Classifications

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  • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
  • H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
  • H04N19/159—Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
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  • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
  • H04N19/174—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a slice, e.g. a line of blocks or a group of blocks
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  • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
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  • H04N19/189—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the adaptation method, adaptation tool or adaptation type used for the adaptive coding
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  • H04N19/42—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation
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  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/63—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding using sub-band based transform, e.g. wavelets
  • H04N19/64—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding using sub-band based transform, e.g. wavelets characterised by ordering of coefficients or of bits for transmission
  • H04N19/645—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding using sub-band based transform, e.g. wavelets characterised by ordering of coefficients or of bits for transmission by grouping of coefficients into blocks after the transform

Definitions

• This disclosure relates to video encoding and video decoding.
• 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 may transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing such video coding techniques.
• Video coding typically involves predicting a block of video data from either an already coded block of video data in the same picture (e.g., intra prediction) or an already coded block of video data in a different picture (e.g., inter prediction).
• Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences.
• a video slice e.g., a video picture or a portion of a video picture
• CTUs coding tree units
• CUs coding units
• Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in neighboring blocks in the same picture.
• Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures.
• Pictures may be referred to as frames, and reference pictures may be referred to as reference frames.
• this disclosure describes techniques related to the coding of multiple prediction blocks into prediction block groups using intra sub-partition (ISP) coding.
• a video coder e.g., video encoder and/or video decoder
• a single prediction block group may include more than one prediction block or subblock of the coding unit.
• a first prediction block group may include a first subblock of a coding unit and a second subblock of the coding unit.
• a video coder may reconstruct samples of prediction blocks included in the first prediction block group independently of the reconstruction of samples of other prediction blocks included in that same prediction block group. For example, the video coder may reconstruct samples of one prediction block before, without, or in parallel with, the reconstruction of samples of another prediction block included in the same prediction block group.
• the prediction block grouping techniques of this disclosure may be implemented when instances of intra sub-partition coding are used to include splitting of coding units, such as vertical splitting, horizontal splitting, a combination of horizontal splitting and vertical splitting, etc.
• the prediction block grouping techniques of this disclosure may be implemented when the prediction block has a relatively narrow dimension (e.g., narrow height, narrow width, etc.), such that the dimensions of the prediction block satisfy a predefined threshold for prediction block grouping.
• One or more techniques described herein for grouping prediction blocks into prediction block groups may be applied to any of the existing video codecs, such as HEVC (High Efficiency Video Coding) or H.266/Versatile Video Coding (VVC) standard, or may be used in any future video coding standards.
• HEVC High Efficiency Video Coding
• VVC Very Low Efficiency Video Coding
• the method comprises performing splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; grouping a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstructing samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• CU coding unit
• ISP intra sub-partition
• a device for coding video data includes a memory configured to store video data and one or more processors implemented in circuitry and configured to perform splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; group a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• CU coding unit
• ISP intra sub-partition
• a non-transitory computer-readable storage medium has stored thereon instructions that, when executed, cause one or more processors to: perform splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; group a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• CU coding unit
• ISP intra sub-partition
• an apparatus for coding video data includes means for performing splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; grouping a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstructing samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• ISP intra sub-partition
• FIG. l is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.
• FIG. 2 is a diagram illustrating example intra prediction modes.
• FIG. 3 is a block diagram illustrating an example of an 8x4 rectangular block.
• FIGS. 4A-4C are block diagrams providing illustrations of mode mapping process(es) for modes outside the diagonal direction range.
• FIG. 5 is a block diagram illustrating wide-angles that are adopted in VTM2.
• FIG. 6 is a block diagram illustrating wider-angles that are adopted in VTM3.
• FIG. 7 is a table that specifies the mapping table between predModelntra and the angle parameter intraPredAngle in VTM3.
• FIG. 8 is a block diagram illustrating example divisions of blocks for intra sub partition coding.
• FIG. 9 is a block diagram illustrating example divisions of blocks for intra sub partition coding.
• FIG. 10 is a block diagram illustrating multiple reference line prediction.
• FIG. 11 is a conceptual diagram illustrating an example of how a coding block may be split into four horizontal planar prediction blocks.
• FIG. 12 is a conceptual diagram illustrating an example of how a coding block may be split into four vertical planar prediction blocks.
• FIG. 13 is a conceptual diagram illustrating an example of such a planar prediction block structure.
• FIG. 14 is a block diagram illustrating how the coding block is split into four prediction blocks.
• FIG. 15 is a block diagram illustrating an example where a 4xN coding block is coded with intra sub-partitions and vertical partitioning.
• FIG. 16 is a conceptual diagram illustrating an example where an MxN coding block is split into four prediction blocks.
• FIG. 17 is a conceptual diagram illustrating an example in which only a vertical intra mode prediction is allowed for 4xN coding blocks that are coded with intra sub-partition coding (ISP) and vertical split.
• ISP intra sub-partition coding
• FIG. 18 is a conceptual diagram illustrating an example in which an 8xN (N > 4) coding block coded with ISP and split vertically.
• FIGS. 19A and 19B are conceptual diagrams illustrating an example quadtree binary tree (QTBT) structure, and a corresponding coding tree unit (CTU).
• QTBT quadtree binary tree
• CTU coding tree unit
• FIG. 20 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.
• FIG. 21 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.
• FIG. 22 is a flowchart illustrating an example method for encoding a current block.
• FIG. 23 is a flowchart illustrating an example method for decoding a current block.
• FIG. 24 is a flowchart illustrating an example method for performing prediction block grouping on a current block of video data.
• this disclosure describes techniques related to improvements to the coding and/or decoding of prediction blocks using prediction block groups in intra sub-partition (ISP) coding. Such techniques may be applied to current or future video coding standards, including the Versatile Video Coding (VVC) standard presently under development.
• VVC Versatile Video Coding
• a video coder may code blocks of video data using ISP coding.
• the video coder may partition blocks of video data into subblocks (e.g., prediction blocks).
• the subblocks may have a relatively narrow size in one or more dimensions.
• a coding unit such as a coding block, may have the dimensions of Width (W) x Height (H).
• W Width
• H Height
• a video coder may code the CU of 4xN using ISP coding.
• the video coder may use vertical splitting or horizontal splitting to partition the CU.
• the video coder may use a combination of vertical splitting and horizontal splitting. In such instances, the video coder may partition a first one or more parts of the CU using vertical splitting and a second one or more parts of the same CU using horizontal splitting.
• the resultant subblocks may have a size of lxN.
• N may be greater than 8 (e.g., H is greater than 8).
• the video coder may utilize row-wise storage of samples.
• narrow subblocks such as those having a dimension below a predefined threshold, may result in the video coder performing inefficient and time-consuming memory access procedures.
• the video coder when performing a memory access procedure, may then access (e.g., read) a higher number of samples from memory compared to the number of samples in the subblock.
• a given memory access procedure may require a video coder to read samples of a first row before reading samples from another row.
• the video coder may then read a minimum of X samples before accessing a target sample in one narrow subblock, where X is greater than the number of samples in that narrow subblock. Due to the narrow shape of lxN and 2xN subblocks, this problem is exacerbated as the number of rows is larger for narrow subblocks. For example, a 4x4 CU may only have four rows.
• a video coder may need to access 16 rows for a 1x16 subblock, even though the subblock has the same number of samples as the 4x4 CU.
• the resultant overhead may cause a video coder to experience delays during the coding process, particularly in the worst case where there are several small coding blocks in high resolution sequences.
• the reconstruction of a subblock in the CU is dependent on the reconstruction of other subblocks in the coding block that precede in decoding order. In such instances, a video coder is likely to experience an increased delay in coding or decoding the CU due to subblocks of this nature.
• a coding unit may be split vertically, horizontally, or a combination of horizontally and vertically, using intra sub-partition (ISP) to form the prediction blocks that may then be grouped into various PBGs.
• ISP intra sub-partition
• Various techniques in this disclosure may be described with reference to a video coder or with reference to video coding, which are intended to be generic terms that can refer to either a video encoder and video encoding or a video decoder. Unless explicitly stated otherwise, it should not be assumed that techniques described with respect to a video encoder or a video decoder cannot be performed by the other of a video encoder or a video decoder. For example, in many instances, a video decoder performs the same, or sometimes a reciprocal, coding technique as a video encoder in order to decode encoded video data. In many instances, a video encoder also includes a video decoding loop, and thus the video encoder performs video decoding as part of encoding video data. Thus, unless stated otherwise, the techniques described in this disclosure with respect to a video decoder may also be performed by a video encoder, and vice versa.
• FIG. l is a block diagram illustrating an example video encoding and decoding system 100 that may perform the techniques of this disclosure.
• the techniques of this disclosure are generally directed to coding (encoding and/or decoding) video data.
• video data includes any data for processing a video.
• video data may include raw, uncoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.
• system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116, in this example.
• source device 102 provides the video data to destination device 116 via a computer-readable medium 110.
• Source device 102 and destination device 116 may comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, or the like.
• source device 102 and destination device 116 may be equipped for wireless communication, and thus may be referred to as wireless communication devices.
• source device 102 includes video source 104, memory 106, video encoder 200, and output interface 108.
• video encoder 200 of source device 102 and video decoder 300 of destination device 116 may be configured to apply the techniques for generalized intra prediction.
• source device 102 represents an example of a video encoding device
• destination device 116 represents an example of a video decoding device.
• a source device and a destination device may include other components or arrangements.
• source device 102 may receive video data from an external video source, such as an external camera.
• destination device 116 may interface with an external display device, rather than including an integrated display device.
• System 100 as shown in FIG. 1 is merely one example.
• any digital video encoding and/or decoding device may perform techniques for generalized intra prediction.
• 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.
• video encoder 200 and video decoder 300 represent examples of coding devices, in particular, a video encoder and a video decoder, respectively.
• devices 102, 116 may operate in a substantially symmetrical manner such that each of devices 102, 116 include video encoding and decoding components.
• system 100 may support one-way or two- way video transmission between video devices 102, 116, e.g., for video streaming, video playback, video broadcasting, or video telephony.
• 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 data for the pictures.
• Video source 104 of source device 102 may include a video capture device, such as a video camera, a video archive containing previously captured raw video, and/or a video feed interface to receive video from a video content provider.
• video source 104 may generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video.
• video encoder 200 encodes the captured, pre-captured, or computer-generated video data.
• Video encoder 200 may rearrange the pictures from the received order (sometimes referred to as“display order”) into a coding order for coding. Video encoder 200 may generate a bitstream including encoded video data. Source device 102 may then output the encoded video data via output interface 108 onto computer-readable medium 110 for reception and/or retrieval by, e.g., input interface 122 of destination device 116. [0046] Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memories. In some example, memories 106, 120 may store raw video data, e.g., raw video from video source 104 and raw, decoded video data from video decoder 300.
• memories 106, 120 may store software instructions executable by, e.g., 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 may also include internal memories for functionally similar or equivalent purposes. Furthermore, memories 106, 120 may store encoded video data, e.g., output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106, 120 may be allocated as one or more video buffers, e.g., to store raw, decoded, and/or encoded video data.
• Computer-readable medium 110 may represent any type of medium or device capable of transporting the encoded video data from source device 102 to destination device 116.
• computer-readable medium 110 represents a
• the communication medium may 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 may modulate a transmission signal including the encoded video data
• input interface 122 may demodulate the received transmission signal, according to a communication standard, such as a wireless communication protocol.
• the communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines.
• the communication medium may form part of a packet- based network, such as a local area network, a wide-area network, or a global network such as the Internet.
• the communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from source device 102 to destination device 116.
• computer-readable medium 110 may include storage device 112.
• Source device 102 may output encoded data from output interface 108 to computer-readable medium 110 (e.g., storage device 112).
• destination device 116 may access encoded data from computer-readable medium 110 (e.g., storage device 112) via input interface 122.
• Storage device 112 may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data.
• computer-readable medium 110 may include file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102.
• Source device 102 may output encoded video data to file server 114 or another intermediate storage device that may store the encoded video generated by source device 102.
• Destination device 116 may access stored video data from file server 114 via streaming or download.
