Advanced deblocking filter (DBF), adaptive loop filter (ALF) and sample adaptive offset (SAO) control and adaptive parameter set (APS) number constraint in video coding

Abstract

An example method includes decoding, via a first syntax level of a video bitstream, a first deblocking filter control syntax element having a value specifying whether deblocking filter information is present in a second syntax level of the bitstream, decoding, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value specifying whether deblocking override is enabled, decoding, responsive to the first deblocking filter control syntax element specifying that deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element, one or more syntax elements specifying deblocking filter information via the second syntax level, and applying deblocking filter to a block of video data based on the deblocking filter information.

Description

[0001] This application claims priority to U.S. Application No. 17 / 303,067, filed May 19, 2021, U.S. Provisional Application No. 63 / 027,704, filed May 20, 2020, and U.S. Provisional Application No. 63 / 028,394, filed May 21, 2020, the entire contents of each of which are incorporated herein by reference. U.S. Application No. 17 / 303,067 claims the benefit of U.S. Provisional Application No. 63 / 027,704, filed May 20, 2020, and U.S. Provisional Application No. 63 / 028,394, filed May 21, 2020. TECHNICAL FIELD

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

[0003] 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 gaming devices, video game consoles, cellular or satellite radio telephones, so-called “smart phones,” video teleconferencing devices, video streaming devices, and the like. 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. The video devices can implement such video coding techniques to transmit, receive, encode, decode, and / or store digital video information more efficiently.

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy of video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) can be partitioned into video blocks, which can also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are coded 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 can be coded by using 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 can be referred to as frames, and reference pictures can be referred to as reference frames. SUMMARY

[0005] In general, this disclosure describes techniques for signaling deblocking filter parameters for video coding. A video coder (e.g., a reconstruction loop of a video decoder or a video encoder) can include a deblocking filter that filters video data based on deblocking parameters (e.g., a deblocking filter threshold β and a clipping value tC). The video coder can signal the deblocking parameters at a first syntax level (e.g., a picture parameter set (PPS)) of a coded video bitstream. When performing deblocking on blocks of video data that reference the PPS, the video coder can utilize the deblocking parameters signaled at the PPS. However, in some scenarios, the video coder can desire to utilize different deblocking parameters for some blocks that reference the PPS.

[0006] To enable some blocks that reference the PPS to utilize deblocking parameters other than the deblocking parameters signaled in the PPS, the video coder can signal alternative deblocking parameters in a second syntax level (e.g., a picture header (PH)). The video coder can signal, via the first syntax level, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information (i.e., alternative deblocking parameters, etc.) can be overridden in the second syntax level. The video coder can also signal, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level. In some examples, when both the first deblocking filter control syntax element and the second deblocking filter control syntax element are true, deblocking filter information can be present in the second syntax level.

[0007] According to one or more aspects of the disclosure, a video decoder can selectively decode alternative deblocking parameters from the second syntax level based on a value of the first deblocking filter control syntax element (i.e., regardless of a value of the second deblocking filter control syntax element). For example, in response to the first deblocking filter control syntax element specifying that deblocking filter information is present in the second syntax level of the bitstream, and regardless of a value of the second deblocking filter control syntax element, the video decoder can decode one or more syntax elements specifying deblocking filter information via the second syntax level. By selectively decoding the one or more syntax elements specifying deblocking filter information based only on the first deblocking filter control syntax element (i.e., and not based on a value of the second deblocking filter control syntax element), techniques of this disclosure can enable a simplification of processing logic, which can reduce processing time and / or improve processing efficiency.

[0008] As one example, a method includes decoding, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream, decoding, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream, decoding, via the second syntax level, one or more syntax elements that specify the deblocking filter information in response to the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element, and applying deblocking filter to a block of video data based on the deblocking filter information.

[0009] As another example, a method includes encoding, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream, encoding, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream, encoding, via the second syntax level, one or more syntax elements that specify the deblocking filter information based on the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element, and applying deblocking filter to a block of video data based on the deblocking filter information.

[0010] As another example, a device includes a memory configured to store at least a portion of a coded video bitstream, one or more processors implemented in circuitry and configured to decode, via a first syntax level of the coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream, decode, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream, decode, via the second syntax level, one or more syntax elements that specify the deblocking filter information in response to the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element, and apply deblocking filter to a block of video data based on the deblocking filter information.

[0011] As another example, an apparatus comprises: a memory configured to store at least a portion of a coded video bitstream; one or more processors implemented in circuitry and configured to: encode, via a first syntax level of the coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream; encode, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream; encode, via the second syntax level, one or more syntax elements that specify the deblocking filter information based on the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element; and apply deblocking filtering to a block of video data based on the deblocking filter information.

[0012] As another example, an apparatus comprises: means for decoding, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream; means for decoding, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream; means for decoding, via the second syntax level, one or more syntax elements that specify the deblocking filter information in response to the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element; and means for applying deblocking filtering to a block of video data based on the deblocking filter information.

[0013] As another example, an apparatus comprises: means for encoding, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream; means for encoding, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream; means for encoding, via the second syntax level, one or more syntax elements that specify the deblocking filter information in response to the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream and regardless of the value of the second deblocking filter control syntax element; and means for applying deblocking filtering to a block of video data based on the deblocking filter information.

[0014] As another example, a computer-readable storage medium storing instructions that cause one or more processors to: decode, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream; decode, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream; in response to the first deblocking filter control syntax element specifying that deblocking filter information is present in the second syntax level of the bitstream, and regardless of the value of the second deblocking filter control syntax element, decode, via the second syntax level, one or more syntax elements that specify the deblocking filter information; and apply deblocking filtering to a block of video data based on the deblocking filter information.

[0015] As another example, a computer-readable storage medium storing instructions that cause one or more processors to: encode, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream; encode, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream; in response to the first deblocking filter control syntax element specifying that deblocking filter information is present in the second syntax level of the bitstream, and regardless of the value of the second deblocking filter control syntax element, encode, via the second syntax level, one or more syntax elements that specify the deblocking filter information; and apply deblocking filtering to a block of video data based on the deblocking filter information.

[0016] 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 DRAWINGS

[0017] Figure 1 FIG. 1 is a block diagram illustrating an example video encoding and decoding system that can perform the techniques of this disclosure.

[0018] Figure 2A and Figure 2B FIGS. 2 and 3 are conceptual diagrams illustrating example quad-tree binary-tree (QTBT) structures and corresponding coding tree units (CTUs).

[0019] Figure 3 FIG. 5 is a block diagram illustrating an example video decoder that can perform the techniques of this disclosure.

[0020] Figure 4 This is a block diagram illustrating an example video decoder that can perform the techniques disclosed herein.

[0021] Figure 5 This is a flowchart illustrating an example method for encoding the current block.

[0022] Figure 6 This is a flowchart illustrating an example method for decoding the current block.

[0023] Figure 7 This is a flowchart illustrating an example technique for decoding deblocking filtered information according to one or more aspects of this disclosure. Detailed Implementation

[0024] Figure 1 This is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of this disclosure. The techniques of this disclosure are generally directed to decoding (encoding and / or decoding) video data. Typically, video data includes any data used for processing video. Thus, video data can include raw, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata such as signaling data.

[0025] like Figure 1 As shown, system 100 includes source device 102, which in this example provides encoded video data to be decoded and displayed by destination device 116. Specifically, source device 102 provides video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 can include any of a wide range of devices, including desktop computers, laptop computers, mobile devices, tablet computers, set-top boxes, handheld telephone devices 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 may therefore be referred to as wireless communication devices.

[0026] exist Figure 1In the example of FIG. 1, source device 102 includes video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes input interface 122, video decoder 300, memory 120, and display device 118. In accordance with this disclosure, video encoder 200 of source device 102 and video decoder 300 of destination device 116 can be configured to apply the techniques for improved syntax element inference. 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, a source device and a 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. Likewise, destination device 116 can interface with an external display device, rather than include an integrated display device.

[0027] As shown in FIG. 1, system 100 includes a source device 102, a destination device 116, and a computer- readable medium 110. Source device 102 generates coded video data, and destination device 116 reconstructs the coded video data for display. Figure 1 System 100 of FIG. 1 is merely one example. In general, any digital video encoding and / or decoding device can perform the techniques for improved syntax element inference. Source device 102 and destination device 116 are merely examples of such coding devices in which source device 102 generates coded video data for transmission to destination device 116. This disclosure refers to a "coding" device as a device that performs coding (encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of coding devices, specifically video encoders and video decoders, respectively. In some examples, source device 102 and destination device 116 can operate in a substantially symmetrical manner to one another, such that each of source device 102 and destination device 116 includes video encoding and decoding components. Hence, system 100 can support one-way or two-way video transmission between source device 102 and destination device 116, e.g., for video streaming, video playback, video broadcasting, or video telephony.

[0028] In general, video source 104 represents a source of video data (i.e., raw, uncoded video data) and provides a sequential series of pictures (also referred to as “frames”) of the video data to video encoder 200, which encodes the data of the pictures. Video source 104 of source device 102 can include a video capture device, such as a video camera, a video archive containing previously captured raw video, and / or a video feed interface to receive video from a video content provider. As a further alternative, video source 104 can generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 can rearrange the pictures from the received order (sometimes referred to as “display order”) into the coding order for coding. Video encoder 200 can generate a bitstream including encoded video data. Source device 102 can then output the encoded video data via output interface 108 onto computer-readable medium 110 for reception and / or retrieval by, for example, input interface 122 of destination device 116.

[0029] Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memories. In some examples, memories 106, 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, 120 can store software instructions executable by, for example, video encoder 200 and video decoder 300, respectively. Although memory 106 and memory 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 can also include internal memories for similar or equivalent purposes. Moreover, memories 106, 120 can store encoded video data, e.g., that is output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106, 120 can be allocated as one or more video buffers, e.g., to store raw decoded video data and / or encoded video data.

[0030] Computer-readable medium 110 can represent any type of medium or device capable of transporting the encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium to enable source device 102 to transmit encoded video data directly to destination device 116 in real-time, e.g., via a radio frequency network or computer-based network. Output interface 108 can modulate the transmission signal including the encoded video data based on a communication standard, such as a wireless communication protocol, and input interface 122 can demodulate the received transmission signal, according to the communication standard. The communication medium can comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium can include routers, switches, base stations, or any other equipment that can be useful to facilitate communication from source device 102 to destination device 116.

[0031] In some examples, source device 102 can output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 can access encoded data from storage device 112 via input interface 122. Storage device 112 can include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data.

[0032] In some examples, source device 102 can output encoded video data to a file server 114 or another intermediate storage device that can store encoded video data generated by source device 102. Destination device 116 can access stored video data from file server 114 via streaming or download. File server 114 can be any type of server device capable of storing encoded video data and transmitting that encoded video data to destination device 116. File server 114 can represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Destination device 116 can access encoded video data from file server 114 through any standard data connection, including an Internet connection. This can include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., DSL, cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on file server 114. File server 114 and input interface 122 can be configured to operate according to a streaming transmission protocol, a download transmission protocol, or a combination thereof.

[0033] Output interface 108 and input interface 122 can represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components operating according to any of a variety of IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 comprise wireless components, output interface 108 and input interface 122 can be configured to transmit data, e.g., encoded video data, according to a cellular communication standard, such as 4G, 4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 can be configured to transmit data, e.g., encoded video data, according to other wireless standards, such as IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee), Bluetooth standards, or the like. In some examples, source device 102 and / or destination device 116 can include respective system on a chip (SOC) devices. For example, source device 102 can include a SOC device to perform the functionality attributed to video encoder 200 and / or output interface 108, and destination device 116 can include a SOC device to perform the functionality attributed to video decoder 300 and / or input interface 122. TM TM In some examples, source device 102 and / or destination device 116 can include respective system on a chip (SOC) devices. For example, source device 102 can include a SOC device to perform the functionality attributed to video encoder 200 and / or output interface 108, and destination device 116 can include a SOC device to perform the functionality attributed to video decoder 300 and / or input interface 122.

[0034] ​The technology disclosed herein can be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission, such as Dynamic Adaptive Streaming (DASH) over HTTP, digital video encoded to a data storage medium, decoding digital video stored on a data storage medium, or other applications.

[0035] The input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 and used by the video decoder 300, such as syntax elements having values ​​describing the characteristics and / or processing of video blocks or other decoding units (e.g., slices, pictures, picture groups, sequences, etc.). The display device 118 displays decoded images of the decoded video data to the 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.

[0036] Although Figure 1 Not shown, but in some examples, the video encoder 200 and video decoder 300 may each be integrated with the audio encoder and / or audio decoder, and may include appropriate MUX-DEMUX units or other hardware and / or software to handle multiplexed streams including both audio and video in a common data stream. Where applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol or other protocols such as User Datagram Protocol (UDP).

[0037] Video encoder 200 and video decoder 300 each can be implemented as any of a variety of suitable encoder and / or decoder circuitry, 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 combinations thereof. When the techniques are implemented partially in software, a device can store instructions for the software in a suitable, non- transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of video encoder 200 and video decoder 300 can be included in one or more encoders or decoders, either of which can be integrated as part of a combined video encoder / decoder (CODEC) in a respective device. A device including video encoder 200 and / or video decoder 300 can comprise an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular telephone.

[0038] Video encoder 200 and video decoder 300 can operate according to a video coding standard, such as ITU-T H.265, also referred to as High Efficiency Video Coding (HEVC) or extensions such as multi-view and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 can operate according to other proprietary or industry standards, such as ITU-T H.266, also referred to as Versatile Video Coding (VVC). A recent draft of the VVC standard is described in Bross, et al., “Versatile Video Coding (Draft 9),” Joint Video Team (JVT) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 18th Meeting: Via Teleconference, April 15-24, 2020, JVET-R2001-V8 (hereinafter “VVC Draft 9”). The techniques of this disclosure, however, are not limited to any particular coding standard.

