Bi-directional Intra Prediction for Video Encoding
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Solution Overview
Problem
Existing video compression technologies face challenges in achieving high compression efficiency and reducing complexity in bi-directional intra prediction, particularly in handling larger block sizes and directional structures, which affects the rate-distortion performance and computational complexity.
Innovation Solution
The method involves selecting a subset of directional intra prediction modes based on the shape of the current block, applying bi-directional intra prediction only to larger block sizes and specific directional modes, and omitting post-filtering to reduce complexity while maintaining performance, thereby improving the trade-off between rate-distortion performance and computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bi-directional intra prediction is applied to all directional modes and block sizes, then rate-distortion performance is improved, but computational complexity increases
Solution Approach 1:
The patent segments the set of directional prediction modes into two subsets: a first subset for which bi-directional intra prediction is applied, and a second subset for which conventional prediction is used. This segmentation allows the system to apply the computationally intensive bi-directional prediction only where most beneficial (typically diagonal directions), while using simpler prediction methods for other directions, thus resolving the contradiction between performance improvement and complexity reduction.
Solution Approach 2:
The patent applies different prediction qualities to different spatial locations and directional modes. Specifically, bi-directional prediction with higher computational quality is applied locally to certain directional modes and block sizes, while simpler prediction methods are applied to other modes and block sizes. This local differentiation optimizes the trade-off between rate-distortion performance and computational complexity by concentrating computational resources where they provide the most benefit.
2Reliability
If bi-directional intra prediction is applied to larger block sizes, then rate-distortion performance is improved, but computational complexity increases
Solution Approach 1:
The patent applies bi-directional intra prediction partially, only to larger block sizes rather than all block sizes. This partial application strategy recognizes that bi-directional prediction provides the most significant performance benefits for larger blocks where spatial redundancy is more pronounced, while avoiding the computational overhead for smaller blocks where the benefit-to-cost ratio is lower.
3Measurement precision
If post-filtering is applied in bi-directional intra prediction, then prediction accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent extracts and removes the post-filtering step from the bi-directional intra prediction process. By taking out the post-filtering operation, the patent maintains the core bi-directional prediction functionality while eliminating the additional computational complexity and processing time that post-filtering would introduce, thus resolving the contradiction between prediction accuracy and computational complexity.
Data Source
AI summary
At least one of the present embodiments generally relates to a method and an apparatus for video encoding and decoding, and more particularly, to a method and an apparatus for low-complexity bi-directional intra prediction. For example, a subset of a plurality of directional intra prediction modes is selected based on a shape of a current block of a picture being encoded or decoded. For a selected intra prediction mode in this subset, a sample value is bi-directionally intra predicted by using two predictors. The two predictors are substantially on a line based on a direction corresponding to the selected directional intra prediction mode. The bi-directional intra prediction may be only applied to large luma blocks, but not chroma blocks in order to reduce the computational complexity. When bi-directional intra prediction is used, the smoothing filtering may be omitted in intra prediction to further reduce the complexity.