asterisk users - Jan 2005 - spandsp and app_rxfax (alternative topic: t38modem)

Dear gods of the PBX (flattery works here, right?) -

I've been pulling my hair out trying to get Asterisk to receive and 
decode a fax using spandsp and app_rxfax.  It seems like it should be 
working.  The fax machine on the other end connects and Asterisk reports 
a fax coming in.  But when it's done all I have is a 2 or 3 KB TIF (see 
attachment).

The console activity looks completely normal:
    -- Starting simple switch on 'Zap/3-1'
    -- Executing SetVar("Zap/3-1", 
"FAXFILE=/var/spool/asterisk/fax/1105043880.0.tif") in new stack
    -- Executing RxFAX("Zap/3-1", 
"/var/spool/asterisk/fax/1105043880.0.tif") in new stack
    -- Hungup 'Zap/3-1'

And there are no errors in the log file.

Here's my config:
  Wildcard TDM40B hardware (Zaptel)
  asterisk-1.0.2
  spandsp-0.0.2pre6
  libtiff-3.6.1 (with the fax fix patches)
  (also tried libtiff-3.6.0 and libtiff-3.5.7)

I've tried multiple sending fax machines and get the same effect.

Any tips on getting this setup working?  I've run out of ideas. 

Alternately, I'd also be willing to offload the DSP processing to a 
HylaFAX machine using some sort of software fax driver.  I tinkered with 
t38modem and chan_h323, but couldn't get it to do anything once the 
HylaFAX machine answered.  So if anybody has any experience with that, 
I'd be interested.

Thanks in advance,
Ryan VanMiddlesworth

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Hmmmm. Did I just ask in the wrong forum, or has _nobody_ experienced image 
corruption using app_rxfax that was NOT due to using the wrong version of 
libtiff?

If that's the case, then my secondary approach is going to have to be:
  PSTN <-> Asterisk + chan_h323 <-> t38modem + Hylafax

Is there anybody that could help me with either of these solutions?

A thousand "thank you"s in advance,

Ryan VanMiddlesworth


On Thursday, January 6th, I wrote:
> I've been pulling my hair out trying to get Asterisk to receive and
> decode a fax using spandsp and app_rxfax.  It seems like it should be
> working.  The fax machine on the other end connects and Asterisk reports
> a fax coming in.  But when it's done all I have is a 2 or 3 KB TIF (see
> attachment).
>
> The console activity looks completely normal:
>     -- Starting simple switch on 'Zap/3-1'
>     -- Executing SetVar("Zap/3-1",
> "FAXFILE=/var/spool/asterisk/fax/1105043880.0.tif") in new stack
>     -- Executing RxFAX("Zap/3-1",
> "/var/spool/asterisk/fax/1105043880.0.tif") in new stack
>     -- Hungup 'Zap/3-1'
>
> And there are no errors in the log file.
>
> Here's my config:
>   Wildcard TDM40B hardware (Zaptel)
>   asterisk-1.0.2
>   spandsp-0.0.2pre6
>   libtiff-3.6.1 (with the fax fix patches)
>   (also tried libtiff-3.6.0 and libtiff-3.5.7)
>
> I've tried multiple sending fax machines and get the same effect.
>
> Any tips on getting this setup working?  I've run out of ideas.
>
> Alternately, I'd also be willing to offload the DSP processing to a
> HylaFAX machine using some sort of software fax driver.  I tinkered with
> t38modem and chan_h323, but couldn't get it to do anything once the
> HylaFAX machine answered.  So if anybody has any experience with that,
> I'd be interested.
>
> Thanks in advance,
> Ryan VanMiddlesworth

On Fri, 7 Jan 2005, Michael Welter wrote:
> Nils Segerdahl wrote:
>
> > I suspected frame slips. But sound quality was ok. Everything was ok.
> > Except maybe to many interrupts on the line cards.
> >
> > But when I changed my devicedriver to one that was more safe regarding
> > lost interrupts it worked like a charm.
>
> Device driver?  TDM device driver?  Would you please explain what you did?
>
Sorry, I was using zaptel patched with bristuff on asterisk 1.0.2
The driver was the bristuff zaphfc driver for Billion hfc isdn cards.
Slackware 10, Linux kernel 2.4.26 on P4 2.8GHZ, libtiff 3.5.7
spandsp 0.2.0r6

After i applied Florians patch it all started working like a charm
(Link to patch on wiki: asterisk zaphfc page)

The patch decreases the risk for lost interrupts as far as I can
understand. So I guess that that was my problem.


/Nils

Michael Welter wrote:
> Steve Underwood wrote:
>
>> If your TIFF are consistently that small you probably have a TIFF 
>> library problem. Frame slips generally give much more eratic results.
If
>
>
> Steve, when you say that some Canon fax machines "disconnect during 
> negotiation", does this negotiation happen at the end of each page?  I
> have a Canon fax that receives complete pages, but never the entire 
> transmission.
>
> Thanks,
>
> BTW, when the Canon disconnects, the Asterisk line remains off-hook.
>
That bug, which seems to be fixed in the spandsp-0.0.2pre6, means the 
Canon machines will not accept a FAX from spandsp at all. There was a 
bit set incorrectly in a control message. The Canon machines, and a few 
less popular ones, decided there was nothing they could do, and hung up.

Regards,
Steve