[Asterisk-Dev] T.38 source code

[Craig Southeren]

On Fri, 02 Sep 2005 10:03:21 +0200
Florian Overkamp <florian at obsimref.com> wrote:

> Hi Craig,
> 
> Craig Southeren wrote:
> > A quick look at the package shows that it looks very much like what it
> > purports to be - a T.38 package for Asterisk.
> > 
> > These guys have done exactly what I was looking at doing, which is using
> > spandsp as engine to encode/decode the T.30 data stream needed for T.38.
> 
> Thanks for that. Does that mean it could be abused in a store/forward 
> scenario as a reliable fax-gateway ?
> 
> T38->Spandsp->TIFF file->Spandsp->Zap ?

Actually, it is more like

T.38 -> spandsp x 0.5 -> TIFF file -> Spandsp -> Zap

because T.38 does not use any of the DSP part of spandsp - just the TIFF
to T.30 parts.

This is basically the same as 

Zap -> spandsp -> TIFF file -> Spandsp -> Zap

except the source is a T.38 call rather than a fax-voice call.

Either approach takes a real-time fax call and converts it into a
non-realtime storage format - a TIFF file. At a later date, this format
can then be played back to a fax machine in real-time again.

This is exactly the fax equivalent of voice mail :)

If you actually want a real-time fax gateway, what you need is:

T.38 -> spandsp -> Zap

That should be perfectly feasible, but it will require someone sawing
off the *other* half of the spandsp code (the T.30 to DSP part, as
opposed to the TIFF to T.38 part) and making that work with T.38.

   Craig


-----------------------------------------------------------------------
 Craig Southeren      craigs at postincrement.com / craigs at voxgratia.org

 Phone:  +61 243654666      ICQ: #86852844
 Fax:    +61 243673140      MSN: craig_southeren at hotmail.com
 Mobile: +61 417231046   Jabber: craigs at jabber.voxgratia.org

 Post Increment - Consulting & Services    http://www.postincrement.com
 Vox Gratia - The Open Source VoIP portal  http://www.voxgratia.org
 Raving Of A Strange Mind - the VoIP blog  http://www.voxgratia.net/blog