Combined residual decoding in video decoding

Abstract

A device for decoding video data includes a processor, which is configured to: generate an inter-frame prediction block and an intra-frame prediction block of a current block of video data; for each sample of the prediction block to be generated: determine a first weight of the sample according to the position of the sample in the prediction block; determine a second weight of the sample according to the position of the sample in the prediction block; apply the first weight to the sample at the position in the inter-frame prediction block to generate a weighted inter-frame prediction sample; apply the second weight to the sample at the position in the intra-frame prediction block to generate a weighted intra-frame prediction sample; and calculate a value of the sample at the position in the prediction block using the weighted inter-frame prediction sample and the weighted intra-frame prediction sample; and decode the current block using the prediction block.

Description

[0001] This application claims the benefit of U.S. Patent Application No. 16 / 810,680, filed on March 5, 2020, U.S. Provisional Patent Application No. 62 / 815,936, filed on March 8, 2019, and U.S. Provisional Patent Application No. 62 / 866,450, filed on June 25, 2019, each of which is incorporated by reference in its entirety. Technical Field

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

[0003] Digital video capabilities may be incorporated into a variety of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones, so-called "smart phones", video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10 Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions of such standards. By implementing such video coding techniques, video devices may more efficiently send, receive, encode, decode, and / or store digital video information.

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction of reference samples in neighboring blocks in the same picture or temporal prediction of reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the invention

[0005] In general, the present disclosure describes techniques for combined residual coding in video coding. As described herein, a video encoder and a video decoder may perform combined residual coding to encode and decode a block of video data. To perform combined residual coding, a video encoder may apply a first residual modification function to the Cb residual data of a block, and apply a second residual modification function to the Cr residual data of a block. The first residual modification function modifies the Cb residual data of a block based on both the original Cb residual data of the block and the Cr residual data of the block. Similarly, the second residual modification function modifies the Cr residual data of a block based on both the original Cr residual data of the block and the Cb residual data of the block. The video decoder applies an inverse residual modification function to the decoded Cb and Cr residual data of the block. By applying the residual modification function, the video encoder may be able to represent the Cb and Cr chrominance residual data using lower values. Lower values ​​can typically be encoded using fewer bits. Therefore, applying the residual modification function may result in higher coding efficiency (e.g., greater compression).

[0006] In one example, the present disclosure describes a method for decoding video data, the method comprising: generating first decoded modified chroma residual data by converting a first set of transform coefficients of a block of the video data from a transform domain to a sample domain by applying an inverse transform; generating second decoded modified chroma residual data by converting a second set of transform coefficients of the block from the transform domain to the sample domain by applying the inverse transform; after generating the first decoded modified chroma residual data, applying a first inverse residual modification function to the first decoded modified chroma residual data to generate first inverse modified chroma residual data; after generating the second decoded modified chroma residual data, applying a second inverse residual modification function to the second decoded modified chroma residual data to generate second inverse modified chroma residual data, wherein the first decoded modified chroma residual data is associated with a first chroma component and the second decoded modified chroma residual data is associated with a second chroma component; and reconstructing the block of the video data based on the first inverse modified chroma residual data and the second inverse modified chroma residual data.

[0007] In another example, the present disclosure describes a method of encoding video data, the method comprising: applying a first residue modification function to first chroma residual data of a block of the video data to produce first modified chroma residual data; encoding the first modified chroma residual data, wherein encoding the first modified chroma residual data comprises, after applying the first residue modification function to the first chroma residual data, applying a forward transform to the first modified chroma residual data to convert the first modified chroma residual data from a sample domain to a transform domain; applying a second residue modification function to the first chroma residual data to generate first modified chroma residual data; encoding the first modified chroma residual data to generate first modified chroma residual data; wherein encoding the first modified chroma residual data comprises applying a forward transform to the first modified chroma residual data to convert the first modified chroma residual data from a sample domain to a transform domain; The modification function is applied to second chroma residual data of the block to produce second modified chroma residual data; and the second modified chroma residual data is encoded, wherein: the first chroma residual data is associated with the first chroma component, and the second chroma residual data is associated with the second chroma component, and encoding the second modified chroma residual data includes, after applying the second residual modification function to the second chroma residual data, applying the forward transform to the second modified chroma residual data to convert the second modified chroma residual data from the sample domain to the transform domain.

[0008] In another example, the present disclosure describes a device for decoding video data, the device comprising: a memory for storing the video data; and one or more processors implemented in a circuit, the one or more processors being configured to: generate first decoded modified chroma residual data by converting a first set of transform coefficients of a block of the video data from a transform domain to a sample domain by applying an inverse transform; generate second decoded modified chroma residual data by converting a second set of transform coefficients of the block from the transform domain to the sample domain by applying the inverse transform; and after generating the first decoded modified chroma residual data, converting a second set of transform coefficients of the block from the transform domain to the sample domain. An inverse residual modification function is applied to the first decoded modified chroma residual data to produce first inverse modified chroma residual data; after producing the second decoded modified chroma residual data, a second inverse residual modification function is applied to the second decoded modified chroma residual data to produce second inverse modified chroma residual data, wherein the first decoded modified chroma residual data is associated with a first chroma component and the second decoded modified chroma residual data is associated with a second chroma component; and blocks of the video data are reconstructed based on the first inverse modified chroma residual data and the second inverse modified chroma residual data.

[0009] In another example, the present disclosure describes a device for encoding video data, the device comprising: a memory for storing the video data; and one or more processors implemented in a circuit, the one or more processors being configured to: apply a first residual modification function to first chroma residual data of a block of the video data to generate first modified chroma residual data; and encode the first modified chroma residual data, wherein the one or more processors are configured such that as part of encoding the first modified chroma residual data, the one or more processors apply a forward transform to the first modified chroma residual data after applying the first residual modification function to the first chroma residual data to encode the first modified chroma residual data. A method of encoding the second modified chroma residual data is provided in accordance with the present invention. The method comprises: converting modified chroma residual data from a sample domain to a transform domain; applying a second residual modification function to the second chroma residual data of the block to produce second modified chroma residual data; and encoding the second modified chroma residual data, wherein: the first chroma residual data is associated with a first chroma component, and the second chroma residual data is associated with a second chroma component, and the one or more processors are configured such that as part of encoding the second modified chroma residual data, the one or more processors apply the forward transform to the second modified chroma residual data after applying the second residual modification function to the second chroma residual data to convert the second modified chroma residual data from the sample domain to the transform domain.

[0010] In another example, the present disclosure describes an apparatus for decoding video data, the apparatus comprising: means for converting a first set of transform coefficients of a block of the video data from a transform domain to a sample domain by applying an inverse transform to generate first decoded modified chroma residual data; means for converting a second set of transform coefficients of the block from the transform domain to the sample domain by applying the inverse transform to generate second decoded modified chroma residual data; means for applying a first inverse residual modification function to the first decoded modified chroma residual data after generating the first decoded modified chroma residual data; The invention relates to a method for reconstructing a block of the video data based on the first inverse modified chroma residual data and the second inverse modified chroma residual data, wherein the first decoded modified chroma residual data is associated with a first chroma component and the second decoded modified chroma residual data is associated with a second chroma component; and a method for reconstructing a block of the video data based on the first inverse modified chroma residual data and the second inverse modified chroma residual data.

[0011] In another example, the present disclosure describes an apparatus for encoding video data, the apparatus comprising: means for applying a first residual modification function to first chroma residual data of a block of the video data to produce first modified chroma residual data; means for encoding the first modified chroma residual data, wherein encoding the first modified chroma residual data comprises means for applying a forward transform to the first modified chroma residual data after applying the first residual modification function to the first chroma residual data to convert the first modified chroma residual data from a sample domain to a transform domain; means for applying a second residual modification function to the first modified chroma residual data to convert the first modified chroma residual data from a sample domain to a transform domain A component for applying a difference modification function to second chroma residual data of the block to produce second modified chroma residual data; and a component for encoding the second modified chroma residual data, wherein: the first chroma residual data is associated with a first chroma component, and the second chroma residual data is associated with a second chroma component, and the component for encoding the second modified chroma residual data includes a component for applying the forward transform to the second modified chroma residual data after applying the second residual modification function to the second chroma residual data to convert the second modified chroma residual data from the sample domain to the transform domain.

[0012] In another example, the present disclosure describes a computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to: generate first decoded modified chroma residual data by converting a first set of transform coefficients of a block of video data from a transform domain to a sample domain by applying an inverse transform; generate second decoded modified chroma residual data by converting a second set of transform coefficients of the block from the transform domain to the sample domain by applying the inverse transform; and, after generating the first decoded modified chroma residual data, apply a first inverse residual modification function to the first decoded modified chroma residual data. to generate first inverse modified chroma residual data; after generating the second decoded modified chroma residual data, applying a second inverse residual modification function to the second decoded modified chroma residual data to generate second inverse modified chroma residual data, wherein the first decoded modified chroma residual data is associated with a first chroma component and the second decoded modified chroma residual data is associated with a second chroma component; and reconstructing a block of the video data based on the first inverse modified chroma residual data and the second inverse modified chroma residual data.

[0013] In another example, the present disclosure describes a computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to: apply a first residual modification function to first chroma residual data of a block of video data to produce first modified chroma residual data; encode the first modified chroma residual data, wherein as part of causing the one or more processors to encode the first modified chroma residual data, execution of the instructions causes the one or more processors to apply a forward transform to the first modified chroma residual data after applying the first residual modification function to the first chroma residual data to convert the first modified chroma residual data from a sample domain to a variable domain; The instructions include the step of applying a second residual modification function to second chroma residual data of the block to generate second modified chroma residual data; and encoding the second modified chroma residual data, wherein: the first chroma residual data is associated with a first chroma component, and the second chroma residual data is associated with a second chroma component, and as part of causing the one or more processors to encode the second modified chroma residual data, execution of the instructions causes the one or more processors to apply the forward transform to the second modified chroma residual data after applying the second residual modification function to the second chroma residual data to convert the second modified chroma residual data from the sample domain to the transform domain.

[0014] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram illustrating an exemplary video encoding and decoding system that may perform the techniques of this disclosure.

[0016] Figure 2 is a block diagram illustrating an example of intra-slice reconstruction using an in-loop luminance reshaper.

[0017] Figure 3 is a block diagram illustrating an example of inter-slice reconstruction using an in-loop brightness reshaper.

[0018] Figure 4 is a block diagram illustrating an example of intra-mode and inter-mode reconstruction with chroma residual scaling.

[0019] Figure 5A and 5B is a conceptual diagram illustrating an exemplary quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0020] Figure 6 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0021] Figure 7 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0022] Figure 8 is a flow chart illustrating an exemplary method for encoding a current block.

[0023] Fig. 9 is a flow chart illustrating an exemplary method for decoding a current block of video data.

[0024] Fig.10 is a flowchart illustrating example operation of a video encoder in accordance with one or more techniques of this disclosure.

[0025] Fig.11 is a flowchart illustrating example operation of a video decoder in accordance with one or more techniques of this disclosure. DETAILED DESCRIPTION

[0026] Video data is usually represented in the YCbCr color space. That is, each pixel of the image can be represented by a luma Y component and two chroma components (Cb and Cr). Representing video data in the YCbCr color space can reduce the redundancy inherent in the red, green, and blue (RGB) color space. However, there can be a significant correlation between the Cb value and the Cr value. Reducing this correlation can achieve better decoding efficiency.

[0027] The present disclosure describes techniques that can reduce cross-component correlation, which can improve coding efficiency. As described herein, a video encoder can apply a residual modification function (RMF) to residual chroma data. A video decoder can apply an inverse RMF to the decoded residual chroma data. The inverse RMF can at least partially reverse the effect of the RMF applied by the video encoder. As described herein, the RMF applied to the residual chroma data of a chroma component can use the residual chroma data of the chroma component and other chroma components. Therefore, two sets of modified chroma residual data are still encoded for different chroma components of a single block, but the video encoder modifies the chroma residual data of the chroma component according to each other. Applying such an RMF can improve coding efficiency. For example, applying such an RMF can reduce the number of bits required to encode video data because applying such an RMF can reduce the value of the chroma residual data.

[0028] In one example, the video encoder may apply a first residual modification function to first chroma residual data of a block of the video data to generate first modified chroma residual data. The video encoder may also encode the first modified chroma residual data. As part of encoding the first modified chroma residual data, the video encoder may apply a forward transform to the first modified chroma residual data after applying the first residual modification function to the first chroma residual data to convert the first modified chroma residual data from a sample domain to a transform domain. In addition, the video encoder may apply a second residual modification function to second chroma residual data of the block to generate second modified chroma residual data. The video encoder may also encode the second modified chroma residual data. The first chroma residual data is associated with a first chroma component, and the second chroma residual data is associated with a second chroma component. As part of encoding the second modified chroma residual data, the video encoder may apply the forward transform to the second modified chroma residual data after applying the second residual modification function to the second chroma residual data to convert the second modified chroma residual data from the sample domain to the transform domain.

[0029] Similarly, the video decoder may generate first decoded modified chroma residual data by converting a first set of transform coefficients of the block of video data from the transform domain to the sample domain by applying an inverse transform. In addition, the video decoder may generate second decoded modified chroma residual data by converting a second set of transform coefficients of the block from the transform domain to the sample domain by applying the inverse transform. After generating the first decoded modified chroma residual data, the video decoder may apply a first inverse residual modification function to the first decoded modified chroma residual data to generate first inverse modified chroma residual data. After generating the second decoded modified chroma residual data, the video decoder may apply a second inverse residual modification function to the second decoded modified chroma residual data to generate second inverse modified chroma residual data. The first decoded modified chroma residual data is associated with a first chroma component, and the second decoded modified chroma residual data is associated with a second chroma component. The video decoder may reconstruct a block of video data based on the first inverse modified chroma residual data and the second inverse modified chroma residual data.

[0030] Figure 1 1 is a block diagram illustrating an exemplary video encoding and decoding system 100 that can perform the techniques of the present disclosure. The techniques of the present disclosure generally relate to decoding (encoding and / or decoding) video data. In general, video data includes any data used to process video. Thus, video data can include original unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0031] like Figure 1As shown in , in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 may include any of a variety of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets (such as smart phones), televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0032] exist Figure 1 In the example of , the source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. The destination device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. According to the present disclosure, the video encoder 200 of the source device 102 and the video decoder 300 of the destination device 116 can be configured to apply the technology for combined residual coding (CRC) of the present disclosure. Therefore, the source device 102 represents an example of a video encoding device, and the destination device 116 represents an example of a video decoding device. In other examples, the source device and the destination device may include other components or arrangements. For example, the source device 102 can receive video data from an external video source (such as an external camera). Similarly, the destination device 116 can be connected to an external display device interface instead of including an integrated display device.

[0033] like Figure 1 The system 100 shown in is only an example. In general, any digital video encoding and / or decoding device can perform the technology for combined residual decoding of the present disclosure. The source device 102 and the destination device 116 are only examples of such decoding devices, wherein the source device 102 generates decoded video data to send to the destination device 116. The present disclosure refers to a "decoding" device as a device that performs decoding (encoding and / or decoding) on ​​data. Therefore, the video encoder 200 and the video decoder 300 represent examples of decoding devices, specifically, examples of video encoders and video decoders, respectively. In some examples, the source device 102 and the destination device 116 can operate in a substantially symmetrical manner, so that each of the source device 102 and the destination device 116 includes a video encoding and decoding component. Therefore, the system 100 can support one-way or two-way video transmission between the source device 102 and the destination device 116, such as for video streaming, video playback, video broadcasting, or video telephony.

