Parameter set signaling for video codecs

Abstract

A video codec may encode and decode, in a picture parameter set (PPS), a syntax element indicating a luma codec tree block size of a codec tree unit (CTU) of a video data picture to which the PPS applies. The video codec may further encode and decode the video data picture to which the PPS applies based on the syntax element in the PPS.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 17 / 029,550, filed on September 23, 2020, which claims the benefit of U.S. Provisional Application No. 62 / 905,235, filed on September 24, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to video encoding and video decoding. Background Art

[0004] Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones, so-called "smart phones", video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10 Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions of such standards. Video devices can more efficiently transmit, receive, encode, decode, and / or store digital video information by implementing such video coding techniques.

[0005] 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 codecs, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as codec tree units (CTUs), codec units (CUs), and / or codec 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 within 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 within 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

[0006] In general, this disclosure describes techniques for signaling information used to decode video data at the picture parameter set (PPS) level in a manner that reduces the parsing dependency between the PPS for a picture of the video data and the sequence parameter set (SPS) for the picture of the video data. These techniques can be applied to common video codec standards and other future video codec standards and can improve the performance of video codecs that parse PPS and SPS.

[0007] The PPS for a video data picture may signal certain syntax elements used to decode the picture. Such syntax elements may include brick syntax elements that may be used to decode bricks of the picture. Signaling these brick syntax elements may depend on various parameter values ​​in the PPS. However, these parameter values ​​may depend on syntax element values ​​included in the SPS for the picture.

[0008] For example, various parameter values ​​in the PPS may depend on the codec tree block size of the codec tree unit of the picture. If the syntax element indicating the codec tree block size of the codec tree unit of the picture is included only in the SPS for the picture and not in the PPS for the picture, parsing the PPS for the picture may depend on parsing the SPS for the picture.

[0009] To resolve this parsing dependency between the PPS for a picture and the SPS for the picture, the PPS may include a syntax element indicating the codec tree block size of the codec tree unit of the picture, which may have the same value as the syntax element indicating the codec tree block size of the codec tree unit of the picture in the SPS for the picture. In this way, the video encoder may be able to determine the parameter value in the PPS for the picture without relying on the syntax element indicating the codec tree block size of the codec tree unit of the picture in the SPS for the picture, thereby reducing the parsing dependency between the PPS and the SPS for the picture.

[0010] Reducing the parsing dependency between the PPS and SPS for video data pictures can improve the performance of encoding and decoding video data pictures, such as by enabling a video decoder to parse the PPS for a video data picture before parsing the SPS for the video data picture, or by enabling a video decoder to parse the PPS and SPS for a video data picture substantially in parallel, thereby increasing the flexibility of the video decoder in parsing the PPS and SPS for the video data picture and decoding the video data picture.

[0011] In one example, a method for encoding and decoding video data includes encoding and decoding, in a picture parameter set (PPS), a syntax element indicating a luma codec tree block size of a codec tree unit (CTU) of a video data picture to which the PPS applies. The method also includes encoding and decoding the video data picture to which the PPS applies based on the syntax element in the PPS.

[0012] In another example, a device for encoding and decoding video data includes a memory configured to store the video data. The device further includes one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: encode and decode a syntax element in a picture parameter set (PPS) indicating a luma codec tree block size of a codec tree unit (CTU) of a video data picture to which the PPS applies; and encode and decode the video data picture to which the PPS applies based on the syntax element in the PPS.

[0013] In another example, an apparatus for video encoding and decoding includes: a component for encoding and decoding, in a picture parameter set (PPS), a syntax element indicating a luma codec tree block size of a codec tree unit (CTU) of a video data picture to which the PPS applies; and a component for encoding and decoding the video data picture to which the PPS applies based on the syntax element in the PPS.

[0014] In another example, a non-transitory computer-readable storage medium is encoded with instructions that, when executed, cause one or more processors to: encode a syntax element in a picture parameter set (PPS) that indicates a luma codec tree block size for a codec tree unit (CTU) of a video data picture to which the PPS applies; and encode and decode the video data picture to which the PPS applies based on the syntax element in the PPS.

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

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

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

[0018] Figure 3 is a conceptual diagram illustrating an example sub-picture layout according to aspects of the present disclosure.

[0019] Figure 4Description from Figure 3 Extract sub-images from the example images.

[0020] Figure 5 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0021] Figure 6 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0022] Figure 7 is a flowchart illustrating an example method for encoding a current block according to the techniques of this disclosure.

[0023] Figure 8 is a flowchart illustrating an example method for decoding a current block according to the techniques of this disclosure.

[0024] Figure 9 is a flow chart illustrating an example technique for signaling parameters of a picture parameter set (PPS) in a manner that reduces parsing dependencies on a sequence parameter set (SPS) in accordance with the techniques of this disclosure. DETAILED DESCRIPTION

[0025] In general, this disclosure describes techniques for signaling information used to decode video data at the picture parameter set (PPS) level in a manner that reduces the dependency between the PPS for a picture of the video data and the sequence parameter set (SPS) for the picture of the video data. As part of encoding the video data, a video encoder may generate parameter sets, such as the PPS and the SPS, for use in decoding the pictures of the video data. The PPS may contain information, such as syntax elements, that applies to a single picture of the video data. The SPS may contain information, such as syntax elements, that applies to all pictures in a picture sequence of the video data and that does not change between pictures within the picture sequence.

[0026] When encoding and decoding a PPS applicable to a picture of video data, a parse dependency may exist between the PPS applicable to the picture and the SPS applicable to the picture, such that parameter values ​​in the PPS may depend on one or more parameter values ​​in the SPS. For example, the PPS may include a conditional statement that is conditional on a variable value. If the variable value depends on a parameter value specified in the SPS, then a parse dependency exists between the PPS and the SPS. When such a parse dependency exists between the PPS for a picture and the SPS for the picture, a video codec (e.g., a video encoder or a video decoder) may not be able to determine the parameter values ​​in the PPS until the video codec has determined one or more parameter values ​​in the SPS on which the parameter values ​​in the PPS depend.

[0027] This parsing dependency may negatively impact the performance of a computer that parses the PPS and SPS, such as preventing a video decoder from parsing the PPS for a video data picture before parsing the SPS for the video data picture and / or preventing a video decoder from parsing the PPS and SPS substantially in parallel, thereby potentially increasing the amount of processing cycles and / or time required to parse the PPS and SPS for a video data picture and potentially degrading the performance of a video codec that parses the PPS and SPS.

[0028] Aspects of the present disclosure include techniques for reducing dependencies between a PPS for a picture of video data and a sequence parameter set (SPS) for the picture of video data. For example, if a variable value in the PPS depends on a parameter value specified in the SPS, the video encoder can encode the parameter value in the PPS that the variable value in the PPS depends on. In another example, if the PPS includes a conditional statement that depends on a variable value in the PPS, and if the variable value depends on the parameter value specified in the SPS, the video encoder can avoid encoding the conditional statement in the PPS, thereby removing the conditional statement from the PPS. These and other techniques are further described below.

[0029] Figure 1 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of the present disclosure. The techniques of the present disclosure are generally directed to encoding and decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data can include original unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0030] like Figure 1 As 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 may include any of a wide range 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 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0031] exist Figure 1In 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, a memory 120, and a display device 118. According to the present disclosure, the video decoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply a technique for signaling PPS parameters in a manner that reduces the reliance on parsing of the SPS. 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 interface with an external display device rather than including an integrated display device.

[0032] like Figure 1 The illustrated system 100 is merely an example. In general, any digital video encoding and / or decoding device can implement techniques for signaling PPS parameters in a manner that reduces reliance on parsing of the SPS. Source device 102 and destination device 116 are merely examples of codec devices, wherein source device 102 generates encoded and decoded video data for transmission to destination device 116. This disclosure refers to a "codec" device as a device that performs encoding and decoding (encoding and / or coding) of data. Thus, video encoder 200 and video decoder 300 represent examples of codec 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 of source device 102 and destination device 116 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.

[0033] Generally, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a continuous sequence of pictures (also referred to as "frames") of video data to video encoder 200, which encodes the picture data. Video source 104 of source device 102 may include a video capture device such as a camera, a video archive containing previously captured raw video, and / or a video feed interface that receives 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 codec order for encoding and decoding. Video encoder 200 may generate a bitstream including the encoded video data. Source device 102 may then output the encoded video data to computer-readable medium 110 via output interface 108 for receipt and / or retrieval, for example, via input interface 122 of destination device 116.

[0034] 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 raw decoded video data from video decoder 300. Additionally or alternatively, memories 106 and 120 can store software instructions, e.g., executable by 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 to achieve functionally similar or equivalent purposes. Furthermore, memories 106 and 120 can store, 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., to store raw decoded and / or encoded video data.

[0035] The computer-readable medium 110 can represent any type of medium or device capable of transmitting encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium for enabling the source device 102 to transmit the encoded video data directly to the destination device 116 in real time, for example, via a radio frequency (RF) network or a computer-based network. The output interface 108 can modulate a transmit signal comprising the encoded video data and the input interface 122 can demodulate a received transmit signal according to 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 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 facilitates communication from the source device 102 to the destination device 116.

[0036] 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 for storing encoded video data, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium.

[0037] In some examples, source device 102 may output the encoded video data to 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.

[0038] The file server 114 may be any type of server device capable of storing encoded video data and transmitting the encoded video data to the destination device 116. The file server 114 may represent a network server (e.g., for a website), a server configured to provide file transfer protocol services (such as the File Transfer Protocol (FTP) or the File Delivery over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. Additionally or alternatively, the file server 114 may implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0039] 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 encoded video data stored on server 114. Input interface 122 may be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from file server 114, or other such protocols for retrieving media data.

[0040] 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 a cellular communication standard such as IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee TM ), Bluetooth TMThe source device 102 and / or the destination device 116 may include corresponding system-on-chip (SoC) devices. For example, the source device 102 may include a SoC device to perform the functions attributed to the video encoder 200 and / or the output interface 108, and the destination device 116 may include a SoC device to perform the functions attributed to the video decoder 300 and / or the input interface 122.

[0041] The techniques of the present disclosure may be applied to video encoding and 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 such as Dynamic Adaptive Streaming over HTTP (DASH), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0042] The input interface 122 of the destination device 116 receives an encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 and also used by the video decoder 300, such as syntax elements with values ​​describing characteristics and / or processing of video blocks or other codec units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to a user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0043] Despite Figure 1 Although not shown, in some examples, the video encoder 200 and the video decoder 300 may each be integrated with an audio encoder and / or an audio decoder and may include appropriate MUX-DEMUX units or other hardware and / or software to process a multiplexed stream including both audio and video in a common data stream. If applicable, the MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0044] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is partially implemented in software, the device may store instructions for the software in a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, any of which can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. A device including the video encoder 200 and / or the video decoder 300 may include an integrated circuit, a microprocessor, and / or a wireless communication device (such as a cellular phone).

