[Freeswitch-dev] how to add t38 support for mod_fax ?

Massimo "CtRiX" Cetra ctrix+fs at navynet.it
Tue Sep 15 07:45:42 PDT 2009

Steve Underwood ha scritto:
> mod_t38gateway is little more than a place marker right now. Looking at 
> how the T.38 engines in spandsp are used in Callweaver might be a better 
> starting point. FS currently lacks a UDPTL transport, but the code for 
> that is available (I'm not sure if ts in SVN, but it exists). It all 
> needs dragging together.
mod_fax is 95% ready to accept t.38.

The main missing parts, the last time i had a look at the problems are:

- support for UDPTL in mod_sofia that lacks the code to parse and
generate it

- (eventually add t.38 over RTP in mod_sofia, but i have not yet seen
any commercial/free switch that does manage it)

- rework switch_rtp to accept t.38 packets to an application.
- A way to signal an application that the channel supports T.38
  (because, for example, mod_fax can be used on wanpipe - no t.38 and on

- A way to force a switchover to t.38, sent from the application to the
channel driver (if supported)
(because mod_fax may request a t.38 switchover to sofia or t38gw may
request one leg to switch to t.38)

- A way to signal the application that a switchover to T.38 has occurred
on the channel driver
(because the remote party may switch to t.38 and the endpoint
application must take care of this)

For the last 3 points, i have no idea how to do it in a clean and
elegant way.


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