Prohibiting unused layers in multi-layered video bitstreams

Abstract

To provide a decoding method and an encoding method for guaranteeing that an unnecessary / unused layer is prohibited in a multi-layer video bit stream.SOLUTION: A decoding method includes the steps of: receiving a video bitstream including a video parameter set (VPS) and a plurality of layers, where each layer is included in at least one output layer set (OLS) specified by the VPS; and decoding a picture from the plurality of layers. An encoding method includes the steps of: generating a plurality of layers and a video parameter set (VPS) specifying the output layer set (OLS), where each layer of the plurality of layers is included in the OLS specified by the VPS; encoding, by a video encoder, the plurality of layers and the VPS into a video bitstream, and storing the video bitstream for communication toward a video decoder.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] Generally, this disclosure describes techniques for multi-layer video bitstreams in video coding. More specifically, this disclosure describes techniques for ensuring that unnecessary and / or unused layers are prohibited in multi-layer video bitstreams in video coding. [Background technology]

[0002] The amount of video data required to render even a relatively short video can be substantial. This can pose challenges when the data is streamed or otherwise communicated across communication networks with limited bandwidth capabilities. Therefore, video data is typically compressed before being communicated across today's telecommunications networks. When the video is stored in storage devices, the size of the video can also be an issue since memory resources may be limited. Video compression devices often use software and / or hardware to code the video data at the source before transmission or storage, thereby reducing the amount of data required to represent a digital video image. The compressed data is then received at the destination by a video decompression device that decodes the video data. With limited network resources and an ever-increasing demand for higher video quality, improved compression and decompression techniques that increase compression ratios with little or no sacrifice in image quality are desirable. Summary of the Invention

[0003] A first aspect is a method of decoding implemented by a video decoder, comprising: receiving, by the video decoder, a video bitstream including a video parameter set (VPS) and a plurality of layers, each layer being included in at least one output layer set (OLS) specified by the VPS; decoding, by the video decoder, a picture from one of the plurality of layers; The present invention relates to a method comprising the steps of:

[0004] The method provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides users with a better user experience when videos are transmitted, received, and / or viewed.

[0005] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the picture is included in an output layer of the at least one OLS, each layer being specified within the OLS.

[0006] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides selecting an output layer from the at least one OLS for decoding.

[0007] Optionally, in any of the aforementioned aspects, another implementation of an aspect provides selecting the picture for decoding from the selected output layer.

[0008] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each layer in the plurality of layers includes a set of video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units, all having a particular value of a layer identifier (ID).

[0009] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the at least one OLS includes two output layers, one of the two output layers referencing the other of the two output layers.

[0010] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the at least one OLS includes more than one output layer.

[0011] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each of the plurality of layers has a layer ID of a particular value specified in the VPS, and one of the layers in the at least one OLS should also have a layer ID of the particular value.

[0012] Optionally, in any of the above aspects, another implementation of this aspect provides displaying the decoded picture on a display of an electronic device.

[0013] Optionally, in any of the aspects described above, another implementation of this aspect includes receiving, by the video decoder, a second video bitstream including a second video parameter set (VPS) and a second plurality of layers, where at least one layer is not included in at least one output layer set (OLS) specified by the second VPS; responsive to the receiving step, taking some other corrective measures to ensure that a compliant bitstream corresponding to the second video bitstream is received before decoding a picture from one of the second plurality of layers; to provide.

[0014] A second aspect relates to a method for encoding a video bitstream performed by a video encoder, the method comprising: generating, by the video encoder, a video parameter set (VPS) specifying a plurality of layers and at least one output layer set (OLS), the video encoder constraining each layer from the plurality of layers to be included in at least one of the OLSs specified by the VPS; encoding, by the video encoder, the plurality of layers and the VPS into a video bitstream; storing the video bitstream for communication by the video encoder to a video decoder; Includes.

[0015] The method provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides users with a better user experience when videos are transmitted, received, and / or viewed.

[0016] Optionally, in any of the above aspects, another implementation of this aspect provides that each of the one or more OLSs includes one or more output layers, each of the output layers including one or more pictures, and no layer is excluded from any of the one or more OLSs.

[0017] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each layer in the plurality of layers includes a set of video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units, all having a particular value of a layer identifier (ID).

[0018] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that one of the OLSs includes two output layers, one of the two output layers referencing the other of the two output layers.

[0019] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that for each of the plurality of layers having a layer ID of a particular value specified in the VPS, one of the layers in the one or more OLSs should also have a layer ID of the particular value.

[0020] A third aspect relates to a decoding device, comprising: a receiver configured to receive a video bitstream including a video parameter set (VPS) and a plurality of layers, each layer being included in at least one output layer set (OLS) specified by the VPS; a memory coupled to the receiver, the memory storing instructions; and a processor coupled to the memory, the processor executing the instructions to cause the decoding device to decode a picture from one of the plurality of layers to obtain a decoded picture; Includes.

[0021] The decoder provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0022] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the picture is included in an output layer of the at least one OLS, each layer being specified within the OLS.

[0023] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the processor is further configured to select an output layer from the at least one OLS before the picture is decoded.

[0024] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the processor is further configured to select the picture from the output layer after the output picture is selected.

[0025] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each layer in the plurality of layers includes a set of video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units, all having a particular value of a layer identifier (ID).

[0026] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the at least one OLS includes two output layers, one of the two output layers referencing the other of the two output layers.

[0027] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that the at least one OLS includes one or more output layers.

[0028] Optionally, in any of the preceding aspects, another implementation of the aspect is the processor executing the instructions to cause the decoding device to further: receiving a second video bitstream including a second video parameter set (VPS) and a second plurality of layers, at least one layer not included in at least one output layer set (OLS) specified by the second VPS; In response to receiving the second video bitstream, some other corrective measures are taken to ensure that a compliant bitstream corresponding to the second video bitstream is received before decoding a picture from one of the second plurality of layers.

[0029] Optionally, in any of the above aspects, another implementation of this aspect provides that a display is configured to display the decoded picture.

[0030] The fourth aspect relates to a decoding device. a memory containing instructions; a processor coupled to the memory, the processor executing the instructions to cause the encoding device to: generating a video parameter set (VPS) specifying a plurality of layers and one or more output layer sets (OLSs), the video encoder being configured to constrain each layer from the plurality of layers to be included in at least one of the OLSs specified by the VPS; a processor for encoding the plurality of layers and the VPS into a video bitstream; a transmitter coupled to the processor, the transmitter configured to transmit the video bitstream towards a video decoder; and Includes.

[0031] The decoder provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0032] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each of the one or more OLSs includes one or more output layers, each of the output layers including one or more pictures.

[0033] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each layer in the plurality of layers includes a set of video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units, all having a particular value of a layer identifier (ID).

[0034] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that one of the OLSs includes two output layers, one of the two output layers referencing the other of the two output layers.

[0035] Optionally, in any of the aforementioned aspects, another implementation of the aspect provides that each of the plurality of layers has a layer ID of a particular value specified in the VPS, and one of the layers in the one or more OLSs should also have a layer ID of the particular value.

[0036] A fifth aspect relates to a coding device, comprising: a receiver configured to receive and encode a picture or to receive and decode a bitstream; a transmitter coupled to the receiver, the transmitter configured to transmit the bitstream to a decoder or to transmit a decoded image to a display; a memory coupled to at least one of the receiver or the transmitter, the memory configured to store instructions; and a processor coupled to the memory, the processor configured to execute the instructions stored in the memory to perform any of the methods disclosed herein; The present invention relates to a coding device including:

[0037] The coding device provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Therefore, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides users with a better user experience when videos are transmitted, received, and / or viewed.

[0038] Optionally, in any of the above aspects, another implementation of this aspect provides a display configured to display the decoded picture.

[0039] A sixth aspect relates to a system, the system comprising: An encoder; a decoder in communication with the encoder, the encoder or decoder comprising a decoding device, an encoding device, or a coding apparatus as disclosed herein; Includes.

[0040] The system provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides users with a better user experience when videos are transmitted, received, and / or viewed.

[0041] A seventh aspect relates to a coding means, the coding means comprising: receiving means configured to receive and encode a picture or to receive and decode a bitstream; a transmitting means coupled to said receiving means, said transmitting means configured to transmit said bitstream to a decoding means or to transmit a decoded image to a display means; a storage means coupled to at least one of the receiving means or the transmitting means, the storage means configured to store instructions; a processing means coupled to said storage means, said processing means being configured to execute the instructions stored on said storage means in order to perform any of the methods described herein; Includes.

[0042] The coding means provides a technique for disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is restricted from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0043] For purposes of clarity, any one of the above-described embodiments may be combined with any one or more of the other above-described embodiments to create new embodiments that are within the scope of the present disclosure.

[0044] The above and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. [Brief description of the drawings]

[0045] 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, where like reference numerals represent like parts.

[0046] [Figure 1] 4 is a flowchart of an exemplary method for coding a video signal.

[0047] [Diagram 2] 1 is a schematic diagram of an example coding and decoding (codec) system for video coding.

[0048] [Diagram 3] FIG. 1 is a schematic diagram illustrating an exemplary video encoder.

[0049] [Figure 4] FIG. 2 is a schematic diagram illustrating an exemplary video decoder.

[0050] [Diagram 5] 1 shows an example of multi-layer coding for spatial scalability.

[0051] [Figure 6] An example of multi-layer coding using output layer sets (OLS) is shown.

[0052] [Figure 7] 1 illustrates an embodiment of a video bitstream.

[0053] [Figure 8] 1 is an embodiment of a method for decoding a coded video bitstream.

[0054] [Figure 9] 1 is an embodiment of a method for coding video bitstreams.

[0055] [Figure 10] 1 is a schematic diagram of a video encoding device;

[0056] [Figure 11] FIG. 2 is a schematic diagram of an embodiment of a coding means; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] It should be understood at the outset that, although illustrative implementations of one or more embodiments are provided below, the disclosed systems and / or methods may be implemented using any number of technologies, whether currently known or existing, and that the present disclosure should in no way be limited to the illustrative implementations, drawings, and technologies described below, including the exemplary designs and implementations shown and described herein, but may be modified within the scope of the appended claims, along with their full range of equivalents.

[0058] The following terms are defined as follows, unless used in a contradictory context herein. In particular, the following definitions are intended to provide further clarity to the present disclosure. However, terms may be described differently in different contexts. Therefore, the following definitions should be considered as supplemental and should not be considered as limiting any other definitions of the descriptions provided for such terms in the present specification.

