[FFmpeg-user] ffmpeg makes some sources darker

[Andy Furniss]

Carl Eugen Hoyos wrote:
> Andy Furniss <adf.lists <at> gmail.com> writes:
>
>> I think it's because the master is flagged as rec709 but the yuv
>> and I guess hevc aren't.
>
> While this is at least likely (sorry for my original comment, I don't
> know what I looked at), the source code seems to disagree:
> colour_primaries etc. are read from both h264 and hevc files and are
> written both when encoding with libx264 and libx265. You could test
> to set them with the following: -color_primaries bt709 -color_trc
> bt709 -colorspace bt709 (with a faster preset), it shouldn't make a
> difference but who knows...
>
> And please also test with -vcodec x264, Carl Eugen

With Jims command line neither libx264 or libx265 pass through the 709
(it's not shown by ffmpeg -i ...).

With the three options above both do show 709.

Haven't had time to think more about the png "issue" yet ie. why does
ffmpeg (seem to) make pngs with two gamma values coded in when the
source is 709 flagged (but not from yuv when 709 is stated as
in_color_matrix).