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Re: [codec] #5: Mention DTMF in requirements

Marc Petit-Huguenin <petithug@acm.org> Sun, 28 March 2010 15:35 UTC

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Date: Sun, 28 Mar 2010 08:36:13 -0700
From: Marc Petit-Huguenin <petithug@acm.org>
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Cc: "codec@ietf.org" <codec@ietf.org>, "stephen.botzko@gmail.com" <stephen.botzko@gmail.com>
Subject: Re: [codec] #5: Mention DTMF in requirements
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I disagree with the "SHOULD".  RFC 4733 and RFC 4734 takes care of DTMF and much
more, so this must be an explicit non-goal.  This is an *Internet* codec that we
are talking about so it should reuse as much as possible of the existing
Internet framework.

And BTW, RFC 473[34] is not out of band, it's codec switching.  RFC 47[34] is an
audio codec, simply very good at compressing a very specific set of
frequencies/phases, and replacing everything else by silence.  RFC 4730 and RFC
2676 are out of band.

On 03/26/2010 03:37 PM, Michael Knappe wrote:
>  I would agree with 'should'. Lot's of dtmf out there still, but also
> out of band options (rfc 2833 / 4733) that make in-band carriage less a
> concern for SIP telephony applications.
> 
> Mik
> 
> *From*: codec-bounces@ietf.org <codec-bounces@ietf.org>
> *To*: Christian Hoene <hoene@uni-tuebingen.de>
> *Cc*: codec@ietf.org <codec@ietf.org>
> *Sent*: Fri Mar 26 18:10:31 2010
> *Subject*: Re: [codec] #5: Mention DTMF in requirements
> 
> Perhaps analog DTMF carriage is a SHOULD?
> 
> I agree that out-of-band is preferable, however, there still are
> scenarios where coded DTMF tones will be sent.  It would be nice (though
> IMHO not essential) for this carriage to work.
> 
> Stephen Botzko
> 
> On Fri, Mar 26, 2010 at 3:04 PM, Christian Hoene <hoene@uni-tuebingen.de
> <mailto:hoene@uni-tuebingen.de>> wrote:
> 
>     Hi,
> 
>     > If the point of this issue to allow this codec to be used to
>     successfully
>     > transit an IP network between two TDM networks,
> 
>     which is not the primary use-case.
> 
>     > I'd suggest that out-of-
>     > band tone transport is far preferable to trying to ensure that the
>     codec
>     > will carry the tones adequately to allow them to be detected after
>     > regeneration.
> 
>     I totally agree. Out-of-band is much better than inband.
> 
>     Sorry for my radical view but I believe that analog DTMF is an old
>     and obsolete technology not worth considering anymore.
> 
>     Christian


-- 
Marc Petit-Huguenin
Personal email: marc@petit-huguenin.org
Professional email: petithug@acm.org
Blog: http://blog.marc.petit-huguenin.org

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