Motion Vector Derivation for Chroma Blocks in Video Coding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing video coding techniques face inefficiencies in determining motion vectors for chroma blocks, particularly in different color formats, which affects processing efficiency and coding performance.
Innovation Solution
A method where a video coder determines motion vectors for chroma blocks based on the color format, specifically using the motion vector of a co-located luma block for 4:4:4 format and averaging motion vectors for 4:2:2 or 4:2:0 formats, to optimize processing and coding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If motion vectors of chroma blocks are determined by averaging motion vectors of multiple luma sub-blocks, then compatibility with different color formats is improved, but processing complexity and number of operations increase
Solution Approach 1:
The patent applies different motion vector derivation methods based on the specific color format being processed. For 4:4:4 color format, it uses direct copying of luma motion vectors to chroma blocks, while for 4:2:0 and 4:2:2 formats, it uses averaging methods. This localized adaptation to different color format requirements resolves the contradiction by optimizing processing for each specific case rather than using a single complex averaging method for all formats.
2Adaptability or versatility
If motion vectors of chroma blocks are determined by averaging motion vectors of multiple luma sub-blocks, then compatibility with different color formats is improved, but coding performance deteriorates
Solution Approach 1:
The patent recognizes that different color formats have different spatial relationships between luma and chroma components. For 4:4:4 format where chroma resolution equals luma resolution, direct copying preserves motion vector accuracy. For 4:2:0 and 4:2:2 formats with lower chroma resolution, averaging provides appropriate smoothing. This localized approach maintains coding performance by matching the derivation method to the specific color format characteristics.
3Device complexity
If the same motion vector derivation method is used for all color formats, then device complexity is reduced, but adaptability to different color formats deteriorates
Solution Approach 1:
The patent changes the motion vector derivation parameter based on the color format identifier. When the color format is detected as 4:4:4, it switches to direct copying mode; when detected as 4:2:0 or 4:2:2, it switches to averaging mode. This parameter-based adaptation allows the system to maintain low complexity for each specific case while being highly adaptable across different color formats.
Data Source
AI summary
Techniques related to derivation of motion vectors of a first color component (e.g., chroma component) from motion vectors of a second color component (e.g., luma component) are described. A video coder (e.g., video encoder or video decoder), for a CU coded in affine mode with 4:4:4 color format, may determine a motion vector for each sub-block of the luma block, and determine a motion vector for each sub-block of the chroma block based only on the motion vector for each co-located (also called collocated) sub-block of the luma block. However, for another CU coded in affine mode but with a color format other than 4:4:4 (e.g., 4:2:2 or 4:2:0), the video coder may determine a motion vector for each sub-block of the chroma block based on an average of two or more motion vectors of sub-blocks of the luma block.