[FFmpeg-user] Improve recording in .mp4 format

[Massimo Battistel]

> Works just fine for me. What are you trying to do exactly?
>

I would like to start a recording, access the file being recorded, seek to
a start point and play for n seconds (while recording).
With .mkv I just can play from the begin, but no seek (I used vlc 2.1.3
under Windows 7).

MB