[FFmpeg-user] Color Channel Expression
jonbae77 at gmail.com
Mon Jul 31 14:51:18 EEST 2017
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
> I see that you wrote a filter for this, but can you please give me an
example of how it works? I don't get it to run.
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