[0045] The video encoder 200 and the video decoder 300 may operate in accordance with a video codec standard such as ITU-T H.265 (also known as High Efficiency Video Codec (HEVC)) or an extension thereof, such as a multi-view and / or scalable video codec 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 Codec (VVC)). A draft of the VVC standard is described in Bross et al., “Versatile Video Coding” (Draft 10), Joint Video Experts Team (JVET) of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 18th Meeting, Geneva, Switzerland, June 22-July 1, 2020, JVET-S2001-vA (hereinafter referred to as “VVC Draft 10”). However, the technology of the present disclosure is not limited to any specific codec standard.

[0046] Typically, the video encoder 200 and the video decoder 300 can perform block-based picture encoding and decoding. The term "block" generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block can include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, the video encoder 200 and the video decoder 300 can encode and decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, the video encoder 200 and the video decoder 300 can encode and decode luminance and chrominance components instead of encoding and decoding red, green, and blue (RGB) data of samples of a picture, where the chrominance components can include both a red chrominance component and a blue chrominance component. In some examples, the video encoder 200 converts received RGB formatted data into a YUV representation before encoding, and the video decoder 300 converts the YUV representation into an RGB format. Alternatively, pre-processing and post-processing units (not shown) can perform these conversions.

[0047] The present disclosure may generally refer to the encoding and decoding of a picture (e.g., encoding and decoding) to include the process of encoding or decoding the data of the picture. Similarly, the present disclosure may refer to the encoding and decoding of a block of a picture to include the process of encoding or decoding the data of the block, for example, prediction and / or residual encoding and decoding. A coded video bitstream typically includes a series of values ​​of syntax elements used to represent codec decisions (e.g., codec mode) and the partitioning of the picture into blocks. Therefore, references to encoding and decoding a picture or block should generally be understood to refer to encoding and decoding the values ​​of the syntax elements that form the picture or block.

[0048] HEVC defines various blocks, including codec units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video codec (such as the video encoder 200) partitions a codec tree unit (CTU) into CUs according to a quadtree structure. That is, the video encoder partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node," and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video codec may further partition the PUs and TUs. For example, in HEVC, the residual quadtree (RQT) represents the partitioning of the TU. In HEVC, PU represents inter-frame prediction data, and TU represents residual data. The intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0049] As another example, the video encoder 200 and the video decoder 300 can be configured to operate according to VVC. According to VVC, a video codec (such as the video encoder 200) partitions a picture into multiple codec tree units (CTUs). The video encoder 200 can partition the CTU according to a tree structure (such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the separation between CU, PU, ​​and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to the codec units (CUs).

[0050] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also known as ternary tree (TT)) partitioning. A ternary tree or ternary tree partitioning is a partitioning that splits a block into three sub-blocks. In some examples, a ternary tree or ternary tree partitioning divides a block into three sub-blocks without dividing the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0051] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma and chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for corresponding chroma components).

[0052] The video encoder 200 and the video decoder 300 can be configured to use per-HEVC quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures. For purposes of explanation, the description of the technology of the present disclosure is presented with respect to QTBT segmentation. However, it should be understood that the technology of the present disclosure is also applicable to video codecs configured to use quadtree segmentation or other types of segmentation.

[0053] In some examples, a CTU includes a codec 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 monochrome picture or a picture coded and decoded using three independent color planes and syntax structures for codec samples. A CTB can be an NxN block of samples for some value of N, such that the division of components into CTBs is a partitioning. A component is an array or a single sample from one of the three arrays (luma and two chroma) that makes up a picture in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array that makes up a picture in monochrome format. In some examples, a codec block is an MxN block of samples for some values ​​of M and N, such that the division of a CTB into codec blocks is a partitioning.

[0054] Blocks (e.g., CTUs or CUs) can be grouped in various ways within a picture. As an example, a tile can refer to a rectangular area of ​​a CTU row within a particular slice in a picture. A slice can be a rectangular area of ​​a CTU within a particular slice column and a particular slice row in a picture. A slice column refers to a rectangular area of ​​a CTU with a height equal to the picture height and a width specified by a syntax element (e.g., 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 (e.g., such as in a picture parameter set) and a width equal to the picture width.

[0055] In some examples, a slice may be partitioned into multiple bricks, each of which may include one or more CTU rows within the slice. A slice that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a proper subset of a slice may not be referred to as a slice.

[0056] Tiles in a picture can also be arranged into slices. A slice can be an integer number of tiles of a picture that can be contained exclusively in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes a contiguous sequence of complete tiles of multiple complete slices or just one slice.

[0057] This disclosure may use "N×N" and "N by N" interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, for example, 16×16 samples or 16 by 16 samples. Typically, a 16×16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Likewise, an N×N 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 N×M samples, where M is not necessarily equal to N.

[0058] The video encoder 200 encodes the video data of the CU for representing prediction and / or residual information and other information. The prediction information indicates how the CU is to be predicted 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.

[0059] 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 from data of a previously coded picture, while intra-frame prediction typically refers to predicting a CU from previously coded data of the same picture. To perform inter-frame prediction, the video encoder 200 may use one or more motion vectors to generate a prediction block. The video encoder 200 may typically perform a motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), or other such difference calculations to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 may use unidirectional prediction or bidirectional prediction to predict the current CU.

[0060] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0061] To perform intra prediction, the video encoder 200 can select an intra prediction mode to generate a prediction block. Some examples of VVC provide sixty-seven intra prediction modes, including various directional modes as well as planar mode and DC mode. Typically, the video encoder 200 selects an intra prediction mode that describes the neighboring samples of the current block (e.g., the block of the CU) from which to predict the samples of the current block. Assuming that the video encoder 200 encodes and decodes CTUs and CUs in raster scan order (from left to right, from top to bottom), such samples can typically be above, above left, or to the left of the current block in the same picture as the current block.

[0062] The video encoder 200 encodes data indicating the prediction mode for the current block. For example, for inter-frame prediction mode, the video encoder 200 may encode data indicating which of various available inter-frame prediction modes to use, as well as motion information for the corresponding mode. For example, for unidirectional or bidirectional inter-frame 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.

[0063] After a prediction, such as intra-frame prediction or inter-frame prediction, of a block, the video encoder 200 may calculate residual data for the block. The residual data, such as a residual block, represents the sample-by-sample difference between the block and a predicted block for the block formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to generate 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 secondary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc., after a primary transform. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0064] As described above, after any transforms used to generate transform coefficients, the video encoder 200 can perform quantization of the transform coefficients. Quantization generally refers to the process of quantizing transform coefficients to potentially reduce the amount of data used to represent the coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 can reduce the bit depth associated with some or all coefficients. For example, the video encoder 200 can round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 can perform a bit-by-bit right shift on the value to be quantized.

[0065] 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 transform coefficients with higher energy (and therefore lower frequency) at the front of the vector and transform coefficients with lower energy (and therefore higher frequency) at the back of the vector. In some examples, the video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce a serialized vector and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode the value of a syntax element that describes metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0066] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. The context may relate to, for example, whether the neighboring values ​​of the symbol are zero. The probability determination may be based on the context assigned to the symbol.

[0067] The video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, to the video decoder 300, such as 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 similarly decode such syntax data to determine how to decode the corresponding video data.

[0068] In this way, the video encoder 200 can generate a bitstream that includes encoded video data, such as syntax elements describing how to partition a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Ultimately, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0069] The bitstream may include a network abstraction layer (NAL) unit. A NAL unit is a syntactic structure that includes an indication of the data type in the NAL unit and bytes containing the data, in the form of a raw byte sequence payload (RBSP) interspersed with emulation prevention bits as necessary. Each NAL unit may include a NAL unit header and may encapsulate an RBSP. The NAL unit header may include a syntax element indicating a NAL unit type code. The NAL unit type code specified by the NAL unit header of the NAL unit indicates the type of the NAL unit. The RBSP may be a syntactic structure that includes an integer number of bytes encapsulated within the NAL unit. In some instances, the RBSP includes zero bits.

[0070] As described above, a bitstream may include representations of coded pictures of video data and associated data. Associated data may include parameter sets. NAL units may encapsulate RBSPs for video parameter sets (VPSs), sequence parameter sets (SPSs), and picture parameter sets (PPSs). A VPS is a syntax structure that includes syntax elements applicable to zero or more complete coded video sequences (CVSs). An SPS is also a syntax structure that includes syntax elements applicable to zero or more complete CVSs. An SPS may include syntax elements that identify the VPS that is active when the SPS is active. Therefore, the syntax elements of a VPS may be more generally applicable than the syntax elements of an SPS. A PPS is a syntax structure that includes syntax elements applicable to zero or more coded pictures. A PPS may include syntax elements that identify the SPS that is active when the PPS is active. The slice header of a slice may include syntax elements that indicate the PPS that is active when the slice is being coded.

[0071] Generally, the video decoder 300 performs a process that is the inverse of the process 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 the syntax elements of the bitstream in a manner substantially similar to (albeit reversed from) the CABAC encoding process of the video encoder 200. The syntax elements can define partitioning information for partitioning a picture into CTUs and partitioning each CTU according to a corresponding partitioning structure, such as a QTBT structure, to define CUs of the CTU. The syntax elements can further define prediction and residual information for a block (e.g., a CU) of video data.

[0072] The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra-frame or inter-frame prediction) and associated prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along block boundaries.

[0073] According to the technology of the present disclosure, a video codec (e.g., video encoder 200 or video decoder 300) may encode and decode a syntax element in a PPS indicating the luma codec tree block size of a video data picture to which the PPS applies, and may encode and decode the video data picture to which the PPS applies based on the syntax element in the PPS.

[0074] The present disclosure may generally refer to "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to the communication of the values ​​of syntax elements and / or other data used to decode the encoded video data. That is, the video encoder 200 may signal the values ​​of syntax elements in the bitstream. Generally, signaling refers to generating values ​​in the bitstream. As described above, the source device 102 may transmit the bitstream to the destination device 116 in substantially real time, or may transmit the bitstream to the destination device 116 in non-real time, such as may occur when storing syntax elements to the storage device 112 for later retrieval by the destination device 116.

[0075] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure 130 and a corresponding codec tree unit (CTU) 132. Solid lines represent quadtree splits, and dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where in this example, 0 indicates a horizontal split and 1 indicates a vertical split. For a quadtree split, there is no need to indicate the split type because the quadtree node splits the block horizontally and vertically into 4 equally sized sub-blocks. Thus, the video encoder 200 can encode, and the video decoder 300 can decode, syntax elements (such as split information) for the region tree level (i.e., solid lines) of the QTBT structure 130 and syntax elements (such as split information) for the prediction tree level (i.e., dashed lines) of the QTBT structure 130. The video encoder 200 can encode video data (such as prediction and transformation data) of the CU represented by the terminal leaf node of the QTBT structure 130, and the video decoder 300 can decode video data (such as prediction and transformation data) of the CU represented by the terminal leaf node of the QTBT structure 130.