[0059] A bitstream is a sequence of bits that includes video data that is compressed for transmission between an encoder and a decoder. An encoder is a device configured to 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 the bitstream for display. A picture is an array of chroma samples and / or an array of luma samples that generate a frame or a field thereof. A picture being encoded or decoded may be referred to as a current picture for clarity of discussion. A reference picture is a picture that includes reference samples that can be used when coding other pictures by reference according to inter-prediction and / or inter-layer prediction. A reference picture list is a list of reference pictures used for inter-prediction and / or inter-layer prediction. Some video coding systems use two reference picture lists, which may be represented as Reference Picture List 1 and Reference Picture List 0. A reference picture list structure is an addressable syntax structure that includes multiple reference picture lists. Inter prediction is a mechanism for coding samples of a current picture by reference to indicated samples in a reference picture different from the current picture, where the reference picture and the current picture are in the same layer. A reference picture list structure entry is an addressable location within a reference picture list structure that indicates a reference picture associated with a reference picture list. A slice header is a part of a coding slice that contains data elements related to all the video data in the tiles represented in the slice. A picture parameter set (PPS) is a parameter set that contains data related to an entire picture. More specifically, a PPS is a syntax structure that contains syntax elements that apply to zero or more entire coding pictures as determined by the syntax elements found in each picture header.A sequence parameter set (SPS) is a parameter set containing data relating to a sequence of pictures. An access unit (AU) is a set of one or more coded pictures associated with the same display time (e.g., the same picture order count) for output from the decoded picture buffer (DPB) (e.g., for display to a user). An access unit delimiter (AUD) is a designator or data structure used to indicate the start of an AU or the boundary between AUs. A decoded video sequence is a sequence of pictures reconstructed by a decoder in preparation for display to a user.

[0060] A network abstraction layer (NAL) unit is a syntax structure that contains data in the form of a Raw Byte Sequence Payload (RBSP), an indication of the type of data, and is interspersed with emulation prevention bytes, if necessary. A video coding layer (VCL) NAL unit is a NAL unit that is coded to contain video data, such as a coded slice of a picture. A non-VCL NAL unit is a NAL unit that contains non-video data, such as syntax and / or parameters that support decoding the video data, performance of conformance checking, or other operations. A layer is a set of VCL NAL units and related non-VCL NAL units that share certain characteristics (e.g., a common resolution, frame rate, picture size, etc.). The VCL NAL units of a layer may share a particular value of the NAL unit header layer identifier (nuh_layer_id). A coded picture is a coded representation of a picture that contains a VCL NAL unit that has a particular value of the NAL unit header layer identifier (nuh_layer_id) in an access unit (AU) and that contains all the coding tree units (CTUs) of the picture. A decoded picture is a picture that is generated by applying a decoding process to a coded picture.

[0061] An output layer set (OLS) is a set of layers in which one or more layers are designated as output layers. An output layer is a layer designated for output (e.g., to a display). The zeroth (0-th) OLS is an OLS that contains only the lowest layer (the layer with the lowest layer identifier) ​​and thus only output layers. A video parameter set (VPS) is a data unit that contains parameters related to the entire video. Inter-layer prediction is a mechanism for coding a current picture in a current layer by referencing a reference picture in a reference layer, where the current picture and the reference picture are included in the same AU and the reference layer contains a lower nuh_layer_id than the current layer.

[0062] The following abbreviations are used herein: coding tree block (CTB), coding tree unit (CTU), coding unit (CU), coded video sequence (CVS), Joint Video Experts Team (JVET), network abstraction layer (NAL), picture order count (POC), Picture Parameter Set (PPS), raw byte sequence payload (RBSP), sequence parameter set (SPS), versatile video coding (VVC), and working draft (WD).

[0063] FIG. 1 is a flow chart of an exemplary operational method 100 of coding a video signal. Specifically, a video signal is encoded by an encoder. The encoding process compresses the video signal by utilizing various mechanisms to reduce the video file size. The smaller file size allows for the transmission of the compressed video file to a user while reducing the associated bandwidth overhead. A decoder then decodes the compressed video file to reconstruct the original video signal for display to the end user. The decoding process is typically a mirror of the encoding process, allowing the decoder to consistently reconstruct the video signal.

[0064] In step 101, a video signal is input to an encoder. For example, the video signal may be an uncompressed video file stored in a memory. As another example, the video file may be captured by a video capture device such as a video camera and encoded to support live streaming of the video. The video file may include both audio and video components. The video component includes a series of image frames that, when viewed in sequence, give the visual impression of motion. The frames include pixels that are represented in terms of light, referred to herein as luma components (or luma samples), and color, referred to herein as chroma components (or chroma samples). In some examples, the frames may also include depth values ​​to support three-dimensional displays.

[0065] At step 103, the video is partitioned into blocks. Partitioning involves subdividing pixels in each frame into square and / or rectangular blocks for compression. For example, in High Efficiency Video Coding (HEVC) (also known as H.265 and MPEG-H Part 2), a frame may first be divided into coding tree units (CTUs), which are blocks of a given size (e.g., 64 pixels by 64 pixels). CTUs contain both luma and chroma samples. The coding tree may be utilized to divide the CTUs into blocks and then iteratively subdivide the blocks until a configuration that supports further encoding is achieved. For example, the luma component of a frame may be subdivided until each block contains relatively homogenous light values. Additionally, the chroma component of a frame may be subdivided until each block contains relatively homogenous color values. Thus, the partitioning mechanism varies depending on the content of the video frame.

[0066] At step 105, various compression mechanisms are utilized to compress the image blocks partitioned at step 103. For example, inter-prediction and / or intra-prediction may be utilized. Inter-prediction is designed to take advantage of the fact that objects in a common scene tend to appear in successive frames. Thus, a block depicting an object in a reference frame does not need to be repeatedly shown in adjacent frames. In particular, an object such as a table may remain in a constant position across multiple frames. Thus, the table may be shown once and adjacent frames may refer back to the reference frame. A pattern matching mechanism may be utilized to match objects across multiple frames. Furthermore, a moving object may be displayed across multiple frames, e.g., due to object motion or camera motion. As a specific example, a video may show a car moving across the screen across multiple frames. To indicate such motion, a motion vector may be utilized. A motion vector is a two-dimensional vector that provides an offset from the coordinates of an object in a frame to the coordinates of the object in a reference frame. Thus, inter-prediction allows an image block in a current frame to be coded as a set of motion vectors that indicate an offset from a corresponding block in a reference frame.

[0067] Intra prediction encodes blocks within a common frame. Intra prediction exploits the fact that luma and chroma components tend to be clustered within a frame. For example, some green patches in a tree tend to be located adjacent to similar green patches. Intra prediction utilizes multiple directional prediction modes (e.g., 33 in HEVC), planar mode, and direct current (DC) mode. The directional modes indicate that the current block is similar / same as the samples of neighboring blocks in the corresponding direction. The planar mode indicates that a series of blocks along a row / column (e.g., a plane) can be interpolated based on the neighboring blocks at the ends of the row. The planar mode effectively indicates a smooth transition of light / color across the row / column by utilizing a relatively constant gradient of changing values. The DC mode is used for boundary smoothing and indicates that the block is similar / same as the average value associated with the samples of all neighboring blocks associated with the angular direction of the directional prediction mode. Thus, intra prediction blocks can represent image blocks as various related prediction modes instead of actual values. Furthermore, inter prediction blocks can represent image blocks as motion vector values ​​instead of actual values. In either case, the prediction block may not accurately represent the image in some cases. Any differences are stored in a residual block. To further compress the file, a transform may be applied to the residual block.

[0068] In step 107, various filtering techniques may be applied. In HEVC, filters are applied according to an in-loop filtering scheme. The block-based prediction described above may result in the generation of blocky images at the decoder. Furthermore, block-based prediction schemes may code blocks and then reconstruct the coded blocks for later use as reference blocks. In-loop filtering schemes apply noise suppression filters, deblocking filters, adaptive loop filters, and sample adaptive offset (SAO) filters iteratively to blocks / filters. These filters mitigate such blocky artifacts so that the coded file can be accurately reconstructed. Furthermore, these filters mitigate artifacts in the reconstructed reference blocks so that they are less likely to cause additional artifacts in subsequent blocks coded based on the reconstructed reference blocks.

[0069] Once the video signal has been partitioned, compressed, and filtered, the resulting data is encoded into a bitstream at step 109. The bitstream includes the data described above and any desired signaling data to support proper video signal reconstruction at the decoder. For example, such data may include partition data, prediction data, residual blocks, and various flags that provide coding instructions to the decoder. The bitstream may be stored in a memory for transmission to the decoder upon request. The bitstream may be broadcast and / or multicast to multiple decoders. The generation of the bitstream is an iterative process. Thus, steps 101, 103, 105, 107, and 109 may occur sequentially and / or simultaneously across multiple frames and blocks. The order shown in FIG. 1 is presented for clarity and ease of discussion and is not intended to limit the video coding process to any particular order.

[0070] In step 111, the decoder receives the bitstream and begins the decoding process. Specifically, the decoder uses an entropy decoding scheme to convert the bitstream into corresponding syntax and video data. In step 111, the decoder uses the syntax from the bitstream to determine the partition of the frame. The partition should match the result of the block partition in step 103. The entropy encoding / decoding as used in step 111 is described below. The encoder generates many options during the compression process, such as selecting a block partition scheme from several possible options based on the spatial location of the values ​​in the input image. Signaling the exact option may utilize a large number of bins. As used herein, a bin is a binary value that is treated as a variable (e.g., a bit value that can change depending on the context). Entropy coding allows the encoder to discard any options that are clearly not feasible in a particular case, leaving a set of acceptable options. Each acceptable option is then assigned a codeword. The length of the codeword is based on the number of allowable choices (e.g., one bin for two choices, two bins for three to four choices, etc.). The encoder then encodes a codeword for the selected choice. This scheme reduces the size of the codeword because it is desirable to uniquely indicate a choice from a small subset of the possible choices, as opposed to uniquely indicating a choice from a potentially large set of all possible choices. The decoder then decodes the choices by determining the set of allowable choices in a similar manner as the encoder. By determining the set of allowable choices, the decoder can read the codeword and determine the choices made by the encoder.

[0071] In step 113, the decoder performs block decoding. Specifically, the decoder uses an inverse transform to generate a residual block. Then, the decoder uses the residual block and a corresponding prediction block to reconstruct an image block according to the partition. The prediction block may include both intra-prediction blocks and inter-prediction blocks generated in the encoder in step 105. The reconstructed image block is then positioned into a frame of the reconstructed video signal according to the partition data determined in step 111. The syntax of step 113 may also be signaled in the bitstream by entropy coding as described above.

