Model parameter derivation for local illumination compensation in mapping domain of luma mapping with chroma scaling in video coding

Abstract

An example device for decoding video data includes a memory configured to store video data and one or more processors implemented in circuitry and communicatively coupled to the memory. The one or more processors are configured to warp a pixel domain reference template block to a mapping domain reference template using a forward mapping function and to derive local illumination compensation (LIC) model parameters from the mapping domain reference template block and a mapping domain neighboring reconstructed template block. The one or more processors are configured to apply the LIC model parameters to a motion compensated prediction signal and to decode the video data based on the application of the LIC model parameters.

Description

[0001] This application claims priority to U.S. Patent Application No. 17 / 356,153, filed June 23, 2021, and U.S. Provisional Application No. 63 / 043,619, filed June 24, 2020, the entire contents of each of which are incorporated herein by reference. U.S. Patent Application No. 17 / 356,153, filed June 23, 2021, claims the benefit of U.S. Provisional Application No. 63 / 043,619, filed June 24, 2020. Technical Field

[0002] This disclosure relates to video encoding and video decoding. Background Technology

[0003] Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcasting systems, personal digital assistants (PDAs), laptops or desktop computers, tablets, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio phones (so-called "smartphones"), video conferencing equipment, video streaming devices, and more. Digital video devices implement video decoding technologies (such as those described in standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 (Part 10, Advanced Video Decoding (AVC)), ITU-T H.265 / High Efficiency Video Decoding (HEVC), and extensions to such standards). By implementing such video decoding technologies, video devices can more efficiently send, receive, encode, decode, and / or store digital video information.

[0004] Video decoding 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 decoding, video slices (e.g., video pictures or portions of video pictures) can be segmented into video blocks, which may also be referred to as decoding tree units (CTUs), decoding units (CUs), and / or decoding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in adjacent blocks within the same picture. Video blocks in an inter-coded (P or B) slice of a picture can use spatial prediction relative to reference samples in adjacent blocks within the same picture or temporal prediction relative to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0005] In summary, this disclosure describes techniques for deriving Local Illuminance Compensation (LIC) parameters during video decoding. Specifically, this disclosure describes techniques for deriving LIC parameters in a Luminance Mapping with Chroma Scaling (LMCS) domain. The techniques of this disclosure can reduce decoding latency and improve decoding efficiency by eliminating the need to load an inverse mapping table from memory for LIC parameter derivation in LMCS.

[0006] In one example, a method includes: shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstruction template block; applying the LIC model parameters to a motion compensation prediction signal; and decoding the video data based on the application of the LIC model parameters.

[0007] In another example, a device includes: a memory configured to store video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors being configured to: shape a pixel-domain reference template block into a mapped-domain reference template block using a forward mapping function; derive local illumination compensation (LIC) model parameters from the mapped-domain reference template block and mapped-domain adjacent reconstructed template blocks; apply the LIC model parameters to a motion-compensated prediction signal; and decode the video data based on the application of the LIC model parameters.

[0008] In another example, a computer-readable storage medium stores instructions that, when executed, cause one or more processors to: shape a pixel-domain reference template block into a mapped-domain reference template block using a forward mapping function; derive local illumination compensation (LIC) model parameters from the mapped-domain reference template block and a mapped-domain adjacent reconstruction template block; apply the LIC model parameters to a motion-compensated prediction signal; and decode the video data based on the application of the LIC model parameters.

[0009] In another example, an apparatus includes: units for shaping a pixel-domain reference template block into a mapped-domain reference template block using a forward mapping function; units for deriving local illumination compensation (LIC) model parameters from the mapped-domain reference template block and a mapped-domain adjacent reconstruction template block; units for applying the LIC model parameters to a motion-compensated prediction signal; and units for decoding the video data based on the application of the LIC model parameters. One or more units for performing any of the techniques described in this disclosure.

[0010] Details of one or more examples are set forth in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the description, drawings, and claims. Attached Figure Description

[0011] Figure 1 This is a block diagram illustrating an example video encoding and decoding system that can perform the techniques described in this disclosure.

[0012] Figure 2A and Figure 2B This is a conceptual diagram showing an example quadtree binary tree (QTBT) structure and its corresponding decoding tree unit (CTU).

[0013] Figure 3 This is a block diagram illustrating an example video encoder that can perform the techniques described in this disclosure.

[0014] Figure 4 This is a block diagram illustrating an example video decoder that can perform the techniques described in this disclosure.

[0015] Figures 5A-5B These are conceptual diagrams illustrating examples of spatial neighbor candidates used for merging patterns and advanced motion vector prediction (AMVP) patterns.

[0016] Figure 6A This is a conceptual diagram illustrating an example of a Time Motion Vector Prediction (TMVP) candidate.

[0017] Figure 6B This is a conceptual diagram illustrating an example of motion vector scaling.

[0018] Figure 7 This is a conceptual diagram illustrating an example of neighboring pixels used to estimate parameters in an illumination compensation (IC) model, where a reference block for the current block is found by using the disparity vector of the current prediction unit (PU).

[0019] Figure 8 This is a conceptual diagram illustrating an example of adjacent samples used to derive IC parameters.

[0020] Figure 9 This is a block diagram illustrating an example of a Luminance Mapping System (LMCS) architecture with chroma scaling.

[0021] Figure 10 This is a block diagram illustrating an example LMCS architecture when using Local Illumination Compensation (LIC).

[0022] Figure 11 This is a block diagram illustrating an example LMCS architecture when using a LIC according to the technology of this disclosure.

[0023] Figure 12This is a flowchart illustrating the LIC parameter derivation technique according to this disclosure.

[0024] Figure 13 This is a flowchart illustrating an example method for encoding the current block according to the technology of this disclosure.

[0025] Figure 14 This is a flowchart illustrating an example method for decoding the current block according to the technology of this disclosure. Detailed Implementation

[0026] In some example video decoders, when both Local Illumination Compensation (LIC) and Luminance Mapping with Chroma Scaling (LMCS) are enabled, LIC is the only inter-frame prediction mode. This requires loading an inverse lookup table at the decoder unit (CU) level to transform the reconstructed signal back to the pixel domain so that the LIC model parameters can then be derived. Unlike the General Video Decoding (VVC) standard, which requires loading this inverse table at the decoder tree unit (CTU) / virtual pipeline data unit (VPDU) / picture level within the loop filtering stage, this additional inverse mapping at the CU level introduces an additional hardware implementation burden to the video decoder's motion compensation module, resulting in potentially longer latency during this motion compensation stage.

[0027] According to the technology disclosed herein, the video decoder can derive LIC parameters based on the mapping domain reference template block and the mapping domain adjacent reconstruction template block, instead of using inverse mapping at the CU level. In this way, the LIC parameters can be derived without reading the inverse mapping table from memory, which can save processing power and reduce decoding latency.

[0028] Figure 1 This is a block diagram illustrating an example video encoding and decoding system 100 capable of performing the techniques of this disclosure. In summary, the techniques of this disclosure relate to decoding (encoding and / or decoding) video data. Typically, video data includes any data used for processing video. Therefore, video data can include raw, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (e.g., signaling data).

[0029] like Figure 1As shown, in this example, system 100 includes source device 102, which provides encoded video data to be decoded and displayed by destination device 116. Specifically, source device 102 provides the video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 can include any of a wide variety of devices, including desktop computers, laptop computers, mobile devices, tablet computers, set-top boxes, mobile phones (such as smartphones), televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receivers, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and may therefore be referred to as wireless communication devices.

[0030] exist Figure 1 In the example, source device 102 includes a video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes an input interface 122, video decoder 300, memory 120, and display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply techniques for LIC parameter derivation. Therefore, source device 102 represents an example of a video encoding device, and destination device 116 represents an example of a video decoding device. In other examples, the source and destination devices may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may interface with an external display device, rather than including an integrated display device.

[0031] exist Figure 1 The system 100 shown is merely an example. Typically, any digital video encoding and / or decoding device can be configured to perform techniques for constraining the derivation of LIC parameters. Source device 102 and destination device 116 are merely examples of such decoding devices, where source device 102 generates decoded video data for transmission to destination device 116. In this disclosure, "decoding device" refers to a device that performs the decoding (e.g., encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of decoding devices (specifically, video encoder and video decoder). In some examples, source device 102 and destination device 116 may operate in a substantially symmetrical manner, such that each of source device 102 and destination device 116 includes video encoding and decoding components. Therefore, system 100 can support one-way or two-way video transmission between source device 102 and destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0032] Typically, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a sequential series of pictures (also referred to as "frames") of the video data to video encoder 200, which encodes the data used for the pictures. Video source 104 of source device 102 may include video capture devices such as cameras, video archive units containing previously captured raw video, and / or video feed interfaces for receiving video from video content providers. Alternatively, video source 104 may generate computer graphics-based data as source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 may encode the captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from their received order (sometimes referred to as "display order") to a decoding order for decoding. Video encoder 200 may generate a bitstream comprising the encoded video data. Then, the source device 102 can output the encoded video data to the computer-readable medium 110 via the output interface 108 so that it can be received and / or retrieved by, for example, the input interface 122 of the destination device 116.

[0033] The memory 106 of source device 102 and the memory 120 of destination device 116 represent general-purpose memory. In some examples, memories 106 and 120 may store raw video data, such as raw video from video source 104 and raw decoded video data from video decoder 300. Alternatively, memories 106 and 120 may store software instructions executable by, for example, video encoder 200 and video decoder 300. Although memories 106 and 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Furthermore, memories 106 and 120 may store, for example, encoded video data output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106 and 120 may be allocated as one or more video buffers, for example, to store raw decoded and / or encoded video data.

[0034] Computer-readable medium 110 can represent any type of medium or device capable of transmitting encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium that enables source device 102 to directly transmit encoded video data to destination device 116 in real time, for example, via a radio frequency network or a computer-based network. Output interface 108 can modulate the transmitted signal including the encoded video data according to a communication standard such as a wireless communication protocol, and input interface 122 can demodulate the received transmitted information according to a communication standard such as a wireless communication protocol. The communication medium can include any wireless or wired communication medium, such as radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network such as a local area network, a wide area network, or a global network such as the Internet. The communication medium can include a router, a switch, a base station, or any other device that may be useful for facilitating communication from source device 102 to destination device 116.

[0035] In some examples, source device 102 can output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 can access encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessible data storage media, such as hard disk drives, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0036] In some examples, source device 102 can output encoded video data to file server 114 or another intermediate storage device that can store the encoded video data generated by source device 102. Destination device 116 can access the stored video data from file server 114 via streaming or downloading.

[0037] File server 114 can be any type of server device capable of storing encoded video data and sending such encoded video data to destination device 116. File server 114 can represent a web server (e.g., for a website), a server configured to provide file transfer protocol services (such as File Transfer Protocol (FTP) or One-Way Transfer File Delivery (FLUTE) protocol), a Content Delivery Network (CDN) device, a Hypertext Transfer Protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS) server, and / or a Network Attached Storage (NAS) device. File server 114 can additionally or alternatively implement one or more HTTP streaming protocols, such as HTTP-based Dynamic Adaptive Streaming (DASH), HTTP Real-Time Streaming (HLS), Real-Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0038] Destination device 116 can access encoded video data from file server 114 via any standard data connection, including an internet connection. This can include wireless channels (e.g., Wi-Fi connections), wired connections (e.g., digital subscriber line (DSL), cable modems, etc.), or combinations thereof, suitable for accessing encoded video data stored on file server 114. Input interface 122 can be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from file server 114, or other such protocols for retrieving media data.

