, prediction, and filtering by other components. For example, the overall coder control component 211 may dynamically increase the complexity of compression to increase the resolution and increase the bandwidth usage, or may decrease the complexity of compression to decrease the resolution and the bandwidth usage. Therefore, the overall coder control component 211 controls the other components of the codec system 200 so as to balance the video signal reconstructed quality with the concerns of the bitrate. The overall coder control component 211 creates control data for controlling the operation of the other components. The control data is also transferred to the header formatter and the CABAC component 231 so as to be encoded into the bitstream for transmitting the parameters for decoding at the decoder.

[0060] The partitioned video signal 201 is also sent to the motion estimation component 221 and the motion compensation component 219 for inter prediction. The frame or slice of the partitioned video signal 201 may be divided into a plurality of video blocks. The motion estimation component 221 and the motion compensation component 219 perform inter prediction 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 execute a plurality of coding paths, for example, to select an appropriate coding mode for each block of the 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. The motion estimation performed by the motion estimation component 221 is a process of generating motion vectors that estimate the motion for video blocks. The motion vectors may indicate, for example, the displacement of the object to be coded relative to the prediction block. The prediction block is a block that has been found to closely match the block to be coded in terms of pixel difference. The prediction block may also be referred to as a reference block. Such pixel difference may be determined by sum of absolute difference (SAD), sum of square difference (SSD), or other difference metrics. HEVC uses several coded objects including CTUs, coding tree blocks (CTBs), and CUs. For example, a CTU can be divided into CTBs, which can then be divided into CBs for inclusion in CUs. A CU can be coded as a prediction unit (PU) containing prediction data and / or a transform unit (TU) containing transformed residual data for the CU. The motion estimation component 221 generates motion vectors, PUs, and TUs by using rate distortion analysis as part of the 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. having the best rate distortion characteristics. The best rate distortion characteristics balance both the quality of video reconstruction (e.g., the amount of data loss due to compression) and the coding efficiency (e.g., the size of the final coding).

[0062] In some examples, the codec system 200 may calculate values of sub-integer pixel positions of reference pictures stored in the decoded picture buffer component 223. For example, the video codec system 200 may interpolate values of 1 / 4 pixel positions, 1 / 8 pixel positions, or other fractional pixel positions of the reference picture. Accordingly, the motion estimation component 221 may perform motion searches for full pixel positions and fractional pixel positions and output motion vectors with fractional pixel accuracy. The motion estimation component 221 calculates motion vectors for PUs of video blocks within an inter-coded slice by comparing the position of the PU to the position of a predicted block of the reference picture. The motion estimation component 221 outputs the calculated motion vectors as motion data to the header format and the CABAC component 231 for encoding and also outputs the motion vectors as motion to the motion compensation component 219.

[0063] Motion compensation performed by the motion compensation component 219 may include fetching or generating a predicted block based on the motion vector determined by the motion estimation component 221. Similarly, in some examples, the motion estimation component 221 and the motion compensation component 219 may be functionally integrated. When receiving a motion vector for a current video block's PU, the motion compensation component 219 may locate the predicted block pointed to by the motion vector. Then, a residual video block is formed by subtracting the pixel values of the predicted block from the pixel values of the currently coded video block, forming values of the pixel differences. Generally, 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 component and the luma component. The predicted block and the residual block are transferred to the transform scaling and quantization component 213.

[0064] The partitioned video signal 201 is also sent to the intra picture estimation component 215 and the intra picture prediction component 217. Similar to 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 perform intra prediction of the current block for blocks within the current frame, as opposed to the inter prediction performed by the motion estimation component 221 and the motion compensation component 219 between frames as described above. In particular, the intra picture estimation component 215 determines an intra prediction mode to use for encoding the current block. In some examples, the intra picture estimation component 215 selects an intra prediction mode appropriate for encoding the current block from a plurality of tested intra prediction modes. The selected intra prediction mode is then transferred to the header format and the CABAC component 231 for encoding.

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

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

[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 to generate a video block containing 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 transform the residual information from the pixel value domain to a transform domain such as the frequency domain. The transform scaling and quantization component 213 is also configured to scale the transformed residual information, for example, based on frequency. Such scaling includes applying scaling coefficients to the residual information such that different frequency information is quantized at different granularities, which may affect the final visual quality of the reconstructed video. The transform scaling and quantization component 213 is also configured to quantize the transform coefficients to further reduce the bitrate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be changed by adjusting the 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. The quantized transform coefficients are transferred to the header format and the CABAC component 231 for encoding in the 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, transform, and / or quantization to reconstruct the residual block in the pixel domain, for example, for later use as a reference block that can serve as a prediction block for other current blocks. The motion estimation component 221 and / or the motion compensation component 219 may calculate a reference block by adding the residual block back to the corresponding prediction block for use in motion estimation of later blocks / frames. A filter is applied to the reconstructed reference block to reduce artifacts created during scaling, quantization, and transformation. Such artifacts could otherwise cause inaccurate predictions (and create further artifacts) when subsequent blocks are predicted.

[0069] The filter control analysis component 227 and the in-loop filter component 225 apply a filter to the residual block and / or the reconstructed image block. For example, to reconstruct the original image block, 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. Then, the filter may be applied to the reconstructed image block. In some examples, the filter may alternatively be applied to the residual block. Similar to the other components in 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 filter applied to the reconstructed reference block is applied to a specific spatial region and includes a plurality of parameters for adjusting how such a filter is applied. The filter control analysis component 227 analyzes the reconstructed reference block to determine where such a filter should be applied and sets the corresponding parameters. Such data is transferred as filter control data for encoding to the header format and the CABAC component 231. The in-loop filter component 225 applies such a filter based on the filter control data. The filter may include a deblocking filter, a noise suppression filter, an SAO filter, and an adaptive loop filter. Such a filter may be applied in the spatial / pixel domain (e.g., the reconstructed pixel block) or in the frequency domain, depending on the example.

[0070] When operating as an encoder, the filtered reconstructed image block, residual block, and / or prediction block 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 transfers 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 prediction blocks, residual blocks, and / or reconstructed image blocks.

[0071] The header format and CABAC component 231 receive data from various components of the codec system 200 and encode such data into a coded bitstream for transmission to the decoder. Specifically, the header format and CABAC component 231 generate various headers to encode control data such as overall control data and filter control data. Further, 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 the 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), the definition of coding contexts for various blocks, an indication of the most likely intra prediction mode, an indication 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 partitioning 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 may be archived for later transmission or acquisition.

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

[0073] Specifically, the partitioned video signal 301 is transferred to an intra-picture prediction component 317 for intra prediction. The intra-picture prediction component 317 may be substantially the same as the intra-picture estimation component 215 and the intra-picture prediction component 217. The partitioned video signal 301 is also transferred to a motion compensation component 321 for inter prediction based on reference blocks in a decoded picture buffer component 323. The motion compensation component 321 may be substantially the same as the motion estimation component 221 and the motion compensation component 219. The prediction blocks and residual blocks from the intra-picture prediction component 317 and the motion compensation component 321 are transferred to a transform and quantization component 313 for transformation and quantization of the residual blocks. The transform and quantization component 313 may be substantially the same as the transform scaling and quantization component 213. The transformed and quantized residual blocks and the corresponding prediction blocks (along with associated control data) are transferred to an entropy coding component 331 for coding into a bitstream. The entropy coding component 331 may be substantially the same as the header format and CABAC component 231.

[0074] The transformed and quantized residual blocks and / or corresponding prediction blocks are also transferred from the transform and quantization component 313 to the inverse transform and quantization component 329 for reconstruction into reference blocks 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. Depending on the example, an in-loop filter within the in-loop filter component 325 is also applied to the residual blocks and / or the reconstructed reference blocks. 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 blocks are then stored in the decoded picture buffer component 323 for use as reference blocks by the motion compensation component 321. The decoded picture buffer component 323 may be substantially similar to the decoded picture buffer component 223.