• File server 114 may be any type of server device capable of storing encoded video data and transmitting that encoded video data to the destination device 116.
• File server 114 may represent a web server (e.g., for a website), a File Transfer Protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device.
• FTP File Transfer Protocol
• NAS network attached storage
• Destination device 116 may access encoded video data from file server 114 through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., digital subscriber line (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 may be configured to operate according to a streaming transmission protocol, a download transmission protocol, or a combination thereof.
• Output interface 108 and input interface 122 may represent wireless
• transmitters/receiver modems
• wired networking components e.g., Ethernet cards
• wireless communication components that operate according to any of a variety of IEEE 802.11 standards, or other physical components.
• interface 108 and input interface 122 comprise wireless components, output
• interface 108 and input interface 122 may be configured to transfer data, such as encoded video data, according to a cellular communication standard, such as 4G, 4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like.
• output interface 108 comprises a wireless transmitter
• output interface 108 and input interface 122 may be configured to transfer data, such as encoded video data, according to other wireless standards, such as an IEEE 802.11 specification, an IEEE 802.15 specification (e.g., ZigBeeTM), a BluetoothTM standard, or the like.
• source device 102 and/or destination device 116 may include respective system-on-a-chip (SoC) devices.
• SoC system-on-a-chip
• source device 102 may include an SoC device to perform the functionality attributed to video encoder 200 and/or output interface 108
• destination device 116 may include an SoC device to perform the functionality attributed to video decoder 300 and/or input interface 122.
• the techniques of this disclosure may be applied to video coding in support of any of a variety of multimedia applications, such as over-the-air television broadcasts, cable television transmissions, satellite television transmissions, Internet streaming video transmissions, such as dynamic adaptive streaming over HTTP (DASH), digital video that is encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.
• multimedia applications such as over-the-air television broadcasts, cable television transmissions, satellite television transmissions, Internet streaming video transmissions, such as dynamic adaptive streaming over HTTP (DASH), digital video that is encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.
• DASH dynamic adaptive streaming over HTTP
• Input interface 122 of destination device 116 receives an encoded video bitstream from computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, or the like).
• the encoded video bitstream may include signaling information defined by video encoder 200, which is also used by video decoder 300, such as syntax elements having values that describe characteristics and/or processing of video blocks or other coded units (e.g., slices, pictures, groups of pictures, sequences, or the like).
• Display device 118 displays decoded pictures of the decoded video data to a user.
• Display device 118 may represent any of a variety of display devices such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.
• CTR cathode ray tube
• LCD liquid crystal display
• plasma display a plasma display
• OLED organic light emitting diode
• video encoder 200 and video decoder 300 may each be integrated with an 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. If applicable, MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol, or other protocols such as the user datagram protocol (UDP).
• MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol, or other protocols such as the user datagram protocol (UDP).
• Video encoder 200 and video decoder 300 each may be implemented as any of a variety of suitable encoder and/or decoder circuitry, such as one or more
• a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure.
• Each of video encoder 200 and video decoder 300 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device.
• a device including video encoder 200 and/or video decoder 300 may comprise an integrated circuit, a microprocessor, and/or a wireless communication device, such as a cellular telephone.
• Video encoder 200 and video decoder 300 may operate according to a video coding standard, such as ITU-T H.265, also referred to as High Efficiency Video Coding (HEVC) or extensions thereto, such as the multi-view and/or scalable video coding extensions.
• video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards, such as the Joint
• VVC Versatile Video Coding
• VVC Draft 4 “Versatile Video Coding (Draft 4),” Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 13 th Meeting: Marrakech, MA, 9-18 Jan. 2019, JVET-M1001-v2 (hereinafter“VVC Draft 4).
• VVC Draft 4 Joint Video Experts Team
• video encoder 200 and video decoder 300 may perform block-based coding of pictures.
• the term“block” generally refers to a structure including data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and/or decoding process).
• a block may include a two-dimensional matrix of samples of luminance and/or chrominance data.
• video encoder 200 and video decoder 300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, and blue (RGB) data for samples of a picture, video encoder 200 and video decoder 300 may code luminance and chrominance components, where the chrominance components may include both red hue and blue hue
• video encoder 200 converts received RGB formatted data to a YUV representation prior to encoding
• video decoder 300 converts the YUV representation to the RGB format.
• pre- and post processing units may perform these conversions.
• This disclosure may generally refer to coding (e.g., encoding and decoding) of pictures to include the process of encoding or decoding data of the picture.
• this disclosure may refer to coding of blocks of a picture to include the process of encoding or decoding data for the blocks, e.g., prediction and/or residual coding.
• An encoded video bitstream generally includes a series of values for syntax elements representative of coding decisions (e.g., coding modes) and partitioning of pictures into blocks.
• references to coding a picture or a block should generally be understood as coding values for syntax elements forming the picture or block.
• HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs).
• a video coder such as video encoder 200 partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video coder partitions CTUs and CUs into four equal, non overlapping squares, and each node of the quadtree has either zero or four child nodes. Nodes without child nodes may be referred to as“leaf nodes,” and CUs of such leaf nodes may include one or more PUs and/or one or more TUs.
• the video coder may further partition PUs and TUs.
• a residual quadtree represents partitioning of TUs.
• PUs represent inter-prediction data
• TUs represent residual data.
• CUs that are intra-predicted include intra-prediction information, such as an intra-mode indication.
• This disclosure may generally use the term partition to represent a block as a TU, PU, or CU, or to represent a plurality of blocks or region that includes multiple blocks.
• video encoder 200 and video decoder 300 may be configured to operate according to JEM or VVC.
• a video coder such as video encoder 200 partitions a picture into a plurality of coding tree units (CTUs).
• Video encoder 200 may partition a CTU according to a tree structure, such as a quadtree-binary tree (QTBT) structure or Multi-Type Tree (MTT) structure.
• QTBT quadtree-binary tree
• MTT Multi-Type Tree
• the QTBT structure removes the concepts of multiple partition types, such as the separation between CUs, PUs, and TUs of HEVC.
• a QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning.
• a root node of the QTBT structure corresponds to a CTU.
• Leaf nodes of the binary trees correspond to coding units (CUs).
• blocks may be partitioned using a quadtree (QT) partition, a binary tree (BT) partition, and one or more types of triple tree (TT) partitions.
• a triple tree partition is a partition where a block is split into three sub blocks.
• a triple tree partition divides a block into three sub-blocks without dividing the original block through the center.
• the partitioning types in MTT e.g., QT, BT, and TT
• video encoder 200 and video decoder 300 may use a single QTBT or MTT structure to represent each of the luminance and chrominance components, while in other examples, video encoder 200 and video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT/MTT structure for the luminance component and another QTBT/MTT structure for both chrominance components (or two QTBT/MTT structures for respective chrominance components).
• Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning per HEVC, QTBT partitioning, MTT partitioning, or other partitioning structures.
• quadtree partitioning per HEVC, QTBT partitioning, MTT partitioning, or other partitioning structures.
• the description of the techniques of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the techniques of this disclosure may also be applied to video coders configured to use quadtree partitioning, or other types of partitioning as well.
• NxN and“N by N” interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, e.g., 16x16 samples or 16 by 16 samples.
• an NxN CU generally has N samples in a vertical direction and N samples in a horizontal direction, where N represents a nonnegative integer value.
• the samples in a CU may be arranged in rows and columns.
• CUs need not necessarily have the same number of samples in the horizontal direction as in the vertical direction.
• CUs may comprise NxM samples, where M is not necessarily equal to N.
• Video encoder 200 encodes video data for CUs representing prediction and/or residual information, and other information.
• the prediction information indicates how the CU is to be predicted in order to form a prediction block for the CU.
• the residual information generally represents sample-by-sample differences between samples of the CU prior to encoding and the prediction block.
• video encoder 200 may 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
• intra-prediction generally refers to predicting the CU from previously coded data of the same picture.
• video encoder 200 may generate the prediction block using one or more motion vectors.
• Video encoder 200 may generally perform a motion search to identify a reference block that closely matches the CU, e.g., in terms of differences between the CU and the reference block.
• Video encoder 200 may calculate a difference metric using a sum of absolute difference (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared differences (MSD), or other such difference calculations to determine whether a reference block closely matches the current CU.
• SAD sum of absolute difference
• SSD sum of squared differences
• MAD mean absolute difference
• MSD mean squared differences
• video encoder 200 may predict the current CU using uni-directional prediction or bi-directional prediction.
• JEM and VVC also provide an affine motion compensation mode, which may be considered an inter-prediction mode.
• affine motion compensation mode which may be considered an inter-prediction mode.
• video encoder 200 may determine two or more motion vectors that represent non-translational motion, such as zoom in or out, rotation, perspective motion, or other irregular motion types.
• video encoder 200 may select an intra-prediction mode to generate the prediction block.
• Some examples of JEM and VVC provide sixty- seven intra-prediction modes, including various directional modes, as well as planar mode and DC mode.
• video encoder 200 selects an intra-prediction mode that describes neighboring samples to a current block (e.g., a block of a CU) from which to predict samples of the current block. Such samples may generally be above, above and to the left, or to the left of the current block in the same picture as the current block, assuming video encoder 200 codes CTUs and CUs in raster scan order (left to right, top to bottom).
• Video encoder 200 encodes data representing the prediction mode for a current block. For example, for inter-prediction modes, video encoder 200 may encode data representing which of the various available inter-prediction modes is used, as well as motion information for the corresponding mode. For uni-directional or bi-directional inter-prediction, for example, video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. Video encoder 200 may use similar modes to encode motion vectors for affine motion compensation mode.
• AMVP advanced motion vector prediction
• Video encoder 200 may use similar modes to encode motion vectors for affine motion compensation mode.
• video encoder 200 may calculate residual data for the block.
• the residual data such as a residual block, represents sample by sample differences between the block and a prediction block for the block, formed using the corresponding prediction mode.
• Video encoder 200 may apply one or more transforms to the residual block, to produce transformed data in a transform domain instead of the sample domain.
• video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to residual video data.
• DCT discrete cosine transform
• an integer transform an integer transform
• wavelet transform or a conceptually similar transform
• video encoder 200 may 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 one or more transforms.
• video encoder 200 may perform quantization of the transform coefficients.
• Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression.
• video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, video encoder 200 may round an n- bit value down to an m- bit value during quantization, where n is greater than m.
• video encoder 200 may perform a bitwise right-shift of the value to be quantized.
• video encoder 200 may scan the transform coefficients, producing a one-dimensional vector from the two-dimensional matrix including the quantized transform coefficients.
• the scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and to place lower energy (and therefore higher frequency) transform coefficients at the back of the vector.
• video encoder 200 may utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy encode the quantized transform coefficients of the vector.
• video encoder 200 may perform an adaptive scan.
• video encoder 200 may entropy encode the one-dimensional vector, e.g., according to context-adaptive binary arithmetic coding (CABAC).
• Video encoder 200 may also entropy encode values for syntax elements describing metadata associated with the encoded video data for use by video decoder 300 in decoding the video data.
• CABAC context-adaptive binary arithmetic coding
• video encoder 200 may assign a context within a context model to a symbol to be transmitted.
• the context may relate to, for example, whether neighboring values of the symbol are zero-valued or not.
• the probability determination may be based on a context assigned to the symbol.
• Video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, to video decoder 300, e.g., in a picture header, a block header, a slice header, or other syntax data, such as a sequence parameter set (SPS), picture parameter set (PPS), or video parameter set (VPS).
• Video decoder 300 may likewise decode such syntax data to determine how to decode corresponding video data.
• video encoder 200 may 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.
• video decoder 300 may receive the bitstream and decode the encoded video data.
• video decoder 300 performs a reciprocal process to that performed by video encoder 200 to decode the encoded video data of the bitstream.
• video decoder 300 may decode values for syntax elements of the bitstream using CAB AC in a manner substantially similar to, albeit reciprocal to, the CABAC encoding process of video encoder 200.
• the syntax elements may define partitioning information for partitioning a picture into CTUs, and partitioning of each CTU according to a corresponding partition structure, such as a QTBT structure, to define CUs of the CTU.
• the syntax elements may further define prediction and residual information for blocks (e.g., CUs) of video data.
