Coded video sequence start access unit in video coding

Abstract

A video decoder may be configured to output layers of video data according to layers specified in an output layer set mode and based on actual layers received in an access unit. Thus, the video coder may be configured to output the actually received layers rather than restarting the video bitstream in situations where the actually received layers do not match the layers specified in the output layer set mode. In another example, a video encoder may disable inter prediction when a sub-picture ID of a sub-picture in a currently coded picture does not match a sub-picture ID of a sub-picture in a reference picture.

Description

[Technical field]

[0001]

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

[0002] This disclosure relates to video encoding and decoding. [Background technology]

[0003] Digital video capabilities may be incorporated into a wide range of devices, including digital televisions, digital direct 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 "smartphones," video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques, such as those described in 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 to such standards. By implementing such video coding techniques, video devices may more efficiently transmit, receive, encode, decode, and / or store digital video information.

[0004]

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. In block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may 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 with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0005]

[0005] Generally, this disclosure describes techniques for coding video data. In one example, this disclosure describes techniques for outputting layers of video data according to an output layer set mode. More specifically, a video decoder may be configured to output layers of video data according to layers specified in an output layer set mode and based on actual layers received in an access unit. In this manner, the video decoder 300 may be configured to output the layers actually received, rather than restarting the video bitstream, in a situation where the layers actually received do not match the layers specified in the output layer set mode. Thus, delay in video output may be reduced and user experience may be improved.

[0006]

[0006] In another example, this disclosure describes techniques for encoding video data when sub-pictures are used. In particular, this disclosure describes techniques for handling prediction decisions when sub-pictures are reordered per picture. In one example, rather than requiring pictures with reordered sub-pictures to be coded using only intra-prediction, a video encoder may still be configured to use inter-prediction for such pictures, but may disable inter-prediction when the sub-picture ID of the sub-picture in the currently coded picture does not match the sub-picture ID of the sub-picture in the reference picture. In this way, inter-prediction may be avoided for the reordered specific sub-picture without requiring intra-prediction to be used for the entire picture. Thus, coding efficiency may be increased.

[0007]

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

[0008]

[0008] In another example, the disclosure describes an apparatus configured to decode video data, the apparatus comprising a memory configured to store one or more layers of the 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, where the output layer set mode specifies a layer ID of a layer to be output, receive one or more layers of the video data, and output at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layers to be output and the received one or more layers, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0009]

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

[0010]

[0010] In another example, the 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, where the output layer set mode specifies a layer ID of a layer to be output, receive one or more layers of the video data, and output at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layers to be output and the received one or more layers, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0011]

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

[0012]

[0012] In another example, the disclosure describes an apparatus configured to encode video data, the apparatus comprising: a memory configured to store one or more layers of the video data; and one or more processors implemented in circuitry and in communication with the memory, the one or more processors configured to: determine whether a first subpicture ID of a first subpicture in a current picture differs from a second subpicture ID of a corresponding subpicture in a reference picture; determine available coding modes based on a determination of whether the first subpicture ID of the first subpicture in the current picture differs from the second subpicture ID of the corresponding subpicture in the reference picture; and encode the first subpicture in one or more of the available coding modes.

[0013]

[0013] In another example, the disclosure describes a device configured to encode video data, the device comprising: means for determining whether a first subpicture ID of a first subpicture in a current picture differs from a second subpicture ID of a corresponding subpicture in a reference picture; means for determining available coding modes based on a determination of whether the first subpicture ID of the first subpicture in the current picture differs from the second subpicture ID of the corresponding subpicture in the reference picture; and means for encoding the first subpicture in one or more of the available coding modes.

[0014]

[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 differs from a second sub-picture ID of a corresponding sub-picture in a reference picture, determine available coding modes based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture differs from the second sub-picture ID of the corresponding sub-picture in the reference picture, and encode the first sub-picture in one or more of the available coding modes.

[0015]

[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 become apparent from the description, drawings, and claims. [Brief description of the drawings]

[0016] [Figure 1]

[0016] FIG. 1 is a block diagram illustrating an example video encoding and decoding system in which the techniques of this disclosure may be implemented. [Figure 2A]

[0017] 1 is a conceptual diagram illustrating an exemplary Quad Tree Binary Tree (QTBT) structure. [Figure 2B] A conceptual diagram showing a corresponding coding tree unit (CTU). [Diagram 3]

[0018] 1 is a block diagram illustrating an example video encoder that may implement the techniques of this disclosure. [Figure 4]

[0019] 1 is a block diagram illustrating an example video decoder that may implement the techniques of this disclosure. [Diagram 5]

[0020] 1 is a flow chart illustrating an example video encoding method. [Figure 6]

[0021] 1 is a flow chart illustrating an example video decoding method. [Figure 7]

[0022] 4 is a flow chart illustrating another exemplary video encoding method. [Figure 8]

[0023] 4 is a flow chart illustrating another exemplary video decoding method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]

[0024] In general, this disclosure describes techniques for coding video data. In one example, this disclosure describes techniques for outputting layers of video data according to an output layer set mode. More specifically, a video decoder may be configured to output layers of video data according to layers specified in an output layer set mode and based on actual layers received in an access unit. In this manner, the video decoder 300 may be configured to output the layers actually received, rather than restarting the video bitstream, in a situation where the layers actually received do not match the layers specified in the output layer set mode. Thus, delays in video output may be reduced and user experience may be improved.

[0018]

[0025] In another example, this disclosure describes techniques for encoding video data when sub-pictures are used. In particular, this disclosure describes techniques for handling prediction decisions when sub-pictures are reordered per picture. In one example, rather than requiring that a picture with reordered sub-pictures be coded using only intra-prediction, a video encoder may still be configured to use inter-prediction for such pictures, but may disable inter-prediction when the sub-picture ID of the sub-picture in the currently coded picture does not match the sub-picture ID of the sub-picture in the reference picture. In this way, inter-prediction may be avoided for the reordered specific sub-picture without requiring that intra-prediction be used for the entire picture. Thus, coding efficiency may be increased.

[0019]

[0026] 1 is a block diagram illustrating an example video encoding and decoding system 100 that may implement the techniques of this disclosure. The techniques of this disclosure are generally directed to coding (encoding and / or decoding) video data. Generally, video data includes any data for processing video. Thus, video data may include raw uncoded video, coded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0020]

[0027] 1, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116, in this example. In particular, 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 comprise 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, and the like. 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.

[0021]

[0028] In the example of FIG. 1, source device 102 includes a video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes an input interface 122, a video decoder 300, memory 120, and a display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 may be configured to apply techniques for coding video data. Thus, source device 102 represents an example of a video encoding device, and destination device 116 represents an example of a video decoding device. In other examples, the source and destination devices 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 interface with an external display device rather than including an integrated display device.

[0022]

[0029] The system 100 shown in FIG. 1 is only an example. In general, any digital video encoding and / or decoding device may implement the techniques for coding video data. The source device 102 and the destination device 116 are only examples of coding devices, such that the source device 102 generates coded video data for transmission to the destination device 116. This disclosure refers to a "coding" device as a device that performs coding (encoding and / or decoding) of data. Thus, the video encoder 200 and the video decoder 300 represent examples of coding devices, specifically video encoders and video decoders, respectively. In some examples, the source device 102 and the destination device 116 may operate substantially symmetrically, such that each of the source device 102 and the destination device 116 includes video encoding and video decoding components. Thus, the system 100 may support unidirectional or bidirectional video transmission between the source device 102 and the destination device 116, for example, video streaming, video playback, video broadcasting, or video telephony.

[0023]

[0030] Generally, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a continuous series of pictures (also called “frames”) of the video data to video encoder 200, which encodes the data for the pictures. Video source 104 of source device 102 may include a video capture device, such as a video camera, a video archive containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. As a further alternative, video source 104 may generate computer graphics-based data as source video, or a combination of live, archived, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from a receiving order (sometimes called a “display order”) to a coding order for coding. Video encoder 200 may generate a bitstream including the encoded video data. The source device 102 may then output the encoded video data via the output interface 108 onto a computer-readable medium 110 for receipt and / or retrieval by, for example, an input interface 122 of the destination device 116 .

[0024]

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

[0025]

[0032] The computer-readable medium 110 may represent any type of medium or device capable of transporting 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 for enabling the source device 102 to transmit 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. The output interface 108 may demodulate a transmission signal including the encoded video data, and the input interface 122 may demodulate a received transmission signal according to a communication standard, such as a wireless communication protocol. The communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may 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 may include a router, a switch, a base station, or any other equipment that may be useful for facilitating communication from the source device 102 to the destination device 116.

[0026]

[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.

[0027]

[0034] In some examples, the 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 the source device 102. The destination device 116 may access the stored video data from the file server 114 via streaming or download. The file server 114 may be any type of server device capable of storing the encoded video data and transmitting the encoded video data to the destination device 116. The 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. The destination device 116 may access the encoded video data from the file server 114 through 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, that is suitable for accessing the encoded video data stored in the file server 114. The file server 114 and the input interface 122 may be configured to operate according to a streaming transmission protocol, a download transmission protocol, or a combination thereof.

[0028]

[0035] The output interface 108 and the input interface 122 may represent a wireless transmitter / receiver, a modem, a wired networking component (e.g., an Ethernet card), a wireless communication component operating according to any of the various IEEE 802.11 standards, or other physical components. In examples in which the output interface 108 and the input interface 122 comprise wireless components, the output interface 108 and the input interface 122 may be configured to transfer 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 in which the output interface 108 comprises a wireless transmitter, the output interface 108 and the input interface 122 may be configured to transfer 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), the Bluetooth standard, etc. In some examples, the source device 102 and / or the destination device 116 may include respective system-on-chip (SoC) devices. For example, the source device 102 may include a SoC device for performing functions attributable to the video encoder 200 and / or the output interface 108, and the destination device 116 may include a SoC device for performing functions attributable to the video decoder 300 and / or the input interface 122.

