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

Thu Mar 6 16:18:01 UTC 2008

It's clear now. Thanks everybody.

Andrea

From: mh at markholloway.com
To: androjoker at hotmail.com; steve.langstaff at citel.com; discussion at sipforum.org
Subject: RE: [SIPForum-discussion] What is the function of telephone-event?
Date: Thu, 6 Mar 2008 08:08:07 -0700

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

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.

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

MSN
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