I see so many people here who ask themselves what can be done for people who use buggy software (video decoders that don't pass the colorimetry information to the video renderer, video renderers that ignore colorimetry information that they get from the decoder), so I feel I should raise the question of whom this truly benefits:
- Those who use buggy software are unlikely to care about precise colorimetry. If they do care, they should switch to a different software anyway.
- Those who use software that properly handles this stuff will, at best, experience no negative effects from such a conversion. Usually, I'd expect that the matrix adaption will indeed harm quality.
So, the matrix adaption brings no real benefit to those whom it's supposed to help (those who should change their playback environment anyway*), while harming those who are already doing it right.
* If anyone is going to mention ffdshow and avisynth processing, I'm just going to tell them to manually insert colormatrix into the avisynth script themselves, if ffdshow can't handle colorimetry.
You'll notice that I have little to no sympathy for people who use broken software. I think that is all right, though, because it's already 2015, and stuff like LAV Filters, which respects colorimetry information, has been around for a long time already. Additionally, I remember that, also quite a while back, MPC-HC fixed EVR (perhaps only EVR-CP, I don't remember that well) to respect colorimetry information also, so the point that there are too few common video renderers that respect colorimetry information, if present, is also invalid.
You'll also notice that I only mentioned software. If the goal is playback on hardware players, then my reasoning becomes invalid, because then the act of "simply switching playback environments" becomes that much harder. And although I'm still in favor of using something that actually does it right for playback, even in those cases, I can acknowledge that this is unreasonable.