[speex-dev] speex preprocess redux

Tom Grandgent
Fri, 06 Aug 2004 15:02:05 -0000

I'm not sure if this is due to the same problem, but I get the
same clipping behavior when trying to use VAD+denoiser on a
particular mic+speaker setup that has significant background noise
(enough to really foul up the codec should the denoiser be turned
off.)  Leaving VAD off and transmitting continuously seems to be
the only way to avoid this clipping.

Another person I regularly communicate with also has a mic+speaker
setup but not much background noise.  With VAD+denoiser enabled,
I never have any trouble hearing him.

This gives me the impression that VAD doesn't function too well
when the input is noisy, even if the denoiser can do an excellent
job of cleaning up the signal.  So it seems that VAD is being
done before denoising, and looking at the code for
speex_preprocess(), I think this is the case.  (Am I wrong?)

Why not do VAD after denoising?  It seems like it would be much
more reliable.

Tom

Tom Harper (tharper@sightspeed.com) wrote:
>
> Steve,
>
> The main problem I am having with the system is clipping off the start
> of someone's speech when they first start talking- the ends of the
sentences
> seem to be handled properly.  I am wondering whether this is the fault of
the
> audio playback system or whether this is a speex issue-
>
> I also get the musical artifacts problem with the denoiser.  This seems to
> be more of a problem on open air mics/speaker combinations.  However,
> this and the issues you pointed out are a minor deal in comparison with the
> clipping problem.
>
> Tom

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