[0039] Output interface 108 and input interface 122 can represent a wireless transmitter / receiver, a modem, a wired networking component (e.g., an Ethernet card), a wireless communication component operating 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 can be configured to transmit data (such as encoded video data) according to cellular communication standards (such as 4G, 4G-LTE (Long Term Evolution), improved LTE, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 can be configured to operate according to other wireless standards (such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee)). TM Bluetooth TMThe 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 for performing the functions assigned to video encoder 200 and / or output interface 108, and destination device 116 may include an SoC device for performing the functions assigned to video decoder 300 and / or input interface 122.

[0040] The technology disclosed herein can be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission (such as HTTP-based Dynamic Adaptive Streaming (DASH)), digital video encoded onto data storage media, decoding digital video stored on data storage media, or other applications.

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

[0042] Despite Figure 1 Not shown, but in some examples, the video encoder 200 and video decoder 300 may each be integrated with the audio encoder and / or audio decoder, and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams including both audio and video in a common data stream. Where applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol or other protocols (such as User Datagram Protocol (UDP)).

[0043] The video encoder 200 and 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 implemented in part in software, the device may 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 this disclosure. Each of the video encoder 200 and video decoder 300 may be included in one or more encoders or decoders, and either encoder or decoder may be integrated as part of a combined encoder / decoder (CODEC) in the respective device. Devices including the video encoder 200 and / or video decoder 300 may include integrated circuits, microprocessors, and / or wireless communication devices (such as cellular phones).

[0044] The video encoder 200 and video decoder 300 can operate according to video decoding standards such as ITU-T H.265 (also known as the High Efficiency Video Coding (HEVC) standard) or extensions thereof such as MultiView or Scalable Video Coding Extensions. Alternatively, the video encoder 200 and video decoder 300 can operate according to other proprietary or industry standards such as ITU-T H.266 (also known as Versatile Video Coding (VVC)). A draft of the VVC standard is described in: Bross et al., “Versatile Video Coding (Draft 9)”, ITU-T SG 16WP 3 and ISO / IEC JTC1 / SC 29 / WG 11 Joint Video Experts Group (JVET), 18th meeting by teleconference, April 15-24, 2020, JVET-R2001-vA (hereinafter referred to as “VVC Draft 9”). However, the technology of this disclosure is not limited to any particular decoding standard.

[0045] Typically, video encoder 200 and video decoder 300 can perform block-based decoding of images. The term "block" generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used during encoding and / or decoding). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, video encoder 200 and video decoder 300 can encode video data represented in YUV (e.g., Y, Cb, Cr) format. That is, instead of decoding the red, green, and blue (RGB) data used for images, video encoder 200 and video decoder 300 can encode both luminance and chrominance components, where chrominance components may include both red hue and blue hue chrominance components. In some examples, video encoder 200 converts the received RGB-formatted data to a YUV representation before encoding, and video decoder 300 converts the YUV representation to RGB format. Alternatively, preprocessing and post-processing units (not shown) can perform these conversions.

[0046] In summary, this disclosure may relate to the decoding (e.g., encoding and decoding) of images to include the process of encoding or decoding the data of an image. Similarly, this disclosure may relate to the decoding of blocks of an image to include the process of encoding or decoding the data used for the blocks (e.g., prediction and / or residual decoding). Encoded video bitstreams typically include a series of values ​​for representing decoding decisions (e.g., decoding modes) and syntax elements that segment the image into blocks. Therefore, references to decoding images or blocks should generally be understood as decoding the values ​​of the syntax elements used to form images or blocks.

[0047] HEVC defines various blocks, including decoding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as a video encoder 200) partitions the decoding tree unit (CTU) into CUs based on a quadtree structure. That is, the video coding device partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. Nodes without child nodes can be called "leaf nodes," and the CU of such leaf nodes can include one or more PUs and / or one or more TUs. The video coding device can further partition the PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents a partition of a TU. In HEVC, PUs represent inter-frame prediction data, while TUs represent residual data. CUs with intra-frame prediction include intra-frame prediction information, such as intra-frame mode indication.

[0048] As another example, video encoder 200 and video decoder 300 can be configured to operate according to VCC. According to VCC, the video decoder (such as video encoder 200) segments the image into multiple decoding tree units (CTUs). Video encoder 200 can segment CTUs according to a tree structure (such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure eliminates the concept of multiple segmentation types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels: a first level based on quadtree segmentation and a second level based on binary tree segmentation. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to decoding 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 (also known as triplet tree (TT)) partitioning. A ternary tree or triplet tree partitioning is a partition in which a block is split into three sub-blocks. In some examples, a ternary tree or triplet tree partitioning divides a block into three sub-blocks without splitting the original block by a center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

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

[0051] The video encoder 200 and video decoder 300 can be configured to use per-HEVC quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures. For illustrative purposes, a description of the techniques of this disclosure is given with respect to QTBT segmentation. However, it should be understood that the techniques of this disclosure can also be applied to video coding apparatuses configured to use quadtree segmentation or other types of segmentation.

[0052] In some examples, a CTU includes a decoded tree block (CTB) of luminance samples, two corresponding CTBs of chrominance samples of an image with three sample arrays, or a CTB of samples of a monochrome image or an image decoded using three separate color planes and a syntax structure for decoding the samples. A CTB can be an N×N block of samples (for some value of N) such that dividing a component into a CTB is a partition. A component is an array or a single sample of one of the three arrays (one luminance and two chrominance) that make up an image in a 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array or array that makes up an image in monochrome format. In some examples, a decoded block is an M×N block of samples (for some values ​​of M and N) such that dividing a CTB into a decoded block is a partition.

[0053] Blocks (e.g., CTUs or CUs) can be grouped in various ways within an image. As an example, a brick can refer to a rectangular area of ​​a row of CTUs within a specific tile in an image. A tile can be a rectangular area of ​​a CTU within a specific tile column and a specific tile row in an image. A tile column refers to a rectangular area of ​​a CTU with a height equal to the height of the image and a width specified by a syntax element (e.g., in an image parameter set). A tile row refers to a rectangular area of ​​a CTU with a height specified by a syntax element (e.g., in an image parameter set) and a width equal to the width of the image.

[0054] In some examples, a tile may be divided into multiple bricks, each brick potentially comprising one or more CTU rows within the tile. A tile that is not divided into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a tile may not be referred to as a tile.

[0055] The bricks in an image can also be arranged as slices. A slice can be an integer number of bricks in the image, which can be uniquely contained within a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes multiple complete tiles or a continuous sequence of complete bricks consisting of only one tile.

[0056] This disclosure uses "NxN" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in the vertical and horizontal dimensions, for example, 16x16 samples or 16 by 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). Similarly, an NxNCU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU can be arranged in rows and columns. Furthermore, a CU does not necessarily need to have the same number of samples in the horizontal direction as it does in the vertical direction. For example, a CU can include NxM samples, where M is not necessarily equal to N.

[0057] The video encoder 200 encodes video data for use in predicting and / or residual information, as well as other information, for the CU. The prediction information indicates how the CU will be predicted to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between a sample of the CU before encoding and the prediction block.

[0058] To predict the Cubic Frame (CU), the video encoder 200 typically forms prediction blocks for the CU using either inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting the CU based on data from previously decoded images, while intra-frame prediction generally refers to predicting the CU based on data from previously decoded images of the same frame. To perform inter-frame prediction, the video encoder 200 can generate prediction blocks using one or more motion vectors. The video encoder 200 can typically perform a motion search to identify, for example, a reference block that closely matches the CU in terms of the difference between the CU and a reference block. The video encoder 200 can calculate a difference metric using the sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), 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 can use unidirectional or bidirectional prediction to predict the current CU.

[0059] Some examples of VCC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In 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 types of motion).

[0060] To perform intra-frame prediction, the video encoder 200 can select an intra-frame prediction mode to generate prediction blocks. Some examples of VCC provide sixty-seven intra-frame prediction modes, including various directional modes, as well as planar and DC modes. Typically, the video encoder 200 selects an intra-frame prediction mode that describes the samples of the current block (e.g., a block of a CU) to be predicted based on, which are the neighboring samples of the current block. Assuming that the video encoder 200 encodes the CTU and CU in raster scan order (from left to right, from top to bottom), such samples can typically be located above, to the upper left, or to the left of the current block within the same image.

[0061] The video encoder 200 encodes data representing the prediction mode used for the current block. For example, for inter-frame prediction modes, the video encoder 200 may encode data indicating which of the various available inter-frame prediction modes is used, as well as motion information for the corresponding mode. For unidirectional or bidirectional inter-frame prediction, for example, the video encoder 200 may use Advanced Motion Vector Prediction (AMVP) or merging modes to encode motion vectors. The video encoder 200 may use similar modes to encode motion vectors used for affine motion compensation modes.

[0062] Following a prediction, such as intra-frame or inter-frame prediction of a block, the video encoder 200 can compute residual data for that block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and the prediction block used to form the block, which is formed using the corresponding prediction mode. The video encoder 200 can apply one or more transforms to the residual block to produce transformed data in the transform domain rather than in the sample domain (also referred to herein as the pixel domain). For example, the video encoder 200 can apply a Discrete Cosine Transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, the video encoder 200 can apply a secondary transform after the first transform, such as a Mode-dependent Inseparable Quadratic Transform (MDNSST), a Signal-dependent Transform, a Karhunen-Loeve Transform (KLT), etc. The video encoder 200 produces transform coefficients after applying one or more transforms.

[0063] As described above, after any transformation to produce transform coefficients, the video encoder 200 can perform quantization of the transform coefficients. Quantization generally refers to the process in which the transform coefficients are quantized to potentially reduce the amount of data used to represent them, thereby providing further compression. By performing the quantization process, the video encoder 200 can reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 can round an n-bit value down to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 can perform a bitwise right shift of the values ​​to be quantized.

[0064] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place higher-energy (and therefore lower-frequency) transform coefficients before the vector and lower-energy (and therefore higher-frequency) transform coefficients after the vector. In some examples, the video encoder 200 can utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy-encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 can perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy-encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic decoding (CABAC). The video encoder 200 can also entropy-encode the values ​​of syntax elements used to describe metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0065] To perform CABAC, the video encoder 200 can assign context within a context model to the symbols to be transmitted. Context may involve, for example, whether the neighboring values ​​of a symbol are zero. Probability determination can be based on the context assigned to the symbols.

[0066] The video encoder 200 can also generate syntax data (such as block-based syntax data, image-based syntax data, and sequence-based syntax data) or other syntax data (such as sequence parameter sets (SPS), image parameter sets (PPS), or video parameter sets (VPS)) for the video decoder 300, for example, in image headers, block headers, or slice headers. Similarly, the video decoder 300 can decode such syntax data to determine how to decode the corresponding video data.