[0076] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes of the first and second levels of the QTBT structure 130. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, indicating the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, indicating the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, indicating the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, indicating the minimum allowed binary tree leaf node size).

[0077] The root node of the QTBT structure corresponding to the CTU can have four child nodes at the first level of the QTBT structure, each of which can be split according to the quadtree partitioning. That is, the nodes at the first level are leaf nodes (no child nodes) or have four child nodes. The example of the QTBT structure 130 represents such nodes as including a parent node and child nodes with solid branches. If the nodes at the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), they can be further split by the corresponding binary tree. The binary tree splitting of a node can be iterated until the node resulting from the split reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such nodes as having dotted branches. The binary tree leaf nodes are called coding units (CUs), which are used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without any further partitioning. As discussed above, CUs can also be referred to as "video blocks" or "blocks."

[0078] In one example of a QTBT partitioning structure, the CTU size is set to 128×128 (a luma sample and two corresponding 64×64 chroma samples), MinQTSize is set to 16×16, MaxBTSize is set to 64×64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate quadtree leaf nodes. Quadtree leaf nodes can have sizes from 16×16 (i.e., MinQTSize) to 128×128 (i.e., the CTU size). If the quadtree leaf node is 128×128, it will not be further split by the binary tree because the size exceeds MaxBTSize (i.e., 64×64 in this example). Otherwise, the quadtree leaf node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node of the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), further splitting is not allowed. When a binary tree node has a width equal to MinBTSize (4 in this example), it means that no further vertical splitting (i.e., division by width) is allowed. Similarly, a binary tree node having a height equal to MinBTSize means that no further horizontal splitting (i.e., division by height) is allowed for the binary tree node. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further segmentation.

[0079] This document discloses a signaling technique for reducing parsing dependencies between parameter sets. The signaling technique disclosed herein can be applied to the Versatile Video Codec (VVC) standard and other future video codec standards.

[0080] Video codec standards include ITU-T H.261, ISO / IEC MPEG-1 Visual, ITU-T H.262 or ISO / IEC MPEG-2 Visual, ITU-T H.263, ISO / IEC MPEG-4 Visual, and ITU-T H.264 (also known as ISO / IEC MPEG-4 AVC), including its Scalable Video Codec (SVC) and Multi-view Video Codec (MVC) extensions. Furthermore, a new video codec standard, High Efficiency Video Codec (HEVC) or ITU-T H.265, including its Range and Screen Content Codec extensions, 3D Video Codec (3D-HEVC), Multi-view Extension (MV-HEVC), and Scalable Extension (SHVC), has recently been developed by the Joint Collaborative Team on Video Coding (JCT-VC) and the Joint Collaborative Team on 3D Video Codec Extension Development (JCT-3V) of the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Moving Picture Experts Group (MPEG).

[0081] In 2016, MPEG and ITU-T VCEG established the Joint Exploratory Video Team (JVET) to explore and develop new video coding tools for the next generation video codec standard VVC. Draft 6 of the VCC standard is described in Bross et al. "Versatile Video Codec (Draft 6)", Joint Video Experts Group (JVET) of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 15th Meeting: Gothenburg, Sweden, July 3-12, 2019, JVET-O2001 (hereinafter referred to as "VCC Draft 6"). The reference software is called the VVC Test Model (VTM). The portion of the VVC Draft 6 that can be improved in the present disclosure is shown in Table 1 below. The video encoder 200 can generate the parameters listed below and the video decoder 300 can decode the parameters to determine how to decode the corresponding video data.

[0082]

[0083]

[0084] Table 1

[0085] As shown in Table 1, the PPS may iterate over slices of a picture to signal syntax elements that signal information about bricks in the slices of the picture. For example, the PPS may signal whether a slice is split into two or more bricks by including a brick syntax element brick_split_flag[i] that indicates whether the i-th slice is split into two or more bricks. The video decoder 300 may be able to infer the value of the brick syntax element brick_split_flag[i] for the i-th slice and other brick information for the i-th slice based at least in part on the value of the derived parameter RowHeight[i], which indicates the row height of the i-th slice. If the row height of the i-th slice is not greater than 1, the video decoder 300 may infer that the value of brick_split_flag[i] is 0, thereby indicating that the i-th slice is not split into two or more bricks. If the row height of the i-th slice is greater than 1, the PPS may instead explicitly signal the brick syntax element brick_split_flag[i].

[0086] In addition, if brick_split_flag[i] is equal to 1, the PPS may also signal that the horizontal brick boundaries of two or more bricks are uniformly distributed across the slice by including a brick syntax element uniform_brick_spacing_flag[i] that indicates whether the bricks in the i-th slice are uniformly distributed across the slice. Similarly, the video decoder 300 may be able to infer the value of the brick syntax element uniform_brick_spacing_flag[i] for the i-th slice based at least in part on the value of the derived parameter RowHeight[i]. If the row height of the i-th slice is not greater than 2, the video codec may avoid signaling uniform_brick_spacing_flag[i] and may instead infer that uniform_brick_spacing_flag[i] is equal to 1. If the row height of the i-th slice is greater than 2, the PPS may instead explicitly signal the brick syntax element uniform_brick_spacing_flag[i].

[0087] As described above, resolving dependencies between an SPS and a PPS referenced by a video data picture may cause a video codec (e.g., video encoder 200 or video decoder 300) to be unable to determine certain parameter values ​​in the PPS until the video encoder has parsed at least a portion of the SPS.

[0088] When decoding a PPS referenced by a video data picture, the video decoder 300 can use the number of slices in the picture to iterate through the slices of the picture in order to decode various parameters of the slices in the picture. Specifically, the PPS can include a conditional loop having a condition based at least in part on the number of slices in the video data picture. When decoding the PPS, the video decoder 300 can also determine the height of the slice row in the picture in units of CTBs to determine whether the values ​​of certain brick syntax elements are signaled in the PPS or whether the video decoder 300 should infer the values ​​of these syntax elements.

[0089] As part of parsing the PPS, the video decoder 300 may determine values ​​for the parameters NumTilesInPic and RowHeight[i], as shown in the PPS portion of Table 1, where the value of the parameter NumTilesInPic corresponds to the number of slices in the picture, and the value of the parameter RowHeight[i] corresponds to the height of the i-th slice row in units of CTBs. The video decoder 300 may derive the values ​​for the parameters NumTilesInPic and RowHeight[i] based at least in part on the picture width and picture height. However, if the values ​​for the picture width and picture height are signaled in the SPS, such as via signaling the syntax elements pic_width_in_luma_samples and pic_height_in_luma_samples in the SPS rather than in the PPS, then determining the values ​​for the parameters NumTilesInPic and RowHeight[i] may rely on parsing the SPS to determine the values ​​for the syntax elements pic_width_in_luma_samples and pic_height_in_luma_samples.

[0090] In the example of Table 1, as part of the reference picture resampling (RPR) adoption, the syntax element pic_width_in_luma_samples and the syntax element pic_height_in_luma_samples have been moved from the SPS to the PPS. Therefore, the values ​​of the parameter NumTilesInPic and the parameter RowHeight[i] in the PPS do not depend on the values ​​of the syntax elements pic_width_in_luma_samples and pic_height_in_luma_samples in the SPS.

[0091] However, the values ​​of the parameters NumTilesInPic and RowHeight[i] may be determined by SPS signaling. Specifically, in addition to the values ​​of the syntax elements pic_width_in_luma_samples and pic_height_in_luma_samples, the values ​​of the parameters NumTilesInPic and RowHeight[i] may also depend on the syntax element log2_ctu_size_minus5 indicating the encoding and decoding of the tree block, which is notified by SPS signaling but not by PPS signaling.

[0092] Therefore, because the value of RowHeight[i] may not be derived at the PPS level due to parsing dependency issues with the SPS, various aspects of the present disclosure describe techniques for signaling syntax elements in the PPS in a manner that resolves such parsing dependency to derive the value of the parameter RowHeight[i].

[0093] In the example of Table 1 above, the PSS portion in the example of Table 1 includes a syntax element num_tiles_in_pic_minus1 indicating the number of slices in the picture referencing the PPS. Therefore, the video decoder 300 may be able to decode the syntax element num_tiles_in_pic_minus1 in the PPS to determine the value of NumTilesInPic corresponding to the number of slices in the picture.

[0094] However, while signaling the syntax element num_tiles_in_pic_minus1 in the PPS can resolve the parsed dependency of the PPS on the SPS to derive the value of NumTilesInPic, signaling the syntax element num_tiles_in_pic_minus1 in the PPS does not resolve the parsed dependency on the SPS to determine the value of the parameter RowHeight[i]. Furthermore, including a syntax element such as num_tiles_in_pic_minus1 indicating the number of slices in a picture can increase the size of the PPS by 33 bits in the worst case, such as in the case of 8K content, e.g., 8192 x 4320 and CtbSize = 32. Thus, not including the syntax element indicating the number of slices in a picture can potentially reduce the size of the PPS by as much as 33 bits.

[0095] However, if the PPS does not include a syntax element indicating the number of slices in a picture, such as the syntax element num_tiles_in_pic_minus1, the video decoder 300 may not be able to determine the number of slices in the picture based on information contained in the PPS, and such an omission may reintroduce a parsing dependency between the PPS and the SPS because the video codec may not be able to infer the number of slices in the picture until the video codec parses the syntax element indicating the size of the codec treeblock in the SPS.

[0096] In another example, as part of parsing a PPS referenced by a picture of video data, the video decoder 300 may parse a conditional statement to determine whether to decode a brick syntax element indicating information about bricks in the picture or whether to infer such information about bricks in the picture. For example, for the i-th slice in the picture, the PPS may signal a syntax element brick_split_flag[i] indicating whether the slice is divided into two or more bricks only if the value of the parameter RowHeight[i] indicating the height of the i-th slice row in units of CTBs is greater than 1. If the value of RowHeight[i] is greater than 1, the video decoder 300 may be able to decode the syntax element brick_split_flag[i] to determine whether the slice is divided into two or more bricks. On the other hand, if the value of RowHeight[i] is not greater than 1, the video decoder 300 may alternatively infer that the slice is not divided into two or more bricks based on the value of RowHeight[i] being not greater than 1.

