[asterisk-dev] Zaptel Echo Cancellation

[Eric "ManxPower" Wieling]

John Lange wrote:
> On Thu, 2006-08-03 at 14:36 +0100, Steve Davies wrote:
> 
>> Note that 16ms is plenty for most echo sources that occur in a real system.
> 
> Would you mind expanding on that? 16ms seems like the bare minimum?
> 
> Is there not an inherient delay of several ms due to CPU and encoding
> overhead etc or is this not a factor in the calculations? I'm just
> wondering what kinds of delays play into this or is the only thing that
> matters the delay on the PSTN before the signal hits the card?

The PSTN delay is what matters.  Echo must be removed at the PSTN interface.


> On a side note; does anyone know of a way to implement hardware echo
> cancellation on a single-span system? Are there external hardware echo
> cancelers that can be added into the equation?

We use Tellabs external EC stuff.  Cheap off of eBay if you know what 
you need.  The Tellabs stuff supports bunches of T-1s, but you can use 
it for just 1 T-1

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