[FFmpeg-user] psnr range

[Le Chiffre]

I have found that the psnr result from the psnr filter, vs the psnr that is
part of libvmaf (calling it via ffmpeg), differs slightly, generally under
1%. I suppose the implementation is different.

This seems ok. What is more interesting is that libvmaf-psnr clearly has a
range up to 60 whereas the ffmpeg psnr seems to go past 90.

1. What's the full range of ffmpeg's psnr value?

2. Is it likely that libvmaf is simply capping the result to 60? Since for
their purposes this might be the limit of perception?

If I take an average over a 15 minute video, I get a 2.3% difference
(ffmpeg is higher), ignoring frames where ffmpeg reports inf psnr. If I cap
to 60, the difference in averages is just 0.01, so this is negligible. But
that's because the number of nearly identical frames (runs of complete
black) is so small.

Should I really just not worry about it?