Parameter set syntax elements and variables in video coding

Abstract

Example methods and apparatus for decoding video data are disclosed. The example apparatus for decoding video data includes a memory configured to store video data, and one or more processors implemented in circuitry and communicatively coupled to the memory. The one or more processors are configured to determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for multiple pictures. The one or more processors are further configured to decode multiple pictures of the video data based on the value of the first syntax element.

Description

[0001] This application claims the benefit of U.S. Application No. 17 / 318,77, filed May 12, 2021, U.S. Provisional Patent Application No. 63 / 024,331, filed May 13, 2020, U.S. Provisional Patent Application No. 63 / 026,609, filed May 18, 2020, and U.S. Provisional Patent Application No. 63 / 028,341, filed May 21, 2020, the entire contents of each of which are incorporated herein by reference. U.S. Application No. 17 / 318,77, filed May 12, 2021, claims the benefit of U.S. Provisional Patent Application No. 63 / 024,331, filed May 13, 2020, U.S. Provisional Patent Application No. 63 / 026,609, filed May 18, 2020, and U.S. Provisional Patent Application No. 63 / 028,341, filed May 21, 2020. Technical Field

[0002] This 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 broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones (so-called "smartphones"), video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding technologies, such as those defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10, Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions to these standards. By implementing such video coding technologies, video devices can more efficiently transmit, receive, encode, decode, and / or store digital video information.

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

[0005] In general, this disclosure describes techniques for coding parameter set syntax elements and variables in video coding. Specifically, this disclosure describes coding syntax elements and variables that indicate whether constraints on video coding may apply, including picture headers in Type 1 bitstreams, derivation processes, constraints, and other video coding techniques.

[0006] In one example, a method includes determining a value of a first syntax element indicating whether a first constraint is applicable, wherein the first constraint is that rectangular slices are not used for a first plurality of pictures; and decoding the first plurality of pictures of the video data according to the value of the first syntax element.

[0007] In one example, a device includes a memory configured to store video data, and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and decode the first plurality of pictures of the video data according to the value of the first syntax element.

[0008] In one example, a non-transitory computer-readable medium includes instructions that, when executed, cause one or more processors to: determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and decode the first plurality of pictures of the video data according to the value of the first syntax element.

[0009] In another example, an apparatus includes means for determining a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and means for decoding the first plurality of pictures of the video data according to the value of the first syntax element.

[0010] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0012] Figure 2A and 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0013] Figure 3 is a conceptual diagram illustrating a prediction example for a Gradual Decoding Refresh (GDR) picture.

[0014] Figures 4A-4B is a conceptual diagram illustrating example sub-layers used for inter-layer reference prediction.

[0015] Figure 5 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0016] Figure 6 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0017] Figure 7 is a flow chart illustrating an example general constraint technique according to the present disclosure.

[0018] Figure 8 is a flowchart illustrating an example method for encoding a current block.

[0019] Figure 9 is a flow chart illustrating an example method for decoding a current block of video data. DETAILED DESCRIPTION

[0020] Some video coding standards and draft standards include constraints on decoded bitstreams. These constraints must be met to ensure that the bitstream conforms to a specific standard or draft standard. In some examples, the constraints may be applied or not applied (e.g., turned on or off). In some examples, the constraints may not exist in the video coding standard or draft standard. In addition, in some video coding standards or draft standards, specific bitstreams are defined, such as Type I bitstreams. For example, a Type I bitstream may be defined as including only Video Coding Layer (VCL) Network Abstraction Layer (NAL) units. However, all elements required to decode the bitstream may not be present in such a bitstream. In this case, unnecessary decoding delays may occur, or unnecessary decoding errors may occur, because the video decoder may not be able to accurately decode the bitstream without the missing elements.

[0021] According to the techniques of this disclosure, constraint flags are disclosed that indicate whether constraints are to be applied. These constraint flags can communicate which features are disabled from a video encoder to a video decoder. In this way, a video decoder can infer the values ​​of other syntax elements based on the constraint flags, without parsing other syntax elements that may be at a lower level (and therefore, if parsed, would more frequently need to be signaled). In this way, signaling bandwidth can be saved, and processing power can be reduced at the video encoder and video decoder, respectively, due to less signaling and parsing.

[0022] According to the techniques of this disclosure, a Type I bitstream can be defined to include picture header (PH) network abstraction layer (NAL) units in addition to VCL NAL units. By additionally including PH NAL units in a Type I bitstream, decoding latency and / or accuracy can be improved because a video decoder may require the PH NAL units to decode video coding layer (VCL) NAL units within a Type I bitstream.

[0023] Figure 1 is a block diagram illustrating an example video encoding and decoding system 100 that can implement the techniques of this disclosure. The techniques of this disclosure are generally directed to decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data can include raw, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (such as signaling data).

[0024] like Figure 1As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides the video data to destination device 116 via a computer-readable medium 110. Source device 102 and destination device 116 can include any of a variety of devices, including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receiver devices, etc. In some cases, source device 102 and destination device 116 can be equipped for wireless communication and, thus, can be referred to as wireless communication devices.

[0025] exist Figure 1 In the example of , 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, the memory 120, and a display device 118. According to the present disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply techniques for improving parameter set syntax elements and variables in VVC. Thus, source device 102 represents an example of a video encoding device, while destination device 116 represents an example of a video decoding device. In other examples, the source device and destination device can include other components or arrangements. For example, source device 102 can receive video data from an external video source (such as an external camera). Similarly, destination device 116 can be connected to an external display device with an interface, rather than including an integrated display device.

[0026] like Figure 1 The illustrated system 100 is merely an example. Generally, any digital video encoding and / or decoding device can implement the techniques for improving parameter set syntax elements and variables in VVC. Source device 102 and destination device 116 are merely examples of such decoding devices, where source device 102 generates decoded video data for transmission to destination device 116. This disclosure refers to a "decoding" device as a device that performs data decoding (encoding and / or decoding). Thus, video encoder 200 and video decoder 300 represent examples of decoding devices, and more specifically, examples of video encoders and video decoders, respectively. In some examples, source device 102 and destination device 116 can operate in a substantially symmetrical manner, such that each includes video encoding and decoding components. Thus, system 100 can support one-way or two-way video transmission between source device 102 and destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0027] Typically, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a series of consecutive pictures (also referred to as "frames") of video data to video encoder 200, where video encoder 200 encodes the data for the pictures. Video source 104 of source device 102 may include a video capture device, such as a video camera, a video archive containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. Alternatively, video source 104 may generate computer graphics-based data as the source video, or a combination of real-time video, archived video, and computer-generated video. In each case, video encoder 200 encodes captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from the order in which they were received (sometimes referred to as "display order") into a decoding order for decoding. Video encoder 200 may generate a bitstream comprising the encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 for receipt and / or retrieval by, for example, input interface 122 of destination device 116 .

[0028] Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memory. In some examples, memories 106 and 120 can store raw video data, e.g., raw video from video source 104 and decoded raw video data from video decoder 300. Additionally or alternatively, memories 106 and 120 can store software instructions executable by, for example, video encoder 200 and video decoder 300, respectively. Although memory 106 and memory 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 can also include internal memory for functionally similar or equivalent purposes. Furthermore, memories 106 and 120 can store encoded video data, e.g., encoded video data output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106 and 120 can be allocated as one or more video buffers, e.g., for storing raw video data, decoded video data, and / or encoded video data.

[0029] Computer-readable medium 110 can represent any type of medium or device capable of transmitting encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium that enables source device 102 to send encoded video data directly to destination device 116 in real time, for example, via a radio frequency network or a computer-based network. Output interface 108 can modulate a transmission signal including the encoded video data, and input interface 122 can demodulate the received transmission signal, in accordance with a communication standard, such as a wireless communication protocol. The communication medium can include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium can include routers, switches, base stations, or any other device that can be used to facilitate communication from source device 102 to destination device 116.

[0030] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0031] In some examples, source device 102 may output encoded video data to a file server 114 or another intermediate storage device, which may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or downloading. File server 114 may be any type of server device capable of storing encoded video data and transmitting the encoded video data to destination device 116. File server 114 may represent a web server (e.g., for a website), a File Transfer Protocol (FTP) server, a content delivery network device, or a Network Attached Storage (NAS) device. Destination device 116 may access the encoded video data from file server 114 via any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a Digital Subscriber Line (DSL), a cable modem, etc.), or a combination of both, suitable for accessing the encoded video data stored on file server 114. File server 114 and input interface 122 may be configured to operate according to a streaming transfer protocol, a download transfer protocol, or a combination thereof.

[0032] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired network components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to a cellular communication standard such as 4G, 4G-LTE (Long Term Evolution), LTE Advanced, 5G, etc. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to other wireless standards such as the IEEE 802.11 specifications, the IEEE 802.15 specifications (e.g., ZigBee TM ), Bluetooth TM Standards, etc.) to transmit data, such as encoded video data. In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include a SoC device for performing the functions attributed to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device for performing the functions attributed to video decoder 300 and / or input interface 122.

[0033] The techniques of the present disclosure may be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission (e.g., Dynamic Adaptive Streaming over HTTP (DASH)), encoding of digital video onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0034] 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 defined by video encoder 200 (which is also used by video decoder 300), such as syntax elements with values ​​describing characteristics and / or processing of video blocks or other coded units (e.g., slices, pictures, groups of pictures, sequences, etc.). Display device 118 displays decoded pictures of the decoded video data to a user. Display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0035] Although not in Figure 1, but in some examples, the video encoder 200 and the video decoder 300 can each be integrated with an audio encoder and / or an audio decoder and can include appropriate MUX-DEMUX units or other hardware and / or software to process a multiplexed stream including audio and video in a common data stream. Where applicable, the MUX-DEMUX units can comply with the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0036] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the techniques are partially implemented in software, a device may store instructions for the software on a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, either of which may be integrated into the corresponding device as part of a combined encoder / decoder (CODEC). A device including the video encoder 200 and / or the video decoder 300 may include an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular phone.

[0037] The video encoder 200 and the video decoder 300 may operate in accordance with a video coding standard, such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC), or an extension thereof, such as the multi-view and / or scalable video coding extension. Alternatively, the video encoder 200 and the video decoder 300 may operate in accordance with 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 Bross et al., "Versatile Video Coding (Draft 9)," which was proposed at the 18th meeting of the Joint Video Experts Group (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC29 / WG 11: Teleconference, April 15-24, 2020, JVET-P2001-v8 (hereinafter referred to as "VVC Draft 9"). However, the techniques of the present disclosure are not limited to any particular coding standard.

[0038] Generally, the video encoder 200 and video decoder 300 can perform block-based decoding of pictures. The term "block" generally refers to a structure containing data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance data and / or chrominance data. Generally, the video encoder 200 and video decoder 300 can decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than decoding red, green, and blue (RGB) data for samples of a picture, the video encoder 200 and video decoder 300 can decode luminance and chrominance components, where the chrominance components may include red-toned and blue-toned chrominance components. In some examples, the video encoder 200 converts received RGB-formatted data to a YUV representation before encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, pre-processing and post-processing units (not shown) can perform these conversions.

[0039] The present disclosure generally relates to the decoding (e.g., encoding and decoding) of a picture to include processes related to encoding or decoding data for the picture. Similarly, the present disclosure may relate to the decoding of a block of a picture to include processes related to encoding or decoding data for the block, such as predictive decoding and / or residual decoding. A coded video bitstream generally includes a series of values ​​for syntax elements used to indicate decoding decisions (e.g., decoding modes) and to partition a picture into blocks. Thus, references to decoding a picture or block should generally be understood to refer to decoding the values ​​for the syntax elements that form the picture or block.

[0040] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (e.g., video encoder 200) divides coding tree units (CTUs) into CUs according to a quadtree structure. That is, the video decoder divides the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node," and a CU of such a leaf node may include one or more PUs and / or one or more TUs. The video decoder may further divide the PUs and TUs. For example, in HEVC, the residual quadtree (RQT) represents the division of the TU. In HEVC, PU represents inter-frame prediction data, and TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0041] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video decoder (such as the video encoder 200) divides a picture into a plurality of coding tree units (CTUs). The 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 partition types, such as the separation between CU, PU, ​​and TU of 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 the coding units (CUs).

[0042] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) partitioning (also known as tritree (TT)). Tritree partitioning or tritree partitioning is used to split a block into three sub-blocks. In some examples, tritree partitioning or tritree partitioning divides a block into three sub-blocks without splitting the original block through the center. Partition types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0043] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for corresponding chroma components).

[0044] The video encoder 200 and the video decoder 300 can be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partitioning structures according to HEVC. For the purpose of explanation, the description of the technology of the present disclosure is presented with respect to QTBT partitioning. However, it should be understood that the technology of the present disclosure can also be applied to video decoders configured to use quadtree partitioning or other types of partitioning.

