[speex-dev] speex preprocess redux

Steve Kann stevek at stevek.com
Tue May 18 06:37:11 PDT 2004

Tom Harper 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 don't seem to get that;  I suppose you've already changed the 
thresholds to make things more sensitive though:

This is what I have now in iaxclient; the first number is the "initial" 
probability to go from not speech -> speech.  The second is to go from 
speech -> not speech.  [the difference implements hysteresis].

/*      if (st->speech_prob> .35 || (st->last_speech < 20 && 
st->speech_prob>.1)) */
      if (st->speech_prob> .30 || (st->last_speech < 20 && 

> 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.

Yes, I get some of that too, but it isn't really bad.  It does obviously 
get worse as the signal to noise ratio gets lower. 

The denoiser isn't perfect, but the consensus amongst people using it 
seems to be that it's good enough to be enabled by default;   So far the 
only problem it's caused for people without noisy environments is the 
occasional thinning;  For people with noisy environments, even with some 
artifacts, the result is much better than the input.


<p>--- >8 ----
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