Rigth now there are very few plugins. From the developers there is MiniDLNA, Transmission, and Firefly. I'm working on Serviio and JDownloader, and someone else is working on Couchpotato/Headphones/Sabanz? (I don't remember that last one).
That's about it. Serviio uses ffmpeg, so that might work for you.
It going to take awhile for plugins to start coming out because they're new and not completely documented.