Motion Vector Derivation Using Temporal Reference Distance
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Solution Overview
Problem
Conventional motion vector calculation methods in temporal direct are limited, leading to suboptimal motion vectors and reduced compression rates in video coding.
Innovation Solution
A method for selecting and calculating motion vectors based on the position and temporal distance of reference blocks relative to the current block, allowing for the derivation of the most suitable motion vector using forward or backward reference vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional temporal direct method is used to calculate motion vector, then the coding process is simple, but the compression rate is reduced due to suboptimal motion vectors
Solution Approach 1:
The patent changes the parameters used for motion vector calculation by introducing temporal distance considerations and selective use of forward/backward reference vectors. Instead of using a fixed conventional method, the system adapts the motion vector derivation parameters based on the temporal relationship between reference pictures, thereby improving compression rate while maintaining coding simplicity.
2Speed
If a single reference motion vector is used for temporal direct, then the calculation is fast, but the motion vector accuracy is insufficient
Solution Approach 1:
The patent introduces dynamics into the motion vector calculation by selectively switching between forward and backward reference vectors based on temporal distance. The system dynamically chooses which reference vector to use depending on the specific coding situation, allowing both fast calculation and improved accuracy without requiring complex computations.
3Device complexity
If reference blocks are selected without considering temporal distance, then the processing is simple, but the motion vector derivation is suboptimal
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing temporal distance information for reference blocks. This preliminary preparation allows the coding process to quickly access and use the most appropriate reference vectors without adding significant complexity during actual motion vector derivation, thereby improving reliability while keeping processing simple.
Data Source
AI summary
A current block included in a current picture included in a coded video stream is decoded by determining a reference picture in the coded video stream, the reference picture being included in one of (i) a first reference picture group of the current block and (ii) a second reference picture group of the current block; selecting a reference motion vector of a reference block in the reference picture such that in situation (A) when the reference block has a first reference motion vector and a second reference motion vector that respectively correspond to the first reference picture group and the second reference picture group, (i) the first reference motion vector is selected when the reference picture is included in the second reference picture group and (ii) the second reference motion vector is selected when the reference picture is included in the first reference picture group, in situation (B) when the reference block has only one reference motion vector, the only reference motion vector is selected, and in situation (C) when the reference block has no reference motion vector, a zero reference motion vector is selected; deriving the motion vector of the current block using the selected one reference motion vector; and decoding the current block using the derived motion vector.