• the residual information may be represented by, for example, quantized transform coefficients.
• Video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of a block to reproduce a residual block for the block.
• Video decoder 300 uses a signaled prediction mode (intra- or inter-prediction) and related prediction information (e.g., motion information for inter-prediction) to form a prediction block for the block.
• Video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block.
• Video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along boundaries of the block.
• video encoder 200 and/or video decoder 300 may perform generalized intra prediction. For instance, video encoder 200 and/or video decoder 300 may code an indication of the performance of generalized prediction for a current coding block of video data; split, based on the indication, the current coding block into one or more prediction blocks; define, based on the one or more prediction blocks, one or more prediction block groups (PBGs);
• PBGs prediction block groups
• a video coder may perform splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks.
• the video coder may perform vertical splitting or horizontal splitting of the CU.
• the video coder may perform splitting of the CU as a combination of vertical splitting and horizontal splitting of the CU.
• the video coder may perform vertical splitting on parts of the CU and perform horizontal splitting on other parts of the CU.
• the video coder may split the CU, via various splitting or partitioning techniques, to form a set of prediction blocks.
• the prediction blocks may include at least a first prediction block and a second prediction block.
• a CU may include a single prediction block.
• the prediction blocks may include narrow vertical blocks, narrow horizontal blocks, or a combination of vertical blocks and horizontal blocks. It should be noted that the term“narrow” in this context generally includes non-square blocks (e.g., rectangular blocks, etc.).
• the video coder may group a plurality of the set of prediction blocks into a first prediction block group (PBG).
• a PBG may include at least two prediction blocks.
• a PBG may include one or more vertical prediction blocks, one or more horizontal prediction blocks, or one or more
• a PBG may include a single prediction block.
• a CU may include PBGs of varying sizes.
• a single CU may include a plurality of PBGs with a first PBG formed by grouping one or more prediction blocks (e.g., vertical, horizontal, or both vertical and horizontal blocks), and a second PBG formed by grouping at least two prediction blocks (e.g., vertical, horizontal, or both vertical and horizontal blocks).
• the single CU may additionally include a third PBG formed by grouping at least two prediction blocks (e.g., vertical blocks, horizontal blocks, or both vertical and horizontal blocks), a fourth PBG formed by grouping at least three prediction blocks (e.g., vertical, horizontal, or both), etc.
• a third PBG formed by grouping at least two prediction blocks (e.g., vertical blocks, horizontal blocks, or both vertical and horizontal blocks)
• a fourth PBG formed by grouping at least three prediction blocks (e.g., vertical, horizontal, or both)
• one or more subsequent CUs may include the same or a different arrangement of prediction blocks and/or PBGs.
• a second CU may include the same or at least a similar partitioning to that of one or more preceding CUs.
• the second CU may include a different partitioning scheme to that of the one or more preceding CUs.
• the video coder may partition a first CU using vertical splitting, the second CU using horizontal splitting, a third CU using a combination of horizontal and vertical splitting, a fourth CU using a different type of horizontal splitting (e.g., to form more or less narrow prediction blocks relative to other partitioned prediction blocks), or any other combinations or variations.
• the video decoder may partition a plurality of CUs using the same partitioning scheme, such as by using vertical splitting to partition at least two CUs.
• the video coder may additionally group the partitioned prediction blocks, for each partitioned CU, differently or the same. For example, the video coder may perform vertical splitting on a first CU to form a group of at least three PBGs, whereas the video coder may perform a similar vertical splitting on one or more subsequent CUs, but to form at least two PBGs.
• the quantity of PBGs for each CU may not necessarily be equal from one partitioned CU to a next partitioned CU, even in cases where the video coder partitions each CU using, for example, vertical splitting. It will be understood that, for sake of brevity, not all options may be explicitly delineated, but that other splitting and/or grouping options may be achieved by one or more of the various techniques, or variations of the techniques, described in this disclosure.
• a video coder may perform an independent reconstruction of such PBGs, as described above and as further described below.
• the video coder may then reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG. For example, the video coder may reconstruct the samples as part of a decoding loop. In other instances, video decoder 300 may split a CU to form a set of prediction blocks and group the prediction blocks into PBGs.
• This disclosure may generally refer to“signaling” certain information, such as syntax elements.
• the term“signaling” may generally refer to the communication of values for syntax elements and/or other data used to decode encoded video data. That is, video encoder 200 may signal values for syntax elements in the bitstream. In general, signaling refers to generating a value in the bitstream.
• source device 102 may transport the bitstream to destination device 116 substantially in real time, or not in real time, such as might occur when storing syntax elements to storage device 112 for later retrieval by destination device 116.
• FIG. 2 is a diagram illustrating example intra prediction modes.
• An example of intra prediction is wide-angle intra prediction.
• the intra prediction of a luma block includes 35 modes, including the Planar prediction mode, DC prediction mode and 33 angular (or directional) prediction modes.
• directional prediction for square blocks in some instances, may use directions between -135 degrees to 45 degrees of a current block 250, such as in the VVC test model 2 (VTM2) (see“Algorithm description for Versatile Video Coding and Test Model 2 (VTM2),”
• rectangular prediction blocks (w > h or w ⁇ h) can increase the coding efficiency based on the characteristics of the content.
• FIG. 3 is a block diagram illustrating an example of an 8x4 rectangular block.
• FIGS. 4A-4C are block diagrams providing illustrations of mode mapping process(es) for modes outside the diagonal direction range.
• a square block CU 402 does not require angular mode remapping.
• FIG. 4B illustrates angular mode remapping for a horizontal non-square block CU 404.
• FIG. 4C illustrates angular mode remapping for a vertical non-square block CU 406.
• FIG. 5 is a block diagram illustrating wide-angle intra-prediction adopted in VTM2.
• wide-angle intra-prediction includes angular intra prediction for square and non-square blocks, such as block 550.
• VTM3 VVC test model 3
• This adoption includes two modifications to unify the angular intra prediction for square and non-square blocks.
• angular prediction directions may be modified to cover diagonal directions of all block shapes.
• angular directions may be kept within the range between the bottom-left diagonal direction and the top-right diagonal direction for all block aspect ratios (square and non-square) as illustrated in FIGS.
• FIG. 6 is a block diagram illustrating wider angles for prediction of blocks 650 that are adopted in VTM3.
• VTM3 defines 95 modes for any block size, only 67 modes may be allowed. The exact modes that are allowed depend on the ratio of block width to block height. This is done by restricting the mode range for certain blocks sizes.
• FIG. 6 provides an illustration of wide angles (-1 to -14, and 67 to 80) in VTM3 beyond modes 2 and 66 for a total of 93 angular modes.
• FIG. 7 is an example mapping table that provides an example mapping between predModelntra and the angle parameter intraPredAnglein VTM3, further details of which are available from“Versatile Video Coding (Draft 3),” 12th JVET Meeting, Macau SAR, CN, Oct. 2018, JVET-L1001 by B. Bross, J. Chen, and S. Liu.
• angular modes with a positive intraPredAngle value are referred to as positive angular modes (mode index ⁇ 18 or >50), while angular modes with a negative intraPredAngle value are referred to as negative angular modes (mode index >18 and ⁇ 50).
• inv Angle Roundf— 256*32 — ) ( 1 )
• intraPredAngle values that are multiples of 32 (i.e. values of 0, 32, 64, 128, 256, 512 in this example) correspond with prediction from non-fractional reference array samples, as is the case in the VTM3 specification.
• Table 2 illustrates diagonal modes corresponding with various block aspect ratios.
• Intra sub-partition coding is described in the following portions of this disclosure.
• Intra sub-partition coding (ISP) (S. De Luxan Hernandez, H. Schwarz, D. Marpe, T. Wiegand (HHI)“CE3: Line-based intra coding mode”, JVET-L0076) is a method by which a coding block (e.g., a coding unit) is split or partitioned into multiple subblocks.
• a coding unit may be split or partitioned into two subblocks, four subblocks, etc.
• a subblock may be referred to as a prediction block.
• each subblock within a coding block is reconstructed in decoding order before the reconstruction of the subsequent subblock in decoding order.
• VVC WD4 the fourth working draft of VVC
• ISP may only be applied to luma coding blocks.
• FIGS. 8 and 9 are block diagrams illustrating example divisions of blocks for ISP coding.
• FIG. 8 illustrates an example of division of 4x8 and 8x4 blocks.
• FIG. 9 illustrates an example of division of all blocks except 4x8, 8x4, and 4x4 blocks.
• One bit is used to signal whether a coding block is split into intra sub-partitions, and a second bit is used to indicate the split type.
• Example split types include horizontal splitting, vertical splitting, vertical and horizontal splitting, etc.
• two different classes of processing orders may be used, which are referred to as normal order and reverse processing order.
• the first sub-partition to be processed is the one containing the top-left sample of the CU and then continuing downwards (horizontal split) or rightwards (vertical split).
• the reverse processing order either starts with the sub-partition containing the bottom-left sample of the CU and continues upwards (horizontal split) or starts with the sub-partition containing the top-right sample of the CU and continues leftwards (vertical split).
• a variation of ISP may use only the normal processing order, such as in WC WD4. It is to be noted that the terms“subblock” and“sub-partitions” may be used interchangeably herein. In any case, both terms refer to the blocks obtained by partitioning a coding block using ISP.
• intra_subpartitions_mode_flag[ x0 ][ yO ] 1 specifies that the current intra coding unit is partitioned into NumIntraSubPartitions[ xO ][ yO ] rectangular transform block sub-partitions.
• intra_subpartitions_mode_flag[ xO ][ yO ] 0 specifies that the current intra coding unit is not partitioned into rectangular transform block sub-partitions.
• intra subpartitions mode flag[ xO ][ yO ] is not present, the value of intra subpartitions mode flag is inferred to be equal to 0.
• an intra sub-partitions split flag may be used to indicate a split type or the split types.
• a intra_subpartitions_split_flag[ xO ][ yO ] may specify a split types or a number of various split types.
• the intra sub-partitions split flag may indicate whether the intra sub-partitions split type is horizontal, vertical, rectangular, a mix of vertical and horizontal, or any other split type.
• intra_subpartitions_mode_flag[ xO ][ yO ] is not present, the video coder may infer the flag to be equal to 0.
• IntraSubPartitionsSplitType specifies the type of split used for the current luma coding block as illustrated in Table 5 below. IntraSubPartitionsSplitType is derived as follows:
• IntraSubPartitionsSplitType is set equal to 0.
• NumlntraSubPartitions specifies the number of transform block sub-partitions into which an intra luma coding block is divided. NumlntraSubPartitions is derived as follows:
• NumlntraSubPartitions is set equal to 2: (1) cbWidth is equal to 4 and cbHeight is equal to 8, or (2) cbWidth is equal to 8 and cbHeight is equal to 4. Otherwise, NumlntraSubPartitions is set equal to 4.
• the samples in the neighbourhood of a coding block are used for intra prediction of the block.
• the reconstructed reference sample lines that are closest to the left and the top boundaries of the coding block are used as the reference samples for intra prediction.
• a video coder may use other samples as references samples, such as samples in the neighbourhood of the coding block or CU.
• FIG. 10 is a block diagram illustrating the reference sample lines that may be used for intra prediction. For each coding block, an index is signalled that indicates the reference line that is used.
• a video coder may only use reference lines with MRLIdx equal to 0, 1 or 3.
• a video coder may code the index to the reference line used for coding the block (e.g., values 0, 1 and 2 indicating lines with MRLIdx 0, 1 and 3, respectively) with truncated unary codeword. Planar and DC modes are not used for the reference line used has MRLIdx > 0.
• the intra sub-partition (ISP) coding of blocks may result in subblocks (e.g., prediction blocks) that have very small size in one or more dimensions.
• subblocks e.g., prediction blocks
• WxH size 4xN
• the resultant subblocks have size lxN when N is greater than 8.
• increasingly narrow subblocks may result in memory access of samples that are more than the number of samples in the subblock.
• accessing the M samples in each row from memory may often involve an overhead, such as accessing more than M samples due to a limitation on the minimum number of samples per access.
