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Sorry, i have been working with acoustic echoes, not very familiar with modem designs. Could u explain 'determined through an exchange between the end-points during startup' in a bit more details? Or sugguest some good ref.? thx --- "Shaw, David G (David)" <> wrote: > For modem, the bulk delay is determined through an > exchange between the end-points during the startup > of the modem. > For voice calls, you will have to come up with a > clever algorithm to determine the delay. > > Dave Shaw > > -----Original Message----- > From: Huo Jiaquan [mailto:] > Sent: Monday, November 17, 2003 8:50 PM > To: > Subject: Re: [echocancel] Re: LEC and NEC > How do u determine the bulk delay for the far-end > echo? > > --- anjuman2 <> wrote: > --- In > , "lee" > > <hao_li@y...> wrote: > > > Can someone tell me what the difference is > between > > a Line Echo > > > Canceller and a Network Echo Canceller? To me, > it > > seems that the > > only > > > difference is the echo path delay. Or say, they > > are just different > > > echo paths. > > > > > > If that's right, then a echo canceller with, > say, > > 128ms delay > > should > > > be able to cancel near end and far end echos. Or > > is there a better > > > approach? > > > > > > Please advice. Thanks. > > > > Dont know the terminology difference between line > > and network EC's. > > But there's a big difference between how to > > implement a near LEC or a > > far LEC. Having one long EC of (say) 128msec is > not > > optimal if in > > fact, there are two distinct sources--a near and a > > far one. The best > > way there is to have two short EC's, one that > spans > > the near-echo > > (typically <16msec) and another that spans the > > far-end echo but with > > a large (also called bulk) delay in front. But the > > second EC could > > also be spanning only 16msec of echo. This > > arrangment is used in > > modems a lot and is computationally very > efficient. > > > > > > > > http://personals.yahoo.com.au - Yahoo! Personals > New people, new possibilities. FREE for a limited > time. > > _____________________________________ > Note: If you do a simple "reply" with your email > client, only the author of > this message will receive your answer. You need to > do a "reply all" if you > want your answer to be distributed to the entire > group. > > _____________________________________ > About this discussion group: > > To Join: > > To Post: > > To Leave: > > Archives: > http://www.yahoogroups.com/group/echocancel > > Other DSP-Related Groups: http://www.dsprelated.com > ">http://docs.yahoo.com/info/terms/ > http://personals.yahoo.com.au - Yahoo! Personals New people, new possibilities. FREE for a limited time. |
RE: Re: LEC and NEC
Started by ●November 21, 2003
