[Freeswitch-users] Issues with T.38 on outgoing fax (sofia T38 invite failed)

Sat Dec 2 15:36:01 UTC 2017

I need to note that all components are SIP based, no other tech involved.

Kevin

2017-12-02 13:41 GMT+01:00 Kevin Olbrich <ko at sv01.de>:

> Hi,
>
> thanks for the link but I was unable to find information on how to
> configure my installation of FreeSwitch 1.6 to make things work.
>
> I think I need to explain a little bit more on what I am planning to do:
> FreeSwitch will be used as a SBC to the carrier. It's firewall is limited
> to the carriers network on the first interface.
> The second interface is a local subnet where an Asterisk 13 server (PBX)
> is located, connecting the phones and ATAs (last with T.38 support).
> For asterisk it is only necessary so set (FAXOPT(gateway)=yes) to have it
> detect CNG on audio and query both legs for T.38 (or receive a request in
> advance).
> It then decides if it goes to passthru mode or transcode.
>
> As far as I understand the FreeSwitch docs, there are these options
> (located in dialplan default before bridge):
>
>> <action application="set" data="fax_enable_t38=true"/> <!-- Enable t.38
>> for this call -->
>> <action application="set" data="fax_enable_t38_request=true"/> <!--
>> Enable t38_gateway to send a t.38 reinvite when a fax tone is detected. If
>> using t38_gateway peer then you need to export this variable instead of set
>> -->
>> <action application="set" data="execute_on_answer=t38_gateway self"/>
>> <!--Execute t38_gateway on answer. self or peer. self: send a reinvite back
>> to the a-leg. peer reinvite forward to the b-leg -->
>
>
> <action application="export" data="fax_enable_t38=true"/> <!-- Required as
>> of v1.6 -->
>> <action application="export" data="t38_passthru=true"/>
>
>
> *What I would like to accomplish is getting as much as T.38 I can get.*
> The ATA should always be able to negotiate T.38 with Asterisk (which seems
> to work atm), FreeSwitch should then negotiate T.38 if Asterisk or the
> carrier asks for it (no CNG detection).
> I am not sure if I can just enable t38_gateway and passthru, this case is
> not listed on confluence or the old wiki. Even if I do, it does not work.
>
> FreeSwitch might need to transcode T.38 to audio for our backup carrier
> who does not support T.38.
>
> Kind regards,
> Kevin
>
> 2017-12-02 9:20 GMT+01:00 Raúl Alexis Betancor Santana <
> rbetancor at gmail.com>:
>
>> Some carriers gateways doesn't like a T.38 invite on advance, usually the
>> order that gives better results for faxing are first invite on PCMU/PCMA
>> (or any other supported codec) and then re-invite to T.38.
>>
>> Take a look at how gonicus gofaxip do-it (https://github.com/gonicus/go
>> faxip)
>>
>> On Fri, Dec 1, 2017 at 10:21 PM, Kevin Olbrich <ko at sv01.de> wrote:
>>
>>> Hi!
>>>
>>> Our carrier supports T.38 for outgoing faxes. I am trying to send faxes
>>> like this:
>>>
>>> originate {origination_caller_id_name='kevin',origination_caller_id_nu
>>>> mber='+49123456789',ignore_early_media=true,absolute_codec_s
>>>> tring='PCMA,PCMU',fax_use_ecm=true,fax_enable_t38=true,fax_
>>>> enable_t38_request=true}sofia/gateway/carrier_1/+4912121212
>>>> &txfax(/opt/faxout.tif)
>>>
>>>
>>>
>>> Log:
>>>
>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.513164 [DEBUG]
>>>> sofia_glue.c:1295 sofia/external/+4912121212 sending invite version: 1.6.19
>>>> -36-7a77e0b 64bit
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa Local SDP:
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa v=0
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa o=FreeSWITCH 1512130268
>>>> 1512130270 IN IP4 123.123.123.123
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa s=FreeSWITCH
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa c=IN IP4 123.123.123.123
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa t=0 0
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa m=image 30466 udptl t38
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxVersion:0
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38MaxBitRate:14400
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxFillBitRemoval
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxRateManagement:transfe
>>>> rredTCF
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxMaxBuffer:2000
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxMaxDatagram:400
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxUdpEC:t38UDPRedundancy
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.533158
>>>> [DEBUG] sofia.c:7084 Channel sofia/external/+4912121212 entering state
>>>> [calling][0]
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.673120
>>>> [DEBUG] sofia.c:6294 sofia/external/+4912121212 T38 invite failed
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.673120
>>>> [DEBUG] sofia.c:7077 Channel sofia/external/+4912121212 skipping state
>>>> [ready][488]
>>>
>>>
>>>
>>> Carrier confirmed that T.38 is possible... What could be the cause for
>>> this? How can I enforce T.38 instead of falling back to g711a (hangup on
>>> failed invite)?
>>>
>>> Thanks.
>>>
>>> Kind regards,
>>> Kevin
>>>
>>> ____________________________________________________________
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>>
>>
>> _________________________________________________________________________
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>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>>
>> Official FreeSWITCH Sites
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>> http://confluence.freeswitch.org
>> http://www.cluecon.com
>>
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>
>
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