Mumble has become popular for voice conferencing within the Debian organisation.
Specific reasons for this popularity:
- simple to set up (compared to Asterisk or FreeSWITCH)
- offers good quality multi-person RTP stream mixing from a central server
- Although Mumble is based on an open protocol, it is not as widespread as other protocols like Jabber and SIP
- Jabber and SIP users (e.g. with desk phones or Google Talk) can't easily join a Mumble conference
- In a world where Jabber servers are becoming more widespread, Mumble server (murmur) becomes an extra process that must be supported
- The mumble server is commonly used with the celt codec, which has raised various concerns
- which SIP proxies (repro and kamailio) support multi-party call set up?
- which Jabber servers (e.g. ejabberd) support multi-party call set up?
Some of the relevant software (maybe not packaged yet):
SIP Express Media server (SEMS): https://github.com/sems-server/sems
SylkServer (servers both SIP and Jabber)