Ffmpeg libraries

Hi, I recently got an Raspberry PI 2, its a great machine, and OSMC is really great, I plan to use it as a media center and a torrent box, I have bought a 5TB external hard disk for that.
Playing movies is great, thanks for your hard work.
Only concern is: I have succefully installed rTorrent and ruTorrent, but when I access ruTorrent it has a message:

screenshots: Plugin will not work. rTorrent user can't access external program (ffmpeg)

when I try to install ffmpeg with

sudo apt-get install ffmpeg

It shows me an error

E: Package 'ffmpeg' has no installation candidate

I am tempted to install an external repository for this but I’m afraid I will damage my installation.

What do you recommend?

ffmpeg is built statically in Kodi, so you won’t break anything with external library


Is there any way to access the ffmpeg capabilities in OSMC from the command line? I have used them in the past to transcode flac files to mp3 using a script.