Fine-Grained Motion Boundary Processing in Video Coding
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Solution Overview
Problem
In video coding systems like HEVC, motion discontinuities at coding unit boundaries lead to visual artifacts and reduced coding efficiency due to differing motion vectors across partitions, which existing overlapped block motion compensation techniques do not adequately address.
Innovation Solution
The method involves determining neighboring coding units with associated motion vectors to generate pre-generated predictors for boundary pixels, using weighting factors to combine these predictors with the current motion vector, thereby improving motion compensation at CU boundaries through fine-grained motion boundary enhancement (MBE) and its variant (fg-MBE).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If block-based motion estimation is used for inter-frame coding, then coding efficiency is improved through temporal redundancy exploitation, but visual artifacts and discontinuities occur at coding unit boundaries due to differing motion vectors
Solution Approach 1:
The patent applies different motion compensation strategies to different regions: boundary pixels use a combination of multiple motion vectors with weighting factors, while interior pixels use the standard single motion vector. This local differentiation resolves the contradiction by improving boundary quality without compromising overall coding efficiency.
Solution Approach 2:
The patent segments the motion compensation process into two distinct paths: one for boundary pixels that incorporates multiple motion vectors, and another for interior pixels that uses the standard motion vector. This segmentation allows the system to address boundary artifacts specifically while maintaining efficient block-based coding elsewhere.
2Manufacturing precision
If multiple motion vectors are combined for boundary pixels to reduce discontinuities, then picture quality at boundaries is improved, but computational complexity and processing overhead increase
Solution Approach 1:
The patent applies the complex multi-vector motion compensation only partially - specifically to boundary pixels that require it - rather than to all pixels in the block. This partial application reduces the overall computational burden while still achieving the quality improvement where needed most.
Solution Approach 2:
The patent performs motion compensation for boundary pixels in advance during the encoding process, generating predicted values that are then used in the reconstruction stage. This preliminary action prevents the need for complex post-processing and reduces overall system complexity.
3Manufacturing precision
If in-loop filtering is applied to reconstructed video to alleviate coding artifacts, then picture quality is enhanced, but additional processing time and computational resources are required
Solution Approach 1:
The patent performs motion boundary enhancement during the encoding process itself, before the video is stored or transmitted. By addressing boundary discontinuities in advance, the patent reduces the need for aggressive post-decoding filtering, thereby saving processing time in the decoding stage while still achieving quality improvement.
Data Source
AI summary
A method and apparatus for deriving fine-grained motion compensated prediction of boundary pixels in a video coding system are disclosed. Embodiments of the present invention determine one or more neighboring coding units (CUs) adjacent to a current coding unit (CU). For each neighboring CU, motion-compensated prediction is derived for each neighboring CU using the MV of the neighboring CU. The pre-generated predictors at a bottom side or a right side of each neighboring CUs are derived and stored on a smallest CU (SCU) basis. The pre-generated predictors and the motion compensated predictor for a current boundary pixel are combined using weighting factors to form a final predictor for the current pixel.