The echo canceller chip used in the Sangoma AFT "D" cards are fully compliant with all the G168 specifications.
David Yat Sin Sangoma Technologies (905) 474-1990 x119 (800) 388-2475 x119 Fax: (905) 474 9223 MSN: [EMAIL PROTECTED] Email: [EMAIL PROTECTED] Website: www.sangoma.com > >Date: Mon, 06 Feb 2006 22:09:34 +0800 > > From: Steve Underwood <[EMAIL PROTECTED]> > > Subject: Re: [Asterisk-Users] BAD/GOOD Echo Cancel > > To: Asterisk Users Mailing List - Non-Commercial Discussion > > <[email protected]> > > Message-ID: <[EMAIL PROTECTED]> > > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > > > James Harper wrote: > > > > >>virtually all software echo cancelers cannot get double echo removed > > >>completly. It can get the first one but not the second one. There > > >> > > >> > > >are > > > > > > > > >>instances where you get a 2nd echo, so ... Asterisk is no exception > > >>from this afaik nothing software only based is. > > >> > > >>If you really want good echo cancelation a hardware solution is the > > >> > > >> > > >way > > > > > > > > >>to go. > > >> > > >> > > >> > > > > > >Just an enquiring mind wanting to know, but how is a > > hardware solution > > >different to a software solution? The echo cancellers in the Digium > > >hardware presumably just use the same sort of algorithms as > > the software > > >versions, so it is just that they are dedicated and perform > > better, that > > >they are closer to the source of the echo, or some other > > thing that I've > > >overlooked? > > > > > > > > There isn't much difference, except for the amount of CPU > > taken, and the > > issue that software echo cancellation forces the device to use very > > short buffers. He's talking rubbish. Hardware echo cancellation > > certainly eases the timing constraints on the E1/T1 card to host > > processor interface. A lot more buffering can occur if the > > host does not > > do echo cancelling. A 20ms buffer on a PCI card will > > practically all the > > quirky timing issues people see go away. However 20ms of > > buffering would > > badly hurt an echo canceller's convergence. > > > > Most hardware cancellers, are actually software cancellers. > > The software > > just runs in a DSP (often a customised one) instead of the host > > processor. Some are a hybrid hardware/software design. Few are pure > > hardware. > > > > There are no standard algorithms for echo cancellation, and > > no standard > > level of performance. Few cancellers which claim G.168 compliance > > actually pass all the tests. If you look in the small print they > > generally say which tests they do pass. Echo cancellers vary a lot in > > performance, and making them truly robust and efficient is still a > > research topic. > > > > Regards, > > Steve > > \ > > _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- Asterisk-Users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