[0067] In this way, the video encoder 200 can generate a bitstream that includes encoded video data, such as syntax elements describing the segmentation of an image into blocks (e.g., CUs) and prediction and / or residual information for those blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0068] Typically, the video decoder 300 performs the reverse process of the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 can use CABAC to decode the values ​​of syntax elements used for the bitstream in a manner substantially similar to, but reversed, the CABAC encoding process of the video encoder 200. Syntax elements can define segmentation information for segmenting images into CTUs, and for segmenting each CTU according to a corresponding segmentation structure (such as a QTBT structure) to define the CUs of the CTU. Syntax elements can also define prediction and residual information for blocks (e.g., CUs) of the video data.

[0069] The residual information can be represented, for example, by quantized transform coefficients. The video decoder 300 can inversely quantize and inversely transform the quantized transform coefficients of the block to reconstruct the residual block used for that block. The video decoder 300 uses a prediction mode (intra-frame prediction or inter-frame prediction) and associated prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for that block. The video decoder 300 can then combine the prediction block and the residual block (on a sample-by-sample basis) to reconstruct the original block. The video decoder 300 can perform additional processing, such as performing a deblocking process to reduce visual artifacts along the block boundaries.

[0070] According to the technology of this disclosure, a method includes: shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstructed template block; applying the LIC model parameters to a motion compensation prediction signal; and decoding video data based on the application of the LIC model parameters.

[0071] According to the technology of this disclosure, an apparatus includes: a memory configured to store video data; and one or more processors implemented in a circuit and communicatively coupled to the memory, the one or more processors being configured to: shape a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; derive local illumination compensation (LIC) model parameters from the mapped domain reference template block and mapped domain adjacent reconstructed template blocks; apply the LIC model parameters to a motion compensation prediction signal; and decode the video data based on the application of the LIC model parameters.

[0072] According to the technology of this disclosure, a computer-readable storage medium stores instructions that, when executed, cause one or more processors to perform the following operations: shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstructed template block; applying the LIC model parameters to a motion compensation prediction signal; and decoding video data based on the application of the LIC model parameters.

[0073] According to the technology of this disclosure, an apparatus includes: units for shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; units for deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and mapped domain adjacent reconstructed template blocks; units for applying the LIC model parameters to a motion compensation prediction signal; and units for decoding video data based on the application of the LIC model parameters. One or more units are used to perform any of the techniques of this disclosure.

[0074] In summary, this disclosure may involve "signaling" certain information (such as syntax elements). The term "signaling" can generally refer to the transmission of values ​​for syntax elements and / or other data for decoding encoded video data. That is, video encoder 200 can signal values ​​for syntax elements in the bitstream. Generally, signaling refers to generating values ​​in the bitstream. As described above, source device 102 can transmit the bitstream to destination device 116 substantially in real time or not in real time (such as when syntax elements are stored in storage device 112 for later retrieval by destination device 116).

[0075] Figure 2A and Figure 2BThis is a conceptual diagram illustrating an example Quadtree Binary Tree (QTBT) structure 130 and its corresponding Coding Tree Unit (CTU) 132. 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 a horizontal split and 1 indicates a vertical split. For quadtree splits, since the quadtree node splits the block horizontally and vertically into four sub-blocks of equal size, there is no need to indicate the split type. Therefore, the video encoder 200 can encode the following, and the video decoder 300 can decode the following: syntax elements (such as split information) for the region tree level (i.e., solid lines) of the QTBT structure 130, and syntax elements (such as split information) for the prediction tree level (i.e., dashed lines) of the QTBT structure 130. The video encoder 200 can encode video data (such as prediction and transform data) for a CU represented by the terminal leaf nodes of the QTBT structure 130, while the video decoder 300 can decode the video data.

[0076] generally, Figure 2B The CTU 132 can be associated with parameters that define the size of the blocks corresponding to the nodes at the first and second levels of the QTBT structure 130. These parameters can include the CTU size (representing the size of the CTU 132 in the sample), the minimum quadtree size (MinQTSize, which represents the minimum allowed quadtree leaf node size), the maximum binary tree size (MaxBTSize, which represents the maximum allowed binary tree root node size), the maximum binary tree depth (MaxBTDepth, which represents the maximum allowed binary tree depth), and the minimum binary tree size (MinBTSize, which represents the minimum allowed binary tree leaf node size).

[0077] The root node corresponding to a CTU in a QTBT structure can have four child nodes at the first level of the QTBT structure, each child node being segmented according to a quadtree partition. That is, the nodes at the first level are leaf nodes (without child nodes) or have four child nodes. An example of QTBT structure 130 represents such a node as including a parent node and child nodes with solid-line branches. If the nodes at the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), these nodes can be further partitioned by the corresponding binary tree. The binary tree partitioning of a node can be iterated until the nodes resulting from the partitioning reach the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). An example of QTBT structure 130 represents such a node as having dashed-line branches. The binary tree leaf nodes are called coding units (CUs), which are used for prediction (e.g., intra-image or inter-image prediction) and transformation without further partitioning. As discussed above, CUs can also be referred to as “video chunks” or “blocks”.

[0078] In one example of a QTBT segmentation 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. First, a quadtree segmentation is applied to the CTU to generate quadtree leaf nodes. Quadtree leaf nodes can have sizes ranging from 16x16 (i.e., MinQTSize) to 128x128 (i.e., the CTU size). If a quadtree leaf node is 128x128, it will not be further split by the binary tree because this 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 used as the root node of the binary tree and has a binary tree depth of 0. When the depth of a binary tree reaches MaxBTDepth (4 in this example), further splitting is not allowed. A binary tree node with a width equal to MinBTSize (4 in this example) means that further vertical splitting (i.e., width-based division) is not allowed for that binary tree node. Similarly, a binary tree node with a height equal to MinBTSize means that further horizontal splitting (i.e., height-based division) is not allowed for that binary tree node. As mentioned above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further splitting.

[0079] Figure 3This is a block diagram illustrating an example video encoder 200 that can perform the techniques described in this disclosure. Figure 3 This disclosure is provided for illustrative purposes and should not be construed as limiting the techniques illustrated and described in this disclosure in a general manner. For illustrative purposes, this disclosure describes a video encoder 200 based on VVC (ITU-T H.266, in deployment) and HEVC (ITU-TH.265) technologies. However, the technologies of this disclosure can be implemented by video encoding devices configured for other video decoding standards.

[0080] exist Figure 3 In the example, 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 coding unit 220. Any or all of the video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy coding unit 220 can be implemented in one or more processors or in processing circuitry. For example, the units of the video encoder 200 can be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0081] The video data storage device 230 can store video data to be encoded by the components of the video encoder 200. The video encoder 200 can obtain data from, for example, a video source 104 (…). Figure 1 The video data memory 230 receives video data stored in the video data memory 230. The DPB 218 can act as a reference picture memory, storing reference video data for use when the video encoder 200 predicts subsequent video data. The video data memory 230 and DPB 218 can be formed from any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 can be on-chip (as shown) with other components of the video encoder 200, or off-chip relative to those components.

[0082] In this disclosure, references to video data memory 230 should not be construed as limited to memory within video encoder 200 (unless so specifically described) or to memory outside video encoder 200 (unless so specifically described). Rather, references to video data memory 230 should be understood as reference memory storing video data received by video encoder 200 for encoding (e.g., video data for the current block to be encoded). Figure 1 The memory 106 can also provide temporary storage for the outputs from the various units of the video encoder 200.

[0083] It shows Figure 3 The various units help to understand the operations performed by the video encoder 200. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide a specific function and are pre-configured regarding the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in terms of 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 (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is generally immutable. In some examples, one or more of these units can be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units can be integrated circuits.

[0084] The video encoder 200 may include an arithmetic logic unit (ALU), an essential function unit (EFU), digital circuitry, analog circuitry, and / or a programmable core, all formed by programmable circuitry. In an example where software executed by programmable circuitry is used to perform the operation of the video encoder 200, memory 106 ( Figure 1 The video encoder 200 may store instructions (e.g., object code) of the software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0085] The video data storage unit 230 is configured to store the received video data. The video encoder 200 can retrieve images of the video data from the video data storage unit 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 storage unit 230 can be the raw video data to be encoded.

[0086] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra-frame prediction unit 226. The mode selection unit 202 may include additional functional units that perform video prediction based on 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.

[0087] Mode selection unit 202 typically coordinates multiple coding paths to test combinations of coding parameters and the rate-distortion values ​​obtained for such combinations. Coding parameters may include segmenting the CTU into CUs, the prediction mode for the CUs, the transformation type of the residual data for the CUs, and the quantization parameters for the residual data for the CUs. Mode selection unit 202 can ultimately select a combination of coding parameters that yields a better rate-distortion value than other tested combinations.

[0088] The video encoder 200 can segment images retrieved from the video data storage 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 can segment the CTUs of the image according to a tree structure (such as the QTBT structure or quadtree structure of HEVC described above). As mentioned above, the video encoder 200 can form one or more CUs by segmenting CTUs according to a tree structure. Such CUs can also generally be referred to as "video blocks" or "blocks".

[0089] Typically, mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra-prediction unit 226) to generate prediction blocks for the current block (e.g., the current CU, or the overlapping portion of PU and TU in HEVC). To perform inter-frame prediction for the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate values ​​representing the similarity between a potential reference block and the current block, for example, based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), etc. Motion estimation unit 222 may typically perform these calculations using sample-by-sample differences between the current block and the considered reference blocks. Motion estimation unit 222 may identify the reference block with the lowest value obtained from these calculations, indicating the reference block that most closely matches the current block.

[0090] Motion estimation unit 222 can generate one or more motion vectors (MVs) that define the position of a reference block in a reference image relative to the position of the current block in the current image. Motion estimation unit 222 can then provide the motion vectors to motion compensation unit 224. For example, for unidirectional inter-frame prediction, motion estimation unit 222 can provide a single motion vector, while for bidirectional inter-frame prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vectors to generate prediction blocks. For example, motion compensation unit 224 can use the motion vectors to retrieve data for the reference blocks. As another example, if the motion vectors have fractional-sample precision, motion compensation unit 224 can interpolate the values ​​used for the prediction blocks according to one or more interpolation filters. Furthermore, for bidirectional inter-frame prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by corresponding motion vectors and combine the retrieved data, for example, by per-sample averaging or weighted averaging.

[0091] As another example, for intra-prediction or intra-prediction decoding, intra-prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, in directional mode, intra-prediction unit 226 can typically mathematically combine the values ​​of adjacent samples and fill these calculated values ​​across the current block in a defined direction to generate a prediction block. As another example, in DC mode, intra-prediction unit 226 can calculate the average of the adjacent samples of the current block and generate a prediction block to include the obtained average for each sample of the prediction block.

[0092] Mode selection unit 202 provides a prediction block to residual generation unit 204. Residual generation unit 204 receives the original, uncoded version of the current block from video data memory 230 and the prediction block from mode selection unit 202. Residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines the residual block for the current block. In some examples, residual generation unit 204 may also determine the difference between sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, one or more subtractor circuits performing binary subtraction may be used to form residual generation unit 204.

