Decoded video sequence start access unit in video decoding

Abstract

A video decoder can be configured to output layers of video data based on the layers specified in the output layer set mode and based on the actual layers received in the access unit. Thus, the video decoder can be configured to output the actual received layers instead of restarting the video bitstream if the actual received layers do not match the layers specified in the output layer set mode. In another example, the video encoder can disable inter-frame prediction when the sub-picture ID of a sub-picture in a currently decoded picture does not match the sub-picture ID of a sub-picture in a reference picture.

Description

[0001] This application claims priority to U.S. Application No. 17 / 196,444, filed on March 9, 2021, U.S. Provisional Application No. 62 / 987,765, filed on March 10, 2020, U.S. Provisional Application No. 63 / 004,241, filed on April 2, 2020, and U.S. Provisional Application No. 63 / 009,230, filed on April 13, 2020, the entire contents of each of which are incorporated herein by reference. U.S. Application No. 17 / 196,444, filed on March 9, 2021, claims the benefit of U.S. Provisional Application No. 62 / 987,765, filed on March 10, 2020, U.S. Provisional Application No. 63 / 004,241, filed on April 2, 2020, and U.S. Provisional Application No. 63 / 009,230, filed on April 13, 2020. Technical Field

[0002] The present disclosure relates to video encoding and video decoding. Background Art

[0003] Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, so-called "smart phones", video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10, Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions of such standards. Video devices can more efficiently transmit, receive, encode, decode, and / or store digital video information by implementing such video coding techniques.

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) can be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture can use spatial prediction relative to reference samples in neighboring blocks in the same picture or temporal prediction relative to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the Invention

[0005] In general, the present disclosure describes techniques for decoding video data. In one example, the present disclosure describes techniques for outputting layers of video data according to an output layer set mode. More specifically, the video decoder can be configured to output layers of video data according to the layers specified in the output layer set mode and based on the actual layers received in the access unit. In this way, the video decoder 300 can be configured to output the actual received layers instead of restarting the video bitstream if the actual received layers do not match the layers specified in the output layer set mode. In this way, the delay in the video output can be reduced and the user experience can be improved.

[0006] In another example, the present disclosure describes techniques for encoding video data when using sub-pictures. Specifically, the present disclosure describes techniques for handling prediction decisions when sub-pictures have been reordered from one picture to the next. In one example, a video encoder can be configured to still use inter-frame prediction for pictures with reordered sub-pictures, rather than requiring such pictures to be decoded using only intra-frame prediction, but inter-frame prediction can be disabled when the sub-picture ID of the sub-picture in the current decoded picture does not match the sub-picture ID of the sub-picture in the reference picture. In this way, inter-frame prediction can be avoided for specific sub-pictures that have been reordered, without requiring intra-frame prediction to be used for the entire picture. In this way, decoding efficiency can be improved.

[0007] In one example of the present disclosure, a method for decoding video data includes: receiving an indication of an output layer set mode, wherein the output layer set mode specifies a layer ID of a layer to be output; receiving one or more layers of video data, wherein the received one or more layers are less than all layers of the layers specified by the output layer set mode; and outputting at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers.

[0008] In another example, the present disclosure describes a device configured to decode video data, the device comprising: a memory configured to store one or more layers of video data; and one or more processors implemented in a circuit and in communication with the memory, the one or more processors configured to: receive an indication of an output layer set pattern, wherein the output layer set pattern specifies a layer ID of a layer to be output; receive one or more layers of video data, wherein the received one or more layers are less than all of the layers specified by the output layer set pattern; and output at least one of the received one or more layers according to the output layer set pattern based on the specified layer to be output and the received one or more layers.

[0009] In another example, the present disclosure describes a device configured to decode video data, the device comprising: a component for receiving an indication of an output layer set mode, wherein the output layer set mode specifies a layer ID of a layer to be output; a component for receiving one or more layers of video data, wherein the received one or more layers are less than all of the layers specified by the output layer set mode; and a component for outputting at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers.

[0010] In another example, the present disclosure describes a non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors of a device configured to decode video data to: receive an indication of an output layer set mode, wherein the output layer set mode specifies a layer ID of a layer to be output; receive one or more layers of video data, wherein the received one or more layers are less than all of the layers specified by the output layer set mode; and output at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers.

[0011] In another example, the present disclosure describes a method for encoding video data, the method comprising: determining whether a first sub-picture ID of a first sub-picture in a current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; determining an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encoding the first sub-picture using one or more of the available decoding modes.

[0012] In another example, the present disclosure describes a device configured to encode video data, the device comprising: a memory configured to store one or more layers of video data; and one or more processors implemented in a circuit and communicating with the memory, the one or more processors configured to: determine whether a first sub-picture ID of a first sub-picture in a current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; determine an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encode the first sub-picture using one or more of the available decoding modes.

[0013] In another example, the present disclosure describes a device configured to encode video data, the device comprising: a component for determining whether a first sub-picture ID of a first sub-picture in a current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; a component for determining an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and a component for encoding the first sub-picture using one or more of the available decoding modes.

[0014] In another example, the present disclosure describes a non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors of a device configured to encode video data to: determine whether a first sub-picture ID of a first sub-picture in a current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; determine an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encode the first sub-picture using one or more of the available decoding modes.

[0015] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0017] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0018] Figure 3 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0019] Figure 4 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0020] Figure 5 is a flowchart illustrating an example video encoding method.

[0021] Figure 6 is a flow chart illustrating an example video decoding method.

[0022] Figure 7 is a flowchart illustrating another example video encoding method.

[0023] Figure 8 is a flowchart illustrating another example video decoding method. DETAILED DESCRIPTION

[0024] In general, the present disclosure describes techniques for decoding video data. In one example, the present disclosure describes techniques for outputting layers of video data according to an output layer set mode. More specifically, the video decoder can be configured to output layers of video data according to the layers specified in the output layer set mode and based on the actual layers received in the access unit. In this way, the video decoder 300 can be configured to output the actual received layers instead of restarting the video bitstream if the actual received layers do not match the layers specified in the output layer set mode. In this way, the delay in the video output can be reduced and the user experience can be improved.

[0025] In another example, the present disclosure describes a technique for encoding video data when using sub-pictures. Specifically, the present disclosure describes a technique for handling prediction decisions when sub-pictures have been reordered from one picture to the next. In one example, a video encoder can be configured to still use inter-frame prediction for pictures with reordered sub-pictures, rather than requiring such pictures to be decoded using only intra-frame prediction, but inter-frame prediction can be disabled when the sub-picture ID of the sub-picture in the current decoded picture does not match the sub-picture ID of the sub-picture in the reference picture. In this way, inter-frame prediction can be avoided for specific sub-pictures that have been reordered, without requiring intra-frame prediction to be used for the entire picture. In this way, decoding efficiency can be improved.

[0026] Figure 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of the present disclosure. The techniques of the present disclosure are generally directed to decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data can include original, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0027] like Figure 1 , in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides the video data to destination device 116 via a computer-readable medium 110. Source device 102 and destination device 116 may include any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets (such as smartphones), televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0028] exist Figure 1In the example of , source device 102 includes video source 104, memory 106, video encoder 200 and output interface 108. Destination device 116 includes input interface 122, video decoder 300, memory 120 and display device 118. According to the present disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply a technology for decoding video data. Therefore, source device 102 represents an example of a video encoding device, while destination device 116 represents an example of a video decoding device. In other examples, the source device and destination device may include other components or arrangements. For example, source device 102 may receive video data from an external video source (such as an external camera). Similarly, destination device 116 may be connected to an external display device instead of including an integrated display device.

[0029] like Figure 1 The system 100 shown in FIG. 1 is merely an example. In general, any digital video encoding and / or decoding device can perform techniques for decoding video data. The source device 102 and the destination device 116 are merely examples of such decoding devices, wherein the source device 102 generates decoded video data for transmission to the destination device 116. This disclosure refers to a "decoding" device as a device that performs decoding (encoding and / or decoding) of data. Thus, the video encoder 200 and the video decoder 300 represent examples of decoding devices, and more specifically, examples of a video encoder and a video decoder, respectively. In some examples, the source device 102 and the destination device 116 can operate in a substantially symmetrical manner, such that each of the source device 102 and the destination device 116 includes video encoding and decoding components. Thus, the system 100 can support one-way or two-way video transmission between the source device 102 and the destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0030] Typically, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a series of consecutive pictures (also referred to as "frames") of video data to video encoder 200, which encodes the picture data. Video source 104 of source device 102 may include a video capture device, such as a camera, a video archive containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. As another alternative, video source 104 may generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from the order in which they are received (sometimes referred to as "display order") into a decoding order for decoding. Video encoder 200 may generate a bitstream comprising encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 for receipt and / or retrieval by, for example, input interface 122 of destination device 116 .

[0031] Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memory. In some examples, memories 106 and 120 can store raw video data, such as raw video from video source 104 and raw, decoded video data from video decoder 300. Additionally or alternatively, memories 106 and 120 can store software instructions executable by, for example, video encoder 200 and video decoder 300, respectively. Although memory 106 and memory 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 can also include internal memory for functionally similar or equivalent purposes. Furthermore, memories 106 and 120 can store, for example, encoded video data output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106 and 120 can be allocated as one or more video buffers, for example, to store raw, decoded, and / or encoded video data.

[0032] The computer-readable medium 110 can represent any type of medium or device capable of transmitting encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to send the encoded video data directly to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. According to a communication standard such as a wireless communication protocol, the output interface 108 can demodulate the transmission signal including the encoded video data, and the input interface 122 can demodulate the received transmission signal. The communication medium can include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium can include routers, switches, base stations, or any other equipment that can help facilitate communication from the source device 102 to the destination device 116.

[0033] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0034] In some examples, source device 102 may output the encoded video data to a file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or downloading. File server 114 may be any type of server device capable of storing and transmitting the encoded video data to destination device 116. File server 114 may represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Destination device 116 may access the encoded video data from file server 114 via any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of both, suitable for accessing the encoded video data stored on file server 114. File server 114 and input interface 122 may be configured to operate according to a streaming protocol, a download transfer protocol, or a combination thereof.

