[asterisk-users] how to set iaxmodem receiving speed

gincantalupo gincantalupo at fgasoftware.com
Thu May 17 09:40:51 CDT 2012


Hi guys, thanks for answers.

That could seem counter-intuitive but it is not. Not to mention the fact 
that information technology is not science, the solution to broken faxes 
is to lower down speed. This works even with normal telco lines even if 
you DO NOT have a pbx (telco technicians even say not to make faxes pass 
thru your PBX). I could ask my customer's telco to lower the speed down 
but it depends on the guy working at the call-center...sometime you talk 
to dummy people who ARE sure it is impossible. But it is not. So, I do 
not want to spend days to convince people working at that telco 
call-center that what I'm asking is feasible and I do not want to tell 
my customer to tell their customer to lower their faxes speed (before 
installing our PBX they were able to send perfect faxes so, why should 
they?).

My idea was to tell iaxmodem not to accept fast speed rates so the fax 
machine on the other side should be forced to negotiate a slower speed 
as if my customer fax weren't virtual as iaxmodem is but a real one.

I suspect that the problem is about the primary lines because I tested 
iaxmodem many times on my LAN and it is (surprisingly :) ) working fine 
(10 good received faxes out of 10 sent!!!) but, as you may know, talking 
to telco technician is a nightmare....they always say problems are 
always on the PBX side... :(

Moreover, after sending a fax, the fax machine beeps correctly as the 
fax was correctly sent without corruption. :o

I hope I have made my point but I'll try do dig deeper inside the 
problem as you suggested me.

Thank you. :)

Giorgio

On 05/17/2012 04:02 PM, Tim Nelson wrote:
> ----- Original Message -----
>> ----- Original Message -----
>>> Hi Steve,
>>>
>>> you are telling me there is no way to set a particular speed on my
>>> iaxmodem in order to force the sender speed?
>>> I have some problems with a customer who gets malformed faxes even
>>> if
>>> no
>>> error occurs. Since I cannot tell the sender to lower its fax
>>> speed,
>>> my
>>> idea is to force my iaxmodem to a lower fixed speed so the sender
>>> is
>>> oblidged to negotiate at that speed (or lower, of course) without
>>> the
>>> customer could realize it, at least at first. :)
>>> There is no ATA in the middle (I'm using it for my tests but my
>>> customer
>>> does not have any), all faxes are received thru a primary channel
>>> to
>>> a
>>> bunch of iaxmodems. Sometimes some faxes are corrupted, that's why
>>> I
>>> thought to lower the speed. I could try to disable ECM but that's
>>> even
>>> harder to do (found nothing on internet).
>>>
>> You're getting corrupted fax data and want to solve that problem by
>> *disabling* ECM? That seems counter-intuitive to me...
>>
>> How are your fax calls coming into your system
>> (PSTN->???->Asterisk->IAXmodem->Hylafax)? If you have VoIP somewhere
>> in the call path, you'll likely keep bashing your head on the table
>> trying to fix problems that will never go away. Also, don't be
>> afraid to recognize sometimes your side (as the receiver) is working
>> perfectly well, and sometimes there just isn't anything you can do
>> about senders on bad lines/sending over VoIP/etc. The quality of a
>> fax session is only as good as the weakest link contained within
>> that session, including the call path from sender to receiver.
> Also, while there are some brilliant experienced people here on the Asterisk lists, you may have better luck and traction by heading over to the iaxmodem and hylafax mailing lists. Or, at least you may get a different audience with different ideas/experience.
>
> --Tim
>
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