I am running CUCM 11 and UCCX 11 with a SIP trunk for PSTN connectivity. I have several UCCX queues that work great internally but as soon as I make a call inbound from the SIP trunk I get audio clipping after a Call Unhold event.
Here is the basic UCCX script:
- call in queue
- call hold
- delay 30 seconds
- call unhold
- Play prompt ( the first 2 seconds of the prompt is clipped off and is just silence)
Here is the call flow:
Here is part of my cube config:
voice service voip
ip address trusted list
allow-connections h323 to h323
allow-connections h323 to sip
allow-connections sip to h323
allow-connections sip to sip
fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback none
midcall-signaling passthru media-change (I've tried this with media-change and without)
I have seen these clipping issues when we call outbound to a PSTN and SIP trunk is not set to send PRACK for 1XX messages.
So you need to make sure SIP trunk is set to send PRACK for all 1XX messages received from service provider.
In the SIP trunk early offer support for voice and video calls should be enabled as well.
I opened a TAC case but the engineer was not able to fix the issue and I needed to get the issue resolved. Unfortunately I just added a couple seconds of padding to each message played in UCCX and all worked fine.
I wish I had found the root problem for the issue instead of putting a work around in place, but I needed to get the call center up and running.