[0039] In general, video encoder 200 and video decoder 300 can perform block-based coding of pictures. The term “block” generally refers to a structure comprising data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block can comprise a two-dimensional matrix of samples of luma and / or chroma data. In general, video encoder 200 and video decoder 300 can code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, blue (RGB) data of picture samples, video encoder 200 and video decoder 300 can code luma and chroma components, where the chroma components can include both red hue and blue hue chroma components. In some examples, video encoder 200 converts received RGB formatted data to a YUV representation prior to encoding, and video decoder 300 converts the YUV representation to the RGB format. Alternatively, pre- and post-processing units (not shown) can perform these conversions.

[0040] The present disclosure can generally relate to coding (e.g., encoding and decoding) pictures to include processes that encode or decode data of pictures. Similarly, the present disclosure can relate to coding blocks of pictures to include processes that encode or decode data of blocks, e.g., prediction and / or residual coding. An encoded video bitstream generally includes a series of values representative of coding decisions (e.g., coding modes) and syntax elements that partition a picture into blocks. Thus, references to coding of pictures or blocks generally should be understood to code values of syntax elements that form the pictures or blocks.

[0041] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder (e.g., video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video coder partitions a CTU and CUs into four equal, non overlapping squares, and each node of the quadtree has either zero or four child nodes. Nodes with zero child nodes can be referred to as “leaf nodes,” and CUs of such leaf nodes can include one or more PUs and / or one or more TUs. The video coder can further partition PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents partitioning of TUs. In HEVC, PUs represent inter-data, while TUs represent residual data. A CU that is intra-predicted includes intra-prediction information, e.g., an intra-mode indication.

[0042] As another example, video encoder 200 and video decoder 300 can be configured to operate according to VVC. According to VVC, a video coder (e.g., video encoder 200) partitions a picture into a plurality of coding tree units (CTUs). Video encoder 200 can partition a CTU according to a tree structure (e.g., a quad-tree binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the multiple separation concepts between CU, PU, and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quad-tree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. Leaf nodes of the binary tree correspond to coding units (CUs).

[0043] In the MTT partitioning structure, blocks can be partitioned using quad-tree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also referred to as triple tree (TT)) partitioning. Ternary tree or triple tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, the ternary tree or triple tree partitions a block into three sub-blocks without splitting the original block through a center. The partitioning types (e.g., QT, BT, and TT) in the MTT can be symmetric or asymmetric.

[0044] In some examples, video encoder 200 and video decoder 300 can use a single QTBT or MTT structure to represent each of luma and chroma components, while in other examples, video encoder 200 and video decoder 300 can use two or more QTBT or MTT structures, e.g., one QTBT / MTT structure for luma components and another QTBT / MTT structure for two chroma components (or two QTBT / MTT structures for respective chroma components).

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

[0046] In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture having three sample arrays, or a sample CTB of a monochrome picture or a picture coded using three separate color planes and syntax structures for coding samples. A CTB can be an NxN block of samples for some value N, such that partitioning a component into CTBs is a partitioning. A component is an array that makes up a picture in a 4:2:0, 4:2:2, or 4:4:4 color format or a single sample from one of the three arrays that make up the picture (one luma and two chroma), or is an array that makes up a picture in a monochrome format or a single sample of an array that makes up the picture. In some examples, a coding block is an MxN block of samples for some values M and N, such that partitioning a CTB into coding blocks is a partitioning.

[0047] Blocks (e.g., CTUs or CUs) can be grouped in various ways in a picture. As one example, a brick can refer to a rectangular region of CTU rows within a particular tile in a picture. A tile can be a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of CTUs having a height equal to a height of the picture and a width specified by a syntax element (e.g., in a picture parameter set). A tile row refers to a rectangular region of CTUs having a height specified by a syntax element (e.g., in a picture parameter set) and a width equal to a width of the picture.

[0048] In some examples, a tile can be partitioned into multiple bricks, each of which can include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks can also be referred to as a brick. However, a brick that is a true subset of a tile cannot be referred to as a tile.

[0049] Bricks in a picture can also be arranged in slices. A slice can be an integer number of bricks of a picture that can be exclusively contained in a single network abstraction layer (NAL) unit. In some examples, a slice either includes multiple complete tiles or only a contiguous sequence of complete bricks of one tile.

[0050] The disclosure can use “NxN” and “N by N” interchangeably to refer to the sample dimensions of a block (e.g., a CU or other video block) in terms of vertical and horizontal dimensions, such as 16x16 samples or 16 by 16 samples. In general, a 16x16 CU will have 16 samples in the vertical direction (y = 16) and 16 samples in the horizontal direction (x = 16). Likewise, an NxN CU will generally have 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 can be arranged in rows and columns. Moreover, a CU need not have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU can include NxM samples, where M need not equal N.

[0051] Video encoder 200 encodes video data for CUs that represent prediction and / or residual information, among other information. Prediction information indicates how to predict a CU in order to form a prediction block for the CU. Residual information generally represents sample-by-sample differences between samples of the CU prior to encoding and the prediction block.

[0052] To predict a CU, video encoder 200 can generally form a prediction block for the CU through inter prediction or intra prediction. Inter prediction generally refers to predicting the CU from data of a previously coded picture, whereas intra prediction generally refers to predicting the CU from previously coded data of the same picture. To perform inter prediction, video encoder 200 can use one or more motion vectors to generate the prediction block. Video encoder 200 can generally perform a motion search to identify a reference block that closely matches the CU, e.g., according to differences between the CU and the reference block. Video encoder 200 can calculate the difference metric using a sum of absolute difference (SAD), a sum of squared differences (SSD), a mean absolute difference (MAD), a mean squared differences (MSD), or other such difference calculations to determine whether a reference block closely matches a current CU. In some examples, video encoder 200 can use uni -prediction or bi-prediction to predict a current CU.

[0053] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter prediction mode. In the affine motion compensation mode, video encoder 200 can determine two or more motion vectors that represent non-translational motion (e.g., zooming or shrinking, rotation, perspective motion, or other irregular types of motion).

[0054] To perform intra prediction, video encoder 200 can select an intra prediction mode to generate the prediction block. Some examples of VVC provide sixty-seven intra prediction modes, including various directional modes, as well as a planar mode and a DC mode. In general, video encoder 200 selects an intra prediction mode that describes neighboring samples of the current block (e.g., a block of a CU) from which to predict samples of the current block. Assuming that video encoder 200 is coding CTUs and CUs in a raster scan order (left to right, top to bottom), these samples can generally be above, above-left, or to the left of the current block in the same picture as the current block.

[0055] Video encoder 200 encodes data representing the prediction mode for the current block. For example, for inter prediction modes, video encoder 200 can encode data representing which of various available inter prediction modes to use, as well as motion information for the corresponding mode. For uni-directional or bi-directional inter prediction, for example, video encoder 200 can encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. Video encoder 200 can use similar modes to encode motion vectors for affine motion compensation modes.

[0056] Following prediction, such as intra prediction or inter prediction of a block, video encoder 200 can calculate residual data for the block. The residual data (e.g., a residual block) represents sample-by-sample differences between the block and a prediction block formed using the corresponding prediction mode. Video encoder 200 can apply one or more transforms to the residual block to produce transformed data in a transform domain instead of the sample domain. For example, video encoder 200 can apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform. Additionally, video encoder 200 can apply a secondary transform following the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), or the like. Video encoder 200 produces transform coefficients following application of the transform(s).

[0057] As noted above, following any transforms to produce transform coefficients, video encoder 200 can perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. By performing the quantization process, video encoder 200 can reduce the bit depth of some or all of the transform coefficients. For example, video encoder 200 can round an n-bit value down to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, video encoder 200 can perform a bit shift to the right of the values to be quantized.

[0058] After quantization, video encoder 200 can scan the transform coefficients, producing a one-dimensional vector from the two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place higher energy (and hence lower frequency) transform coefficients earlier in the vector, and lower energy (and hence higher frequency) transform coefficients later in the vector. In some examples, video encoder 200 can utilize a pre-defined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, video encoder 200 can perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, video encoder 200 can entropy encode the one-dimensional vector, e.g., according to context adaptive binary arithmetic coding (CABAC). Video encoder 200 can also entropy encode values for syntax elements describing metadata associated with the encoded video data for use by video decoder 300 when decoding the video data.

[0059] To perform CABAC, video encoder 200 can assign a context within a context model to a symbol to be transmitted. The context can relate to, for example, whether neighboring values of the symbol are zero-valued or not. Probability determination can be based on the context assigned to the symbol.

[0060] Video encoder 200 can also generate syntax data, e.g., block-based syntax data, picture-based syntax data, and sequence-based syntax data, for video decoder 300, e.g., in a picture header, a block header, a slice header, or other syntax data (e.g., sequence parameter set (SPS), picture parameter set (PPS), or video parameter set (VPS)). Video decoder 300 can also decode such syntax data to determine how to decode corresponding video data.

[0061] In this way, video encoder 200 can generate a bitstream including encoded video data, e.g., syntax elements describing partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Ultimately, video decoder 300 can receive the bitstream and decode the encoded video data.

[0062] In general, video decoder 300 performs a reciprocal process to that performed by video encoder 200 to decode encoded video data of the bitstream. For example, video decoder 300 can decode values for syntax elements of the bitstream using CABAC in a manner substantially similar to, but reciprocal to, the CABAC encoding process of video encoder 200. The syntax elements can define partitioning information for partitioning a picture into CTUs, and partitioning each CTU according to a corresponding partition structure (e.g., a QTBT structure) to define CUs of the CTU. The syntax elements can further define prediction and residual information for blocks (e.g., CUs) of the video data.

[0063] The residual information can be represented by, for example, quantized transform coefficients. Video decoder 300 can inverse quantize and inverse transform the quantized transform coefficients of a block to reproduce a residual block for the block. Video decoder 300 forms a prediction block for the block using the signaled prediction mode (intra prediction or inter prediction) and related prediction information (e.g., motion information for inter prediction). Video decoder 300 can then combine (on a sample-by-sample basis) the prediction block and the residual block to reproduce the original block. Video decoder 300 can perform additional processing such as performing a deblocking process to reduce visual artifacts along boundaries of the blocks.

[0064] Video encoder 200 can encode and video decoder 300 can decode one or more syntax elements that specify filtering parameters used by filters of video encoder 200 and to be used by filters of video decoder 300. Example filters include, but are not limited to, an adaptive loop filter (ALF), a deblocking filter, and a sample adaptive offset (SAO) filter. These syntax elements can be coded in a picture header (PH), a block header, a slice header (SH), or other syntax data (e.g., a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS)).

[0065] In VVC Draft 9, when ALF / SAO is enabled, an advanced enable flag appears in the picture header (PH) or slice header (SH).

[0066] PH:

[0067]

[0068] Semantics of the picture-level ALF control flag:

[0069] ph_alf_enabled_flag equal to 1 specifies that the adaptive loop filter is enabled and can be used for the current picture. ph_alf_enabled_flag equal to 0 specifies that the adaptive loop filter is disabled and is not used for the current picture. When not present, ph_alf_enabled_flag is inferred to be equal to 0.

[0070] ph_alf_cb_flag equal to 0 specifies that the adaptive loop filter is disabled and is not applied to the Cb color component of the current picture. ph_alf_cb_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cb color component of the current picture. When ph_alf_cb_flag is not present, it is inferred to be equal to 0.

[0071] ph_alf_cr_flag equal to 0 specifies that the adaptive loop filter is disabled and is not applied to the Cr color component of the current picture. ph_alf_cr_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cr color component of the current picture. When ph_alf_cr_flag is not present, it is inferred to be equal to 0.

[0072] ph_cc_alf_cb_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter for the Cb color component is enabled and can be used for the current picture. ph_cc_alf_cb_enabled_flag equal to 0 specifies that the cross-component adaptive loop filter for the Cb color component is disabled and is not used for the current picture. When not present, ph_cc_alf_cb_enabled_flag is inferred to be equal to 0.

[0073] ph_cc_alf_cr_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter for the Cr color component is enabled and can be used for the current picture. ph_cc_alf_cr_enabled_flag equal to 0 specifies that the cross-component adaptive loop filter for the Cr color component is disabled and is not used for the current picture. When not present, ph_cc_alf_cr_enabled_flag is inferred to be equal to 0.

[0074]

[0075] Semantics of picture-level SAO control flags:

[0076] ph_sao_luma_enabled_flag equal to 1 specifies that SAO is enabled and can be used for the luma component of the current picture. ph_sao_luma_enabled_flag equal to 0 specifies that SAO is disabled and is not used for the luma component of the current picture. When ph_sao_luma_enabled_flag is not present, it is inferred to be equal to 0.

[0077] ph_sao_chroma_enabled_flag equal to 1 specifies that SAO is enabled and can be used for the chroma component of the current picture. ph_sao_chroma_enabled_flag equal to 0 specifies that SAO is disabled and is not used for the chroma component of the current picture. When ph_sao_chroma_enabled_flag is not present, it is inferred to be equal to 0.

[0078] SH:

[0079]

[0080]

[0081] Semantics of slice-level ALF control flags:

[0082] sh_alf_enabled_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Y, Cb or Cr color components in the slice. sh_alf_enabled_flag equal to 0 specifies that the adaptive loop filter is disabled and is not applied to all color components in the slice. When not present, the value of sh_alf_enabled_flag is inferred to be equal to ph_alf_enabled_flag.

[0083] sh_alf_cb_flag equal to 0 specifies that the adaptive loop filter is not applied to the Cb color component of the current slice. sh_alf_cb_flag equal to 1 specifies that the adaptive loop filter is applied to the Cb color component of the current slice. When sh_alf_cb_flag is not present, it is inferred to be equal to ph_alf_cb_flag.

[0084] sh_alf_cr_flag equal to 0 specifies that the adaptive loop filter is not applied to the Cr color component of the current slice. sh_alf_cr_flag equal to 1 specifies that the adaptive loop filter is applied to the Cr color component of the current slice. When sh_alf_cr_flag is not present, it is inferred to be equal to ph_alf_cr_flag.

