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EP-4740475-A1 - LOCAL ILLUMINATION COMPENSATION MODEL INHERITANCE

EP4740475A1EP 4740475 A1EP4740475 A1EP 4740475A1EP-4740475-A1

Abstract

A method for using local illumination compensation (LIC) in video coding is provided. A video coder receives data to be encoded or decoded as a current block of pixels of a current picture of a video. The video coder inherits a previously used linear model that is derived based on template samples neighboring two or more previously coded blocks. The video coder applies the inherited linear model to an initial predictor of the current block to generate a final predictor of the current block. The video coder encodes or decodes the current block by using the final predictor. The video coder inherits the linear model by inheriting scaling and offset parameters, as well as information regarding the derivation of the linear model. The linear model may be a spatial candidate, a non-adjacent spatial candidate, a historical candidate, or a temporal candidate.

Inventors

  • CHUANG, CHENG-YEN
  • TSAI, CHIA-MING
  • LO, CHIH-HSUAN
  • CHEN, CHING-YEH
  • CHEN, YI-WEN
  • CHUANG, TZU-DER
  • HSU, CHIH-WEI
  • TSENG, HSIN-YI

Assignees

  • MediaTek Inc.

Dates

Publication Date
20260513
Application Date
20240705

Claims (15)

  1. A video coding method comprising: receiving data to be encoded or decoded as a current block of pixels of a current picture of a video; inheriting a previously used linear model that is derived based on template samples neighboring two or more previously coded blocks; applying the inherited linear model to an initial predictor of the current block to generate a final predictor of the current block; and encoding or decoding the current block by using the final predictor.
  2. The video coder of claim 1, wherein the linear model is for local illumination compensation (LIC) .
  3. The video coder of claim 1, wherein inheriting the linear model comprises inheriting information regarding a derivation of the linear model.
  4. The video coder of claim 1, wherein inheriting the linear model comprises inheriting a scaling parameter and an offset parameter.
  5. The video coder of claim 1, wherein the initial predictor is a reference block identified by a motion vector of the current block.
  6. The video coder of claim 1, wherein the linear model is inherited from a spatial neighbor of the current block.
  7. The video coder of claim 1, wherein the linear model is inherited from a non-adjacent spatial neighbor of the current block.
  8. The video coder of claim 1, wherein the inherited linear model is identified by using a history table that stores a history of one or more previously used linear models.
  9. The video coder of claim 1, wherein the linear model is inherited from a neighboring position of a corresponding position of the current block in a reference picture.
  10. The video coder of claim 9, wherein the neighboring position is constrained to be within a region in the reference picture that is defined based on the corresponding position of the current block in the reference picture.
  11. The video coder of claim 1, further comprising constructing a candidate list that includes one or more linear models, wherein inheriting the linear model comprises signaling or receiving a selection of the linear model from the constructed candidate list.
  12. The video coder of claim 11, wherein candidates in the candidate list are assigned indices according to modeling errors of the candidates, wherein the modeling error of a candidate is computed by comparing reconstructed neighboring samples of the current block with samples generated by applying the candidate linear model to neighboring samples of a reference block.
  13. An electronic apparatus comprising: a video coder circuit configured to perform operations comprising: receiving data to be encoded or decoded as a current block of pixels of a current picture of a video; inheriting a previously used linear model that is derived based on template samples neighboring two or more previously coded blocks; applying the inherited linear model to an initial predictor of the current block to generate a final predictor of the current block; and encoding or decoding the current block by using the final predictor.
  14. A video decoding method comprising: receiving data to be decoded as a current block of pixels of a current picture of a video; inheriting a previously used linear model that is derived based on template samples neighboring two or more previously coded blocks; applying the inherited linear model to an initial predictor of the current block to generate a final predictor of the current block; and reconstructing the current block by using the final predictor.
  15. A video encoding method comprising: receiving data to be encoded as a current block of pixels of a current picture of a video; inheriting a previously used linear model that is derived based on template samples neighboring two or more previously coded blocks; applying the inherited linear model to an initial predictor of the current block to generate a final predictor of the current block; and encoding the current block by using the final predictor.

