On Tuesday 14 October 2008 02:10:39 Olivier wrote: > 2008/10/13 Tilghman Lesher <[EMAIL PROTECTED]> > > > <snip> > > > > Pray tell, how do you echo cancel in both directions? Wouldn't that > > necessitate cancelling echo before it occurs on the line (sort of a white > > noise/pink noise kind of operation)? Seems like modelling a projectile > > such > > that when it reaches its target, the atmospheric stresses during its > > flight turn it into a perfect sphere (and with about the same likelihood > > of success). > > So, bottom line is "you can't cancel echo in both directions", right ? > > I read from > http://lists.digium.com/pipermail/asterisk-dev/2006-January/017774.html > > : <http://lists.digium.com/pipermail/asterisk-dev/2006-January/017774.html> > > "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." > > It seems it could also have been written this way : > "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." > > > 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 ? > If Alice is on the VoIP side and Bob on the ISDN/PSTN side, which one will > benefit from EC ?
Neither. As both sides are digital, no 2-wire echo is possible, only acoustic echo. -- Tilghman _______________________________________________ -- 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
