[speex-dev] speex preprocess redux

[Steve Kann]

Tom Harper wrote:

> 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?

<p>Beats me :)

I've found the denoiser to work very well on open-air microphones.

<p>One thing I've found in using the preprocessor that I need to find a 
solution for is that sometimes the denoiser is incorrectly detecting 
speech as noise.  This happens when a speaker speaks for a while, and 
the denoiser tries to remove their intonation (i.e. the sound of their 
voicebox; the vowels).  The result is that towards the ends of 
sentences, their voice gets "thinned" out.

I'd like to find out how to "slow down" the rate of adaptation within 
the denoiser to make this less likely to happen.  I assume that the 
tradeoff is that it will adapt more slowly to changing noise patterns 
(or initial noise).  I'm just not sure where to do that; maybe if I had 
the "Cohen Paper" it would help :)

-SteveK

>
> Thanks,
> Tom
>
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