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:

> What are the advantages of T31 over T30 ?


T.30 is the spec for fax protocol.  T.31 is the spec for a Class 1 fax 
modem.

So T.31 is a layer that allows something else to perform fax protocol 
(T.30) through it.

There may be some intrinsic value to handling faxing through a T.31 
interface, adding certain default tolerances or behaviors; however, I'm 
not certain what they would be.

Thus in the IAXmodem + HylaFAX scenario T.30 is being performed by the 
HylaFAX Class 1 driver whereas with rxfax/txfax T.30 is being performed 
by rxfax/txfax/spandsp.

Neither approach is inherently better than the other, I would suspect; 
however, I would guess that HylaFAX, having been around for 17+ years 
now, and with me and others watching hundreds and hundreds of thousands 
of faxes pass through it and continually tweaking and improving the 
software... well, I would suspect that it's a bit more mature than the 
other approach (no offense at all intended to Steve).

> One thing I'm missing right now (but I haven't looked at what can be
> done to fix it), is that rxfax add useful bits of information at the
> top of the page (faxid, time of call etc),  while hylafax leave it
> empty.


HylaFAX, especially in ECM mode, takes effort in preserving the image 
data sent by the sender exactly as the sender delivered it.  So by 
default HylaFAX doesn't get into the business of tampering with the 
image - whether that be changing image compression formats, resolution, 
or adding markings to the image itself.  If you want to add that kind of 
information to the image then you can do it in your delivery mechanism 
(usually FaxDispatch)... however all of the information that you seek is 
available in the TIFF tags which will be displayed with the 'faxinfo' 
utility or through the hfaxd-client protocol.

> yesterday, while doing my test, i found out that iaxmodem would
> unregister from asterisk once in a while (running on the local
> interface), what i've done around that is set up  more iaxmodem than I
> need, however at one stage I had to restart the iaxmodem for it to
> reconnect as after a few minutes there were still non-registered
> modem. 


I assume that you're using iaxmodem-0.1.16.  If not, then you should 
update.  If you are, then you'll probably want to take that bug report 
to the iaxmodem forums ... see http://iaxmodem.sourceforge.net.

If you're using hylafax.org's HylaFAX and running faxaddmodem then it 
has the tendency to kill off the iaxmodem process... and that could 
cause what you're seeing.

Thanks,

Lee.