[0034] In general, the video source 104 represents the source of video data (i.e., the original unencoded video data) and provides a series of consecutive pictures (also referred to as "frames") of the video data to the video encoder 200, which encodes the data of the pictures. The video source 104 of the source device 102 may include a video capture device, such as a camera, a video archive containing previously captured original video, and / or a video feed interface for receiving video from a video content provider. As another alternative, the video source 104 may generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In each case, the video encoder 200 encodes the captured, pre-captured, or computer-generated video data. The video encoder 200 may rearrange the pictures from the receiving order (sometimes referred to as the "display order") to the decoding order for decoding. The video encoder 200 may generate a bitstream including the encoded video data. The source device 102 may then output the encoded video data to the computer-readable medium 110 via the output interface 108 for receiving and / or obtaining by, for example, the input interface 122 of the destination device 116.

[0035] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memories. In some examples, the memories 106, 120 may store raw video data, such as 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 that may be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although the memory 106 and the memory 120 are shown as separate from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 may also include internal memories with functionally similar or equivalent purposes. In addition, the memories 106, 120 may store, for example, encoded video data output from the video encoder 200 and input to the video decoder 300. In some examples, a portion of the memories 106, 120 may be allocated as one or more video buffers to, for example, store raw, decoded and / or encoded video data.

[0036] The computer-readable medium 110 may represent any type of medium or device capable of transmitting the encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to transmit the encoded video data directly to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. The output interface 108 may modulate a transmission signal including the encoded video data, and the input interface 122 may demodulate the received transmission signal according to a communication standard, such as a wireless communication protocol. The communication medium may include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium may include a router, a switch, a base station, or any other equipment that may help facilitate communication from the source device 102 to the destination device 116.

[0037] In some examples, computer-readable medium 110 may include storage device 112. Source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0038] In some examples, computer-readable medium 110 may include file server 114 or another intermediate storage device that can store the encoded video data generated by source device 102. Source device 102 may output the encoded video data to file server 114 or another intermediate storage device that can store the encoded video generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or downloading. File server 114 may be any type of server device capable of storing the encoded video data and sending the encoded video data to destination device 116. File server 114 may represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Destination device 116 may access the encoded video data from file server 114 via any standard data connection including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of the above two suitable for accessing the encoded video data stored on file server 114. The file server 114 and the input interface 122 may be configured to operate according to a streaming transfer protocol, a download transfer protocol, or a combination thereof.

[0039] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired network connection components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to cellular communication standards such as 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to other wireless standards (such as, IEEE 802.11 specifications, IEEE802.15 specifications (e.g., ZigBee TM ), Bluetooth TM Standards, etc.) to transmit data, such as encoded video data. In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include an SoC device to perform functions attributed to video encoder 200 and / or output interface 108, and destination device 116 may include an SoC device to perform functions attributed to video decoder 300 and / or input interface 122.

[0040] The techniques disclosed herein may be applied to support video decoding for any of a variety of multimedia applications, such as over-the-air television broadcasts, cable television transmissions, satellite television transmissions, Internet streaming video transmissions such as HTTP Dynamic Adaptive Streaming (DASH), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0041] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 (which is also used by the video decoder 300), such as syntax elements with values ​​describing characteristics and / or processing of video blocks or other decoded 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. The display device 118 may represent any of a variety of display devices, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0042] although Figure 1 2, but 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 multiplexing-demultiplexing (MUX-DEMUX) units or other hardware and / or software to handle a multiplexed stream including both audio and video in a common data stream. If applicable, the MUX-DEMUX unit may comply with the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0043] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is partially implemented in software, the device can store instructions for the software in a suitable non-transitory computer-readable medium and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, any of which can be integrated as part of a combined encoder / decoder (CODEC) in a corresponding device. A device including the video encoder 200 and / or the video decoder 300 may include an integrated circuit, a microprocessor, and / or a wireless communication device (such as a cellular phone).

[0044] The video encoder 200 and the video decoder 300 may operate according to a video coding standard, such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC), or an extension thereof, such as multi-view and / or scalable video coding extensions. Alternatively, the video encoder 200 and the video decoder 300 may operate according to other proprietary or industry standards, such as the Joint Exploration Test Model (JEM) or ITU-T H.266, also known as Versatile Video Coding (VVC). The latest draft of the VVC standard is described in "Versatile Video Coding (Draft 4)" JVET-M1001-v5 (hereinafter referred to as "VVC Draft 4") published by Bross et al. at the 13th meeting of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11 in Marrakech, Morocco from January 9 to 18, 2019. However, the techniques of this disclosure are not limited to any particular coding standard.

[0045] Typically, the video encoder 200 and the video decoder 300 may perform block-based decoding of a picture. 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 include a two-dimensional matrix of samples of brightness and / or chroma data. Typically, the video encoder 200 and the video decoder 300 may decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, the video encoder 200 and the video decoder 300 may decode brightness and chroma components instead of decoding red, green, and blue (RGB) data of samples of a picture, wherein the chroma component may include both red-hued and blue-hued chroma components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation before encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, a pre-processing unit and a post-processing unit (not shown in the figure) may perform these conversions.

[0046] The present disclosure may generally relate to decoding (e.g., encoding and decoding) a picture to include the process of encoding or decoding the data of the picture. Similarly, the present disclosure may relate to decoding a block of a picture to include the process of encoding or decoding the data of the block, such as prediction and / or residual decoding. The encoded video bitstream typically includes a series of values ​​of syntax elements representing decoding decisions (e.g., decoding modes) and partitioning of the picture into blocks. Therefore, references to decoding a picture or a block should generally be understood as decoding the values ​​of the syntax elements used to form the picture or the block.

[0047] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder (such as video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video coder partitions the CTU and the CU into four identical 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 TU. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of a TU. In HEVC, a PU represents inter-prediction data, and a TU represents residual data. An intra-predicted CU includes intra-prediction information, such as an intra-mode indication.

[0048] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to JEM or VVC. According to JEM or VVC, a video decoder (such as the video encoder 200) partitions a picture into multiple coding tree units (CTUs). The video encoder 200 may partition the CTU according to a tree structure, such as a quadtree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure removes the concept of multiple partition types, such as the spacing between CUs, PUs, and TUs of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0049] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) partitioning. Ternary tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, ternary tree partitioning divides a block into three sub-blocks without dividing the original block by the center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0050] In some examples, video encoder 200 and video decoder 300 may use a single QTBT or MTT structure to represent each of the luma and chroma components, while in other examples, video encoder 200 and video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for two chroma components (or two QTBT / MTT structures for corresponding chroma components).

[0051] The video encoder 200 and the video decoder 300 may be configured to use quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures per HEVC. For explanation purposes, the description of the techniques of the present disclosure is presented with respect to QTBT segmentation. However, it should be understood that the techniques of the present disclosure may also be applied to video decoders configured to use quadtree segmentation or other types of segmentation.

[0052] This disclosure may use "NxN" and "N times N" interchangeably to refer to the sample size of a block (such as a CU or other video block) with respect to vertical and horizontal dimensions, for example, 16x16 samples or 16 times 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Likewise, an NxN CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in columns and rows. Furthermore, a CU does not necessarily have the same number of samples in the horizontal direction and in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

[0053] The video encoder 200 encodes the video data of the CU representing the prediction and / or residual information and other information. The prediction information indicates how the CU will be predicted to form the prediction block of the CU. The residual information generally represents the sample-by-sample difference between the prediction block and the samples of the CU before encoding.

[0054] To predict a CU, the 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 use one or more motion vectors to generate a prediction block. The video encoder 200 may typically perform a motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), or other such difference calculations to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 may use unidirectional prediction or bidirectional prediction to predict the current CU.

[0055] Some examples of JEM and VVC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0056] To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of JEM and VVC provide sixty-seven intra prediction modes, including various directional modes as well as planar and DC modes. Typically, the video encoder 200 selects an intra prediction mode from which samples of the current block are predicted, which describes samples adjacent to the current block (e.g., a block of a CU). Assuming that the video encoder 200 codes CTUs and CUs in raster scan order (left to right, top to bottom), such samples may typically be above, above left, or to the left of the current block in the same picture as the current block.

[0057] The video encoder 200 encodes data representing the prediction mode of the current block. For example, for the inter-frame prediction mode, the video encoder 200 may encode data representing which mode of various available inter-frame prediction modes is used and the motion information of the corresponding mode. For example, for unidirectional or bidirectional inter-frame prediction, the video encoder 200 may encode the motion vector using advanced motion vector prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode the motion vector of the affine motion compensation mode.

[0058] After prediction of a block (such as intra prediction or inter prediction), the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a prediction block formed using a corresponding prediction mode for the block. The video encoder 200 may apply one or more transforms to the residual block to generate transformed data in a transform domain rather than a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0059] As noted above, after any transforms that produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing a quantization process, 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 down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0060] After quantization, the video encoder 200 may scan the transform coefficients to produce a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and lower energy (and therefore higher frequency) transform coefficients at the back of the vector. In some examples, the video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode syntax elements representing the transform coefficients in the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode values ​​of syntax elements describing metadata associated with the encoded video data for use by the video decoder 300 to decode the video data.

[0061] To perform CABAC, video encoder 200 may assign context within a context model to a symbol to be sent. The context may relate to, for example, whether neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0062] Video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, for example in a picture header, a block header, a slice header, or other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS), to video decoder 300. Video decoder 300 may likewise decode such syntax data to determine how to decode the corresponding video data.

[0063] In this way, the video encoder 200 may generate a bitstream including encoded video data (e.g., syntax elements describing the 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.

[0064] In general, the video decoder 300 performs a process that is inverse to the process performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of the syntax elements of the bitstream in a manner substantially similar to but inverse to the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for partitioning a picture into CTUs and partitioning of each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define CUs of the CTU. The syntax elements may further define prediction and residual information for a block (e.g., a CU) of video data.

[0065] The video decoder 300 may inversely quantize and inversely transform the quantized transform coefficients of the block to reproduce a residual block of the block. The video decoder 300 uses the signaled prediction mode (intra-frame or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block with the residual block (sample by sample) to reproduce the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along block boundaries.

[0066] As mentioned above, the video encoder 200 and the video decoder 300 may apply CABAC encoding and decoding to the values ​​of the syntax elements. To apply CABAC encoding to the syntax elements, the video encoder 200 may binarize the values ​​of the syntax elements to form a series of one or more bits, which are referred to as "bins". In addition, the video encoder 200 may identify a coding context. The coding context may identify the probability of an interval having a specific value. For example, the coding context may indicate a 0.7 probability of coding a 0-value interval and a 0.3 probability of coding a 1-value interval. After identifying the coding context, the video encoder 200 may divide the interval into a lower sub-interval and an upper sub-interval. One of the sub-intervals may be associated with a value of 0, while the other sub-interval may be associated with a value of 1. The width of the sub-interval may be proportional to the probability indicated by the identified coding context with respect to the associated value. If the interval of the syntax element has a value associated with the lower sub-interval, the encoded value may be equal to the lower boundary of the lower sub-interval. If the same interval of the syntax element has a value associated with an upper subinterval, the encoded value may be equal to the lower boundary of the upper subinterval. To encode the next interval of the syntax element, video encoder 200 may repeat these steps, where the interval is the subinterval associated with the encoded bit value. When video encoder 200 repeats these steps for the next interval, video encoder 200 may use a modified probability based on the probability indicated by the identified coding context and the actual value of the encoded interval.

[0067] When the video decoder 300 performs CABAC decoding on the value of the syntax element, the video decoder 300 may identify the coding context. The video decoder 300 may then divide the interval into a lower subinterval and an upper subinterval. One of the subintervals may be associated with a value of 0, while the other subinterval may be associated with a value of 1. The width of the subinterval may be proportional to the probability indicated by the identified coding context regarding the associated value. If the encoded value is within the lower subinterval, the video decoder 300 may decode the interval having the value associated with the lower subinterval. If the encoded value is within the upper subinterval, the video decoder 300 may decode the interval having the value associated with the upper subinterval. In order to decode the next interval of the syntax element, the video decoder 300 may repeat these steps, where the interval is a subinterval containing the encoded value. When the video decoder 300 repeats these steps for the next interval, the video decoder 300 may use a modified probability based on the probability indicated by the identified coding context and the decoded interval. Video decoder 300 may then de-binarize the interval to recover the value of the syntax element.

[0068] In some cases, the video encoder 200 may encode the interval using bypass CABAC coding. It may cost less to perform bypass CABAC coding on the interval than to perform conventional CABAC coding on the interval. In addition, performing bypass CABAC coding may allow for higher parallelization and throughput. Intervals encoded using bypass CABAC coding may be referred to as "bypass intervals". Grouping bypass intervals together may increase the throughput of the video encoder 200 and the video decoder 300. The bypass CABAC coding engine may be able to code several intervals in a single cycle, while the conventional CABAC coding engine may only be able to code a single interval in one cycle. The bypass CABAC coding engine may be simpler because the bypass CABAC coding engine does not select a context and may adopt a probability of 1 / 2 for two codewords (0 and 1). Therefore, in bypass CABAC coding, the interval is directly split into two halves.

[0069] In addition, as mentioned above, the bitstream may include representations of coded pictures of video data and associated data. The associated data may include parameter sets. A network abstraction layer (NAL) unit may encapsulate a raw byte sequence payload (RBSP) of a video parameter set (VPS), a sequence parameter set (SPS), and a picture parameter set (PPS). A VPS is a syntax structure that includes syntax elements applied to zero or more complete coded video sequences (CVSs). An SPS is also a syntax structure that includes syntax elements applied to zero or more complete CVSs. An SPS may include syntax elements that identify a VPS that is in effect when an SPS is in effect. Therefore, the syntax elements of a VPS may be more generally applicable than the syntax elements of an SPS. A PPS is a syntax structure that includes syntax elements applied to zero or more coded pictures. A PPS may include syntax elements that identify an SPS that is in effect when a PPS is in effect. A slice header of a slice may include syntax elements that indicate a PPS that is in effect when a slice is being coded.

[0070] Color video plays a major role in multimedia systems, where various color spaces are used to represent colors efficiently. A color space specifies a color with a digital value using multiple components. A commonly used color space is the RGB color space, where colors are represented as a combination of three primary color component values ​​(red, green, and blue).

[0071] For color video compression, the YCbCr color space has been widely used. See A. Ford and A. Roberts' technical report "Colour space conversions" at the University of Westminster in London in August 1998. YCbCr can be converted from the RGB color space via a linear transformation, and the redundancy between different components (i.e., cross-component redundancy) is significantly reduced in the YCbCr color space. Since the Y signal conveys brightness (luminance) information, one advantage of YCbCr is that it has reverse compatibility with black and white TV. In addition, the chroma (chrominance) bandwidth can be reduced by subsampling the Cb and Cr components in a 4:2:0 chroma sampling format, which has a significantly smaller subjective impact than the subsampling in RGB. Due to these advantages, YCbCr has become the primary color space in video compression. There are also other color spaces used in video compression, such as YCoCg. In this document, regardless of the actual color space used, Y, Cb and Cr are used to represent the three color components in the video compression scheme. Although cross-component redundancy is significantly reduced in the YCbCr color space, there is still correlation between the three color components. In particular, for the decoding of 4:4:4 chroma format video, various methods have been studied to improve video decoding performance by further reducing the correlation. As described in "Block adaptive inter-color compensation algorithm for RGB 4:4:4 video coding" by BCSong, YGLee and NHKim (IEEE Trans.CircuitsSyst.Video Technol., Vol. 18, No. 10, pp. 1447-1451, October 2008), a scaling factor and an offset are used for each block to predict the chroma signal from the reconstructed luminance signal.

