[SIPForum-discussion] What is the function of telephone-event?

[Mark Holloway]

G729 does not support inband DTMF because the codec compresses the audio.
You must use out of band.  Therefore, telephone-event is used to tell the
other endpoint how it should receive DTMF tones.  If you are using G711 you
should be able to support inband.  If you are using a compressed codec you
should consider using out of band.  This can be RFC 2833 or SIP Info Method.
Regardless, not supporting telephone-event reflects a poor SIP
implementation in my opinion. 

 

 

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Andrea Puddu
Sent: Thursday, March 06, 2008 7:09 AM
To: Steve Langstaff; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] What is the function of telephone-event?

 

Thanks Steve.

Why did you talk about low bit-rate codec? I understood the matter about
dtfm out of band, but it is not clear to me why it should impact low bit
rate codec (e.g. g729).

Thanks,

Andrea





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Subject: RE: [SIPForum-discussion] What is the function of telephone-event?
Date: Thu, 6 Mar 2008 05:01:34 -0800
From: steve.langstaff at citel.com
To: androjoker at hotmail.com; discussion at sipforum.org

"telephone-event" is a method for passing e.g. DTMF signalling in an RTP
stream.

 

The "101" (or any payload type in the range 96-127) refers to a dynamic
payload type.

 

So a stream that negotiates to use "101 telephone-event" may e.g. pass
keypresses

using RTP payload type 101 rather than "in-band".

 

The risks you face in removing telephone event support are that if you are
using a

low bitrate codec such as G.729, or you are using equipment that does not
expect

to see DTMF "in-band" then users may lose the ability to control e.g. IVR
equipment.

 


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From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Andrea Puddu
Sent: 06 March 2008 12:15
To: discussion at sipforum.org
Subject: [SIPForum-discussion] What is the function of telephone-event?

Hello guys,

as the network here does not completely support "telephone event" in SDP
they asked me to set up phones to not include "telephone event".
I have looked at some RFCs .... but I couldn't understand what the telephone
events are useful to.

Do you see any risk to remove the telephone event, in particular the 101
telephone event?

thanks 1000.

Andrea

 


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MSN Video Interviste, <http://video.msn.com/?mkt=it-it>  concerti, news e
videoclip! Solo su MSN Video! 

 

  _____  

MSN Video Interviste, <http://video.msn.com/?mkt=it-it>  concerti, news e
videoclip! Solo su MSN Video!

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