We performed extensive testing and narrowed down the issue to 4:2:2 codecs, specifically ProResHQ and DNxHD.
First spotted in 2015 during a series we finished - at the time we blamed it on Apple codec.
Our workaround was to exclusively use 444 codecs in Resolve, then generate the deliverables in Avid MediaComposer.
Fast forward to present day, the issue is still present in both 14.1.1 Studio and non-studio versions.
It can also be reproduced on Win systems, of course not with ProRes.
Essentially, red and blue channels are rendered with lower levels. So blacks go below zero.
The full scale is altered, blacks, mids, whites. Green does not seem to be affected. This is in comparison with original/source footage as well as with a 4444 render.
Tested with various footage: camera originals, graphic files, Resolve own test generators(bars), tested on all available versions between 11 and 14, on both Mac and PCs.
Educated guess, as already mentioned in this thread: there seems to be a flaw in the way Resolve performs the RGB to YUV calculation.
FWIW, MediaComposer on Mac and PC renders identical levels for 422 vs. 444 codecs. No level shift there.
We're prepping a support case with BMD with samples, screenshots, waveforms, etc.
cheers,
BG
www.finale.tv