[0072] In "RCE1: Descriptions and Results for Experiments 1, 2, 3, and 4" by W. Pu, W.-S. Kim, J. Chen, J. Sole, and M. Karczewicz (Joint Collaboration Group on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, JCTVC-00202, Geneva, November 2013), cross-component prediction (CCP) is performed in the residual domain. The chroma residual signal is predicted at the encoder side using the reconstructed luma residual signal as:

[0073] Δr C (x,y)=rC (x,y)-(α×r′ L (x,y))>>3 (1)

[0074] And the chroma residual signal is compensated at the decoder side as:

[0075] r′ C (x,y)=Δr′ C (x,y)+(α×r′ L (x,y))>>3 (2)

[0076] where r C (x,y) and r′ C (x,y) represents the original and reconstructed chroma residual samples at position (x,y). Δr C (x,y) and Δr′ C (x,y) represents the final chroma residual sample after cross-component prediction. r′ L (x,y) is the reconstructed luma residual sample value. The weighting factor α is explicitly signaled in the bitstream for each chroma transform unit in HEVC. The cross-component residual prediction method is adopted in the format and range extension of the HEVC standard for 4:4:4 chroma sampling format video decoding, which is performed for both intra-frame prediction residuals and inter-frame prediction residuals. The cross-component residual prediction method is also proposed for 4:2:0 video format decoding, but it is not adopted due to limited decoding benefits. In addition to using luma to predict the chroma component, it is also proposed that the prediction can be applied between two chroma components, that is, the reconstructed early-coded Cb residual is used to predict the Cr residual. See A. Khairat, T. Nguyen, M. Siekmann, D. Marpe, “Non-RCE1: Extended Adaptive Inter-Component Prediction” (Joint Collaboration Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, JCTVC-O0150, Geneva, November 2013). U.S. Patent Publication Nos. 2016 / 0219283, published on July 28, 2016, 2016 / 0277762, published on September 22, 2016, 2018 / 0077426, published on March 15, 2018, 2018 / 0176594, published on June 21, 2018, and 2019 / 0007688, published on January 3, 2019, also describe aspects of cross-component prediction.

[0077] In 4:2:0 chroma video coding, a method called linear model (LM) prediction mode has been well studied during the development of the HEVC standard. See J. Chen, V. Seregin, W.-J. Han, J.-S. Kim, B.-M. Joen, "CE6.a.4: Chroma intra prediction by reconstructed luma samples" (Joint Collaboration Team on Video Coding (JCT-VC) of ITU-T SG16WP3 and ISO / IEC JTC1 / SC29 / WG11, JCTVC-E266, Geneva, March 16-23, 2011). In LM prediction mode, chroma samples are predicted based on reconstructed luma samples of the same block using the following linear model:

[0078] pred C (i,j)=α·rec L (i,j)+β (3)

[0079] where pred C (i,j) represents the prediction of the chroma samples in the block, and rec L (i, j) represents the downsampled reconstructed luma sample of the same block. The parameters α and β are derived by minimizing the regression error between the neighboring reconstructed luma samples and chroma samples around the current block.

[0080]

[0081] The parameters α and β are analyzed as follows:

[0082]

[0083] β=(∑y i -α·∑x i ) / N (6)

[0084] where x i is the downsampled reconstructed brightness reference sample, y i are the reconstructed chrominance reference samples, and N is the number of reference samples used.

[0085] In-loop reshapers were adopted at the 13th JVET meeting. See J. Lainema, “CE7-related: Joint coding of chrominance residuals” (13th JVET meeting, Marrakech, Morocco, January 2019, JVET-M0305 (hereinafter referred to as “JVET-M0305”)) and X. Xiu, P. T. Lu, P. Hanhart, R. Vanam, Y. He, Y. Ye, T. Lu, F. Pu, P. Yin, W. Husak, T. Chen, “Description of SDR, HDR, and 360° video coding technology proposal by InterDigital Communications and Dolby Laboratories” (JVET-J0015, San Diego, USA, April 2018). The in-loop luma reshaper is implemented as a pair of lookup tables (LUTs), but only one of the two LUTs needs to be signaled (via piecewise linear modeling) because the other can be calculated from the signaled LUT. Each LUT is a one-dimensional, 10-bit, 1024-entry mapping table (1D-LUT) for 10-bit video. One LUT converts the input luma code value Y i (Original domain) mapped to the changed value Y r :Y r =FwdLUT[Y i ] (reshape domain) of the forward LUT (FwdLUT). The other LUT is the inverse LUT (InvLUT), which converts the modified code value Y r (reshape domain) maps to (Original domain): ( Represents Y i reconstructed value).

[0086] Figure 2 is a block diagram showing an example of intra slice reconstruction using an in-loop luminance reshaper. For intra slices, the InvLUT ( Figure 2 ).exist Figure 2 In FIG, the grey shaded blocks indicate the signals in the reshaped domain: luma residual, intra luma prediction and intra luma reconstruction. More specifically, as Figure 2 As shown in the example of FIG. 1 , the video decoder 300 may perform CABAC decoding (denoted as CABAC -1 ), inverse quantization (denoted as Q -1 ) and the reverse transformation (denoted as T -1)(150). In addition, the video decoder 300 can convert the luma residual sample (Y res ) is added to the intra-predicted sample (Y' pred ) to perform intra prediction (152) and reconstruction (154). In addition, video decoder 300 may perform an inverse reshaping operation (156). Video decoder 300 may apply one or more loop filters (LF) to the output of the inverse reshaping operation (158). The result may be stored in a decoded picture buffer (DPB) (160).

[0087] Figure 3 is a block diagram illustrating an example of inter-frame slice reconstruction using an in-loop brightness reshaper. Figure 3 ), both FwdLUT and InvLUT are applied. LUT is applied before loop filtering for both intra and inter slices. Figure 3 In the figure, the grey shaded blocks indicate signals in the reshaped domain: luma residual, intra luma prediction, and intra luma reconstruction. Although the term "slice" is used herein to refer to a set of coding tree units signaled in a NAL unit, it should be understood that the discussion also applies to other spatial partitions of pictures such as tile groups (used in VVC).

[0088] For an inter-frame slice (or tile group), the FwdLUT maps the motion compensated values ​​in the original domain to the reshaped domain (FwdLUT[Y pred ]). InvLUT then maps the inter-frame reconstructed values ​​in the reshaped domain to the inter-frame reconstructed values ​​in the original domain exist Figure 3 In the example of , intra prediction is always performed in the reshaped domain regardless of the slice type. With such an arrangement, intra prediction can start immediately after reconstruction of the previous TU.

[0089] exist Figure 3 In the example of FIG. 1 , the video decoder 300 may perform CABAC decoding (denoted as CABAC -1 ), inverse quantization (denoted as Q -1 ) and the reverse transformation (denoted as T -1 )(170). In addition, the video decoder 300 may perform intra prediction (172) or motion compensation (184) and forward reshaping process (174) for the block. The video decoder 300 may perform intra prediction (172) or motion compensation (184) and forward reshaping process (174) for the block. res ) is added to the predicted sample (Y′ pred ) to perform the reconstruction (176). Figure 3 In the example of , if intra prediction is used to predict a block, intra prediction is used to predict the predicted sample (Y′ pred)(172). The video decoder 300 performs intra prediction in the reshaped domain. However, the video decoder 300 performs inter prediction in the non-reshaped domain. Therefore, if the block is predicted using inter prediction, the video decoder 300 performs motion compensation (184) and a forward reshaping operation (174) to convert the predicted samples produced by the motion compensation (184) to the reshaped domain.

[0090] Additionally, after reconstruction (176), video decoder 300 may perform an inverse reshaping operation (178). Video decoder 300 may apply one or more loop filters (LF) to the output of the inverse reshaping operation (180). The result may be stored in a decoded picture buffer (DPB) (182). Data from the DPB may be used for motion compensation (184) and then may be used for forward reshaping (174) in subsequent blocks.

[0091] The reshaping model syntax may signal a piecewise linear (PWL) model with 16 segments. The 1024-entry mapping table is constructed by linear interpolation using the 16-segment PWL model. Conceptually, the PWL model may be implemented as follows. Assume x1, x2 are two input pivot points, and y1, y2 are their corresponding output pivot points for one segment. The output value y for any input value x between x1 and x2 may be interpolated by the following equation:

[0092] y=((y2-y1) / (x2-x1))*(x-x1)+y1

[0093] In a fixed point implementation, the above equation can be rewritten as:

[0094] y=((m*x+2 FP_PREC-1 )>>FP_PREC)+c

[0095] where m is a scalar, c is an offset, and FP_PREC is a constant value used to specify the precision.

[0096] Figure 4 is a block diagram illustrating an example of intra-mode and inter-mode reconstruction using chroma residual scaling (CRS). Chroma residual scaling or CRS ( Figure 4 ) Compensates for the interaction of luma and chroma signals. Chroma residual scaling is applied at TU level.

[0097] Encoder side: C ResScale =C Res *C Scale =C Res / C ScaleInv (7)

[0098] Decoder side: C Res =C ResScale / C Scale =C ResScale *C ScaleInv (8)

[0099] C Res is the original chrominance residual signal, and C ResScale is the scaled chroma residual signal. C Scale is the scaling factor calculated using FwdLUT and converted to its inverse C ScaleInv The multiplication can be performed at the decoder side instead of division, thus reducing the implementation complexity. Figure 4 In the figure, the grey shaded blocks indicate the signals in the reshaped domain: luma residual, intra luma predicted, and intra luma reconstructed. Under the PWL model, for any input luma value in each luma PWL range, the same chroma scaling value is used. Therefore, the luma-dependent chroma scaling is simplified to be calculated for each luma PWL range instead of each luma code value and stored in the LUT cScaleInv[pieceIdx] (16-segment granularity). The scaling operation at both the encoder and decoder sides is implemented in fixed-point integer arithmetic by the following equations:

[0100] c'=sign(c)*((abs(c)*s+2 CSCALE_FP_PREC-1 )>>CSCALE_FP_PREC)

[0101] Where c is the chroma residual, s is the chroma residual scaling factor from cScaleInv[pieceIdx], pieceIdx is determined by the corresponding average luminance value of the TU, and CSCALE_FP_PREC is a constant value of the specified precision.

[0102] Calculate C in the following steps ScaleInv Values:

[0103] 1. If the intra mode is used, the average value of the intra-predicted luminance value is calculated; if the inter mode is used, the average value of the forward reshaped inter-predicted luminance value is calculated. That is, the average luminance value avgY′ is calculated in the reshaped domain TU .

[0104] 2. In avgY′ TU Find the index idx of the brightness range in the reverse mapping PWL to which it belongs.

[0105] 3.C ScaleInv =cScaleInv[idx]

[0106] exist Figure 4In the example of FIG. 1 , the video decoder 300 may perform CABAC decoding (CABAC -1 ), inverse quantization (Q -1 ) and the reverse transformation (T -1 )(240). The output of block 240 may include luma residual data (Y res ) and scaled chrominance data (C resScale If the block is encoded using intra mode, the video decoder 300 may perform an intra prediction process (242) for the current block to generate luma prediction data (Y' p Alternatively, if the block is encoded using inter-mode, the video decoder 300 may perform motion compensation (252) and a forward reshaping process (244) for the current block to generate luma prediction data (Y' p The video decoder 300 may perform a res ) and predicted data (Y' pred ) A luma reconstruction process (246) is performed to reconstruct luma samples. Video decoder 300 may use the reconstructed luma data for intra prediction of subsequent blocks.

[0107] In addition, Figure 4 In the example of , video decoder 300 may perform an inverse reshaping process on the reconstructed luma data of the current block (247). Video decoder 300 may apply one or more loop filters (LF) to the output of the inverse reshaping operation (248). Video decoder 300 may store the result in a decoded picture buffer (250). The data in the decoded picture buffer may be used to perform motion compensation on subsequent blocks of video data (252). Figure 4 In the example of FIG. 1 , the video decoder 300 may also determine an average luminance value (avgY′) for the current transform unit. TU ) and the chroma residual scaling factor (C scaleInv )(254). Video decoder 300 may determine the chroma residual scaling factor as described above.

[0108] exist Figure 4 In the example of FIG. 1 , video decoder 300 may perform a chroma residual scaling process (256) to scale the scaled chroma residual data for the current block to generate chroma residual data (C ) for the current block. res ). The video decoder 300 may perform a chroma residual scaling process by multiplying samples of the scaled chroma residual data by a chroma residual scaling factor. Figure 4 In the example of FIG. 2 , the video decoder 300 may perform an intra prediction process ( 257 ) or a motion compensation process ( 258 ) to generate chroma prediction data (C predThe video decoder 300 may perform a reconstruction process based on the chroma residual data (C res ) and the chroma prediction data to reconstruct the chroma data of the current block (259). Video decoder 300 may apply one or more loop filters (LF) to the output of the inverse reshaping operation (260). Video decoder 300 may store the resulting data in a decoded picture buffer (262).

[0109] A method for joint decoding of Cb-Cr chroma residuals is described in JVET-M0305. In this method, a single joint residual block is used to describe the residuals of both Cb and Cr blocks in the same transform unit. On the encoder side, the algorithm uses the average of the positive Cb residual and the negative Cr residual as input to the transform and quantization process. If this mode is activated, a single residual block is decoded. The residual of the Cr block is generated by negating the decoded joint residual. On the decoder side, when the joint residual mode is in effect, the indicated joint residual is added to the Cb prediction block and subtracted from the Cr prediction block. Since a single residual is used to represent the residuals of both blocks, the chroma quantization parameter (QP) offset parameter is reduced by 2 when the joint chroma residual mode is in effect.

[0110] If the coded block flag (cbf) is true for both Cb and Cr, the joint residual mode is indicated by a flag in the bitstream. The bitstream syntax and decoding process for the joint residual follow those for the Cb residual in VTM3. See J. Chen, Y. Ye, S. Kim, "Algorithm description for Versatile Video Coding and Test Model 3 (VTM3)" (12th JVET Meeting, Macau SAR, China, October 2018, JVET-L1002).

[0111] In Core Experiment Test CE7.1 (H. Schwarz, M. Coban, C. Auyeung, "Description of Core Experiment 7 (CE7): Quantization and coefficient coding", 13th JVET Meeting, Marrakech, Morocco, January 2019, JVET-M1027), the method is integrated with the in-loop chroma residual scaler (CRS) as follows:

[0112] Encoder side:

[0113] Cb residual: (resCb(x,y)–resCr(x,y)) / 2→CRS→T→Q(Qp+jointCbCrQpOffset)

[0114] Cr residual: 0

[0115] Decoder side:

[0116] Cb residual: invQ→invT→invCRS→resCb(x,y)'

[0117] Cr residual: -resCb(x,y)'

[0118] where CRS is the forward chroma residual scaler, invCRS is the inverse chroma residual scaler, T is the forward transform, Q is the forward quantization, invT is the inverse transform, and invQ is the inverse quantization.

