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

Abstract: In-loop filters have been comprehensively explored during the development of video coding standards due to their remarkable noise-reduction capabilities. In the early stage of video coding, in-loop filters, such as the deblocking filter, sample adaptive offset, and adaptive loop filter, were performed separately for each component. Recently, cross-component filters were studied to improve chroma fidelity by exploiting correlations between the luma and chroma channels. This paper introduces 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 present the origin, development, and status of cross-component filters in the current video coding standards. Finally, we conduct discussions on the further evolutions of cross-component filters.

Keywords: cross-component in-loop filter; adaptive loop filter; sample adaptive offset; video coding