[OT] rather advanced video editing question

[Petrus de Calguarium]

Michael Cronenworth wrote:

> You can use ffmpeg to take the two clips and output one with the
> video/audio tracks you want or use "kdenlive" to do the same thing in a
> graphical interface.
> 
> 
kdenlive always crashes and avidemux never seems to work for me. I guess I am 
unfamiliar with it and I am not sure whether I can save as flv.

I am comfortable with ffmpeg and have used it for simpler tasks a lot.

Would you please be more specific about the actual ffmpeg command so that I can 
concatenate file1 video + file2 video and overlay file3 audio.