Re: [asterisk-users] spandsp 0.0.3 RxFax fax =?ISO-8859-1?Q?_reception crashes bristuffed_asterisk_1=2E2=2E13_[?= Virusgeprüft]

[Lee Howard]

Jean-Yves Avenard wrote:

> I don't see why rxfax would be less reliable than iaxmodem/hylafax as
> it's using the same spandsp to receive fax.


spandsp is a dsp library with lots of pieces to it.  IAXmodem uses the 
T.31 portion (the Class 1 modem) which uses the actual DSP parts of 
V.21, V.29, and V.27ter (and potentially V.17).  However, the bulk of 
the fax protocol is actually performed by the HylaFAX Class 1 driver.  
With txfax/rxfax it does not use the T.31 portion, using the T.30 
portion of spandsp, instead, and thus also does not use the same fax 
protocol driver as does the HylaFAX+IAXmodem combination.  So the only 
thing the same are the DSPs... V.21, V.29, V.27ter (and potentially V.17).

So it is entirely possible for users to find IAXmodem+HylaFAX fax 
operation to be substantially different from txfax/rxfax.

> The only difference I can think of is iaxmodem disable V17 reception
> within spandsp which is known to be a bit unreliable in reception. 


txfax/rxfax do not attempt to use V.17 by default, either, to the best 
of my knowledge.

The difference is in the approach to handling fax protocol.

Lee.