[0035] The output interface 108 and the input interface 122 may represent wireless transmitters / receivers, modems, wired network connection components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where the output interface 108 and the input interface 122 include wireless components, the output interface 108 and the input interface 122 may be configured to transmit data, such as encoded video data, according to a cellular communication standard such as 4G, 4G-LTE (Long Term Evolution), LTE-Advanced, 5G, etc. In some examples where the output interface 108 includes a wireless transmitter, the output interface 108 and the input interface 122 may be configured to transmit data, such as encoded video data, according to other wireless standards such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee 5G), or the like. TM ),Bluetooth TM Standards, etc.) to transmit data, such as encoded video data. In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include a SoC device to perform the functions attributed to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device to perform the functions attributed to video decoder 300 and / or input interface 122.

[0036] The techniques of the present disclosure may be applied to support video decoding for any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission such as Dynamic Adaptive Streaming over HTTP (DASH), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0037] The input interface 122 of the destination device 116 receives an encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 (which is also used by the video decoder 300), such as syntax elements with values ​​describing characteristics and / or processing of video blocks or other coded units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays decoded pictures of the decoded video data to a user. The display device 118 may represent any of a variety of display devices, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0038] although Figure 1Although not shown, in some examples, the video encoder 200 and the video decoder 300 can each be integrated with an audio encoder and / or an audio decoder and can include appropriate MUX-DEMUX units or other hardware and / or software to process a multiplexed stream including both audio and video in a common data stream. If applicable, the MUX-DEMUX unit can comply with the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0039] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is partially implemented in software, the device can store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, either of which can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. A device including the video encoder 200 and / or the video decoder 300 can include an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular phone.

[0040] The video encoder 200 and the video decoder 300 may operate according to a video coding standard, such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC), or extensions thereof, such as multi-view and / or scalable video coding extensions. Alternatively, the video encoder 200 and the video decoder 300 may operate according to other proprietary or industry standards, such as ITU-T H.266, also known as Versatile Video Coding (VVC). Bross et al., published “Universal Video Coding (Draft 8)” JVET-Q2001-vD (hereinafter referred to as “VVC Draft 8”) at the 17th meeting of ITU-T SG 16WP3 and ISO / IEC JTC 1 / SC 29 / WG 11 in Brussels from January 7 to 17, 2020, describe the latest draft of the VVC standard. However, the technology of the present disclosure is not limited to any particular coding standard.

[0041] Typically, the video encoder 200 and video decoder 300 may perform block-based coding of pictures. The term "block" generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luma and / or chroma data. Typically, the video encoder 200 and video decoder 300 may decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than decoding the red, green, and blue (RGB) data of samples of a picture, the video encoder 200 and video decoder 300 may decode luma and chroma components, where the chroma components may include both red-hue and blue-hue chroma components. In some examples, the video encoder 200 converts the received RGB-formatted data to a YUV representation prior to encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, pre-processing and post-processing units (not shown) may perform these conversions.

[0042] The present disclosure may generally refer to the decoding (e.g., encoding and decoding) of a picture to include the process of encoding or decoding the data of the picture. Similarly, the present disclosure may refer to the decoding of a block of a picture to include the process of encoding or decoding the data of the block, such as prediction and / or residual decoding. A coded video bitstream typically includes a series of values ​​for syntax elements that represent decoding decisions (e.g., decoding modes) and partitioning of the picture into blocks. Therefore, references to decoding a picture or block should generally be understood to refer to decoding the values ​​of the syntax elements that form the picture or block.

[0043] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as the video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video decoder partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node," and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video decoder may further partition the PUs and TUs. For example, in HEVC, the residual quadtree (RQT) represents the partitioning of the TU. In HEVC, a PU represents inter-frame prediction data, and a TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0044] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video decoder (such as the video encoder 200) partitions a picture into multiple coding tree units (CTUs). The video encoder 200 may partition the CTU according to a tree structure such as a quadtree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure removes the concept of multiple partition types, such as the separation between CUs, PUs, and TUs of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0045] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also known as ternary tree (TT)) partitioning. A ternary tree or ternary tree partitioning is a partitioning in which a block is divided into three sub-blocks. In some examples, the ternary tree or ternary tree partitioning divides the block into three sub-blocks without dividing the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0046] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma and chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for respective chroma components).

[0047] The video encoder 200 and the video decoder 300 can be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partitioning structures according to HEVC. For explanation purposes, the description of the technology of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the technology of this disclosure can also be applied to video decoders configured to use quadtree partitioning or other types of partitioning.

[0048] Blocks (e.g., CTUs or CUs) can be grouped in a picture in various ways. As an example, a tile can refer to a rectangular area of ​​a CTU row within a particular tile in a picture. A tile can be a rectangular area of ​​a CTU within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular area of ​​a CTU with a height equal to the height of the picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile row refers to a rectangular area of ​​a CTU with a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the width of the picture.

[0049] In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a tile may not be referred to as a tile.

[0050] Tiles in a picture can also be arranged in slices. A slice can be an integer number of tiles of a picture that can be contained exclusively in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes a contiguous sequence of multiple complete tiles or just complete tiles of a single tile.

[0051] This disclosure may use "NxN" and "N by N" interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, e.g., 16x16 samples or 16 by 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Likewise, an NxN CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in columns and rows. Furthermore, a CU need not necessarily have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

[0052] The video encoder 200 encodes video data representing prediction and / or residual information and other information for a CU. The prediction information indicates how the CU will be predicted to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0053] To predict a CU, the video encoder 200 may typically form a prediction block for the CU through inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU from data of a previously decoded picture, while intra-frame prediction generally refers to predicting a CU from previously decoded data of the same picture. To perform inter-frame prediction, the video encoder 200 may use one or more motion vectors to generate a prediction block. The video encoder 200 may typically perform a motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), or other such difference calculations to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 may use unidirectional prediction or bidirectional prediction to predict the current CU.

[0054] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0055] To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of VVC provide sixty-seven intra prediction modes, including various directional modes as well as planar and DC modes. Typically, the video encoder 200 selects an intra prediction mode from which to predict samples of the current block, which describes neighboring samples of the current block (e.g., a block of a CU). Assuming that the video encoder 200 decodes CTUs and CUs in raster scan order (left to right, top to bottom), such samples may typically be above, above-left, or to the left of the current block in the same picture as the current block.

[0056] The video encoder 200 encodes data indicating a prediction mode for the current block. For example, for inter-frame prediction mode, the video encoder 200 may encode data indicating which of various available inter-frame prediction modes to use and motion information corresponding to the mode. For example, for unidirectional or bidirectional inter-frame prediction, the video encoder 200 may use advanced motion vector prediction (AMVP) or merge mode to encode motion vectors. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0057] After a prediction (such as intra-frame prediction or inter-frame prediction of a block), the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a prediction block formed for the block using the corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to produce transformed data in a transform domain rather than a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying the one or more transforms.

[0058] As noted above, after any transforms that produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to the process by which transform coefficients are quantized to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 may round an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0059] After quantization, the video encoder 200 may scan the transform coefficients to produce a one-dimensional vector from the two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and lower energy (and therefore higher frequency) transform coefficients at the back of the vector. In some examples, the video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce a serialized vector and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode the values ​​of syntax elements that describe metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0060] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. For example, the context may relate to whether the symbol's neighboring values ​​are zero. The probability determination may be based on the context assigned to the symbol.

[0061] The video encoder 200 may also generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, to the video decoder 300, for example, in a picture header, a block header, a slice header, or other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). The video decoder 300 may also decode such syntax data to determine how to decode the corresponding video data.

[0062] In this way, the video encoder 200 can generate a bitstream including encoded video data (e.g., syntax elements describing the partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks). Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0063] In general, the video decoder 300 performs a process that is inverse to that performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of syntax elements of the bitstream in a manner substantially similar to, but inverse to, the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for partitioning a picture into CTUs and partitioning each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define CUs of the CTUs. The syntax elements may also define prediction and residual information for a block of video data (e.g., a CU).

[0064] The residual information can be represented by, for example, quantized transform coefficients. The video decoder 300 can inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra-frame or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 can then combine the prediction block with the residual block (sample by sample) to reproduce the original block. The video decoder 300 can perform additional processing, such as performing a deblocking process to reduce visual artifacts along block boundaries.

[0065] According to the technology of the present disclosure, the video decoder 300 can receive one or more layers of video data and output layers of the one or more layers according to an output layer set mode, wherein the output layer set mode outputs the layer with the highest layer ID that has been received. In one example, the video decoder 300 can be configured to receive an indication of an output layer set mode, wherein the output layer set mode specifies the layer ID of the layer to be output; receive one or more layers of video data, wherein the one or more layers received are less than all layers of the layers specified by the output layer set mode; and output at least one layer of the one or more layers received according to the output layer set mode based on the specified layer to be output and the one or more layers received.

[0066] In another example, the video decoder 300 may receive one or more layers of video data and output all layers of the one or more layers according to an output layer set mode that outputs all layers present in the received one or more layers.

[0067] In another example, the video encoder 200 and the video decoder 300 may set the picture output flag to zero if the nuh_layer_id of the current picture is not equal to the nuh_layer_id of the output layer specified in the output layer set.

[0068] In another example, the video encoder 200 and the video decoder 300 may code the adaptive parameter set in one or more of a picture header or a slice header, and code the video data according to information in the adaptive parameter set.

[0069] In another example, the video encoder 200 and the video decoder 300 apply a constraint for reordering sub-pictures of a current picture when a previously decoded picture has reordered sub-pictures and the previously decoded picture is used as a reference picture by the current picture; and decode the current picture according to the constraint. For example, the video encoder 200 may be configured to determine whether a first sub-picture ID of a first sub-picture in the current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; determine available decoding modes based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encode the first sub-picture using one or more of the available decoding modes.

[0070] This disclosure may generally refer to "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to the communication of values ​​for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal the values ​​of syntax elements in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As mentioned above, source device 102 may transmit the bitstream to destination device 116 in substantially real time or in non-real time, such as when storing syntax elements to storage device 112 for later retrieval by destination device 116.

[0071] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, and dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where in this example, 0 indicates horizontal split and 1 indicates vertical split. For quadtree splits, there is no need to indicate the split type because the quadtree node splits the block horizontally and vertically into 4 sub-blocks of equal size. Therefore, the video encoder 200 can encode syntax elements (such as split information) at the region tree level (i.e., solid lines) of the QTBT structure 130 and syntax elements (such as split information) at the prediction tree level (i.e., dashed lines) of the QTBT structure 130, and the video decoder 300 can decode these syntax elements. The video encoder 200 may encode video data (such as prediction data and transform data) of the CU represented by the terminal leaf node of the QTBT structure 130 , and the video decoder 300 may decode the video data.