[0072] In step 115, filtering is performed on the frames of the reconstructed video signal in a manner similar to step 107 in the encoder. For example, a noise suppression filter, a deblocking filter, an adaptive loop filter, and an SAO filter may be applied to the frames to remove blocking artifacts. Once the frames are filtered, the video signal can be output to a display in step 117 for viewing by an end user.

[0073] 2 is a schematic diagram of an exemplary coding and decoding (codec) system 200 for video coding. Specifically, the codec system 200 provides functionality to support the implementation of the operational method 100. The codec system 200 is generalized to show components utilized in both an encoder and a decoder. The codec system 200 receives and partitions a video signal as described above with respect to steps 101 and 103 in the operational method 100, resulting in a partitioned video signal 201. The codec system 200 then compresses the partitioned video signal 201 into a coding bitstream when operating as an encoder as described above with respect to steps 105, 107, and 109 in the method 100. When operating as a decoder, the codec system 200 generates an output video signal from the bitstream as described above with respect to steps 111, 113, 115, and 117 in the operational method 100. Codec system 200 includes a general coder control component 211, a transform scaling and quantization component 213, an intra picture estimation component 215, an intra picture prediction component 217, a motion compensation component 219, a motion estimation component 221, a scaling and inverse transform component 229, a filter control analysis component 227, an in-loop filter component 225, a decoded picture buffer component 223, and a header format and context adaptive binary arithmetic coding (CABAC) component 231. Such components are coupled as shown. In FIG. 2, the black lines indicate the movement of data to be encoded / decoded, while the dashed lines indicate the movement of control data that controls the operation of the other components. The components of codec system 200 may all be present in an encoder. A decoder may include some of the components of codec system 200.For example, the decoder may include an intra picture prediction component 217, a motion compensation component 219, a scaling and inverse transform component 229, an in-loop filter component 225, and a decoded picture buffer component 223. These components are described herein.

[0074] 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 utilizes various partitioning modes to subdivide the blocks of pixels into smaller blocks of pixels. These blocks can then be further subdivided into smaller blocks. The blocks may be referred to as nodes on the coding tree. Larger parent nodes are partitioned into smaller child nodes. The number of times a node is subdivided is referred to as the depth of the node / coding tree. The partitioned blocks may be included in a coding unit (CU) in some cases. For example, a CU may be a subpart of a CTU that includes a luma block, a red differential chroma (Cr) block, and a blue differential chroma (Cb) block, as well as the corresponding syntax instructions for the CU. The partitioning modes may include a binary tree (BT), a triple tree (TT), and a quad tree (QT), which are used to partition a node into 2, 3, or 4 child nodes, each of varying shapes depending on the partitioning mode used. The partitioned video signal 201 is forwarded to a general coder control component 211, a transform scaling and quantization component 213, an intra picture estimation component 215, a filter control analysis component 227, and a motion estimation component 221 for compression.

[0075] The generic coder control component 211 is configured to make decisions related to coding of images of a video sequence into a bitstream according to application constraints. For example, the generic coder control component 211 manages optimization of bitrate / bitstream size versus reconstruction quality. Such decisions may be based on storage space / bandwidth availability and image resolution requirements. The generic coder control component 211 also manages buffer utilization in terms of conversion speed to mitigate buffer underrun and overrun issues. To address these issues, the generic coder control component 211 manages partitioning, prediction, and filtering by other components. For example, the generic coder control component 211 may dynamically increase compression complexity to increase resolution and increase bandwidth usage or decrease compression complexity to reduce resolution and bandwidth usage. Thus, the generic coder control component 211 controls other components of the codec system 200 to balance video signal reconstruction quality and bitrate concerns. The generic coder control component 211 generates control data that controls the operation of other components. Control data is also forwarded to the header format and CABAC component 231 to be encoded into the bitstream for signaling parameters for decoding at the decoder.

[0076] The partitioned video signal 201 is also sent to a motion estimation component 221 and a motion compensation component 219 for inter prediction. A frame or slice of the partitioned video signal 201 may be divided into multiple video blocks. The motion estimation component 221 and the motion compensation component 219 perform inter predictive coding of the received video blocks with respect to one or more blocks in one or more reference frames to provide temporal prediction. The codec system 200 may perform multiple coding passes, for example to select an appropriate coding mode for each block of video data.

[0077] The motion estimation component 221 and the motion compensation component 219 may be highly integrated, but are shown separately for conceptual purposes. Motion estimation performed by the motion estimation component 221 is a process that generates motion vectors that estimate motion for a video block. A motion vector may indicate the location of a coding object with respect to, for example, a predictive block. A predictive block is a block that is found to closely match a block to be coded in terms of pixel differences. A predictive block may also be referred to as a reference block. Such pixel differences may be determined by sum of absolute difference (SAD), sum of square difference (SSD), or other difference metrics. HEVC utilizes several coding objects including CTUs, coding tree blocks (CTBs), and CUs. For example, a CTU may be divided into CTBs, which in turn may be divided into CBs for inclusion in CUs. A CU may be coded as a prediction unit (PU), which contains prediction data, and / or a transform unit (TU), which contains transformed residual data of the CU. The motion estimation component 221 uses rate-distortion analysis as part of a rate-distortion optimization process to generate motion vectors, PUs, and TUs. For example, the motion estimation component 221 may determine multiple reference blocks, multiple motion vectors, etc. for a current block / frame, and may select the reference block, motion vector, etc. with optimal rate-distortion characteristics. The optimal rate-distortion characteristics balance both the quality of the video reconstruction (e.g., the amount of data lost due to compression) and the coding efficiency (e.g., the size of the final encoding).

[0078] In some examples, the codec system 200 may calculate values ​​for sub-integer picture positions of the reference picture stored in the decoded picture buffer component 223. For example, the video codec system 200 may interpolate values ​​for quarter-pixel positions, eighth-pixel positions, or other fractional pixel positions of the reference picture. Thus, the motion estimation component 221 may perform motion search with respect to the full pixel positions and the fractional pixel positions and output motion vectors with fractional pixel accuracy. The motion estimation component 221 calculates motion vectors for the PUs of the video blocks in the inter-coding slices by comparing the positions of the PUs with the positions of the predictive blocks of the reference pictures. The motion estimation component 221 outputs the calculated motion vectors as motion data to the header format and CABAC component 231 for encoding and motion to the motion compensation component 219.

[0079] The motion compensation performed by the motion compensation component 219 may include fetching or generating a predictive block based on the motion vector determined by the motion estimation component 221. Again, the motion estimation component 221 and the motion compensation component 219 may be functionally integrated in some examples. Upon receiving the motion vector of the PU of the current video block, the motion compensation component 219 may locate the predictive block pointed to by the motion vector. A residual video block is then formed by subtracting pixel values ​​of the predictive block from pixel values ​​of the current video block being coded to form pixel difference values. In general, the motion estimation component 221 performs motion estimation with respect to the luma component, and the motion compensation component 219 uses the motion vector calculated based on the luma component for both the chroma and luma components. The predictive block and the residual block are forwarded to the transform scaling and quantization component 213.

[0080] The partitioned video signal 201 is also sent to an intra picture estimation component 215 and an intra picture prediction component 217. As with the motion estimation component 221 and the motion compensation component 219, the intra picture estimation component 215 and the intra picture prediction component 217 may be highly integrated, but are shown separately for conceptual purposes. Instead of inter prediction performed by the inter-frame motion estimation component 221 and the motion compensation component 219 as described above, the intra picture estimation component 215 and the intra picture prediction component 217 intra predict the current block with respect to a block in the current frame. In particular, the intra picture estimation component 215 determines an intra prediction mode to be used to encode the current block. In some examples, the intra picture estimation component 215 selects an appropriate intra prediction mode for encoding the current block from a plurality of tested intra prediction modes. The selected intra prediction mode is then forwarded to the header format and CABAC component 231 for encoding.

[0081] For example, the intra picture estimation component 215 calculates rate-distortion values ​​for various tested intra prediction modes using a rate-distortion analysis, and selects an intra prediction mode with optimal rate-distortion characteristics among the tested modes. The rate-distortion analysis generally determines the amount of distortion (or error) between a coded block and an original uncoded block that was coded to generate the coded block, as well as the bit rate (e.g., number of bits) used to generate the coded block. The intra picture estimation component 215 calculates a ratio from the distortion and rate for various coded blocks to determine which intra prediction mode exhibits the optimal rate-distortion value for the block. Furthermore, the intra picture estimation component 215 may be configured to code the depth blocks of the depth map using a depth modeling mode (DMM) based on a rate-distortion optimization (RDO).

[0082] The intra picture prediction component 217 may generate a residual block from the prediction block based on a selected intra prediction mode determined by the intra picture estimation component 215 when implemented in an encoder, or may read the residual block from the bitstream when implemented in a decoder. The residual block includes value differences between the prediction block and the original block, represented as a matrix. The residual block is then forwarded to the transform scaling and quantization component 213. The intra picture estimation component 215 and the intra picture prediction component 217 may operate on both luma and chroma components.

[0083] The transform scaling and quantization component 213 is configured to further compress the residual block. The transform scaling and quantization component 213 applies a transform, such as a discrete cosine transform (DCT), a discrete sine transform (DST), or a conceptually similar transform, to the residual block to generate a video block including residual transform coefficient values. A wavelet transform, an integer transform, a subband transform, or other types of transforms may also be used. The transform may convert the residual information from a pixel value domain to a transform domain, such as a frequency domain. The transform scaling and quantization component 213 is also configured to scale the transformed residual information, for example based on frequency. Such scaling includes applying a scaling factor to the residual information. As a result, different frequency information is quantized with different granularity, which may affect the final visual quality of the reconstructed video. The transform scaling and quantization component 213 is also configured to quantize the transform coefficients to further reduce the bit rate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be varied by adjusting a quantization parameter. In some examples, the transform scaling and quantization component 213 may then perform a scan of a matrix containing the quantized transform coefficients. The quantized transform coefficients are forwarded to the header format and CABAC component 231 for encoding into the bitstream.

[0084] The scaling and inverse transform component 229 applies the inverse operations of the transform scaling and quantization component 213 to support motion estimation. The scaling and inverse transform component 229 applies inverse scaling, transformation, and / or quantization to reconstruct a residual block in the pixel domain for later use as a reference block that may become, for example, a predictive block for another current block. The motion estimation component 221 and / or the motion compensation component 219 may calculate a reference block by adding the residual block back to the corresponding predictive block for use in motion estimation of a later block / frame. A filter is applied to the reconstructed reference block to reduce artifacts created during the scaling, quantization, and transformation. Such artifacts may otherwise cause inaccurate predictions (and generate additional artifacts) when subsequent blocks are predicted.

