bCTUboundary condition for CCLM filtering incorrect

[bheng]

The isFirstRowOfCtu condition is calculated in xGetLumaRecPixels( ), as shown below:

isFirstRowOfCtu = ((pu.block(COMPONENT_Cb).y)&(((pu.cs->sps)->getMaxCUWidth() >> 1) - 1)) == 0;

Here it uses the vertical position of the PU rather than the vertical position of the TU. For implicitly split TUs within a PU (due to maxTrafoSize), this can give the wrong result.

I believe something like the following would fix the problem.

isFirstRowOfCtu = ((chromaArea.y)&(((pu.cs->sps)->getMaxCUWidth() >> 1) - 1)) == 0;

[chiaming]

It is also incorrect for always shifting CTU size by 1 without considering chroma color format. I suggest to fix the issue by:

isFirstRowOfCtu = ( lumaArea.y & ((pu.cs->sps)->getCTUSize() - 1) ) == 0;

[fbossen]

​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/merge_requests/1165