[0072] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes at the first and second levels of the QTBT structure 130. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, indicating the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, indicating the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, indicating the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, indicating the minimum allowed binary tree leaf node size).

[0073] The root node of the QTBT structure corresponding to the CTU can have four child nodes at the first level of the QTBT structure, each of which can be split according to the quadtree partitioning. That is, the nodes of the first level are leaf nodes (no child nodes) or have four child nodes. The example of the QTBT structure 130 represents such a node as including a parent node and child nodes with solid lines for branching. If the node of the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the node can be further split by the corresponding binary tree. The binary tree splitting of a node can be iterated until the node resulting from the split reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such a node as having a dotted line for branching. The binary tree leaf node is called a decoding unit (CU), which is used for prediction (e.g., intra-frame picture or inter-frame picture prediction) and transformation without any further partitioning. As discussed above, a CU can also be referred to as a "video block" or "block."

[0074] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (luminance sample and two corresponding 64x64 chroma samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate quadtree leaf nodes. The size of the quadtree leaf node can range from 16x16 (i.e., MinQTSize) to 128x128 (i.e., the CTU size). If the quadtree leaf node is 128x128, the leaf quadtree node will not be further split by the binary tree because the size exceeds MaxBTSize (i.e., 64x64, in this example). Otherwise, the quadtree leaf node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node of the binary tree, and its binary tree depth is 0. When the binary tree depth reaches MaxBTDepth (4 in this example), further splitting is not allowed. A binary tree node with a width equal to MinBTSize (4 in this example) implies that no further vertical splits are allowed. Similarly, a binary tree node with a height equal to MinBTSize implies that no further horizontal splits are allowed for the binary tree node. As mentioned above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further partitioning.

[0075] Figure 3 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 3This is provided for illustrative purposes and should not be considered limiting of the techniques as broadly illustrated and described in this disclosure. For illustrative purposes, this disclosure describes a video encoder 200 based on techniques for VVC (ITU-T H.266, under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video encoding devices configured for other video coding standards.

[0076] exist Figure 3 In the example of FIG, the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 can be implemented in one or more processors or processing circuits. For example, the units of the video encoder 200 can be implemented as one or more circuits or logic elements as part of a hardware circuit or as part of a processor of an FPGA or an ASIC. Moreover, the video encoder 200 can include additional or alternative processors or processing circuits to perform these and other functions.

[0077] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives video data stored in the video data memory 230. The DPB 218 can act as a reference picture memory that stores reference video data for use in predicting subsequent video data by the video encoder 200. The video data memory 230 and the DPB 218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and the DPB 218 can be provided by the same memory device or by separate memory devices. In various examples, the video data memory 230 can be on-chip with the other components of the video encoder 200 as shown, or off-chip relative to those components.

[0078] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory internal to the video encoder 200 (unless specifically described as such), or to memory external to the video encoder 200 (unless specifically described as such). Rather, references to the video data memory 230 should be understood as reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data of a current block to be encoded). Figure 1 Memory 106 may also provide temporary storage for outputs from various units of video encoder 200 .

[0079] Figure 3 Various units are shown to assist in understanding the operations performed by the video encoder 200. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. A fixed-function circuit refers to a circuit that provides a specific function and has preset operations that can be performed. A programmable circuit refers to a circuit that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For example, a programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more of the units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0080] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed from programmable circuits. In an example where the operation of the video encoder 200 is performed using software executed by programmable circuits, the memory 106 ( Figure 1 ) may store instructions (eg, object code) for software that video encoder 200 receives and executes, or another memory (not shown) within video encoder 200 may store such instructions.

[0081] The video data memory 230 is configured to store the received video data. The video encoder 200 can retrieve the picture of the video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 can be the original video data to be encoded.

[0082] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units to perform video prediction according to other prediction modes. For example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0083] Mode selection unit 202 typically coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values ​​for such combinations. The encoding parameters may include the partitioning of CTUs into CUs, the prediction mode for a CU, the transform type for the residual data of a CU, the quantization parameter for the residual data of a CU, etc. Mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0084] The video encoder 200 may partition a picture retrieved from the video data memory 230 into a series of CTUs and pack one or more CTUs into a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure, such as the QTBT structure described above or the quadtree structure of HEVC. As described above, the video encoder 200 may form one or more CUs from the partitioned CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks."

[0085] Typically, mode select unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of a PU and TU in HEVC). For inter prediction of the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate values ​​representing how similar potential reference blocks are to the current block, such as based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), and the like. Motion estimation unit 222 may typically perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block with the lowest value from these calculations, indicating the reference block that most closely matches the current block.

[0086] Motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of the current block in the current picture. Motion estimation unit 222 may then provide the motion vectors to motion compensation unit 224. For example, for unidirectional inter prediction, motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, motion estimation unit 222 may provide two motion vectors. Motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, motion compensation unit 224 may interpolate values ​​for the prediction block based on one or more interpolation filters. Furthermore, for bidirectional inter prediction, motion compensation unit 224 may retrieve data for two reference blocks identified by their respective motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0087] As another example, for intra prediction or intra prediction coding, the intra prediction unit 226 may generate a prediction block from samples of neighboring current blocks. For example, for directional mode, the intra prediction unit 226 may generally mathematically combine the values ​​of neighboring samples and pad these calculated values ​​in a defined direction across the current block to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 may calculate the average of samples neighboring the current block and generate a prediction block to include this calculated average for each sample of the prediction block.

[0088] Mode selection unit 202 provides the prediction block to residual generation unit 204. Residual generation unit 204 receives the original, unencoded version of the current block from video data memory 230 and the prediction block from mode selection unit 202. Residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, residual generation unit 204 may also determine the difference between sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0089] In the example where the mode select unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As indicated above, the size of a CU may refer to the size of the luma coding block of the CU, and the size of a PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra prediction, and symmetric PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter prediction.

[0090] In an example where mode select unit 202 does not further partition a CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of the luma coding block of the CU. Video encoder 200 and video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0091] For other video coding techniques such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding (as a few examples), mode selection unit 202 generates a prediction block for the current block being encoded via the corresponding unit associated with the coding technique. In some examples, such as palette mode coding, mode selection unit 202 may not generate a prediction block, but instead generate syntax elements that indicate how to reconstruct the block based on the selected palette. In such a mode, mode selection unit 202 may provide these syntax elements to entropy coding unit 220 to be encoded.

[0092] As described above, the residual generation unit 204 receives video data for a current block and a corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0093] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform multiple transforms on the residual block, such as a primary transform and a secondary transform, such as a rotation transform. In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0094] Quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode select unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce a loss of information, and therefore, the quantized transform coefficients may have lower precision than the original transform coefficients generated by transform processing unit 206.

[0095] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (albeit potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples from the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0096] Filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0097] The video encoder 200 stores the reconstructed block in the DPB 218. For example, in an example where the operation of the filter unit 216 is not performed, the reconstruction unit 214 may store the reconstructed block in the DPB 218. In an example where the operation of the filter unit 216 is performed, the filter unit 216 may store the filtered reconstructed block in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve a reference picture formed from the reconstructed (and potentially filtered) block from the DPB 218 to perform inter-frame prediction on blocks of subsequently encoded pictures. In addition, the intra-frame prediction unit 226 may use the reconstructed block of the current picture in the DPB 218 to perform intra-frame prediction on other blocks in the current picture.

[0098] In general, entropy coding unit 220 may entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 may entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 may entropy encode prediction syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from mode selection unit 202. Entropy coding unit 220 may perform one or more entropy encoding operations on the syntax elements (which is another example of video data) to generate entropy-encoded data. For example, entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioned entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, entropy coding unit 220 may operate in a bypass mode, in which the syntax elements are not entropy encoded.

[0099] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required to reconstruct blocks of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0100] The operations described above are described with respect to blocks. Such descriptions should be understood as operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are the luma and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are the luma and chroma components of a PU.

[0101] In some examples, the operations performed for luma coding blocks do not need to be repeated for chroma coding blocks. As an example, the operations for identifying the motion vector (MV) and reference picture for the luma coding block do not need to be repeated to identify the MV and reference picture for the chroma blocks. Instead, the MV of the luma coding block can be scaled to determine the MV for the chroma blocks, and the reference picture can be the same. As another example, the intra prediction process can be the same for luma coding blocks and chroma coding blocks.

[0102] Video encoder 200 represents an example of a device configured to code an adaptation parameter set in one or more of a picture header or a slice header, and to code video data according to information in the adaptation parameter set.

[0103] In another example, the video encoder 200 applies a constraint for reordering sub-pictures of a current picture when a previously decoded picture has reordered sub-pictures and the previously decoded picture is used as a reference picture by the current picture, and decodes the current picture according to the constraint. As will be explained in more detail below, the video encoder 200 can be configured to determine whether a first sub-picture ID of a first sub-picture in the current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture, determine available decoding modes based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture, and encode the first sub-picture using one or more of the available decoding modes.

[0104] Figure 4 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 4 This is provided for illustrative purposes and is not intended to limit the techniques broadly exemplified and described in this disclosure. For illustrative purposes, this disclosure describes a video decoder 300 based on techniques for VVC (ITU-T H.266, under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video coding devices configured for other video coding standards.

[0105] exist Figure 4In the example of FIG, video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or processing circuits. For example, the units of video decoder 300 may be implemented as one or more circuits or logic elements as part of a hardware circuit or as part of a processor of an FPGA or an ASIC. Furthermore, video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0106] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units to perform prediction according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0107] The CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of the video decoder 300. The video data stored in the CPB memory 320 may be, for example, received from the computer-readable medium 110 ( Figure 1 ). CPB memory 320 may include a CPB that stores coded video data (e.g., syntax elements) from a coded video bitstream. Furthermore, CPB memory 320 may store video data other than syntax elements for coded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, which video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the coded video bitstream. CPB memory 320 and DPB 314 may be formed from any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0108] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) to retrieve the decoded video data. That is, memory 120 may store data as discussed above in conjunction with CPB memory 320. Likewise, when some or all of the functionality of video decoder 300 is implemented in software to be performed by processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0109] Figure 4 The various units shown in FIG are shown to aid in understanding the operations performed by the video decoder 300. The units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 3 , fixed-function circuits refer to circuits that provide specific functions and have preset operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more of the units can be different circuit blocks (fixed-function or programmable), and in some examples, one or more of the units can be integrated circuits.

