Have you tried the opposite, disable T.38 and use G711a/u for the payload.
We have had far greater success with the G711a/u RTP. T.38 still seems to be
very hit and miss cross devices be it ATA or even a real fax machine.
Cheers
Greg
________________________________
Greg Lipschitz | Founder & CEO | The Summit Group
g...@thesummitgroup.com.au
thesummitgroup.com.au
1300 049 749
Level 1, 39 Railway Road, Blackburn VIC 3130
The Summit Group
From: VoiceOps <voiceops-boun...@voiceops.org> on behalf of Nelson Hicks
<nels...@socket.net>
Sent: Saturday, October 1, 2016 4:47:30 AM
To: voiceops@voiceops.org
Subject: [VoiceOps] Problems with T.38 fax with Grandstream GXW-4248
We have a customer with multiple Grandstream GXW-4248 voice gateways
that wants to use T.38 for sending and receiving faxes. They are running
the most recent release (1.0.5.16). We have tested this successfully
with other devices, including a Grandstream HT-702 and a Grandstream
GXW-4004, but when configuring the Grandstream GXW-4248 the same way,
the audio from the Grandstream to the fax machine cuts out at the
renegotiation to T.38 and does not resume. When looking at a packet
capture of the fax call, the Re-INVITE appears successful, but the first
and only UDPTL packet sent by the Grandstream is reported as malformed
by Wireshark:
ITU-T Recommendation T.38
[Stream setup by SDP (frame 510)]
[Stream frame: 510]
[Stream Method: SDP]
UDPTLPacket
seq-number: 32768
primary-ifp-packet
type-of-msg: t30-indicator (0)
something unknown here [too long
integer(per_normally_small_nonnegative_whole_number)]
[Expert Info (Warn/Undecoded): something unknown
here [too long integer(per_normally_small_nonnegative_whole_number)]]
[something unknown here [too long
integer(per_normally_small_nonnegative_whole_number)]]
[Severity level: Warn]
[Group: Undecoded]
[Malformed Packet: T.38]
[Expert Info (Error/Malformed): Malformed Packet (Exception occurred)]
[Malformed Packet (Exception occurred)]
[Severity level: Error]
[Group: Malformed]
Does anyone have any experience with trying to use T.38 with a
Grandstream GXW-4248?
Thanks,
--
Nelson Hicks
Network Operations
SOCKET
(573) 817-0000 ext. 210
nels...@socket.net
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