Patent Application
20240348770
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), ITU-T H.266/Versatile Video Coding (VVC), and extensions of such standards, as well as proprietary video codecs/formats such as AOMedia Video 1 (AV1) that was developed by the Alliance for Open Media. The video devices may transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing such video coding techniques.
Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs) and/or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction 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.
In general, this disclosure describes techniques for generating prediction samples based on two or more reference chroma blocks and/or a reference chroma block and one or more sub-blocks. For some video coding techniques, a reference block may be pointed to by a vector (e.g., motion vector or block vector), but the reference block may not match original pixels (e.g., in the reference picture for motion vector or current picture for block vector). This disclosure describes example techniques for fusing multiple reference chroma blocks to remove the errors between original pixels and prediction samples. That is, in one or more examples, the example techniques include generating prediction samples for the chroma block based on the two or more reference chroma blocks and/or generating prediction samples for a coding unit (CU) based on the one or more sub-blocks and the at least one reference block.
In one or more examples, a video coder (e.g., video encoder or video decoder) may be configured to determine the two or more reference chroma blocks based on co-located luma blocks that are co-located with the chroma block. The video coder may fuse the two or more reference chroma blocks to generate the prediction samples used to encoding or decoding the chroma block.
In this manner, the example techniques may generate prediction samples that are better predictors for the chroma block as compared to other techniques for generating prediction samples. Accordingly, the difference between the actual chroma block and the prediction samples may be reduced relative to other techniques, resulting in reduced signaling and efficient bandwidth utilization.
In one example, this disclosure describes a method of encoding or decoding video data, the method comprising: for a chroma block of a picture, determining luma blocks that are co-located with the chroma block; determining two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fusing the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encoding or decoding the chroma block based on the prediction samples.
In one example, this disclosure describes a device for encoding or decoding video data, the device comprising: one or more memories configured to store the video data; and processing circuitry coupled to the one or more memories and configured to: for a chroma block of a picture, determine luma blocks that are co-located with the chroma block; determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fuse the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encode or decode the chroma block based on the prediction samples.
In one example, this disclosure describes a computer-readable storage medium storing instructions thereon that when executed cause one or more processors to: for a chroma block of a picture, determine luma blocks that are co-located with the chroma block; determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fuse the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encode or decode the chroma block based on the prediction samples.
The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.
A video coder (e.g., video encoder or video decoder) may be configured to determine prediction samples (e.g., a prediction block) that are used to predict a current block. For instance, a video encoder may signal information for residual values indicative of a difference between the prediction samples and the current block, and a video decoder may add the residual values to the prediction samples to reconstruct the current block.
In some cases, a reference block, used to generate the prediction samples, may not match the original pixels of the current block. This disclosure describes example techniques to fuse multiple reference chroma blocks (e.g., with a derived set of weighting factors) to remove the errors between original pixels and prediction samples. As one example, the disclosure describes techniques to fuse multiple reference chroma blocks derived by block vectors of collocated (i.e., co-located) luma blocks. As another example, the disclosure describes techniques to fuse one boundary sub-blocks (e.g., top and left boundary sub-blocks) of a luma or chroma CU with a reference block derived by the information of neighboring block.
By generating prediction samples based on the example fusing techniques, the prediction samples may be a better prediction of the samples of the current block, as compared to other techniques. Therefore, the residual values may be smaller, and the amount of information that is signaled may be reduced, as compared to other techniques. Accordingly, the example techniques may promote efficient bandwidth utilization for the technology of video coding, such as by generating prediction samples that are closer to the value of the current block being encoded or decoded.
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System 100 as shown in
In general, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a sequential series of pictures (also referred to as “frames”) of the video data to 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. As a further alternative, 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. In each case, 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.
Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memories. In some examples, 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. Additionally or alternatively, 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. In one example, computer-readable medium 110 represents a communication medium to enable source device 102 to transmit encoded video data directly to destination device 116 in real-time, e.g., via a radio frequency network or computer-based network. Output interface 108 may modulate a transmission signal including the encoded video data, and input interface 122 may demodulate the received transmission signal, according to a communication standard, such as a wireless communication protocol. The communication medium may include 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.
In some examples, source device 102 may output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data.
In some examples, source device 102 may output encoded video data to file server 114 or another intermediate storage device that may store the encoded video data 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 server configured to provide a file transfer protocol service (such as File Transfer Protocol (FTP) or File Delivery over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS) server, and/or a network attached storage (NAS) device. File server 114 may, additionally or alternatively, implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, or the like.
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. Input interface 122 may be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from file server 114, or other such protocols for retrieving media data.
Output interface 108 and input interface 122 may represent wireless transmitters/receivers, 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. In examples where output interface 108 and input interface 122 include 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. In some examples where output interface 108 includes 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., ZigBee™), a Bluetooth™ standard, or the like. In some examples, source device 102 and/or destination device 116 may include respective system-on-a-chip (SoC) devices. For example, source device 102 may include an SoC device to perform the functionality attributed to video encoder 200 and/or output interface 108, and 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.
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 liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.
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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 microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device 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 implement video encoder 200 and/or video decoder 300 in processing circuitry such as an integrated circuit and/or a microprocessor. Such a device may be a wireless communication device, such as a cellular telephone, or any other type of device described herein.
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. Alternatively, video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards, such as ITU-T H.266, also referred to as Versatile Video Coding (VVC). In other examples, video encoder 200 and video decoder 300 may operate according to a proprietary video codec/format, such as AOMedia Video 1 (AV1), extensions of AV1, and/or successor versions of AV1 (e.g., AV2). In other examples, video encoder 200 and video decoder 300 may operate according to other proprietary formats or industry standards. The techniques of this disclosure, however, are not limited to any particular coding standard or format. In general, video encoder 200 and video decoder 300 may be configured to perform the techniques of this disclosure in conjunction with any video coding techniques that use motion vectors (e.g., samples from a reference picture different than picture that includes block being encoded or decoded) or block vectors (e.g., samples from the same picture that includes block being encoded or decoded).