[0110] The video decoder 300 may include an ALU, an EFU, digital circuits, analog circuits, and / or a programmable core formed from programmable circuits. In examples where the operation of the video decoder 300 is performed by software executed on the programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) for the software that the video decoder 300 receives and executes.

[0111] The entropy decoding unit 302 may receive the encoded video data from the CPB and perform entropy decoding on the video data to reproduce syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0112] Typically, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (where the block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0113] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or a transform mode indication. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and also determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block comprising the transform coefficients.

[0114] After inverse quantization unit 306 forms a transform coefficient block, inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

[0115] In addition, prediction processing unit 304 generates a prediction block based on the prediction information syntax element entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, motion compensation unit 316 may generate the prediction block. In this case, the prediction information syntax element may indicate a reference picture in DPB 314 from which the reference block is retrieved, and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 may generally generate a prediction block in a manner substantially similar to that described with respect to motion compensation unit 224 ( Figure 3 ) to perform the inter-frame prediction process in the manner described.

[0116] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 may generally generate a prediction block in a manner substantially similar to that described with respect to the intra-prediction unit 226 ( Figure 3 The intra prediction process is performed in the manner described in the preceding text. The intra prediction unit 318 can retrieve data of neighboring samples of the current block from the DPB 314.

[0117] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

[0118] The filter unit 312 may perform one or more filtering operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0119] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in examples where the operations of the filter unit 312 are not performed, the reconstruction unit 310 may store the reconstructed block to the DPB 314. In examples where the operations of the filter unit 312 are performed, the filter unit 312 may store the filtered reconstructed block to the DPB 314. As discussed above, the DPB 314 may provide reference information such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation to the prediction processing unit 304. In addition, the video decoder 300 may output a decoded picture (e.g., decoded video) from the DPB 314 for subsequent presentation on a display such as a video processor. Figure 1 on the display device 118 of the display device.

[0120] As will be explained in more detail below, the video decoder 300 represents an example of a video decoding device that includes a memory configured to store video data, and one or more processing units implemented in circuitry and configured to receive one or more layers of the video data and output layers of the one or more layers according to an output layer set mode, wherein the output layer set mode outputs the layer with the highest layer ID that has been received. In another example, the video decoder 300 can be configured to receive an indication of an output layer set mode, wherein the output layer set mode specifies layer IDs of layers to be output; receive one or more layers of video data, wherein the one or more layers received are less than all of the layers specified by the output layer set mode; and output at least one layer of the one or more layers received according to the output layer set mode based on the specified layer to be output and the one or more layers received.

[0121] In another example, the video decoder 300 may receive one or more layers of video data and output all layers of the one or more layers according to an output layer set mode that outputs all layers present in the received one or more layers.

[0122] In another example, the video decoder 300 may set the picture output flag to zero if the nuh_layer_id of the current picture is not equal to the nuh_layer_id of the output layer specified in the output layer set.

[0123] In another example, the video decoder 300 may code the adaptive parameter set in one or more of a picture header or a slice header, and code the video data according to the information in the adaptive parameter set.

[0124] In another example, the video decoder 300 applies a constraint for reordering sub-pictures of a current picture, and codes the current picture according to the constraint, if a previously decoded picture has reordered sub-pictures and the previously decoded picture is used as a reference picture by the current picture.

[0125] VVC draft 8 includes the following definitions, including definitions for the Coded Video Sequence Start (CVSS) access unit (AU).The CVSS AU is the first AU in the bitstream.

[0126] Coded Video Sequence (CVS): a sequence of AUs consisting of a CVSS AU, followed by zero or more AUs that are not CVSS AUs (including all subsequent AUs, but excluding any subsequent AU that is a CVSS AU), in decoding order.

[0127] Coded Video Sequence Start (CVSS) AU: An AU in which there is a PU for each layer in the CVS and the coded picture in each PU is a CLVSS picture.

[0128] 7.4.2.4.2 AU order and its association with CVS

[0129] A bitstream consists of one or more CVSs.

[0130] CVS consists of one or more AUs. The order of PUs and their association with AUs is described in clause 7.4.2.4.3.

[0131] The first AU of CVS is a CVSS AU, where each current PU is a CLVSS PU, which is either an IRAP PU with NoOutputBeforeRecoveryFlag equal to 1 or a GDR PU with NoOutputBeforeRecoveryFlag equal to 1.

[0132] Each CVSS AU should have a PU for each of the layers present in the CVS.

[0133] A requirement for bitstream conformance is that, when present, the next AU following an AU containing an EOS NAL unit shall be a CVSS AU.

[0134] VVC draft 8 also includes the following definitions:

[0135] Access Unit (AU) - a set of PUs that belong to different layers and contain coded pictures associated with the same time for output from the DPB.

[0136] Picture Unit (PU) - a set of NAL units that are associated with each other according to a specified classification rule, are consecutive in decoding order, and contain exactly one coded picture.

[0137] Coding layer video sequence start (CLVSS) PU—a PU where the coded picture is a CLVSS picture.

[0138] Intra Random Access Point (IRAP) - an AU where there is a PU for each layer in the CVS and the coded picture in each PU is an IRAP picture.

[0139] IRAP PU - a PU where the coded picture is an IRAP picture.

[0140] Progressive Decoding Refresh (GDR) PU—a PU where the coded picture is a GDR picture.

[0141] End of Sequence (EOS)

[0142] Video Coding Layer (VCL) Network Abstraction Layer (NAL) unit - a collective term for coded slice NAL units and a subset of NAL units with a reserved value of nal_unit_type that are classified as VCL NAL units in this specification.

[0143] VVC draft 8 also specifies the constraint that there should be at least one VLC NAL (e.g., slice) for each layer included in the output layer set:

[0144] There is at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​in LayerIdInOls[opOlsIdx] in BitstreamToDecode.

[0145] The output layer set (OLS) mode (i.e., which layers are output) is defined by ols_mode_idc signaled in the VPS:

[0146] 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 includes layers with layer indices from 0 to i (inclusive), and for each OLS, only the highest layer in the OLS is output.

[0147] In this context, the "highest layer" is the layer with the highest layer id value.

[0148] 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 includes layers with layer indices from 0 to i (inclusive), and for each OLS, all layers in the OLS are output.

[0149] 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 output layer is explicitly signaled and the other layers are direct or indirect reference layers of the output layer of the OLS.

[0150] The value of ols_mode_idc shall be in the range of 0 to 2, inclusive. The value 3 of ols_mode_idc is reserved for future use by ITU-T | ISO / IEC.

[0151] 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.

[0152] In VVC draft 8, the decoding process starts with sub-bitstream extraction, where the video decoder 300 is configured to remove NAL units of layers not included in the OLS identified by the OLS index. Since this process is specified for the OLS index, the video decoder 300 should be configured to re-initiate the sub-bitstream extraction process when the OLS index changes, which means that the first AU should be a CVSS AU containing PUs for each layer present in the CVS. This means that only intra slices should be used to decode pictures in the lowest layer (e.g., the base layer).

[0153] When the OLS mode specifies that only the highest layer is output, or when all layers included in the OLS are output (e.g., based on the value of ols_mode_idc), the video decoder 300 outputs only the highest layer specified in the OLS or outputs all layers specified in the OLS based on the current constraint that the first picture (CVSS AU) in VVC draft 8 should contain the VCL NAL (slice) of all layers. However, in some decoding scenarios, the highest layer may not exist in the AU, or not all layers specified in the OLS may exist in the AU.

[0154] For example, in a video conferencing scenario with low bandwidth, the client (e.g., the video decoder 300) may receive only base layer (e.g., lower quality) pictures. When the bandwidth increases, the client may start receiving the base layer and one or more enhancement layer pictures (e.g., better quality pictures) without using CVSS AUs. For example, with the addition of enhancement layer VCL NAL units, base layer decoding may continue using only inter-layer prediction. However, the constraints in VVC draft 8 prohibit such decoding scenarios because the OLS index needs to be changed to specify other output layers. The OLS index is changed, so the OLS mode restarts the bitstream. For example, the video encoder 200 may be configured to signal the I picture of the base layer, which results in additional overhead.

[0155] In another example, for some coding scenarios when all layers are output, the layers may have different frame rates, meaning that some AUs may not have pictures present for all layers. However, based on the current definition in VVC draft 8, the i-th OLS includes layers with layer indices from 0 to i (inclusive), and for each OLS, all layers in the OLS are output. However, not all layers may be present in an AU.

[0156] This disclosure describes various techniques for addressing the above-mentioned issues. The techniques of this disclosure can be used independently or in any combination. Example implementations of the present disclosure are described below with respect to VVC Draft 8. Additions to VVC Draft 8 are shown between the tags <ADD> and < / ADD>. Deletions from VVC Draft 8 are shown between the tags <DEL> and < / DEL>.

[0157] In one example of the present disclosure, it is proposed to modify the OLS mode definition so that the video decoder 300 can be configured to output only the current layer in the AU and not require all layers to be present in the CVSS AU. For example, when only the highest layer in the output mode is utilized, the video decoder 300 can be configured to output only the highest layer actually present in a specific AU, rather than outputting the highest layer specified in the OLS indicated in the VPS.

[0158] In one example, the video decoder 300 may receive a bitstream of video data comprising a plurality of AUs. The video decoder 300 may receive and decode a syntax element (e.g., ols_mode_idc) associated with the bitstream of video data, wherein the syntax element indicates an OLS mode for the bitstream. The syntax element (e.g., ols_mode_idc) may be received and decoded from a VPS. The video decoder 300 may be configured to operate according to the OLS mode indicated by the syntax element for the AU associated with the VPS in which the syntax element is received.

[0159] In one example, a syntax element (e.g., ols_mode_idc) indicates that the OLS mode specifies that the highest layer specified in the OLS is to be output. In this example, the video decoder 300 can be configured to output the highest layer actually received in the AU of the bitstream, rather than being restricted to outputting only the highest layer specified in the OLS. That is, in some cases, the highest layer actually received in the AU may not match the highest layer specified in the OLS.

[0160] In more detail, assume that there are two layers (layer 0 and layer 1) included in the OLS and the highest layer (e.g., layer 1) is output. VVC draft 8 requires the video decoder 300 to always output layer 1. According to the technology of the present disclosure, the video decoder 300 can be configured to output only the highest layer present in the AU. If the AU includes only layer 0, the video decoder 300 is configured to decode layer 0 and output layer 0. If another AU has both layer 0 and layer 1, the video decoder 300 is configured to decode layer 1 and output layer 1.