[0085] The filter control analysis component 227 and the in-loop filter component 225 apply filters to the residual block and / or to the reconstructed image block. For example, the transformed residual block from the scaling and inverse transform component 229 may be combined with the corresponding prediction block from the intra picture prediction component 217 and / or the motion compensation component 219 to reconstruct the original image block. The filter may then be applied to the reconstructed image block. In some examples, the filter may be applied to the residual block instead. As with the other components of FIG. 2, the filter control analysis component 227 and the in-loop filter component 225 may be highly integrated and implemented together, but are shown separately for conceptual purposes. The filters applied to the reconstructed reference block are applied to a particular spatial region and include multiple parameters to adjust how such filters are applied. The filter control analysis component 227 analyzes the reconstructed reference block to determine when such filters should be applied and sets the corresponding parameters. Such data is forwarded to the header format and CABAC component 231 as filter control data for encoding. The in-loop filter component 225 applies such filters based on the filter control data. The filters may include deblocking filters, noise suppression filters, SAO filters, and adaptive loop filters. Such filters may be applied in the spatial / pixel domain (e.g., on reconstructed pixel blocks) or in the frequency domain, depending on the example.

[0086] When operating as an encoder, the filtered reconstructed image blocks, residual blocks, and / or prediction blocks are stored in the decoded picture buffer component 223 for later use in motion estimation as described above. When operating as a decoder, the decoded picture buffer component 223 stores and forwards the reconstructed and filtered blocks towards a 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.

[0087] The header format and CABAC component 231 receives data from various components of the codec system 200 and encodes such data into a coding bitstream for transmission towards the decoder. In particular, the header format and CABAC component 231 generates various headers for encoding control data such as general control data and filter control data. Furthermore, prediction data including intra prediction and motion data, as well as residual data in the form of quantized transform coefficient data, are all encoded in the bitstream. The final bitstream contains all information desired by the decoder to reconstruct the original partitioned video signal 201. Such information may also include an intra prediction mode index table (also called a codeword mapping table), definitions of the coding contexts of various blocks, indications of the most likely intra prediction mode, indications of partition information, etc. Such data may be encoded by utilizing entropy coding. For example, the information may be encoded by utilizing context adaptive variable length coding (CAVLC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy coding technique. Following entropy coding, the coded bitstream may be transmitted to another device (e.g., a video decoder) or stored for later transmission or retrieval.

[0088] 3 is a block diagram illustrating an example video encoder 300. The video encoder 300 may be utilized to implement the encoding functionality of the codec system 200 and / or to implement steps 101, 103, 105, 107 and / or 109 of the method of operation 100. The encoder 300 partitions an input video signal to result in a partitioned video signal 301 that is substantially similar to the partitioned video signal 201. The partitioned video signal 301 is then compressed and encoded into a bitstream by components of the encoder 300.

[0089] Specifically, the partitioned video signal 301 is forwarded to an intra picture prediction component 317 for intra prediction. The intra picture prediction component 317 may be substantially similar to the intra picture estimation component 215 and the intra picture prediction component 217. The partitioned video signal 301 is also forwarded to a motion compensation component 321 for inter prediction based on a reference block in a decoded picture buffer component 323. The motion compensation component 321 may be substantially similar to the motion estimation component 221 and the motion compensation component 219. The prediction block and the residual block from the intra picture prediction component 317 and the motion compensation component 321 are forwarded to a transform and quantization component 313 for transforming and quantizing the residual block. The transform and quantization component 313 may be substantially similar to the transform scaling and quantization component 213. The transformed and quantized residual block and the corresponding prediction block (together with related control data) are forwarded to an entropy coding component 313 for coding into a bitstream. The entropy coding component 331 may have a header format substantially similar to the CABAC component 231 .

[0090] The transformed and quantized residual block and / or the corresponding prediction block are also forwarded from the transform and quantization component 313 to the inverse transform and quantization component 329 for reconstructing into a reference block for use by the motion compensation component 321. The inverse transform and quantization component 329 may be substantially similar to the scaling and inverse transform component 229. An in-loop filter in the in-loop filter component 325 is also applied to the residual block and / or the reconstructed reference block, depending on the example. The in-loop filter component 325 may be substantially similar to the filter control analysis component 227 and the in-loop filter component 225. The in-loop filter component 325 may include multiple filters as discussed with respect to the in-loop filter component 225. The filtered block is then stored in the decoded picture buffer component 323 for use as a reference block by the motion compensation component 321. The decoded picture buffer component 323 may be substantially similar to the decoded picture buffer component 223.

[0091] 4 is a block diagram illustrating an example video decoder 400. The video encoder 400 may be utilized to implement the decoding functionality of the codec system 200 and / or to implement steps 111, 113, 115 and / or 117 of the method of operation 100. The decoder 400 receives a bitstream, for example from the encoder 300, and generates a reconstructed output video signal based on the bitstream for display to an end user.

[0092] The bitstream is received by the entropy decoding component 433. The entropy decoding component 433 is configured to implement an entropy decoding scheme such as CAVLC, CABAC, SBAC, PIPE coding, or other entropy coding techniques. For example, the entropy decoding component 433 may utilize header information to provide context to interpret additional data encoded as codewords in the bitstream. The decoded information includes any desired information for decoding the video signal, such as general control data, filter control data, partition information, motion data, prediction data, and quantized transform coefficients from the residual block. The quantized transform coefficients are forwarded to the inverse transform and quantization component 429 for reconstruction into the residual block. The inverse transform and quantization component 429 may be similar to the inverse transform and quantization component 329.

[0093] The reconstructed residual block and / or the prediction block are forwarded to the intra picture prediction component 417 for reconstructing into an 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 identify the location of a reference block in a frame and applies a residual block to the result to reconstruct an intra predicted image block. The reconstructed intra predicted image block and / or the residual block, and the corresponding inter prediction data are forwarded to the decoded picture buffer component 423 via the in-loop filter component 425, which may be substantially similar to the decoded picture buffer component 223 and the in-loop filter component 225, respectively. The in-loop filter component 425 filters the reconstructed image block, the residual block, and / or the 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 forwarded to the motion compensation component 421 for inter prediction. The motion compensation component 421 may be substantially similar to the motion estimation component 221 and / or the motion compensation component 219. Specifically, the motion compensation component 421 utilizes a motion vector from a reference block to generate a prediction block and provides a residual block to the result to reconstruct an image block. The resulting reconstructed block may be forwarded to the decoded picture buffer component 423 via an in-loop filter component 425. The decoded picture buffer component 423 may continue to store additional reconstructed image blocks that can be reconstructed into frames according to the partition information. Such frames may be arranged in a sequence. The sequence is output to a display as a reconstructed output video signal.

[0094] With the above in mind, video compression techniques perform spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. In block-based video coding, video slices (i.e., video pictures or portions of video pictures) may be partitioned into video blocks, which may also be referred to as tree blocks, coding tree blocks (CTBs), coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are coded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may utilize spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. A POC is a variable associated with each picture that uniquely identifies the associated picture among all pictures in a coded layer video sequence (CLVS), indicates when the associated picture is output from the DPB, and indicates the position of the associated picture in output order relative to the output order positions of other pictures in the same CLVS that should be output from the DPB. A flag is a variable or single-bit syntax element that can take one of two possible values: 0 and 1.

[0095] Spatial or temporal prediction results in a predictive block of the block to be coded. The residual data represents pixel differences between the original block to be coded and the predictive block. Inter-coding blocks are coded according to a motion vector pointing to a block of reference samples forming the predictive block, and the residual data indicating the difference between the coding block and the predictive block. Intra-coding blocks are coded according to an intra-coding mode and the residual data. For further compression, the residual data may be transformed from the pixel domain to a transform domain, resulting in residual transform coefficients, which may then be quantized. The quantized transform coefficients may first be organized into a two-dimensional array and scanned to generate a one-dimensional vector of transform coefficients, and entropy coding may be applied to achieve even more compression.

[0096] Image and video compression has experienced rapid growth, resulting in a variety of coding standards. Such video coding standards include Advanced Video Coding (AVC), also known as ITU-TH.261, International Organization for Standardization / International Electrotechnical Commission (ISO / IEC), MPEG-1 Part2, ITU-TH.262 or ISO / IEC MPEG-2 Part2, ITU-TH.263, ISO / IEC MPEG-4 Part2, ITU-T H.264 or ISO / IEC MPEG-4 Part 10, High Efficiency Video Coding (HEVC), also known as ITU-T H.265 or MPEG-H Part2. AVC includes Scalable Video Coding (SVC), Multiview Video Coding (MVC), and Multiview Video Coding plus Depth. HEVC includes extensions such as Scalable HEVC (SHVC), Multiview HEVC (MV-HEVC), and 3D HEVC (3D-HEVC).

[0097] There is also a new coding standard named Versatile Video Coding (VVC) by the ITU-T and ISO / IEC joint video experts team (JVET). The VVC standard has several working drafts, but one working draft (WD) of VVC in particular is referenced here: B. Bross, J. Chen, and S. Liu, "Versatile Video Coding (Draft5)", JVET-N1001-v3, 13th JVET Meeting, March 27, 2019 (VVC Draft5).

[0098] Scalability in video coding is 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 (SNR) scalability, multi-view scalability, etc. When a multi-layer coding technique is used, a picture or a portion thereof may be coded (1) without using a reference picture, i.e., by using intra prediction, (2) by referencing a reference picture that is in the same layer, i.e., by using inter prediction, or (3) by referencing a reference picture that is in another layer, i.e., by using inter-layer prediction. A reference picture used for inter-layer prediction of a current picture is called an inter-layer reference picture (ILRP).

[0099] 5 is a schematic diagram illustrating an example of layer-based prediction 500, as may be performed to determine an MV, for example, in the block compression step 105, the block decoding step 113, the motion estimation component 221, the motion compensation component 219, the motion compensation component 321, and / or the motion compensation component 421. The layer-based prediction 500 is compatible with unidirectional inter prediction and / or bidirectional inter prediction, but may also be performed between pictures of different layers.

