Opus is a new audio codec covering a wide range of use cases. You can read more about the codec (at least) here and here.
If you want to get started with it, just try a freshly rebuild gstreamer-plugins-bad-free package which packages the opus plugin.
You will be able to use the en- and decoders in your normal gst pipeline.
It should soon land as an update on Fedora near you.
The update has landed in updates testing:
su -c 'yum update --enablerepo=updates-testing gstreamer-plugins-bad-free-0.10.23-11.fc18'