[0075] FIG. 4 is a block diagram showing an exemplary video decoder 400. The video decoder 400 may be used to implement the decoding function of the codec system 200 and / or to implement steps 111, 113, 115, and / or 117 of the operation method 100. The decoder 400 receives, for example, a bitstream from the encoder 300 and generates an output video signal reconstructed 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 method such as CAVLC, CABAC, SBAC, PIPE coding or other entropy coding techniques. For example, the entropy decoding component 433 may use the header information to provide a context for interpreting further data encoded as codewords within the bitstream. The decoded information includes any desired information for decoding the video signal, such as overall control data, filter control data, partition information, motion data, prediction data, and quantized transform coefficients from residual blocks. The quantized transform coefficients are transferred to the inverse transform and quantization component 429 for reconstruction into residual blocks. 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 prediction block is transferred to the intra-picture prediction component 417 to reconstruct the image block based on the 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 a prediction mode to determine the reference block within the frame, applies the residual block to the result, and reconstructs the intra prediction image block. The reconstructed intra prediction image block and / or residual block and the corresponding inter prediction data are transferred to the decoded picture buffer component 423 via the in-loop filter component 425. The decoded picture buffer component 423 and the in-loop filter component 425 may be substantially similar to the decoded picture buffer component 223 and the in-loop filter component 225, respectively. The in-loop filter component 425 filters the reconstructed image block, residual block and / or prediction 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 transferred 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 uses the motion vector from the reference block to generate a prediction block, applies the residual block to the result, and reconstructs the image block. The resulting reconstructed block may also be transferred to the decoded picture buffer component 423 via the in-loop filter component 425. The decoded picture buffer component 423 continues to store further reconstructed image blocks, which can be reconstructed into a frame via partition information. Such a frame may also be placed in a sequence. The sequence is output to the display as the reconstructed output video signal.

[0078] FIG. 5 is a schematic diagram showing an exemplary 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 show an exemplary application for layers within 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. The inter-layer prediction 521 is applied between pictures 511, 512, 513, and 514 and pictures 515, 516, 517, and 518 in different layers. In the illustrated example, pictures 511, 512, 513, and 514 are part of layer N+1 532, and pictures 515, 516, 517, and 518 are part of layer N 531. Layers such as layer N 531 and / or layer N+1 532 are groups of pictures all related to the same values of characteristics such as similar size, quality, resolution, signal-to-noise ratio, capabilities, 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 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 to support decoding of video data, performing compliance 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, in this example, pictures 511, 512, 513, and 514 within layer N+1 532 have a larger picture size (e.g., greater height and width, and thus more samples) than pictures 515, 516, 517, and 518 within layer N 531. However, such pictures can be separated between layer N+1 532 and layer N 531 by other characteristics. Only two layers, namely layer N+1 532 and layer N 531, are shown, but a set of pictures can be separated into any number of layers based on the relevant characteristics. Layer N+1 532 and layer N 531 may also be indicated by a layer ID. The layer ID is an item of data associated with a picture and indicates that the picture is part of the layer in which it is shown. Thus, each of pictures 511 - 518 may be associated with a corresponding layer ID to indicate which of 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 for the layer containing the NAL unit (e.g., slices and / or parameters of pictures within the layer). Layers associated with lower quality / bitstream sizes, such as layer N 531, are generally assigned lower layer IDs and are called lower layers. Further, layers associated with higher quality / bitstream sizes, such as layer N+1 532, are generally assigned higher layer IDs and are called upper layers.

[0081] Pictures 511 to 518 within different layers 531 to 532 are configured to be displayed as options. As a specific example, if a smaller picture is desired, the decoder may decode and display picture 515 at the current display time, or if a larger picture is desired, the decoder may decode and display picture 511 at the current display time. Thus, pictures 511 to 514 in the upper layer N+1 532 contain substantially the same image data as the corresponding pictures 515 to 518 in the 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 picture data as picture 516, and so on.

[0082] Pictures 511 to 518 can be coded by referring to other pictures 511 to 518 within the same layer N 531 or N+1 532. Coding a picture by referring to other pictures within the same layer results in inter prediction 523. Inter prediction 523 is indicated by the solid arrows. For example, picture 513 may be coded by using inter prediction 523 with one or two of pictures 511, 512, and / or 514 within layer N+1 532 as references, where one picture is referred to for uni-directional inter prediction and / or two pictures are referred to for bi-directional inter prediction. Further, picture 517 may be coded by adopting inter prediction 523 with one or two of pictures 515, 516, and / or 518 within layer N 531 as references, where one picture is referred to for uni-directional inter prediction and / or two pictures are referred to for bi-directional inter prediction. When a picture is used as a reference for other pictures within the same layer when performing inter prediction 523, the picture may be called a reference picture. For example, picture 512 may be a reference picture used to code picture 513 according to inter prediction 523. Inter prediction 523 can 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 the indicated samples in a reference picture different from the current picture, where the reference picture and the current picture are in the same layer.

[0083] Pictures 511 to 518 can also be coded by referring to other pictures 511 to 518 in different layers. This process is known as inter-layer prediction 521 and is indicated by the dashed arrows. Inter-layer prediction 521 is a mechanism for coding samples of the current picture by referring to the indicated samples in the reference picture, where the current picture and the reference picture are in different layers and thus have different layer IDs. For example, a picture in the lower layer N 531 can be used as a reference picture for coding the corresponding picture in the upper layer N+1 532. As a specific example, picture 511 can be coded by referring to 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 restricted such that the current picture, like picture 511, can only use inter-layer reference pictures that are in the same AU as picture 515 and in a lower layer. An AU is a set of pictures related to a specific output time in a video sequence, and thus an AU can contain only one picture per layer. When multiple layers (e.g., more than two) are available, inter-layer prediction 521 can encode / decode the current picture based on multiple inter-layer reference pictures at a level lower than the current picture.

[0084] A video encoder can use a multi-layer video sequence 500 to encode pictures 511 - 518 via many different combinations and / or permutations of inter prediction 523 and inter-layer prediction 521. For example, picture 515 may be coded according to intra prediction. Then, pictures 516 - 518 can be coded according to inter prediction 523 by using picture 515 as a reference picture. Further, picture 511 may be coded according to inter-layer prediction 521 by using picture 515 as an inter-layer reference picture. Then, pictures 512 - 514 can 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 for different coding mechanisms. By coding a picture of the upper layer N+1 532 based on a picture of the lower layer N 531, the upper layer N+1 532 can avoid using intra prediction, which has a 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 minimum / lowest quality pictures and thus to coding the 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 an operation, layers such as layer N 531 and layer N+1 532 may be included in the OLS525. The OLS525 is a set of layers in which one or more layers are designated as output layers. The output layer is the layer designated for output (e.g., to a display). For example, layer N 531 may be included only to support the 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, the OLS525 includes layer N+1 532 as the output layer. The OLS525 may include many layers in different combinations. For example, the output layer within the OLS525 can be coded according to the inter-layer prediction 521 based on one, two, or many lower layers. Further, the OLS525 may include more than one output layer. Thus, the OLS525 may include one or more output layers and any support layers necessary to reconstruct the output layer. The multi-layer video sequence 500 can be coded by using many different OLS525s each using a different combination of layers.

[0086] As a specific example, the 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, etc. that are coded according to the inter-layer prediction 521. The video sequence may be coded for several scalable characteristics such as signal to noise ratio (SNR), frame rate, picture size, etc. Then, the OLS 525 can be created for each acceptable characteristic. For example, the OLS 525 for the first resolution may include only layer N 531, the OLS 525 for the second resolution may include layer N 531 and layer N+1 532, and the OLS for the third resolution may include layer N 531, layer N+1 532, layer N+2, etc. In this way, the OLS 525 can be transmitted to enable the decoder to decode any version of the multi-layer video sequence 500, regardless of the network conditions, hardware constraints, etc.