[0100] Layer-based prediction 500 is applied between pictures 511, 512, 513, and 514 and pictures 515, 516, 517, and 518 in different layers. In the illustrated example, pictures 511, 512, 513, and 514 are part of layer N+1 532, and pictures 515, 516, 517, and 518 are part of layer N 531. A layer, such as layer N 531 and / or layer N+1 532, is a group of pictures that are all related to similar value characteristics, such as similar size, quality, resolution, signal-to-noise ratio, capacity, etc. Thus, pictures 511, 512, 513, and 514 in layer N+1 532 have a larger picture size (e.g., larger height and width, and therefore more samples) than pictures 515, 516, 517, and 518 in layer N 531 in this example. However, such pictures may be separated between Layer N+1 532 and Layer N 531 by other characteristics. Although only two layers, Layer N+1 532 and Layer N 531, are shown, the set of pictures may be separated into any number of layers based on relevant characteristics. Layer N+1 532 and Layer N 531 may be indicated by a Layer ID, which is an item of data associated with a picture and indicates which layer the picture is part of. Thus, each picture 511-518 may be associated with a corresponding Layer ID to indicate which Layer N+1 532 or Layer N 531 contains the corresponding view.

[0101] Pictures 511-518 in different layers 531-532 are configured to be displayed alternatively. Thus, pictures 511-518 in different layers 531-532 may share the same time identifier (ID) and may be included in the same AU. As used herein, an AU is a collection of one or more coded pictures associated with the same display time for output from the DPB. For example, if a smaller picture is desired, the decoder may decode and display picture 515 at the current display time, and if a larger picture is desired, the decoder may decode and display picture 511 at the current display time. Thus, pictures 511-514 in upper layer N+1 532 contain substantially the same image data as corresponding pictures 515-518 in lower layer N 531 (despite differences in picture size). Specifically, picture 511 contains substantially the same image data as picture 515, picture 512 contains substantially the same image data as picture 516, and so on.

[0102] Pictures 511-518 can be coded by referencing other pictures 511-518 in the same layer N 531 or N+1 532. Coding a picture by referencing another picture in the same layer results in inter-prediction 523, which is a compatible unidirectional inter-prediction and / or bidirectional inter-prediction. Inter-prediction 523 is indicated by a solid arrow. For example, picture 513 may be coded by employing inter-prediction 523 using one or two of pictures 511, 512, and / or 514 in layer N+1 532 as references, where one picture is referenced for unidirectional inter-prediction and / or two pictures are referenced for bidirectional inter-prediction. Furthermore, picture 517 may be coded by employing inter prediction 523 using one or two of pictures 515, 516, and / or 518 in layer N 531 as references, where one picture is referenced for unidirectional inter prediction and / or two pictures are referenced for bidirectional inter prediction. If a picture is used as a reference for another picture in the same layer when performing inter prediction 523, the picture may be referred to as a reference picture. For example, picture 512 may be a reference picture used to code picture 513 according to inter prediction 523. Inter prediction 523 may also be referred to as intra-layer prediction in a multi-layer context. Thus, inter prediction 523 is a mechanism for coding samples of a current picture by reference to indicated samples in a reference picture different from the current picture, where the reference picture and the current picture are in the same layer.

[0103] Pictures 511-518 may also be coded by referencing other pictures 511-518 in different layers. This process is known as interlayer prediction 521 and is indicated by the dashed arrows. Interlayer prediction 521 is a mechanism for coding samples of a current picture by referencing indicated samples in a reference picture when the current picture and the reference picture are in different layers and therefore have different layer IDs. For example, a picture in lower layer N 531 may be used as a reference picture to code a corresponding picture in upper layer N+1 532. As a specific example, picture 511 may be coded by referencing picture 515 according to interlayer prediction 521. In such a case, picture 515 is used as an interlayer reference picture. An interlayer reference picture is a reference picture used for interlayer prediction 521. In most cases, interlayer prediction 521 is constrained such that a current picture, such as picture 511, can only use interlayer reference pictures that are included in the same AU and are in a lower layer, such as picture 515. If multiple layers (eg, two or more) are available, inter-layer prediction 521 can encode / decode the current picture based on multiple inter-layer reference pictures at a lower level than the current picture.

[0104] A video encoder can use layer-based prediction 500 to encode pictures 511-518 through many different combinations and / or permutations of inter prediction 523 and inter layer prediction 521. For example, picture 515 may be coded according to intra prediction. Pictures 516-518 can then be coded according to inter prediction 523 by using picture 515 as a reference picture. Furthermore, picture 511 may be coded according to inter layer prediction 521 by using picture 515 as an inter layer reference picture. Pictures 512-514 can then be coded according to inter prediction 523 by using picture 511 as a reference picture. In this way, a reference picture can function as both a single layer reference picture and an inter layer reference picture for different coding mechanisms. By coding upper layer N+1 532 picture based on lower layer N 531 picture, upper layer N+1 532 can avoid using intra prediction, which has much lower coding efficiency than inter prediction 523 and inter layer prediction 521. Thus, the poor coding efficiency of intra prediction may be limited to pictures with the smallest / lowest quality and therefore may be limited to coding a minimum amount of video data. Pictures used as reference pictures and / or interlayer reference pictures may be indicated in entries of a reference picture list included in a reference picture list structure.

[0105] Each AU 506 in Figure 5 may contain several pictures. For example, one AU 506 may contain pictures 511 and 515. Another AU 506 may contain pictures 512 and 516. In effect, each AU 506 is a set of one or more coded pictures associated with the same display time (e.g., the same time ID) for output from a decoded picture buffer (DPB) (e.g., for display to a user). Each AUD 508 is a designator or data structure used to indicate the start of an AU (e.g., AU 508) or the boundaries between AUs.

[0106] Previous H.26x video coding families have provided support for scalability in profiles other than those for single-layer coding. Scalable video coding (SVC) is a scalable extension of AVC / H.264 that provides support for spatial, temporal and quality scalability. In SVC, a flag is signaled in each macroblock (MB) in an EL picture to indicate whether the EL MB is predicted using co-located blocks from the lower layer. Predictions from co-located blocks may include texture, motion vectors and / or coding modes. An SVC implementation cannot directly reuse unmodified H.264 / AVC implementations in its design. The syntax and decoding process of SVC EL macroblocks are different from those of H.264 / AVC.

[0107] Scalable HEVC (SHVC) is an extension of the HEVC / H.265 standard that provides support for spatial and quality scalability, multiview HEVC (MV-HEVC) is an extension of HEVC / H.265 that provides support for multiview scalability, and 3DHEVC (3D-HEVC) is an extension of HEVC / H.264 that provides support for more advanced and efficient three-dimensional (3D) video coding than MV-HEVC. It should be noted that temporal scalability is included as an integral part of the single-layer HEVC codec. The design of the multi-layer extension of HEVC exploits the idea that decoded pictures used for inter-layer prediction come only from the same access unit (AU) and are treated as long-term reference pictures (LTRPs) and assigned a reference index in the reference picture list together with other temporal reference pictures of the current layer. Inter-layer prediction (ILP) is achieved at the prediction unit (PU) level by setting the value of a reference index to reference an inter-layer reference picture in a reference picture list.

[0108] Notably, both reference picture resampling and spatial scalability features require resampling of the reference picture or a part thereof. Reference picture resampling (RPR) can be realized either at the picture level or at the coding block level. However, when RPR is referred to as a coding feature, it is a feature for single-layer coding. Even so, it is possible or desirable from a codec design point of view to use the same resampling filter for both the RPR feature of single-layer coding and the spatial scalability feature of multi-layer coding.

[0109] FIG. 6 shows an example of layer-based prediction 600 utilizing an output layer set (OLS), for example as performed to determine MV in block compression step 105, block decoding step 113, motion estimation component 221, motion compensation component 219, motion compensation component 321, and / or motion compensation component 421. Layer-based prediction 500 is compatible with unidirectional inter prediction and / or bidirectional inter prediction, but also between pictures of different layers. The layer-based prediction in FIG. 6 is similar to that in FIG. 5. Therefore, for the sake of brevity, a full description of layer-based prediction will not be repeated.

[0110] Some of the layers in the coded video sequence (CVS) 690 in FIG. 6 are included in an OLS. An OLS is a set of layers where one or more layers are designated as output layers. An output layer is a layer of the OLS that is output. FIG. 6 shows three different OLSs, namely OLS1, OLS2, and OLS3. As shown, OLS1 includes layer N 631 and layer N+1 632. OLS2 includes layer N 631, layer N+1 632, layer N+2 633, and layer N+1 634. OLS3 includes layer N 631, layer N+1 632, and layer N+2 633. Although three OLSs are shown, a different number of OLSs may be used in practical applications.

[0111] Each of the different OLSs may include any number of layers. The different OLSs are generated to accommodate the coding capabilities of a variety of different devices having various coding capabilities. For example, OLS1 may include only two layers and be generated to accommodate a mobile phone having a relatively limited coding capability. On the other hand, OLS2 may include four layers and be generated to accommodate a large screen television that can decode more layers than a mobile phone. OLS3 may include three layers and be generated to accommodate a personal computer, laptop computer, or tablet computer that can decode more layers than a mobile phone but cannot decode most layers like a large screen television.

[0112] The layers in FIG. 6 can all be independent of each other. That is, each layer can be coded without using inter-layer prediction (ILP). In this case, the layer is called a broadcast layer. One or more of the layers in FIG. 6 may be coded using ILP. Whether a layer is a broadcast layer or whether some of the layers are coded using ILP is signaled by a flag in the video parameter set (VPS), which is discussed more fully below. When some layers use ILP, the layer dependencies between the layers are also signaled in the VPS.

[0113] In an embodiment, when a layer is a broadcast layer, only one layer is selected for decoding and output. In an embodiment, when some layers use ILP, all layers (e.g., the entire bitstream) are designated for decoding and certain of the layers are designated as output layers. The one or more output layers may be, for example, 1) only the top layer, 2) all layers, or 3) a set of lower layers designated as the top layer. For example, when a set of lower layers designated as the top layer are designated for output by a flag in the VPS, layer N+3 634 from OLS2 (which is the top layer) and layers N 631 and N+1 632 (which are the lower layers) are output.

[0114] Continuing with reference to FIG. 6, some layers are not included in any of the OLSs. For example, layer N+4 635 is not included in any of OLS1, OLS2, or OLS3. Such layers are called unused layers. Unfortunately, SHVC and MV-HEVC allow such unused layers to be included in a multi-layer video bitstream. This unnecessarily taxes coding resources and reduces coding efficiency.

[0115] A technique for disallowing unused layers in a multi-layer video bitstream is disclosed herein. That is, any layer that is not used in at least one output layer set (OLS) is constrained from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (also known as "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides users with a better user experience when videos are transmitted, received, and / or viewed.

[0116] FIG. 7 illustrates an embodiment of a video bitstream 700. As used herein, the video bitstream 700 may also refer to a coding video bitstream, a bitstream, or variations thereof. As illustrated in FIG. 7, the bitstream 700 includes at least one picture unit (PU) 701. Although three PUs 701 are illustrated in FIG. 7, in actual applications, a different number of PUs 701 may be present in the bitstream 700. Each PU 701 is a set of NAL units that includes exactly one coding picture (e.g., picture 714), consecutive in decoding order, associated with each other according to a specified classification rule.

