[asterisk-users] fax transmission

[Lee Howard]

Thomas Kenyon wrote:

> Doug Lytle wrote:
>
>> iaxmodem is the component that will allow you to use all of your 8 
>> ports on the ISDN card as software modems.  It works very well.
>>
> It is worth noting that it works best if the asterisk server with the 
> linecard is the same machine as the hylafax server. (although afaik 
> most problems with remote servers are now fixed in the latest release).


Unfortunately, the problem with using iaxmodem remotely from the 
Asterisk server (jitter disrupting the audio) is not something that can 
be fixed from the software-side of things.  The 0.1.16 release included 
a type of fixed jitterbuffer that helps iaxmodem prevent itself from 
mistaking jitter as carrier loss when there still should be carrier or 
vice-versa (carrier when there should not be).  This fixed jitterbuffer 
was not working right until the 0.2.0 release, however.  So this 
jitterbuffer cannot recover the disrupted audio, although it does help 
mitigate the effects of it.

The only true fix must come by eliminating the causes of jitter - and 
that usually means placing iaxmodem on the Asterisk system.  The 
iaxmodem documentation does discuss this in detail.

Thanks,

Lee.