[0093] In the example where mode selection unit 202 divides a CU into PUs, each PU can be associated with a luma prediction unit and a corresponding chroma prediction unit. Video encoder 200 and video decoder 300 can support PUs of various sizes. As noted above, the size of a CU can refer to the size of the luma decoding block of the CU, while the size of a PU can refer to the size of the luma prediction unit of the PU. Assuming a particular CU size is 2Nx2N, video encoder 200 can support PU sizes of 2Nx2N or NxN for intra-frame prediction, and 2Nx2N, 2NxN, Nx2N, NxN, or similar symmetrical PU sizes for inter-frame prediction. Video encoder 200 and video decoder 300 can also support asymmetric segmentation for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0094] In an example where the mode selection unit 202 does not further divide the CU into PUs, each CU can be associated with a luminance decoding block and a corresponding chrominance decoding block. As mentioned above, the size of the CU can refer to the size of the luminance decoding block of the CU. The video encoder 200 and the video decoder 300 can support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0095] For other video decoding techniques (such as block-based copy mode decoding, affine mode decoding, and linear model (LM) mode decoding), mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the decoding technique. In some examples (such as palette mode decoding), mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how the block will be reconstructed based on a selected palette. In such a mode, mode selection unit 202 can provide these syntax elements to entropy coding unit 220 for encoding.

[0096] As described above, the residual generation unit 204 receives video data for the current block and the corresponding prediction block. Then, the residual generation unit 204 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.

[0097] Transform processing unit 206 applies one or more transformations to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 can apply various transformations to the residual block to form the transform coefficient block. For example, transform processing unit 206 can apply a discrete cosine transform (DCT), direction transform, Karhunen-Loeve transform (KLT), or conceptually similar transformations to the residual block. In some examples, transform processing unit 206 can perform multiple transformations on the residual block, such as primary and secondary transformations (e.g., rotation transformations). In some examples, transform processing unit 206 does not apply any transformations to the residual block.

[0098] Quantization unit 208 can quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 can quantize the transform coefficients of the transform coefficient block based on the quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode selection unit 202) can adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may cause information loss, and therefore, the quantized transform coefficients may have lower accuracy compared to the original transform coefficients produced by transform processing unit 206.

[0099] The inverse quantization unit 210 and the inverse transform processing unit 212 can apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct the residual block from the transform coefficient block. The reconstruction unit 214 can generate a reconstructed block corresponding to the current block based on the reconstructed residual block and the prediction block generated by the mode selection unit 202 (although potentially with some degree of distortion). For example, the reconstruction unit 214 can add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate the reconstructed block.

[0100] Filter unit 216 can perform one or more filtering operations on the reconstructed block. For example, filter unit 216 can perform deblocking to reduce block artifacts along the edges of the CU. In some examples, the operations of filter unit 216 can be skipped.

[0101] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in an example where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In an example where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve a reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction of blocks in subsequently encoded pictures. Additionally, the intra-frame prediction unit 226 can use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction of other blocks in the current picture.

[0102] Typically, entropy coding unit 220 can entropy-encode syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 can entropy-encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 can entropy-encode predictive syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from mode selection unit 202. Entropy coding unit 220 can perform one or more entropy coding operations on syntax elements, another example of video data, to generate entropy-encoded data. For example, entropy coding unit 220 can perform context-adaptive variable-length decoding (CAVLC), CABAC, variable-to-variable (V2V) length decoding, syntax-based context-adaptive binary arithmetic decoding (SBAC), probabilistic interval partitioned entropy (PIPE) decoding, exponential Golomb coding, or another type of entropy coding operation on the data. In some examples, entropy coding unit 220 can operate in a bypass mode where syntax elements are not entropy-encoded.

[0103] The video encoder 200 can output a bitstream that includes entropy-encoded syntax elements required for reconstructing slices or blocks of images. Specifically, the entropy coding unit 220 can output a bitstream.

[0104] The above operations are described in relation to the blocks. Such a description should be understood as referring to the operations used for the luma decoding block and / or the chroma decoding block. As mentioned above, in some examples, the luma decoding block and the chroma decoding block are the luma and chroma components of the CU. In some examples, the luma decoding block and the chroma decoding block are the luma and chroma components of the PU.

[0105] In some examples, it is not necessary to repeat the operations performed for the luma decoding block for the chroma decoding block. As an example, it is not necessary to repeat the operations used to identify the motion vector (MV) and reference image for the luma decoding block to identify the MV and reference image for the chroma block. Specifically, the MV for the luma decoding block can be scaled to determine the MV for the chroma block, and the reference image can be the same. As another example, the intra-frame prediction process can be the same for both the luma and chroma decoding blocks.

[0106] Figure 4 This is a block diagram illustrating an example video decoder 300 capable of performing the techniques described herein. Figure 4 This disclosure is provided for illustrative purposes and does not limit the techniques illustrated and described in this disclosure in a general manner. For illustrative purposes, this disclosure describes a video decoder 300 based on VVC (ITU-T H.266, in deployment) and HEVC (ITU-T H.265) technologies. However, the technologies of this disclosure can be implemented by video decoding devices configured for other video decoding standards.

[0107] exist Figure 4 In the example, the video decoder 300 includes a decoded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 can be implemented in one or more processors or in processing circuitry. For example, units of the video decoder 300 can be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0108] The prediction processing unit 304 includes a motion compensation unit 316 and an intra-frame prediction unit 318. The prediction processing unit 304 may include an addition unit that performs predictions based on other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0109] CPB memory 320 can store video data to be decoded by components of video decoder 300, such as encoded video bitstreams. For example, it can be stored from computer-readable medium 110 ( Figure 1 The video data stored in the CPB memory 320 is obtained. The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. Additionally, the CPB memory 320 may store video data other than the syntax elements of the decoded picture, such as temporary data representing the output from various units of the video decoder 300. The DPB 314 typically stores decoded pictures, which the video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and DPB 314 may be formed of any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. The CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300, or off-chip relative to those components.

[0110] Alternatively or concurrently, in some examples, the video decoder 300 can be derived from the memory 120 ( Figure 1 The decoded video data is retrieved. In other words, memory 120 can utilize CPB memory 320 to store data, as discussed above. Similarly, when some or all of the functions of video decoder 300 are implemented using software to be executed by the processing circuitry of video decoder 300, memory 120 can store instructions to be executed by video decoder 300.

[0111] It shows Figure 4 The various units shown help to understand the operations performed by the video decoder 300. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Similar to... Figure 3Fixed-function circuits refer to circuits that provide a specific function and are pre-configured regarding the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in terms of 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 (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is typically immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units may be integrated circuits.

[0112] The video decoder 300 may include an ALU, EFU, digital circuitry, analog circuitry, and / or a programmable core formed by programmable circuitry. In an example where the operation of the video decoder 300 is performed by software executing on the programmable circuitry, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0113] Entropy decoding unit 302 can receive encoded video data from the CPB and perform entropy decoding on the video data to reconstruct the syntax elements. Prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0114] Typically, the video decoder 300 reconstructs the image on a block-by-block basis. The video decoder 300 can perform the reconstruction operation on each block individually (where the block currently being reconstructed (i.e., decoded) can be referred to as the "current block").

[0115] Entropy decoding unit 302 can entropy decode the syntax elements of the quantized transform coefficients that define the quantized transform coefficient block, as well as transform information such as quantization parameters (QPs) and / or transform mode indications. Inverse quantization unit 306 can use the QPs associated with the quantized transform coefficient block to determine the degree of quantization, and similarly, determine the degree of inverse quantization to be applied by inverse quantization unit 306. Inverse quantization unit 306 can, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 can thus form a transform coefficient block including the transform coefficients.

[0116] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 can apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 can apply the inverse DCT, inverse integer transform, inverse Karhunen-Loeve transform (KLT), inverse rotation transform, inverse direction transform, or another inverse transform to the transform coefficient block.

[0117] Furthermore, the prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy-decoded by the entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-frame predicted, the motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax elements may indicate the reference picture from which the reference block is to be retrieved in the DPB 314, and a motion vector identifying the position of the reference block in the reference picture relative to the position of the current block in the current picture. The motion compensation unit 316 can typically be configured with respect to the motion compensation unit 224 ( Figure 3 The method described is basically similar to the way the inter-frame prediction process is performed.

[0118] In some examples, the motion compensation unit 316 can use the inter-frame decoding tool LIC and LMCS. In such examples, the motion compensation unit 316 can use a forward mapping function to shape the pixel domain reference template block into a mapped domain reference template block. The motion compensation unit 316 can derive LIC model parameters from the mapped domain reference template block and the mapped domain adjacent reconstructed template blocks. The motion compensation unit 316 can then apply the LIC model parameters to the motion compensation prediction signal.

[0119] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, then intra-prediction unit 318 can generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, intra-prediction unit 318 can typically be configured with respect to intra-prediction unit 226 ( Figure 3 The intra-prediction process is performed in a manner substantially similar to that described above. The intra-prediction unit 318 can retrieve data from neighboring samples of the current block from the DPB 314.

[0120] Reconstruction unit 310 can reconstruct the current block using the prediction block and the residual block. For example, reconstruction unit 310 can reconstruct the current block by adding the samples of the residual block to the corresponding samples of the prediction block.

[0121] Filter unit 312 can perform one or more filter operations on the reconstructed block. For example, filter unit 312 can perform a deblocking operation to reduce block artifacts along the edges of the reconstructed block. The operation of filter unit 312 is not necessarily performed in all examples.

[0122] The video decoder 300 can store the reconstructed blocks in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 can store the reconstructed blocks in the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 can store the filtered reconstructed blocks in the DPB 314. As discussed above, the DPB 314 can provide reference information (such as samples of the current image for intra-frame prediction and samples of previously decoded images for subsequent motion compensation) to the prediction processing unit 304. Furthermore, the video decoder 300 can output decoded images (e.g., decoded video) from the DPB 314 for use in applications such as... Figure 1 The subsequent presentation on display devices such as display device 118.

[0123] In this manner, 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 circuitry and configured to: shape a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; derive local illumination compensation (LIC) model parameters from the mapped domain reference template block and the mapped domain adjacent reconstruction template block; apply the LIC model parameters to a motion compensation prediction signal; and decode the video data based on the application of the LIC model parameters.

[0124] As stated above, this disclosure relates to Local Illumination Compensation (LIC) in video decoding. The techniques of this disclosure can be applied to any existing video codec, such as HEVC (High-Efficiency Video Decoding), VVC (Various Video Decoding), Basic Video Decoding (EVC), or can be high-efficiency decoding tools in any future video decoding standard. The following sections of this disclosure discuss HEVC techniques and work in VVC related to LIC.

[0125] Video decoding standards include ITU-T H.261, ISO / IEC MPEG-1 Vision, ITU-T H.262 or ISO / IEC MPEG-2 Vision, ITU-T H.263, ISO / IEC MPEG-4 Vision, and ITU-T H.264 (also known as ISO / IEC MPEG-4 AVC), including its Scalable Video Decoding (SVC) and Multi-View Video Decoding (MVC) extensions.

[0126] In addition, a new video decoding standard (called High Efficiency Video Decoding (HEVC) or ITU-T H.265, including its Range Extension, Multi-View Extension (MV-HEVC) and Scalable Extension (SHVC)) has recently been developed by the Joint Collaborative Team for Video Decoding (JCT-VC), the Joint Collaborative Team for the Development of 3D Video Decoding Extensions (JCT-3V) of the ITU-T Video Decoding Experts Group (VCEG), and the ISO / IEC Cinema Experts Group (MPEG).