[0117] In an embodiment, each PU 701 includes one or more of a decoding capability information (DCI) 702, a video parameter set (VPS) 704, a sequence parameter set (SPS) 706, a picture parameter set (PPS) 708, a picture header (PH) 712, and a picture 714. Each of the DCI 702, VPS 704, SPS 706, and PPS 708 may be collectively referred to as a parameter set. In an embodiment, other parameter sets not shown in FIG. 7 may be included in the bitstream 700, such as an adaptation parameter set (APS), which is a syntax structure that includes syntax elements that apply to zero or more slices as determined by zero or more syntax elements found in a slice header.

[0118] The DCI 702, which may also be referred to as a decoding parameter set (DPS) or decoder parameter set, is a syntax structure that contains syntax elements that apply to the entire bitstream. The DCI 702 contains parameters that remain constant for the lifetime of a video bitstream (e.g., bitstream 700), which can translate to the lifetime of a session. The DCI 702 can contain profile, level, and subprofile information to determine a maximum complexity interoperability point that is guaranteed never to be exceeded, even if splicing of video sequences occurs within a session. It can further contain optional constraint flags, which indicate that the video bitstream is constrained in the use of certain features, as indicated by the values ​​of those flags. This allows a bitstream to be labeled as not using certain tools, specifically enabling resource allocation in decoder implementations. Like all parameter sets, the DCI 702 is present when first referenced, meaning it must be referenced by the first picture of a video sequence and transmitted between the first NAL units of the bitstream. Multiple DCIs 702 can be present in a bitstream, but the values ​​of syntax elements therein cannot be contradictory when referenced.

[0119] The VPS 704 contains decoding dependencies or information for the reference picture set configuration of the enhancement layers. The VPS 704 provides an overall perspective or view of the scalable sequence, including what types of operation points are provided, the operation point profiles, tiers, and levels, and several other high level characteristics of the bitstream that can be used as the basis for session negotiation, content selection, etc.

[0120] In an embodiment, when some of the layers are indicated to use ILP, the VPS 704 indicates that the total number of OLSs specified by the VPS is equal to the number of layers, indicates that the i-th OLS includes layers with layer indices from 0 to i, inclusive, and indicates that for each OLS, only the top layer in the OLS is output.

[0121] In an embodiment, the VPS 704 includes syntax and semantics corresponding to CLVS and / or OLS in a video bitstream. The following syntax and semantics corresponding to the VPS 704 may be used to implement embodiments disclosed herein.

[0122] The syntax for the VPS 704 may be as follows: [Table 1-1] [Table 1-2]

[0123] The semantics for the VPS 704 may be as follows: In an embodiment, the VPS 704 includes one or more of the flags and parameters described below.

[0124] The VPS raw byte sequence payload (RBSP) should be available for decoding before it is referenced, and should be included in at least one access unit that has TemporalId provided through external means or equal to 0, and the VPS NAL unit that contains the VPS RBSP should have nuh_layer_id equal to vps_layer_id[0].

[0125] All VPS NAL units with a particular value of vps_video_parameter_set_id in a CVS should have the same content. vps_video_parameter_set_id provides an identifier for the VPS for reference by other syntax elements. vps_max_layers_minus1 plus 1 specifies the maximum number of layers allowed in each CVS that references the VPS. vps_max_sub_layers_minus1 plus 1 specifies the maximum number of temporal sublayers that may exist in each CVS that references the VPS. The value of vps_max_sub_layers_minus1 should be in the range 0 to 6, inclusive.

[0126] vps_all_independent_layers_flag equal to 1 specifies that all layers in the CVS are coded independently without using inter-layer prediction. vps_all_independent_layers_flag equal to 0 specifies that one or more of the layers in the CVS may use inter-layer prediction. When not present, the value of vps_all_independent_layers_flag is inferred to be equal to 1. When vps_all_independent_layers_flag is equal to 1, the value of vps_independent_layer_flag[i] is inferred to be equal to 1. When vps_all_independent_layers_flag is equal to 0, the value of vps_independent_layer_flag[0] is inferred to be equal to 1.

[0127] vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer. For any two non-negative integer values ​​of m and n, when m is less than n, the value of vps_layer_id[m] should be less than vps_layer_id[n]. vps_independent_layer_flag[i] equal to 1 specifies that the layer with index i does not use inter-layer prediction. vps_independent_layer_flag[i] equal to 0 specifies that the layer with index i may use inter-layer prediction and vps_layer_dependency_flag[i] is present in the VPS. When not present, the value of vps_independent_layer_flag[i] is inferred to be equal to 1.

[0128] vps_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer of the layer with index i. vps_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer of the layer with index i. When vps_direct_dependency_flag[i][j] is not present for i and j in the range 0 to vps_max_layers_minus1, inclusive, it is inferred to be equal to 0.

[0129] The variable DirectDependentLayerIdx[i][j], which specifies the jth direct dependent layer of the ith layer, is derived as follows.

number

[0130] The variable GeneralLayerIdx[i], which specifies the layer index of the layer with nuh_layer_id equal to vps_layer_id[i], is derived as follows:

number

[0131] each_layer_is_an_ols_flag equal to 1 specifies that each output layer set contains only one layer, and each layer in the bitstream is itself an output layer set where the single layer contained is the only output layer. each_layer_is_an_ols_flag equal to 0 specifies that an output layer 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 inferred to be equal to 1. Otherwise, when vps_all_independent_layers_flag is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 0.

[0132] ols_mode_idc equal to 0 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i inclusive, and for each OLS, only the top layer in the OLS is output. ols_mode_idc equal to 1 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i inclusive, and for each OLS, all layers in the OLS are output. ols_mode_idc equal to 2 specifies that the total number of OLSs specified by the VPS is explicitly signaled, and for each OLS, the top layer and the set of lower layers in the explicitly signaled OLS are output. The value of ols_mode_idc should be in the range of 0 to 2 inclusive. The value ols_mode_idc of 3 is reserved for future use by ITU-T / ISO / IEC. When vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, the value of ols_mode_idc is inferred to be equal to 2.

[0133] num_output_layer_sets_minus1 plus 1 specifies the total number of OLS specified by the VPS when ols_mode_idc is equal to 2.

[0134] The variable TotalNumOlss, which specifies the total number of OLSs specified by the VPS, is derived as follows:

number

[0135] layer_included_flag[i][j] specifies whether the jth layer (i.e., the layer with nuh_layer_id equal to vps_layer_id[j]) is included in the ith OLS when ols_mode_idc is equal to 2. layer_included_flag[i][j] equal to 1 specifies that the jth layer is included in the ith OLS. layer_included_flag[i][j] equal to 0 specifies that the jth layer is not included in the ith OLS.

[0136] The variable NumLayersInOls[i], which specifies the number of layers in the i-th OLS, and the variable LayerIdInOls[i][j], which specifies the nuh_layer_id value of the j-th layer in the i-th OLS, are derived as follows:

number

[0137] The variable OlsLayerIdx[i][j], which specifies the OLS layer index of the layer with nuh_layer_id equal to LayerIdInOls[i][j], is derived as follows:

number

[0138] The lowest layer in each OLS should be an independent layer, i.e. for each i in the range 0 to TotalNumOlss-1, inclusive, the value of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]] should be equal to 1.

[0139] Each layer should be included in at least one OLS specified by the VPS. That is, there may be at least one pair of values ​​i and j for each layer with a particular value of nuh_layer_idnuhLayerId equal to one of vps_layer_id[k] for k ranging from 0 to vps_max_layers_minus1 inclusive, where i ranges from 0 to TotalNumOlss-1 inclusive and j ranges from NumLayersInOls[i]-1 inclusive, such that the value of LayerIdInOls[i][j] is equal to nuhLayerId.

[0140] Any layer in the OLS should be an output layer of the OLS or a reference layer (direct or indirect) of the output layer of the OLS.

[0141] vps_output_layer_flag[i][j] specifies whether the jth layer in the ith OLS is output when ols_mode_idc is equal to 2. vps_output_layer_flag[i] equal to 1 specifies that the jth layer in the ith OLS is output. vps_output_layer_flag[i] equal to 0 specifies that the jth layer in the ith OLS is not output. 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] is inferred to be equal to 1.

[0142] For the variable OutputLayerFlag[i][j], a value of 1 specifies that the jth layer in the ith OLS is output, a value of 0 specifies that the jth layer in the ith OLS is not output, and is derived as follows:

number

[0143] NOTE: The 0th OLS only includes the bottom layer (i.e. the layer with nuh_layer_id equal to vps_layer_id[0]), and for the 0th OLS, only the included layers are output.

[0144] vps_constraint_info_present_flag equal to 1 specifies that the general_constraint_info() syntax structure is present in the VPS. vps_constraint_info_present_flag equal to 0 specifies that the general_constraint_info() syntax structure is not present in the VPS.

[0145] vps_reserved_zero_7bits should be equal to 0 in bitstreams conforming to this version of this VVC draft. Other values ​​of vps_reserved_zero_7bits are reserved for future use by ITU-T / ISO / IEC. In embodiments, decoders should ignore the value of vps_reserved_zero_7bits.

[0146] general_hrd_params_present_flag equal to 1 specifies that the syntax elements num_units_in_tick and time_scale and the syntax structure general_hrd_parameters() are present in the SPS RBSP syntax structure. general_hrd_params_present_flag equal to 0 specifies 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.

[0147] num_units_in_tick is the number of time units of a clock running at a frequency of time_scale Hz that corresponds to one increment (called a clock tick) of the clock tick counter. num_units_in_tick should be greater than 0. A clock tick is in seconds and is equal to num_units_in_tick divided by time_scale. For example, when the picture rate of a video signal is 25 Hz, time_scale may be equal to 27,000,000, num_units_in_tick may be equal to 1,080,000, and therefore a clock tick may be equal to 0.04 seconds.

[0148] time_scale is the number of time units that elapse in one second. For example, a time coordinate system that measures time using a 27MHz clock has a time_scale of 27,000,000. The value of time_scale should be greater than 0.

[0149] vps_extension_flag equal to 0 specifies that vps_extension_data_flag is not present in the VPS RBSP syntax structure. vps_extension_flag equal to 1 specifies that the vps_extension_data_flag syntax element is present in the VPS RBSP syntax structure.

