Mumble is an open source, low-latency, high quality voice chat software primarily intended for use while gaming. Mumble has an extremely fast response time offering high-quality audio with extremely low ms. This allows audio to be heard in a more real-time manner as opposed to other VoIP software such as Ventrilo, Teamspeak, Skype, Raidcall and others.
An in-game overlay is also available which displays users talking in the channel. Snapshot builds offer FPS and time in the overlay as well.
A special element of Mumble is its Positional Audio feature. Mumble's Positional Audio feature is facilitated through the use of a memory-mapped file using the Link plugin format. Guild Wars 2 provides the necessary positional data to the memory-mapped file, which in turn is accessed by Mumble to provide the positional audio effect. API developers can access the memory-mapped file in order to read character information that includes position and map identification, to name a few.
For documentation on the data contained within the MumbleLink file, see API:MumbleLink