Intra Prediction Line Update for Smoother Directional Coding
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Solution Overview
Problem
Existing video coding standards like H.266/Versatile Video Coding (VVC) and the exploratory compression model (ECM) inefficiently utilize local correlation between neighbor pixels in intra prediction, particularly in directional modes, leading to luminance discontinuities and suboptimal compression efficiency.
Innovation Solution
Intra prediction methods that utilize predicted values from the previous adjacent line, incorporating position-dependent pixel compensation (PDPC) to improve compression efficiency, especially for vertical, horizontal, and directional modes with integer slopes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If initial prediction is made using reference lines only, then the prediction process is simple, but local correlation between neighbor pixels is not efficiently utilized
Solution Approach 1:
The patent applies PDPC processing to the previous line before using it as reference for the current line prediction. This preliminary processing of the previous line's predicted values enhances the correlation information available, allowing the prediction to better utilize local pixel correlations while maintaining a straightforward line-by-line prediction structure.
2Productivity
If PDPC processing is applied to improve local correlation utilization, then compression efficiency improves, but the prediction process becomes more complex
Solution Approach 1:
The patent segments the prediction process into distinct stages: initial prediction using reference lines, PDPC processing of the previous line, and then using the updated previous line values for current line prediction. This segmentation allows PDPC to be applied in a controlled manner to specific lines, improving compression efficiency while managing complexity through structured processing steps.
Solution Approach 2:
The patent extends the prediction approach from traditional 2D reference line usage to incorporate the temporal dimension of previously processed lines. By applying PDPC to previous lines and using those updated values as references, the method adds a time-based dimension to the prediction process, better capturing local correlations across multiple lines.
3Device complexity
If line-by-line prediction is used, then processing is simplified, but luminance discontinuities occur at line boundaries
Solution Approach 1:
The patent implements a feedback mechanism where the predicted values from the previous line, after PDPC processing, are fed back as reference values for the current line prediction. This feedback loop ensures that discontinuities at line boundaries are reduced because the current line prediction is informed by the actually processed previous line values, creating smoother transitions and improving luminance continuity.
Data Source
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AI summary
The present systems and methods are an intra prediction method for directional modes, where the initial predictions of pixels are made using the predicted values in the previous adjacent line. The position dependent pixel compensation (PDPC) process is applied to the initial prediction if applicable. In the systems and methods, the predicted value at a pixel depends not only on the reference sample(s) but on the PDPC update in the previous line. This prediction method may be applied to purely vertical and purely horizontal prediction modes and to the directional modes having integer slopes. That is, the prediction modes when the predictor values for the target pixels match directly with reference samples. The PDPC process may be modified to account for this line by line prediction process. The systems and methods have the potential to improve the compression efficiency.