• Wiegand (HHI), “CE3: Intra Sub-Partitions Coding Mode,” JVET-M0102) is to restrict the prediction of lxN subblocks to VER prediction mode such that they are not dependent on the reconstruction of other subblocks in the coding block.
• this proposed solution also results in limiting the intra modes allowed for the coding block, which results in coding inefficiency.
• This disclosure proposes techniques to improve the design of sub-partition coding of CUs.
• One or more of the techniques disclosed here may be implemented separately or implemented together in any combination.
• a video coder may perform generalized prediction of subblocks (e.g., prediction blocks).
• the video coder may code an indication (e.g., a syntax element) to perform generalized prediction for a coding block.
• the indication to perform generalized prediction may involve an indication that the coding block is coded with ISP.
• the indication to perform generalized prediction may apply to only blocks with certain properties, e.g., when the block width is within a threshold range, or when the block height is within a threshold range, or when the number of samples in the block is within a threshold range, or when the sum of the block width and block height is within a threshold range, or when the minimum or maximum of the block width and block height is within a threshold range.
• a subset of intra modes may be defined from the set of allowed intra modes for the block.
• generalized prediction may only apply to the block when the block is coded with an intra mode that belongs to the subset.
• the indication may be inferred by the block
• the video coder may split a coding unit into one or more prediction blocks.
• the video coder may define one or more prediction block groups (PBGs).
• a PBG may include one or more prediction blocks.
• the prediction of any sample in a PBG may not be directly dependent on the predicted value of any other sample in the PBG.
• a video coder may reconstruct samples of prediction blocks included in a first PBG independently of samples of other prediction blocks included in the same PBG. In this way, the prediction of samples in the first PBG is not dependent on the predicted value of other samples in the first PBG.
• each PBG contains exactly one prediction block.
• each PBG may contain npB prediction blocks (e.g., a prediction block quantity).
• the video coder may determine the value of npB based on the width and height of the coding unit.
• the video coder may determine the value of npe based on the number of samples of the coding unit or on the number of samples and the width and height of the coding unit.
• the video coder may also use the split type (e.g., horizontal, vertical, rectangular, a mix of horizontal and vertical, etc.) and/or the intra mode (e.g., angular, etc.) to determine the value of npe for a coding unit or coding block.
• the video coder may specify prediction blocks that are not rectangular in shape.
• the restriction that“the prediction of any sample in a PBG may not be dependent on the predicted value of any other sample in the PBG” may be relaxed.
• the restriction of prediction dependence of samples within a PBG may still be considered valid as long as the regular intra prediction (without the post-prediction filtering operations) do not result in a dependence.
• the restriction may not apply to dependence due to position dependent intra prediction combination (PDPC), boundary filtering or other similar operations.
• each prediction block in a coding block may be contained in one and only one PBG. In some examples, this restriction may be stricter. For example, it may be restricted that each prediction block in a coding block must be contained in one PBG, and only one PBG.
• the video coder may specify a decoding order of the PBGs; the decoding order may be defined such that samples in a PBG PI do not depend on the samples in a PBG P2 when PI precedes P2 in decoding order.
• the video coder may specify a set of available reference samples (described below).
• the video coder may obtain a predicted value for a sample in the PBG based on the available reference samples for the PBG and the intra mode used for prediction.
• a video coder may perform generalized planar prediction.
• the video coder may define a set of prediction blocks for a coding block
• the video coder may code one or more of the prediction blocks with a Planar mode.
• the video coder may perform the determination to split a coding block into planar prediction blocks by one or more of the following:
• An indication in the bitstream (e.g., a flag) that the block is to be split into planar prediction blocks.
• the coding block may be indicated to be coded by the Planar mode.
• the indication may be that the coding block is coded using ISP.
• Planar prediction blocks may be indicated by a separate mode value MPPB.
• MPPB coded prediction block
• the determination may be inferred based on certain block characteristics and other syntax elements in the bitstream. For example, a block with a certain maximum number of samples and coded with ISP may be split into planar prediction blocks.
• the video coder may determine the number of planar prediction blocks, NPPB, and the splitting decisions, by one or more of the following: NPPB may be signalled in the bitstream (e.g., for all blocks or for blocks with certain characteristics) or derived based on the block characteristics and other syntax elements in the bitstream.
• NPPB may be signalled in the bitstream (e.g., for all blocks or for blocks with certain characteristics) or derived based on the block characteristics and other syntax elements in the bitstream.
• the NPPB may be set equal to the number of intra sub-partition blocks for a coding block.
• the value of NPPB may be set equal to 4.
• the split direction or method may be determined by the block characteristics or derived from syntax elements in the bitstream.
• the block may be split horizontally into NPPB planar prediction blocks.
• the decision to split horizontally may, for example, be determined by whether a horizontal split direction is indicated.
• FIG. 11 is a conceptual diagram illustrating an example of how a coding block may be split into four horizontal planar prediction blocks.
• the video coder may split the block vertically into NPPB planar prediction blocks.
• the video coder may determine whether to split vertically based on whether a vertical split direction is indicated, for example.
• FIG. 12 is a conceptual diagram illustrating an example of how a coding block may be split into four vertical planar prediction blocks.
• the video coder may split the block horizontally and vertically resulting in a total of NPPB planar prediction blocks.
• the video coder may determine whether to split horizontally and vertically based on one or more
• the video coder may determine whether to split horizontally and vertically when no split direction is indicated.
• the block may be split into NPPB rectangular regions, that share the same top-left sample as the coding block and each rectangular region successively containing the one before it. Starting with the smallest block which is defined as the first planar prediction block, samples that belong to the next rectangular region but do not belong to the previous rectangular region are said to constitute the succeeding planar prediction block.
• FIG. 13 is a conceptual diagram illustrating an example of such a planar prediction block structure.
• the video coder may also predict a planar prediction block by a method that is similar to the planar prediction mode.
• the video coder may define a coding order for the prediction blocks.
• the coding order may be defined by considering the following (a. through d.):
• the top-left sample may not be defined, and the representative sample may be specified as the left-most sample that is in the top-most row of samples of the prediction block. It must be understood that the coding order may be also specified with other definitions of representative samples.
• b Define a scan order of representative samples (e.g., raster scan, zigzag scan).
• a prediction block that has a representative sample earlier in the scan order is coded earlier than a prediction block that has a representative sample later in the scan order.
• d Similar definition of coding order may also be specified for prediction block groups.
• the video coder may specify a planar prediction block group (Planar PBG), including one or more planar prediction blocks, similar to the idea of PBG discussed above.
• Planar PBG planar prediction block group
• the boundaries between the planar prediction blocks may be smoothed by applying filtering across the prediction block boundaries within the coding block.
• filtering is lowpass filtering.
• a second example is the processing performed in PDPC mode.
• a third example is a deblocking filter process. These processes may be applied as a second processing step after prediction or as a post processing step.
• planar prediction blocks are only some examples for illustrating the concept.
• the samples in the coding block may be split into spatial regions that are defined as planar prediction blocks, and one or more methods disclosed in this application may be applied to them.
• blocks coding blocks, prediction blocks, etc.
• coding blocks may apply to luma blocks or chroma blocks (or both), or in general to coding blocks of any component of the video.
• a video coder may determine the availability of reference samples. For each PBG, the available reference samples may be specified as follows:
• the set of available reference samples are the same for all the prediction blocks in the coding block. There may be multiple implementations of such a system. As one example, reference sample derivation process is unchanged, and changes are made to the prediction process. The set of available reference samples is derived once for the coding block. In some examples, changes may be made to the prediction process to ensure that the reference samples may not be immediately adjacent to the prediction block, or as specified by MRLIdx relative to the prediction block.
• the reference sample derivation is changed, and no changes are made to the prediction process.
• the available reference samples for a prediction block are derived from the set of available reference samples for the coding block.
• the derivation may result in derived values of the reference samples for the prediction block at positions that correspond with reference sample line used (i.e., based on the value of MRLIdx).
• the predicted samples from preceding PBG in decoding order are marked as unavailable.
• the processed values of previously coded PBG of the same coding block may be used for intra prediction of a PBG, in addition to the reference samples from the neighbouring coding blocks.
• the processed values refer to the reconstructed samples of the PBG.
• the processed values refer to the reconstructed samples of the PBG before loop filtering/post-filtering operations.
• the processed values refer to the predicted samples of the PBG.
• a video coder may perform transform coding.
• the prediction of samples in a block may be performed by one or more methods described herein.
• the techniques in this section may also apply to coding blocks that are not predicted using generalized prediction as described above.
• the video coder may apply a transform to the residual samples in a PBG.
• a set of applicable shapes may be defined such that the video coder may apply a transform to all the samples of the applicable shape.
• the applicable shape may include square and/or rectangular shapes.
• transform coding of the block may be performed by taking the entire coding block as one block. In such examples, only one transform coding may apply to the samples in the coding block irrespective of the number of prediction blocks defined therein.
• the video coder may apply transform coding to a PBG when the shape of the PBG is an applicable shape on which the transform may be applied.
• the transform may be applied to the samples of the PBG.
• the video coder may apply transform coding to one or more subsets of samples in a PBG such that the samples in each such subset form an applicable shape.
• the subsets of the PBG may be constrained to be mutually exclusive.
• the subsets of the PBG collectively may be constrained to include all the samples of the PBG.
• applying a transform may also include a transform-skip decision on the block, whereby the sample values of the block are unchanged, an identity transform is applied, or a scaled identity transform is applied.
• a video coder may code some prediction blocks in a PBG with transform skip.
• the video coder may code some prediction blocks with other types of transform.
• the decision of applying a transform kernel or transform skip may be inferred (e.g., based on block characteristics, intra mode, neighbouring blocks) or signalled in the bitstream.
• a subblock partitioning scheme may be defined for the transform coding that is different from the prediction blocks specified.
• a transform block group (TBG) may be defined using transform subblocks similarly as defined for prediction blocks.
• TBG transform block group
• One or more techniques described above may apply to TBGs.
• prediction blocks may be of size 2xN
• prediction block groups may be of size 4xN
• transform blocks may be of size 4xN.
• prediction blocks may be of size 2xN
• prediction block groups may be of size 4xN
• transform blocks may be of size 2xN for a 8xN coding block.
• a video coder may disallow certain intra modes.
• Several intra modes are defined (e.g., angular and non-angular) for intra prediction of blocks.
• intra modes e.g., angular and non-angular
• For PBGs only a subset of the intra modes may be specified to be allowed modes.
• certain intra modes may be disallowed for PBGs.
• the determination of disallowed intra modes may be reached by considering one or more of the following: (1) split direction, (2) coding block width, height, or a function of width and the height, (3) prediction block width, height, or a function of width and the height, or (4) above block characteristics of neighbouring coding blocks, and intra mode used to code the neighbouring coding blocks.
• a prediction block group is specified to have a minimum width of four samples.
• vertical partitioning of a coding block of size 4xN may result in subblocks of width 1 or 2 and vertical partitioning of 8xN coding blocks may result in subblocks of width 2 or 4.
• FIG. 14 is a block diagram illustrating how a coding block 1402 is split into four prediction blocks (PB1-PB4).
• coding block 1402 may be an 8xN coding block that a video coder codes with ISP and with a vertical split.
• prediction blocks PB1, PB2, PB3, and PB4 are of size 2xN.
• Prediction block groups PBG1 and PBG2 are defined with a minimum width (nW) of 4 samples.
• PBG1 is a prediction block group of size 4xN
• PBG2 is a second prediction block group of size 4xN, also.
• the samples of PBG1 are predicted from the neighbouring reference samples. In some examples, the predicted value of samples in PBG1 may not depend on other sample values in PBG1.
• the samples of PBG2 are predicted from the neighbouring reference samples and from the predicted samples of PBG1.
• the transform block (e.g., transform unit (TU)) may be defined to be of the same size as the prediction block.
• the video coder may determine a size of the TU to be equal to a size of any one prediction block included in a PBG.
• the samples of PBG2 may be predicted from reference samples from neighbouring coding blocks and from reconstructed samples belonging to the area of PBG1, or only from the reference samples from neighbouring coding blocks.
• FIG. 15 is a block diagram illustrating an example where a video coder may code coding block 1502 with ISP and vertical partitioning.
