asterisk users - May 2004 - RFD: With echo and other distortion, can ulaw/alaw line quality ever be good enough for faxing?

Folks,

I've been following recent discussions regarding echo and echo training with
much interest, since it's a problem we've never been able to eliminate
here.

We're facing two challenges presently, and they may be related (or not):

a) Cisco 7960s in the office here echo back to our staff, but the customer
hears decent sound.
b) We've yet to be able to pass faxes through asterisk, despite trying a
number of approaches

A bit about our setup:

Two analog lines come into the office, into the FXO card of an CAC ADIT 600.
These are 'connected' to the TDM interface of the ADIT, and go out to
Asterisk via 2 channels of a a 24-channel fxs_ks line into a port of a
TE405P. We have two other ports on the TE405P occupied by digital fax
boards, connected to asterisk via AT&T 5ESS PRI. And of course there's
the
7960 handsets, connected directly to a switch at 100MBps (fdx).

Challenge a)
========In terms of looking into a), we started with:

http://asterisk.sohoskyway.net/Asterisk_Doc/current/docs-html/x939.html

Clearly some of the details are outdated, since the echo canceller options
live in zconfig.h now, not a Makefile, but it's a decent starting point.
Which gives rise to my first question - which echo canceler should we be
using? We have Steve, Steve 2, and Mark 1-3, with an aggressive option with
3 that could make calls scratchy ;-)

Is there any conventional wisdom here?

Next question ... we have control over gain at the zaptel level, and also at
the ADIT level apparently. Which should we use when trying to adjust things
with ztmonitor?

Next question ... it's not clear to me what the target is with ztmonitor.
Are we shooting for tx and rx levels that are balanced. and about 50% of the
scale at their max energy? I found that when I called a voicemail service
and listened to the auto-attendant that the RX meter of ztmonitor was about
50%, but I found the TX meter fluctuated wildly when I spoke. I could reduce
my voice level slightly and it would be very low energy, but with a slight
increase in volume it was pegged. The settings I made seemed to do nothing
to change this (I stop asterisk, unload and reload all zaptel modules, and
restart astertisk between each test).

Is this really supposed to work? I've managed to get the connection
extremely distorted with some settings, but have yet to make a change that
improved the quality or removed the echo.

Challenge b)
=======
In some ways, this is the most worrying problem for us, since we would love
to be able to pass faxes through asterisk reliably, and from the traffic on
this list and the fine efforts of Mr. Underwood, it seems many others would
too. People have spoken here of the nearly immediate echo cancelation on
pure TDM circuits, and so I would have thought we'd escape the echo problems
above in either of the following setups:

i) Plain ole' HP fax machine plugged into TDM400 FXS card
ii) Brooktrout/Eicon fax board connected to TE405P

In practice we're rarely able to train with the remote fax machine when
dialing to an outside line through asterisk and the ADIT 600. If we do
manage to get connected and the connection supports ECM error correction, we
can see lots of retransmitted frames which again points to very poor line
quality. In contrast, by connecting directly to the analog lines we can send
faxes all day with the trusty little HP ... ie: the lines aren't inherently
bad.

I guess what I'm looking for here is a sanity check ... are we trying to
push the limits here, or should this stuff be working much better than this?
We're willing to invest some time getting faxing to work, but I'd hate
to
ask people here to dedicate their time and energy to something that's never
really going to work well due to limitations in Asterisk/zaptel technology.

-Darren

--
Darren Nickerson
Senior Sales & Support Engineer
iFax Solutions, Inc. www.ifax.com
darren.nickerson@ifax.com
+1.215.438.4638
+1.215.243.8335 (fax

Folks,

The silence was deafening ... I had a few private replies but overall I'd
have to conclude that most people on this list aren't interested in faxing
thru Asterisk. You're all probably jazzed about VoIP and fax is forgotten
for now ;-)

We have learned the answer to _one_ of the questions I asked below - the
Adit channel bank's gain controls can be usefully applied to adjust each of
the incoming telephone lines independently, and by combining the Adit's gain
setting with Asterisk's, fun and good things can be made to happen ;-)

Another interesting observation is that echo can be seen visually when using
ztmonitor. Muting one side of the call (the RX side), and speaking from my
handset I can see my voice appear stongly on the TX side, and then I can see
the echo appearing on the RX side at an attenuated level, but it follows my
voice perfectly ;-)  I spend half a day talking to myself, and I have to
say, for the first time in ages I was running out of things to say! :-)

In other interesting news, updating zapel from CVS seems to have made things
significantly better. I had CVS from about 4 weeks ago previously, so
perhaps something was amiss. We can actually get faxes transmitting now, and
although they fail about 30% of the time, this is definitely progress.

