[asterisk-users] Asterisk 1.6 and fax

[David Backeberg]

On Mon, Sep 13, 2010 at 4:33 PM, Stanislav Korsei <korsei at rinogo.com> wrote:
> Hello!
> I've created clean installation of Asterisk 1.6.2.11 with spandsp 0.0.5.
> When i try to receive fax I get:
> [Sep 13 00:45:59] WARNING[3283]: app_fax.c:432 transmit_audio: channel
> 'SIP/crocus-ua-00000004' refused to negotiate T.38
> [Sep 13 00:46:02] WARNING[3283]: app_fax.c:223 phase_e_handler: Error
> transmitting fax. result=49: The call dropped prematurely.
> [Sep 13 00:46:02] WARNING[3283]: app_fax.c:817 transmit: Transmission error
>
> I definitely know that this peer supports T.38 because it works on Lynksys
> PAP2T.

There are lots of devices that 'support' T.38, but the problem is that
they 'support' it differently. If you want to have fun, read the
release notes for a Cisco voice IOS, and grep for the word T.38 to see
the long list of known broken situations.

Just because it's 'supported', doesn't mean it works. Internet
Explorer 'supports' html, but good luck getting it to act like a
standards-compliant web browser.

Try turning off the T.38 and do analog passthrough, or try using two
T.38 PAP2Ts. Or even better, don't use fax if you can avoid it.