CN116648910A

CN116648910A - Symbol prediction for multiple color components in video coding

Info

Publication number: CN116648910A
Application number: CN202180086651.5A
Authority: CN
Inventors: 王洪涛; J·陈; M·卡尔切维茨
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2020-12-29
Filing date: 2021-12-22
Publication date: 2023-08-25

Abstract

An example method includes: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Description

Symbol prediction for multiple color components in video coding

Cross reference

The present application claims priority from U.S. application Ser. No. 17/645,439, filed on 21 and 12 months 2020, and U.S. provisional application Ser. No. 63/131,615, filed on 29, 12 and 2020, both of which are incorporated herein by reference in their entireties. U.S. application Ser. No. 17/645,439, filed on 12/21 of 2021, claims the benefit of U.S. provisional application Ser. No. 63/131,615, filed on 29 of 12/2020.

Technical Field

The present disclosure relates to video encoding and video decoding.

Background

Digital video capabilities can be integrated 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, electronic book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, so-called "smartphones", video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding (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, section 10, advanced Video Coding (AVC), ITU-T H.265/High Efficiency Video Coding (HEVC), and extensions of such standards. Video devices may more efficiently transmit, receive, encode, decode, and/or store digital video information by implementing such video coding techniques.

Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or eliminate 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 slices of intra coding (I) of a picture are encoded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video 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. A picture may be referred to as a frame and a reference picture may be referred to as a reference frame.

Disclosure of Invention

In general, this disclosure describes techniques for coding video data using symbol prediction performed based on multiple color components of the video data. In order to predict the sign values of coefficients in a plurality of coefficients of a transform block, a video coder (e.g., a video encoder and/or video decoder) may reconstruct the transform block using both positive and negative values of the sign values of the coefficients. Each block reconstruction using candidate symbol values may be referred to as a hypothesis reconstruction. The video coder may evaluate a two-hypothesis reconstruction of the sign of the coefficient with a cost function and select the hypothesis reconstruction that minimizes the cost function, giving a predicted sign value for the coefficient of the transform block. However, in some examples, multiple blocks may be affected by the predicted symbol value. For example, in the case where the transform block is a chroma residual joint coding (JCCR) transform block, the video decoder generates multiple transform blocks from the JCCR transform block, each corresponding to a different color component, which may all be affected by the prediction symbol value. Performing symbol prediction based on only one color component may be suboptimal because one hypothetical reconstruction may be valid for one color component but not good for the other color component.

In accordance with one or more techniques of this disclosure, a video coder (e.g., a video encoder and/or a video decoder) may perform symbol prediction based on multiple color components of video data. For example, when performing symbol prediction on JCCR transform blocks used to generate multiple transform blocks (e.g., cb transform block and Cr transform block) that each correspond to a different color component, a video coder may perform symbol prediction based on the multiple color components. The techniques of this disclosure may improve symbol prediction by performing symbol prediction based on multiple color components. Improved symbol prediction may reduce the number of bits required to signal a symbol. In this way, the techniques of this disclosure may improve coding efficiency.

In one example, a method of decoding video data includes: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using JCCR; generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

In another example, a method of encoding video data includes: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using JCCR; generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

In another example, an apparatus for coding video data includes means for predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using JCCR; means for generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and means for reconstructing the block of video data based on the plurality of residual blocks.

In another example, a computer-readable storage medium storing instructions that, when executed, cause one or more processors of a video decoder to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using JCCR; generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

Drawings

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

Fig. 2A and 2B are conceptual diagrams illustrating an example quadtree binary tree (QTBT) structure and corresponding decoding tree units (CTUs).

Fig. 3 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

Fig. 4 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

Fig. 5 is a conceptual diagram illustrating coefficient scanning of an 8 x 8 transform block containing 4 coefficient groups in HEVC.

Fig. 6 is a conceptual diagram illustrating an example of coefficient sign prediction.

Fig. 7 is a flowchart illustrating an example method for encoding a current block in accordance with the techniques of this disclosure.

Fig. 8 is a flowchart illustrating an example method for decoding a current block in accordance with the techniques of this disclosure.

Fig. 9 is a flowchart illustrating an example method of decoding a current block using symbol prediction based on multiple color components in accordance with the techniques of this disclosure.

Detailed Description

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

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

In the example of fig. 1, source device 102 includes video source 104, memory 106, video encoder 200, and output interface 108. The target device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. In accordance with the present disclosure, the video encoder 200 of the source device 102 and the video decoder 300 of the target device 116 may be configured to apply techniques for symbol prediction of multiple color components. Thus, the source device 102 represents an example of a video encoding device, while the target device 116 represents an example of a video decoding device. In other examples, the source device and the target device may include other components or arrangements. For example, the source device 102 may receive video data from an external video source (e.g., an external camera). Similarly, the target device 116 may interface with an external display device rather than include an integrated display device.

The system 100 shown in fig. 1 is merely one example. In general, any digital video encoding and/or decoding device may perform techniques for symbol prediction of multiple color components. Source device 102 and destination device 116 are merely examples of such transcoding devices in which source device 102 generates transcoded video data for transmission to destination device 116. The present disclosure refers to a "decoding" device as a device that performs data decoding (encoding and/or decoding). Accordingly, the video encoder 200 and the video decoder 300 represent examples of a decoding apparatus, specifically, examples of a video encoder and a video decoder, respectively. In some examples, the source device 102 and the target device 116 may operate in a substantially symmetrical manner such that each of the source device 102 and the target device 116 includes video encoding and decoding components. Thus, the system 100 may support unidirectional or bidirectional video transmission between the source device 102 and the target device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

In general, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a sequence of consecutive pictures (also referred to as "frames") of video data to video encoder 200, which video encoder 200 encodes the data of the pictures. The video source 104 of the 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 that receives video from a video content provider. As another alternative, video source 104 may generate computer graphics-based data as the source video, or a combination of real-time video, archived video, and computer-generated video. In each case, the video encoder 200 encodes captured, pre-captured, or computer-generated video data. The video encoder 200 may rearrange the pictures from the received order (sometimes referred to as the "display order") into a coding order for coding. The video encoder 200 may generate a bitstream comprising encoded video data. The source device 102 may then output the encoded video data via the output interface 108 onto the computer readable medium 110 for receipt and/or retrieval through, for example, the input interface 122 of the target device 116.

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

Computer-readable medium 110 may represent any type of medium or device capable of transmitting encoded video data from source device 102 to destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to send encoded video data directly to the target device 116 in real-time, e.g., via a radio frequency network or a computer-based network. According to a communication standard, such as a wireless communication protocol, output interface 108 may modulate a transmit signal including encoded video data, and input interface 122 may demodulate a received transmit signal. 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 device operable to facilitate communication from the source device 102 to the target device 116.

In some examples, source device 102 may output encoded data from output interface 108 to storage device 112. Similarly, the target device 116 may access encoded data from the storage device 112 via the input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media for storing encoded video data such as a hard drive, blu-ray disc, DVD, CD-ROM, flash memory, volatile or nonvolatile memory, or any other suitable digital storage media.

In some examples, source device 102 may output the encoded video data to file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102. The target device 116 may access the stored video data from the 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 the encoded video data to target device 116. File server 114 may represent a web server (e.g., for a website), a server configured to provide file transfer protocol services (e.g., 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. The file server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as dynamic adaptive streaming over HTTP (DASH), HTTP real-time streaming (HLS), real-time streaming protocol (RTSP), HTTP dynamic streaming, and the like.

The target device 116 may access the encoded video data from the file server 114 through any standard data connection, including an internet connection. This may include a wireless channel (e.g., wi-Fi connection), a wired connection (e.g., digital Subscriber Line (DSL), cable modem, etc.), or a combination of both, adapted to access encoded video data stored on the file server 114. The input interface 122 may be configured to operate in accordance with any one or more of the various protocols discussed above for retrieving or receiving media data from the 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 network components (e.g., ethernet cards), wireless communication components operating in accordance with any of a variety of IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 comprise wireless components, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to a cellular communication standard (e.g., 4G-LTE (long term evolution), LTE-advanced, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to communicate in accordance with other wireless standards (e.g., IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., zigBee) ^TM ) Bluetooth (R) ^TM Standard, etc.) to transmit data, such as encoded video data. In some examples, source device 102 and/or target device 116 may include respective system-on-chip (SoC) devices. For example, source device 102 may include a SoC device to perform the functions attributed to video encoder 200 and/or output interface 108, and target device 116 may include a SoC device to perform the functions attributed to video decoder 300 and/or input interface 122.

The techniques of this disclosure may be applied to support video coding for any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission, such as dynamic adaptive streaming over HTTP (DASH), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer readable medium 110 (e.g., communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 that is also used by the video decoder 300, such as syntax elements having values describing characteristics and/or processing of video blocks or other coding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The 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.

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

Video encoder 200 and video decoder 300 may each be implemented as any of a variety of suitable encoder and/or decoder circuits, such as one or more microprocessors, digital Signal Processors (DSPs), application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented in part 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 the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, any of which may be integrated in a respective device as part of a combined encoder/decoder (CODEC). Devices including video encoder 200 and/or video decoder 300 may include integrated circuits, microprocessors, and/or wireless communication devices, such as cellular telephones.

Video encoder 200 and video decoder 300 may operate in accordance with a video coding standard (e.g., ITU-t h.265, also known as High Efficiency Video Coding (HEVC)) or an extension thereof (e.g., multiview and/or scalable video coding extension). Alternatively, video encoder 200 and video decoder 300 may operate in accordance with other proprietary or industry standards, such as ITU-T h.266, also known as universal video coding (VVC). In Bross et al, "Versatile Video Coding (Draft 10)" ("Universal video coding (Draft 5)"), joint video expert group (JVET) of ITU-T SG 16WP 3 and ISO/IEC JTC 1/SC 29/WG 11, conference 18: the VVC standard draft is described in jfet-S2001-vA (hereinafter referred to as "VVC draft 10") at teleconference, month 6, 22 to month 7, 1 in 2020. However, the techniques of this disclosure are not limited to any particular coding standard.