[0045] In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples for a picture with three sample arrays, or a CTB of samples for a picture coded using three separate color planes or a monochrome picture, and syntax structures used to code the samples. A CTB can be an NxN block of samples with N being a certain value, such that the division of components into CTBs is performed. A component is an array or a single sample from one of three arrays (luma and two chroma), where the three arrays make up a picture in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample from an array that makes up a picture in monochrome format. In some examples, a coding block is an MxN block of samples with M and N being certain values, such that the division of the CTB into coding blocks is performed.

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

[0047] In some examples, a slice can be divided into multiple bricks, each of which can contain one or more CTU rows within the slice. A slice that is not divided into multiple bricks can also be referred to as a brick. However, a brick that is a true subset of a slice may not be referred to as a slice.

[0048] Tiles in a picture can also be arranged in slices. A slice is an integer number of tiles of a picture that can be contained exclusively in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes several complete slices, or a complete block of a contiguous sequence of slices.

[0049] This disclosure may use "NxN" and "N×N" interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in the vertical and horizontal dimensions, for example, 16x16 samples or 16×16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxN CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. Furthermore, a CU does not necessarily have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

[0050] The video encoder 200 encodes video data for a CU representing prediction information and / or residual information, as well as other information. The prediction information indicates how to predict the CU in order to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

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

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

[0053] To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of VVC provide 67 intra prediction modes, including various directional modes, as well as a planar mode and a DC mode. Typically, the video encoder 200 selects an intra prediction mode that describes neighboring samples of a current block (e.g., a block of a CU), where samples of the current block are predicted from the neighboring samples. Assuming that the video encoder 200 decodes CTUs and CUs in raster scan order (left to right, top to bottom), such samples may typically be above, above and to the left, or to the left of the current block in the same picture as the current block.

[0054] The video encoder 200 encodes data indicating a prediction mode for the current block. For example, for inter-prediction mode, the video encoder 200 may encode data indicating which of various available inter-prediction modes was used, as well as motion information for the corresponding mode. For example, for unidirectional inter-prediction or bidirectional inter-prediction, the video encoder 200 may encode motion vectors using Advanced Motion Vector Prediction (AMVP) or Merge Mode. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0055] After a prediction, such as intra-frame prediction or inter-frame prediction, for a block, the video encoder 200 may calculate residual data for the block. The residual data, such as a residual block, represents the sample-by-sample difference between the block and a prediction block for the block formed using the corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to produce transformed data in a transform domain rather than a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, the video encoder 200 may apply a second transform, such as a mode-dependent non-separable quadratic transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc., after the first transform. After applying the one or more transforms, the video encoder 200 produces transform coefficients.

[0056] As described above, after any transforms used to produce transform coefficients, the video encoder 200 may perform quantization on the transform coefficients. Quantization generally refers to a process used to quantize the transform coefficients to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 may quantize the transform coefficients during quantization. n - The bit value is rounded down to m -bit value, where n Greater than m In some examples, to perform quantization, video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0057] After quantization, the video encoder 200 may scan the transform coefficients to produce a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher-energy (and therefore lower-frequency) transform coefficients at the beginning of the vector and lower-energy (and therefore higher-frequency) transform coefficients at the end of the vector. In some examples, the video encoder 200 may utilize a predefined scan order to scan the quantized transform coefficients to produce a sequenced vector and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode values ​​for syntax elements used to describe metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0058] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. For example, the context may relate to whether the neighboring values ​​of the symbol are zero. The probability determination may be based on the context assigned to the symbol.

[0059] The video encoder 200 may also generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, to the video decoder 300, for example, in a picture header, a block header, a slice header, or other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). The video decoder 300 may also decode such syntax data to determine how to decode the corresponding video data.

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

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

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

[0063] This disclosure may generally refer to "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to the transmission of values ​​for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal values ​​for syntax elements in a bitstream. Generally, signaling refers to generating values ​​in the bitstream. As described above, source device 102 may transmit the bitstream to destination device 116 in substantially real time or in non-real time, such as may occur when storing syntax elements on storage device 112 for later retrieval by destination device 116.

[0064] Figure 2A and 2Bis a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, and dashed lines represent binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) was used, where, in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. For quadtree splitting, no split type needs to be indicated because the quadtree node splits the block horizontally and vertically into four equally sized sub-blocks. Accordingly, the video encoder 200 can encode, and the video decoder 300 can decode, syntax elements (e.g., split information) for the region tree level (i.e., solid lines) in the QTBT structure 130 and syntax elements (e.g., split information) for the prediction tree level (i.e., dashed lines) in the QTBT structure 130. The video encoder 200 may encode and the video decoder 300 may decode video data, such as prediction data and transform data, for the CU represented by the terminal leaf node in the QTBT structure 130 .

[0065] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes in the QTBT structure 130 at the first and second levels. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, indicating the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, indicating the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, indicating the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, indicating the minimum allowed binary tree leaf node size).

[0066] The root node of the QTBT structure corresponding to a CTU can have four child nodes at the first level of the QTBT structure, each of which can be partitioned according to a quadtree partitioning scheme. That is, nodes at the first level are either leaf nodes (no child nodes) or have four child nodes. The example QTBT structure 130 shows such nodes as including a parent node and child nodes with solid lines for branching. If the nodes at the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), these nodes can be further partitioned using the corresponding binary tree. Binary tree splitting of a node can be performed iteratively until the resulting node reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example QTBT structure 130 shows such nodes with dashed lines for branching. Binary tree leaf nodes are called coding units (CUs) and are used for prediction (e.g., intra-picture prediction or inter-picture prediction) and transforms without requiring any further partitioning. As mentioned above, a CU may also be referred to as a "video block" or a "block."

[0067] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (a luma sample and two corresponding 64x64 chroma samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate quadleaf nodes. Quadleaf nodes can have sizes ranging from 16x16 (i.e., MinQTSize) to 128x128 (i.e., the CTU size). If the quadleaf node is 128x128, it will not be further split using the binary tree because its size exceeds MaxBTSize (64x64 in this example). Otherwise, the quadleaf node will be further split using the binary tree. Therefore, the quadleaf node is also the root node of the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splits are allowed. When the width of a binary tree node is equal to MinBTSize (4 in this example), this means that no further horizontal splits are allowed. Similarly, when the height of a binary tree node is equal to MinBTSize, no further vertical splits are allowed for that binary tree node. As mentioned above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further partitioning.

[0068] As mentioned above, some video coding standards and draft standards include constraints on the coded bitstream. Constraints are restrictions that can be placed on a bitstream. One such video coding standard is VVC. VVC has been developed by the Joint Video Experts Team (JVET) of ITU-T and ISO / IEC to enable a wider range of compression capabilities beyond HEVC. VVC draft 9 specifies standardized bitstream and picture formats, high-level syntax (HLS) and semantics, and parsing and decoding processes. VVC draft 9 also specifies profile / layer / level (PTL) restrictions, byte stream formats, hypothetical reference decoders, and supplemental enhancement information (SEI) in appendices.

[0069] VVC draft 9 inherits many advanced features of HEVC, such as the network abstraction layer (NAL) unit and parameter set concepts, slice and wavefront parallel processing, layered decoding, and the use of SEI messages as supplementary data signaling. For example, a parameter set may include information applicable to a sequence, a picture, a video, etc., which may be signaled by the video encoder 200 or received and parsed by the video decoder 300 and used by the video decoder 300 to decode the video data in the coded bitstream. Additional advanced features are introduced in VVC, including the concepts of rectangular slices and sub-pictures, picture resolution adaptation, mixed NAL unit types, picture headers (PHs), gradual decoding refresh (GDR) pictures, virtual boundaries, and reference picture lists (RPLs) for reference picture management.

[0070] In VVC draft 9, a number of signaling conditions or semantic constraints are specified on parameter set syntax elements, and on variables that the video decoder 300 can derive from the syntax elements for use in the decoding process.

[0071] Several issues related to syntax elements and variables in VVC draft 9 are identified as follows:

[0072] VVC draft 9 specifies that "When sps_gdr_enabled_flag is equal to 1 and the PicOrderCntVal of the current picture is greater than or equal to the recoveryPointPocVal of the associated GDR picture, the current decoded picture and subsequent decoded pictures in output order are exact matches to corresponding pictures produced by starting the decoding process from the previous IRAP picture that precedes the associated GDR picture in decoding order, when present." However, no RPL constraints are specified to guarantee an exact match. sps_grd_enabled_flag is a syntax element in the SPS that indicates whether GDR pictures can appear in a coded layer video sequence (CLVS) that references the SPS. The PicOrderCntVal of a picture represents the POC value of the picture.

[0073] The derivation of the variable NumSubLayersInLayerInOLS in VVC draft 9 is problematic for sub-bitstream extraction. This disclosure includes an updated derivation process. In VVC draft 9, the variable NumSubLayersInLayerInOLS indicates the number of sub-layers in a layer in the output layer set.

[0074] A number of semantics for general constraint flags are described in this disclosure to address various issues.

[0075] A number of new general constraint flags are introduced in this disclosure to address various issues.

[0076] In this disclosure, semantic constraints are specified for the syntax element sps_max_sublayers_minus1. In VVC draft 9, sps_max_sublayers_minus1 is a syntax element in the SPS. sps_max_sublayers_minus1 plus 1 specifies the maximum number of temporal sublayers that can exist in each CLVS that references the SPS. VVC draft 9 specifies that the value of sps_max_sublayers_minus1 should be in the range of 0 to vps_max_sublayers_minus1 (inclusive).

[0077] Several syntax elements such as sps_num_subpics_minus1, pps_num_exp_tile_columns_minus1, pps_num_exp_tile_rows_minus1, and pps_tile_idx_delta_present_flag may be explicitly signaled in the parameter set, and their values ​​may be inferred under certain conditions. sps_num_subpics_minus1 plus 1 specifies the number of subpictures in each picture in the CLVS.

[0078] The PH NAL shall be present in the bitstream in VVC Annex C - Hypothetical Reference Decoder.

[0079] Multiple syntax elements in a parameter set should be specified in a manner, ie, in a consistent manner.

[0080] The techniques of this disclosure may address one or more of these issues.The examples provided in this disclosure may be used individually or in any combination.

[0081] Now let's discuss the reference list constraints for GDR pictures. In some cases, pictures after a GDR picture can reference pictures before the GDR picture. When a GDR picture is the first picture of a video sequence, it may not be possible to decode all recovery pictures correctly. As specified in VVC Draft 9, a picture that is associated with the current GDR picture and has a PicOrderCntVal that is less than recoveryPointPocVal is called a recovery picture of the GDR picture. A recovering picture may also be referred to as a recovery point picture in this article. In VVC Draft 9, the recovery_poc_cnt syntax element specifies the recovery point of a decoded picture in output order. When the current picture is a GDR picture, a video coder (e.g., video encoder 200 or video decoder 300) may derive the variable recoveryPointPocVal as follows:

[0082] recoveryPointPocVal = PicOrderCntVal + recovery_poc_cnt

[0083] Furthermore, as indicated in VVC Draft 9,

[0084] If the current picture is a GDR picture and there is a picture picA with PicOrderCntVal equal to recoveryPointPocVal that follows the current GDR picture in decoding order in the CLVS, then picture picA is called the recovery point picture. Otherwise, the first picture in output order in the CLVS with PicOrderCntVal greater than recoveryPointPocVal is called the recovery point picture. The recovery point picture should not precede the current GDR picture in decoding order.

[0085] Figure 3 is a conceptual diagram illustrating a prediction example for a Gradual Decoding Refresh (GDR) picture. Figure 3 An example of the prediction relationship for a GDR picture 140 is shown. Figure 3In the example, a picture having an arrow pointing to another picture indicates that the other picture can use the picture with the origin of the arrow as a reference picture. For example, picture 144 can use picture 142 as a reference picture. According to one or more techniques of the present disclosure, in order to ensure that pictures after the recovery point picture can be correctly decoded, reference to pictures before GDR picture 140 or pictures before pictures with a POC value equal to the recovery POC value should not be allowed. For example, picture 146 with a POC value of 4 should be able to reference positive recovery picture 144 with a POC of 3, but cannot reference positive recovery picture 142 with a POC of 2 (indicated by the outward arrow with an x) because POC 2 is before POC 3 and positive recovery picture 144 is a positive recovery picture. In one example, the prediction constraints are specified as follows:

[0086] When the current picture follows a recovery point picture with the same nuh_layer_id value in both decoding order and output order, there shall be no pictures referenced by active entries in RefPicList[0] or RefPicList[1] that precede the recovery point picture in output order or decoding order.

[0087] In another example, the prediction constraints may be specified as follows:

[0088] When the current picture follows a recovery point picture with the same nuh_layer_id value in both decoding order and output order, there shall be no pictures referenced by entries in RefPicList[0] or RefPicList[1] that precede the recovery point picture in output order or decoding order.

[0089] exist Figure 3 In the example of , picture 146 with POC 4 should not reference any pictures before the picture being restored 144 , because these restored pictures may not be decoded correctly when random access occurs at the GDR picture.

[0090] Additional constraints to further ensure that inter-layer reference pictures are decodable are specified as follows:

[0091] When the current picture follows a recovery point picture with the same nuh_layer_id value in both decoding order and output order, there shall be no pictures referenced by ILRP active entries in RefPicList[0] or RefPicList[1] that precede the recovery point picture in output order or decoding order of the associated GDR picture with nuh_layer_id equal to refPicLayerId.