[0127] ITU-T VCEG (Q6 / 16) and ISO / IEC MPEG (JTC 1 / SC 29 / WG 11) are investigating the potential need for standardization of future video decoding technologies with compression capabilities significantly exceeding those of the HEVC standard (including its current extensions and recent extensions to screen content decoding and high dynamic range decoding). These two groups are conducting this exploration under a collaborative effort known as the Joint Video Exploration Group (JVET) to evaluate compression technology designs proposed by their experts in this field. The algorithmic description of Universal Video Decoding and Test Model 9 (VTM 9) can also be referred to as JVET-R2002.

[0128] We will now discuss the CU structure and motion vector prediction in HEVC. In HEVC, the largest decoding unit in a slice is the CTB or CTU. The CTB contains a quadtree, whose nodes are decoding units.

[0129] In the HEVC master profile, the CTB size can range from 16x16 to 64x64 (but technically, an 8x8 CTB size is also supported). CUs can range from the same size as the CTB to as small as 8x8. Each CU is decoded using a mode (e.g., inter-frame or intra-frame). When inter-frame decoding is performed on a CU, it can be further divided into 2 or 4 PUs, or, without further division, become a single PU. When a CU contains two PUs, they can be rectangles of half the size or two rectangles, where one PU is 1 / 4 the size of the CU and the other is 3 / 4 the size of the CU. When inter-frame decoding is performed on a CU, each PU has a set of motion information derived using a unique inter-frame prediction mode.

[0130] Now let's discuss motion vector prediction. In the HEVC standard, there are two inter-frame prediction modes, known as PU merging (skipping is considered a special case of merging) and Advanced Motion Vector Prediction (AMVP) mode.

[0131] In AMVP or merge mode, a candidate list of motion vector predictors (MVs) is maintained for multiple MVs. The MV of the current PU and the reference index in merge mode are generated by retrieving a candidate from the MV candidate list.

[0132] The MV candidate list can contain up to five candidates for the merge mode and two candidates for the AMVP mode. The merge candidates can contain a set of motion information, such as motion vectors and reference indices corresponding to the reference picture lists (list 0 (L0) and list 1 (L1)). If the merge candidates are identified by the merge index, the video decoder 300 can determine the reference picture and associated motion vectors for predicting the current block. On the other hand, in AMVP mode for each potential prediction direction from list 0 or list 1, the reference index and the MV predictor (MVP) index for the MV candidate list need to be explicitly signaled (e.g., by the video encoder 200), since AMVP candidates only contain motion vectors. In AMVP mode, the predicted motion vectors can be further refined. Candidates for both modes can be similarly derived from the same spatially and temporally adjacent blocks.

[0133] Figures 5A-5B These are conceptual diagrams illustrating examples of spatial neighbor candidates used for merging patterns and Advanced Motion Vector Predictor (AMVP) patterns. For a specific PU (PU0 400), it is possible to... Figure 5A -B shows the adjacent block derivation space MV candidates, but the techniques used to generate candidates from blocks are different for merge and AMVP modes.

[0134] For example, in merge mode, the video decoder 300 can be configured according to... Figure 5A The derivation shown in the diagram yields a maximum of four spatial MV candidates. The order is as follows: left (0), top (1), top right (2), bottom left (3), and top left (4), as shown in the diagram. Figure 5A As shown in the diagram. For example, video encoder 200 or video decoder 300 can be configured according to... Figure 5A The sequential derivation shown has a maximum of four spatial MV candidates.

[0135] In AVMP mode, adjacent blocks are divided into two groups: the left group consists of blocks 0 and 1 to the left of PU0 402, and the upper group consists of blocks 2, 3, and 4 above PU0 402, as shown below. Figure 5BAs shown in the diagram. For each group, potential candidates in adjacent blocks that reference the same reference image as the reference image indicated by the signaled reference index have the highest priority to be selected to form the final candidates for that group. For example, video encoder 200 or video decoder 300 can select candidates in adjacent blocks that reference the same reference image as the reference image indicated by the signaled reference index to form the final candidates. In some cases, none of the adjacent blocks may contain motion vectors pointing to the same reference image. Therefore, if no such candidate can be found, video decoder 300 can scale the first available candidates to form the final candidates. In this way, any temporal distance differences can be compensated for.

[0136] Now we discuss temporal motion vector prediction in HEVC. Temporal motion vector predictor (TMVP) candidates (if enabled and available) are added to the MV candidate list after spatial motion vector candidates. For example, video encoder 200 or video decoder 300 can add TMVP candidates to the MV candidate list after spatial motion vector candidates. The process for deriving motion vectors for TMVP candidates is the same for both merge and AMVP modes. However, in some examples, the target reference index used for TMVP candidates is set to 0 in merge mode.

[0137] Figure 6A This is a conceptual diagram illustrating an example of a Time Motion Vector Prediction (TMVP) candidate. The main block used for TMVP candidate derivation is located in the lower right block outside the shared PU. Figure 6A The block 410 is shown as "T" to compensate for the offset of the upper and left blocks used to generate spatially adjacent candidates. However, if the block is located outside the current CTB line (e.g., block 414) or motion information is unavailable, the video encoder 200 or video decoder 300 can replace the center block 412 of the PU with the lower right block co-located outside the PU.

[0138] The video encoder 200 or video decoder 300 can derive motion vectors for TMVP candidates from the co-location PU of the co-location image indicated at the slice level. The motion vectors used for the co-location PU are called co-location MVs.

[0139] Figure 6B This is a conceptual diagram illustrating an example of motion vector scaling. Similar to the time-direct mode in AVC, to derive TMVP candidate motion vectors, the co-located MV 424 needs to be scaled to compensate for time distance differences, such as... Figure 6B As shown. For example, the current time distance 422 is different from the co-location time distance 420. Therefore, the video encoder 200 or the video decoder 300 can scale the co-location MV 424 proportionally to the difference between the current time distance 422 and the co-location time distance 420.

[0140] Now we discuss other aspects of motion prediction in HEVC. Several aspects of merging and AMVP modes are described below. Motion vector scaling: The value of a motion vector is proportional to the distance between the images at rendering time. A motion vector associates two images (i.e., a reference image and an image containing the motion vector, e.g., a containing image). When using one motion vector to predict another, the video encoder 200 or video decoder 300 calculates the distance between the containing image and the reference image based on the Picture Order Count (POC) value.

[0141] For a motion vector to be predicted, the associated containing image and reference image may differ. Therefore, the video encoder 200 or video decoder 300 can calculate a new distance (based on POC). The video encoder 200 or video decoder 300 scales the motion vector based on these two POC distances. For spatially adjacent candidates, the containing image used for two motion vectors is the same, while the reference image is different. In HEVC, motion vector scaling is applied to both TMVP and AMVP for spatially and temporally adjacent candidates.

[0142] If the motion vector candidate list is incomplete, the video encoder 200 or video decoder 300 generates artificial MV candidates and inserts them at the end of the list until the MV candidate list has all candidates (e.g., the list is full). In merge mode, there are two types of artificial MV candidates: combined candidates derived only for B-slice derivation and zero candidates used only for AMVP (if the first type does not provide enough artificial candidates to fill the MV candidate list).

[0143] For each pair of candidates that is already in the candidate list and has the necessary motion information, a bidirectional combined motion vector candidate is derived by combining the motion vector of the first candidate (referring to the image in list 0) and the motion vector of the second candidate (referring to the image in list 1).

[0144] Now let's discuss the pruning process used for candidate insertion. Candidates from different blocks might happen to be identical, which reduces the efficiency of merging / AMVP candidate lists. A pruning process can be applied to address this issue. For example, the video encoder 200 or video decoder 300 can compare one candidate in the current candidate list with other candidates to avoid inserting the same candidate to some extent. To reduce complexity, only limited pruning is applied instead of comparing each potential candidate with all other existing candidates.

[0145] Local illumination compensation is now discussed. An overview of illumination compensation proposed for HEVC is given. In JCTVC-C041, Partition-Based Illumination Compensation (PBIC) is proposed. PBIC differs from Weighted Prediction (WP), where the video encoder 200 can indicate and signal parameters at the slice level. Using PBIC, the video encoder 200 can enable / disable PBIC and signal the PBIC model parameters at the PU level to handle local illumination variations.

[0146] Similar to WP, Illuminance Compensation (IC) also has a scaling factor (also denoted by a) and an offset (also denoted by b) as well as a right shift of 6. The IC flag is decoded for each PU (e.g., by video encoder 200) to indicate whether the IC is applicable to the current PU. If the IC is applied to the current PU, video encoder 200 can signal the set of IC parameters (e.g., a and b) to video decoder 300, which can then use this set of IC parameters for motion compensation. In the case of dual prediction, video encoder 200 can signal two scaling factors (one for each prediction direction) and one offset. To save bits spent on IC parameters, the chroma component shares the scaling factor with the luminance component and uses a fixed offset of 128.

[0147] An overview of ICs in 3D-HEVC is now provided. In 3D-HEVC, ICs are enabled for inter-view prediction. The ICs in 3D-HEVC differ from the WP and PBICs in video encoder 200, where IC parameters are explicitly signaled. For ICs in 3D-HEVC, the video decoder (e.g., video decoder 300) derives IC parameters based on neighboring samples of the current CU and neighboring samples of the reference block.

[0148] The IC is only applied to 2Nx2N split mode. For AMVP mode, the video encoder 200 signals an IC flag for each CU predicted from the inter-view reference image. For merge mode, to save bits, the video encoder 200 only signals the IC flag when the merge index of the PU is not equal to 0. The IC is not applied to CUs predicted only from the time reference image.

[0149] The linear IC model used in inter-view prediction is shown in equation (1):

[0150] p(i,j)=a*r(i+dv x ,j+dv y +b), where (i,j)∈PU c (1)

[0151] Here, PU c (i,j) is the current PU, and (i,j) is the PU.c The coordinates of the pixels in (dv) x ,dv y ) is PU c The disparity vector. p(i,j) is the disparity vector of PU. c The prediction is given by r, which is a reference image of the PU from the adjacent view, and a and b are parameters of the linear IC model.

[0152] Figure 7 This is a conceptual diagram illustrating an example of neighboring pixels used to estimate parameters in an IC model, where a reference block for the current block is found using the disparity vector of the current PU. To estimate parameters a and b for the PU, the video decoder 300 uses two sets of pixels, such as... Figure 7 As shown:

[0153] 1) Available reconstructable adjacent pixels in the left column and top row of the current CU 430 (including the CU of the current PU); and

[0154] 2) The corresponding neighboring pixels of the current CU's reference block 440 (indicated by gray circles). The reference block of the current CU is found by using the disparity vector of the current PU.

[0155] For example, Rec neig 432and Rec refneig 442 represents the set of adjacent pixels used by the current CU 430 and the reference block 440 of the current CU 430, respectively, and 2N represents Rec neig and Rec refneig The number of pixels in the image. Therefore, a and b can be calculated as:

[0156]

[0157]

[0158] In some cases, only 'a' is used in the linear model, and 'b' is always set to 0, or only 'b' is used, and 'a' is always set to 1. For example, a video encoder 200 or a video decoder 300 may use only 'a' or only 'b' in the linear model.

[0159] Local Illuminance Compensation (LIC) in JVET is now discussed. LIC is based on a linear model for illuminance variations, using a scaling factor a (where the shift is fixed at 6) and an offset b. LIC is adaptively enabled or disabled for each inter-mode decoding unit (CU).

