asterisk users - Oct 2008 - echo over digital line

Hi,

I'm using a 4-port BRI card (b410p) to make and receive calls (via
chan_misdn):
http://www.digium.com/en/products/digital/b410p.php

This card supposedly has hardware echo cancellation.

How can I check that echo cancellation is actually ON (taps, etc) on a given
misdn channel (like with the "zap show channel X" command).
"misdn show channel X" doesn't seem to show more info than
"misdn show channels" and in any case there's no info on echo
cancellation. I also issued an "misdn toggle echocancel mISDN/1-u2528"
(on a live call) and flipped several times between echo ON/OFF without
subjectively noticing any difference (it's odd because I was calling from a
SIP softphone to a remote POTS analog phone and the latter usually experiences
echo issues). I couldn't reproduce the echo problem today but in some
occasions the remote POTS called party complains they hear echo of their own
voice (the "called" user has a standard analog phone, no headsets,
etc., and usually never has echo problems).

According to this article:
http://www.audiodesignline.com/howto/206800151;jsessionid=UJRLVDJCJT2QMQSNDLPSKHSCJUNN2JVN?pgno=1
I (on the Asterisk system) should take care of the remote user's echo issue,
ie. either my BRI card or my Asterisk add-on software should correctly echo
cancel.

How can one disable hardware echo cancellation altogether on the b410p?

Which software echo cancellation can I try on misdn channels (apart from the
experimental oslec on misdn)?

Is there a way to see the "echo cancellation details" of a live call?

Thanks,

Vieri

Hi,

These questions are very pertinent and I would be also very curious to read
answers.
I hope these simple lines would encourage readers to respond.

Cheers
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Vieri wrote:
> According to this article:
>
http://www.audiodesignline.com/howto/206800151;jsessionid=UJRLVDJCJT2QMQSNDLPSKHSCJUNN2JVN?pgno=1
> I (on the Asterisk system) should take care of the remote user's echo
issue, ie. either my BRI card or my Asterisk add-on software should correctly
echo cancel.
No, that is not correct. The echo cancellers used in
Zaptel/DAHDI/mISDN/etc. (software or hardware) are used to cancel the
echo generated by the far end of the near end party's voice. In your
example, any echo of your own voice (input via your SIP phone and sent
out over the ISDN network) generated by the remote analog PSTN line
would be cancelled so that you would not hear it.

It is not possible to cancel echo that the far end party hears, it must
be cancelled as near as possible to the device hearing the echo.

-- 
Kevin P. Fleming
Director of Software Technologies
Digium, Inc. - "The Genuine Asterisk Experience" (TM)