[0029]

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

[0030]

[0037] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, the storage device 112, the file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 that is also used by the video decoder 300, such as syntax elements having values ​​that describe 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.

[0031]

[0038] 1, in some examples, the video encoder 200 and the video decoder 300 may each be integrated with an audio encoder and / or an audio decoder and may include appropriate MUX-DEMUX units, or other hardware and / or software, to handle multiplexed streams that include both audio and video in a common data stream. Where applicable, the MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol or other protocols, such as the User Datagram Protocol (UDP).

[0032]

[0039] The video encoder 200 and the video decoder 300 may 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 techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to implement the techniques of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (codec) in the respective device. The device including the video encoder 200 and / or the video decoder 300 may comprise an integrated circuit, a microprocessor, and / or a wireless communication device such as a cellular phone.

[0033]

[0040] Video encoder 200 and 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 multiview and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards, such as ITU-T H.266, also known as Generic Video Coding (VVC). A recent draft of the VVC standard is described in Bross et al., "Versatile Video Coding (Draft 8)," Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, 17th Meeting, Brussels, Belgium, January 7-17, 2020, JVET-Q2001-vD (hereinafter, "VVC Draft 8"). However, the techniques of this disclosure are not limited to any particular coding standard.

[0034]

[0041] Generally, the video encoder 200 and the 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 an encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Generally, the video encoder 200 and the video decoder 300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, and blue (RGB) data for a sample of a picture, the video encoder 200 and the video decoder 300 may code a luminance component and a chrominance component, where the chrominance component may include both red and blue hues of chrominance components. In some examples, the video encoder 200 converts received RGB format data to a YUV representation prior to encoding, and the video decoder 300 converts the YUV representation to the RGB format. Alternatively, pre-processing and post-processing units (not shown) may perform these conversions.

[0035]

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

[0036]

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

[0037]

[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 coder (such as the video encoder 200) partitions a picture into multiple coding tree units (CTUs). The video encoder 200 may partition the CTUs according to a tree structure, such as a quad-tree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure eliminates the concept of multiple partition types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels, a first level partitioned according to a quad-tree partition and a second level partitioned according to a binary tree partition. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0038]

[0045] In the MTT partitioning structure, blocks may be partitioned using quad tree (QT) partitioning, binary tree (BT) partitioning, and one or more types of triple tree (TT) (also called ternary tree (TT)) partitioning. A triple tree or ternary tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, a triple tree or ternary tree partitioning splits a block into three sub-blocks without splitting the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) may be symmetric or asymmetric.

[0039]

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

[0040]

[0047] Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partition structures in accordance with HEVC. For purposes of explanation, the description of the techniques of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the techniques of this disclosure may also be applied to video coders configured to use quadtree partitioning, or other types of partitioning as well.

[0041]

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

[0042]

[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.

[0043]

[0050] The bricks in a picture may also be arranged into slices. A slice may be an integer number of bricks of a picture that may be contained entirely in a single network abstraction layer (NAL) unit. In some examples, a slice includes either several complete tiles or only a continuous sequence of complete bricks of one tile.

[0044]

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

[0045]

[0052] The video encoder 200 encodes video data for a CU that represents prediction and / or residual information, as well as other information. The prediction information indicates how the CU should be predicted to form a predictive block for the CU. The residual information generally represents sample-by-sample differences between samples of the CU prior to encoding and the predictive block.

[0046]

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

[0047]

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

[0048]

[0055] To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a predictive block. Some examples of VVC provide 67 intra prediction modes, including various directional modes, as well as planar and DC modes. In general, the video encoder 200 selects an intra prediction mode that describes neighboring samples relative to a current block (e.g., a block of a CU) from which samples of the current block should be predicted. Such samples may generally be above, to the left of, or to the left of the current block in the same picture as the current block, assuming that the video encoder 200 codes the CTUs and CUs in raster scan order (left to right, top to bottom).

[0049]

[0056] Video encoder 200 encodes data representing a prediction mode for the current block. For example, in an inter prediction mode, video encoder 200 may encode data representing which of various available inter prediction modes is used, as well as motion information for the corresponding mode. For example, in unidirectional or bidirectional inter prediction, video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. Video encoder 200 may use similar modes to encode motion vectors for affine motion compensation modes.

[0050]

[0057] Following prediction, such as intra- or inter-prediction, of a block, the video encoder 200 may calculate residual data for the block. The residual data, such as a residual block, represents sample-by-sample differences between the block and a predictive block for the block formed using a 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 the 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. Additionally, the video encoder 200 may apply a secondary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc., following the first transform. The video encoder 200 produces transform coefficients following application of the one or more transforms.

[0051]

[0058] As mentioned above, following any transformation to produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. By performing a 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.

[0052]

[0059] Following quantization, the video encoder 200 may scan the transform coefficients to produce a one-dimensional vector from a 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 rear of the vector. In some examples, the video encoder 200 may utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy code the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform an adaptive scan. After scanning the quantized transform coefficients to form the one-dimensional vector, the video encoder 200 may entropy code the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy code values ​​for syntax elements describing metadata associated with the encoded video data for use by the video decoder 300 in decoding the video data.

[0053]

[0060] To implement CABAC, the video encoder 200 may assign a context in a context model to a symbol to be transmitted. The context may relate, for example, to whether neighboring values ​​of the symbol are zero-valued or not. The probability determination may be based on the context assigned to the symbol.

[0054]

[0061] Video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, for 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). Video decoder 300 may similarly decode such syntax data to determine how to decode corresponding video data.

[0055]

[0062] In this manner, video encoder 200 may generate a bitstream including syntax elements that describe encoded video data, e.g., partitions of a picture into blocks (e.g., CUs) and predictive and / or residual information for the blocks. Finally, video decoder 300 may receive the bitstream and decode the encoded video data.

[0056]

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

[0057]

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

[0058]

[0065] According to the techniques of this disclosure, the video decoder 300 may 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, where the output layer set mode outputs a layer having a received highest layer ID. In one example, the video decoder 300 may be configured to receive an indication of an output layer set mode, where the output layer set mode specifies a layer ID of a layer to be output, 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, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0059]

[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, where the output layer set mode outputs all layers present in the received one or more layers.

[0060]

[0067] In another example, video encoder 200 and video decoder 300 may set a picture output flag to 0 if the nuh_layer_id of the current picture is not equal to the nuh_layer_id of an output layer specified in the output layer set.

[0061]

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

[0062]

[0069] In another example, the video encoder 200 and the video decoder 300 may be configured to apply a constraint for reordering sub-pictures for 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 code 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 the reference picture, and determine available coding modes and encode the first sub-picture in one or more of the available coding 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.

[0063]

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

[0064]

[0071] 2A and 2B are conceptual diagrams illustrating an exemplary quad-tree binary tree (QTBT) structure 130 and corresponding coding tree unit (CTU) 132. Solid lines represent quad-tree splitting, and dotted lines indicate binary tree splitting. At each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which splitting type (i.e., horizontal or vertical) is used, where in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. In quad-tree splitting, there is no need to indicate the splitting type, since the quad-tree node splits the block horizontally and vertically into four sub-blocks with equal size. Thus, video encoder 200 may encode, and video decoder 300 may decode, syntax elements (such as splitting information) for the region tree level (i.e., solid lines) of QTBT structure 130 and syntax elements (such as splitting information) for the prediction tree level (i.e., dashed lines) of QTBT structure 130. Video encoder 200 may encode, and video decoder 300 may decode, video data, such as prediction and transform data, for CUs represented by terminal leaf nodes of QTBT structure 130.

[0065]

[0072] 2B may be associated with parameters that define the sizes of blocks corresponding to nodes of the QTBT structure 130 at the first and second levels. These parameters may include a CTU size (representing the size of the CTU 132 in a sample), a minimum quad tree size (MinQTSize representing the minimum allowable quad tree leaf node size), a maximum binary tree size (MaxBTSize representing the maximum allowable binary tree root node size), a maximum binary tree depth (MaxBTDepth representing the maximum allowable binary tree depth), and a minimum binary tree size (MinBTSize representing the minimum allowable binary tree leaf node size).

[0066]

[0073] The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, each of which may be partitioned according to a quadtree partition. That is, the nodes at the first level are either leaf nodes (without child nodes) or have four child nodes. The example QTBT structure 130 represents such a node including a parent node and a child node with solid lines for branching. If the nodes at the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes may be further partitioned by their respective binary trees. The binary tree splitting of one node may be repeated until the nodes resulting from the split reach the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example QTBT structure 130 represents such a node with dashed lines for branching. The binary tree leaf nodes are called coding units (CUs), and the CUs are used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without further partitioning. As explained above, a CU may also be referred to as a "video block" or a "block."

[0067]

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

[0068]

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

[0069]

[0076] 3, 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, 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 DPB 218, and an entropy coding unit 220 may be implemented in one or more processors or processing circuits. For example, the units of video encoder 200 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor in an FPGA, an ASIC, etc. Moreover, video encoder 200 may include additional or alternative processors or processing circuits for performing these and other functions.

[0070]

[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 stored in the video data memory 230, for example, from the video source 104 (FIG. 1). The DPB 218 may 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 may be formed by any of a variety of memory devices, such as synchronous dynamic random access memory (DRAM), including DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and the DPB 218 may be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 may be on-chip with the other components of the video encoder 200, as shown, or off-chip relative to those components.

