均衡器源代码

/* * Copyright (C) 2002-2006 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 1.2 2006/01/15 00:17:46 liebremx Exp $ */ #include "iir_cfs.h" #include <stdio.h> #include <math.h> /*************************** * IIR filter coefficients * ***************************/ #pragma pack(push,1) static sIIRCoefficients iir_cf10_11k_11025[10] ; static sIIRCoefficients iir_cf10_22k_22050[10] ; static sIIRCoefficients iir_cforiginal10_44100[10] ; static sIIRCoefficients iir_cforiginal10_48000[10] ; static sIIRCoefficients iir_cf10_44100[10] ; static sIIRCoefficients iir_cf10_48000[10] ; static sIIRCoefficients iir_cf15_44100[15] ; static sIIRCoefficients iir_cf15_48000[15] ; static sIIRCoefficients iir_cf25_44100[25] ; static sIIRCoefficients iir_cf25_48000[25] ; static sIIRCoefficients iir_cf31_44100[31] ; static sIIRCoefficients iir_cf31_48000[31] ; #pragma pack(pop) /****************************************************************** * 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 } }; /************* * Functions * *************/ /* Get the coeffs for a given number of bands and sampling frequency */ sIIRCoefficients* get_coeffs(int *bands, int sfreq, bool use_xmms_original_freqs) { 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; 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; 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 = (float)(2.0 * x0); bands[n].coeffs[i].alpha = (float)(2.0 * ALPHA(x0)); bands[n].coeffs[i].gamma = (float)(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 */