[Speex-dev] Preprocessor denoise. Does it work?

Steve Kann skann at horizonwimba.com
Tue Feb 27 15:55:55 PST 2007

Andy Ross wrote:
> Jean-Marc Valin wrote:
>> The noise suppressor will only attempt to remove stationary noise,
>> such as thermal noise, fans, ... The AGC can indeed do strange
>> things in these cases, but it's been improved in svn (compared to
>> 1.2beta1).
> OK, then the problem is that I misunderstood the feature.  I assumed
> that dynamic squelch was part of it, but it's really something more
> along the lines of active noise cancellation.  That's fine, I'll work
> on improving my own squelch code.
>> Congratulations. If it works better on your data, then use it. It'll
>> just fail miserably in other conditions, but you may not care about
>> those.
> Uh, production applications almost always require squelch, no?  This
> is no less true today than it was in the days of analog transmitters.
> Note that mobile phones don't transmit low-value transients, even if
> I'm typing right next to them.  While it's certainly true that the
> fixed-threshold static peak implementation I banged out isn't going to
> work everywhere, some more elaborate variation would be really nice to
> have in speex.

It is -- in this case, you would use the result of speex_preprocess() to 
signal to your application whether or not to replace the audio with 
comfort noise (or, zeros if you prefer).


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