In general, 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). For example, a block may include a two-dimensional matrix of samples of luminance and/or chrominance data. In general, 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 chrominance components. In some examples, video encoder 200 converts received RGB formatted data to a YUV representation prior to encoding, and video decoder 300 converts the YUV representation to the RGB format. Alternatively, pre- and post-processing units (not shown) 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. Similarly, 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. Thus, 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). According to HEVC, 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. For example, in HEVC, a residual quadtree (RQT) represents partitioning of TUs. In HEVC, PUs represent inter-prediction data, while TUs represent residual data. CUs that are intra-predicted include intra-prediction information, such as an intra-mode indication.
As another example, video encoder 200 and video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder (such as video encoder 200) partitions a picture into a plurality of 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. 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 CUs.
In an MTT partitioning structure, blocks may be partitioned using a quadtree (QT) partition, a binary tree (BT) partition, and one or more types of triple tree (TT) (also called ternary tree (TT)) partitions. A triple or ternary tree partition is a partition where a block is split into three sub-blocks. In some examples, a triple or ternary 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), may be symmetrical or asymmetrical.
When operating according to the AV1 codec, video encoder 200 and video decoder 300 may be configured to code video data in blocks. In AV1, the largest coding block that can be processed is called a superblock. In AV1, a superblock can be either 128×128 luma samples or 64×64 luma samples. However, in successor video coding formats (e.g., AV2), a superblock may be defined by different (e.g., larger) luma sample sizes. In some examples, a superblock is the top level of a block quadtree. Video encoder 200 may further partition a superblock into smaller coding blocks. Video encoder 200 may partition a superblock and other coding blocks into smaller blocks using square or non-square partitioning. Non-square blocks may include N/2×N, N×N/2, N/4×N, and N×N/4 blocks. Video encoder 200 and video decoder 300 may perform separate prediction and transform processes on each of the coding blocks.
AV1 also defines a tile of video data. A tile is a rectangular array of superblocks that may be coded independently of other tiles. That is, video encoder 200 and video decoder 300 may encode and decode, respectively, coding blocks within a tile without using video data from other tiles. However, video encoder 200 and video decoder 300 may perform filtering across tile boundaries. Tiles may be uniform or non-uniform in size. Tile-based coding may enable parallel processing and/or multi-threading for encoder and decoder implementations.
In some examples, 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, QTBT partitioning, MTT partitioning, superblock partitioning, or other partitioning structures.
In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture that has three sample arrays, or a CTB of samples of a monochrome picture or a picture that is coded using three separate color planes and syntax structures used to code the samples. A CTB may be an N×N block of samples for some value of N such that the division of a component into CTBs is a partitioning. A component is an array or single sample from one of the three arrays (luma and two chroma) that compose a picture in 4:2:0, 4:2:2, or 4:4:4 color format or the array or a single sample of the array that compose a picture in monochrome format. In some examples, a coding block is an M×N block of samples for some values of M and N such that a division of a CTB into coding blocks is a partitioning.
The blocks (e.g., CTUs or CUs) may be grouped in various ways in a picture. As one example, a brick may refer to a rectangular region of CTU rows within a particular tile in a picture. A tile may be a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of CTUs having a height equal to the height of the picture and a width specified by syntax elements (e.g., such as in a picture parameter set). A tile row refers to a rectangular region of CTUs having a height specified by syntax elements (e.g., such as in a picture parameter set) and a width equal to the width of the picture.
In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a tile may not be referred to as a tile. The bricks in a picture may also be arranged in a slice. A slice may be an integer number of bricks of a picture that may be exclusively contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes either a number of complete tiles or only a consecutive sequence of complete bricks of one tile.
This disclosure may use “N×N” and “N by N” interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, e.g., 16×16 samples or 16 by 16 samples. In general, a 16×16 CU will have 16 samples in a vertical direction (y=16) and 16 samples in a horizontal direction (x=16). Likewise, an N×N 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. Moreover, CUs need not necessarily have the same number of samples in the horizontal direction as in the vertical direction. For example, CUs may include N×M 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.
To predict a CU, 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, whereas intra-prediction generally refers to predicting the CU from previously coded data of the same picture. To perform inter-prediction, 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. In some examples, video encoder 200 may predict the current CU using uni-directional prediction or bi-directional prediction.
Some examples of VVC also provide an affine motion compensation mode, which may be considered an inter-prediction mode. In affine motion compensation 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.
To perform intra-prediction, video encoder 200 may select an intra-prediction mode to generate the prediction block. Some examples of VVC provide sixty-seven intra-prediction modes, including various directional modes, as well as planar mode and DC mode. In general, 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.
AV1 includes two general techniques for encoding and decoding a coding block of video data. The two general techniques are intra prediction (e.g., intra frame prediction or spatial prediction) and inter prediction (e.g., inter frame prediction or temporal prediction). In the context of AV1, when predicting blocks of a current frame of video data using an intra prediction mode, video encoder 200 and video decoder 300 do not use video data from other frames of video data. For most intra prediction modes, video encoder 200 encodes blocks of a current frame based on the difference between sample values in the current block and predicted values generated from reference samples in the same frame. Video encoder 200 determines predicted values generated from the reference samples based on the intra prediction mode.
Following prediction, such as intra-prediction or inter-prediction of a block, 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. For example, 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. Additionally, 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.
As noted above, following any transforms to produce transform coefficients, 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. By performing the quantization process, video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, video encoder 200 may round an n-bit value down to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, video encoder 200 may perform a bitwise right-shift of the value to be quantized.
Following quantization, 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. In some examples, 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. In other examples, video encoder 200 may perform an adaptive scan. After scanning the quantized transform coefficients to form the one-dimensional vector, 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.
To perform CABAC, 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.
In this manner, 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. Ultimately, video decoder 300 may receive the bitstream and decode the encoded video data.
In general, video decoder 300 performs a reciprocal process to that performed by video encoder 200 to decode the encoded video data of the bitstream. For example, video decoder 300 may decode values for syntax elements of the bitstream using CABAC 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 of 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.
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. As noted above, 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.
