[FFmpeg-user] Automatically Stretch Contrast

[Eric Duran]

I'm trying to write a filter that will automatically stretch the contrast
of an input video.

The method I thought of is:

1) Separate the L, U and V channels.

2) Apply histeq to the L channel.

3) Recombine the channels.

I'm new to ffmpeg, so I've been able to do 1 and 2, but not sure how to
implement #3. What I have so far is:

ffmpeg -i in.mkv -vf extractplanes=y,histeq=strength=0.3:intensity=1 out.mkv

Which extracts the L channel and autocontrasts it, but I'm not sure how to
recombine it with the U and V channels. Maybe use mergeplanes? Help!