ffmpeg unmet dependencies error in ubuntu 12.04

While I was trying to install ffmpeg

apt-get says it is already installed

but I was not able to fire ffmpeg as command

so I tried to remove it and then install it again

it said unmet dependencies

then I added 2 repositories to my sources.list file

nano /etc/apt/sources.list.d/ffmpeg.list
deb http://www.deb-multimedia.org wheezy main non-free
deb http://ftp.de.debian.org/debian sid main

then I installed 3 packages
apt-get install libopus0
apt-get install libavcodec54
apt-get install ffmpeg

and finally I got my ffmpeg command available.