[asterisk-users] Fax solution for Asterisk

[Lee Howard]

Gordon Henderson wrote:
> Something that's always confused me - IAXmodem is built on spandsp. RxFAX 
> is also built on spandsp. RxFAX gets one step closer to the data stream 
> (no copper/IP in the way), so why are people using (& suggesting) Hylafax 
> over RxFAX?
>   

spandsp includes a lot of stuff.   In spandsp there are the fax modems: 
V.21, V.27ter, V.29, and V.17.  There is also a Class 1/1.0 DCE 
interface (T.31).  There is also a T.30 (fax protocol) driver.  There is 
also a T.38 driver in there.  There is other stuff there, too.

IAXmodem uses the fax modems and the T.31 DCE... its main purpose being 
to function with other applications that have their own Class 1 T.30 
drivers such as HylaFAX.

RxFAX (and TxFAX) also uses the fax modems, but doesn't use the T.31 
DCE, but instead uses the T.30 driver.

So the difference underneath the hood really has to do with where the 
fax protocol engine/driver is.  When using IAXmodem the protocol is done 
by HylaFAX.  When using RxFAX/TxFAX the protocol is done within spandsp.

Thanks,

Lee.