[asterisk-users] Faxing with asterisk

[Steve Underwood]

Steve Underwood wrote:
> Fabio Mosti wrote:
>   
>> Hi All,
>>
>> I need to setup asterisk to receive fax.
>>
>> I'm try Spandsp (opensource) and Attrafax (commercial) both on
>> asterisk 1.4.23) but the results are disappointing.
>> with spandsp many times the fax arrives cut.
>> with Attrafax i have some problem.
>>
>> Anyone have any idea or solution (Opensource or commercial) to suggest me ?
>>   
>>     
> You have two solutions which give trouble, and you assume the problem is 
> with them, and not something else in your system. Interesting logic.
>
> You don't indicate the kind of setup you are using. If you are trying to 
> FAX over a VoIP connection, its probably that connection making FAXes 
> fail. If you are using mISDN, it is probably that making FAXes fail. If 
> you are using zaptel to bring in FAXes from the PSTN, spandsp should 
> work well.
>
> If you are using the agx addons to interface spandsp to asterisk, they 
> have just been updated to work with the latest spandsp. This should be 
> more robust in its error recovery than the older versions of spandsp. 
> However, with a good connection to the PSTN you shouldn't be hitting 
> recovery conditions often enough for that to be too serious.
>   
One more thing - check your gains. Modems adapt to varying signal 
levels, and are very insensitive to gain. However, I have received 
numerous wave files for analysis from different people using Asterisk 
where the gain is so crazily high that the signal is in a continuous 
clipping condition. There is no way anything can be reliably decoded 
from that. Voice over these channels must sound dreadful, yet some 
people will swear their system is working fine. :-\

Steve