Convertophile's back-end has been re-written completely! Well, at least the part of it which interfaces with FFmpeg, which is the actual back-end. You can find the new back-end, "FFCommander," here! I've abstracted it completely. If you ever wanted to write a C# app on your own which uses FFmpeg, it's not really a bad option. I've found all the available open-source wrappers to be really clunky, so FFCommander just speaks with FFmpeg executables directly through the command line.

Also, compression with hardware acceleration works now. Enjoy!