• coding block 1502 may be a 4xN coding block.
• the prediction blocks (PB1-PB4) may be of size lxN.
• a PBG may be defined to have a width of at least four samples.
• the video coder may group the four prediction blocks (PB1-PB4) into one prediction block group (e.g., PBG1).
• PBG1 may be a PBG of size 4xN.
• the generalized prediction (specifying prediction blocks and prediction block groups described herein) only applies to a subset of blocks that satisfy one or more criteria, which may depend on block size, block shapes, subblock width and heights, intra modes, etc.
• the condition may only apply to coding blocks that generate subblocks that have a width less than or equal to 2.
• the condition may apply to subblocks that have a total number of samples less than or equal to 32 samples.
• the samples of all prediction blocks of a coding block are predicted from the reconstructed reference samples of the neighbouring coding blocks.
• the transform unit size may be equal to the size of the prediction block.
• FIG. 16 is a conceptual diagram illustrating an example where an MxN coding block 1602 is split into four prediction blocks (e.g., PB1-PB4).
• the prediction blocks (PB1-PB4) have a size of (M/4)xN.
• the reference samples 1604 are used as the reference samples for the four prediction blocks. There is no dependence between the predicted samples of one prediction block to the other. For example, there is no dependence between the predicted samples of PB1 and the predicted samples of PB2, PB3, or PB4.
• the four predicted subblocks may be predicted in parallel.
• the four subblocks (PB1-PB4) may be considered together as one block for prediction.
• the four subblocks (PB1-PB4) may be considered together as one PBG for prediction.
• a video coder may predict the samples of some coding blocks using at least one prediction block group having a width of four samples, and some other coding units are predicted with restricted intra modes.
• the following restrictions are added in the specification that apply to the coding of 4xN coding blocks and 8xN coding blocks that are coded with ISP.
• FIG. 17 is a conceptual diagram illustrating an example in which a video coder is only allowed to perform vertical intra (VER Intra) mode prediction for a 4xN coding block 1702 that the video coder codes with ISP and vertical split. That is, FIG. 17 shows an example of how the vertically split sub-partitions of a 4xN coding block 1702 may only use vertical intra mode for prediction.
• coding block 1702 may have a height of at least an 8-sample size (N > 8). In such examples, coding block 1702 may be split into four lxN subpartitions (e.g., subblocks, prediction blocks).
• the inverse transform operation is still performed at the lxN sub-partition level.
• the prediction of samples is performed on prediction block groups (PBG) four samples in width.
• PBG prediction block groups
• a video coder may identify two PBGs to each have a size of 4xN.
• FIG. 18 shows an example of how an 8xN sub-partition is split into two prediction regions (PBG1 or region 1 and PBG2 or region 2) of size 4xN each, and four transforms of size 2xN each. In the example of FIG.
• a video coder may code an 8xN (N > 4) coding block 1802 with ISP and vertical split.
• the video coder may perform prediction on 4xN prediction regions (or PBG).
• the transform (SP) size may be 2xN.
• the prediction of the region 2 is dependent on the reconstruction of the region 1. Thus, the prediction of any sample within the coding block 1802 is only dependent on
• the four-line residuals of size lxN and similarly in FIG. 18, within one prediction region (prediction region 1 or 2), and the two residual blocks of 2xN can be generated in parallel or together in one step.
• the vertical inverse transform operation of the two 2xN sub-partitions within each prediction region may be performed by considering the region as a 4xN block because the vertical transform for all the sub-partitions in ISP is identical.
• the horizontal transform may also be done for the 2xN sub-partitions in parallel, either by separate processing, or by considering the two sub-partitions as a single 4xN block and the horizontal inverse transform operation as a combination of the two smaller horizontal inverse transform operations.
• Table 6 summarizes the partition sizes for prediction sizes and transform sizes.
• the prediction sizes and transform sizes may be different for other coding block sizes.
• the prediction and transform sizes may be as specified for ISP in VVC WD4.
• VVC WD5 Changes to relevant sections of the specification in the fifth working draft of VVC (hereinafter“VVC WD5” and available at phenix.it- sudparis.eu/jvet/doc_end_user/documents/14_Geneva/wgl l/JVET-N1001-v8.zip, are provided below with change marks. Deleted items are shown with strikethrough and added items are shown with bold italics.
• a video encoder may use the following inputs in order to perform a coding process:
• Output of the process is a modified reconstructed picture before in-loop filtering.
• IntraSubPartitionsSplitType is equal to NO ISP SPLIT and nTbW is greater than maxTbSize or nTbH is greater than maxTbSize, the following ordered steps apply (1. through 5.):
• newTbW ( nTbW > maxTbSize ) ? ( nTbW / 2 ) : nTbW and
• newTbH ( nTbH > maxTbSize ) ? ( nTbH 12 ) : nTbH.
• nTbW is greater than maxTbSize
• the general decoding process for intra blocks as specified in this clause is invoked with the location ( xTbO, yTbO ) set equal to ( xTbO + newTbW, yTbO ), the transform block width nTbW set equal to newTbW and the height nTbH set equal to newTbH, the intra prediction mode predModelntra, and the variable cldx as inputs, and the output is a modified reconstructed picture before in-loop filtering. [0190] 4.
• nTbH is greater than maxTbSize
• the general decoding process for intra blocks as specified in this clause is invoked with the location ( xTbO, yTbO ) set equal to ( xTbO, yTbO + newTbH ), the transform block width nTbW set equal to newTbW and the height nTbH set equal to newTbH, the intra prediction mode predModelntra, and the variable cldx as inputs, and the output is a modified reconstructed picture before in-loop filtering.
• nTbW is greater than maxTbSize and nTbH is greater than maxTbSize
• the general decoding process for intra blocks as specified in this clause is invoked with the location ( xTbO, yTbO ) set equal to ( xTbO + newTbW, yTbO + newTbH ), the transform block width nTbW set equal to newTbW and the height nTbH set equal to newTbH, the intra prediction mode predModelntra, and the variable cldx as inputs, and the output is a modified reconstructed picture before in-loop filtering.
• the video coder may derive the following variables.
• a video coder may derive a plurality of variables, including nW, nH, xPartlncrement, yPartlncrement, nPbW and pbFactor.
• the video coder may derive such variables using Eqs. (6) through (11), as follows:
• a video coder may apply the following ordered steps (1.
• a video coder may invoke an intra sample prediction process as specified in clause 8.4.5.2. In such examples, video coder may invoke the intra sample prediction process with the location
• the output is an (nPbW)x(nH) array resSamples (e.g., residual sample array).
• the output may be an (nW)x(nH) array resSamples.
• the following changes may restrict intra prediction mode to vertical intra mode for some block sizes.
• Example changes are made to the signalling in Section 7.3.7.5 of VVC WD5. Deleted items are shown with strikethrough and added items are shown with italics.
• Example changes are made to the Derivation Process for luma intra prediction mode in Section 8.4.3 of VVC WD5. Deleted items are shown with strikethrough and added items are shown with italics.
• a video coder may perform a derivation process for luma intra prediction mode. Inputs to this process include: (1) a luma location ( xCb , yCb ) specifying the top-left sample of the current luma coding block relative to the top-left luma sample of the current picture, (2) a variable cbWidth specifying the width of the current coding block in luma samples, and/or (3) a variable cbHeight specifying the height of the current coding block in luma samples.
• a video coder may derive the luma intra prediction mode IntraPredModeY[ xCb ][ yCb ].
• Table 8 specifies the value for the intra prediction mode
• IntraPredModeY[ xCb ][ yCb ] is derived as follows: If
• BdpcmFlag[ xCb ][ yCb ] is equal to 1 or i n t ra_l u a n ot_p 1 an ar fl ag [ xCb ][ yCb ] is equal to 0, IntraPredModeY[ xCb ][ yCb ] is set equal to INTRA PLANAR. Otherwise if IntraSubPartitionsSplitType is equal to ISP VER SPLIT and cbWidth is equal to 4, IntraPredmodeY [ xCb ][ yCb ] is set equal to INTRA ANGULAR50.
• intra luma_not_planar_flag[ xCb ][ yCb ] is equal to 1
• the neighbouring locations ( xNbA, yNbA ) and ( xNbB, yNbB ) are set equal to ( xCb - 1, yCb + cbHeight - 1 ) and ( xCb + cbWidth - 1, yCb - 1 ), respectively.
• FIGS. 19A and 19B are conceptual diagram illustrating an example QTBT structure 130, and a corresponding coding tree unit (CTU) 132.
• the solid lines represent quadtree splitting, and dotted lines indicate binary tree splitting.
• each split (i.e., non-leaf) node of the binary tree one flag is signaled to indicate which splitting type is used (e.g., horizontal, vertical, etc.).
• a value of 0 may indicate horizontal splitting and a value of 1 may indicate vertical splitting.
• video encoder 200 may encode, and video decoder 300 may decode, syntax elements (such as splitting information) for a region tree level (i.e., the first level) of QTBT structure 130 (i.e., the solid lines) and syntax elements (such as splitting information) for a prediction tree level (i.e., the second level) of QTBT structure 130 (i.e., the dashed lines).
• Video encoder 200 may encode, and video decoder 300 may decode, video data, such as prediction and transform data, for CUs represented by terminal leaf nodes of QTBT structure 130.
• CTU 132 of FIG. 19B may be associated with parameters defining sizes of blocks corresponding to nodes of QTBT structure 130 at the first and second levels. These parameters may include a CTU size (representing a size of CTU 132 in samples), a minimum quadtree size (MinQTSize, representing a minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, representing a maximum allowed binary tree root node size), a maximum binary tree depth
• MaxBTDepth representing a maximum allowed binary tree depth
• MinBTSize representing the minimum allowed binary tree leaf node size
• the root node of a QTBT structure corresponding to a CTU may have four child nodes at the first level of the QTBT structure, each of which may be partitioned according to quadtree partitioning. That is, nodes of the first level are either leaf nodes (having no child nodes) or have four child nodes.
• the example of QTBT structure 130 represents such nodes as including the parent node and child nodes having solid lines for branches. If nodes of the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes can be further partitioned by respective binary trees. The binary tree splitting of one node can be iterated until the nodes resulting from the split reach the minimum allowed binary tree leaf node size
• the example of QTBT structure 130 represents such nodes as having dashed lines for branches.
• the binary tree leaf node is referred to as a coding unit (CU), which is used for prediction (e.g., intra-picture or inter-picture prediction) and transform, without any further partitioning.
• CUs may also be referred to as“video blocks,” “coding blocks,” or“blocks.”
• the CTU size is set as 128x128 (luma samples and two corresponding 64x64 chroma samples), the
• MinQTSize is set as 16x16
• MaxBTSize is set as 64x64
• MinBTSize for both width and height
• MaxBTDepth is set as 4.
• the quadtree partitioning is applied to the CTU first to generate quad-tree leaf nodes.
• the quadtree leaf nodes may have a size from 16x16 (i.e., the MinQTSize) to 128x128 (i.e., the CTU size). If the quadtree leaf node is 128x128, the node will not be further split by the binary tree, since the size exceeds the MaxBTSize (i.e., 64x64, in this example). Otherwise, the quadtree leaf node will be further partitioned by the binary tree.
• the quadtree leaf node is also the root node for the binary tree and has the binary tree depth as 0.
• the binary tree depth reaches MaxBTDepth (4, in this example)
• no further splitting is permitted.
• the binary tree node has width equal to MinBTSize (4, in this example)
• it implies that no further vertical splitting is permitted.
• a binary tree node having a height equal to MinBTSize implies that no further horizontal splitting is permitted for that binary tree node.
• leaf nodes of the binary tree are referred to as CUs, and are further processed according to prediction and transform without further partitioning.
• FIG. 20 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure.
• FIG. 20 is provided for purposes of explanation and should not be considered limiting of the techniques as broadly exemplified and described in this disclosure.
• this disclosure describes video encoder 200 in the context of video coding standards such as the HEVC video coding standard and the H.266 video coding standard in development.
• video coding standards such as the HEVC video coding standard and the H.266 video coding standard in development.
