Hi,
Could this software/service be used to support functionality to transcode video/audio on upload for MediaWiki? http://pandastream.com/
It says it has "Support for the numerous encoding profiles FFmpeg supports" and according to the Wikipedia article this includes Ogg Theora and Vorbis.
As a service it uses Amazon's Web Services, but I guess it would be cheaper for WMF to run it on its own services.
They call themselves open source and I don't know what this license is called, but it certainly seems very liberal: http://github.com/newbamboo/panda/tree/master/LICENSE
cheers Brianna