Get the okay for copy + pasted ffmpeg code

[chrisranderson]

From https://github.com/chrisranderson/beholder/issues/33#issuecomment-318533909.

[jart]

At Google, we're sort of not allowed to check-in multiple third party projects into one directory. We'd probably have to pull out that file, set up a third party directory for it, write the metadata, get approval, and all that jazz. It would take us quite a bit of time. Would be simpler to probably just write a quick one-off function.