[0071]

[0078] In this disclosure, references to video data memory 230 should not be construed as limited to memory internal to video encoder 200 unless specifically so described, or to memory external to video encoder 200 unless specifically so described. Instead, references to video data memory 230 should be understood as a reference memory that stores video data that video encoder 200 receives for encoding (e.g., video data for a current block to be encoded). Memory 106 of FIG. 1 may also provide temporary storage of outputs from various units of video encoder 200.

[0072]

[0079] The various units in FIG. 3 are shown to aid 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 is preset with respect to the operations that may be performed. A programmable circuit refers to a circuit that may be programmed to perform various tasks and to provide flexible functionality in the operations that may 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 software or firmware instructions. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operations that the fixed-function circuit performs is generally unchanging. In some examples, one or more of the units may be separate circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

[0073]

[0080] The video encoder 200 may include an arithmetic logic unit (ALU), a basic functional unit (EFU), a programmable core formed of digital circuits, analog circuits, and / or programmable circuits. In examples in which the operations of the video encoder 200 are implemented using software executed by a programmable circuit, the memory 106 (FIG. 1) may store instructions (e.g., object code) of the software that the video encoder 200 receives and executes, or another memory (not shown) within the video encoder 200 may store such instructions.

[0074]

[0081] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve pictures 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 may be raw video data to be encoded.

[0075]

[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 for performing video prediction according to other prediction modes. By way of 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.

[0076]

[0083] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of the CTU into CUs, prediction modes for the CUs, transform types for residual data of the CUs, quantization parameters for residual data of the CUs, etc. The mode selection unit 202 may finally select a combination of encoding parameters that has a rate-distortion value that is better than other tested combinations.

[0077]

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

[0078]

[0085] In general, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for a current block (e.g., the current CU, or in HEVC, the overlapping portion of the PU and TU). For inter prediction of the current block, the motion estimation unit 222 may perform 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 the DPB 218). In particular, the motion estimation unit 222 may calculate a value representing how similar a potential reference block is to the current block according to, for example, a sum of absolute differences (SAD), a sum of squared differences (SSD), a mean absolute difference (MAD), a mean squared difference (MSD), etc. The motion estimation unit 222 may generally perform these calculations using a sample-by-sample difference between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block having the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0079]

[0086] The 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 a current block in a current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, in unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while in bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then generate a predictive block using the motion vectors. For example, the motion compensation unit 224 may use the motion vectors to retrieve data of the reference block. As another example, if the motion vectors have sub-sample precision, the motion compensation unit 224 may interpolate values ​​for the predictive block according to one or more interpolation filters. Moreover, in bidirectional inter prediction, the motion compensation unit 224 may retrieve data for the two reference blocks identified by the respective motion vectors and combine the retrieved data, for example, through sample-wise averaging or weighted averaging.

[0080]

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

[0081]

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

[0082]

[0089] In an example where the mode selection unit 202 partitions a 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 having 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 2N×2N, the video encoder 200 may support a PU size of 2N×2N or N×N for intra prediction, and a symmetric PU size of 2N×2N, 2N×N, N×2N, N×N, or the like for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

[0083]

[0090] In examples where the mode select unit 202 does not further partition the CUs 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. The video encoder 200 and the video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

[0084]

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

[0085]

[0092] As described above, the residual generation unit 204 receives the video data for a current block and the corresponding predictive 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 sample-by-sample differences between the predictive block and the current block.

[0086]

[0093] 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"). Transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, 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, transform processing unit 206 may perform multiple transforms on the residual block, e.g., a linear transform and a secondary transform such as a rotation transform. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0087]

[0094] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. The 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. The video encoder 200 (e.g., via the mode selection 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 result in loss of information, and thus the quantized transform coefficients may have less precision than the original transform coefficients produced by transform processing unit 206.

[0088]

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

[0089]

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

[0090]

[0097] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in examples where the operations of the filter unit 216 are not performed, the reconstruction unit 214 may store the reconstructed blocks in the DPB 218. In examples where the operations of the filter unit 216 are performed, the filter unit 216 may store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve reference pictures formed from the reconstructed (and potentially filtered) blocks from the DPB 218 to inter predict blocks of a later-encoded picture. Additionally, the intra prediction unit 226 may use the reconstructed blocks in the DPB 218 of the current picture to intra predict other blocks in the current picture.

[0091]

[0098] In general, the entropy encoding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy encoding unit 220 may entropy encode quantized transform coefficient blocks from the quantization unit 208. As another example, the entropy encoding unit 220 may entropy encode predictive syntax elements (e.g., motion information for inter prediction, or intra mode information for intra prediction) from the mode selection unit 202. The entropy encoding unit 220 may perform one or more entropy encoding operations on syntax elements, which are another example of video data, to generate entropy encoded data. For example, the entropy encoding 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, the entropy encoding unit 220 may operate in a bypass mode in which syntax elements are not entropy coded.

[0092]

[0099] The video encoder 200 may output a bitstream that includes entropy-encoded syntax elements needed to reconstruct blocks of a slice or picture. In particular, the entropy encoding unit 220 may output the bitstream.

[0093]

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

[0094]

[0101] In some examples, operations performed with respect to luma coding blocks do not need to be repeated for chroma coding blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks do not need to be repeated to identify MVs and reference pictures for chroma blocks. Rather, the MVs for luma coding blocks may be scaled to determine the MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0095]

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

[0096]

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

[0097]

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

[0098]

[0105] In the example of FIG. 4, the 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 the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 314 may be implemented in one or more processors or processing circuits. For example, the units of the 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, an ASIC. Moreover, the video decoder 300 may include additional or alternative processors or processing circuits for performing these and other functions.

[0099]

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

[0100]

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

[0101]

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

[0102]

[0109] The various units shown in FIG. 4 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. As with FIG. 3, a fixed-function circuit refers to a circuit that provides a specific function and is preset with respect to the operations that may be performed. A programmable circuit refers to a circuit that may be programmed to perform various tasks and to provide flexible functionality in the operations that may 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 software or firmware instructions. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operations that the fixed-function circuit performs is generally unchanging. In some examples, one or more of the units may be separate circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

[0103]

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

[0104]

[0111] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to recover the 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.

[0105]

[0112] In general, the video decoder 300 reconstructs a picture on a block-by-block basis. The video decoder 300 may perform a reconstruction operation on each block individually (wherein the block currently being reconstructed, i.e., decoded, may be referred to as the “current block”).

[0106]

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

[0107]

[0114] After the inverse quantization unit 306 forms the transform coefficient block, the 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, the 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 transform, or another inverse transform to the transform coefficient block.

[0108]

[0115] Further, prediction processing unit 304 generates a predictive block according to 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 a predictive block. In this case, the prediction information syntax element may indicate a reference picture in DPB 314 from which to retrieve the reference block, as well as a motion vector that identifies the location of the reference block in the reference picture relative to the location of the current block in the current picture. Motion compensation unit 316 may generally perform an inter prediction process in a manner substantially similar to that described with respect to motion compensation unit 224 (FIG. 3).

[0109]

[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 predictive block according to the intra prediction mode indicated by the prediction information syntax element. Again, the intra prediction unit 318 may generally perform an intra prediction process in a manner substantially similar to that described with respect to the intra prediction unit 226 (FIG. 3). The intra prediction unit 318 may retrieve data of neighboring samples for the current block from the DPB 314.

[0110]

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

[0111]

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

[0112]

[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 in 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 in the DPB 314. As described above, the DPB 314 may provide reference information to the prediction processing unit 304, such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation. Moreover, the video decoder 300 may output the decoded picture (e.g., decoded video) from the DPB 314 for subsequent presentation on a display device, such as the display device 118 of FIG. 1.

[0113]

[0120] As described in more detail below, the video decoder 300 represents one example of a video decoding device including a memory configured to store video data and one or more processing units implemented in a circuit, the one or more processing units configured to receive one or more layers of the video data and output a layer of the one or more layers according to an output layer set mode, where the output layer set mode outputs a layer having a received highest layer id. In another example, the video decoder 300 may be configured to receive an indication of an output layer set mode, where the output layer set mode specifies a layer id of a layer to be output, 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, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0114]

[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, where the output layer set mode outputs all layers present in the received one or more layers.

[0115]

[0122] In another example, the video decoder 300 may set a picture output flag to 0 if the nuh_layer_id of the current picture is not equal to the nuh_layer_id of an output layer specified in the output layer set.

[0116]

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

[0117]

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

[0118]

[0125] VVC Draft 8 includes the following definitions, including a definition for a coded video sequence start (CVSS) access unit (AU): A CVSS AU is the first AU in a bitstream. coded video sequence (CVS): A sequence of AUs that consists, in decoding order, of a CVSS AU followed by zero or more AUs that are not CVSS AUs, including all subsequent AUs up to but not including a subsequent AU that is a CVSS AU. Coded Video Sequence Start (CVSS) AU: An AU where there is a PU for each layer in the CVS and the coded pictures in each PU are CLVSS pictures. 7.4.2.4.2 Ordering of AUs and their association with CVS A bitstream consists of one or more CVSs. A CVS consists of one or more AUs. The ordering of PUs and their association to AUs is explained in section 7.4.2.4.3. The first AU of a CVS is a CVSS AU, where each present PU is a CLVSS PU that is either an IRAP PU with NoOutputBeforeRecoveryFlag equal to 1 or a GDR PU with NoOutputBeforeRecoveryFlag equal to 1. Each CVSS AU shall have a PU for each layer present in the CVSS. When present, it is a bitstream conformance requirement that the next AU after the AU containing the EOS NAL unit shall be a CVSS AU.