As noted above, versatile Video Coding (VVC), a latest video coding standard, was developed by Joint Video Experts Team (JVET) of ITU-T and ISO/IEC to achieve substantial compression capability beyond HEVC for a broad range of applications. VVC specification has been finalized in July 2020 and published by both ITU-T and ISO/IEC. The VVC specification specifies normative bitstream and picture formats, high level syntax (HLS) and coding unit level syntax, and the parsing and decoding process. VVC also specifies profiles/tiers/levels (PTL) restrictions, byte stream format, hypothetical reference decoder and supplemental enhancement information (SEI) in the annex.
Starting from April 2021, JVET has been developing an Enhanced Compression Model (ECM) software: M. Coban, F. L. Léannec, M. G. Sarwer, and J. Ström, “Algorithm description of Enhanced Compression Model 8 (ECM 8),” JVET-AC2025, Apr. 2023, to enhance compression capability beyond VVC. The set of coding tools in the ECM software encompasses all functional blocks in the hybrid video coding framework, including intra prediction, inter prediction, transform and coefficient coding, in-loop filtering, and entropy coding. The example techniques described in this disclosure can be applied to ECM and video codecs such as VVC, AV1, etc.
In ECM-8.0, there are 13 intra modes for chroma intra mode coding, which are categorized into 2 chroma mode list: CCLM mode list and non-CCLM mode list. The CCLM mode list includes six cross-component linear model modes, i.e., LM, and LM_L, LM_T, MMLM, MMLM_L, and MMLM_T. The non-CCLM mode list includes one direct BV (DBV) mode (JVET-AC0071, entitled “EE2-3.1: Direct block vector mode for chroma prediction,” by Huo et al.), one chroma DIMD mode (JVET-Z0051, entitled “Ee2-1.2: On chroma intra prediction,” by Li et al.), and five traditional intra modes, i.e., direct mode (DM) and default modes.
As shown in
For instance,
Overlapped Block Motion Compensation (OBMC) is a prediction blending method based on the current MV information and the neighboring MV information. There are two OBMC modes: CU-Boundary OBMC mode and Subblock-Boundary OBMC mode.
For example, one motion vector for CU 700 may point to block B1702. Block B1702 is one example of an original block. One motion vector for the above block to CU 700 may point to block BT (block top) 706. Block BT 706 is one example of an OBMC block. Video encoder 200 and video decoder 300 may multiply samples of block B1702 by “a” and multiple samples of block BT 706 by “b,” and add the result to generate blended block 710. The value of a and b, in this case, is based on the distance of portion co-located with block B1702 to the boundary (e.g., left or right boundary) of CU 700.
As another example, one motion vector for CU 700 may point to block B2704. Block B2704 is one example of an original block. One motion vector for the left block to CU 700 may point to block BL (block left) 708. Block BL 708 is one example of an OBMC block. Video encoder 200 and video decoder 300 may multiply samples of block B2704 by “a” and multiple samples of block BL 708 by “b,” and add the result to generate blended block 712. The value of a and b, in this case, is based on the distance of portion co-located with block B2704 to the boundary (e.g., above or below boundary) of CU 700.
ECM adopted an intraTMP mode (JVET-AB0130, entitled “EE2-1.14: IntraTMP adaptation for camera-captured content,” by Naser et al.) as shown in
In some cases, a reference block may not match to original pixels. This disclosure describes example techniques to fuse multiple reference blocks (e.g., with a derived set of weighting factors) to remove the errors between original pixels and prediction samples. One example of the techniques includes fusing multiple reference chroma blocks derived by block vectors (BVs) of collocated (i.e., co-located) luma blocks. One example of the techniques includes fusing one of top and left boundary subblocks of a luma or chroma CU with a reference block derived by the information of neighboring block. To the extent feasible, the example techniques may be combined as well. For instance, the example techniques are described as related to fusion of reference blocks derived by direct BV, and fusion of reference sub-blocks derived by neighboring blocks. However, to the extent possible, these example techniques may be combined or performed separately.
With respect to fusion of reference blocks derived by direct BV, video encoder 200 or video decoder 300 may fuse multiple reference chroma blocks derived by chroma BVs.
In one example, the chroma BVs are derived from the luma BVs of the collocated luma blocks as shown in
In one or more examples, video encoder 200 and video decoder 300 may determine block vectors (BVs) for luma blocks TL, TR, C, BR, and BL. Based on the BVs for the luma blocks, video encoder 200 and video decoder 300 may determine reference chroma blocks 902A and 902B for chroma block 900. For example, assume that bv1 is a scaled version of the block vector of one of luma blocks TL, TR, C, BR, and BL of
There may be various ways in which video encoder 200 and video decoder 300 may determine the reference chroma blocks that are used for fusing. As one example, video encoder 200 and video decoder 300 may determine the block vectors of two or more co-located luma blocks that are co-located with chroma block 900. Video encoder 200 and video decoder 300 may construct a chroma block vector list from the luma block vector of the co-located luma blocks. For instance, video encoder 200 and video decoder 300 may determine the block vector for luma block TL and add that block vector, or scaled version of that block vector, to the chroma block vector list. Video encoder 200 and video decoder 300 may determine the block vector luma block TR and add that block vector, or scaled version of that block vector, to the chroma block vector list, and so forth.
In one example, video encoder 200 may signal and video decoder 300 may receive indices into the chroma block vector list that identify the block vectors. Video encoder 200 and video decoder 300 may utilize the block vectors retrieved from the chroma block vector list to determine two or more reference chroma blocks (e.g., reference chroma block 902A and reference chroma block 902B). Video encoder 200 and video decoder 300 may then fuse the two or more reference chroma blocks to generate prediction samples for chroma block 900.
In some examples, after initially constructing the chroma block vector list, video encoder 200 and video decoder 300 may reorder the chroma block vector list to generate the final chroma block vector list. For instance, a block vector candidate reorder is performed by comparing template adjacent to reference block and the template adjacent to current block.
