Sub-Pixel Motion Vector Refinement With Error Surface Fitting
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Solution Overview
Problem
Current video codecs face challenges in achieving accurate motion estimation with reduced computational complexity and signaling overhead, particularly in decoder-side motion vector refinement, which affects the efficiency of video coding and decoding.
Innovation Solution
A method for obtaining sub-pixel accurate delta motion vectors through iterative refinement operations using cost functions, with early exit conditions and parametric error surface fitting, applied in decoder-side motion vector refinement systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative refinement operations are performed to improve motion vector accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies early exit conditions that allow the iterative refinement process to terminate before completing all planned iterations when sufficient accuracy is achieved. This partial action approach maintains measurement precision while reducing device complexity by avoiding unnecessary computational steps
Solution Approach 2:
The patent dynamically adjusts refinement parameters such as search range and iteration count based on content characteristics and accuracy requirements. This allows the system to optimize between measurement precision and device complexity by adapting the refinement process to specific scenarios
2Measurement precision
If more refinement operations are performed, then measurement precision improves, but loss of time increases
Solution Approach 1:
The patent implements early exit mechanisms that stop refinement operations when predetermined accuracy thresholds are met or when time constraints are approached. This ensures sufficient measurement precision while minimizing loss of time by avoiding excessive refinement iterations
Solution Approach 2:
The patent employs periodic refinement operations where refinement is performed at specific intervals or stages rather than continuously. This periodic approach maintains measurement precision while reducing loss of time by concentrating computational effort at critical points in the decoding process
3Measurement precision
If sub-pixel accurate refinement is applied, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent segments the sub-pixel refinement process into discrete, manageable stages with different precision levels. This segmentation allows the system to achieve sub-pixel accuracy while controlling device complexity by breaking down the complex refinement operation into simpler, modular steps
Solution Approach 2:
The patent adjusts refinement parameters such as search range, step size, and iteration count based on content characteristics and accuracy requirements. This dynamic parameter adjustment enables sub-pixel accurate refinement while managing device complexity by adapting the refinement process to specific scenarios
Data Source
AI summary
Given that decoder side motion vector refinement/derivation is a normative aspect of a coding system, the encoder will also have to perform the same error surface technique in order to not have any drift between the encoder's reconstruction and the decoder's reconstruction. Hence, all aspects of all embodiments are applicable to both encoding and decoding systems. In template matching, the refinement movement occurs only in the reference starting from the sub-pixel accurate center that is derived based on the explicitly signaled merge index or implicitly through cost evaluations. In bilateral matching (with or without averaged template), the refinements start in the reference lists L0 and L1 starting from the respective sub-pixel accurate centers that are derived based on the explicitly signaled merge index or implicitly through cost evaluations.