This may or may not be a problem on your box.
If you find that ffmpeg is being held back and/or you are having problems with vlc-nox, then this is what I had to do.
1. Comment out the Debian unstable/sid repo
2. apt-get remove --purge ffmpeg
(This will remove other files too, don't worry, we'll get them back)
3. apt-get install ffmpeg
4. Re-enable Debian unstable/sid repos
5. apt-get update & apt-get dist-upgrade (or if you prefer apt-get upgrade)
All should be ok.