[0085] sh_cc_alf_cb_enabled_flag equal to 0 specifies that the cross-component filter is disabled and not applied to the Cb color component. sh_cc_alf_cb_enabled_flag equal to 1 specifies that the cross-component filter is enabled and can be applied to the Cb color component. When sh_cc_alf_cb_enabled_flag is not present, it is inferred to be equal to ph_cc_alf_cb_enabled_flag.

[0086] sh_cc_alf_cr_enabled_flag equal to 0 specifies that the cross-component filter is disabled and not applied to the Cr color component. sh_cc_alf_cr_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter is enabled and can be applied to the Cr color component. When sh_cc_alf_cr_enabled_flag is not present, it is inferred to be equal to ph_cc_alf_cr_enabled_flag.

[0087]

[0088] sh_sao_luma_flag equal to 1 specifies that SAO is enabled for the luma component in the current slice. sh_sao_luma_flag equal to 0 specifies that SAO is disabled for the luma component in the current slice. When sh_sao_luma_flag is not present, it is inferred to be equal to ph_sao_luma_enabled_flag.

[0089] sh_sao_chroma_flag equal to 1 specifies that SAO is enabled for the chroma component in the current slice. sh_sao_chroma_flag equal to 0 specifies that SAO is disabled for the chroma component in the current slice. When sh_sao_chroma_flag is not present, it is inferred to be equal to ph_sao_chroma_enabled_flag.

[0090] In VVC Draft 9, the maximum number of APSs of each adaptive parameter set (APS) type is limited. Given an APS ID and an APS type, an APS can be a suffix APS or a prefix APS. When any prefix APS NAL units are present in a picture unit (PU), they shall be located before the first VCL unit of the PU. When any suffix APS NAL units are present in a PU, they shall be located after the last VCL unit of the PU. In a PU, a suffix APS and a prefix APS with the same APS ID and APS type can have different content.

[0091] An example deblocking filter parameter signal in picture header (PH) is described below. In VVC Draft 9, when both pps_deblocking_filter_override_enabled_flag and pps_dbf_info_in_ph_flag are equal to 1, deblocking filter control parameters can be present in the picture header.

[0092]

[0093]

[0094] The signaling of the above SAO / ALF parameters can have one or more drawbacks. When the enabling flag is not present in the PH and is inferred to be equal to 0, according to the semantics, the tool (e.g., deblocking) is disabled and not used for the current picture. However, in the slice header, there can be a corresponding enabling flag, and this flag can have the value 1, which means that the tool is enabled and can be used for the current slice.

[0095] Table 1: Truth table for ph_alf_enabled_flag and sh_alf_enabled_flag

[0096]

[0097] For example, as shown in Table 1 above, when sh_alf_enabled_flag is equal to 1, a conflict with the definition of ph_alf_enabled_flag can occur when sps_alf_enable_flag is 1 and pps_alf_info_in_ph_flag is 0. In particular, when ph_alf_enabled_flag is not present in the picture header, it is inferred to be equal to 0. This means that ALF is not applied to the current picture. However, when sps_alf_enabled_flag is 1 and pps_alf_info_in_ph_flag is 0, sh_alf_enabled_flag is present in the slice header of the bitstream. The value of sh_als_enabled_flag can be equal to 1. This means that ALF can be applied to the current slice, which can be further indicated by the ALF enabling flag of the coding tree block. This conflicts with the definition of ph_alf_enabled_flag being equal to 0, i.e., ALF is disabled for the entire picture.

[0098] Similar issues can exist for other flags (e.g., ph alf cb flag, ph alf cr flag, ph cc alf cb enabled flag, ph cc alf cr enabled flag, ph sao luma enabled flag, and ph sao chroma enabled flag). For example, other flags can have signaling scenarios in which there are conflicting definitions in certain scenarios. Syntax elements with conflicting definitions can be undesirable.

[0099] As another example, the value pps dbf info in ph flag can be 1 only when pps_deblocking_filter_override_enabled_flag is equal to 1 in the PPS.

[0100]

[0101] Accordingly, pps_deblocking_filter_override_enabled_flag is redundant in the PH.

[0102] Furthermore, the aforementioned APS techniques can have one or more drawbacks. In a picture unit (PU), if a signaled suffix APS and a referenced APS have the same APS ID and APS type, it can be necessary to store the content of both APSs. Thus, two APSs of memory are used, which means that in some implementations the memory requirements are doubled. Let n i denote the maximum number of APSs with type i, if n i suffix APSs with type i are signaled, 2*n i APSs with type i can be required, such that the content of the referenced APS is not overwritten by the content of the suffix APS with the same APS ID. This additional memory requirement can be undesirable.

[0103] The present disclosure provides solutions to the aforementioned problems, where the disclosed techniques can be used individually or in any combination. Implementation examples are provided as being marked with respect to VVC Draft 9.

[0104] According to one or more techniques of this disclosure, a video coder can utilize inference rules such that values of syntax elements are inferred to resolve a conflict between an inferred value in a picture header and a possibility of enabling a tool control parameter in a slice. As one example, a video decoder can infer (and a video encoder can similarly selectively signal) that a picture header syntax element is equal to a tool control flag signaled in, for example, an SPS, when the syntax is not present. In another example, a video decoder can infer that a picture header syntax element is 0 only when the syntax is not present. For example, when a tool control flag signaled in, for example, an SPS, is disabled, then a video decoder can infer that a picture header syntax (tool control flag in PH) is disabled. For another example, when a chroma component is not present in the bitstream, e.g., the SPS only indicates that chroma is present in the bitstream, a video coder can infer that a picture header syntax related to chroma (chroma tool control flag) is equal to being disabled. In another example, when a syntax element is not present and the inferred picture header would not be used for the syntax element in the slice header, a video coder can not infer the picture header syntax.

[0105] As discussed above, the techniques of this disclosure can be applicable to multiple control syntax elements. Specific examples are provided below for SAO and ALF syntax elements.

[0106] As a first example, the techniques of this disclosure can implement the following for SAO syntax elements:

[0107] When ph_sao_luma_enabled_flag is not present in the bitstream, the value of ph_sao_luma_enabled_flag can be inferred to be equal to the value of sps_sao_enable_flag of the referenced SPS.

[0108] When ph_sao_chroma_enabled_flag is not present in the bitstream, if SAO is enabled in the SPS and the chroma type is not 4:0:0, ph_sao_chroma_enabled_flag can be inferred to be equal to 1; otherwise, it can be inferred to be equal to 0.

[0109] This first example for SAO syntax elements can be impacted by the following changes to VVC Draft 9, where the content in <delete> ……< / delete> < tag is removed and the content in <new> ……< / new> < tag is added:

[0110] ph_sao_luma_enabled_flag equal to 1 specifies that SAO is enabled and can be used for the luma component of the current picture. ph_sao_luma_enabled_flag equal to 0 specifies that SAO is disabled and is not used for the luma component of the current picture. When ph_sao_luma_enabled_flag is not present, it is inferred to be equal to 0. <delete> 0< / delete> <new>sps_sao_enable_flag< / new> .

[0111] ph_sao_chroma_enabled_flag equal to 1 specifies that SAO is enabled and can be used for the chroma component of the current picture. ph_sao_chroma_enabled_flag equal to 0 specifies that SAO is disabled and is not used for the chroma component of the current picture. When ph_sao_chroma_enabled_flag is not present, <delete>It is inferred to be equal to 0.< / delete> <new>It is inferred as follows.

[0112] - When sps_sao_enable_flag is equal to 1 and ChromaArrayType is not equal to 0, ph_sao_chroma_enabled_flag is inferred to be equal to 1.

[0113] - Otherwise, ph_sao_chroma_enabled_flag is inferred to be equal to 0.< / new>

[0114] As a second example, the techniques of this disclosure can implement the following for SAO syntax elements:

[0115] When ph_sao_luma_enabled_flag is not present in the bitstream and SAO is disabled in the SPS, ph_sao_luma_enabled_flag can be inferred to be 0.

[0116] When ph_sao_chroma_enabled_flag is not present in the bitstream, if SAO is disabled in the SPS or the chroma type is 4:0:0, ph_sao_chroma_enabled_flag can be inferred to be equal to 0.

[0117] This second example for SAO syntax elements can be impacted by the following changes to VVC Draft 9, where the content in the <delete> ……< / delete> tag is removed and the content in the <new> ……< / new> tag is added:

[0118] ph_sao_luma_enabled_flag equal to 1 specifies that SAO is enabled and can be used for the luma component of the current picture. ph_sao_luma_enabled_flag equal to 0 specifies that SAO is disabled and is not used for the luma component of the current picture. When ph_sao_luma_enabled_flag is not present <new>and sps_sao_enable_flag is equal to 0< / new> , it is inferred to be equal to 0.

[0119] ph_sao_chroma_enabled_flag equal to 1 specifies that SAO is enabled and can be used for chroma components of the current picture. ph_sao_chroma_enabled_flag equal to 0 specifies that SAO is disabled and not used for chroma components of the current picture. When ph_sao_chroma_enabled_flag is not present, <new>if sps_sao_enable_flag is equal to 0 or ChromaArrayType is equal to 0< / new> then it is inferred to be equal to 0.

[0120] As a third example, the techniques of this disclosure can implement the following for ALF syntax elements:

[0121] When ph_alf_enabled_flag is not present in the bitstream and ALF is disabled in the SPS, ALF can be disabled for the current picture.

[0122] When ph_alf_cb_flag is not present in the bitstream and one of the following conditions is satisfied:

[0123] • ALF is disabled in the SPS

[0124] • the chroma type is 4:0:0,

[0125] • ALF is disabled for the current picture

[0126] then ALF can be disabled for Cb components in the current picture.

[0127] Alternatively, when ph_alf_cb_flag is not present in the bitstream and one of the following conditions is satisfied:

[0128] • the chroma type is 4:0:0,

[0129] • ALF is disabled for the current picture

[0130] then ALF can be disabled for Cb components in the current picture.

[0131] When ph_alf_cr_flag is not present in the bitstream and one of the following conditions is satisfied:

[0132] • ALF is disabled in the SPS,

[0133] • the chroma type is 4:0:0,

[0134] • ALF is disabled for the current picture

[0135] then ALF can be disabled for Cr components in the current picture.

[0136] Alternatively, when ph_alf_cr_flag is not present in the bitstream and one of the following conditions is satisfied:

[0137] • chroma_type is 4:0:0,

[0138] • ALF is disabled for the current picture

[0139] then ALF can be disabled for the Cr component in the current picture

[0140] When ph_cc_alf_cb_enabled_flag is not present in the bitstream and one of the following conditions is satisfied:

[0141] • CCALF is disabled in the SPS,

[0142] • ALF is disabled for the current picture

[0143] then CCALF can be disabled for the Cb component in the current picture.

[0144] When ph_cc_alf_cr_enabled_flag is not present in the bitstream and one of the following conditions is satisfied:

[0145] • CCALF is disabled in the SPS,

[0146] • ALF is disabled for the current picture

[0147] then CCALF can be disabled for the Cr component in the current picture.

[0148] When sh_alf_cb_flag is not present, sh_alf_cb_flag can be inferred as:

[0149] - equal to 0 if ALF is disabled for the slice or ALF is disabled for the Cb component of the current picture (ALF is disabled for the Cb component in the current slice);

[0150] - equal to 1 otherwise (ALF is enabled for the Cb component in the current slice).

[0151] When sh_alf_cr_flag is not present, sh_alf_cr_flag can be inferred as:

[0152] - equal to 0 if ALF is disabled for the slice or ALF is disabled for the Cr component of the current picture (ALF is disabled for the Cr component in the current slice);

[0153] - equal to 1 otherwise (ALF is enabled for the Cr component in the current slice).

[0154] When sh_cc_alf_cb_enabled_flag is not present, sh_cc_alf_cb_enabled_flag can be inferred to be equal to 0.

[0155] - If ALF is disabled for the slice or CC ALF is disabled for the Cb component of the current picture, equal to 0 (CC ALF is disabled for the Cb component in the current slice);

[0156] - Otherwise, equal to 1 (CC ALF is enabled for the Cb component in the current slice).

[0157] When sh_cc_alf_cr_enabled_flag is not present, sh_cc_alf_cr_enabled_flag can be inferred to be equal to 0.

[0158] - If ALF is disabled for the slice or CC ALF is disabled for the Cb component of the current picture, equal to 0 (CC ALF is disabled for the Cb component in the current slice);

[0159] - Otherwise, equal to 1 (CC ALF is enabled for the Cb component in the current slice).

[0160] This third example for the ALF syntax elements can be impacted by the following changes in VVC Draft 9, where the content in <delete> ……< / delete> tag is removed and the content in <new> ……< / new> tag is added:

[0161] ph_alf_enabled_flag equal to 1 specifies that the adaptive loop filter is enabled and can be used for the current picture. ph_alf_enabled_flag equal to 0 specifies that the adaptive loop filter is disabled and is not used for the current picture. When not present, <new>if sps_alf_enabled_flag is equal to 0< / new> ph_alf_enabled_flag is inferred to be equal to 0.

