i wrote a blog post about this a day ago, and maybe it answers your question a bit.
I found out today that the codec being used when making a PSTN call is now in some special conditions G711
G711 may be used for calls to the PSTN depending on a number of network characteristics:
- Round trip delay of less than 20ms
- Call originates from the LAN
So why change from RTAudio since we have been told that it is so superior? Well apparently RTAudio uses more CPU and is a wide band codec witch can not be used in a PSTN call anyway.
But if Communicator detects changes in the network characteristics, such as an increase in the round trip delay, the codec will automatically switch to RTAudio in order to ensure the call continues without issues.
Tommy Clarke | http://www.cinline.se