Constrained Overlapped Block Motion Compensation in Video Coding
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Solution Overview
Problem
Overlapped Block Motion Compensation (OBMC) in video coding systems increases system bandwidth and complexity, especially when used with other coding tools like Bi-directional Optical Flow (BIO), due to redundant processes and additional data access, leading to higher computational requirements and memory bandwidth issues.
Innovation Solution
Implementing constraints on OBMC application based on block size, shape, and prediction direction, such as applying OBMC only to smaller blocks or uni-prediction modes, and using conditional syntax signaling to reduce unnecessary operations and data access, thereby optimizing bandwidth and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OBMC is applied to improve coding gain and reduce block boundary artifacts, then coding efficiency is improved, but system bandwidth and computational complexity increase
Solution Approach 1:
The patent applies different OBMC strategies to different regions: full OBMC with multiple motion vectors for boundary pixels, and simplified or no OBMC for non-boundary pixels. This local differentiation reduces overall computational complexity while maintaining coding efficiency at critical boundary regions where artifacts occur most frequently.
Solution Approach 2:
The patent segments the block processing into boundary pixels and non-boundary pixels, applying OBMC operations selectively. By dividing the processing scope and applying complexity-reducing constraints to specific segments (non-boundary areas), the overall system bandwidth and computational load are reduced while preserving the essential artifact-reduction function at boundaries.
2Manufacturing precision
If OBMC is applied with multiple motion vectors to reduce artifacts, then visual quality at block boundaries is improved, but computational complexity and memory bandwidth increase
Solution Approach 1:
The patent uses multiple motion vectors and full OBMC processing specifically for boundary pixels where visual quality improvement is most needed, while using simplified or no OBMC for non-boundary pixels. This localized application of complex processing maintains high visual quality at critical boundaries while reducing overall computational and memory bandwidth requirements.
Solution Approach 2:
The patent applies partial OBMC action by using multiple motion vectors and full processing only where necessary (boundary pixels), rather than applying it uniformly to all pixels. This partial application achieves the necessary visual quality improvement at boundaries without the excessive computational complexity and memory bandwidth that would result from universal application.
Data Source
AI summary
A method and apparatus use an Inter coding tool and OBMC (Overlapped Block Motion Compensation). According to one implementation, a method of video coding using OBMC (Overlapped Block Motion Compensation) operates by receiving input data associated with a current block, wherein the input data correspond to pixel data to be coded at an encoder side or coded data to be decoded at a decoder side, applying the OBMC to the current block depending on one or more constraints, and signaling an OBMC syntax conditionally at the encoder side or parsing the OBMC syntax conditionally at the decoder side for the current block, wherein the OBMC syntax indicates whether the OBMC is applied to the current block.