Jim Worrall wrote:
I’m not really looking for perfection, just don’t want the transcodes to be
darker on any device.
So my testing has shown, for both libx264 and libx265, the problem is
solved (meaning the pngs come out with the same luminosity, which
is good enough for me) either of two ways, using ffmpeg options:
-color_primaries bt709 -color_trc bt709 -colorspace bt709
or using x264/5 params:
-x264-params colormatrix=bt709:colorprim=bt709:transfer=bt709
These alternatives are not quite parallel, I know. Frankly I don’t
really understand them. I’m guessing colormatrix is the only one
needed but haven’t tested. In any case, it seems ffmpeg or libx26* needs
this direction.
Well I’m really confused now. When I went back to the full source
file (rather than the 1 minute clipped from it, which was a
stream copy), the transcode with x265-params came out BRIGHTER
than the source. My head’s about to explode. I’m just going
to stick with this result.
Ouch, did the new file show as 709 with
ffmpeg -i newfile.mkv
I can't reproduce this one myself x265-params seems to work.
If for some reason the newfile didn't get flagged as 709 then it could
be possible to get brighter with different colours in a scene.
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