[0087] FIG. 6 is a schematic diagram showing an exemplary video sequence 600 having an OLS configured for multi-view scalability. The video sequence 600 is a specific example of the multi-layer video sequence 500. Thus, the video sequence 600 can be encoded by an encoder such as the codec system 200 and / or the encoder 300, for example, according to method 100, and decoded by a decoder such as the codec system 200 and / or the decoder 400. The video sequence 600 is useful for scalability.

[0088] The exemplary video sequence 600 includes OLSs 620, 621, and 622, which may be substantially the same as OLS 525. Although three OLSs are shown, any number of OLSs may be used. Each of the OLSs 620, 621, and 622 is referenced by an OLS index and includes one or more layers. Specifically, OLSs 620, 621, and 622 include layer 630, layer 630 and layer 631, and layers 630, 631, and 632, respectively. Layers 630, 631, and 632 may be substantially the same as layer N 531 and layer N+1 532. Layers 630, 631, and 632 are referenced by a layer index. The video sequence 600 includes the same number of layers as the number of OLSs. Specifically, OLS 620 having the lowest OLS index includes layer 630 having the lowest layer index. Each other OLS includes all the layers of the previous OLS having a lower OLS index plus one. For example, OLS 621 has a higher OLS index than OLS 620 and includes layers 630 and 631, which are all the layers of OLS 620 plus one. Similarly, OLS 622 has a higher OLS index than OLS 621 and includes layers 630, 631, and 632, which are all the layers of OLS 621 plus one. This pattern may continue until reaching the layer having the highest layer index and the OLS having the highest OLS index.

[0089] Furthermore, layer 630 is the base layer. All the other layers 631 and 632 are enhancement layers coded according to inter-layer prediction based on all the layers having lower layer indices. Specifically, layer 630 is the base layer and is not coded according to inter-layer prediction. Layer 631 is an enhancement layer coded according to inter-layer prediction based on layer 630. Furthermore, layer 632 is an enhancement layer coded according to inter-layer prediction based on layers 630 and 631. As a result, OLS620 will include layer 630 which has the lowest quality SNR and / or the smallest image size. Since OLS620 does not use any inter-layer prediction at all, OLS620 can be completely decoded without referring to any layer except layer 630. OLS621 includes layer 631 which has a higher quality SNR and / or image size than layer 630. Since OLS621 also includes layer 630, layer 631 can be completely decoded according to inter-layer prediction. Similarly, OLS622 includes layer 632 which has a higher quality SNR and / or image size than layers 630 and 631. Since OLS622 also includes layers 630 and 631, layer 632 can be completely decoded according to inter-layer prediction. Therefore, video sequence 600 is coded to scale for any pre-selected SNR and / or image size by sending the corresponding OLS622, 621 or 620 to the decoder. When more of OLS622, 621 and 620 are used, video sequence 600 can scale for more SNR image qualities and / or image sizes.

[0090] Therefore, video sequence 600 can support spatial scalability. Spatial scalability enables video sequence 600 to be coded into layers 630, 631, and 632 such that each OLS 620, 621, and 622 is arranged with layers 630, 631, and 632 containing sufficient data for decoding video sequence 600 into corresponding output screen sizes. Therefore, spatial scalability may include a set of layers (e.g., layer 630) for decoding video for a smartphone screen, a set of layers (e.g., layers 630, 631, 632) for decoding video for a large TV screen, and a set of layers (e.g., layers 630, 631) for intermediate screen sizes. SNR scalability enables video sequence 600 to be coded into layers 630, 631, and 632 such that each OLS 620, 621, and 622 is arranged with layers 630, 631, and 632 containing sufficient data for decoding video sequence 600 at different SNRs. Therefore, SNR scalability may include a set of layers (e.g., layer 630) that can be decoded for low-quality video, high-quality video (e.g., layers 630, 631, and 632), and various intermediate video qualities (e.g., layers 630 and 631) to support different network conditions.

[0091] The present disclosure provides efficient signaling to enable the accurate and efficient use of video sequence 600 having multiple layers. As an example, layers 630, 631, and 632 may all be designated as output layers. Then, the decoder can select and render layers 630, 631, and 632 as desired to realize multiple views. To support this realization method, the coding of video sequence 600 may be indicated according to the ols_mode_idc syntax element. For example, the ols_mode_idc syntax element may identify video sequence 600 as OLS mode 1. Thus, the ols_mode_idc syntax element can be set to 1 and transmitted in the bitstream to indicate that video sequence 600 is to be used. Thus, the decoder can receive any OLS and, based on ols_mode_idc, determine that the number of OLSs 620, 621, and 622 is the same as the number of layers 630, 631, and 632, and that the current OLS ID of i indicates that the current OLS includes a set of layers having IDs from 0 to i, and that all layers within the current OLS are output layers. Then, the decoder can decode and display layers 630, 631, and / or 632 from OLSs 620, 621, and / or 622 as desired to realize multiple views.

[0092] FIG. 7 is a schematic diagram showing an exemplary bitstream 700 including OLSs configured for multi-view scalability. For example, bitstream 700 can be generated by codec system 200 and / or encoder 300 for decoding by codec system 200 and / or decoder 400 according to method 100. Further, bitstream 700 may include coded multi-layer video sequence 500 and / or video sequence 600.

[0093] The bitstream 700 includes a VPS 711, one or more Sequence Parameter Sets (SPSs) 713, a plurality of picture parameter sets (PPSs) 715, a plurality of slice headers 717, and picture data 720. The VPS 711 includes data related to the overall bitstream 700. For example, the VPS 711 may include OLS, layer, and / or sublayer related to the data used in the bitstream 700. The SPS 713 includes sequence data common to all pictures within the coded video sequence included in the bitstream 700. For example, each layer may include one or more coded video sequences, and each coded video sequence may refer to the SPS 713 for corresponding parameters. The parameters within the SPS 713 can include picture size, bit depth, coding tool parameters, bitrate limits, and the like. Note that each sequence refers to the SPS 713, but in some examples, a single SPS 713 can include data for multiple sequences. The PPS 715 includes parameters applicable to the overall picture. Thus, each picture within the video sequence may refer to the PPS 715. Note that each picture refers to the PPS 715, but in some examples, a single PPS 715 can include data for multiple pictures. For example, multiple similar pictures may be coded according to similar parameters. In such cases, a single PPS 715 may include data for such similar pictures. The PPS 715 can indicate coding tools, quantization parameters, offsets, etc. available for slices within the corresponding picture.

[0094] Slice header 717 contains parameters specific to each slice 727 within picture 725. Thus, in a video sequence, there may be one slice header 717 per slice 727. The slice header 717 may include slice type information, POC, reference picture list, prediction weight, tile entry point, deblocking parameters, etc. In some examples, it should be noted that bitstream 700 may also include a picture header which is a syntax structure containing parameters applicable to all slices 727 within a single picture. For this reason, the picture header and slice header 717 may be used interchangeably in some contexts. For example, certain parameters may be moved between the slice header 717 and the picture header depending on whether such parameters are common to all slices 727 within picture 725.

[0095] 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 layer 723 of picture 725. Layer 723 may be organized into OLS 721. OLS 721 may be substantially similar to OLS 525, 620, 621 and / or 622. Specifically, OLS 721 is a set of layers 723 where one or more layers 723 are designated as output layers. When layer 723 includes multi-view video, all of layer 723 may be designated as output layers. For example, bitstream 700 may be coded to include several OLS 721 having video coded at different resolutions, frame rates, picture 725 sizes, etc. In response to a request by a decoder, a sub-bitstream extraction process can remove all but the requested OLS 721 from bitstream 700. The encoder can then transmit to the decoder a bitstream 700 containing only the requested OLS 721, and thus only the video satisfying the requested criteria.

[0096] Layer 723 may be substantially similar to layer N 531, layer N+1 532, and / or layers 631, 632 and / or 633. Layer 723 is generally a set of encoded pictures 725. Layer 723 may be formally defined as a set of VCL NAL units that share specified characteristics (e.g., common resolution, frame rate, image size, etc.) when decoded. Picture 725 may be coded as a set of VCL NAL units. Layer 723 also includes related non-VCL NAL units to support the decoding of VCL NAL units. The VCL NAL units of layer 723 may share a specific value of the exemplary layer ID, nuh_layer_id. Layer 723 may be a simulcast layer coded without inter-layer prediction, or layer 723 coded according to inter-layer prediction based on other layers.

