Title: RFC4733 DTMF not detected with PJSIP SIP trunk, but in-band DTMF works
Hello everyone,
I am having trouble receiving RFC4733 DTMF through a SIP trunk using chan_pjsip.
My setup:
- Asterisk version: [Asterisk version]
- OS: Debian running in VirtualBox
- SIP transport: UDP
- Channel driver: chan_pjsip
- SIP provider: AliveNet / NeoSIP in Japan
Asterisk makes an outbound call to a mobile phone, and the dialplan uses Read() to collect keypad input from the person answering.
With in-band DTMF, I can receive digits, but detection is unreliable. I would like to use RFC4733 instead.
I tried setting dtmf_mode=rfc4733 on the trunk endpoint, but keypad input was not detected. During troubleshooting, I also saw the endpoint still showing inband after changing the configuration, so I am unsure whether the setting was applied correctly.
I have contacted the provider to ask whether they support RFC4733, but this has not yet been confirmed.
Could someone help me understand:
- How can I verify that the active endpoint and a new call are actually using the intended DTMF mode?
- Which parts of the SIP/SDP exchange should I check to confirm that telephone-event has been negotiated?
- How can I determine whether incoming RTP contains DTMF events, or whether the provider is delivering only audible DTMF tones?
- Which logs and configuration sections should I provide to troubleshoot this?
I can provide my Asterisk version, sanitized pjsip.conf, SIP/SDP traces, and RTP/DTMF debug logs.
Thank you for your help.