[Freeswitch-users] Detecting the origin of voice activity using VAD

[Anthony Minessale]

i think that's what mod_vmd does

On Mon, Mar 2, 2009 at 11:16 AM, Andy Spitzer <woof at nortel.com> wrote:

> Woof!
>
> On Sun, 01 Mar 2009 21:28:18 -0500, Brian West <brian at freeswitch.org>
> wrote:
>
> > NO.  You want something that people THINK exists and works well...
> > Reliable human/voice detection doesn't exist in ANY form.
>
> I beg to differ.  See http://www.freepatentsonline.com/5521967.html for
> one way to do it.  It works rather well and can quickly descriminate between
> voice and tone.  I've no idea who owns that patent now (not me, for sure).
>
> There is a simpler, less reliable way of differentiating voice from tone,
> that as far as I know isn't patented.  If you compare the RMS power levels
> of sequential 40 mS periods, call progress tones will have very consistent
> power levels from sample to sample.  So if 5 or more 40 mS periods have
> about the same power measurement (within say, 2%), it's a tone.  Voice will
> have dramatic power level differences over that same period.  This works
> very well in today's telephony environment, where tones are computer
> generated.  In the old days when ringback tone was generated off the audio
> hum from the 20 Hz ring voltage generator...not so well.
>
> --Woof!
>
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-- 
Anthony Minessale II

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