[0119]

[0126] VVC Draft 8 also includes the following definitions: 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. Picture unit (PU) - A set of NAL units that are related to each other according to specified classification rules, are consecutive in decoding order, and contain exactly one coded picture. coded layer video sequence start (CLVSS) PU - a PU whose coded picture is a CLVSS picture. Intra random access point (IRAP) - An AU where there is a PU for each layer in the CVS and the coded pictures in each PU are IRAP pictures. IRAP PU--A PU whose coded picture is an IRAP picture. Gradual decoding refresh (GDR) PU - A PU whose coded picture is a GDR picture. End of sequence (EOS) video coding layer (VCL) network abstraction layer (NAL) unit - a generic term for coded slice NAL units and the subset of NAL units with reserved values ​​of nal_unit_type that are categorized as VCL NAL units in this specification.

[0120]

[0127] VVC Draft 8 also specifies the constraint that there should be at least one VLC NAL (eg, slice) for each layer included in the output layer set. 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.

[0121]

[0128] The output layer set (OLS) mode (i.e., which layers are output) is defined by the ols_mode_idc signaled in the VPS. ols_mode_idc equal to 0 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer index from 0 to i inclusive, and for each OLS, only the topmost layer in the OLS is output. In this context, the "highest layer" is the layer with the highest layer id value. ols_mode_idc equal to 1 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices from 0 to i inclusive, and for each OLS, all layers in the OLS are output. ols_mode_idc equal to 2 specifies that the total number of OLSs specified by the VPS is explicitly signaled, the output layers are explicitly signaled for each OLS, and the other layers are layers that are direct or indirect reference layers of the output layers of the OLS. The value of ols_mode_idc shall be in the range 0 to 2, inclusive. The value 3 of ols_mode_idc is reserved for future use by ITU-T|ISO / IEC. When vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, the value of ols_mode_idc is inferred to be equal to 2.

[0122]

[0129] 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 that are not included in the OLS identified by the OLS index. Since this process is specified for the OLS index, when the OLS index changes, the video decoder 300 should be configured to restart the sub-bitstream extraction process, which means that the first AU shall be the CVSS AU that contains a PU for each of the layers present in the CVSS. This means that the pictures in the lowest layer (e.g., base layer) shall be coded using only intra slices.

[0123]

[0130] Based on the current constraint in VVC Draft 8 that when the OLS mode specifies to output only the top layer or when all layers included in the OLS are output, the first picture (CVSS AU) shall contain the VCL NAL (slice) of all layers, the video decoder 300 outputs only the top layer specified in the OLS or all layers specified in the OLS. However, in some coding scenarios, the top layer may not be present in the AU or not all layers specified in the OLS are present in the AU.

[0124]

[0131] For example, in a video conferencing scenario with low bandwidth, a client (e.g., video decoder 300) may receive only base layer (e.g., lower quality) pictures. When the bandwidth increases, the client may start receiving base layer pictures and one or more enhancement layer pictures (e.g., better quality pictures) without using CVSS AUs. For example, base layer coding may continue with enhancement layer VCL NAL units added using only inter-layer prediction. However, constraints in VVC draft 8 prohibit such coding scenarios because the OLS index needs to be changed to specify other output layers. Changing the OLS index, and therefore the OLS mode, restarts the bitstream. For example, video encoder 200 may be configured to signal an I-picture for the base layer, which creates extra overhead.

[0125]

[0132] In another example, for some coding scenarios when all layers are output, layers may have different frame rates, which means that some AUs may not have pictures of all layers present. However, based on the current definition in VVC Draft 8, the i-th OLS includes layers with layer indexes 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.

[0126]

[0133] This disclosure describes various techniques that address the above-mentioned problems. The techniques of this disclosure may be used independently or in any combination. An example implementation of the present disclosure is described below for VVC Draft 8. An addition to VVC Draft 8 is the tag <add> From tag< / add> The removal from VVC Draft 8 was indicated by the tag <del> From tag< / del> It is shown between.

[0127]

[0134] 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 layers present in an AU and not have to have all layers that should be present in a CVSS AU. For example, instead of outputting the top layer specified in the OLS indicated in the VPS, when only the top layer in the output mode is utilized, the video decoder 300 can be configured to output only the top layer that is actually present in a particular AU.

[0128]

[0135] In one example, the video decoder 300 may receive a bitstream of video data including multiple AUs. The video decoder 300 may receive and decode a syntax element (e.g., ols_mode_idc) associated with the bitstream of video data, where 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 from which the syntax element was received.

[0129]

[0136] In one example, a syntax element (e.g., ols_mode_idc) indicates that the OLS mode specifies that the top layer specified in the OLS should be output. In this example, the video decoder 300 may be configured to output the top layer actually received in the AU of the bitstream, rather than being limited to only outputting the top layer specified in the OLS. That is, in some situations, the top layer actually received in the AU may not match the top layer specified in the OLS.

[0130]

[0137] More specifically, assume there are two layers (layer 0 and layer 1) included in the OLS, and the highest layer is output (e.g., layer 1). VVC Draft 8 requires that the video decoder 300 always output layer 1. In accordance with the techniques of this disclosure, the video decoder 300 may be configured to output only the highest layer present in the AU. If the AU contains only layer 0, the video decoder 300 is configured to decode and output layer 0. If another AU has both layer 0 and layer 1, the video decoder 300 is configured to decode and output layer 1.

[0131]

[0138] Thus, in one example of this 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, where the output layer set mode outputs a layer having a 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, where the output layer set mode specifies a layer ID of a layer to be output, 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, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0132]

[0139] In a more specific example, the video decoder 300 may receive one or more layers of video data in a video coding layer (VCL) network abstraction layer (NAL) unit (e.g., a slice), where the received one or more layers are less than all of the layers specified by the output layer set mode. In an example, the video decoder 300 may receive a VCL NAL unit (e.g., a slice) that is less than all of the layers specified in the output layer set. Rather than restarting the bitstream, the video decoder 300 outputs the layers that were 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 top layer in the output layer set) should be output. If the actual top layer specified in the output layer set mode was not received, the video decoder 300 outputs the top layer that was actually received. Similarly, if the output layer set mode specifies that all layers in the output layer set should be output, then video decoder 300 outputs all layers that were actually received, even if fewer than all of the layers specified in the output layer set were actually received.

[0133]

[0140] In a further example, to receive one or more layers of the video data, the video decoder 300 is configured to receive one or more layers of the video data in an access unit. Furthermore, to output at least one layer of the one or more layers, the video decoder 300 is configured to output at least one layer of the received one or more layers according to an output layer set mode based on a 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 top layer is to be output. In this example, to output at least one layer of the one or more layers, the video decoder 300 is configured to output a layer having the top layer id actually received in the access unit. In this way, the video decoder 300 may be configured to decode and output layers according to a particular OLS mode without restarting the bitstream in situations where the number and type of output layers received in an AU change. Thus, delay in video output may be reduced and user experience may be improved.

[0134]

[0141] Similar techniques may be applied in the case of an OLS mode that specifies that all layers are output. In accordance with the techniques of this disclosure, rather than requiring the video decoder 300 to always output all layers specified for an OLS mode in the VPS, the video decoder 300 may be configured to output all layers that are actually present in a particular AU. Thus, the video decoder 300 may output fewer or more layers for some AUs compared to other AUs, even for the same OLS mode.

[0135]

[0142] In this example, as described above, video decoder 300 may receive a bitstream of video data including multiple AUs. Video decoder 300 may receive and decode a syntax element (e.g., ols_mode_idc) associated with the bitstream of video data, where 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. 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 from which the syntax element was received.

[0136]

[0143] In this example, a syntax element (e.g., ols_mode_idc) indicates that the OLS mode specifies that all layers specified in the OLS should be output. In this example, video decoder 300 may be configured to output all layers actually received in an AU of the bitstream, rather than being limited to outputting all of the layers specified in the OLS.

[0137]

[0144] More specifically, assume there are three layers (layer 0, layer 1, and layer 2) included in the OLS. In one OLS mode (e.g., ols_mode_idc equal to 1), VVC draft 8 requires that the video decoder 300 always output all of the specified layers (e.g., layer 0, layer 1, and layer 2). In accordance with the techniques of this disclosure, the video decoder 300 may be configured to output only the layers that are actually present in the AU. If the AU includes only layer 0 and layer 2, the video decoder 300 is configured to decode 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 and output layer 0 and layer 1. If another AU has each of layer 0, layer 1, and layer 2, the video decoder 300 is configured to decode and output layer 0, layer 1, and layer 2.

[0138]

[0145] Thus, in another example of the present disclosure, the video decoder 300 may be configured to 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, where 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 should be output. To output at least one layer of the one or more layers, the video decoder 300 is configured to output all layers actually received in the access unit. Again, according to the techniques of this disclosure, the video decoder 300 may be configured to decode and output layers according to a particular OLS mode without restarting the bitstream in situations where the number and type of output layers received in an AU change. Thus, delay in video output may be reduced and user experience may be improved.

[0139]

[0146] When a custom mode of OLS (e.g., ols_mode_idc=2) is used, outputting only layers that are present may not be applied, and instead, the video decoder 300 is configured to output layers specified in the OLS, since it may be the intention to have all specified layers to be output. In some examples, the technique of outputting only layers that are present in an AU may be applied.

[0140]

[0147] For example, in a video conferencing scenario, the OLS is specified to output the highest layer present in a particular AU, rather than the highest layer contained in the OLS. This allows for a gradual switch from the base layer to the enhancement layer(s) without having to specify a new OLS index and avoiding the bitstream resetting or restarting the CVS. The proposed approach has an advantage in compression efficiency, since no I-pictures are needed in the lowest layer (base layer).

