Break ffmpeg transcoding out of nginx container

[duckfullstop]

Bringing ffmpeg into the nginx container seems a bit silly, considering nginx is supposed to really just be a reverse proxy / RTMP endpoint. As such, it'd probably make sense to have ffmpeg spun out to a separate container (that way it can be scaled independently).

You'd need to find some way of signalling to the ffmpeg container to begin / end transcoding; right now it's done with an exec_push config variable which calls a script (which then runs ffmpeg). You could probably just modify this script to signal to the ffmpeg container to start transcoding with the appropriate options.

If I had more time I'd probably make this a Kubernetes call to spin up a ffmpeg container on demand, but alas, that seems horribly overkill for this implementation.