The T.38 and open source

Abstracted from:

http://www.voxgratia.net/blog/archives/2005/08/fax_facts.html

1.T.38 should not be confused with the similar-sounding T.37 which uses a totally different approach. Whereas T.38 is intended for realtime fax transmision using an encapsulated T.30 data stream, T.37 is intended for "store and forward" applications. It requires the fax data to be converted into TIFF format and then encoded using base64 into a text message and then transmitted using SMTP.

2.T.38 solves most of the problems with sending fax over an IP network. A T.38 fax call uses 20% of the bandwidth than the modulated audio approach because it is now a stream of bits at an average speed of 14400 bps rather than a stream of audio samples at 64000 bps.

3. Asterisk supports T.38 fax pass-through, origination and termination. It does

not support gateway operation.

4.Asterisk 1.6 support G.711 and T.38 FAX origination and termination. T.38 gateway features are still in development.

5 more of T.38 open source informations:

http://www.voip-info.org/wiki/view/T.38

6.more of Asterisk T.38:

http://www.voip-info.org/tiki-index.php?page=Asterisk%20T.38

7.What is T38modem ?

• It is not a modem.

• From a FAX application's view point (e.g. HylaFAX) T38modem looks like a class 1 FAX modem pool.

• From an IP network view point it's a H.323 endpoint with T.38 FAX support. Recent versions also support SIP.

• From your view point it's a gateway between a fax application and an IP network.

8.Open source components:

• t38modem : as the modem pool of Hylafax, t38modem serves as the T.38 gateway for the T.38 machine

• asterisk : (Fax) machine with T.38 capability, currently, the T.38 gateway feature is under development

Technorati 標籤: T.38, Fax over IP