In general, video encoder 200 and video decoder 300 may perform block-based picture coding. The term "block" generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used in an encoding and/or decoding process). For example, a block may comprise a two-dimensional matrix of samples of luminance and/or chrominance data. In general, video encoder 200 and video decoder 300 may decode video data represented in YUV (e.g., Y, cb, cr) format. That is, the video encoder 200 and the video decoder 300 may code luminance and chrominance components, rather than red, green, and blue (RGB) data for samples of a picture, where the chrominance components may include both red and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB format data to a YUV representation prior to encoding, and the video decoder 300 converts the YUV representation to RGB format. Alternatively, the pre-processing unit and the post-processing unit (not shown) may perform these conversions.

The present disclosure may generally relate to coding (e.g., encoding and decoding) a picture to include a process of encoding or decoding data of the picture. Similarly, the present disclosure may relate to coding a block of a picture to include processes that encode or decode data of the block, such as prediction and/or residual coding. The encoded video bitstream typically includes a series of values representing coding decisions (e.g., coding modes) and syntax elements that partition a picture into blocks. Thus, references to coding a picture or block should generally be understood as coding the values of syntax elements that make up the picture or block.

HEVC defines various blocks, including Coding Units (CUs), prediction Units (PUs), and Transform Units (TUs). According to HEVC, a video encoder, such as video encoder 200, partitions Coding Tree Units (CTUs) 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 zero or four child nodes. A node without child nodes may be referred to as a "leaf node," and a CU of such a leaf node may include one or more PUs and/or one or more TUs. The video coder may further partition the PU and the TU. For example, in HEVC, a Residual Quadtree (RQT) represents a partition of TUs. In HEVC, PUs represent inter prediction data and TUs represent residual data. The intra-predicted CU includes intra-prediction information, such as an intra-mode indication.

As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder (e.g., video encoder 200) partitions a picture into a plurality of Coding Tree Units (CTUs). The video encoder 200 may partition the ctu.qtbt structure according to a tree structure (e.g., a quadtree binary tree (QTBT) structure or a multi-type tree (MTT) structure) that eliminates the concept of multiple partition types, e.g., partitioning between CUs, PUs, and TUs of HEVC.

In the MTT partitioning structure, blocks may be partitioned using a Quadtree (QT) partition, a Binary Tree (BT) partition, and one or more types of Trigeminal Tree (TT) (also referred to as Ternary Tree (TT)) partitions. A trigeminal or ternary tree partition is a partition in which a block is split into three sub-blocks. In some examples, a trigeminal or ternary tree partition divides a block into three sub-blocks, without centrally dividing the initial block. The segmentation types (e.g., QT, BT, and TT) in MTT may be symmetrical or asymmetrical.

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

The video encoder 200 and video decoder 300 may be configured to use per HEVC quadtree splitting, QTBT splitting, MTT splitting, or other splitting structures. For purposes of illustration, a description of the presently disclosed technology is presented for QTBT segmentation. However, it should be understood that the techniques of this disclosure may also be applied to video decoders configured to use quadtree partitioning or other types of partitioning.

In some examples, the CTU includes a Coding Tree Block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture having three sample arrays, or CTBs of samples of a monochrome picture or a picture coded using three separate color planes and syntax structures for coding the samples. CTBs may be blocks of nxn samples for some value of N, such that dividing a component into CTBs is a partition. The components are from the following 4:2: 0. 4:2:2 or 4:4: the color format of 4 constitutes an array or a single sample of one of the three arrays (luminance and two chromaticities) of the picture, or an array or a single sample of an array of the picture in a monochrome format. In some examples, the coding block is a block of mxn samples for some values of M and N, such that dividing CTBs into coding blocks is a partition.

Blocks (e.g., CTUs or CUs) may be grouped in pictures in various ways. For example, a brick (brick) may refer to a rectangular region of CTU rows within a particular tile (tile) in a picture. A tile may be a rectangular region of CTUs in a picture within a particular tile column and a particular tile row. A tile column refers to a rectangular region of CTUs whose height is equal to the height of a picture and whose width is specified by syntax elements (e.g., in a picture parameter set). A tile row refers to a rectangular region of a CTU that has a height specified by a syntax element (e.g., in a picture parameter set) and a width equal to the width of a picture.

In some examples, a tile may be partitioned into a plurality of tiles, where each tile may include one or more rows of CTUs within the tile. A block that is not divided into a plurality of bricks may also be referred to as a brick. However, bricks that are a proper subset of tiles may not be referred to as tiles.

The bricks in the picture may also be arranged in slices. Slices may be integer multiples of tiles of a picture, which may be contained exclusively in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes a number of complete tiles, or a continuous sequence of complete tiles of only one tile.

The present disclosure may use "nxn" and "N by N" interchangeably to refer to the sample dimension of a block (e.g., CU or other video block) in both vertical and horizontal aspects, such as 16 x 16 samples or 16 by 16 samples. Generally, a 16×16CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Likewise, an nxn CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU may be arranged in rows and columns. Further, a CU does not have to have the same number of samples in the horizontal direction as in the vertical direction, e.g., a CU may include n×m samples, where M is not necessarily equal to N.

The video encoder 200 encodes video data of a CU representing prediction and/or residual information, as well as other information. The prediction information indicates how to predict the CU, forming a prediction block for the CU. Residual information generally represents a sample-by-sample difference between samples of a CU before encoding and a prediction block.

To predict a CU, video encoder 200 may typically form a prediction block for the CU by inter-prediction or intra-prediction. Inter prediction generally refers to predicting a CU from data of a previously coded picture, while intra prediction generally refers to predicting a CU from previously coded data of the same picture. To perform inter prediction, the video encoder 200 may generate a prediction block using one or more motion vectors. The video encoder 200 may typically perform a motion search to identify reference blocks that closely match the CU, for example, in terms of differences between the CU and the reference blocks. The video encoder 200 may calculate a difference metric using a Sum of Absolute Differences (SAD), a Sum of Squared Differences (SSD), a Mean Absolute Difference (MAD), a Mean Squared Difference (MSD), and or other such difference calculations to determine whether the reference block closely matches the current CU. In some examples, video encoder 200 may use unidirectional prediction or bi-directional prediction to predict the current CU.

Some examples of VVCs also provide affine motion compensation modes, which may be considered inter prediction modes. In affine motion compensation mode, the video encoder 200 may determine two or more motion vectors representing non-translational motion, such as zoom in or out, rotation, perspective motion, or other irregular motion types.

To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of VVCs provide sixty-seven intra-prediction modes, including various directional modes, as well as planar modes and DC modes. In general, the video encoder 200 selects an intra prediction mode describing neighboring samples to a current block (e.g., a block of a CU) to predict samples of the current block from the neighboring samples. Assuming that video encoder 200 codes CTUs and CUs in raster scan order (left to right, top to bottom), such samples may typically be above, top left, or left of the current block in the same picture as the current block.

The video encoder 200 encodes data representing a prediction mode of the current block. For example, for inter prediction modes, the video encoder 200 may encode data representing which of the various available prediction modes is used, as well as motion information for the corresponding modes. For unidirectional or bi-directional inter prediction, for example, the video encoder 200 may encode the motion vectors using Advanced Motion Vector Prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode the motion vectors for the affine motion compensation mode.

After prediction, such as intra prediction or inter prediction of a block, the video encoder 200 may calculate residual data of the block. Residual data (such as a residual block) represents a sample-by-sample difference between a block and a prediction block of the block formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to generate transform data in the 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 the residual video data. In addition, the video encoder 200 may apply a secondary transform, such as a mode dependent inseparable secondary transform (MDNSST), a signal dependent transform, a karhun-Loeve transform (KLT), etc., after the first transform. The video encoder 200 generates transform coefficients after applying one or more transforms.

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

After quantization, the video encoder 200 may scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place higher energy (and therefore lower frequency) coefficients in front of the vector and lower energy (and therefore higher frequency) transform coefficients in back of the vector. In some examples, video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce serialized vectors, and then entropy encode the quantized transform coefficients of the vectors. In other examples, video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC), the video encoder 200 may entropy encode the one-dimensional vector. The video encoder 200 may also entropy encode values of syntax elements that describe metadata associated with the encoded video data for use by the video decoder 300 in decoding the video data.

To perform CABAC, the video encoder 200 may assign contexts within the context model to symbols to be transmitted. The context may relate to, for example, whether the adjacent value of the symbol is a zero value. The probability determination may be based on the context assigned to the symbol.

The video encoder 200 may further generate syntax data to the video decoder 300, such as in a picture header, a block header, a slice header, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, or other syntax data, such as a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), or a Video Parameter Set (VPS). The video decoder 300 may similarly decode such syntax data to determine how to decode the corresponding video data.

In this way, 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. Finally, the video decoder 300 may receive the bitstream and decode the encoded video data.

In general, the video decoder 300 performs the inverse of the process performed by the video encoder 200 to decode encoded video data of a bitstream. For example, the video decoder 300 may decode the values of the syntax elements of the bitstream using CABAC in a substantially similar (although opposite) manner to the CABAC encoding process of the video encoder 200. The syntax element may define partition information for partitioning a picture into CTUs and defining CUs of the CTUs by partitioning each CTU according to a corresponding partition structure such as a QTBT structure. Syntax elements may further define prediction and residual information for blocks of video data (e.g., CUs).

