Reference Sample Interpolation Filtering for Chroma Prediction
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Solution Overview
Problem
Existing video coding technologies face challenges in achieving high compression ratios with minimal sacrifice in picture quality, particularly in handling intra prediction processes for coding blocks, especially for chroma components.
Innovation Solution
A method for intra prediction in video coding that involves obtaining a bitstream for a coding block, determining an intra prediction mode, and generating reference samples based on a predefined index value, where the index indicates the color component, and using padded reference samples or predefined values to enhance prediction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional intra prediction is used for chroma components, then compression ratio is improved, but picture quality deteriorates
Solution Approach 1:
The patent applies different prediction strategies to different chroma components (Cb and Cr) based on their specific characteristics. For Cb component, it uses left and top reference samples, while for Cr component, it uses only top reference samples. This localized differentiation improves prediction accuracy for each component without compromising overall compression efficiency.
Solution Approach 2:
The patent changes the prediction parameters by introducing an index variable (cb_idx or cr_idx) that determines whether to use padded reference samples or perform conventional prediction. When the index equals zero, padded reference samples are used; otherwise, conventional prediction is applied. This parameter-based control optimizes the balance between compression ratio and picture quality.
2Measurement precision
If additional padded reference samples are obtained for prediction, then prediction accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent performs preliminary padding of reference samples before the prediction process. By pre-padding the reference sample arrays with boundary values (such as the value of the top-left corner pixel), the prediction process can directly use these padded samples without additional complexity during the actual prediction stage. This preliminary preparation reduces overall processing complexity while maintaining prediction accuracy.
Solution Approach 2:
The patent copies boundary pixel values to create padded reference samples. Instead of performing complex calculations to generate additional reference samples, it simply copies the top-left corner pixel value to fill the padded positions. This copying approach significantly reduces processing complexity while providing sufficient prediction accuracy for chroma components.
3Manufacturing precision
If index-based conditional sampling is implemented, then chroma component quality is enhanced, but computational overhead increases
Solution Approach 1:
The patent extracts the chroma component index (cb_idx or cr_idx) from the prediction parameters and uses it as a conditional flag. When the index equals zero, the system takes the path of using padded reference samples; when non-zero, it takes the conventional prediction path. This extraction and conditional branching approach enhances chroma quality for specific components while minimizing unnecessary computational overhead for others.
Data Source
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AI summary
A method of intra prediction process of a coding block, the method comprising: obtaining a bitstream for the coding block; obtaining a value of intra prediction mode for the coding block, according to the bitstream for the coding block; obtaining a value of an index for the coding block in accordance with the bitstream; obtaining a set of reference samples for the coding block, wherein in case the value of the index for the coding block is equal to a predefined value, the set of reference samples comprises samples of a reconstructed block and additional samples; wherein in case the value of the index for the coding block is not equal to the predefined value, the set of reference samples comprises samples of the reconstructed block and does not comprise additional samples; obtaining a prediction value of a sample comprised in the coding block, according to the value of intra prediction mode for the coding block and the set of reference samples.