DTMF information.

admin
Joined:

Re: DTMF information.

Posted:Mon 21 of Sep, 2009 (09:12 UTC)
See SIP DTMF Signalling
There are 3 common ways of sending DTMF on SIP Calls: INFO, RFC-2833, and in-band.
In your example invite, the lines:
a=rtpmap:100 telephone-event/8000
a=fmtp:100 0-15
indicate that RFC 2833 style DTMF is being use.
sebyfrancis
Joined: Wed 16 of Sep, 2009

DTMF information.

Posted:Wed 16 of Sep, 2009 (03:02 UTC)
Hi,

I've a SIP capture file and would like to see the info regarding DTMF, whether it is setup to send "out of band" or "in-band" (RFC-2833)? In which message should i look this info?

In particular, i'm trying to find it in INVITE message. Here is a sample one: Could you please help me to understand this:

INVITE sip:1234567890@x.x.x.x:5060 SIP/2.0
Via: SIP/2.0/UDP y.y.y.y:5060;branch=z9hG4bK02B057e13c82ec4ab9c
From: <sip:1234567891@y.y.y.y;isup-oli=0>;tag=gK0205c4cf
To: <sip:1234567890@x.x.x.x>
Call-ID: 2369_3059@y.y.y.y
CSeq: 31769 INVITE
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,REGISTER,INFO,SUBSCRIBE,NOTIFY,PRACK,UPDATE,OPTIONS
Accept: application/sdp, application/isup, application/dtmf, application/dtmf-relay, multipart/mixed
Contact: <sip:1234567891@y.y.y.y:5060>
P-Preferred-Identity: <sip:1234567891@y.y.y.y:5060>
P-Charge-Info: sip:1234567890@y.y.y.y:5060
Supported: timer,100rel
Session-Expires: 3600
Min-SE: 90
Content-Length: 280
Content-Disposition: session; handling=required
Content-Type: application/sdp

v=0
o=Sonus_UAC 15387 903 IN IP4 y.y.y.y
s=SIP Media Capabilities
c=IN IP4 y.y.y.z
t=0 0
m=audio 7642 RTP/AVP 0 18 100
a=rtpmap:0 PCMU/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:100 telephone-event/8000
a=fmtp:100 0-15
a=sendrecv
a=maxptime:20

Sebb.