Affine Motion Vector Derivation for Video Coding Merge Candidates
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Solution Overview
Problem
Existing video coding standards, such as VVC, face challenges in efficiently deriving translational motion vectors for affine-coded blocks, which affects coding efficiency and video quality.
Innovation Solution
The proposed method involves determining derived motion vectors for a current block using affine models associated with affine-coded reference blocks or sub-blocks, and incorporating these derived motion vectors into a merge list as translational motion vector candidates for predictive encoding or decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If affine models are used to derive motion vectors for coded blocks, then motion representation accuracy is improved, but computational complexity increases
Solution Approach 1:
The current block is divided into multiple sub-blocks, and affine motion vectors are derived separately for each sub-block. This segmentation allows the complex affine transformation to be applied locally to smaller regions, improving motion representation accuracy while managing computational complexity through localized processing.
Solution Approach 2:
Affine motion vector derivation is applied selectively only to blocks that benefit from it, rather than uniformly to all blocks. The method determines whether a block should use affine modeling based on specific criteria, applying the computationally intensive affine transformation only where necessary to improve motion accuracy.
2Productivity
If more motion vector candidates are included in the merge list, then coding efficiency is improved, but bitstream complexity increases
Solution Approach 1:
Derived affine motion vectors are merged into the existing merge candidate list alongside traditional motion vector candidates. This combines the benefits of both affine modeling and conventional merge mode, providing the encoder with more candidate choices to select from, thereby improving coding efficiency without requiring a completely separate candidate list.
Solution Approach 2:
The method introduces new parameters for affine motion modeling (such as control point motion vectors and affine transformation coefficients) that are only encoded when affine mode is selected. This allows the system to maintain flexibility in the bitstream by conditionally including additional parameters only when they provide benefit, managing bitstream complexity through selective parameter encoding.
Data Source
AI summary
Methods and apparatus of video coding are disclosed. According to this method, input data comprising pixel data for a current block to be encoded at an encoder side or encoded data of the current block to be decoded at a decoder side is received. When one or more reference blocks or sub-blocks of the current block are coded in an affine mode, the following coding process is applied: one or more derived MVs (Motion Vectors) are determined for the current block according to one or more affine models associated with said one or more reference blocks or sub-blocks; a merge list comprising at least one of said one or more derived MVs as one translational MV candidate is generated; and predictive encoding or decoding is applied to the input data using information comprising the merge list.