Adaptive Reference Pixel Filtering for Intra Prediction
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Solution Overview
Problem
Existing image compression methods, such as those in MPEG and H.264/AVC, face challenges in intra prediction when some or all adjacent reference pixels are unavailable, leading to large differences between prediction blocks and original blocks, which affects compression efficiency.
Innovation Solution
An apparatus that generates and filters reference pixels adaptively based on the intra prediction mode and size of the prediction block, including generating reference pixels when they are unavailable, and applying filters to minimize the difference between prediction and original blocks, particularly for directional intra prediction modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing intra prediction methods are used when reference pixels are unavailable, then the encoding process can proceed, but the difference between prediction block and original block becomes large, reducing compression efficiency
Solution Approach 1:
The patent applies preliminary action by generating virtual reference pixels before the intra prediction process when actual reference pixels are unavailable. The virtual reference pixel generation unit creates synthetic reference pixels at positions where original reference pixels are missing, ensuring that the prediction process can proceed with accurate reference data. This preliminary generation of reference pixels prevents large prediction errors and maintains compression efficiency.
Solution Approach 2:
The patent uses an intermediary approach by introducing a virtual reference pixel as a mediator between the unavailable actual reference pixel and the prediction block. The virtual reference pixel generation unit acts as an intermediary that synthesizes missing reference information based on available neighboring pixels, allowing the intra prediction to proceed accurately without direct access to the original reference pixels.
2Manufacturing precision
If reference pixels are filtered adaptively for all prediction modes, then prediction accuracy improves, but computational complexity increases
Solution Approach 1:
The patent applies local quality by selectively applying filtering only to virtual reference pixels in directional intra prediction modes where reference pixel accuracy is critical, rather than uniformly filtering all reference pixels in all modes. The filter processing unit determines whether filtering is necessary based on the prediction mode and reference pixel availability, applying filtering locally only where it provides significant benefit. This approach maintains prediction accuracy for directional modes while avoiding unnecessary computational complexity in other modes.
Data Source
AI summary
Provided is an apparatus for encoding and decoding an image that adaptively filters reference pixels according to an intra prediction mode and a size of a prediction block, and generates the prediction block according to the intra prediction mode. When the reference pixels for a second directional intra prediction mode are filtered, the reference pixels for a first directional intra prediction mode, that is closer to an intra prediction mode having a direction of 45° with reference to a horizontal mode than the second directional intra prediction mode is, are also filtered. The first and the second intra prediction modes exist between the horizontal mode and the intra prediction mode having the direction of 45° with reference to the horizontal mode. The number of intra prediction modes in which the filter is applied increases as the size of the prediction block increases.