2008/10/11 Eric ManxPower Wieling <[EMAIL PROTECTED]> > > <snip> > Where did you hear that media gateways "filter one-way only"? > > Hi ,
Reading over this reply, it seems to me that having EC working in one direction is not a so well known fact. Could we say : 1. EC working in one direction is the general case but some of us were not aware of that (I was not, for instance) 2. or this is not so widespread use and some private architectures involve EC working in both directions ? For instance, what about Cisco Call Manager ? Reading this http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtmland specifically reading "IP Phone user hears echo" paragraph, I can't say which direction(s) is (are) involved (as article don't mention which voice is echoed). Another interesting thing to note in this paper is the "solution is to use a load ID on the IP phone, which includes echo suppression on the handset and headset" (PSTN phone user hears echo). Does it imply echo cancelling is mostly done inside phones ? In an IP phone, is it more cost effective to use 2-wires connections (which produces echo) AND echo cancellation systems to suppress echo than to use 4-wires connections which don't produce echo in the first place ? Does it also imply that Cisco IP phones use 2-wires connections ? Cheers
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