Picture Header Intra Random Access Pictures and Progressive Decoder Refresh Signaling in Video Coding

Abstract

A method for processing video data includes: obtaining a bitstream and locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in an encoded picture in the bitstream. Locating the IRAP or GDR picture may include: obtaining a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture. The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit.

Description

[0001] This application claims priority to U.S. Application No. 17 / 130,759, filed on Dec. 22, 2020, which claims the benefit of U.S. Provisional Patent Application 62 / 953,035, filed on Dec. 23, 2019, the entire contents of each of which are incorporated herein by reference. Technical Field

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

[0003] Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital live 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 game devices, video game consoles, cellular or satellite radiotelephones (so-called "smart phones"), video teleconferencing devices, video streaming devices, etc. Digital video devices implement video decoding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 (Part 10, Advanced Video Coding (AVC)), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions of such standards. By implementing such video decoding techniques, video devices can send, receive, encode, decode, and / or store digital video information more efficiently.

[0004] Video decoding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in a video sequence. For block-based video decoding, a video slice (e.g., a video picture or a portion of a video picture) can be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in adjacent blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture can be encoded using spatial prediction relative to reference samples in adjacent blocks in the same picture or temporal prediction relative 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] Generally, the present disclosure describes techniques related to signaling intra-random access pictures (IRAP) or gradual decoding refresh (GDR) pictures in video coding. For example, the present disclosure describes techniques where a video encoder can signal a syntax element in a picture header network abstraction layer (NAL) unit. The syntax element indicates that the picture associated with the picture header must be an IRAP or GDR picture. The syntax element can enable a device (such as a device including a video decoder) to locate the picture header associated with an IRAP or GDR picture without searching for the picture header NAL unit in the NAL unit stream.

[0006] In one example, the present disclosure describes a method of processing video data, the method including: obtaining a bitstream including a set of encoded pictures including the video data; and locating an intra-random access picture (IRAP) or a gradual decoder refresh (GDR) picture in the encoded pictures in the bitstream, where locating the IRAP or GDR picture includes: obtaining a syntax element from a picture header network abstraction layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an intra-random access picture (IRAP) or a gradual decoder refresh (GDR) picture; and determining, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0007] In another example, the present disclosure describes a method of encoding video data, the method including: generating encoded pictures for a set of pictures of the video data; and including a picture header network abstraction layer (NAL) unit in a bitstream including the encoded pictures, where the picture header NAL unit includes a syntax element indicating that the picture associated with the picture header NAL unit must be an intra-random access picture (IRAP) or a gradual decoder refresh (GDR) picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0008] In another example, the present disclosure describes an apparatus for processing video data. The apparatus includes: a memory configured to store encoded pictures of video data; and one or more processors implemented in circuitry, the one or more processors being configured to: locate an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in an encoded picture in a bitstream, wherein the one or more processors are configured to, as part of locating the IRAP or GDR picture, perform the following operations: obtain a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that a picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and determine, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in a set of encoded pictures.

[0009] In another example, the present disclosure describes an apparatus for encoding video data. The apparatus includes: a memory configured to store video data; and one or more processors implemented in circuitry, the one or more processors being configured to: generate encoded pictures for a set of pictures of video data; and include a picture header Network Abstraction Layer (NAL) unit in a bitstream including the encoded pictures, wherein the picture header NAL unit includes a syntax element indicating that a picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in a set of encoded pictures.

[0010] In another example, the present disclosure describes an apparatus for processing video data, the apparatus comprising: a unit for obtaining a bitstream including a set of encoded pictures of video data; and a unit for locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein the unit for locating an IRAP or GDR picture comprises: a unit for obtaining a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and a unit for determining, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0011] In another example, the present disclosure describes an apparatus for encoding video data, the apparatus comprising: a unit for generating encoded pictures for a set of pictures of video data; and a unit for including a picture header Network Abstraction Layer (NAL) unit in a bitstream including the encoded pictures, wherein the picture header NAL unit includes a syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0012] In another example, the present disclosure describes a computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform the following operations: obtain a bitstream including a set of encoded pictures of video data; and locate an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein the instructions that cause the one or more processors to locate the IRAP or GDR picture include instructions that, when executed, cause the one or more processors to perform the following operations: obtain a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and determine, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0013] In another example, the present disclosure describes a computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform the following operations: generate encoded pictures for a set of pictures of video data; and include a picture header Network Abstraction Layer (NAL) unit in a bitstream including the encoded pictures, where the picture header NAL unit includes a syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0014] Details of one or more examples are set forth in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may execute the techniques of the present disclosure.

[0016] Figure 2 is a block diagram illustrating an example video encoder that may execute the techniques of the present disclosure.

[0017] Figure 3 is a block diagram illustrating an example video decoder that may execute the techniques of the present disclosure.

[0018] Figure 4 is a flowchart showing an example method for encoding a current block.

[0019] Figure 5 is a flowchart showing an example method for decoding a current block of video data.

[0020] Figure 6 is a flowchart showing example operations of a video encoder in accordance with one or more techniques of the present disclosure.

[0021] Figure 7 is a flowchart showing example operations for processing video data in accordance with one or more techniques of the present disclosure. DETAILED DESCRIPTION

[0022] The ability to start playing a video at a random point in the video is an important feature of modern video coding. In the Versatile Video Coding (VVC) and other video coding standards, random access can be achieved by encoding a specific type of picture as an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture. In VVC, IRAP and GDR pictures can be identified based on the NAL unit type of the Network Abstraction Layer (NAL) unit of the encoded slice containing the IRAP and GDR pictures. In addition, in VVC, a picture is associated with a picture header NAL unit, which is signaled in the bitstream order before the NAL unit of the encoded slice containing the picture. Thus, when performing random access, a device (e.g., a video decoder) can identify the NAL unit whose NAL unit type indicates that the encoded slice contained therein belongs to an IRAP or GDR picture. Then, the device must search backward in the bitstream to find the picture header so that the device can decode the IRAP or GDR picture, or search forward for the picture header for later decoding.

[0023] Searching backward in this way may slow down the process of performing random access. The present disclosure describes techniques that can address this problem. In one example, a video encoder can generate an encoded picture for a set of pictures of video data. In this example, the video encoder can include a picture header NAL unit in the bitstream including the encoded picture. The picture header NAL unit includes a syntax element that indicates that the picture associated with the picture header NAL unit must be an IRAP or a Gradual Decoder Refresh (GDR) picture. Due to this syntax element, a device performing random access can directly identify the picture header NAL unit as being associated with an IRAP or GDR picture without having to search backward in the bitstream to find the picture header NAL unit.

[0024] Figure 1FIG. 0 is a block diagram illustrating an example video encoding and decoding system 100 that may implement the techniques of the present disclosure. The techniques of the present disclosure generally relate to decoding (encoding and / or decoding) video data. Generally, video data includes any data for processing video. Thus, video data may include raw unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (e.g., signaling data).

[0025] As Figure 1 shown in FIG. 5, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. 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 include any of a variety of devices, including desktop computers, notebook computers (i.e., laptop computers), tablet computers, set-top boxes, cellular phones such as smart phones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and may thus be referred to as wireless communication devices.

[0026] In Figure 1 the example of FIG. 10, source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. Destination device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. According to the present disclosure, video encoder 200 of source device 102 and video decoder 300 of destination device 116 may be configured to apply techniques related to techniques for signaling intra random access pictures (IRAP) or progressive decoding refresh (GDR) pictures in video decoding. 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, source device and destination device may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may interface with an external display device rather than include an integrated display device.

[0027] As Figure 1The system 100 shown is merely an example. Generally, any digital video encoding and / or decoding device may perform techniques related to the techniques for signaling IRAP or GDR pictures in video coding. The source device 102 and the destination device 116 are merely examples of such coding devices, where the source device 102 generates encoded video data for transmission to the destination device 116. This disclosure refers to a "coding" device as a device that performs coding (e.g., encoding and / or decoding) of data. Thus, the video encoder 200 and the video decoder 300 represent examples of coding devices, specifically, a video encoder and a video decoder, respectively. In some examples, the source device 102 and the destination device 116 may operate in a substantially symmetric manner such that each of the source device 102 and the destination device 116 includes video encoding and decoding components. Thus, the system 100 may support unidirectional or bidirectional video transmission between the source device 102 and the destination device 116, e.g., for video streaming, video playback, video broadcasting, or video telephony.

[0028] Generally, the video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a sequential series of pictures (also referred to as "frames") of the video data to the video encoder 200, which encodes the data for the pictures. The video source 104 of the source device 102 may include a video capture device, such as a camera, a video archive unit containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. As another alternative, the video source 104 may generate computer graphics-based data as the source video, or generate a combination of live video, archived video, and computer-generated video. In each case, the video encoder 200 may encode the captured, pre-captured, or computer-generated video data. The video encoder 200 may reorder the pictures from the received order (sometimes referred to as the "display order") into a coding order for coding. The video encoder 200 may generate a bitstream including the encoded video data. Then, the source device 102 may output the encoded video data via the output interface 108 onto a computer-readable medium 110 to be received and / or retrieved by, for example, the input interface 122 of the destination device 116.

[0029] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general 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 that can be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although the memories 106 and 120 are shown separately from the video encoder 200 and the video decoder 300 in this example, 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. Further, 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 memories 106, 120 may be allocated as one or more video buffers, e.g., to store raw decoded and / or encoded video data.

[0030] The computer-readable medium 110 may represent any type of medium or device capable of transferring encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to directly send the encoded video data to the destination device 116 in real time, e.g., via a radio frequency network or a computer-based network. According to a communication standard such as a wireless communication protocol, the output interface 108 may modulate the transmission signal including the encoded video data, and the input interface 122 may demodulate the received transmission signal. The communication medium may include any wireless or wired communication medium, such as the 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 routers, switches, base stations, or any other device that may be useful for facilitating communication from the source device 102 to the destination device 116.

[0031] In some examples, the computer-readable medium 110 may include a storage device 112. The source device 102 may output the encoded data from the output interface 108 to the storage device 112. Similarly, the destination device 116 may access the encoded data from the storage device 112 via the input interface 122. The storage device 112 may include any data storage medium among various distributed or locally accessible data storage media, such as a hard disk drive, a Blu-ray disc, a DVD, a CD-ROM, a flash memory, a volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0032] In some examples, the computer-readable medium 110 may include a file server 114 or another intermediate storage device that can store the encoded video data generated by the source device 102. The source device 102 may output the encoded video data to the file server 114 or another intermediate storage device that can store the encoded video generated by the source device 102. The destination device 116 may access the stored video data from the file server 114 via streaming or downloading. The file server 114 may be any type of server device capable of storing the encoded video data and sending 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 via any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a Digital Subscriber Line (DSL), a cable modem, etc.), or a combination of both, suitable for accessing the encoded video data stored on the file server 114. The file server 114 and the input interface 122 may be configured to operate according to a streaming protocol, a download transfer protocol, or a combination thereof.

[0033] 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 one of the various IEEE 802.11 standards, or other physical components. In examples where the output interface 108 and the input interface 122 include wireless components, the output interface 108 and the input interface 122 may be configured to transmit data (such as encoded video data) according to a cellular communication standard (such as 4G, 4G-LTE (Long Term Evolution), enhanced LTE, 5G, etc.). In some examples where the output interface 108 includes a wireless transmitter, the output interface 108 and the input interface 122 may be configured to operate according to other wireless standards (such as the IEEE 802.11 specifications, the IEEE 802.15 specifications (e.g., ZigBee TM )、Bluetooth TMtransfer data (such as encoded video data) according to standards, etc. In some examples, source device 102 and / or destination device 116 may include corresponding system-on-a-chip (SoC) devices. For example, source device 102 may include an SoC device for performing functions belonging to video encoder 200 and / or output interface 108, and destination device 116 may include an SoC device for performing functions belonging to video decoder 300 and / or input interface 122.

[0034] The techniques of the present disclosure can be applied to video coding to support any multimedia application among various multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission (such as HTTP-based Dynamic Adaptive Streaming over HTTP (DASH)), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0035] Input interface 122 of destination device 116 receives an encoded video bitstream from computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling information such as the following syntax elements defined by video encoder 200 (which is also used by video decoder 300): The syntax elements have values that describe the characteristics and / or processing of video blocks or other coding units (e.g., slices, pictures, groups of pictures, sequences, etc.). Display device 118 displays the decoded pictures of the decoded video data to the user. Display device 118 may represent any of various 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.