[0161] Thus, in one example of the present disclosure, the video decoder 300 may be configured to receive one or more layers of video data and output a layer of the one or more layers according to an output layer set mode, wherein the output layer set mode outputs the layer with the highest layer ID present in the received one or more layers. In other words, the video decoder 300 may be configured to receive an indication of an output layer set mode, wherein the output layer set mode specifies the layer IDs of the layers to be output; receive one or more layers of video data, wherein the received one or more layers are less than all of the layers of the layers specified by the output layer set mode; and output at least one layer of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers.

[0162] In a more specific example, the video decoder 300 may receive one or more layers of video data in video coding layer (VCL) network abstraction layer (NAL) units (e.g., slices), where the one or more layers received are fewer than all of the layers specified by the output layer set mode. In one example, the video decoder 300 may receive fewer than all of the VCL NAL units (e.g., slices) for the layers specified in the output layer set. Rather than restarting the bitstream, the video decoder 300 will output the layers actually received according to the output layer set mode. For example, the output layer set mode may specify that a particular layer (e.g., the highest layer in the output layer set) is to be output. If the actual highest layer specified in the output layer set mode is not received, the video decoder 300 will output the highest layer actually received. Similarly, if the output layer set mode specifies that all layers in the output layer set are to be output, the video decoder 300 will output all of the layers actually received, even if fewer than all of the layers specified in the output layer set are not actually received.

[0163] In another example, to receive one or more layers of video data, the video decoder 300 is configured to receive the one or more layers of video data in an access unit. Furthermore, to output at least one of the one or more layers, the video decoder 300 is configured to output at least one of the received one or more layers according to an output layer set mode based on the specified layer ID of the layer to be output and the one or more layers actually received in the access unit. In one example, the output layer set mode specifies that the highest layer is to be output. In this example, to output at least one of the one or more layers, the video decoder 300 is configured to output the layer with the highest layer ID actually received in the access unit. In this manner, the video decoder 300 can be configured to decode and output the layers according to a specific OLS mode without restarting the bitstream, even if the number and type of output layers received in the AU changes. This reduces delays in video output and improves the user experience.

[0164] Similar techniques can be applied to the case where an OLS mode is specified to output all layers. According to the techniques of the present disclosure, the video decoder 300 can be configured to output all layers actually present in a particular AU, rather than requiring the video decoder 300 to always output all layers specified for the OLS mode in the VPS. Therefore, even for the same OLS mode, the video decoder 300 can output fewer or more layers for some AUs than for other AUs.

[0165] In this example, similar to the above, the video decoder 300 may receive a bitstream of video data including a plurality of AUs. The video decoder 300 may receive and decode a syntax element (e.g., ols_mode_idc) associated with the bitstream of video data, wherein the syntax element indicates an OLS mode for the bitstream. The syntax element (e.g., ols_mode_idc) may be received and decoded from a VPS. The video decoder 300 may be configured to operate according to the OLS mode indicated by the syntax element for the AU associated with the VPS in which the syntax element is received.

[0166] In this example, the syntax element (e.g., ols_mode_idc) indicates that the OLS mode specifies that all layers specified in the OLS are to be output. In this example, the video decoder 300 can be configured to output all layers actually received in the AU of the bitstream, rather than being limited to outputting all layers in the layers specified in the OLS.

[0167] In more detail, assume that there are three layers (layer 0, layer 1, and layer 2) included in the OLS. In one OLS mode (e.g., ols_mode_idc is equal to 1), VVC draft 8 requires the video decoder 300 to always output all layers in the specified layer (e.g., layer 0, layer 1, and layer 2). According to the technology of the present disclosure, the video decoder 300 can be configured to output only the layers actually present in the AU. If the AU includes only layer 0 and layer 2, the video decoder 300 is configured to decode layer 0 and layer 2 and output layer 0 and layer 2. If another AU has both layer 0 and layer 1, the video decoder 300 is configured to decode layer 0 and layer 1 and output layer 0 and layer 1. If yet another AU has each of layer 0, layer 1, and layer 2, the video decoder 300 is configured to decode layer 0, layer 1, and layer 2 and output layer 0, layer 1, and layer 2.

[0168] Therefore, in another example of the present disclosure, the video decoder 300 can be configured to receive one or more layers of video data and output all layers in the one or more layers according to an output layer set mode, wherein the output layer set mode outputs all layers present in the received one or more layers. For example, the output layer set mode specifies that all received layers are to be output. In order to output at least one layer of the one or more layers, the video decoder 300 is configured to output all layers that have been actually received in the access unit. Similarly, according to the technology of the present disclosure, the video decoder 300 can be configured to decode and output layers according to a specific OLS mode without restarting the bitstream when the number and type of output layers received in the AU changes. In this way, the delay in the video output can be reduced and the user experience can be improved.

[0169] When a custom mode of OLS is used (e.g., ols_mode_idc=2), outputting only the current layer may not be applied, and instead, the video decoder 300 is configured to output the layer specified in the OLS, as it may be the intention to output all specified layers. In some examples, a technique of outputting only the current layer in an AU may be applied.

[0170] For example, in a video conferencing scenario, the OLS is specified not to output the highest layer included in the OLS, but rather the highest layer present in a specific AU. This allows for a gradual switch from the base layer to the enhancement layer without specifying a new OLS index and avoiding bitstream resets or restarting the CVS. Since I pictures are not required in the lowest layer (base layer), the proposed method has an advantage in compression efficiency.

[0171] In another example, in a video decoding scenario when more than one layer is specified in the OLS, the video decoder 300 can be configured to start the decoding process from a CVSS AU, where there is only one layer that can be output, such as the lowest (base) layer. Later in the bitstream, when bandwidth increases, the video decoder 300 can switch to the enhancement layer. In another example, the first picture (e.g., CVSS AU) should include at least the lowest layer specified in the OLS / CVS or all independent layers included in the OLS / CVS.

[0172] Another advantage of the proposed technology is that it allows video encoder 200 and / or video decoder 300 to remove dependent higher layers from the bitstream without specifying another OLS for this situation. In some cases, since the OLS is specified in the VPS, specifying another OLS may mean rewriting the VPS.

[0173] In VVC Draft 8, in one example, the proposed method can be implemented as follows: Additions to VVC Draft 8 are shown between the tags <ADD> and < / ADD>. Deletions from VVC Draft 8 are shown between the tags <DEL> and < / DEL>.

[0174] • Each CVSS AU should have a PU for each <ADD>independent< / ADD> layer present in the CVS.

[0175] • Each CVSS AU shall have a PU for the <ADD>lowest nuh_layer_id layer< / ADD> present in the CVS.

[0176] In addition, the semantics of ols_mode_idc are modified as follows:

[0177] 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 includes layers with layer indices from 0 to i (inclusive), and for each OLS, only the highest <ADD>current< / ADD> layer in <DEL>OLS< / DEL> is output.

[0178] 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 includes layers with layer indices from 0 to i (inclusive), and for each OLS, outputs <DEL>all <ADD>current < / ADD> layers in <DEL>OLS.

[0179] The current layer in the ols_mode_idc semantics above can mean the current layer in the output AU or the current layer in the output CVS. In addition, the "is output" and "are output" in the semantics above can be modified to "can be output" because the PictureOutputFlag of the output layer may be set to 0, in which case other layer pictures can be output.

[0180] Additionally, the constraint requiring the presence of at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​in LayerIdInOls[opOlsIdx] in BitstreamToDecode is removed.

[0181] In one example, the following language was removed from VVC Draft 8:

[0182] <del> There is at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​in LayerIdInOls[opOlsIdx] in BitstreamToDecode.< / del>

[0183] The above removal allows for situations where only one layer (e.g., the lowest layer or base layer) is always present and more than one layer is included in the OLS without requiring other layers to be in the bitstream. In this case, for example, in a mode where the highest current layer is output, the same OLS can be used, whereas VVC draft 8 requires the video encoder 200 to specify another OLS for such output.

[0184] In another example, instead of removing the constraint requiring at least one VCL NAL unit where nuh_layer_id is equal to each of the nuh_layer_id values ​​in LayerIdInOls[opOlsIdx] in BitstreamToDecode, the constraint is modified so that in the bitstream to be decoded, there is at least one VCL NAL for each independent layer in the bitstream or at least one VCL NAL for a layer present in a CVSS AU.

[0185] In one example, the modified constraint may be expressed as follows:

[0186] There is at least one VCL NAL unit with nuh_layer_id equal to each of the independent layer's nuh_layer_id values ​​in LayerIdInOls[opOlsIdx] in BitstreamToDecode.

[0187] In another example, if it is still desired to maintain the current design in VVC Draft 8, that is, the only layer specified as the output layer in OLS can be output, then for all pictures of the layer that is not the output layer in OLS, the picture output flag PictureOutputFlag that controls whether the picture is output should be set to 0.

[0188] In one example, the above example can be implemented in VVC Draft 8 as follows:

[0189] PictureOutputFlag is set as follows:

[0190] - Set PictureOutputFlag to 0 if one of the following conditions is true:

[0191] - The current picture is a RASL picture and the NoOutputBeforeRecoveryFlag of the associated IRAP picture is equal to 1.

[0192] - gdr_enabled_flag is equal to 1, and the current picture is a GDR picture with NoOutputBeforeRecoveryFlag equal to 1.

[0193] - gdr_enabled_flag is equal to 1, and the current picture is associated with a GDR picture with NoOutputBeforeRecoveryFlag equal to 1, and PicOrderCntVal of the current picture is less than RpPicOrderCntVal of the associated GDR picture.

[0194] -sps_video_parameter_set_id is greater than 0, ols_mode_idc is equal to 0, and the current AU contains a picture picA that satisfies all of the following conditions:

[0195] -<DEL>PicA has PictureOutputFlag equal to 1.

[0196] - nuh_layer_id nuhLid of PicA is greater than nuh_layer_id nuhLid of the current picture.

[0197] -<ADD>The nuh_layer_id of the current picture is not equal to the nuh_layer_id of the output layer specified in OLS, that is, OutputLayerIdInOls[TargetOlsIdx][0] is not equal to the nuh_layer_id of the current picture. < / ADD>

[0198] - PicA belongs to the output layer of OLS (ie, OutputLayerIdInOls[TargetOlsIdx][0] is equal to nuhLid).

[0199] -sps_video_parameter_set_id is greater than 0, ols_mode_idc is equal to 2, and ols_output_layer_flag[TargetOlsIdx][GeneralLayerIdx[nuh_layer_id]] is equal to 0.

