[Asterisk-Users] SoftFAX/spndsp

[Alex Volkov]

Steve,

Many thanks for your work, first of all.
We have also been testing spandsp lib with rxfax * app here via RTP/ULAW (on
LAN, direct from Sipura SPA2000 and GS HT-286 to *). It seems to be getting
better with each new release of spandsp ;-). We do not get any more fast
carrier training problems with various PC fax modems and a couple HP
all-in-one fax machines, but the received faxes (tiff files) still come out
garbled.
It works much better with fax modems, faxing from win2000 using its 'native'
fax driver. The line errors usually begin somewhere around scanline 1700 (in
fine resolution; 200 dpi ?) and after that everything is garbled. With HP
fax machines, the line errors start immediately and everything is garbled.
It also takes an awful long time to transmit a single page (retransmits?).
The only thing that is readable in faxes received from HP machines is the
header with date, TSI name/number and page # (is that generated by spandsp
or transmitted in the image by the fax?).
In both of above cases, the negotiated protocol is V.29 at 9600bps. I can
send the logs if you want, they tend to get too big for inclusion in this
email with all those line errors. I can also send the received .tiffs.
Now, the question I had was if it is practically possible to fax over
RTP/ULAW with asterisk. Do you think some changes to asterisk RTP stack
might be necessary to accomplish this? It seems very promising as it is
right now. Transmitting a fax over POTS with the same fax modems into
asterisk with an X100P board works like a charm! But we could not try the
same with the fax machines -- don't have a spare line right now.

Cheers!
Alex.

----- Original Message -----
From: "Steve Underwood" <steveu at coppice.org>
To: <asterisk-users at lists.digium.com>
Sent: Friday, March 19, 2004 2:02 PM
Subject: [Asterisk-Users] SoftFAX/spndsp


> Hi,
>
> I have investigated some more fax machines that did not work with
> spandsp, and made it more tolerant.
> ftp://ftp.opencall.org/pub/spandsp/spandsp-0.0.1c.tar.gz is the result.
>  From what I have seen in today's investigations, I think this one will
> work with considerably more quirky fax machines and bad phone lines.
>
> Regards,
> Steve
>
>