[asterisk-users] res_fax T.38 Gateway with SpanDSP - Force ReINVITE?

[Larry Moore]

On 24/10/2014 12:47 AM, Tim Nelson wrote:
> ----- Original Message -----
>>
>>
>> On 22/10/2014 11:23 AM, Tim Nelson wrote:
>>> Greetings-
>>>
>>> Working with the T.38 gateway functionality that is sparsely
>>> documented
>>> [1], I'm attempting to get the following functional:
>>>
>>
>> What type of endpoint are you using which is originating the call and
>> is
>> it T.38 capable?
>>
>
> The originating endpoint is an IAXmodem controlled by Hylafax. Actual call flow is IAXmodem --G.711u via localhost-->  Asterisk (old version with no T.38 support) --G.711u-->  Asterisk 11.x --G.711u/T.38-->  ITSP
>
> The problem lies on the Asterisk 11.x system not being able to reinvite to T.38 on the call leg with the ITSP, and given the ITSP does not do this either, the call is stuck in G.711u with varying performance. :/
>
> --Tim
>


IAXmodem (other host on network) -> Asterisk 1.2 (IAX) -> Asterisk 1.8 
with Fax Gateway Patch -> SIP provider -> PSTN Fax destination

I have successfully sent a fax using a full page image via an Asterisk 
1.2 system which forwards the request to my Asterisk 1.8 over an IAX 
channel, Asterisk 1.8 has the T.38 Fax Gateway patch installed. The 
outbound call triggered the T.38 gateway and the fax was received 
without error. I have ECM disabled in my IAX modem configuration in Hylafax.

I don't have Asterisk 11 running to test with at this time however I 
confirmed the T.38 Gateway functions in Asterisk 11 when testing it.


     -- Accepting AUTHENTICATED call from 192.168.54.18:
        > requested format = ulaw,
        > requested prefs = (ulaw|alaw|slin),
        > actual format = alaw,
        > host prefs = (alaw|ulaw),
        > priority = mine
     -- Executing [<PSTN Number>@FAX-T30:1] Dial("IAX2/faxgw-iax-1210", 
"SIP/<PSTN Number>@itsp-fax,55") in new stack
   == Using SIP RTP TOS bits 184
     -- Called SIP/<PSTN Number>@itsp-fax
     -- SIP/itsp-fax-0000000b is making progress passing it to 
IAX2/faxgw-iax-1210
     -- SIP/itsp-fax-0000000b is making progress passing it to 
IAX2/faxgw-iax-1210
   == Using SIP RTP TOS bits 184
     -- SIP/itsp-fax-0000000b answered IAX2/faxgw-iax-1210
[Oct 25 23:24:11] NOTICE[27896]: channel.c:4220 __ast_read: Dropping 
incompatible voice frame on IAX2/faxgw-iax-1210 of format slin since our 
native format has changed to 0x8 (alaw)
     -- Got Fax Tone CED Chan SIP/itsp-fax-0000000b [1] Sending T.38 
Params Peer Is IAX2/faxgw-iax-1210 [0]
     -- Request on IAX2/faxgw-iax-1210 [0] Storing I: 
SIP/itsp-fax-0000000b [1]
   == Using UDPTL TOS bits 184
     -- Negotiated on SIP/itsp-fax-0000000b [4] Ignoring I: 
IAX2/faxgw-iax-1210 [0]
     -- T.38 Gateway starting for chan SIP/itsp-fax-0000000b and peer 
IAX2/faxgw-iax-1210

pbx*CLI> iax2 show channels
Channel               Peer             Username    ID (Lo/Rem)  Seq 
(Tx/Rx)  Lag      Jitter  JitBuf  Format  FirstMsg    LastMsg
IAX2/faxgw-iax-1210   192.168.54.18    faxgw-iax   01210/00004 
00010/00005  00000ms  -0001ms  0000ms  alaw    Rx:NEW      Tx:ACK
1 active IAX channel
pbx*CLI> fax show sessions

Current FAX Sessions:

Channel              Tech       FAXID      Type  Operation  State 
File(s)
SIP/itsp-fax-0000000 Spandsp    1          T.38  receive    Active 
(null)

1 FAX sessions

     -- Executing [h at FAX-T30:1] GotoIf("IAX2/faxgw-iax-1210", "0?2:3") 
in new stack
     -- Goto (FAX-T30,h,3)
     -- Executing [h at FAX-T30:3] NoOp("IAX2/faxgw-iax-1210", "Finish 
if_FAX-T30_37") in new stack
     -- Executing [h at FAX-T30:4] NoOp("IAX2/faxgw-iax-1210", "Call/Fax 
Ended 2014-10-25 23:27:38 +0800") in new stack
     -- Connection Statistics
         Bit Rate :14400
         ECM : No
         Pages : 1
   == Spawn extension (FAX-T30, <PSTN Number>, 1) exited non-zero on 
'IAX2/faxgw-iax-1210'
     -- Hungup 'IAX2/faxgw-iax-1210'