Sub-Pixel Motion Vector Refinement for FRUC Video Coding
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Solution Overview
Problem
Existing video encoding technologies, particularly in HEVC, face inefficiencies in the refinement of motion vectors at sub-pixel levels, which affect coding efficiency and complexity.
Innovation Solution
A method for refining motion vectors at sub-pixel positions using decoder-side derivation, involving multiple search steps at increasing sub-pixel resolutions and pattern-based evaluations, tailored to the signal characteristics and edge directions within the video frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motion vector refinement is performed at higher sub-pixel resolutions, then motion vector prediction accuracy is improved, but computational complexity increases
Solution Approach 1:
The refinement process is divided into multiple search steps, each operating at a different sub-pixel resolution level. The method segments the refinement task into coarse and fine stages, where early steps use lower resolution for computational efficiency and later steps use higher resolution for precision, thereby resolving the contradiction between accuracy and complexity
Solution Approach 2:
The method dynamically adjusts the sub-pixel resolution based on the search step progression. Starting from coarser resolutions and progressively moving to finer resolutions, the system adapts the computational precision to the current stage of refinement, achieving high accuracy when needed while maintaining lower complexity during initial stages
2Productivity
If multiple search steps at increasing sub-pixel resolutions are used, then coding efficiency is improved, but processing time increases
Solution Approach 1:
The method performs preliminary search steps at lower sub-pixel resolutions before conducting more time-consuming searches at higher resolutions. This preliminary action quickly establishes a good initial motion vector estimate, reducing the time needed for subsequent high-precision refinements and improving overall coding efficiency
Solution Approach 2:
The refinement process uses periodic search steps alternating between different resolution levels. By organizing the search in periodic cycles of varying precision, the system achieves a balance between processing time and coding efficiency, with each period contributing to progressive improvement without excessive time expenditure
Data Source
AI summary
A method and a device for encoding or decoding video data. It concerns more particularly the encoding according to a particular encoding mode using a decoder side motion vector derivation mode referenced as frame-rate up conversion mode or FRUC mode. In FRUC merge mode, the derivation process comprises a refinement step to increase the accuracy of the obtained motion vector at the sub-pixel level. This process involves the evaluation of different sub-pixel position around the obtained motion vector according to different patterns. The present invention has been devised to improve the known refinement step. It aims at improving the coding efficiency by considering the characteristics of the matching type and/or the signal inside the templates.