For example, video encoder 200 and video decoder 300 may determine respective candidate reference chroma blocks based on respective block vectors for the luma blocks. Stated another way, for each block vector for two or more co-located luma blocks, video encoder 200 and video decoder 300 may determine a candidate reference chroma block. As an example, video encoder 200 and video decoder 300 may utilize the block vector for luma block C, determine a candidate block vector (e.g., based on scaling, if needed, the block vector luma block C), and determine a candidate reference chroma block that is pointed to by the candidate block vector. Video encoder 200 and video decoder 300 may repeat such operations for each of the block vectors of co-located luma blocks that are to be evaluated. This way, video encoder 200 and video decoder 300 would have determined a set of candidate reference chroma blocks. The actual reference chroma blocks that used may be from this set of candidate reference chroma blocks.
Video encoder 200 and video decoder 300 may determine respective costs of the respective candidate reference chroma blocks. One example way of determining respective costs is based on template matching techniques. As shown in
Video encoder 200 and video decoder 300 may determine respective costs based on comparing template 904 to respective templates of the candidate reference chroma blocks (e.g., compare template 904 to template 906, compare template 904 to template 908, and so forth). One example comparison technique is to determine sum of absolute difference (SAD). Another example comparison techniques is mean-square-errors (MSE). Other example comparison techniques are possible.
With the respective costs of the candidate reference chroma blocks, video encoder 200 and video decoder 300 may reorder the chroma block vector list. For instance, video encoder 200 and video decoder 300 may reorder the chroma block vector list such that the candidate reference chroma blocks with lower cost (e.g., better matching with template 904) are earlier in the chroma block vector list, and candidate reference chroma blocks with higher cost (e.g., worse matching with template 904) are later in the chroma block vector list.
In some examples, the chroma block vectors of neighboring chroma blocks (e.g., chroma blocks that neighbor chroma block 900) may also be included in the chroma block vector list. Video encoder 200 and video decoder 300 may similarly determine the respective costs of candidate reference chroma blocks that are pointed to by the block vectors of neighboring chroma blocks, and reorder the chroma block vector list accordingly.
Video encoder 200 may signal and video decoder 300 may receive indices into the chroma block vector list (e.g., after reordering). Video decoder 300 may then determine the reference chroma blocks (e.g., based on the chroma blocks that are pointed to by the block vectors retrieved from the chroma block vector list, possibly after scaling). Video encoder 200 and video decoder 300 may fuse the reference chroma blocks to generate the prediction samples for chroma block 900.
However, in some examples, signaling into the chroma block vector list may not be necessary. For example, after video encoder 200 and video decoder 300 determine which candidate reference chroma blocks have the lowest respective costs, video encoder 200 and video decoder 300 may select the N (e.g., 2 to 5) candidate reference chroma blocks having the lowest respective costs as the reference chroma blocks. Video encoder 200 and video decoder 300 may fuse the reference chroma blocks to generate the prediction samples. Accordingly, in one or more examples, the reference chroma blocks with minimum template matching TM costs are fused to generate the predictors (e.g., prediction samples) for current chroma block 900.
Stated another way, for a chroma block of a picture, video encoder 200 and video decoder 300 may determine luma blocks that are co-located with the chroma block, and determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture. Video encoder 200 and video decoder 300 may generate prediction samples for the chroma block based on the two or more reference chroma blocks (e.g., fusing the two or more reference chroma blocks), and block vector encode or decode the chroma block based on the prediction samples (e.g., encode or decode the chroma block based on the prediction samples generated from samples in the same picture as the chroma block).
Video encoder 200 and video decoder 300 may fuse the two or more reference chroma blocks to generate the prediction samples. The fusing of the two or more reference chroma blocks (e.g., reference chroma blocks 902A and 902B) may include averaging the two or more reference chroma blocks and/or scaling and summing the two or more reference chroma blocks, as described in more detail. For instance, video encoder 200 and video decoder 300 may determine respective weights for the two or more reference chroma blocks, where fusing includes fusing the two or more reference chroma blocks based on the respective weights.
As described above, video encoder 200 and video decoder 300 may compare template adjacent to reference chroma blocks (e.g., template 906 and template 908) and the template adjacent to current chroma block 900 (e.g., template 904) to determine costs and determine which reference chroma blocks to use. That is, there may be multiple block vectors of co-located luma blocks, and each block refer may point to a candidate reference chroma block (e.g., “candidate” because this reference chroma block may be selected, but also possible that it is not selected as a reference chroma block). Accordingly, video encoder 200 and video decoder 300 may determine respective candidate reference chroma blocks based on each of the block vectors for the luma blocks, and determine respective costs of the respective candidate reference chroma blocks. That is, video encoder 200 and video decoder 300 may determine the cost associated with each of the candidate reference chroma blocks. Video encoder 200 and video decoder 300 may select two or more of the candidate reference chroma blocks based on the respective costs to determine the two or more reference chroma blocks. For example, determining the respective costs may including determining an amount of matching between a first template adjacent the respective candidate reference chroma blocks (e.g., templates 906 and 908) and a second template adjacent the chroma block 900 (e.g., template 904).
To fuse the reference chroma blocks, video encoder 200 and video decoder 300 may apply weighting factors to each of the reference chroma blocks. For instance, assume that reference chroma blocks 902A and 902B are selected as the reference chroma blocks that are to be fused. Video encoder 200 and video decoder 300 may determine a first weight that is applied to samples of reference chroma block 902A and a second weight that is applied to samples of reference chroma block 902B. Video encoder 200 and video decoder 300 may add the weighted samples together to determine the prediction samples. In some examples, video encoder 200 and video decoder 300 may simply average (e.g., without weighting) the samples of reference chroma block 902A and reference chroma block 902B to fuse reference chroma block 902A and reference chroma block 902B and generate the prediction samples.
There may be various ways in which video encoder 200 and video decoder 300 may determine the weights, also called weighting factors. For instance, the weighting factors of fusion may be derived by TM (template matching) costs, where a reference block is applied a larger weight factor if lower TM cost. In one some examples, the weighting factors are derived by minimizing mean square errors (MMSE) between template of current block and the sum of templates of used reference chroma blocks.
