[Speex-dev] Re: aec

[Jason Harper]

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
> > > > 
> > > 
> > 
> > 
>