[0036] Although not shown in Figure 1 In some examples, both video encoder 200 and video decoder 300 may 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 process a multiplexed stream including both audio and video in a common data stream. If applicable, the MUX-DEMUX unit may follow the ITU H.223 multiplexer protocol or other protocols, such as the User Datagram Protocol (UDP).

[0037] Video encoder 200 and video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the techniques are implemented partially in software, the device may store instructions for the software in a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of the present disclosure. Each of video encoder 200 and video decoder 300 may be included in one or more encoders or decoders, and any of the encoders or decoders may be integrated as part of a combined encoder / decoder (CODEC) in a corresponding device. Devices including video encoder 200 and / or video decoder 300 may include integrated circuits, microprocessors, and / or wireless communication devices (such as cellular telephones).

[0038] 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 an extension thereof (such as multi-view 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 Versatile Video Coding (VVC). The latest draft of the VVC standard is described in the following document: Bross et al., "Versatile Video Coding (Draft 7)", Joint Video Team (JVT) of ITU-T SG 16 WP 3 and ISO / IEC JTC1 / SC 29 / WG 11, 16th meeting: Geneva, Switzerland, October 1-11, 2019, JVET-P2001-v14 (hereinafter referred to as "VVC Draft 7"). However, the techniques of the present disclosure are not limited to any particular coding standard.

[0039] Generally, video encoder 200 and video decoder 300 may perform block - based coding of pictures. The term "block" generally refers to a structure that includes data to be processed (e.g., data to be encoded, decoded, or otherwise used during the encoding and / or decoding process). For example, a block may include a two - dimensional matrix of samples of luminance and / or chrominance data. Generally, video encoder 200 and video decoder 300 may code video data represented in YUV (e.g., Y, Cb, Cr) format. That is, instead of coding the red, green, and blue (RGB) data of the samples for a picture, video encoder 200 and video decoder 300 may code the luminance and chrominance components, where the chrominance components may include both the red - hue and blue - hue chrominance components. In some examples, video encoder 200 converts the received RGB - formatted data to YUV representation before encoding, and video decoder 300 converts the YUV representation to RGB format. Alternatively, pre - processing and post - processing units (not shown) may perform these conversions.

[0040] The present disclosure generally may relate to coding (e.g., encoding and decoding) of pictures to include processes of encoding or decoding data of pictures. Similarly, the present disclosure may relate to coding of blocks of pictures to include processes of encoding or decoding data for blocks (e.g., prediction and / or residual coding). An encoded video bitstream generally includes a series of values for syntax elements representing coding decisions (e.g., coding modes) and the partitioning of pictures into blocks. Thus, references to coding of pictures or blocks generally should be understood as coding of the values of the syntax elements used to form the pictures or blocks.

[0041] 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) divides a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video coder divides the CTU and CUs into four equal, non - overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video coder may further divide the PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of TUs. In HEVC, a PU represents inter - prediction data, while a TU represents residual data. An intra - predicted CU includes intra - prediction information, such as an intra - mode indication.

[0042] As another example, video encoder 200 and video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder (such as video encoder 200) divides a picture into multiple coding tree units (CTUs). Video encoder 200 may divide the CTUs according to a tree structure, such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure eliminates the concept of multiple partitioning types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels: a first level divided according to quadtree partitioning and a second level divided according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0043] In the MTT partitioning structure, quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also referred to as a trinary tree (TT)) partitioning may be used to partition a block. Ternary tree or trinary tree partitioning is a partitioning in which a block is divided into three sub-blocks. In some examples, the ternary tree or trinary tree partitioning divides a block into three sub-blocks without dividing the original block through the center. The partitioning types in the MTT (e.g., QT, BT, and TT) may be symmetric or asymmetric.

[0044] In some examples, video encoder 200 and video decoder 300 may use a single QTBT or MTT structure to represent each of the luminance component and the chrominance components, while 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 the two chrominance components (or two QTBT / MTT structures for the respective chrominance components).

[0045] Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partitioning structures per HEVC. For purposes of explanation, the description of the techniques of the present disclosure is given with respect to QTBT partitioning. However, it should be understood that the techniques of the present disclosure may also be applied to video coders configured to use quadtree partitioning or other types of partitioning.

[0046] Blocks (e.g., CTUs or CUs) can be grouped in a picture in various ways. As an example, a brick can refer to a rectangular region of CTU rows within a particular tile in the picture. A tile can be a rectangular region of CTUs within a particular tile column and a particular tile row in the picture. A tile column refers to a rectangular region of CTUs that has a height equal to the height of the picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile row refers to a rectangular region of CTUs that has a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the width of the picture.

[0047] In some examples, a tile can be divided into multiple bricks, and each brick can include one or more CTU rows within the tile. A tile that is not divided into multiple bricks can also be referred to as a brick. However, a brick that is a proper subset of a tile cannot be referred to as a tile.

[0048] Bricks in a picture can also be arranged in slices. A slice can be an integer number of bricks of the picture that can be uniquely contained within a single network abstraction layer (NAL) unit. In some examples, a slice includes multiple complete tiles or a contiguous sequence of complete bricks of only one tile.

[0049] The present disclosure can interchangeably use "NxN" and "N times N" to refer to the sample size of a block (such as a CU or other video block) in the vertical and horizontal dimensions. For example, 16x16 samples or 16 times 16 samples. Generally, a 16x16 CU will have 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 can be arranged in rows and columns. Additionally, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU can include NxM samples, where M does not necessarily equal N.

[0050] Video encoder 200 encodes video data for the representation prediction and / or residual information of a CU and other information. The prediction information indicates how the CU is to be predicted to form a prediction block for the CU. The residual information generally represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0051] To predict a CU, video encoder 200 can generally form a prediction block for the CU through inter - frame prediction or intra - frame prediction. Inter - frame prediction generally refers to predicting a CU based on data from previously decoded pictures, while intra - frame prediction generally refers to predicting a CU based on previously decoded data of the same picture. To perform inter - frame prediction, video encoder 200 can use one or more motion vectors to generate a prediction block. Video encoder 200 can generally perform a motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. Video encoder 200 can calculate a difference metric using the sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculations to determine whether the reference block closely matches the current CU. In some examples, video encoder 200 can use uni - directional prediction or bi - directional prediction to predict the current CU.

[0052] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter - frame prediction mode. In the affine motion compensation mode, video encoder 200 can determine two or more motion vectors representing non - translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0053] To perform intra - frame prediction, video encoder 200 can select an intra - frame prediction mode to generate a prediction block. Some examples of VVC provide sixty - seven intra - frame prediction modes, including various directional modes, as well as a planar mode and a DC mode. Generally, video encoder 200 selects an intra - frame prediction mode that describes the neighboring samples of the current block (e.g., the block of the CU) from which the samples of the current block are to be predicted. Assuming video encoder 200 decodes CTUs and CUs in raster scan order (from left to right, top to bottom), such samples can generally be above, top - left, or to the left of the current block in the same picture as the current block.

[0054] Video encoder 200 encodes data representing the prediction mode for the current block. For example, for an inter - frame prediction mode, video encoder 200 can encode data representing which of the various available inter - frame prediction modes is used and the motion information for the corresponding mode. For uni - directional or bi - directional inter - frame prediction, for example, video encoder 200 can use advanced motion vector prediction (AMVP) or the merge mode to encode the motion vectors. Video encoder 200 can use a similar mode to encode the motion vectors for the affine motion compensation mode.

[0055] After prediction (such as intra prediction or inter prediction of a block), video encoder 200 may compute residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a predicted block for the block, where the predicted block is formed using a corresponding prediction mode. Video encoder 200 may apply one or more transforms to the residual block to produce transformed data in the transform domain rather than in the sample domain. For example, 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, video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. Video encoder 200 produces transform coefficients after applying one or more transforms.

[0056] As noted above, after any transform that produces transform coefficients, video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to the process in which the transform coefficients are quantized to potentially reduce the amount of data used to represent the transform coefficients, thus providing further compression. By performing the quantization process, video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, video encoder 200 may round an n-bit value down to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, video encoder 200 may perform a bitwise right shift on the value to be quantized.

[0057] After quantization, 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 the higher energy (and thus lower frequency) transform coefficients at the front of the vector and the lower energy (and thus higher frequency) transform coefficients at the back of the vector. In some examples, video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce a serialized vector, and then entropy code the quantized transform coefficients of the vector. In other examples, video encoder 200 may perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, video encoder 200 may entropy code the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). Video encoder 200 may also entropy code the values of syntax elements used to describe metadata associated with the encoded video data for use by video decoder 300 when decoding the video data.

[0058] To perform CABAC, the video encoder 200 may assign contexts within a context model to symbols to be sent. The context may relate to, for example, whether adjacent values of the symbol are zero values. Probability determination may be based on the context assigned to the symbol.

[0059] The video encoder 200 may further generate syntax data for the video decoder 300, for example, in a picture header, a block header, a slice header, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, or other syntax data (such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). Similarly, the video decoder 300 may decode such syntax data to determine how to decode the corresponding video data. A picture header is a syntax structure that contains syntax elements applicable to all slices of a decoded picture.

[0060] In this way, the video encoder 200 may generate a bitstream including the encoded video data, for example, syntax elements that describe the partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Ultimately, the video decoder 300 may receive the bitstream and decode the encoded video data.

[0061] Generally, the video decoder 300 performs a process opposite to that performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values of the syntax elements for the bitstream in a manner that is substantially similar to, but opposite to, the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for dividing a picture into CTUs and for dividing each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define the CUs of the CTU. The syntax elements may also define prediction and residual information for blocks (e.g., CUs) of the video data.

[0062] The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse-quantize and inverse-transform the quantized transform coefficients of a block to reproduce the residual block for the block. The video decoder 300 uses the signaled prediction mode (intra prediction or inter prediction) and associated prediction information (e.g., motion information for inter prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

[0063] A bitstream can include a sequence of Network Abstraction Layer (NAL) units. A NAL unit is a syntax structure that includes an indication of the type of data in the NAL unit and bytes that contain the data in the form of a Raw Byte Sequence Payload (RBSP), with emulation prevention bits inserted as necessary. Each NAL unit can include a NAL unit header and can encapsulate the RBSP. The NAL unit header can include a syntax element that indicates a NAL unit type code. The NAL unit type code specified by the NAL unit header of a NAL unit indicates the type of the NAL unit. The RBSP can be a syntax structure that contains an integral number (which is encapsulated within the NAL unit) of bytes. In some cases, the RBSP includes zero bits.

[0064] In HEVC, VVC, and other video coding specifications, each NAL unit includes a syntax element (e.g., nal_unit_type) that indicates the NAL unit type of the NAL unit. Additionally, the video decoder 300 can identify the NAL unit as being associated with one of a plurality of picture types based on the NAL unit type of the NAL unit. These picture types can include Instantaneous Decoding Refresh (IDR) pictures, Clean Random Access (CRA) pictures, Temporal Sub-layer Access (TSA) pictures, Broken Link Access (BLA) pictures, and encoded pictures that are not IDR, CRA, or TSA pictures.

[0065] Ideally, channel switching and hopping performed in this manner should be carried out with a minimum amount of latency. HEVC, VVC, and other video coding specifications provide mechanisms for achieving random access to a bitstream. Random access refers to decoding a bitstream starting from an encoded picture that is not the first encoded picture in the bitstream. In various video applications such as broadcasting and streaming, random access to a bitstream may be required. Random access to a bitstream can enable a user to listen to a program at any time, switch between different channels, jump to a specific part of a video, or switch to a different bitstream for stream adaptation (e.g., adaptation of bitrate, frame rate, spatial resolution, etc.). Channel switching and hopping can be achieved by including random access pictures at fixed intervals in the video bitstream. Random access can be achieved by inserting Intra Random Access Point (IRAP) pictures at fixed intervals into the bitstream. Example types of IRAP pictures include IDR pictures, CRA pictures, and BLA pictures. Thus, IDR pictures, CRA pictures, and BLA pictures are collectively referred to as IRAP pictures. An access unit that contains an IRAP picture in the base layer can be referred to herein as an IRAP access unit.

