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 use heroku-buildpack-multi to combine it with a real buildpack.
To use this buildpack, you should prepare .buildpacks file that contains this buildpack url and your real buildpack url.
$ ls
.buildpacks
...
$ cat .buildpacks
https://github.com/heroku/heroku-buildpack-python.git
https://github.com/akomic/heroku-buildpack-ffmpeg.git
https://github.com/akomic/heroku-buildpack-ffmpegthumbnailer.git
$ heroku create --buildpack https://github.com/ddollar/heroku-buildpack-multi.git
$ git push heroku master
...
You can verify installing ffmpeg by following command.
$ heroku run "ffmpeg -version"