[0162] ph_alf_cb_flag equal to 0 specifies that the adaptive loop filter is disabled and is not applied to the Cb color component of the current picture. ph_alf_cb_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cb color component of the current picture. When ph_alf_cb_flag is not present in the bitstream, <new>ph_alf_cb_flag is inferred to be equal to 0 if one of the following conditions is true:

[0163] - sps_alf_enabled_flag is equal to 0

[0164] - ChromaArrayTypel is equal to 0

[0165] - ph_alf_enabled_flag is equal to 0< / new>

[0166] Alternatively, ph_alf_cb_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cb color component of the current picture. ph_alf_cb_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cb color component of the current picture. When ph_alf_cb_flag is not present in the bitstream, <new>ph_alf_cb_flag is inferred to be equal to 0 if one of the following conditions is true:

[0167] - ChromaArrayTyp equal to 0

[0168] - ph_alf_enabled_flag equal to 0< / new>

[0169] ph_alf_cr_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cr color component of the current picture. ph_alf_cr_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cr color component of the current picture. When ph_alf_cr_flag is not present in the bitstream, <new>ph_alf_cr_flag is inferred to be equal to 0 if one of the following conditions is true:

[0170] - sps_alf_enabled_flag is equal to 0

[0171] - ChromaArrayType is equal to 0

[0172] - ph_alf_enabled_flag is equal to 0< / new>

[0173] Alternatively, ph_alf_cr_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cr color component of the current picture. ph_alf_cr_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cr color component of the current picture. When ph_alf_cr_flag is not present in the bitstream, <new>ph_alf_cr_flag is inferred to be equal to 0 if one of the following conditions is met:

[0174] - ChromaArrayType is equal to 0

[0175] - ph_alf_enabled_flag is equal to 0< / new>

[0176] sh_alf_cb_flag equal to 0 specifies that the adaptive loop filter is not applied to the Cb color component of the current slice. sh_alf_cb_flag equal to 1 specifies that the adaptive loop filter is applied to the Cb color component of the current slice. When sh_alf_cb_flag is not present, <new>sh alf cb flag is inferred as follows:

[0177] - If sh alf enabled flag is equal to 0 or ph alf cb flag is equal to 0, sh alf cb flag is inferred to be equal to 0

[0178] - Otherwise (both sh alf enabled flag and ph alf cb flag are equal to 1), sh alf cb flag is inferred to be equal to 1< / new>

[0179] sh_alf_cr_flag equal to 0 specifies that the adaptive loop filter is not applied to the Cr color component of the current slice. sh_alf_cr_flag equal to 1 specifies that the adaptive loop filter is applied to the Cr color component of the current slice. When sh_alf_cr_flag is not present, <new>sh_alf_cr_flag is inferred as follows:

[0180] - If sh_alf_enabled_flag is equal to 0 or ph_alf_cr_flag is equal to 0, sh_alf_cr_flag is inferred to be equal to 0

[0181] - Otherwise (both sh_alf_enabled_flag and ph_alf_cr_flag are equal to 1), sh_alf_cr_flag is inferred to be equal to 1< / new>

[0182] ph_cc_alf_cb_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter for the Cb color component is enabled and can be used for the current picture. ph_cc_alf_cb_enabled_flag equal to 0 specifies that the cross-component adaptive loop filter for the Cb color component is disabled and not used for the current picture. When not present, ph_cc_alf_cb_enabled_flag is inferred to be equal to 0, <new>If one of the following conditions is satisfied:

[0183] - sps_ccalf_enabled_flag is equal to 0

[0184] - ph_alf_enable_flag is equal to 0< / new>

[0185] ph_cc_alf_cr_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter for the Cr color component is enabled and can be used for the current picture. ph_cc_alf_cr_enabled_flag equal to 0 specifies that the cross-component adaptive loop filter for the Cr color component is disabled and is not used for the current picture. When not present, ph_cc_alf_cr_enabled_flag is inferred to be equal to 0. <new>If one of the following conditions is satisfied:

[0186] - sps_ccalf_enabled_flag is equal to 0

[0187] - ph_alf_enable_flag is equal to 0< / new>

[0188] sh_cc_alf_cb_enabled_flag equal to 0 specifies that the cross-component filter is disabled and is not applied to the Cb color component. sh_cc_alf_cb_enabled_flag equal to 1 specifies that the cross-component filter is enabled and can be applied to the Cb color component. When sh_cc_alf_cb_enabled_flag is not present, it is inferred as follows:

[0189] - <new>If sh_alf_enabled_flag is equal to 0 or ph_cc_alf_cb_enabled_flag is equal to 0, sh_cc_alf_cb_enabled_flag is inferred to be equal to 0

[0190] - Otherwise (both sh_alf_enabled_flag and ph_cc_alf_cb_enabled_flag are equal to 1), sh_cc_alf_cb_enabled_flag is inferred to be equal to 1< / new>

[0191] sh_cc_alf_cr_enabled_flag equal to 0 specifies that the cross-component filter is disabled and is not applied to the Cr color component. sh_cc_alf_cr_enabled_flag equal to 1 specifies that the cross-component filter is enabled and can be applied to the Cr color component. When sh_cc_alf_cr_enabled_flag is not present, it is inferred as follows:

[0192] - <new>If sh_alf_enabled_flag is equal to 0 or ph_cc_alf_cr_enabled_flag is equal to 0, sh_cc_alf_cr_enabled_flag is inferred to be equal to 0

[0193] - Otherwise (both sh_alf_enabled_flag and ph_cc_alf_cr_enabled_flag are equal to 1), sh_cc_alf_cr_enabled_flag is inferred to be equal to 1< / new>

[0194] As a fourth example, the techniques of this disclosure can implement the following for ALF syntax elements:

[0195] When ph_alf_enabled_flag is not present in the bitstream, if ALF is disabled in the SPS, ALF can be disabled for the current picture; otherwise (ALF is enabled in the SPS), ALF can be enabled for the current picture.

[0196] When ph_alf_cb_flag is not present in the bitstream, if ALF is disabled in the SPS or the chroma type is 4:0:0 or ALF is disabled for the current picture, ALF can be disabled for the Cb component of the current picture; otherwise, ALF can be enabled for the Cb component of the current picture.

[0197] Alternatively, when ph_alf_cb_flag is not present in the bitstream, ALF can be disabled for the Cb component of the current picture if the chroma type is 4:0:0 or ALF is disabled for the current picture; otherwise, ALF can be enabled for the Cb component of the current picture.

[0198] When ph_alf_cr_flag is not present in the bitstream, ALF can be disabled for the Cr component of the current picture if ALF is disabled in the SPS or the chroma type is 4:0:0 or ALF is disabled for the current picture; otherwise, ALF can be enabled for the Cr component of the current picture.

[0199] Alternatively, when ph_alf_cr_flag is not present in the bitstream, ALF can be disabled for the Cr component of the current picture if the chroma type is 4:0:0 or ALF is disabled for the current picture; otherwise, ALF can be enabled for the Cr component of the current picture.

[0200] When ph_cc_alf_cb_enabled_flag is not present in the bitstream, and if ALF is disabled for the current picture or CCALF is disabled in the SPS, CCALF can be disabled for the Cb component of the current picture; otherwise, CCALF can be enabled for the Cb component of the current picture.

[0201] When ph_cc_alf_cr_enabled_flag is not present in the bitstream, and if ALF is disabled for the current picture or CCALF is disabled in the SPS, CCALF can be disabled for the Cr component of the current picture; otherwise, CCALF can be enabled for the Cr component of the current picture.

[0202] When sh_alf_cb_flag is not present, sh_alf_cb_flag can be inferred as follows:

[0203] - 0 if ALF is disabled for the slice or ALF is disabled for the Cb component of the current picture (ALF is disabled for the Cb component of the current slice);

[0204] - 1 otherwise (ALF is enabled for the Cb component in the current slice).

[0205] When sh_alf_cr_flag is not present, sh_alf_cr_flag can be inferred as follows:

[0206] - 0 if ALF is disabled for the slice or ALF is disabled for the Cr component of the current picture (ALF is disabled for the Cr component in the current slice);

[0207] - Otherwise, 1 (CC ALF is enabled for the Cb component in the current slice).

[0208] When sh_cc_alf_cb_enabled_flag is not present, sh_cc_alf_cb_enabled_flag can be inferred as follows:

[0209] - If ALF is disabled for the slice or CC ALF is disabled for the Cb component of the current picture, 0 (CC ALF is disabled for the Cb component in the current slice);

[0210] - Otherwise, 1 (CC ALF is enabled for the Cb component in the current slice).

[0211] When sh_cc_alf_cr_enabled_flag is not present, sh_cc_alf_cr_enabled_flag can be inferred as follows:

[0212] - If ALF is disabled for the slice or CC ALF is disabled for the Cb component of the current picture, 0 (CC ALF is disabled for the Cb component in the current slice);

[0213] - Otherwise, 1 (CC ALF is enabled for the Cb component in the current slice).

[0214] This fourth example for the ALF syntax elements can be impacted by the following changes in VVC Draft 9, where the content in the <delete> ……< / delete> tag is removed and the content in the <new> ……< / new> tag is added:

[0215] ph_alf_enabled_flag equal to 1 specifies that the adaptive loop filter is enabled and can be used for the current picture. ph_alf_enabled_flag equal to 0 specifies that the adaptive loop filter is disabled and not used for the current picture. When not present, ph_alf_enabled_flag is inferred to be equal to <delete> 0< / delete> <new>sps_alf_enabled_flag< / new> .

[0216] ph_alf_cb_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cb color component of the current picture. ph_alf_cb_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cb color component of the current picture. When ph_alf_cb_flag is not present in the bitstream: <new>ph_alf_cb_flag is inferred to be equal to 0 if one of the following conditions is true:

[0217] - sps_alf_enabled_flag is equal to 0

[0218] - ChromaArrayTypel is equal to 0

[0219] - ph_alf_enabled_flag is equal to 0

[0220] Otherwise, ph_alf_cb_flag is inferred to be equal to 1.< / new>

[0221] Alternatively, ph_alf_cb_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cb color component of the current picture. ph_alf_cb_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cb color component of the current picture. When ph_alf_cb_flag is not present in the bitstream, it is inferred as follows: <new>ph_alf_cb_flag is inferred to be equal to 0 if one of the following conditions is met:

[0222] - ChromaArrayTyp equal to 0

[0223] - ph_alf_enabled_flag equal to 0

[0224] Otherwise, ph_alf_cb_flag is inferred to be equal to 1.< / new>

[0225] ph_alf_cr_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cr color component of the current picture. ph_alf_cr_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cr color component of the current picture. When ph_alf_cr_flag is not present in the bitstream, it is inferred as follows: <new>ph_alf_cr_flag is inferred to be equal to 0 if one of the following conditions is true:

[0226] - sps_alf_enabled_flag is equal to 0

[0227] - ChromaArrayTypel is equal to 0

[0228] - ph_alf_enabled_flag is equal to 0

[0229] Otherwise, ph_alf_cr_flag is inferred to be equal to 1.< / new>

[0230] Alternatively, ph_alf_cr_flag equal to 0 specifies that the adaptive loop filter is disabled and not applied to the Cr color component of the current picture. ph_alf_cr_flag equal to 1 specifies that the adaptive loop filter is enabled and can be applied to the Cr color component of the current picture. When ph_alf_cr_flag is not present in the bitstream, it is inferred as follows: <new>ph_alf_cr_flag is inferred to be equal to 0 if one of the following conditions is true:

[0231] - ChromaArrayTypel is equal to 0

[0232] - ph_alf_enabled_flag is equal to 0

[0233] Otherwise, ph_alf_cr_flag is inferred to be equal to 1.< / new>

[0234] sh_alf_cb_flag equal to 0 specifies that the adaptive loop filter is not applied to the Cb color component of the current slice. sh_alf_cb_flag equal to 1 specifies that the adaptive loop filter is applied to the Cb color component of the current slice. When sh_alf_cb_flag is not present, <new>sh alf cb flag is inferred as follows:

[0235] - If sh alf enabled flag is equal to 0 or ph alf cb flag is equal to 0, sh alf cb flag is inferred to be equal to 0

[0236] - Otherwise (both sh alf enabled flag and ph alf cb flag are equal to 1), sh alf cb flag is inferred to be equal to 1< / new>

[0237] sh_alf_cr_flag equal to 0 specifies that the adaptive loop filter is not applied to the Cr color component of the current slice. sh_alf_cr_flag equal to 1 specifies that the adaptive loop filter is applied to the Cr color component of the current slice. When sh_alf_cr_flag is not present, sh_alf_cr_flag is inferred as follows:

[0238] - <new>If sh alf enabled flag is equal to 0 or ph alf cr flag is equal to 0, sh alf cr flag is inferred to be equal to 0;

[0239] - Otherwise (both sh alf enabled flag and ph alf cr flag are equal to 1), sh alf cr flag is inferred to be equal to 1< / new>

[0240] ph_cc_alf_cb_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter for the Cb color component is enabled and can be used for the current picture. ph_cc_alf_cb_enabled_flag equal to 0 specifies that the cross-component adaptive loop filter for the Cb color component is disabled and not used for the current picture. When not present, <new>ph_cc_alf_cb_enabled_flag is inferred to be equal to 0 if one of the following conditions is true:

[0241] - sps_ccalf_enabled_flag is equal to 0

[0242] - ph_alf_enable_flag is equal to 0

[0243] Otherwise, ph_cc_alf_cb_enabled_flag is inferred to be equal to 1.< / new>

[0244] ph_cc_alf_cr_enabled_flag equal to 1 specifies that the cross-component adaptive loop filter for the Cr color component is enabled and can be used for the current picture. ph_cc_alf_cr_enabled_flag equal to 0 specifies that the cross-component adaptive loop filter for the Cr color component is disabled and is not used for the current picture. When not present, ph_cc_alf_cr_enabled_flag is inferred to be equal to 0. <new>ph_cc_alf_cr_enabled_flag is inferred to be equal to 0 if one of the following conditions is met:

[0245] - sps_ccalf_enabled_flag is equal to 0

[0246] - ph_alf_enable_flag is equal to 0

[0247] Otherwise, ph_cc_alf_cr_enabled_flag is inferred to be equal to 1.< / new>

[0248] sh_cc_alf_cb_enabled_flag equal to 0 specifies that the cross-component filter is disabled and is not applied to the Cb color component. sh_cc_alf_cb_enabled_flag equal to 1 specifies that the cross-component filter is enabled and can be applied to the Cb color component. When sh_cc_alf_cb_enabled_flag is not present, it is inferred as follows:

[0249] - <new>If sh_alf_enabled_flag is equal to 0 or ph_cc_alf_cb_enabled_flag is equal to 0, sh_cc_alf_cb_enabled_flag is inferred to be equal to 0;

[0250] - Otherwise (both sh_alf_enabled_flag and ph_cc_alf_cb_enabled_flag are equal to 1), sh_cc_alf_cb_enabled_flag is inferred to be equal to 1.< / new>

[0251] sh_cc_alf_cr_enabled_flag equal to 0 specifies that the cross-component filter is disabled and is not applied to the Cr color component. sh_cc_alf_cr_enabled_flag equal to 1 specifies that the cross-component filter is enabled and can be applied to the Cr color component. When sh_cc_alf_cr_enabled_flag is not present, it is inferred as follows:

[0252] - <new>If sh_alf_enabled_flag is equal to 0 or ph_cc_alf_cr_enabled_flag is equal to 0, sh_cc_alf_cr_enabled_flag is inferred to be equal to 0;

[0253] - Otherwise (both sh_alf_enabled_flag and ph_cc_alf_cr_enabled_flag are equal to 1), sh_cc_alf_cr_enabled_flag is inferred to be equal to 1< / new>

[0254] According to one or more techniques of this disclosure, a method of coding video data includes coding, via a first syntax level of a coded video bitstream, a first tool control flag having a value specifying whether a first tool is enabled; in response to the tool control flag specifying that the particular tool is not enabled, inferring, in a second syntax level, a value of a second tool control flag to be the value of the first tool control flag, the second tool control flag specifying whether the first tool can be used; and selectively using the first tool on a block of the video data based on the value of the second tool control flag.

