Nonlinear CC-ALF Chroma Correction for Video Coding Efficiency
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Solution Overview
Problem
Conventional video coding techniques, such as CC-ALF, apply linear filtering to chroma samples based on luma samples, which is inefficient for generating corrected values, leading to a need for improved methods to enhance video coding efficiency and quality.
Innovation Solution
Implement nonlinear cross-component adaptive loop filtering (nonlinear CC-ALF) to generate corrected chroma component values by inputting luma ALF output, enhancing chroma ALF output through summation with corrected values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If linear filtering operation is applied to luma samples in conventional CC-ALF, then the processing is simple and fast, but the video coding efficiency and image enhancement effect are insufficient
Solution Approach 1:
The patent changes the mathematical model parameter from linear to nonlinear (specifically polynomial-based nonlinear model) to improve chroma component correction accuracy. This allows the system to capture more complex luma-chroma relationships that linear filtering cannot represent, thereby improving video coding efficiency and image enhancement without requiring a complete architectural change
Solution Approach 2:
The patent combines linear filtering and nonlinear modeling in a hybrid approach. The system first applies conventional linear CC-ALF filtering, then adds polynomial-based nonlinear correction terms to the chroma components. This composite approach leverages the simplicity of linear filtering while enhancing it with nonlinear accuracy, resolving the contradiction between processing simplicity and enhancement effectiveness
2Manufacturing precision
If linear filtering is used for chroma correction, then the computational load is low, but the corrected values do not sufficiently enhance chroma components
Solution Approach 1:
The patent implements partial nonlinear correction by applying polynomial-based adjustments only to specific chroma components where nonlinear effects are most beneficial. Rather than fully transforming the entire filtering pipeline, the system adds selective nonlinear correction terms to the chroma correction process, achieving improved accuracy with moderate computational overhead
Solution Approach 2:
The patent introduces polynomial correction terms as an intermediary layer between the linear filtering stage and the final chroma output. These intermediary nonlinear terms mediate the relationship between luma and chroma components, allowing the system to maintain the efficiency of linear filtering while achieving higher precision through the added polynomial correction layer
Data Source
AI summary
A method and an apparatus are disclosed for video coding CC-ALF based on a nonlinear cross-component relation. A video decoding device obtains a reconstructed frame that is an output of a sample adaptive offset (SAO) filter and generates an adaptive loop filter output (ALF output) by inputting the reconstructed frame into an adaptive loop filter (ALF). The ALF output includes a luma ALF output and a chroma ALF output. The video decoding device generates corrected values of a chroma component by inputting the luma ALF output into a nonlinear cross-component ALF (nonlinear CC-ALF) and generates an enhanced chroma ALF output by summing the corrected values of the chroma component and the chroma ALF output.