[0097] Picture 725 is an array of luma samples and / or an array of chroma samples that creates a frame or a field thereof. For example, Picture 725 may be an output for display or a coded image that may be used to support the coding of other Picture 725s for output. Picture 725 may include a set of VCL NAL units. Picture 725 includes one or more slices 727. A slice 727 may be defined as an integer number of complete tiles of Picture 725 or an integer number of consecutive complete coding tree units (CTUs) (e.g., within a tile) that are exclusively included in a single NAL unit, specifically a VCL NAL unit. A slice 727 is further divided into CTUs and / or coding tree blocks (CTBs). A CTU is a group of samples of a predetermined size that can be partitioned by a coding tree. A CTB is a subset of a CTU and includes a luma component or a chroma component of the CTU. The CTU / CTB is further divided into coding blocks based on a coding tree. The coding blocks can then be encoded / decoded according to a prediction mechanism.

[0098] The present disclosure includes mechanisms for supporting spatial and / or SNR scalability for multi-view video, for example, by using video sequence 600. For example, VPS 711 may include ols_mode_idc 735. ols_mode_idc 735 is a syntax element that indicates information related to the number of OLSs 721, layer 723 of OLSs 721, and output layer 723 within OLSs 721. The output layer 723 is any layer specified to be output by the decoder, rather than simply being used for reference-based coding. ols_mode_idc 735 may be set to 0 or 2 for coding other types of video. ols_mode_idc 735 can be set to 1 for spatial and / or SNR scalability for multi-view video. For example, ols_mode_idc 735 can be set to 1 to indicate that the total number of OLSs 721 within the video sequence is equal to the total number of layers 723 specified by VPS 711, the i-th OLS 721 includes layers from 0 to i, and for each OLS 721, all layers included in OLS 721 are output layers. This set of conditions may describe video sequence 600 having any number of OLSs 721. The advantage of using ols_mode_idc 735 is that ols_mode_idc 735 provides bit savings. Decoders within the application system generally receive only a single OLS. However, ols_mode_idc 735 also provides bit savings in an encoded bitstream that includes multiple OLSs where much data is shared, thus providing savings at the streaming server and bandwidth savings for transmitting such a bitstream. Specifically, the advantage of setting ols_mode_idc 735 to 1 is to support use cases such as multi-view applications, where two or more views each represented by one layer are output and displayed simultaneously.

[0099] In some examples, VPS711 also includes a VPS maximum layer minus 1 (vps_max_layers_minus1) 737 syntax element. The vps_max_layers_minus1 737 is a syntax element that conveys the number of layers 723 specified by VPS700, and thus the maximum number of layers 723 allowed in the corresponding coded video sequence within bitstream 700. The ols_mode_idc735 may refer to the vps_max_layers_minus1 737 syntax element. For example, the ols_mode_idc735 may indicate that the total number of OLSs721 is equal to the number of layers 723 specified by vps_max_layers_minus1 737.

[0100] Furthermore, VPS711 may include each_layer_is_an_ols_flag733. each_layer_is_an_ols_flag733 is a syntax element that conveys whether each OLS721 within bitstream 700 contains a single layer 723. For example, when scalability is not used, each OLS721 may contain a single simulcast layer. Thus, each_layer_is_an_ols_flag733 can be set (e.g., to 0) to indicate that one or more OLS721s contain more than one layer 723 to support scalability. Thus, each_layer_is_an_ols_flag733 can be used to support scalability. For example, the decoder can inspect each_layer_is_an_ols_flag733 to determine that some of the OLS721s contain more than one layer 723. When each_layer_is_an_ols_flag733 is set to 0 and ols_mode_idc735 is set to 1 (or 0 when used in a different mode), the total number of OLSs (TotalNumOlss) can be set equal to vps_max_layers_minus1 737. TotalNumOlss is a variable used by both the decoder and the hypothetical reference decoder (HRD) in the encoder. TotalNumOlss is a variable used to store the number of OLS721s based on the data within bitstream 700. Then, TotalNumOlss can be used for decoding at the decoder or for bitstream 700 error inspection in the HRD at the encoder.

[0101] VPS711 may also include a VPS layer identifier (vps_layer_id[i]) 731 syntax element. vps_layer_id[i] 731 is an array that stores the layer ID (e.g., nuh_layer_id) of each layer. Thus, vps_layer_id[i] 731 indicates the layer ID of the i-th layer.

[0102] The decoder or HRD may use the data in the VPS711 to determine the configurations of OLS721 and layer 723. In a specific example, the number of layers in the i-th OLS (numLayersInOls[i]) and the layer ID in the OLS (LayerIdInOLS[i][j]) that specifies the nuh_layer_id value of the j-th layer in the i-th OLS are as follows, that is, NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1,i<TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i]=1 LayerIdInOls[i][0]=vps_layer_id[i] }else if(ols_mode_idc==0||ols_mode_idc==1){ NumLayersInOls[i]=i+1 for(j=0;j<NumLayersInOls[i];j++) LayerIdInOls[i][j]=vps_layer_id[j] derived as such, where vps_layer_id[i] is the i-th VPS layer identifier, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a flag indicating whether each layer is an OLS, specifying whether at least one OLS contains more than one layer.

[0103] The data within VPS711 can be used to support SNR and / or spatially scalable layers 723 that include multi-view video. The layer 723 can be encoded and can be included in OLS721. The encoder can transmit a bitstream 700 including the required OLS721 and VPS711 to a decoder. Then, the decoder can use the information within VPS711 to accurately decode the layer 723 within OLS721. This approach supports coding efficiency while supporting scalability. Specifically, the decoder can quickly determine the number of layers 723 within OLS721, determine that all layers within OLS721 are output layers, and decode the output layers according to inter-layer prediction. Then, the decoder can select the output layers to be rendered to achieve multi-view. Thus, the decoder may receive the layer 723 necessary to decode the views for multi-view, and the decoder can decode and display pictures 725 from the layer 723 as desired. In this way, the total number of encoded layers 723 may not affect the decoding process, and one or more of the above errors can be avoided. Thus, the disclosed mechanism improves the functions of the encoder and / or decoder. Further, the disclosed mechanism can reduce the bitstream size and thus reduce the processor, memory, and / or network resource utilization in both the encoder and decoder.

[0104] The above information will be described in more detail here. Hierarchical video coding is also referred to as scalable video coding or video coding with scalability. Scalability in video coding may be supported by using multi-layer coding techniques. A multi-layer bitstream includes a base layer (BL) and one or more enhancement layers (EL). Examples of scalability include spatial scalability, quality / signal-to-noise ratio (SNR) scalability, multi-view scalability, frame rate scalability, etc. When multi-layer coding techniques are used, a picture or a part thereof may be coded without using a reference picture (intra prediction), may be coded by referring to a reference picture in the same layer (inter prediction), and / or may be coded by referring to a reference picture in another layer (inter-layer prediction). A reference picture used for inter-layer prediction of the current picture is called an inter-layer reference picture (ILRP). FIG. 5 shows an example of multi-layer coding for spatial scalability where pictures in different layers have different resolutions.

[0105] Some video coding families provide support for scalability in a profile separate from the profile 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, a flag is transmitted for each macroblock (MB) in the EL picture to indicate whether the EL MB is predicted using the block at the same position from the lower layer. Prediction from the block at the same position may include texture, motion vectors, and / or coding modes. The implementation of SVC may not directly reuse the implementation of unmodified AVC in these designs. The SVC EL macroblock syntax and decoding process are different from the AVC syntax and decoding process.

