[speex-dev] More Speex (pre-processing) Options

[Tongbiao Li]

This is only remotely related: just out of curiosity, does
speex_preprocess work very well for you ?

It only works to certain extend for me, and does not seem to completely
remove noise from sound card.  Even if you unplug the microphone, it
still could not get rid of the noise.

Any idea how it could be totally eliminated ?

<p>Thanks

<p><p>-----Original Message-----
From: Tom Harper [mailto:harper at archila.com] 
Sent: Wednesday, November 26, 2003 10:18 AM
To: speex-dev at xiph.org
Subject: Re: [speex-dev] More Speex (pre-processing) Options

Hi,

Thanks, that gave me some ideas.  I have tried calling speex_echo_cancel
and speex_preprocess separately and jointly, with a number of different 
filter lengths,
and using the cancelled and non-cancelled data as input to the
pre-filter, 
with
and without the residual echo, etc. but there doesn't appear to be valid

data in the
echo or the cancelled frame any way I try it.

Back to the drawing board (and eagerly awaiting the next release),

Tom

At 05:28 AM 11/26/2003, Tom Grandgent wrote:
>I don't think the echo canceller works yet.  The best I could
>get it to do is trash my audio.  If it does work, some sample
>code demonstrating its use would be really appreciated...
>
>Here is what Jean-Marc has said about it in the past:
>
> > What should I use for a filter length for speex_echo_state_init()?
>
>"Well, it depends on your problem. The filter length represents the
>maximum delay of the echo. For acoustic echo, that value is generally
>higher than for line echo. You'll need to experiment, but a value
around
>500 (for 8 kHz) might be a good start."
>
> > [question about params for echo canceller function]
>
>"Actually, ref is the incoming frame (with echo), echo is the outgoing
>frame (that has only the echo) and out is the echo-cancelled frame. As
>for Yout, it is an estimation of the residual echo that can be sent to
>the denoiser so that residual echo can be removed as well. Note that
>this last feature is still experimental."
>
>
>Tom Harper (harper at archila.com) wrote:
> >
> > Hi,
> >
> > So I have had a chance to delve deeper into  the new pre-processing
> > code-  I was also able to get VAD, AGC, Denoising, etc working
inside 
> of the
> > current release candidate (1.0.3).   For some reason, the 1.1.2
> > release didn't properly encode/decode in our system (on windows)
> > and I haven't had time to determine why.  In any case, all of the
features
> > jointly work very well- great job!
> >
> > I realize the echo cancellation element may still be in development,

> but I am
> > having trouble getting that part of the preprocessor to work.  When
> > I don't pass NULL into the speex_preprocess for the echo parameter,
things
> > seem to go haywire- some memory appears to be getting trampled
somewhere
> > (this is probably my fault).  Maybe I am misunderstanding the
purpose 
> of this
> > parameter?  Except for the first few packets, the preprocessor
> > appears to be removing all audio- The algorithm I am using passes in
a 
> recently
> > decoded frame...  Any ideas?  Do I need to set some settings in
somewhere
> > in order for this to work properly?
> >
> > Thanks,
> > Tom
>
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