Intra Prediction Device Chroma Correction for Encoding Efficiency
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Solution Overview
Problem
Cross-component intra prediction modes like CCIP_A and CCIP_L suffer from uneven energy distribution in prediction residuals, leading to decreased prediction accuracy and encoding efficiency due to the distance from the edge areas used to calculate the linear model.
Innovation Solution
An intra prediction device that calculates a linear model using decoded pixels from multiple directions around a target block and includes a corrector to adjust predicted pixels based on the positions of the decoded pixels used for the model, improving prediction accuracy and encoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If cross-component intra prediction uses decoded pixels only on top or only on left of target block, then calculation complexity is reduced, but prediction accuracy deteriorates due to uneven energy distribution in prediction residuals
Solution Approach 1:
The patent segments the prediction process into two distinct parts: (1) linear model calculation using decoded pixels from top and left edges, and (2) correction process using chroma pixels from the same edges. This segmentation allows each part to specialize - the linear model captures general trends while the correction term addresses local inaccuracies, thereby resolving the contradiction between simplified calculation and accurate prediction.
Solution Approach 2:
The patent applies local quality by introducing a correction term that is specifically tailored to different regions of the target block. The correction uses chroma pixels from top and left edges to adjust predictions in areas where the linear model alone is insufficient, ensuring that each region receives appropriate correction based on its specific characteristics rather than applying a uniform correction across the entire block.
2Measurement precision
If linear model uses decoded pixels from both top and left edges, then prediction accuracy improves, but calculation complexity increases
Solution Approach 1:
The patent merges the advantages of both top-edge and left-edge pixel usage by incorporating decoded chroma pixels from both edges into the correction term. This merging allows the system to capture chroma characteristics from multiple directions while maintaining a relatively simple linear model calculation, thereby achieving high prediction accuracy without excessive computational complexity.
Solution Approach 2:
The patent introduces dynamic adaptivity by allowing the correction term to be selectively applied based on the specific characteristics of each target block. The system dynamically adjusts the prediction process by calculating the correction term only when beneficial, and using different combinations of top and left edge pixels depending on the local image characteristics, thus optimizing the balance between accuracy and complexity.
3Measurement precision
If correction process uses all available chroma pixels around target block, then prediction accuracy improves, but encoding complexity increases
Solution Approach 1:
The patent extracts only the necessary chroma pixels from the top and left edges of the target block for the correction process, rather than using all available chroma pixels around the block. This selective extraction reduces the number of pixels that need to be processed while still capturing the essential chroma characteristics needed for accurate correction, thereby reducing encoding complexity while maintaining prediction accuracy.
Data Source
AI summary
An intra predictor (181) for performing intra prediction on each of blocks obtained by dividing an original image in the form of a frame, the intra predictor (181) includes; a linear model calculator (1811a) configured to calculate a linear model of the luminance component and the chroma component of the target block using decoded pixel values of the luminance component and decoded pixel values of the chroma component around the target block on which the intra prediction is performed; a chroma component predictor (1811b) configured to predict pixel values of the chroma component of the target block by applying the linear model calculated by the linear model calculator (1811a) to decoded pixel values of a luminance component of the target block; and a chroma component corrector (1812) configured to correct predicted pixel values of the chroma component obtained by the chroma component predictor (1811b) using decoded pixel values that were not used to calculate a linear model by the linear model calculator (1811a) of decoded pixel values around the target block.