Bi-Predictive Motion Vectors Using Long-Term Reference Pictures
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Solution Overview
Problem
Existing moving picture coding systems face inefficiencies due to frequent scene changes, which result in high bit rates because they often resort to intra mode coding, generating more bits compared to inter mode coding, especially when scene changes occur frequently.
Innovation Solution
The method determines motion vectors for current image blocks based on reference picture indices, using long-term or short-term reference pictures to switch between inter mode and intra mode coding, and adjusts forward and backward motion vectors in the direct mode based on the type of reference picture, optimizing coding efficiency by reducing bit usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intra mode coding is used when scene changes occur, then coding accuracy is improved, but bit rate increases
Solution Approach 1:
The patent changes the parameter of reference picture selection by introducing long-term reference pictures and using reference picture indices to switch between short-term and long-term references. This allows the system to adapt to scene changes by selecting appropriate reference pictures, maintaining coding accuracy while reducing bit rate through more efficient inter-mode coding after scene changes.
Solution Approach 2:
The patent implements dynamic switching between intra mode and inter mode coding based on scene change detection and reference picture index analysis. The system dynamically adjusts coding mode selection and reference picture usage to optimize the balance between coding accuracy and bit rate, rather than statically using intra mode for all scene changes.
2Quantity of substance
If inter mode coding is used frequently, then bit rate is reduced, but coding efficiency decreases during scene changes
Solution Approach 1:
The patent changes the reference picture parameter by introducing long-term reference pictures and reference picture indices. This allows inter mode coding to maintain efficiency during scene changes by selectively using long-term references when scene changes are detected, rather than defaulting to intra mode, thus preserving coding efficiency while maintaining low bit rate.
Solution Approach 2:
The patent introduces reference picture indices as an intermediary mechanism that mediates between intra mode and inter mode coding. The reference picture index indicates whether to use short-term or long-term reference pictures, enabling smooth transition and optimal selection between coding modes based on scene change conditions, thereby maintaining coding efficiency without sacrificing bit rate efficiency.
3Quantity of substance
If direct mode is used for B pictures, then overhead bits are reduced, but motion vector accuracy decreases
Solution Approach 1:
The patent changes the motion vector determination parameter by introducing reference picture index-based selection. Instead of always using scaled motion vectors from co-located blocks, the system uses the reference picture index to determine whether to directly copy motion vectors or use scaled versions, thereby maintaining motion vector accuracy while still reducing overhead bits through direct mode usage.
4Adaptability or versatility
If scene change detection is performed frequently, then coding adaptability is improved, but processing complexity increases
Solution Approach 1:
The patent changes the scene change detection parameter by using reference picture index analysis instead of full scene change detection. The system detects scene changes by analyzing changes in reference picture indices between consecutive pictures, which is a simpler parameter to monitor than full scene content analysis. This maintains coding adaptability while reducing processing complexity.
Data Source
AI summary
In one embodiment, the method includes determining a motion vector of a current image block equal to a motion vector of an image block based on a reference picture index indicating a reference picture for the image block. For example, the motion vector of the current image block may be equal to the motion vector of the image block if the reference picture index indicates a long-term reference picture for the image block.