[0150] vps_extension_data_flag may have any value. Its presence and value do not affect decoder compliance with the profile specified in this version of this specification. Decoders conforming to this version of this specification SHOULD ignore all vps_extension_data_flag syntax elements.

[0151] SPS 706 contains data that is common to all pictures in a sequence of pictures (SOP). SPS 706 is a syntax structure that contains syntax elements that apply to zero or more entire CLVSs, as determined by the content of syntax elements found in the PPS referenced by syntax elements found in each picture header. In contrast, PPS 708 contains data that is common to an entire picture. PPS 708 is a syntax structure that contains syntax elements that apply to zero or more entire coded pictures, as determined by the content of syntax elements found in each picture header (e.g., PH 712).

[0152] DCI 702, VPS 704, SPS 706, and PPS 708 are included in different types of Network Abstraction Layer (NAL) units. A NAL unit is a syntax structure that contains an indication of the type of data that follows (e.g., coding video data). NAL units are classified into video coding layer (VCL) and non-VCL NAL units. VCL NAL units contain data that represent values ​​of samples in a video picture, while non-VCL NAL units contain any relevant additional information, such as parameter sets (important data that is applicable to many VCL NAL units) and supplemental extension information (timing information and other supplemental data that is not necessary for decoding the values ​​of samples in a video picture, but that may increase the usefulness of the decoded video signal).

[0153] In an embodiment, DCI 702 is included in a non-VCL NAL unit designated as a DCI NAL unit or a DPS NAL unit. That is, a DCI NAL unit has a DCI NAL unit type (NUT) and a DPS NAL unit has a DPS NUT. In an embodiment, VPS 704 is included in a non-VCL NAL unit designated as a DPS NAL unit. Thus, the VPS NAL unit has a VPS NUT. In an embodiment, SPS 706 is a non-VCL NAL unit designated as an SPS NAL unit. Thus, the SPS NAL unit has an SPS NUT. In an embodiment, PPS 708 is included in a non-VCL NAL unit designated as a PPS NAL unit. Thus, the PPS NAL unit has a PPS NUT.

[0154] PH 712 is a syntax structure that includes syntax elements that apply to all slices (e.g., slice 718) of a coding picture (e.g., picture 714). In an embodiment, PH 712 is a new type of non-VCL NAL unit designated as a PH NAL unit. Thus, a PH NAL unit has a PH NUT (e.g., PH_NUT). In an embodiment, each PU 701 includes one and only one PH 712. That is, a PU 701 includes a single or isolated PH 712. In an embodiment, exactly one PH NAL unit exists for each picture 701 in the bitstream 700.

[0155] In an embodiment, a PH NAL unit associated with PH 712 has a temporal ID and a layer ID. The temporal ID identifier indicates the location of the PH NAL unit in time relative to other PH NAL units in a bitstream (e.g., bitstream 701). The layer ID indicates the layer (e.g., layer 531 or layer 532) that contains the PH NAL unit. In an embodiment, the temporal ID is similar to, but distinct from, the POC. The POC uniquely identifies each picture in sequence. In a single-layer bitstream, the temporal ID and the POC will be the same. In a multi-layer bitstream (e.g., see FIG. 5), pictures in the same AU have different POCs but the same temporal ID.

[0156] In an embodiment, a PH NAL unit precedes a VCL NAL unit that contains the first slice 718 of the associated picture 714. This establishes an association between the PH 712 and a slice 718 of the picture 714 associated with the PH 712 without having to have a picture header ID signaled in the PH 712 and referenced from a slice header 720. Thus, it can be inferred that all VCL NAL units between two PHs 712 belong to the same picture 714, and the picture 714 is associated with the first PH 712 between the two PHs 712. In an embodiment, the first VCL NAL unit following a PH 712 contains the first slice 718 of the picture 714 associated with the PH 712.

[0157] In an embodiment, the PH NAL units follow a picture level parameter set (e.g., PPS) or a higher level parameter set (e.g., DCI (aka DPS), VPS, SPS, PPS, etc.) with temporal and layer IDs that are both smaller than the temporal and layer IDs of the PH NAL units, respectively. As a result, those parameter sets are not repeated within a picture or access unit. This ordering allows PH712 to be resolved immediately: parameter sets that contain parameters related to an entire picture are placed before the PH NAL units in the bitstream; those that contain parameters for only a portion of a picture are placed after the PH NAL units.

[0158] As one alternative, the PH NAL units follow a picture level parameter set and a prefix supplemental enhancement information (SEI) message, or a higher level parameter set, such as a DCI (also known as DPS), VPS, SPS, PPS, APS, SEI message.

[0159] A picture 714 is an array of luma samples in monochrome format, or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color formats. In an embodiment, each PU 701 contains one and only one picture 714. Thus, within each PU 701, there is only one PH 712 and only one picture 714 corresponding to that PH 712. That is, a PU 701 contains a single or isolated picture 714.

[0160] Pictures 714 may be frames or fields. However, in one CVS 716, all pictures 714 are frames or all pictures 714 are fields. A CVS 716 is a coded layer video sequence (CLVS) for each coded layer video sequence (CLVS) in the video bitstream 700. Notably, if the video bitstream 700 contains a single layer, then the CVS 716 and the CLVS are the same. Only when the video bitstream 700 contains multiple layers (e.g., as shown in Figures 5 and 6), do the CVS 716 and the CLVS differ.

[0161] Each picture 714 includes one or more slices 718. A slice 718 is an integer number of complete tiles or an integer number of contiguous complete CTU rows within a tile of a picture (e.g., picture 714). Each slice 718 is exclusively contained in a single NAL unit (e.g., a VCL NAL unit). A tile (not shown) is a CTU of a rectangular region within a particular tile column and a particular tile row within a picture (e.g., picture 714). A CTU (not shown) is a CTB of luma samples, two corresponding CTBs of chroma samples for a picture with three sample arrays, or a CTB of samples for a monochrome picture or a picture coded with three separate color planes and a syntax structure used to code the samples. A CTB (not shown) may be an N×N block of samples for some value of N. As a result, the division of a component into CTBs is a partition. A block (not shown) is an M×N (M columns×N rows) array of samples (e.g., pixels), or an M×N array of transform coefficients.

[0162] In an embodiment, each slice 718 includes a slice header 720. The slice header 720 is a part of the coding slice 718 that contains data elements related to all tiles or CTU rows within the tile represented in the slice 718. That is, the slice header 720 includes information about the slice 718, such as the slice type, which reference pictures are used, etc.

[0163] The pictures 714 and their slices 718 contain data related to the image or video being encoded or decoded, and thus may simply be referred to as the payload or data being carried within the bitstream 700.

[0164] Those skilled in the art will appreciate that the bitstream 700 may include other parameters and information in practical applications.

[0165] FIG. 8 is an embodiment of a decoding method 800 implemented by a video decoder (e.g., video decoder 400). Method 800 may be executed after a bitstream is received directly or indirectly from a video encoder (e.g., video encoder 300). Method 800 improves the decoding process by disallowing unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is constrained from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (a.k.a. "codec") in video coding is improved over current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0166] At block 802, a video decoder receives a video bitstream including a VPS (e.g., VPS 704) and multiple layers (e.g., Layer N 631, Layer N+1 632, etc.). In an embodiment, each layer is included in at least one OLS (e.g., OLS1, OLS2, etc.) specified by the VPS. That is, for each layer with a particular value of nuh_layer_id, nuhLayerId is equal to one of k vps_layer_id[k] in the range of 0 to vps_max_layers_minus1, inclusive, and there should be at least one pair of values ​​of i and j, where i ranges from 0 to TotalNumOlss-1, inclusive, and j ranges from NumLayersInOls[i]-1, inclusive, such that the value of LayerIdInOls[i][j] is equal to nuhLayerId.

[0167] In an embodiment, a video decoder expects each layer to be included in at least one OLS (e.g., OLS1, OLS2, etc.) specified by the VPS, based on VVC or some other standard as described above. However, if the decoder determines that this condition is not true, the decoder may detect an error, signal the error, request that the received bitstream (or portions thereof) be retransmitted, or take some other corrective measures to ensure that a compliant bitstream is received.

[0168] The nuh_layer_id is signaled in the bitstream and is used to determine the nuhLayerId. Each of nuh_layer_id and nuhLayerId contains an identifier (ID) used to uniquely identify a layer. The vps_layer_id[k] is used to specify the layer ID within the VPS 704. The vps_max_layers_minus1 is used to specify the maximum number of layers in the OLS. The TotalNumOlss is used to specify the total number of OLSs contained in the CLVS and / or bitstream, and finally, the NumLayersInOls specifies the number of layers in the OLS.

[0169] In an embodiment, each and every layer available to the decoder is specified in the VPS received by the decoder, i.e., the VPS received by the decoder specifies all layers, regardless of whether each layer is included in the OLS received by the decoder. In an embodiment, each and every OLS generated by the encoder is specified in the VPS received by the decoder, i.e., the VPS received by the decoder specifies all OLSs, regardless of whether that OLS is received by the decoder.

[0170] In an embodiment, each layer in the plurality of layers includes a set of video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units that all have a particular value of a layer identifier (ID). In an embodiment, the at least one OLS includes two output layers, one of the two output layers referencing the other of the two output layers. In an embodiment, the at least one OLS includes one or more output layers. In an embodiment, for each of the plurality of layers having a particular value of layer ID specified in the VPS, one of the layers in the at least one OLS should also have a particular value of layer ID.

[0171] At block 804, the video decoder decodes a picture (e.g., picture 615) from one of the layers. In an embodiment, the picture is included in at least one output layer of the OLS.

[0172] In an embodiment, the method 800 further includes selecting an output layer from the at least one OLS before the decoding step. In an embodiment, the method 800 further includes selecting a picture from the output layer after the output layer is selected.

[0173] Once the pictures are decoded, they may be used to produce or generate an image or video sequence for display to a user on a display or screen of an electronic device (e.g., a smartphone, tablet, laptop, personal computer, etc.).

[0174] FIG. 9 is an embodiment of a method 900 for encoding a video bitstream implemented by a video encoder (e.g., video encoder 300). Method 900 may be performed when pictures (e.g., from a video) are encoded into a video bitstream and sent to a video decoder (e.g., video decoder 400). Method 900 improves the encoding process by prohibiting unused layers in a multi-layer video bitstream. That is, any layer that is not used in at least one output layer set (OLS) is constrained from being included in the multi-layer bitstream. This avoids having irrelevant information in the coding process and improves coding efficiency. Thus, the coder / decoder (a.k.a. "codec") in video coding is improved with respect to current codecs. In practical terms, the improved video coding process provides a better user experience for users when videos are transmitted, received, and / or viewed.