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

As discussed above, video encoder 200 may encode and video decoder 300 may decode transform coefficients. For example, to perform transform coefficient coding according to HEVC, a video coder (e.g., video encoder 200 and/or video decoder 300) may divide a block of transform coefficients (TB) by Coefficient Groups (CGs), where each CG may represent a 4 x 4 sub-block. As one example, a 32×32 TU may be divided into a total of 64 CG, and a 16×16 TU may be divided into a total of 16 CG. The video coder may perform entropy coding on the TBs in CG units. The video decoder may decode the CG within the TB according to a given scan order. As each CG is coded, the video coder may scan and code coefficients within the current CG according to a particular predefined scan order for a 4 x 4 block. In JEM (Joint exploration mode (JEM), ieeeexplore. Ieeee. Org/document/8861068), CG size may be 4X 4 or 2X 2, depending on whether the height or width of one TB is equal to 2. Fig. 5 is a conceptual diagram showing coefficient scanning of 8×8 TBs containing 4 CGs in HEVC.

For each color component, the video coder may signal a flag to indicate whether the current TB has at least one non-zero coefficient. For example, a video coder may signal a Coded Block Flag (CBF) or coded block pattern (CPB) with a value indicating whether the current TB has at least one non-zero coefficient. If there is at least one non-zero coefficient, the video coder may explicitly signal the position in the TB of the last significant coefficient in the coefficient scan order relative to the coordinates of the upper left corner of the TB. The vertical or horizontal component of the coordinates may be represented by its prefix and suffix, where the prefix may be binarized with a Truncated Rice (TR) and the suffix is binarized with a fixed length.

With this decoded position and the CG's coefficient scan order, the video decoder can signal a flag for the CG other than the last CG (in scan order) that indicates whether the CG contains non-zero coefficients. For those CGs that may contain non-zero coefficients, the video coder may signal the significance flag, coefficient absolute value, and sign information of the non-zero coefficients for each coefficient according to a predefined 4 x 4 coefficient scan order. In the HEVC transform coefficient entropy coding scheme, if a symbol bit is coded, it may always be bypass coded, i.e., no context is applied, and 1 bit is always coded for each symbol bit using an Equal Probability (EP) assumption.

Symbol data hiding is discussed below. For CG, and depending on the standard, when using symbol data concealment (SDH), the video decoder may omit decoding the symbols of the last non-zero coefficient (in reverse scan order), which is the first non-zero coefficient in forward scan order. Instead, the symbol value may be embedded into and determined from the parity of the sum of the levels of the CG using a predefined convention (even corresponding to "+", odd corresponding to "-"). The standard for using SDH may be the distance between the first and last non-zero coefficients of the CG in scan order. If the distance is equal to or greater than a threshold (e.g., 4 samples), SDH may be used.

Coefficient symbol prediction is discussed below. In order to improve the decoding efficiency of symbol bit information, a coefficient symbol prediction method is proposed in the literature. A symbol prediction method is proposed above JEM.

To predict the sign of one coefficient, the video coder may reconstruct the Transform Block (TB) using both positive and negative values of this sign, and each block reconstruction using candidate sign values may be referred to as a hypothesis reconstruction. The video coder may evaluate the two hypothesis reconstruction with a given spatial cost function and minimize the hypothesis of the cost function to give the predicted symbol value.

Furthermore, to predict multiple symbols of a TB, e.g., N symbols, a video coder may reconstruct the TB using different combinations of candidate symbol predictors, including a total of 2 ^N A different hypothesis is reconstructed. Similarly, the video coder may evaluate each hypothesis by a given spatial cost function, and minimize the hypothesis of the cost function gives a predicted symbol value combination.

The cost function typically uses one of the hypotheses to measure the spatial discontinuity between the previously reconstructed neighboring pixels and the reconstructed block currently tested. The assumption showing the smoothest pixel value transition at the block boundary of the current block may be regarded as the best prediction.

Fig. 6 is a conceptual diagram illustrating coefficient sign prediction. In the example of fig. 6, costs are measured using the leftmost and uppermost pixels that are assumed to be reconstructed.

The video coder may determine the cost according to the following equation:

in the above equation, (2 p _{x,_1} -p _{x,_2} ) And (2 p) _{_1,y} -p _{_2,y} ) The term is the predicted component, and p _x,0 And p _0,y The term is the hypothesized reconstruction component.

In the particular symbol prediction scheme depicted in fig. 6, the encoder may initially dequantize the TU and then select the n coefficients of the symbol to be predicted. The coefficients may be scanned in raster scan order and when n coefficients to be processed are collected, dequantized values exceeding a defined threshold are prioritized over values below the threshold.

With these n values, one can look like the followingExecution 2 ⁿ A simplified boundary reconstruction: each unique combination of symbols for the n coefficients is reconstructed once.

To reduce the complexity of performing symbol prediction, a video coder may perform template-based hypothesis reconstruction. For a particular hypothesis reconstruction, the video coder may reconstruct only the leftmost and uppermost pixels of the block according to the inverse transform added to the block prediction. While the first (vertical) inverse transform has been completed, the second (horizontal) inverse transform only needs to create the leftmost and uppermost pixel outputs and is therefore faster. An additional flag "topLeft" may be added to the inverse transform function to allow this.

In addition, by using a "stencil" system, the number of times the inverse transform operation is performed is reduced. In this way, when predicting n symbols in a block, a video coder may perform n+1 inverse transform operations:

1. a single inverse transform is performed on the dequantized coefficients, with the values of all predicted symbols set to positive. This corresponds to a boundary reconstruction of the first hypothesis once added to the prediction of the current block.

2. For each of the n coefficients whose sign has been predicted, an inverse transform operation is performed on the otherwise empty block containing the corresponding dequantized (and positive) coefficient as its only non-empty element. The leftmost and uppermost boundary values are saved in a so-called "template" for later use in reconstruction.

Boundary reconstruction of the latter hypothesis may begin by obtaining an appropriate saved reconstruction of the previous hypothesis, which only requires changing the single prediction sign from positive to negative in order to construct the desired current hypothesis. This change in sign can then be approximated by doubling and subtracting the hypothesized boundary from the template corresponding to the predicted sign. After determining the cost value, if the boundary reconstruction is known to be re-used to construct the following assumptions, the boundary reconstruction is saved.

Template name	How to create
		T001	inv xformsingle+ve 1 ^st sign-hidden coeff
T010	inv xformsingle+ve 2 ^nd sign-hidden coeff
		T100	inv xformsingle+ve 3 ^rd sign-hidden coeff

The table above shows save/restore and template application in the case of 3-symbol 8-entry. Note that these approximations may be used only in the symbol prediction process, and not in the final reconstruction process.

For transform coefficients with larger magnitudes, symbol prediction generally provides a better opportunity to achieve correct prediction. This is because incorrect symbol predictions with larger magnitude transform coefficients typically show more variance in boundary sample smoothness.

With symbol prediction, instead of decoding explicit symbol values, a video decoder may decode the correctness of the symbol prediction. For example, to predict coefficient symbols that actually have positive values, if the predicted symbols are also positive, i.e., the symbol prediction is correct, the video coder may code a "0" bin (bin). Otherwise, if the sign of the prediction is negative, i.e., the sign prediction is incorrect, the video coder may code a "1" bin. In this way, the video coder may utilize the level value (magnitude) of the transform coefficient as a context for coding the correctness of the symbol prediction, as a larger magnitude of the transform coefficient tends to be a higher "0" bin opportunity.

Joint coding of chroma residuals is discussed below. Chroma residual joint coding (JCCR) is a video coding tool that jointly codes chroma residuals. When JCCR is used, a single block of transform coefficients is signaled for multiple color components. JCCR is part of VVC, which is one of the latest video coding standards. At VVC, TU-level JCCR flags are supported when at least one chroma CBF is non-zero. If the JCCR flag is true, the decoder parses a single coefficient block from the bitstream and derives a pixel residual block of the chroma component from the single residual block.

Cross component linear model prediction (CCLM) is discussed below. CCLM is a predictive method to reduce cross component redundancy. The VVC video coding standard employs CCLM. When CCLM is used, chroma prediction samples are generated by applying a linear model to the collocated luma samples as shown in the following equation:

pred _C (i,j)＝α·rec _L ′(i,j)+β

wherein pred is _C (i, j) represents predicted chroma samples in the CU, and rec _L (i, j) denotes the downsampled reconstructed luma samples of the same CU.

The foregoing techniques may suffer from one or more disadvantages. For example, considering only one color component (e.g., for symbol prediction) may be suboptimal when reconstructed samples of multiple color components may be affected by the current transform block (e.g., in the case of using CCLM or JCCR modes). In particular, one hypothetical reconstruction may be valid for one color component, but not good for the other color component.

In accordance with the techniques of this disclosure, a video coder (e.g., video encoder 200 and/or video decoder 300) may consider multiple color components when performing symbol prediction for residual coding. For example, when performing symbol prediction on JCCR transform blocks used to generate multiple transform blocks (e.g., cb transform block and Cr transform block) that each correspond to a different color component, a video coder may perform symbol prediction based on the multiple color components.

Part a. Joint symbol prediction of multiple transform blocks. As an example of considering multiple color components in symbol prediction, a video coder may jointly perform symbol prediction of the multiple color components. Multiple color components with interdependence may be selected to perform joint symbol prediction. The selection of the color component may be based on predefined rules and/or signaled information in the bitstream. Generating a hypothetical reconstruction of all involved color components and deriving therefrom a joint Cost (Cost _joint ). The predicted value of the symbol involved is determined by minimizing the joint cost value.