[0106] Scalable HEVC (SHVC) is an extension of HEVC that provides support for spatial and quality scalability. Multiview HEVC (MV-HEVC) is an extension of HEVC that provides support for multiview scalability. 3D HEVC (3D-HEVC) is an extension of HEVC that provides support for 3D video coding that is more advanced and efficient than MV-HEVC. Temporal scalability may be included as an essential part of a single-layer HEVC codec. In the multi-layer extension of HEVC, the decoded pictures used for inter-layer prediction are derived only from the same access unit and are treated as long-term reference pictures (LTRPs). Such pictures are assigned reference indices within the reference picture list together with other temporal reference pictures within 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 the inter-layer reference picture within the reference picture list. Spatial scalability resamples the reference picture or a part thereof when the ILRP has a different spatial resolution from the current picture being encoded or decoded. Resampling of the reference picture can be achieved either at the picture level or at the coding block level.

[0107] VVC may also support hierarchical video coding. The VVC bitstream can include multiple layers. The layers can all be independent of each other. For example, each layer can be coded without using inter-layer prediction. In this case, the layer is also called a simulcast layer. In some cases, some of the layers are coded using ILP. The flag in the VPS can indicate whether the layer is a simulcast layer or whether some layers use ILP. When some layers use ILP, the layer dependency between the layers is also signaled in the VPS. Different from SHVC and MV-HEVC, VVC may not need to specify an OLS. The OLS includes a specified set of layers, and one or more layers in the set of layers are specified as output layers. The output layer is the layer of the OLS that is output. In some implementations of VVC, when the 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. Further, a specific layer among the layers is specified as the output layer. The output layer may be indicated as only the highest layer, all layers, or the set of lower layers indicated by the highest layer.

[0108] The above aspects include certain problems. In some video coding systems, when inter-layer prediction is used, it is specified that the entire bitstream and all layers are decoded, and a specific layer within the layers is designated as the output layer. The output layer may be indicated as only the highest layer, all layers, or all layers including a set of lower layers indicated by the highest layer. To simplify the description of the problem, two layers may be used by a higher layer that uses a lower layer for inter-layer prediction reference. For multi-view scalability, the system should specify the use of only the lower layer (decoding and output of only the lower layer). The system should also specify the use of both layers (decoding and output of both layers). Unfortunately, this is not possible in some video coding systems.

[0109] Generally, the present disclosure describes a method for simple and efficient signaling of an output layer set (OLS) for multi-view scalability. The description of the technology is based on VVC by ITU-T and ISO / IEC's JVET. However, the technology also applies to hierarchical video coding based on other video codec specifications.

[0110] One or more of the above problems may be solved as follows. Specifically, the present disclosure includes a simple and efficient method for signaling of OLS for spatial and SNR scalability. A video coding system may use a VPS to indicate that some layers use ILP, the total number of OLSs specified by the VPS is equal to the number of layers, the i-th OLS includes layers with layer indices from 0 to i, and for each OLS, only the highest layer within the OLS is output.

[0111] An exemplary implementation of the above mechanism is as follows. The syntax of an exemplary video parameter set is as follows. [Table 1] TIFF2025089317000003.tif192170

[0112] The semantics of an exemplary video parameter set are as follows. The VPS RBSP should be made available for the decoding process before being referenced, should be included in at least one access unit having a TemporalId equal to 0, or should be provided through an external mechanism. The VPS NAL unit containing the VPS RBSP should have a nuh_layer_id equal to vps_layer_id[0]. All VPS NAL units having a specific value of vps_video_parameter_set_id within a CVS should have the same content. The vps_video_parameter_set_id provides an identifier for the VPS for reference by other syntax elements. One plus vps_max_layers_minus1 specifies the maximum allowable number of layers within each CVS that references the VPS. One plus vps_max_sub_layers_minus1 specifies the maximum number of temporal sub-layers that can exist in each CVS that references the VPS. The value of vps_max_sub_layers_minus1 should be in the range of 0 to 6 inclusive.

[0113] The vps_all_independent_layers_flag may be set equal to 1 to specify that all layers within the CVS are coded independently without using inter-layer prediction. The vps_all_independent_layers_flag may be set equal to 0 to specify that one or more of the layers within the CVS may use inter-layer prediction. When it does not exist, the value of the vps_all_independent_layers_flag is assumed to be equal to 1. When the vps_all_independent_layers_flag is equal to 1, the value of vps_independent_layer_flag[i] is assumed to be equal to 1. When the vps_all_independent_layers_flag is equal to 0, the value of vps_independent_layer_flag[0] is assumed to be equal to 1. 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]. The 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. The vps_independent_layer_flag[i] may be set equal to 0 to specify that the layer with index i may use inter-layer prediction and that vps_layer_dependency_flag[i] exists in the VPS. When it does not exist, the value of vps_independent_layer_flag[i] is assumed to be equal to 1.

[0114] 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 for 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 for the layer with index i. When vps_direct_dependency_flag[i][j] does not exist for i and j in the range of 0 or more and vps_max_layers_minus1 or less, vps_direct_dependency_flag[i][j] is presumed to be equal to 0. The variable DirectDependentLayerIdx[i][j] that specifies the j-th direct dependent layer of the i-th layer is derived as follows, that is, 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 as follows.

[0115] The variable GeneralLayerIdx[i] that specifies the layer index of the layer having nuh_layer_id equal to vps_layer_id[i] is derived as follows, that is, for(i = 0; i <= vps_max_layers_minus1; i++) GeneralLayerIdx[vps_layer_id[i]] = i as follows.

[0116] 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 itself within the bitstream is an output layer set, by virtue of a single included layer being the output layer only. each_layer_is_an_ols_flag may be set equal to 0 to specify that the output layer set may contain more than one layer. If vps_max_layers_minus1 is equal to 0, the value of each_layer_is_an_ols_flag is presumed 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 presumed to be equal to 0.

[0117] 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, and for each OLS, only the highest layer within 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, 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 is explicitly communicated, and for each OLS, the highest layer within the OLS and the set of explicitly communicated lower layers are output. The value of ols_mode_idc should be in the range from 0 to 2 inclusive. The value 3 of 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, the value of ols_mode_idc is presumed to be equal to 2.

[0118] Adding 1 to num_output_layer_sets_minus1 specifies the total number of OLSs specified by the VPS when ols_mode_idc is equal to 2. The variable TotalNumOlss that specifies the total number of OLSs specified by the VPS is derived as follows, that is, 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 is derived as follows.

[0119] When ols_mode_idc is equal to 2, layer_included_flag[i][j] specifies whether the j-th layer (for example, the layer with nuh_layer_id equal to vps_layer_id[j]) is included in the i-th OLS. layer_included_flag[i][j] may be set equal to 1 to specify that the j-th layer is included in the i-th OLS. layer_included_flag[i][j] may be set equal to 0 to specify that the j-th layer is not included in the i-th OLS.

[0120] The variable NumLayersInOls[i] that specifies the number of layers in the i-th OLS and the variable LayerIdInOls[i][j] that specifies the nuh_layer_id value of the j-th layer in the i-th OLS are derived as follows, that is, NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i = 1; i < TotalNumOlss; i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i] = 1 LayerIdInOls[i][0] = vps_layer_id[i] } else if(ols_mode_idc == 0 || ols_mode_idc == 1){ NumLayersInOls[i] = i + 1 for(j = 0; j < NumLayersInOls[i]; j++) LayerIdInOls[i][j] = vps_layer_id[j] } else if(ols_mode_idc == 2){ for(k = 0, j = 0; k <= vps_max_layers_minus1; k++) if(layer_included_flag[i][k]) LayerIdInOls[i][j++] = vps_layer_id[k] NumLayersInOls[i] = j } } It may be derived as follows.

[0121] The variable OlsLayeIdx[i][j] that specifies the OLS layer index of the layer having nuh_layer_id equal to LayerIdInOls[i][j] may be derived as follows, that is, for(i = 0; i < TotalNumOlss; i++) for j = 0; j < NumLayersInOls[i]; j++) OlsLayeIdx[i][LayerIdInOls[i][j]] = j It may be derived as follows.

