Encoder Chroma Weighting for Palette Coding
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Solution Overview
Problem
The existing palette coding mode in HEVC SCC encounters suboptimal computation when up-sampling non-4:4:4 content to a 4:4:4 sampling scheme, as it fails to effectively account for the impact of discarded Chroma components during the encoding process.
Innovation Solution
Assigning weights to the values of subsampled colour components based on their existence in the input pixels, allowing for a more accurate representation of the pre-encode block, which improves the encoding efficiency by adjusting the contribution of Chroma components that are discarded due to subsampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If up-sampling is performed to convert non-4:4:4 content to 4:4:4 sampling scheme, then the encoding compatibility is improved, but the computation complexity increases and the encoding efficiency deteriorates
Solution Approach 1:
The patent segments the Chroma component processing by identifying which pixels have original Chroma values and which need up-sampled values. This segmentation allows the encoder to selectively apply different processing paths: using original values where available and up-sampled values where needed, thereby reducing unnecessary computation while maintaining 4:4:4 compatibility.
Solution Approach 2:
The patent applies local quality by treating different pixel locations differently based on their Chroma component availability. Pixels with original Chroma values are processed with full precision, while pixels requiring up-sampling are processed with adjusted weights. This localized approach optimizes computation by avoiding uniform high-complexity processing across the entire block.
2Adaptability or versatility
If up-sampling is performed to convert non-4:4:4 content to 4:4:4 sampling scheme, then the encoding compatibility is improved, but the encoding efficiency deteriorates
Solution Approach 1:
The patent changes the parameter of Chroma component weight assignment based on pixel location and original sampling scheme. By dynamically adjusting the weight of Chroma components during distortion calculation - using higher weights for pixels with original Chroma values and lower weights for up-sampled pixels - the encoder achieves better encoding efficiency while maintaining compatibility with 4:4:4 requirements.
3Ease of operation
If equal weights are assigned to all Chroma components during up-sampling, then the processing simplicity is maintained, but the distortion measurement accuracy deteriorates
Solution Approach 1:
The patent applies local quality by assigning different weights to Chroma components based on their origin. Pixels that originally had Chroma values in the subsampled format receive higher weights, while pixels that received up-sampled Chroma values receive lower weights. This differentiated weighting improves distortion measurement accuracy without significantly complicating the processing, as it builds upon the existing up-sampling framework.
Data Source
AI summary
The invention relates to the encoding of pixel blocks. To apply some encoding tools, an input 4:2:0 block is upsampled into a 4:4:4 block. Each color component of the 4:4:4 block has thus the same importance when evaluating a distortion measure. To vary the influence of the color components depending on their impact on the decoding, the invention provides assigning weights to the color components of pixels of the 4:4:4 block depending on whether the corresponding color components exist in the 4:2:0 block, due to the subsampling. In such a case, any measure is evaluated using the weighted color components. This approach may apply to the palette coding mode, for instance when updating the color component values of a palette entry upon building, or selecting the closest palette entry to a pixel currently considered, or also determining whether a palette entry predictor may be used instead of a palette entry.