[OpenSIPS-Users] T.38 detection/redirect in OpenSIPS

[Brett Nemeroff]

I don't think there is any way to do this without an RTP capable device in
the mix.

What you may be able to do is have asterisk detect that it's a fax, then
reject it if it is.. I don't know if you can do all that without answering
the call.

Then you can forward it back to the proxy if it is a fax with maybe a
prefix.

A lot of assumptions in there. Would like to hear if you find something that
works. Not sure if you can SIP Spiral yet in asterisk anyway. ;)
-Brett


On Wed, Mar 17, 2010 at 10:51 AM, David J. <david at styleflare.com> wrote:

> Matt,
>
> I am for sure probably wrong, but I think you would need Asterisk or
> Variant to Determine that it is a Fax Call,
> I dont think UAC's send T38 information without negotiating with the
> other side who request that it is capable, then it brings you to Jeff's
> answer.
>
> See above.
>
>
> Matthew S. Crocker wrote:
> > Can OpenSIPS make routing decisions based on the SDP information in an
> INVITE?
> >
> > Lets say I have the following config
> >
> > PSTN -> t.38 Gateway -> OpenSIPS ->  UserAgent
> >
> > I have a TN from the PSTN routed to the UserAgent,  I'd like to provide a
> service so the user can use the TN for both voice & faxing.
> >
> > Voice call goes through normally (g.711 g.729 codec)
> >
> > Fax call starts off as a normal voice call (INVITE, 180, 183, 200).  Once
> the call is answered the originating end (PSTN) starts sending fax tones.
> The Gateway hears the fax tones and attempts to RE-INVITE with T.38 in the
> SDP.  I'd like OpenSIPS to see the T.38 capability in the SDP and redirect
> the call to a fax->e-mail gateway.  So,  the 2nd INVITE comes in, OpenSIPS
> sends the INVITE to the fax gateway and a BYE to the user.  The fax gateway
> does a 200 and negotiates T.38 with the PSTN gateway.
> >
> > I know I can route the call through Asterisk and have it do a quiet
> answer and listen for the modem sounds.  I'd like to avoid using Asterisk
> for all RTP traffic and only use it for the fax gateway traffic (i.e. once
> it has been determined to be a fax Asterisk steps in and handled the T38 ->
> E-mail)
> >
> > -Matt
> >
> >
>
>
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