[0160] Figure 8This is a conceptual diagram illustrating an example of neighboring samples used to derive IC parameters. When the LIC is applied to the CU, the video encoder 200 or video decoder 300 employs a least-squares error method to derive parameters a and b using neighboring samples of the current CU and their corresponding reference samples. More specifically, as... Figure 8 As shown, neighboring samples (shown as circles with diagonal lines) of the CU's secondary sampling (2:1 secondary sampling) and corresponding pixels in the reference image (shown as circles with checkbox patterns and identified by motion information of the current CU or sub-CU) are used. IC parameters are derived and applied to each prediction direction. For example, neighboring samples of the secondary sampling of PU 450 and PU 452, as well as the current CU (which includes PU 450 and PU 452), are depicted. Reference block 454, which serves as the reference block for PU 450 in List 0, and neighboring samples of the secondary sampling of reference block 454 are also shown.

[0161] When decoding the CU using merge mode, the LIC flag is copied from adjacent blocks in a manner similar to motion information copying in merge mode. When encoding the CU using other methods (e.g., without merging mode), the video encoder 200 signals the video decoder 300 to indicate whether the LIC flag is applied.

[0162] Now let's discuss Weighted Prediction (WP). HEVC supports WP, where a scaling factor (denoted by a), a shift (denoted by s), and an offset (denoted by b) are used in motion compensation. Assuming the pixel value at position (x,y) in the reference image is p(x,y), then p'(x,y) = ((a*p(x,y)+(1<<(s-1)))>>s)+b instead of p(x,y) is used as the predicted value in motion compensation.

[0163] When motion compensation (WP) is enabled, for each reference image in the current slice, the video encoder 200 signals a flag to be received by the video decoder 300 to indicate whether WP is applied to the reference image. If WP is applied to a reference image, the video encoder 200 sends a set of WP parameters (e.g., a, s, and b) to the video decoder 300, and the video decoder 300 uses this set of WP parameters for motion compensation from the reference image. For flexible enabling / disabling of WP for the luma and chroma components, the video encoder 200 can separately signal the WP flag and WP parameters for the luma and chroma components. In WP, the same set of WP parameters is used for all pixels in a reference image.

[0164] Figure 9This is a block diagram illustrating an example of a Luminance Mapping with Chroma Scaling (LMCS) architecture. In VVC, a decoding tool called LMCS is added as a new processing block before the loop filter. LMCS has two main components: 1) an in-loop mapping of the luminance component based on an adaptive piecewise linear model; and 2) for the chrominance component, applying luminance-dependent chrominance residual scaling. Figure 9 The LMCS architecture is illustrated from the perspective of a decoder (such as video decoder 300). For example, video decoder 300 can implement, for instance... Figure 9 The LMCS is depicted in the diagram. For example, the video decoder 300 can process inverse quantization and inverse transform 500, perform intra-frame luma prediction 504, and add the luma prediction to the luma residual in the reconstruction 502 in the mapped domain. The video decoder 300 can process loop filters 506 and 516 (such as deblocking filters, adaptive loop filters, and sample adaptive offsets), perform motion compensation 510 and 514, perform intra-frame chroma prediction 512, add the chroma prediction to the chroma residual 522, and store the decoded picture as a reference picture 508 and 520 in the original (e.g., unmapped) domain. The forward mapping of the luma signal in forward shaping 524, the inverse mapping of the luma signal in inverse shaping 526, and the luma-dependent chroma scaling process 528 are LMCS function blocks. As with most other tools in VVC, the video encoder 200 can use the SPS flag to enable / disable LMCS at the sequence level.

[0165] We now discuss luminance mapping with a piecewise linear model. In-loop mapping of the luminance component adjusts the dynamic range of the input signal by redistributing codewords across the dynamic range, thereby improving compression efficiency. Luminance mapping uses the forward mapping function FwdMap and the corresponding inverse mapping function InvMap. The video encoder 200 uses a piecewise linear model with 16 equal segments to signal the FwdMap function. Since the video decoder 300 can derive the InvMap function from the FwdMap function, it does not need to signal the InvMap function.

[0166] The video encoder 200 signals the luminance mapping model in the Adaptive Parameter Set (APS) syntax structure, where aps_params_type is set to equal to 1 (LMCS_APS). Up to four LMCSAPS can be used in the decoded video sequence. In this example, only one LMCS APS is used for the image. The video encoder 200 can signal the luminance mapping model using a piecewise linear model. The piecewise linear model divides the dynamic range of the input signal into 16 equal segments, and for each segment, the linear mapping parameters of that segment can be expressed using the number of codewords assigned to that segment. For example, for a 10-bit input, by default, each of the 16 segments will have 64 codewords assigned to that segment. The signaled number of codewords is used to calculate the scaling factor and adjust the mapping function for that segment accordingly. At the slice level, the video encoder 200 signals the LMCS enable flag to indicate, as... Figure 9 Whether the LMCS procedure described herein applies to the current slice. If LMCS is enabled for the current slice, the video encoder 200 notifies the aps_id in the slice header with a signal to identify the APS carrying the luminance mapping parameters.

[0167] Each i-th segment (i = 0…15) of the FwdMap piecewise linear model is defined by two input pivot points InputPivot[] and two output (mapping) pivot points MappedPivot[].

[0168] Calculate InputPivot[] and MappedPivot[] as follows (assuming 10-bit video):

[0169] 1) OrgCW = 64

[0170] 2) For i = 0:16, InputPivot[i] = i * OrgCW

[0171] 3) For i = 0:16, MappedPivot[i] is calculated as follows:

[0172] MappedPivot[0] = 0;

[0173] for(i=0;i<16;i++)

[0174] MappedPivot[i+1]=MappedPivot[i]+SignalledCW[i]

[0175] Where SignalledCW[i] is the number of codewords used for the i-th segment, which is signaled.

[0176] exist Figure 9The diagram illustrates forward reshaping (524) and inverse reshaping (526). These boxes represent forward reshaping of data from the pixel domain (also known as the original domain) to the mapped domain and inverse reshaping of data from the mapped domain to the pixel domain, respectively. Figure 9 As shown, for an inter-frame decoded block, motion compensation prediction is performed in the original domain (e.g., motion compensation 510), and then the motion compensation prediction signal is transformed to the mapped domain (e.g., by forward shaping 524). In other words, the motion compensation prediction block Y is calculated based on the reference signal in DPB 508. pred Subsequently, the video decoder 300 applies the FwdMap function (e.g., forward shaping 524) to map or shape the luminance prediction blocks in the original domain to the mapped domain, Y′. pred =FwdMap(Y pred For intra-decoded blocks, the FwdMap function is not applied because intra-prediction 504 is performed in the mapping domain. This is done when computing the reconstructed block Y. r Subsequently, the video decoder 300 applies the InvMap function (e.g., inverse integer 526) to transform the reconstructed luminance values ​​in the mapped domain back to the reconstructed luminance values ​​in the original domain. Apply the InvMap function (e.g., inverse integer 526) to both intra-decoded and inter-decoded luminance blocks.

[0177] The brightness mapping process (forward and / or inverse mapping) can be implemented using lookup tables (LUTs) or real-time computation. If LUTs are used, FwdMapLUT and InvMapLUT can be pre-computed and pre-stored for use at the tile group level, and the forward and inverse mappings can be simply implemented as FwdMap(Y) respectively. pred =FwdMapLUT[Y pred ] and InvMap(Y r =InvMapLUT[Y r Alternatively, real-time computation can be used. Take the forward mapping function FwdMap as an example. To determine the segment to which a luminance sample belongs, the video decoder 300 can right-shift the sample value by 6 bits (corresponding to 16 equal segments). The video decoder 300 can then retrieve the linear model parameters used for that segment and apply them in real-time to calculate the mapped luminance value. Let i be the segment index, a1 and a2 be InputPivot[i] and InputPivot[i+1] respectively, and b1 and b2 be MappedPivot[i] and MappedPivot[i+1] respectively. The FwdMap function can be as follows:

[0178] FwdMap(Y pred )=((b2-b1) / (a2-a1))*(Y pred-a1)+b1 (4)

[0179] The InvMap function can be computed in real time in a similar manner. Typically, the segments in the mapping domain are not of equal size. Therefore, the most straightforward inverse mapping process would require the video decoder 300 to make comparisons to determine which segment the current sample value belongs to. This comparison increases the complexity of the decoder. Therefore, VVC imposes a bitstream constraint on the value of the output pivot point MappedPivot[i] as follows. Assume the range of the mapping domain ([0, 1023] for a 10-bit video) is divided into 32 equal segments. If MappedPivot[i] is not a multiple of 32, then MappedPivot[i+1] and MappedPiot[i] cannot belong to the same segment among the 32 equal-sized segments; for example, MappedPivot[i+1] >> (BitDepthY-5) should not be equal to MappedPivot[i] >> (BitDepthY-5). Due to this bitstream constraint, the InvMap function can also be performed using a simple right shift of 5 bits (which corresponds to 32 equal-sized segments) to determine the segment to which a sample value belongs.

[0180] We now discuss luma-dependent chroma residual scaling. Chroma residual scaling is designed to compensate for the interaction between the luma signal and its corresponding chroma signal. The video encoder 200 signals whether chroma residual scaling is enabled at the slice level. If luma mapping is enabled, the video encoder 200 signals an additional flag to indicate whether luma-dependent chroma residual scaling is enabled. Luma-dependent chroma residual scaling is disabled when luma mapping is not used. Furthermore, luma-dependent chroma residual scaling is always disabled for chroma blocks with an area less than or equal to 4.

[0181] Chroma residual scaling depends on the average of the reconstructed adjacent luma samples from the top and / or left of the current Virtual Pipeline Data Unit (VPDU). If the current CU is inter-frame 128x128, inter-frame 128x64, or inter-frame 64x128, the video decoder 300 applies a chroma residual scaling factor derived for the CU associated with the first VPDU to all chroma transform blocks in that CU. Let avgYr represent the average of the reconstructed adjacent luma samples (see [link to documentation]). Figure 9 The video decoder 300 calculates C using the following steps. ScaleInv Value:

[0182] 1) Use the InvMap function to find the index Y of the piecewise linear model to which avgYr belongs. Idx .

[0183] 2)C ScaleInv =cScaleInv[YIdx ], where cScaleInv[] is a 16-segment LUT pre-computed table based on the value of SignalledCW[i] and the offset values ​​for the chroma residual scaling process notified by the signal in the APS.

[0184] Unlike sample-based brightness mapping, C ScaleInv This is a constant value for the entire chroma block. For C... ScaleInv Apply chroma residual scaling as follows:

[0185] Video Encoder 200:C ResScale =C Res *C Scale =C Res / C ScaleInv

[0186] Video Decoder 300:C Res =C ResScale / C Scale =C Resscale *C Scaleinv

[0187] Figure 10 This is a block diagram illustrating an example LMCS architecture when using Local Illumination Compensation (LIC). Figure 10 In the example, with Figure 9 Blocks similar to each other in the block are numbered the same. When LMCS is enabled, the luminance component is compared to the adjacent reconstructed samples (Rec) of the current CU. neig It is necessary to convert from the mapped domain back to the pixel domain before the motion compensation operation. Figure 10 The LMCS architecture with LIC enabled is shown. In the luminance motion compensation loop, before the video decoder 300 can derive the LIC model parameters a and b in the pixel domain, the video decoder 300 can use a CU-level inverse lookup table to map the reconstructed luminance signal (Yr) back to the pixel domain (denoted as Rec). neig This inverse mapping is represented by inverse shaping 530 between reconstruction 502 and motion compensation 510.

