Chroma Prediction Mapping for IBC Video Coding Blocks
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Solution Overview
Problem
The existing video coding standards, such as H.266/Versatile Video Coding (VVC), suffer from inaccurate chroma prediction due to unreasonable setting of chroma prediction modes in the Intra block copy (IBC) mode, leading to degraded coding efficiency, especially for screen content types.
Innovation Solution
A method is provided to determine a first block vector parameter for a current block, establish a mapping relationship between color components based on reference samples, and use this relationship to predict the chroma component values, thereby improving chroma prediction accuracy and reducing bit rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the IBC mode is used for a luma block with default chroma prediction mode setting, then the coding process is simple, but the chroma prediction accuracy deteriorates
Solution Approach 1:
The patent applies different chroma prediction mode settings based on the specific block characteristics. When IBC mode is detected for luma blocks, the patent selectively applies chroma copy mode or scaled chroma copy mode with adjusted reference block selections, rather than using a uniform default setting. This local adaptation improves chroma prediction accuracy for IBC blocks while maintaining simplicity for other block types.
Solution Approach 2:
The patent dynamically adjusts the chroma prediction approach based on the luma block's prediction mode. The system detects whether IBC mode is used and automatically switches between different chroma prediction strategies (chroma copy, scaled chroma copy, or traditional modes), making the chroma prediction process adaptive rather than static.
2Device complexity
If traditional chroma prediction modes are used in IBC scenario, then the device complexity is low, but the coding efficiency deteriorates
Solution Approach 1:
The patent performs preliminary detection of the luma block's prediction mode before determining the chroma prediction approach. By identifying IBC mode usage in advance, the system can pre-select the appropriate chroma prediction strategy (such as chroma copy mode with adjusted reference blocks), avoiding complex real-time calculations and improving overall coding efficiency with minimal additional complexity.
Solution Approach 2:
The patent changes key parameters of the chroma prediction process when IBC mode is detected, including the reference block selection, the prediction mode type, and the scaling factors. These parameter adjustments are triggered automatically based on the luma block characteristics, improving coding efficiency without requiring complex additional processing.
3Quantity of substance
If inaccurate chroma prediction is used, then the bit rate remains high, but the codec efficiency deteriorates
Solution Approach 1:
The patent uses feedback from the luma block prediction results to guide chroma prediction. By detecting whether IBC mode was used for luma and using this information to select appropriate chroma prediction modes, the system creates a feedback loop that improves chroma prediction accuracy and reduces the residual energy, thereby lowering the bit rate required for encoding chroma residuals while improving overall codec efficiency.
Data Source
AI summary
Provided are a coding method, a decoding method, a bitstream, a coder, a decoder and a storage medium. The method includes: determining a first BV parameter of a current block; on the basis of the first BV parameter, determining a first color-component reference sample and a second color-component reference sample which correspond to the current block, and based on the first color-component reference sample and the second color-component reference sample, establishing a mapping relationship between a first color component and a second color component; and based on the mapping relationship and a sample value of the first color component of the current block, determining a predicted value of the second color component of the current block. In this way, the accuracy of chroma prediction can be improved, the bit rate is reduced, and the codec efficiency can also be improved.