[asterisk-users] Fax with T.38

[Thomas Deillon]

Hi all,

I make mistakes in my explanation, so I will try to re-explain my problem…

I want to send fax with FoIP.
Analog Fax ← PSTN →  PATTON SN4960 ←T.38→ Asterisk ←T.38→ PATTON M-ATA ←Analog→ Analog Fax 2

In the Patton SN4960 configuration I have :
profile voip FOIP
  codec 1 g729 rx-length 20 tx-length 20 no-silence-suppression
  codec 2 g711alaw64k rx-length 30 tx-length 30 no-silence-suppression
  codec 3 g711ulaw64k rx-length 30 tx-length 30 no-silence-suppression
  dtmf-relay signaling
  dejitter-max-delay 100
  fax transmission 1 relay t38-udp
  fax redundancy low-speed 2 high-speed 1
  fax detection fax-frames
  modem transmission 1 bypass g711alaw64k
  modem bypass-method nse

On Patton M-ATA :
1. codec alaw
2. codec ulaw
3. codec g729
No silence suppression on these codecs. 
I not use this option “FAX without T.38(Use G.711 fax)”


On asterisk side I have:
[general]
context=default         
bindport=5060        
bindaddr=0.0.0.0               
srvlookup=yes         
disallow=all                   
allow=alaw                    
dtmfmode = rfc2833              
rtcachefriends=yes
realm=vtxvoip
useragent=VTX SIP
rtupdate=yes
language=en
tos=184
notifyringing=yes
t38pt_udptl=yes

And t38pt_udptl=yes in the 2 PATTONs sip accounts …


Then, I made a trace when I call from Analog FAX 2 to Analog fax 1 ….
I received T.38 packets from the Patton sn4960 but no T.38 packets go through the Asterisk …. And on the asterisk I have 3 WARNINGS:

[Feb 15 10:05:24] WARNING[9167]: channel.c:3033 ast_channel_make_compatible: No path to translate from SIP/sip_trunk_gva-01-0071e6b0(256) to SIP/0xxx0379xx-0070a490(8)
[Feb 15 10:05:33] WARNING[9163]: channel.c:2702 set_format: Unable to find a codec translation path from alaw to g729
[Feb 15 10:05:33] WARNING[9163]: channel.c:2702 set_format: Unable to find a codec translation path from alaw to g729


What I really not understand it’s why asterisk try to translate from ulaw to g729 !!!
I disallow all and allow just the alaw codec … more than this, I remove the g729 licence file … 

Do you have an idea for me ??

Thanks a lot,

Thomas