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Date: Mon, 26 Jun 1995 07:43:40 +0100
From: Tony Robinson <ajr@compute.demon.co.uk>
Message-Id: <199506260643.HAA02477@compute.demon.co.uk>
To: ajr4@compute.demon.co.uk
Status: R

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From: robert.fung@citicorp.com (Robert Fung)
Newsgroups: comp.dsp
Subject: Re: Whistle Recognition
Date: 25 Jun 1995 23:45:21 GMT
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Somewhat faster code for retrieving a frequency magnitude used
in whistle.c. The sample size should perhaps be increased to
pervent the output magnitudes from getting too close together
making relative comparions difficult.


double fft2(double hz) /* FASTER FT */
{  /* double real[SAMPSIZE] */
 #define SAMPSIZE 128
 #define SAMPRATE 8000.00
 double creal=0,cimag=0,temp=2.0*M_PI*hz/SAMPRATE,g=-temp;
 double *p=&real;
 int x;
 for (x=0; x<SAMPSIZE; x++)
 {    g+=temp;
      creal+=(*p)  *(cos(g));
      cimag+=(*p++)*(sin(g));
 }
 return(abs(cimag)+abs(creal));
}