SpeexRTP

From XiphWiki

Speex over RTP

While Ogg is the native file format for speex data, an RTP encapsulation is a natural fit with the codec's low latency design.

Fortunately, unlike Vorbis and Theora, Speex has no required setup headers, so the application is easy. A draft exists. It just needs to be reviewed and then taken through the formal ratification process with the IETF.