[0097] Similarly, for the i-th slice in a picture, where the slice is divided into two or more bricks, the PPS may signal a syntax element uniform_brick_spacing_flag[i] indicating whether the horizontal brick boundaries of the two or more bricks are uniformly distributed across the slice only if the value of the parameter RowHeight[i] indicating the height of the i-th slice row in units of CTBs is greater than 2. If the value of RowHeight[i] is greater than 2, the video decoder 300 may be able to decode the syntax element uniform_brick_spacing_flag[i] to determine whether the horizontal brick boundaries of the two or more bricks in the slice are uniformly distributed across the slice. On the other hand, if the value of RowHeight[i] is not greater than 2, the video decoder 300 may instead infer that the horizontal brick boundaries of the two or more bricks in the slice are uniformly distributed across the slice based on the value of RowHeight[i] being not greater than 2.

[0098] As described above, determining the height of a slice row for a video data picture may introduce a parsing dependency between the PPS and the SPS, both of which apply to the video data picture and the SPS. Specifically, the value of the parameter RowHeight[i], which is the height in CTBs of the slice row for the i-th slice in the picture, may depend on information in the SPS. That is, when parsing the PPS, the video decoder 300 may not be able to determine the value of the parameter RowHeight[i] based solely on information decoded from the PPS, but may instead need to determine the value of the parameter RowHeight[i] based on information decoded from the SPS. Therefore, when parsing the PPS, the video decoder 300 may not be able to determine the value of the parameter RowHeight[i] for the i-th slice of the picture independently of parsing the SPS and evaluate conditional statements that depend on the value of RowHeight[i].

[0099] The video decoder 300 may be able to derive both the number of slices in a picture and the height of slice rows for slices of the picture in units of CTBs based at least in part on the codec treeblock size of the picture. Thus, if the PPS includes a value indicating the codec treeblock size for a picture, the video decoder 300 may be able to derive both the number of slices in a picture and the height of slice rows for slices of the picture in units of CTBs (e.g., RowHeight[i]) without requiring a parsing dependency on the SPS and without requiring the PPS to explicitly signal a syntax element indicating the number of slices in the picture. Because signaling the codec treeblock size for a picture may require only 2 additional bits when compared to up to 33 bits that may be required to signal the number of slices in the picture, including a syntax element indicating the codec treeblock size for a picture in the PPS may reduce the size of the PPS.

[0100] According to aspects of the present disclosure, the signaling of the syntax element num_tiles_in_pic_minus1 is removed from the PPS, which instead signals information about the codec tree block size (CtbSize). Specifically, pps_log2_ctu_size_minus5 may be required in the PPS along with pic_width_in_luma_samples and pic_height_in_luma_samples to derive the values ​​of PicWidthInCtbsY and PicHeightInCtbsY, which can infer the values ​​of NumTilesInPic and RowHeight[i]. Furthermore, the signaling of pps_log2_ctu_size_minus5 may require 2 additional bits, but in the worst case for 8K content, such as 8192x 4320 and codec tree block size (CtbSize) = 32, removing the syntax element num_tiles_in_pic_minus1 may save up to 33 bits.

[0101] That is, according to various aspects of the present disclosure, to reduce the parsing dependency between the PPS and the SPS, instead of including a syntax element indicating the number of slices in a picture in a PPS referenced by a video data picture, the PPS referenced by the picture may instead include a syntax element indicating the codec tree block size for the picture. The video decoder 300 may decode the syntax element to determine the value of the codec tree block size for the picture, and may derive the number of slices in the picture and the height of a slice row for a slice of the picture in units of CTBs (e.g., RowHeight[i]) based on the value of the codec tree block size for the picture.

[0102] The PPS for a picture may include a syntax element indicating the number of slices in the picture, which may be a syntax element pps_log2_ctu_size_minus5, which specifies the luma codec treeblock size for each CTU in the picture minus 5. Specifically, the syntax element pps_log_2_ctu_size_minus5 may have the same value as the syntax element log2_ctu_size_minus5 in the SPS for the picture. Thus, the video encoder may determine the codec treeblock size (CtbSize) from the syntax element pps_log2_ctu_size_minus5 by adding 5 to the value of the syntax element pps_log2_ctu_size_minus5 and left-shifting the resulting sum by 1, such that CtbSize = 1 << (pps_log2_ctu_size_minus5 + 5). In the PPS for a picture, by signaling a syntax element pps_log_2_ctu_size_minus5 having the same value as the syntax element log2_ctu_size_minus5 in the SPS for the picture, the present disclosure removes the parsing dependency between the PPS and the SPS to determine the values ​​of the parameters NumTilesInPic and RowHeight[i], because these parameter values ​​can be derived from the syntax element pps_log_2_ctu_size_minus5 in the PPS instead of from the syntax element log_2_ctu_size_minus5 in the SPS.

[0103] The syntax changes for VVC draft 6 version 14 are described in Table 2, where <delete>< / delete> The content between <add>< / add> The content between them is added to the grammar.

[0104]

[0105]

[0106]

[0107]

[0108]

[0109] Table 2

[0110] As shown in Table 2, a video codec (e.g., video encoder 200 or video decoder 300) may encode or decode a syntax element pps_log2_ctu_size_minus5 in the PPS, indicating the luma codec treeblock size of the video data picture to which the PPS applies, wherein the syntax element pps_log2_ctu_size_minus5 has the same value as the syntax element log2_ctu_size_minus5 in the SPS. That is, the video encoder 200 may encode the syntax element pps_log2_ctu_size_minus5 in the PPS, and the video decoder 300 may decode the syntax element pps_log2_ctu_size_minus5.

[0111] The video decoder 300 may determine the luma codec treeblock size of a picture based on the syntax element pps_log2_ctu_size_minus5 in the PPS. Because the syntax element pps_log2_ctu_size_minus5 indicates the log2 luma codec treeblock size of a CTU in the picture minus 5, the video decoder 300 may determine the luma codec treeblock size CtbSize of the CTU in the picture by adding 5 to the value of the syntax element pps_log2_ctu_size_minus5 and shifting the resulting sum left by 1, such as CtbSize = 1 << (pps_log2_ctu_size_minus5 + 5).

[0112] The video codec may also encode and decode a conditional loop in the PPS that has a condition based at least in part on the number of slices in the video data picture. For example, the video encoder 200 may encode and decode a conditional loop in the PPS that is based at least in part on a variable NumTilesInPic corresponding to the number of slices in the video data picture for (i=0; brick_splitting_present_flag && i<=NumTilesInPic+1; i++), and the video decoder 300 may decode the conditional loop in the PPS.

[0113] When the video decoder 300 decodes a conditional loop having a condition based at least in part on the variable NumTilesInPic corresponding to the number of slices in a video data picture in a PPS, the video decoder 300 may determine the value of the variable NumTilesInPic in order to evaluate the condition i <= NumTilesInPic + 1. As discussed above, the video decoder 300 may determine the value of the variable NumTilesInPic based at least in part on the picture width in luma samples (as indicated by the syntax element pic_width_in_luma_samples), the picture height in luma samples (as indicated by the syntax element pic_height_in_luma_samples), and the luma codec tree block size CtbSize of the CTU in the picture (as derived from the syntax element pps_log2_ctu_size_minus5). Therefore, once the value of the variable NumTilesInPic is determined, the video encoder 200 may iterate the conditional loop based at least in part on the value of the variable NulTiles.

[0114] As described above, because the video decoder 300 may be able to determine the number of slices in a video data picture without requiring the PPS to include a syntax element indicating the number of slices in the picture, the video codec may avoid encoding and decoding the syntax element indicating the number of slices in the picture in the PPS. That is, the video encoder 200 may avoid encoding the syntax element indicating the number of slices in the picture in the PPS, and the video encoder 200 may avoid decoding any syntax element indicating the number of slices in the PPS.

[0115] As shown in Table 2, the video codec may also encode and decode conditional statements in the PPS, the conditional statements having conditions based at least in part on the height of a slice row of a picture to which the PPS applies. For example, the video encoder 200 may encode in the PPS conditional statements if(RowHeight[i]>1) and if(RowHeight[i]>2) based at least in part on a variable RowHeight[i] corresponding to the height, in CTBs, of the i-th slice row of the video data picture, and the video decoder 300 may decode the conditional statements in the PPS.

[0116] When the video decoder 300 decodes a conditional statement (e.g., if(RowHeight[i]>1) and if(RowHeight[i]>2)) in the PPS that is based at least in part on a variable RowHeight corresponding to the height of the i-th slice row in units of CTBs of a video data picture, the video decoder 300 may determine the value of the variable RowHeight[i] in order to evaluate the conditions RowHeight[i]>1 and / or RowHeight[i]>2. As discussed above, the video decoder 300 may determine the value of the variable RowHeight[i] based at least in part on the luma codec tree block size CtbSize of the CTU in the picture (e.g., derived from the syntax element pps_log2_ctu_size_minus5). Thus, once the value of the variable RowHeight[i] is determined, the video decoder 300 may evaluate the conditional statement, such as by evaluating if(RowHeight[i]>1) and / or if(RowHeight[i]>2).

[0117] When the video decoder 300 decodes the conditional statement if(RowHeight[i]>1) by determining the value of the variable RowHeight[i] corresponding to the height of the i-th slice row of the video data picture in units of CTBs, the video decoder 300 may evaluate the conditional statement if(RowHeight[i]>1) to determine whether the PPS signals a syntax element brick_split_flag[i] indicating whether the i-th slice of the video data picture is divided into two or more bricks. When evaluating the conditional statement if(RowHeight[i]>1), if the video decoder 300 determines that the conditional statement evaluates to true (i.e., the value of the variable RowHeight[i] is greater than 1), the video decoder 300 may decode the syntax element brick_split_flag[i] indicating whether the i-th slice of the video data picture is divided into two or more bricks in the PPS. However, when evaluating the conditional statement if(RowHeight[i]>1), if the video decoder 300 determines that the conditional statement evaluates to false (i.e., the value of the variable RowHeight[i] is not greater than 1), the video decoder 300 may instead infer that the i-th slice of the video data picture is not divided into two or more bricks.

[0118] Similarly, when the video decoder 300 decodes the conditional statement if(RowHeight[i]>2) by determining the value of the variable RowHeight[i] corresponding to the height of the i-th slice row of the video data picture in units of CTBs, the video decoder 300 can evaluate the conditional statement if(RowHeight[i]>2) to determine whether the PPS signals the syntax element uniform_brick_spacing_flag[i], which indicates whether one or more horizontal brick boundaries are uniformly distributed across the i-th slice of the video data picture divided into two or more bricks. Upon evaluating the conditional statement if(RowHeight[i]>2), if the video decoder 300 determines that the conditional statement evaluates to true (i.e., the value of the variable RowHeight[i] is greater than 2), the video decoder 300 may decode, in the PPS, a syntax element uniform_brick_spacing_flag[i] that indicates whether one or more horizontal brick boundaries are uniformly distributed across the i-th slice of the video data picture that is partitioned into two or more bricks. However, upon evaluating the conditional statement if(RowHeight[i]>2), if the video decoder 300 determines that the conditional statement evaluates to false (i.e., the value of the variable RowHeight[i] is not greater than 2), the video decoder 300 may instead infer that one or more horizontal brick boundaries are uniformly distributed across the i-th slice of the video data picture that is partitioned into two or more bricks.

