Chroma Block Prediction via Luma-Derived Reference Fusion
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Solution Overview
Problem
Existing video coding techniques face challenges in accurately predicting chroma blocks, leading to errors between original pixels and prediction samples, which affects bandwidth utilization and encoding efficiency.
Innovation Solution
The proposed solution involves determining co-located luma blocks to derive reference chroma blocks and fusing them to generate prediction samples for chroma blocks, using block vectors to improve prediction accuracy and reduce signaling information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single reference chroma block is used for prediction, then the encoding complexity is low, but the prediction accuracy is insufficient leading to larger errors between original pixels and prediction samples
Solution Approach 1:
The current picture is divided into multiple reference chroma blocks by utilizing block vectors from multiple co-located luma blocks. Instead of using a single reference block, the method segments the reference selection into multiple candidates (first reference chroma block, second reference chroma block, etc.), each derived from different luma block positions. This segmentation allows the system to select or combine multiple reference blocks to improve prediction accuracy while managing complexity through structured selection processes.
2Reliability
If multiple reference chroma blocks are used to improve prediction accuracy, then the errors between original pixels and prediction samples are reduced, but the signaling information and bandwidth requirements increase
Solution Approach 1:
The method merges multiple reference chroma blocks by combining their prediction samples through weighted averaging or selection. Instead of transmitting separate reference blocks, the encoder fuses the information from multiple reference chroma blocks into a single prediction signal. This merging approach maintains high prediction accuracy while reducing signaling overhead, as the fused prediction samples can be derived at the decoder using the same block vector information without requiring additional transmitted data for each reference block.
3Productivity
If traditional reference block selection is used, then the encoding process is simple, but the residual values and bandwidth utilization are suboptimal
Solution Approach 1:
Block vectors serve as intermediaries that link co-located luma blocks to reference chroma blocks. Instead of directly selecting reference chroma blocks based on simple position indicators, the method uses block vectors as intermediary data structures that carry positional and contextual information. This intermediary approach enables more accurate reference block selection by leveraging the block vector information, which in turn reduces residual values and improves bandwidth utilization without significantly increasing encoding complexity.
Data Source
AI summary
A method of encoding or decoding video data includes for a chroma block of a picture, determining luma blocks that are co-located with the chroma block; determining two or more reference chroma blocks based on block vectors for the luma blocks, the block vectors pointing to locations within the picture; fusing the two or more reference chroma blocks to generate prediction samples for the chroma block; and block vector encoding or decoding the chroma block based on the prediction samples.