[0200] - Otherwise, PictureOutputFlag is set equal to pic_output_flag.

[0201] In yet another example, for pictures belonging to the output layer in OLS, pic_output_flag or PictureOutputFlag should always be set to 1, or at least one picture in an AU or PU should have pic_output_flag or PictureOutputFlag equal to 1.

[0202] To account for incomplete CVSS AUs (e.g., not all layers specified in the OLS are present), in another example of the present disclosure, the video encoder 200 and the video decoder 300 may be configured to decode CVSS AUs using revised definitions of CVSS AUs and IRAP AUs to account for the aforementioned incompleteness. The revised definitions are as follows, where additions to VVC Draft 8 are shown between the tags <ADD> and < / ADD>. Deletions from VVC Draft 8 are shown between the tags <DEL> and < / DEL>.

[0203] Coded Video Sequence Start (CVSS) AU: An AU where <DEL> there is a PU for each layer in the CVS and < / DEL> the coded picture in each <ADD>current< / ADD> PU is a CLVSS picture.

[0204] Intra Random Access Point (IRAP) AU: an AU where <DEL> there is a PU for each layer in the CVS and < / DEL> the coded picture in each <ADD> current < / ADD> PU is an IRAP picture.

[0205] The final definition (eg, without labels) is shown below.

[0206] Coded Video Sequence Start (CVSS) AU: An AU in which the coded picture in each current PU is a CLVSS picture.

[0207] Intra Random Access Point (IRAP) AU: An AU in which the coded picture in each current PU is an IRAP picture.

[0208] In another example, the present disclosure proposes that layer switching from one layer to another (e.g., for output) can only occur at access units (AUs) that have only IRAP picture units (PUs) or GDR picture units (PUs) or pictures. This is to prohibit the situation where a layer can be decoded starting from an AU that does not have a lower layer as an IRAP picture or a GDR picture. In one example, the aforementioned technique can be implemented as follows:

[0209] Coding layer video sequence start (CLVSS) picture: A coded picture that is an IRAP picture with NoOutputBeforeRecoveryFlag equal to 1 or a GDR picture with NoOutputBeforeRecoveryFlag equal to 1.

[0210] In addition, a constraint may be added to the CLVSS definition that CLVSS is for pictures of all current layer AUs that only have IRAP PUs or GDR PUs.

[0211] In another example, the definition of CLVSS PU can be expressed as follows:

[0212] Coding layer video sequence start (CLVSS) PU: where the coded picture is <ADD>

[0213] PU of CLVSS picture of IRAP AU or GDR AU.

[0214] Coding layer video sequence start (CLVSS) PU: where the coded picture is <ADD>

[0215] Where all PUs are IRAP PUs or GDR PUs of AUs with <ADD> / CLVSS pictures.

[0216] In another example that can be used instead of or in addition to the above techniques, the video encoder 200 and the video decoder 300 can be configured to operate according to a constraint that requires VCL NAL units of other layers that are not present in the previous IRAP AU or GDR AU. In one example, such a constraint is implemented as follows:

[0217] For any PU that is not a CLVSS PU of an AU with only IRAP or GDR PUS, there shall be no VLC NAL with a nuh_layer_id that is not present in the associated IRAP AU or GDR AU.

[0218] In another example, the constraint may be expressed as follows:

[0219] A CLVSS PU shall be a PU in an AU that has only IRAP PUs or GDR PUs for all current layers.

[0220] Embed APS into the image header or slice header

[0221] Another technique of the present disclosure includes embedding an adaptation parameter set (APS) signaled in a picture header (PH) or a slice header (SH).

[0222] In VVC draft 8, APS is signaled in a separate NAL unit with a NAL header and byte alignment at the end of the APS. If many APSs are signaled (e.g., at each picture), the bits required to signal the NAL header and byte alignment may add considerable overhead, thus reducing coding efficiency.

[0223] To avoid this additional overhead, the present disclosure proposes configuring the video encoder 200 to embed the APS into other existing NAL units (e.g., PH NAL units or VCL NAL (slice) units). In this case, there is no additional overhead associated with the APSNAL header and ALS byte alignment.

[0224] To indicate a coding mode in which the APS is embedded in the PH or SH, the video encoder 200 may be configured to signal a flag in another parameter set (such as a VPS, SPS, or PPS). In other examples, the video encoder 200 may signal a flag in the PH, SH, or elsewhere. The video encoder 200 may be configured to encode and signal a flag indicating a coding mode in which the APS is embedded in the PH or SH in more than one location (e.g., in the SPS) to indicate that such a mode may be used in the CVS and then in the PH or SH to indicate that the APS is embedded in the PH or SH.

[0225] When the video decoder 300 parses an APS payload or a raw byte sequence payload (RBSP), the video decoder 300 processes either payload in the same manner as an APS signaled in a separate APS NAL unit. For example, the video decoder 300 may store the APS payload in an APS buffer and may replace the previous APS content in the buffer with the APS content received in the embedded APS when the old APS and the received APS have the same APS parameter set ID.

[0226] Since more than one APS can be signaled, when using this embedded mode, the video encoder 200 can signal a syntax element to specify the number of embedded APSs. This syntax element can depend on a flag indicating the use of the embedded APS mode. For example, the video encoder 200 and the video decoder 300 can be configured to decode the syntax element specifying the number of embedded APSs when the flag indicates that the embedded APS mode is enabled.

[0227] In some examples, only one APS may be embedded. In this case, there may be no need to signal the number of embedded APSs. Other APSs may be signaled using existing mechanisms (e.g., using the APS NAL). Additionally, in other examples, only specific types of APSs (e.g., ALF APSs) may be embedded, including parameters for one or more sets of ALFs.

[0228] The same techniques described above can be applied to other parameter sets, such as VPS, SPS, PPS, etc. In this case, all parameter sets can be signaled in one NAL unit.

[0229] IRAP NAL unit type (NUT) constraints for reordered sub-pictures

[0230] In some examples of VVC, the video encoder 200 can be configured to signal a sub-picture layout in the SPS. A sub-picture is a sub-region of a picture that is treated as a picture for some coding techniques (e.g., prediction). The sub-picture layout defines the size and position of the sub-pictures within the picture. In some examples, the video encoder 200 can be configured to reorder sub-pictures from picture to picture, where the mapping of sub-picture IDs to sub-picture layouts is signaled in the PPS. In this context, sub-picture reordering means that corresponding sub-pictures in a previously decoded picture and a current picture (i.e., sub-pictures covering the same portion of the picture) can be different, i.e., the sub-pictures have different sub-picture IDs.

[0231] The relevant parts of VVC draft 8 are provided below:

[0232] When the current picture is not the first picture of the CLVS, for each value of i in the range of 0 to sps_num_subpics_minus1 (inclusive), if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the previous picture in decoding order in the same layer, the nal_unit_type of all decoded slice NAL units of the sub-picture with sub-picture index i in the current picture shall be equal to a specific value in the range of IDR_W_RADL to CRA_NUT (inclusive).

[0233] According to the above constraints, if sub-picture reordering occurs, all slices in the sub-pictures of the current picture should be IRAP slices. The problem with the constraints of VVC draft 8 is that IRAP slices are required even if the previously decoded picture also has reordered sub-pictures. In this way, the previous picture may not be used as a reference picture by the current picture, and the constraints of VVC draft 8 require the encoder to signal the relevant sub-pictures as IRAP slices, that is, not using inter-frame prediction.

[0234] In one example of the present disclosure, the video encoder 200 may be configured to encode pictures with reordered sub-pictures according to relaxed constraints relative to VVC draft 8. For example, the video encoder 200 may be configured to apply constraints to prediction for certain sub-pictures only when a previously decoded picture has reordered sub-pictures and is used as a reference picture by the current picture. In another example, the video encoder 200 may be configured to apply constraints to prediction for certain sub-pictures if a previously decoded picture has reordered sub-pictures and is used as an active reference picture by the current picture (i.e., the picture is included in a reference picture list).

[0235] In another example, instead of requiring an IRAP slice type when using sub-picture reordering, this requirement is replaced by disabling and / or not allowing the use of inter prediction if the reference picture has reordered sub-pictures. In one example, a requirement is that the slice should be of I slice type. If inter-layer prediction is allowed, any slice type can be used, but only intra-layer prediction and inter-layer prediction are allowed.

[0236] In another example, the constraint can be expressed as follows: If a corresponding sub-picture in a reference picture (e.g., an active reference picture) (i.e., having a different sub-picture ID than the currently decoded sub-picture) is reordered, the video encoder 200 can be configured to not use such reference picture for predicting the slice of the corresponding sub-picture in the current picture.

[0237] For example, the video encoder 200 may be configured to determine whether the reference picture of the currently encoded sub-picture has a reordered sub-picture. If so, the video encoder 200 may determine whether the sub-picture ID of the currently encoded sub-picture is different from the sub-picture ID of the corresponding position in the reference picture. If the sub-picture ID of the currently encoded sub-picture is different from the sub-picture ID of the corresponding position in the reference picture, the video encoder 200 may disable inter-frame prediction for the reference picture. If the sub-picture ID of the currently encoded sub-picture is not different from the sub-picture ID of the corresponding position in the reference picture, the video encoder 200 may enable inter-frame prediction for the reference picture as a possible decoding mode.

[0238] The above example can be implemented as a constraint in VVC as follows:

[0239] For each value of i in the range of 0 to sps_num_subpics_minus1 (inclusive), if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the reference picture, then such reference picture should not be used to predict the slice NAL unit of the sub-picture with sub-picture index i in the current picture.

[0240] Therefore, in one example of the present disclosure, the video encoder 200 can be configured to determine whether the first sub-picture ID of a first sub-picture in a current picture is different from the second sub-picture ID of a corresponding sub-picture in a reference picture. The corresponding sub-picture in the reference picture is a sub-picture having the same position as the currently decoded sub-picture in the current picture. The video encoder 200 can determine an available decoding mode based on determining whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture. The video encoder 200 can then use one or more of the available decoding modes to encode the first sub-picture.

[0241] For example, the video encoder 200 may also be configured to disable inter-frame prediction for a reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is different from the first sub-picture ID of the first sub-picture in the current picture. Alternatively, the video encoder 200 may use a different decoding mode to encode the first sub-picture. Other decoding modes may include intra-frame prediction, inter-frame prediction relative to different reference pictures (e.g., where the sub-picture IDs match), or another decoding mode. The video encoder 200 may also be configured to enable inter-frame prediction for a reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is the same as the first sub-picture ID of the first sub-picture in the current picture. This does not mean that the video encoder 200 must use such a reference picture as a reference in inter-frame prediction, but only allows inter-frame prediction to be performed on the reference picture.

