[Asterisk-Users] Asterisk mangling faxes

[Jim Sneeringer]

Darren,

Thanks so much for your help.

Do you know if there is other fax software that supports ECM?

Also, why should Asterisk introduce a lot of noise? (Faxes work fine without
Asterisk or with the old phone system.) I'm using a 2.4GHz Pentium 4 with
two X100P's and two TDM400P's. Faxes are garbled even when there is no other
load, and nothing else has changed except to replace the old switch with
Asterisk. I have tried attaching the fax to different cards and using
different FXO lines, and faxes are always garbled, so I don't think it is
some kind of sample defect in the hardware.

What could I try that might reduce this noise?

Thanks again.

Jim

-----Original Message-----
From: asterisk-users-admin at lists.digium.com
[mailto:asterisk-users-admin at lists.digium.com] On Behalf Of Darren Nickerson
Sent: Wednesday, March 10, 2004 11:58 AM
To: asterisk-users at lists.digium.com
Subject: Re: [Asterisk-Users] Asterisk mangling faxes

Jim,

For the sake of argument, let's assume something about your Asterisk setup
is introducing acoustic artifacts like crackles, pops, echoes etc into the
fax transmission. The best way to overcome something like that is to make
sure your fax transmissions use ECM error correction whenever possible. That
allows you to retransmit scanlines that got destroyed by the noise.Your
garden variety desktop fax machine will usually support ECM, but I'm
thinking it's quite likely your winfax setup won't.

Note that ECM isn't going to always save you ... if things are so bad that
you can't train at the beginning of the call there's not much ECM can do.
The best idea is to locate the source of any audio degradation and squash it
there, rather than trying to send faxes over poor quality connections.

-Darren

-- 
Darren Nickerson
Senior Sales & Support Engineer
iFAX Solutions, Inc. www.ifax.com
darren.nickerson at ifax.com
+1.215.438.4638 ext 8106 office
+1.215.243.8335 fax


----- Original Message ----- 
From: "Jim Sneeringer" <j at snee.us>
To: <asterisk-users at lists.digium.com>
Sent: Wednesday, March 10, 2004 11:47 AM
Subject: RE: [Asterisk-Users] Asterisk mangling faxes


> I'm having the same symptoms using X100P's, TDM400P's and WinFax, and have
> and have had no luck correcting it. I don't have a standalone fax machine
to
> test with.
>
> Does anyone know if this a problem whenever faxes are sent and received
with
> a modem, or is it specifically WinFax? Is there any other way to
accomplish
> the goal of computer faxing with Asterisk?
>
> Jim
>
> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com
> [mailto:asterisk-users-admin at lists.digium.com] On Behalf Of Bisker, Scott
> (7805)
> Sent: Wednesday, March 10, 2004 8:50 AM
> To: asterisk-users at lists.digium.com
> Subject: RE: [Asterisk-Users] Asterisk mangling faxes
>
> Michiel,
>
> Are you using WinFax? or one of the Products Based on Winfax?  I've seen
> this on all of our WinFax Stations, but none of our standalone Fax
machines.
>
> -sb
>
>
> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com
> [mailto:asterisk-users-admin at lists.digium.com]On Behalf Of michiel betel
> Sent: Wednesday, March 10, 2004 9:40 AM
> To: asterisk-users at lists.digium.com
> Subject: [Asterisk-Users] Asterisk mangling faxes
>
>
> Hi list,
>
> Faxes come in over an E1 line  (on an TE410P) here and then are sent to
> an analog fax machine attached to a T1 (also on the TE410P) &
> channelbank (CAC1).
> Problem is that almost all faxes we send out and receive are mangled...
> either only halve pages or very stretched text etc.
> Setup in extensions.conf is just:
>
> exten => ${NN_FAX},1,Answer
> exten => ${NN_FAX},2,Dial(Zap/49,80)
> exten => ${NN_FAX},3,Hangup
>
> echocancel is off for Zap/49 since the path is TDM only....
>
> Any pointers to where to look??
>
> Thanks, Michiel
>
>
>
>
>
>
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