Constrained PDPC Intra Prediction for Video Coding
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Solution Overview
Problem
Existing video coding standards face challenges in efficiently determining pixel values within coding units, particularly in handling complex intra prediction modes and bitstream structures.
Innovation Solution
The method involves generating predictors for pixel values within a coding unit using one or more generated predictors, including a first level predictor based on neighboring pixels and an intra prediction mode, and optionally a second level predictor if combined with the first level prediction mode during encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second level intra prediction process (PDPC) is combined with the first level intra prediction mode, then pixel value determination accuracy is improved, but encoder complexity increases
Solution Approach 1:
The intra prediction process is segmented into two distinct levels: first level intra prediction using neighboring pixels and prediction modes, and second level intra prediction (PDPC) using reconstructed pixels from decoded picture buffer. This segmentation allows selective application of the more complex second level process only when beneficial, rather than applying it uniformly to all predictions.
Solution Approach 2:
The patent applies partial action by conditionally combining the second level PDPC process with the first level prediction only for specific pixels within the current block that meet certain criteria (e.g., distance from block boundary, prediction mode type). This partial application reduces overall complexity while maintaining accuracy where most needed.
2Measurement precision
If multiple intra prediction modes are supported (67 modes in JVET), then prediction accuracy is improved, but processing complexity increases
Solution Approach 1:
The 67 intra prediction modes are segmented into different categories (e.g., planar, DC, angular directions) with different levels of complexity. The patent applies second level PDPC selectively to certain mode categories rather than all modes, reducing processing complexity while maintaining accuracy for the most beneficial cases.
Solution Approach 2:
Different prediction modes receive different levels of processing enhancement. The patent applies second level PDPC with varying intensity or applicability depending on the local characteristics of each prediction mode, rather than uniformly enhancing all modes. This local quality approach optimizes the balance between accuracy improvement and complexity increase.
3Reliability
If second level prediction is applied to all pixels, then video quality is improved, but bitrate increases
Solution Approach 1:
The patent applies second level PDPC prediction partially rather than to all pixels. Specific criteria determine which pixels receive the enhanced prediction (e.g., pixels at certain distances from block boundaries, pixels in specific spatial regions). This partial application reduces the bitrate overhead while maintaining video quality where it provides the most benefit.
Solution Approach 2:
The enhancement is applied with local quality considerations, where different regions or types of pixels within the block receive different levels of prediction enhancement based on their local characteristics and the potential quality improvement they can achieve.
Data Source
AI summary
A second level intra prediction mode can be combined with one or more of sixty-seven JVET intra prediction modes during encoding of a coding unit in a video bitstream. Embodiments include making a position dependent intra prediction combination (PDPC) mode available as the second level intra prediction mode. In embodiments, when a PDPC (position dependent intra prediction combination) mode is enabled, the second level intra prediction is combined with one of the 67 selected intra predictor modes. In embodiments, the PDPC mode is only enabled or available for a predetermined subset of intra prediction modes (out of 67 possible modes), in order to reduce encoder complexity and potentially improve coding efficiency. The PDPC mode may be identifies as enabled or available by a list of modes or signaling in the video bitstream.