[0242] All of the techniques mentioned above may be used independently or in any combination.

[0243] Figure 5 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and Figure 3 ) is described, but it should be understood that other devices may be configured to perform similar Figure 5 method of method.

[0244] In this example, the video encoder 200 first predicts the current block (350). For example, the video encoder 200 may form a prediction block for the current block. The video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, the video encoder 200 may calculate the difference between the original, unencoded block of the current block and the prediction block. The video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the transform coefficients (358). For example, the video encoder 200 may encode the transform coefficients using CAVLC or CABAC. The video encoder 200 may then output the entropy-encoded data for the block (360).

[0245] Figure 6 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and Figure 4 ) is described, but it should be understood that other devices may be configured to perform similar Figure 6 method of method.

[0246] The video decoder 300 may receive entropy-encoded data for a current block, such as entropy-encoded prediction information and entropy-encoded data corresponding to transform coefficients of a residual block for the current block (370). The video decoder 300 may entropy decode the entropy-encoded data to determine prediction information for the current block and regenerate transform coefficients for the residual block (372). The video decoder 300 may predict the current block (374), for example, using intra-frame prediction or inter-frame prediction as indicated by the prediction information for the current block, to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the regenerated transform coefficients (376) to produce a block of quantized transform coefficients. The video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (378). The video decoder 300 may finally decode the current block by combining the prediction block with the residual block (380).

[0247] Figure 7 is a flowchart illustrating another example video encoding method. Figure 7 The technology can be performed by one or more structural units of the video encoder 200.

[0248] In one example of the present disclosure, the video encoder 200 may be configured to determine whether a first sub-picture ID of a first sub-picture in a current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture (700); and determine an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture (702). The video encoder 200 may also encode the first sub-picture using one or more of the available decoding modes (704).

[0249] In one example, to determine the available decoding modes, the video encoder 200 may be further configured to disable inter-frame prediction for the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is different from the first sub-picture ID of the first sub-picture in the current picture. In another example, to encode the first sub-picture using one or more of the available decoding modes, the video encoder 200 may be further configured to encode the first sub-picture using a decoding mode other than inter-frame prediction for the reference picture.

[0250] In another example, in order to determine the available decoding mode, the video encoder 200 can also be configured to enable inter-frame prediction for the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is not different from the first sub-picture ID of the first sub-picture in the current picture.

[0251] In one example, the corresponding sub-picture in the reference picture has the same position as the first sub-picture in the current picture.

[0252] In another example, the video encoder 200 may be further configured to encode the adaptation parameter set in one or more of a picture header or a slice header of the current picture. For example, to encode the adaptation parameter set in one or more of a picture header or a slice header of the current picture, the video encoder 200 may be further configured to encode the adaptation parameter set in one or more of a picture header network abstraction layer (NAL) unit or a slice header NAL unit of the current picture. The video encoder 200 may also be configured to encode a syntax element indicating the number of adaptation parameter sets encoded in one or more of a picture header or a slice header.

[0253] Figure 8 is a flowchart illustrating another example video decoding method. Figure 8 The technology can be performed by one or more structural units of the video decoder 300.

[0254] In one example, the video decoder 300 may be configured to receive an indication of an output layer set mode, wherein the output layer set mode specifies a layer ID of a layer to be output (800); and receive one or more layers of video data, wherein the received one or more layers are less than all of the layers specified by the output layer set mode (802). The video decoder 300 may also be configured to output at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers (804).

[0255] In a particular example, to receive one or more layers of video data, the video decoder 300 may also be configured to receive one or more layers of video data in a video coding layer (VCL) network abstraction layer (NAL) unit, wherein the received one or more layers are fewer than all of the layers specified by the output layer set mode.

[0256] In one example, in order to receive one or more layers of video data, the video decoder 300 can also be configured to receive one or more layers of video data in an access unit, and in order to output at least one of the received one or more layers, the video decoder 300 can also be configured to output at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the one or more layers received in the access unit.

[0257] In another example, the output layer set mode specifies that the highest layer among the specified layer IDs is to be output, and wherein in order to output at least one layer among the received one or more layers, the video decoder 300 can also be configured to output the layer with the highest layer ID that has been actually received in the access unit.

[0258] In another example, the output layer set mode specifies that all layers in the specified layer ID are to be output, and wherein in order to output at least one layer of the received one or more layers, the video decoder 300 can also be configured to output all layers that have actually been received in the access unit.

[0259] In another example, the video decoder 300 can also be configured to set the picture output flag to zero when the layer id of the current picture is not equal to the layer index specified in the output layer set mode; and output at least one layer of the one or more layers based on the picture output flag.

[0260] Other illustrative aspects of the disclosure are described below.

[0261] Aspect 1A - A method for decoding video data, the method comprising: receiving one or more layers of video data; and outputting layers of the one or more layers according to an output layer set mode, wherein the output layer set mode outputs the layer with the highest layer id that has been received.

[0262] Aspect 2A—The method of aspect 1A, wherein receiving one or more layers of video data comprises receiving one or more layers of video data in an access unit.

[0263] Aspect 3A—The method of aspect 1A, wherein receiving the one or more layers of video data comprises receiving one or more layers of video data in a coded video sequence.

[0264] Aspect 4A - A method for decoding video data, the method comprising: receiving one or more layers of video data; and outputting all layers of the one or more layers according to an output layer set mode, wherein the output layer set mode outputs all layers present in the received one or more layers.

[0265] Aspect 5A - A method of decoding video data, the method comprising: setting a picture output flag to zero if a nuh_layer_id of a current picture is not equal to the nuh_layer_id of an output layer specified in an output layer set.

[0266] Aspect 6A—A method of coding video data, the method comprising: coding an adaptive parameter set in one or more of a picture header or a slice header; and coding the video data according to information in the adaptive parameter set.

[0267] Aspect 7A - A method of decoding video data, the method comprising: applying a constraint for reordering sub-pictures of a current picture when a previously decoded picture has reordered sub-pictures and the previously decoded picture is used as a reference picture by the current picture; and decoding the current picture according to the constraint.

[0268] Aspect 8A - A method of decoding video data, the method comprising: decoding a coded video sequence start (CVSS) access unit (AU), wherein not all layers are present in the CVSS AU.

[0269] Aspect 9A - A method of decoding video data, the method comprising: decoding a decoding layer video sequence start (CLVSS) picture, wherein the CLVSS picture is a decoded picture, and the decoded picture is an intra random access point (IRAP) picture or a progressive decoding refresh (GDR) picture.

[0270] Aspect 10A - The method according to any combination of aspects 1A to 9A.

[0271] Aspect 11A - The method of any of aspects 1A to 10A, wherein coding comprises decoding.

[0272] Aspect 12A—The method of any of aspects 1A to 10A, wherein decoding comprises encoding.

[0273] Aspect 13A - An apparatus for decoding video data, the apparatus comprising one or more means for performing the method according to any of aspects 1A to 12A.

[0274] Aspect 14A - The apparatus of aspect 13A, wherein the one or more components include one or more processors implemented in circuitry.

[0275] Aspect 15A - The apparatus of any of Aspects 13A and 14A, further comprising a memory to store video data.

[0276] Aspect 16A - The apparatus of any of Aspects 13A to 15A, further comprising a display configured to display the decoded video data.

[0277] Aspect 17A - The device of any of Aspects 13A to 16A, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0278] Aspect 18A - The apparatus of any of aspects 13A to 17A, wherein the apparatus comprises a video decoder.

[0279] Aspect 19A - The apparatus of any of aspects 13A to 18A, wherein the apparatus comprises a video encoder.

[0280] Aspect 20A - A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any one of aspects 1A to 12A.

[0281] Aspect 1B - A method for decoding video data, the method comprising: receiving an indication of an output layer set mode, wherein the output layer set mode specifies a layer ID of a layer to be output; receiving one or more layers of video data, wherein the received one or more layers are less than all of the layers specified by the output layer set mode; and outputting at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers.

[0282] Aspect 2B - A method according to Aspect 1B, wherein receiving one or more layers of video data includes: receiving one or more layers of video data in a video coding layer (VCL) network abstraction layer (NAL) unit, wherein the received one or more layers are less than all layers in the layers specified by the output layer set mode.

[0283] Aspect 3B - A method according to Aspect 1B, wherein receiving one or more layers of video data includes receiving one or more layers of video data in an access unit, and wherein outputting at least one of the received one or more layers includes outputting at least one of the received one or more layers according to an output layer set mode based on a specified layer to be output and the received one or more layers in the access unit.

[0284] Aspect 4B - A method according to Aspect 3B, wherein the output layer set mode specifies that the highest layer in the specified layer ID is to be output, and wherein outputting at least one layer of the one or more received layers includes outputting the layer with the highest layer ID that has been actually received in the access unit.

[0285] Aspect 5B - A method according to aspect 3B, wherein the output layer set mode specifies that all layers in the specified layer ID are to be output, and wherein outputting at least one layer of the one or more layers includes outputting all layers that have been actually received in the access unit.

[0286] Aspect 6B - The method according to any combination of Aspects 1B to 5B further includes: setting the picture output flag to zero when the layer id of the current picture is not equal to the layer index specified in the output layer set mode; and outputting at least one layer of the one or more layers based on the picture output flag.

[0287] Aspect 7B - The method of any combination of Aspects 1B to 6B, further comprising: displaying a picture of at least one layer including outputs in one or more layers.

[0288] Aspect 8B - A device configured to decode video data, the device comprising: a memory configured to store one or more layers of video data; and one or more processors implemented in circuitry and in communication with the memory, the one or more processors configured to: receive an indication of an output layer set mode, wherein the output layer set mode specifies a layer ID of a layer to be output; receive one or more layers of video data, wherein the received one or more layers are less than all of the layers specified by the output layer set mode; and output at least one of the received one or more layers according to the output layer set mode based on the specified layer to be output and the received one or more layers.

[0289] Aspect 9B - An apparatus according to aspect 8B, wherein, to receive one or more layers of video data, the one or more processors are further configured to: receive one or more layers of video data in a video coding layer (VCL) network abstraction layer (NAL) unit, wherein the one or more layers received are less than all of the layers specified by the output layer set mode.