As described above, in the case of performing symbol prediction on a single block having N prediction symbols. There is 2 ^N Different combinations of symbols and selecting one of them as a prediction set. In this example, the video coder may jointly perform symbol predictions for different color components, and the prediction symbols for the involved color components may be combined to produce a joint set of prediction symbols, as shown in equation (1) below. The video coder may predict a Set of symbols (Set _color ) Performing a joint operation (U):

let N _joint ＝size(Set _joint ) There isDifferent symbol combinations. For each combination, a hypothetical reconstruction of all involved color components is generated, and a joint Cost (Cost) is derived based on these hypothetical reconstructions _joint )。Cost _joint Used as a criterion for determination, wherein a combination of symbols is selected as a predicted subset of the predictively coded symbols.

One special case of joint set generation is when multiple involved color components share a single transform block. For example, when chroma residual joint coding (JCCR) is applied and symbol prediction is performed on Cb and Cr jointly,therefore->Several examples of this special case will be described below.

Part B. Symbol prediction of the current transform block. As another example of considering multiple color components in symbol prediction, a video coder may consider multiple components when performing symbol prediction on a single transform block. This example may be applied when there are other color component(s) that depend on the current color component. In this case, each hypothesis reconstruction may be evaluated based not only on the current color component, but also on other color component(s) that may be affected by the current color component. Can apply the derived joint Cost (Cost _joint ) Is a different method of (a):

the hypothetical reconstruction of all involved color components is generated and the joint cost is derived based on all these hypothetical reconstructions, as described in section a above.

For some of the color component(s) involved, a hypothesis reconstruction is generated for cost calculation. While for the other component(s) simplified criteria may be applied. For example, in the case of a cross-component linear model (CCLM) in VVC, instead of further generating hypothetical reconstruction(s) of chroma component(s), the chroma prediction block(s) corresponding to chroma component(s) may be generated based on hypothetical reconstruction of luma (Y) component(s), which may be used to derive joint Cost (Cost) _joint )。

Part C. The video coder may apply one or more conditions that use symbol prediction based on the plurality of color components. Examples of the techniques of this disclosure may define rule(s) to determine whether to jointly make symbol predictions for multiple transform blocks (as described above in section a) or to consider multiple color components when performing symbol predictions for a current transform block on a transform block (as described above in section B). The rule(s) may be predefined for the encoder and decoder, signaled in the bitstream, or executed in a combined manner.

For example, for a luma block used in a Cross Component Linear Model (CCLM) in VVC, if the corresponding chroma block has a coded block flag equal to zero (e.g., meaning no non-zero coefficients), then the chroma block is considered in the sign prediction of the luma block. In this case, the hypothetical reconstruction of the corresponding chroma block is equal to the prediction block generated from the hypothetical reconstruction of the luma block. When performing symbol prediction of a luminance block, it may not be necessary to derive sample residuals of the chrominance blocks.

Part D. Deriving the joint cost of the plurality of color components. In order to take into account the plurality of color components, a Cost value derived from all the involved color components may be required (referred to as 'joint Cost', cost _joint ). For example, the cost of each involved color component is calculated independently, and the joint cost is derived as a combination of cost values for all involved color components, as shown in equation (2), where S represents the set of color components involved in the sign-predictive coding of the coefficients. The weights of the different color components may be fixed, derived based on predefined rule(s) at the encoder and decoder side, or controlled by syntax element(s) signaled in the bitstream.

In a special case, one of the weights may be 1, while all other weights are 0. The joint cost may then be equivalent to selecting one color component, and the video coder may use the joint cost to perform symbol prediction of the current block.

The techniques of this disclosure are incorporated into examples of chroma residual joint coding. In a video coder, a transform block may correspond to a block of pixel residuals for a plurality of color components, e.g., joint coding of chroma residual coding in VVC (JCCR). In this caseThe Cb and Cr components share a transform block. Cb when decoding a pair of JCCR&Set when Cr blocks jointly perform symbol prediction (as described in section a) _joint ＝∪ _{color∈{Cb,Cr}} Set _color ＝Set _Cb ＝Set _Cr When generating the prediction symbols of the transform block, the hypothetical reconstruction of all involved color components can be evaluated. Export Cost may be used _joint Is a different method of (a). For example, use of the joint Cost described in section D _joint And (3) export:

wherein S represents a chrominance color component, and w _color Representing the weights of the color components color.

The following describes how a video coder may derive w _color Is described.

For example, a fixed value of 1 is used as a cost weight for different chroma color formats.

In this case, the Cost is combined _joint Can be derived as:

as another example, the chrominance components are scanned in a particular order (which order may be derived from predefined rules and/or information signaled in the bitstream), the weight of the first chrominance component in the bitstream with a non-zero CBF is set to 1, and

the other component(s) use 0. In the case of VVC, the chrominance component s=

{ Cb, cr }, in the order "1: cb,2: cr "is an example, and the weights of Cb and Cr are derived as follows:

if(CBF_Cb！＝0)

{

w _Cb ＝1；

w _Cr ＝0；

}

else//CBF _Cb ＝＝0&&CBF _Cr ！＝0

{

w _Cb ＝0；

w _Cr ＝1；

}

as yet another example, the weight of each color component may also be derived based on the corresponding CBF value. For example, if the CBF value of a color component is 0, the weight of the color component is set to 0, otherwise the weight is set to 1. In the case of a VVC, the first and second regions,

the chrominance components s= { Cb, cr }, and the weights w _Cb ，w _Cr Is derived as follows:

w _Cb ＝0；

w _Cr ＝0；

if(CBF_Cb！＝0)

{

w _Cb ＝1；

}

if(CBF _Cr ！＝0)

{

w _Cr ＝1；

}

examples of incorporating the techniques of this disclosure may be incorporated into a decoding tool (e.g., CCLM, CCP). In a video decoder, prediction between color components may be applied to exploit correlation between different color components of a video signal. For example, cross-component prediction (CCP) in HEVC range extension and cross-component linear model (CCLM) in VVC. For a transform block of a particular color component a, if there are other color component(s) that depend on a, the symbol prediction of the transform block may be performed jointly for both a and the color component it depends on. In this case, examples described in, for example, a portion a (for example, performing symbol prediction on a plurality of color components in combination) or a portion B (for example, performing symbol prediction on a single color component, but considering the influence on a plurality of color components) may be applied.

In the case of CCLM mode, the techniques of this disclosure may be applied to related color components as a result of the CCLM mode in which luma blocks are used for one or more chroma components.

1. For example, for a luma transform block, if one or more chroma blocks use the luma block to perform a CCLM mode, for each hypothesized reconstruction of the luma component, CCLM predictors (hypothesized CCLM predictors) of the corresponding chroma component(s) are generated and evaluated. The joint cost is derived based on the hypothesized reconstruction of the luma component and the hypothesized CCLM predictor(s) of the chroma component. Alternatively, the conditions described in section C may be applied to control when this embodiment may be used. One example of such a condition is to use this example only when the corresponding chrominance component(s) have cbf=0. (in this case, the hypothetical CCLM predictor for the color component is equal to the hypothetical reconstruction.)

2. As another example, for a luma transform block, if one or more chroma blocks use the luma block to perform CCLM mode, a hypothesis reconstruction is generated for all involved color components to perform symbol prediction. In this case, the residual of the chroma component(s) is generated and added to the hypothetical CCLM predictor to find the chroma hypothesis reconstruction. Symbol prediction is also used if the chrominance component(s). Then the symbol predictions are jointly performed.

3. Similar to example 2, this example generates a hypothetical reconstruction for both luma and related chroma components when CCLM is used, but only when chroma does not use symbol prediction.

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

Fig. 2A and 2B are conceptual diagrams illustrating an example quadtree binary tree (QTBT) structure 130 and corresponding decoding tree units (CTUs) 132. The solid line represents a quadtree split and the dashed line indicates a binary tree split. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) to use, where 0 indicates a horizontal split and 1 indicates a vertical split in this example. For quadtree splitting, the split type need not be indicated because the quadtree node splits the block horizontally and vertically into 4 sub-blocks of equal size. Accordingly, the video encoder 200 and the video decoder 300 may encode and decode syntax elements (e.g., split information) for the region tree level (i.e., solid line) of the QTBT structure 130 and syntax elements (e.g., split information) for the prediction tree level (i.e., dashed line) of the QTBT structure 130, respectively. The video encoder 200 and the video decoder 300 may encode and decode video data (such as prediction and transform data) for CUs represented by the terminal leaf nodes of the QTBT structure 130, respectively.

In general, the CTU132 of fig. 2B may be associated with parameters defining the size of the blocks corresponding to the nodes of the QTBT structure 130 of the first and second levels. These parameters may include CTU size (representing the size of CTU132 in the sample), minimum quadtree size (MinQTSize representing minimum allowed quadtree node size), maximum binary tree size (MaxBTSize representing maximum allowed binary tree root node size), maximum binary tree depth (MaxBTDepth representing maximum allowed binary tree depth), and minimum binary tree size (MinBTSize representing minimum allowed binary tree node size).

The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, each of which may be partitioned according to a quadtree partition. That is, the nodes of the first level are leaf nodes (no child nodes) or have four child nodes. An example of QTBT structure 130 represents nodes that include a parent node and child nodes with solid branches. If the node of the first level is not greater than the maximum allowed binary tree root node size (MaxBTSize), the node may be further partitioned by a corresponding binary tree. The binary tree partitioning of a node may be iterated until the nodes generated by the partitioning reach a minimum allowed binary tree leaf node size (MinBTSize) or a maximum allowed binary tree depth (MaxBTDepth). An example of QTBT structure 130 represents such nodes as having dashed branches. Binary leaf nodes are referred to as Coding Units (CUs) that are used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without any further partitioning. As discussed above, a CU may also be referred to as a "video block" or "block.