[0141]

[0148] In another example, in a video coding scenario when two or more layers are specified in the OLS, the video decoder 300 may be configured to start the decoding process from the CVSS AU, where there is only one layer that can be output, e.g., the lowest (base) layer. Later in the bitstream, the video decoder 300 may switch to an enhancement layer when the bandwidth is increased. In another example, the first picture (e.g., the CVSS AU) shall include at least the lowest layer specified in the OLS / CVS, or all non-dependent layers included in the OLS / CVS.

[0142]

[0149] Another advantage of the proposed technique is that the video encoder 200 and / or the video decoder 300 are enabled to remove dependent upper layers from the bitstream without specifying a different OLS in such cases. In some cases, specifying a different OLS may mean rewriting the VPS, since the OLS is specified in the VPS.

[0143]

[0150] In VVC Draft 8, in one example, the proposed method can be implemented as follows: An addition to VVC Draft 8 is the tag <add> From tag< / add> The removal from VVC Draft 8 was indicated by the tag <del> From tag< / del> It is shown between.

[0144] Each CVSS AU is a <add> Independent< / add>It is assumed that there is a PU for each layer.

[0145] Each CVSS AU exists in CVS <add> Bottom layer nuh_layer_id< / add> shall have PU for. In addition, the semantics of ols_mode_idc is modified as follows: ols_mode_idc equal to 0 means that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indexes from 0 to i inclusive, and for each OLS <del> OLS< / del> The highest of <add> exist< / add> Specifies that only the layer is to be output. ols_mode_idc equal to 1 means that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indexes from 0 to i inclusive, and for each OLS <del> During OLS< / del> All <add> exist< / add> Specifies that a layer is to be output.

[0146]

[0151] The layer(s) present in the above ols_mode_idc semantics may mean that the layer(s) present in the AU are output or the layers present in the CVS are output. Furthermore, "is output" and "are output" in the above semantics may be modified to "may be output" because the PictureOutputFlag for the output layer can be set to 0, in which case other layer pictures may be output.

[0147]

[0152] Furthermore, the constraint requiring that there be 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.

[0148]

[0153] As an example, the following language would be removed from VVC Draft 8: <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>

[0154] The above elimination allows for the case where only one layer (e.g., the lowest or base layer) is always present, or for two or more layers to be included in the OLS without requiring the other layers to be in the bitstream. In this case, for example, in a mode that outputs the highest present layer, the same OLS may be used, and VVC Draft 8 requires that video encoder 200 specify a different OLS for such output.

[0149]

[0155] In another example, instead of removing the constraint requiring that there be at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​in LayerIdInOls[opOlsIdx] in BitstreamToDecode, the constraint is modified such that at least one VCL NAL of each independent layer is present in the bitstream to be decoded, or at least a VCL NAL of a layer present in the CVSS AU is present in the bitstream.

[0150]

[0156] In one example, the modified constraints may be expressed as follows: There is at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​of the independent layers in LayerIdInOls[opOlsIdx] in BitstreamToDecode.

[0151]

[0157] In another example, if there is still a desire to keep the current design in VVC Draft 8, i.e., only layers specified in the OLS as output layers can be output, the picture output flag PictureOutputFlag, which controls whether a picture is output, shall be set to 0 for all pictures whose layers are not output layers in the OLS.

[0152]

[0158] In one example, the above example can be implemented in VVC Draft 8 as follows: PictureOutputFlag is set as follows: - PictureOutputFlag is set equal to 0 if one of the following conditions is true:

[0153] - The current picture is a RASL picture and the associated IRAP picture's NoOutputBeforeRecoveryFlag is equal to 1.

[0154] - gdr_enabled_flag is equal to 1 and the current picture is a GDR picture with NoOutputBeforeRecoveryFlag equal to 1.

[0155] - gdr_enabled_flag is equal to 1, the current picture is associated with a GDR picture that has NoOutputBeforeRecoveryFlag equal to 1, and PicOrderCntVal of the current picture is less than RpPicOrderCntVal of the associated GDR picture.

[0156] - 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:

[0157] - <del>picA has PictureOutputFlag equal to 1.

[0158] - picA has a nuh_layer_id nuhLid that is greater than the nuh_layer_id nuhLid of the current picture.< / del> - <add> The nuh_layer_id of the current picture is not equal to the nuh_layer_id of the output layer specified in the OLS, i.e., OutputLayerIdInOls[TargetOlsIdx][0] is not equal to the current picture nuh_layer_id.< / add> - picA belongs to the output layer of OLS (i.e., OutputLayerIdInOls[TargetOlsIdx][0] is equal to nuhLid).

[0159] - 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. - Otherwise, PictureOutputFlag is set equal to pic_output_flag.

[0160]

[0159] In yet another example, pic_output_flag or PictureOutputFlag is always set to 1 for pictures belonging to an output layer in an OLS, or at least one picture in an AU or PU has pic_output_flag or PictureOutputFlag equal to 1.

[0161] To allow for incomplete CVSS AUs (e.g., not all layers specified in OLS are present), in another example of this disclosure, video encoder 200 and video decoder 300 may be configured to code CVSS AUs using revised definitions of CVSS AUs and IRAP AUs to allow for the incomplete cases described above. The revised definitions are as follows, where the additions to VVC Draft 8 are the tags <add> From tag< / add> The removal from VVC Draft 8 was indicated by the tag <del> From tag< / del> It is shown between.

[0162] Coded Video Sequence Start (CVSS) AU: <del> There is a PU for each layer in CVS.< / del> ,each <add> exist< / add> The coded picture in the PU is a CLVSS picture. AU.

[0163]

[0162] Intra Random Access Point (IRAP) AU: <del> There is a PU for each layer in CVS.< / del> ,each <add> exist< / add> A coded picture in a PU is an IRAP picture. AU.

[0164]

[0163] The final definition (eg, without tags) is given below:

[0165]

[0164] Coded Video Sequence Start (CVSS) AU: An AU in which the coded pictures in each present PU are CLVSS pictures.

[0166]

[0165] Intra Random Access Point (IRAP) AU: An AU in which the coded picture in each existing PU is an IRAP picture.

[0167]

[0166] In another example, the present disclosure proposes that layer switching from one layer to another, for example for output, can only occur in an access unit (AU) that has only an IRAP or GDR picture unit (PU) or picture. This is to prohibit the case where a layer can start decoding from an AU that does not have a lower layer as an IRAP or GDR picture. In one example, the above technique can be implemented as follows. Coded Layer Video Sequence Start (CVLSS) picture: A coded picture that is an IRAP picture with NoOutputBeforeRecoveryFlag equal to 1 or a GDR picture with NoOutputBeforeRecoveryFlag equal to 1.

[0168]

[0167] Furthermore, a constraint may be added to the CLVSS definition that the CLVSS is a picture of an AU that has only IRAP or GDR PUs for all present layers.

[0169]

[0168] In another example, the definition of CLVSS PU may be expressed as follows: Coded Layer Video Sequence Start (CVLSS) PU: A coded picture begins <add> IRAP AU or GDR AU< / add> PU which is a CLVSS picture. Coded Layer Video Sequence Start (CVLSS) PU: A coded picture begins <add> In an AU where all PUs are IRAP PUs or GDR PUs< / add> PU which is a CLVSS picture.

[0170] In another example, which may be used instead of or in addition to the above techniques, video encoder 200 and video decoder 300 may be configured to operate according to a constraint requiring that no VCL NAL units of other layers are present in a previous IRAP or GDR AU. In one example, such a constraint is implemented as follows: For any PU that is not a CLVSS PU of an AU that has only IRAP or GDR PUs, there shall be no VLC NAL with nuh_layer_id that is not present in the associated IRAP AU or GDR AU.

[0171]

[0170] In another example, the constraints may be expressed as follows: A CLVSS PU shall be a PU in an AU that has only IRAP or GDR PUs for all present layers.

[0172]

[0171] APS embedded in a picture header or slice header

[0172] Another technique of this disclosure involves embedding adaptation parameter set (APS) signaling in the picture header (PH) or slice header (SH).

[0173] In VVC Draft 8, APSs are signaled in separate NAL units, which have a NAL header and byte alignment at the end of the APS. If many APSs are signaled, for example in every picture, the bits required to signal the NAL header and byte alignment may add up to a significant overhead and thus reduce coding efficiency.

[0174] To avoid this extra overhead, this disclosure proposes that video encoder 200 be configured to embed the APS in other existing NAL units, such as PH NAL units or VCL NAL (slice) units, without the extra overhead associated with the APS NAL header and ALS byte alignment.

[0175] To indicate the 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 the VPS, SPS, or PPS. In other examples, the video encoder 200 may signal a flag in the PH, in the SH, or elsewhere. The video encoder 200 may be configured to encode a flag indicating the coding mode in which the APS is embedded in the PH or SH and signal it in more than one place, for example, 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.

[0176]

[0176] When the video decoder 300 parses an APS payload or raw byte sequence payload (RBSP), the video decoder 300 may treat either of those payloads 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 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.

[0177]

[0177] Because more than one APS may be signaled, when this embedded mode is used, video encoder 200 may signal a syntax element to specify the number of embedded APS. This syntax element may be conditional on a flag indicating that the embedded APS mode is used. For example, video encoder 200 and video decoder 300 may be configured to code a syntax element that specifies the number of embedded APS when a flag indicates that the embedded APS mode is enabled.

[0178] In some examples, only one APS may be embedded. In this case, it may not be necessary to signal the number of embedded APSs. Other APSs may be signaled using existing mechanisms, for example, using the APS NAL. Furthermore, in other examples, only APSs of a particular type may be embedded, for example, an ALF APS that includes parameters for one or more sets of ALFs.

