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[fernando.berretta at g...]

Hi,

Could some one let me know if a fax is received through a FXO card
connected to * and fax machine is connected to a Linksys FXS device
which support T38, is T38 going to be used for faxes which comes from
PSTN or go through PSTN ? or because of Asterisk T38 passthrough support
it is not possible ? so is for this scenery better to use external FXO
gateways with t38 support ?

Regards,
Fernando

[rob at hillis.dyndns.org]

Not unless you're running CallWeaver or Asterisk 1.6.0-beta4. Asterisk
has had passthrough support for T.38 for a while (somewhere in 1.4 it
became available IIRC) but is currently completely incapable of
terminating or encoding a fax call to T.38.

The only real option available at the moment is to keep one PSTN line on
an ATA with an FXO port and T.38 support available and direct calls from
the fax machines through to it. However, I should point out that while
I believe this should be possible, I haven't actually tried it myself.
Fernando Berretta wrote:

[steveu at coppice.org]

Rob Hillis wrote:

[rob at hillis.dyndns.org]

T.38 is a codec in exactly the same way that GSM or G.729 is a codec, so
yes it /can/ be used at the same time as any other codec - just that
only /one/ codec will be used at a time. What often happens is that the
call will initially be established with a codec such as G.729 or G.711a,
but once fax tones are detected the call will change codecs to T.38.

According to the release notes for 1.6.0-b4...

- 11873, Added core API changes to handle T.38 origination and termination
(The version of app_fax in Asterisk-addons now supports this.)
This should be all that is necessary to run a T.38 gateway.


Steve Underwood wrote:

[support at ocg.ca]

Will the built-in T.38 support eliminate the need for spandsp? I'm curious
how this will affect iaxmodem.

MD
_____

From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Rob Hillis
Sent: Saturday, February 23, 2008 7:12 AM
To: Asterisk Users List
Subject: Re: [asterisk-users] FXO Cards - T38


T.38 is a codec in exactly the same way that GSM or G.729 is a codec, so yes
it can be used at the same time as any other codec - just that only one
codec will be used at a time. What often happens is that the call will
initially be established with a codec such as G.729 or G.711a, but once fax
tones are detected the call will change codecs to T.38.

According to the release notes for 1.6.0-b4...


- 11873, Added core API changes to handle T.38 origination and termination

(The version of app_fax in Asterisk-addons now supports this.)

This should be all that is necessary to run a T.38 gateway.


Steve Underwood wrote:

Rob Hillis wrote:



Not unless you're running CallWeaver or Asterisk 1.6.0-beta4. Asterisk

has had passthrough support for T.38 for a while (somewhere in 1.4 it

became available IIRC) but is currently completely incapable of

terminating or encoding a fax call to T.38.





I thought * was still not capable for T.38 gateway operation. Doesn't

beta 4 just added T.38 termination? And, I believe it misses out some

key elements of doing that properly. Note that T.38 termination is an

addon, so it can't be used with, say, G.729.



The only real option available at the moment is to keep one PSTN line on

an ATA with an FXO port and T.38 support available and direct calls from

the fax machines through to it. However, I should point out that while

I believe this should be possible, I haven't actually tried it myself.







Steve





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[steveu at coppice.org]

T.38 is not a codec. A codec has one input and one output. T.38 is an
interactive protocol. This, however, has nothing to do with what I said.
If you use G.729 in the same asterisk as my spandsp library, you are
breaking my licence conditions.

Steve
Rob Hillis wrote:

[digium at sanguinarius...]

Steve Underwood wrote:

[digium at sanguinarius...]

Michelle Dupuis wrote:

[digium at sanguinarius...]

Steve Underwood wrote:

[zoachien at securax.org]

I think you are missing something.
Steve means that since its in add-ons its probably a GPL addition and
not compatible with the g729 licensing.

A t.38 gateway involves more than origination and termination, those 2
are pretty easy and do not involve any modems, the gatewaying is the
harder part.

Zoa.
Rob Hillis wrote:

[support at ocg.ca]

Wow, an answer phrased in the form of a flame...

A more supportive tone might actually encourage the Asterisk userbase to
grow!

[digium at sanguinarius...]

Michelle Dupuis wrote:

[rob at hillis.dyndns.org]

About the only reason for eliminating SpanDSP is compatibility with the
GPL license. Remember that /any/ feature added to the free version of
Asterisk is going to be added to ABE as well - ergo, the licensing of
any libraries required need to be compatible with a /non/-open source
license.
Thomas Kenyon wrote:

[rob at hillis.dyndns.org]

T.38 is for all intents and purposes a codec. It's purpose is to
re-encode a fax transmission as a data stream to be re-assembled at the
other end as if it were a fax call. Seems to me to be pretty close to
the definition of a codec to me.

Your original comment was that you cannot use T.38 and G.729 in Asterisk
at the same time. On a technical level, this is /not/ true, especially
if the T.38 implementation does not rely on SpanDSP. (whether or not
such an implementation exists is another question) Breaking license
conditions is a separate issue altogether.

You also appear to have answered another one of your questions on this
forum to someone else ("why on earth would you want to remove SpanDSP as
a dependency?") by telling us that you can't run G.729 at the same time
as T.38.

I'm also curious as to why you assert that using G.729 in Asterisk
(/not/ ABE) at the same time as a T.38 implementation that relies on
SpanDSP since these are two completely separate plugins that are
installed and acquired separately. That's almost like asserting that
you can't run any commercial X application if you've installed my XYZ
web browser on the same machine. Just because they use a common
software base (X in this instance) /doesn't/ mean that you're violating
the GPL by running non commercial software on the same machine.

A more meaningful interpretation of the GPL would be that you either can
or can't run a T.38 implementation with Asterisk /full stop/. Either
the license is compatible, or it isn't. Trying to force any other
interpretation on people will end up with you being dismissed as an
extremist.
Steve Underwood wrote:

[tzafrir.cohen at xorco...]

On Sun, Feb 24, 2008 at 04:35:35PM +1100, Rob Hillis wrote: