Starting in version 3.5, Miro supports video conversions. This
requires ffmpeg and, for conversion to Theora, ffmpeg2theora.

Unfortunately these cannot be shipped in the main Fedora repositories
due to patent issues, but if you live in a legal jurisdiction where
software patents are not valid, feel free to enable a third-party
repository and install the missing components as such:

# yum install ffmpeg ffmpeg2theora

Note that binary distributions of ffmpeg often are not compiled with
libfaac support, due to licensing issues, so you might not be able to
generate MP4 files. Conversion to Ogg Theora/Vorbis and MP3 should
work fine.

For more details, see:
http://www.getmiro.com/userguide/troubleshooting.html