[FFmpeg-user] Color Channel Expression

[Jon bae]

2017-07-31 10:30 GMT+02:00 Paul B Mahol <onemda at gmail.com>:

>
> What exactly you tried?
>
> Perhaps you want premultiply filter?
>
> Yes I have a video and a lower third, and I want to overlay the lower
third. But my alpha channel from the lower third is not pre-devided with
the alpha channel, so  I need to do a channel division in ffmpeg.
Something like:

ffmpeg -i video.mp4 -i lowerthird.png -filter_complex
[1:v]geq=r=r/a:g=g/a:b=b/a[gq];[0:v][gq]overlay ... output.mp4