I can not give you specifics on how to install FFMPEG correctly as I am not a server tech. I have shown FFMPEG works althougth I know the binary I found only does like wmv and avi video's as it states. The documentation on FFMPEG is very sketchy as after many years its still beta software not even having a final release yet.
The command we use is this
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We include this as an option if you have it on the server but we make no guarantees on what video types your server's install supports.