Mumble moving on to Opus codec?

[roxarn]

So now that the developement of CELT has stopped/CELT has been merged into the Opus codec, will mumble be moving on to using the opus codec? And if so, how soon and how would it affect backwards compatability to older clients using CELT?

[razunter]

Would be great.

[kissaki]

Integrating Opus into Mumble has been the plan for a long time now.

In fact, Opus is already available in the current source, and (potential) snapshots.

Mumble has been using a codec agreement for some time now, as in the past additionally to Celt 0.7, Speex was used for low bitrates. Since Celt 0.11 has been integrated into Mumble, Speex has been dropped, but the codec agreement logic is still in place so the clients will use Celt 0.11 when everyone has it, or 0.7 as a fallback. Opus goes in there transparently - when all clients can use Opus, Opus is used. If not, the client will fall back to a common codec.

1.2.4 (and the source/snapshots) introduce a server-side threshold, which can be set so Opus is used even if a specified percentage of users do not have it. This threshold is zero by default, at the moment - so everyone will have to have Opus in order for it to be used - to make sure everyone can talk and hear. Server admins can however change it, so e.g. if > 50% of ppl have Opus, Opus is used - or to host Opus-only servers.

At a later time, the threshold will also be used for the switch-over of deprecating Celt in favour of Opus, when enough people will have recent enough versions of Mumble - much like the 1.1.x backwards compatibility client will die with Mumble 1.2.4 as pretty much everybody has moved to 1.2.x by now.