[0122] The lowest layer within each OLS should be an independent layer. In other words, for each i in the range from 0 to TotalNumOlss - 1, the value of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]] should be equal to 1. Each layer may be included in at least one OLS specified by the VPS. In other words, for each layer having a specific value of nuh_layer_id (for example, nuhLayerId is equal to one of vps_layer_id[k] for k in the range from 0 to vps_max_layers_minus1), there should exist at least one pair of values of i and j, where i is in the range from 0 to TotalNumOlss - 1 and j is in the range including NumLayersInOls[i] - 1, such that the value of LayerIdInOls[i][j] is equal to nuhLayerId. Any layer within an OLS shall be considered as the output layer of the OLS or a (direct or indirect) reference layer to the output layer of the OLS.

[0123] vps_output_layer_flag[i][j] specifies whether the j-th layer within the i-th OLS is output when ols_mode_idc is equal to 2. vps_output_layer_flag[i] may be set equal to 1 to specify that the j-th layer within the i-th OLS is output. vps_output_layer_flag[i] may be set equal to 0 to specify that the j-th layer within the i-th OLS is not output. When vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, the value of vps_output_layer_flag[i] can be presumed to be equal to 1.

[0124] The variable OutputLayerFlag[i][j], where the value 1 specifies that the j-th layer within the i-th OLS is output and the value 0 specifies that the j-th layer within the i-th OLS is not output, is as follows, that is, 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] } It may be derived as follows.

[0125] The 0th OLS includes only the lowest layer (e.g., the layer having the nuh_layer_id equal to vps_layer_id[0]), and for the 0th OLS, only the included layers are output. The vps_constraint_info_present_flag may be set equal to 1 to specify that the general_constraint_info() syntax structure exists in the VPS. The vps_constraint_info_present_flag may be set equal to 0 to specify that the general_constraint_info() syntax structure does not exist in the VPS. The vps_reserved_zero_7bits should be equal to 0 in a compliant bitstream. Other values for vps_reserved_zero_7bits are reserved. The decoder should ignore the value of vps_reserved_zero_7bits.

[0126] The general_hrd_params_present_flag may be set equal to 1 to indicate 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. The general_hrd_params_present_flag may be set equal to 0 to indicate 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 operating at a frequency of time_scale Hertz (Hz) corresponding to one increment of a clock tick counter (referred to as a clock tick). num_units_in_tick should be greater than 0. The clock tick in seconds is equal to the quotient of 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, and as a result, the clock tick may be equal to 0.04 seconds.

[0127] The time_scale is the number of time units that elapse in one second. For example, a time coordinate system that measures time using a 27 megahertz (MHz) clock has a time_scale of 27000000. The value of time_scale should be greater than 0. The vps_extension_flag may be set equal to 0 to specify that the vps_extension_data_flag syntax element does not exist in the VPS RBSP syntax structure. The 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. The vps_extension_data_flag may have any value. The presence and value of vps_extension_data_flag do not affect the decoder's compliance with the profile. A compliant decoder should ignore all vps_extension_data_flag syntax elements.

[0128] FIG. 8 is a schematic diagram of an exemplary video coding device 800. The video coding device 800 is suitable for implementing the examples / embodiments of the disclosure as described herein. The video coding device 800 includes a transceiver unit (Tx / Rx) 810 that includes a downstream port 820, an upstream port 850, and / or a transmitter and / or receiver for communicating data upstream and / or downstream over a network. The video coding device 800 also includes a processor 830 that includes 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-to-electrical (OE) components, electrical-to-optical (EO) components, and / or wireless communication components coupled to the upstream port 850 and / or the downstream port 820 for communication of data over an electrical, optical, or wireless communication network. The video coding device 800 may also include an input and / or output (I / O) device 860 for communicating data to and from a user. The I / O device 860 may include output devices such as a display for displaying video data, a speaker for outputting audio data, etc. The I / O device 860 may also include input devices such as a keyboard, a mouse, a trackball, etc., and / or corresponding interfaces for interacting with such output devices.

[0129] Processor 830 is implemented by hardware and software. 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). Processor 830 communicates with downstream port 820, Tx / Rx 810, upstream port 850, and memory 832. Processor 830 includes a coding module 814. Coding module 814 implements embodiments of the disclosure described herein, such as methods 100, 900, and 1000, which may use multi-layer video sequence 500, video sequence 600, and / or bitstream 700. Coding module 814 may also implement any other method / mechanism described herein. Further, coding module 814 may implement codec system 200, encoder 300, and / or decoder 400. For example, coding module 814 may be used to code a video sequence into layers and / or OLSs to support multi-view scalability. For example, coding module 814 may encode and / or decode the ols_mode_idc syntax element into / from the VPS in the bitstream. The ols_mode_idc syntax element can indicate that the total number of OLSs in the video sequence is equal to the total number of layers specified by the VPS, the i-th OLS includes layers from 0 to i, and all layers within the OLS are output for each OLS. Thus, coding module 814 may use the ols_mode_idc syntax element to indicate / determine that all layers received from scalable video can be decoded and displayed as desired to implement multi-view video.Therefore, when coding video data, the coding module 814 enables the video coding device 800 to have additional functions and / or coding efficiency. Therefore, the coding module 814 improves the functions of the video coding device 800 and addresses problems specific to the video coding field. Further, the coding module 814 causes the video coding device 800 to transition to different states. Alternatively, the coding module 814 can 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).

[0130] The memory 832 includes one or more memory types such as disks, tape drives, solid state drives, read only memory (ROM), random access memory (RAM), flash memory, ternary content-addressable memory (TCAM), static random-access memory (SRAM), etc. The memory 832 may be used as an overflow data storage device to store such programs when a program is selected for execution and to store instructions and data read during program execution.

[0131] FIG. 9 is a flowchart of an exemplary method 900 for encoding a video sequence having an OLS configured for multi-view scalability, such as the multi-layer video sequence 500 and / or the video sequence 600 within the bitstream 700. The method 900 may be used by an encoder such as the codec system 200, the encoder 300, and / or the video coding device 800 when executing the method 100.

[0132] Method 900 may begin when an encoder receives a video sequence and determines to encode the video sequence as a scalable multi-view video sequence within a layer set and OLS, for example, based on user input. The video sequence may be configured to support multi-views and may be coded to support SNR scalability, spatial scalability, scalability due to other characteristics described herein, or combinations thereof. In step 901, the encoder may encode a bitstream that includes one or more OLSs that include one or more layers of the coded picture. For example, the layers may include a base layer having the lowest layer ID and various enhancement layers having increasing layer IDs. Each enhancement layer having a layer ID of j may be coded according to inter-layer prediction based on the base layer and any enhancement layer having a layer ID less than j. The OLS may include an OLS ID, which may be indicated by i to distinguish it from the layer ID of j. For example, there may be one OLS per layer. Thus, the OLS having an OLS ID of i may include an output layer having a layer ID of j, where i is equal to i. The OLS having an OLS ID of i may also include all layers having layer IDs from 0 to j-1. In this example, all layers may be set as output layers. As an example, the OLS having an OLS ID of 5 may include layers 0 to 5, and each layer is indicated as an output layer.

[0133] In step 903, the encoder encodes the VPS into a bitstream. The OLS and layer configuration may be indicated by the VPS. The VPS includes the ols_mode_idc syntax element. The ols_mode_idc can be set to specify that the total number of OLSs specified by the VPS is equal to the number of layers specified by the VPS. Further, the ols_mode_idc can be set to specify that the i-th OLS includes layers having layer indices greater than or equal to 0 and i and / or j (e.g., in this case, i is equal to j) or less. The ols_mode_idc may also be set to specify that for each OLS, all layers within each OLS are output layers. For example, the ols_mode_idc may be set to one of several modes. When the ols_mode_idc is set to 1, the above mode may be transmitted. In some examples, the VPS may also include vps_max_layers_minus1 that specifies the number of layers specified by the VPS. This is also the maximum allowable number of layers within each CVS that refers to the VPS. The ols_mode_idc may refer to vps_max_layers_minus1.

