Kind of, I think the various ec algorithms train differently, but they
end up with a list of numbers which represent how much of the primary
sound to replay (inverted of course) and when, so in my case the ec
needs to take the current sample, and subtract the value of the sample
3.5ms ago to cancel out the echo.
The actual algorithm looks a bit like:
Sn = current sample
Sn-1, Sn-128 = previous samples
E1-E128 are the recorded coefficients
S0 = S0 + Sn-1 * E1 + Sn-2 * E2 + ... Sn-128 * E128
But anyone else feel free to step in to correct me!
Thanks
James
________________________________
From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Eric
Bishop
Sent: Sunday, 15 January 2006 12:08
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] echo tail stats
Wouldn't that large spike be the primary sound rather than the echo?
On 1/15/06, James Harper <james.harper@bendigoit.com.au > wrote:
Here's the graph of the echo coefficients I grabbed from a x100p card on
my asterisk server. If my interpretation is correct, it shows that most
of the echo comes in at about the 28th tap, and assuming a sample rate
of 8000hz, that would be about 3.5ms.
Will that tell you the sort of things you need to know?
Thanks
james
________________________________
From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Eric
Bishop
Sent: Sunday, 15 January 2006 11:06
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] echo tail stats
Yes, plese do post it....
On 1/15/06, James Harper <james.harper@bendigoit.com.au> wrote:
I'm working on some code to be able to preload the echo cancellers (and
obviously dump the data too, which I've already done). I should have a
patch ready tonight or tomorrow.
If you are interested I can attach a plot of the coefficients against
time which might tell you the sort of thing you need to know if you
could do it on your data. The image is only an 11k gif... would it be
okay to post it to the list?
James
________________________________
From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Eric
Bishop
Sent: Sunday, 15 January 2006 10:11
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: [Asterisk-Users] echo tail stats
Does anyone know how to determine the echo tail size (in ms) of a
particular call?
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