In one example of a QTBT split structure, CTU size is set to 128×128 (luminance samples and two corresponding 64×64 chrominance samples), minQTSize is set to 16×16, maxBTSize is set to 64×64, minBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. The quadtree partitioning is first applied to CTUs to generate quadtree leaf nodes. The size of the quadtree nodes may range from 16×16 (i.e., minQTSize) to 128×128 (i.e., CTU size). If the quadtree node is 128 x 128, then the leaf quadtree node is not split further by the binary tree because it exceeds MaxBTSize (i.e., 64 x 64 in this example). Otherwise, the quadtree leaf nodes will be further partitioned by the binary tree. Thus, the quadtree leaf node is also the root node of the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. Having a binary tree node with a width equal to MinBTSize (4 in this example) means that no further vertical splitting (i.e., partitioning of the width) of the binary tree node is allowed. Similarly, having a binary tree node with a height equal to MinBTSize means that no further horizontal splitting (i.e., partitioning of the height) of the binary tree node is allowed. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to predictions and transforms without further segmentation.

Fig. 3 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. FIG. 3 is provided for purposes of illustration and should not be considered limiting of the techniques broadly illustrated and described in this disclosure. For purposes of illustration, this disclosure describes a video encoder 200 according to techniques of VVC (ITU-t h.266, being developed) and HEVC (ITU-t h.265). However, the techniques of this disclosure may be performed by video encoding devices configured to other video coding standards.

In the example of fig. 3, video encoder 200 includes video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, decoded Picture Buffer (DPB) 218, and entropy encoding unit 220. Any or all of video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy encoding unit 220 may be implemented in one or more processors or processing circuits. For example, the elements of video encoder 200 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Furthermore, video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

Video data memory 230 may store video data to be encoded by components of video encoder 200. Video encoder 200 may receive video data stored in video data store 230 from, for example, video source 104 (fig. 1). DPB 218 may serve as a reference picture memory that stores reference video data for predicting subsequent video data by video encoder 200. Video data memory 230 and DPB 218 may be formed from any of a variety of memory devices, such as Dynamic Random Access Memory (DRAM), including Synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 may be provided by the same memory device or separate memory devices. In various examples, as shown, video data memory 230 may be located on-chip with other components of video encoder 200, or off-chip with respect to those components.

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

The various units of fig. 3 are shown to aid in understanding the operations performed by video encoder 200. These units may be implemented as fixed function circuits, programmable circuits or a combination thereof. The fixed function circuit refers to a circuit that provides a specific function and presets an operation that can be performed. Programmable circuitry refers to circuitry that is programmable to perform various tasks and provide flexible functionality in the operations that can be performed. For example, the programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by instructions of the software or firmware. Fixed function circuitry may execute software instructions (e.g., receive parameters or output parameters) but the type of operation that fixed function circuitry performs is typically unchanged. In some examples, one or more of the units may be different circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be integrated circuits.

The video encoder 200 may include an Arithmetic Logic Unit (ALU), a basic function unit (EFU), digital circuitry, analog circuitry, and/or a programmable core formed from programmable circuitry. In examples where the operations of video encoder 200 are performed using software executed by programmable circuitry, memory 106 (fig. 1) may store instructions (e.g., object code) of the software received and executed by video encoder 200, or another memory (not shown) within video encoder 200 may store such instructions.

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

The mode selection unit 202 comprises a motion estimation unit 222, a motion compensation unit 224 and an intra prediction unit 226. The mode selection unit 202 may include additional functional units to perform video prediction according to other prediction modes. As an example, 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, and the like.

The mode selection unit 202 typically coordinates multiple encoding passes (pass) to test combinations of encoding parameters and resulting rate distortion values for such combinations. The coding parameters may include dividing the CTI into CUs, prediction modes of the CUs, transform types of residual data of the CUs, quantization parameters of residual data of the CUs, etc. Mode selection unit 202 may ultimately select a combination of coding parameters that has better rate-distortion values than other tested combinations.

Video encoder 200 may segment pictures retrieved from video data store 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 may partition CTUs of a picture according to a tree structure (e.g., QTBT structure of HEVC or quadtree structure described above). As described above, the video encoder 200 may form one or more CUs by dividing CTUs according to a tree structure. Such CUs may also be commonly referred to as "video blocks" or "blocks"

In general, mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or in HEVC, the overlapping portion of PU and TU). For inter prediction of the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218). Specifically, the motion estimation unit 222 may calculate a value representing the degree of similarity of the potential reference block to the current block, for example, from a Sum of Absolute Differences (SAD), a Sum of Squared Differences (SSD), a Mean Absolute Difference (MAD), a Mean Squared Difference (MSD), and the like. The motion estimation unit 222 may typically perform these calculations using sample-by-sample differences between the current block and the reference block being considered. The motion estimation unit 222 may identify the reference block having the lowest value from these calculations, which indicates the reference block that most closely matches the current block.

The motion estimation unit 222 may form one or more Motion Vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in a current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then generate a prediction block using the motion vector. For example, the 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, the motion compensation unit 224 may interpolate the value of the prediction block according to one or more interpolation filters. Furthermore, for bi-directional inter prediction, the motion compensation unit 224 may retrieve data of two reference blocks identified by respective motion vectors and combine the retrieved data, e.g. by sample-wise averaging or weighted averaging.

As another example, for intra prediction or intra prediction coding, intra prediction unit 226 may generate a prediction block from samples adjacent to the current block. For example, for directional modes, intra-prediction unit 226 may typically mathematically combine the values of neighboring samples and populate these calculated values in a defined direction across the current block to produce a predicted block. As another example, for the DC mode, the intra prediction unit 226 may calculate an average value of neighboring samples to the current block, and generate a prediction block to include the resultant average value of each sample of the prediction block.

The mode selection unit 202 supplies the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original, unencoded version of the current block from the video data store 230 and the prediction block from the mode selection unit 202. The residual generation unit 204 calculates a sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines the residual block of the current block. In some examples, residual generation unit 204 may also determine differences between sample values in the residual block to generate the residual block using Residual Differential Pulse Code Modulation (RDPCM). In some examples, residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

In examples where mode selection unit 202 partitions a CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. Video encoder 200 and video decoder 300 may support PUs having various sizes. As described above, the size of a CU may refer to the size of a 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 2n×2n or n×n PU sizes for intra prediction, as well as 2n×2n, 2n× N, N ×2N, N ×n or similar symmetric PU sizes for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2nxnu, 2nxnd, nl×2n, and nr×2n for inter prediction.

In examples where mode selection unit 202 does not further partition the CUs into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of a luma coding block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2nx2n, 2nxn, or nx2n.

For other video coding techniques, such as intra-block copy mode coding, affine mode coding, and Linear Model (LM) mode coding as some examples, mode selection unit 202 generates a prediction block for a block currently being coded via various units associated with the coding technique. In some examples, such as palette mode coding, mode selection unit 202 may not generate a prediction block, but rather generate syntax elements that indicate a manner of reconstructing a block based on the selected palette. In this mode, the mode selection unit 202 may provide these syntax elements to the entropy encoding unit 220 for encoding.

As described above, the residual generation unit 204 receives video data of the current block and the corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. In order to generate the residual block, the residual generation unit 204 calculates a sample-by-sample difference between the prediction block and the current block.

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

The quantization unit 208 may quantize the transform coefficients in the block of transform coefficients to generate a block of quantized transform coefficients. The quantization unit 208 may quantize transform coefficients of the block of transform coefficients according to a Quantization Parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce information loss and, therefore, the quantized transform coefficients may have lower accuracy than the original transform coefficients generated by the transform processing unit 206.

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

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

Video encoder 200 stores the reconstructed block in DPB 218. For example, in an example in which the operation of filtering unit 216 is not performed, reconstruction unit 214 may store the reconstructed block to DPB 218. In an example of performing the operation of filtering unit 216, filtering unit 216 may store the filtered reconstructed block to DPB 218. Motion estimation unit 222 and motion compensation unit 224 may retrieve a reference picture formed from the reconstructed (and potentially filtered) block from DPB 218 to inter-predict a block of a subsequently encoded picture. In addition, intra-prediction unit 226 may use reconstructed blocks in DPB 218 of the 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, the entropy encoding unit 220 may entropy encode the quantized transform coefficient block from the quantization unit 208. As another example, the entropy encoding unit 220 may entropy encode a prediction syntax element (e.g., motion information for inter prediction or intra mode information for intra prediction) from the mode selection unit 202. The entropy encoding unit 220 may perform one or more entropy encoding operations on syntax elements that are another example of video data to generate entropy encoded data. For example, the 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 coding operation, or another type of entropy coding operation for data. In some examples, entropy encoding unit 220 may operate in bypass mode where syntax elements are not entropy encoded.

The video encoder 200 may output a bitstream including entropy encoded syntax elements required to reconstruct blocks of slices or pictures. In particular, the entropy encoding unit 220 may output a bitstream.

The above operations are described with respect to blocks. Such description should be understood as the operation for a luma coding block and/or a chroma coding block. As described above, in some examples, the luma and chroma coding blocks are the luma and chroma components of the CU. In some examples, the luma and chroma coding blocks are luma and chroma components of the PU.

In some examples, for chroma coding blocks, the operations performed for luma coding blocks need not be repeated. As one example, in order to identify a Motion Vector (MV) and a reference picture of a chroma block, an operation for identifying a Motion Vector (MV) and a reference picture of a luma coding block need not be repeated. Instead, the MVs of the luma coding block may be scaled to determine the MVs of the chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for both luma and chroma coded blocks.

Video encoder 200 represents an example of a device configured to encode video data, comprising a memory configured to store video data, and one or more processing units implemented in circuitry and configured to predict symbols of residual data of color components of a block of video data based on a plurality of color components of the block of video data; and reconstruct the block of video data based on the predicted symbols.

