[Speex-dev] VAD with speex_preprocess()

Paul Gryting paul.gryting at teligy.com
Tue Mar 8 08:16:49 PST 2005

In speexenc.c, speex_preprocess() is not called unless AGC or denoise is
If only VAD is enabled, it does not get called.

speex_preprocess() has vad_enabled specific code to detect voice activity.
   if (st->vad_enabled)
      is_speech = speex_compute_vad(st, ps, mean_prior, mean_post);

    return is_speech;

Some questions for the knowledgable:
Is speex_preprocess() needed to use vad?

Can speex_preprocess() be used to detect silent frames if vad is enabled,
but not agc or denoise?
What internally does speex do differntly for silent frames when VAD is


-----Original Message-----
From: speex-dev-bounces at xiph.org [mailto:speex-dev-bounces at xiph.org]On
Behalf Of Tom Grandgent
Sent: Tuesday, March 08, 2005 8:46 AM
To: Meir Yeshurun; speex-dev at xiph.org
Subject: Re: [Speex-dev] VAD with speex_preprocess()

speex_preprocess() isn't covered in the manual, is it?  But, it's very
easy to use.  If it returns non-zero, voice was detected.


"Meir Yeshurun" <mt_yeshurun at hotmail.com> wrote:
> I would like to use speex_preprocess() for voice activity detection. I
> the comments in speex_preprocess.h and the relevant paragraphs in the
> manual. Is there anywhere I can find more information on how to use this
> function?
> Thanks for your help,
> Steve

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