For instance, assume that video encoder 200 and video decoder 300 determined a first TM cost (e.g., SAD) between template 906 and template 904, and a second TM cost between template 908 and template 904. Assume that the first TM cost is less than the second TM cost. In this example, video encoder 200 and video decoder 300 may weight the samples of reference chroma block 902A greater than the samples of reference chroma block 902B.
There may be other ways in which to determine the weights. In some examples, video encoder 200 and video decoder 300 may determine a weighting factor derivation operation. For instance, video encoder 200 may signal and video decoder 300 may receive an index into a list of weighting factor derivation techniques to indicate which weighting factors derivation operation is used for current chroma block 900. In one example, there are 4 fusion modes: (1) no fusion, (2) fusion with weights derived by TM costs, (3) fusion with weights derived by MMSE, and (4) fusion with fixed weights. The fixed weights may be signaled or determined.
In the above examples, it is not necessary that every single block vector of every single co-located luma block is considered. For instance, the number of block vectors derived from luma collocated (co-located) blocks is decided based on TM costs. For example, video encoder 200 and video decoder 300 may fuse a reference chroma block “I” with the best reference chroma block “j” if the TM cost i is close to the minimum TM cost j (ex: TM_cost_i<threshold*TM_cost_j, where threshold is a pre-assigned positive value).
With respect to fusion of reference sub-blocks derived by neighboring blocks, this disclosure describes extending OBMC to CUs coded with non-inter mode, e.g., intra mode, intraTMP mode, etc. When OBMC is applied to a CU coded with intraTMP mode, the boundary subblocks (e.g., block B1702 and block B2704 in
When OBMC is applied to a CU block (e.g., no matter if inter mode or non-inter mode), video encoder 200 and video decoder 300 may use BV of a neighboring block (e.g., block BT 706 and block BL 708 in
Accordingly, in one or more examples, video encoder 200 and video decoder 300 may be configured to determine one or more sub-blocks of a coding unit (CU), and determine at least one reference block based on at least one vector of at least one proximate block to the CU. Video encoder 200 and video decoder 300 may generate prediction samples for the CU based on the one or more sub-blocks and the at least one reference block, and encode or decode the CU based on the prediction samples.
In some examples, the one or more sub-blocks of the CU are at boundary of the CU. For instance, the one or more sub-blocks are a top and left boundary sub-blocks of the CU. In some examples, the CU is a luma CU or a chroma CU.
To generate prediction samples, video encoder 200 and video decoder 300 may fuse the one or more sub-blocks and the at least one reference block. Fusing may include averaging the one or more sub-blocks and the at least one reference block and/or scaling and summing the one or more sub-blocks and the at least one reference block.
In the example of
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 (
In this disclosure, reference to video data memory 230 should not be interpreted as being limited to memory internal to video encoder 200, unless specifically described as such, or memory external to video encoder 200, unless specifically described as such. Rather, reference to video data memory 230 should be understood as reference memory that stores video data that video encoder 200 receives for encoding (e.g., video data for a current block that is to be encoded). Memory 106 of
The various units of
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. In examples where the operations of video encoder 200 are performed using software executed by the programmable circuits, memory 106 (
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, a 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.
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 memory 230 into a series of CTUs, and encapsulate one or more CTUs within a slice. Mode selection unit 202 may partition a CTU of the picture in accordance with a tree structure, such as the MTT structure, QTBT structure, superblock structure, or the quad-tree structure described above. As 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.”
In general, 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). For inter-prediction of a current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218). In particular, 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.
Motion estimation unit 222 may form one or more motion vectors (MVs) that defines 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, e.g., through sample-by-sample averaging or weighted averaging.
When operating according to the AV1 video coding format, motion estimation unit 222 and motion compensation unit 224 may be configured to encode coding blocks of video data (e.g., both luma and chroma coding blocks) using translational motion compensation, affine motion compensation, overlapped block motion compensation (OBMC), and/or compound inter-intra prediction.
As another example, for intra-prediction, or intra-prediction coding, 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.
When operating according to the AV1 video coding format, intra-prediction unit 226 may be configured to encode coding blocks of video data (e.g., both luma and chroma coding blocks) using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, chroma-from-luma (CFL) prediction, intra block copy (IBC), and/or color palette mode. Mode selection unit 202 may include additional functional units to perform video prediction in accordance with other prediction modes.
Mode selection unit 202 provides the prediction block to residual generation unit 204. Residual generation unit 204 receives a raw, unencoded version of the current block from video data memory 230 and the prediction block from mode selection unit 202. Residual generation unit 204 calculates 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. In some examples, 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). In some examples, residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.
In examples where mode selection unit 202 partitions CUs into PUs, 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. Assuming that the size of a particular CU is 2N×2N, video encoder 200 may support PU sizes of 2N×2N or N×N for intra prediction, and symmetric PU sizes of 2N×2N, 2N×N, N×2N, N×N, or similar for inter prediction. Video encoder 200 and video decoder 300 may also support asymmetric partitioning for PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.
In examples where mode selection unit 202 does not further partition a CU into PUs, each CU may be associated with a luma coding block and corresponding chroma coding blocks. As above, 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 2N×2N, 2N×N, or N×2N.
For other video coding techniques such as an intra-block copy mode coding, an affine-mode coding, and linear model (LM) mode coding, as some 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.
As described above, 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. For example, 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. In some examples, 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. In some examples, transform processing unit 206 does not apply transforms to a residual block.
When operating according to AV1, transform processing unit 206 may apply 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. For example, transform processing unit 206 may apply a horizontal/vertical transform combination that may include a discrete cosine transform (DCT), an asymmetric discrete sine transform (ADST), a flipped ADST (e.g., an ADST in reverse order), and an identity transform (IDTX). When using an identity transform, the transform is skipped in one of the vertical or horizontal directions. In some examples, transform processing may be skipped.
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.
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.
When operating according to AV1, 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. In other examples, filter unit 216 may apply a constrained directional enhancement filter (CDEF), which may be applied after deblocking, and may include the application of non-separable, non-linear, low-pass directional filters based on estimated edge directions. Filter unit 216 may also include a loop restoration filter, which is applied after CDEF, and may include a separable symmetric normalized Wiener filter or a dual self-guided filter.
