Solved Duplicate DTMF Signals being send (Outbound through twilio)

[Grant Moxom]

We have 3CX setup to make outbound calls through twilio.
When we call an external digital receptionist it asks us to input a number (1-5). If we enter a number (eg 5) the digital receptions hears us pressing "5" multiple times. We only press it once though.
The PCAP from 3cx also shows repeated inputs (even though we only pressed it once) and the same is shown from the trunk end (twilio) that it is recieving muliple inputs.
Any idea why this is happening and how we can fix it?

 

[ChrisC_3CX]

The fact that you see it being sent multiple times is actually expected and is nothing out of the ordinary. Since yu've already got a packet capture, what I recommend you check for next is the packets denoting the end of the DTMF input. You will not see these in the SIP Flow so you could filter the capture with "rtpevent". You should see something like this:


As you can see there are 5 packets to denoting a single DTMF input and then 3 packets denoting the end. The number of packets denoting the DTMF input may vary depending on the endpoint used (IP Phone, 3CX App, etc) but the "end" packets should be three.


To get a bit more info on this:

When we call an external digital receptionist it asks us to input a number (1-5). If we enter a number (eg 5) the digital receptions hears us pressing "5" multiple times

• Just to clarify, how have you determined that this is what is happening?

• Could you also let us know what version 3CX you are running and what the endpoint is?

• Does this issue only occur when you call this specific external IVR? Have you tried other external IVRs and faced the same issue?

• Does everything work fine if you call an internal IVR(one within this same 3CX Instance)?

 

[Grant Moxom]

Thanks for your reply.
1: THere are 3 end packets as your describe

2: This is happening on UK numers, not sure if it happens on German numbers (where we are located)
3: Version = 16.0.9 - Endpoint = Webclient + Android app (in this case I was testing with the android app)
4: It happens for our UK team on all of the external IVR's - don't know a german IVR to test against and an internal IVR works fine
5: Calling the IVR from my personal phone works fine

Thanks fro your help

 

[ChrisC_3CX]

Could you give the following a try and let me know what happens:

1. In the Management Console go to SIP Trunks and edit the Twilio SIP Trunk.
2. Go to Options and scroll down to where it says "Codecs"
3. Remove all Codecs except G.711 U-law. You should end up with this:

4. Click on OK on the top and then try reproducing the issue again. Do you get the same behavior?

 

[Grant Moxom]

Ah thanks, (though A-law is the right one for my region)
That fixed that issues - however a-law from the webclient is problematic (this is a known problem in the webclient) because the webclient forces opus which means it is transcoded in 3CX side and the 3cx Transcoding is not as good as the twilio transcoding - therefore I have to send the data to twilio as OPUS so call quality is not sacrificed. That said I'd be happy to use A-LAW from JUST the phone application which does support it - but if I set the extension to only use alaw and keep opus as a possible codec in the trunk it still sends through OPUS for some reason meaning I get the same issue as always

 

[ChrisC_3CX]

In that case, do bear in mind that in 3CX v18 DTMF should work just fine even when using OPUS so you'll be able to revert the settings once you upgrade if you prefer.

 

[Grant Moxom]

Upgrading is difficult though as I can't slowly migrate people away from the 3cx extension and instead have to completely redesign their way of working rather than slowly move them. But all good thanks a lot this answers my question.

 

[ChrisC_3CX]

You're very welcome!

Please feel free to start a new thread should you need anything else.