[0119] Therefore, the video codec can encode and decode the video data picture to which the PPS applies according to the syntax element pps_log2_ctu_size_minus5. That is, the video encoder 200 can encode the video data picture to which the PPS applies according to the syntax element pps_log2_ctu_size_minus5, such as by encoding the syntax element pps_log2_ctu_size_minus5 in the PPS, and the video decoder 300 can decode the video data picture to which the PPS applies according to the syntax element pps_log2_ctu_size_minus5, such as by decoding the syntax element pps_log2_ctu_size_minus5 in the PPS.

[0120] According to some aspects of the present disclosure, instead of or in addition to the codec, in the syntax element pps_log2_ctu_size_minus5 for reducing the parsing dependency between the PPS and the SPS, aspects of the present disclosure include additional techniques for reducing the parsing dependency between the PPS and the SPS.

[0121] As discussed above, a parsing dependency of PPS on SPS can be introduced by adding syntactic conditional checks for RowHeight[i] (such as conditional statements if(RowHeight[i]>1) and if(RowHeight[i]>2)) to brick_split_flag[i] and uniform_brick_spacing_flag[i], respectively. Since HLS experts agreed to remove the dependency on SPS in the PPS syntax, this issue should be resolved in the next version of the VVC specification. There are several proposed changes to address this issue:

[0122] Solution 1: The above dependency can be resolved by simply replacing the conditional checks such as if(RowHeight[i]>1) and if(RowHeight[i]>2) in a semantically correct grammar. Table 3 below describes the proposed grammar changes to VVC draft 6 version 14, where <delete>< / delete> The content between <add>< / add> The content between them is added to the grammar.

[0123]

[0124]

[0125]

[0126] Table 3

[0127] As shown in Table 3, the video encoder can eliminate the parsing dependency between the PPS and the SPS caused by deriving the value of the variable RowHeight[i] by eliminating the conditional statements with RowHeight[i] as a condition (e.g., conditional statements if(RowHeight[i]>1) and if(RowHeight[i]>2)) from the PPS. Therefore, the PPS portion in Table 3 does not include the variable RowHeight[i] or the conditional statements with RowHeight[i] as a condition. Therefore, the video encoder 200 can avoid encoding the conditional statements with RowHeight[i] as a condition in the PPS, and the video decoder 300 can avoid decoding the conditional statements with RowHeight[i] as a condition in the PPS.

[0128] Solution 2: The parsing dependency between the PPS and the SPS caused by RowHeight[i] can also be resolved by adding a new syntax element to specify the value of RowHeight[i] in the i-th slice. Specifically, the PPS can include a syntax element row_height_minus1 indicating the height of the i-th slice row of the video data picture minus 1. In addition, the conditional statements in the PPS with RowHeight[i] as a condition (such as the conditional statements if(RowHeight[i]>1) and if(RowHeight[i]>2)) are replaced with conditional statements with the syntax element row_height_minus1[i] as a condition (such as the conditional statements if(row_height_minus1[i]>0 and if(row_height_minus1[i]>1)).

[0129] Table 4 below describes the syntax changes to VVC draft 6 version 14, where <delete>< / delete> The content between <add>< / add> The content between them is added to the grammar.

[0130]

[0131]

[0132]

[0133] Table 4

[0134] As shown in Table 4, the video encoder 200 may encode, in the PPS applicable to the video data picture, a syntax element row_height_minus1 indicating the height of the i-th slice row of the video data picture minus 1. The video encoder 200 may also encode, in the PPS, the conditional statements if(row_height_minus1[i]>0) and if(row_height_minus1[i]>1) to replace the conditional statements if(RowHeight[i]>1) and if(RowHeight[i]>2)), respectively.

[0135] The video decoder 300 may decode the syntax element row_height_minus1 in the PPS to determine the height of the i-th slice row of the video data picture minus 1.

[0136] When the video decoder 300 decodes the conditional statement if(row_height_minus1[i]>0), because the video decoder has determined the height of the i-th slice row of the video data picture minus 1 from decoding the syntax element row_height_minus1 in the PPS, the video decoder 300 can evaluate the conditional statement if(row_height_minus1[i]>0) to determine whether the PPS signals the syntax element brick_split_flag[i] indicating whether the i-th slice of the video data picture is divided into two or more bricks. If the video decoder 300 determines that the conditional statement evaluates to true (i.e., the value of row_height_minus1 is greater than 0) when evaluating the conditional statement if(row_height_minus1[i]>0), the video decoder 300 can decode the syntax element brick_split_flag[i] in the PPS indicating whether the i-th slice of the video data picture is divided into two or more bricks. However, if the video decoder 300 determines that the conditional statement evaluates to false (i.e., the value of row_height_minus1[i] is not greater than 0) when evaluating the conditional statement if(row_height_minus1[i]>0), the video decoder 300 may instead infer that the i-th slice of the video data picture is not divided into two or more tiles.

[0137] Similarly, when the video decoder 300 decodes the conditional statement if(row_height_minus1[i]>1), the video decoder 300 may evaluate the conditional statement if(row_height_minus1[i]>1) to determine whether the PPS signals a syntax element uniform_brick_spacing_flag[i] indicating whether one or more horizontal brick boundaries are uniformly distributed across the i-th slice of the video data picture partitioned into two or more bricks. If the video decoder 300 determines, when evaluating the conditional statement if(row_height_minus1[i]>1), that the conditional statement evaluates to true (i.e., the value of row_height_minus1[i] is greater than 1), the video decoder 300 may decode, in the PPS, a syntax element uniform_brick_spacing_flag[i] indicating whether one or more horizontal brick boundaries are uniformly distributed across the i-th slice of the video data picture partitioned into two or more bricks. However, if the video decoder 300 determines when evaluating the conditional statement if(row_height_minus1[i]>1) that the conditional statement evaluates to false (i.e., the value of row_height_minus1[i] is not greater than 1), the video decoder 300 may instead infer that one or more horizontal tile boundaries are evenly distributed across the i-th slice of the video data picture that is partitioned into two or more tiles.

[0138] As mentioned above, in VVC draft 6, the syntax elements brick_split_flag[i] and uniform_brick_spacing[i] in PPS can be conditioned on the parameter RowHeight[i]. However, the index of the parameter RowHeight[i] for brick_split_flag[i] and uniform_brick_spacing[i] should be RowHeight[i%(num_tile_columns_minus1+1)] instead of RowHeight[i], because the index value of RowHeight is in the range of 0 to num_tile_rows_minus1, including the end value.

[0139] According to aspects of the present disclosure, the parameter RowHeight[i] can be replaced in the syntax by a new parameter TileHeight[i], where TileHeight[i] is derived as RowHeight[i%(num_tile_columns_minus1+1)] in Section 6.5.1 of VCC Draft 6 Version 14. Thus, the syntax elements brick_split_flag[i] and uniform_brick_spacing[i] in the PPS can be conditioned on the parameter TileHeight[i] instead of RowHeight[i].

[0140] Table 5 describes the syntax changes to VCC draft 6 version 14, where the following are removed from the syntax: <delete>< / delete> The content between <add>< / add> The content between them is added to the grammar.

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147] Table 5

[0148] Aspects of the present disclosure are directed to solving problems associated with sub-picture extraction. A video data picture may have one or more sub-pictures, where each sub-picture may contain one or more slices that collectively cover a rectangular area of ​​the picture, and a video codec may extract one or more sub-pictures from a video data picture. These problems with sub-picture extraction include how to extract sub-pictures from the original picture of the video data, how to design sub-picture IDs to identify which sub-pictures to extract, and how to interact between different parameter sets (e.g., PPS and SPS) and slice headers.

[0149] Figure 3 is a conceptual diagram illustrating an example sub-picture layout according to various aspects of the present disclosure. Figure 5 As shown, an example picture 150 of video data may include 4 sub-pictures: sub-picture 0, sub-picture 1, sub-picture 2, and sub-picture 3, and 6 slices: slice 0, slice 1, slice 2, slice 3, slice 4, and slice 5, wherein each sub-picture includes at least one slice. Sub-picture 0 includes slice 0 and slice 1, sub-picture 2 includes slice 3, slice 4, and slice 5. Figure 1Includes stripe 2 and stripe 3, sub-image 2 includes stripe 4, sub-image Figure 3 Includes strip 5.

[0150] To address issues related to sub-image extraction, various aspects of this disclosure propose the following techniques:

[0151] 1) Add the PPS flag num_subpicture_in_pic_minus1 to specify the number of sub-pictures extracted from the original picture. Specifically, the PPS referenced by the video data picture may include a syntax element num_subpicture_in_pic_minus1, which indicates the number of sub-pictures extracted from the picture. The value of the syntax element num_subpicture_in_pic_minus1 may be the number of sub-pictures extracted from the picture minus 1, and the value of the syntax element num_subpicture_in_pic_minus1 may be in the range of 0 to the number of sub-pictures in the picture minus 1, inclusive, to indicate the number of sub-pictures extracted from the picture.

[0152] 2) Add the PPS syntax element subpicture_id[i] to specify the subpicture ID of the extracted subpicture. Specifically, the PPS referenced by the video data picture may include the syntax element subpicture_id[i], which indicates the subpicture ID for each subpicture in the picture. The maximum value of i may be the value of the syntax element num_subpicture_in_pic_minus1. Furthermore, the value of subpicture_id[i] may be in the range of 0 to the number of subpictures in the picture minus 1, inclusive.

[0153] 3) Add a slice header syntax element slice_subpicture_id to specify the subpicture_id value of the slice in use. The value of the syntax element slice_subpicture_id may be required to be one of the values ​​of subpicture_id[i].

[0154] The SPS applicable to a video data picture may include a syntax element subpic_grid_idx[i][j] indicating the index of a sub-picture in the picture, and the SPS syntax may derive the sub-picture index for each grid from the syntax element subpic_grid_idx[i][j]. Figure 3 In the example shown, the value of subpic_grid_idx[i][j] can be in the range of 0 to 3, inclusive.