[0092] Thus, in some examples, a device (e.g., destination device 116 or another device) may obtain a bitstream comprising an encoded representation of video data and may determine that the bitstream does not conform to a video coding standard based on the bitstream violating a constraint requiring that when a current picture follows a recovery point picture having the same value of a NAL unit header layer identifier (e.g., nuh_layer_id) in both decoding order and output order, there shall not be a picture referenced by an inter-layer reference prediction (ILRP) active entry in a first reference picture list (e.g., RefPicList[0]) or a second reference picture list (e.g., RefPicList[1]) that precedes the recovery point picture in output order or decoding order of an associated gradual decoding refresh (GDR) picture having a NAL unit header layer identifier equal to a reference picture layer identifier (e.g., refPicLayerId).

[0093] Similarly, in some examples, the video encoder 200 may obtain video data and may encode the video data to generate a bitstream such that the bitstream does not violate a constraint requiring that, when a current picture follows a recovery point picture having the same value of a NAL unit header layer identifier in both decoding order and output order, there should not be a picture referenced by an ILRP active entry in the first reference picture list or the second reference picture list that precedes the recovery point picture in output order or decoding order of an associated GDR picture having a NAL unit header layer identifier that is equal to the reference picture layer identifier.

[0094] Composite constraints can be specified as follows:

[0095] When the current picture follows a recovery point picture with the same nuh_layer_id value in both decoding order and output order, there shall be no pictures in the layer with an associated GDR picture with nuh_layer_id equal to the nuh_layer_id of the reference picture that precede the recovery point picture in output order or decoding order, referenced by active entries in RefPicList[0] or RefPicList[1].

[0096] Accordingly, in some examples, a device (e.g., destination device 116 or another device) may obtain a bitstream including an encoded representation of video data and may determine that the bitstream does not conform to a video coding standard based on the bitstream violating a constraint requiring that when a current picture follows a recovery point picture having the same value of a NAL unit header layer identifier (e.g., nuh_layer_id) in both decoding order and output order, there should not be a reference picture referenced by an active entry in a first reference picture list (e.g., RefPicList[0]) or a second reference picture list (e.g., RefPicList[1]) that precedes the recovery point picture in output order or decoding order for an associated GDR picture in a layer having a NAL unit header layer identifier that is equal to the NAL unit header layer identifier of the reference picture.

[0097] Similarly, in some examples, the video encoder 200 can obtain video data and can encode the video data to generate a bitstream such that the bitstream does not violate a constraint requiring that, when a current picture follows a recovery point picture having the same value of a NAL unit header layer identifier (e.g., nuh_layer_id) in both decoding order and output order, there should not be a reference picture referenced by an active entry in a first reference picture list (e.g., RefPicList[0]) or a second reference picture list (e.g., RefPicList[1]) that precedes the recovery point picture in output order or decoding order for an associated GDR picture in a layer having a NAL unit header layer identifier that is equal to the NAL unit header layer identifier of the reference picture.

[0098] Now let's discuss the derivation of NumSubLayersInLayerInOLS. In VVC draft 9, when the kth layer is a direct dependent layer of the i-th layer, the number of sublayers of the k-th layer used as the ILRP for decoding the i-th layer is represented by max_tid_il_ref_pics_plus1[i][k]. When the k-th layer is not a direct dependent layer of the i-th layer, but both layers are included in the same output layer set (OLS), the k-th layer is the output layer or an indirect dependent layer of the i-th layer. When the k-th layer is an output layer, the variable NumSubLayersInLayerInOLS will be derived to be equal to vps_max_sub_layers_minus1 plus 1. Otherwise, the value of NumSubLayersInLayerInOLS is derived according to the OLS mode and layer dependency. For example, the video encoder 200 or the video decoder 300 can derive the variable NumSubLayersInLayerInOLS.

[0099] Figures 4A-4Bis a conceptual diagram illustrating example sub-layers used for inter-layer reference prediction. Figures 4A-4B Shows several examples of the number of sublayers used for ILRP between different layers in OLS, where layer 2 is the output layer. For example, Figure 4A Layer 0 154 , layer 1 152 , and layer 2 150 are depicted. Figure 4B Depicted are layer 0 160 , layer 1 158 , and layer 2 156 . According to VVC draft 9, when layer k is a direct dependent layer of layer m , where m is less than or equal to i but greater than k, a video coder (e.g., video encoder 200 or video decoder 300 ) derives NumSubLayersInLayerInOLS[i][k] as the smallest sublayer among NumSubLayersInLayerInOLS[i][m] and NumSubLayersInLayerInOLS[m][k].

[0100] exist Figure 4A In the case shown, when the minimum value of NumSubLayersInLayerInOLS[2][1] and NumSubLayersInLayerInOLS[1][0] is derived to be equal to 4, the value of NumSubLayersInLayerInOLS[2][0] is derived to be equal to 4. However, in Figure 4B , the value of NumSubLayersInLayerInOLS[2][0] is derived to be equal to 5, and the 5 sublayers of layer 0 160 are insufficient to decode layer 1 58 which is used to decode layer 2 156 for output.

[0101] According to the technology of the present disclosure, the recommended derivation process deduce that: when the kth layer is a direct dependent layer of the mth layer, where m is less than or equal to i but greater than k, NumSubLayersInLayerInOLS[i][k] has a maximum number of sublayers of NumSubLayersInLayerInOLS[m][k].

[0102] According to the techniques of this disclosure, the derivation of NumSubLayersInLayerInOLS can be updated as follows. <d> ...< / d> To mark, insert text with a mark ... to mark.

[0103]

[0104]

[0105]

[0106]

[0107] The semantic constraints on the general constraint flags will now be discussed. General constraint flags are used in the bitstream to indicate that specific decoding features or tools are restricted or disabled, and the value of a particular constraint flag can be determined by the values ​​of other constraint flags. The following semantic constraints apply to the general constraint information syntax element (e.g., the general constraint flag). The video encoder 200 or the video decoder 300 can apply such constraints.

[0108] – When intra_only_constraint_flag is 1, the values ​​of no_ref_pic_resampling_constraint_flag, all_layers_independent_constraint_flag, and no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1.

[0109] – When no_ref_pic_resampling_constraint_flag is 1, the value of no_res_change_in_clvs_constraint_flag shall be equal to 1.

[0110] – When one_subpic_per_pic_constraint_flag is 1, the value of no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1.

[0111] – When no_cra_constraint_flag is 1, the value of no_rasl_constraint_flag shall be equal to 1.

[0112] –The values ​​of no_idr_constraint_flag, no_cra_constraint_flag, and no_gdr_constraint_flag shall not all be equal to 1.

[0113] In another example, the following semantic constraints apply to the general constraint information syntax element (eg, general constraint flag).

[0114] – when intra_only_constraint_flag When 1, no_ref_pic_resampling_constraint_flag, all_layers_independent_constraint_flag, no_mixed_nalu_types_in_pic_constraint_flag, no_trail_constraint_flag, no_stsa_constraint_flag, no_rasl_constraint_flag, no_radl_constraint_flag and The value of no_gdr_constraint_flag should be equal to 1.

[0115] – When no_ref_pic_resampling_constraint_flag is 1, the value of no_res_change_in_clvs_constraint_flag shall be equal to 1.

[0116] – When one_subpic_per_pic_constraint_flag is 1, the value of no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1

[0117] – When no_cra_constraint_flag is 1, the value of no_rasl_constraint_flag shall be equal to 1.

[0118] –The values ​​of no_idr_constraint_flag, no_cra_constraint_flag, and no_gdr_constraint_flag shall not all be equal to 1.

[0119] – When no_affine_motion_constraint_flag is equal to 1, the value of no_prof_constraint_flag shall be equal to 1.

[0120] – When max_chroma_format_constraint_idc is equal to 0, the value of no_chroma_qp_offset_contraint_flag shall be equal to 1.

[0121] – When intra_only_constraint_flag is equal to 1, the value of no_sbt_constraint_flag shall be equal to 1.

[0122] – When no_transform_skip_constraint_flag is equal to 1, the value of no_bdpcm_constraint_flag shall be equal to 1.

[0123] – When one_subpic_per_pic_constraint_flag is equal to 1, sps_num_subpics_minus1 shall be equal to 0.

[0124] – When one_tile_per_pic_constraint_flag and one_slice_per_pic_constraint_flag are both equal to 1, pps_no_pic_partition_flag shall be 1.

[0125] Now let's discuss other general constraint flags. According to one or more techniques of the present disclosure, multiple additional general constraint flags can be defined. Any one or any combination of the following additional general constraint flags can be defined as follows:

[0126] –general_non_HRD_constraint_flag equal to 1 specifies that no Hypothesized Reference Decoder (HRD) related SEI messages (BP, PT, DU information SEI messages) shall be present in the OlsInScope bitstream.

[0127] general_non_HRD_constraint_flag equal to 0 does not implement this constraint.

[0128] – general_non_dependent_RAP_constraint_flag equal to 1 specifies that no dependent random access point indication SEI message shall be present in the OlsInScope bitstream. general_non_dependent_RAP_constraint_flag equal to 0 does not enforce this constraint.

[0129] –general_non_omnidirectional_video_constraint_flag equal to 1 specifies that no omnidirectional video specific SEI messages shall be present in the OlsInScope bitstream. general_non_omnidirectional_video_constraint_flag equal to 0 does not enforce this constraint.

[0130] – no_VUI_constraint_flag equal to 1 specifies that sps_vui_parameters_present_flag is equal to 0. no_VUI_constraint_flag equal to 0 does not enforce this constraint. In VVC draft 9, sps_vui_parameters_present_flag (or vui_parameters_present_flag in SPS) equal to 1 specifies that the syntax structure vui_parameters() is present in the SPS RBSP syntax structure. vui_parameters_present_flag equal to 0 specifies that the syntax structure vui_parameters() is not present in the SPS RBSP syntax structure.

[0131] –max_layers_constraint_idc specifies that vps_max_layers_minus1 should be in the range of 0 to max_layers_idc - 1 (inclusive). In VVC draft 9, vps_max_layers_minus1 plus 1 specifies the maximum number of layers allowed in each CVS that references the VPS. In addition, in some examples, when single_layer_constraint_flag is equal to 1, max_layers_constraint_idc should be equal to 0.

[0132] –max_sublayers_constraint_idc specifies that vps_max_sublayers_minus1 should be in the range of 0 to max_sublayers_idc-1 (inclusive). In VVC draft 9, vps_max_sublayers_minus1 plus 1 specifies the maximum number of temporal sublayers that can exist in the layers of each CVS that references the VPS. In VVC draft 9, the value of vps_max_sublayers_minus1 should be in the range of 0 to 6 (inclusive).

[0133] –max_subpics_constraint_idc specifies that sps_num_subpics_minus1 should be in the range of 0 to max_subpics_idc - 1 (inclusive). In VVC draft 9, sps_num_subpics_minus1 plus 1 specifies the number of subpictures in each picture in the CLV. The value of sps_num_subpics_minus1 should be in the range of 0 to Ceil(pic_width_max_in_luma_samples ÷ CtbSizeY) * Ceil(pic_height_max_in_luma_samples ÷ CtbSizeY) − 1 (inclusive). When not present, the value of sps_num_subpics_minus1 is inferred to be equal to 0. In some examples, when one_subpic_per_pic_constraint_flag is equal to 1, max_subpics_constraint_idc should be equal to 0.

[0134] – no_pic_partition_constraint_flag equal to 1 specifies that pps_no_pic_partition_flag shall be equal to 1. no_pic_partition_constraint_flag equal to 0 does not enforce this constraint. When no_pic_partition_constraint_flag is equal to 1, the values ​​of one_tile_per_pic_constraint_flag, one_slice_per_pic_constraint_flag, and one_subpic_per_pic_constraint_flag shall be equal to 1. In VVC draft 9, pps_no_pic_partition_flag equal to 1 specifies that picture partitioning is not applied to each picture of the referenced pps. pps_no_pic_partition_flag equal to 0 specifies that each picture of the referenced pps may be partitioned into multiple slices or slices.

[0135] – no_rectangular_slice_constraint_flag equal to 1 specifies that pps_rect_slice_flag should be equal to 0. no_rectangular_slice_constraint_flag equal to 0 does not implement this constraint.

[0136] – no_raster_scan_slice_constraint_flag equal to 1 specifies that pps_rect_slice_flag shall be equal to 1. No such constraint is enforced when no_raster_scan_slice_constraint_flag equal to 0. When one_tile_per_pic_constraint_flag is 1 or one_subpic_per_pic_constraint_flag is 1, the value of no_raster_scan_slice_constraint_flag shall be equal to 1.

[0137] – one_slice_per_subpicture_constraint_flag equal to 1 specifies that the value of pps_single_slice_per_subpic_flag shall be equal to 1, one_slice_per_subpicture_constraint_flag equal to 0 does not implement this constraint.