[0188] When both LIC and LMCS are enabled, LIC is the only inter-frame prediction mode. It requires the video decoder (such as video decoder 300) to load an inverse lookup table at the CU level to convert the reconstructed signal back to the pixel domain for LIC model parameter derivation, as LMCS is an image-level tool. Unlike VVC standardization (which requires loading this inverse table at the CTU / VPDU / picture level during the loop filtering stage), this additional inverse mapping at the CU level introduces an additional hardware implementation burden to the motion compensation module of video decoder 300, potentially leading to longer latency during the motion compensation stage.

[0189] Figure 11 This is a block diagram illustrating an example LMCS architecture using a LIC according to the technology described in this disclosure. Figure 11 In the example, with Figure 9 Blocks similar to each other in the pixel domain are numbered as the same block. The derivation of LIC model parameters in the alternative domain is now discussed. According to the techniques of this disclosure, the video decoder 300 can use the same derivation process for LIC parameters, but applies the derivation process directly in the mapping domain. The video decoder 300 can directly apply the obtained model parameters to motion-compensated samples in the pixel domain. For example, a CU-level forward lookup table can be used to transform or shape a pixel-domain reference template block from the pixel domain to the mapping domain to determine the mapping domain reference template block. For example, the video decoder 300 can use a forward mapping function (e.g., forward shaping 532) to shape a pixel-domain reference template block into a mapping domain reference template block. Figure 11 As shown, both the mapped domain reference template block (e.g., shown as exiting forward shaping 532 and entering motion compensation 510) and the mapped domain adjacent reconstruction template block (e.g., shown as exiting reconstruction 502 and entering motion compensation 510) are used, as they operate on the pixel domain signal to derive the LIC model parameters a and b. For example, with Figure 9 The examples are different, Rec refneig and Rec neig Both are input to motion compensation 510. The derived model parameters (along with a shift of N, where N is an integer (integer shift, e.g., 6) are applied to the motion-compensated prediction signal in the pixel domain via motion compensation 510. Therefore, the CU-level inverse lookup table can be completely avoided, which reduces latency and improves the decoding efficiency of the video decoder 300. For example, the video decoder 300 can derive LIC model parameters a and b using a mapped domain reference template block and a mapped domain adjacent reconstruction template block (as they operate on the pixel domain signal). The video decoder 300 can then apply the LIC model parameters a and b to the motion-compensated prediction signal in the pixel domain.

[0190] In another example, the video decoder 300 can apply the derived model parameters to the mapped motion compensation prediction signal, rather than to the pixel-domain motion compensation prediction signal.

[0191] The same technique for deriving LIC model parameters in the mapping domain can be extended to other dynamic range mappings (denoted as the substitution domain). Given the forward and inverse mapping functions for dynamic range mappings, the aforementioned techniques can be directly applied. Figure 11 The architecture is the same. For example, the video decoder 300 can use the gamma function FwdMap(x) = A*x. rAs a forward mapping function, where A and r are constant values. For example, the mapping function can also have a polynomial form, such as FwdMap(x) = ∑ i∈{0,1,…,n} a i x i , where a i Let FwdMap(x) represent real numbers, which are the coefficients of a polynomial function of x. These coefficients can be trained frame-by-frame and signaled in the APS. Based on the reverse lookup of FwdMap(x), the inverse mapping function can be easily derived. For example, FwdMap(x0), FwdMap(x1), ... and FwdMap(x... i All values ​​are mapped to a single value, for example, y. j Then the video decoder 300 can determine the inverse function InvMap(y). j One of the entries in ) is one of x0, x1, ... and xi, or their weighted average.

[0192] Figure 12 This is a flowchart illustrating the LIC parameter derivation technique according to the present disclosure. The video decoder 300 can shape a pixel domain reference template block into a mapped domain reference template block using a forward mapping function (550). For example, the video decoder 300 can use an LMCS to map the luminance component of the reference template block to create the mapped domain reference template block. The video decoder 300 can derive LIC model parameters from the mapped domain reference template block and the mapped domain adjacent reconstructed template block (552). For example, instead of loading an inverse mapping table from memory, the video decoder 300 can determine the inverse mapping function based on the table and apply the inverse mapping function to the mapped domain reference template block and the mapped domain adjacent reconstructed template block before deriving the LIC parameters. The video decoder 300 can then derive the LIC parameters based on the mapped domain reference template block and the mapped domain adjacent reconstructed template block.

[0193] The video decoder 300 can apply LIC model parameters to the motion-compensated prediction signal (554). For example, the video decoder 300 can apply LIC model parameters to the prediction sample after the video decoder 300 performs motion compensation on the prediction sample.

[0194] The video decoder 300 can decode video data based on the application of LIC model parameters (556). For example, the video decoder 300 can decode LIC-compensated motion-compensated prediction signals.

[0195] In some examples, applying LIC model parameters also includes applying an integer shift to the motion-compensated prediction signal. In some examples, the integer shift is a right shift of 6 bits.

[0196] In some examples, the motion compensation prediction signal is in the pixel domain. In other examples, the motion compensation prediction signal is in the mapping domain.

[0197] In some examples, the forward mapping function includes FwdMap(Y_pred) = ((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the brightness prediction signal, i is the segment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapping pivot point of i, and b2 is the mapping pivot point of i+1. In some examples, the forward mapping function includes a gamma function. In some examples, the gamma function includes FwdMap(x) = A*xr, where A and r are constant values. In some examples, the forward mapping function includes a polynomial function. In some examples, the polynomial function includes FwdMap(x) = ∑i∈{0,1,…,n}a i x i , where a i Let x be a real number, which is the coefficient of a polynomial function of x.

[0198] In some examples, LIC model parameters are applied on a unit-by-unit (CU) basis. For example, video decoder 300 may apply LIC model parameters on a unit-by-unit basis. In some examples, video decoder 300 may determine that luminance mapping with chroma scaling is enabled for the CU.

[0199] Figure 13 This is a flowchart illustrating an example method for encoding a current block according to the technology of this disclosure. The current block may include the current CU. Although regarding video encoder 200 ( Figure 1 and 3 The description is provided, but it should be understood that other devices can be configured to perform the same actions. Figure 13 Similar to the method.

[0200] In this example, the video encoder 200 initially predicts the current block (350). For example, the video encoder 200 can form a prediction block for the current block. For example, the video encoder 200 can use any of the various LIC and LMCS techniques described above to form the prediction block. Then, the video encoder 200 can compute a residual block for the current block (352). To compute the residual block, the video encoder 200 can compute the difference between the original unencoded block and the prediction block for the current block. Then, the video encoder 200 can transform the residual block and quantize the transform coefficients of the residual block (354). Next, the video encoder 200 can scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 can entropy encode the transform coefficients (358). For example, the video encoder 200 can use CAVLC or CABAC to encode the transform coefficients. The video encoder 200 can then output the entropy-encoded data of the block (360).

[0201] Figure 14 This is a flowchart illustrating an example method for decoding a current block of video data according to the technology of this disclosure. The current block may include the current CU. Although regarding the video decoder 300 ( Figure 1 and 4 The description is provided, but it should be understood that other devices can be configured to perform the same actions. Figure 14 Similar to the method.

[0202] The video decoder 300 can receive entropy-coded data for the current block (e.g., entropy-coded prediction information and entropy-coded data for the transform coefficients of the residual block corresponding to the current block) (370). The video decoder 300 can entropy decode the entropy-coded data to determine the prediction information for the current block and reproduce the transform coefficients of the residual block (372). The video decoder 300 can predict the current block, for example, using an intra-frame or inter-frame prediction mode as indicated by the prediction information for the current block (374), to compute a prediction block for the current block. For example, the video decoder 300 can use any of the various LIC and LMCS techniques described above to form the prediction block. As part of predicting the current block, the video decoder 300 can use... Figure 12 The prediction technique used is the same as or the inverse prediction technique used in the video decoder. The video decoder 300 then performs an inverse scan (376) on the reproduced transform coefficients to create a block of quantized transform coefficients. The video decoder 300 then performs inverse quantization on the transform coefficients and applies the inverse transform to the transform coefficients to produce a residual block (378). Finally, the video decoder 300 decodes the current block by combining the predicted block and the residual block (380).

[0203] By deriving LIC model parameters from the mapping domain reference template block and the mapping domain adjacent reconstruction template block, the video decoder 300 can avoid loading the inverse mapping table from memory, thereby reducing decoding latency and improving processing efficiency.

[0204] The following numbered clauses illustrate one or more aspects of the devices and technologies described in this disclosure.

[0205] Clause 1A, a method for decoding video data, the method comprising: shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstruction template block; applying the LIC model parameters to a motion compensation prediction signal; and decoding the video data based on the application of the LIC model parameters.

[0206] Clause 2A, the method according to Clause 1A, wherein applying the LIC model parameters further includes: applying an integer shift.

[0207] Clause 3A, the method described in Clause 2A, wherein the integer shift is a right shift of 6.

[0208] Clause 4A, the method according to Clause 1A, wherein the motion compensation prediction signal is in the pixel domain.

[0209] Clause 5A, the method according to Clause 1A, wherein the motion compensation prediction signal is in the mapping domain.

[0210] Clause 6A, the method according to Clause 1A, wherein the forward mapping function comprises FwdMap(Y_pred) = ((b2-b1) / (a2-a1))*(Y_pred-a1)+b1.

[0211] Clause 7A, the method according to Clause 1A, wherein the forward mapping function includes a gamma function.

[0212] Clause 8A, the method according to Clause 7A, wherein the gamma function comprises FwdMap(x) = A*xr, where A and r are constant values.

[0213] Clause 9A, the method according to Clause 7A, wherein the forward mapping function comprises a polynomial function.

[0214] Clause 10A, the method according to Clause 9A, wherein the polynomial function includes FwdMap(x)=∑i∈{0,1,…,n}a i x i , where a iLet x represent a real number, which is the coefficient of a polynomial function of x.

[0215] Clause 11A, the method according to Clause 1A further includes: deriving an inverse mapping function based on the forward mapping function; and applying the inverse mapping function to shape the adjacent reconstruction template block of the mapping domain.

[0216] Clause 12A, the method according to any one of Clauses 1A-11A, wherein decoding includes decoding.

[0217] Clause 13A, the method according to any one of Clauses 1A-12A, wherein decoding includes encoding.

[0218] Clause 14A, an apparatus for decoding video data, the apparatus comprising one or more units for performing the method according to any one of Clauses 1A-13A.

[0219] Clause 15A, the device as described in Clause 14A, wherein the one or more units include one or more processors implemented in a circuit.

[0220] The device according to any one of Clauses 14A and 15A, further includes: a memory for storing the video data.

[0221] The device according to any one of Clauses 14A-16A, under Clause 17A, further includes: a display configured to display decoded video data.

[0222] Clause 18A, the device pursuant to any one of Clauses 14A-17A, wherein the device includes one or more of a camera, computer, mobile device, broadcast receiver device or set-top box.

[0223] Clause 19A, the device according to any one of Clauses 14A-18A, wherein the device includes a video decoder.