Description

LOCAL ILLUMINATION COMPENSATION MODEL INHERITANCE CROSS REFERENCE TO RELATED PATENT APPLICATION (S) The present disclosure is part of a non-provisional application that claims the priority benefit of U.S. Provisional Patent Application Nos. 63/525,424, 63/513,905, 63/589,356, and 63/620,210, filed on 7 July 2023, 17 July 2023, 11 October 2023, and 12 January 2024, respectively. Contents of above-listed applications are herein incorporated by reference. TECHNICAL FIELD The present disclosure relates generally to video coding. In particular, the present disclosure relates to methods of coding pixel blocks by local illumination compensation (LIC) . BACKGROUND Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section. High-Efficiency Video Coding (HEVC) is an international video coding standard developed by the Joint Collaborative Team on Video Coding (JCT-VC) . HEVC is based on the hybrid block-based motion-compensated DCT-like transform coding architecture. The basic unit for compression, termed coding unit (CU) , is a 2Nx2N square block of pixels, and each CU can be recursively split into four smaller CUs until the predefined minimum size is reached. Each CU contains one or multiple prediction units (PUs) . Versatile video coding (VVC) is the latest international video coding standard developed by the Joint Video Expert Team (JVET) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11. The input video signal is predicted from the reconstructed signal, which is derived from the coded picture regions. The prediction residual signal is processed by a block transform. The transform coefficients are quantized and entropy coded together with other side information in the bitstream. The reconstructed signal is generated from the prediction signal and the reconstructed residual signal after inverse transform on the de-quantized transform coefficients. The reconstructed signal is further processed by in-loop filtering for removing coding artifacts. The decoded pictures are stored in the frame buffer for predicting the future pictures in the input video signal. In VVC, a coded picture is partitioned into non-overlapped square block regions represented by the associated coding tree units (CTUs) . The leaf nodes of a coding tree correspond to the coding units (CUs) . A coded picture can be represented by a collection of slices, each comprising an integer number of CTUs. The individual CTUs in a slice are processed in raster-scan order. A bi-predictive (B) slice may be decoded using intra prediction or inter prediction with at most two motion vectors and reference indices to predict the sample values of each block. A predictive (P) slice is decoded using intra prediction or inter prediction with at most one motion vector and reference index to predict the sample values of each block. An intra (I) slice is decoded using intra prediction only. A CTU can be partitioned into one or multiple non-overlapped coding units (CUs) using the quadtree (QT) with nested multi-type-tree (MTT) structure to adapt to various local motion and texture characteristics. A CU can be further split into smaller CUs using one of the five split types: quad-tree partitioning, vertical binary tree partitioning, horizontal binary tree partitioning, vertical center-side triple-tree partitioning, horizontal center-side triple-tree partitioning. Each CU contains one or more prediction units (PUs) . The prediction unit, together with the associated CU syntax, works as a basic unit for signaling the predictor information. The specified prediction process is employed to predict the values of the associated pixel samples inside the PU. Each CU may contain one or more  transform units (TUs) for representing the prediction residual blocks. A transform unit (TU) is comprised of a transform block (TB) of luma samples and two corresponding transform blocks of chroma samples and each TB correspond to one residual block of samples from one color component. An integer transform is applied to a transform block. The level values of quantized coefficients together with other side information are entropy coded in the bitstream. The terms coding tree block (CTB) , coding block (CB) , prediction block (PB) , and transform block (TB) are defined to specify the 2-D sample array of one-color component associated with CTU, CU, PU, and TU, respectively. Thus, a CTU consists of one luma CTB, two chroma CTBs, and associated syntax elements. A similar relationship is valid for CU, PU, and TU. For each inter-predicted CU, motion parameters consisting of motion vectors, reference picture indices and reference picture list usage index, and additional information are used for inter-predicted sample generation. The motion parameter can be signalled in an explicit or implicit manner. When a CU is coded with skip mode, the CU is associated with one PU and has no sign