[0066] If the necessary parameter set is available when it is needed to be activated, the IRAP pictures in the decoding order and all subsequent non-random access skipped leading (RASL) pictures can be correctly decoded without performing the decoding process on any pictures before the IRAP pictures in the decoding order. There may be pictures in the bitstream that contain only I slices that are not IRAP pictures (i.e., slices in which the video decoder can use intra prediction but not inter prediction).

[0067] An IDR picture contains only I slices. An IDR picture can be the first picture in the bitstream in decoding order or can appear later in the bitstream. Each IDR picture is the first picture of an encoded video sequence in decoding order. Pictures following an IDR picture in decoding order cannot use pictures decoded before the IDR picture as references. Thus, a bitstream that relies on IDR pictures for random access can have significantly lower decoding efficiency compared to a bitstream that uses additional types of random access pictures. An IDR access unit is an access unit that contains an IDR picture.

[0068] An IDR picture may cause the decoding process to mark all reference pictures as "not used for reference". Since reference pictures marked as "not used for reference" can be removed from the decoded picture buffer (DPB) that stores reference pictures, an IDR picture can "clear" the DPB. All encoded pictures following an IDR picture in decoding order can be decoded without inter prediction based on any pictures before the IDR picture in decoding order. The first picture of each encoded video sequence in decoding order is an IDR picture or a BLA picture, or a CRA picture that is also the first picture of the bitstream. When the encoded picture in the base layer of an access unit is an IDR picture, the access unit can be referred to as an IDR access unit. In some examples, the decoded video sequence is a sequence of access units in decoding order that includes or consists of: an IDR access unit, followed by zero or more access units that are not IRAP access units, where NoRaslOutputFlag is equal to 1, including all subsequent access units up to any subsequent IDR access unit but not including any subsequent IDR access unit.

[0069] However, since an IDR picture starts an encoded video sequence and may always clear the DPB, pictures following an IDR picture in decoding order cannot use pictures decoded before the IDR picture in decoding order as references. To improve decoding efficiency, a CRA picture can allow pictures that are after the CRA picture in decoding order but before the CRA picture in output order to use pictures decoded before the CRA as references.

[0070] CRA picture types facilitate decoding starting from any random access point (RAP) in the middle of a video sequence. Inserting CRA pictures in a video sequence may be more efficient than inserting IDR pictures in the same video sequence. In HEVC and potentially other video coding specifications, a bitstream starting from a CRA picture can be a compliant bitstream.

[0071] CRA pictures allow pictures that are after the CRA picture in decoding order but before the CRA picture in output order to use pictures decoded before the CRA picture as references. Pictures that are after the CRA picture in decoding order but before the CRA picture in output order are referred to as leading pictures associated with the CRA picture (or leading pictures of the CRA picture). A CRA access unit is an access unit in which the encoded picture of the base layer is a CRA picture.

[0072] If decoding starts from an IDR picture or a CRA picture that appears before the CRA picture in decoding order, the leading pictures of the CRA picture may be correctly decoded. However, when a random access starting from the CRA picture occurs, the leading pictures of the CRA picture may not be decodable. Therefore, a video decoder typically decodes the leading pictures of the CRA picture during random access decoding. To prevent error propagation starting from reference pictures (which may not be available depending on the decoding start position), pictures that are after the CRA picture in both decoding order and output order may not use any pictures (including leading pictures) that are before the CRA picture in either decoding order or output order as references.

[0073] BLA pictures typically originate from a bitstream spliced at the position of a CRA picture, and at the splicing point in the spliced bitstream, the spliced CRA picture is changed to a BLA picture. A BLA access unit is an access unit that contains a BLA picture in the base layer. One difference between BLA pictures and CRA pictures is as follows. For a CRA picture, if decoding starts from a RAP picture that is before the CRA picture in decoding order, the associated leading pictures are correctly decodable. However, when a random access starting from the CRA picture occurs (i.e., when decoding starts from the CRA picture, or in other words, when the CRA picture is the first picture in the bitstream), the leading pictures associated with the CRA picture may not be correctly decodable. In contrast, even when decoding starts from a RAP picture that is before the BLA picture in decoding order, there may be no scenario where the leading pictures associated with the BLA picture are decodable.

[0074] Even when a particular CRA picture or a particular BLA picture is the first picture in a bitstream, some leading pictures associated with the particular CRA picture or the particular BLA picture may be correctly decodable. These leading pictures may be referred to as decodable leading pictures (DLPs). Other leading pictures may be referred to as non-decodable leading pictures (NLPs). An NLP may also be referred to as a picture marked as discarded (TFD).

[0075] GDR may enable a device to decode a picture set (such as a sequence of pictures arranged in decoding order or a series of pictures). Such a picture sequence is referred to herein as a "GDR picture set" or a "GDR set". When traversing the entire GDR set (e.g., when reaching the end of the GDR set), the video decoding device may randomly access one or more encoded pictures that are after the set in decoding order. In various examples, the video decoding device may correctly or accurately decode all of the last picture of the GDR set. In such an example, the first picture in the GDR set may represent a "GDR picture", and the last picture in the GDR set may represent a "recovery point picture". Subsequently, the recovery point picture may represent a picture in which the entire picture is included in a "refresh" or "foreground" region. Thus, the picture is gradually refreshed as a series of pictures in the GDR set until the picture is fully refreshed at the recovery point picture. The video decoding device may use specific SEI messages (such as a "recovery point" SEI message and / or a "region refresh information" SEI message) to determine the boundaries of the GDR set and other information related to the GDR set.

[0076] In VVC Draft 7, a slice NAL unit has a NAL unit type (NUT) that indicates IDR_W_RADL, IDR_N_LP, CRA_NUT, GDR_NUT, which correspond to IRAP or GDR picture slice data. A slice NAL unit with NAL unit type IDR_W_RADL is associated with an IDR picture having a randomly accessible decodable leading picture. A slice NAL unit with NAL unit type IDR_N_LP is associated with an IDR picture having no leading picture. A slice NAL unit with NAL unit type CRA_NUT is associated with a CRA picture. A slice NAL unit with NAL unit type GDR_NUT is associated with a GDR picture. Before the slice data is a NAL unit having a picture header NAL unit type (NUT) (PH_NUT). In VVC Draft 7, to locate an IRAP or GDR picture in the bitstream, a device will need to first locate a slice having an IDR_W_RADL, IDR_N_LP, CRA_NUT, or GDR_NUT NAL unit type and then backtrack and locate the picture header associated with that slice. It may be desirable to directly locate a randomly accessible picture or GDR picture by signaling a randomly accessible picture or GDR picture in the picture header in order to speed up the process of locating randomly accessible pictures and GDR pictures.

[0077] According to the techniques of the present disclosure, a field or flag indicating an IRAP (or type of IRAP) or GDR picture is indicated at the start of or near the start of the picture header. The corresponding PH_NUT along with the flag will make the detection of IRAP and GDR pictures simpler. The following examples illustrate two solutions: a first technique that is based on signaling a flag (e.g., irap_or_gdr_pic_flag); and a second technique that includes signaling a field (e.g., irap_gdr_idc) that signals a specific type of IRAP or GDR picture.

[0078] According to the first technique of the present disclosure, the picture header RBSP includes a flag (e.g., irap_or_gdr_pic_flag) that can indicate that the picture associated with the picture header RBSP must be an IRAP or GDR picture. In the following text and throughout the present disclosure, changes to the text in VVC Draft 7 are marked using the <!>…< / !> tags. Deletions from the text of VVC Draft 7 are marked using the <dlt> …< / dlt> tags.

[0079] ====================================================================VVC Draft 7 Changes Start====================================================================

[0080] 7.3.2.6 Picture Header RBSP Syntax

[0081]

[0082] 7.4.3.6 Picture Header RBSP Semantics

[0083] The PH contains information common to all slices of the decoded picture associated with the PH.

[0084] <!>An irap_or_gdr_pic_flag equal to 1 specifies that the picture associated with the PH is an IRAP or GDR. An irap_or_gdr_pic_flag equal to 0 specifies that the picture associated with the PH is neither an IRAP nor a GDR picture.< / !>

[0085] A non_reference_picture_flag equal to 1 specifies that the picture associated with the PH is never used as a reference picture.

[0086] A non_reference_picture_flag equal to 0 specifies that the picture associated with the PH may or may not be used as a reference picture.

[0087] A gdr_pic_flag equal to 1 specifies that the picture associated with the PH is a GDR picture. A gdr_pic_flag equal to 0 specifies that the picture associated with the PH is not a GDR picture. <!>When absent, it is inferred to be equal to 0.< / !>

[0088] ======================================================End of VVC Draft 7 Changes======================================================

[0089] Thus, according to the first technique of the present disclosure, the video encoder 200 may generate encoded pictures for a set of pictures of video data. Additionally, the video encoder 200 may include a picture header NAL unit in a bitstream including the encoded pictures. In some examples, the picture header NAL unit includes a first syntax element (e.g., irap_or_gdr_pic_flag) that indicates whether the picture associated with the picture header NAL unit is an IRAP or GDR picture. In some examples, the first syntax element indicates that the picture associated with the picture header NAL unit is neither an IRAP nor a GDR picture. In some examples, the first syntax element indicates that the picture associated with the picture header NAL unit is not an IRAP but is a GDR picture. In some examples, the first syntax element indicates that the picture associated with the picture header NAL unit may or may not be an IRAP but is likely not a GDR picture. The picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit. The picture associated with the picture header NAL unit is located in the set of encoded pictures. If the picture header NAL unit is the picture header NAL unit before the first encoded slice NAL unit of a picture, the picture may be associated with the picture header NAL unit.

[0090] Similarly, in some examples, the video decoder 300 or another device (e.g., an intermediate network device, etc.) may obtain a bitstream including a set of encoded pictures of video data; and locate an IRAP or GDR picture among the encoded pictures in the bitstream, where locating the IRAP or GDR picture includes: obtaining a first syntax element (e.g., irap_or_gdr_pic_flag) from a picture header NAL unit in the bitstream that indicates whether the picture associated with the picture header NAL unit is an IRAP or GDR picture. In some examples, the first syntax element indicates that the picture associated with the picture header NAL unit is not an IRAP but may be a GDR picture. In some examples, the first syntax element indicates that the picture associated with the picture header NAL unit may or may not be an IRAP but is likely not a GDR picture. The picture header NAL unit may contain syntax elements that apply to all segments of the picture associated with the picture header NAL unit. The picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0091] According to the second technique of the present disclosure, a field indicating the IDR, CRA, GDR type is included in the picture header. For example, in the example shown below, a 2-bit field (e.g., irap_gdr_idc) is added to the picture header RBSP as shown below:

[0092] ==========================Start of VVC Draft 7 Changes==================================

[0093] 7.3.2.6 Picture Header RBSP Syntax

[0094]

[0095] 7.4.3.6 Picture Header RBSP Semantics

[0096] The PH contains information common to all slices of the decoded picture associated with the PH.

[0097] <!>An irap_gdr_idc equal to 0 indicates a picture that is not an IRAP or GDR. An irap_gdr_pic_idc equal to 1 indicates an IDR picture, an irap_gdr_pic_idc equal to 2 indicates a CRA picture. An irap_gdr_pic_idc equal to 3 indicates a GDR picture.< / !>

[0098] A non_reference_picture_flag equal to 1 specifies that the picture associated with the PH is never used as a reference picture. A non_reference_picture_flag equal to 0 specifies that the picture associated with the PH may or may not be used as a reference picture.

[0099] <dlt>When gdr_pic_flag is equal to 1, it specifies that the picture associated with PH is a GDR picture. When gdr_pic_flag is equal to 0, it specifies that the picture associated with PH is not a GDR picture. < / dlt>

[0100] The recovery_poc_cnt specifies the recovery point of the decoded pictures in output order. If the current picture is a GDR picture associated with the PH, and there exists a picture picA in the CLVS that follows the current GDR picture in decoding order and the PicOrderCntVal of the picture picA is equal to the PicOrderCntVal of the current GDR picture plus the value of recovery_poc_cnt, then the picture picA is called a recovery point picture. Otherwise, the first picture in output order whose PicOrderCntVal is greater than the PicOrderCntVal of the current picture plus the value of recovery_poc_cnt is called a recovery point picture. In decoding order, the recovery point picture shall not be before the current GDR picture. The value of recovery_poc_cnt shall be in the range of 0 to MaxPicOrderCntLsb-1 (inclusive).

