<div dir="ltr"><br><br><div class="gmail_quote">2008/10/10 Eric ManxPower Wieling <span dir="ltr"><<a href="mailto:eric@fnords.org">eric@fnords.org</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;">
All calls with a 2-wire analog piece have echo. You cannot perceive the<br>
echo because it happens so fast on non-VoIP connections. On VoIP calls<br>
you have significant extra latency while causes you you to perceive the<br>
echo.</blockquote><div>Do you mean "generated locally" or "generated distantly" ?<br><br>I understand that VoIP extra latency sometrimes renders perceivable what was unperceivable before.<br>What suprises me is to hear that media getways "filter one-way only" : as 2-wires analog devices produce echo, and every phone has 2-wires analog audio, in every call you've got at least 2 sources of echo : one in each endpoint.<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Echo must be removed before the call is converted to VoIP -- in<br>
your case the Media Gateway is the device that must remove echo.</blockquote><div><br>So, if Alice is hearing its own voice, <br>1. where does it most probably come from ?<br>2. where should it be removed ?<br><br>For both, I would reply :<br>
1. it most probably comes from Bob's phone (as other devices in-between are digital so voice can't leak from there),<br>2. Alice voice echo should canceled at every location: Bob's PBX, PSTN network (ISDN in the case I had in mind) and Alice's Media gateway<br>
<br>Do you agree ?<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
<div><div></div><div class="Wj3C7c"><br>
Olivier wrote:<br>
> Hi,<br>
><br>
> I'm using the following setup :<br>
> Alice ---- IPPhone ------<LAN>----- Media gateway ----<PSTN> ------- Phone<br>
> ---- Bob<br>
><br>
> For certain calls, users complains about echo : they can ear their own voice<br>
> in their handset, though media gateway echo cancel is turned on.<br>
><br>
> I'm wondering how this echo cancelation engine is supposed to work.<br>
> My understanding of echo is that most probably, when users complains about<br>
> earing their own voice, that means that distant phone or nearby equipment is<br>
> "leaking" : Bob's phone is sending Alice's voice signal back to Alice.<br>
><br>
> So, to properly cancel, I would say Media gateway should substract from<br>
> incoming signal the signal that left the media gateway few ms before.<br>
><br>
> Discussing here and there, some say that Media Gateway never work this way :<br>
> it would only filters out locally generated echo.<br>
> Do you agree with that ?<br>
> If positive, then what can you do, if Bob's phone generate much echo ?<br>
><br>
> Regards<br>
><br>
><br>
><br>
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