[0138] For example, the video encoder 200 or the video decoder 300 may determine a value of a first syntax element (e.g., no_rectangular_slice_constraint_flag) indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures (e.g., rectangular slices are not allowed). The video encoder 200 or the video decoder 300 may decode the first plurality of pictures of the video data according to the value of the first syntax element, or decode the pictures according to the value of the first syntax element. For example, the video encoder 200 may encode the first plurality of pictures according to the value of the first syntax element, or the video decoder 300 may decode the first plurality of pictures according to the value of the first syntax element. In some examples, the value of the first syntax element indicates that the first constraint is applicable, and the video encoder 200 or the video decoder 300 may determine, based on the value of the first syntax element indicating that the first constraint is applicable, that a value associated with a second syntax element (e.g., pps_rect_slice_flag) for the plurality of pictures is equal to 0, wherein the value of the second syntax element of 0 indicates that rectangular slices are not used for each picture in the plurality of pictures to which the picture parameter set applies.

[0139] For example, the video encoder 200 or the video decoder 300 may determine the value of a third syntax element (e.g., one_slice_per_subpicture_constraint_flag) that indicates whether a second constraint applies, namely, that each sub-picture in the second plurality of pictures must contain only one slice. The video encoder 200 or the video decoder 300 may decode each sub-picture in the second plurality of pictures based on the value of the third syntax element. For example, the video encoder 200 may encode each sub-picture in the second plurality of pictures based on the value of the third syntax element, or the video decoder 300 may decode each sub-picture in the second plurality of pictures based on the value of the third syntax element. In some examples, the value of the third syntax element indicates that the second constraint applies, and the video encoder 200 or the video decoder 300 may determine, based on the value of the third syntax element indicating that the second constraint applies, that the value associated with the fourth syntax element indicates that each sub-picture in the second plurality of pictures to which the picture parameter set applies contains only one slice. In some examples, the value of the third syntax element is equal to 1, and the value of the fourth syntax element is equal to 1.

[0140] In another example, the general constraint information flags can be categorized into several syntactic substructures, and each substructure can be regulated by a corresponding presence flag. Thus, related flags can be grouped together. Profiles, layers, and levels can specify default values ​​for each general constraint flag, and bitstreams conforming to the profile, layer, and level may not need to carry some or all of the general constraint flags, thereby saving signaling bandwidth and processing power.

[0141] For example, there may be three categories for general constraint information: general_capability_constraint_info(), general_coding_tool_constraint_info(), and general_nal_unit_type_constraint_info(). general_capability_constraint_info() contains flags for specifying decoding capability constraints, general_coding_tool_constraint_info() contains flags for specifying decoding tool constraints, and general_nal_unit_type_constraint_info() contains flags for specifying the availability of NAL unit types in bitstream constraints.

[0142] Each substructure signaling can be regulated by the presence flag shown in Table 1. When the corresponding presence flag is 1, the universal constraint substructure exists; otherwise, when the corresponding presence flag is 0, the value of the universal constraint flag in the substructure is inferred to be equal to a default value (e.g., 0 or other value).

[0143]

[0144] Tables 2, 3, and 4 show the constraint substructure syntax for existing common constraint flags.

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] In the above example, OlsInScope refers to one or more OLSs within the scope. In VVC Draft 9, when the syntax structure profile_tier_level() is included in a VPS, OlsInScope refers to one or more OLSs specified by the VPS. When the syntax structure profile_tier_level() is included in an SPS, OlsInScope refers to an OLS that includes only the lowest layer among the layers that reference the SPS, and this lowest layer is an independent layer.

[0153] Now let's discuss semantic constraints. The video encoder 200 can signal the maximum number of sublayers in both the VPS and the SPS. However, when all layers have the same number of sublayers, the maximum number of sublayers signaled in the VPS and the SPS may be different, which may cause problems for the video decoder 300 in determining the correct number of sublayers. To avoid this ambiguity, a constraint can be added to require that the number of sublayers signaled in the VPS and the SPS be the same. In one example, the semantic constraint of the syntax element sps_max_sublayers_minus1 is implemented as follows:

[0154] When vps_video_parameter_set_id is greater than 0 and vps_all_layers_same_num_sublayers_flag is equal to 1, the value of sps_max_sublayers_minus1 shall be equal to the value of vps_max_sublayers_minus1.

[0155] When sps_video_parameter_set_id is greater than 0 and vps_all_layers_same_num_sublayers_flag is equal to 1, the value of sps_max_sublayers_minus1 shall be equal to the value of vps_max_sublayers_minus1.

[0156] When pps_single_slice_per_subpic_flag does not exist in the corresponding PPS, the value of pps_single_slice_per_subpic_flag is inferred to be equal to 1. When pps_rect_slice_flag is equal to 1, pps_single_slice_per_subpic_flag does not exist. However, when there are no available sub-pictures, it does not make sense to infer that the value of pps_single_slice_per_subpic_flag is equal to 1. According to the techniques of this disclosure, the semantic constraints of pps_single_slice_per_subpic_flag can be updated as follows:

[0157] pps_single_slice_per_subpic_flag equal to 1 specifies that each sub-picture consists of one and only one rectangular slice. pps_single_slice_per_subpic_flag equal to 0 specifies that each sub-picture may consist of one or more rectangular slices. When not present, the value of pps_single_slice_per_subpic_flag is inferred to be equal to the value of pps_no_pic_partition_flag.

[0158] Now let's discuss the syntax element signaling conditions: When the picture width and height are less than CtbSizeY, the SPS syntax element sps_num_subpics_minus1 may not be explicitly signaled, as shown in Table 5 below. The value of sps_num_subpics_minus1 may be inferred to be equal to 0.

[0159] In another example, the following bitstream conformance requirement may be implemented: when the maximum picture width (sps_pic_width_max_in_luma_samples) and / or the maximum picture height (sps_pic_height_max_in_luma_samples) is less than or equal to CtbSizeY, the value of sps_num_subpics_minus1 shall be equal to 0.

[0160] The next syntax table shows an example implementation that adds the notation <! >...< / !> Indicates the condition.

[0161]

[0162] sps_pic_width_max_in_luma_samples is a syntax element used to indicate the maximum width in luma samples of each decoded picture that references the SPS. pic_height_max_in_luma_samples specifies the maximum height in luma samples of each decoded picture that references the SPS.

[0163] When the picture width or height is less than CtbSizeY, pps_num_exp_tile_columns_minus1 and pps_num_exp_tile_rows_minus1 may not be explicitly signaled, as shown in Table 6 below. For example, the video encoder 200 may avoid signaling pps_num_exp_tile_columns_minus1 and pps_num_exp_tile_rows_minus1. The syntax element pps_num_exp_tile_columns_minus1 plus 1 specifies the number of explicitly provided slice column widths. The syntax element pps_num_exp_tile_rows_minus1 plus 1 specifies the number of explicitly provided slice row heights. In another example, the following semantic constraint may be implemented: the bitstream conforms to the requirement that the value of pps_num_exp_tile_columns_minus1 shall be equal to 0 when the value of pps_pic_width_in_luma_samples is less than or equal to CtbSizeY. Furthermore, in this example, the bitstream conforms to the requirement that the value of pps_num_exp_tile_rows_minus1 shall be equal to 0 when the value of pps_pic_height_in_luma_sample is less than or equal to CtbSizeY.

[0164]

[0165] In another example, the syntax elements pps_tile_column_width_minus1[i] and pps_tile_row_height_minus1[i] can also be adjusted as shown in Table 7 below. When the picture width is less than or equal to the CTB size, the slice column width pps_tile_column_width_minus1[0] is equal to PicWidthInCtbsY – 1. When the picture height is less than or equal to the CTB size, the slice row height pps_tile_row_height_minus1[0] is equal to PicHeightInCtbsY – 1.

[0166]

[0167] When there is only one CTB in a picture, the picture cannot be divided into multiple slices or slices, so the syntax element should not be allowed to be signaled, or the syntax element should not be allowed to indicate the picture partitioning, which can save signaling bandwidth and processing power in this case.

[0168] To ensure that there is no picture partitioning, in one example, the syntax element pps_no_pic_partition_flag may be semantically constrained as follows:

[0169] The bitstream conforms to the requirement that the value of pps_no_pic_partition_flag shall be equal to 1 when the values ​​of pps_pic_width_in_luma_samples and pps_pic_height_in_luma_samples are both less than or equal to CtbSizeY.

[0170] When there is only one slice in a picture, the PPS syntax element pps_tile_idx_delta_present_flag may not be explicitly signaled, as shown in Table 8 below. In VVC draft 9, tile_idx_delta_present_flag equal to 0 specifies that the syntax element tile_idx_delta[i] is not present in the PPS, and all pictures referencing the PPS are divided into rectangular slice rows and rectangular slice columns in slice raster order. tile_idx_delta_present_flag equal to 1 specifies that the syntax element tile_idx_delta[i] may be present in the PPS, and all rectangular slices in the pictures referencing the PPS are specified in the order indicated by the values ​​of tile_idx_delta[i] in increasing i. If not present, the value of tile_idx_delta_present_flag is inferred to be 0.

[0171] In another example, semantic constraints may be imposed on pps_tile_idx_delta_present_flag as follows:

[0172] The bitstream conforms to the requirement that the value of pps_tile_idx_delta_present_flag shall be equal to 0 when there is only one slice in the picture.

[0173]

[0174] In VVC draft 9, the syntax element pps_num_slices_in_pic_minus1 (may also be marked as num_slices_in_pic_minus1 or other forms) plus 1 specifies the number of rectangular slices in each picture that references the PPS. NumTilesInPic is equal to the number of slices in the picture (e.g., number of slice columns * number of slice rows).

[0175] In another example, when the picture width is less than or equal to CtbSizeY, all slices share the same width, the syntax element pps_tile_idx_delta_val[i] may not be explicitly signaled, and the slice index of the slice containing the first CTU in the slice may be derived. For example, the video decoder 300 may derive the slice index of the slice containing the first CTU in the slice. When the picture height is less than or equal to CtbSizeY, all slices share the same height, the syntax element pps_tile_idx_delta_val[i] may not be explicitly signaled, and the slice index of the slice containing the first CTU in the slice may be derived.

[0176] Table 9 shows the signaling conditions for pps_tile_idx_delta_present_flag.

[0177]

[0178] Semantic constraints may be enforced on the pps_tile_idx_delta_present_flag as follows.

[0179] When NumTilesInPic is equal to 1, or the value of pps_pic_width_in_luma_samples is less than or equal to CtbSizeY, or the value of pps_pic_height_in_luma_samples is less than or equal to CtbSizeY, the value of pps_tile_idx_delta_present_flag shall be equal to 0.

[0180] Now let's discuss the hypothetical reference decoder (HRD). In VVC draft 9, the picture header (PH) NAL unit type is not present in Type I bitstreams, and Type I bitstreams contain only video coding layer (VCL) NAL units. The PH may be necessary for VCL-NAL parsing and decoding, so the PH NAL unit should be included in the Type I bitstream along with the VCL NAL. For example, the video decoder 300 may require the PH NAL unit to parse and decode the VCL NAL unit.

[0181] For example, PH NAL should be included in the HRD process. In one example, when the following is described, as indicated by the notation<!----> and<!--!--> A PH NAL MAY be included in a Type 1 bitstream when present:

[0182] The first type, called Type 1 bitstream, is a NAL unit stream containing: only VCL NAL units<!----> (when the VCL NAL unit has sh_picture_header_in_slice_header_flag equal to 1), or a PH NAL unit and the VCL NAL unit following the PH NAL unit<!--!--> , and NAL units with nal_unit_type equal to FD_NUT for all AUs in the bitstream (padding data NAL units).

[0183] In VVC draft 9, sh_picture_header_in_slice_header_flag equal to 1 specifies that the PH syntax structure exists in the slice header. sh_picture_header_in_slice_header_flag equal to 0 specifies that the PH syntax structure does not exist in the slice header.

[0184] In another example, when using the notation<!----> …<!--!--> The PH NAL unit shall be conveyed to HDR when the following directive is present:

[0185] All DCI NAL units, when applicable, all VPS, SPS, PPS referenced in VCL NAL units,<!----> PH<!--!--> and APS, and appropriate BP, PT, and DU information SEI messages shall be delivered to the HRD in a timely manner in the bitstream (via non-VCL NAL units) or by other means not specified in this specification.

[0186] In Annexes C and D, the following conditions are also met for the inclusion of DCI NAL units, VPS, SPS, PPS, APS,<!----> PH<!--!--> Definition of the "presence" of non-VCL NAL units in a BP SEI message, a PT SEI message, or a DU information SEI message: when those NAL units (or only some of them) are delivered to the decoder (or to the HRD) by other means not specified in this specification.

[0187] We now discuss the semantic changes to VVC draft 9. The semantics of many syntax elements should be specified in one way rather than two (e.g., consistently across syntax elements), as follows: <d> ...< / d> Mark the suggested deletion with a ... Marker Insertion:

[0188] vps_max_tid_ref_present_flag[i] equal to 1 specifies the syntax element vps_max_tid_il_ref_pics_plus1[i][j] <d> yes< / d> Can be If present, vps_max_tid_ref_present_flag[i] equal to 0 specifies the syntax element vps_max_tid_il_ref_pics_plus1[i][j].