Video encoder 200 stores reconstructed blocks in DPB 218. For instance, in examples where operations of filter unit 216 are not performed, reconstruction unit 214 may store reconstructed blocks to DPB 218. In examples where operations of filter unit 216 are performed, 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. In addition, intra-prediction unit 226 may use reconstructed blocks in DPB 218 of a current picture to intra-predict other blocks in the current picture.
In general, 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. For example, entropy encoding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a Probability Interval Partitioning Entropy (PIPE) coding operation, an Exponential-Golomb encoding operation, or another type of entropy encoding operation on the data. In some examples, 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. In particular, entropy encoding unit 220 may output the bitstream.
In accordance with AV1, entropy encoding unit 220 may be configured as a symbol-to-symbol adaptive multi-symbol arithmetic coder. A syntax element in AV1 includes an alphabet of N elements, and a context (e.g., probability model) includes a set of N probabilities. Entropy encoding unit 220 may store the probabilities as n-bit (e.g., 15-bit) cumulative distribution functions (CDFs). Entropy encoding unit 220 may perform recursive scaling, with an update factor based on the alphabet size, to update the contexts.
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. As described above, in some examples, the luma coding block and chroma coding blocks are luma and chroma components of a CU. In some examples, the luma coding block and the chroma coding blocks are luma and chroma components of a PU.
In some examples, operations performed with respect to a luma coding block need not be repeated for the chroma coding blocks. As one example, operations to identify a motion vector (MV) and reference picture for a luma coding block need not be repeated for identifying a 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 intra-prediction process may be the same for the luma coding block and the chroma coding blocks.
Video encoder 200 represents an example of a device configured to encode video data including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to for a chroma block of a picture, determine luma blocks that are co-located with the chroma block, determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture, generate prediction samples for the chroma block based on the two or more reference chroma blocks (e.g., via fusing), and block vector encode the chroma block based on the prediction samples.
Video encoder 200 also represents an example of a device configured to encode video data including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to determine one or more sub-blocks of a coding unit (CU), determine at least one reference block based on at least one vector of at least one proximate block to the CU, generate prediction samples for the CU based on the one or more sub-blocks and the at least one reference block, and encode the CU based on the prediction samples.
In the example of
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.
When operating according to AV1, motion compensation unit 316 may be configured to decode coding blocks of video data (e.g., both luma and chroma coding blocks) using translational motion compensation, affine motion compensation, OBMC, and/or compound inter-intra prediction, as described above. Intra-prediction unit 318 may be configured to decode coding blocks of video data (e.g., both luma and chroma coding blocks) using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, CFL, IBC, and/or color palette mode, as described above.
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 (
Additionally or alternatively, in some examples, video decoder 300 may retrieve coded video data from memory 120 (
The various units shown in
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.
In general, 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.
After inverse quantization unit 306 forms the transform coefficient block, inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.
Furthermore, 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 (
As another example, if the prediction information syntax elements indicate that the current block is intra-predicted, 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 (
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. In examples where operations of filter unit 312 are performed, filter unit 312 may store the filtered reconstructed blocks to DPB 314. As discussed above, 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. Moreover, video decoder 300 may output decoded pictures (e.g., decoded video) from DPB 314 for subsequent presentation on a display device, such as display device 118 of
Video decoder 300 represents an example of a device configured to encode video data including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to for a chroma block of a picture, determine luma blocks that are co-located with the chroma block, determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture, generate prediction samples for the chroma block based on the two or more reference chroma blocks (e.g., via fusing), and block vector decode the chroma block based on the prediction samples.
Video decoder 300 also represents an example of a device configured to encode video data including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to determine one or more sub-blocks of a coding unit (CU), determine at least one reference block based on at least one vector of at least one proximate block to the CU, generate prediction samples for the CU based on the one or more sub-blocks and the at least one reference block, and decode the CU based on the prediction samples.
In this example, video encoder 200 initially predicts the current block (400). For example, video encoder 200 may form a prediction block for the current block. In accordance with techniques described in this disclosure, video encoder 200 may generate prediction samples of a prediction block by fusing two or more reference chroma blocks. Video encoder 200 may select the two or more reference chroma blocks based on block vectors of co-located luma blocks.
Video encoder 200 may then calculate a residual block for the current block (402). To calculate the residual block, video encoder 200 may calculate a difference between the original, unencoded block and the prediction block for the current block. Video encoder 200 may then transform the residual block and quantize transform coefficients of the residual block (404). Next, video encoder 200 may scan the quantized transform coefficients of the residual block (406). During the scan, or following the scan, video encoder 200 may entropy encode the transform coefficients (408). For example, video encoder 200 may encode the transform coefficients using CAVLC or CABAC. Video encoder 200 may then output the entropy encoded data of the block (410).
Video decoder 300 may receive entropy encoded data for the current block, such as entropy encoded prediction information and entropy encoded data for transform coefficients of a residual block corresponding to the current block (500). Video decoder 300 may entropy decode the entropy encoded data to determine prediction information for the current block and to reproduce transform coefficients of the residual block (502).
Video decoder 300 may predict the current block (504), 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. In accordance with techniques described in this disclosure, video decoder 300 may generate prediction samples of a prediction block by fusing two or more reference chroma blocks. Video decoder 300 may select the two or more reference chroma blocks based on block vectors of co-located luma blocks.
Video decoder 300 may then inverse scan the reproduced transform coefficients (506), to create a block of quantized transform coefficients. Video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (508). Video decoder 300 may ultimately decode the current block by combining the prediction block and the residual block (510).
