[speex-dev] speex preprocess redux

Tom Harper tharper at sightspeed.com
Tue May 18 23:22:40 PDT 2004

Jean Marc,

Thanks for the advice.   The estimate update may come in handy.

I have had some time to play with the adaptation time.  I tried
making the adaptation time 80, 160 and 320.  It seemed like
the smaller value was actually the best in my initial testing,
but I need to test this against a more noisy setup than I have here.

I am guessing that for vad a shorter adaptation time is probably
better for most situations?


At 07:55 PM 5/17/2004, Jean-Marc Valin wrote:
>The speex_preprocess_estimate_update(....) function is only used when you want
>to perform adaptation without running the denoiser (e.g. when using
>push-to-talk). In most cases, you probably won't need it though.
>Second thing, if you want to make adaptation slower, look for a modulo (%) in
>the code and increase the value next to it (default is %100 or something 
>like that).
>As for the VAD, it's a really difficult problem because 1) the latency is 
>and 2) some people want different things from it (some want it to transmit
>everything but the stationary background noise, others want only speech). BTW,
>VAD doesn't need to be after the denoiser since it estimates the noise 
>Quoting Tom Harper <tharper at sightspeed.com>:
> > Hi All & Jean Marc,
> >
> > Once again I find myself delving into the pre-processing code to fiddle
> > with the VAD, AGC and denoising code.
> >
> > Where i am at is that I have implemented all of Steve Kann's mods, and
> > they are 90% of the way there in terms of working, except that I am still
> > having issues denoising open air mics.  But that is tangential to my
> > question-
> >
> > I was wondering what the following function is supposed to be used for:
> > speex_preprocess_estimate_update(....)
> >
> > I couldn't find anywhere in the code that references it- it appears to
> > update
> > the noise estimate without denoising anything- ?  If so, does this need to
> > be called for AGC to work, or?
> >
> > Thanks,
> > Tom


Tom Harper - tharper at sightspeed.com
Lead Software Engineer
SightSpeed - A Roda Group Affiliated Company

918 Parker St, Suite A14
Berkeley, CA 94710

Phone: 510.665.2920
Cell: 415.378.3779


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