[FFmpeg-user] scale overlay video

[Alex Vasilenko]

Hello, 

Thanks to Liam and Paul now I know how to overlay watermark at the beginning of the video. But there's different problem:
I need to scale watermark width to the video width - 20px. I know it's possible to use movie=watermark, scale=width:height, but the problem is that I don't know the original width/height of the video and there can be other filters that alter source video dimensions (e.g. scale, tranpose).

So the question is: is it possible to get dimensions of different video stream in scale filter?

Thanks in advance,
-- 
Alex Vasilenko