[Asterisk-Dev] Voice detection

[Chris Albertson]

The "magic words" to use for Google are "VOX DSP Algorithm"
"VOX" means "Voice Operated Switch" and is very common in
simplex radio.  It is a kind of automatic "push to talk switch"

Yes Spinx would have something like this some place in it but
then so would any teliphony codec that did silence surpression.

The basic idea is a compute the power in the audio, apply a _very_
low (on order of about 1Hz) pass filter and threshold the result.
You may want two thresholds one for on one for off to provide
stability. (Remember the idea of a dead band in servo systems?)
Filter responce and the threshholds should be user adjustable

Yes, I've been looking a spinx for some time now.  I think it is
"ready for prime time" for simple applcations like voice dialing
a phone number or yes/no to an IVR system.  

--- Brad Waite <brad at wcubed.net> wrote:
> Steven Critchfield wrote:
> 
> > On Thu, 2003-10-02 at 21:36, Brad Waite wrote:
> > 
> >>Does anyone know if there's public voice detection algorithms
> available?  I've 
> >>scoured the net for the last hour or so, and I can't come up with
> anything 
> >>except a few proprietary or embedded solutions.
> >>
> >>I know dsp.c uses goertzel algorithms for DTMF detection, but how
> does one 
> >>detect voice?
> >>
> >>I dunno, maybe detecting voice isn't the way to go.  I want to
> begin playback of 
> >>a file after a phone/answering machine has answered.
> > 
> > 
> > Argghh telemarketing....
> 
> Argghh voice mail notification...  (among other non-telemarketing
> things)  :)
> 
> > shouldn't you detect silence and then start?
> 
> Possibly, but I would think that between the last ring and the speech
> there 
> could be enough silence to return a false positive.
> 
> As it turns out, it appears that Festival's cousin, Sphinx, might be
> the ticket. 
>   Sphinx not only detects voice, but is a full Open Source speech
> recognition 
> engine.  In my mind, that opens up worlds of possibilities with *. 
> Anyone else 
> up for it?
> 
> BTW, more on Sphinx can be found at
> http://fife.speech.cs.cmu.edu/sphinx/.
> 
> Brad Waite
> 
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=====
Chris Albertson
  Home:   310-376-1029  chrisalbertson90278 at yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson at aero.org
  KG6OMK

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