[Asterisk-Dev] FAX Subsystem discussion.

[John Harragin]

I have been thinking about the issues regarding transmitting faxs over VoIP
asterisk networks. I have a couple of ideas I want to toss around with you
guys. What I currently have in mind is fax client & server applications.
These would basically be the same but the server would be a tdm gateway -
where the faxes transmitted and received are handed off to the telco.

The fax client would send and receive documents to local devices (fax
machines, network printers, email, PCs, etc. - but only the fax machines are
really necessary, as the server could do everything else) outgoing documents
would be queued until the entire document is received. The queued file would
then be sent to the server app where it would be transmitted out the tdm
gateway. Incoming documents would work in a similar manor.

This strategy would be simpler than trying to get iax, echocans and delays
to work smoothly with fax traffic. Additionally, the image quality would be
better and the negotiated transmission rates would be maximized.

We could probably find an existing fax server or rendering library, to
incorporate into the asterisk app, to do most of the work. It would have to
be lightweight so it didn't bog down the asterisk program. Would the use of
gpl code be OK for apps? A bit of notification code would need to be written
in addition to the app interface.

Tips, suggestions, criticism or info on fax applications that would be
suitable for this purpose?

John