[0189] sps_idr_rpl_present_flag equal to 1 specifies the reference picture list syntax element <d> yes< / d> Can be Present in the slice header of an IDR picture (or, in some examples, an IDR VCL NAL unit). sps_idr_rpl_present_flag equal to 0 specifies that the reference picture list syntax element is not present in the slice header of an IDR picture (or, in some examples, an IDR VCL NAL unit).

[0190] sps_bdof_control_present_in_ph_flag equal to 1 specifies ph_bdof_disabled_flag <d> yes< / d> Can bePresent in the PH referencing the SPS. sps_bdof_control_present_in_ph_flag equal to 0 specifies that ph_bdof_disabled_flag is not present in the PH referencing the SPS. When sps_bdof_control_present_in_ph_flag is not present, the value of sps_bdof_control_present_in_ph_flag is inferred to be equal to 0.

[0191] sps_dmvr_control_present_in_ph_flag is equal to 1 and specifies ph_dmvr_disabled_flag <d> yes< / d> Can be Present in the PH referencing the SPS. sps_dmvr_control_present_in_ph_flag equal to 0 specifies that ph_dmvr_disabled_flag is not present in the PH referencing the SPS. When sps_dmvr_control_present_in_ph_flag is not present, the value of sps_dmvr_control_present_in_ph_flag is inferred to be equal to 0.

[0192] sps_prof_control_present_in_ph_flag equal to 1 specifies ph_prof_disabled_flag <d> yes< / d> Can be Present in the PH referencing the SPS. sps_prof_control_present_in_ph_flag equal to 0 specifies that ph_prof_disabled_flag is not present in the PH referencing the SPS. When sps_prof_control_present_in_ph_flag is not present, the value of sps_prof_control_present_in_ph_flag is inferred to be equal to 0.

[0193] pps_sao_info_in_ph_flag equal to 1 specifies SAO filter information <d> yes< / d> Can be Present in the PH syntax structure, but not in slice headers referencing PPS that do not contain a PH syntax structure. pps_sao_info_in_ph_flag equal to 0 specifies that SAO filter information is not present in the PH syntax structure and may be present in slice headers referencing PPS. When not present, the value of pps_sao_info_in_ph_flag is inferred to be equal to 0.

[0194] pps_alf_info_in_ph_flag is equal to 1 to specify ALF information <d> yes< / d> Can be Present in the PH syntax structure, but not in slice headers referencing PPS that do not contain the PH syntax structure. pps_alf_info_in_ph_flag equal to 0 specifies that ALF information is not present in the PH syntax structure and may be present in slice headers referencing PPS. When not present, the value of pps_alf_info_in_ph_flag is inferred to be equal to 0.

[0195] pps_output_flag_present_flag equal to 1 specifies the syntax element ph_pic_output_flag <d> yes< / d> Can be Present in the PH referencing the PPS. pps_output_flag_present_flag equal to 0 specifies that the syntax element ph_pic_output_flag is not present in the PH referencing the PPS.

[0196] pps_cu_qp_delta_enabled_flag equal to 1 specifies the syntax elements ph_cu_qp_delta_subdiv_intra_slice and ph_cu_qp_delta_subdiv_inter_slice. At least one of _qp_delta_abs and cu_qp_delta_sign_flag may be present in transform unit syntax and palette coding syntax.pps_cu_qp_delta_enabled_flag equal to 0 specifies that the syntax elements ph_cu_qp_delta_subdiv_intra_slice and ph_cu_qp_delta_subdiv_inter_slice are not present in the PH referencing the PPS, and the syntax elements cu_qp_delta_abs and cu_qp_delta_sign_flag are not present in transform unit syntax and palette coding syntax.

[0197] Figure 5 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 5This is provided for purposes of explanation and should not be considered limiting of the techniques broadly illustrated and described in this disclosure. For purposes of explanation, this disclosure describes a video encoder 200 based on techniques of VVC (under development, ITU-T H.266) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video coding devices configured to conform to other video coding standards.

[0198] exist Figure 5 In the example of FIG, video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filtering unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filtering unit 216, the DPB 218, and the entropy coding unit 220 may be implemented in one or more processors or processing circuits. For example, the units of video encoder 200 may be implemented as one or more circuits or logic elements as part of a hardware circuit or as part of a processor ASIC in an FPGA. Furthermore, video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0199] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives video data stored in the video data memory 230. The DPB 218 can act as a reference picture memory for storing reference video data, which is used by the video encoder 200 to predict subsequent video data. The video data memory 230 and the DPB 218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and the DPB 218 can be provided by the same memory device or separate memory devices. In various examples, as shown in the figure, the video data memory 230 can be on-chip with other components of the video encoder 200, or off-chip relative to those components.

[0200] In this disclosure, references to video data memory 230 should not be construed as limited to memory internal to the video encoder 200, unless specifically described as such, or memory external to the video encoder 200, unless specifically described as such. Rather, references to video data memory 230 should be understood as referring to memory that stores video data received by the video encoder 200 for encoding (e.g., video data for the current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from the various units of the video encoder 200 .

[0201] Figure 5 The various units are shown to help understand the operations performed by the video encoder 200. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide a specific function and are preset in the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally constant. 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 integrated circuits.

[0202] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed of a programmable circuit. In an example in which the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store instructions (eg, object code) for software received and executed by video encoder 200, or another memory within video encoder 200 (not shown) may store such instructions.

[0203] The video data memory 230 is configured to store received video data. The video encoder 200 can obtain a picture of video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 can be the original video data to be encoded.

[0204] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units for performing video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0205] The mode selection unit 202 typically coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values ​​for such combinations. The encoding parameters may include the division of a CTU into CUs, a prediction mode for a CU, a transform type for residual data of a CU, a quantization parameter for residual data of a CU, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations. In some examples, the mode selection unit 202 may determine to apply a constraint regarding not allowing rectangular slices. The mode selection unit 202 may determine a value for a first syntax element (e.g., no_rectangular_slice_constraint_flag) that indicates whether a first constraint is applicable, wherein the first constraint is that no rectangular slices are allowed.

[0206] The video encoder 200 may divide a picture obtained from the video data memory 230 into a series of CTUs and encapsulate one or more CTUs into 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 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 the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks."

[0207] Typically, mode select unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of a PU and TU in HEVC). For inter prediction of the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate values ​​representing how similar potential reference blocks are to the current block, for example, based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), etc. Motion estimation unit 222 may typically perform these calculations using the sample-by-sample differences between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block with the lowest value from these calculations, indicating the reference block that most closely matches the current block.

[0208] 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 the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional 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 for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate the values ​​for the prediction block using one or more interpolation filters. Furthermore, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0209] As another example, for intra prediction or intra prediction encoding, the intra prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 can generally mathematically combine the values ​​of adjacent samples and pad these calculated values ​​on the current block in a defined direction to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 can calculate the average value of adjacent samples of the current block and generate a prediction block to include this average value for each sample of the prediction block.

[0210] Mode selection unit 202 provides the prediction block to residual generation unit 204. Residual generation unit 204 receives the original, unencoded version of the current block from video data memory 230 and the prediction block from mode selection unit 202. Residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, residual generation unit 204 may also determine the difference between sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, residual generation unit 204 may be implemented using one or more subtractor circuits that perform binary subtraction.

[0211] In the example where the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As described above, the size of a CU may refer to the size of the luma (luminance) coding block of the CU, and the size of a PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra-frame prediction, and symmetric PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar for inter-frame prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0212] In an example where the mode selection unit 202 does not further divide the CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of the luma coding block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0213] For other video coding techniques (such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding, as a few examples), the mode selection unit 202 generates a prediction block for the current block being encoded via the corresponding unit associated with the coding technique. In some examples, such as palette mode coding, the mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how to reconstruct the block based on the selected palette. In such a mode, the mode selection unit 202 may provide these syntax elements to the entropy coding unit 220 for encoding.

[0214] As described above, the residual generation unit 204 receives video data for a current block and a corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0215] The transform processing unit 206 applies one or more transforms to the residual block to generate a transform coefficient block (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform multiple transforms on the residual block, for example, 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.

[0216] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. The quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode select unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may result in a loss of information, and therefore, the quantized transform coefficients may have a lower precision than the original transform coefficients produced by the transform processing unit 206.

[0217] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although possibly with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples from the prediction block generated by the mode selection unit 202 to produce a reconstructed block.

[0218] Filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0219] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in examples where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In examples where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can obtain a reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction on blocks of subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed blocks in the DPB 218 of the current picture to perform intra-frame prediction on other blocks in the current picture.

[0220] In general, entropy coding unit 220 may entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 may entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 may entropy encode prediction syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from mode selection unit 202, or syntax elements indicating whether constraints are applicable. Entropy coding unit 220 may perform one or more entropy encoding operations on syntax elements, another example of video data, to generate entropy-encoded data. For example, entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioning entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, entropy encoding unit 220 may operate in a bypass mode in which syntax elements are not entropy encoded.

[0221] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required to reconstruct a block of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0222] The operations described above are described with respect to blocks. This description should be understood as operations for luma decoding blocks and / or chroma decoding blocks. As described above, in some examples, the luma decoding blocks and chroma decoding blocks are the luma components and chroma components of a CU. In some examples, the luma decoding blocks and chroma decoding blocks are the luma components and chroma components of a PU.

[0223] In some examples, operations performed for luma-coded blocks do not need to be repeated for chroma-coded blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for chroma-coded blocks do not need to be repeated for identifying motion vectors (MVs) and reference pictures for luma-coded blocks. Instead, the MVs for luma-coded blocks can be scaled to determine the MVs for chroma-coded blocks, and the reference pictures can be the same. As another example, the intra prediction process can be the same for luma-coded blocks and chroma-coded blocks.

[0224] Video encoder 200 represents an example device configured to encode video data, comprising: a memory configured to store the video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and encode the first plurality of pictures of the video data in accordance with the value of the first syntax element.

[0225] Video encoder 200 also represents an example of a device configured to encode video data, including a memory configured to store video data, one or more processing units implemented in circuitry and configured to perform any of the methods or techniques described in this disclosure.

[0226] Figure 6 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 6 This is provided for purposes of explanation and does not limit the techniques generally illustrated and described in this disclosure. For purposes of explanation, this disclosure describes a video decoder 300 based on techniques of VVC (under development, ITU-T H.266) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video coding devices configured to conform to other video coding standards.

[0227] exist Figure 6In the example of FIG, video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or processing 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 in an FPGA. Furthermore, video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0228] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units for performing prediction according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0229] The CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of the video decoder 300. The video data stored in the CPB memory 320 may be, for example, received from the computer-readable medium 110 ( Figure 1 ). The CPB memory 320 may include a CPB that stores coded video data (e.g., syntax elements) from the coded video bitstream. Furthermore, the CPB memory 320 may store video data other than syntax elements for decoded pictures, such as temporary data representing outputs from various units of the video decoder 300. The DPB 314 typically stores decoded pictures, which the video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures in the coded video bitstream. The CPB memory 320 and the DPB 314 may be formed from any of a variety of memory devices, such as DRAM (including SDRAM), MRAM, RRAM, or other types of memory devices. The CPB memory 320 and the DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300 or off-chip relative to these components.

[0230] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) to obtain decoded video data. That is, memory 120 may store data together with CPB memory 320 as described above. Similarly, when some or all of the functions of video decoder 300 are implemented in software to be executed by the processing circuit of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0231] Figure 6 The various units shown are shown to aid in understanding the operations performed by the video decoder 300. These units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 5 , fixed-function circuits refer to circuits that provide specific functions and are preset in the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally unchanged. 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 integrated circuits.

[0232] The video decoder 300 may include an ALU, an EFU, digital circuits, analog circuits, and / or a programmable core formed by programmable circuits. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0233] The entropy decoding unit 302 may receive the encoded video data from the CPB and perform entropy decoding on the video data to reproduce syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0234] Typically, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (wherein a block currently being reconstructed, ie, decoded, may be referred to as a "current block").

[0235] The entropy decoding unit 302 may entropy decode syntax elements, where the syntax elements define quantized transform coefficients for a quantized transform coefficient block, and transform information (such as a quantization parameter (QP) and / or a transform mode indication). In some examples, the entropy decoding unit 302 may entropy decode the value of a syntax element that indicates whether a constraint is to be applied. The entropy decoding unit 302 may determine the value of a first syntax element that indicates whether a first constraint is applicable, where the first constraint is that no rectangular slices are allowed.

[0236] The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine the degree of quantization and, similarly, the degree of inverse quantization to be applied by the inverse quantization unit 306. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block comprising the transform coefficients.

[0237] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

[0238] In addition, prediction processing unit 304 generates a prediction block based on the prediction information syntax element entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, motion compensation unit 316 may generate a prediction block. In this case, the prediction information syntax element may indicate a reference picture in DPB 314 from which to obtain the reference block, and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 may generally generate a prediction block in a manner substantially similar to that described with respect to motion compensation unit 224 ( Figure 5 In some examples, the prediction processing unit may apply a first constraint regarding not allowing rectangular slices based on the first syntax element indicating that rectangular slices are not allowed.