[0119] Model-based cross-component residual prediction requires either model parameter estimation at the decoder side, which implies increased implementation cost at the video decoder 300 , or model parameters need to be signaled, which adversely affects coding efficiency and requires parameters to be decoded from the bitstream.

[0120] Due to the asymmetric processing of the two chroma channels, the joint Cb-Cr decoding method that combines the two chroma residuals into a single residual coded into the bitstream may be affected by chroma artifacts. For example, in JVET-M0305, it is assumed that the Cr residual is the inverse of the joint residual, which is a rough approximation. In addition, the method requires adjusting the quantization parameter applied to the joint residual after the transform and adjusting the λ parameter on the encoder side for rate-distortion optimization in order to properly decode the joint residual and achieve decoding gain. The quantization parameter offset can be signaled. However, determining the exact value can be an additional burden for the video encoder 200.

[0121] The present disclosure describes techniques that can solve one or more of the problems described above. The techniques of the present disclosure can avoid signaling and decoding model parameters for model-based cross-component residual prediction, and can avoid adjusting quantization parameters in the joint Cb-CR decoding method described above. Nevertheless, the techniques of the present disclosure can reduce the correlation between Cb samples and Cr samples, and thereby provide decoding efficiency gains. The examples provided below and elsewhere in the present disclosure can be applied independently, or one or more of the examples can be applied together.

[0122] The following portion of the present disclosure describes techniques for combined residual coding (CRC). According to the techniques for combined residual coding, Cb residual blocks and Cr residual blocks (resCb(x,y) and resCr(x,y)) having sizes (width and height) are processed using residual modification functions (RMFs) F1(x,y) and F2(x,y) to obtain modified residuals that are subsequently forward transformed (T), quantized (Q), and entropy coded (E) at the video encoder 200, as shown in Table 1 below.

[0123] Table 1

[0124]

[0125]

[0126] At the video decoder 300 in Table 1, after entropy decoding (invE), inverse quantization (invQ), and inverse transformation (invT), the inverse RMFs invF1(x,y) and invF2(x,y) are applied to the decoded residuals resCb(x,y)' and resCr(x,y)' to obtain residuals resCb(x,y)" and resCr(x,y)", which are added to the predictions predCb(x,y) and predCr(x,y) to obtain reconstructed recCb(x,y) and recCr(x,y).

[0127] In one example, functions F1 and F2 are subtraction and summation, respectively, and inverse functions invF1 and invF2 are summation and subtraction, respectively. Normalization factors 1 / N1, 1 / N2, 1 / M1, 1 / M2 and rounding terms A1, A2, B1, B2 may be part of these functions:

[0128] i)F1(x,y)=(resCb(x,y)–resCr(x,y)+A1) / N1(Equation 1.ai)

[0129] ii)F2(x,y)=(resCb(x,y)+resCr(x,y)+A2) / N2 (Equation 1.a.ii)

[0130] iii)invF1(x,y)=(resCr(x,y)'+resCb(x,y)'+B1) / M1 (Equation 1.a.iii)

[0131] iv)invF2(x,y)=(resCr(x,y)'-resCb(x,y)'+B2) / M2 (Equation 1.a.iv)

[0132] In one example, N1=N2=2, A1=A2=1 (or 0), and M1=M2=1, B1=B2=0. In another example, Among them, the factor is approximately equal to (181 / 256), and in this case, A1=A2=B1=B2=128 (or 0). In some examples, all values ​​of residual blocks resCb(x,y), resCr(x,y), resCb(x,y)', or resCr(x,y)' may be zero, or one or more residual blocks may be omitted from the above equations.

[0133] In another example, functions F1 and F2 are summation and subtraction, respectively, and inverse functions invF1 and invF2 are also summation and subtraction, respectively. Normalization factors 1 / N1, 1 / N2, 1 / M1, 1 / M2 and rounding terms A1, A2, B1, B2 may be part of these functions:

[0134] i)F1(x,y)=(resCb(x,y)+resCr(x,y)+A1) / N1(Equation 1.bi)

[0135] ii)F2(x,y)=(resCb(x,y)-resCr(x,y)+A2) / N2(Equation 1.b.ii)

[0136] iii)invF1(x,y)=(resCb(x,y)'+resCr(x,y)'+B1) / M1 (Equation 1.b.iii)

[0137] iv)invF2(x,y)=(resCb(x,y)'-resCr(x,y)'+B2) / M2 (Equation 1.b.iv)

[0138] In one example, N1=N2=2, A1=A2=1 (or 0), and M1=M2=1, B1=B2=0. In another example, Among them, the factor is approximately equal to (181 / 256), and in this case, A1=A2=B1=B2=128 (or 0). In some examples, all values ​​of residual blocks resCb(x,y), resCr(x,y), resCb(x,y)', or resCr(x,y)' may be zero, or one or more residual blocks may be omitted from the above equations.

[0139] In some examples, functions F1 and F2 are subtraction and summation with unequal normalization factors, respectively, and inverse functions invF1 and invF2 are summation and subtraction with unequal normalization factors, respectively. Normalization factors 1 / N10, 1 / N11, 1 / N20, 1 / N21, 1 / M10, 1 / M11, 1 / M20, 1 / M21 and rounding terms A10, A11, A20, A21, B10, B11, B20, B21 may be part of these functions:

[0140] i)F1(x,y)=(resCb(x,y)+A10) / N10–(resCr(x,y)+A11) / N11(Equation 1.ci)

[0141] ii)F2(x,y)=(resCb(x,y)+A20) / N20+(resCr(x,y)+A21) / N21 (Equation 1.c.ii)

[0142] iii)invF1(x,y)=(resCr(x,y)'+B10) / M10+(resCb(x,y)'+B11) / M11 (Equation 1.c.iii)

[0143] iv) invF2(x,y) = (resCr(x,y)'+B20) / M20 – (resCb(x,y)'+B21) / M21 (Equation 1.c.iv)

[0144] In one example, in equations 1.ci, 1.c.ii, 1.c.iii, and 1.c.iv, N10=N11=1 and A10=A11=0; N20=N21=2 and A20=A21=0; M10=1 and B10=0; M11=2 and B11=1; M20=1 and B20=0; M21=2 and B21=0. Therefore, in this example, equations 1.ci, 1.c.ii, 1.c.iii, and 1.c.iv can be rewritten as:

[0145] i)F1(x,y)=resCb(x,y)–resCr(x,y)(Equation 1.cv)

[0146] ii)F2(x,y)=(resCb(x,y)+resCr(x,y)) / 2(Equation 1.c.vi)

[0147] (1)invF1(x,y)=resCr(x,y)'+(resCb(x,y)'+1) / 2 (Equation 1.c.vii)

[0148] (2)invF2(x,y)=resCr(x,y)'–resCb(x,y)' / 2 (Equation 1.c.viii)

[0149] All values ​​of residual blocks resCb(x,y), resCr(x,y), resCb(x,y)′, or resCr(x,y)′ may be zero, or one or more residual blocks may be omitted from the above equations.

[0150] In some examples of the present disclosure, the CRS process may be applied together with the RMF. For example, in examples where the CRS process is applied together with the RMF, the RMFs F1(x, y) and F2(x, y) may be applied after the CRS scaled residuals resCb(x, y) and resCr(x, y) (e.g., by the video encoder 200). Conversely, in this example, the inverse RMFs invF1(x, y) and invF2(x, y) are applied before the invCRS scaling process (e.g., by the video decoder 300).

[0151] In the example where the CRS process is applied together with the RMF, the RMFs F1(x,y) and F2(x,y) may be applied by the video encoder 200 before the CRS has scaled the residuals resCb(x,y) and resCr(x,y). Conversely, in this example, the inverse RMFs invF1(x,y) and invF2(x,y) are applied by the video decoder 300 after the invCRS scaling process.

[0152] In some examples, the normalization factors 1 / N, 1 / M and rounding terms A, B as defined above may be integrated with a transform coefficient scaling process as part of a forward transform process T, and conversely, with an inverse transform coefficient scaling as part of an inverse transform process invT. In other words, the normalization factors and scaling terms may be combined. In some such examples, the CRS scaling process is not applied (e.g., by the video encoder 200 or the video decoder 300). In some examples in which the normalization factors and rounding terms are integrated with the transform coefficient scaling process as part of the forward transform process T, the CRS scaling process is applied before the RMFs F1(x,y) and F2(x,y), and conversely, the inverse RMFs invF1(x,y) and invF2(x,y) are applied before the invCRS scaling process.

[0153] In some examples where the normalization factors and rounding terms are integrated with the transform coefficient scaling process as part of the forward transform process T, the RMFs F1(x,y) and F2(x,y) are applied before the CRS scaled residuals resCb(x,y) and resCr(x,y), and conversely, the inverse RMFs invF1(x,y) and invF2(x,y) are applied after the invCRS scaling process. In this case, the CRS scaling may also be integrated with the transform coefficient scaling process as part of the forward transform process T, and conversely, with the inverse transform coefficient scaling as part of the inverse transform process invT.

[0154] Alternatively, in an example where the normalization factors and rounding terms are integrated with a transform coefficient scaling process as part of a forward transform process T, the normalization factors 1 / N, 1 / M and rounding terms A, B as defined above may be fully or partially replaced by a modified quantization parameter value (offsetQp in Table 1).

[0155] Furthermore, in some examples of the present disclosure, RMF F1(x, y), F2(xy) may be applied after the forward transform process T and before quantization Q (e.g., by the video encoder 200). Conversely, inverse RMF invF1(x, y), invF2(x, y) may be applied after inverse quantization invQ and before inverse transform process invT (e.g., by the video decoder 300).

[0156] In this example, the transform skip mode may be applied with combined residual coding. Thus, in some examples, the video encoder 200 does not apply a forward transform (e.g., DCT, DST, etc.), but instead applies RMF. Likewise, in some examples, the video decoder 300 does not apply an inverse transform (e.g., inverse DCT, inverse DST, etc.), but instead applies inverse RMF.

[0157] In a similar manner as described above, the luma residual block resY(x,y) may be combined with the chroma residual blocks resCb(x,y) and resCr(x,y) correspondingly. For example, in one such example, RMF F3(x,y) is applied to resY(x,y) and resCb(x,y) (e.g., by the video encoder 200). Additionally, RMF F4(x,y) is applied to resY(x,y) and resCr(x,y) (e.g., by the video encoder 200). Furthermore, in this example, inversely, the inverse RMF of F3 (i.e., invF3(x,y)) and the inverse RMF of F4 (i.e., invF4(x,y)) are applied (e.g., by the video decoder 300). In one example, F3, F4, invF3, and invF4 may be expressed as:

[0158] ·F3=(A1*resY+B1*resCB+D1) / N1

[0159] ·F4=(A2*resY+B2*resCR+D2) / N2

[0160] invF3 = (A3*F3-B3*F4+D3) / N3

[0161] invF4 = (A4*F3-B4*F4+D4) / N4

[0162] In another example of combining luma residual blocks with chroma residual blocks correspondingly, RMF F5(x,y) is applied to resY(x,y) as well as resCb(x,y) and resCr(x,y) (e.g., by video decoder 200). Conversely, invF5(x,y) is applied (e.g., by video decoder 300). In one example, F5 and invF5 can be expressed as:

[0163] ·F5=(A1*resY+B1*resCB+C1*resCR+D1) / N1

[0164] invF5=(A3*F5+D3) / N3

[0165] In the case of a 4:2:0 chroma video format, for example, RMF F3, F4, F5 may include downsampling of the resY(x,y) residual block (with or without filtering) or upsampling of the resCb(x,y) and resCr(x,y) blocks (with or without interpolation). The CRC techniques of the present disclosure may also be applied to 4:4:4 video formats, etc., in which case downsampling or upsampling may not be required.

[0166] The CRC tool of the present disclosure may be enabled by signaling a binary flag in an SPS, PPS, slice or tile group header, etc. In addition, a CRC flag (crc_flag) may be signaled in a transform unit syntax or a residual coding syntax to enable the CRC tool for a transform unit. Thus, the video encoder 200 may signal the CRC flag in the bitstream, and the video decoder 300 may obtain the CRC flag from the bitstream.

[0167] In some examples, the signaling of the CRC flag depends on the presence of a particular standard. For example, in one example, if the coding block flag (cbf) of the Cb residual block (cbf_cb) is true, crc_flag may be signaled (e.g., by the video encoder 200). The cbf of the residual block indicates whether all values ​​of the transform coefficients of the residual block are zero. In the case where the transform skip mode is applied, the transform coefficients of the residual block may be in the sample domain. In a second example, if the coding block flag (cbf) of the Cr residual block (cbf_cr) is true, crc_flag may be signaled (e.g., by the video encoder 200). In a third example, if cbf_cb is true or cbf_cr is true, crc_flag may be signaled (e.g., by the video encoder 200). In yet another example, if cbf_cb and cbf_cr are true, crc_flag may be signaled (e.g., by the video encoder 200).

[0168] In an example where crc_flag is signaled if cbf_cb is true and cbf_cr is also true, a second flag may be signaled for each transform unit (e.g., by the video encoder 200) indicating whether to signal both residuals (F1(x,y) and F2(x,y), as defined in equations 1.ai) and 1.a.ii)) or only one of the two residuals, i.e., by forcing F1(x,y) or F2(x,y) to zero. The forcing may be fixed (e.g., only F2(x,y) but not F1(x,y) may be forced to zero); or variable (where either F1(x,y) or F2(x,y) may be forced to zero). For the latter case, another flag may be signaled to indicate which residual is forced to zero. One motivation for doing this is that forcing one residual to zero may be cheap in terms of rate, but may cause more distortion. Thus, the video encoder 200 may have the flexibility to adjust itself in terms of rate-distortion tradeoff. In another example, these flags (the number of signaled residuals and which residuals are forced to zero) may be signaled at the SPS, PPS, slice, or tile group header rather than at the transform unit level.

[0169] In some examples, crc_flag may be context coded or bypass coded (e.g., by the video encoder 200 and the video decoder 300). Multiple contexts may be used with contexts depending on the cbf_cb or cbf_cr value, depending on the neighboring or current block mode (intra, inter, current picture reference, etc.), depending on the transform skip flag, depending on block size characteristics (width, height, ratio), depending on whether dual or shared coding trees are used, and the like. In addition, when the crc flag is parsed after cbf_cr, different contexts of the crc flag may be applied depending on whether cbf_cr is true. When the crc flag is parsed before cbf_cr, different contexts of the cbf_cr may be applied depending on the value of the crc flag in that case. A new context may be defined depending on the crc flag value, or an existing context of the cbf_cr component may be modified depending on the crc flag value.

[0170] In some examples, one or more CRC methods may be used to decode the samples (eg, one method may involve RMF F1 A (x,y) and F2 A (x,y), while another approach may involve RMF F1 B (x,y) and F2 B (x, y)). The determination of the CRC method to be used by the decoder may be made by one or more of the following examples (e.g., by the video encoder 200 and the video decoder 300). In one example, a list of available (or possible) CRC methods may be determined by analyzing the correlation between the high-pass filtered versions of the original Cb and Cr components. The analysis may occur offline and may be performed based on a wide variety of content to determine which CRC methods provide compression efficiency gains. In some examples, a list of available (or possible) CRC methods may be determined by analyzing picture textures or block textures and mapping features to a list. Different CRC methods may use different RMFs. The CRC method to be used may be determined by an indication in the bitstream specifying the CRC method to be used (e.g., a flag or index to a list of CRC methods). Alternatively, the video encoder 200 and the video decoder 300 may determine the CRC method based on one or more characteristics of the block. Such characteristics may include, but are not limited to, whether the slice or tile group type is intra-frame or inter-frame type, CPR (current picture reference), whether a dual or shared decoding tree is used, residual block size or aspect ratio, or other characteristics of the block. Video encoder 200 and video decoder 300 may code one or more components of the video using the determined CRC method based on the determination.

