[Speex-dev] Re: aec

[Jean-Marc Valin]

Are you sure you're not just inverting the two inputs?

	Jean-Marc

On Wed, 2005-11-09 at 22:16 -0800, Jason Harper wrote:
> I ran some further tests on mdf and here are the
> results:
> 1. reduced tail length to 100ms, aligned mic and
> speaker signals to within 10ms - almost no echo
> attenuation
> 2. aligned mic and speaker signals to within 5 samples
> - still almost no echo attenuation
> 3. ran testecho using the same file for mic and
> speaker - very good echo cancellation (of course this
> is expected, but I needed to do a sanity check)
> 4. ran the same file for mic and speaker, but had the
> mic signal delayed by 10ms - OK echo cancellation, but
> noticeably degraded over previous test
> 5. same file for mic and speaker, but mic signal
> delayed by 40ms - noticeable echo attenuation, but
> still a large echo.
> 
> So far my testing is only showing good echo
> cancellation when the exact same file is being used
> and is pretty closely aligned.
> 
> -Jason
> 
> --- Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
> wrote:
> 
> > 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
> > > > > 
> > > > 
> > > 
> > > 
> > 
> 
>