[0239] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Similarly, the intra-prediction unit 318 may generate a prediction block in the same manner as described with respect to the intra-prediction unit 226 ( Figure 5 The intra prediction process is performed in a manner substantially similar to that described in the preceding claims. The intra prediction unit 318 may obtain data of neighboring samples of the current block from the DPB 314.

[0240] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

[0241] The filtering unit 312 may perform one or more filtering operations on the reconstructed block. For example, the filtering unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filtering unit 312 may not necessarily be performed in all examples.

[0242] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in examples when the operations of the filtering unit 312 are not performed, the reconstruction unit 310 may store the reconstructed block to the DPB 314. In examples when the operations of the filtering unit 312 are performed, the filtering unit 312 may store the filtered reconstructed block to the DPB 314. As described above, the DPB 314 may provide reference information to the prediction processing unit 304, such as samples of the current picture for intra-frame prediction and samples of previously decoded pictures for subsequent motion compensation. In addition, the video decoder 300 may output a decoded picture (e.g., decoded video) from the DPB 314 for subsequent use in, for example, Figure 1 The display device 118 is displayed on the display device.

[0243] The video decoder 300 may represent an example of a decoder configured to decode video data, including a memory configured to store video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and decode the first plurality of pictures of the video data in accordance with the value of the first syntax element.

[0244] Video decoder 300 may also represent 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 perform any of the methods or techniques described in this disclosure.

[0245] Figure 7is a flowchart illustrating an example general constraint technique according to the present disclosure. The video encoder 200 or the video decoder 300 may determine a value for a first syntax element that indicates whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures (330). For example, the video encoder 200 may perform multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values ​​for those combinations. The video encoder 200 may determine, based on the resulting rate-distortion values, that the first constraint should be applied. In this case, the video encoder 200 may determine a value for the first syntax element to indicate that the first constraint is applied. Alternatively, the video encoder 200 may determine, based on the resulting rate-distortion values, that the first constraint should not be applied. In this case, the video encoder 200 may determine a value for the first syntax element to indicate that the first constraint is not applied. The video encoder 200 may signal the first syntax element in a bitstream of encoded video data.

[0246] For example, the video decoder 300 may receive a first syntax element in a bitstream of encoded video data. The video decoder 300 may determine a value of the first syntax element by parsing the first syntax element.

[0247] The video decoder 300 may decode the first plurality of pictures of the video data according to the value of the first syntax element (332). For example, the video encoder 200 may encode the first plurality of pictures of the video data according to the value of the first syntax element. For example, if the video encoder 200 determines that the first constraint applies, the video encoder 200 may encode the first plurality of pictures of the video data with the first constraint applied (e.g., according to the value of the first syntax element indicating that the first constraint is applicable). Alternatively, if the video encoder 200 determines that the first constraint does not apply, the video encoder 200 may encode the first plurality of pictures of the video data without applying the first constraint (e.g., according to the value of the first syntax element indicating that the first constraint is not applicable).

[0248] For example, the video decoder 300 may decode the first plurality of pictures based on the value of the first syntax element. For example, if the value of the first syntax element indicates that the first constraint is applicable, the video decoder 300 may decode the first plurality of pictures based on the value of the first syntax element indicating that the first constraint is applicable. For example, the video decoder 300 may decode the first plurality of pictures while applying the first constraint. Alternatively, if the value of the first syntax element indicates that the first constraint is not applicable, the video decoder 300 may decode the first plurality of pictures based on the value of the first syntax element indicating that the first constraint is not applicable. For example, the video decoder 300 may decode the first plurality of pictures without applying the first constraint.

[0249] In some examples, a value of the first syntax element indicates that the first constraint is applicable, and the video encoder 200 or the video decoder 300 may determine, based on the value of the first syntax element indicating that the first constraint is applicable, that a value associated with a second syntax element for the first plurality of pictures is equal to 0, wherein the value 0 for the second syntax element indicates that rectangular slices are not used for each picture in the first plurality of pictures to which the picture parameter set is applicable. In some examples, the first syntax element is no_rectangular_slice_constraint_flag and the second syntax element is pps_rect_slice_flag.

[0250] In some examples, the video encoder 200 or the video decoder 300 may determine a value of a third syntax element indicating whether a second constraint is applicable, wherein each sub-picture in the second plurality of pictures must contain only one slice, and decode the second plurality of pictures according to the value of the third syntax element. For example, the video encoder 200 may encode the second plurality of pictures according to the value of the third syntax element, or the video decoder 300 may decode the second plurality of pictures according to the value of the third syntax element.

[0251] In some examples, the value of the third syntax element indicates that the second constraint is applicable, and the video encoder 200 or the video decoder 300 may determine, based on the value of the third syntax element indicating that the second constraint is applicable, that the value associated with the fourth syntax element indicates that each sub-picture in the second plurality of pictures to which the picture parameter set applies includes only one slice. In some examples, the third syntax element includes one_slice_per_subpicture_constraint_flag, and the fourth syntax element includes pps_single_slice_per_subpic_flag.

[0252] In some examples, the video decoder 300 may receive a type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; and decode the at least one PH NAL unit and the at least one VCL NAL unit.

[0253] In some examples, the video encoder 200 may encode at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit, and send a type I bitstream that includes at least one PH NAL unit and at least one VCL NAL unit.

[0254] Figure 8 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and 5 ) is described, but it should be understood that other devices may be configured to perform similar Figure 8 In some examples, while encoding the current block, the video encoder 200 may also use Figure 7 technology.

[0255] In this example, the video encoder 200 initially predicts a current block (350). For example, the video encoder 200 may form a prediction block for the current block. In some examples, when predicting the current block, the video encoder 200 may determine to apply constraints, such as a constraint for prohibiting rectangular stripes. The video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, the video encoder 200 may calculate the difference between the original, unencoded block and the prediction block for the current block. The video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the transform coefficients (358). For example, the video encoder 200 may encode the transform coefficients using CAVLC or CABAC. The video encoder 200 may then output entropy encoded data for the block (360). In some examples, while encoding the current block, the video encoder 200 may also employ Figure 7 technology.

[0256] Figure 9 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and 6 ) is described, it should be understood that other devices may be configured to perform similar Figure 9 method of method.

[0257] The video decoder 300 may receive entropy-encoded data for a current block, such as entropy-encoded prediction information and entropy-encoded data for coefficients of a residual block corresponding to the current block (370). The video decoder 300 may entropy decode the entropy-encoded data to determine the prediction information for the current block and regenerate the coefficients of the residual block (372). For example, the entropy decoder may determine the value of a syntax element indicating whether a constraint (such as rectangular slices are not allowed) is to be applied. The video decoder 300 may predict the current block (374), for example, using an intra-frame or inter-frame prediction mode indicated by the prediction information for the current block, to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the regenerated coefficients (376) to create a block of quantized transform coefficients. The video decoder 300 may then inverse quantize and inverse transform the transform coefficients to produce a residual block (378). The video decoder 300 may ultimately decode the current block (380) by merging the prediction block and the residual block.

[0258] By utilizing a general constraint flag that indicates whether a constraint is to be applied, and inferring values ​​of other syntax elements based on the general constraint flag, rather than signaling and parsing other syntax elements that may be at a lower level, the techniques of this disclosure may save signaling bandwidth and processing power at the video encoder 200 and the video decoder 300. Furthermore, by including the PH NAL unit in a Type 1 bitstream, decoding latency and / or accuracy may be improved, since a video decoder may need the PH NAL unit to decode the VCL NAL unit in the Type 1 bitstream.

[0259] The following numbered clauses illustrate one or more aspects of the devices and techniques described in this disclosure.

[0260] Article 1A. A method of processing video data, the method comprising:

[0261] obtaining a bitstream comprising an encoded representation of the video data; and

[0262] The bitstream is determined to be compliant with a video coding standard based on the bitstream including a current picture that references a picture that precedes a gradual decoding refresh (GDR) picture or references any picture that precedes a picture having a picture order count (POC) value equal to an applicable recovery POC value.

[0263] Clause 2A. A method according to clause 1A, wherein determining that the bitstream does not conform to the video coding standard comprises determining that the bitstream does not conform to the video coding standard based on a determination that, when the current picture follows a recovery point picture having the same nuh_layer_id value in both decoding order and output order, there is a picture referenced by an active entry in RefPicList[0] or RefPicList[1] that precedes that recovery point picture in output order or decoding order.

[0264] Clause 3A. A method according to any of Clauses 1A-2A, wherein the bitstream is a first bitstream and the method further comprises: obtaining a second bitstream comprising an encoded representation of second video data; and decoding the second video data based on determining that the bitstream conforms to the video decoding standard.

[0265] Article 4A. A method of encoding video data, the method comprising:

[0266] Obtaining video data; and encoding the video data subject to a constraint that does not allow a current picture to reference a picture that precedes a gradual decoding refresh (GDR) picture or a picture that precedes a picture order count (POC) value that is equal to an applicable recovery POC value.

[0267] Clause 5A. A method according to clause 4A, wherein the constraint requires that: when the current picture follows a recovery point picture with the same nuh_layer_id value in both decoding order and output order, there shall be no pictures referenced by active entries in RefPicList[0] or RefPicList[1] that precede that recovery point picture in output order or decoding order.

[0268] Article 1B. A method of processing video data, the method comprising:

[0269] obtaining a bitstream comprising an encoded representation of the video data; and

[0270] determining that the bitstream does not conform to the video coding standard based on a determination that one or more of the following constraints are not satisfied: when intra_only_constraint_flag is 1, the values ​​of no_ref_pic_resampling_constraint_flag, all_layers_independent_constraint_flag, and no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1; when no_ref_pic_resampling_constraint_flag is 1, the value of no_res_change_in_clvs_constraint_flag shall be equal to 1; when one_subpic_per_pic_constraint_flag is 1, the value of no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1; and when no_cra_constraint_flag is 1, the value of no_rasl_constraint_flag shall be equal to 1; The values ​​of no_idr_constraint_flag, no_cra_constraint_flag, and no_gdr_constraint_flag shall not all be equal to 1.

[0271] Clause 2B. The method of clause 1B, wherein the bitstream is a first bitstream and the method further comprises: obtaining a second bitstream comprising an encoded representation of second video data; and decoding the second video data based on determining that the bitstream conforms to the video coding standard.

[0272] Article 3B. A method of encoding video data, the method comprising: obtaining video data; and encoding the video data subject to one or more of the following constraints: when intra_only_constraint_flag is 1, the values ​​of no_ref_pic_resampling_constraint_flag, all_layers_independent_constraint_flag, and no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1; when no_ref_pic_resampling_constraint_flag is 1, the value of no_res_change_in_clvs_constraint_flag shall be equal to 1; when one_subpic_per_pic_constraint_flag is 1, the value of no_mixed_nalu_types_in_pic_constraint_flag shall be equal to 1; when no_cra_constraint_flag is 1, the value of no_rasl_constraint_flag shall be equal to 1; The values ​​of no_idr_constraint_flag, no_cra_constraint_flag, and no_gdr_constraint_flag shall not all be equal to 1.

[0273] Article 1C. A method of processing video data, the method comprising:

[0274] Obtaining a bitstream comprising an encoded representation of the video data, the bitstream for one or more output layer sets within a coverage range; and determining, based on syntax elements in the bitstream, whether a constraint applies, the constraint specifying that no hypothetical reference decoder (HRD)-related supplemental enhancement information (SEI) messages should be present in the bitstream.

[0275] Article 2C. A method of processing video data, the method comprising:

[0276] Obtaining a bitstream comprising an encoded representation of the video data, the bitstream being for one or more output layer sets within a coverage range; and determining, based on syntax elements in the bitstream, whether a constraint applies, the constraint specifying that no dependent random access point indication supplemental enhancement information (SEI) messages should be present in the bitstream.

[0277] Article 3C. A method of processing video data, the method comprising:

[0278] Obtaining a bitstream comprising an encoded representation of the video data, the bitstream for one or more output layer sets within a coverage range; and determining, based on syntax elements in the bitstream, whether a constraint applies, the constraint specifying that no omni-directional video-specific supplemental enhancement information (SEI) messages should be present in the bitstream.

[0279] Article 4C. A method of processing video data, the method comprising:

[0280] Obtaining a bitstream comprising an encoded representation of the video data; and determining, based on syntax elements in the bitstream, whether a constraint applies, the constraint specifying that no omni-directional video-specific supplemental enhancement information (SEI) messages should be present in the bitstream.

[0281] Article 5C. A method of processing video data, the method comprising:

[0282] Obtain a bitstream comprising an encoded representation of the video data; and determine, based on a first syntax element in the bitstream, whether a constraint applies, the constraint specifying that a second syntax element in the bitstream indicates that a video availability information syntax structure is not present in a sequence parameter set (SPS) raw byte sequence payload (RBSP) syntax structure.