[0171] Furthermore, in some examples of the present disclosure, the quantization parameter value Qp used by the forward quantization process Q and the inverse quantization process invQ may be modified by the offsetQp1 value and the offsetQp2 value, as shown in Table 1. Such offsetQp value may be a default value, or it may be signaled in the bitstream (SPS, PPS, adaptive parameter set (APS), slice or tile group header, unit header, etc.). The default value or signaled value may depend on whether the slice or tile group type is intra or inter type, CPR (current picture reference), whether dual or shared coding trees are used, residual block size or aspect ratio, etc. The signaling may depend on whether a flag indicates whether the combined residual coding tool is enabled or disabled.

[0172] In some examples, the CRC method is not allowed for blocks with certain characteristics. For example, the CRC method is not allowed for blocks with less than a threshold number of samples (e.g., 16). In other examples, other characteristics of the block (including but not limited to width, height, aspect ratio, neighboring block characteristics, signaled values ​​of cbf_flag or other syntax elements, etc.) can be used to specify blocks where the CRC method may not be allowed.

[0173] The present disclosure may generally refer to "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to transmitting the values ​​of syntax elements and / or other data used to decode the encoded video data. That is, the video encoder 200 may signal the values ​​of syntax elements in the bitstream. Generally, signaling refers to generating values ​​in the bitstream. As mentioned above, the source device 102 may transmit the bitstream to the destination device 116 substantially in real time, or not in real time, such as may occur when the syntax elements are stored to the storage device 112 for later retrieval by the destination device 116.

[0174] Figure 5A and 5B2 is a conceptual diagram showing an exemplary quadtree binary tree (QTBT) structure 290 and a corresponding coding tree unit (CTU) 292. Solid lines represent quadtree splits, while dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. For quadtree splitting, there is no need to indicate the split type because the quadtree node splits a block horizontally and vertically into 4 sub-blocks of equal size. Therefore, the video encoder 200 can encode syntax elements (such as split information) for the region tree level (i.e., the first level) of the QTBT structure 290 (i.e., solid lines) and syntax elements (such as split information) for the prediction tree level (i.e., the second level) of the QTBT structure 290 (i.e., dashed lines), and the video decoder 300 can decode it. For a CU represented by a terminal leaf node of the QTBT structure 290 , the video encoder 200 may encode video data such as prediction data and transform data, and the video decoder 300 may decode the video data.

[0175] generally, Figure 5B The CTU 292 may be associated with parameters defining the size of blocks corresponding to nodes of the QTBT structure 290 at the first and second levels. These parameters may include a CTU size (indicating the size of the CTU 292 in samples), a minimum quadtree size (MinQTSize, indicating the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, indicating the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, indicating the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, indicating the minimum allowed binary tree leaf node size).

[0176] The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, and each child node may be segmented according to the quadtree segmentation. That is, the nodes of the first level are leaf nodes (without child nodes) or have four child nodes. The example of the QTBT structure 290 represents such nodes as including parent nodes and child nodes, where solid lines represent branches. If the nodes of the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), they may be further segmented by the corresponding binary tree. The binary tree splitting of a node may be iteratively performed until the node generated by the splitting reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 290 represents such nodes as representing branches with dotted lines. The binary tree leaf node is called a coding unit (CU), which is used for prediction (e.g., intra-frame picture or inter-frame picture prediction) and transformation without any further segmentation. As discussed above, a CU may also be referred to as a "video block" or "block".

[0177] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (luminance sample and two corresponding 64x64 chrominance samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate a quadtree leaf node. The size of the quadtree leaf node can be from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the quadtree leaf node is 128x128, it will not be further split by the binary tree because the size exceeds MaxBTSize (i.e., 64x64, in this example). Otherwise, the quadtree leaf node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node of the binary tree and its binary tree depth is 0. When the binary tree depth reaches MaxBTDepth (4 in this example), further splitting is not allowed. When the width of a binary tree node is equal to MinBTSize (4 in this example), this implies that no further vertical splits are allowed. Similarly, a binary tree node with a height equal to MinBTSize implies that no further horizontal splits are allowed for the binary tree node. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further segmentation.

[0178] Figure 6 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 6The above description is provided for explanation purposes and should not be considered as limiting the techniques broadly exemplified and described in this disclosure. For explanation purposes, this disclosure describes the video encoder 200 in the context of video coding standards such as the HEVC video coding standard and the H.266 video coding standard under development. However, the techniques of this disclosure are not limited to these video coding standards and may be generally applicable to video encoding and decoding.

[0179] exist Figure 6 In the example of , the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy encoding unit 220. In addition, in Figure 6 In the example of , the video encoder 200 may include a residual modification unit 205 and an inverse residual modification unit 213. Any or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the residual modification unit 205, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the inverse residual modification unit 213, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 may be implemented in one or more processors or processing circuits. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0180] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) stored in the video data memory 230. DPB218 can act as a reference picture memory, which stores reference video data for use when the video encoder 200 predicts subsequent video data. Video data memory 230 and DPB218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or a separate memory device. In various examples, video data memory 230 can be on the chip with other components of the video encoder 200 as shown, or off the chip relative to those components.

[0181] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory internal to the video encoder 200 (unless specifically described as such), or limited to memory external to the video encoder 200 (unless specifically described as such). Rather, references to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data of a current block to be encoded). Figure 1 Memory 106 may also provide temporary storage for outputs from various units of video encoder 200 .

[0182] Show Figure 6 Various units are provided to assist in understanding the operations performed by the video encoder 200. The unit may be implemented as a fixed-function circuit, a programmable circuit, or a combination thereof. A fixed-function circuit refers to a circuit that provides a specific functionality and pre-sets the executable operations. A programmable circuit refers to a circuit that can be programmed to perform various tasks and provide flexible functionality in the executable operations. For example, a programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more 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.

[0183] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store object code for software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0184] The video data memory 230 is configured to store received video data. The video encoder 200 may retrieve a picture of video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be original video data to be encoded.

[0185] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units to perform video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0186] Mode selection unit 202 typically coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of CTUs into CUs, prediction modes for CUs, transform types for residual data for CUs, quantization parameters for residual data for CUs, etc. Mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0187] The video encoder 200 may partition a picture obtained from the video data memory 230 into a series of CTUs, and pack one or more CTUs into a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure, such as the QTBT structure described above or the quadtree structure of HEVC. As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. This CU may also be generally referred to as a "video block" or "block".

[0188] Typically, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of the PU and TU in HEVC). For inter-frame prediction of the current block, the 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 decoded pictures stored in the 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, based on the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may generally perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block having the minimum value produced by these calculations, thereby indicating the reference block that most closely matches the current block.

[0189] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of the reference block in the reference picture relative to the position of the current block in the 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 use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate values ​​for the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0190] As another example, for intra prediction or intra prediction coding, the intra prediction unit 226 may generate a prediction block from samples neighboring the current block. For example, for directional mode, the intra prediction unit 226 may generally mathematically combine the values ​​of neighboring samples and fill in these calculated values ​​in a defined direction across the current block to generate a prediction block. As another example, for DC mode, the intra prediction unit 226 may calculate an average of samples neighboring the current block and generate a prediction block to include such a resulting average for each sample of the prediction block.

[0191] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, the residual generation unit 204 may also determine the difference between the sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0192] In an example where the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As indicated above, the size of the CU may refer to the size of the luma coding block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra-prediction, and symmetric PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or the like for inter-prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-prediction.

[0193] In examples where the mode selection unit does not further partition a CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As indicated above, the size of a CU may refer to the size of the luma coding block of the CU. Video encoder 200 and video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0194] For other video coding techniques such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding (to name a few examples), mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the coding technique. In some examples such as palette mode coding, mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how to reconstruct the block based on the selected palette. In such modes, mode selection unit 202 may provide these syntax elements to entropy encoding unit 220 for encoding.

[0195] As described above, the residual generation unit 204 receives video data for a current block and a corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0196] According to one or more techniques of the present disclosure, the residual modification unit 205 may apply the RMF to the residual chroma data generated by the residual generation unit 204. For example, the residual modification unit 205 may apply a first residual modification function to the first chroma residual data of the block of video data to generate first modified chroma residual data. The residual modification unit 205 may apply a second residual modification function to the second chroma residual data of the block to generate second modified chroma residual data. In this example, the first chroma residual data is associated with a first chroma component (e.g., Cb), and the second chroma residual data is associated with a second chroma component (e.g., Cr). The residual modification unit 205 does not apply the RMF to the residual luma data.

[0197] The transform processing unit 206 applies one or more transforms to the residual block (e.g., the block of modified residual data produced by applying the RMF) to produce a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform multiple transforms on the residual block, such as a primary transform and a secondary transform, such as a rotation transform. In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0198] Quantization unit 208 may quantize transform coefficients in a transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. Video encoder 200 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 (e.g., via mode selection unit 202). Quantization may introduce a loss of information, and therefore, the quantized transform coefficients may have a lower precision than the original transform coefficients generated by transform processing unit 206.

[0199] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform to the quantized transform coefficient block, respectively, to reconstruct the residual block according to the transform coefficient block. According to one or more examples of the present disclosure, the inverse residual modification unit 213 may apply an inverse RMF to the decoded modified chroma residual data generated by the inverse transform processing unit 212. The inverse RMF applied by the inverse residual modification unit 213 may be the inverse of the RMF applied by the residual modification unit 205. Therefore, the inverse residual modification unit 213 may generate a residual block. The inverse residual modification unit 213 does not apply the inverse RMF to the residual luminance data.

[0200] The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although it may have 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.

[0201] Filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blockiness artifacts along the edges of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0202] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in examples where the operation of the filter unit 216 is not required, the reconstruction unit 214 may store the reconstructed blocks to the DPB 218. In examples where the operation of the filter unit 216 is required, the filter unit 216 may store the filtered reconstructed blocks to the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may obtain a reference picture formed by the reconstructed (and possibly filtered) blocks from the DPB 218 to perform inter-frame prediction on blocks of subsequently encoded pictures. In addition, the intra-frame prediction unit 226 may use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction on other blocks in the current picture.

[0203] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode the quantized transform coefficient blocks from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode the prediction syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on the syntax elements (which is another example of video data) to generate entropy-encoded data. For example, the entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioned entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy coding unit 220 may operate in a bypass mode in which the syntax elements are not entropy encoded.

[0204] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required to reconstruct blocks of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0205] The operations described above are for block descriptions. This description should be understood as operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are the luma and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are the luma and chroma components of a PU.

[0206] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As one example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks need not be repeated to identify MVs and reference pictures for chroma blocks. Rather, the MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0207] Video encoder 200 represents an example of a device configured to encode video data, the device comprising: a memory configured to store video data; and one or more processing units implemented in a circuit and configured to: apply a first residual modification function to first chroma residual data to produce first modified chroma residual data; encode the first modified chroma residual data; apply a second residual modification function to second chroma residual data to produce second modified chroma residual data; and encode the second modified chroma residual data, wherein the first chroma residual data is associated with a first chroma component and the second chroma residual data is associated with a second chroma component.

[0208] Figure 7 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 7 It is provided for explanation purposes and is not a limitation of the techniques widely exemplified and described in this disclosure. For explanation purposes, this disclosure describes the video decoder 300 according to the techniques of JEM, VVC, and HEVC. However, the techniques of this disclosure may be performed by video decoding devices configured for other video decoding standards.

[0209] exist Figure 7In the example of , the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. According to one or more techniques of the present disclosure, the video decoder 300 also includes an inverse residual modification unit 309. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the inverse residual modification unit 309, the reconstruction unit 310, the filter unit 312, and the DPB 314 may be implemented in one or more processors or processing circuits. In addition, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0210] 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 that perform predictions 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, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0211] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. The video bitstream may be, for example, stored from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. Moreover, memory 320 may store video data other than syntax elements of decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, which video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or a separate memory device. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0212] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) to obtain the decoded video data. That is, memory 120 may store data as discussed above with respect to CPB memory 320. Likewise, when some or all of the functionality of video decoder 300 is implemented in software to be executed by the processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0213] Show Figure 7 The various units shown in the figure are used to assist in understanding the operations performed by the video decoder 300. The units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 6 , fixed-function circuits refer to circuits that provide specific functionality and pre-set the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. 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 units may be integrated circuits.

[0214] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuit, an on-chip or off-chip memory may store instructions (e.g., object code) of the software that the video decoder 300 receives and executes.

[0215] The entropy decoding unit 302 may receive the encoded video data from the CPB memory 320 and entropy decode the video data to reproduce the syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the inverse residual modification unit 309, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0216] Generally, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (wherein a block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0217] The entropy decoding unit 302 may entropy decode the quantized transform coefficients and syntax elements defining the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or a transform mode indication. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and also determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0218] 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. According to one or more examples of the present disclosure, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate decoded modified chroma residual data. In one example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block. Because the current block may include a luma component and two chroma components, the inverse transform processing unit 308 may generate decoded luma residual data, first decoded modified chroma residual data, and second decoded modified chroma residual data for the current block.

[0219] According to one or more techniques of the present disclosure, the inverse residual modification unit 309 may apply an inverse RMF to the decoded modified chroma residual data. Thus, the inverse residual modification unit 309 may apply a first inverse residual modification function to the first decoded modified chroma residual data (e.g., Cb residual data) to generate first inverse modified chroma residual data. Additionally, the inverse residual modification unit 309 may apply a second inverse residual modification function to the second decoded modified chroma residual data (e.g., Cr residual data) to generate second inverse modified chroma residual data.

[0220] In addition, prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-predicted, motion compensation unit 316 may generate a prediction block. In this case, the prediction information syntax elements may indicate a reference picture in DPB 314 from which the reference block is taken and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 may generally be substantially similar to the instructions for motion compensation unit 224 ( Figure 6 ) performs the inter-frame prediction process in the manner described.

[0221] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Moreover, the intra-prediction unit 318 may generally be substantially similar to the intra-prediction unit 226 ( Figure 6 The intra prediction process is performed in the manner described in ). The intra prediction unit 318 can obtain data of samples adjacent to the current block from the DPB 314.

[0222] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block (e.g., the block of residual chroma data generated by the inverse residual modification unit 309). 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. According to the technology of the present disclosure, the residual block may be the inversely modified chroma residual data generated by the inverse residual modification unit 309.

[0223] The filter unit 312 may perform one or more filtering operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0224] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in examples where the operations of the filter unit 312 are not performed, the reconstruction unit 310 may store the reconstructed block to the DPB 314. In examples where the operations of the filter unit 312 are performed, the filter unit 312 may store the filtered reconstructed block to the DPB 314. As discussed above, the DPB 314 may provide reference information such as samples of the current picture for intra-frame prediction and previously decoded pictures for subsequent motion compensation to the prediction processing unit 304. In addition, the video decoder 300 may output the decoded picture from the DPB for subsequent presentation on a display such as a Figure 1 on a display device 118 of the display device.