[0224] Clause 20A, the device according to any one of Clauses 14A-19A, wherein the device includes a video encoder.

[0225] Clause 21A, a computer-readable storage medium having instructions stored thereon, which, when executed, cause one or more processors to perform the method according to any one of Clauses 1A-11A.

[0226] Clause 1B, a method for decoding video data, the method comprising: shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstruction template block; applying the LIC model parameters to a motion compensation prediction signal; and decoding the video data based on the application of the LIC model parameters.

[0227] Clause 2B, the method according to Clause 1B, wherein applying the LIC model parameters further includes: applying an integer shift to the motion compensation prediction signal.

[0228] Clause 3B, the method described in Clause 2B, wherein the integer shift is a right shift of 6 bits.

[0229] Clause 4B, the method according to any one of Clauses 1B-3B, wherein the motion compensation prediction signal is in the pixel domain.

[0230] Clause 5B, the method according to any one of Clauses 1B-3B, wherein the motion compensation prediction signal is in the mapping domain.

[0231] Clause 6B, the method according to any one of Clauses 1B-5B, wherein the forward mapping function comprises FwdMap(Y_pred) = ((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the luminance prediction signal, i is the segment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapping pivot point of i, and b2 is the mapping pivot point of i+1.

[0232] Clause 7B, the method according to any one of Clauses 1B-5B, wherein the forward mapping function comprises a gamma function.

[0233] Clause 8B, the method described in accordance with Clause 7B, wherein the gamma function comprises FwdMap(x) = A*xr, where A and r are constant values.

[0234] Clause 9B, the method according to any one of Clauses 1B-5B, wherein the forward mapping function comprises a polynomial function.

[0235] Clause 10B, the method according to Clause 9B, wherein the polynomial function includes FwdMap(x)=∑i∈{0,1,…,n}a i x i , where a i Let x represent a real number, which is the coefficient of a polynomial function of x.

[0236] Clause 11B, the method according to any one of Clauses 1B-10B, wherein the LIC model parameters are applied based on decoding units (CUs).

[0237] Clause 12B, the method described in Clause 11B, further includes: determining that a luminance mapping with chroma scaling is enabled for the CU.

[0238] Clause 13B, an apparatus for decoding video data, the apparatus comprising: a memory configured to store the video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors being configured to: shape a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; derive local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstruction template block; apply the LIC model parameters to a motion compensation prediction signal; and decode the video data based on the application of the LIC model parameters.

[0239] Clause 14B, the device pursuant to Clause 13B, wherein, as part of applying the LIC model parameters, the one or more processors are further configured to apply an integer shift to the motion compensation prediction signal.

[0240] Clause 15B, the device described in Clause 14B, wherein the integer shift is a right shift of 6.

[0241] Clause 16B, the device according to any one of Clauses 13B-15B, wherein the motion compensation prediction signal is in the pixel domain.

[0242] Clause 17B, the device according to any one of Clauses 13B-15B, wherein the motion compensation prediction signal is in the mapping domain.

[0243] Clause 18B, the device according to any one of Clauses 13B-17B, wherein the forward mapping function comprises FwdMap(Y_pred) = ((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the luminance prediction signal, i is the segment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapping pivot point of i, and b2 is the mapping pivot point of i+1.

[0244] Clause 19B, the device according to any one of Clauses 13B-17B, wherein the forward mapping function includes a gamma function.

[0245] Clause 20B, the device pursuant to Clause 19B, wherein the gamma function comprises FwdMap(x) = A*xr, where A and r are constant values.

[0246] Clause 21B, the device according to any one of Clauses 13B-17B, wherein the forward mapping function comprises a polynomial function.

[0247] Clause 22B, the device according to Clause 21B, wherein the polynomial function includes FwdMap(x)=∑i∈{0,1,…,n}a i x i , where a i Let x represent a real number, which is the coefficient of a polynomial function of x.

[0248] Clause 23B, the device pursuant to any one of Clauses 13B-22B, wherein the one or more processors are configured to apply the LIC model parameters based on a decoding unit (CU).

[0249] Clause 24B, the device as described in Clause 23B, wherein the one or more processors are further configured to: determine that luminance mapping with chroma scaling is enabled for the CU.

[0250] The device according to any one of Clauses 25B and 13B-24B further includes: a display configured to display the video data.

[0251] The device under Clause 26B, or any one of Clauses 13B-25B, further includes: a camera configured to capture the video data.

[0252] Clause 27B, the device pursuant to any one of Clauses 13B-26B, wherein said device includes a mobile phone.

[0253] Clause 28B, a non-transitory computer-readable storage medium having instructions stored thereon, which, when executed, cause one or more processors to: shape a pixel-domain reference template block into a mapped-domain reference template block using a forward mapping function; derive local illumination compensation (LIC) model parameters from the mapped-domain reference template block and a mapped-domain adjacent reconstruction template block; apply the LIC model parameters to a motion-compensated prediction signal; and decode the video data based on the application of the LIC model parameters.

[0254] Clause 29B, an apparatus for decoding video data, the apparatus comprising: units for shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function; units for deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain adjacent reconstruction template block; units for applying the LIC model parameters to a motion compensation prediction signal; and units for decoding the video data based on the application of the LIC model parameters.

[0255] It should be recognized that, based on the examples, certain actions or events of any technique described herein may be performed in a different order, and may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for implementing the technique). Furthermore, in some examples, actions or events may be performed concurrently rather than sequentially, for example, through multithreaded processing, interrupt handling, or multiple processors.

[0256] In one or more examples, the described functionality can be implemented using hardware, software, firmware, or any combination thereof. If implemented in software, the functionality can be stored or transmitted as one or more instructions or code on or through a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium can include a computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium or a communication medium, including, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this way, a computer-readable medium can 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 can be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, code, and / or data structures for implementing the techniques described in this disclosure. Computer program products can include computer-readable media.

[0257] For example, rather than limiting, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, flash memory, or any other medium capable of storing desired program code in the form of instructions or data structures and accessible by a computer. Furthermore, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (e.g., infrared, radio, and microwave), then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology (e.g., infrared, radio, and microwave) is included in the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but rather refer instead to non-transient tangible storage media. As used herein, disks and optical discs include compact optical discs (CDs), laser optical discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, wherein disks typically magnetically copy data, while optical discs utilize lasers to optically copy data. Combinations of the above items should also be included within the scope of computer-readable media.

[0258] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuitry" as used herein can refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into combined codecs. Furthermore, the techniques can be implemented entirely within one or more circuit or logic elements.

[0259] The technologies disclosed herein can be implemented in a wide variety of devices or apparatuses, including wireless mobile phones, integrated circuits (ICs), or a set of ICs (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed technologies, but they do not necessarily need to be implemented through different hardware units. Specifically, as described above, the various units can be combined in a codec hardware unit, or provided by a collection of interoperable hardware units (including one or more processors as described above) combined with appropriate software and / or firmware.

[0260] Various examples have been described. These and other examples are within the scope of the appended claims.

Claims

1. A method for decoding video data, the method comprising: The pixel domain reference template block is shaped into a mapped domain reference template block using a forward mapping function, wherein the forward mapping function includes: FwdMap(Y_pred)=((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the brightness prediction signal, i is the segment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapped pivot point of i, and b2 is the mapped pivot point of i+1; The parameters of the Local Illuminance Compensation (LIC) model are derived from the mapping domain reference template block and the mapping domain adjacent reconstruction template block; The LIC model parameters are applied to the motion-compensated prediction signal; and The video data is decoded based on the application of the LIC model parameters.

2. The method according to claim 1, wherein, The application of the LIC model parameters also includes applying an integer shift to the motion compensation prediction signal.

3. The method according to claim 2, wherein, The integer shift is a right shift of 6 bits.

4. The method according to claim 1, wherein, The motion compensation prediction signal is in the pixel domain.

5. The method according to claim 1, wherein, The motion compensation prediction signal is in the mapping domain.

6. The method according to claim 1, wherein, The LIC model parameters are applied based on the decoding unit (CU).

7. The method according to claim 6, further comprising: It was determined that luminance mapping with chroma scaling was enabled for the CU.

8. An apparatus for decoding video data, the apparatus comprising: A memory configured to store the video data; as well as One or more processors, implemented in a circuit and communicatively coupled to the memory, are configured to: The pixel domain reference template block is shaped into a mapped domain reference template block using a forward mapping function, wherein the forward mapping function includes: FwdMap(Y_pred)=((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the luminance prediction signal. i is the fragment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapping pivot point of i, and b2 is the mapping pivot point of i+1. The parameters of the Local Illuminance Compensation (LIC) model are derived from the mapping domain reference template block and the mapping domain adjacent reconstruction template block; The LIC model parameters are applied to the motion-compensated prediction signal; and The video data is decoded based on the application of the LIC model parameters.

9. The device according to claim 8, wherein, As part of applying the LIC model parameters, the one or more processors are also configured to: An integer shift is applied to the motion compensation prediction signal.

10. The device according to claim 9, wherein, The integer shift is a right shift of 6 bits.

11. The device according to claim 8, wherein, The motion compensation prediction signal is in the pixel domain.

12. The device according to claim 8, wherein, The motion compensation prediction signal is in the mapping domain.

13. The device according to claim 8, wherein, The one or more processors are configured to apply the LIC model parameters based on the decoding unit (CU).

14. The device according to claim 13, wherein, The one or more processors are further configured to: It was determined that luminance mapping with chroma scaling was enabled for the CU.

15. The device according to claim 8, further comprising: A display, configured to display the video data.

16. The device according to claim 8, further comprising: A camera configured to capture the video data.

17. The device according to claim 8, wherein, The device includes a mobile phone.

18. A non-transitory computer-readable storage medium having instructions stored thereon, said instructions, when executed, causing one or more processors to perform the following operations: The pixel-domain reference template block is shaped into a mapped-domain reference template block using a forward mapping function, where... The forward mapping function includes: FwdMap(Y_pred)=((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the brightness prediction signal, i is the segment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapping pivot point of i, and b2 is the mapping pivot point of i+1; The parameters of the Local Illuminance Compensation (LIC) model are derived from the mapping domain reference template block and the mapping domain adjacent reconstruction template block; The LIC model parameters are applied to the motion-compensated prediction signal; and The video data is decoded based on the application of the LIC model parameters.

19. The non-transitory computer-readable storage medium according to claim 18, wherein, As part of applying the LIC model parameters, the instructions cause the one or more processors to perform the following operations: An integer shift is applied to the motion compensation prediction signal.

20. An apparatus for decoding video data, the apparatus comprising: A unit for shaping a pixel domain reference template block into a mapped domain reference template block using a forward mapping function, wherein the forward mapping function includes: FwdMap(Y_pred)=((b2-b1) / (a2-a1))*(Y_pred-a1)+b1, where Y_pred is the luminance prediction signal, i is the segment index, a1 is the input pivot point of i, a2 is the input pivot point of i+1, b1 is the mapped pivot point of i, and b2 is the mapped pivot point of i+1; Units for deriving local illumination compensation (LIC) model parameters from the mapping domain reference template block and the mapping domain adjacent reconstruction template block; A unit for applying the LIC model parameters to a motion-compensated prediction signal; and A unit for decoding the video data based on the application of the LIC model parameters.

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