Adaptive Loop Filter Selection via Rate-Distortion Cost Analysis
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Solution Overview
Problem
Existing video coding techniques face challenges in efficiently applying adaptive loop filters due to high computational complexity and multi-pass encoding requirements, which can lead to increased delay and power consumption, especially in hardware decoding systems.
Innovation Solution
A method and system that determine whether to apply an adaptive loop filter based on rate-distortion costs, enabling ALF operations only where they provide improvements, and using predefined coefficients for intra- and inter-coding modes to reduce computational complexity and delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adaptive loop filter is applied to all reconstructed blocks, then video quality is improved, but computational complexity increases
Solution Approach 1:
The patent applies adaptive loop filter selectively to specific reconstructed blocks based on local characteristics such as gradient magnitude and block type, rather than uniformly to all blocks. This local quality approach maintains video quality in regions where filtering is beneficial while avoiding unnecessary computation in regions where it would not improve quality, thus resolving the contradiction between video quality improvement and computational complexity reduction.
Solution Approach 2:
The patent implements partial action by applying the adaptive loop filter to only a subset of reconstructed blocks that meet specific criteria (e.g., non-skipped blocks, non-intra-blocks, blocks with sufficient gradient magnitude). This partial application strategy achieves adequate video quality improvement without the excessive computational cost of applying the filter to all blocks, effectively balancing quality and complexity.
2Manufacturing precision
If adaptive loop filter is applied to all reconstructed blocks, then video quality is improved, but processing time increases
Solution Approach 1:
By evaluating local block characteristics and applying the filter only where needed, the patent reduces the total number of filtering operations, thereby decreasing processing time while maintaining video quality in critical regions.
Solution Approach 2:
The selective application to partial blocks meeting specific criteria significantly reduces processing time compared to universal application, while still achieving meaningful video quality improvement in the blocks where filtering is most beneficial.
3Manufacturing precision
If adaptive loop filter is applied to all reconstructed blocks, then video quality is improved, but power consumption increases
Solution Approach 1:
The patent reduces power consumption by limiting adaptive loop filter operations to specific reconstructed blocks based on local characteristics, thereby reducing the total energy expenditure of the filtering process while maintaining video quality where it matters most.
Solution Approach 2:
By applying the filter to only a partial set of blocks that meet defined criteria, the patent achieves adequate video quality improvement with significantly reduced power consumption compared to applying the filter to all blocks.
4Productivity
If rate-distortion optimization is used to determine filter application, then coding efficiency is improved, but computational complexity increases
Solution Approach 1:
The patent computes rate-distortion costs locally for individual blocks or small groups of blocks rather than for the entire frame, enabling coding efficiency improvements through selective filtering while keeping the computational complexity manageable through localized evaluation.
Data Source
AI summary
Systems and methods for applying an adaptive loop filter (ALP) in video coding are provided. The method may include determining a first rate-distortion cost of applying the adaptive loop filter on a reconstructed block. The reconstructed block includes a reconstructed version of an image block of an image frame from a video. The method may further include determining a second rate-distortion cost of not applying the adaptive loop filter on the reconstructed block. The method may additionally include determining whether to apply the adaptive loop filter for processing the reconstructed block based on the first rate-distortion cost and the second rate-distortion cost.