[asterisk-users] echo over digital line

[Vieri]

--- On Tue, 10/14/08, Kevin P. Fleming <kpfleming at digium.com> 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.

Clear enough.

So in other words, if an "Asterisk VoIP extension" calls a remote number (or vice versa) and the only echo is the remote's voice exclusively on the remote device then I guess that:

1) on the Asterisk end EC is working as expected
2) the remote end lacks or has inefficient EC
3) I dismiss the problem and blame the remote party's PBX or service provider

Thanks,

Vieri