[Asterisk-Users] Asterisk and Hylafax, on the same box

[Mike]

Armin,

Thanks a lot for the very detailed answer.  I'll have to take a long look at
the CAPI interfaces and see how I can pull all this off, it's all very new
to me, but at least I understand that with an Eicon card, I could share a T1
between Asterisk and Hylafax.  I'm not clear on whether I could receive fax
and voice on the same DID though (if its Fax, Hylafax takes care of it, if
its voice, Asterisk does)...

Mike

  

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Armin
Schindler
Sent: March 31, 2006 7:20 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] Asterisk and Hylafax, on the same box

On Fri, 31 Mar 2006, Olivier Krief wrote:
> 2006/3/31, Armin Schindler <armin at melware.de>:
> 
> > Yes, this is possible of course with the Eicon Diva Server PRI (T1)
card.
> > This card provides a CAPI interface where you can connect 
> > Asterisk(with
> > chan-capi) and any other CAPI based application like Hylafax.
> >
> > You can e.g. configure chan-capi to use 20 channels and the 
> > remaining channels configured in Hylafax.
> > When you use a Eicon Diva Server with DSPs on board, you don't need 
> > to worry about CPU power, because fax-receive is done on the DIVA 
> > card.
> > So you don't need to 'bridge' something here, it just works.
> >
> > Armin
> 
> 
> Armin,
> 
> Do you mean you could dynamically share E1/T1 channels between 
> Asterisk and Hylafax applications ?

Yes, CAPI provides all available controllers (ports) and its channels to
every application at the same time.

> For example, for each incoming call to a given fax number, Capi driver 
> would trigger Hylafax software to process incoming fax and at the same 
> time, Asterisk software would be smart enough to use other channels 
> for outgoing calls ?

Yes, via the CAPI interface you don't reference a real b-channel, this is
done by the driver of the ISDN card which provides the CAPI interface.

Using CAPI, the applications can (and have to) decide which calls they want
to get signaled or which are ignored when they are meant for another
service. E.g. the following example is not possible with CAPI:
You have one number (and the same BC) for two services assigned. If you are
using one application, which can switch to another server by some rule, then
it is okay. But two applications must be configured to serve the own
numbers/services only.
Another thing is, the application does not know about busy channels. This
means if you have a 23 channel line and 10 lines are busy with hylafax at
the moment, then chan-capi (or another application) can use 13 channels
only, of course. So if you have configured chan-capi with e.g. 15 channels
to use, chan-capi will just return 'busy : no circuit/channel available'.
But this is all configuration stuff and when configured correctly, it works
very good.

There are even more capabilities. For example Eicon is doing a lot. Their
Diva Server cards do provide a RTP interface via CAPI (new chan-capi will
support this). Which means coding and anti-jitterbuffer is done on the ISDN
card, chan-capi just 'pushes' the RTP packets onto the card...

With rcapid and a patched version of the libcapi.so, you can even have the
ISDN hardware on one server and the applications on other servers connected
via CAPIoverTCP (bintec protocol in that case).
I use this because my faxing application (just the capifaxrecvd) runs on my
local maschine instead of the ISDN/Asterisk/Gateway server.
 
> If this understanding is correct, what is the downside ?
> Why don't everybody use chan-capi ?

CAPI comes originally from the Windows world, but is a common ISDN API
standard www.capi.org. So if there would be CAPI drivers for all of these
ISDN cards, you can use CAPI (chan-capi).
So the missing part is the card-driver. Currently I know of three CAPI based
hardware:
1) Eicon Diva Server (all cards including analog ports) with full CAPI 2.0 
   and VoIP/T.38 extensions.
2) AVM (basic CAPI 2.0)
3) mISDN driver for passive cards (hscx/hfc/...)
   and on BSD with i4b!



Armin

(www.chan-capi.org ;-)
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