[Asterisk-Users] Asterisk and T38 Fax

[Jorge Mendoza]

See:
http://bugs.digium.com/view.php?id=5090

Jorge

Andy Kuo wrote:
> Hi,
>
> I tried to connect two T.38 capable SIP ATA's through Asterisk.
> I had canreinvite=yes and the 2 ATA's did talk directly to each other,
> but fax still failed.
>
> >From Ethereal captures, I think the problem was when the originating
> ATA is ready to set up a T.38 session, it sends a message to the
> destination ATA to get ready for receiving T.38 packets. 
> Unfortunately, Asterisk did not pass that message to the destination,
> so even though the actual T.38 packets did go directly to the
> destination, the destination ATA doesn't know it needs to switch to
> T.38 mode.
>
> What I am wondering is, if I can somehow configure the ATA's to be
> locked to T.38 only, no voice calls allowed, will it work? (since it
> is ONLY for receiving T.38 packets, we don't care if Asterisk pass on
> the message to the destination to switch to T.38)
>
> Any thoughts on whether this will work or this is just a crazy idea?
>
> Thanks.
> Andy
>
>
>
>
> On 2/21/06, Lee Howard <faxguy at howardsilvan.com> wrote:
>   
>> Carey Mould wrote:
>>
>>     
>>> How can I get asterisk to work with faxes in my configuration? I have
>>> a WAN with Asterisk at the centre and Mediatrix 1104 gateways at the
>>> end nodes providing tone to legacy PBX's and fax machines. The
>>> Asterisk is connected to the PSTN via a Digium single port t1.
>>>
>>> The end nodes are connected via frame-relay 128kbps links. I want to
>>> use g.729 between the end nodes and the Asterisk box at the centre.
>>> TheMediatrix box supports T38.  In my reading I am not seeing where
>>> asterisk supports T38.
>>>       
>> I believe that currently Asterisk SVN supports T.38 pass-through to some
>> extent.  Others here would be able to comment on that more fully.
>> However, what you're seeking is T.38 gateway support, and Asterisk does
>> not support that at the present.  I know that there is some intention
>> with spandsp to get T.38 gateway support there (so Asterisk would
>> eventually support T.38 gateway via Unicall), but I suspect that's a
>> long way off for your present needs.  Again, I'm not really the one to
>> be able to comment on this in detail.
>>
>> I'm not sure if the OpenH323 project (which I know supports at least
>> T.38 pass-through) supports T.38 gateway, but even if it did, getting
>> OpenH323 and Asterisk to work together may be difficult at best.  I'm
>> not really the one to be able to comment on that in detail, either.
>>
>> So for the time being I would consider that Asterisk does not support
>> the T.38 features that you need to make this work and that you look at a
>> different approach to getting your faxing working.
>>
>>     
>>> 1) If a fax machine connected to the Meditrix box sends a fax to a
>>> location on the PSTN (legacy fax machine) where is the T38 converted
>>> back?
>>>       
>> That's what a T.38 gateway does.  Asterisk doesn't do it.
>>
>>     
>>> 2)Does Asterisk handle this?
>>>       
>> No.  Not yet anyway.
>>
>>     
>>> 3) How do I configure Asterisk to do this
>>>       
>> You can't presently.
>>
>>     
>>> 4) What is the significance on the Digium web site where they have a
>>> CYA on the T1 board not  supporting faxes ?
>>>       
>> You probably are referring to these support statements on virtually all
>> of their products: "The current state of faxing is incomplete and will
>> not be supported."
>>
>> Well, it pretty much means what it says.  I don't think you'll get any
>> significant degree of support from Digium if you run into trouble with
>> faxing using their hardware.
>>
>> All of that said, can you push a fax call through an Asterisk PBX?
>> Yes.  Search the archives and you'll see it can be done.
>>
>> Lee.
>>
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