[Asterisk-Users] RFD: With echo and other distortion, can ulaw/alaw line quality ever be good enough for faxing?

[Michael Shuler]

Actually my Sipura with 2.02 through * with a T100 is faxing without any
problems....

----------------------------------------

Michael Shuler, C.E.O.
BitWise Systems, Inc.
1301 W. Pioneer Parkway
Peoria, IL 61615
Office: (217) 585-0357
Cell: (309) 657-6365
Fax: (309) 213-3500
E-Mail: mike at bwsys.net
Customer Service: (877) 976-0711 

> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com 
> [mailto:asterisk-users-admin at lists.digium.com] On Behalf Of 
> Ryan Thrash
> Sent: Wednesday, May 05, 2004 11:28 PM
> To: asterisk-users at lists.digium.com
> Subject: Re: [Asterisk-Users] RFD: With echo and other 
> distortion, can ulaw/alaw line quality ever be good enough for faxing?
> 
> 
> Still way to early to tell any definitive results, but here's my 
> preliminary observations:
> 
> 1) Forget faxing through an ATA for now. If you need echo 
> canceling for 
> voice quality, it kills faxing. Otherwise, you can get faxing 
> to work, 
> sometimes with echo canceling turned off. It would be nice to 
> enable/disable echo canceling on a per extension basis instead of 
> globally (think 100 DIDs on 23 channels...).
> 
> 2) PRI T1 -> T100P -> TDM10B -> Analog fax appears to work fine with 
> minimal configuration!
> 
> I'd be interested in working/testing the fax side of the equation. It 
> really *should* work in Asterisk. I find your comment below 
> about echo 
> canceling changes particularly interesting. We have multiple daily 
> complaints of echo at the office, despite the fact that voice calls 
> come in on a T1 PRI. The theory as I've been told is that you 
> *shouln't* need echo canceling with a T1. My experience is 
> totally the 
> opposite. I wonder if there's something I could get Allegiance to 
> tweak? I feel for you on the tech support response... got a very 
> similar one myself.
> 
> HTH,
> Ryan Thrash
> 
> On May 5, 2004, at 2:35 PM, Darren Nickerson wrote:
> 
> > Folks,
> >
> > The silence was deafening ... I had a few private replies 
> but overall 
> > I'd
> > have to conclude that most people on this list aren't interested in 
> > faxing
> > thru Asterisk. You're all probably jazzed about VoIP and fax is 
> > forgotten
> > for now ;-)
> >
> > We have learned the answer to _one_ of the questions I 
> asked below - 
> > the
> > Adit channel bank's gain controls can be usefully applied to adjust 
> > each of
> > the incoming telephone lines independently, and by combining the 
> > Adit's gain
> > setting with Asterisk's, fun and good things can be made to 
> happen ;-)
> >
> > Another interesting observation is that echo can be seen 
> visually when 
> > using
> > ztmonitor. Muting one side of the call (the RX side), and speaking 
> > from my
> > handset I can see my voice appear stongly on the TX side, 
> and then I 
> > can see
> > the echo appearing on the RX side at an attenuated level, but it 
> > follows my
> > voice perfectly ;-)  I spend half a day talking to myself, 
> and I have 
> > to
> > say, for the first time in ages I was running out of things 
> to say! :-)
> >
> > In other interesting news, updating zapel from CVS seems to 
> have made 
> > things
> > significantly better. I had CVS from about 4 weeks ago 
> previously, so
> > perhaps something was amiss. We can actually get faxes transmitting 
> > now, and
> > although they fail about 30% of the time, this is 
> definitely progress.
> >
> > Another data point, is that MARK3 echo cancellation is 
> audibly worse 
> > under
> > our particular conditions. We're using MARK2 with the 
> aggressive option
> > enabled, and while occasional flares of distorted (but attenuated) 
> > echo can
> > be heard, it's much easier to have conversations with customers! I'm
> > disappointed nobody commented on the echo cancelation options in the
> > source... I can only assume nobody actually knows the 
> origins of any 
> > of them
> > any more, and the other ones are mostly anachronisms that 
> are no longer
> > useful, and MARK2 is the clear winner.
> >
> > Unfortunately, the news from Digium's technical support is 
> not good. 
> > Here's
> > what they had to say in response to our inquiry about faxing:
> >
> > "Faxing in asterisk is only at varied levels of support and is
> > definitely not at a production level.  However, if you wish 
> to work on
> > this we wouldn't mind at all :-).  The source code is of course free
> > to your disposal."
> >
> > I'm not sure I understand that this support rep is saying to me ... 
> > we've
> > had much success faxing from one PRI to another with them both 
> > connected to
> > Asterisk via a TE400P. Asterisk doesn't even break a sweat. We're 
> > rarely
> > getting the theoretical maximum of 33,600 that we can get with a T1 
> > loopback
> > though, so something's slightly amiss, but it's only when 
> we try to go 
> > out
> > to the PSTN that things start to fall apart badly.
> 
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