[0175] At block 902, the video encoder generates a VPS (e.g., VPS 704) that specifies a number of layers (e.g., N 631, Layer N+1 632, etc.) and one or more OLSs (e.g., OLS1, OLS2, etc.). In an embodiment, each layer from the number of layers is included in at least one of the OLSs specified by the VPS. That is, for each layer with a particular value of nuh_layer_id, nuhLayerId is equal to one of k vps_layer_id[k] in the range of 0 to vps_max_layers_minus1, inclusive, and there should be at least one pair of values ​​of i and j, where i ranges from 0 to TotalNumOlss-1, inclusive, and j ranges from NumLayersInOls[i]-1, inclusive, such that the value of LayerIdInOls[i][j] is equal to nuhLayerId. In an embodiment, the video encoder is constrained such that each layer from the plurality of layers is included in at least one of the OLSs specified by the VPS. That is, the video encoder is required to have a layer from the plurality of layers included in at least one of the OLSs specified by the VPS. Such a constraint or requirement ensures that the bitstream complies with, for example, VVC or some other standard modified as set forth herein. However, the encoder may be capable of operating in other modes that are not constrained, for example when operating under a different standard or a different version of the same standard.

[0176] The nuh_layer_id is signaled in the bitstream and is used to determine the nuhLayerId. Each of nuh_layer_id and nuhLayerId contains an identifier (ID) used to uniquely identify a layer. The vps_layer_id[k] is used to specify the layer ID within the VPS 704. The vps_max_layers_minus1 is used to specify the maximum number of layers in the OLS. The TotalNumOlss is used to specify the total number of OLSs contained in the CLVS and / or bitstream. Finally, the NumLayersInOls specifies the number of layers in the OLS.

[0177] In an embodiment, each of the one or more OLSs includes one or more output layers, each of the output layers including one or more pictures. In an embodiment, each layer in the plurality of layers includes a set of video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units, all having a particular value of a layer identifier (ID).

[0178] In an embodiment, one of the OLSs includes two output layers, one of which references the other of the two output layers. In an embodiment, for each of a plurality of layers having a particular value of Layer ID specified in the VPS, one of the layers in the one or more OLSs should also have a particular value of Layer ID.

[0179] In an embodiment, a hypothetical reference decoder (HRD) located in the encoder checks all layers and the OLS. If the HRD finds a layer that does not exist in any OLS as described herein, the HRD returns a compliance test error. That is, the HRD compliance test ensures that there are no unused layers. Thus, the encoder encodes according to the no unused layers requirement, but the HRD enforces this requirement.

[0180] At block 904, the video encoder encodes the layers and the VPS into a video bitstream. At block 906, the video encoder stores the video bitstream for communication to the video decoder. The video bitstream may be stored in memory until the video bitstream is transmitted to the video decoder. Once received by the video decoder, the encoded video bitstream may be decoded (e.g., as described above) to produce or generate images or video sequences for display to a user on a display or screen of an electronic device (e.g., a smartphone, tablet, laptop, personal computer, etc.).

[0181] 10 is a schematic diagram of a video coding device 1000 (e.g., video encoder 300 or video decoder 400) according to an embodiment of the present disclosure. The video coding device 1000 is suitable for implementing embodiments of the disclosure as described herein. The video coding device 1000 includes ingress ports 1010 and receiver units (Rx) 1020 for receiving data, a processor, logic unit, or central processing unit (CPU) 1030 for processing data, transmitter units (Tx) 1040 and egress ports 1050 for transmitting data, and a memory 1060 for storing data. The video coding device 1000 may also include optical-to-electrical (OE) components and electrical-to-optical (EO) components for egress or ingress of optical or electrical signals connected to an ingress port 1010, a receiver unit 1020, a transmitter unit 1040, and an egress port 1050.

[0182] The processor 1030 is implemented by hardware and software. The processor 1030 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), and digital signal processors (DSPs). The processor 1030 communicates with the ingress port 1010, the receiver unit 1020, the transmitter unit 1040, the egress port 1050, and the memory 1060. The processor 1030 includes a coding module 1070. The coding module 1070 implements the above-disclosed embodiments. For example, the coding module 1070 implements, processes, prepares, or provides various codec functions. The inclusion of the coding module 1070 thus provides substantial improvements to the functionality of the video coding device 1000 and provides transformation of the video coding device 1000 into different states. Alternatively, the coding module 1070 is implemented as instructions stored in memory 1060 and executed by the processor 1030 .

[0183] Video coding device 1000 may also include input and / or output (I / O) devices 1080 for communicating data to and from a user. I / O devices 1080 may include output devices such as a display for displaying video data, speakers for outputting audio data, etc. I / O devices 1080 may also include input devices such as a keyboard, mouse, trackball, etc., and / or corresponding interfaces for interfacing with such output devices.

[0184] Memory 1060 may include one or more disks, tape drives, and solid state drives, and may be used to store programs when they are selected for execution and as overflow data storage to store instructions and data read during execution of the programs. Memory 1060 may be volatile and / or non-volatile, and may be read-only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random-access memory (SRAM).

[0185] 11 is a schematic diagram of an embodiment of a means for coding 1100. In an embodiment, the means for coding 1100 is implemented in a video coding device 1102 (e.g., video encoder 300 or video decoder 400). The video coding device 1102 includes a means for receiving 1101. The means for receiving 1101 is configured to receive a picture to encode or to receive a bitstream to decode. The video coding device 1102 includes a means for transmitting 1107 coupled to the means for receiving 1101. The means for transmitting 1107 is configured to transmit the bitstream to a decoder or to transmit the decoded image to a display means (e.g., one of the I / O devices 1080).

[0186] The video coding device 1102 includes a storage means 1103. The storage means 1103 is coupled to at least one of the receiving means 1101 or the transmitting means 1107. The storage means 1103 is configured to store instructions. The video coding device 1102 further includes a receiving means 1105. The processing means 1105 is coupled to the storage means 1103. The processing means 1105 is configured to execute the instructions stored in the storage means 1103 in order to perform the methods disclosed herein.

[0187] It should be further understood that the steps of the exemplary methods described herein do not necessarily have to be performed in the order described, and the order of steps of such methods should be understood to be merely exemplary. Similarly, additional steps may be included in such methods, and certain steps may be omitted or combined in methods according to various embodiments of the present disclosure.

[0188] Although several embodiments have been provided in this disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the disclosure. The examples of the present invention should be considered illustrative and not restrictive, and are not intended to be limited to the details given herein. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0189] Additionally, the techniques, systems, subsystems, and methods described and illustrated in various embodiments may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items illustrated or discussed as being coupled or directly coupled or in communication with each other may be indirectly coupled or in communication through some interface, device, or intermediate component, whether electrical, mechanical, or otherwise. Other examples of modifications, substitutions, and alterations will be ascertained by those skilled in the art and may be made without departing from the spirit and scope of the present disclosure.

Claims

1. 1. A program which, when executed by a video decoder, causes the video decoder to perform a method, the method comprising: receiving, by the video decoder, a video bitstream including a video parameter set (VPS) and a plurality of layers, each layer being included in at least one output layer set (OLS) specified by the VPS, each layer being specified within the OLS and including LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls [i][j] specifies the nuhLayerId of the jth layer in the ith OLS; and decoding, by the video decoder, a picture from one of the plurality of layers.

2. 1. A program that, when executed by a video encoder, causes the video encoder to perform a method, the method comprising: generating, by the video encoder, a video parameter set (VPS) specifying a plurality of layers and one or more output layer sets (OLSs), the video encoder constraining each layer from the plurality of layers to be included in at least one of the OLSs specified by the VPS, each layer being specified within the OLS and including LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls [i][j] specifies the nuhLayerId of the jth layer in the ith OLS; encoding, by the video encoder, the plurality of layers and the VPS into a video bitstream; storing the video bitstream for communication by the video encoder to a video decoder; and

3. An apparatus for storing a bitstream, the apparatus comprising: at least one storage medium; and at least one communication interface; the at least one communication interface is configured to receive or transmit the bitstream; the at least one storage medium is configured to store the bitstream; The bitstream includes a video parameter set (VPS) and a plurality of layers, each layer being included in at least one output layer set (OLS) specified by the VPS, each layer being specified within the OLS, and each layer being included in at least one output layer set (OLS) specified by LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls The apparatus, wherein [i][j] specifies the nuhLayerId of the jth layer in the ith OLS.

4. 1. A method for storing a bitstream, comprising the steps of: receiving or transmitting a bitstream over a communications interface; storing the bitstream in one or more storage media, the bitstream including a video parameter set (VPS) and a plurality of layers, each layer included in at least one output layer set (OLS) specified by the VPS, each layer being specified within the OLS and each layer being represented by LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls A method in which [i][j] specifies the nuhLayerId of the jth layer in the ith OLS.

5. An apparatus for transmitting a bitstream, comprising: At least one storage medium configured to store at least one bitstream, the bitstream including a video parameter set (VPS) and a plurality of layers, each layer included in at least one output layer set (OLS) specified by the VPS, each layer being specified within the OLS and having LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls a storage medium, wherein [i][j] specifies the nuhLayerId of the jth layer in the ith OLS; at least one processor configured to obtain one or more bitstreams from one of the at least one storage media and transmit the one or more bitstreams to a destination device.

6. 1. A method for transmitting a bitstream, comprising: Storing at least one bitstream in at least one storage medium, the bitstream including a video parameter set (VPS) and a plurality of layers, each layer being included in at least one output layer set (OLS) specified by the VPS, each layer being specified within the OLS and having LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls [i][j] specifies the nuhLayerId of the jth layer in the ith OLS; obtaining one or more bitstreams from one of the at least one storage medium; transmitting the one or more bitstreams to a destination device.

7. 1. A system for processing a bitstream, comprising: an encoding device; one or more storage devices; and a decoding device; The encoding device is configured to obtain a video signal and to encode the video signal to obtain one or more bitstreams, the bitstream including a video parameter set (VPS) and a plurality of layers, each layer being included in at least one output layer set (OLS) specified by the VPS, each layer being specified within the OLS and having LayerIdInOls The value of [i][j] is equal to nuhLayerId, i is in the range 0 to TotalNumOlss-1, and j is equal to NumLayersInOls [i]-1, the TotalNumOlss specifies the total number of OLSs specified by the VPS, and the NumLayersInOls [i] specifies the number of layers in the i-th OLS, and the LayerIdInOls [i][j] specifies the nuhLayerId of the jth layer in the ith OLS, the one or more storage devices are adapted to store the one or more bitstreams; The system, wherein the decoder is used to decode the one or more bitstreams.

Images