CCALF with Tiles, Slices, Virtual Boundaries

[bheng]

The CCALF code in the "isCrossedByVirtualBoundaries" section of AdaptiveLoopFilter::ALFProcess( ) seems to be incorrect.

First, the pointer to the luma source block is derived as follows, which uses the chroma size and is missing an xPos/yPos offset.

const Area blkSrc(0, 0, w >> chromaScaleX, h >> chromaScaleY);

I believe changing this to something like the following may work:

const Area blkSrc(xPos, yPos, width, height);

Second, the CCALF code seems to ignore all the boundaries. The original luma buffer is used rather than a extracted/padded version. So, the filtering uses luma pixels across these boundaries.

[fbossen]

The call to CCALF does indeed not use the correct parameters in that case. Can you have a look at ​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/merge_requests/1280 ? The luma input to CCALF is supposed to be the same as the input to the regular luma ALF. Thanks.