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

I agree that there is a pretty strong consensus that carriage of "analog"
fax and modem signals is a non-requirement.  If by "payload switching" we
are talking about switching codecs, then that is beyond the charter scope.

I am thinking that we are getting a bit too focused on testing methods.  In
my view it would be more efficient to capture use cases, and derive MUST and
SHOULD requirements from them first.  Then go back and figure out what we
will test and how we will test it.

Stephen Botzko

On Tue, Apr 6, 2010 at 7:47 AM, Kevin P. Fleming <kpfleming@digium.com>wrote:

> Raymond (Juin-Hwey) Chen wrote:
>
> > 2. Did you ever test your CODEC for other telephony signals, such as
> > /ANSam, ANS, CED, and CI tones? These tones are needed in order to
> > detect modems and fax machines and switch to an appropriate payload.
> > What about progress tones?
> > [Raymond]: No, we didn’t.  However, if these are single-frequency tones,
> > I would expect that it should be easier for a typical codec to pass
> > these tones than to pass the dual-frequency DTMF signals without causing
> > significant degradation in the subsequent processing of these tones.
>
> This is pretty much a dead-end based on the other comments on this list,
> but in general, no, most of these tones are *not* single-frequency
> simple tones. ANSam, for example, is a single frequency, but is
> amplitude modulated. There are also variants that have phase reversals,
> and these must be preserved for them to be discriminated from the
> non-phase-reversal versions.
>
> --
> Kevin P. Fleming
> Digium, Inc. | Director of Software Technologies
> 445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
> skype: kpfleming | jabber: kfleming@digium.com
> Check us out at www.digium.com & www.asterisk.org
>
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