That's the main reason I opened this thread as it surprised me a bit ...
>
>
> Any 2-wire analog leg will be a source of echo. Many, many, many calls
> do not have a 2-wire leg.
Even in handset audio circuit ?
I was thinking that any handset is a potential echo source due to this audio
circuit ...
Do you agree ?
> Think cell/mobile or endpoints with PRI or T-1.
>
> >
> >> Echo must be removed before the call is converted to VoIP -- in
> >> your case the Media Gateway is the device that must remove echo.
> >
> >
> > So, if Alice is hearing its own voice,
> > 1. where does it most probably come from ?
> > 2. where should it be removed ?
>
> > For both, I would reply :
> > 1. it most probably comes from Bob's phone (as other devices
in-between
> are
> > digital so voice can't leak from there),
> > 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
>
> If you (Alice) are hearing echo then the echo canceling can be done any
> time after it leaves Bob's 2-wire circuit but before the audio is
> converted to VoIP on your end.
>
> Telcos echo cancel cell/mobile phone calls (also a high latency path)
> and long distance calls, but almost never do EC on local calls. This
> is why you seldom get echo when calling a mobile phone or a long
> distance number -- you mostly get it on local calls.
That's what I thought after reading white papers here and there
>
>
> --
> Consulting and design services for LAN, WAN, voice and data. Based near
> Birmingham, AL. Now accepting clients worldwide. Contact me for Tellabs
> echo canceling systems. Also see http://www.fnords.org/skillslist.html
>
> _______________________________________________
> -- Bandwidth and Colocation Provided by http://www.api-digital.com --
>
> asterisk-users mailing list
> To UNSUBSCRIBE or update options visit:
> http://lists.digium.com/mailman/listinfo/asterisk-users
>
------=_Part_107123_31753339.1223751188551
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
<div dir="ltr"><br><br><div
class="gmail_quote">2008/10/11 Eric ManxPower Wieling <span
dir="ltr"><<a href="mailto:eric at
fnords.org">eric at
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;">
<div class="Ih2E3d"><br>
<br>
Olivier wrote:<br>
> 2008/10/10 Eric ManxPower Wieling <<a href="mailto:eric
at fnords.org">eric at fnords.org</a>><br>
><br>
>> 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.<br>
><br>
> Do you mean "generated locally" or
"generated distantly" ?<br>
><br>
> I understand that VoIP extra latency sometrimes renders perceivable
what was<br>
> unperceivable before.<br>
> What suprises me is to hear that media getways "filter one-way
only" : as<br>
> 2-wires analog devices produce echo, and every phone has 2-wires
analog<br>
> audio, in every call you've got at least 2 sources of echo :
one in each<br>
> endpoint.<br>
<br>
</div>Where did you hear that media gateways "filter one-way
only"?</blockquote><div><br>From a media gateway
vendor (mentioning its own products capabilities).<br>That's the
main reason I opened this thread as it surprised me a bit ...<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>
<br>
Any 2-wire analog leg will be a source of echo. Many, many, many
calls<br>
do not have a 2-wire leg.</blockquote><div>Even in handset audio
circuit ?<br>I was thinking that any handset is a potential echo source
due to this audio circuit ...<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;">
Think cell/mobile or endpoints with PRI or T-1.<br>
<div class="Ih2E3d"><br>
><br>
>> 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.<br>
><br>
><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<br>
> digital so voice can't leak from there),<br>
> 2. Alice voice echo should canceled at every location: Bob's
PBX, PSTN<br>
> network (ISDN in the case I had in mind) and Alice's Media
gateway<br>
<br>
</div>If you (Alice) are hearing echo then the echo canceling can be done
any<br>
time after it leaves Bob's 2-wire circuit but before the audio
is<br>
converted to VoIP on your end.<br>
<br>
Telcos echo cancel cell/mobile phone calls (also a high latency path)<br>
and long distance calls, but almost never do EC on local calls.
This<br>
is why you seldom get echo when calling a mobile phone or a long<br>
distance number -- you mostly get it on local
calls.</blockquote><div><br>That's what I thought
after reading white papers here and there <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>
<font color="#888888"><br>
--<br>
Consulting and design services for LAN, WAN, voice and data. Based
near<br>
Birmingham, AL. Now accepting clients worldwide. Contact me for
Tellabs<br>
echo canceling systems. Also see <a
href="http://www.fnords.org/skillslist.html"
target="_blank">http://www.fnords.org/skillslist.html</a><br>
</font><div><div></div><div
class="Wj3C7c"><br>
_______________________________________________<br>
-- Bandwidth and Colocation Provided by <a
href="http://www.api-digital.com"
target="_blank">http://www.api-digital.com</a> --<br>
<br>
asterisk-users mailing list<br>
To UNSUBSCRIBE or update options visit:<br>
<a
href="http://lists.digium.com/mailman/listinfo/asterisk-users"
target="_blank">http://lists.digium.com/mailman/listinfo/asterisk-users</a><br>
</div></div></blockquote></div><br></div>
------=_Part_107123_31753339.1223751188551--
