Overview of Cross-Component In-loop Filters in Video Coding Standards

2026-07-13

AI Summary

Traditional video coding typically applies in-loop filtering independently to luma and chroma components, failing to exploit their inherent correlation for improved reconstruction quality. This study provides a systematic review of cross-component in-loop filtering techniques, with a focus on the technical principles and evolutionary trajectory of Cross-Component Adaptive Loop Filtering (CCALF) and Cross-Component Sample Adaptive Offset (CCSAO). The analysis demonstrates that leveraging luma-chroma correlation through cross-component filtering effectively mitigates compression artifacts, enhances chroma fidelity, and improves pixel-level reconstruction accuracy. These findings offer both theoretical grounding and practical guidance for the design of advanced in-loop filters in future video coding standards.

Abstract

In-loop filters have been comprehensively explored during the development of video coding standards due to their remarkable noise-reduction capability. In the early stage of video coding, in-loop filters, such as Deblocking Filter, Sample Adaptive Offset, and Adaptive Loop Filter, were performed separately for each component. Recently, cross-component filters were studied to improve the chroma fidelity by exploiting correlations between the luma and chroma channels. This paper summarizes the cross-component filters used in the state-of-the-art video coding standard. Specifically, it includes the Cross-Component Adaptive Loop Filter and Cross-Component Sample Adaptive Offset. Cross-component filters aim to reduce compression artifacts based on the correlation between different components and provide more accurate pixel reconstruction values. In this paper, we introduce the origin, development, and status of cross-component filters in the current video coding standards. Finally, we had some discussions on the further evolutions of cross-component filters.

Problem

• cross-component filtering
• chroma fidelity
• compression artifacts
• video coding standards
• pixel reconstruction

Innovation

• Cross-Component Filtering
• Adaptive Loop Filter
• Sample Adaptive Offset
• Video Coding Standards
• Chroma Reconstruction