Video Inter-Prediction Using Bi-Directional Optical Flow
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Solution Overview
Problem
Existing video compression techniques face challenges in achieving high encoding efficiency and image quality due to increasing picture sizes, resolutions, and frame rates, particularly in inter-prediction methods.
Innovation Solution
A coding tool that compensates for various motions of objects by using bi-directional optical flow and weighted bi-prediction, where the bi-directional optical flow process is applied when luma and chroma weights of reference pictures are consistent, enhancing inter-prediction performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional inter-prediction methods are used, then encoding complexity is low, but compression performance and image quality deteriorate due to inability to compensate for various object motions
Solution Approach 1:
The patent applies bi-directional optical flow to calculate motion vectors by analyzing temporal changes between reference pictures. This transforms the prediction approach from simple block-based motion compensation to a more sophisticated method that captures temporal dynamics, thereby improving prediction accuracy for objects with complex motions while managing encoding complexity through selective application.
2Manufacturing precision
If bi-directional optical flow is applied to all blocks, then prediction accuracy improves, but encoding complexity and processing time increase significantly
Solution Approach 1:
The patent selectively applies bi-directional optical flow to specific blocks or regions where it provides the most benefit, rather than uniformly applying it to all blocks. This partial application strategy maintains prediction accuracy for complex motion regions while avoiding the excessive processing overhead of universal application, thus balancing quality improvement with encoding efficiency.
3Manufacturing precision
If picture size, resolution, and frame rate are increased, then image quality improves, but data volume and required compression ratio increase
Solution Approach 1:
The patent replaces traditional block-based motion estimation mechanisms with bi-directional optical flow that operates on pixel-level intensity changes. This substitution enables more accurate motion compensation for high-resolution and high-frame-rate content, reducing the residual error and thereby decreasing the amount of data that needs to be encoded and transmitted.
Data Source
AI summary
A video encoding method, video decoding method, and an apparatus are disclosed. The methods and the apparatus are configured to: determine first and second reference pictures and first and second motion vectors for bi-prediction by decoding a bitstream; generate a first reference block from the first reference picture referenced by the first motion vector and generate a second reference block from the second reference picture referenced by the second motion vector; and generate a prediction block of the target block using the first and second reference blocks. The predictor includes a first coding tool configured to generate the prediction block of the target block by performing a bi-directional optical flow process using the first and second reference blocks.