[0155] exist Figure 3In the example of FIG150, if sub-picture 1 and sub-picture 3 are to be extracted from picture 150, the recommended syntax elements num_subpicture_in_pic_minus1 and subpicture_id[i] in the PPS and the syntax element slice_subpicture_id in the slice header for picture 150 are as follows: Figure 6 The signaling notification is as shown in:

[0156]

[0157] Table 6

[0158] Figure 4 Description from Figure 3 Extract sub-images from the example image 150. Figure 4 As shown, sub-picture 1 and sub-picture 3 are extracted from picture 150. To specify that sub-picture 1 and sub-picture 3 are extracted from picture 150, the PPS applicable to picture 150 may include a syntax element num_subpicture_in_pic_minus1 having a value of 1 to indicate that two sub-pictures are extracted from picture 150. The PPS applicable to picture 150 may also include two subpicture_id[i] syntax elements indicating the two sub-pictures extracted from picture 150. Specifically, the PPS may include a syntax element subpicture_id[0] having a value of 1 to indicate that the first sub-picture extracted from picture 150 has a sub-picture ID of 1, and may include a syntax element subpicture_id[1] having a value of 3 to indicate that the second sub-picture extracted from picture 150 has a sub-picture ID of 3.

[0159] like Figure 4 As shown, sub-picture 1 includes slices 2 and 3, and sub-picture 3 includes slice 5. Therefore, the slice header for each of slices 2, 3, and 5 may include a syntax element slice_subpicture_id indicating the sub-picture to which the slice belongs. Therefore, the slice header for slice 2 and the slice header for slice 3 may each include a syntax element slice_subpicture_id having a value of 1 to indicate that slices 2 and 3 belong to sub-picture 1. Similarly, the slice header for slice 5 may include a syntax element slice_subpicture_id having a value of 3 to indicate that slice 5 belongs to sub-picture 3.

[0160] The syntax changes to VVC draft 6 version 14 are described in Table 7, where <delete>< / delete> The content between <add>< / add> The content between them is added to the grammar.

[0161]

[0162]

[0163]

[0164]

[0165] Table 7

[0166] As shown in Table 7, a video codec (e.g., video encoder 200 or video decoder 300) may encode and decode a codec syntax element num_subpicture_in_pic_minus1 indicating the number of sub-pictures in a picture to which the PPS of the video data applies in the PPS. That is, the video encoder 200 may encode the syntax element num_subpicture_in_pic_minus1 in the PPS, and the video decoder 300 may decode the syntax element num_subpicture_in_pic_minus1 in the PPS.

[0167] The video codec may also encode, in the PPS, a syntax element subpicture_id[i] indicating a subpicture ID for each subpicture in the video data picture. That is, the video encoder may encode a syntax element subpicture_id[i] indicating a subpicture ID for each subpicture in the video data picture, and the video decoder 300 may decode the syntax element subpicture_id[i] in the PPS.

[0168] The video codec may thus encode the video data picture according to the syntax element num_subpicture_in_pic_minus and the syntax element subpicture_id[1] in the PPS. The video encoder 200 may encode the video data picture according to the syntax element num_subpicture_in_pic_minus and the syntax element subpicture_id[1] in the PPS, and the video decoder 300 may decode the video data picture according to the syntax element num_subpicture_in_pic_minus and the syntax element subpicture_id[1] in the PPS.

[0169] As can be seen in Table 7, the video codec may also encode a syntax element slice_subpicture_id indicating a sub-picture ID of a slice of the video data picture in a slice header of the slice of the video data picture. That is, the video encoder 200 may encode the syntax element slice_subpicture_id in the slice header, and the video decoder 300 may decode the syntax element slice_subpicture_id in the slice header.

[0170] Figure 5 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 5 This is provided for the purpose of explanation and should not be considered as limiting the techniques as broadly exemplified and described in this disclosure. For the purpose of explanation, this disclosure describes a video encoder 200 based on techniques of VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video encoding devices configured to other video codec standards.

[0171] exist Figure 5 In the example of FIG, the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 can be implemented in one or more processors or processing circuits. For example, the units of the video encoder 200 can be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Moreover, the video encoder 200 can include additional or alternative processors or processing circuits to perform these and other functions.

[0172] 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 be used as a reference picture memory that stores reference video data for use by the video encoder 200 in prediction of 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, the video data memory 230 can be on the same chip as the other components of the video encoder 200 as shown, or off-chip relative to those components.

[0173] In this disclosure, references to video data memory 230 should not be construed as limited to memory internal to video encoder 200, unless specifically described as such, or memory external to video encoder 200, unless specifically described as such. Rather, references to video data memory 230 should be understood as references to memory storing video data received by video encoder 200 for encoding (e.g., video data for a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage of outputs from the various units of the video encoder 200 .

[0174] illustrate Figure 5 The various units of the video encoder 200 are described to help understand the operations performed by the video encoder 200. These units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. A fixed-function circuit refers to a circuit that provides a specific function and has preset operations that can be performed. A programmable circuit refers to a circuit that can be programmed to perform various tasks and provide flexible 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. A fixed-function circuit can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units may be integrated circuits.

[0175] 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 where 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 the video encoder 200, or another memory within the video encoder 200 (not shown) may store such instructions.

[0176] The video data memory 230 is configured to store received video data. The video encoder 200 may retrieve video data pictures from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be original video data to be encoded.

[0177] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units to perform video prediction according to other prediction modes. For example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, and the like.

[0178] The mode selection unit 202 typically coordinates multiple coding passes to test combinations of coding parameters and the resulting rate-distortion values ​​for such combinations. The coding parameters may include the partitioning of a CTU into CUs, the prediction mode for a CU, the transform type for the residual data of a CU, the quantization parameter for the residual data of a CU, etc. The mode selection unit 202 may ultimately select a combination of coding parameters that has a better rate-distortion value than other tested combinations.

[0179] The video encoder 200 may partition a picture retrieved 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 partition the CTUs of the picture according to a tree structure, such as the QTBT structure described above or the quadtree structure of HEVC. As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be collectively referred to as "video blocks" or "blocks."

[0180] 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, in HEVC, the overlapping portion of a PU and TU). For inter prediction of the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate values ​​indicating how similar potential reference blocks are to the current block, such as based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), and the like. Motion estimation unit 222 may typically perform these calculations using sample-by-sample differences between the current block and the reference block being considered. Motion estimation unit 222 may identify the reference block with the smallest value from these calculations, indicating the reference block that most closely matches the current block.

[0181] Motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in a current picture. Motion estimation unit 222 may then provide the motion vectors to motion compensation unit 224. For example, for unidirectional inter prediction, motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, motion estimation unit 222 may provide two motion vectors. Motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, motion compensation unit 224 may interpolate values ​​for the prediction block based on one or more interpolation filters. Furthermore, for bidirectional inter prediction, motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0182] As another example, for intra prediction or intra prediction codecs, the intra prediction unit 226 may generate a prediction block from samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 may generally mathematically combine the values ​​of the adjacent samples and pad these calculated values ​​in a defined direction across the current block to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 may calculate the average of the samples adjacent to the current block and generate a prediction block to include the obtained average for each sample of the prediction block.

[0183] 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 the 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.

[0184] In the example where the mode select unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As described above, the size of a CU may refer to the size of the luma codec 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 support 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 for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0185] In an example where the mode selection unit 202 does not further partition the CU into PUs, each CU may be associated with a luma codec block and a corresponding chroma codec block. As described above, the size of a CU may refer to the size of the luma codec block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0186] For other video codecs such as intra-block copy mode codecs, affine mode codecs, and linear model (LM) mode codecs, as some examples, the mode selection unit 202 generates a prediction block for the current block being encoded via the corresponding unit associated with the codec. In some examples such as palette mode codecs, 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.

[0187] 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.

[0188] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform multiple transforms on the residual block, such as a primary transform and a secondary transform such as a rotation transform. In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0189] Quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode select unit 202) may adjust the degree of quantization applied to the coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce a loss of information, and therefore, the quantized transform coefficients may have lower precision than the original transform coefficients produced by transform processing unit 206.

[0190] 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 value 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 value block generated by the mode selection unit 202 to generate the reconstructed block.

[0191] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0192] The video encoder 200 stores the reconstructed block 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 block 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 block in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve a reference picture formed by the reconstructed (and possibly filtered) block from the DPB 218 to perform inter-frame prediction on blocks of subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed block in the DPB 218 of the current picture to perform intra-frame prediction on other blocks in the current picture.

[0193] In general, entropy coding unit 220 may entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 may entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 may entropy encode prediction syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from mode selection unit 202. Entropy coding unit 220 may perform one or more entropy coding 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 coding unit 220 may operate in a bypass mode in which syntax elements are not entropy encoded.

[0194] In some examples, entropy coding unit 220 can encode NAL units that encapsulate RBSPs for video parameter sets (VPSs), sequence parameter sets (SPSs), and picture parameter sets (PPSs). Thus, entropy coding unit 220 can perform the techniques described herein, such as reducing the parsing dependency between the PPS and the SPS by encoding a syntax element in the PPS that indicates the luma codec tree block size for the picture to which the PPS applies. Entropy coding unit 220 can encode the picture blocks of the video data to which the PPS applies based on the syntax elements in the PPS, such as by encoding the RBSP for the PPS in the bitstream.

[0195] The video encoder 200 may output a bitstream including entropy-coded syntax elements, NAL units, etc. required for reconstructing a slice block or a picture block. Specifically, the entropy coding unit 220 may output a bitstream.

[0196] The operations described above are for block descriptions. This description should be understood as operations for luma codec blocks and / or chroma codec blocks. As described above, in some examples, the luma codec block and the chroma codec block are the luma and chroma components of a CU. In some examples, the luma codec block and the chroma codec block are the luma and chroma components of a PU.

[0197] In some examples, the operations performed for luma codec blocks do not need to be repeated for chroma codec blocks. As an example, the operations for identifying the motion vector (MV) and reference picture for a luma codec block do not need to be repeated in order to identify the MV and reference picture for a chroma block. Instead, the MV of the luma codec block can be scaled to determine the MV for the chroma blocks, and the reference picture can be the same. As another example, the intra prediction process can be the same for luma and chroma codec blocks.

[0198] Video encoder 200 represents an example of a device configured to encode video data, the device including a memory configured to store the video data and one or more processing units implemented in circuitry and configured to encode, in a picture parameter set (PPS), a syntax element indicating a luma codec tree block size for a picture of the video data to which the PPS applies, and to encode the picture of the video data to which the PPS applies based on the syntax element in the PPS.

[0199] Figure 6 is a block diagram illustrating an exemplary video decoder 300 that may perform the techniques of this disclosure. Figure 6 This is for illustrative purposes only and is not intended to limit the techniques broadly illustrated and described in this disclosure. For illustrative purposes, this disclosure describes video decoder 300 based on techniques from VCC (ITU-T H.266, under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video codec devices configured for other video codec standards.