For a chroma block of a picture, the processing circuitry may be configured to determine luma blocks that are co-located with the chroma block (1000). For instance, referring to
The processing circuitry may determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture (1002). For instance, the processing circuitry may determine respective candidate reference chroma blocks based on respective block vectors for the luma blocks. As an example, the processing circuitry may utilize the block vectors for each of luma blocks TL, TR, C, BL, and BR of
The processing circuitry may determine respective costs of the respective candidate reference chroma blocks. As one example, to determine the respective costs, the processing circuitry may determine an amount of matching between a first template adjacent the respective candidate reference chroma blocks and a second template adjacent the chroma block. For instance, referring to
To determine the two or more reference chroma blocks, the processing circuitry may select two or more of the candidate reference chroma blocks based on the respective costs. As one example, the processing circuitry may select the N candidate reference chroma blocks associated with the lowest cost. As another example, the processing circuitry may construct a chroma block vector list based on the respective costs. For instance, the processing circuitry may construct an initial chroma block vector list based on the block vectors of the co-located luma blocks, and possibly, including block vectors of neighboring chroma blocks. The processing circuitry may reorder the initial chroma block vector list based on the respective costs (e.g., lowest cost to highest cost) to construct the chroma block vector list. To select two or more of the candidate reference chroma blocks, the processing circuitry may select two or more of the candidate reference chroma blocks based on the chroma block vector list. As one example, video encoder 200 may signal and video decoder 300 may receive indices into the chroma block vector list.
The processing circuitry may be configured to fuse the two or more reference chroma blocks to generate prediction samples for the chroma block (1004). As one example, the processing circuitry may average the two or more reference chroma blocks, or may scale and sum the two or more reference chroma blocks. For instance, assume that that reference chroma blocks are reference chroma block 902A and reference chroma block 902B. In one example, the processing circuitry may average samples (e.g., add and divide by two) corresponding samples in reference chroma block 902A and reference chroma block 902B to generate the prediction samples. As another example, the processing circuitry may scale each sample in reference chroma block 902A and reference chroma block 902B and sum the results of corresponding samples to generate the prediction samples.
As further examples, the processing circuitry may determine respective weights for the two or more reference chroma blocks. For instance, the processing circuitry may determine a first weight that is used to scale samples of reference chroma block 902A and a second weight that is used to scale samples of reference chroma block 902B. To fuse, the processing circuitry may be configured to fuse the two or more reference chroma blocks 902A and 902B based on the respective weights.
There may be various ways to determine the weights (e.g., the first weight and the second weight). As one example, the processing circuitry may determine respective costs of the two or more reference chroma blocks. For instance, the processing circuitry may determine a first cost based on SAD or MSE between template 906 and template 904 and a second cost based on SAD or MSE between template 908 and template 904.
The processing circuitry may determine respective weights based on the respective costs. For example, if the first cost is less than the second cost, than the first weight applied to samples of reference chroma block 902A is greater than the second weight applied to samples of reference chroma block 902B so that the contribution of reference chroma block 902A is greater in the prediction samples. If the second cost is less than the first cost, than the second weight applied to samples of reference chroma block 902B is greater than the first weight applied to samples of reference chroma block 902A so that the contribution of reference chroma block 902B is greater in the prediction samples.
As another example, the processing circuitry may determine a weighting factor derivation operation. The processing circuitry may determine respective weights based on the weighting factor derivation operation. For instance, video encoder 200 may signal and video decoder 300 may receive information that indicates whether the weights are derived based on TM (e.g., SAD), MSE, or fixed weights (e.g., where the fixed weights are predefined or signaled).
The processing circuitry may block vector encode or decode the chroma block based on the prediction samples (1006). As one example, block vector encoding or decoding the chroma block may be decoding the chroma block. To decode the chroma block, the processing circuitry may be configured to determine residual values (e.g., via decoding) indicative of a difference between the prediction samples and the chroma block. The processing circuitry may add the residual values to the prediction samples to reconstruct the chroma block.
As another example, block vector encoding or decoding the chroma block may be encoding the chroma block. To encode the chroma block, the processing circuitry may determine residual values indicative of a difference between the prediction samples and the chroma block, and signal information indicative of the residual values.
The following numbered clauses illustrate one or more aspects of the devices and techniques described in this disclosure.
Clause 1. A method of encoding or decoding video data, the method comprising: for a chroma block of a picture, determining luma blocks that are co-located with the chroma block; determining two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; generating prediction samples for the chroma block based on the two or more reference chroma blocks; and block vector encoding or decoding the chroma block based on the prediction samples.
Clause 2. The method of clause 1, wherein generating prediction samples comprise fusing the two or more reference chroma blocks.
Clause 3. The method of clause 2, where fusing the two or more reference chroma blocks comprises averaging the two or more reference blocks and/or scaling and summing the two or more reference blocks.
Clause 4. The method of any of clauses 2 and 3, further comprising: determining respective weights for the two or more reference chroma blocks, wherein fusing comprises fusing the two or more reference blocks based on the respective weights.
Clause 5. The method of any of clauses 1-4, further comprising: determining respective candidate reference chroma blocks based on each of the block vectors for the luma blocks; and determining respective costs of the respective candidate reference chroma blocks, wherein determining the two or more reference chroma blocks comprises selecting two or more of the candidate reference chroma blocks based on the respective costs.
Clause 6. The method of clause 5, wherein determining the respective costs comprises determining an amount of matching between a first template adjacent the respective candidate reference chroma blocks and a second template adjacent the chroma block.
Clause 7. A method of encoding or decoding video data, the method comprising: determining one or more sub-blocks of a coding unit (CU); determining at least one reference block based on at least one vector of at least one proximate block to the CU; generating prediction samples for the CU based on the one or more sub-blocks and the at least one reference block; and encoding or decoding the CU based on the prediction samples.
Clause 8. The method of clause 7, wherein the one or more sub-blocks of the CU are at boundary of the CU.
Clause 9. The method of any of clauses 7 and 8, wherein generating prediction samples comprises fusing the one or more sub-blocks and the at least one reference block.
Clause 10. The method of clause 9, where fusing comprises averaging the one or more sub-blocks and the at least one reference block and/or scaling and summing the one or more sub-blocks and the at least one reference block.
Clause 11. The method of any of clauses 7-10, wherein the one or more sub-blocks are a top and left boundary sub-blocks of the CU.
Clause 12. The method of any of clauses 7-11, wherein the CU is a luma CU or a chroma CU.
Clause 13. A device for encoding or decoding video data, the device comprising: memory configured to store the video data; and one or more processors implanted in circuitry and coupled to the memory, the one or more processors are configured to perform the method of any of clauses 1-6 or 7-12.
