Blended Predictors for Overlapped Block Motion Compensation
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Solution Overview
Problem
High-Efficiency Video Coding (HEVC) standard faces challenges in reducing computational complexity and bandwidth requirements for Overlapped Block Motion Compensation (OBMC) due to high computational complexity and increased bandwidth demands, especially when applied to sub-block motion compensation.
Innovation Solution
The method involves partitioning a current block into overlapped sub-blocks, determining sub-block motion vectors, and deriving initial predictors through motion compensation, with the option to blend predictors using weighted sums for overlapped regions, and using integer motion vectors to simplify the OBMC process, reducing computational complexity and bandwidth by adapting the number of OBMC blending lines and employing short-tap interpolation filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OBMC is applied to sub-block motion compensation to improve visual quality and reduce block artifacts, then coding efficiency is improved, but computational complexity and bandwidth requirements increase significantly
Solution Approach 1:
The current block is divided into multiple sub-blocks, and OBMC is applied selectively to overlapped regions between adjacent sub-blocks. This segmentation approach allows the patent to apply OBMC only where needed (at boundaries) rather than across the entire block, thereby improving visual quality at partition boundaries while reducing overall computational complexity compared to applying OBMC to the whole block.
Solution Approach 2:
Different processing approaches are applied to different regions: overlapped regions use OBMC with weighted blending of motion predictors, while non-overlapped regions use standard motion compensation. This local differentiation ensures high visual quality at boundaries where artifacts occur, while maintaining lower computational complexity in non-boundary regions.
2Reliability
If OBMC is applied to sub-block motion compensation to reduce block artifacts, then visual quality is improved, but bandwidth requirements increase
Solution Approach 1:
By segmenting the block into sub-blocks and applying OBMC only to overlapped regions, the patent reduces the total number of pixels requiring OBMC processing compared to applying it to the entire block. This selective application decreases the bandwidth required for transmitting motion compensation data while maintaining visual quality at critical boundary regions.
3Device complexity
If integer motion vectors are used to simplify OBMC process, then computational complexity is reduced, but motion compensation precision decreases
Solution Approach 1:
Integer motion vectors are used for generating OBMC predictors in overlapped regions, which simplifies computation. The patent accepts a trade-off where precision is maintained in non-overlapped regions using standard fractional MV processing, while overlapped regions use the computationally simpler integer MV approach. This local differentiation balances complexity and precision requirements.
Data Source
AI summary
Exemplary video processing methods and apparatuses for coding a current block by overlapped sub-block motion compensation split the current block into overlapped sub-blocks, determine a sub-block MV for each overlapped sub-block, derive an initial predictor for each sub-block by motion compensation using the sub-block MV, derive a final predictor for each overlapped region by blending the initial predictors of the overlapped region, and encode or decode the current block based on the final predictors. Exemplary video processing methods and apparatuses for coding blocks with OBMC generate a converted MV by changing a MV to an integer MV or changing a MV component to an integer component, derive an OBMC region by motion compensation using the converted MVs, and encode or decode the blocks by blending an OBMC predictor with an original predictor.