freeswitch/src/mod/applications/mod_avmd/desa2.c

#ifndef __DESA2_H__
#include <stdio.h>
#ifdef WIN32
#include <float.h>
#define ISNAN(x) (!!(_isnan(x)))
#else
#define ISNAN(x) (isnan(x))
#endif
#include "buffer.h"
#include "desa2.h"
#include "options.h"

#ifdef FASTMATH
#include "fast_acosf.h"
#endif

extern double desa2(circ_buffer_t *b, size_t i)
{
    double d;
    double n;
    double x0;
    double x1;
    double x2;
    double x3;
    double x4;
    double x2sq;
    double result;

    x0 = GET_SAMPLE((b), (i));
    x1 = GET_SAMPLE((b), ((i) + 1));
    x2 = GET_SAMPLE((b), ((i) + 2));
    x3 = GET_SAMPLE((b), ((i) + 3));
    x4 = GET_SAMPLE((b), ((i) + 4));

    x2sq = x2 * x2;

    d = 2.0 * ((x2sq) - (x1 * x3));
    if(d == 0.0) return 0.0;

    n = ((x2sq) - (x0 * x4)) - ((x1 * x1) - (x0 * x2)) - ((x3 * x3) - (x2 * x4));


#ifdef FASTMATH
    result = 0.5 * (double)fast_acosf((float)n/d);
#else
    result = 0.5 * acos(n/d);
#endif

    if(ISNAN(result)){
	result = 0.0;
    }


    return result;

}

#endif