Fig. 4 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Fig. 4 is provided for illustrative purposes and is not limiting of the techniques broadly illustrated and described in this disclosure. For purposes of illustration, this disclosure describes a video decoder 300 in accordance with techniques of VVC (ITU-t h.266, being developed) and HEVC (ITU-t h.265). However, the techniques of this disclosure may be performed by video coding devices configured to other video coding standards.

In the example of fig. 4, video decoder 300 includes Coded Picture Buffer (CPB) memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and Decoded Picture Buffer (DPB) 314. Any or all of CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or processing circuits. For example, the elements of video decoder 300 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

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

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

Additionally or alternatively, in some examples, video decoder 300 may retrieve decoded video data from memory 120 (fig. 1). That is, memory 120 may store data as discussed above with CPB memory 320. Likewise, when some or all of the functions of video decoder 300 are implemented in software that is executed by the processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

Various units shown in fig. 4 are shown to aid in understanding the operations performed by video decoder 300. These units may be implemented as fixed function circuits, programmable circuits or a combination thereof. Similar to fig. 3, the fixed function circuit refers to a circuit that provides a specific function and presets operations that can be performed. Programmable circuitry refers to circuitry that is programmable to perform various tasks and provide flexible functionality in the operations that can be performed. For example, the programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by instructions of the software or firmware. Fixed function circuitry may execute software instructions (e.g., receive parameters or output parameters) but the type of operation that fixed function circuitry performs is typically unchanged. In some examples, one or more of the units may be different circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be integrated circuits.

The video decoder 300 may include an ALU, an EFU, digital circuitry, analog circuitry, and/or a programmable core formed from programmable circuitry. In examples where the operations of video decoder 300 are performed by software executing on programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by video decoder 300.

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

In general, the video decoder 300 reconstructs pictures on a block-by-block basis. The video decoder 300 may perform a reconstruction operation on each block separately (where the block currently being reconstructed (i.e., decoded) may be referred to as a "current block").

The entropy decoding unit 302 may entropy decode syntax elements defining quantized transform coefficients of the quantized transform coefficient block and transform information such as Quantization Parameters (QPs) and/or transform mode indications. The inverse quantization unit 306 may determine a quantization degree using a QP associated with the quantized transform coefficient block and, as such, determine an inverse quantization degree for application by the inverse quantization unit 306. The inverse quantization unit 306 may perform, for example, a bit-wise left shift operation to inversely quantize the quantized transform coefficients. The inverse quantization unit 306 may thus form a transform coefficient block including the transform coefficients.

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

Further, the prediction processing unit 304 generates a prediction block from the prediction information syntax element entropy-decoded by the entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter predicted, the motion compensation unit 316 may generate the prediction block. In this case, the prediction information syntax element may indicate a reference picture in the DPB 314 from which the reference block is to be retrieved, and a motion vector identifying a position of the reference block in the reference picture relative to a position of the current block in the current picture. Motion compensation unit 316 may generally perform inter-prediction processing in a substantially similar manner as described with respect to motion compensation unit 224 (fig. 3).

As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate the prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, intra-prediction unit 318 may generally perform intra-prediction processing in a manner substantially similar to that described with respect to intra-prediction unit 226 (fig. 3). Intra-prediction unit 318 may retrieve data for neighboring samples of the current block from DPB 314.

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

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

Video decoder 300 may store the reconstructed block in DPB 314. For example, in an example in which the operation of the filtering unit 312 is not performed, the reconstruction unit 310 may store the reconstruction block to the DPB 314. In an example of performing the operation of filtering unit 312, filtering unit 312 may store the filtered reconstructed block to DPB 314. As described above, DPB 314 may provide reference information to prediction processing unit 304, such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation. Further, video decoder 300 may output decoded pictures (e.g., decoded video) from DPB 314 for subsequent presentation on a display device 118, such as fig. 1.

In this manner, video decoder 300 represents an example of a video decoding device that includes a memory configured to store video data, and one or more processing units implemented in circuitry and configured to predict symbols of residual data of color components of a block of video data based on a plurality of color components of the block of video data; and reconstruct the block of video data based on the predicted symbols.

Fig. 7 is a flowchart illustrating an example method for encoding a current block in accordance with the techniques of this disclosure. The current block may include the current CU. Although described with respect to video encoder 200 (fig. 1 and 3), it should be understood that other devices may be configured to perform a method similar to the method of fig. 7.

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

Fig. 8 is a flowchart illustrating an example method for decoding a current block of video data in accordance with the techniques of this disclosure. The current block may include the current CU. Although described with respect to video decoder 300 (fig. 1 and 4), it should be understood that other devices may be configured to perform a method similar to the method of fig. 8.

The video decoder 300 may receive entropy-encoded data of the current block, such as entropy-encoded prediction information and entropy-encoded data of transform coefficients of a residual block corresponding to the current block (370). The video decoder 300 may entropy-decode the entropy-encoded data to determine prediction information of the current block and reproduce transform coefficients of the residual block (372). The video decoder 300 may predict the current block, for example, using an intra or inter prediction mode indicated by prediction information of the current block, to calculate a predicted block of the current block (374). The video decoder 300 may then inverse scan the reproduced transform coefficients to create a block of quantized transform coefficients (376). The video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to generate a residual block (378). The video decoder 300 may finally decode the current block by combining the prediction block and the residual block (380).

Fig. 9 is a flowchart illustrating an example method of decoding a current block using symbol prediction based on multiple color components in accordance with the techniques of this disclosure. The current block may include a current transform block (TU). Although described with respect to video decoder 300 (fig. 1 and 4), it should be understood that other devices may be configured to perform a method similar to the method of fig. 9. For example, video encoder 200 (fig. 1 and 3) may be configured to perform a method similar to the method of fig. 9 (e.g., by inverse transform processing unit 212).

Video decoder 300 may predict a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR) (902). For example, the inverse transform processing unit 308 of the video decoder 300 may generate a plurality of hypothesis reconstructions, including a first hypothesis reconstruction with a positive sign and a second hypothesis reconstruction with a negative sign. The inverse transform processing unit 308 may evaluate the multiple hypothesis reconstructions using the cost function and select the symbol corresponding to the hypothesis reconstruction having the lowest cost value as the predicted symbol of the coefficient.

To predict a symbol using a cost function, the inverse transform processing unit 308 may determine a joint cost value for the plurality of color components. For example, since the prediction symbols of the coefficients of the joint residual block affect residual blocks (e.g., cb residual block and Cr residual block) of a plurality of color components generated based on the joint residual block, the inverse transform processing unit 308 may evaluate the cost of the plurality of color components. In some examples, the inverse transform processing unit 308 may determine the joint cost value by determining the joint cost value as a weighted sum of cost values of the plurality of color components. For example, the inverse transform processing unit 308 may determine the joint cost value by at least: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight. As a specific example, the inverse transform processing unit 308 may determine the joint cost value according to the following equation:

Wherein Cost is _joint Is the joint cost value, w _color Is the weight of a specific color component among the plurality of color components, S represents a set including the plurality of color components, and Cost _color Is the cost value of that particular color component.

As discussed above, the inverse transform processing unit 308 may determine weights (e.g., w _color ). For example, the inverse transform processing unit 308 may determine a first weight of a first color component (e.g., cb) and determine a second weight of a second color component (e.g., cr). In some examples, the inverse transform processing unit 308 may determine the weights based on which of a plurality of color components including Cb color components and Cr color components has a non-zero Coded Block Flag (CBF) earlier in the scan order. As one example, where Cb color components are scanned in scan order before Cr color components, the inverse transform processing unit 308 may determine that the first weight is 1 and the second weight is 0 in response to determining that the Cb color components have a non-zero CBF. As another example, in the case where Cb color components are scanned before Cr color components in scan order, the inverse transform processing unit 308 may determine that the first weight is 0 and the second weight is 1 in response to determining that the Cb color components have zero CBF and the Cr color components have non-zero CBF. As yet another example, in response to determining that the Cb color component has a non-zero CBF, the inverse transform processing unit 308 may determine that the first weight is 1, and in response to determining that the Cr color component has a non-zero CBF, the inverse transform processing unit 308 may determine that the second weight is 1.

As discussed above, the inverse transform processing unit 308 may determine a plurality of joint cost values (e.g., a plurality of hypotheses) to predict the sign of the coefficients of the joint residual block. For example, the inverse transform processing unit 308 may determine a first joint cost value for the plurality of color components for a negative sign (e.g., perform reconstruction if the sign is negative); and determining a second joint cost value for the plurality of color components for the positive symbol (e.g., performing reconstruction if the symbol is positive). As described above, to determine the cost value, the inverse transform processing unit 308 may select the symbol corresponding to the most favorable (e.g., lowest) joint cost value. As one example, in response to determining that the first joint cost value (e.g., the joint cost value for a negative sign) is less than the second joint cost value (e.g., the joint cost value for a positive sign), the inverse transform processing unit 308 may predict the sign to be negative. As another example, in response to determining that the second joint cost value is less than the first joint cost value, the inverse transform processing unit 308 may predict that the sign is positive.

Although described above as being performed for a single coefficient of the plurality of coefficients of the joint residual block, in some examples, the inverse transform processing unit 308 may perform a similar process to predict the sign of other coefficients of the plurality of coefficients of the joint residual block. By predicting one or more symbols based on multiple color components, the techniques of this disclosure may enable more efficient signaling of video data. In particular, more accurate symbol predictions that may be produced by the techniques of this disclosure may reduce the number of symbols that need to be signaled in the bitstream.

