[FFmpeg-user] time padding when muxing

[Roger Pack]

> Suppose I have a 1 minute video and a 2 minute audio track.
>
> I want a muxed version:
>   20 sec black,  the 1 min video, 40 sec black
> along with the 2min audio-track.
>
> Is this possible using a single command?

I wonder if it's possible by inputting a single "black image" for the
first x seconds...but that doesn't feel too elegant either...
-r