[SIPForum-discussion] DTMF tones and digit in SIP

[Broussard, Dan]

If you use a codec other than G.711 you are going to have a hard time
running DTMF over the RTP. 
Also IETF has made RFC 2976 [SIP INFO] obsolete since RFC 2543 is
replaced by RFC 3261.
Your only real alternative is to use RFC 2833 to recognize and transmit
DTMF.  

Dan Broussard
Level 3 Communications

-----Original Message-----
From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of MULTACH, JEFF
(ATTLABS)
Sent: Thursday, September 13, 2007 8:45 AM
To: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] DTMF tones and digit in SIP

It is unclear if the question is in regards to the reason for DTMF or
the method used to carry it.

Along the first path of discussion, DTMF signals in the middle of
applications can be distorted, especially when using codecs which
perform compression. Therefore there is a need to have a method to carry
this in a manner so that they can be accurately reproduced.

This is true not only for IVR type systems (including voice mail
systems) but also for many alarm systems, a case which is often
overlooked.

Alarm systems have multiple ways of transmitting their signals based on
their design. One of which is using a rigid DTMF sequence, so not only
does recognizing the DTMF tone become important but also the duration of
that tone.

-----Original Message-----
From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Sai Prabhakar
Varanasi
Sent: Thursday, September 13, 2007 1:56 AM
To: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] DTMF tones and digit in SIP

DTMF digits are mainly useful for IVR applications. 


Thanks & Regards,

Sai Prabhakar Varanasi,


-----Original Message-----
From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Sumanta Sen
Sent: Thursday, September 13, 2007 9:19 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] DTMF tones and digit in SIP

Hi All,

What is the practical purpose of carrying DTMF digits in SIP using INFO
or RTP Payload ?

Thanks,
Sumanta


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