We have a client with a UC560 (8.0.5 software pack) using a SIP trunk for PSTN connection. Calls work fine. However, this client has been complaining about poor MoH sound quality. The SIP trunk is using G.729, so we're transcoding from G.711 for MoH (and CUE), but even running the trunk as G.711 has made no difference. The complaints are distorted or dropped audio, and have occurred with several different sources (both .au files and external sources).
Basically, my question is: How do you get good MoH quality over a SIP trunk? Is there a particular source (or type of content) that works better than others?
This client has been complaining about this for weeks, and I none of my testing has been able to do much of anything. Any advice would be appreciated.
Amos Data Systems
Try disabling Voice Activation Detection (no vad). G.729 & MoH isn't a great combo to begin with but using VAD makes it worse. VAD can also influence the quality of MoH on G.711.
Interested to hear how the VAD suggestion works?
Also interested to know the SLA guaranteed by the Sip Trunk SP and if they have a demarcation router at customer facility?
it's some CLI work. Here's an example (this is from an CME-UC520 SIP trunk over an IPSEC connection):
dial-peer voice 21000101 voip
description ** Outgoing internal call to SIP trunk **
destination-pattern 2.. *** other site has 2xx DNs***
session protocol sipv2
session target ipv4:172.16.50.126
ip qos dscp cs5 media
ip qos dscp cs4 signaling
This is an CME 4.3 based example. The CME assumes G.729 as default (at least the command codec G.729 disappears after adding).
I'll make this change as soon as I can and let you guys know what happens.
To Steven: there is no router from the provider onsite. Not sure about the SLA. I'd have to check into that.
My only thought there, was that QOS markings for RTP media may be getting stripped off and that could be a contributor (the wide open Internet) with no service level agreement.
If MOH doesnt sound bad locally especially.
You could probably test out the MOH quality during off peak hours to see if they is any difference. CCA does not support it but in CLI there are commands you can use to buffer the audio file using system memory. That would help out with the choppy audio. Alternatively you could also record the original MOH file at a higher bit rate so that when you convert it to an au file you will have less of an audio loss.
I wonder if we could use PCM Capture.
The PCM Capture window appears when you choose Troubleshoot > Telephony Diagnostics > PCM Capture.
From this window, you can troubleshoot voice quality or audio issues by generating a PCM (pulse code modulation) capture for a specific voice port, as instructed by Cisco support.