[0200] exist Figure 6In the example of FIG. 3 , video decoder 300 includes a codec picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or processing circuits. For example, the units of video decoder 300 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Furthermore, video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0201] Prediction processing unit 304 includes motion compensation unit 316 and intra prediction unit 318. Prediction processing unit 304 may include additional units to perform prediction according to other prediction modes. As an example, prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, video decoder 300 may include more, fewer, or different functional components.

[0202] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. The video data may be obtained, for example, from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. Furthermore, CPB memory 320 may store video data other than syntax elements of encoded or decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, which video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may be formed from any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0203] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) retrieves the coded video data. That is, the memory 120 may use the CPB memory 320 to store the data described above. Similarly, when some or all of the functions of the video decoder 300 are implemented in software to be executed by the processing circuit of the video decoder 300, the memory 120 may store instructions to be executed by the video decoder 300.

[0204] Figure 6 The various units shown in FIG 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 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 units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units may be integrated circuits.

[0205] The video decoder 300 may include an ALU, an EFU, digital circuits, analog circuits, and / or a programmable core formed by programmable circuits. In examples where the operation of the video decoder 300 is performed by software executed on the programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) for the software that the video decoder 300 receives and executes.

[0206] Entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to reproduce syntax elements. Prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0207] Typically, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (where the block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0208] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block, as well as transform information, such as a quantization parameter (QP) and / or transform mode indication(s). The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and, similarly, a 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.

[0209] In some examples, the entropy decoding unit 302 can decode the NAL unit in the bitstream, which encapsulates the RBSP for the video parameter set (VPS), sequence parameter set (SPS), and picture parameter set (PPS). The entropy decoding unit 302 can decode these VPS, SPS, and PPS to derive various parameter values ​​for decoding the video data block.

[0210] Therefore, entropy decoding unit 302 can perform the techniques described herein to reduce the parsing dependency between the PPS and the SPS, such as by decoding a syntax element PPS-applicable object in the PPS that indicates the luma codec treeblock size of the picture. Video decoder 300 can thus decode the PPS-applicable picture blocks of the video data according to the syntax elements in the PPS.

[0211] After inverse quantization unit 306 forms a transform coefficient block, inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the coefficient block.

[0212] In addition, prediction processing unit 304 generates a prediction value 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 can generate the prediction value block. In this case, the prediction information syntax element can indicate a reference picture in DPB 314 from which the reference block is retrieved, as well as 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 can generally be substantially similar to the process described with respect to motion compensation unit 224 ( Figure 5 ) to perform the inter-frame prediction process in the manner described.

[0213] 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 value block according to the intra-prediction mode indicated by the prediction information syntax element. Likewise, the intra-prediction unit 318 may generally generate a prediction value block in a manner substantially similar to that described with respect to the intra-prediction unit 226 ( Figure 5 ) to perform the intra prediction process. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0214] The reconstruction unit 310 may reconstruct the current block using the prediction value block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction value block to reconstruct the current block.

[0215] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 need not be performed in all examples.

[0216] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in examples where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block in the DPB 314. In examples where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered reconstructed block in the DPB 314. As described above, the DPB 314 may provide reference information to the prediction processing unit 304, such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation. In addition, the video decoder 300 may output the decoded picture from the DPB for subsequent presentation on a video display such as a video display. Figure 1 on the display device 118 of the display device.

[0217] In this manner, the video decoder 300 represents an example of a video decoding device that includes a memory configured to store video data and one or more processing units implemented in a circuit and configured to decode a syntax element in a picture parameter set (PPS) indicating a luma codec tree block size for a picture of the video data to which the PPS applies, and to decode the picture of the video data to which the PPS applies based on the syntax element in the PPS.

[0218] Figure 7 is a flowchart illustrating an example method for encoding a current block according to the techniques of this disclosure. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and Figure 5 ) is described, but it should be understood that other devices may be configured to perform similar Figure 7In 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. 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).

[0219] During or after the scan, video encoder 200 may entropy encode the transform coefficients (358). For example, video encoder 200 may encode the transform coefficients using CAVLC or CABAC. Video encoder 200 may also encode, in a picture parameter set (PPS), a syntax element indicating the luma codec tree block size for the picture of the video data to which the PPS applies, and may entropy encode the picture of the video data to which the PPS applies based on the syntax element in the PPS. Video encoder 200 may then output entropy encoded data for the block (360).

[0220] Figure 8 is a flowchart illustrating an example method for decoding a current block of video data according to the techniques of this disclosure. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and Figure 6 ) is described, but it should be understood that other devices may be configured to perform similar Figure 8 method.

[0221] The video decoder 300 may receive entropy coded data for a current block, such as entropy coded prediction information and entropy coded data for transform coefficients of a residual block corresponding to the current block (370). The video decoder 300 may entropy decode the entropy coded data to determine prediction information for the current block and reproduce the transform coefficients of the residual block (372). The video decoder 300 may also decode, in a picture parameter set (PPS), a syntax element indicating a luma codec tree block size for a picture of the video data to which the PPS applies, and may decode the picture of the video data to which the PPS applies based on the syntax element in the PPS.

[0222] The video decoder 300 may predict the current block (374), for example, using an intra-frame or inter-frame prediction mode as indicated by the prediction information for the current block to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the reproduced transform coefficients (376) to create a quantized transform coefficient block. The video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (378). The video decoder 300 may ultimately decode the current block (380) by combining the prediction block and the residual block.

[0223] Figure 9 is a flowchart illustrating an example technique for signaling parameters of a picture parameter set (PPS) in a manner that reduces parsing dependencies on a sequence parameter set (SPS) in accordance with the techniques of this disclosure. Figure 1 and Figure 5 ) and video decoder 300( Figure 1 and Figure 6 ) is described, but it should be understood that other devices may be configured to perform similar Figure 9 method.

[0224] like Figure 9 As shown, one or more processors of a video codec, such as video encoder 200 or video decoder 300, may encode or decode, in a picture parameter set (PPS), a syntax element indicating a luma codec treeblock size for a codec tree unit (CTU) of a video data picture to which the PPS applies (402). The one or more processors of the video codec may encode or decode, based on the syntax element in the PPS, the video data picture to which the PPS applies (404).

[0225] In some examples, the syntax element indicating the luma codec treeblock size of a CTU of a video data picture indicates the luma codec treeblock size of the CTU of the video data picture minus 5. In some examples, the syntax element comprises a syntax element pps_log2_ctu_size_minus5. In some examples, the syntax element pps_log2_ctu_size_minus5 has the same value as the syntax element log2_ctu_size_minus5 in a sequence parameter set (SPS) applicable to the video data picture.

[0226] In some examples, the one or more processors of the video codec may further encode in the PPS a conditional loop having a condition based at least in part on the number of slices in the video data picture. The one or more processors of the video codec may further determine the number of slices in the video data picture based at least in part on a luma codec block tree size for the video data picture indicated by a syntax element and iterate the conditional loop based at least in part on the number of slices in the video data picture.

[0227] In some examples, the PPS does not include a second syntax element indicating the number of slices in a picture of the video data.

[0228] In some examples, the one or more processors of the video codec may further encode a conditional statement in the PPS, the conditional statement having a condition based at least in part on a height of an i-th slice row of the video data picture. The one or more processors of the video codec may further determine the height of the i-th slice row of the video data picture based at least in part on a luma codec block tree size of the video data picture indicated by the syntax element.

[0229] In some examples, the one or more processors of the video codec may further infer, based on a height of an i-th slice row of the video data picture, that the i-th slice of the video data picture is not divided into two or more tiles. In some examples, the one or more processors of the video codec may further infer, based on a height of an i-th slice row of the video data picture, that one or more horizontal tile boundaries are evenly distributed across the i-th slice of the video data picture that is divided into two or more tiles.

[0230] In some examples where the syntax elements include a first syntax element, one or more processors of the video codec may further encode and decode a second syntax element in the PPS indicating a number of sub-pictures in the video data picture, encode and decode a third syntax element in the PPS indicating a sub-picture ID for each sub-picture in the video data picture, and encode and decode the video data picture based on the second syntax element in the PPS and the third syntax element in the PPS.

[0231] In some examples, one or more processors of the video codec may further encode or decode a fourth syntax element indicating a sub-picture ID for a slice of the video data picture in a slice header for the slice of the video data picture, and encode or decode the video data picture according to the fourth syntax element in the slice header.

[0232] In some examples, encoding and decoding may include decoding, such that the video codec includes video decoder 300. In some examples, the video codec may display a picture of video data.

[0233] In some examples, coding and decoding may include encoding, such that the video codec includes video encoder 200. In some examples, the video codec may capture a picture of video data.

[0234] This disclosure includes the following examples.

[0235] Example 1. A method for encoding and decoding video data, the method comprising: signaling one or more brick information for a slice of video data, wherein a value of the one or more brick information corresponds to a value of a row height of the slice; and encoding and decoding the video data.

[0236] Example 2. The method of Example 1, wherein the one or more brick information includes a brick split flag, and wherein if the value of the row height of the slice is 1, the value of the brick split flag is 0.

[0237] Example 3. The method of Example 1, wherein the one or more brick information includes a brick split flag, and wherein if the value of the row height of the slice is 2, the value of the brick split flag is 1.

[0238] Example 4. The method of any one of Examples 1 to 3, wherein encoding and decoding includes decoding.

[0239] Example 5. A method as described in any one of Examples 1 to 4, wherein encoding and decoding includes encoding.

[0240] Example 6. A method for encoding and decoding video data, the method comprising: determining, for a slice in the video data, whether to signal one or more brick information for the slice based at least in part on specifying a row height value for the slice; and encoding and decoding the video data based at least in part on determining whether to signal one or more brick information for the slice.

[0241] Example 7. The method of Example 6, further comprising inferring a value for the line height for the slice if the syntax element is not present.

[0242] Example 8. The method of any one of Examples 6 to 7, wherein encoding and decoding includes decoding.

[0243] Example 9. The method of any one of Examples 6 to 8, wherein encoding and decoding includes encoding.

[0244] Example 10. A method of encoding and decoding video data, the method comprising: signaling one or more syntax elements indicating one or more sub-pictures extracted from a picture in the video data; and encoding and decoding the video data based at least in part on the one or more syntax elements.

[0245] Example 11. The method of Example 10, wherein encoding and decoding includes decoding.

[0246] Example 12. The method of any one of Examples 10 and 11, wherein encoding and decoding includes encoding.

[0247] Example 13. A device for encoding and decoding video data, the device comprising one or more components for performing the method of any one of Examples 1 to 5.

[0248] Example 14. The apparatus of Example 13, wherein the one or more components include one or more processors implemented in circuitry.

[0249] Example 15. The apparatus of any of Examples 13 and 14, further comprising a memory for storing video data.

[0250] Example 16. The apparatus of any one of Examples 13 to 15, further comprising a display configured to display the decoded video data.

