Wide-Angle Intra Prediction With PDPC for Rectangular Blocks
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Solution Overview
Problem
Existing video encoding standards inefficiencies arise from using angular intra prediction directions that are not adapted to the shape of rectangular blocks, leading to asymmetry and inefficiency in predicting pixels, particularly for rectangular blocks with unequal width and height.
Innovation Solution
Adapt intra prediction directions based on the shape of the block, modifying the number and orientation of prediction modes for rectangular blocks, and extending position-dependent intra prediction combination (PDPC) to include wide-angle modes, ensuring all pixels can benefit from PDPC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If angular intra prediction directions are used for rectangular blocks, then prediction can be performed, but the prediction accuracy deteriorates due to asymmetry and lack of adaptation to block shape
Solution Approach 1:
The patent applies different prediction direction sets based on the block shape characteristics. For rectangular blocks, it uses a first set of prediction directions that are asymmetric and adapted to the block's aspect ratio, while for square blocks it uses a second set of prediction directions. This local adaptation ensures that each block type receives the most appropriate prediction directions for its specific geometry, thereby improving prediction accuracy without forcing a one-size-fits-all approach.
Solution Approach 2:
The patent dynamically selects the appropriate prediction direction set based on the block shape parameters (width and height relationships). The system adapts the prediction directions in real-time according to whether the block is rectangular or square, allowing the prediction mechanism to be flexible and responsive to different block configurations rather than being static and uniform.
2Productivity
If standard intra prediction modes are used for all blocks, then implementation is simple, but compression efficiency deteriorates for rectangular blocks
Solution Approach 1:
The patent changes the parameters of the prediction system by introducing different sets of prediction directions based on block shape. Instead of using a fixed set of angular directions for all blocks, it modifies the prediction direction parameters according to block aspect ratio, enabling better compression efficiency for rectangular blocks while maintaining a manageable level of complexity through systematic parameter selection.
3Measurement precision
If position-dependent intra prediction combination (PDPC) is extended to wide-angle modes, then prediction accuracy improves, but computational complexity increases
Solution Approach 1:
The patent segments the prediction process by applying PDPC selectively to specific wide-angle modes rather than uniformly to all prediction modes. This segmentation allows the system to extend PDPC to where it provides the most benefit (wide-angle modes for rectangular blocks) while avoiding unnecessary computational overhead in other modes, thereby balancing accuracy improvement with computational complexity management.
Data Source
AI summary
Methods and apparatus for performing intra prediction in an encoder or a decoder for non-square blocks enable a combination of reference samples from a row above the non-square block and a row to the left of the non-square block to be used for the prediction. In one embodiment, a weighted combination of reference samples are used. In another embodiment, the angles of prediction are extended in the longer direction of the non-square block, such that less angles of prediction are used in the shorter direction.