FFmpeg is a free software project that produces libraries and programs for handling multimedia data.
This package has been removed from Ubuntu 14.04 and was replaced by Libav. This decision has been reversed so that FFmpeg is available now in Ubuntu 15.04 again, but there is still no official package for 14.04.
This tutorial explains the steps to install FFmpeg in Ubuntu 14.04.
Step1: Add the repository.
Step2: Update the package list.
Step3: Install FFmpeg
#apt-get install ffmpeg