Another data point, is that MARK3 echo cancellation is audibly worse under
our particular conditions. We're using MARK2 with the aggressive option
enabled, and while occasional flares of distorted (but attenuated) echo can
be heard, it's much easier to have conversations with customers! I'm
disappointed nobody commented on the echo cancelation options in the
source... I can only assume nobody actually knows the origins of any of them
any more, and the other ones are mostly anachronisms that are no longer
useful, and MARK2 is the clear winner.

Unfortunately, the news from Digium's technical support is not good.
Here's
what they had to say in response to our inquiry about faxing:

"Faxing in asterisk is only at varied levels of support and is
definitely not at a production level.  However, if you wish to work on
this we wouldn't mind at all :-).  The source code is of course free
to your disposal."

I'm not sure I understand that this support rep is saying to me ...
we've
had much success faxing from one PRI to another with them both connected to
Asterisk via a TE400P. Asterisk doesn't even break a sweat. We're rarely
getting the theoretical maximum of 33,600 that we can get with a T1 loopback
though, so something's slightly amiss, but it's only when we try to go
out
to the PSTN that things start to fall apart badly.

-Darren

--
Darren Nickerson
Senior Sales & Support Engineer
iFax Solutions, Inc. www.ifax.com
darren.nickerson@ifax.com
+1.215.438.4638
+1.215.243.8335 (fax)

----- Original Message ----- 
From: "Darren Nickerson" <darren.nickerson@ifax.com>
To: <asterisk-users@lists.digium.com>
Sent: Tuesday, May 04, 2004 12:35 AM
Subject: [Asterisk-Users] RFD: With echo and other distortion, can ulaw/alaw
line quality ever be good enough for faxing?