[0225] Thus, the video decoder 300 represents an example of a video decoding device, which includes: a memory configured to store video data; and one or more processing units implemented in a circuit and configured to: apply a first inverse residual modification function to first decoded modified chroma residual data to produce first inverse modified chroma residual data; apply a second inverse residual modification function to second decoded modified chroma residual data to produce second inverse modified chroma residual data, wherein the first decoded modified chroma residual data is associated with a first chroma component and the second decoded modified chroma residual data is associated with a second chroma component; and reconstruct blocks of video data based on the first inverse modified chroma residual data and the second inverse modified chroma residual data.

[0226] Figure 8 2 is a flowchart illustrating an exemplary method for encoding a current block. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and Figure 6 ), but it should be understood that other devices may be configured to perform similar Figure 8 method of method of method.

[0227] In this example, the video encoder 200 first predicts the current block (350). For example, the video encoder 200 may form a prediction block for the current block. The video encoder 200 may then calculate a residual block for the current block (352). In other words, the video encoder 200 may calculate luma residual data and chroma residual data for the current block. To calculate the residual block, the video encoder 200 may calculate the difference between samples of the original unencoded block of the current block and corresponding samples of the prediction block. For example, to calculate a Cb residual block, the video encoder 200 may calculate the difference between Cb samples of the original unencoded block of the current block and corresponding Cb samples of the prediction block.

[0228] According to one or more techniques of this disclosure, video encoder 200 may apply a residual modification function to chroma residual data of a current block to produce modified chroma residual data (353). Video encoder 200 may then transform the residual block to produce transform coefficients and quantize the transform coefficients of the residual block (354). That is, video encoder 200 may then apply a forward transform that converts the modified chroma residual data to a transform domain, such as a frequency domain, thereby producing transform coefficients. Video encoder 200 may then quantize the transform coefficients. In other examples, video encoder 200 may apply the residual modification function after applying the forward transform.

[0229] Next, video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, video encoder 200 may entropy encode the transform coefficients (358). For example, video encoder 200 may encode the transform coefficients using CAVLC or CABAC. Video encoder 200 may then output entropy encoded data for the block (360).

[0230] Fig. 9 is a flowchart illustrating an exemplary method for decoding a block of current video data. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and Figure 7 ), but it should be understood that other devices may be configured to perform similar Fig. 9 method of method of method.

[0231] The video decoder 300 may receive entropy coded data for a current block, such as entropy coded data and entropy coded prediction information corresponding to a transform coefficient of a residual block of the current block (370). The video decoder 300 may entropy decode the entropy coded data to determine prediction information for the current block and reproduce the transform coefficients of the residual block (372). The video decoder 300 may predict the current block (374), for example, using intra-frame or inter-frame prediction as indicated by the prediction information of the current block, to calculate the prediction block of the current block. The video decoder 300 may then reverse scan the reproduced transform coefficients (376) to produce a block of quantized transform coefficients. The video decoder 300 may then inverse quantize and inverse transform the transform coefficients to produce a residual block (378). The video decoder 300 may perform actions 372 to 378 for each color component of the current block. Thus, the video decoder 300 may produce a Y residual block, a Cb residual block, and a Cr residual block for the current block. The Cb residual block may be residual chroma data after the first decoding, and the Cr residual block may be residual chroma data after the second decoding. In other examples, the Cr residual block may be considered as residual chroma data after the first decoding, and the Cb residual block may be considered as residual chroma data after the second decoding. According to one or more techniques of the present disclosure, the video decoder 300 may apply an inverse residual modification function to the decoded residual chroma data (379). The video decoder 300 may apply the inverse residual modification function to the decoded residual chroma data according to any of the examples provided elsewhere in the present disclosure. In other examples, the video decoder 300 may apply the inverse residual modification function before applying the inverse transform.

[0232] The video decoder 300 may finally decode the current block by combining the prediction block with the residual block (380).For example, the video decoder 300 may add samples of the color component of the prediction block to corresponding samples of the residual block of the color component for each of the color components.

[0233] Fig.10 is a flow chart illustrating an example operation of video encoder 200 in accordance with one or more techniques of this disclosure. Fig.10 In the example of , video encoder 200 may apply a first residual modification function to first chroma residual data of a block of video data to generate first modified chroma residual data (400). For example, video encoder 200 may apply a residual modification function as described in any of equations 1.ai, 1.bi, 1.ci, 1.cv or another residual modification function.

[0234] In addition, Fig.10 In an example of , the video encoder 200 may encode first modified chroma residual data (402). As part of encoding the first modified chroma residual data, the video encoder 200 may apply a forward transform (e.g., a discrete cosine transform, a discrete sine transform, or another type of transform) that converts the first modified chroma residual data from a sample domain to a transform domain such as a frequency domain (404). The data in the sample domain indicates the value of the sample (e.g., luma value, Cb value, Cr value). By applying the forward transform to the first modified chroma residual data, the video encoder 200 may generate a first block of transform coefficients. In addition, as part of encoding the first modified chroma residual data, the video encoder 200 may quantize the transform coefficients in the first block of transform coefficients. In addition, the video encoder 200 may apply entropy encoding to syntax elements representing the quantized first block of transform coefficients. In some examples, the video encoder 200 may skip the application of the forward transform. In other words, the video encoder 200 may use a transform skip mode for the current block. For convenience of explanation, if a transform skip mode is used for a current block, the present disclosure may use the term 'transform coefficient' so as to be applied to residual data.

[0235] In addition, video encoder 200 may apply a second residual modification function to the second chroma residual data of the block to generate second modified chroma residual data (406). For example, video encoder 200 may apply a residual modification function as described in any of equations 1.a.ii, 1.b.ii, 1.c.ii, 1.c.vi, or another residual modification function.

[0236] The video encoder 200 may encode the second modified chroma residual data (408). The first chroma residual data is associated with the first chroma component, and the second chroma residual data is associated with the second chroma component. As part of encoding the second modified chroma residual data, the video encoder 200 may apply a forward transform (e.g., a discrete cosine transform, a discrete sine transform, or another type of transform) that converts the second modified chroma residual data from a sample domain to a transform domain such as a frequency domain (410). By applying the forward transform to the second modified chroma residual data, the video encoder 200 may generate a second block of transform coefficients. In addition, as part of encoding the second modified chroma residual data, the video encoder 200 may quantize the transform coefficients in the second block of transform coefficients. In addition, the video encoder 200 may apply entropy encoding to syntax elements representing the quantized second block of transform coefficients. In some examples, the video encoder 200 may skip the application of the forward transform.

[0237] In some examples, before applying the first residual modification function, the video encoder 200 may determine whether to apply the first residual modification function or the third residual modification function to the first chroma residual data to generate the first modified chroma residual data. Similarly, before applying the second residual modification function, the video encoder 200 may determine whether to apply the second residual modification function or the fourth residual modification function to the second chroma residual data to generate the second modified chroma residual data. Thus, the video encoder 200 may determine which residual modification function to apply to the first residual chroma data and the second residual chroma data.

[0238] The video encoder 200 may determine which residual modification function to apply in one of a variety of ways. For example, in some examples, the video encoder 200 may determine whether to apply a first residual modification function or a third residual modification function to the first chroma residual data to generate a first modified chroma residual data based on one or more characteristics of the block. In addition, the video encoder 200 may determine whether to apply a second residual modification function or a fourth residual modification function to the second chroma residual data to generate a second modified chroma residual data based on one or more characteristics of the block. Such characteristics of the block may include one or more of the following: whether the slice or tile containing the block is an intra-frame type or an inter-frame type, whether the current picture reference is used with the block, whether a dual or shared decoding tree is used with the block, the size of the block, the aspect ratio of the block, or other characteristics of the block. For example, the video encoder 200 may determine to use the first residual modification function if the block is in an I slice, or determine to use the third residual modification function if the block is in a P slice or a B slice. An I slice is a slice that allows intra-frame prediction but does not allow inter-frame prediction. A P slice is a slice that allows intra prediction and unidirectional inter prediction but not bidirectional inter prediction. A B slice is a slice that allows intra prediction, unidirectional inter prediction, and bidirectional inter prediction.

[0239] In some examples, video encoder 200 may signal in the bitstream data indicating whether the first residual modification function or the third residual modification function is applied to the first chroma residual data to produce the first modified chroma residual data. Similarly, video encoder 200 may signal in the bitstream data indicating whether the second residual modification function or the fourth residual modification function is applied to the second chroma residual data to produce the second modified chroma residual data. For example, one or more syntax elements signaled in the bitstream may specify which residual modification function is applied.

[0240] In some examples, the video encoder 200 may apply the CRS process together with applying the residual modification function. For example, in some examples, after applying the first inverse residual modification function to the first chroma residual data to produce the first modified chroma residual data, the video encoder 200 may apply the CRS process to the first inverse modified chroma residual data. Additionally, in this example, after applying the second residual modification function to the second chroma residual data to produce the second modified chroma residual data, the video encoder 200 may apply the CRS process to the second modified chroma residual data. For example, to apply the CRS process, the video encoder 200 may apply Equation 7, as described elsewhere in this disclosure.

[0241] In other examples, as part of applying the first residual modification function to the first chroma residual data to generate the first modified chroma residual data, the video encoder 200 may apply the CRS process to the first chroma residual data. Additionally, in this example, as part of applying the second residual modification function to the second chroma residual data to generate the second modified chroma residual data, the video encoder 200 may apply the CRS process to the second chroma residual data. As part of applying the first and second residual modification functions according to any of the examples provided elsewhere in this disclosure, the video encoder 200 may apply the CRS process.

[0242] Fig.11 is a flow chart illustrating example operation of video decoder 300 in accordance with one or more techniques of this disclosure. Fig.11In an example of , the video decoder 300 may generate first decoded modified chroma residual data (450) by applying an inverse transform to convert a first set of transform coefficients of a block of video data from a transform domain to a sample domain. For example, the video decoder 300 may apply an inverse DCT transform that converts the first set of transform coefficients from a frequency domain to a sample domain. Additionally, the video decoder 300 may generate second decoded modified chroma residual data (452) by applying an inverse transform to convert a second set of transform coefficients of the block from a transform domain to a sample domain. The first decoded modified chroma residual data is associated with a first chroma component (e.g., Cb), and the second decoded modified chroma residual data is associated with a second chroma component (e.g., Cr).

[0243] In addition, Fig.11 In the example of , video decoder 300 may apply a first inverse residual modification function to the first decoded modified chroma residual data to generate first inverse modified chroma residual data (454). For example, video decoder 300 may apply an inverse residual modification function as described in any of equations 1.a.iii, 1.b.iii, 1.c.iii, 1.c.vii, or another inverse residual modification function.

[0244] Video decoder 300 may apply a second inverse residual modification function to the second decoded modified chroma residual data to generate second inverse modified chroma residual data (456). For example, video decoder 300 may apply an inverse residual modification function as described in any of equations 1.a.iv, 1.b.iv, 1.c.iv, 1.c.viii, or another inverse residual modification function.

[0245] Additionally, video decoder 300 may reconstruct a block of video data based on the first inverse-modified chroma residual data and the second inverse-modified chroma residual data (458). For example, video decoder 300 may add samples of the first inverse-modified chroma residual data to corresponding samples of the predicted block of the first chroma component. Additionally, in this example, video decoder 300 may add samples of the second inverse-modified chroma residual data to corresponding samples of the predicted block of the second chroma component. In other words, video decoder 300 may add the first inverse-modified chroma residual data to the first predicted chroma data to obtain first reconstructed chroma data for the block, and add the second inverse-modified chroma residual data to the second predicted chroma data to obtain second reconstructed chroma data for the block.

[0246] In some examples, before applying the first inverse residual modification function, the video decoder 300 may determine whether to apply the first inverse residual modification function or the third inverse residual modification function to the first decoded modified chroma residual data to generate the first inverse modified chroma residual data. Similarly, before applying the second inverse residual modification function, the video decoder 300 may determine whether to apply the second inverse residual modification function or the fourth inverse residual modification function to the second decoded modified chroma residual data to generate the second inverse modified chroma residual data. Thus, the video decoder 300 may determine which residual modification function to apply to the first decoded residual chroma data and the second decoded residual chroma data.

[0247] The video decoder 300 may determine which reverse residual modification function to apply in one of a variety of ways. For example, in some examples, the video decoder 300 may determine whether to apply the first reverse residual modification function or the third reverse residual modification function to the first decoded modified chroma residual data to generate the first reverse modified chroma residual data based on one or more characteristics of the block. In addition, the video decoder 300 may determine whether to apply the second reverse residual modification function or the fourth reverse residual modification function to the second decoded modified chroma residual data to generate the second reverse modified chroma residual data based on one or more characteristics of the block. Such characteristics of the block may include one or more of the following: whether the slice or tile containing the block is an intra-frame type or an inter-frame type, whether the current picture reference is used with the block, whether the dual or shared decoding tree is used with the block, the size of the block, the aspect ratio of the block, or other characteristics of the block. For example, the video decoder 300 may determine to use the first reverse residual modification function when the block is in an I slice, or determine to use the third reverse residual modification function when the block is in a P slice or a B slice.

[0248] In some examples, the video decoder 300 may determine, based on data signaled in the bitstream, whether to apply a first inverse residual modification function or a third inverse residual modification function to the first decoded modified chroma residual data to produce the first inverse modified chroma residual data. Similarly, the video decoder 300 may determine, based on data signaled in the bitstream, whether to apply a second inverse residual modification function or a fourth inverse residual modification function to the second decoded modified chroma residual data to produce the second inverse modified chroma residual data. For example, one or more syntax elements signaled in the bitstream may specify which inverse residual modification function to use.

[0249] In some examples, the video decoder 300 may apply a reverse CRS process along with applying a reverse residual modification function. For example, in some examples, before applying a first reverse residual modification function to the first decoded modified chroma residual data to produce the first reverse modified chroma residual data, the video decoder 300 may apply a reverse CRS process to the first decoded modified chroma residual data. Additionally, in this example, before applying a second reverse residual modification function to the second decoded modified chroma residual data to produce the second reverse modified chroma residual data, the video decoder 300 may apply a reverse CRS process to the second decoded modified chroma residual data. For example, to apply the reverse CRS process, the video decoder 300 may apply Equation 8, as described elsewhere in the present disclosure.

[0250] In other examples, as part of applying the first inverse residual modification function to the first decoded modified chroma residual data to generate the first inverse modified chroma residual data, the video decoder 300 may apply the inverse CRS process to the first decoded modified chroma residual data. Additionally, in this example, as part of applying the second inverse residual modification function to the second decoded modified chroma residual data to generate the second inverse modified chroma residual data, the video decoder 300 may apply the inverse CRS process to the second decoded modified chroma residual data.

[0251] The following enumerated paragraphs provide a non-limiting list of examples of the techniques of this disclosure.

[0252] Example 1A. A method for decoding video data, the method comprising: applying a first inverse residual modification function to first decoded chroma residual data (i.e., first decoded modified chroma residual data in the context of video decoding) to produce first modified decoded chroma residual data (i.e., first inversely modified decoded chroma residual data in the context of video decoding); applying a second inverse residual modification function to second decoded chroma residual data (i.e., second decoded modified chroma residual data in the context of video decoding) to produce second modified decoded chroma residual data (i.e., second inversely modified decoded chroma residual data in the context of video decoding), wherein the first decoded chroma residual data is associated with a first chroma component and the second decoded chroma residual data is associated with a second chroma component; reconstructing a block of video data based on the first modified decoded chroma residual data and the second modified decoded chroma residual data.