[0101] Annotation 1 – When the gdr_enabled_flag is equal to 1 and the PicOrderCntVal of the current picture is greater than or equal to the RpPicOrderCntVal of the associated GDR picture, the current and subsequent decoded pictures in the output order exactly match the corresponding pictures generated by starting the decoding process from the previous IRAP picture (when present) in the decoding order that is before the associated GDR picture.

[0102] ========================================================================= End of VVC Draft 7 Changes =========================================================================

[0103] Thus, in some examples, the video encoder 200 may generate encoded pictures for a collection of pictures of video data. Additionally, the video encoder 200 may include in the bitstream including the encoded pictures a picture header NAL unit, a first syntax element (e.g., irap_gdr_idc), the first syntax element indicating whether the picture associated with the picture header NAL unit is: (i) neither an IRAP nor a GDR picture, (ii) an IDR picture, (iii) a CRA picture, or (iv) a GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the collection of encoded pictures.

[0104] Similarly, in some examples, a device (e.g., the video decoder 300 or another type of device) may obtain a bitstream including a collection of encoded pictures of video data. The device may locate an IRAP or GDR picture in the encoded pictures in the bitstream. As part of locating the IRAP or GDR picture, the device may obtain from the picture header NAL unit in the bitstream a first syntax element (e.g., irap_gdr_idc), the first syntax element indicating whether the picture associated with the picture header NAL unit is: (i) neither an IRAP nor a GDR picture, (ii) an IDR picture, (iii) a CRA picture, or (iv) a GDR picture. Based on the first syntax element indicating that the picture associated with the NAL unit is an IRAP or GDR picture, the device has thus located the IRAP or GDR picture. The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit. The picture associated with the picture header NAL unit is in the collection of encoded pictures.

[0105] PH_IRAP_GDR_NUT for indicating an IRAP or GDR picture

[0106] According to the third technique of the present disclosure, the NAL unit type can be defined for the picture header to indicate the picture header associated with an IRAP or GDR picture. In other words, an IRAP or GDR picture can be indicated as part of a PH_NUT. A specific PH_NUT type can directly indicate the start of a random access picture or the start of a progressive decoder refresh. This can be achieved in multiple ways. An example is described below, where a single PH_IRAP_GDR_NUT type indicates an IRAP_GDR type PH_NUT, and the IRAP_GDR type PH_NUT only indicates that the picture is an IRAP or GDR picture without specifying a specific type. The slices associated with the picture header will carry the sub-IRAP or GDR type in their NUT.

[0107] ================================================================VVC Draft 7 Changes Start================================================================

[0108] 7.3.2.6 Picture Header RBSP Syntax

[0109]

[0110] 7.4.3.6 Picture Header RBSP Semantics

[0111] The PH contains information common to all slices of the decoded picture associated with the PH.

[0112] The non_reference_picture_flag being equal to 1 specifies that the picture associated with the PH is never used as a reference picture.

[0113] The non_reference_picture_flag being equal to 0 specifies that the picture associated with the PH may or may not be used as a reference picture.

[0114] The gdr_pic_flag being equal to 1 specifies that the picture associated with the PH is a GDR picture. The gdr_pic_flag being equal to 0 specifies that the picture associated with the PH is not a GDR picture. <!When not present, it is inferred to be equal to 0. < / !>

[0115] Table 5 – NAL Unit Type Codes and NAL Unit Type Categories

[0116]

[0117] ================================================================VVC Draft 7 Changes End================================================================

[0118] Thus, in some examples, the video encoder 200 may generate encoded pictures for a picture set of video data. In such examples, the video encoder 200 may include picture header NAL units in a bitstream including the encoded pictures. The NAL unit type of the picture header NAL unit indicates whether the picture associated with the picture header NAL unit is: (i) an IRAP or GDR picture, or (ii) the picture associated with the picture header NAL unit is neither an IRAP picture nor a GDR picture. The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0119] Similarly, in one example, a device (e.g., the video decoder 300 or another device) may obtain a bitstream including a set of encoded pictures of video data. In this example, the device may locate an IRAP or GDR picture in the encoded pictures in the bitstream. As part of locating the IRAP or GDR picture, the device may determine whether the picture associated with the picture header NAL unit is: (i) an IRAP or GDR picture, or (ii) the picture associated with the picture header NAL unit is neither an IRAP picture nor a GDR picture based on the NAL unit type of the picture header NAL unit in the bitstream. In this example, the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0120] According to a fourth technique of the present disclosure, the slice layer NUT may be signaled in the picture header. For example, according to a fourth technique of the present disclosure, it is proposed to carry the slice layer NUT (e.g., IDR_W_RADL, CRA_NUT, TRAIL_NUT,...) in the PH_NUT. In this case, the slice may have a generic SLICE_NUT without the need for a specific NUT, since the specific NUT will be carried in the picture header associated with the slice. A NAL unit with a NAL unit type of TRAIL_NUT is associated with a trailing picture. The trailing picture is associated with an IRAP or GDR picture, and in the decoding order, the trailing picture follows the IRAP or GDR picture. For pictures carrying a mixed NAL unit type, a generic PH_NUT may be used. For pictures with a mixed NAL unit type, in this case, the individual slice types may be signaled in the slice header. For example, the irap_gdr_idc field in the slice header may indicate the subtype (i.e., IDR_W_RADL, IDR_N_LP, CRA, GDR).

[0121] In such examples, a picture header is mandatory for each picture. In other examples of the present disclosure, the PH is not mandatory for each picture. When the mixed_nalu_types_in_pic_flag is equal to 1, a slice-layer specific NUT can be signaled as a PH NUT type at the PH, and the slice-layer NUT can be replaced with a SLICE_NUT indication with an IRAP or GDR indication signaled in the slice header. Except for the mixed_nal_unit_case, the NAL unit type at the slice header level is derived from the associated PH_NUT type.

[0122] ========================================================================VVC Draft 7 Changes Start========================================================================

[0123] 7.4.3.4 Picture Parameter Set RBSP Semantics

[0124] The mixed_nalu_types_in_pic_flag being equal to 1 specifies that each picture related to the PPS has more than one VCL NAL unit, and the VCL NAL units do not have the same nal_unit_type value, and the picture is not an IRAP picture.

[0125] The mixed_nalu_types_in_pic_flag being equal to 0 specifies that each picture related to the PPS has one or more VCL NAL units, and the VCL NAL units of each picture related to the PPS have the same nal_unit_type value.

[0126] When the no_mixed_nalu_types_in_pic_constraint_flag is equal to 1, the value of the mixed_nalu_types_in_pic_flag shall be equal to 0.

[0127] For each slice in picture picA where the nal_unit_type value nalUnitTypeA is in the range from IDR_W_RADL to CRA_NUT (inclusive) (and picture picA also contains one or more slices with another value of nal_unit_type, i.e., the value of the mixed_nalu_types_in_pic_flag of picture picA is equal to 1), the following applies:

[0128] – The slice shall belong to subpicA of the corresponding subpic_treated_as_pic_flag[i] whose value is equal to 1.

[0129] – The slice shall not belong to the subpicture of picA that contains NAL units with nal_unit_type not equal to nalUnitTypeAVCL.

[0130] – For all subsequent PUs in the CLVS in the decoding order, RefPicList[0] and RefPicList[1] of the slice in subpicA

[0131] shall not contain any pictures in the active entries that are before picA in the decoding order.

[0132] 7.3.7.1 General slice header syntax

[0133]

[0134] <!>An irap_gdr_idc equal to 0 indicates an IDR_W_RADL picture. An irap_gdr_pic_idc equal to 1 indicates an IDR_N_LP picture. An irap_gdr_idc equal to 2 indicates a CRA picture. An irap_gdr_idc equal to 3 indicates a GDR picture.< / !>

[0135] ==========================VVC Draft 7 Changes End==========================

[0136] Thus, in some examples, the video encoder 200 may generate a bitstream that includes a set of encoded pictures of video data and picture header NAL units associated with the pictures in the set of encoded pictures. As part of generating the bitstream, the video encoder 200 may include a first syntax element in the bitstream that indicates the presence of multiple MAL unit types in the picture associated with the picture header NAL unit. Based on the presence of multiple NAL unit types in the picture associated with the picture header NAL unit, the video encoder 200 may include a second syntax element in the picture header NAL unit. The second syntax element indicates whether the picture associated with the picture header NAL unit is (i) an IDR picture with RADL, (ii) an IDR picture without a leading picture, (iii) a CRA picture, or (iv) a GDR picture.

[0137] Similarly, in this example, a device (e.g., video decoder 300 or another device) may obtain a bitstream including a set of encoded pictures of video data and picture header NAL units associated with the pictures in the set of encoded pictures. The device may obtain a second syntax element from the picture header NAL unit based on a first syntax element indicating that there are multiple NAL unit types present in the picture associated with the picture header NAL unit, where the second syntax element indicates whether the picture associated with the picture header NAL unit is (i) an instantaneous decoder refresh (IDR) picture with a random access decodable lead (RADL) picture, (ii) an IDR picture without a lead picture, (iii) a clean random access (CRA) picture, or (iv) a gradual decoder refresh (GDR) picture.

[0138] In the VVC (Draft 7) specification, if a picture is a GDR picture, recovery_poc_cnt is signaled in the PH. For the case of a hybrid NAL unit where a GDR slice can be combined with an IRAP slice, a non-GDR picture is produced. The recovery_poc_cnt for the GDR slice needs to be signaled. According to the fifth technique of the present disclosure, recovery_poc_cnt can be signaled at the sub-picture / slice level, or the definition of the gdr_pic_flag flag can be changed to include hybrid NAL unit types in a picture with GDR slices.

[0139] =====================================================================VVC Draft 7 Changes Start=====================================================================

[0140] 7.3.7.1 General Slice Header Syntax

[0141]

[0142] The recovery_poc_cnt specifies the recovery point of the decoded pictures in the output order. If the current picture is a GDR picture associated with a PH, and there exists a picture picA in the CLVS that follows the current GDR picture in the decoding order and whose PicOrderCntVal is equal to the PicOrderCntVal of the current GDR picture plus the value of recovery_poc_cnt, then the picture picA is called a recovery point picture. Otherwise, the first picture in the output order whose PicOrderCntVal is greater than the PicOrderCntVal of the current picture plus the value of recovery_poc_cnt is called a recovery point picture. In the decoding order, the recovery point picture shall not be before the current GDR picture. The value of recovery_poc_cnt shall be in the range of 0 to MaxPicOrderCntLsb-1 (inclusive).

[0143] Note 1 – When the gdr_enabled_flag is equal to 1 and the PicOrderCntVal of the current picture is greater than or equal to the RpPicOrderCntVal of the associated GDR picture, the current and subsequent decoded pictures in the output order exactly match the corresponding pictures generated by starting the decoding process from the previous IRAP picture (when present) that precedes the associated GDR picture in the decoding order.

[0144] 3.1 Progressive Decoding Refresh (GDR) Pictures: Each VCL NAL unit has a picture with a nal_unit_type equal to GDR_NUT.

[0145] 7.4.3.6 Picture Header RBSP Semantics

[0146] The PH contains information that is common to all slices of the decoded picture associated with the PH.

[0147] The non_reference_picture_flag being equal to 1 specifies that the picture associated with the PH is never used as a reference picture.

[0148] The non_reference_picture_flag being equal to 0 specifies that the picture associated with the PH may or may not be used as a reference picture.

[0149] The gdr_pic_flag being equal to 1 specifies that the picture associated with the PH <dlt>Yes< / dlt> <!> contains <!> GDR <dlt>Picture< / dlt> <!> slices < / !>. The gdr_pic_flag being equal to 0 specifies that the picture associated with the PH is not a GDR picture.

