<div dir="ltr"><br><div class="gmail_quote">2008/10/13 Tilghman Lesher <span dir="ltr"><<a href="mailto:tilghman@mail.jeffandtilghman.com">tilghman@mail.jeffandtilghman.com</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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</div>Pray tell, how do you echo cancel in both directions? Wouldn't that<br>
necessitate cancelling echo before it occurs on the line (sort of a white<br>
noise/pink noise kind of operation)? Seems like modelling a projectile such<br>
that when it reaches its target, the atmospheric stresses during its flight<br>
turn it into a perfect sphere (and with about the same likelihood of success).<br>
<br>
--<br>
<font color="#888888">Tilghman<br>
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</div></div></blockquote></div><br>Hi,<br><br>Thanks for replying.<br><br>So, bottom line is "you can't cancel echo in both directions", right ?<br><br>I read from <a href="http://lists.digium.com/pipermail/asterisk-dev/2006-January/017774.html" target="_blank">http://lists.digium.com/pipermail/asterisk-dev/2006-January/017774.html :</a><br>
"Generally speaking there is only one direction of echo cancellation needed: towards the 4-wire (digital) party. Any echo heard by the 2-wire party is normally acoustic echo, which we don't try to alleviate."<br>
<br>It seems it could also have been written this way :<br>"Echo cancellation in both directions can't be done and generally speaking there is only one direction of echo cancellation
needed: towards the 4-wire (digital) party. Any echo heard by the
2-wire party is normally acoustic echo, which we don't try to
alleviate."<br><br><br>Anyway, excuse me if my question seems naive but, when using a media gateway between PRI (digital) and VoIP, which are respectively the 2-wire and the 4-wire sides as both technologies use 4-wire connections ?<br>
If Alice is on the VoIP side and Bob on the ISDN/PSTN side, which one will benefit from EC ?<br>Will Alice stop to hear echo of its own voice or Bob's voice (I've never met this case but I'm not a reference on this) ?<br>
Will Bob stop to hear echo from its own voice or Alice's voice (I've never met this case but I'm not a reference on this) ?<br><br>Regards<br><br></div>