[0283] Article 6C. A method of processing video data, the method comprising:

[0284] Obtaining a bitstream comprising an encoded representation of the video data; and determining, based on a first syntax element in the bitstream, whether a constraint applies, the constraint specifying that a second syntax element in the bitstream should be in a range of 0 to a maximum-layers syntax element - 1, wherein the second syntax element specifies a maximum number of layers allowed in each coded video sequence that references a video parameter set.

[0285] Article 7C. A method of processing video data, the method comprising:

[0286] Obtaining a bitstream comprising an encoded representation of the video data; and determining, based on a first syntax element in the bitstream, whether a constraint applies, the constraint specifying that a second syntax element in the bitstream should be in a range of 0 to a maximum-sub-layer syntax element - 1, wherein the second syntax element specifies a maximum number of sub-layers allowed in each coded video sequence that references a video parameter set.

[0287] Article 8C. A method of processing video data, the method comprising:

[0288] Obtaining a bitstream comprising an encoded representation of the video data; and determining, based on a first syntax element in the bitstream, whether a constraint applies, the constraint specifying that a second syntax element in the bitstream should be in a range of 0 to a maximum-sub-picture syntax element - 1, wherein the second syntax element specifies a maximum number of sub-pictures allowed in each picture in a coded layer video sequence.

[0289] Article 9C. A method of processing video data, the method comprising:

[0290] Obtaining a bitstream comprising an encoded representation of the video data; and determining, based on a first syntax element in the bitstream, whether a constraint applies, the constraint specifying that a second syntax element in the bitstream should indicate that picture partitioning is not applied to each picture that references a picture parameter set.

[0291] Clause 10C. The method of any of Clauses 1C-9C, further comprising decoding the bitstream.

[0292] Article 11C. A method of encoding video data, the method comprising:

[0293] Obtain video data; and encode the video data so that a bitstream includes one or more of the following: a first syntax element indicating whether a first constraint applies, the first constraint specifying that no hypothetical reference decoder (HRD)-related supplemental enhancement information (SEI) messages should be present in the bitstream; a second syntax element indicating whether a second constraint applies, the second constraint specifying that no dependent random access point indication SEI messages should be present in the bitstream; a third syntax element indicating whether a third constraint applies, the third constraint specifying that no omnidirectional video-specific SEI messages should be present in the bitstream; a fourth syntax element indicating whether a fourth constraint applies, the fourth constraint specifying that a fifth syntax element indicates that there is no video availability information syntax structure in a sequence parameter set (SPS) raw byte sequence payload (RBSP) syntax structure; a sixth syntax element indicating whether a fifth constraint applies, the fifth constraint specifying that a fifth syntax element indicates that there is no video availability information syntax structure in a sequence parameter set (SPS) raw byte sequence payload (RBSP) syntax structure. a seventh syntax element shall be in the range of 0 to a maximum-layers syntax element -1, wherein the seventh syntax element specifies the maximum number of allowed layers in each coded video sequence that references a video parameter set; an eighth syntax element that indicates whether a sixth constraint applies, wherein the sixth constraint specifies that a ninth syntax element in the bitstream shall be in the range of 0 to a maximum-sub-layers syntax element -1, wherein the ninth syntax element specifies the maximum number of allowed sub-layers in each coded video sequence that references a video parameter set; a tenth syntax element that indicates whether a seventh constraint applies, wherein the seventh constraint specifies that an eleventh syntax element shall be in the range of 0 to a maximum-sub-picture syntax element -1, wherein the eleventh syntax element specifies the maximum number of allowed sub-pictures in each picture in the coded layer video sequence; or a twelfth syntax element that indicates whether an eighth constraint applies, wherein the eighth constraint specifies that the thirteenth syntax element shall indicate that picture partitioning is not applied to each picture that references a picture parameter set.

[0294] Article 1D. A method of processing video data, the method comprising:

[0295] Obtaining a bitstream comprising an encoded representation of the video data; and determining that the bitstream does not conform to the video coding standard based on violating a constraint specifying that when vps_video_parameter_set_id is greater than 0 and vps_all_layers_same_num_sublayers_flag is equal to 1, the value of sps_max_sublayers_minus1 shall be equal to the value of vps_max_sublayers_minus1.

[0296] Clause 2D. The method of clause 1D, wherein the bitstream is a first bitstream, the method comprising decoding the second bitstream based on the second bitstream conforming to the video coding standard, the second bitstream comprising a second encoded representation of the video data.

[0297] Article 3D. A method of encoding video data, the method comprising:

[0298] Obtaining the video data; and encoding the video data to comply with a constraint specifying that when vps_video_parameter_set_id is greater than 0 and vps_all_layers_same_num_sublayers_flag is equal to 1, the value of sps_max_sublayers_minus1 shall be equal to the value of vps_max_sublayers_minus1.

[0299] Article 1E. A method of decoding video data, the method comprising:

[0300] Determining, based on a maximum width of each decoded picture referencing a sequence parameter set (SPS) being greater than a size of a coding treeblock or a maximum height of each decoded picture referencing the SPS being greater than the size of the coding treeblock, that a bitstream includes a syntax element indicating a number of sub-pictures in each picture in a coded layer video sequence; and decoding the bitstream based in part on the syntax element based on the bitstream including the syntax element.

[0301] Article 2E. A method of encoding video data, the method comprising:

[0302] Based on a maximum width of each decoded picture referencing a sequence parameter set (SPS) being greater than a size of a coding treeblock, or a maximum height of each decoded picture referencing the SPS being greater than the size of the coding treeblock, signaling a syntax element in a bitstream including an encoded representation of the video data, the syntax element indicating a number of sub-pictures in each picture in a coded layer video sequence.

[0303] Article 1F. A method for processing video data, the method comprising:

[0304] At least one of the following is performed: based on a width in units of luma samples of each picture referencing a picture parameter set (PPS) being greater than a size of a luma coding tree block of a picture referencing the PPS, determining that a bitstream includes a first syntax element indicating a number of slice column widths explicitly provided in the PPS, or based on a height in units of luma samples of each picture referencing the PPS being greater than a size of a luma coding tree block of a picture referencing the PPS, determining that a bitstream includes a second syntax element indicating a number of slice column heights explicitly provided in the PPS; and decoding the picture referencing the PPS based on the slice column widths and the slice column heights.

[0305] Article 2F. A method for encoding video data, the method comprising: signaling in a bitstream a first syntax element indicating a number of slice column widths explicitly provided in a picture parameter set (PPS) based on a width in units of luma samples of each picture referencing the PPS being greater than a size of a luma coding tree block of a picture referencing the PPS; or signaling in a bitstream a second syntax element indicating a number of slice column heights explicitly provided in the PPS based on a height in units of luma samples of each picture referencing the PPS being greater than a size of a luma coding tree block of a picture referencing the PPS; and encoding a picture referencing the PPS based on the slice column widths and the slice column heights.

[0306] Article 1G. A method for processing video data, the method comprising:

[0307] Determining, based on each of the following conditions being true, that a bitstream includes a first syntax element: (i) the number of slices in each picture referencing a picture parameter set (PPS) minus one is greater than one, (ii) the number of slices in each picture referencing the PPS is greater than one, (iii) the width in units of luma samples of each picture referencing the PPS is greater than the size of a luma coding treeblock of a picture referencing the PPS, and (iv) the height in units of luma samples of each picture referencing the PPS is greater than the size of a luma coding treeblock of a picture referencing the PPS, wherein the first syntax element indicates whether a second syntax element is present in the PPS and all pictures referencing the PPS are partitioned into rectangular slice rows and rectangular slice columns in slice raster order; and based on the first syntax element indicating that the second syntax element is present in the PPS: parsing the second syntax element from the bitstream; and using the second syntax element to decode a picture referencing the PPS.

[0308] Article 2G. The method according to Article 1G further includes: determining that the bitstream does not comply with the video decoding standard based on the following constraint being violated: when the number of slices in each picture referencing the PPS is equal to 1, or the width in luma units of each picture referencing the PPS is less than or equal to the size of the luma decoding tree block of the picture referencing the PPS, or the height in luma units of each picture referencing the PPS is less than or equal to the size of the luma decoding tree block of the picture referencing the PPS, the first syntax element shall indicate that the second syntax element is not present in the PPS, and all pictures referencing the PPS are divided into rectangular slice rows and rectangular slice columns in slice raster order.

[0309] Article 3G. A method for encoding video data, the method comprising:

[0310] Signaling, in a bitstream including a first syntax element based on each of the following conditions being true: (i) the number of slices in rectangular slices in each picture referencing a picture parameter set (PPS) minus one is greater than one, (ii) the number of slices in each picture referencing the PPS is greater than one, (iii) the width in units of luma samples of each picture referencing the PPS is greater than the size of a luma coding treeblock of a picture referencing the PPS, and (iv) the height in units of luma samples of each picture referencing the PPS is greater than the size of a luma coding treeblock of a picture referencing the PPS, wherein the first syntax element indicates whether a second syntax element is present in the PPS and all pictures referencing the PPS are partitioned into rectangular slice rows and rectangular slice columns in slice raster order; and signaling, from the bitstream, the second syntax element based on the first syntax element indicating that the second syntax element is present in the PPS.

[0311] Clause 4G. The method according to clause 3G, generating the bitstream to conform to a video coding standard based on the violation of the following constraint: when the number of slices in each picture referencing the PPS is equal to 1, or the width in luma units of each picture referencing the PPS is less than or equal to the size of the luma coding tree block of the picture referencing the PPS, or the height in luma units of each picture referencing the PPS is less than or equal to the size of the luma coding tree block of the picture referencing the PPS, the first syntax element shall indicate that the second syntax element is not present in the PPS, and all pictures referencing the PPS are divided into rectangular slice rows and rectangular slice columns in slice raster order.

[0312] Article 1H. A method of processing video data, the method comprising:

[0313] obtaining a bitstream comprising an encoded representation of the video data; and

[0314] The bitstream is determined to be non-compliant with a video coding standard based on the bitstream violating a constraint requiring that, when a current picture follows a recovery point picture having the same value of a network abstraction layer (NAL) unit header layer identifier in both decoding order and output order, there shall not be a picture referenced by an inter-layer reference prediction (ILRP) active entry in a first reference picture list or a second reference picture list that precedes the recovery point picture in output order or decoding order of an associated gradual decoding refresh (GDR) picture having a NAL unit header layer identifier that is equal to a reference picture layer identifier.

[0315] Article 2H. A method of encoding video data, the method comprising: obtaining video data; and encoding the video data to generate a bitstream such that the bitstream does not violate a constraint requiring that, when a current picture follows a recovery point picture having the same value of a network abstraction layer (NAL) unit header layer identifier in both decoding order and output order, there shall be no pictures referenced by inter-layer reference prediction (ILRP) active entries in a first reference picture list or a second reference picture list that precede the recovery point picture in output order or decoding order of an associated gradual decoding refresh (GDR) picture having a NAL unit header layer identifier that is equal to a reference picture layer identifier.

[0316] Article 1. A method for processing video data, the method comprising:

[0317] obtaining a bitstream comprising an encoded representation of the video data; and

[0318] The bitstream is determined to be non-compliant with a video coding standard based on the bitstream violating a constraint requiring that, when a current picture follows a recovery point picture having the same value of a network abstraction layer (NAL) unit header layer identifier in both decoding order and output order, there shall not be a reference picture referenced by an active entry in a first reference picture list or a second reference picture list in output order or decoding order of an associated gradual decoding refresh (GDR) picture in a layer having a NAL unit header layer identifier that is equal to the NAL unit header layer identifier of the reference picture that precedes the recovery point picture in output order or decoding order.

[0319] Article 2I. A method of encoding video data, the method comprising:

[0320] Obtaining video data; and encoding the video data to generate a bitstream such that the bitstream does not violate a constraint requiring that, when a current picture follows a recovery point picture having the same value of a network abstraction layer (NAL) unit header layer identifier in both decoding order and output order, there should not be a reference picture referenced by an active entry in a first reference picture list or a second reference picture list in output order or decoding order of an associated gradual decoding refresh (GDR) picture having a NAL unit header layer identifier equal to that of a reference picture in a layer that precedes the recovery point picture in output order or decoding order.

[0321] Article 1J. A method of processing video data, the method comprising:

[0322] obtaining a bitstream comprising an encoded representation of the video data; and

[0323] The bitstream is determined to be non-compliant with a video coding standard based on the bitstream violating any constraints set forth in this disclosure.

[0324] Article 2J. A method of encoding video data, the method comprising:

[0325] Obtaining video data; and encoding the video data to generate a bitstream such that the bitstream does not violate any constraints set forth in this disclosure.

[0326] Clause 1K. An apparatus for processing or encoding video data, the apparatus comprising one or more units for performing the method of any of Clauses 1A-2J.

[0327] Clause 2K. The apparatus of clause 1K, wherein the one or more units comprise one or more processors implemented in circuitry.

[0328] Article 3K. The apparatus of any of Articles 1K and 2K, further comprising a memory for storing the video data.

[0329] Clause 4K. The apparatus of any one of Clauses 1K-3K, further comprising: a display configured to display the decoded video data.