[0150] =====================End of VVC Draft 7 Changes=====================

[0151] Thus, in some examples, the video encoder 200 may generate encoded pictures for a set of pictures of video data and picture header NAL units associated with the pictures in the set of encoded pictures. The video encoder 200 may include a first syntax element in a slice header that indicates the presence of multiple NAL unit types in a picture associated with a picture header NAL unit, and the NAL unit type of the picture header NAL unit is a GDR picture NAL unit type. Based on the presence of multiple NAL unit types in a picture associated with a picture header NAL unit and the NAL unit type of the picture header NAL unit being a GDR picture NAL unit type, the video encoder 200 may include a second syntax element in the picture header that indicates a recovery point.

[0152] Similarly, in some examples, the video decoder 300 or another device may obtain a set of encoded pictures including video data and picture header NAL units associated with the pictures in the set of encoded pictures. The video decoder 300 may obtain a second syntax element indicating a recovery point based on the first syntax element indicating the presence of multiple NAL unit types in a picture associated with a picture header NAL unit and the NAL unit type of the picture header NAL unit being a GDR picture NAL unit type.

[0153] The present disclosure may generally relate to "signaling" certain information (such as syntax elements). The term "signaling" may generally refer to the conveyance of values for syntax elements and / or other data used to decode encoded video data. That is, the video encoder 200 may signal the values for syntax elements in a bitstream. Generally, signaling refers to generating values in a bitstream. As noted above, the source device 102 may transmit the bitstream to the destination device 116 substantially in real time or not in real time (such as may occur when storing the syntax elements to the storage device 112 for later retrieval by the destination device 116).

[0154] Figure 2 is a block diagram illustrating an example video encoder 200 that may perform the techniques of the present disclosure. Figure 2It is provided for purposes of explanation and should not be construed as a limitation on the technology generally illustrated and described in this disclosure. For purposes of explanation, this disclosure describes video encoder 200 in the context of video coding standards such as the HEVC video coding standard and the H.266 / VVC video coding standard under development. However, the technology of this disclosure is not limited to these video coding standards and is generally applicable to video encoding and decoding.

[0155] In Figure 2 the example of, video encoder 200 includes video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, decoded picture buffer (DPB) 218, and entropy coding unit 220. Any or all of video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy coding unit 220 may be implemented in one or more processors or in processing circuitry. 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, ASIC, or FPGA. Additionally, video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0156] Video data memory 230 may store video data to be encoded by components of video encoder 200. Video encoder 200 may receive the video data stored in video data memory 230 from, for example, video source 104 ( Figure 1 ). DPB 218 may act as a reference picture memory that stores reference video data for use in predicting subsequent video data by video encoder 200. Video data memory 230 and DPB 218 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 may be provided by the same memory device or separate memory devices. In various examples, video data memory 230 may be on-chip (as shown) with other components of video encoder 200 or off-chip relative to those components.

[0157] In the present disclosure, a reference to the video data memory 230 should not be construed as limited to a memory within the video encoder 200 (unless specifically described as such) or a memory external to the video encoder 200 (unless specifically described as such). Rather, a reference to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data for a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from various units of the video encoder 200.

[0158] illustrates Figure 2 various units to assist in understanding the operations performed by the video encoder 200. These units may be implemented as fixed-function circuitry, programmable circuitry, or a combination thereof. Fixed-function circuitry refers to circuitry that provides a specific function and is pre-set with respect to the operations that can be performed. Programmable circuitry refers to circuitry that can be programmed to perform various tasks and provides flexible functionality with respect to the operations that can be performed. For example, programmable circuitry may execute software or firmware that causes the programmable circuitry to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuitry may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuitry are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units may be integrated circuits.

[0159] The video encoder 200 may include an arithmetic logic unit (ALU), a basic function unit (EFU), digital circuitry, analog circuitry, and / or a programmable core formed of programmable circuitry. In examples where software executed by programmable circuitry is used to perform the operations of the video encoder 200, the memory 106 ( Figure 1 ) may store the instructions (e.g., object code) of the software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0160] 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 the original video data to be encoded.

[0161] 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 that perform video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, a 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.

[0162] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values for such combinations. The encoding parameters may include the division of CTUs into CUs, the prediction mode for a CU, the transform type for the residual data of a CU, the quantization parameter for the residual data of a CU, etc. The mode selection unit 202 may ultimately select the combination of encoding parameters that has a better rate-distortion value compared to other tested combinations.

[0163] The video encoder 200 may divide a picture retrieved from the video data memory 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 may divide the CTUs of the picture according to a tree structure, such as the QTBT structure or the quadtree structure of HEVC described above. As described above, the video encoder 200 may form one or more CUs by dividing the CTUs according to a tree structure. Such CUs may generally also be referred to as "video blocks" or "blocks".

[0164] Generally, 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 the current block (e.g., the current CU, or the overlapping portion of the PU and TU in HEVC). For inter prediction of the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously encoded pictures stored in the DPB 218). In particular, the motion estimation unit 222 may calculate a value representing how closely a potential reference block will resemble the current block, for example, according to the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may generally use the per-sample difference between the current block and the considered reference block to perform these calculations. The motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0165] 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, for uni-directional inter prediction, the motion estimation unit 222 may provide a single motion vector, and for bi-directional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. 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 fractional sample accuracy, the motion compensation unit 224 may interpolate values for the prediction block according to one or more interpolation filters. Further, for bi-directional inter prediction, the motion compensation unit 224 may retrieve data of two reference blocks identified by the respective motion vectors and combine the retrieved data, e.g., by per-sample averaging or weighted averaging.

[0166] As another example, for intra prediction or intra prediction coding, the intra prediction unit 226 may generate a prediction block based on samples adjacent to the current block. For example, for a directional mode, the intra prediction unit 226 may generally mathematically combine values of adjacent samples and fill the calculated values across the current block in a defined direction to produce the prediction block. As another example, for a DC mode, the intra prediction unit 226 may calculate an average value of adjacent samples of the current block and generate a prediction block to include the resulting average value for each sample of the prediction block.

[0167] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives an original, unencoded 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 the per-sample difference between the current block and the prediction block. The resulting per-sample difference defines 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 coding modulation (RDPCM). In some examples, one or more subtractor circuits performing binary subtraction may be used to form the residual generation unit 204.

[0168] Further, in some examples, the mode selection unit 202 may determine whether a picture is to be encoded as an IRAP, GDR picture or another type of picture. The mode selection unit 202 may also generate a picture header for the encoded picture. Thus, in Figure 2In the example where the mode selection unit 202 includes a picture header unit 229. The picture header unit 229 may generate a picture header according to any technique of the present disclosure. For example, the picture header unit 229 may generate a picture header NAL unit including syntax elements that indicate that the picture associated with the picture header NAL unit must be an IRAP or GDR picture. The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit.

[0169] In the example where the mode selection unit 202 divides a CU into PUs, each PU may be associated with a luminance prediction unit and a corresponding chrominance prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As pointed out above, the size of a CU may refer to the size of the luminance decoding block of the CU, and the size of a PU may refer to the size of the luminance prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra prediction, and PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar symmetric PU sizes for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter prediction.

[0170] In the example where the mode selection unit 202 does not further divide a CU into PUs, each CU may be associated with a luminance decoding block and a corresponding chrominance decoding block. As above, the size of a CU may refer to the size of the luminance decoding block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0171] For other video decoding techniques (to name a few examples, such as intra-block copy mode decoding, affine mode decoding, and linear model (LM) mode decoding), the mode selection unit 202 generates a prediction block for the current block being encoded via the corresponding unit associated with the decoding technique. In some examples (such as palette mode decoding), the mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating the manner in which the block is to be reconstructed based on the selected palette. In such a mode, the mode selection unit 202 may provide these syntax elements to the entropy encoding unit 220 for encoding.

[0172] As described above, the residual generation unit 204 receives video data for the current block and the corresponding prediction block. Then, the residual generation unit 204 generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the per-sample difference between the prediction block and the current block.

[0173] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form a transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform multiple transforms on the residual block, e.g., a primary transform and a secondary transform (such as a rotation transform). In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0174] 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 the 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 cause information loss, and thus, the quantized transform coefficients may have lower precision compared to the original transform coefficients generated by the transform processing unit 206.

[0175] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct the residual block based on the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add the samples of the reconstructed residual block to the corresponding samples of the prediction block generated by the mode selection unit 202 to produce the reconstructed block.

[0176] The filter unit 216 may perform one or more filter operations on the reconstructed block. For example, the filter unit 216 may perform a deblocking operation to reduce block effect artifacts along the edges of the CU. In some examples, the operation of the filter unit 216 may be skipped.

[0177] Video encoder 200 stores the reconstructed blocks in DPB 218. For example, in an example where the operation of filter unit 216 is not required, reconstruction unit 214 may store the reconstructed blocks into DPB 218. In an example where the operation of filter unit 216 is required, filter unit 216 may store the filtered reconstructed blocks into DPB 218. Motion estimation unit 222 and motion compensation unit 224 may retrieve reference pictures formed by the reconstructed (and potentially filtered) blocks from DPB 218 to perform inter prediction on blocks of subsequently encoded pictures. Additionally, intra prediction unit 226 may use the reconstructed blocks of the current picture in DPB 218 to perform intra prediction on other blocks in the current picture.

[0178] Generally, entropy coding unit 220 may perform entropy coding on syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 may perform entropy coding on the quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 may perform entropy coding on prediction syntax elements (e.g., motion information for inter prediction or intra mode information for intra prediction) from mode selection unit 202. Entropy coding unit 220 may perform one or more entropy coding operations on syntax elements as another example of video data to generate entropy-coded data. For example, entropy coding unit 220 may perform context-adaptive variable length coding (CAVLC) operations, CABAC operations, variable-variable (V2V) length coding operations, syntax-based context-adaptive binary arithmetic coding (SBAC) operations, probability interval partitioning entropy (PIPE) coding operations, exponential Golomb coding operations, or another type of entropy coding operation on the data. In some examples, entropy coding unit 220 may operate in a bypass mode where the syntax elements are not entropy coded.

[0179] Video encoder 200 may output a bitstream that includes the entropy-coded syntax elements required to reconstruct the blocks of a slice or picture. In particular, entropy coding unit 220 may output the bitstream.

[0180] The operations described above are described with respect to blocks. Such descriptions should be understood as operations for luminance decoding blocks and / or chrominance decoding blocks. As described above, in some examples, the luminance decoding block and chrominance decoding block are the luminance component and chrominance component of a CU. In some examples, the luminance decoding block and chrominance decoding block are the luminance component and chrominance component of a PU.

[0181] In some examples, there is no need to repeat the operations performed on the luma coding blocks for the chroma coding blocks. As an example, there is no need to repeat the operations for identifying the motion vectors (MVs) and reference pictures for the luma coding blocks to identify the MVs and reference pictures for the chroma blocks. Rather, the MVs for the luma coding blocks can be scaled to determine the MVs for the chroma blocks, and the reference pictures can be the same. As another example, the intra prediction process can be the same for the luma coding blocks and the chroma coding blocks.

[0182] Video encoder 200 represents an example of a device configured to encode video data, the device including: a memory configured to store video data; and one or more processing units implemented in circuitry and configured to: generate encoded pictures for a set of pictures of the video data; and include a picture header NAL unit in a bitstream including the encoded pictures, where the picture header NAL unit includes a first syntax element that indicates that the picture associated with the picture header NAL unit must be an IRAP or GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of encoded pictures.

[0183] In some examples, the processing unit of video encoder 200 can be configured to: generate encoded pictures for a set of pictures of the video data; and include a picture header NAL unit in a bitstream including the encoded pictures, where a first syntax element indicates whether the picture associated with the picture header NAL unit is: (i) neither an IRAP picture nor a GDR picture, (ii) an IDR picture, (iii) a CRA picture, or (iv) a GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of encoded pictures.

[0184] In some examples, the processing unit of video encoder 200 can be configured to: generate encoded pictures for a set of pictures of the video data; and include a picture header NAL unit in a bitstream including the encoded pictures, where the NAL unit type of the picture header NAL unit indicates whether the picture associated with the picture header NAL unit is: (i) an IRAP or GDR picture, or (ii) the picture associated with the picture header NAL unit is neither an IRAP picture nor a GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of encoded pictures.

