Outbound Calls: ringing audio not always audible

[davide.bonavita]

Hi there,
We updated 3CX some weeks ago but only in the last few days this started to happen.
Only randomly when the users make outbound calls they don't hear any ringtone, they only hear the callee audio once the call is connected.

I've checked the dumps and it seems the providers (both Twilio and DIDWW) do send a 180 and a 183 code right away.
It this particular case no one answered after 60 seconds, but the number is indeed ringing when we call it from a mobile.



The annoying thing is that some users tried tried to log off and back on again (Desktop web app on Windows) without success, but if they completely restart the computer it starts to work well again... But only for a while.
Nothing has changed in our setup, the users are all working from home all around the world. The firewall test shows all green and I've also tried to restart the instances (it happens on both our servers).

Happy to provide more info if needed.

Thank you for your help!

 

[OlegR_3CX]

Hello Davide.

Typically 183 contains SDP (as seen in your screenshot too) and is used to play media before the call is connected, so you will need to check if the silence is in the audio stream?

 

[mbelsky]

I have seen something like that for users using a USB headset, where they will randomly not hear outgoing ringing, but will hear the audio after the call picks up. I fix it by going to Sound Settings (in Windows) > scroll to bottom and go to App volume and device preferences > for each Teams entry (I have either 2 or 3 usually), change both the Speakers and Microphone drop downs for each Teams entry to the headset device. If already on the headset device, change all to Default and then back to the headset.

 

[davide.bonavita]

A bit of update, : checking and comparing our pcaps with Twilio's we figured out the issue is on the carrier side (Vodafone España and Telefonica), they are sending empty audio streams. They opened a trouble ticket with them