On Tuesday 10 January 2006 22:50, Boris Benko wrote: > > Here, it is clearly stated, that BT 101 (and 102, too) implements *LINE > ECHO CANCELATION*. Please, take a look: > > http://www.thevoipconnection.com/store/catalog/product_16192_Grandstream_Bu >dgeTone_BT102.html
They can say that their phone can save the whales but it would be quite hard to believe. In the same way, affirming that a SIP phone with a several tens of milliseconds long (and varying!) delay loop, with maybe a compressing codec can cancel the *remote* echo is hard to believe, even considering that it not *supposed* to do it. Even considering zero network delay, 20ms and small, 8ms, jitter buffers you have a delay loop of 56ms, which is already too much for a 256-taps echo canceller.... and if you add a compressing codec it will become much more difficult. Network echo cancellers with tails up to 128ms do exist but I don't think *budget*ones have 30 MIPS of DSP capacity to implement a kind of cancellation they are not *supposed* to be doing. Let's say that I am at best skeptical with regard to far-end echo cancellation done by IP phones. > In both cases, I have heard the annoying echo. When I used the SNOM 190 > IP phone, I have clearly heard the echo in both cases. In a minute > later, I have used the BT 101 phone and the echo from the first case was > gone, but not in the second case. In both cases, SNOM 190 and BT 101 > were connected to my (*), with the vISDN v0.14, asterisk is 1.0.9 > version, kernel 2.6.13, the system is FC4. Echo is not always a constant, it may depend on many factors you cannot control. For example, the phone attenuation attenuates the echo two times, little differences in sound attenuation can result in notable echo differences. > Regarding the acustic echo cancellation (g.167 or something close to > it).Please correct me, if I am wrong... This type of cancellation is > needed in cases, when the voice from the speaker comes to the > microphone, due to several reasons - for example when using a laptop > with speakers and the microphone. Yes. Several phones with handsfree mode have AEC, the others mute the speaker when detecting speech (shortcut solution :). Bye, -- Daniele Orlandi _______________________________________________ Visdn-hackers mailing list [email protected] https://mailman.uli.it/mailman/listinfo/visdn-hackers