[0134] As an example, the video sequence can be decoded in a hypothetical reference decoder (HRD) in the decoder and / or encoder for standard verification purposes. When decoding the video sequence, the variable of the total number of OLSs (TotalNumOlss) for the video sequence can be set equal to vps_max_layers_minus1 plus 1 when each_layer_is_an_ols_flag in the VPS is set to 0, when ols_mode_idc is set to 0, or when ols_mode_idc is set to 1. As a specific example, the number of layers (NumLayersInOls[i]) within the i-th OLS and the layer ID (LayerIdInOLS[i][j]) within the OLS that specifies the nuh_layer_id value of the j-th layer within the i-th OLS are as follows, that is, NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1,i<TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i]=1 LayerIdInOls[i][0]=vps_layer_id[i] }else if(ols_mode_idc==0||ols_mode_idc==1){ NumLayersInOls[i]=i+1 for(j=0;j<NumLayersInOls[i];j++) LayerIdInOls[i][j]=vps_layer_id[j] It can be derived as follows, where vps_layer_id[i] is the i-th VPS layer identifier, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a flag indicating whether each layer is an OLS, specifying whether at least one OLS contains more than one layer. Given the OLS ID and the output layer ID, the HRD in the encoder can start decoding the coded pictures in the output layer by using inter-layer prediction to perform a compliance check to ensure that the video conforms to the standard.

[0135] In step 905, the encoder can store the bitstream for communicating to the decoder. For example, the decoder may recognize the OLS available (e.g., via other protocols such as dynamic adaptive streaming over hypertext transfer protocol (DASH) for communication and / or hypertext transfer protocol). The decoder can select and request the OLS with the highest ID that can be properly decoded / displayed by the decoder. For example, in the case of spatial scalability, the decoder can request the OLS having the multi-view video and picture size related to the screen connected to the decoder. In the case of SNR scalability, the decoder can request the highest ID OLS having the multi-view video that can be decoded in light of the current network conditions (e.g., in light of the available communication bandwidth). Then, the encoder and / or the intermediate cache or content server can transmit the OLS and the related layer to the decoder for decoding. Thus, the encoder can create a multi-view video sequence that can be scaled up or down based on the needs of the decoder.

[0136] FIG. 10 is a flowchart of an exemplary method 1000 for decoding a video sequence including an OLS configured for multi-view scalability, such as multi-layer video sequence 500 and / or video sequence 600 within bitstream 700. Method 1000 may be used by a decoder such as codec system 200, decoder 400, and / or video coding device 800 when executing method 100.

[0137] Method 1000 may start when a decoder begins to receive a bitstream including an OLS having a set of layers of a scalable multi-view video sequence, for example, as a result of Method 900. The video sequence may be coded to support SNR scalability, spatial scalability, scalability by other characteristics described herein, or combinations thereof. In step 1001, the decoder can receive a bitstream including the OLS and the VPS. For example, the OLS may include one or more layers of coded pictures. The layers may include a base layer having the lowest layer ID and various enhancement layers having increasing layer IDs. Each enhancement layer having a layer ID of j may be coded according to inter-layer prediction based on the base layer and any enhancement layer having a layer ID less than j. The OLS may include an OLS ID, which may be indicated by i to distinguish it from the layer ID of j. For example, there may be one OLS per coded bitstream per layer. Thus, the OLS having an OLS ID of i may include an output layer having a layer ID of j, where i is equal to i. The OLS received with an OLS ID of i may also include all layers having layer IDs from 0 to j - 1. In this example, all layers may be set as output layers. As an example, the received OLS having an OLS ID of 5 may include layers 0 to 5, and each layer is indicated as an output layer. The configuration of the OLS and the layers may be indicated by the VPS.

[0138] For example, the VPS includes an ols_mode_idc syntax element. The ols_mode_idc can be set to specify that the total number of OLSs specified by the VPS is equal to the number of layers specified by the VPS. Further, the ols_mode_idc can be set to specify that the i-th OLS includes layers having layer indices greater than or equal to 0 and less than or equal to i and / or j (for example, in this case, i is equal to j). The ols_mode_idc may also be set to specify that for each OLS, all layers within each OLS are output layers. For example, the ols_mode_idc may be set to one of several modes. When the ols_mode_idc is set to 1, the above mode may be transmitted. In some examples, the VPS may also include a vps_max_layers_minus1 that specifies the number of layers specified by the VPS. This is also the maximum allowable number of layers within each CVS that refers to the VPS. The ols_mode_idc may refer to the vps_max_layers_minus1.

[0139] In step 1003, the decoder can determine the output layer based on the ols_mode_idc in the VPS. As a specific example, when determining the configuration of a video sequence, the variable of the total number of OLSs (TotalNumOlss) for the video sequence can be set to be equal to vps_max_layers_minus1 plus 1 when each_layer_is_an_ols_flag in the VPS is set to 0, when the ols_mode_idc is set to 0, or when the ols_mode_idc is set to 1. As a specific example, the number of layers in the i-th OLS (NumLayersInOls[i]) and the layer ID within the OLS that specifies the nuh_layer_id value of the j-th layer in the i-th OLS (LayerIdInOLS[i][j]) are as follows, that is, NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i = 1; i < TotalNumOlss; i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i]=1 LayerIdInOls[i][0]=vps_layer_id[i] } else if(ols_mode_idc == 0 || ols_mode_idc == 1){ NumLayersInOls[i]=i + 1 for(j = 0; j < NumLayersInOls[i]; j++) LayerIdInOls[i][j]=vps_layer_id[j] It can be derived as follows, where vps_layer_id[i] is the identifier of the i-th VPS layer, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a flag indicating whether each layer is an OLS, specifying whether at least one OLS contains more than one layer.

[0140] In step 1005, using the ID of the output layer, the decoder can decode the coded picture from the output layer and generate the decoded picture. For example, the decoder can use inter-layer prediction to decode all of the output layers and decode the upper layers based on the lower layers as desired. The decoder can also select layers to implement multi-view. In step 1007, the decoder can transfer the decoded picture for display as part of the decoded video sequence. For example, the decoder can transfer the decoded picture from the first layer for display on the first screen (or a part thereof), and transfer the picture from the second layer set for display on the second screen (or a part thereof).

[0141] As a specific example, the decoder may recognize OLSs available (e.g., via other protocols such as dynamic adaptive streaming over hypertext transfer protocol (DASH) over communication and / or hypertext transfer protocol). The decoder can select and request the OLS with the highest ID that can be properly decoded / displayed by the decoder. For example, in the case of spatial scalability, the decoder can request an OLS having a picture size related to the screen connected to the decoder. In the case of SNR scalability, the decoder can request the highest ID OLS that can be decoded in light of the current network conditions (e.g., in light of the available communication bandwidth). Then, the encoder and / or the intermediate cache or content server can transmit the OLS and related layers to the decoder for decoding to support multi-view. Accordingly, the encoder can create a multi-view video sequence that can be scaled up or down based on the needs of the decoder. Then, the decoder can decode the received video sequence as required when using method 1000.

[0142] FIG. 11 is a schematic diagram of an exemplary system 1100 for coding a video sequence having OLSs configured for multi-view scalability, such as multi-layer video sequence 500 and / or video sequence 600 within bitstream 700. System 1100 may be implemented by an encoder and decoder such as codec system 200, encoder 300, decoder 400, and / or video coding device 800. Further, system 1100 may be used when implementing methods 100, 900, and / or 1000.

[0143] System 1100 includes a video encoder 1102. The video encoder 1102 includes an encoding module 1105 for encoding a bitstream including one or more OLSs including one or more layers of coded pictures. Further, the encoding module 1105 is for encoding a VPS into the bitstream, and the VPS includes an ols_mode_idc that specifies that all layers within each OLS are output layers for each OLS. The video encoder 1102 further includes a storage module 1106 for storing the bitstream for communication to a decoder. The video encoder 1102 further includes a transmission module 1107 for transmitting the bitstream towards a video decoder 1100. The video encoder 1102 may be further configured to execute any of the steps of method 900.

