I've been doing some tests, considering the possibility of moving to NVENC for the projects I previously reserved for x265, since I was assuming that x265 had better compressibility at the same file sizes, even though it was slower due to it being on the CPU, but some tests I've been doing seem to suggest that may not necessarily be true, but I need to do more tests to confirm that.
Anyway, one of these tests would involve HDR content, and in order to do that I am using setparams to set color space values. For my tests that's enough for now, but if I ended up using this workflow for my full projects, I'd need to make use of the "Mastering Display" and "Content Light Level" sections of the Side Data tab, as NVENC doesn't have its own sections for those settings like x265 does.
However, I noticed Maximum Luminance was limited to 4000 nits. While I of course do not have a display greater than 4000 nits, much of what I work with is video game content which can regularly exceed that. The problem is, if MaxMDL is considerably lower than the MaxCLL, many TVs will assume anything above MaxMDL should be clipped, and so it will use tonemapping curves that aren't the most optimal for the content. The HDR10 spec allows for content up to the 10,000 nit level, and MaxMDL should be allowed to be set that high as well.
Similarly, MinMDL seems to have a minimum of 0.001, whereas I am using an OLED that has absolute perfect blacks, so I'd prefer to set this to exactly 0, since most of my content does indeed make use of perfect blacks.
So are these limitations put in place by something in ffmpeg, or were these just values you placed here based on some other information perhaps? If these could be expanded to allow the full range of 0 through 10,000, that would probably be better. Min Luminance doesn't need to go that high of course, but if you have a screen with a 1000:1 native contrast ratio and 1000 nits, then its minimum black level would be 1 nit, which isn't unrealistic, so I'd probably place the upper limit for that maybe at 5. Although I don't think many TVs actually do anything with the MinMDL setting, but it would just be better to have a wider range of possible values if possible.