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/*
* Copyright (C) 2002-2005 Felipe Rivera <liebremx at users.sourceforge.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*
* Coefficient stuff
*
* $Id: iir_cfs.c,v 1.1 2005/10/17 01:57:59 liebremx Exp $
*/
#include "iir_cfs.h"
#include <stdio.h>
#include <math.h>
/***************************
* IIR filter coefficients *
***************************/
static sIIRCoefficients iir_cf10_11k_11025[10] __attribute__((aligned));
static sIIRCoefficients iir_cf10_22k_22050[10] __attribute__((aligned));
static sIIRCoefficients iir_cforiginal10_44100[10] __attribute__((aligned));
static sIIRCoefficients iir_cforiginal10_48000[10] __attribute__((aligned));
static sIIRCoefficients iir_cf10_44100[10] __attribute__((aligned));
static sIIRCoefficients iir_cf10_48000[10] __attribute__((aligned));
static sIIRCoefficients iir_cf15_44100[15] __attribute__((aligned));
static sIIRCoefficients iir_cf15_48000[15] __attribute__((aligned));
static sIIRCoefficients iir_cf25_44100[25] __attribute__((aligned));
static sIIRCoefficients iir_cf25_48000[25] __attribute__((aligned));
static sIIRCoefficients iir_cf31_44100[31] __attribute__((aligned));
static sIIRCoefficients iir_cf31_48000[31] __attribute__((aligned));
/******************************************************************
* Definitions and data structures to calculate the coefficients
******************************************************************/
static const double band_f011k[] =
{ 31, 62, 125, 250, 500, 1000, 2000, 3000, 4000, 5500
};
static const double band_f022k[] =
{ 31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 11000
};
static const double band_f010[] =
{ 31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 16000
};
static const double band_original_f010[] =
{ 60, 170, 310, 600, 1000, 3000, 6000, 12000, 14000, 16000
};
static const double band_f015[] =
{ 25,40,63,100,160,250,400,630,1000,1600,2500,4000,6300,10000,16000
};
static const double band_f025[] =
{ 20,31.5,40,50,80,100,125,160,250,315,400,500,800,
1000,1250,1600,2500,3150,4000,5000,8000,10000,12500,16000,20000
};
static const double band_f031[] =
{ 20,25,31.5,40,50,63,80,100,125,160,200,250,315,400,500,630,800,
1000,1250,1600,2000,2500,3150,4000,5000,6300,8000,10000,12500,16000,20000
};
#define GAIN_F0 1.0
#define GAIN_F1 GAIN_F0 / M_SQRT2
#define SAMPLING_FREQ 44100.0
#define TETA(f) (2*M_PI*(double)f/bands[n].sfreq)
#define TWOPOWER(value) (value * value)
#define BETA2(tf0, tf) \
(TWOPOWER(GAIN_F1)*TWOPOWER(cos(tf0)) \
- 2.0 * TWOPOWER(GAIN_F1) * cos(tf) * cos(tf0) \
+ TWOPOWER(GAIN_F1) \
- TWOPOWER(GAIN_F0) * TWOPOWER(sin(tf)))
#define BETA1(tf0, tf) \
(2.0 * TWOPOWER(GAIN_F1) * TWOPOWER(cos(tf)) \
+ TWOPOWER(GAIN_F1) * TWOPOWER(cos(tf0)) \
- 2.0 * TWOPOWER(GAIN_F1) * cos(tf) * cos(tf0) \
- TWOPOWER(GAIN_F1) + TWOPOWER(GAIN_F0) * TWOPOWER(sin(tf)))
#define BETA0(tf0, tf) \
(0.25 * TWOPOWER(GAIN_F1) * TWOPOWER(cos(tf0)) \
- 0.5 * TWOPOWER(GAIN_F1) * cos(tf) * cos(tf0) \
+ 0.25 * TWOPOWER(GAIN_F1) \
- 0.25 * TWOPOWER(GAIN_F0) * TWOPOWER(sin(tf)))
#define GAMMA(beta, tf0) ((0.5 + beta) * cos(tf0))
#define ALPHA(beta) ((0.5 - beta)/2.0)
struct {
sIIRCoefficients *coeffs;
const double *cfs;
double octave;
int band_count;
double sfreq;
} bands[] = {
{ iir_cf10_11k_11025, band_f011k, 1.0, 10, 11025.0 },
{ iir_cf10_22k_22050, band_f022k, 1.0, 10, 22050.0 },