Clause 14. The device of clause 13, further comprising a display configured to display decoded video data.
Clause 15. The device of any of clauses 13 and 14, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.
Clause 16. The device of any of clauses 13-15, wherein the device comprises a video decoder.
Clause 17. The device of any of clauses 13-15, wherein the device comprises a video encoder.
Clause 18. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of clauses 1-6 or 7-12.
Clause 19. A device for encoding or decoding video data, the device comprising means for performing the method of any of clauses 1-6 and 7-12.
Clause 1A. A method of encoding or decoding video data, the method comprising: for a chroma block of a picture, determining luma blocks that are co-located with the chroma block; determining two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fusing the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encoding or decoding the chroma block based on the prediction samples.
Clause 2A. The method of clause 1A, wherein fusing the two or more reference chroma blocks comprises at least one of: averaging the two or more reference chroma blocks; or scaling and summing the two or more reference chroma blocks.
Clause 3A. The method of any of clauses 1A and 2A, further comprising: determining respective weights for the two or more reference chroma blocks, wherein fusing comprises fusing the two or more reference chroma blocks based on the respective weights.
Clause 4A. The method of clause 3A, further comprising: determining respective costs of the two or more reference chroma blocks, wherein determining respective weights comprises determining respective weights based on the respective costs.
Clause 5A. The method of any of clauses 3A or 4A, further comprising: determining a weighting factor derivation operation, wherein determining respective weights comprises determining respective weights based on the weighting factor derivation operation.
Clause 6A. The method of any of clauses 1A-5A, further comprising: determining respective candidate reference chroma blocks based on respective block vectors for the luma blocks; and determining respective costs of the respective candidate reference chroma blocks, wherein determining the two or more reference chroma blocks comprises selecting two or more of the candidate reference chroma blocks based on the respective costs.
Clause 7A. The method of clause 6A, wherein determining the respective costs comprises determining an amount of matching between a first template adjacent the respective candidate reference chroma blocks and a second template adjacent the chroma block.
Clause 8A. The method of any of clauses 6A or 7A, further comprising: constructing a chroma block vector list based on the respective costs, wherein selecting two or more of the candidate reference chroma blocks comprises selecting two or more of the candidate reference chroma blocks based on the chroma block vector list.
Clause 9A. The method of any of clauses 1A-8A, wherein block vector encoding or decoding the chroma block comprises decoding the chroma block, and wherein decoding the chroma block comprises: determining residual values indicative of a difference between the prediction samples and the chroma block; and adding the residual values to the prediction samples to reconstruct the chroma block.
Clause 10A. The method of any of clauses 1A-9A, wherein block vector encoding or decoding the chroma block comprises encoding the chroma block, and wherein encoding the chroma block comprises: determining residual values indicative of a difference between the prediction samples and the chroma block; and signaling information indicative of the residual values.
Clause 11A. A device for encoding or decoding video data, the device comprising: one or more memories configured to store the video data; and processing circuitry coupled to the one or more memories and configured to: for a chroma block of a picture, determine luma blocks that are co-located with the chroma block; determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fuse the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encode or decode the chroma block based on the prediction samples.
Clause 12A. The device of clause 11A, wherein to fuse the two or more reference chroma blocks, the processing circuitry is configured to at least one of: average the two or more reference chroma blocks; or scale and sum the two or more reference chroma blocks.
Clause 13A. The device of any of clauses 11A and 12A, wherein the processing circuitry is configured to: determine respective weights for the two or more reference chroma blocks, wherein to fuse, the processing circuitry is configured to fuse the two or more reference chroma blocks based on the respective weights.
Clause 14A. The device of clause 13A, wherein the processing circuitry is configured to: determine respective costs of the two or more reference chroma blocks, wherein to determine respective weights, the processing circuitry is configured to determine respective weights based on the respective costs.
Clause 15A The device of clauses 13A and 14A, wherein the processing circuitry is configured to: determine a weighting factor derivation operation, wherein to determine respective weights, the processing circuitry is configured to determine respective weights based on the weighting factor derivation operation.
Clause 16A. The device of clauses 11A-15A, wherein the processing circuitry is configured to: determine respective candidate reference chroma blocks based on respective block vectors for the luma blocks; and determine respective costs of the respective candidate reference chroma blocks, wherein to determine the two or more reference chroma blocks, the processing circuitry is configured to select two or more of the candidate reference chroma blocks based on the respective costs.
Clause 17A. The device of clause 16A, wherein to determine the respective costs, the processing circuitry is configured to determine an amount of matching between a first template adjacent the respective candidate reference chroma blocks and a second template adjacent the chroma block.
Clause 18A. The device of clauses 16A and 17A, wherein the processing circuitry is configured to: construct a chroma block vector list based on the respective costs, wherein to select two or more of the candidate reference chroma blocks, the processing circuitry is configured to select two or more of the candidate reference chroma blocks based on the chroma block vector list.
Clause 19A. The device of any of clauses 11A-18A, wherein the processing circuitry is configured to: determine residual values indicative of a difference between the prediction samples and the chroma block; and at least one of: add the residual values to the prediction samples to reconstruct the chroma block; or signal information indicative of the residual values.
Clause 20A. A computer-readable storage medium storing instructions thereon that when executed cause one or more processors to: for a chroma block of a picture, determine luma blocks that are co-located with the chroma block; determine two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fuse the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encode or decode the chroma block based on the prediction samples.
It is to be recognized that depending on the example, certain acts or events of any of the techniques described herein can be performed in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the techniques). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially.
In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to 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. In this manner, 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.
By way of example, and not limitation, such computer-readable storage media may include one or more of 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. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that 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, as used herein, 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.
Instructions may be executed by one or more processors, such as one or more DSPs, general purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the terms “processor” and “processing circuitry,” as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.
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). 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.
Various examples have been described. These and other examples are within the scope of the following claims.
This application claims benefit of U.S. Provisional Application No. 63/495,979, filed Apr. 13, 2023, the entire contents of which are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 63495979 | Apr 2023 | US |
