Bilateral and CCSAO In-Loop Filtering for Chroma Ringing Reduction

The patent combines bilateral filtering with CCSAO filtering into a unified in-loop filtering process. The bilateral filter and CCSAO filter work together synergistically, where the bilateral filter reduces ringing artifacts through its distance-weighted and intensity-weighted filtering mechanism, while CCSAO provides cross-component sample adaptive offset correction. This merged approach effectively removes ringing artifacts in chroma components that traditional filters alone cannot eliminate.

The patent employs a composite filtering approach by integrating two different filtering mechanisms (bilateral filter and CCSAO filter) into a single processing pipeline. The bilateral filter uses a composite weighting function that combines spatial distance weights and intensity difference weights, creating a composite filtering effect that adapts to local image characteristics and effectively suppresses ringing artifacts while preserving edges.

The bilateral filter applies different filter weights to different samples based on their local characteristics. Samples closer to the central sample and with similar intensity values receive higher weights, while distant or dissimilar samples receive lower weights. This local quality approach allows the filter to adapt to local image structures, effectively reducing ringing artifacts in smooth regions while preserving edges, without requiring uniform complex processing across the entire image.

The patent applies bilateral filtering selectively rather than uniformly across all samples. By using CCSAO to identify regions where filtering is most beneficial and applying bilateral filtering primarily in those regions, the system achieves effective artifact removal without the full computational cost of applying bilateral filtering to every sample in the image.