[Speex-dev] Re: aec

Jason Harper jhharper1 at yahoo.com
Thu Nov 3 22:36:18 PST 2005

I've tried some further debugging to see what mdf is
actually doing.  Instead of sending:
tmp_out = (float)ref[i] - st->y[i+st->frame_size]
to the output, I just sent
to see what was being subtracted from the microphone
input.  When I open this in Audacity, I see a very
small signal at about -40dBm.  The actual echo in my
sample has a power closer to -20dBm.  So, when the
-40dBm estimated echo is removed from the -20dBm
actual echo there is almost no perceived difference in
the echo power.
I'm sure that there are others on the list that have
had good success with the echo cancellation module. 
Could anyone point me to reference test files that are
known to work well in testecho.
I'd like to figure out if there is some characteristic
of my echo that makes it incompatible with this echo
cancellation algorithm, or whether there is just some
configuration problem in my implementation.
Thanks for your time; advice is greatly appreciated.


> I have incorporated the speex echo cancellation into
> my softphone project, but wasn't getting great
> results.  I decided to simplify the problem, by
> recording speaker and mic files and running
> testecho. 
> I've been pretty happy with the preprocess module
> and
> I wanted to focus on the mdf, so I commented out the
> call to preprocess in testecho.
> When I run testecho my output file looks almost
> identicle to my mic file.  I don't see any reduction
> in the power level of the echo.  I've looked through
> some of the previous posts to this group and have
> tried the obvious, such as increasing my filter
> length
> and reversing the order of the files passed into the
> application.
> Looking at the files in Audacity, the echo lags by
> about 180ms.  I have experimented with filter
> lengths
> up to 2 seconds.
> I'm open to suggestions. 

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