Bi-directional Optical Flow Switching Logic for Video Coding
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Solution Overview
Problem
Existing video coding systems face challenges in determining whether to perform bi-directional optical flow (BDOF) for coding blocks, which affects the efficiency of video compression and transmission.
Innovation Solution
An apparatus comprising one or more processors is configured to determine whether to perform BDOF for a coding block by comparing the distances between the coding block's picture and reference pictures listed in different reference picture lists, and to decode or encode the block based on this determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If BDOF is performed for all coding blocks, then motion compensation accuracy is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent changes the parameter of reference picture selection by comparing POC differences between first and second reference pictures. When the POC differences are equal, BDOF is applied; when they differ, conventional motion compensation is used. This parameter-based conditional approach optimizes the balance between accuracy and complexity.
Solution Approach 2:
The patent segments the video coding process by dividing coding blocks into two groups: those where BDOF is applied (when POC differences are equal) and those where conventional motion compensation is used (when POC differences differ). This segmentation allows selective application of the computationally intensive BDOF algorithm only where beneficial.
2Measurement precision
If BDOF is applied to all coding blocks, then video quality is improved, but bandwidth and storage requirements increase
Solution Approach 1:
The patent uses POC difference equality as a parameter to control the application of BDOF. By changing this parameter-based decision criterion, the system achieves better video quality only where reference pictures are equally distant, thereby reducing overall bandwidth consumption compared to universal BDOF application.
Solution Approach 2:
Instead of applying BDOF to all coding blocks (excessive action), the patent applies it only to blocks where the POC differences of reference pictures are equal (partial action). This partial application achieves quality improvement where needed while avoiding unnecessary bandwidth consumption.
3Adaptability or versatility
If reference pictures with different POC differences are used, then temporal flexibility is improved, but motion estimation accuracy deteriorates
Solution Approach 1:
The patent changes the decision parameter from always using available reference pictures to comparing their POC differences. When POC differences are equal, motion estimation accuracy is maintained through BDOF; when they differ, temporal flexibility is preserved through conventional methods, resolving the contradiction.
Data Source
AI summary
An apparatus may be configured to determine a reference picture listed in a first reference picture list and a reference picture listed in a second reference picture list, for a coding block. The apparatus may be configured to determine whether to perform bi-directional optical flow (BDOF) for the coding block based at least in part on whether a distance between a picture associated with the coding block and the reference picture listed in the first reference picture list differs from a distance between the picture associated with the coding block and the reference picture listed in the second reference picture list. The apparatus may be configured to decode the coding block based on the determination of whether to perform BDOF for the coding block.