{ iir_cforiginal10_44100, band_original_f010, 1.0, 10, 44100.0 },
{ iir_cforiginal10_48000, band_original_f010, 1.0, 10, 48000.0 },
{ iir_cf10_44100, band_f010, 1.0, 10, 44100.0 },
{ iir_cf10_48000, band_f010, 1.0, 10, 48000.0 },
{ iir_cf15_44100, band_f015, 2.0/3.0, 15, 44100.0 },
{ iir_cf15_48000, band_f015, 2.0/3.0, 15, 48000.0 },
{ iir_cf25_44100, band_f025, 1.0/3.0, 25, 44100.0 },
{ iir_cf25_48000, band_f025, 1.0/3.0, 25, 48000.0 },
{ iir_cf31_44100, band_f031, 1.0/3.0, 31, 44100.0 },
{ iir_cf31_48000, band_f031, 1.0/3.0, 31, 48000.0 },
{ 0, 0, 0, 0, 0 }
};
/*************
* Functions *
*************/
/* Get the coeffs for a given number of bands and sampling frequency */
sIIRCoefficients* get_coeffs(int *bands, int sfreq)
{
sIIRCoefficients *iir_cf = 0;
switch(sfreq)
{
case 11025: iir_cf = iir_cf10_11k_11025;
*bands = 10;
break;
case 22050: iir_cf = iir_cf10_22k_22050;
*bands = 10;
break;
case 48000:
switch(*bands)
{
case 31: iir_cf = iir_cf31_48000; break;
case 25: iir_cf = iir_cf25_48000; break;
case 15: iir_cf = iir_cf15_48000; break;
default:
/*iir_cf = use_xmms_original_freqs ?
iir_cforiginal10_48000 :
iir_cf10_48000;*/
iir_cf = iir_cforiginal10_48000;
break;
}
break;
default:
switch(*bands)
{
case 31: iir_cf = iir_cf31_44100; break;
case 25: iir_cf = iir_cf25_44100; break;
case 15: iir_cf = iir_cf15_44100; break;
default:
/*iir_cf = use_xmms_original_freqs ?
iir_cforiginal10_44100 :
iir_cf10_44100;*/
iir_cf = iir_cforiginal10_44100;
break;
}
break;
}
return iir_cf;
}
/* Get the freqs at both sides of F0. These will be cut at -3dB */
static void find_f1_and_f2(double f0, double octave_percent, double *f1, double *f2)
{
double octave_factor = pow(2.0, octave_percent/2.0);
*f1 = f0/octave_factor;
*f2 = f0*octave_factor;
}
/* Find the quadratic root
* Always return the smallest root */
static int find_root(double a, double b, double c, double *x0) {
double k = c-((b*b)/(4.*a));
double h = -(b/(2.*a));
double x1 = 0.;
if (-(k/a) < 0.)
return -1;
*x0 = h - sqrt(-(k/a));
x1 = h + sqrt(-(k/a));
if (x1 < *x0)
*x0 = x1;
return 0;
}
/* Calculate all the coefficients as specified in the bands[] array */
void calc_coeffs()
{
int i, n;
double f1, f2;
double x0;
n = 0;
for (; bands[n].cfs; n++) {
double *freqs = (double *)bands[n].cfs;
for (i=0; i<bands[n].band_count; i++)
{
/* Find -3dB frequencies for the center freq */
find_f1_and_f2(freqs[i], bands[n].octave, &f1, &f2);
/* Find Beta */
if ( find_root(
BETA2(TETA(freqs[i]), TETA(f1)),
BETA1(TETA(freqs[i]), TETA(f1)),
BETA0(TETA(freqs[i]), TETA(f1)),
&x0) == 0)
{
/* Got a solution, now calculate the rest of the factors */
/* Take the smallest root always (find_root returns the smallest one)
*
* NOTE: The IIR equation is
* y[n] = 2 * (alpha*(x[n]-x[n-2]) + gamma*y[n-1] - beta*y[n-2])
* Now the 2 factor has been distributed in the coefficients
*/
/* Now store the coefficients */
bands[n].coeffs[i].beta = 2.0 * x0;
bands[n].coeffs[i].alpha = 2.0 * ALPHA(x0);
bands[n].coeffs[i].gamma = 2.0 * GAMMA(x0, TETA(freqs[i]));
#ifdef DEBUG
printf("Freq[%d]: %f. Beta: %.10e Alpha: %.10e Gamma %.10e\n",
i, freqs[i], bands[n].coeffs[i].beta,
bands[n].coeffs[i].alpha, bands[n].coeffs[i].gamma);
#endif
} else {
/* Shouldn't happen */
bands[n].coeffs[i].beta = 0.;
bands[n].coeffs[i].alpha = 0.;
bands[n].coeffs[i].gamma = 0.;
printf(" **** Where are the roots?\n");
}
}// for i
}//for n
}
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