CTI Dialling - No audio until call connected

[richardwvm]

Hi Folks,

We seem to have an issue in testing, whereby calls placed via 3CXPhone in CTI mode with Snom 821 handsets result in no ringing and the audio only starts when the call is connected.

If I dial on the handset it rings and call connects, I dial the same number via 3CXPhone and I get silence until the call connects.

Is there something configuration I have missed that needs to be different? I haven't packet captured yet to see if there is a difference in the SIP negotiation, but that is probably the next step.

Regards,

Richard.

 

[NickD_3CX]

Is the snom phone a Local Extension or a Remote Extension behind an SBC? Also is the 3CXPhone on the same LAN as the snom?

I network capture would probably answer the question though immediately...

 

[richardwvm]

Hi Nick,

Thanks for the reply; everything on the local network subnet, so very basic set up. I haven't progressed this much yet as it would seem to be less clear cut than I originally thought.

The symptoms are actually intermittent, although always when dialling from 3CXPhone rather than the handset. So I need to be able to packet capture dialling with 3CXPhone when it works properly and when it doesn't.

Will post when I have more.

Regards.

Richard.

 

[richardwvm]

Okay, so a little progress made on this one. It would seem that it also does it if you CTI dial internally as well as externally.

As such I've packet captured the SIP session for an internal call, which is easier to replicate and also rules out any gateway devices or SIP trunks as factors. This is simply CLI dialling a colleague internally using 3CXPhone.

Not sure if this is helpful or not as to my untrained eye at least the session looks pretty normal.

Regards,

Richard.

 

[NickD_3CX]

If this was a call that had no audio, I can't see anything wrong with the capture either. The only thing I can suggest as a test, because the 2 extensions exchange audio directly between themselves by default so the capture does not contain any audio, is enabling "PBX Delivers Audio" for those 2 extensions from their extension settings and see if the issue remains. Also enable "PBX Delivers Audio" for any VoIP Gateways and/or VoIP Providers you have as well and see how it goes.

 

[richardwvm]

Yeah I was going to give this a try, but wanted to see if there was anything else I may have missed. Kinda resisted it thus far as for me it kinda misses the point if the PBX has to handle all the audio streams, when the hardware is designed to do point to point.

When I get more time, I'll give it a go and see if it makes any difference.