• the techniques of this disclosure are not limited to these video coding standards, and are applicable generally to video encoding and decoding.
• video encoder 200 includes video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, decoded picture buffer (DPB) 218, and entropy encoding unit 220.
• Any or all of video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy encoding unit 220 may be implemented in one or more processors or in processing circuitry.
• video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.
• Video data memory 230 may store video data to be encoded by the components of video encoder 200.
• Video encoder 200 may receive the video data stored in video data memory 230 from, for example, video source 104 (FIG. 1).
• DPB 218 may 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 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices.
• Video data memory 230 and DPB 218 may be provided by the same memory device or separate memory devices.
• video data memory 230 may be on-chip with other components of video encoder 200, as illustrated, or off-chip relative to those components.
• 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 that is to be encoded). Memory 106 of FIG. 1 may also provide temporary storage of outputs from the various units of video encoder 200.
• the various units of FIG. 20 are illustrated to assist with understanding the operations performed by video encoder 200.
• the units may 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.
• programmable circuits may 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 may 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.
• one or more of the units may be distinct circuit blocks (fixed-function or programmable), and in some examples, the one or more units may be integrated circuits.
• Video encoder 200 may include arithmetic logic units (ALUs), elementary function units (EFUs), digital circuits, analog circuits, and/or programmable cores, formed from programmable circuits.
• ALUs arithmetic logic units
• EFUs elementary function units
• digital circuits analog circuits
• programmable cores formed from programmable circuits.
• memory 106 FIG. 1 may store the object code of the software that video encoder 200 receives and executes, or another memory within video encoder 200 (not shown) may store such instructions.
• Video data memory 230 is configured to store received video data.
• Video encoder 200 may retrieve a picture 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 may be raw video data that is to be encoded.
• Mode selection unit 202 includes a motion estimation unit 222, motion compensation unit 224, and an intra-prediction unit 226. Mode selection unit 202 may include additional functional units to perform video prediction in accordance with other prediction modes. As examples, mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of motion estimation unit 222 and/or motion compensation unit 224), an affine unit, a linear model (LM) unit, or the like.
• LM linear model
• Mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values for such combinations.
• the encoding parameters may include partitioning of CTUs into CUs, prediction modes for the CUs, transform types for residual data of the CUs, quantization parameters for residual data of the CUs, and so on.
• Mode selection unit 202 may ultimately select the combination of encoding parameters having rate-distortion values that are better than the other tested combinations.
• Video encoder 200 may partition a picture retrieved from video data
• Mode selection unit 202 may partition a CTU of the picture in accordance with a tree structure, such as the QTBT structure or the quad-tree structure of HEVC described above.
• video encoder 200 may form one or more CUs from partitioning a CTU according to the tree structure.
• Such a CU may also be referred to generally as a“video block” or“block.”
• mode selection unit 202 also controls the components thereof (e.g., motion estimation unit 222, motion compensation unit 224, and intra-prediction unit 226) to generate a prediction block for a current block (e.g., a current CU, or in HEVC, the overlapping portion of a PU and a TU).
• motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218).
• motion estimation unit 222 may calculate a value representative of how similar a potential reference block is to the current block, e.g., according to sum of absolute difference (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared differences (MSD), or the like. Motion estimation unit 222 may generally perform these calculations using sample-by-sample differences between the current block and the reference block being considered. Motion estimation unit 222 may identify a reference block having a lowest value resulting from these calculations, indicating a reference block that most closely matches the current block.
• SAD sum of absolute difference
• SSD sum of squared differences
• MAD mean absolute difference
• MSD mean squared differences
• Motion estimation unit 222 may form one or more motion vectors (MVs) that define the positions of the reference blocks in the reference pictures relative to the position of the current block in a current picture. Motion estimation unit 222 may then provide the motion vectors to motion compensation unit 224. For example, for uni-directional inter-prediction, motion estimation unit 222 may provide a single motion vector, whereas for bi-directional inter-prediction, motion estimation unit 222 may provide two motion vectors. Motion compensation unit 224 may then generate a prediction block using the motion vectors. For example, motion compensation unit 224 may retrieve data of the reference block using the motion vector. As another example, if the motion vector has fractional sample precision, motion compensation unit 224 may interpolate values for the prediction block according to one or more interpolation filters. Moreover, for bi-directional inter-prediction, motion compensation unit 224 may retrieve data for two reference blocks identified by respective motion vectors and combine the retrieved data, such as through sample-by-sample averaging or weighted averaging.
• MVs motion vectors
• intra-prediction unit 226 may generate the prediction block from samples neighboring the current block. For example, for directional modes, intra-prediction unit 226 may generally mathematically combine values of neighboring samples and populate these calculated values in the defined direction across the current block to produce the prediction block. As another example, for DC mode, intra-prediction unit 226 may calculate an average of the neighboring samples to the current block and generate the prediction block to include this resulting average for each sample of the prediction block.
• Mode selection unit 202 provides the prediction block to residual generation unit 204.
• Residual generation unit 204 receives a raw, uncoded version of the current block from video data memory 230 and the prediction block from mode selection unit 202. Residual generation unit 204 calculates sample-by-sample differences between the current block and the prediction block. The resulting sample-by-sample differences define a residual block for the current block.
• residual generation unit 204 may also determine differences between sample values in the residual block to generate a residual block using residual differential pulse code modulation (RDPCM).
• RPCM residual differential pulse code modulation
• residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.
• each PU may be associated with a luma prediction unit and corresponding chroma prediction units.
• Video encoder 200 and video decoder 300 may support PUs having various sizes. As indicated above, the size of a CU may refer to the size of the luma coding block of the CU and the size of a PU may refer to the size of a luma prediction unit of the PU.
• video encoder 200 may support PU sizes of 2Nx2N or NxN for intra prediction, and symmetric PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar for inter prediction.
• Video encoder 200 and video decoder 300 may also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N.
• each CU may be associated with a luma coding block and corresponding chroma coding blocks.
• the size of a CU may refer to the size of the luma coding block of the CU.
• the video encoder 200 and video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.
• mode selection unit 202 For other video coding techniques such as an intra-block copy mode coding, an affine-mode coding, and linear model (LM) mode coding, as a few examples, mode selection unit 202, via respective units associated with the coding techniques, generates a prediction block for the current block being encoded. In some examples, such as palette mode coding, mode selection unit 202 may not generate a prediction block, and instead generate syntax elements that indicate the manner in which to reconstruct the block based on a selected palette. In such modes, mode selection unit 202 may provide these syntax elements to entropy encoding unit 220 to be encoded.
• mode selection unit 202 via respective units associated with the coding techniques, generates a prediction block for the current block being encoded.
• mode selection unit 202 may not generate a prediction block, and instead generate syntax elements that indicate the manner in which to reconstruct the block based on a selected palette. In such modes, mode selection unit 202 may provide these syntax elements to entropy encoding unit 220 to be encoded.
• residual generation unit 204 receives the video data for the current block and the 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 calculates sample-by-sample differences between the prediction block and the current block.
• Transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a“transform coefficient block”).
• Transform processing unit 206 may apply various transforms to a residual block to form the transform coefficient block.
• transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to a residual block.
• transform processing unit 206 may perform multiple transforms to a residual block, e.g., a primary transform and a secondary transform, such as a rotational transform.
• transform processing unit 206 does not apply transforms to a residual block.
• Quantization unit 208 may quantize the transform coefficients in a transform coefficient block, to produce a quantized transform coefficient block. Quantization unit 208 may quantize transform coefficients of a transform coefficient block according to a quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient blocks associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce loss of information, and thus, quantized transform coefficients may have lower precision than the original transform coefficients produced by transform processing unit 206.
• QP quantization parameter
• Inverse quantization unit 210 and inverse transform processing unit 212 may apply inverse quantization and inverse transforms to a quantized transform coefficient block, respectively, to reconstruct a residual block from the transform coefficient block.
• Reconstruction unit 214 may produce a reconstructed block corresponding to the current block (albeit potentially with some degree of distortion) based on the reconstructed residual block and a prediction block generated by mode selection unit 202. For example, reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples from the prediction block generated by mode selection unit 202 to produce the reconstructed block.
• Filter unit 216 may perform one or more filter operations on reconstructed blocks. For example, filter unit 216 may perform deblocking operations to reduce blockiness artifacts along edges of CUs. Operations of filter unit 216 may be skipped, in some examples.
• Video encoder 200 stores reconstructed blocks in DPB 218. For instance, in examples where operations of filter unit 216 are not needed, reconstruction unit 214 may store reconstructed blocks to DPB 218. In examples where operations of filter unit 216 are needed, filter unit 216 may store the filtered reconstructed blocks to DPB 218.
• Motion estimation unit 222 and motion compensation unit 224 may retrieve a reference picture from DPB 218, formed from the reconstructed (and potentially filtered) blocks, to inter-predict blocks of subsequently encoded pictures.
• intra-prediction unit 226 may use reconstructed blocks in DPB 218 of a current picture to intra-predict other blocks in the current picture.
• entropy encoding unit 220 may entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy encoding unit 220 may entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy encoding unit 220 may entropy encode prediction syntax elements (e.g., motion information for inter-prediction or intra-mode information for intra-prediction) from mode selection unit 202. Entropy encoding unit 220 may perform one or more entropy encoding operations on the syntax elements, which are another example of video data, to generate entropy-encoded data.
• prediction syntax elements e.g., motion information for inter-prediction or intra-mode information for intra-prediction
• entropy encoding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CAB AC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SB AC) operation, a Probability Interval Partitioning Entropy (PIPE) coding operation, an Exponential-Golomb encoding operation, or another type of entropy encoding operation on the data.
• entropy encoding unit 220 may operate in bypass mode where syntax elements are not entropy encoded.
• Video encoder 200 may output a bitstream that includes the entropy encoded syntax elements needed to reconstruct blocks of a slice or picture.
• entropy encoding unit 220 may output the bitstream.
• the operations described above are described with respect to a block. Such description should be understood as being operations for a luma coding block and/or chroma coding blocks.
• the luma coding block and chroma coding blocks are luma and chroma components of a CU.
• the luma coding block and the chroma coding blocks are luma and chroma components of a PU.
• operations performed with respect to a luma coding block need not be repeated for the chroma coding blocks.
• operations to identify a motion vector (MV) and reference picture for a luma coding block need not be repeated for identifying an MV and reference picture for the chroma blocks. Rather, the MV for the luma coding block may be scaled to determine the MV for the chroma blocks, and the reference picture may be the same. As another example, the MV for the luma coding block may be scaled to determine the MV for the chroma blocks, and the reference picture may be the same. As another example, the
• intra-prediction process may be the same for the luma coding blocks and the chroma coding blocks.
• Video encoder 200 may be configured to perform any of the prediction block grouping techniques described in this disclosure. For instance, intra-prediction unit 226 may perform ISP coding to partition a coding unit (CU) to subblocks (e.g., prediction blocks). In addition, intra-prediction unit 226 may group the subblocks into prediction block groups. In this way, video encoder 200 may be considered to include one or more processors implemented in circuitry and configured to perform splitting (e.g., vertical splitting) of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks. The prediction blocks may include at least a first prediction block and a second prediction block. Video encoder 200 may then group a plurality of the set of prediction blocks into a first prediction block group (PBG). In addition, video encoder 200 may reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• PBG first prediction block group
• FIG. 21 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure.
• FIG. 21 is provided for purposes of explanation and is not limiting on the techniques as broadly exemplified and described in this disclosure.
• this disclosure describes video decoder 300 according to the techniques of JEM, VVC, and HEVC.
• the techniques of this disclosure may be performed by video coding devices that are configured to other video coding standards.
• video decoder 300 includes coded picture buffer (CPB) memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and decoded picture buffer (DPB) 314.
• CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or in processing circuitry.
• video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.
• Prediction processing unit 304 includes motion compensation unit 316 and intra prediction unit 318. Prediction processing unit 304 may include additional units to perform prediction in accordance with other prediction modes. As examples, prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of motion compensation unit 316), an affine unit, a linear model (LM) unit, or the like. In other examples, video decoder 300 may include more, fewer, or different functional components.
• CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by the components of video decoder 300.