[0253] Example 2A. A method according to Example 1A, wherein reconstructing the block includes: adding the first modified decoded chroma residual data to the first predicted chroma data to obtain first reconstructed chroma data for the block; and adding the second modified decoded chroma residual data to the second predicted chroma data to obtain second reconstructed chroma data for the block.

[0254] Example 3A. A method according to any one of Examples 1A to 2A, wherein: the first inverse residual modification function is: invF1(x,y)=(resCr(x,y)'+resCb(x,y)'+B1) / M1, the second inverse residual modification function is: invF2(x,y)=(resCr(x,y)'-resCb(x,y)'+B2) / M2, wherein resCb(x,y)' is the first decoded chroma residual data, resCr(x,y)' is the second decoded chroma residual data, B1 and B2 are rounding terms, and 1 / M1 and 1 / M2 are normalization factors.

[0255] Example 4A. A method according to any one of Examples 1A to 2A, wherein: the first inverse residual modification function is: invF1(x,y)=(resCb(x,y)'+resCr(x,y)'+B1) / M1, the second inverse residual modification function is: invF2(x,y)=(resCb(x,y)'-resCr(x,y)'+B2) / M2, wherein resCb(x,y)' is the first decoded chroma residual data, resCr(x,y)' is the second decoded chroma residual data, B1 and B2 are rounding terms, and 1 / M1 and 1 / M2 are normalization factors.

[0256] Example 5A. A method according to any one of Examples 1A to 2A, wherein: the first inverse residual modification function is: invF1(x,y)=(resCr(x,y)'+B10) / M10+(resCb(x,y)'+B11) / M11, the second inverse residual modification function is: invF2(x,y)=(resCr(x,y)'+B20) / M20-resCb(x,y)'+B21) / M21, wherein resCb(x,y)' is the first decoded chroma residual data, resCr(x,y)' is the second decoded chroma residual data, B10, B11, B20 and B21 are rounding terms, and 1 / M10, 1 / M11, 1 / M20 and 1 / M21 are normalization factors.

[0257] Example 6A. A method according to any one of Examples 1A to 5A, wherein the method further includes: applying a first inverse chroma residual scaling (CRS) process to the first modified decoded chroma residual data; and applying a second inverse CRS process to the second modified decoded chroma residual data.

[0258] Example 7A. A method according to any one of Examples 1A to 6A, wherein: applying the first inverse residual modification function includes applying the first inverse residual modification function after inverse quantizing the first decoded chroma residual data and before applying the inverse transform process, and applying the second inverse residual modification function includes applying the second inverse residual modification function after inverse quantizing the second decoded chroma residual data and before applying the inverse transform process.

[0259] Example 8A. The method of any one of Examples 3A to 5A, wherein resCr(x,y)′ or resCb(x,y)′ is replaced with resY(x,y)′, wherein resY(x,y)′ is the decoded luma residual data.

[0260] Example 9A. The method of any one of Examples 1A to 8A, further comprising obtaining, from a bitstream comprising an encoded representation of video data, a flag indicating whether to apply the first inverse residual modification function and the second inverse residual modification function.

[0261] Example 10A. The method of Example 9A, wherein a coded block flag (CBF) is signaled if the flag is true for the first chroma component and the CBF for the second chroma component is true.

[0262] Example 11A. A method according to Example 10A, wherein the flag is a first flag and the method further includes obtaining a second flag from the bitstream, the second flag being used for a transform unit, the second flag indicating which of the following applies: (i) signaling both the first decoded chroma residual data and the second decoded chroma residual data, and (ii) signaling only one of the first decoded chroma residual data and the second decoded chroma residual data.

[0263] Example 12A. The method of Example 11A, further comprising obtaining from the bitstream a third flag indicating which of the first decoded chroma residual data and the second decoded chroma residual data is forced to zero.

[0264] Example 13A. A method according to any one of Examples 9A to 12A, wherein the flag indicating whether to apply the first inverse residual modification function and the second inverse residual modification function is a first flag and the method further includes: obtaining the CBF of a first chrominance component from the bitstream; selecting a context of the first flag based on the CBF of the first chrominance component; and entropy decoding the first flag using the selected context.

[0265] Example 14A. A method according to any one of Examples 9A to 12A, wherein a flag indicating whether to apply the first inverse residual modification function and the second inverse residual modification function is a first flag and the method further includes: selecting a context of the CBF of the first chroma component based on the first flag; and entropy decoding the CBF of the first chroma component using the selected context.

[0266] Example 15A. The method according to any one of Examples 1A to 14A further includes: determining a first inverse residual modification function from a plurality of available first inverse residual modification functions; and determining a second inverse residual modification function from a plurality of available second inverse residual modification functions.

[0267] Example 16A. The method according to any one of Examples 1A to 15A further includes: before applying a first inverse residual modification function to the first decoded chroma residual data: inverse quantizing the first quantized chroma transform data based on a quantization parameter and a first quantization parameter offset; and applying an inverse transform to the inverse quantized first quantized chroma transform data to generate first decoded chroma residual data, and before applying a second inverse residual modification function to the second decoded chroma residual data: inverse quantizing the second quantized chroma transform data based on the quantization parameter and the second quantization parameter offset; and applying an inverse transform to the second inverse quantized second quantized chroma transform data to generate second decoded chroma residual data.

[0268] Example 17A. The method of Example 16A, further comprising obtaining at least one of the first quantization parameter offset or the second quantization parameter offset from a bitstream comprising an encoded representation of the video data.

[0269] Example 18A. The method according to any one of Examples 1A to 17A further includes: determining whether to allow the application of the first inverse residual modification function based on one or more characteristics of the block; determining whether to allow the application of the second inverse residual modification function based on one or more characteristics of the block.

[0270] Example 1B. A method for encoding video data, the method comprising: applying a first residual modification function to first chroma residual data to produce first modified chroma residual data; encoding the first modified chroma residual data; applying a second residual modification function to second chroma residual data to produce second modified chroma residual data; and encoding the second modified chroma residual data, wherein the first chroma residual data is associated with a first chroma component and the second chroma residual data is associated with a second chroma component.

[0271] Example 2B. The method of Example 1B, wherein encoding the modified chroma residual data comprises: applying a forward transform to the modified chroma residual data to produce transform data; and quantizing the transform data to produce quantized transform data.

[0272] Example 3B. A method according to any one of Examples 1B to 2B, wherein: the first residual modification function is: F1(x,y) = (resCb(x,y) - resCr(x,y) + A1) / N1, the second residual modification function is: F2(x,y) = (resCb(x,y) + resCr(x,y) + A2) / N2, wherein resCb(x,y) is the first chrominance residual data, resCr(x,y) is the second chrominance residual data, A1 and A2 are rounding terms, and 1 / N1 and 1 / N2 are normalization factors.

[0273] Example 4B. A method according to any one of Examples 1B to 2B, wherein: the first residual modification function is: F1(x,y)=(resCb(x,y)+resCr(x,y)+A1) / N1, the second residual modification function is: F2(x,y)=(resCb(x,y)-resCr(x,y)+A2) / N2, wherein resCb(x,y) is the first chrominance residual data, resCr(x,y) is the second chrominance residual data, A1 and A2 are rounding terms, and 1 / N1 and 1 / N2 are normalization factors.

[0274] Example 5B. A method according to any one of Examples 1B to 2B, wherein: the first residual modification function is: F1(x,y) = (resCb(x,y) + A10) / N10 – (resCr(x,y) + A11) / N11, the second residual modification function is: the second residual modification function is: F2(x,y) = (resCb(x,y) + A20) / N20 + (resCr(x,y) + A21) / N21, wherein resCb(x,y) is the first chrominance residual data, resCr(x,y) is the second chrominance residual data, A10, A11, A20 and A21 are rounding terms, and 1 / N10, 1 / N11, 1 / N20 and 1 / N21 are normalization factors.

[0275] Example 6B. A method according to any one of Examples 1B to 5B, wherein: the method further includes: applying a chroma residual scaling (CRS) to first chroma residual data; and applying the CRS to second chroma residual data, applying the first residual modification function includes applying the first residual modification function to the first chroma residual data after applying the CRS to the first chroma residual data, and applying the second residual modification function includes applying the second residual modification function to the second chroma residual data after applying the CRS to the second chroma residual data.

[0276] Example 7B. A method according to any one of Examples 1B to 6B, wherein: applying a first residual modification function includes applying a forward transform process to first chroma residual data and before quantizing the first chroma residual data, and applying a second residual modification function includes applying a forward transform process to second chroma residual data and before quantizing the second chroma residual data.

[0277] Example 8B. The method of any of Examples 3B to 5B, wherein resCr(x,y) or resCb(x,y) is replaced with resY(x,y)′, wherein resY(x,y)′ is luma residual data.

[0278] Example 9B. The method of any one of Examples 1B to 8B, further comprising signaling, in a bitstream comprising an encoded representation of the video data, a flag indicating whether the first residual modification function and the second residual modification function are applied.

[0279] Example 10B. The method of Example 9B, wherein if a coded block flag (CBF) of a first chroma component is true and a CBF of the second chroma component is true, then the flag is signaled.

[0280] Example 11B. A method according to Example 10B, wherein the flag is a first flag and the method further includes including a second flag in the bitstream, the second flag being used for a transform unit, the second flag indicating which of the following applies: (i) signaling both the first chroma residual data and the second chroma residual data, and (ii) signaling only one of the first chroma residual data and the second chroma residual data.

[0281] Example 12B. The method of Example 11B, wherein the method further comprises including in the bitstream a third flag indicating which of the first chroma residual data and the second chroma residual data is forced to zero.

[0282] Example 13B. A method according to any one of Examples 9B to 12B, wherein a flag indicating whether to apply a first residual modification function and a second residual modification function is a first flag, and the method further includes: including a CBF of a first chrominance component in a bitstream; selecting a context of the first flag based on the CBF of the first chrominance component; and entropy encoding the first flag using the selected context.

[0283] Example 14B. A method according to any one of Examples 9B to 12B, wherein a flag indicating whether to apply the first residual modification function and the second residual modification function is a first flag and the method further includes: selecting a context of the CBF of the first chrominance component based on the first flag; and entropy encoding the CBF of the first chrominance component using the selected context.

[0284] Example 15B. The method of any one of Examples 1B to 14B, further comprising: determining a first residual modification function from among a plurality of available first residual modification functions; and determining a second residual modification function from among a plurality of available second residual modification functions.

[0285] Example 16B. The method according to any one of Examples 1B to 15B further includes: after applying the first residual modification function to the first chroma residual data: applying a transform to the first chroma residual data to generate first chroma transform data; and quantizing the first chroma transform data based on a quantization parameter and a first quantization parameter offset; and after applying the second residual modification function to the second chroma residual data: applying the transform to the second chroma residual data to generate second chroma transform data; and quantizing the first chroma transform data based on the quantization parameter and the second quantization parameter offset.

[0286] Example 17B. The method of Example 16B, further comprising: signaling at least one of the first quantization parameter offset or the second quantization parameter offset in a bitstream comprising an encoded representation of the video data.

[0287] Example 18B. The method according to any one of Examples 1B to 17B further includes: determining whether the first residual modification function is not allowed to be applied based on one or more characteristics of the block; determining whether the second residual modification function is not allowed to be applied based on one or more characteristics of the block.

[0288] Example 1C. An apparatus for decoding video data, the apparatus comprising one or more components for performing the method according to any of Examples 1A to 18A or 1B to 18B.

[0289] Example 2C. The apparatus of Example 1C, wherein the one or more components include one or more processors implemented in a circuit.

[0290] Example 3C. The apparatus of any one of Examples 1C to 2C further comprising a memory for storing video data.

[0291] Example 4C. The apparatus of any of Examples 1C to 3C, further comprising a display configured to display the decoded video data.

[0292] Example 5C. A device according to any of Examples 1C to 4C, wherein the device includes one or more of the following: a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0293] Example 6C. The apparatus of any of Examples 1C to 5C, wherein the apparatus comprises a video decoder.

[0294] Example 7C. An apparatus according to any of Examples 1C to 6C, wherein the apparatus comprises a video encoder.

[0295] Example 8C. A computer-readable storage medium having instructions stored thereon, which, when executed, cause one or more processors to perform a method according to any one of Examples 1A to 18A or 1B to 18B.

[0296] It should be appreciated that, depending on the example, certain actions or events of any technique described herein may be performed in a different order, may be added, combined, or excluded entirely (e.g., not all described actions or events are required to practice the technique). In addition, in some examples, actions or events may be performed simultaneously, e.g., via multithreading, interrupt handling, or multiple processor execution, rather than sequentially.

[0297] 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 as one or more instructions or codes on a computer-readable medium or sent on a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium (which corresponds to a tangible medium such as a data storage medium) or a communication medium, which includes any medium that facilitates, for example, the transmission of a computer program from one place to another 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). A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, codes, and / or data structures for implementing the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0298] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program codes in the form of instructions or data structures and can be accessed by a computer. Moreover, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are sent from a website, server or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio and microwaves, coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio and microwaves are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals or other temporary media, but are directed to non-temporary, tangible storage media. Disks and optical disks as used herein include compact discs (CDs), laser optical disks, optical optical disks, digital versatile discs (DVDs), floppy disks and blue-ray discs, wherein disks generally reproduce data magnetically, and optical disks reproduce data optically by means of lasers. The above combination should also be included in the scope of computer-readable media.

[0299] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuit systems. Therefore, the terms "processor" and "processing circuitry" as used herein may refer to any of the aforementioned structures or any other structures suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding or incorporated in a combined codec. Moreover, the technology may be fully implemented in one or more circuits or logic elements.

[0300] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs), or a set of ICs (e.g., chipsets). Various components, modules, or units are described in the present disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily need to be implemented by different hardware units. More specifically, as described above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperable hardware units (including one or more processors as described above) in combination with appropriate software and / or firmware.

[0301] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: generating decoded modified chroma residual data by applying an inverse transform to convert a set of transform coefficients for a block of the video data from a transform domain to a sample domain; decoding a flag from a video bitstream including said video data; After generating the decoded modified chroma residual data, applying a first inverse residual modification function to the decoded modified chroma residual data to generate first inverse modified chroma residual data; applying a second inverse residual modification function to the decoded modified chroma residual data to produce second inverse modified chroma residual data; as well as reconstructing the block of the video data based on the first inverse-modified chroma residual data and the second inverse-modified chroma residual data; The first inverse residual modification function and the second inverse residual modification function are determined by the flag.

2. The method of claim 1 , wherein reconstructing the block comprises: adding the first inverse modified chroma residual data to first predicted chroma data to obtain first reconstructed chroma data for the block; as well as The second inverse modified chroma residual data is added to second predicted chroma data to obtain second reconstructed chroma data for the block.

3. The method according to claim 1, wherein the method further comprises: determining whether to apply the first inverse residual modification function or a third inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data; as well as A determination is made whether to apply the second inverse residual modification function or a fourth inverse residual modification function to the decoded modified chroma residual data to generate the second inverse modified chroma residual data.