[0185] In some examples, the processing unit of video encoder 200 may be configured to: generate a bitstream that includes a set of encoded pictures of video data and picture header network abstraction layer (NAL) units associated with the pictures in the set of encoded pictures, wherein generating the bitstream includes: including a second syntax element in the picture header NAL unit based on a first syntax element indicating that there are multiple NAL unit types in the picture associated with the picture header NAL unit, wherein the second syntax element indicates whether the picture associated with the picture header NAL unit is: (i) an IDR with RADL, (ii) an IDR picture without a leading picture, (iii) a CRA picture, or (iv) a GDR picture.

[0186] In some examples, the processing unit of video encoder 200 may be configured to: generate encoded pictures for a set of pictures of video data and picture header NAL units associated with the pictures in the set of encoded pictures; and include a syntax element indicating a recovery point based on a syntax element indicating that there are multiple NAL unit types in the picture associated with the picture header NAL unit and the NAL unit type of the picture header NAL unit is the GDR picture NAL unit type.

[0187] Figure 3 FIG. is a block diagram illustrating an example video decoder 300 that may execute the techniques of the present disclosure. Figure 3 is provided for explanatory purposes and is not a limitation of the techniques broadly illustrated and described in the present disclosure. For explanatory purposes, the present disclosure describes video decoder 300 in accordance with the techniques of VVC and HEVC. However, the techniques of the present disclosure may be performed by video decoding devices configured for other video coding standards.

[0188] In Figure 3 example, 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) 134. Any or all of the CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 134 may be implemented in one or more processors or in processing circuitry. For example, the units of video decoder 300 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Additionally, video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0189] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include an addition unit that performs prediction according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, a block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0190] The CPB memory 320 may store video data to be decoded by components of the video decoder 300, such as an encoded video bitstream. For example, the video data stored in the CPB memory 320 may be obtained from a computer-readable medium 110 ( Figure 1 ). The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. In addition, the CPB memory 320 may store video data other than the syntax elements of the decoded pictures, such as temporary data representing the outputs of the respective units of the video decoder 300. The DPB 314 generally stores decoded pictures, and the video decoder 300 may output decoded pictures and / or use the decoded pictures 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 of any of various 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 or off-chip relative to the other components of the video decoder 300.

[0191] Additionally or alternatively, in some examples, the video decoder 300 may retrieve the encoded video data from a memory 120 ( Figure 1 ). That is, the memory 120 may utilize the CPB memory 320 to store data as discussed above. Similarly, when some or all of the functions of the video decoder 300 are implemented with software to be executed by the processing circuitry of the video decoder 300, the memory 120 may store instructions to be executed by the video decoder 300.

[0192] Shown in Figure 3 The various units shown in help to understand the operations performed by the video decoder 300. These units may be implemented as fixed-function circuitry, programmable circuitry, or a combination thereof. Similar to Figure 2, A fixed - function circuit refers to a circuit that provides a specific function and is pre - set with respect to the operations that can be performed. A programmable circuit refers to a circuit that can be programmed to perform various tasks and provides flexible functionality with respect to the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. A fixed - function circuit can execute software instructions (e.g., to receive parameters or output parameters), but the type of operations performed by the fixed - function circuit is generally immutable. In some examples, one or more of these units can be different circuit blocks (fixed - function or programmable), and in some examples, one or more of these units can be an integrated circuit.

[0193] Video decoder 300 can include an ALU, EFU, digital circuits, analog circuits, and / or programmable cores formed by programmable circuits. In an example where the operations of video decoder 300 are performed by software executed on the programmable circuit, on - chip or off - chip memory can store the instructions (e.g., object code) of the software that video decoder 300 receives and executes.

[0194] The entropy decoding unit 302 can receive the encoded video data from the CPB memory 320 and perform entropy decoding on the video data to reproduce the syntax elements. The prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 can generate the decoded video data based on the syntax elements extracted from the bitstream.

[0195] In Figure 3 the example, video decoder 300 includes a random access unit 321 that can enable video decoder 300 to perform random access. As part of performing random access, random access unit 321 can locate IRAP and GDR pictures and associated picture headers according to one or more techniques of the present disclosure. For example, in one example, random access unit 321 can locate an IRAP or GDR picture in the encoded pictures in the bitstream. As part of locating an IRAP or GDR picture, random access unit 321 can obtain a syntax element from the picture header NAL unit in the bitstream, which indicates that the picture associated with the picture header NAL unit must be an IRAP or GDR picture. Random access unit 321 can determine that the picture associated with the picture header NAL unit is an IRAP or GDR picture based on the syntax element.

[0196] Generally, video decoder 300 reconstructs pictures block - by - block. Video decoder 300 can perform the reconstruction operation on each block individually (where the block that is currently being reconstructed (i.e., decoded) can be referred to as the “current block”).

[0197] The entropy decoding unit 302 can perform entropy decoding on the syntax elements of the quantized transform coefficients that define the quantized transform coefficient block and the transform information (such as quantization parameter (QP) and / or transform mode indication). The inverse quantization unit 306 can use the QP associated with the quantized transform coefficient block to determine the quantization level, and similarly, determine the inverse quantization level to be applied by the inverse quantization unit 306. The inverse quantization unit 306 can, for example, perform a bitwise left shift operation to inverse-quantize the quantized transform coefficients. The inverse quantization unit 306 can thus form a transform coefficient block including the transform coefficients.

[0198] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 can 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 can apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotation transform, an inverse direction transform, or another inverse transform to the transform coefficient block.

[0199] In addition, the prediction processing unit 304 generates a prediction block according to the prediction information syntax elements entropy decoded by the entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, the motion compensation unit 316 can generate a prediction block. In this case, the prediction information syntax element can indicate the reference picture in the DPB 314 from which the reference block is to be retrieved, and the motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. The motion compensation unit 316 can generally perform the inter-prediction process in a manner substantially similar to the manner described with respect to the motion compensation unit 224 ( Figure 2 ).

[0200] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 can generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 can generally perform the intra-prediction process in a manner substantially similar to the manner described with respect to the intra-prediction unit 226 ( Figure 2 ). The intra-prediction unit 318 can retrieve the data of the neighboring samples of the current block from the DPB 314.

[0201] The reconstruction unit 310 can use the prediction block and the residual block to reconstruct the current block. For example, the reconstruction unit 310 can add the samples of the residual block to the corresponding samples of the prediction block to reconstruct the current block.

[0202] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce block effect artifacts along the edges of the reconstructed block. The operation of the filter unit 312 is not necessarily performed in all examples.

[0203] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block into the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered reconstructed block into the DPB 314. As discussed above, the DPB 314 may provide reference information (such as the current picture for intra prediction and samples of previously decoded pictures for subsequent motion compensation) to the prediction processing unit 304. In addition, 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 Figure 1 the display device 118.

[0204] In this way, the video decoder 300 represents an example of a video decoding device that includes: a memory configured to store video data; and one or more processing units implemented in circuitry and configured to: obtain a bitstream including a set of encoded pictures of video data; and locate an IRAP or GDR picture in the encoded pictures in the bitstream, where locating the IRAP or GDR picture includes: obtaining a first syntax element from a picture header NAL unit in the bitstream, the first syntax element indicating that the picture associated with the picture header NAL unit must be an IRAP or GDR picture; and determining, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture. The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0205] In some examples, the processing unit of video decoder 300 is configured to: obtain a bitstream including a set of encoded pictures of video data; and locate an Instantaneous Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein locating the IRAP or GDR picture includes: obtaining a first syntax element from a picture header NAL unit in the bitstream, the first syntax element indicating whether the picture associated with the picture header NAL unit is: (i) neither an IRAP nor a GDR picture, (ii) an Instantaneous Decoding Refresh (IDR) picture, (iii) a Clean Random Access (CRA) picture, or (iv) a GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0206] In some examples, the processing unit of video decoder 300 is configured to: obtain a bitstream including a set of encoded pictures of video data; and locate an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein locating the IRAP or GDR picture includes: determining, based on the Network Abstraction Layer (NAL) unit type of the picture header NAL unit in the bitstream, whether the picture associated with the picture header NAL unit is: (i) an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, or (ii) the picture associated with the picture header NAL unit is neither an IRAP picture nor a GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0207] In some examples, the processing unit of video decoder 300 is configured to: obtain a bitstream that includes a set of encoded pictures of video data and picture header Network Abstraction Layer (NAL) units associated with the pictures in the set of encoded pictures; and obtain a second syntax element from the picture header NAL unit based on the first syntax element indicating the presence of multiple NAL unit types in the picture associated with the picture header NAL unit, wherein the second syntax element indicates whether the picture associated with the picture header NAL unit is (i) an Instantaneous Decoding Refresh (IDR) with a Random Access Decodable Leading (RADL) picture, (ii) an IDR picture without a leading picture, (iii) a Clean Random Access (CRA) picture, or (iv) a Gradual Decoder Refresh (GDR) picture.

[0208] In some examples, the processing unit of video decoder 300 is configured to: obtain a bitstream that includes a set of encoded pictures of video data and picture header Network Abstraction Layer (NAL) units associated with the pictures in the set of encoded pictures; and obtain a syntax element indicating a recovery point based on a syntax element indicating that there are multiple NAL unit types in a picture associated with a picture header NAL unit and that the NAL unit type of the picture header NAL unit is a Progressive Decoder Refresh (GDR) picture NAL unit type.

[0209] Figure 4 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although described with respect to video encoder 200 ( Figure 1 and 2 ), it should be understood that other devices may be configured to perform methods similar to those of Figure 4 .

[0210] In this example, video encoder 200 initially predicts a current block (350). For example, video encoder 200 may form a prediction block for the current block. Then, video encoder 200 may calculate a residual block for the current block (352). To calculate the residual block, video encoder 200 may calculate the difference between the original unencoded block and the prediction block for the current block. Then, video encoder 200 may transform and quantize the transform coefficients of the residual block (354). Next, video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, video encoder 200 may entropy encode the transform coefficients (358). For example, video encoder 200 may use CAVLC or CABAC to encode the transform coefficients. Then, video encoder 200 may output the entropy-encoded data of the block (360).

[0211] Figure 5 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although described with respect to video decoder 300 ( Figure 1 and 3 ), it should be understood that other devices may be configured to perform methods similar to those of Figure 5 .

[0212] Video decoder 300 may receive entropy-coded data for a current block, such as entropy-coded prediction information and entropy-coded data of transform coefficients for a residual block corresponding to the current block (370). Video decoder 300 may entropy-decode the entropy-coded data to determine prediction information for the current block and reproduce the transform coefficients of the residual block (372). Video decoder 300 may predict the current block, for example, using an intra or inter prediction mode indicated by the prediction information for the current block (374), to calculate a prediction block for the current block. Then, video decoder 300 may perform an inverse scan on the reproduced transform coefficients (376) to create a block of quantized transform coefficients. Then, video decoder 300 may perform inverse quantization and inverse transformation on the transform coefficients to generate a residual block (378). Finally, video decoder 300 may decode the current block by combining the prediction block and the residual block (380).

[0213] Figure 6 is a flowchart showing an example operation of video encoder 200 according to one or more techniques of the present disclosure. In Figure 6 example, video encoder 200 may generate encoded pictures for a set of pictures of video data (600). For example, video encoder 200 may encode pictures, for example, as described with respect to Figure 2 described.

[0214] In addition, video encoder 200 may include a picture header NAL unit in a bitstream including the encoded pictures (602). The picture header NAL unit includes syntax elements (e.g., irap_or_gdr_pic_flag), which indicate that the picture associated with the picture header NAL unit must be an IRAP or GDR picture. For example, if the syntax element is equal to 1, the syntax element may indicate that the picture associated with the picture header NAL unit is an IRAP or GDR picture, rather than any other type of picture. The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit. The picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0215] Figure 7 is a flowchart showing an example operation for processing video data according to one or more techniques of the present disclosure. Processing video data may include: decoding video data, processing video data for transmission to other devices, and other actions involving video data. Figure 7 The operations of may be performed by video decoder 300, destination device 116, or another device (such as an intermediate network device). For ease of explanation, the present disclosure is described with reference to video decoder 300 Figure 7 .