[0251] Example 17. The device of any one of Examples 13 to 16, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0252] Example 18. The apparatus of any one of Examples 13 to 17, wherein the apparatus comprises a video decoder.

[0253] Example 19. The apparatus of any one of Examples 13 to 18, wherein the apparatus comprises a video encoder.

[0254] Example 20. A device for encoding and decoding video data, the device comprising one or more components for performing the method of any one of Examples 6 to 9.

[0255] Example 21. The apparatus of Example 20, wherein the one or more components include one or more processors implemented in a circuit.

[0256] Example 22. The apparatus of any of Examples 20 and 21, further comprising a memory for storing video data.

[0257] Example 23. The apparatus of any one of Examples 20 to 22, further comprising a display configured to display the decoded video data.

[0258] Example 24. The device of any one of Examples 20 to 23, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0259] Example 25. The apparatus of any one of Examples 20 to 24, wherein the apparatus comprises a video decoder.

[0260] Example 26. The device of any one of Examples 20 to 25, wherein the device comprises a video encoder.

[0261] Example 27. An apparatus for encoding and decoding video data, the apparatus comprising one or more components for performing the method of any one of Examples 10 to 12.

[0262] Example 28. The apparatus of Example 27, wherein the one or more components include one or more processors implemented in a circuit.

[0263] Example 29. The apparatus of any of Examples 27 and 28, further comprising a memory for storing video data.

[0264] Example 30. The apparatus of any one of Examples 27 to 29, further comprising a display configured to display the decoded video data.

[0265] Example 31. The device of any one of Examples 27 to 30, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0266] Example 32. The apparatus of any one of Examples 27 to 31, wherein the apparatus comprises a video decoder.

[0267] Example 33. The apparatus of any one of Examples 27 to 32, wherein the apparatus comprises a video encoder.

[0268] Example 34. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any one of Examples 1 to 5.

[0269] Example 35. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any one of Examples 6 to 9.

[0270] Example 36. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any one of Examples 10 to 12.

[0271] Example 37. A device for encoding and decoding video data, the device comprising: a component for signaling one or more brick information for a slice of video data, wherein the value of the one or more brick information corresponds to the value of the row height of the slice; and a component for encoding and decoding the video data.

[0272] Example 38. A device for encoding and decoding video data, the device comprising: a component for determining, for a slice in the video data, whether to signal one or more brick information for the slice based at least in part on specifying a row height value for the slice; and a component for encoding and decoding the video data based at least in part on determining whether to signal one or more brick information for the slice.

[0273] Example 39. A device for encoding and decoding video data, the device comprising: a component for signaling one or more syntax elements indicating one or more sub-pictures extracted from a picture in the video data; and a component for encoding and decoding the video data based at least in part on the one or more syntax elements.

[0274] It should be appreciated that, depending on the example, certain actions or events of any of the techniques described herein may be performed in a different sequence, may be added, combined, or omitted entirely (e.g., not all described actions or events are required to practice the techniques). Furthermore, in some examples, actions or events may be performed simultaneously rather than sequentially, such as through multithreading, interrupt processing, or multiple processors.

[0275] 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 sent via a computer-readable medium as one or more instructions or codes 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 including, 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) non-transitory tangible computer-readable storage media, or (2) communication media such as signals or carrier waves. Data storage media may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include computer-readable media.

[0276] As an example, and not a 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 can be accessed by a computer. Moreover, any connection is properly referred to as a computer-readable medium. As an example, if a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology (such as infrared, radio and microwave) is used to send instructions from a website, server or other remote source, the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology (such as infrared, radio and microwave) is 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 temporary media, but rather refer to non-temporary tangible storage media. As used herein, disks and optical disks include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs use lasers to reproduce data optically. Combinations of the above should also be included within the scope of computer-readable media.

[0277] Instructions may be executed by one or more processors, such as one or more DSPs, general-purpose microprocessors, ASICs, 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 structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Furthermore, the techniques may be fully implemented in one or more circuits or logic elements.

[0278] The techniques of this disclosure can be implemented in a variety of devices or apparatuses, including wireless handheld devices, integrated circuits (ICs), or IC sets (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize the functional aspects of devices configured to perform the disclosed techniques, but they do not necessarily require implementation by different hardware units. Instead, as described above, the various units can be combined in a codec hardware unit, or provided by a collection of interoperable hardware units (including one or more processors as described above) in combination with appropriate software and / or firmware.

[0279] 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: decoding, from a picture parameter set (PPS) using a conditional statement having a condition based at least in part on a height of an i-th slice row of a picture of the video data, a syntax element indicating a luma codec tree block size of a codec tree unit (CTU) of a picture of the video data to which the PPS applies, wherein the syntax element indicating the luma codec tree block size of the codec tree unit in the PPS has the same value as the syntax element indicating the luma codec tree block size of the CTU of the picture in a sequence parameter set (SPS) for the picture; as well as determining a number of slices in a picture of the video data and a height of an i-th slice row of the picture of the video data based at least in part on a luma codec treeblock size for the picture of the video data indicated by the syntax element; as well as A picture of the video data to which the PPS applies is decoded according to the syntax element in the PPS and the number of slices in the picture.

2. The method according to claim 1, wherein The syntax element indicating a luma codec treeblock size of a CTU of a picture of the video data indicates a luma codec treeblock size of a CTU of the picture of the video data minus 5.

3. The method according to claim 2, wherein: The syntax elements include the syntax element pps_log2_ctu_size_minus5.

4. The method according to claim 3, wherein: The syntax element pps_log2_ctu_size_minus5 has the same value as the syntax element log2_ctu_size_minus5 in the sequence parameter set (SPS) applicable to the picture of the video data.

5. The method according to claim 1, wherein Decoding the syntax element includes: Decoding the syntax elements in the PPS using a conditional loop, the conditional loop having a condition based at least in part on the number of slices in a picture of the video data, decoding the syntax elements in the PPS using the conditional loop comprising iterating the conditional loop based at least in part on the number of slices in the picture of the video data.

6. The method of claim 1, wherein: The PPS does not include a second syntax element indicating the number of slices in a picture of the video data.

7. The method of claim 1 , further comprising: It is inferred based on a height of an i-th slice row of the picture of the video data that the i-th slice of the picture of the video data is not divided into two or more tiles.

8. The method of claim 1 , further comprising: Based on a height of an i-th slice row of the picture of the video data, one or more horizontal tile boundaries are inferred to be evenly distributed across an i-th slice of the picture of the video data divided into two or more tiles.

9. The method of claim 1, wherein: The syntax element includes a first syntax element, and the method further includes: decoding, from the PPS, a second syntax element indicating a number of sub-pictures in a picture of the video data; and decoding, from the PPS, a third syntax element indicating a sub-picture ID for each sub-picture in a picture of the video data, The decoding of the picture of the video data further includes encoding and decoding the picture of the video data according to the second syntax element in the PPS and the third syntax element in the PPS.

10. The method of claim 9, further comprising: decoding, from a slice header for a slice of a picture of the video data, a fourth syntax element indicating the sub-picture ID for a slice of the picture of the video data; as well as A picture of the video data is decoded according to the fourth syntax element in the slice header.

11. A device for decoding video data, the device comprising: a memory configured to store video data; as well as one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: decoding, from a picture parameter set (PPS) using a conditional statement having a condition based at least in part on a height of an i-th slice row of a picture of the video data, a syntax element indicating a luma codec tree block size of a codec tree unit (CTU) of a picture of the video data to which the PPS applies, wherein the syntax element indicating the luma codec tree block size of the codec tree unit in the PPS has the same value as the syntax element indicating the luma codec tree block size of the CTU of the picture in a sequence parameter set (SPS) for the picture; as well as determining a number of slices in a picture of the video data and a height of an i-th slice row of the picture of the video data based at least in part on a luma codec treeblock size for the picture of the video data indicated by the syntax element; as well as A picture of the video data to which the PPS applies is decoded according to the syntax element in the PPS and the number of slices in the picture.

12. The apparatus of claim 11, wherein: The syntax element indicating a luma codec treeblock size of a CTU of a picture of the video data indicates a luma codec treeblock size of a CTU of the picture of the video data minus 5.

13. The apparatus of claim 12, wherein: The syntax elements include the syntax element pps_log2_ctu_size_minus5.

14. The apparatus of claim 13, wherein: The syntax element pps_log2_ctu_size_minus5 has the same value as the syntax element log2_ctu_size_minus5 in the sequence parameter set (SPS) applicable to the picture of the video data.

15. The apparatus of claim 11, wherein: The one or more processors are further configured to: Decoding the syntax elements in the PPS using a conditional loop, the conditional loop having a condition based at least in part on a number of slices in a picture of the video data, decoding the syntax elements in the PPS using the conditional loop comprising iterating the conditional loop based at least in part on the number of slices in the picture of the video data.

16. The apparatus of claim 11, wherein: The PPS does not include a second syntax element indicating the number of slices in a picture of the video data.

17. The apparatus of claim 11, wherein: The one or more processors are further configured to: It is inferred based on a height of an i-th slice row of the picture of the video data that the i-th slice of the picture of the video data is not divided into two or more tiles.

18. The apparatus of claim 11, wherein: The one or more processors are further configured to: Based on a height of an i-th slice row of the picture of the video data, one or more horizontal tile boundaries are inferred to be evenly distributed across an i-th slice of the picture of the video data divided into two or more tiles.

19. The apparatus of claim 11, wherein: The syntax elements include a first syntax element, and wherein the one or more processors are further configured to: decoding, from the PPS, a second syntax element indicating a number of sub-pictures in a picture of the video data; decoding, from the PPS, a third syntax element indicating a sub-picture ID for each sub-picture in a picture of the video data; and A picture of the video data is decoded according to the second syntax element in the PPS and the third syntax element in the PPS.

20. The apparatus of claim 19, wherein: The one or more processors are further configured to: decoding, from a slice header for a slice of a picture of the video data, a fourth syntax element indicating the sub-picture ID for a slice of the picture of the video data; as well as A picture of the video data is decoded according to the fourth syntax element in the slice header.

21. The apparatus of claim 11, further comprising a display configured to display the decoded picture.

22. The apparatus of claim 11, wherein: The apparatus comprises a video encoder, wherein, to encode and decode the syntax elements, the one or more processors are configured to encode the syntax elements, and wherein, to encode and decode the pictures, the one or more processors are configured to encode the pictures.

23. The apparatus of claim 22, wherein: The device includes a camera configured to capture pictures of the video data.

24. A device for video decoding, comprising means for performing the method according to any one of claims 1-10.

25. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any one of claims 1-10.

26. A computer program product comprising computer instructions which, when executed by a processor, cause the processor to perform the method of any one of claims 1 to 10.

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