VoIP Mailing List Archives

[tculjaga at gmail.com]

Hi,

is there any way to route fax calls according to the call capability?

I mean .. if the fax call supports T.38 i'd like to route it to a T.38 capable gateway. All other fax calls (meaning inband) should be handled by FS/SpanDSP.
Of course, I know that every fax call starts as a voice call and upon fax tone detection additional capabilities are being negotiated(T.38 or G711). Can it be done in early media, before the call is even answered?



So, here the goal is to have a T.38 capable GW handling T.38 calls while SpanDSP handling T.30...


Any chance to do that with FS?

[msc at freeswitch.org]

On Tue, Sep 15, 2009 at 8:45 AM, Tihomir Culjaga <tculjaga@gmail.com (tculjaga@gmail.com)> wrote:

[tculjaga at gmail.com]

Hi Michael, thanks for your response.

i think it will be enough to check the call capability... we always know the call is fax. We just need to apply the correct protocol


let's suppose you have 2 incoming calls:

1. SDP containing G711, gsm, T.38 caps
2. SDP containing G711, gsm caps

the caps will be known on within INVITE message and FS can act accordingly.

• If there is no T.38 support within SDP, start fax application (SpanDSP).
• If there is T.38 suport within the SDP, route the call to some predefined gateway meant for T.38 fax receiving.

In both cases, the fax should be received .

So, any chance to route the call according to T.38 caps within SDP message?



Now, for sending faxes there is some challenge.... we still have 2 calls:

we start sending a fax inband (SpanDSP) as this is the only thing we know... and:

• if we receive 200 OK with SDP containing G711, anyCaps => continue with InBand Fax
• if we receive 200 OK with DSP containing anyCompressedCaps, T.38 => drop the call without sending ACK to 200 OK ... and move the fax to be sent into a different directory.

well, as i said, while receiving faxes will work 100%, sending is tricky... but it might work.

what do you guys think?

T.




On Thu, Sep 17, 2009 at 10:51 PM, Michael Collins <msc@freeswitch.org (msc@freeswitch.org)> wrote:

[mike at jerris.com]

You have access to the full sdp in channel vars, so you can condition on those with regex.

Mike


On Sep 17, 2009, at 6:25 PM, Tihomir Culjaga wrote: