[Freeswitch-users] Re- DTMF 2833 issue

[Andrew Keil]

To FreeSWITCH Users,

I have just noticed when making calls internationally to the UK from Australia that the following SDP sometimes happens when the call lands on FreeSWITCH:

d5f14e47-2156-4236-be16-4eef1b7e9d3d 2018-10-04 06:59:28.819816 [DEBUG] sofia.c:7301 Remote SDP:
d5f14e47-2156-4236-be16-4eef1b7e9d3d v=0
d5f14e47-2156-4236-be16-4eef1b7e9d3d o=sbc-uk-mr-dh05a 451499 139728 IN IP4 XXX.XXX.XXX.XXX
d5f14e47-2156-4236-be16-4eef1b7e9d3d s=sip call
d5f14e47-2156-4236-be16-4eef1b7e9d3d c=IN IP4 XXX.XXX.XXX.XXX
d5f14e47-2156-4236-be16-4eef1b7e9d3d t=0 0
d5f14e47-2156-4236-be16-4eef1b7e9d3d m=audio 62754 RTP/AVP 8
d5f14e47-2156-4236-be16-4eef1b7e9d3d a=rtpmap:8 PCMA/8000
d5f14e47-2156-4236-be16-4eef1b7e9d3d a=ptime:20

This then creates the following message around call answer:

d5f14e47-2156-4236-be16-4eef1b7e9d3d 2018-10-04 06:59:28.839799 [DEBUG] switch_core_media.c:5766 No 2833 in SDP. Liberal DTMF mode adding 101 as telephone-event.

>From this point on DTMF is NOT detected by the FreeSWITCH IVR service.  I assume I would then need to use mod_dptools: start_dtmf to detect the DTMF tones within the channel.  Which I am yet to test.

However my main question is whether there is a channel variable that would enable me to check whether 2833 support is not inside the SDP?

Regards,

Andrew Keil


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