Cross-Component Adaptive Loop Filter for Video Coding
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Solution Overview
Problem
Current video coding systems face challenges in effectively enhancing picture quality due to coding artefacts, particularly in the quantization process, and existing adaptive loop filters do not adequately address the specific needs of chroma component refinement in cross-component processing.
Innovation Solution
The implementation of multiple Cross-Component Adaptive Loop Filters (CC-ALF) with non-linear clipping operations and precise filter coefficient alignment, along with signalling techniques for improved chroma sample processing, is introduced to refine chroma components using luma sample values, allowing for variable block sizes and context-coded flags for efficient filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple CC-ALF filters are used to refine chroma components, then video decoding quality is improved, but device complexity increases
Solution Approach 1:
The patent divides the chroma filtering process into multiple separate CC-ALF filters, each handling different aspects of chroma refinement. Instead of using a single complex filter, the solution segments the filtering into multiple specialized filters that can be selectively applied, improving quality while managing complexity through modular processing.
Solution Approach 2:
The patent implements dynamic filter selection where the choice of which CC-ALF filters to apply is determined based on picture characteristics and coding conditions. The filtering process adapts dynamically by selecting appropriate filters from the set of available CC-ALF filters, allowing the system to optimize between quality and complexity on a per-picture or per-block basis.
2Manufacturing precision
If non-linear clipping operations are applied in CC-ALF processing, then chroma sample refinement is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary clipping operations on chroma samples before applying the CC-ALF filtering. By pre-processing the chroma samples with clipping to limit extreme values, the subsequent filtering operations work with already-bounded data, improving refinement quality while reducing the computational burden during the main filtering stage.
3Stability of the object's composition
If filter coefficient alignment is precisely performed across multiple CC-ALF filters, then filtering consistency is improved, but signalling costs increase
Solution Approach 1:
The patent applies different filter coefficient alignment strategies to different CC-ALF filters based on their specific requirements. Instead of uniformly aligning all filters, the solution allows each filter to have its own alignment characteristics where needed, while sharing alignment information where possible, thereby improving filtering consistency while optimizing signalling efficiency.
Data Source
AI summary
Methods and apparatus for loop-filter processing of reconstructed video are disclosed. According to one method, multiple CC-ALF (Cross-Component Adaptive Loop Filter) filters are used. Selection of the multiple CC-ALF filters can be signalled in one APS (Adaptation Parameter Set). According to another method, the CC-ALF can be implemented according to the difference between a to-be-process sample and its neighbouring sample.