The inverse transform processing unit 308 may generate coefficients of a respective residual block of the plurality of residual blocks for each respective color component of the plurality of color components and based on the plurality of coefficients of the joint residual block (904). For example, the inverse transform processing unit 308 may generate a Cb residual block and a Cr residual block according to one of three sub-modes supported by VVC. The inverse transform processing unit 308 may derive a sub-mode index from a combination of CBF values of the chroma components. If cbf_cb= 1 and cbf_cr= 0, the sub-mode index is 1. If cbf_cb= 1 and cbf_cr= 1, the sub-mode index is 2. Otherwise (cbf_cb= 0 and cbf_cr= 1), the sub-mode index is 3. The following table shows how the inverse transformed joint coefficient block (resJointC) is converted to Cb and Cr pixel residuals (resCb and resCr).

The inverse transform processing unit 308 may derive the value of CSign from the ph_joint_cbcr_sign_flag in the picture header:

CSign＝1–2*ph_joint_cbcr_sign_flag

the inverse transform processing unit 308 may reconstruct the block of video data based on the plurality of residual blocks (906). For example, similar to operation 380 of fig. 8, the reconstruction unit 310 may combine the respective reconstructed prediction blocks of the color components with their respective residual blocks. For example, reconstruction unit 310 may add the value of the Cb residual block to the value of the Cb prediction block (e.g., generated by prediction processing unit 304) to generate a reconstructed Cb block and add the value of the Cr residual block to the value of the Cr prediction block (e.g., generated by prediction processing unit 304) to generate a reconstructed Cr block.

The following numbered clauses may illustrate one or more aspects of the present disclosure:

clause 1A. A method of decoding video data, the method comprising: predicting a sign of residual data of the color components of the block of video data based on the plurality of color components of the block of video data; and reconstructing the block of video data based on the predicted symbols.

Clause 2A the method of clause 1A, wherein predicting the symbol comprises: symbols of a plurality of color components of a block of video data are jointly predicted.

Clause 3A the method of clause 2A, wherein the joint prediction symbol comprises: determining a joint cost value for the plurality of color components; and predicting the sign of the plurality of color components based on the determined joint cost value.

Clause 4A the method according to clause 3A, wherein determining the joint cost value comprises determining the joint cost value according to the following equation:

wherein Cost is _joint Is the joint cost value, w _color Is the weight of a specific color component among the plurality of color components, S represents a set including the plurality of color components, and Cost _color Is the cost value of a particular color component.

Clause 5A. The method according to any of clauses 1A to 4A, wherein decoding comprises decoding.

Clause 6A the method of any of clauses 1A to 5A, wherein decoding comprises encoding.

Clause 7A an apparatus for decoding video data, the apparatus comprising one or more components for performing the method of any of clauses 1A-6A.

Clause 8A the device of clause 7A, wherein the one or more components comprise one or more processors implemented in circuitry.

Clause 9A the apparatus according to any of clauses 6A and 8A, further comprising a memory for storing video data.

Clause 10A the device according to any of clauses 6A to 9A, further comprising a display configured to display the decoded video data.

Clause 11A the device according to any of clauses 6A to 10A, 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 12A the device according to any of clauses 6A to 11A, wherein the device comprises a video decoder.

Clause 13A the device according to any of clauses 6A to 12A, wherein the device comprises a video encoder.

Clause 14A computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform the method of any of clauses 1A-6A.

Clause 1B a method of decoding video data, the method comprising: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 2B the method of clause 1B, wherein predicting the symbol comprises: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 3B the method of clause 2B, wherein determining the joint cost value comprises determining the joint cost value as a weighted sum of cost values of the plurality of color components.

Clause 4B the method according to clause 3B, wherein determining the joint cost value as a weighted sum of the cost values of the plurality of color components comprises determining the joint cost value according to the following equation:

Clause 5B the method according to clause 3B, further comprising: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

Clause 6B the method of clause 5B, wherein determining the first weight and the second weight comprises: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 7B the method of clause 6B, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 8B the method of clause 7B, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 9B the method of clause 7B, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 10B the method according to clause 7B, further comprising: in response to determining that the Cb color component has a non-zero CBF, determining that the first weight is 1; and in response to determining that the Cr color component has a non-zero CBF, determining that the second weight is 1.

Clause 11B the method of clause 2B, wherein determining the joint cost value for the plurality of color components comprises: determining a first joint cost value for the plurality of color components for the negative sign; and determining a second combined codebook value for the plurality of color components for the positive symbol, wherein the sign of the prediction residual data comprises: responsive to determining that the first joint cost value is less than the second joint cost value, the predicted sign is negative; and in response to determining that the second joint cost value is less than the first joint cost value, the predicted symbol is positive.

Clause 12B. A method of encoding video data, the method comprising: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 13B the method of clause 12B, wherein predicting the symbol comprises: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 14B the method of clause 13B, wherein determining the joint cost value comprises determining the joint cost value as a weighted sum of cost values for the plurality of color components.

Clause 15B the method of clause 14B, wherein determining the joint cost value as a weighted sum of the cost values of the plurality of color components comprises determining the joint cost value according to the following equation:

Clause 16B the method of clause 14B, further comprising: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

Clause 17B the method of clause 16B, wherein determining the first weight and the second weight comprises: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 18B the method of clause 17B, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 19B the method of clause 18B, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 20B the method of clause 18B, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 21B the method of clause 18B, further comprising: in response to determining that the Cb color component has a non-zero CBF, determining that the first weight is 1; and in response to determining that the Cr color component has a non-zero CBF, determining that the second weight is 1.

Clause 22B the method of clause 13B, wherein determining the joint cost value for the plurality of color components comprises: determining a first joint cost value for the plurality of color components for the negative sign; and determining a second combined codebook value for the plurality of color components for the positive symbol, wherein the sign of the prediction residual data comprises: responsive to determining that the first joint cost value is less than the second joint cost value, the predicted sign is negative; and in response to determining that the second joint cost value is less than the first joint cost value, the predicted symbol is positive.

Clause 23B an apparatus for decoding video data, the apparatus comprising: a memory configured to store video data; and one or more processors implemented in the circuitry and configured to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 24B the device of clause 23B, wherein, to predict the symbol, the one or more processors are configured to: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 25B the device of clause 24B, wherein, to determine the joint cost value, the one or more processors are configured to determine the joint cost value as a weighted sum of the cost values of the plurality of color components.

Clause 26B the device of clause 25B, wherein the one or more processors are further configured to: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

Clause 27B, the device of clause 26B, wherein, to determine the first weight and the second weight, the one or more processors are configured to: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 28B the device of clause 27B, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 29B the device of clause 28B, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 30B the device of clause 28B, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 31B an apparatus for encoding video data, the apparatus comprising: a memory configured to store video data; and one or more processors implemented in the circuitry and configured to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 32B the device of clause 31B, wherein, to predict the symbol, the one or more processors are configured to: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 33B the device of clause 32B, wherein, to determine the joint cost value, the one or more processors are configured to determine the joint cost value as a weighted sum of the cost values of the plurality of color components.

Clause 34B the device of clause 33B, wherein the one or more processors are further configured to: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

The apparatus of clause 35B, wherein, to determine the first weight and the second weight, the one or more processors are configured to: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 36B the device of clause 35B, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 37B the device of clause 36B, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 38B the device of clause 36B, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 39B an apparatus for decoding video data, the apparatus comprising: means for predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); means for generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and means for reconstructing the block of video data based on the plurality of residual blocks.

Clause 40B, a computer-readable storage medium storing instructions that, when executed, cause one or more processors of a video decoder to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 1C a method of decoding video data, the method comprising: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 2C the method of clause 1C, wherein predicting the symbol comprises: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 3C the method of clause 2C, wherein determining the joint cost value comprises determining the joint cost value as a weighted sum of cost values of the plurality of color components.

Clause 4C the method of clause 3C, wherein determining the joint cost value as a weighted sum of the cost values of the plurality of color components comprises determining the joint cost value according to the following equation:

Clause 5C the method according to clause 3C or 4C, further comprising: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

Clause 6C the method of clause 5C, wherein determining the first weight and the second weight comprises: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 7C the method of clause 6C, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 8C the method of clause 7C, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 9C the method of clause 7C or 8C, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 10C the method of clause 7C, further comprising: in response to determining that the Cb color component has a non-zero CBF, determining that the first weight is 1; and in response to determining that the Cr color component has a non-zero CBF, determining that the second weight is 1.

Clause 11C the method of any of clauses 2C to 10C, wherein determining the joint cost value for the plurality of color components comprises: determining a first joint cost value for the plurality of color components for the negative sign; and determining a second combined codebook value for the plurality of color components for the positive symbol, wherein the sign of the prediction residual data comprises: responsive to determining that the first joint cost value is less than the second joint cost value, the predicted sign is negative; and in response to determining that the second joint cost value is less than the first joint cost value, the predicted symbol is positive.

Clause 12C a method of encoding video data, the method comprising: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 13C the method of clause 12C, wherein predicting the symbol comprises: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 14C the method of clause 13C, wherein determining the joint cost value comprises determining the joint cost value as a weighted sum of cost values of the plurality of color components.

Clause 15C the method of clause 14C, wherein determining the joint cost value as a weighted sum of the cost values of the plurality of color components comprises determining the joint cost value according to the following equation:

Clause 16C the method of clause 14C or 15C, further comprising: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

Clause 17C the method of clause 16C, wherein determining the first weight and the second weight comprises: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 18C the method of clause 17C, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 19C the method of clause 18C, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 20C the method of clause 18C or 19C, wherein the Cb color component is scanned before the Cr color component in scan order, the method further comprising: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 21C the method of clause 18C, further comprising: in response to determining that the Cb color component has a non-zero CBF, determining that the first weight is 1; and in response to determining that the Cr color component has a non-zero CBF, determining that the second weight is 1.

The method of clause 22C, according to any of clauses 13C to 21C, wherein determining the joint cost value for the plurality of color components comprises: determining a first joint cost value for the plurality of color components for the negative sign; and determining a second combined codebook value for the plurality of color components for the positive symbol, wherein the sign of the prediction residual data comprises: responsive to determining that the first joint cost value is less than the second joint cost value, the predicted sign is negative; and in response to determining that the second joint cost value is less than the first joint cost value, the predicted symbol is positive.

