Woof!

On Sun, 01 Mar 2009 21:28:18 -0500, Brian West <br...@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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