[0255] According to one or more techniques of this disclosure, a method of coding video data includes coding, via a first syntax level of a coded video bitstream, a first tool control flag having a value specifying whether a first tool is enabled; in response to the tool control flag specifying that the particular tool is not enabled, inferring, in a second syntax level, a value of a second tool control flag to be the value of the first tool control flag, the second tool control flag specifying whether the first tool can be used; and selectively using the first tool on a block of the video data based on the value of the second tool control flag.

[0256] According to one or more techniques disclosed herein, a video decoder can selectively signal deblocking filter (DBF) information based on pps_dbf_info_in_ph_flag. In other words, the video decoder can signal DBF information based on the value of pps_dbf_info_in_ph_flag, regardless of the value of pps_deblocking_filter_override_enabled_flag. As shown below, the DBF information may include one or more of the following syntax elements: ph_deblocking_filter_override_flag, ph_deblocking_filter_disabled_flag, ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2.

[0257] This fourth example targeting ALF syntax elements may be affected by the following changes in VVC Draft 9, where the deletion of... <delete> ……< / delete> Content in the tag:

[0258]

[0259]

[0260] A value of 1 for `pps_deblocking_filter_override_enabled_flag` indicates that `ph_deblocking_filter_override_flag` exists in the PH referencing PPS, or `sh_deblocking_filter_override_flag` exists in the slice header referencing PPS. A value of 0 for `pps_deblocking_filter_override_enabled_flag` indicates that `ph_deblocking_filter_override_flag` does not exist in the PH referencing PPS, or `sh_deblocking_filter_override_flag` does not exist in the slice header referencing PPS. When it does not exist, the value of `pps_deblocking_filter_override_enabled_flag` is inferred to be 0.

[0261] ph_deblocking_filter_override_flag equal to 1 specifies that deblocking parameters are present in the PH. ph_deblocking_filter_override_flag equal to 0 specifies that deblocking parameters are not present in the PH. When not present, the value of ph_deblocking_filter_override_flag is inferred to be equal to 0.

[0262] ph_deblocking_filter_disabled_flag equal to 1 specifies that the operation of applying deblocking filtering is not applied for slices associated with such PHs where sh_deblocking_filter_disabled_flag is not present in the SH and is inferred to be equal to 1 or sh_deblocking_filter_disabled_flag is present in the SH and is equal to 1; and also specifies that the operation of applying deblocking filtering is applied for slices associated with such PHs where sh_deblocking_filter_disabled_flag is not present in the SH and is inferred to be equal to 0 or sh_deblocking_filter_disabled_flag is present in the SH and is equal to 0.

[0263] ph_deblocking_filter_disabled_flag equal to 0 specifies that the operation of applying deblocking filtering is applied for slices associated with such PHs where sh_deblocking_filter_disabled_flag is not present in the SH and is inferred to be equal to 0 or sh_deblocking_filter_disabled_flag is present in the SH and is equal to 0; and also specifies that the operation of applying deblocking filtering is not applied for slices associated with such PHs where sh_deblocking_filter_disabled_flag is not present in the SH and is inferred to be equal to 1 or sh_deblocking_filter_disabled_flag is present in the SH and is equal to 1.

[0264] Alternatively:

[0265] When pps_dbf_info_in_ph_flag is equal to 1, ph_deblocking_filter_disabled_flag equal to 1 specifies that the operation of applying deblocking filtering is not applied for slices associated with the PH, and ph_deblocking_filter_disabled_flag equal to 0 specifies that the operation of applying deblocking filtering is applied for slices associated with the PH.

[0266] When ph_deblocking_filter_disabled_flag is not present, it is inferred as follows:

[0267] - If both pps_deblocking_filter_disabled_flag and ph_deblocking_filter_override_flag are equal to 1, the value of ph_deblocking_filter_disabled_flag is inferred to be equal to 0.

[0268] - Otherwise (pps_deblocking_filter_disabled_flag or ph_deblocking_filter_override_flag is equal to 0), the value of ph_deblocking_filter_disabled_flag is inferred to be equal to pps_deblocking_filter_disabled_flag.

[0269] ph_luma_beta_offset_div2 and ph_luma_tc_offset_div2 specify the deblocking parameter offsets (divided by 2) for beta and tC that are applied to the luma component of the slice associated with the PH. The values of both ph_luma_beta_offset_div2 and ph_luma_tc_offset_div2 shall be in the range of -12 to 12, inclusive. When not present, the values of ph_luma_beta_offset_div2 and ph_luma_tc_offset_div2 are inferred to be equal to pps_luma_beta_offset_div2 and pps_luma_tc_offset_div2, respectively.

[0270] ph_cb_beta_offset_div2 and ph_cb_tc_offset_div2 specify the deblocking parameter offsets (divided by 2) for beta and tC that are applied to the Cb component of the slice associated with the PH. The values of both ph_cb_beta_offset_div2 and ph_cb_tc_offset_div2 shall be in the range of -12 to 12, inclusive. When not present, the values of ph_cb_beta_offset_div2 and ph_cb_tc_offset_div2 are inferred to be equal to ph_luma_beta_offset_div2 and ph_luma_tc_offset_div2, respectively.

[0271] ph_cr_beta_offset_div2 and ph_cr_tc_offset_div2 specify the deblocking parameter offsets (divided by 2) for beta and tC, which are applied to the Cr component of slices associated with the PH. The values of both ph_cr_beta_offset_div2 and ph_cr_tc_offset_div2 shall be in the range of -12 to 12, inclusive. When not present, the values of ph_cr_beta_offset_div2 and ph_cr_tc_offset_div2 are inferred to be equal to ph_luma_beta_offset_div2 and ph_luma_tc_offset_div2, respectively.

[0272] APS memory requirement constraints. As discussed above, the memory requirements of APS in VVC Draft 9 can be undesirable in some examples. According to one or more techniques of this disclosure, a video coder (e.g., video encoder 200 and / or video decoder 300) can limit the number (e.g., quantity) of current (signaled) suffix APS NAL units and the number of referenced APSs. For example, for each APS type in a PU, the video coder can limit the sum of the number of current (signaled) suffix APS NAL units and the number of referenced APSs that exist to not exceed a limit (e.g., a threshold or an upper bound). Additionally, in a PU, the video coder can prevent the current (signaled) suffix APS NAL units and the referenced APSs in the PU from having the same APS ID. In this way, the memory requirements of APSs can be reduced.

[0273] In another example, for each APS type, the video coder can prevent the number of current (signaled) suffix APS NAL units in a PU from exceeding a first limit and prevent the number of referenced APSs in the PU from exceeding a second limit. The two limits can be the same or different. The sum of the two limits can not exceed a third limit. For example, the first limit is 6, the second limit is 2, and the third limit is 8. For another example, the first limit is equal to the third limit; the second limit in a PU can be adaptive and can be equal to the third limit minus the number of uniquely referenced APSs in that PU.

[0274] In some examples, the coding scheme (e.g., number of bits / descriptor used) for the APS syntax elements can be adjusted based on one of the above limitations. For ALF, x can be equal to ceil(log2(second limitation + 1)). As shown below, the number of bits used to code ph num alf aps ids luma and / or sh num alf aps ids luma can be based on the value of the second limitation. For example, when the second limitation is 8, x is equal to 4, and both ph num alf aps ids luma and sh num alf aps ids luma should not be greater than 8. As a bitstream conformance constraint, it can be required that the number of luma APSs referred to in a picture or slice cannot exceed the second limitation.

[0275]

[0276]

[0277]

[0278]

[0279]

[0280] In another example, for each APS type, any two signaled APS NAL units in a PU should not have the same APS ID.

[0281] In another example, for each APS type, any two existing (can be signaled or referred) suffix APS NAL units in a PU should not have the same APS ID.

[0282] In another example, for each APS type, any two existing (can be signaled or referred) prefix APS NAL units in a PU should not have the same APS ID.

[0283] In another example, for each APS type, in a PU, a signaled suffix APS cannot have the same APS ID as a referred APS.

[0284] According to techniques of this disclosure, a method of encoding video data includes limiting a number of suffix adaptation parameter set (APS) network abstraction layer (NAL) units of a particular APS type present in a picture of the video data to be less than or equal to a first threshold number, limiting a number of referenced APSs of the APS type in the picture of the video data to be less than or equal to a second threshold number, and encoding, in a coded video bitstream, one or more syntax elements specifying the number of APS NAL units of the particular APS type present and / or one or more syntax elements specifying the number of referenced APSs of the particular APS type.

[0285] This disclosure can generally refer to “signaling” certain information, e.g., syntax elements. The term “signaling” generally refers to the communication of values for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 can signal values for syntax elements in a bitstream. Generally, signaling refers to generating values in a bitstream. As noted above, source device 102 can transmit the bitstream to destination device 116 in substantially real time or not in real time, e.g., as can occur when syntax elements are stored to storage device 112 for later retrieval by destination device 116.

[0286] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, and dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where 0 indicates a horizontal split and 1 indicates a vertical split in this example. For quadtree splits, no split type indication is needed because quadtree nodes split a block horizontally and vertically into 4 equally-sized sub-blocks. Thus, video encoder 200 can encode and video decoder 300 can decode syntax elements (e.g., split information) for the region tree level (i.e., solid lines) of the QTBT structure 130 and syntax elements (e.g., split information) for the prediction tree level (i.e., dashed lines) of the QTBT structure 130. For a CU represented by a terminal leaf node of the QTBT structure 130, video encoder 200 can encode and video decoder 300 can decode video data such as prediction and transform data.

[0287] In general, Figure 2BA CTU 132 can be associated with parameters defining the size of blocks corresponding to nodes of the QTBT structure 130 at the first and second levels. These parameters can include a CTU size (representing the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, representing the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, representing the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, representing the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, representing the minimum allowed binary tree leaf node size).

[0288] A root node of a QTBT structure corresponding to a CTU can have four child nodes at the first level of the QTBT structure, each of which can be partitioned according to quadtree partitioning. That is, a node at the first level is either a leaf node (having no child nodes) or has four child nodes. The example of the QTBT structure 130 represents such a node as including a parent node and child nodes with solid lines for branches. If a node at the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the node can be further partitioned by a corresponding binary tree. The binary tree split of a node can be iterated until the split results in nodes that reach the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such a node as having dashed lines for branches. Binary tree leaf nodes are referred to as coding units (CUs), which are used for prediction (e.g., intra- or inter-prediction) and transform without any further partitioning. As discussed above, a CU can also be referred to as a “video block” or “block.”

[0289] In one example of the QTBT partitioning structure, the CTU size is set to 128x128 (luma samples and two corresponding 64x64 chroma samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quaternary tree partitioning is first applied to the CTU to generate quaternary tree leaf nodes. A quaternary tree leaf node can have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If a quaternary tree leaf node is 128x128, the leaf quaternary tree node will not be further split by the binary tree because its size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the quaternary tree leaf node will be further partitioned by the binary tree. Thus, the quaternary tree leaf node is also the root node of the binary tree, and the binary tree depth is 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. When a binary tree node has a width equal to MinBTSize (4 in this example), this means no further vertical splitting is allowed. Similarly, a height of a binary tree node equal to MinBTSize means no further horizontal splitting of the binary tree node is allowed. As noted above, leaf nodes of the binary tree are referred to as CUs and are further processed according to prediction and transform without further partitioning.

[0290] Figure 3 FIG. 1 is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure. Figure 3 FIG. 1 is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure.

[0291] In Figure 3In the example of FIG. 2, video encoder 200 includes video data memory 230, mode select unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, decoded picture buffer (DPB) 218, and entropy encoding unit 220. Any or all of video data memory 230, mode select unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy encoding unit 220 can be implemented in one or more processors or in processing circuitry. For instance, the units of video encoder 200 can be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor (ASIC) as a FPGA. Moreover, video encoder 200 can include additional or alternative processors or processing circuitry to perform these and other functions.

[0292] Video data memory 230 can store video data to be encoded by the components of video encoder 200. Video encoder 200 can receive the video data stored in video data memory 230 from, for example, video source 104 Figure 1 DPB 218 can act as a reference picture memory that stores reference video data for use in prediction of subsequent video data by video encoder 200. Video data memory 230 and DPB 218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magneto resistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, video data memory 230 can be on-chip with other components of video encoder 200, as illustrated, or off-chip relative to those components.

[0293] In this disclosure, reference to video data memory 230 should not be interpreted as being 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, reference to video data memory 230 should be understood as reference memory that stores video data that video encoder 200 receives for encoding (e.g., video data for a current block to be encoded). Figure 1 Memory 106 of source device 102 can also provide temporary storage of the outputs from the various units of video encoder 200.