[0179] The same techniques described above may be applied to other parameter sets, e.g., VPS, SPS, PPS, and / or others, in which case all parameter sets may be signaled in one NAL unit.

[0180] IRAP NAL Unit Type (NUT) Constraints for Reordered Subpictures

[0181] In one example of VVC, the video encoder 200 may 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 location of the sub-picture within the picture. In some examples, the video encoder 200 may be configured to reorder sub-pictures on a picture-by-picture basis, 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 a picture, may be different, i.e., they have different sub-picture IDs.

[0181]

[0182] The relevant portions of VVC Draft 8 are provided below. When the current picture is not the first picture in the CLVS, for each value of i in the range from 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 the same layer and in decoding order, then nal_unit_type for all coded slice NAL units of subpictures in the current picture with subpicture index i shall be equal to a particular value in the range from IDR_W_RADL to CRA_NUT, inclusive.

[0182]

[0183] According to the above constraint, when sub-picture reordering is performed, all slices in the sub-pictures of the current picture shall be IRAP slices. The problem with the VVC Draft 8 constraint is that IRAP slices are required even if the previously decoded picture also has a reordered sub-picture. Thus, the previous picture may not be used as a reference picture by the current picture, and the VVC Draft 8 constraint requires the encoder to signal the related sub-picture as an IRAP slice, i.e., not to use inter prediction.

[0183]

[0184] In one example of this disclosure, video encoder 200 may be configured to encode pictures with reordered sub-pictures according to constraints that are relaxed relative to VVC Draft 8. For example, video encoder 200 may be configured to apply prediction constraints for some 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, video encoder 200 may be configured to apply prediction constraints for some sub-pictures if a previously decoded picture has reordered sub-pictures and is used as an active reference picture (i.e., the picture is included in a reference picture list) by the current picture.

[0184]

[0185] In another example, instead of requiring an IRAP slice type when sub-picture reordering is used, such a requirement is replaced with disabling and / or not allowing the use of inter prediction if a reference picture has a reordered sub-picture. In one example, it is required that slices have an I slice type. If inter-layer prediction is enabled, any slice type may be used, but only allows intra- and inter-layer prediction.

[0185]

[0186] In another example, the constraint may be expressed as follows: If a corresponding sub-picture in a reference picture (e.g., an active reference picture) is reordered (i.e., has a different sub-picture ID than the currently coded sub-picture), video encoder 200 may be configured to not use such reference picture to predict a slice of the corresponding sub-picture in the current picture.

[0186]

[0187] For example, video encoder 200 may be configured to determine whether a reference picture for a currently encoded subpicture has a reordered subpicture. If the reference picture has a reordered subpicture, video encoder 200 may determine whether a subpicture ID for the currently encoded subpicture is different from a subpicture ID for a corresponding location in the reference picture. If the subpicture ID for the currently encoded subpicture is different from a subpicture ID for a corresponding location in the reference picture, video encoder 200 may disable inter prediction for the reference picture. If the subpicture ID for the currently encoded subpicture is not different from a subpicture ID for a corresponding location in the reference picture, video encoder 200 may enable inter prediction for the reference picture as a possible coding mode.

[0187]

[0188] The above example can be implemented as a constraint in VVC as follows:

[0188]

[0189] For each value of i in the range 0 to sps_num_subpics_minus1, inclusive, if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of a reference picture, such reference picture shall not be used to predict a slice NAL unit of a subpicture in the current picture with subpicture index i.

[0189]

[0190] Thus, in one example of this disclosure, 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. The corresponding sub-picture in the reference picture is a sub-picture having the same location as the currently coded sub-picture in the current picture. Video encoder 200 may determine an available coding mode based on a determination of 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. Video encoder 200 may then encode the first sub-picture in one or more of the available coding modes.

[0190]

[0191] For example, the video encoder 200 may be further configured to disable inter 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 encode the first sub-picture using a different coding mode. Other coding modes may include intra prediction, inter prediction for a different reference picture (e.g., if the sub-picture IDs match), or another coding mode. The video encoder 200 may be further configured to enable inter 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 prediction, but only that inter prediction for that reference picture is enabled.

[0191]

[0192] All of the above techniques may be used independently or in any combination.

[0192]

[0193] 5 is a flowchart illustrating an example method for encoding a current block. The current block may comprise a current CU. Although described with respect to video encoder 200 (FIGS. 1 and 3), it should be understood that other devices may be configured to implement a method similar to that of FIG.

[0193]

[0194] In this example, video encoder 200 may first predict the current block (350). For example, video encoder 200 may form a predictive block for the current block. Video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, video encoder 200 may calculate a difference between an original uncoded block and a predictive block for the current block. Video encoder 200 may then transform the residual block and quantize transform coefficients of the residual block (354). Video encoder 200 may then scan the quantized transform coefficients of the residual block (356). During or following the scan, video encoder 200 may entropy code the transform coefficients (358). For example, video encoder 200 may code the transform coefficients using CAVLC or CABAC. Video encoder 200 may then output entropy coded data for the block (360).

[0194]

[0195] 6 is a flowchart illustrating an example method for decoding a current block of video data. The current block may comprise a current CU. Although described with respect to video decoder 300 (FIGS. 1 and 4), it should be understood that other devices may be configured to perform a method similar to that of FIG.

[0195]

[0196] The video decoder 300 may receive entropy coded data for the current block, such as the entropy coded prediction information and the entropy coded data for the transform coefficients of the residual block that correspond to the current block (370). The video decoder 300 may entropy decode the entropy coded data to determine the prediction information for the current block and to reconstruct the transform coefficients of the residual block (372). The video decoder 300 may predict the current block, e.g., using the intra prediction or inter prediction mode indicated by the prediction information for the current block, to compute a predictive block for the current block (374). The video decoder 300 may then inverse scan the reconstructed transform coefficients to create a block of quantized transform coefficients (376). The video decoder 300 may then dequantize 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 predictive block and the residual block (380).

[0196]

[0197] 7 is a flowchart illustrating another example video encoding method. The technique of FIG. 7 may be implemented by one or more structural units of the video encoder 200.

[0197]

[0198] In one example of this disclosure, video encoder 200 may be configured to determine whether a first sub-picture ID of a first sub-picture in a current picture differs from a second sub-picture ID of a corresponding sub-picture in a reference picture (700) and determine an available coding mode based on the determination of whether the first sub-picture ID of the first sub-picture in the current picture differs from the second sub-picture ID of the corresponding sub-picture in the reference picture (702). Video encoder 200 may further encode the first sub-picture in one or more of the available coding modes (704).

[0198]

[0199] In one example, to determine the available coding modes, video encoder 200 may be further configured to disable inter prediction for the reference picture if a second sub-picture ID of a corresponding sub-picture in the reference picture is different from a first sub-picture ID of the first sub-picture in the current picture. In a further example, to encode the first sub-picture in one or more of the available coding modes, video encoder 200 may be further configured to encode the first sub-picture in a coding mode other than inter prediction for the reference picture.

[0199]

[0200] In another example, to determine the available coding modes, the video encoder 200 may be further configured to enable inter prediction on the reference picture if the second sub-picture ID of the corresponding sub-picture in the reference picture does not differ from the first sub-picture ID of the first sub-picture in the current picture.

[0200]

[0201] In one example, the corresponding sub-picture in the reference picture has the same location as the first sub-picture in the current picture.

[0201]

[0202] In a further example, video encoder 200 may be further configured to encode the adaptive parameter set in one or more of the picture header or slice header of the current picture. For example, to encode the adaptive parameter set in one or more of the picture header or slice header of the current picture, video encoder 200 may be further configured to encode the adaptive parameter set in one or more of the picture header network abstraction layer (NAL) units or slice header NAL units of the current picture. Video encoder 200 may be further configured to encode a syntax element indicating the number of adaptive parameter sets encoded in the one or more of the picture header or slice header.

[0202]

[0203] 8 is a flowchart illustrating another example video decoding method. The technique of FIG. 8 may be implemented by one or more structural units of the video decoder 300.

[0203]

[0204] In one example, the video decoder 300 may be configured to receive an indication of an output layer set mode, where the output layer set mode specifies a layer ID of a layer to be output (800), and to receive one or more layers of video data, where 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 be further configured to output at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layer to be output and the received one or more layers.

[0204]

[0205] In a particular example, to receive one or more layers of video data, the video decoder 300 may be further configured to receive the one or more layers of video data in a video coding layer (VCL) network abstraction layer (NAL) unit, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0205]

[0206] In one example, to receive one or more layers of the video data, the video decoder 300 may be further configured to receive the one or more layers of the video data in an access unit, and, to output at least one layer of the received one or more layers, the video decoder 300 may be further configured to output the at least one layer of the received one or more layers according to an output layer set mode based on the specified layer to be output and the received one or more layers in the access unit.

[0206]

[0207] In another example, the output layer set mode specifies that the highest layer of a specified layer ID should be output, and to output at least one layer of the one or more received layers, the video decoder 300 may be further configured to output the layer having the highest layer ID actually received in the access unit.

[0207]

[0208] In a further example, the output layer set mode specifies that all layers of a specified layer ID should be output, and in order to output at least one layer of the received one or more layers, the video decoder 300 may be further configured to output all layers actually received in the access unit.

[0208]

[0209] In another example, the video decoder 300 may be further configured to set a picture output flag to 0 if the layer id of the current picture is not equal to the layer index specified in the output layer set mode, and to output at least one layer of the one or more layers based on the picture output flag.

[0209]

[0210] Other exemplary aspects of the present disclosure are described below.

