Webcenter content 12c now has certified FFMpeg as a video conversion agent in place of FlipFactory (11g used it) . There is a sample in the documentation as well for this and gives a sample extraRenditions file . Here is the link for it:
http://docs.oracle.com/middleware/1221/wcc/WCCAA/GUID-71432403-9484-4FCF-8494-7AE5EC7D3C75.htm#WCCAA284
The best part with ffmpeg is the ease of installing it and use .
Another application which is supported is Telestream Vantage but it involves multiple dependency for installation .