Well now I am confused, a recording of an echo is not the same thing as the real thing. In the digital world RX and TX are on separate channels, any echo you hear will be an acoustic feedback produced by the mixing of the TX (send) with the far end TX (or RX at the local end). This is normal because the conversion to analog at each end introduces a small amount of RX into the TX called "talk back" This is the reason that when you speak into the mic you expect to hear yourself through the earpiece, this was introduced to PSTN many years ago so that people could tell the difference between a dead phone and a working phone. (pick up any analog phone and you'll see what I mean). Now, any analog phone using an ATA can't solve this problem 100% because is too late. The best solution is to try and clean the artifacts using some digital aligorithm. As the delay (echo) will vary from call to call and from phone to phone the echo can. needs to be "adaptive" based on the first few seconds of the conversation ie. "training". Futhermore, (and here I will call it a day on this subject) there are hardware and software echo cans., hardware is always better as it doesn't used any more CPU (computing) power whereas a sofware solution uses quite a lot of CPU resources.
ALL all THE the BEST best :) Henry L.Coleman [VoIP-PBX.ca] ------------------------------------------------- > John Lange< > On Mon, 2009-04-20 at 16:56 -0400, Simon P. Ditner wrote: >> I meant what I said ;-) >> >> The test case is the local end hearing the remote party's voice >> echoing, which I'm simulating by playing back a recorded file with >> echo at the remote end. > > Ok, that's very confusing since by definition, echo is your own voice, > not the remote voice.... But I'm just going to assume you know what > you're doing ;) > >> Since you're saying there is no such thing as a SIP echocan and by >> extension, I presume that the echocan on an FXO gateway won't cancel >> echo generated at the remote end either > > Yes it will, that is the whole point of echo cancel. Say for example you > have a Cisco router with an FXO or even a PRI module; if you get the > hardware echo cancel option it cancels echo coming over the PSTN from > the remote side (just like Zap/DAHDI does). > >> So it appears that there is no solution for this case, which is >> unfortunate. > > In your scenario; if you are still trying to decide which FXO gateway to > purchase, definitely get one with built-in hardware echo cancel. They > are of course much more expensive but that is the correct solution. > > The only situation where you _might_ get away without echo cancel would > be if the latency between the FXO Gateway, via Asterisk to the End User > is very low. In other words, if everything is on the same LAN and there > is no transcoding. > > -- > John Lange > http://www.johnlange.ca > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > > > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