[0210]

[0211] Aspect 1A - A method of coding video data, the method comprising: receiving one or more layers of the video data; and outputting a layer of the one or more layers according to an output layer set mode, wherein the output layer set mode outputs a layer having a highest layer id received.

[0211]

[0212] Aspect 2A - The method of aspect 1A, wherein receiving one or more layers of video data comprises receiving the one or more layers of video data in an access unit.

[0212]

[0213] Aspect 3A - The method of aspect 1A, wherein receiving one or more layers of video data comprises receiving one or more layers of video data in a coded video sequence.

[0213]

[0214] Aspect 4A - A method of coding 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, where the output layer set mode outputs all layers present in the received one or more layers.

[0214]

[0215] Aspect 5A - A method of coding video data, the method comprising setting a picture output flag to 0 if the 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.

[0215]

[0216] 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 in accordance with information in the adaptive parameter set.

[0216]

[0217] Aspect 7A - A method of coding video data, the method comprising: applying a constraint for reordering a sub-picture to a current picture when a previously decoded picture has a reordered sub-picture and the previously decoded picture is used as a reference picture by a current picture; and coding the current picture in accordance with the constraint.

[0217]

[0218] Aspect 8A - A method of coding video data, the method comprising: coding a Coded Video Sequence Start (CVSS) Access Unit (AU), wherein not all layers are present in the CVSS AU.

[0218]

[0219] Aspect 9A - A method of coding video data, the method comprising: coding a coding layer video sequence start (CLVSS) picture, wherein the CLVSS picture is a coded picture that is an intra random access point (IRAP) picture or a gradual decoding refresh (GDR) picture.

[0219]

[0220] Embodiment 10A - The method of any combination of embodiments 1A to 9A.

[0220]

[0221] Example 11A - A method as in any of examples 1A to 10A, wherein the coding comprises decoding.

[0221]

[0222] Example 12A - The method of any of examples 1A to 10A, wherein the coding comprises encoding.

[0222]

[0223] Aspect 13A - A device for coding video data, comprising one or more means for performing the method described in any of aspects 1A to 12A.

[0223]

[0224] Embodiment 14A -A device as described in embodiment 13A, wherein the one or more means comprise one or more processors implemented in circuitry.

[0224]

[0225] Embodiment 15A - A device as described in any of embodiments 13A and 14A, further comprising a memory for storing video data.

[0225]

[0226] Example 16A - The device of any of examples 13A to 15A, further comprising a display configured to display the decoded video data.

[0226]

[0227] Aspect 17A - A device as described in 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.

[0227]

[0228] Example 18A - A device according to any of examples 13A to 17A, wherein the device comprises a video decoder.

[0228]

[0229] Example 19A - A device according to any of examples 13A to 18A, wherein the device comprises a video encoder.

[0229]

[0230] Aspect 20A - A computer-readable storage medium storing instructions that, when executed, cause one or more processors to perform a method according to any of aspects 1A to 12A.

[0230]

[0231] Aspect 1B - A method of decoding video data, the method comprising: receiving an indication of an output layer set mode, where the output layer set mode specifies a layer ID of a layer to be output; and outputting at least one of the received one or more layers in accordance with the output layer set mode based on the specified layers to be output and the received one or more layers, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0231]

[0232] Aspect 2B - The method of aspect 1B, wherein receiving one or more layers of video data comprises 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 of the layers specified by the output layer set mode.

[0232]

[0233] Aspect 3B - The method described in aspect 1B, wherein receiving one or more layers of video data comprises receiving one or more layers of video data in an access unit, and outputting at least one layer of the received one or more layers comprises outputting at least one layer of the received one or more layers in accordance with an output layer set mode based on a specified layer to be output and the received one or more layers in the access unit.

[0233]

[0234] Aspect 4B - The method described in aspect 3B, wherein the output layer set mode specifies that the highest layer of a specified layer ID should be output, and outputting at least one layer of the received one or more layers comprises outputting a layer having the highest layer ID actually received in the access unit.

[0234]

[0235] Aspect 5B - The method described in aspect 3B, wherein the output layer set mode specifies that all layers of a specified layer ID should be output, and outputting at least one layer of the one or more layers comprises outputting all layers actually received in the access unit.

[0235]

[0236] Example 6B - A method of any combination of examples 1B to 5B, further comprising setting a picture output flag to 0 if 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.

[0236]

[0237] Embodiment 7B - The method of any combination of embodiments 1B to 6B, further comprising displaying a picture including the outputted at least one layer of the one or more layers.

[0237]

[0238] Aspect 8B - An apparatus configured to decode video data, the apparatus comprising: a memory configured to store one or more layers of the 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; receive one or more layers of the video data, where the output layer set mode specifies a layer ID of a layer to be output; and output at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layers to be output and the received one or more layers, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0238]

[0239] Aspect 9B - The device described in 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, where the received one or more layers are less than all of the layers specified by the output layer set mode.

[0239]

[0240] Embodiment 10B - The apparatus of claim 8B, wherein, to receive one or more layers of video data, the one or more processors are further configured to receive the one or more layers of video data in an access unit, and, to output at least one layer of the received one or more layers, the one or more processors are further configured to output at least one layer of the received one or more layers in accordance with an output layer set mode based on a specified layer to be output and the received one or more layers in the access unit.

[0240]

[0241] Aspect 11B - The apparatus of aspect 10B, wherein the output layer set mode specifies that the highest layer of a specified layer ID should be output, and to output at least one layer of the received one or more layers, the one or more processors are further configured to output the layer having the highest layer ID actually received in the access unit.

[0241]

[0242] Aspect 12B - The apparatus of aspect 10B, wherein the output layer set mode specifies that all layers of a specified layer ID should be output, and wherein, to output at least one layer of the received one or more layers, the one or more processors are further configured to output all layers actually received in the access unit.

[0242]

[0243] Example 13B - An apparatus of any combination of examples 8B to 12B, wherein the one or more processors are further configured to set a picture output flag to 0 if 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.

[0243]

[0244] Embodiment 14B -The apparatus of any combination of embodiments 8B to 12B, further comprising a display configured to display a picture including the outputted at least one of the one or more layers.

[0244]

[0245] Aspect 15B - A method of encoding video data, the method comprising: determining whether a first sub-picture ID of a first sub-picture in a current picture differs from a second sub-picture ID of a corresponding sub-picture in a reference picture; determining available coding modes based on a determination of whether the first sub-picture ID of the first sub-picture in the current picture differs from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encoding the first sub-picture in one or more of the available coding modes.

[0245]

[0246] Aspect 16B - The method of aspect 15B, wherein determining the available coding modes comprises disabling inter prediction for the reference picture if a second subpicture ID of a corresponding subpicture in the reference picture is different from a first subpicture ID of a first subpicture in the current picture.

[0246]

[0247] Embodiment 17B - The method of embodiment 16B, wherein encoding the first subpicture in one or more of the available coding modes comprises encoding the first subpicture in a coding mode other than inter prediction relative to a reference picture.

[0247]

[0248] Aspect 18B - The method of aspect 15B, wherein determining the available coding modes comprises enabling inter prediction for the reference picture if a second subpicture ID of a corresponding subpicture in the reference picture does not differ from a first subpicture ID of a first subpicture in the current picture.

[0248]

[0249] Embodiment 19B - The method of any combination of embodiments 15B to 18B, wherein the corresponding subpicture in the reference picture has the same location as the first subpicture in the current picture.

[0249]

[0250] Example 20B - The method of any combination of examples 15B to 19B, further comprising encoding the adaptive parameter set in one or more of a picture header or slice header of the current picture.

[0250]

[0251] Aspect 21B - The method of aspect 20B, wherein encoding an adaptive parameter set in one or more of a picture header or slice header of the current picture comprises encoding the adaptive parameter set in one or more of a picture header network abstraction layer (NAL) unit or slice header NAL unit of the current picture.

[0251]

[0252] Example 22B - The method of example 20B, further comprising encoding a syntax element indicating the number of adaptation parameter sets encoded in one or more of the picture header or slice header.

[0252]

[0253] Embodiment 23B - The method of any combination of embodiments 15B to 22B, further comprising capturing a current picture with a camera.

[0253]

[0254] Aspect 24B - An apparatus configured to encode video data, the apparatus comprising: a memory configured to store a current picture of the video data; and one or more processors implemented in a circuit and in communication 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 differs from a second sub-picture ID of a corresponding sub-picture in a reference picture; determine available coding modes based on a determination of whether the first sub-picture ID of the first sub-picture in the current picture differs from the second sub-picture ID of the corresponding sub-picture in the reference picture; and encode the first sub-picture in one or more of the available coding modes.

[0254]

[0255] Aspect 25B - The apparatus described in aspect 24B, wherein to determine available coding modes, the one or more processors are further configured to disable inter prediction for a reference picture if a second subpicture ID of a corresponding subpicture in the reference picture is different from a first subpicture ID of a first subpicture in the current picture.

[0255]

[0256] Example 26B - The apparatus described in example 25B, further configured such that, to encode the first subpicture in one or more of the available coding modes, the one or more processors encode the first subpicture in a coding mode other than inter prediction relative to the reference picture.

[0256]

[0257] Aspect 27B - The apparatus described in aspect 24B, wherein to determine available coding modes, the one or more processors are further configured to enable inter prediction for the reference picture if the second subpicture ID of a corresponding subpicture in the reference picture is not different from the first subpicture ID of the first subpicture in the current picture.

[0257]

[0258] Embodiment 28B - The apparatus of any combination of embodiments 24B to 27B, wherein the corresponding subpicture in the reference picture has the same location as the first subpicture in the current picture.

