This is a Heroku buildpack for using ffmpeg in your project.
It doesn't do anything else, so to actually compile your app you should combine it with a real buildpack.
To make it work with Ruby (Rails) buildpack do:
$ heroku buildpacks:add https://github.com/heroku/heroku-buildpack-ruby
$ heroku buildpacks:add https://github.com/znupy/heroku-buildpack-ffmpeg-x264-ogg
$ git push heroku master
...
You can verify installing ffmpeg by following command.
$ heroku run "ffmpeg -version"
If you want to use your own ffmpeg binary, fork and rewrite following line.
https://github.com/shunjikonishi/heroku-buildpack-ffmpeg/blob/master/bin/compile#L10