[Freeswitch-users] Faxing transcoding issues.

[Andrew Cassidy]

Ok lets go into details a little more:

User <--> FS <--> Provider

When User sends a fax, provider detects tones and renegotiates with t38. I
can handle this case fine using sip_execute_on_image=t38_gateway

Now, one way or another I also want the a-leg to be t38 if possible. Be
that via reinvite from FS or sepcifically requested by User. I can't make
this work at all.

If FreeSWITCH renegotiates with User and User rejects T38, Freeswitch does
not reinvite with the original codecs.

If User requests t38, fax negotiation fails in some cases, although that
may be irrelevant.

So, here's my current configuration, that kind of works:

<action application="export" data="fax_enable_t38=true" />
<action application="export" data="sip_execute_on_image=t38_gateway self
nocng" />

To test the User end (in this case another FreeSWITCH box for testing):

With T38:

originate {execute_on_answer='t38_gateway
peer',fax_verbose=true,ignore_early_media=true,fax_ident=xxxx,fax_header='Test
Fax',absolute_codec_string=PCMA,origination_caller_id_number=xxxx}sofia/gateway/xxxx/xxxx
&txfax('/home/andrew/test_fax.tiff')

Without T38:

originate {execute_on_answer='t38_gateway
peer',fax_verbose=true,ignore_early_media=true,fax_ident=xxxx,fax_header='Test
Fax',absolute_codec_string=PCMA,origination_caller_id_number=xxxx}sofia/gateway/xxxx/xxxx
&txfax('/home/andrew/test_fax.tiff')

However, the following fails:

originate
{fax_enable_t38=true,fax_enable_t38_request=true,fax_verbose=true,ignore_early_media=true,fax_ident=xxxx,fax_header='Test
Fax',absolute_codec_string=PCMA,origination_caller_id_number=xxxx}sofia/gateway/xxxx/xxxx
&txfax('/home/andrew/test_fax.tiff')

I think this configuration will work for now, the User end can decide
freely if they want to send t38 requests to FS or not.

On 4 August 2016 at 14:39, Brian West <brian at freeswitch.org> wrote:

> You also do NOT want pass thru set if you're doing this.
>
> On Thu, Aug 4, 2016 at 4:02 AM, Andrew Cassidy <
> andrew at cassidywebservices.co.uk> wrote:
>
>> Hi all,
>>
>> Just realised the server I'm having issues with is an old wheezy server
>> running 1.4.26. I will test with latest and report back.
>>
>> Kind regards,
>>
>> On 4 August 2016 at 09:55, Andrew Cassidy <
>> andrew at cassidywebservices.co.uk> wrote:
>>
>>> Good morning all,
>>>
>>> I've been playing with faxing and t38 over the last few days. I use a
>>> wholesale provider who detects and reinvites for t38, and have implemented
>>> the same in my systems. Passing t38 through unmodified is not an issue.
>>>
>>> The issue I do have, is in the event that the sender refuses the
>>> reinvite, I'd like freeswitch to transcode. In theory, this is set up
>>> correctly, but see this error message repeated over and over and ultimately
>>> the fax fails:
>>>
>>> [DEBUG] mod_spandsp_fax.c:1756 sofia/external/xxx at provider.com Error
>>> decoding UDPTL (172 bytes)
>>>
>>> Every other scenario I have worked through is working fine.
>>>
>>> For reference, the fax-specific dialplan entries:
>>>
>>> <action application="export" data="fax_enable_t38=true"/>
>>> <action application="export" data="fax_enable_t38_request=true"/>
>>> <action application="export" data="t38_passthru=true"/>
>>> <action application="export"
>>> data="nolocal:sip_execute_on_image=t38_gateway self" />
>>> <action application="set" data="execute_on_answer=t38_gateway peer" />
>>>
>>> Thanks in advance.
>>>
>>> --
>>> *Andrew Cassidy BSc (Hons) MBCS SSCA*
>>> Managing Director
>>>
>>> 03303 880 960 andrew at cassidyweb.co.uk <andrew at cassidywebservices.co.uk>
>>> www.cassidyweb.co.uk <http://www.cassidywebservices.co.uk>
>>>
>>
>>
>>
>> --
>> *Andrew Cassidy BSc (Hons) MBCS SSCA*
>> Managing Director
>>
>> 03303 880 960 andrew at cassidyweb.co.uk <andrew at cassidywebservices.co.uk>
>> www.cassidyweb.co.uk <http://www.cassidywebservices.co.uk>
>>
>> _________________________________________________________________________
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>
>
>
> --
>
> *Brian West*
> brian at freeswitch.org
>
>
> *Twitter: @FreeSWITCH , @briankwest*
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>
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-- 
*Andrew Cassidy BSc (Hons) MBCS SSCA*
Managing Director

03303 880 960 andrew at cassidyweb.co.uk <andrew at cassidywebservices.co.uk>
www.cassidyweb.co.uk <http://www.cassidywebservices.co.uk>
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