[0294] Figure 3 The various units shown for video encoder 200 are shown to assist with understanding the operations performed by video encoder 200. The units can be implemented as fixed- function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide particular functionality, and are preset on 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 instance, programmable circuits can execute software or firmware that cause the programmable circuits to operate in the manner defined by instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuits perform are generally immutable. In some examples, one or more of the units can be distinct circuit blocks (fixed-function or programmable), and in some examples, one or more of the units can be integrated circuits.

[0295] Video encoder 200 can include arithmetic logic units (ALUs), elementary function units (EFUs), digital circuits, analog circuits, and / or programmable cores formed from programmable circuits. In examples where the operations of video encoder 200 are performed using software executed by the programmable circuits, memory 106 Figure 1 ) can store the instructions (e.g., object code) of the software that video encoder 200 receives and executes, or another memory within video encoder 200 (not shown) can store such instructions.

[0296] Video data memory 230 is configured to store video data to be encoded. Video encoder 200 can retrieve pictures of the video data from video data memory 230 and provide the video data to residual generation unit 204 and mode selection unit 202. Video data in video data memory 230 can be raw video data that is to be encoded.

[0297] Mode selection unit 202 includes motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226. Mode selection unit 202 can include additional functional units to perform video prediction from other prediction modes. As examples, mode selection unit 202 can include a palette unit, an intra-block copy unit (which can be part of motion estimation unit 222 and / or motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0298] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and rate-distortion values resulting from such combinations. The encoding parameters can include partitioning of CTUs into CUs, prediction modes for CUs, transform types for residual data of CUs, quantization parameters for residual data of CUs, and so on. The mode selection unit 202 can ultimately select the combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0299] The video encoder 200 can partition a picture retrieved from the video data memory 230 into a series of CTUs, and encapsulate one or more CTUs within a slice. The mode selection unit 202 can partition the CTUs of the picture according to a tree structure, such as the QTBT structure described above or the quad-tree structure of HEVC. As described above, the video encoder 200 can form one or more CUs from partitioning a CTU according to the tree structure. Such CUs can also be generally referred to as “video blocks” or “blocks.”

[0300] In general, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for a current block (e.g., a current CU, or in HEVC, an overlapping portion of a PU and a TU). For inter prediction of a current block, the motion estimation unit 222 can 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 the DPB 218). Specifically, the motion estimation unit 222 can compute values that are representative of how similar a potential reference block is to the current block, e.g., according to a sum of absolute difference (SAD), a sum of squared differences (SSD), a mean absolute difference (MAD), a mean squared differences (MSD), and so on. The motion estimation unit 222 can generally perform these computations using sample-by-sample differences between a reference block under consideration and the current block. The motion estimation unit 222 can identify the reference block with the lowest value resulting from these computations, thereby indicating the reference block that most closely matches the current block.

[0301] Motion estimation unit 222 can form one or more motion vectors (MVs) that define locations of reference blocks in a reference picture relative to a location of a current block in the current picture. Motion estimation unit 222 can then provide the motion vector(s) to motion compensation unit 224. For example, for single prediction, motion estimation unit 222 can provide a single motion vector, while for bi-prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vector(s) to generate a predicted block. For example, motion compensation unit 224 can use the motion vector(s) to retrieve data for a reference block. As another example, if the motion vector(s) have fractional sample precision, motion compensation unit 224 can interpolate values for the predicted block according to one or more interpolation filters. Further, for bi-prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by the respective motion vectors and combine the retrieved data, e.g., by sample-wise averaging or weighted averaging.

[0302] As another example, for intra prediction or intra prediction coding, intra prediction unit 226 can generate a predicted block from samples neighboring the current block. For example, for directional modes, intra prediction unit 226 can mathematically combine values of neighboring samples and fill these computed values across the current block in a defined direction to produce the predicted block. As another example, for a DC mode, intra prediction unit 226 can compute an average of neighboring samples of the current block and generate the predicted block to include this resulting average for each sample of the predicted block.

[0303] Mode selection unit 202 provides the predicted block to residual generation unit 204. Residual generation unit 204 receives an original, unencoded version of the current block from video data memory 230 and the predicted block from mode selection unit 202. Residual generation unit 204 computes a sample-wise difference between the current block and the predicted block. The resulting sample-wise difference defines a residual block for the current block. In some examples, residual generation unit 204 can also determine differences between sample values in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, residual generation unit 204 can form using one or more subtractor circuits that perform binary subtraction.

[0304] In examples in which mode selection unit 202 partitions a CU into PUs, each PU can be associated with a luma prediction unit and corresponding chroma prediction units. Video encoder 200 and video decoder 300 can support PUs having various sizes. As noted above, a size of a CU can refer to a size of the luma coding block of the CU, and a size of a PU can refer to a size of the luma prediction unit of the PU. Assuming that a particular CU has a size of 2Nx2N, video encoder 200 can support 2Nx2N or NxN PU sizes for intra-prediction, and 2Nx2N, 2NxN, Nx2N, NxN, or similar symmetric PU sizes for inter-prediction. Video encoder 200 and video decoder 300 can also support non-symmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-prediction.

[0305] In examples in which mode selection unit 202 does not further partition a CU into PUs, each CU can be associated with a luma coding block and corresponding chroma coding blocks. As described above, a size of a CU can refer to a size of the luma coding block of the CU. Video encoder 200 and video decoder 300 can support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0306] For other video coding techniques (e.g., intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding, as a few examples), mode selection unit 202 generates, via a respective unit associated with the coding technique, a prediction block for the current block being encoded. In some examples, such as palette mode coding, mode selection unit 202 can not generate a prediction block, but rather generate syntax elements that indicate a manner in which to reconstruct the block based on a selected palette. In such modes, mode selection unit 202 can provide the syntax elements to entropy encoding unit 220 for encoding.

[0307] As described above, residual generation unit 204 receives video data for a current block and a corresponding prediction block. Residual generation unit 204 then generates a residual block for the current block. To generate the residual block, residual generation unit 204 computes, sample-by-sample, differences between the prediction block and the current block.

[0308] Transform processing unit 206 applies one or more transforms to the residual block to produce a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 can apply various transforms to the residual block to form the transform coefficient block. For example, transform processing unit 206 can apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform. In some examples, transform processing unit 206 can perform multiple transforms, e.g., a primary transform and a secondary transform (e.g., a rotational transform), on the residual block. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0309] Quantization unit 208 can quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 can quantize transform coefficients in 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) can adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization introduces loss of information, thus quantized transform coefficients can have a lower precision than the original transform coefficients produced by transform processing unit 206.

[0310] Inverse quantization unit 210 and inverse transform processing unit 212 can apply inverse quantization and inverse transforms, respectively, to a quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. Reconstruction unit 214 can produce a reconstructed block corresponding to the current block (albeit potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by mode select unit 202. For example, reconstruction unit 214 can add samples of the reconstructed residual block to corresponding samples from the prediction block generated by mode select unit 202 to produce the reconstructed block.

[0311] Filter unit 216 can perform one or more filtering operations on the reconstructed block. For example, filter unit 216 can perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 can be skipped.

[0312] Video encoder 200 stores the reconstructed blocks in DPB 218. For example, in examples where the operations of filter unit 216 are not needed, reconstruction unit 214 can store the reconstructed blocks to DPB 218. In examples where the operations of filter unit 216 are needed, filter unit 216 can store the filtered reconstructed blocks to DPB 218. Motion estimation unit 222 and motion compensation unit 224 can retrieve reference pictures formed from the reconstructed (and potentially filtered) blocks in DPB 218 to inter-predict blocks of a subsequently encoded picture. In addition, intra-prediction unit 226 can use reconstructed blocks in DPB 218 of the current picture to intra-predict other blocks in the current picture.

[0313] In general, entropy encoding unit 220 can entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy encoding unit 220 can entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy encoding unit 220 can entropy encode prediction syntax elements (e.g., motion information for inter-prediction or intra-mode information for intra-prediction) from mode select unit 202. Entropy encoding unit 220 can perform one or more entropy encoding operations on syntax elements, as another example of video data, to generate entropy encoded data. For example, entropy encoding unit 220 can 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 encoding operation on the data. In some examples, entropy encoding unit 220 can operate in a bypass mode in which syntax elements are not entropy encoded.

[0314] Video encoder 200 can output a bitstream that includes the entropy encoded syntax elements needed to reconstruct blocks of a slice or picture. In particular, entropy encoding unit 220 can output the bitstream.

[0315] The operations described above are described in terms of blocks. Such description should be understood to be operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are luma components and chroma components of CUs. In some examples, the luma coding blocks and chroma coding blocks are luma components and chroma components of PUs.

[0316] In some examples, operations performed with respect to chroma coding blocks need not be repeated with respect to luma coding blocks. As one example, operations to identify a motion vector (MV) and a reference picture for a luma coding block need not be repeated to identify an MV and a reference picture for a chroma block. Rather, the MV for the luma coding block can be scaled to determine the MV for the chroma block, and the reference picture can be the same. As another example, the intra prediction process can be the same for luma coding blocks and chroma coding blocks.

[0317] A video encoder 200 represents an example of a device configured to encode video data, including a memory configured to store video data, and one or more processing units implemented in circuitry, the one or more processing units configured to: encode, via a first syntax level of a coded video bitstream, a first tool control flag having a value specifying whether a particular tool is enabled; responsive to the tool control flag specifying that the particular tool is not enabled, infer, in a second syntax level, a value of a second tool control flag to specify whether the first tool can be used; and selectively use / apply the first tool on blocks of the video data based on the value of the second tool control flag.

[0318] A video encoder 200 represents an example of a device configured to encode video data, including a memory configured to store video data, and one or more processing units implemented in circuitry, the one or more processing units configured to: encode, via a first syntax level of a coded video bitstream, a first tool control flag having a value specifying whether a particular tool is enabled; responsive to the tool control flag specifying that the particular tool is not enabled, infer, in a second syntax level, a value of a second tool control flag to specify that the first tool is not used; and selectively use / apply the first tool on blocks of the video data based on the value of the second tool control flag.

[0319] A video encoder 200 represents an example of a device configured to encode video data, including a memory configured to store video data, and one or more processing units implemented in circuitry, the one or more processing units configured to: limit a number of suffix adaptive parameter set (APS) network abstraction layer (NAL) units of a particular APS type present in a picture of the video data to be less than or equal to a first threshold number; limit a number of referenced APSs of the APS type in the picture of the video data to be less than or equal to a second threshold number; and encode, in a coded video bitstream, one or more syntax elements specifying the number of APS NAL units of the particular APS type present and / or one or more syntax elements specifying the number of referenced APSs of the particular APS type.

[0320] Figure 4 This is a block diagram illustrating an example video decoder 300 that can perform the techniques disclosed herein. Figure 4 This disclosure is provided for illustrative purposes and is not intended to limit the techniques broadly illustrated and described herein. For illustrative purposes, this disclosure describes a video decoder 300 based on VVC (ITU-T H.266, under development) and HEVC (ITU-T H.265) technologies. However, the techniques of this disclosure can be implemented by video decoding devices configured for other video decoding standards.

[0321] exist Figure 4 In the example, the video decoder 300 includes a decoded 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 filtering unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filtering unit 312, and DPB 314 can be implemented in one or more processors or in a processing circuitry. For example, units of the video decoder 300 can be implemented as one or more circuit or logic elements as part of a hardware circuitry or as part of a processor (ASIC) of an FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuitry for performing these and other functions.

[0322] The prediction processing unit 304 includes a motion compensation unit 316 and an intra-frame prediction unit 318. The prediction processing unit 304 may include additional units for performing predictions based on other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0323] CPB memory 320 can store video data to be decoded by components of video decoder 300, such as encoded video bitstreams. For example, it can be stored from computer-readable medium 110 ( Figure 1) to obtain video data stored in CPB memory 320. CPB memory 320 can include a CP that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. Also, CPB memory 320 can store video data other than syntax elements of coded pictures, such as temporary data representing outputs of the various units of video decoder 300. DPB 314 generally stores decoded pictures, which video decoder 300 can 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 can be formed by 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 can be provided by the same memory devices or separate memory devices. In various examples, CPB memory 320 can be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0324] Additionally or alternatively, in some examples, video decoder 300 can retrieve coded video data from memory 120 Figure 1 ) stores data as discussed above with regard to CPB memory 320. Likewise, when some or all of the functionality of video decoder 300 is implemented in software to be executed by processing circuitry of video decoder 300, memory 120 can store the instructions to be executed by video decoder 300.

[0325] Figure 4 The various units shown in FIG. 3B are shown to assist with understanding the operations performed by video decoder 300. The units can be implemented as fixed- function circuits, programmable circuits, or a combination thereof. Similar to Figure 3 , fixed-function circuits refer to circuits that provide particular functionality and are preset on the operations they can perform. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations they can perform. For instance, programmable circuits can execute software or firmware that cause the programmable circuits to operate in ways defined by instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuits perform are generally immutable. In some examples, one or more of the units can be distinct circuit blocks (fixed-function or programmable) and, in some examples, one or more of the units can be integrated circuits.

[0326] Video decoder 300 can include ALUs, EFUs, digital circuits, analog circuits, and / or programmable cores formed from programmable circuitry. In examples where the operations of video decoder 300 are performed by software executing on the programmable circuitry, on-chip or off-chip memory can store instructions (e.g., object code) of the software that video decoder 300 receives and executes.

[0327] Entropy decoding unit 302 can receive 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 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0328] In general, video decoder 300 reconstructs a picture on a block-by-block basis. Video decoder 300 can perform reconstruction operations individually for each block (where the block that is currently being reconstructed (i.e., decoded) can be referred to as the “current block”).

