Bi-prediction Coding Motion Vector Scaling Method
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Solution Overview
Problem
Existing bi-prediction coding methods for moving image compression face challenges in complexity, coding efficiency, and bit rate consumption, particularly when only a forward motion vector is transmitted in symmetric mode coding.
Innovation Solution
A bi-prediction coding method using multiple reference pictures that selects and codes a coding target motion vector and a non-coding target motion vector based on calculated motion vectors, improving coding efficiency by efficiently transmitting motion vectors and reducing bit rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If joint motion search is performed to determine optimal forward and backward motion vectors, then prediction accuracy is maximized, but computational complexity becomes very high
Solution Approach 1:
The patent divides the bidirectional motion estimation into two separate unidirectional estimations. First, forward motion vectors are estimated from past reference pictures to the current picture. Then, backward motion vectors are estimated from future reference pictures to the current picture. This segmentation allows each estimation to be performed independently with reduced computational complexity while maintaining prediction accuracy.
Solution Approach 2:
The patent performs preliminary unidirectional motion estimation to obtain forward and backward motion vectors before combining them for bidirectional prediction. By pre-calculating the motion vectors from each direction separately, the system avoids the complexity of simultaneous joint optimization while ensuring accurate motion compensation.
2Device complexity
If independent forward and backward motion vector search is performed, then computational complexity is reduced, but coding efficiency deteriorates
Solution Approach 1:
The patent uses feedback from the independently estimated forward and backward motion vectors to improve the bidirectional prediction. The motion vectors obtained from unidirectional estimation serve as initial values or constraints for the final bidirectional prediction, ensuring that the simplified approach still achieves good coding efficiency by leveraging the motion information from both temporal directions.
3Measurement precision
If both forward and backward motion vectors are transmitted, then prediction accuracy is maintained, but bit rate increases
Solution Approach 1:
The patent extracts and transmits only the essential motion information needed for bidirectional prediction. By performing independent unidirectional estimation, the system can derive the necessary motion vectors without transmitting redundant data, thus reducing the bit rate while maintaining prediction accuracy through intelligent motion vector derivation and selection.
Data Source
AI summary
An image decoding method and an image decoding apparatus is provided. The method comprises recovering a first motion vector corresponding to a first decoding reference picture based on the entropy decoded bit stream, calculating a second motion vector corresponding to a second decoding reference picture by scaling the first motion vector based on a first temporal distance between the current picture and the first decoding reference picture and a second temporal distance between the current picture and the second decoding reference picture, generating a prediction block relating to a current block in the current picture, based on the calculated second motion vector, generating a residual block relating to the current block through a residual data decoding process based on the entropy decoded bit stream, and recovering the current block based on the prediction block and the residual block.