[Asterisk-Users] T.38 fax with SIP devices

[Clay Reiche]

Mark,
 
Try forcing ulaw on the devices, make a successful ulaw voice call, then try
the fax again.
 
Clay

________________________________

From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Mark Dutton
Sent: Thursday, April 07, 2005 7:01 AM
To: asterisk-users at lists.digium.com
Subject: [Asterisk-Users] T.38 fax with SIP devices


Hi there
 
I have a SIP ATA with a fax machine attached and a SIP FXO gateway to the
PSTN. When I try to send faxes in either direction, I get nothing but stony
silence. I have changed the gateway and the ATA to peer to peer mode to test
them and they happily do the T.38 thing and faxes flow.
 
It seems that they initially negotiate a G.729 codec, which is what I want
and then when the receiving end detects the fax machine, it wants to
re-negotiate and use the t38fax codec. This is the working the Micronet
devices use at least.
 
When I put the units into proxy mode and run them through Asterisk, they fail
at the negotiation stage.
 
Now I have learned from my dealings with Asterisk and the newsgroup that
Asterisk does not do T.38. However, why should it not let devices do T.38? My
debug messages from Asterisk don't show it saying no, but the gateways don't
wont' setup the T.38 on Asterisk.
 
I have chanded sip.conf to allow=all and there are no explicit rules in the
registrations for the gateways.
 
Does anyone have an idea here? 
 
For this venture to be truly usable, I have to be able to get FAX working at
this basic level.
 
Regards
 
Mark Dutton
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