[0329] Entropy decoding unit 302 can entropy decode syntax elements defining quantized transform coefficients of a quantized transform coefficient block, as well as transform information (e.g., quantization parameter (QP) and / or transform mode indications). Inverse quantization unit 306 can use a QP associated with the quantized transform coefficient block to determine a degree of quantization, and thereby determine a degree of inverse quantization for inverse quantization unit 306 to apply. For example, inverse quantization unit 306 can perform a bitshift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 can thereby form a transform coefficient block comprising transform coefficients.

[0330] After inverse quantization unit 306 forms the transform coefficient block, inverse transform processing unit 308 can apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, inverse transform processing unit 308 can apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve Transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

[0331] Further, prediction processing unit 304 generates the prediction block from the prediction information syntax elements entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-predicted, motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax elements can indicate a reference picture in DPB 314 from which to retrieve a reference block, and a motion vector identifying a position of the reference block in the reference picture relative to a position of the current block in the current picture. Motion compensation unit 316 can generally operate in a substantially similar manner as motion compensation unit 224 (FIG. 2) described above with regard to FIG. 2. Figure 3The inter prediction unit 318 can perform the inter prediction process in a manner substantially similar to that described with respect to the inter prediction unit 226 (FIG. 2) above.

[0332] As another example, if the prediction information syntax element indicates that the current block is intra predicted, the intra prediction unit 318 can generate the prediction block according to an intra prediction mode indicated by the prediction information syntax element. Again, the intra prediction unit 318 can perform the intra prediction process in a manner substantially similar to that described with respect to the intra prediction unit 226 (FIG. 2) above. Figure 3 ) The intra prediction unit 318 can retrieve data for neighboring samples of the current block from the DPB 314.

[0333] The reconstruction unit 310 can reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 can add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

[0334] The filter unit 312 can perform one or more filtering operations on the reconstructed block. For example, the filter unit 312 can perform a deblocking operation to reduce blocking artifacts along edges of the reconstructed block. The operations of the filter unit 312 are not necessarily performed in all examples.

[0335] The video decoder 300 can store the reconstructed block in the DPB 314. For example, in examples in which the operations of the filter unit 312 are not performed, the reconstruction unit 310 can store the reconstructed block to the DPB 314. In examples in which the operations of the filter unit 312 are performed, the filter unit 312 can store the filtered reconstructed block to the DPB 314. As discussed above, the DPB 314 can provide reference information to the prediction processing unit 304, e.g., samples of the current picture for intra prediction and samples of previously decoded pictures for subsequent motion compensation. In addition, the video decoder 300 can output decoded pictures (e.g., decoded video) from the DPB 314 for subsequent presentation on a display device, such as the display device 118 of FIG. 1. Figure 1

[0336] In this way, the video decoder 300 represents an example of a video decoding device that includes a memory configured to store video data, and one or more processing units implemented in circuitry and configured to: decode, via a first syntax level of a coded video bitstream, a first tool control flag having a value that specifies whether a first tool is enabled; responsive to the tool control flag specifying that the particular tool is not enabled, infer, in a second syntax level, a value of a second tool control flag as the value of the first tool control flag, the second tool control flag specifying whether the first tool can be used; and selectively use / apply the first tool on blocks of the video data based on the value of the second tool control flag. ​

[0337] Video decoder 300 represents an example of a device configured to encode video data, including a memory configured to store video data, and one or more processing units implemented in circuitry, the one or more processing units configured to: decode, via a first syntax level of a coded video bitstream, a first tool control flag having a value that specifies whether a particular first tool is enabled; responsive to the tool control flag specifying that the particular first tool is not enabled, infer a value of a second tool control flag in a second syntax level to specify that the first tool is not used; and selectively use / apply the first tool on a block of the video data based on the value of the second tool control flag.

[0338] Figure 5 is a flowchart illustrating an example method for encoding a current block. The current block can include a current CU. Although described with respect to video encoder 200 Figure 1 and Figure 3 ), it should be understood that other devices can be configured to perform methods similar to the method of Figure 5 .

[0339] In this example, video encoder 200 initially predicts a current block (350). For example, video encoder 200 can form a prediction block for the current block. Video encoder 200 can then calculate a residual block for the current block (352). To calculate the residual block, video encoder 200 can calculate the difference between the original, unencoded block and the prediction block for the current block. Video encoder 200 can then transform the residual block and quantize the transform coefficients of the residual block (354). Next, video encoder 200 can scan the quantized transform coefficients of the residual block (356). During or after the scan, video encoder 200 can entropy encode the transform coefficients (358). For example, video encoder 200 can encode the transform coefficients using CAVLC or CABAC. Video encoder 200 can then output the entropy encoded data for the block (360).

[0340] Figure 6 is a flowchart illustrating an example method for decoding a current block of video data. The current block can include a current CU. Although described with respect to video decoder 300 Figure 1 and Figure 4 ), it should be understood that other devices can be configured to perform methods similar to the method of Figure 6 .

[0341] Video decoder 300 can receive entropy encoded data for a current block, e.g., entropy encoded prediction information and entropy encoded data for transform coefficients of a residual block corresponding to the current block (370). Video decoder 300 can entropy decode the entropy encoded data to determine prediction information for the current block and reproduce transform coefficients of the residual block (372). Video decoder 300 can predict the current block, e.g., using an intra prediction mode or an inter prediction mode indicated by the prediction information for the current block (374) to calculate a prediction block for the current block. Video decoder 300 can then inverse scan the reproduced transform coefficients (376) to create a block of quantized transform coefficients. Video decoder 300 can then inverse quantize the transform coefficients and apply inverse transforms to the transform coefficients to produce a residual block (378). Video decoder 300 can finally decode the current block by combining the prediction block and the residual block (380).

[0342] Figure 7 is a flowchart illustrating an example technique for coding deblocking filter information according to one or more aspects of the present disclosure. While described with respect to video decoder 300 Figure 1 and Figure 4 ), it should be understood that other devices can be configured to perform methods similar to the method of Figure 7 .

[0343] Video decoder 300 can decode, via a first syntax level of a coded video bitstream, a deblocking filter control syntax element having a value that specifies whether deblocking override is enabled (702). For example, entropy decoding unit 302 can decode, from at least a portion of the coded video bitstream stored at CPB memory 320, a second deblocking filter control syntax element (e.g., pps_deblocking_filter_override_enabled_flag) from a picture parameter set (PPS) syntax level.

[0344] Based on the deblocking filter control syntax element specifying that deblocking override is not enabled (704, “No” branch) (e.g., a value of pps_deblocking_filter_override_enabled_flag is 0), video decoder 300 can determine that the bitstream does not include alternative deblocking information and apply deblocking to the video data (712). For example, filtering unit 312 can apply deblocking to the video data using the beta and tC parameter values signaled in the PPS.

[0345] Based on the deblocking filter control syntax element specifying that deblocking override is enabled (704, "Yes" branch) (e.g., the value of pps_deblocking_filter_override_enabled_flag is 1), video decoder 300 can decode, via a first syntax level of the coded video bitstream, another deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream (706). For example, entropy decoding unit 302 can decode, from at least a portion of the coded video bitstream stored at CPB memory 320, the first deblocking filter control syntax element (e.g., pps_dbf_info_in_ph_flag) from the PPS syntax level. In this way, video decoder 300 can selectively decode the first deblocking filter control syntax element (i.e., pps_dbf_info_in_ph_flag) based on the value of the second deblocking filter control syntax element (i.e., pps_deblocking_filter_override_enabled_flag).

[0346] Based on the other deblocking filter control syntax element specifying that deblocking filter information is not present in the second syntax level of the bitstream (708, "No" branch) (e.g., the value of pps_dbf_info_in_ph_flag is 0), video decoder 300 can determine that the bitstream does not include alternative deblocking information and apply deblocking to the video data (712). For example, filtering unit 312 can apply deblocking to the video data using the beta and tc parameter values signaled in the PPS.

[0347] In response to the first deblocking filter control syntax element specifying that deblocking filter information is present in a second syntax level of the bitstream (the "No" branch of 708), and regardless of the value of the second deblocking filter control syntax element, video decoder 300 can decode the one or more syntax elements specifying deblocking filter information via the second syntax level (710). For example, entropy decoding unit 302 can decode the value of one or more of the following: ph_deblocking_filter_override_flag, ph_deblocking_filter_disabled_flag, ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2. Thus, in response to the first deblocking filter control syntax element specifying that deblocking filter information is present in a second syntax level of the bitstream, and regardless of the value of the second deblocking filter control syntax element, video decoder 300 can decode the one or more syntax elements specifying deblocking filter information via the second syntax level.

[0348] Video decoder 300 can apply deblocking filtering to the block of video data based on the deblocking filter information (712). For example, filtering unit 312 can apply deblocking to the video data using the beta and tc parameter values. As discussed above, the beta and tc parameter values can be signaled in the first syntax level (e.g., PPS) or the second syntax level (e.g., PH). For example, when the beta and tc parameter values are signaled in the PH, filtering unit 312 can determine the values of the beta and tc parameter values based on the values of one or more of the following: ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2 syntax elements.

[0349] The following numbered clauses can illustrate one or more aspects of the present disclosure:

[0350] Clause 1A. A method of coding video data, the method comprising: coding, via a first syntax level of a coded video bitstream, a first tool control flag having a value that specifies whether a first tool is enabled; responsive to the tool control flag specifying that the particular tool is not enabled, inferring, in a second syntax level, a value of a second tool control flag as the value of the first tool control flag, the second tool control flag specifying whether the first tool can be used; and selectively using the first tool on a block of the video data based on the value of the second tool control flag.

[0351] Clause 2A. The method of clause 1A, wherein the first syntax level comprises a sequence parameter set (SPS).

[0352] Clause 3A. The method of clause 1A or clause 2A, wherein the second syntax level comprises a picture header (PH) or a slice header (SH).

[0353] Clause 4A. The method of any of clauses 1A-3A, wherein the first tool control flag comprises a sps_sao_enable_flag syntax element, and wherein the second tool control flag comprises a ph_sao_luma_enabled_flag or a ph_sao_chroma_enabled_flag.

[0354] Clause 5A. The method of any of clauses 1A-4A, wherein the first tool comprises a sample adaptive offset (SAO) filter.

[0355] Clause 6A. The method of any of clauses 1A-3A, wherein the first tool control flag comprises a sps_alf_enabled_flag syntax element, and wherein the second tool control flag comprises a ph_alf_enabled_flag.

[0356] Clause 7A. The method of any of clauses 1A-3A, wherein the first tool control flag comprises a sps_ALF_enabled_flag syntax element, and wherein the second tool control flag comprises a ph_alf_cb_flag or a ph_alf_cr_flag.

[0357] Clause 8A. The method of any of clauses 1A-3A, 6A, or 7A, wherein the first tool comprises an adaptive loop filter (ALF).

[0358] Clause 1B. A method of coding video data, the method comprising: coding, via a first syntax level of a coded video bitstream, a first tool control flag having a value that specifies whether a particular tool is enabled; in response to the tool control flag specifying that the particular tool is not enabled, inferring, in a second syntax level, a value of a second tool control flag to specify that the particular tool is not used; and selectively using the particular tool on a block of the video data based on the value of the second tool control flag.

[0359] Clause 2B. The method of clause 1B, wherein the first syntax level comprises a sequence parameter set (SPS).

[0360] Clause 3B. The method of clause 1B or clause 2B, wherein the second syntax level comprises a picture header (PH) or a slice header (SH).

[0361] Clause 4B. The method of any of clauses 1B-3B, wherein the first tool control flag comprises a sps_sao_enable_flag syntax element, and wherein the second tool control flag comprises a ph_sao_luma_enabled_flag or a ph_sao_chroma_enabled_flag.

[0362] Clause 5B. The method of any of clauses 1B-4B, wherein the particular tool comprises a sample adaptive offset (SAO) filter.

[0363] Clause 6B. The method of any of clauses 1B-3B, wherein the first tool control flag comprises a sps_alf_enabled_flag syntax element, and wherein the second tool control flag comprises a ph_alf_enabled_flag.

[0364] Clause 7B. The method of any of clauses 1B-3B or 6B, wherein the particular tool comprises an adaptive loop filter (ALF).

[0365] Clause 1C. A method of encoding video data, the method comprising: limiting a number of suffix adaptive parameter set (APS) network abstraction layer (NAL) units of a particular APS type present in a picture of the video data to be less than or equal to a first threshold number; limiting a number of referenced APSs of the APS type in the picture of the video data to be less than or equal to a second threshold number; and encoding, in a coded video bitstream, one or more syntax elements that specify the number of APS NAL units of the particular APS type present and / or one or more syntax elements that specify the number of referenced APSs of the particular APS type.

[0366] Clause 2C. The method of clause 1C, wherein the first threshold number is equal to the second threshold number.

[0367] Clause 3C, the method of clause 1C, wherein the first threshold number is different than the second threshold number.

[0368] Clause 4C, the method of any of clauses 1C-3C, further comprising: determining the first threshold number and the second threshold number such that a sum of the first threshold number and the second threshold number is less than a third threshold number.

[0369] Clause 5C, the method of any of clauses 1C-4C, wherein the one or more syntax elements that specify the number of referenced APSs of the APS type comprise a ph num alf aps ids luma syntax element and / or a sh num alf aps ids luma syntax element.

[0370] Clause 6C, the method of any of clauses 1C-5C, further comprising: encoding, in the coded video bitstream, the suffix APS NAL unit to have a different APS identifier (ID).

[0371] Clause 7C, the method of any of clauses 1C-6C, further comprising: encoding, in the coded video bitstream, the plurality of prefix APS NAL units to have different APS IDs.

[0372] Clause 8C, the method of clause 7C, further comprising: encoding, in the coded video bitstream, the plurality of prefix APS NAL units and the suffix APS NAL unit to have different APS IDs.