[0330] Clause 5K. The device of any of Clauses 1K-4K, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0331] Clause 6K. The apparatus of any of Clauses 1K-5K, wherein the apparatus comprises a video decoder.

[0332] Clause 7K. The apparatus of any of Clauses 1K-6K, wherein the apparatus comprises a video encoder.

[0333] Item 8K. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of Items 1A-2J.

[0334] Article 1L. A method of decoding video data, the method comprising:

[0335] Determining a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and decoding the first plurality of pictures of the video data according to the value of the first syntax element.

[0336] Clause 2L. The method of clause 1L, further comprising: determining, based on the value of the first syntax element indicating that the first constraint is applicable, a value associated with a second syntax element for the first plurality of pictures to be equal to 0, wherein the value of 0 for the second syntax element indicates that rectangular slices are not used for each picture in the first plurality of pictures to which the picture parameter set applies.

[0337] Clause 3L. The method of clause 1L, further comprising: determining a value of a third syntax element indicating whether a second constraint is applicable, wherein the second constraint is that each sub-picture in the second plurality of pictures must contain only one slice; and decoding each sub-picture in the second plurality of pictures according to the value of the third syntax element.

[0338] Article 4L, a method according to Article 3L, further comprising: determining, based on the value of the third syntax element indicating that the second constraint is applicable, that a value associated with the fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies contains only one slice.

[0339] Clause 5L. The method of any of Clauses 1L-4L, further comprising: receiving a type I bitstream, the type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; and decoding the at least one PH NAL unit and the at least one VCL NAL unit.

[0340] Article 6L. An apparatus for decoding video data, the apparatus comprising:

[0341] a memory configured to store the video data, and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and decode the first plurality of pictures of the video data in accordance with the value of the first syntax element.

[0342] Clause 7L. The apparatus of clause 6L, wherein the one or more processors are further configured to: determine, based on the value of the first syntax element indicating that the first constraint is applicable, a value associated with a second syntax element for the first plurality of pictures to be equal to 0, wherein the value of 0 for the second syntax element indicates that a rectangular slice is not used for each picture in the first plurality of pictures to which the picture parameter set applies.

[0343] Clause 8L. The apparatus of clause 6L, wherein the one or more processors are further configured to: determine a value of a third syntax element indicating whether a second constraint is applicable, wherein the second constraint is that each sub-picture in the second plurality of pictures must contain only one slice; and decode each sub-picture in the second plurality of pictures according to the value of the third syntax element.

[0344] Clause 9L. An apparatus according to clause 8L, wherein the one or more processors are further configured to: determine, based on the value of the third syntax element indicating that the second constraint is applicable, that a value associated with the fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies contains only one slice.

[0345] Clause 10L. The apparatus of any of Clauses 6L-9L, wherein the one or more processors are further configured to: receive a type I bitstream, the type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; and decode the at least one PH NAL unit and the at least one VCL NAL unit.

[0346] Item 11L. A non-transitory computer-readable medium storing instructions that, when executed, cause one or more processors to: determine a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and decode the first plurality of pictures of the video data in accordance with the value of the first syntax element.

[0347] Clause 12L. The non-transitory computer-readable medium of clause 11L, wherein the instructions further cause the one or more processors to: determine, based on the value of the first syntax element indicating that the first constraint is applicable, a value associated with a second syntax element for the first plurality of pictures to be equal to 0, wherein the value of 0 for the second syntax element indicates that a rectangular slice is not used for each picture in the first plurality of pictures to which the picture parameter set is applicable.

[0348] Clause 13L. The non-transitory computer-readable medium of clause 11L, wherein the instructions further cause the one or more processors to: determine a value of a third syntax element indicating whether a second constraint is applicable, the second constraint being that each sub-picture in a second plurality of pictures must contain only one slice; and decode each sub-picture in the second plurality of pictures in accordance with the value of the third syntax element.

[0349] Clause 14L. The non-transitory computer-readable medium of clause 13L, wherein the instructions further cause the one or more processors to: determine, based on the value of the third syntax element indicating that the second constraint is applicable, that a value associated with a fourth syntax element indicates that each sub-picture in the second plurality of pictures to which the picture parameter set applies contains only one slice.

[0350] Clause 15L. The non-transitory computer-readable medium of any of Clauses 11L-14L, wherein the instructions further cause the one or more processors to: receive a type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; and decode the at least one PH NAL unit and the at least one VCL NAL unit.

[0351] Clause 16L. An apparatus for decoding video data, the apparatus comprising: means for determining a value of a first syntax element indicating whether a first constraint is applicable, the first constraint being that rectangular slices are not used for a first plurality of pictures; and means for decoding the first plurality of pictures of the video data in accordance with the value of the first syntax element.

[0352] Clause 17L. The apparatus of clause 16L, further comprising means for determining, based on the value of the first syntax element indicating that the first constraint is applicable, that a value associated with a second syntax element for the first plurality of pictures is equal to 0, wherein a value of 0 for the second syntax element indicates that a rectangular slice is not used for each picture in the first plurality of pictures to which the picture parameter set is applicable.

[0353] Clause 18L. The apparatus of clause 16L, further comprising: means for determining a value of a third syntax element indicating whether a second constraint is applicable, wherein the second constraint is that each sub-picture in the second plurality of pictures must contain only one slice; and means for decoding each sub-picture in the second plurality of pictures in accordance with the value of the third syntax element.

[0354] Clause 19L. The apparatus of clause 18L, further comprising: means for determining, based on the value of the third syntax element indicating that the second constraint is applicable, that a value associated with a fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies includes only one slice.

[0355] Clause 20L. The apparatus of any of Clauses 16L-19L, further comprising: means for receiving a type I bitstream, the type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; and means for decoding the at least one PH NAL unit and the at least one VCL NAL unit.

[0356] It should be appreciated that, depending on the examples, certain actions or events in any of the techniques described herein may be performed in a different order, added, combined, or omitted altogether (e.g., not all described actions or events are required to practice the techniques). Furthermore, in certain examples, actions or events may be performed concurrently, for example, through multithreading, interrupt handling, or multiple processors, rather than sequentially.

[0357] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted through a computer-readable medium as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to tangible media such as data storage media, or communication media, which includes, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this manner, computer-readable media may generally correspond to (1) a non-transitory, tangible computer-readable storage medium or (2) a communication medium such as a signal or carrier wave. Data storage media 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 computer-readable media.

[0358] By way of example, and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store the required program code in the form of instructions or data structures and that is accessible by a computer. Furthermore, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies (such as infrared, radio, and microwave), the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies (such as infrared, radio, and microwave) are all included in the definition of 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 rather refer to non-transitory, tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, with disks typically reproducing data magnetically, while discs reproduce data optically using lasers. Combinations of the above are also included within the scope of computer-readable media.

[0359] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, as used herein, the terms "processor" and "processing circuitry" may refer to any of the aforementioned structures or any other structures suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Furthermore, these techniques may be fully implemented in one or more circuits or logic elements.

[0360] The techniques of this disclosure can be implemented in a variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed techniques, but they do not necessarily require implementation 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.

[0361] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: determining a value of a first syntax element indicating whether a first general constraint of a set of one or more general constraints is applicable, the first general constraint being that rectangular slices are not used for a first plurality of pictures of the video data; inferring a value associated with a second syntax element for the first plurality of pictures to be equal to 0 based on the value of the first syntax element indicating that the first general constraint is applicable, wherein the value of 0 for the second syntax element indicates that rectangular slices are not used for each picture among the first plurality of pictures to which the picture parameter set applies; and The first plurality of pictures of the video data are decoded according to a value of the first syntax element and a value of the second syntax element.

2. The method according to claim 1, wherein The first syntax element and the second syntax element are different syntax elements.

3. The method according to claim 1, further comprising: determining a value of a third syntax element indicating whether a second general constraint of the set of one or more general constraints is applicable, the second general constraint being that each sub-picture in the second plurality of pictures must contain only one slice; and Each sub-picture among the second plurality of pictures is decoded according to the value of the third syntax element.

4. The method according to claim 3, further comprising: Based on the value of the third syntax element indicating that the second general constraint is applicable, determining that a value associated with a fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies includes only one slice, wherein the third syntax element and the fourth syntax element are different syntax elements.

5. The method according to claim 1, further comprising: receiving a type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; as well as The at least one PH NAL unit and the at least one VCL NAL unit are decoded.

6. A device for decoding video data, the device comprising: a memory configured to store the video data, and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: determining a value of a first syntax element indicating whether a first general constraint of a set of one or more general constraints is applicable, the first general constraint being that rectangular slices are not used for a first plurality of pictures of the video data; inferring a value associated with a second syntax element for the first plurality of pictures to be equal to 0 based on the value of the first syntax element indicating that the first general constraint is applicable, wherein the value of 0 for the second syntax element indicates that rectangular slices are not used for each picture among the first plurality of pictures to which the picture parameter set applies; and The first plurality of pictures of the video data are decoded according to a value of the first syntax element and a value of the second syntax element.

7. The apparatus according to claim 6, wherein The first syntax element and the second syntax element are different syntax elements.

8. The apparatus according to claim 6, wherein The one or more processors are further configured to: determining a value of a third syntax element indicating whether a second general constraint of the set of one or more general constraints is applicable, the second general constraint being that each sub-picture in the second plurality of pictures must contain only one slice; and Each sub-picture among the second plurality of pictures is decoded according to the value of the third syntax element.

9. The apparatus according to claim 8, wherein The one or more processors are further configured to: Based on the value of the third syntax element indicating that the second general constraint is applicable, determining that a value associated with a fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies includes only one slice, wherein the third syntax element and the fourth syntax element are different syntax elements.

10. The apparatus according to claim 6, wherein The one or more processors are further configured to: receiving a type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; as well as The at least one PH NAL unit and the at least one VCL NAL unit are decoded.

11. A non-transitory computer-readable medium storing instructions that, when executed, cause one or more processors to: determining a value of a first syntax element indicating whether a first general constraint of a set of one or more general constraints is applicable, the first general constraint being that rectangular slices are not used for a first plurality of pictures of the video data; Based on the value of the first syntax element indicating that the first general constraint is applicable, inferring a value associated with a second syntax element for the first plurality of pictures to be equal to 0, wherein a value of 0 for the second syntax element indicates that a rectangular slice is not used for each picture among the first plurality of pictures to which the picture parameter set applies; as well as The first plurality of pictures of the video data are decoded according to a value of the first syntax element and a value of the second syntax element.

12. The non-transitory computer-readable medium of claim 11, wherein: The first syntax element and the second syntax element are different syntax elements.

13. The non-transitory computer-readable medium of claim 11, wherein: The instructions further cause the one or more processors to: determining a value of a third syntax element indicating whether a second general constraint of the set of one or more general constraints is applicable, the second general constraint being that each sub-picture in the second plurality of pictures must contain only one slice; and Each sub-picture among the second plurality of pictures is decoded according to the value of the third syntax element.

14. The non-transitory computer-readable medium of claim 13, wherein: The instructions further cause the one or more processors to: Based on the value of the third syntax element indicating that the second general constraint is applicable, determining that a value associated with a fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies includes only one slice, wherein the third syntax element and the fourth syntax element are different syntax elements.

15. The non-transitory computer-readable medium of claim 11, wherein: The instructions further cause the one or more processors to: receiving a type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; as well as The at least one PH NAL unit and the at least one VCL NAL unit are decoded.

16. A device for decoding video data, the device comprising: means for determining a value of a first syntax element indicating whether a first general constraint of a set of one or more general constraints is applicable, the first general constraint being that rectangular slices are not used for a first plurality of pictures of the video data; means for inferring, based on the value of the first syntax element indicating that the first general constraint is applicable, that a value associated with a second syntax element for the first plurality of pictures is equal to 0, wherein the value of 0 for the second syntax element indicates that rectangular slices are not used for each picture in the first plurality of pictures to which the picture parameter set applies; as well as Means for decoding the first plurality of pictures of the video data according to a value of the first syntax element and a value of the second syntax element.

17. The apparatus according to claim 16, wherein The first syntax element and the second syntax element are different syntax elements.

18. The apparatus of claim 16, further comprising: means for determining a value of a third syntax element indicating whether a second general constraint of the set of one or more general constraints is applicable, the second general constraint being that each sub-picture of the second plurality of pictures must contain only one slice; and Means for decoding each sub-picture of the second plurality of pictures according to a value of the third syntax element.

19. The apparatus according to claim 18, further comprising: means for determining, based on the value of the third syntax element indicating that the second general constraint is applicable, that a value associated with a fourth syntax element indicates that each sub-picture among the second plurality of pictures to which the picture parameter set applies includes only one slice, wherein the third syntax element and the fourth syntax element are different syntax elements.

20. The apparatus of claim 16, wherein: The device further comprises: for receiving a type I bitstream, the type I bitstream comprising at least one picture header (PH) network abstraction layer (NAL) unit and at least one video coding layer (VCL) NAL unit; and Means for decoding the at least one PH NAL unit and the at least one VCL NAL unit.

Images