Encoder issue with LMCSUpdateCtrl==2

[ksuehring]

We encoded a 10-bit non-CTC sequence with a few black frames in the beginning with low-delay configuration (luma: 121, cb: 514, cr: 514)

Surprisingly the black frames get reconstructed as white (luma: 929, cb: 514, cr: 514), already in the first intra frame. The encoder reports luma PSNR of ~2dB, decoder matches the encoder.

This effect does not happen with RA or AI configurations.

We traced the issue back to the parameter LMCSUpdateCtrl being set equal to 2 in LD config.

I checked different encoder code locations, which have a dependency on the LMCSUpdateCtrl parameter. So far I found that the problem relates to the model parameters being set in EncReshape.cpp around line 850, but not exactly which parameter.

[taoranlu]

A MR is created for fixing this issue:
​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/merge_requests/1394

[ksuehring]

The MR is merged.