Asymmetric In-Loop Filtering Across Virtual Boundaries

The patent implements asymmetric in-loop filtering at virtual boundaries by applying different filtering operations to pixels on opposite sides of the boundary. Specifically, pixels in the refreshed area use filtering that prevents dependency on non-refreshed area data, while pixels in the non-refreshed area use filtering that compensates for the asymmetric treatment. This asymmetric approach resolves the contradiction by maintaining filtering consistency through coordinated asymmetric operations rather than identical symmetric operations.

The patent applies different filtering strategies to different local regions around the virtual boundary. Pixels adjacent to the boundary in the refreshed area receive different treatment than pixels in the non-refreshed area, with each region's filtering tailored to its specific decoding constraints. This local differentiation allows the system to maintain overall filtering consistency while preserving decoding accuracy in each local region.

The patent segments the filtering process into distinct operations for pixels on opposite sides of the virtual boundary. Pixels in the refreshed area undergo filtering that segments out dependencies on non-refreshed area data, while pixels in the non-refreshed area undergo separate filtering that compensates for this segmentation. This segmentation approach maintains filtering quality by ensuring each segment operates with reliable data while preserving overall filtering effectiveness.

The patent introduces an intermediary mechanism at the virtual boundary that mediates the flow of coding information between refreshed and non-refreshed areas. This intermediary prevents direct use of potentially incorrect decoding information from non-refreshed areas while still allowing filtered pixels to contribute to their respective areas' reconstruction. The intermediary maintains filtering quality by controlling information flow rather than completely blocking it.