[asterisk-dev] Adding Octastic Soft-Echo to external SIP adapters

[Steven Critchfield]

On Mon, 2007-05-07 at 10:33 -0500, Eric "ManxPower" Wieling wrote:
> critch wrote:
> > On Mon, 2007-05-07 at 19:54 +0500, Vazir wrote:
> >> PSTN (MY CALLING CARD CUSTOMERS) <---> CISCO AS5350 <---> 
> >> VOIP SIDE (SATELLITE ~600mc roundtrip - 300 mc oneway!)
> >>
> >> So the echo is generated by the VOIP side. I can hear it 
> >> very well is I switch off echo cancellation on the CISCO
> > 
> > If you hear the echo, it was produced on the other end. You audio went
> > out and came back. So assuming you are on one side and your customers
> > are on the PSTN, the echo happened on the PSTN and is supposed to be
> > cancelled by the cisco before becoming voip. If you turn off the echo
> > cancel on the cisco, it just digitizes what came back on the wire and
> > sends the echo and all to you.
> 
> I usually explain "VoIP" echo like this:
> 
> When you are talking and in a small room you do not hear echo.  The echo 
> is there, after all your voice is bouncing off the walls and coming back 
> to you.  However, because the delay between you hearing your voice and 
> the sound being bounced back off the walls is so short you do not 
> actually perceive the echo.
> 
> When you are in a large room and are talking you hear echo.  There is 
> NOTHING different about being in a small room .vs. a large room with 
> regards to echo EXCEPT that in a large room the delay between you 
> hearing your voice and you hearing the sound reflected from the walls is 
> much greater and so you perceive the echo.

That is a great way of explaining why latency causes you to
hear/experience the echo more. 
  
-- 
Steven Critchfield <critch at basesys.com>