RPR - Sub-PU Grouping

[bheng]

In the function InterPrediction::xSubPuMC( ), the optimization used to group identical SBTMVP motion vector blocks together into larger blocks for interpolation cannot be used with RPR.

RPR generates different results when it is applied to a small (8x8) block versus a larger combined block. Therefore, the optimization mentioned above will change the results.

Either the optimization needs to be removed, or the following code needs a check for scaled reference pictures, so that the grouping is not applied in this case.

if (laterMi == curMi)
{

length += secStep;

}
else
{

break;

}

Note that the PU::isRefPicSameSize( ) function doesn’t seem to work for this purpose, since I believe pu.refIdx[0/1] are set based on the default SBTMVP vector. Even if this default vector doesn’t require scaling, one of the 8x8 sub-blocks might.

[bheng]

Potential fixes for this issue are available in the following merge request:

​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/merge_requests/997

[XiangLi]

​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/merge_requests/1051