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EP-4740472-A1 - METHODS AND APPARATUS FOR ADAPTIVE INTER CROSS-COMPONENT PREDICTION FOR CHROMA CODING

EP4740472A1EP 4740472 A1EP4740472 A1EP 4740472A1EP-4740472-A1

Abstract

A method and apparatus for coding colour pictures using coding tools including one or more cross component models related modes are disclosed. According to this method, whether to code the second-colour block using inter CCP (Cross-Component Prediction) is determined. In response to the inter CCP being not applied to the second-colour block: the second-colour block is encoded or decoded using regular inter/IBC prediction without cross-component information. In response to the inter CCP being applied to the second-colour block: a candidate list comprising one or more cross-component model candidates is derived; and the second-colour block is encoded or decoded using information comprising the candidate list, wherein if one or more target cross-component model candidates are selected for the second-colour block, prediction data for the second-colour block is generated by applying one or more corresponding cross-component models associated with said one or more target cross-component model candidates to the first-colour block.

Inventors

  • TSENG, HSIN-YI
  • CHIANG, Man-Shu
  • TSAI, CHIA-MING
  • CHUANG, CHENG-YEN
  • HSU, CHIH-WEI
  • CHEN, YI-WEN

Assignees

  • MEDIATEK INC.

Dates

Publication Date
20260513
Application Date
20240705

Claims (20)

  1. A method of coding colour pictures using coding tools including one or more cross component models related modes, the method comprising: receiving input data associated with a current block comprising a first-colour block and a second-colour block, wherein the input data comprises pixel data to be encoded at an encoder side or data associated with the current block to be decoded at a decoder side; determining whether to code the second-colour block using inter CCP (Cross-Component Prediction) ; in response to the inter CCP being not applied to the second-colour block: encoding or decoding the second-colour block using regular inter prediction or regular IBC prediction without cross-component information; in response to the inter CCP being applied to the second-colour block: deriving a candidate list comprising one or more cross-component model candidates; and encoding or decoding the second-colour block using information comprising the candidate list, wherein if one or more target cross-component model candidates are selected for the second-colour block, prediction data for the second-colour block is generated by applying one or more corresponding cross-component models associated with said one or more target cross-component model candidates to the first-colour block.
  2. The method of Claim 1, wherein when the inter CCP is applied to the second-colour block, the first-colour block is coded in the regular inter prediction or in the regular IBC prediction without the cross-component information.
  3. The method of Claim 1, wherein the inter CCP corresponds to inter CCLM (Cross-Component Linear Model) or inter CCCM (Convolutional Cross-Component Model) .
  4. The method of Claim 1, wherein whether to code the second-colour block using the inter CCP is indicated by signalling.
  5. The method of Claim 4, wherein said signalling refers to a flag in TU, TB, CU or CB level.
  6. The method of Claim 5, wherein the flag is signalled only when Cbf (Coding block flag) is non-zero and an enabling flag for the inter or IBC (Intra Block Copy) mode is true.
  7. The method of Claim 5, wherein the flag is coded using one or more contexts.
  8. The method of Claim 1, wherein when the inter CCP is applied to the second-colour block, additional signalling is used to select said one or more target cross-component model candidates from the candidate list.
  9. The method of Claim 8, wherein when multiple target cross-component model candidates are selected, the prediction data for the second-colour block is generated by blending corresponding multiple cross-component models associated with the multiple target cross-component model candidates.
  10. The method of Claim 8, wherein the additional signalling corresponds to using an index coded by truncated unary coding with or without context.
  11. The method of Claim 1, wherein the inter CCP is signalled or parsed only when one or more size conditions of the current block are satisfied.
  12. The method of Claim 11, wherein said one or more size conditions of the current block comprise block width, block height, or block area being larger or smaller than a pre-defined threshold.
  13. The method of Claim 1, wherein when the inter CCP is applied to the second-colour block, said one or more target cross-component model candidates from the candidate list are determined implicitly or according to one or more rules.
  14. The method of Claim 13, wherein at least one of CCLM_LT (Cross-Component Linear Model with Left and Top templates) , MMLM_LT (Multi-Mode CCLM with Left and Top templates) , and CCCM_LT (Convolutional Cross-Component Model with Left and Top templates) is always used as said one or more target cross-component model candidates.
  15. The method of Claim 13, wherein said one or more rules are determined depending on block width, block height, or block area.
  16. The method of Claim 13, wherein said one or more rules are determined depending on boundary matching.
  17. The method of Claim 1, wherein one target cross-component model candidate is selected from the candidate list, and the prediction data is blended with second prediction data corresponding to an angular or planar mode to form final prediction data for the second-colour block.
  18. The method of Claim 17, wherein an index is signalled or parsed to indicate said one target cross-component model candidate selected from the candidate list.
  19. The method of Claim 1, wherein whether the inter CCP is used in the current block is determined depending on an enabling flag.
  20. The method of Claim 19, wherein the enabling flag is signalled or parsed in a bitstream, or is inferred.

Description

METHODS AND APPARATUS FOR ADAPTIVE INTER CROSS-COMPONENT PREDICTION FOR CHROMA CODING CROSS REFERENCE TO RELATED APPLICATIONS The present invention is a non-Provisional Application of and claims priority to U.S. Provisional Patent Application No. 63/511,922, filed on July 5, 2023. The U.S. Provisional Patent Application is hereby incorporated by reference in its entirety. FIELD OF THE INVENTION The present invention relates to video coding system. In particular, the present invention discloses adaptive inter cross-component prediction and adjusted prediction for chroma components. BACKGROUND AND RELATED ART Versatile video coding (VVC) is the latest international video coding standard developed by the Joint Video Experts Team (JVET) of the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG) . The standard has been published as an ISO standard: ISO/IEC 23090-3: 2021, Information technology -Coded representation of immersive media -Part 3: Versatile video coding, published Feb. 2021. VVC is developed based on its predecessor HEVC (High Efficiency Video Coding) by adding more coding tools to improve coding efficiency and also to handle various types of video sources including 3-dimensional (3D) video signals. Fig. 1A illustrates an exemplary adaptive Inter/Intra video encoding system incorporating loop processing. For Intra Prediction 110, the prediction data is derived based on previously coded video data in the current picture. For Inter Prediction 112, Motion Estimation (ME) is performed at the encoder side and Motion Compensation (MC) is performed based on the result of ME to provide prediction data derived from other picture (s) and motion data. Switch 114 selects Intra Prediction 110 or Inter Prediction 112 and the selected prediction data is supplied to Adder 116 to form prediction errors, also called residues. The prediction error is then processed by Transform (T) 118 followed by Quantization (Q) 120. The transformed and quantized residues are then coded by Entropy Encoder 122 to be included in a video bitstream corresponding to the compressed video data. The bitstream associated with the transform coefficients is then packed with side information such as motion and coding modes associated with Intra prediction and Inter prediction, and other information such as parameters associated with loop filters applied to underlying image area. The side information associated with Intra Prediction 110, Inter prediction 112 and in-loop filter 130, is provided to Entropy Encoder 122 as shown in Fig. 1A. When an Inter-prediction mode is used, a reference picture or pictures have to be reconstructed at the encoder end as well. Consequently, the transformed and quantized residues are processed by  Inverse Quantization (IQ) 124 and Inverse Transformation (IT) 126 to recover the residues. The residues are then added back to prediction data 136 at Reconstruction (REC) 128 to reconstruct video data. The reconstructed video data may be stored in Reference Picture Buffer 134 and used for prediction of other frames. As shown in Fig. 1A, incoming video data undergoes a series of processing in the encoding system. The reconstructed video data from REC 128 may be subject to various impairments due to a series of processing. Accordingly, in-loop filter 130 is often applied to the reconstructed video data before the reconstructed video data are stored in the Reference Picture Buffer 134 in order to improve video quality. For example, deblocking filter (DF) , Sample Adaptive Offset (SAO) and Adaptive Loop Filter (ALF) may be used. The loop filter information may need to be incorporated in the bitstream so that a decoder can properly recover the required information. Therefore, loop filter information is also provided to Entropy Encoder 122 for incorporation into the bitstream. In Fig. 1A, Loop filter 130 is applied to the reconstructed video before the reconstructed samples are stored in the reference picture buffer 134. The system in Fig. 1A is intended to illustrate an exemplary structure of a typical video encoder. It may correspond to the High Efficiency Video Coding (HEVC) system, VP8, VP9, H. 264 or VVC. The decoder, as shown in Fig. 1B, can use similar or portion of the same functional blocks as the encoder except for Transform 118 and Quantization 120 since the decoder only needs Inverse Quantization 124 and Inverse Transform 126. Instead of Entropy Encoder 122, the decoder uses an Entropy Decoder 140 to decode the video bitstream into quantized transform coefficients and needed coding information (e.g. ILPF information, Intra prediction information and Inter prediction information) . The Intra prediction 150 at the decoder side does not need to perform the mode search. Instead, the decoder only needs to generate Intra prediction according to Intra prediction information received from the Entropy Decoder 140. Furthermore, for Inter prediction, the decoder only needs to per