Adaptive Loop Filter Signaling for 360-Degree Video Artifact Reduction

The patent segments the video picture into multiple tiles with discontinuous boundaries, and applies different filtering strategies to different regions. Specifically, it prevents in-loop filtering across virtual boundaries that separate different faces in 360-degree video, while allowing filtering within continuous regions. This segmentation approach maintains filtering coverage in valid areas while avoiding artifact generation at face boundaries.

The patent applies local quality control by differentiating between regions where filtering should be applied and regions where it should be prevented. It uses virtual boundary detection to identify discontinuous edges between faces, and selectively disables filtering operations across these specific boundaries while maintaining filtering in continuous regions. This local differentiation ensures high visual quality at face boundaries while preserving filtering benefits in other areas.

The patent segments the filtering operation into regions across virtual boundaries and regions within continuous areas. By preventing filtering across virtual boundaries and applying it within continuous regions, the patent achieves effective filtering where it matters while avoiding redundant or harmful operations at boundaries, thus improving coding efficiency without sacrificing filtering effectiveness in critical areas.

The patent applies partial filtering action by selectively enabling filtering only in regions where it produces beneficial effects. Instead of applying filtering uniformly across the entire picture including across discontinuous boundaries, it applies filtering partially - specifically within continuous regions and excluding boundary regions. This partial action approach maintains filtering effectiveness in valid areas while reducing overall processing overhead and improving coding efficiency.

The patent extracts and removes outside samples that would cause artifacts when used across virtual boundaries. It identifies samples located across discontinuous boundaries and excludes them from filtering operations, using only samples within continuous regions. This extraction of problematic samples prevents artifact generation while maintaining filtering accuracy using only correlated samples from within the same face.

The patent applies preliminary anti-action by preventing the use of outside samples across virtual boundaries before artifacts can be generated. It proactively identifies virtual boundaries and blocks access to samples across these boundaries, thereby preventing the harmful effect of artifact generation rather than correcting it afterward. This preliminary prevention maintains filtering accuracy using only safe, correlated samples.