4. The method according to claim 3, wherein: determining whether to apply the first inverse residual modification function or the third inverse residual modification function comprises determining whether to apply the first inverse residual modification function or the third inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data based on one or more characteristics of the block; and Determining whether to apply the second inverse residual modification function or the fourth inverse residual modification function includes determining whether to apply the second inverse residual modification function or the fourth inverse residual modification function to the decoded modified chroma residual data to generate the second inverse modified chroma residual data based on the one or more characteristics of the block.

5. The method of claim 4, wherein the characteristics of the block include one or more of: whether a slice or tile containing the block is of intra type or inter type, whether a current picture reference is used with the block, whether a dual or shared coding tree is used with the block, a size of the block, or an aspect ratio of the block.

6. The method according to claim 3, wherein: determining whether to apply the first inverse residual modification function or the third inverse residual modification function comprises determining whether to apply the first inverse residual modification function or the third inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data based on data signaled in a bitstream; and Determining whether to apply the second inverse residual modification function or the fourth inverse residual modification function includes determining whether to apply the second inverse residual modification function or the fourth inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data based on the data signaled in the bitstream.

7. The method according to claim 1, wherein: The first inverse residual modification function is: invF1(x,y)=(resCr(x,y)'+B10) / M10+(resCb(x,y)'+B11) / M11, The second inverse residual modification function is: invF2(x,y)=(resCr(x,y)'+B20) / M20-(resCb(x,y)'+B21) / M21, Where resCb(x,y)′ is the first decoded modified chroma residual data, resCr(x,y)′ is the second decoded modified chroma residual data, B10, B11, B20 and B21 are rounding terms, and M10, M11, M20 and N21 are normalization factors.

8. The method according to claim 1, further comprising: applying an inverse chroma residual scaling CRS process to the decoded modified chroma residual data before applying the first inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data; as well as The inverse CRS process is applied to the decoded modified chroma residual data before applying the second inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data.

9. The method according to claim 1, further comprising: applying an inverse CRS process to the decoded modified chroma residual data as part of applying the first inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data; as well as As part of applying the second inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data, applying the inverse CRS process to the decoded modified chroma residual data.

10. A method for encoding video data, the method comprising: applying a residual modification function to first chroma residual data for a block of the video data and second chroma residual data for the block of the video data to produce modified chroma residual data, wherein the first chroma residual data is associated with a first chroma component and the second chroma residual data is associated with a second chroma component; encoding the modified chroma residual data, wherein encoding the modified chroma residual data comprises, after applying the residual modification function to the first chroma residual data and the second chroma residual data, applying a forward transform to the modified chroma residual data to convert the modified chroma residual data from a sample domain to a transform domain; as well as A flag is encoded in a video bitstream including the video data, wherein the flag indicates a first inverse residual modification function and a second inverse residual modification function to be applied by a decoder to the encoded modified chroma residual data.

11. The method according to claim 10, wherein the method further comprises: determining whether to apply a first residual modification function or a third residual modification function to the first chroma residual data to generate the modified chroma residual data; as well as A determination is made whether to apply a second residual modification function or a fourth residual modification function to the second chroma residual data to generate the modified chroma residual data.

12. The method according to claim 11, wherein: Determining whether to apply the first residual modification function or the third residual modification function comprises determining whether to apply the first residual modification function or the third residual modification function to the first chroma residual data to produce the modified chroma residual data based on one or more characteristics of the block; and Determining whether to apply the second residual modification function or the fourth residual modification function comprises determining whether to apply the second residual modification function or the fourth residual modification function to the second chroma residual data to produce the modified chroma residual data based on the one or more characteristics of the block.

13. The method of claim 12, wherein the characteristics of the block include one or more of: whether a slice or tile containing the block is of intra type or inter type, whether a current picture reference is used with the block, whether a dual or shared coding tree is used with the block, a size of the block, or an aspect ratio of the block.

14. The method according to claim 11, wherein the method further comprises: signaling in a bitstream data indicating whether to apply the first residual modification function or the third residual modification function to generate the modified chroma residual data; as well as Data indicating whether to apply the second residual modification function or the fourth residual modification function to generate the modified chroma residual data is signaled in the bitstream.

15. The method of claim 10, wherein: The first residual modification function is: F1(x,y)=(resCb(x,y)+A10) / N10–(resCr(x,y)+A11) / N11, The second residual modification function is: F2(x,y)=(resCb(x,y)+A20) / N20+(resCr(x,y)+A21) / N21, Wherein resCb(x, y) is the first chrominance residual data, resCr(x, y) is the second chrominance residual data, A10, A11, A20 and A21 are rounding terms, and N10, N11, N20 and N21 are normalization factors.

16. The method according to claim 15, further comprising: After applying the first residual modification function to the first chroma residual data to produce the modified chroma residual data, applying a chroma residual scaling CRS process to the modified chroma residual data; as well as After applying the second residual modification function to the second chroma residual data to generate the modified chroma residual data, applying the CRS process to the modified chroma residual data.

17. The method according to claim 15, further comprising: as part of applying the first residual modification function to the first chroma residual data to produce the modified chroma residual data, applying a CRS process to the first chroma residual data; as well as As part of applying the second residual modification function to the second chroma residual data to produce the modified chroma residual data, the CRS process is applied to the second chroma residual data.

18. A device for decoding video data, the device comprising: A memory, the memory being used to store the video data; as well as One or more processors implemented in circuitry, the one or more processors being configured to: generating decoded modified chroma residual data by converting a first set of transform coefficients of the block of video data from a transform domain to a sample domain by applying an inverse transform; decoding a flag from a video bitstream including said video data; After generating the decoded modified chroma residual data, applying a first inverse residual modification function to the decoded modified chroma residual data to generate first inverse modified chroma residual data; applying a second inverse residual modification function to the decoded modified chroma residual data to produce second inverse modified chroma residual data; as well as reconstructing the block of the video data based on the first inverse-modified chroma residual data and the second inverse-modified chroma residual data; The first inverse residual modification function and the second inverse residual modification function are determined by the flag.

19. The apparatus of claim 18, wherein the one or more processors are configured such that, as part of reconstructing the block, the one or more processors: adding the first inverse modified chroma residual data to first predicted chroma data to obtain first reconstructed chroma data for the block; and The second inverse modified chroma residual data is added to second predicted chroma data to obtain second reconstructed chroma data for the block.

20. The device of claim 18, wherein the one or more processors are further configured to: determining whether to apply the first inverse residual modification function or a third inverse residual modification function to the decoded modified chroma residual data to generate the first inverse modified chroma residual data; and A determination is made whether to apply the second inverse residual modification function or a fourth inverse residual modification function to the decoded modified chroma residual data to generate the second inverse modified chroma residual data.

21. The apparatus of claim 20, wherein The one or more processors are configured such that, as part of determining whether to apply the first inverse residual modification function or the third inverse residual modification function, the one or more processors determine, based on one or more characteristics of the block, whether to apply the first inverse residual modification function or the third inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data; and The one or more processors are configured such that as part of determining whether to apply the second inverse residual modification function or the fourth inverse residual modification function, the one or more processors determine whether to apply the second inverse residual modification function or the fourth inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data based on the one or more characteristics of the block.

22. The apparatus of claim 21, wherein the characteristics of the block include one or more of: whether a slice or tile containing the block is of intra type or inter type, whether a current picture reference is used with the block, whether a dual or shared coding tree is used with the block, a size of the block, or an aspect ratio of the block.

23. The apparatus of claim 20, wherein the one or more processors being configured such that, as part of determining whether to apply the first inverse residual modification function or the third inverse residual modification function, the one or more processors determine, based on data signaled in a bitstream, whether to apply the first inverse residual modification function or the third inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data; and The one or more processors are configured such that as part of determining whether to apply the second inverse residual modification function or the fourth inverse residual modification function, the one or more processors determine, based on the data signaled in the bitstream, whether to apply the second inverse residual modification function or the fourth inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data.

24. The apparatus of claim 18, wherein The first inverse residual modification function is: invF1(x,y)=(resCr(x,y)'+B10) / M10+(resCb(x,y)'+B11) / M11, The second inverse residual modification function is: invF2(x,y)=(resCr(x,y)'+B20) / M20-(resCb(x,y)'+B21) / M21, Where resCb(x,y)′ is the first decoded modified chroma residual data, resCr(x,y)′ is the second decoded modified chroma residual data, B10, B11, B20 and B21 are rounding terms, and M10, M11, M20 and N21 are normalization factors.

25. The device of claim 18, wherein the one or more processors are further configured to: applying an inverse chroma residual scaling CRS process to the decoded modified chroma residual data before applying the first inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data; and The inverse CRS process is applied to the decoded modified chroma residual data before applying the second inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data.

26. The device of claim 18, wherein the one or more processors are configured to: As part of applying the first inverse residual modification function to the decoded modified chroma residual data to produce the first inverse modified chroma residual data, applying an inverse CRS process to the decoded modified chroma residual data; and As part of applying the second inverse residual modification function to the decoded modified chroma residual data to produce the second inverse modified chroma residual data, applying the inverse CRS process to the decoded modified chroma residual data.

27. The device of claim 18, further comprising a display configured to display the decoded video data.

28. The device of claim 18, wherein the device comprises one or more of: a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

29. A device for encoding video data, the device comprising: A memory, the memory being used to store the video data; as well as One or more processors implemented in circuitry, the one or more processors being configured to: applying a residual modification function to first chroma residual data for a block of the video data and second chroma residual data for the block of the video data to produce modified chroma residual data, wherein the first chroma residual data is associated with a first chroma component and the second chroma residual data is associated with a second chroma component; encoding the modified chroma residual data, wherein the one or more processors are configured such that, as part of encoding the modified chroma residual data, the one or more processors, after applying the residual modification function to the first chroma residual data and the second chroma residual data, apply a forward transform to the modified chroma residual data to convert the modified chroma residual data from a sample domain to a transform domain; as well as A flag is encoded in a video bitstream including the video data, wherein the flag indicates a first inverse residual modification function and a second inverse residual modification function to be applied by a decoder to the encoded modified chroma residual data.

30. The device of claim 29, wherein the one or more processors are further configured to: determining whether to apply a first residual modification function or a third residual modification function to the first chroma residual data to generate the modified chroma residual data; and A determination is made whether to apply a second residual modification function or a fourth residual modification function to the second chroma residual data to generate the modified chroma residual data.

31. The apparatus of claim 30, wherein The one or more processors are configured such that, as part of determining whether to apply the first residual modification function or the third residual modification function, the one or more processors determine, based on one or more characteristics of the block, whether to apply the first residual modification function or the third residual modification function to the first chroma residual data to produce the modified chroma residual data; and The one or more processors are configured such that as part of determining whether to apply the second residual modification function or the fourth residual modification function, the one or more processors determine whether to apply the second residual modification function or the fourth residual modification function to the second chroma residual data to produce the modified chroma residual data based on the one or more characteristics of the block.

32. The apparatus of claim 31 , wherein the characteristics of the block comprise one or more of: whether a slice or tile containing the block is of intra type or inter type, whether a current picture reference is used with the block, whether a dual or shared coding tree is used with the block, a size of the block, or an aspect ratio of the block.

33. The device of claim 30, wherein the one or more processors are further configured to: signaling in a bitstream data indicating whether to apply the first residual modification function or the third residual modification function to generate the modified chroma residual data; and Data indicating whether to apply the second residual modification function or the fourth residual modification function to generate the modified chroma residual data is signaled in the bitstream.

34. The apparatus of claim 29, wherein The first residual modification function is: F1(x,y)=(resCb(x,y)+A10) / N10–(resCr(x,y)+A11) / N11, The second residual modification function is: F2(x,y)=(resCb(x,y)+A20) / N20+(resCr(x,y)+A21) / N21, Wherein resCb(x, y) is the first chrominance residual data, resCr(x, y) is the second chrominance residual data, A10, A11, A20 and A21 are rounding terms, and N10, N11, N20 and N21 are normalization factors.

35. The apparatus of claim 34, wherein the one or more processors are further configured to: After applying the first residual modification function to the first chroma residual data to generate the modified chroma residual data, applying a chroma residual scaling CRS process to the modified chroma residual data; and After applying the second residual modification function to the second chroma residual data to generate the modified chroma residual data, applying the CRS process to the modified chroma residual data.

36. The device of claim 34, wherein the one or more processors are further configured to: As part of applying the first residual modification function to the first chroma residual data to produce the modified chroma residual data, applying a CRS process to the first chroma residual data; and As part of applying the second residual modification function to the second chroma residual data to produce the modified chroma residual data, the CRS process is applied to the second chroma residual data.

37. The device of claim 29, wherein the device comprises one or more of: a camera, a computer, or a mobile device.

38. A device for decoding video data, the device comprising: means for generating decoded modified chroma residual data by converting a set of transform coefficients for a block of said video data from a transform domain to a sample domain by applying an inverse transform; means for decoding a flag from a video bitstream comprising said video data; means for applying a first inverse residual modification function to the decoded modified chroma residual data after generating the decoded modified chroma residual data to generate first inverse modified chroma residual data; means for applying a second inverse residual modification function to said decoded modified chroma residual data to produce second inverse modified chroma residual data; as well as means for reconstructing the block of the video data based on the first inverse-modified chroma residual data and the second inverse-modified chroma residual data; The first inverse residual modification function and the second inverse residual modification function are determined by the flag.

39. A device for encoding video data, the device comprising: means for applying a residual modification function to first chroma residual data for a block of the video data and second chroma residual data for the block of the video data to produce modified chroma residual data, wherein the first chroma residual data is associated with a first chroma component and the second chroma residual data is associated with a second chroma component; means for encoding the modified chroma residual data, wherein encoding the modified chroma residual data comprises means for applying a forward transform to the modified chroma residual data to convert the modified chroma residual data from a sample domain to a transform domain after applying the residual modification function to the first chroma residual data and the second chroma residual data; as well as Means for encoding a flag in a video bitstream comprising said video data, wherein said flag indicates a first inverse residual modification function and a second inverse residual modification function to be applied by a decoder to encoded modified chroma residual data.

40. A computer-readable storage medium having stored thereon instructions which, when executed, cause one or more processors to: generating decoded modified chroma residual data by applying an inverse transform to convert a set of transform coefficients for a block of video data from a transform domain to a sample domain; decoding a flag from a video bitstream including the video data; After generating the decoded modified chroma residual data, applying a first inverse residual modification function to the decoded modified chroma residual data to generate first inverse modified chroma residual data; applying a second inverse residual modification function to the decoded modified chroma residual data to produce second inverse modified chroma residual data; as well as reconstructing the block of the video data based on the first inverse-modified chroma residual data and the second inverse-modified chroma residual data; The first inverse residual modification function and the second inverse residual modification function are determined by the flag.

41. A computer-readable storage medium having stored thereon instructions which, when executed, cause one or more processors to: applying a residual modification function to first chroma residual data for a block of video data and second chroma residual data for the block of video data to produce modified chroma residual data, wherein the first chroma residual data is associated with a first chroma component and the second chroma residual data is associated with a second chroma component; encoding the modified chroma residual data, wherein execution of the instructions causes the one or more processors to, as part of causing the one or more processors to encode the modified chroma residual data, apply a forward transform to the modified chroma residual data to convert the modified chroma residual data from a sample domain to a transform domain after applying the residual modification function to the first chroma residual data and the second chroma residual data; as well as A flag is encoded in a video bitstream including the video data, wherein the flag indicates a first inverse residual modification function and a second inverse residual modification function to be applied by a decoder to the encoded modified chroma residual data.

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