[0216] In Figure 7 the example of, video decoder 300 obtains a bitstream (700) that includes a set of encoded pictures of video data. In addition, video decoder 300 may locate an IRAP or GDR picture (702) in the encoded pictures in the bitstream. As part of locating the IRAP or GDR picture, video decoder 300 may obtain a syntax element (e.g., irap_or_gdr_pic_flag) from a picture header NAL unit in the bitstream, and the syntax element indicates that the picture associated with the picture header NAL unit must be an IRAP or GDR picture (704). Video decoder 300 may determine that the picture associated with the picture header NAL unit is an IRAP or GDR picture based on the syntax element (706). The picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit. The picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0217] In addition, in Figure 7 the example of, video decoder 300 may decode the picture associated with the picture header NAL unit (708). For example, video decoder 300 may decode the picture as described with respect to Figure 3 In other examples, after the device locates the IRAP or GDR picture, the device may provide an indication of the location of the IRAP and GDR pictures to another device, for example, for decoding the pictures.

[0218] The following is a non-limiting list of aspects of one or more techniques according to the present disclosure.

[0219] Aspect 1A, a method for processing video data, the method includes: obtaining a bitstream that includes a set of decoded pictures of video data; and locating an Intra Random Access Picture (IRAP) or Gradual Decoder Refresh (GDR) picture in the decoded pictures in the bitstream, where locating the IRAP or GDR picture includes: obtaining a first syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, and the first syntax element indicates whether the picture associated with the picture header NAL unit is an Intra Random Access Picture (IRAP) or Gradual Decoder Refresh (GDR) picture or the picture associated with the picture header NAL unit is neither an IRAP nor a GDR picture, where: the picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of decoded pictures.

[0220] Aspect 2A. The method according to Aspect 1A further includes: obtaining a second syntax element from a picture header NAL unit based on a first syntax element indicating that a picture associated with the picture header NAL unit is an IRAP or GDR picture, the second syntax element indicating whether the picture associated with the picture header NAL unit is a GDR picture.

[0221] Aspect 3A. The method according to any one of Aspects 1A - 2A further includes: decoding a picture associated with a picture header NAL unit.

[0222] Aspect 4A. A method for encoding video data, the method includes: generating a decoded picture for a set of pictures of the video data; and including a picture header network abstraction layer (NAL) unit in a bitstream including the decoded picture, wherein the picture header NAL unit includes a first syntax element indicating whether the picture associated with the picture header NAL unit is an intra random access picture (IRAP) or a progressive decoder refresh (GDR) picture or the picture associated with the picture header NAL unit is neither an IRAP nor a GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of decoded pictures.

[0223] Aspect 5A. The method according to Aspect 4A, wherein based on the picture being an IRAP or GDR picture, the picture header NAL unit includes a second syntax element indicating whether the picture is a GDR picture.

[0224] Aspect 1B. A method for processing video data, the method includes: obtaining a bitstream including a set of decoded pictures of the video data; and locating an intra random access picture (IRAP) or a progressive decoder refresh (GDR) picture in the decoded pictures in the bitstream, wherein locating the IRAP or GDR picture includes: obtaining a first syntax element from a picture header network abstraction layer (NAL) unit in the bitstream, the first syntax element indicating whether the picture associated with the picture header NAL unit is: (i) neither an intra random access picture (IRAP) nor a progressive decoder refresh (GDR) picture, (ii) an instantaneous decoding refresh (IDR) picture, (iii) a clean random access (CRA) picture, or (iv) a GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of decoded pictures.

[0225] Aspect 2B. The method according to Aspect 1B further includes: obtaining a second syntax element from a picture header NAL unit based on that the first syntax element indicates that the picture associated with the picture header NAL unit is a GDR picture, where the second syntax element indicates a recovery point for the picture associated with the picture header NAL unit.

[0226] Aspect 3B. The method according to any one of Aspects 1B - 2B further includes: decoding the picture associated with the picture header NAL unit.

[0227] Aspect 4B. A method for encoding video data, the method includes: generating decoded pictures for a set of pictures of the video data; and including a picture header network abstraction layer (NAL) unit in a bitstream including the decoded pictures, where a first syntax element indicates whether the picture associated with the picture header NAL unit is: (i) neither an intra random access picture (IRAP) nor a progressive decoder refresh (GDR) picture, (ii) an instantaneous decoding refresh (IDR) picture, (iii) a clean random access (CRA) picture, or (iv) a GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of decoded pictures.

[0228] Aspect 5B. The method according to Aspect 4B further includes: including a second syntax element in the picture header NAL unit based on that the picture associated with the picture header NAL unit is a GDR picture, where the second syntax element indicates a recovery point for the picture associated with the picture header NAL unit.

[0229] Aspect 1C. A method for processing video data, the method includes: obtaining a bitstream including a set of decoded pictures of the video data; and locating an intra random access picture (IRAP) or a progressive decoder refresh (GDR) picture in the decoded pictures in the bitstream, where locating the IRAP or GDR picture includes: determining whether the picture associated with the picture header network abstraction layer (NAL) unit in the bitstream is: (i) an intra random access picture (IRAP) or a progressive decoder refresh (GDR) picture, or (ii) the picture associated with the picture header NAL unit is neither an IRAP picture nor a GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of decoded pictures.

[0230] Aspect 2C. The method according to Aspect 1C further includes: obtaining a second syntax element from a picture header NAL unit based on that the NAL unit type of the picture header NAL unit indicates that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where the second syntax element indicates whether the picture associated with the picture header NAL unit is a GDR picture.

[0231] Aspect 3C. The method according to any one of Aspects 1C - 2C further includes: decoding the picture associated with the picture header NAL unit.

[0232] Aspect 4C. A method for encoding video data, the method includes: generating decoded pictures for a set of pictures of the video data; and including a picture header network abstraction layer (NAL) unit in a bitstream including the decoded pictures, where the NAL unit type of the picture header NAL unit indicates whether the picture associated with the picture header NAL unit is: (i) an Intra Random Access Picture (IRAP) or a Progressive Decoder Refresh (GDR) picture, or (ii) the picture associated with the picture header NAL unit is neither an IRAP picture nor a GDR picture, where: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of decoded pictures.

[0233] Aspect 5C. The method according to Aspect 4C further includes: including a second syntax element in the picture header NAL unit based on that the picture associated with the picture header NAL unit is a GDR picture, where the second syntax element indicates whether the picture associated with the picture header NAL unit is a GDR picture.

[0234] Aspect 1D. A method for processing video data, the method includes: obtaining a bitstream, the bitstream including a set of decoded pictures of the video data and picture header network abstraction layer (NAL) units associated with the pictures in the set of decoded pictures; and obtaining a second syntax element from the picture header NAL unit based on that a first syntax element indicates the presence of multiple NAL unit types in the picture associated with the picture header NAL unit, where the second syntax element indicates whether the picture associated with the picture header NAL unit is (i) an Instantaneous Decoder Refresh (IDR) with a Random Access Decodable Lead (RADL) picture, (ii) an IDR picture without a leading picture, (iii) a Clean Random Access (CRA) picture, or (iv) a Progressive Decoder Refresh (GDR) picture.

[0235] Aspect 2D. The method according to Aspect 1D, wherein: the picture header NAL unit is a first picture header NAL unit, and the method further includes: obtaining a second picture header NAL unit from the bitstream; and determining the picture type of the picture associated with the second picture header NAL unit based on the NAL unit type of the second picture header NAL unit, based on a third syntax element indicating that there are no multiple NAL unit types in the picture associated with the second picture header NAL unit.

[0236] Aspect 3D. The method according to any one of Aspects 1D-2D, further including at least one of the following operations: decoding the picture associated with the first picture header NAL unit, and decoding the picture associated with the second picture header NAL unit.

[0237] Aspect 4D. A method for encoding video data, the method including: generating a bitstream, the bitstream including a set of decoded pictures of the video data and picture header network abstraction layer (NAL) units associated with the pictures in the set of decoded pictures, wherein generating the bitstream includes: including a second syntax element in the picture header NAL unit based on a first syntax element indicating that there are multiple NAL unit types in the picture associated with the picture header NAL unit, wherein the second syntax element indicates whether the picture associated with the picture header NAL unit is (i) an instantaneous decoder refresh (IDR) picture with a random access decodable lead (RADL), (ii) an IDR picture without a leading picture, (iii) a clean random access (CRA) picture, or (iv) a gradual decoder refresh (GDR) picture.

[0238] Aspect 5D. The method according to Aspect 4D, wherein: the picture header NAL unit is a first picture header NAL unit, and generating the bitstream further includes: including a second picture header NAL unit in the bitstream, wherein, based on there being no multiple NAL unit types in the picture associated with the second picture header NAL unit, the NAL unit type of the second picture header indicates the picture type of the picture associated with the second picture header NAL unit.

[0239] Aspect 1E. A method for processing video data, the method including: obtaining a bitstream, the bitstream including a set of decoded pictures of the video data and picture header network abstraction layer (NAL) units associated with the pictures in the set of decoded pictures; and obtaining a syntax element indicating a recovery point based on a syntax element indicating that there are multiple NAL unit types in the picture associated with the picture header NAL unit and the NAL unit type of the picture header NAL unit being a gradual decoder refresh (GDR) picture NAL unit type.

[0240] Aspect 2E. The method according to Aspect 1E further includes: decoding a picture associated with a picture header NAL unit.

[0241] Aspect 3E. A method for encoding video data, the method includes: generating decoded pictures for a set of pictures of the video data and picture header Network Abstraction Layer (NAL) units associated with the pictures in the set of decoded pictures; and including a syntax element indicating a recovery point based on a syntax element indicating that there are multiple NAL unit types in a picture associated with a picture header NAL unit and the NAL unit type of the picture header NAL unit is a Progressive Decoder Refresh (GDR) picture NAL unit type.

[0242] Aspect 1F. The method according to any of Aspects 1A - 5A, 1B - 3B, 1C - 3C, 1D - 3D, 1E or 2E further includes: performing random access of the bitstream starting from an IRAP or GDR picture.

[0243] Aspect 2F. The method according to Aspect 1F, wherein performing random access of the bitstream starting from an IRAP picture includes at least one of the following: clean random access, instantaneous decoder refresh, or discontinuous link access procedure.

[0244] Aspect 3F. The method according to Aspect 1F, wherein performing random access of the bitstream starting from a GDR picture includes: performing a progressive decoding refresh procedure.

[0245] Aspect 1G. A device for decoding video data, the device includes one or more units for performing the method according to any of Aspects 1A - 3F.

[0246] Aspect 2G. The device according to Aspect 1G, wherein the one or more units include one or more processors implemented in a circuit.

[0247] Aspect 3G. The device according to any of Aspects 1G and 2G further includes: a memory for storing video data.

[0248] Aspect 4G. The device according to any of Aspects 1G - 3G further includes: a display configured to display the decoded video data.

[0249] Aspect 5G. The device according to any of Aspects 1G - 4G, wherein the device includes at least one of the following: a camera, a computer, a mobile device, a broadcast receiver device, or a set - top box.

[0250] Aspect 6G. The device according to any of Aspects 1G - 5G, wherein the device includes a video decoder.

[0251] Aspect 7G. The apparatus according to any one of Aspects 1G - 6G, wherein the apparatus includes a video encoder.

[0252] Aspect 8H. A computer - readable storage medium having instructions stored thereon, which when executed cause one or more processors to perform the method according to any one of Aspects 1A - 3F.

[0253] Aspect 1I. A method of processing video data, the method comprising:

[0254] obtaining a bitstream comprising a set of encoded pictures including video data; and locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein locating the IRAP or GDR picture comprises: obtaining a syntax element from a picture - header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture - header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and determining, based on the syntax element, that the picture associated with the picture - header NAL unit is an IRAP or GDR picture, wherein: the picture - header NAL unit contains syntax elements applied to all slices of the picture associated with the picture - header NAL unit, and the picture associated with the picture - header NAL unit is located in the set of encoded pictures.

[0255] Aspect 2I. The method according to Aspect 1I, wherein the syntax element is a first syntax element, and the method further comprises: obtaining a second syntax element from the picture - header NAL unit based on the first syntax element indicating that the picture associated with the picture - header NAL unit is an IRAP or GDR picture, the second syntax element indicating whether the picture associated with the picture - header NAL unit is a GDR picture.

