We have UC520 connected via SIP trunk to a provider. We have been experiencing bad quality when more than one line is connected to a conferencing system outside. So lets say more than one person call this conferencing system through the SIP trunk from multiple extensions. The audio when people are speaking is very choppy and robotic. As soon as all except one drop out, it becomes normal.
We have over 30 mbits/sec of bandwidth available at all time so I am not sure what could be causing this.
Have disabled VAD and looked at this article http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a008019ab88.shtml
but cannot figure it out. ANy help would be appreciated.