Motion Vector Clipping for Lower-Bit Video Decoding
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Solution Overview
Problem
The increasing demand for high-resolution, high-quality image/video data, particularly in formats like 4K or 8K and immersive media, leads to higher transmission and storage costs due to the increased amount of information, necessitating a more efficient compression technology.
Innovation Solution
A method and apparatus for deriving a motion vector using clipping to reduce the number of bits required to represent the motion vector, specifically applying clipping to affine control point motion vectors derived through an affine model, and controlling motion vector precision by removing significant bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution, high-quality image/video data is transmitted and stored, then image quality is improved, but transmission cost and storage cost increase
Solution Approach 1:
The patent changes the precision parameter of motion vectors by applying clipping operations to limit the range of motion vector values. This reduces the number of bits required to encode motion vectors, thereby decreasing the overall data amount while maintaining acceptable image quality through controlled precision reduction
2Measurement precision
If the precision of motion vector is increased, then coding accuracy is improved, but the number of bits required to represent the motion vector increases
Solution Approach 1:
The patent directly changes the precision parameter by applying clipping operations that constrain motion vector values to a limited range. This parameter change reduces the bit representation requirement from potentially 18+ bits to 16 bits or less, achieving a trade-off between precision and information loss
Solution Approach 2:
The patent extracts and removes the most significant bits (MSBs) of motion vector values through clipping operations. By taking out the upper bits that contribute least to precision while consuming most bits, the patent reduces the overall bit count while preserving the essential precision information
3Productivity
If clipping is applied to motion vector to reduce bit count, then compression efficiency is improved, but motion vector accuracy may be reduced
Solution Approach 1:
The patent applies parameter changes by setting specific clipping ranges for motion vectors based on the picture width and height. This dynamic parameter adjustment optimizes the balance between compression efficiency and motion vector accuracy for different resolution content
Data Source
AI summary
Provided is an image decoding method performed by a decoding apparatus including deriving a temporary reference motion vector for a current block included in a current picture, deriving a reference motion vector for the current block by applying clipping to the temporary reference motion vector, deriving a motion vector for the current block based on the reference motion vector, deriving a predicted block for the current block based on the motion vector for the current block, and generating a reconstructed picture for the current picture based on the predicted block for the current block, wherein a number of bits of a binary code representing the reference motion vector is less than a number of bits of a binary code representing the temporary reference motion vector.