sudo apt-get install ffmpeg
я полуучаю Package 'ffmpeg' has no installation candidate
ffmpeg was replaced in previous releases by the avconv program from the libav project.
To install avconv you need to install the libav-tools package:
sudo apt-get install libav-tools
avconv is very similar to ffmpeg, but they also have some differences in syntax.
Edit: It seems Ubuntu 16.04LTS has again ffmpeg in their repositories,
so libav-tools is a dummy package and only creates an alias
avconv -> ffmpeg (and others)