[0256] Aspect 3I. The method according to Aspect 1I or 2I, further comprising: decoding the picture associated with the picture - header NAL unit.

[0257] Aspect 4I. A method of encoding video data, the method comprising: generating encoded pictures for a set of pictures of the video data; and including a picture - header Network Abstraction Layer (NAL) unit in a bitstream comprising the encoded pictures, wherein the picture - header NAL unit includes a syntax element indicating that the picture associated with the picture - header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: the picture - header NAL unit contains syntax elements applied to all slices of the picture associated with the picture - header NAL unit, and the picture associated with the picture - header NAL unit is located in the set of encoded pictures.

[0258] Aspect 5I. The method according to aspect 4I, wherein the method further comprises: including a second syntax element indicating whether the picture is a GDR picture in the picture header NAL unit based on whether the picture is an IRAP or GDR picture.

[0259] Aspect 6I. A device for processing video data, the device comprising: a memory configured to store encoded pictures of video data; and one or more processors implemented in circuitry, the one or more processors being configured to: locate an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in a bitstream, wherein the one or more processors are configured such that as part of locating the IRAP or GDR picture, the one or more processors perform the following operations: obtain a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and determine, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in a set of encoded pictures.

[0260] Aspect 7I. The device according to aspect 6I, wherein the syntax element is a first syntax element, and the one or more processors are further configured to: obtain a second syntax element from the picture header NAL unit based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, the second syntax element indicating whether the picture associated with the picture header NAL unit is a GDR picture.

[0261] Aspect 8I. The device according to aspect 6I or 7I, wherein the one or more processors are further configured to: decode the picture associated with the picture header NAL unit.

[0262] Aspect 9I. A device for encoding video data, the device comprising: a memory configured to store video data; and one or more processors implemented in circuitry, the one or more processors being configured to: generate an encoded picture for a set of pictures of the video data; and include a picture header Network Abstraction Layer (NAL) unit in a bitstream comprising the encoded picture, wherein the picture header NAL unit comprises syntax elements that indicate that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of encoded pictures.

[0263] Aspect 10I. The device according to Aspect 9I, wherein the one or more processors are further configured to: include a second syntax element in the picture header NAL unit indicating whether the picture is a GDR picture based on whether the picture is an IRAP or GDR picture.

[0264] Aspect 11I. A device for processing video data, the device comprising: a unit for obtaining a bitstream comprising a set of encoded pictures of the video data; and a unit for locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein the unit for locating the IRAP or GDR picture comprises: a unit for obtaining syntax elements from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax elements indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and a unit for determining, based on the syntax elements, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is in the set of encoded pictures.

[0265] Aspect 12I. The device according to Aspect 11I, wherein the syntax element is a first syntax element, and the device further comprises: a unit for obtaining a second syntax element from the picture header NAL unit based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, the second syntax element indicating whether the picture associated with the picture header NAL unit is a GDR picture.

[0266] Aspect 13I. The device according to Aspect 11I or 12I, wherein the device further comprises: a unit for decoding the picture associated with the picture header NAL unit.

[0267] Aspect 14I. A device for encoding video data, the device comprising: a unit for generating an encoded picture for a set of pictures of the video data; and a unit for including a picture header Network Abstraction Layer (NAL) unit in a bitstream comprising the encoded pictures, wherein the picture header NAL unit comprises syntax elements that indicate that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0268] Aspect 15I. The device according to Aspect 14I, wherein the device further comprises: a unit for including a second syntax element indicating whether the picture is a GDR picture in the picture header NAL unit based on whether the picture is an IRAP or GDR picture.

[0269] Aspect 16I. A computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform the following operations: obtaining a bitstream comprising a set of encoded pictures of video data; and locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein the instructions that cause the one or more processors to locate the IRAP or GDR picture comprise instructions that, when executed, cause the one or more processors to perform the following operations: obtaining syntax elements from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax elements indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and determining, based on the syntax elements, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0270] Aspect 17I. The computer-readable storage medium according to Aspect 16I, wherein the syntax element is a first syntax element, and the instructions further cause the one or more processors to perform the following operations: obtaining a second syntax element from the picture header NAL unit based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, the second syntax element indicating whether the picture associated with the picture header NAL unit is a GDR picture.

[0271] Aspect 18I. The computer-readable storage medium according to Aspect 16I or 17I, wherein the instructions, when executed, further cause one or more processors to perform the following operations: decode a picture associated with a picture header NAL unit.

[0272] Aspect 19I. A computer-readable storage medium having instructions stored thereon, the instructions, when executed, cause one or more processors to perform the following operations: generate an encoded picture for a set of pictures of video data; and include a picture header network abstraction layer (NAL) unit in a bitstream including the encoded picture, wherein the picture header NAL unit includes syntax elements that indicate that the picture associated with the picture header NAL unit must be an intra random access picture (IRAP) or a progressive decoder refresh (GDR) picture, wherein: the picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and the picture associated with the picture header NAL unit is located in the set of encoded pictures.

[0273] Aspect 20I. The computer-readable storage medium according to Aspect 19I, wherein the instructions, when executed, further cause one or more processors to perform the following operations: include a second syntax element indicating whether the picture is a GDR picture in the picture header NAL unit based on whether the picture is an IRAP or GDR picture.

[0274] It should be recognized that, according to an example, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or completely omitted (e.g., not all of the described actions or events are necessary for implementing the techniques). Additionally, in certain examples, the actions or events may be performed, for example, concurrently by multithreading, interrupt handling, or multiple processors rather than sequentially.

[0275] In one or more examples, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality 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. The computer-readable medium may include a computer-readable storage medium (which corresponds to a tangible medium such as a data storage medium) or 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, the computer-readable medium generally may correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium such as a signal or a carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, code, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0276] By way of example, and not limitation, such computer-readable storage media can include 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 can be used to store the desired program code in the form of instructions or data structures and that can be accessed by a computer. Additionally, any connection is properly termed a computer-readable medium. For example, if the 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), then 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 transient media, but instead are directed to non-transitory tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), and Blu-ray disc, where disks typically reproduce data magnetically, while discs use lasers to optically reproduce data. Combinations of the above should also be included within the scope of computer-readable media.

[0277] The instructions can 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 circuitry. Thus, as used herein, the terms "processor" and "processing circuitry" can refer to any one of the foregoing structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Further, the techniques can be implemented entirely within one or more circuits or logic elements.

[0278] The techniques of the present disclosure can be implemented in a variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or a group of ICs (e.g., a chipset). Various components, modules, or units are described in the present disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but are not necessarily implemented by distinct hardware units. Rather, as described above, the various units can be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors as described above, in conjunction with appropriate software and / or firmware.

Claims

1. A method for processing video data, the method comprising: Obtain a bitstream that includes a set of encoded pictures of the video data; and Locate an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture among the encoded pictures in the bitstream, wherein locating the IRAP or GDR picture includes: Obtain a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and Determine, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: The picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is located in the set of encoded pictures.

2. The method according to claim 1, wherein, The syntax element is a first syntax element, and the method further includes: Based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, obtain a second syntax element from the picture header NAL unit, the second syntax element indicating whether the picture associated with the picture header NAL unit is a GDR picture.

3. The method according to claim 1, further comprising: Decode the picture associated with the picture header NAL unit.

4. A method for encoding video data, the method comprising: Generate encoded pictures for a set of pictures of the video data; and Include a picture header Network Abstraction Layer (NAL) unit in a bitstream that includes the encoded pictures, wherein the picture header NAL unit includes a syntax element that indicates that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: The picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is located in the set of encoded pictures.

5. The method according to claim 4, wherein, The method further includes: Based on the picture being an IRAP or GDR picture, include a second syntax element in the picture header NAL unit indicating whether the picture is a GDR picture.

6. A device for processing video data, the device comprising: A memory configured to store encoded pictures of the video data; and One or more processors implemented in a circuit, the one or more processors being configured to: Locate an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture among the encoded pictures in the bitstream, wherein the one or more processors are configured such that as part of locating the IRAP or GDR picture, the one or more processors perform the following operations: Obtain a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and Determine, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, wherein: The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is located in a set of encoded pictures.

7. The device according to claim 6, wherein, The syntax element is a first syntax element, and the one or more processors are further configured to: Obtain a second syntax element from the picture header NAL unit based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, the second syntax element indicating whether the picture associated with the picture header NAL unit is a GDR picture.

8. The device according to claim 6, wherein, The one or more processors are further configured to: decode the picture associated with the picture header NAL unit.

9. A device for encoding video data, the device comprising: A memory configured to store the video data; And One or more processors implemented in circuitry, the one or more processors being configured to: Generate encoded pictures for a set of pictures of the video data; and Include a picture header Network Abstraction Layer (NAL) unit in a bitstream including the encoded pictures, wherein the picture header NAL unit includes a syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, wherein: The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is located in the set of encoded pictures.

10. The device according to claim 9, wherein, The one or more processors are further configured to: include a second syntax element indicating whether the picture is a GDR picture in the picture header NAL unit based on the picture being an IRAP or GDR picture.

11. A device for processing video data, the device comprising: A unit for obtaining a bitstream of a set of encoded pictures including the video data; And A unit for locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, wherein the unit for locating the IRAP or GDR picture includes: A unit for obtaining a syntax element from a picture header Network Abstraction Layer (NAL) unit in the bitstream, the syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and A unit for determining, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where: The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is in the set of encoded pictures.

12. The device according to claim 11, wherein, The syntax element is a first syntax element, and the device further includes: A unit for obtaining a second syntax element from the picture header NAL unit based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where the second syntax element indicates whether the picture associated with the picture header NAL unit is a GDR picture.

13. The device according to claim 11, wherein, The device further includes: a unit for decoding the picture associated with the picture header NAL unit.

14. A device for encoding video data, the device comprising: A unit for generating encoded pictures for a set of pictures of the video data; And A unit for including a picture header network abstraction layer (NAL) unit in a bitstream including the encoded pictures, where the picture header NAL unit includes a syntax element indicating that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture, where: The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is in the set of encoded pictures.

15. The device according to claim 14, wherein, The device further includes: a unit for including, in the picture header NAL unit, a second syntax element indicating whether the picture is a GDR picture based on the picture being an IRAP or GDR picture.

16. A computer-readable storage medium having instructions stored thereon, which when executed cause one or more processors to perform the following operations: Obtain a bitstream including a set of encoded pictures of video data; And Locating an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture in the encoded pictures in the bitstream, where the instructions for causing the one or more processors to locate the IRAP or GDR picture include instructions that, when executed, cause the one or more processors to perform the following operations: Obtaining a syntax element from a picture header network abstraction layer (NAL) unit in the bitstream, where the syntax element indicates that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture; and Determining, based on the syntax element, that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where: The picture header NAL unit contains syntax elements applied to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is in the set of encoded pictures.

17. The computer-readable storage medium according to claim 16, wherein, The syntax element is a first syntax element, and the instructions further cause the one or more processors to perform the following operations: Obtain a second syntax element from the picture header NAL unit based on the first syntax element indicating that the picture associated with the picture header NAL unit is an IRAP or GDR picture, where the second syntax element indicates whether the picture associated with the picture header NAL unit is a GDR picture.

18. The computer-readable storage medium according to claim 16, wherein,When executed, the instruction further causes the one or more processors to perform the following operations: decode the picture associated with the picture header NAL unit.

19. A computer-readable storage medium having instructions stored thereon, the instructions, when executed, causing one or more processors to perform the following operations: Generate encoded pictures for a set of pictures of video data; and Include a picture header network abstraction layer (NAL) unit in a bitstream including the encoded pictures, wherein, The picture header NAL unit includes a syntax element that indicates that the picture associated with the picture header NAL unit must be an Intra Random Access Picture (IRAP) or a Progressive Decoder Refresh (GDR) picture, where: The picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit, and The picture associated with the picture header NAL unit is in the set of encoded pictures.

20. The computer-readable storage medium according to claim 19, wherein, When executed, the instruction further causes the one or more processors to perform the following operations: include, in the picture header NAL unit, a second syntax element indicating whether the picture is a GDR picture based on the picture being an IRAP or GDR picture.

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