• the video data stored in CPB memory 320 may be obtained, for example, from computer-readable medium 110 (FIG. 1).
• CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream.
• CPB memory 320 may store video data other than syntax elements of a coded picture, such as temporary data representing outputs from the various units of video decoder 300.
• DPB 314 generally stores decoded pictures, which video decoder 300 may output and/or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream.
• CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices.
• DRAM dynamic random access memory
• SDRAM synchronous DRAM
• MRAM magnetoresistive RAM
• RRAM resistive RAM
• CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices.
• CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.
• video decoder 300 may retrieve coded video data from memory 120 (FIG. 1). That is, memory 120 may store data as discussed above with CPB memory 320. Likewise, memory 120 may store instructions to be executed by video decoder 300, when some or all of the functionality of video decoder 300 is implemented in software to be executed by processing circuitry of video decoder 300.
• the various units shown in FIG. 21 are illustrated to assist with understanding the operations performed by video decoder 300.
• the units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Similar to FIG. 20, 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 may 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 may 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.
• one or more of the units may be distinct circuit blocks (fixed-function or programmable), and in some examples, the one or more units may be integrated circuits.
• Video decoder 300 may include ALUs, EFUs, digital circuits, analog circuits, and/or programmable cores formed from programmable circuits. In examples where the operations of video decoder 300 are performed by software executing on the
• programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) of the software that video decoder 300 receives and executes.
• Entropy decoding unit 302 may 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 may generate decoded video data based on the syntax elements extracted from the bitstream.
• video decoder 300 reconstructs a picture on a block-by-block basis.
• Video decoder 300 may perform a reconstruction operation on each block individually (where the block currently being reconstructed, i.e., decoded, may be referred to as a “current block”).
• Entropy decoding unit 302 may entropy decode syntax elements defining quantized transform coefficients of a quantized transform coefficient block, as well as transform information, such as a quantization parameter (QP) and/or transform mode indication(s).
• Inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and, likewise, a degree of inverse quantization for inverse quantization unit 306 to apply.
• Inverse quantization unit 306 may, for example, perform a bitwise left-shift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 may thereby form a transform coefficient block including transform coefficients.
• inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block.
• inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.
• KLT Karhunen-Loeve transform
• prediction processing unit 304 generates a prediction block according to prediction information syntax elements that were 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 may generate the prediction block. In this case, the prediction information syntax elements may indicate a reference picture in DPB 314 from which to retrieve a reference block, as well as a motion vector identifying a location of the reference block in the reference picture relative to the location of the current block in the current picture. Motion compensation unit 316 may generally perform the inter-prediction process in a manner that is substantially similar to that described with respect to motion compensation unit 224 (FIG. 20).
• intra-prediction unit 318 may generate the prediction block according to an intra-prediction mode indicated by the prediction information syntax elements. Again, intra-prediction unit 318 may generally perform the intra-prediction process in a manner that is substantially similar to that described with respect to intra-prediction unit 226 (FIG. 20). Intra-prediction unit 318 may retrieve data of neighboring samples to the current block from DPB 314.
• Reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.
• Filter unit 312 may perform one or more filter operations on reconstructed blocks. For example, filter unit 312 may perform deblocking operations to reduce blockiness artifacts along edges of the reconstructed blocks. Operations of filter unit 312 are not necessarily performed in all examples.
• Video decoder 300 may store the reconstructed blocks in DPB 314. For instance, in examples where operations of filter unit 312 are not performed,
• reconstruction unit 310 may store reconstructed blocks to DPB 314.
• filter unit 312 may store the filtered reconstructed blocks to DPB 314.
• DPB 314 may provide reference information, such as samples of a current picture for intra-prediction and previously decoded pictures for subsequent motion compensation, to prediction processing unit 304.
• video decoder 300 may output decoded pictures from DPB 314 for subsequent presentation on a display device, such as display device 118 of FIG. 1.
• Video decoder 300 may be configured to perform any of the prediction block grouping techniques described in this disclosure. For instance, intra-prediction unit 318 may perform ISP coding to partition a coding unit (CU) to subblocks (e.g., prediction blocks). In addition, intra-prediction unit 318 may group the subblocks into prediction block groups. In this way, video decoder 300 may be considered to include one or more processors implemented in circuitry and configured to perform splitting (e.g., vertical splitting) of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks. The prediction blocks may include at least a first prediction block and a second prediction block. Video decoder 300 may group a plurality of the set of prediction blocks into a first prediction block group (PBG). In addition, video decoder 300 may reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• PBG first prediction block group
• FIG. 22 is a flowchart illustrating an example method for encoding a current block.
• the current block may comprise a current CU.
• video encoder 200 FIGGS. 1 and 20
• other devices may be configured to perform a method similar to that of FIG. 22.
• video encoder 200 initially predicts the current block (350). For example, video encoder 200 may form a prediction block for the current block. Video encoder 200 may then calculate a residual block for the current block (352). In other words, video encoder 200 may calculate luma residual data and chroma residual data for the current block. To calculate a residual block, video encoder 200 may calculate a difference between the original, uncoded block and the prediction block for the current block. Video encoder 200 may then transform and quantize coefficients of the residual block (354). Next, video encoder 200 may scan the quantized transform coefficients of the residual block (356). During the scan, or following the scan, video encoder 200 may entropy encode the transform coefficients (358).
• video encoder 200 may encode the transform coefficients using CAVLC or CAB AC. Video encoder 200 may then output the entropy encoded data of the block (360). Video encoder 200 may implement a reconstruction loop. For instance, video encoder 200 may implement a reconstruction loop to reconstruct coded video data using the prediction block grouping techniques described in this disclosure.
• FIG. 23 is a flowchart illustrating an example method for decoding a current block of video data.
• the current block may comprise a current CU.
• video decoder 300 FIGGS. 1 and 21
• other devices may be configured to perform a method similar to that of FIG. 23.
• Video decoder 300 may receive entropy coded data for the current block, such as entropy coded prediction information and entropy coded data for transform coefficients of a residual block corresponding to the current block (370). Video decoder 300 may entropy decode the entropy coded data to determine prediction information for the current block and to reproduce transform coefficients of the residual block (372). Video decoder 300 may predict the current block (374), e.g., using an intra- or inter-prediction mode as indicated by the prediction information for the current block, to calculate a prediction block for the current block. Video decoder 300 may then inverse scan the reproduced transform coefficients (376), to create a block of quantized transform coefficients.
• entropy coded data for the current block such as entropy coded prediction information and entropy coded data for transform coefficients of a residual block corresponding to the current block (370).
• Video decoder 300 may entropy decode the entropy coded data to determine prediction information for
• Video decoder 300 may then inverse quantize and inverse transform the coefficients to produce a residual block (378). Video decoder 300 may ultimately decode the current block by combining the prediction block and the residual block (380). Video decoder 300 may reconstruct samples of the current block using the prediction block grouping techniques described in this disclosure.
• FIG. 24 is a flowchart illustrating an example method for performing prediction block grouping on a current block of video data.
• the current block may comprise a current CU.
• video encoder 200 FIGGS. 1 and 20
• video decoder 300 FIGS. 1 and 21
• other devices may be configured to perform a method similar to that of FIG. 24.
• a video coder may perform splitting (e.g., vertical splitting) of a coding unit (CU) of video data using intra sub-partition (ISP). For example, the video coder may perform vertical and/or horizontal splitting of a first CU to form a set of prediction
• the video coder may perform vertical splitting of a first CU to form a set of prediction blocks.
• the set of prediction blocks may include all prediction blocks of the CU or only a subset of the prediction blocks of the CU. That is, the video coder may form a set of prediction blocks that does not necessarily include all prediction blocks of the CU.
• the video coder may perform splitting of the first CU to form a first set of prediction blocks and one or more other sets of prediction blocks.
• the one or more other sets of prediction blocks may be mutually exclusive of one another and of the first set of prediction blocks.
• the sets of prediction blocks may overlap with one another to some extent, such that one portion of a CU may be partitioned into more than one prediction block. While various techniques of this disclosure describe video coders partitioning CUs into a set of prediction blocks, the techniques of this disclosure are not so limited, and a video coder may partition a CU into multiple sets of prediction blocks.
• the prediction blocks of a set of prediction blocks may include at least a first prediction block and a second prediction block (e.g., at least two vertical prediction blocks).
• the first prediction block comprises a sample width of less than or equal to two.
• the first prediction block may have a sample width of 1 or 2.
• the second prediction block may have a sample width of 1 or 2.
• the first prediction block and the second prediction block may have a same width.
• the first prediction block and the second prediction block may both have a sample width of 2.
• the first prediction block and the second prediction block may have different widths, such as first prediction block having a width of 2 and the second prediction block having a width of 1.
• a third prediction block may be included in the first PBG, such that the first PBG may have a width of at least a 4 sample size.
• the video coder may group, from a set of prediction blocks, a plurality of prediction blocks into a first prediction block group (PBG) (2404).
• the video coder may group one or more prediction blocks from a first set of prediction blocks into a first PBG.
• the video coder may group, from the first set of prediction blocks, a first prediction block and a second prediction block into a first PBG.
• the first PBG may only include one prediction block from the first set of prediction blocks.
• the video coder may group a first set of prediction blocks of a CU to form one or more PBGs.
• the video coder may group the PBGs similarly or differently relative to one or more other sets of prediction blocks of the same CU.
• the video coder may group, into a first PBG, at least one vertical prediction block from a first set of prediction blocks and at least one horizontal prediction block from the same set of prediction blocks.
• the video coder may group, into a second PBG, at least one vertical prediction block from a second set of prediction blocks and at least one horizontal prediction block from the second set of prediction blocks.
• the video coder may instead group, into the second PBG, only vertical prediction blocks from the second set of prediction blocks and/or only horizontal prediction blocks from the second set of prediction blocks, where the first set of prediction blocks includes only vertical subblocks, only horizontal subblocks, a mix of vertical and horizontal blocks, etc., and the second set of prediction blocks includes only vertical subblocks, only horizontal subblocks, a mix of vertical and horizontal blocks, etc.
• the video coder may only group a particular type of prediction blocks into PBGs.
• the video coder may only group, into PBGs, those prediction blocks that are the result of the vertical splitting part of the overall splitting scheme. As such, the video coder may forego grouping prediction blocks that the video coder partitioned differently (e.g., using horizontal splitting).
• the video coder may form groups that include a vertical prediction block and one or more horizontal prediction blocks that neighbor the vertical prediction block.
• the video coder may additionally form groups including any leftover prediction blocks (e.g., non-neighboring prediction blocks) or may determine not to form groups for certain prediction blocks in the one or more sets of prediction blocks of a CU.
• the video coder may only group prediction blocks that are of a particular size (e.g., a size that satisfies a predefined size threshold).
• a PBG may be specified to have a minimum dimension of nW samples.
• the dimension size may apply to the height, width or a function derived from the height and width (e.g., width*height).
• the video coder may reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG (2406).
• a video coder may reconstruct samples of prediction blocks
• a video coder may reconstruct samples from one group that are dependent on the reconstruction of samples from another group when the video coder performs a sequential operation. That is, the sequential operation involves first reconstructing one or more samples from a first group and then reconstructing one or more samples from another group based on the samples from the first group.
• independent reconstruction may involve a parallel procedure in which a video coder reconstructs samples from a first prediction block of a first PBG in parallel with, or at substantially the same time (e.g., without a necessary time delay), as the video coder reconstructs samples from a second prediction block that is in the same first PBG.
• the video coder may reconstruct samples of the first prediction block independently of samples of the second prediction block.
• the restriction of prediction dependence of samples within a PBG may still be considered valid as long as the regular intra prediction (without the post-prediction filtering operations) do not result in a dependence.
• the restriction may not apply to dependence due to PDPC, boundary filtering or other similar operations.
• a video coder may form a second PBG, such that a single CU includes at least two PBGs.
• the video coder may group one or more prediction blocks into a first PBG.
• the video coder may group a second set of prediction blocks into a second PBG.
• the prediction blocks of each PBG may include a non-overlapping set of prediction blocks. That is, the prediction blocks of one PBG may be mutually exclusive of the prediction blocks of another PBG.