[0373] Clause 1D, a method of coding video data, the method comprising: coding, via a first syntax level of a coded video bitstream, a first deblocking filter control syntax element having a value that specifies whether deblocking filter information is present in a second syntax level of the bitstream; coding, via the first syntax level of the coded video bitstream, a second deblocking filter control syntax element having a value that specifies whether a deblocking override syntax element is present in the second syntax level of the bitstream; in response to the first deblocking filter control syntax element specifying that the deblocking filter information is present in the second syntax level of the bitstream, and regardless of the value of the second deblocking filter control syntax element, decoding, via the second syntax level, one or more syntax elements that specify the deblocking filter information; and applying deblocking filter to a block of the video data based on the deblocking filter information.

[0374] Clause 2D, the method of clause 1D, wherein the first syntax level comprises a sequence parameter set (SPS).

[0375] The method of clause 3D, clause ID, or clause 2D, wherein the second syntax level comprises a picture header (PH) or a slice header (SH).

[0376] The method of clause 4D, any of clauses ID-3D, wherein one or more of: the first deblocking filter control syntax element comprises a pps dbf info in ph flag syntax element, the second deblocking filter control syntax element comprises a pps deblocking filter override enabled flag syntax element, and / or the one or more syntax elements that specify deblocking filter information comprises one or more of: a ph deblocking filter override flag, a ph deblocking filter disabled flag, a ph luma beta offset div 2, a ph luma tc offset div 2, a ph cb beta offset div 2, a ph cb tc offset div 2, a ph cr beta offset div 2, and a ph cr tc offset div 2.

[0377] The method of clause IE, any of clauses 1A-4D, wherein the coding comprises decoding.

[0378] The method of clause 2E, any of clauses 1A-1E, wherein the coding comprises encoding.

[0379] Clause 3E, an apparatus for coding video data, the apparatus comprising one or more units for performing the method of any of clauses 1A-2E.

[0380] Clause 4E, the apparatus of clause 3E, wherein the one or more units comprise one or more processors implemented in circuitry.

[0381] Clause 5E, the apparatus of any of clauses 3E and 4E, further comprising: a memory to store the video data.

[0382] Clause 6E, the apparatus of any of clauses 3E-5E, further comprising: a display configured to display decoded video data.

[0383] Clause 7E, the apparatus of any of clauses 3E-6E, wherein the apparatus comprises one or more of: a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0384] Clause 8E, the apparatus of any of clauses 3E-7E, wherein the apparatus comprises a video decoder.

[0385] Clause 9E, the device of any of clauses 3E-8E, wherein the device comprises a video encoder.

[0386] Clause 10E, a computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of clauses 1A-2E.

[0387] It is recognized that depending on the example, certain acts or events of any of the techniques described herein can be performed in a different sequence, can be added, modified or omitted (e.g., not all described acts or events are required to practice the techniques), or can be performed concurrently in any combination (e.g., through concurrent or parallel processing). Furthermore, certain acts or events can be performed at least partially concurrently with, in parallel with, or in some cases, in response to, one another. In some embodiments, the above described techniques can be implemented by a processor, such as the processor 102 of FIG. 1, which can access instructions for causing the processor to perform the techniques described herein. These instructions can be stored on or transmitted (e.g., downloaded or transferred) across one or more computer- readable media, such as the computer-readable storage media described herein.

[0388] In one or more examples, the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored on or transmitted across one or more computer-readable media, such as a computer-readable storage medium or a computer-readable transmission medium, which can be any medium that facilitates transfer of a computer program from one place to another. Computer-readable storage media can be tangible and non-transitory. A computer-readable storage medium can include one or more computer-readable storage devices, which do not include signals. Computer-readable storage media can include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage and / or transmission of information such as computer readable instructions, data structures, program code, or other data. Computer-readable storage media can include, but are not limited to, RAM, ROM, EEPROM, solid state drives (SSDs), flash memory, phase-change memory ("PCM"), optical media, magnetic media, and / or any other computer-readable storage medium that can be used to store and / or transfer computer-readable instructions and / or other computer-readable data, and / or any combination thereof. Computer-readable storage media can also include, but are not limited to, media that can be accessed via a wired connection, wireless connection, or any other desired means of accessing media.

[0389] By way of example, and not limitation, such computer-readable storage media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other storage medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any

[0390] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, as used herein the term "processor" and "processing circuitry" can refer to any of the foregoing circuitry and / or circuitry for

[0391] The techniques of this disclosure can be implemented in a variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize their implementation as software or hardware modules within the device, but do not necessarily imply that they must be implemented in a specific way. For example, a component, module, or unit can also include programs, routines, objects, components, data structures, or other

[0392] 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: The first deblocking filter control syntax element is decoded via a first syntax level of the decoded video bitstream. The first deblocking filter control syntax element has a value specifying whether deblocking filter information exists in a second syntax level of the bitstream. The first syntax level includes a picture parameter set (PPS), and the second syntax level includes a picture header (PH). The second deblocking filter control syntax element is decoded via the first syntax level of the decoded video bitstream, and the second deblocking filter control syntax element has a value specifying whether deblocking overlay is enabled. In response to the first deblocking control syntax element specifying that the deblocking information exists in the second syntax level of the bitstream, and regardless of the value of the second deblocking control syntax element, one or more syntax elements specifying the deblocking information are decoded via the second syntax level; and Based on the deblocking filtering information, deblocking filtering is applied to blocks of the video data.

2. The method according to claim 1, wherein, Decoding the first deblocking filter control syntax element includes: The first deblocking filter control syntax element is selectively decoded based on the value of the second deblocking filter control syntax element.

3. The method according to claim 2, wherein, One or more of the following: The first deblocking filter control syntax element includes the pps_dbf_info_in_ph_flag syntax element. The second deblocking filter control syntax element includes the pps_deblocking_filter_override_enabled_flag syntax element, and / or The one or more syntax elements specifying deblocking filter information include one or more of the following: ph_deblocking_filter_override_flag, ph_deblocking_filter_disabled_flag, ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2.

4. A method for encoding video data, the method comprising: A first deblocking filter control syntax element is encoded via a first syntax level of the decoded video bitstream. The first deblocking filter control syntax element has a value specifying whether deblocking filter information exists in a second syntax level of the bitstream. The first syntax level includes a picture parameter set (PPS), and the second syntax level includes a picture header (PH). The second deblocking filter control syntax element is encoded via the first syntax level of the decoded video bitstream, and the second deblocking filter control syntax element has a value specifying whether deblocking overlay is enabled. Based on the first deblocking control syntax element, the deblocking information is specified to exist in the second syntax level of the bitstream, and regardless of the value of the second deblocking control syntax element, one or more syntax elements specifying the deblocking information are encoded via the second syntax level; and Based on the deblocking filtering information, deblocking filtering is applied to blocks of the video data.

5. The method according to claim 4, wherein, Encoding the first deblocking filter control syntax element includes: The first deblocking filter control syntax element is selectively encoded based on the value of the second deblocking filter control syntax element.

6. The method according to claim 5, wherein, One or more of the following: The first deblocking filter control syntax element includes the pps_dbf_info_in_ph_flag syntax element. The second deblocking filter control syntax element includes the pps_deblocking_filter_override_enabled_flag syntax element, and / or The one or more syntax elements specifying deblocking filter information include one or more of the following: ph_deblocking_filter_override_flag, ph_deblocking_filter_disabled_flag, ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2.

7. An apparatus for decoding video data, the apparatus comprising: A memory configured to store at least a portion of the decoded video bitstream; One or more processors, which are implemented in a circuit device and configured to: The first deblocking filter control syntax element is decoded via a first syntax level of the decoded video bitstream. The first deblocking filter control syntax element has a value specifying whether deblocking filter information exists in a second syntax level of the bitstream. The first syntax level includes a picture parameter set (PPS), and the second syntax level includes a picture header (PH). The second deblocking filter control syntax element is decoded via the first syntax level of the decoded video bitstream, and the second deblocking filter control syntax element has a value specifying whether deblocking overlay is enabled. In response to the first deblocking control syntax element specifying that the deblocking information exists in the second syntax level of the bitstream, and regardless of the value of the second deblocking control syntax element, one or more syntax elements specifying the deblocking information are decoded via the second syntax level; and Based on the deblocking filtering information, deblocking filtering is applied to blocks of the video data.

8. The apparatus of claim 7, further comprising a display device configured to display an image comprising blocks of the video data.

9. The device according to claim 7, wherein, In order to decode the first deblocking filter control syntax element, the one or more processors are configured to: The first deblocking filter control syntax element is selectively decoded based on the value of the second deblocking filter control syntax element.

10. The device according to claim 9, wherein, One or more of the following: The first deblocking filter control syntax element includes the pps_dbf_info_in_ph_flag syntax element. The second deblocking filter control syntax element includes the pps_deblocking_filter_override_enabled_flag syntax element, and / or The one or more syntax elements specifying deblocking filter information include one or more of the following: ph_deblocking_filter_override_flag, ph_deblocking_filter_disabled_flag, ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2.

11. An apparatus for encoding video data, the apparatus comprising: A memory configured to store at least a portion of the decoded video bitstream; One or more processors, which are implemented in a circuit device and configured to: A first deblocking filter control syntax element is encoded via a first syntax level of the decoded video bitstream. The first deblocking filter control syntax element has a value specifying whether deblocking filter information exists in a second syntax level of the bitstream. The first syntax level includes a picture parameter set (PPS), and the second syntax level includes a picture header (PH). The second deblocking filter control syntax element is encoded via the first syntax level of the decoded video bitstream, and the second deblocking filter control syntax element has a value specifying whether deblocking overlay is enabled. Based on the first deblocking control syntax element, the deblocking information is specified to exist in the second syntax level of the bitstream, and regardless of the value of the second deblocking control syntax element, one or more syntax elements specifying the deblocking information are encoded via the second syntax level; and Based on the deblocking filtering information, deblocking filtering is applied to blocks of the video data.

12. The device of claim 11, further comprising a camera configured to capture images comprising blocks of the video data.

13. The device according to claim 11, wherein, In order to encode the first deblocking filter control syntax element, the one or more processors are configured to: The first deblocking filter control syntax element is selectively encoded based on the value of the second deblocking filter control syntax element.

14. The device according to claim 13, wherein, One or more of the following: The first deblocking filter control syntax element includes the pps_dbf_info_in_ph_flag syntax element. The second deblocking filter control syntax element includes the pps_deblocking_filter_override_enabled_flag syntax element, and / or The one or more syntax elements specifying deblocking filter information include one or more of the following: ph_deblocking_filter_override_flag, ph_deblocking_filter_disabled_flag, ph_luma_beta_offset_div2, ph_luma_tc_offset_div2, ph_cb_beta_offset_div2, ph_cb_tc_offset_div2, ph_cr_beta_offset_div2, and ph_cr_tc_offset_div2.

15. A video decoding device, comprising: A unit for decoding a first deblocking filter control syntax element via a first syntax level of a decoded video bitstream, the first deblocking filter control syntax element having a value specifying whether deblocking filter information exists in a second syntax level of the bitstream, wherein the first syntax level includes a picture parameter set (PPS) and the second syntax level includes a picture header (PH). A unit for decoding a second deblocking filter control syntax element via the first syntax level of the decoded video bitstream, the second deblocking filter control syntax element having a value specifying whether deblocking overlay is enabled. A unit for decoding one or more syntax elements specifying the deblocking information via the second syntax level in response to a first deblocking control syntax element indicating that the deblocking information exists in the second syntax level of the bitstream, and regardless of the value of the second deblocking control syntax element; and A unit for applying deblocking filtering to blocks of video data based on the deblocking filtering information.

16. A video encoding device, comprising: A unit for encoding a first deblocking filter control syntax element via a first syntax level of a decoded video bitstream, the first deblocking filter control syntax element having a value specifying whether deblocking filter information exists in a second syntax level of the bitstream, wherein the first syntax level includes a picture parameter set (PPS) and the second syntax level includes a picture header (PH). A unit for encoding a second deblocking filter control syntax element via the first syntax level of the decoded video bitstream, the second deblocking filter control syntax element having a value specifying whether deblocking overlay is enabled. A unit for encoding one or more syntax elements specifying the deblocking information via the second syntax level in response to a first deblocking control syntax element specifying that the deblocking information exists in the second syntax level of the bitstream, and regardless of the value of the second deblocking control syntax element; and A unit for applying deblocking filtering to blocks of video data based on the deblocking filtering information.

17. A computer-readable storage medium storing instructions, which, when executed, cause one or more processors to perform the following operations: The first deblocking filter control syntax element is decoded at a first syntax level of the decoded video bitstream. This first deblocking filter control syntax element has a value specifying whether deblocking filter information exists in a second syntax level of the bitstream. The first syntax level includes the Picture Parameter Set (PPS), and the second syntax level includes the Picture Header (PH); The second deblocking filter control syntax element is decoded via the first syntax level of the decoded video bitstream, and the second deblocking filter control syntax element has a value specifying whether deblocking overlay is enabled. In response to the first deblocking filter control syntax element specifying that the deblocking filter information exists in the second syntax level of the bitstream, and regardless of the value of the second deblocking filter control syntax element, one or more syntax elements specifying the deblocking filter information are decoded via the second syntax level; as well as Based on the deblocking filtering information, deblocking filtering is applied to blocks of video data.

18. A computer-readable storage medium storing instructions, which, when executed, cause one or more processors to perform the following operations: The first deblocking filter control syntax element is encoded at a first syntax level of the decoded video bitstream. This first deblocking filter control syntax element has a value specifying whether deblocking filter information exists in a second syntax level of the bitstream. The first syntax level includes the Picture Parameter Set (PPS), and the second syntax level includes the Picture Header (PH); The second deblocking filter control syntax element is encoded via the first syntax level of the decoded video bitstream, and the second deblocking filter control syntax element has a value specifying whether deblocking overlay is enabled. Based on the first deblocking filter control syntax element, the deblocking filter information is specified to exist in the second syntax level of the bitstream, and regardless of the value of the second deblocking filter control syntax element, one or more syntax elements specifying the deblocking filter information are encoded via the second syntax level; as well as Based on the deblocking filtering information, deblocking filtering is applied to blocks of video data.

Images