[0258]

[0259] Example 29B - An apparatus of any combination of examples 24B to 28B, wherein the one or more processors are further configured to encode the adaptive parameter set in one or more of the picture headers or slice headers of the current picture.

[0259]

[0260] Aspect 30B - The apparatus described in aspect 29B, wherein the one or more processors are further configured to encode the adaptive parameter set in one or more picture headers or slice headers of the current picture, the adaptive parameter set being encoded in one or more picture header network abstraction layer (NAL) units or slice header NAL units of the current picture.

[0260]

[0261] Example 31B - The apparatus described in example 29B, wherein the one or more processors are further configured to encode a syntax element indicating a number of adaptive parameter sets encoded in one or more of the picture headers or slice headers.

[0261]

[0262] Embodiment 32B - The apparatus of any combination of embodiments 24B to 31B, further comprising a camera configured to capture a current picture.

[0262]

[0263] In accordance with the above examples, it should be appreciated that some acts or events of any of the techniques described herein may be performed in a different sequence, added, merged, or omitted entirely (e.g., not all described acts or events may be necessary to the practice of the techniques). Moreover, in some examples, acts or events may be performed simultaneously rather than sequentially, for example, through multi-threaded processing, interrupt processing, or multiple processors.

[0263]

[0264] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or may include a communication medium, which includes any medium that facilitates transfer of a computer program from one place to another, for example according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium, such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0264]

[0265] By way of example and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media.

[0265]

[0266] The 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 circuits. Thus, the terms "processor" and "processing circuitry" as used herein may refer to any of the above structures, or any other structures suitable for implementing the techniques described herein. Furthermore, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a composite codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0266]

[0267] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or sets of ICs (e.g., chipsets). In this disclosure, various components, modules, or units have been described to highlight functional aspects of devices configured to implement the disclosed techniques, but those components, modules, or units do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors described above, along with suitable software and / or firmware.

[0267]

[0268] Various examples have been described. These and other examples are within the scope of the following claims. The invention as described in the claims of the original application is set forth below. [C1] 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; outputting 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; A method comprising: [C2] Receiving the one or more layers of video data includes: receiving the one or more layers of video data in a Video Coding Layer (VCL) Network Abstraction Layer (NAL) unit, where the received one or more layers are less than all of the layers specified by the output layer set mode; The method of claim C1, comprising: [C3] receiving the one or more layers of video data comprises receiving the one or more layers of video data in an access unit; The method of C1, wherein outputting the at least one layer of the received one or more layers comprises outputting the at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layer to be output and the received one or more layers in the access unit. [C4] the output layer set mode specifies that the top layer of the specified layer ID should be output; The method of C3, wherein outputting the at least one layer of the received one or more layers comprises outputting the layer having a highest layer ID actually received in the access unit. [C5] the output layer set mode specifies that all layers of the specified layer ID should be output; The method of C3, wherein outputting the at least one layer of the one or more layers comprises outputting all layers actually received in the access unit. [C6] If the layer id of the current picture is not equal to the layer index specified in the output layer set mode, setting a picture output flag to 0; outputting the at least one layer of the one or more layers based on the picture output flag; The method of C1, further comprising: [C7] Displaying a picture including the outputted at least one layer of the one or more layers. The method of C1, further comprising: [C8] An apparatus configured to decode video data, said apparatus comprising: a memory configured to store one or more layers of video data; one or more processors implemented in circuitry and in communication with the memory; wherein the one or more processors: 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; outputting 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; An apparatus configured to: [C9] To receive the one or more layers of video data, the one or more processors: receiving the one or more layers of video data in a Video Coding Layer (VCL) Network Abstraction Layer (NAL) unit, where the received one or more layers are less than all of the layers specified by the output layer set mode; The apparatus of C8, further configured to: [C10] To receive the one or more layers of video data, the one or more processors are further configured to receive the one or more layers of video data in an access unit; The apparatus of C8, wherein to output the at least one layer of the received one or more layers, the one or more processors are further configured to output the at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layer to be output and the received one or more layers in the access unit. [C11] the output layer set mode specifies that the top layer of the specified layer ID should be output; The apparatus of C10, wherein, to output the at least one layer of the received one or more layers, the one or more processors are further configured to output the layer having a highest layer ID actually received in the access unit. [C12] the output layer set mode specifies that all layers of the specified layer ID should be output; The apparatus of C10, wherein, to output the at least one layer of the received one or more layers, the one or more processors are further configured to output all layers actually received in the access unit. [C13] The one or more processors: If the layer id of the current picture is not equal to the layer index specified in the output layer set mode, set a picture output flag to 0; outputting the at least one layer of the one or more layers based on the picture output flag; The apparatus of C8, further configured to: [C14] A display configured to display a picture including the output at least one of the one or more layers. The apparatus of C8, further comprising: [C15] A method for encoding video data, the method comprising the steps of: 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 coding 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 a corresponding sub-picture in the reference picture; encoding the first sub-picture in one or more of the available coding modes; A method comprising: [C16] determining the available coding modes comprises: disabling inter 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. The method of claim 15, comprising: [C17] encoding the first sub-picture in one or more of the available coding modes, encoding the first sub-picture in a coding mode other than inter prediction relative to the reference picture; The method of claim 16, comprising: [C18] determining the available coding modes comprises: enabling inter 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. The method of claim 15, comprising: [C19] The method of C15, wherein the corresponding sub-picture in the reference picture has the same location as the first sub-picture in the current picture. [C20] encoding an adaptation parameter set in one or more of the picture header or slice header of the current picture. The method of C15, further comprising: [C21] encoding the adaptation parameter set in one or more of the picture header or the slice header of the current picture, 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; The method of claim C20, comprising: [C22] encoding a syntax element indicating the number of adaptation parameter sets encoded in the one or more of the picture headers or slice headers. The method of C20, further comprising: [C23] Capturing the current picture with a camera. The method of C13, further comprising: [C24] An apparatus configured to encode video data, said apparatus comprising: a memory configured to store a current picture of the video data; one or more processors implemented in circuitry and in communication with the memory; wherein the one or more processors: determining 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; determining an available coding mode based on the determination whether the first sub-picture ID of the first sub-picture in the current picture is different from the second sub-picture ID of a corresponding sub-picture in the reference picture; encoding the first sub-picture in one or more of the available coding modes; An apparatus configured to: [C25] To determine the available coding modes, the one or more processors disabling inter 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. The apparatus of C24, further configured to: [C26] To encode the first subpicture in one or more of the available coding modes, the one or more processors: encoding the first sub-picture in a coding mode other than inter prediction relative to the reference picture; The apparatus of C25, further configured to: [C27] To determine the available coding modes, the one or more processors enabling inter 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. The apparatus of C24, further configured to: [C28] The apparatus of C24, wherein the corresponding sub-picture in the reference picture has the same location as the first sub-picture in the current picture. [C29] The one or more processors: encoding an adaptation parameter set in one or more of a picture header or slice header of the current picture; The apparatus of C24, further configured to: [C30] To encode the adaptation parameter set in one or more of the picture header or the slice header of the current picture, the one or more processors: 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; The apparatus of C27, further configured to: [C31] The one or more processors: encoding a syntax element indicating a number of adaptation parameter sets encoded in the one or more of the picture header or slice header. The apparatus of C29, further configured to: [C32] A camera configured to capture the current picture. The apparatus of C24, further comprising:

Claims

1. 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 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; outputting at least one layer 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 of the received one or more layers comprises outputting the at least one layer of the received one or more layers in accordance with the output layer set mode based on the specified layer to be output and the received one or more layers in the access unit; wherein outputting the at least one layer of the received one or more layers comprises, if the output layer set mode specifies that a highest layer of the specified layer IDs should be output, outputting the layer having a highest layer ID actually received in the access unit. A method comprising:

2. Receiving the one or more layers of video data includes: receiving the one or more layers of video data in a Video Coding Layer (VCL) Network Abstraction Layer (NAL) unit, where the received one or more layers are less than all of the layers specified by the output layer set mode; The method of claim 1 , comprising:

3. If the layer id of the current picture is not equal to the layer index specified in the output layer set mode, setting a picture output flag to 0; outputting the at least one layer of the one or more layers based on the picture output flag; The method of claim 1 further comprising:

4. Displaying a picture including the outputted at least one of the one or more layers. The method of claim 1 further comprising:

5. 1. An apparatus configured to decode video data, said apparatus comprising: a memory configured to store one or more layers of video data; one or more processors implemented in circuitry and in communication with the memory; wherein the one or more processors: 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; outputting at least one layer 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, for receiving the one or more layers of video data, the one or more processors are further configured to receive the one or more layers of video data in an access unit; wherein, for outputting the at least one layer of the received one or more layers, the one or more processors are further configured to output the at least one layer 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 in the access unit; wherein, for outputting the at least one layer of the received one or more layers, the one or more processors are further configured to, if the output layer set mode specifies that a highest layer of the specified layer IDs should be output, output the layer having a highest layer ID actually received in the access unit. An apparatus configured to:

6. To receive the one or more layers of video data, the one or more processors: receiving the one or more layers of video data in a Video Coding Layer (VCL) Network Abstraction Layer (NAL) unit, where the received one or more layers are less than all of the layers specified by the output layer set mode; The apparatus of claim 5 , further configured to:

7. The one or more processors: If the layer id of the current picture is not equal to the layer index specified in the output layer set mode, setting a picture output flag to 0; outputting the at least one layer of the one or more layers based on the picture output flag; The apparatus of claim 5 , further configured to:

8. a display configured to display a picture including the output at least one of the one or more layers. The apparatus of claim 5 further comprising:

Images