• the video coder may reconstruct samples of prediction blocks included in the second PBG independently of samples of other prediction blocks included in the second PBG.
• the video coder may, in some examples, reconstruct samples of prediction blocks included in a second PBG based on samples of the prediction blocks included in the first PBG. That is, the reconstruction of samples in one PBG may be dependent on the reconstruction of samples in another PBG. In such examples, the video coder may still maintain the prediction independence of samples within a single PBG. In some examples, the prediction of samples included in the second PBG may not be based on the prediction blocks included in the first PBG, but instead may be based on the prediction blocks included in another CU, such as a neighboring CU.
• the video coder may divide the CU into one or more transform blocks.
• a size of the transform block may be equal to a size of the first prediction block or any one prediction block of the CU.
• the size of the transform block may be less than the size of the smallest prediction block included in the first PBG.
• the size of the transform block may be less than the size of the aggregate total size of the prediction blocks included in the first PBG.
• the transform block may have a size that is equal to the size of the PBG.
• a first transform block associated with the first PBG may have a size equal to the size of a first prediction block or a second prediction block included in the first PBG.
• a video coder may generate a prediction sample array having a width equal to an aggregated width of at least the first prediction block and the second prediction block. For example, the video coder may output an array of size
• the video coder may, when reconstructing samples of prediction blocks, generate the prediction sample array having a width equal to an aggregated width of at least the first prediction block and the second prediction block.
• a video coder may determine a quantity of prediction block groups based on a width of the coding unit and a width of the first prediction block.
• the video coder may code the CU in accordance with the quantity of prediction block groups such that the CU comprises the quantity of prediction block groups.
• the quantity of prediction block groups may be referred to herein as pbFactor (e.g., prediction block group factor).
• the video coder may calculate pbFactor by dividing the width of the CU by the width of a prediction block group.
• the width of a PBG may be predefined to have at least a width of a sample size of 4.
• the video coder may calculate pbFactor by dividing the subblock width (e.g., the prediction block width) by the width of the PBG (e.g., the minimum width of a PBG). For example, when the subblock has a width of 1 or 2, the video coder may calculate pbFactor by dividing the subblock width by the width of the PBG, such as by dividing by four when the PBG has a sample width of four. In another example, when the width of the CU is 8 sample sizes and the prediction block group is 4 sample sizes, the video coder may calculate pbFactor to equal 2. That is, the number or quantity of PBGs for the CU may be equal to 2 PBGs.
• the prediction block width and the PBG width may have the same width.
• a video coder may group a prediction block of width four into a PBG of width four. That is, a video coder may group a prediction block of width X into a single PBG of the same width, where X is greater than or equal to a predefined threshold number.
• the predefined threshold number may be four.
• the video coder may group a first prediction block of width four and a second prediction block of width eight into a single PBG of width eight.
• the video coder may only include a portion of the second prediction block into the PBG group, such as by further partitioning the second prediction block in order to achieve a particular PBG group size.
• width size in certain contexts, the techniques of this disclosure are not so limited, and it will be understood that other constraints and/or considerations may similarly apply to the grouping of prediction blocks into PBGs.
• the PBG may have a particular height limitation (e.g., a four sample size height) or in another example, a combination of height and width constraints and/or considerations may similarly apply to the grouping of prediction blocks into PBGs (e.g., a PBG may have a minimum HxW size of MxN, where M and N may not necessarily be equal.
• the example method of FIG. 24 as described may be performed by one or more processors implemented in circuitry.
• the one or more processors may be included in a video encoder or in some examples, may be included in a video decoder.
• Illustrative examples of the disclosure include:
• Example 1 A method of coding video data, the method comprising: performing splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; grouping a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstructing samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• ISP intra sub-partition
• Example 2 A method according to Example 1, wherein grouping the plurality of the set of prediction blocks into the first PBG comprises grouping a first plurality of the set of prediction blocks into the first PBG, the method further comprising: grouping a second plurality of the set of prediction blocks into a second PBG, the second plurality of the set of prediction blocks and the first plurality of the set of prediction blocks including a non-overlapping set of prediction blocks; and reconstructing samples of prediction blocks included in the second PBG independently of samples of other prediction blocks included in the second PBG.
• Example 3 A method according to Example 2, wherein reconstructing samples of prediction blocks included in the second PBG comprises reconstructing samples of prediction blocks included in the second PBG based on samples of the prediction blocks included in the first PBG.
• Example 4 A method according to any of Examples 1 through 3, wherein the first PBG comprises a sample size width of at least four.
• Example 5 A method according to any of Examples 1 through 4, wherein a first transform block associated with the first PBG has a size equal to the size of the first prediction block.
• Example 6 A method according to any of Examples 1 through 5, wherein reconstructing samples of prediction blocks comprises: generating a prediction sample array having a width equal to an aggregated width of at least the first prediction block and the second prediction block.
• Example 7 A method according to any of Examples 1 through 6, wherein the first prediction block comprises a sample width of less than or equal to two.
• Example 8 A method according to Example 7, wherein the first prediction block and the second prediction block are of a same width.
• Example 9 A method according to any of Examples 1 through 8, further comprising: determining a quantity of prediction block groups based on a width of the coding unit and a width of the first prediction block; coding the CU in accordance with the quantity of prediction block groups such that the CU comprises the quantity of prediction block groups.
• Example 10 A method according to any of Examples 1 through 9, wherein the method is performed by one or more processors.
• Example 11 A method according to any of Examples 1 through 10, further comprising: encoding, in a coded video bitstream, one or more syntax elements that represent prediction information for the CU of video data and one or more syntax elements that represent residual data for the CU of video data.
• Example 12 A method according to any of Examples 1 through 11, further comprising: decoding, from a coded video bitstream, one or more syntax elements that represent prediction information for the CU of video data and one or more syntax elements that represent residual data for the CU of video data.
• Example 13 A method according to any of Examples 1 through 12, wherein performing splitting of the CU includes splitting the CU using one or more of vertical splitting, horizontal splitting, or a combination of horizontal and vertical splitting.
• Example 14 A device for coding video data, the device comprising one or more means for performing the methods of any of Examples 1 through 13.
• the device of Example 14 may include a memory configured to store video data; and one or more processors implemented in circuitry and configured to: perform splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; group a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• CU coding unit
• ISP intra sub-partition
• Example 15 A device according to Example 14, wherein to group the plurality of the set of prediction blocks into the first PBG, the one or more processors are configured to group a first plurality of the set of prediction blocks into the first PBG, and wherein the one or more processors are further configured to: group a second plurality of the set of prediction blocks into a second PBG, the second plurality of the set of prediction blocks and the first plurality of the set of prediction blocks including a non-overlapping set of prediction blocks; and reconstruct samples of prediction blocks included in the second PBG independently of samples of other prediction blocks included in the second PBG.
• Example 16 A device according to Example 15, wherein to reconstruct samples of prediction blocks included in the second PBG, the one or more processors are configured to reconstruct samples of prediction blocks included in the second PBG based on samples of the prediction blocks included in the first PBG.
• Example 17 A device according to any of Examples 14 through 16, wherein the first PBG comprises a sample size width of at least four.
• Example 18 A device according to any of Examples 14 through 17, wherein a first transform block associated with the first PBG has a size equal to the size of the first prediction block.
• Example 19 A device according to any of Examples 14 through 18, wherein to reconstruct the samples of prediction blocks, the one or more processors are configured to: generate a prediction sample array having a width equal to an aggregated width of at least the first prediction block and the second prediction block.
• Example 20 A device according to any of Examples 14 through 19, wherein the first prediction block comprises a sample width of less than or equal to two.
• Example 21 A device according to Example 20, wherein the first prediction block and the second prediction block are of a same width.
• Example 22 A device according to any of Examples 14 through 21, wherein the one or more processors are further configured to: determine a quantity of prediction block groups based on a width of the coding unit and a width of the first prediction block; and code the CU in accordance with the quantity of prediction block groups such that the CU comprises the quantity of prediction block groups.
• Example 23 A device according to any of Examples 14 through 22, wherein the one or more processors are included in a video encoder.
• Example 24 A device according to any of Examples 14 through 23, wherein the one or more processors are included in a video decoder.
• Example 25 A device according to any of Examples 14 through 24, wherein to perform splitting of the CU, the one or more processors are configured to split the CU using vertical splitting.
• a computer-readable storage medium can be provided storing instructions that when executed cause one or more processors of a device for decoding and/or encoding video data to: perform splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; group a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• CU coding unit
• ISP intra sub-partition
• an apparatus for encoding video data includes: means for performing vertical splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks, the prediction blocks including at least a first prediction block and a second prediction block; means for grouping a plurality of prediction blocks from the set of prediction blocks into a first prediction block group (PBG); and means for reconstructing samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.
• ISP intra sub-partition
• Example 26 A method of coding video data, the method comprising: coding an indication of a performance of generalized prediction for a current coding block of video data; splitting, based on the indication, the current coding block into one or more prediction blocks; defining, based on the one or more prediction blocks, one or more prediction block groups (PBGs); determining a coding order of the PBGs; and coding the PBGs in the coding order.
• PBGs prediction block groups
• Example 27 A method according to Example 26, wherein coding the PBGs comprises: obtaining a predicted value for a sample in a current PBG based on available reference samples for the current PBG and an intra mode used for prediction.
• Example 28 A method according to any of Examples 26 or 27, wherein:
• splitting the current coding block into one or more prediction blocks comprises splitting the current coding block into prediction blocks of size 4xN, only a vertical intra prediction mode is allowed for prediction of the prediction blocks and an indication of an intra prediction mode for the prediction blocks is not signaled in a bitstream that includes an encoded representation of the video data.
• Example 29 A method according to any of Examples 26 through 28, wherein coding comprises decoding.
• Example 30 A method according to any of Examples 26 through 28, wherein coding comprises encoding.
• Example 31 A device for coding video data, the device comprising one or more means for performing the methods of any of Examples 26 through 30.
• the device of Example 31 may include one or more processors configured to: code an indication of a performance of generalized prediction for a current coding block of video data; split, based on the indication, the current coding block into one or more prediction blocks; define, based on the one or more prediction blocks, one or more prediction block groups (PBGs); determine a coding order of the PBGs; and code the PBGs in the coding order.
• PBGs prediction block groups
• Example 32 A device according to Example 31, wherein the one or more means comprise one or more processors implemented in circuitry.
• Example 33 A device according to any of Examples 31 or 32, further comprising a memory to store the video data.
• Example 34 A device according to any of Examples 31 through 33, further comprising a display configured to display decoded video data.
• Example 35 A device according to any of Examples 31 through 34, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.
• Example 36 A device according to any of Examples 31 through 35, wherein the device comprises a video decoder.
• Example 37 A device according to any of Examples 31 through 36, wherein the device comprises a video encoder.
• a computer-readable storage medium can be provided storing instructions that when executed cause one or more processors of a device for decoding and/or encoding video data to: code an indication of a performance of generalized prediction for a current coding block of video data; split, based on the indication, the current coding block into one or more prediction blocks; define, based on the one or more prediction blocks, one or more prediction block groups (PBGs);
• PBGs prediction block groups
• an apparatus for encoding video data includes: means for coding an indication of the performance of generalized prediction for a current coding block of video data; means for splitting, based on the indication, the current coding block into one or more prediction blocks; means for defining, based on the one or more prediction blocks, one or more prediction block groups (PBGs); means for determining a coding order of the PBGs; and means for coding the PBGs in the coding order.
• PBGs prediction block groups
• Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol.
• computer- readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave.
• Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure.
• a computer program product may include a computer-readable medium.
• such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that 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 connection is properly termed a computer-readable medium.
• coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.
• DSL digital subscriber line
• computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media.
• Disk and disc includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
• 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.
• DSPs digital signal processors
• ASICs application specific integrated circuits
• FPGAs field programmable gate arrays
• 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.
• DSPs digital signal processors
• ASICs application specific integrated circuits
• FPGAs field programmable gate arrays
• the terms“processor” and “processing circuity,” as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein.
• the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined code
• the techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set).
• IC integrated circuit
• a set of ICs e.g., a chip set.
• Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

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