Clause 23C an apparatus for decoding video data, the apparatus comprising: a memory configured to store video data; and one or more processors implemented in the circuitry and configured to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 24C the device of clause 23C, wherein, to predict the symbol, the one or more processors are configured to: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 25C the device of clause 24C, wherein, to determine the joint cost value, the one or more processors are configured to determine the joint cost value as a weighted sum of the cost values of the plurality of color components.

Clause 26C the device of clause 25C, wherein the one or more processors are further configured to: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

Clause 27C the device of clause 26C, wherein, to determine the first weight and the second weight, the one or more processors are configured to: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 28C the device of clause 27C, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 29C the device of clause 28C, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 30C, the device of clause 28, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 31C an apparatus for encoding video data, the apparatus comprising: a memory configured to store video data; and one or more processors implemented in the circuitry and configured to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

Clause 32C the device of clause 31C, wherein, to predict the symbol, the one or more processors are configured to: determining a joint cost value for the plurality of color components; and predicting the sign based on the joint cost value.

Clause 33C the device of clause 32C, wherein, to determine the joint cost value, the one or more processors are configured to determine the joint cost value as a weighted sum of the cost values of the plurality of color components.

Clause 34C the device of clause 33C, wherein the one or more processors are further configured to: determining a first weight for a first color component of the plurality of color components; determining a second weight for a second color component of the plurality of color components; and determining a weighted sum of cost values for the plurality of color components based on the first weight and the second weight.

The apparatus of clause 35C, wherein, to determine the first weight and the second weight, the one or more processors are configured to: the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in the scan order.

Clause 36C the device of clause 35C, wherein the first color component is a Cb color component and the second color component is a Cr color component.

Clause 37C the device of clause 36C, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

Clause 38C the device of clause 36C, wherein the Cb color component is scanned before the Cr color component in scan order, and wherein the one or more processors are further configured to: in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

Clause 39C an apparatus for decoding video data, the apparatus comprising: means for predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); means for generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and means for reconstructing the block of video data based on the plurality of residual blocks.

Clause 40C, a computer-readable storage medium storing instructions that, when executed, cause one or more processors of a video decoder to: predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of the block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR); generating, for each respective color component of the plurality of color components, and based on the plurality of coefficients of the joint residual block, coefficients of the respective residual block of the plurality of residual blocks; and reconstructing a block of video data based on the plurality of residual blocks.

It should be appreciated that, depending on the example, certain acts or events of any of the techniques described herein can be performed in a different order, may be added, combined, or eliminated entirely (e.g., not all of the described acts or events are necessary for the practice of the techniques). Further, in some examples, actions or events may be performed in parallel, such as by 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. The computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium (e.g., a data storage medium), or a communication medium 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, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementing the techniques described in this disclosure. The computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Further, any connection is properly termed a computer-readable medium. For example, if the instructions are sent 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.

The 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. Thus, the terms "processor" and "processing circuitry" as used herein may refer to any one of the foregoing structures or any other structure suitable for implementation of the techniques described herein. Furthermore, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated into a combined decoder. Furthermore, the techniques may be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a variety of devices or apparatuses including a wireless handset, an Integrated Circuit (IC), or a collection of ICs, e.g., a collection of chips. 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, the various units may be combined in a decoder hardware unit or provided by a collection of interoperable hardware units (including one or more processors as described above) along with appropriate software and/or firmware.

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

Claims

1. A method of decoding video data, the method comprising:

predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data coded using chroma residual joint coding (JCCR) based on a plurality of color components of the block;

generating coefficients of a respective residual block of a plurality of residual blocks for each respective color component of the plurality of color components and based on the plurality of coefficients of the joint residual block; and

reconstructing the block of video data based on the plurality of residual blocks.

2. The method of claim 1, wherein predicting the symbol comprises:

determining a joint cost value for the plurality of color components; and

the symbol is predicted based on the joint cost value.

3. The method of claim 2, wherein determining the joint cost value comprises determining the joint cost value as a weighted sum of cost values of the plurality of color components.

4. A method according to claim 3, wherein determining the joint cost value as a weighted sum of cost values of the plurality of color components comprises determining the joint cost value according to the following equation:

Wherein Cost is _joint Is the joint cost value, w _color Is the weight of a specific color component of the plurality of color components, S represents a set including the plurality of color components, and Cost _color Is the cost value of the particular color component.

5. A method according to claim 3, further comprising:

determining a first weight for a first color component of the plurality of color components;

determining a second weight for a second color component of the plurality of color components; and

the weighted sum of cost values for the plurality of color components is determined based on the first weight and the second weight.

6. The method of claim 5, wherein determining the first weight and the second weight comprises:

the first weight and the second weight are determined based on which of the plurality of color components has a non-zero Coded Block Flag (CBF) earlier in a scan order.

7. The method of claim 6, wherein the first color component is a Cb color component and the second color component is a Cr color component.

8. The method of claim 7, wherein the Cb color component is scanned before the Cr color component in the scan order, the method further comprising:

In response to determining that the Cb color component has a non-zero CBF, the first weight is determined to be 1 and the second weight is determined to be 0.

9. The method of claim 7, wherein the Cb color component is scanned before the Cr color component in the scan order, the method further comprising:

in response to determining that the Cb color component has zero CBF and the Cr color component has non-zero CBF, the first weight is determined to be 0 and the second weight is determined to be 1.

10. The method of claim 7, further comprising:

in response to determining that the Cb color component has a non-zero CBF, determining that the first weight is 1; and

in response to determining that the Cr color component has a non-zero CBF, the second weight is determined to be 1.

11. The method of claim 2, wherein determining the joint cost value for the plurality of color components comprises:

determining a first joint cost value for the plurality of color components for a negative sign; and

determining a second combined codebook value for the plurality of color components for a positive symbol, wherein predicting the symbol of the residual data comprises:

in response to determining that the first joint cost value is less than the second joint cost value, predicting that the sign is negative; and

In response to determining that the second joint cost value is less than the first joint cost value, the sign is predicted to be positive.

12. A method of encoding video data, the method comprising:

13. The method of claim 12, wherein predicting the symbol comprises:

determining a joint cost value for the plurality of color components; and

the symbol is predicted based on the joint cost value.

14. The method of claim 13, wherein determining the joint cost value comprises determining the joint cost value as a weighted sum of cost values of the plurality of color components.

15. The method of claim 14, wherein determining the joint cost value as a weighted sum of cost values of the plurality of color components comprises determining the joint cost value according to the following equation:

16. The method of claim 14, further comprising:

17. The method of claim 16, wherein determining the first weight and the second weight comprises:

18. The method of claim 17, wherein the first color component is a Cb color component and the second color component is a Cr color component.

19. The method of claim 18, wherein the Cb color component is scanned before the Cr color component in the scan order, the method further comprising:

20. The method of claim 18, wherein the Cb color component is scanned before the Cr color component in the scan order, the method further comprising:

21. The method of claim 18, further comprising:

22. The method of claim 13, wherein determining the joint cost value for the plurality of color components comprises:

23. An apparatus for decoding video data, the apparatus comprising:

a memory configured to store video data; and

one or more processors implemented in circuitry and configured to:

24. The device of claim 23, wherein to predict the symbol, the one or more processors are configured to:

determining a joint cost value for the plurality of color components; and

the symbol is predicted based on the joint cost value.

25. The device of claim 24, wherein to determine the joint cost value, the one or more processors are configured to determine the joint cost value as a weighted sum of cost values of the plurality of color components.

26. The device of claim 25, wherein the one or more processors are further configured to:

a weighted sum of cost values for the plurality of color components is determined based on the first weight and the second weight.

27. The device of claim 26, wherein to determine the first weight and the second weight, the one or more processors are configured to:

28. The device of claim 27, wherein the first color component is a Cb color component and the second color component is a Cr color component.

29. The device of claim 28, wherein the Cb color component is scanned before the Cr color component in the scan order, and wherein the one or more processors are further configured to:

30. The device of claim 28, wherein the Cb color component is scanned before the Cr color component in the scan order, and wherein the one or more processors are further configured to:

31. An apparatus for encoding video data, the apparatus comprising:

a memory configured to store video data; and

one or more processors implemented in circuitry and configured to:

32. The device of claim 31, wherein to predict the symbol, the one or more processors are configured to:

Determining a joint cost value for the plurality of color components; and

the symbol is predicted based on the joint cost value.

33. The device of claim 32, wherein to determine the joint cost value, the one or more processors are configured to determine the joint cost value as a weighted sum of cost values of the plurality of color components.

34. The device of claim 33, wherein the one or more processors are further configured to:

35. The device of claim 34, wherein to determine the first weight and the second weight, the one or more processors are configured to:

36. The device of claim 35, wherein the first color component is a Cb color component and the second color component is a Cr color component.

37. The device of claim 36, wherein the Cb color component is scanned before the Cr color component in the scan order, and wherein the one or more processors are further configured to:

38. The device of claim 36, wherein the Cb color component is scanned before the Cr color component in the scan order, and wherein the one or more processors are further configured to:

39. An apparatus for coding video data, the apparatus comprising:

means for predicting a sign of a coefficient of a plurality of coefficients of a joint residual block of a block of video data based on a plurality of color components of the block of video data coded using chroma residual joint coding (JCCR);

means for generating coefficients of a respective one of a plurality of residual blocks for each respective one of the plurality of color components and based on the plurality of coefficients of the joint residual block; and

Means for reconstructing the block of video data based on the plurality of residual blocks.

40. A computer-readable storage medium storing instructions that, when executed, cause one or more processors of a video coder to: