Adaptive Color Transform and BDPCM Joint Use in Video Coding
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Solution Overview
Problem
Current video coding technologies face inefficiencies due to the mutual exclusivity of adaptive color transform (ACT) and block-based delta pulse code modulation (BDPCM) modes, which can lead to differing prediction signals for luma and chroma blocks, negative quantization parameters when ACT is enabled, and lack of support for lossless coding.
Innovation Solution
The proposed solution involves enabling chroma BDPCM mode based on the usage of ACT and luma BDPCM mode, inferring BDPCM prediction directions, and applying clipping operations on quantization parameters to ensure positive values, while allowing ACT and BDPCM modes to be used in a mutually exclusive manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ACT mode and BDPCM mode are used in a mutually exclusive manner, then device complexity is reduced, but coding efficiency deteriorates due to differing prediction signals for luma and chroma blocks
Solution Approach 1:
The patent merges ACT mode and BDPCM mode into a unified coding framework where both modes can be applied to the same video block. The encoder/decoder determines whether to apply ACT, BDPCM, or both based on block characteristics, allowing luma and chroma blocks to use consistent prediction signals while maintaining manageable device complexity through standardized mode selection logic.
Solution Approach 2:
The patent introduces dynamic mode selection where the coding mode (ACT, BDPCM, or both) is determined adaptively based on block characteristics such as size, content type, and prediction mode. This dynamic approach allows the system to optimize coding efficiency for each block while maintaining overall complexity through structured decision rules.
2Measurement precision
If ACT mode is enabled, then color transform accuracy is improved, but quantization parameters become negative which causes decoding issues
Solution Approach 1:
The patent applies preliminary anti-action by preemptively adjusting quantization parameters before the ACT transform is applied. The encoder/decoder offsets QP values to account for the energy increase introduced by ACT, ensuring that QP remains non-negative throughout the coding process while preserving the accuracy benefits of ACT.
Solution Approach 2:
The patent changes the QP parameter through adaptive offset adjustments based on the application of ACT mode. The QP offset is dynamically modified according to block characteristics and ACT configuration, allowing the system to maintain both color transform accuracy and parameter validity through continuous parameter optimization.
3Device complexity
If chroma BDPCM mode is disabled when ACT is enabled, then mode complexity is reduced, but coding efficiency deteriorates due to mismatched prediction signals
Solution Approach 1:
The patent implements dynamic chroma BDPCM mode selection that adapts based on whether ACT is applied to the corresponding luma block. When ACT is enabled for luma, chroma BDPCM can also be enabled with coordinated mode selection, allowing both luma and chroma to use consistent prediction approaches. This dynamic coordination improves chroma coding efficiency while maintaining manageable complexity through structured mode dependency rules.
Data Source
AI summary
Methods, systems and devices for implementing adaptive color transform (ACT) and block based delta pulse code modulation (BDPCM) during image/video encoding or decoding are described. An example method of video processing includes determining, for a conversion between a current video unit of a video that is a chroma video unit and a bitstream representation of the video, whether a block-based delta pulse code modulation (BDPCM) mode is available based on a rule, and performing the conversion based on the determining. The rule is based on whether an adaptive color transform (ACT) mode is used for coding the current video unit and/or whether the BDPCM mode is used for coding a luma video unit corresponding to the current video unit.