[0290] Aspect 10B - An apparatus according to aspect 8B, wherein, in order to receive one or more layers of video data, the one or more processors are further configured to receive one or more layers of video data in an access unit, and wherein, in order to output at least one of the received one or more layers, the one or more processors are further configured to output at least one of the received one or more layers according to an output layer set mode based on a specified layer to be output and the received one or more layers in the access unit.

[0291] Aspect 11B - An apparatus according to Aspect 10B, wherein the output layer set mode specifies that the highest layer among the specified layer IDs is to be output, and wherein in order to output at least one layer among the received one or more layers, the one or more processors are also configured to output the layer with the highest layer ID that has been actually received in the access unit.

[0292] Aspect 12B - An apparatus according to Aspect 10B, wherein the output layer set mode specifies that all layers in the specified layer ID are to be output, and wherein in order to output at least one layer of the received one or more layers, the one or more processors are also configured to output all layers that have actually been received in the access unit.

[0293] Aspect 13B - An apparatus according to any combination of Aspects 8B to 12B, wherein the one or more processors are further configured to: set a picture output flag to zero when the layer id of the current picture is not equal to the layer index specified in the output layer set mode; and output at least one layer of the one or more layers based on the picture output flag.

[0294] Aspect 14B - The apparatus of any combination of Aspects 8B to 12B, further comprising: a display configured to display a picture of at least one layer including outputs in one or more layers.

[0295] Aspect 15B - A method for encoding video data, the method comprising: determining whether a first sub-picture ID of a first sub-picture in a current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; determining an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encoding the first sub-picture using one or more of the available decoding modes.

[0296] Aspect 16B - The method of aspect 15B, wherein determining the available coding modes comprises disabling inter-frame prediction for the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is different from the first sub-picture ID of the first sub-picture in the current picture.

[0297] Aspect 17B - The method of aspect 16B, wherein encoding the first sub-picture using one or more of the available coding modes comprises encoding the first sub-picture using a coding mode other than inter-prediction of a reference picture.

[0298] Aspect 18B—The method of aspect 15B, wherein determining the available coding modes comprises enabling inter-frame prediction for the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is not different from the first sub-picture ID of the first sub-picture in the current picture.

[0299] Aspect 19B - The method according to any combination of aspects 15B to 18B, wherein the corresponding sub-picture in the reference picture has the same position as the first sub-picture in the current picture.

[0300] Aspect 20B - The method according to any combination of Aspects 15B to 19B, further comprising: encoding the adaptation parameter set in one or more of a picture header or a slice header of the current picture.

[0301] Aspect 21B - A method according to aspect 20B, wherein encoding the adaptation parameter set in one or more of a picture header or a slice header of the current picture includes: encoding the adaptation parameter set in one or more of a picture header network abstraction layer (NAL) unit or a slice header NAL unit of the current picture.

[0302] Aspect 22B - The method of aspect 20B, further comprising encoding a syntax element indicating a number of adaptation parameter sets encoded in one or more of a picture header or a slice header.

[0303] Aspect 23B - The method according to any combination of aspects 15B to 22B, further comprising: capturing the current picture using a camera.

[0304] Aspect 24B - A device configured to encode video data, the device comprising: a memory configured to store a current picture of the video data; and one or more processors implemented in a circuit and communicating with the memory, the one or more processors configured to: determine whether a first sub-picture ID of a first sub-picture in the current picture is different from a second sub-picture ID of a corresponding sub-picture in a reference picture; determine an available decoding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encode the first sub-picture using one or more of the available decoding modes.

[0305] Aspect 25B - An apparatus according to Aspect 24B, wherein, in order to determine the available decoding mode, the one or more processors are further configured to: disable inter-frame prediction for the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is different from the first sub-picture ID of the first sub-picture in the current picture.

[0306] Aspect 26B - An apparatus according to Aspect 25B, wherein, in order to encode the first sub-picture using one or more of the available decoding modes, the one or more processors are further configured to: encode the first sub-picture using a decoding mode other than inter-frame prediction of the reference picture.

[0307] Aspect 27B - An apparatus according to Aspect 24B, wherein, in order to determine the available decoding mode, the one or more processors are further configured to: enable inter-frame prediction for the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture is not different from the first sub-picture ID of the first sub-picture in the current picture.

[0308] Aspect 28B - The method of any combination of aspects 24B to 27B, wherein the corresponding sub-picture in the reference picture has the same position as the first sub-picture in the current picture.

[0309] Aspect 29B - The apparatus of any combination of Aspects 24B to 28B, wherein the one or more processors are further configured to: encode the adaptation parameter set in one or more of a picture header or a slice header of the current picture.

[0310] Aspect 30B - An apparatus according to Aspect 29B, wherein, in order to encode the adaptation parameter set in one or more of a picture header or a slice header of the current picture, the one or more processors are further configured to: encode the adaptation parameter set in one or more of a picture header network abstraction layer (NAL) unit or a slice header NAL unit of the current picture.

[0311] Aspect 31B - The apparatus of Aspect 29B, wherein the one or more processors are further configured to: encode a syntax element indicating a number of adaptation parameter sets encoded in one or more of a picture header or a slice header.

[0312] Aspect 32B - The apparatus of any combination of Aspects 24B to 31B, further comprising: a camera configured to capture a current picture.

[0313] It should be appreciated that, depending on the example, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or excluded entirely (e.g., not all described actions or events are required to practice the technique). Furthermore, in some examples, actions or events may be performed concurrently, for example, through multithreading, interrupt handling, or execution by multiple processors, rather than sequentially.

[0314] In one or more examples, the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or codes on a computer-readable medium or sent via a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include computer-readable storage media (which corresponds to tangible media such as data storage media) or communication media, which includes any media that facilitates, for example, the transfer of a computer program from one place to another according to a communication protocol. Thus, computer-readable media can generally correspond to (1) non-transitory tangible computer-readable storage media, or (2) communication media (such as, a signal or carrier wave). Data storage media can be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures for implementing the techniques described in this disclosure. A computer program product can include computer-readable media.

[0315] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, flash memory, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Moreover, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are sent from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, then the definition of medium includes coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other temporary media, but rather are directed to non-temporary, tangible storage media. Disks and optical disks as used herein include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs reproduce data optically with the aid of lasers. The above combinations should also be included within the scope of computer-readable media.

[0316] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuit systems. Thus, as used herein, the terms "processor" and "processing circuitry" may refer to any of the aforementioned structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding or incorporated into a combined codec. Furthermore, the techniques may be fully implemented in one or more circuits or logic elements.

[0317] The techniques of this disclosure can be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but they do not necessarily need to be implemented by different hardware units. Rather, as described above, the various units can be combined in a codec hardware unit, or provided by a collection of interoperable hardware units (including one or more processors as described above) in combination with appropriate software and / or firmware.

[0318] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: receiving an indication of an output layer set mode, wherein the output layer set mode specifies layer IDs of layers to be output; receiving one or more layers of video data, wherein the received one or more layers are fewer than all of the layers specified by the output layer set mode; as well as outputting at least one of the received one or more layers according to the output layer set mode based on the designated layer to be output and the received one or more layers; wherein receiving the one or more layers of video data comprises receiving the one or more layers of video data in an access unit; wherein outputting the at least one layer among the received one or more layers comprises outputting the at least one layer among the received one or more layers according to the output layer set mode based on the designated layer to be output and the one or more layers received in the access unit; Wherein, when the output layer set mode specifies that the highest layer in the specified layer ID is to be output, outputting the at least one layer among the received one or more layers includes outputting the layer with the highest layer ID that has been actually received in the access unit.

2. The method of claim 1 , wherein receiving the one or more layers of video data comprises: The one or more layers of video data are received in video coding layer (VCL) network abstraction layer (NAL) units, wherein the received one or more layers are less than all layers specified by the output layer set mode.

3. The method according to claim 1, wherein When the output layer set mode specifies that all layers in a specified layer ID are to be output, outputting the at least one layer among the one or more layers includes outputting all layers that have been actually received in the access unit.

4. The method according to claim 1, further comprising: If the layer id of the current picture is not equal to the layer index specified in the output layer set mode, set the picture output flag to zero; as well as The at least one layer of the one or more layers is output based on the picture output flag.

5. The method according to claim 1, further comprising: A picture of at least one layer including outputs from the one or more layers is displayed.

6. An apparatus configured to decode video data, the apparatus comprising: at least one memory comprising instructions; and one or more processors configured to execute the instructions so that the apparatus: receiving an indication of an output layer set mode, wherein the output layer set mode specifies layer IDs of layers to be output; receiving one or more layers of video data, wherein the received one or more layers are fewer than all of the layers specified by the output layer set mode; as well as outputting at least one of the received one or more layers according to the output layer set mode based on the designated layer to be output and the received one or more layers; Wherein, to receive the one or more layers of video data, the one or more processors are further configured to cause the apparatus to: receive the one or more layers of video data in an access unit; Wherein, to output the at least one layer among the received one or more layers, the one or more processors are further configured to cause the apparatus to: output the at least one layer among the received one or more layers according to the output layer set mode based on the designated layer to be output and the one or more layers received in the access unit; In which, in order to output at least one of the one or more received layers, the one or more processors are further configured to enable the device to: when the output layer set mode specifies that the highest layer in the specified layer ID is to be output, output the layer with the highest layer ID that has been actually received in the access unit.

7. The apparatus of claim 6, wherein to receive the one or more layers of video data, the one or more processors are further configured to cause the apparatus to: The one or more layers of video data are received in video coding layer (VCL) network abstraction layer (NAL) units, wherein the received one or more layers are less than all of the layers specified by the output layer set mode.

8. The device according to claim 6, wherein When the output layer set mode specifies that all layers in the specified layer ID are to be output, in order to output at least one of the received one or more layers, the one or more processors are also configured to cause the device to output all layers that have been actually received in the access unit.

9. The apparatus of claim 6, wherein the one or more processors are further configured to cause the apparatus to: If the layer id of the current picture is not equal to the layer index specified in the output layer set mode, set the picture output flag to zero; and The at least one layer of the one or more layers is output based on the picture output flag.

10. The apparatus according to claim 6, further comprising: A display is configured to display a picture of at least one layer including outputs of the one or more layers.

11. A device configured to decode video data, the device comprising means for performing the method according to any one of claims 1-5.

12. A non-transitory computer-readable storage medium storing instructions, which, when executed, cause one or more processors of a device to be configured to decode video data to perform the method according to any one of claims 1-5.

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