[Speex-dev] small patch for preprocess

Steve Kann stevek at stevek.com
Mon Oct 31 06:39:53 PST 2005

Jean-Marc Valin wrote:

>>Add the ability to set adaptation time and min noise duration, 
>What do you use that for in practice?

I use this same ideas:

(1) As far as "min noise duration", I basically run the preprocessor VAD 
inside of some code which continues to call audio "speech" for about 10 
frames past the last time the preprocessor called it speech.  In theory, 
if the VAD were perfect, I'd be calling 10 extra (non-speech) frames 
speech, but in practice, this helps reduce false-negatives,  and only 
gives my up to 10 extra false-positives at the end of each spurt.
    I think I do this now in app_conference, but not in iaxclient anymore.
around line 66.

(2) In my distribution of things with the preprocessor, I've slowed the 
adaption time (I think this is the same as tom has), because otherwise, 
I've gotten both false-negatives on VAD, and the related issue where the 
denoiser was removing the speech intonations of particularly monotonic 
 (actually, looking at it now, it seems that the slower adaptation 
constant I've used is what's in SVN now).
    if (st->nb_preprocess%250==0)


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