[Speex-dev] Re: aec

[Jean-Marc Valin]

This kind of behaviour is odd. One of the reason could be the fact that
you're using a really long impulse response. Try syncing your signals
and making the tail length more in the order of 100 ms to 300 ms.

	Jean-Marc

Le dimanche 06 novembre 2005 à 21:25 -0800, Jason Harper a écrit :
> Thanks for alerting me to the new changes.  I just
> tried the latest code from SVN, but unfortunately I
> still have just about the same results.  The estimated
> echo that gets subtracted from the actual echo is such
> a small signal that it doesn't really result in any
> noticeable echo attenuation.
> I currently have my filter size set to 2 seconds even
> though the echo in my microphone file is only about
> 180ms delayed from the signal in my speaker file.  I
> also double checked that the endianess of my is
> correct, and that I am providing the files to testecho
> in the correct order.
> Do you think that there could be some characteristics
> to my echo that make it not work with the mdf
> algorithm?  How much echo attenuation should I expect
> from the mdf algorithm before the preprocess?  Are
> there any test speaker and mic files that I could run
> against testecho to see how it handles other acoustic
> echos?
> 
> -Jason
> 
> --- Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
> wrote:
> 
> > I've recently made changes to the AEC. Please try
> > the code in SVN and
> > see if it works better.
> > 
> > 	Jean-Marc
> > 
> > Le jeudi 03 novembre 2005 à 22:36 -0800, Jason
> > Harper a écrit :
> > > 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
> > > st->y[i+st->frame_size]
> > > 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.
> > > 
> > > -Jason
> > > 
> > > ---
> > > > 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. 
> > > 
> > > _______________________________________________
> > > Speex-dev mailing list
> > > Speex-dev at xiph.org
> > > http://lists.xiph.org/mailman/listinfo/speex-dev
> > > 
> > 
> 
>