Chroma Motion Vector Refinement Using Reconstructed Luma Blocks
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Solution Overview
Problem
Current video coding standards like VVC and ECM may not always select the best merge candidates for motion vectors, leading to suboptimal compression efficiency due to shared motion vectors for luma and chroma components, which can result in inefficient encoding and decoding processes.
Innovation Solution
Refine motion vectors for chroma blocks using the reconstructed luma block if luma is coded first, or vice versa, by comparing the reconstructed block with prediction blocks within a small predefined area to select the best motion vector for chroma components, ensuring both encoder and decoder agree on the refined motion vector without additional signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If motion vectors are shared between luma and chroma components, then device complexity is reduced, but compression efficiency deteriorates
Solution Approach 1:
The patent segments the motion vector processing into separate luma and chroma components. Instead of using a single shared motion vector for both luma and chroma, the system independently determines motion vectors for each component, allowing optimized compression for each while maintaining manageable complexity through structured processing
Solution Approach 2:
The patent applies local quality by allowing different motion vector refinement processes for luma and chroma blocks based on their specific characteristics. The system refines motion vectors independently for each component, adapting the refinement process to the local needs of each block type rather than applying a uniform approach
2Productivity
If motion vectors are refined independently for luma and chroma, then compression efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges the motion vector refinement processes by using the same refinement mechanism and search area for both luma and chroma components. This unified approach allows independent refinement for each component while avoiding the complexity of separate specialized processes, as both components benefit from the same refined motion vector determination methodology
3Measurement precision
If a large search area is used for motion vector refinement, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies local quality by using a small, fixed search area around the predicted motion vector position rather than a large comprehensive search area. This localized search approach maintains sufficient precision for accurate motion vector refinement while significantly reducing the computational time required, as the search is confined to a limited region rather than the entire image
Data Source
AI summary
In an inter-frame prediction process for frames of video, a luma block is selected to be coded first for a current coding unit to form a reconstructed luma block of the current coding unit. MV(s) are refined that point from the luma block to a prediction luma block in a reference picture of the video. One of the refined MV(s) is selected to code chroma blocks for the current coding unit. In an inter-frame prediction process for frames of video, chroma blocks are selected to be coded first for a current coding unit to form reconstructed chroma blocks of the current coding unit. MV(s) are refined that point from the reconstructed chroma blocks to prediction chroma blocks in a reference picture of the video. One of the refined MV(s) is selected to code a luma block for the current coding unit.