[SIPForum-discussion] SIP UAs that allow in-call SDP param changes?

[Jeff Wright]

That's not a bad idea.  I do have a couple of ATAs in our test lab and I'll see which ones support fax (either T.38 or G.711 passthrough).  Thanks for the tip.

Jeffrey Wright
System Test Engineering Manager
Aztek Networks



-----Original Message-----
From: Anthony Orlando [mailto:avorlando at yahoo.com]
Sent: Sat 1/5/2008 2:13 AM
To: Jeff Wright; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] SIP UAs that allow in-call SDP param changes?
 
You say you'd like to change codec preferences.  Would
a codec change itself work for you?  If so do you have
a couple of ATA's and faxes?  You could set the ATA's
up for a low bit rate codec with g.711 fallback.  Make
a call with the fax handset then send a fax with the
call still up.  You would obviously need a fax on the
other end as well.

What should happen is that the call is established
with the low bit rate codec then when the ATA detects
a fax it should change to G.711.

Anthony

--- Jeff Wright <JWright at azteknetworks.net> wrote:

> Does anyone know of a SIP UA that allows for in-call
> SDP parameter
> changes?  For instance, I'd like to be able to
> change codecs (via a
> re-INVITE and subsequent renegotiation) while a call
> is up.  
> 
>  
> 
> My overall motivation is to be able to run a test to
> force a call flow
> something akin to Example 3.7 in RC3665
> <http://tools.ietf.org/html/rfc3665> .  That example
> shows an IP address
> change, but I was hoping that I could similarly
> force a re-INVITE to
> occur if I changed codec preferences in a UA while a
> call was up.  So
> far, I've not found a UA that supports this (ZoIPer
> and X-Lite both
> allow me to change the preferred codecs while a call
> is up but they
> don't renegotiate with my new choice).  I also tried
> changing the IP
> address of my PC in the middle of the call, but
> neither call agent does
> anything about that, either.
> 
>  
> 
> Jeffrey D. Wright
> 
> Aztek Networks, Inc.
> 
>  
> 
> 
> 
>  
> 
> > _______________________________________________
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