> Folks,
>
> I've been following recent discussions regarding echo and echo training
with
> much interest, since it's a problem we've never been able to
eliminate
here.
>
> We're facing two challenges presently, and they may be related (or
not):
>
> a) Cisco 7960s in the office here echo back to our staff, but the customer
> hears decent sound.
> b) We've yet to be able to pass faxes through asterisk, despite trying
a
> number of approaches
>
> A bit about our setup:
>
> Two analog lines come into the office, into the FXO card of an CAC ADIT
600.
> These are 'connected' to the TDM interface of the ADIT, and go out
to
> Asterisk via 2 channels of a a 24-channel fxs_ks line into a port of a
> TE405P. We have two other ports on the TE405P occupied by digital fax
> boards, connected to asterisk via AT&T 5ESS PRI. And of course
there's the
> 7960 handsets, connected directly to a switch at 100MBps (fdx).
>
> Challenge a)
> ========> In terms of looking into a), we started with:
>
> http://asterisk.sohoskyway.net/Asterisk_Doc/current/docs-html/x939.html
>
> Clearly some of the details are outdated, since the echo canceller options
> live in zconfig.h now, not a Makefile, but it's a decent starting
point.
> Which gives rise to my first question - which echo canceler should we be
> using? We have Steve, Steve 2, and Mark 1-3, with an aggressive option
with
> 3 that could make calls scratchy ;-)
>
> Is there any conventional wisdom here?
>
> Next question ... we have control over gain at the zaptel level, and also
at
> the ADIT level apparently. Which should we use when trying to adjust
things
> with ztmonitor?
>
> Next question ... it's not clear to me what the target is with
ztmonitor.
> Are we shooting for tx and rx levels that are balanced. and about 50% of
the
> scale at their max energy? I found that when I called a voicemail service
> and listened to the auto-attendant that the RX meter of ztmonitor was
about
> 50%, but I found the TX meter fluctuated wildly when I spoke. I could
reduce
> my voice level slightly and it would be very low energy, but with a slight
> increase in volume it was pegged. The settings I made seemed to do nothing
> to change this (I stop asterisk, unload and reload all zaptel modules, and
> restart astertisk between each test).
>
> Is this really supposed to work? I've managed to get the connection
> extremely distorted with some settings, but have yet to make a change that
> improved the quality or removed the echo.
>
> Challenge b)
> =======>
> In some ways, this is the most worrying problem for us, since we would
love
> to be able to pass faxes through asterisk reliably, and from the traffic
on
> this list and the fine efforts of Mr. Underwood, it seems many others
would
> too. People have spoken here of the nearly immediate echo cancelation on
> pure TDM circuits, and so I would have thought we'd escape the echo
problems
> above in either of the following setups:
>
> i) Plain ole' HP fax machine plugged into TDM400 FXS card
> ii) Brooktrout/Eicon fax board connected to TE405P
>
> In practice we're rarely able to train with the remote fax machine when
> dialing to an outside line through asterisk and the ADIT 600. If we do
> manage to get connected and the connection supports ECM error correction,
we
> can see lots of retransmitted frames which again points to very poor line
> quality. In contrast, by connecting directly to the analog lines we can
send
> faxes all day with the trusty little HP ... ie: the lines aren't
inherently
> bad.
>
> I guess what I'm looking for here is a sanity check ... are we trying
to
> push the limits here, or should this stuff be working much better than
this?
> We're willing to invest some time getting faxing to work, but I'd
hate to
> ask people here to dedicate their time and energy to something that's
never
> really going to work well due to limitations in Asterisk/zaptel
technology.
>
> -Darren
>
> --
> Darren Nickerson
> Senior Sales & Support Engineer
> iFax Solutions, Inc. www.ifax.com
> darren.nickerson@ifax.com
> +1.215.438.4638
> +1.215.243.8335 (fax
>
> _______________________________________________
> Asterisk-Users mailing list
> Asterisk-Users@lists.digium.com
> http://lists.digium.com/mailman/listinfo/asterisk-users
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users
>

Hello,

We are proud to officially release our worldwide IAX termination
service. We offer IAX termination from any Asterisk
server or IAX softphone. With your own Asterisk server our system allows
you to send as many simultaneous calls as you want for termination
using only ONE Diamond account. This works well for call centers,
and medium to large PBX deployments. We have a really good reseller 
program for all the Asterisk consultants out there. This is described on
the "opportunity" page at our www.diamondcard.us site.  

Account signups can be done online with a valid credit card, e-gold.com or 
goldmoney.com account. We have complete up to the second online call
traffic, billing statement and instant recharge features.

There are no monthly or signup fees. You prepay for your
minutes and thats it. You can get started for as little as $5.00.

We have a lot of other value added services that are available
with your account but I need to be brief here. 

Our site is at www.diamondcard.us. For online support or sales questions
you can reach us on Yahoo messenger instant chat at
dreamtime_net@yahoo.com or ICQ 36768098.

Please let me know if you have any questions.

Sincerely,

Stephen Karrington
Dreamtime. net Inc.
www.diamondcard.us

Corporate Office
101 California Street, 22nd Floor
San Francisco, CA 94111-5802

Voice - 877-203-9308
Fax - 310-943-2606

Dreamtime is your global choice for worldwide communication services, viral 
marketing software and direct sales
channel automation.

===8<==============Original message text==============On Thu, 27 May 2004,
Chris Sullivan wrote:
> Your rates page still has no useful information.  Can you guys at least
> put some rates up somewhere?
They have their rates available at
http://www.diamondcard.us/exec/voip-rep-acc-type?secRel=/secondary/corporate&priRel=/templates&secId=corporate

It is not user-friendly, but their rates are posted. I prefer the rates
published in plain text, so I can copy/paste into my spreadsheet and
compare which one offers the best rate for a selected country... Also,
avoid visiting their page with a browser other than exploder... their
javascript is also not mozzila-friendly...

-- Hi Hermann,

We will get around to doing another type of price list where its all
in one sheet. The link above is not complete. That could be a reason
for your error.

Please tell me what kind of error you are getting and what
browser and version number do you have? Thanks.

S

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===8<===========End of original message text===========