[0144] System 1100 also includes a video decoder 1110. The video decoder 1110 includes a receiving module 1111 for receiving a bitstream including OLSs and a VPS, where the OLSs include one or more layers of coded pictures and the VPS includes an ols_mode_idc that specifies that all layers within each OLS are output layers for each OLS. The video decoder 1100 further includes a determination module 1113 for determining output layers based on the ols_mode_idc within the VPS. The video decoder 1110 further includes a decoding module 1115 for decoding coded pictures from the output layers and generating decoded pictures. The video decoder 1110 further includes a transfer module 1115 for transferring the decoded pictures for display as part of a decoded video sequence. The video decoder 1110 may be further configured to execute any of the steps of method 1000.

[0145] The first component is directly coupled to the second component when there is no intervening component other than a line, trace, or other medium between the first component and the second component. The first component is indirectly coupled to the second component when there is an intervening component other than a line, trace, or other medium between the first component and the second component. The term "coupled" and its variations include both being directly coupled and being indirectly coupled. The use of the term "about" means a range that includes ±10% of the subsequent number, unless otherwise specified.

[0146] It should also be understood that the steps of the exemplary methods described herein need not necessarily be performed in the order described, and that the order of such method steps is to be regarded merely as exemplary. Similarly, in methods consistent with various embodiments of the present disclosure, additional steps may be included in such methods, certain steps may be omitted, or steps may be combined.

[0147] Although several embodiments are provided in the present disclosure, it can 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 present disclosure. This example is to be considered illustrative and not restrictive, and its intention is not to be limited to the details given herein. For example, various elements or components may be combined or integrated into other systems, or certain features may be omitted or not implemented.

[0148] Furthermore, the technologies, systems, subsystems, and methods described and illustrated as separate or discrete in various embodiments may be combined or integrated with other systems, components, technologies, or methods without departing from the scope of the present disclosure. Other examples of modifications, substitutions, and changes can be elucidated by those skilled in the art and may be made without departing from the spirit and scope disclosed herein.

Claims

1. A method implemented by a decoder, the method comprising: receiving, by a receiver of the decoder, a bitstream including an output layer set (OLS) and a video parameter set (VPS), the OLS including one or more layers of a coded picture, the VPS including an OLS mode identification code (ols_mode_idc) that specifies, for each OLS, that all layers in the each OLS are output layers; determining, by a processor of the decoder, the output layer based on the ols_mode_idc in the VPS; decoding, by the processor of the decoder, the coded pictures from the output layer to generate decoded pictures; The method includes:

2. The method of claim 1 , wherein the ols_mode_idc specifies that a total number of OLSs specified by the VPS is equal to a number of layers specified by the VPS.

3. The method of claim 1 or 2, wherein the ols_mode_idc specifies that the i-th OLS includes layers having layer indices 0 to i, inclusive.

4. The method of claim 1 , wherein ols_mode_idc is equal to 1.

5. 5. The method of claim 1, wherein the VPS includes a VPS max layers minus 1 (vps_max_layers_minus1) that specifies the number of layers specified by the VPS, which is the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS.

6. 6. The method of claim 1, wherein the total number of OLSs (TotalNumOlss) is equal to vps_max_layers_minus1 plus 1 when the ols_mode_idc is equal to 0 or when the ols_mode_idc is equal to 1.

7. The number of layers in the ith OLS (NumLayersInOls [i]) and a Network Abstraction Layer (NAL) unit header layer identifier (nuh_layer_id) value (LayerIdInOLS[i]) of the jth layer in the ith OLS. [i][j]) is expressed as follows, i.e. NumLayersInOls[0] = 1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1,i <TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i] = 1 LayerIdInOls[i][0]=vps_layer_id[i] }else if(ols_mode_idc==0||ols_mode_idc==1){ NumLayersInOls[i]=i+1 for(j=0;j <NumLayersInOls[i];j++) LayerIdInOls[i][j]=vps_layer_id[j] where vps_layer_id[i] is the i-th VPS layer identifier, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a each layer is an OLS flag specifying whether at least one OLS contains more than one layer.

8. 1. A method implemented by an encoder, the method comprising: encoding, by a processor of the encoder, a bitstream including one or more output layer sets (OLS) including one or more layers of the coded picture; encoding, by the processor, a video parameter set (VPS) into the bitstream, the VPS including an output layer set (OLS) mode identification code (ols_mode_idc) that specifies, for each OLS, that all layers in the each OLS are output layers; storing, by a memory coupled to the processor, the bitstream for communication to a decoder; The method includes:

9. The method of claim 8 , wherein the ols_mode_idc specifies that a total number of OLSs specified by the VPS is equal to a number of layers specified by the VPS.

10. The method of claim 8 or 9, wherein the ols_mode_idc specifies that the i-th OLS includes layers with layer indices 0 to i, inclusive.

11. The method according to claim 8 , wherein ols_mode_idc is equal to 1.

12. 12. The method of claim 8, wherein the VPS includes a VPS max layers minus 1 (vps_max_layers_minus1) that specifies the number of layers specified by the VPS, which is the maximum allowable number of layers in each coded video sequence (CVS) that references the VPS.

13. 13. The method of claim 8, wherein the total number of OLSs (TotalNumOlss) is equal to vps_max_layers_minus1 plus 1 when the ols_mode_idc is equal to 0 or when the ols_mode_idc is equal to 1.

14. The number of layers in the ith OLS (NumLayersInOls [i]) and a Network Abstraction Layer (NAL) unit header layer identifier (nuh_layer_id) value (LayerIdInOLS[i]) of the jth layer in the ith OLS. [i][j]) is expressed as follows, i.e. NumLayersInOls[0] = 1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1,i <TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i] = 1 LayerIdInOls[i][0]=vps_layer_id[i] }else if(ols_mode_idc==0||ols_mode_idc==1){ NumLayersInOls[i]=i+1 for(j=0;j <NumLayersInOls[i];j++) LayerIdInOls[i][j]=vps_layer_id[j] where vps_layer_id[i] is the i-th VPS layer identifier, TotalNumOlss is the total number of OLSs specified by the VPS, and each_layer_is_an_ols_flag is a each layer is an OLS flag specifying whether at least one OLS contains more than one layer.

15. 1. A video coding device comprising: a processor; a receiver coupled to the processor; a memory coupled to the processor; and a transmitter coupled to the processor, A video coding device, wherein the processor, receiver, memory and transmitter are configured to perform the method of any one of claims 1 to 14.

16. A non-transitory computer-readable medium containing a computer program product for use by a video coding device, comprising: A non-transitory computer-readable medium, the computer program product comprising computer-executable instructions stored on the non-transitory computer-readable medium, the computer program product, when executed by a processor, causing the video coding device to perform the method of any one of claims 1 to 14.

17. A decoder comprising: receiving means for receiving a bitstream including an output layer set (OLS) and a video parameter set (VPS), the OLS including one or more layers of a coded picture, the VPS including an OLS mode identification code (ols_mode_idc) for each OLS that specifies that all layers in each OLS are output layers; A determining means for determining the output layer based on the ols_mode_idc in the VPS; decoding means for decoding a coded picture from the output layer to generate a decoded picture; transfer means for transferring the decoded pictures for display as part of a decoded video sequence; A decoder including:

18. A decoder according to claim 17, further arranged to perform a method according to any one of claims 1 to 7.

19. 1. An encoder comprising: encoding means for encoding a bitstream including one or more output layer sets (OLS) including one or more layers of a coded picture, and encoding a video parameter set (VPS) into the bitstream, the VPS including an output layer set (OLS) mode identification code (ols_mode_idc) that specifies for each OLS that all layers in each OLS are output layers; storage means for storing said bitstream for communication to a decoder; An encoder that includes

20. 20. The encoder of claim 19, further configured to perform a method according to any one of claims 8 to 14.

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