LowPassFilter.cpp File Reference

#include "config.h"
#include <complex>
#include <math.h>
#include "LowPassFilter.h"

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Macros
#define	SPN   0.00001

Functions
static void	shelve (double cf, double boost, double *a0, double *a1, double *a2, double *b1, double *b2)

Macro Definition Documentation

SPN

#define SPN   0.00001

Definition at line 66 of file LowPassFilter.cpp.

Referenced by shelve().

Function Documentation

shelve()

static void shelve ( double  cf, double  boost, double *  a0, double *  a1, double *  a2, double *  b1, double *  b2  )

static

Definition at line 68 of file LowPassFilter.cpp.

References SPN.

Referenced by Kwave::LowPassFilter::normed_setfilter_shelvelowpass().

{
    double a, A, F, tmp, b0, recipb0, asq, F2, gamma2, siggam2, gam2p1;
    double gamman, gammad, ta0, ta1, ta2, tb0, tb1, tb2, aa1, ab1;

    a = tan(M_PI * (cf - 0.25));
    asq = a * a;
    A = pow(10.0, boost / 20.0);
    if ((boost < 6.0) && (boost > -6.0)) F = sqrt(A);
    else if (A > 1.0) F = A / sqrt(2.0);
    else F = A*sqrt(2.0);

    F2 = F * F;
    tmp = A * A - F2;
    if (fabs(tmp) <= SPN) gammad = 1.0;
    else gammad = pow((F2 - 1.0) / tmp, 0.25);
    gamman = sqrt(A) * gammad;

    gamma2 = gamman * gamman;
    gam2p1 = 1.0 + gamma2;
    siggam2 = 2.0 * sqrt(2.0) / 2.0 * gamman;
    ta0 = gam2p1 + siggam2;
    ta1 = -2.0 * (1.0 - gamma2);
    ta2 = gam2p1 - siggam2;

    gamma2 = gammad * gammad;
    gam2p1 = 1.0 + gamma2;
    siggam2 = 2.0 * sqrt(2.0) / 2.0 * gammad;
    tb0 = gam2p1 + siggam2;
    tb1 = -2.0 * (1.0 - gamma2);
    tb2 = gam2p1 - siggam2;

    aa1 = a * ta1;
    *a0 = ta0 + aa1 + asq * ta2;
    *a1 = 2.0 * a * (ta0 + ta2) + (1.0 + asq) * ta1;
    *a2 = asq * ta0 + aa1 + ta2;

    ab1 = a * tb1;
    b0 = tb0 + ab1 + asq * tb2;
    *b1 = 2.0 * a * (tb0 + tb2) + (1.0 + asq) * tb1;
    *b2 = asq * tb0 + ab1 + tb2;

    recipb0 = 1.0 / b0;
    *a0 *= recipb0;
    *a1 *= recipb0;
    *a2 *= recipb0;
    *b1 *= recipb0;
    *b2 *= recipb0;
}

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