Subject: RE: [SIP] DTMF digit handling

From: Christian Huitema <[email-masked]>
Date: Tue, 11 Jul 2000 09:27:56 -0700

> >        +-----------+
> >        | media     |
> >        | server    |
> >        |           | x   control
> >        +-----------+  xx
> >                         x
> >             .            x
> >             .       +---------+
> >            .        | app     |
> >            .        | server  | \
> >        RTP.      /  |         |  \
> >           .     /   +---------+  \ SIP
> >          .     /                  \
> >          .    / SIP                \
> >         .    /                      +-------+
> >     +-------+                       |       |
> >     |       |                       |       |
> >     |       |                       | UAS   |
> >     | UAC   |...................... |       |
> >     |       |                       |       |
> >     +-------+         RTP           +-------+

I would add one point. We are in year 2000, not 1980. Engineering for DTMF
is fine, but the next release of the "media server" in the above picture is
likely to use voice recognition, not DTMF. There have always be two camps
when it comes to carrying DTMF, in-band as in the RTP solution detailed
above, and out of band through the signalling channel, as proposed many
times. The two camps have been resorting to all kinds of comparison,
essentially balancing transmission overhead, which is lower in the
out-of-band scenario, and architecture simplicity, as in the above diagram.
But if you were architecting the system for voice recognition, then there
would be no debate whatsoever. To enable voice recognition, you will
definitely need an in band solution! The advantage of the above diagram is
thus obvious: designing the call flows for in-band carrying of DTMF enables
us to use the same flows for DTMF and voice recognition.

_______________________________________________
SIP mailing list
[email-masked]
http://lists.bell-labs.com/mailman/listinfo/sip

---

From: Michael Thomas <[email-masked]>
Date: Tue, 11 Jul 2000 09:37:45 -0700 (PDT)

> us to use the same flows for DTMF and voice recognition.

   Of course, if you're talking about in-band voice
   recognition which is monitoring a call, you're
   begging the privacy question. I might want my
   LindaTripper to listen in, but I sure don't want
   yours... or worse, a service provider's!

	       Mike

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 11 Jul 2000 12:41:59 -0400

Christian Huitema wrote:
> definitely need an in band solution! 

Agree 100%. Furthermore, once you do that, you'd really like your system
not to
look or work fundamentally differently if speech recognition is used as
opposed to
DTMF. Having them both come through the same, in-band stream provides
this uniformity
of interface. In fact, if the DTMF was carried through INFO, it would be
difficult to write
scripted applications (ala VoiceXML), since then the app server would
sometimes need
to handle the user input component of the script (when DTMF over SIP was
used), and
other times not (when speech recongition is used). Very bad. 

-Jonathan R.

-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

---

From: "Rajeev Gupta" <[email-masked]>
Date: Tue, 11 Jul 2000 12:27:25 -0700

To Christian's point:

> likely to use voice recognition, not DTMF.

There is a whole class of voice-activated applications that can be enabled
with IP voice. Essentially, the ingress gateway will multi-unicast the media
stream - one stream going to the current callee, other streams going to
multiple media servers (speech recognition, IVR,...). Note that different
sampling rates, codecs and other voice processing can be used on different
streams.

For example, "voice dialing" can be enabled by allowing the user to speak
certain keywords (as opposed to punching a long '#') which the media server
will recognize, and switch the call to a differnt call/service e.g. speaking
"keyword-XXX Dial 555-1212" will connect to new number 555-1212. Note that
the media stream for keyword recognition can be much more sparse than the
one for voice conversation e.g. only speech samples after certain silence
periods need be transmitted on this stream. Further, the media server does
not have to be contiuously "connected" to this media stream, since it is not
a TDM port, and hence the media server resources can be shared very
effectively among multiple users.

With this architecture, service providers can enable fancy services like
voice dialing for a fraction of the cost in a TDM architecture. As for
privacy concerns, you can choose whether you want this service or not (no
different than today's calling card applications).

Rajeev Gupta
empowerTel Networks
475 Sycamore Drive, Milpitas, CA 95035
Phone: +1 408 519 7136
Fax: +1 408 519 7399
mailto:[email-masked]
http://www.empowertel.com