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path: root/filters/equalizer.c
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 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 ``` ``````/* (C) Guenter Geiger */ /* These filter coefficients computations are taken from http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt written by Robert Bristow-Johnson */ #include #ifdef _MSC_VER #pragma warning( disable : 4244 ) #pragma warning( disable : 4305 ) #endif #include #include "filters.h" /* ------------------- equ ----------------------------*/ static t_class *equ_class; void equ_bang(t_rbjfilter *x) { t_atom at[5]; t_float omega = e_omega(x->x_freq,x->x_rate); t_float alpha = e_alpha(x->x_bw*0.01,omega); t_float b0 = 1 + alpha*e_A(x->x_gain); t_float b1 = -2.*cos(omega); t_float b2 = 1 - alpha*e_A(x->x_gain); t_float a0 = 1 + alpha/e_A(x->x_gain); t_float a1 = -2.*cos(omega); t_float a2 = 1 - alpha/e_A(x->x_gain); /* post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw);*/ if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) { post("equ: filter unstable -> resetting"); a0=1.;a1=0.;a2=0.; b0=1.;b1=0.;b2=0.; } SETFLOAT(at,-a1/a0); SETFLOAT(at+1,-a2/a0); SETFLOAT(at+2,b0/a0); SETFLOAT(at+3,b1/a0); SETFLOAT(at+4,b2/a0); outlet_list(x->x_obj.ob_outlet,&s_list,5,at); } void equ_float(t_rbjfilter *x,t_floatarg f) { x->x_freq = f; equ_bang(x); } static void *equ_new(t_floatarg f,t_floatarg g,t_floatarg bw) { t_rbjfilter *x = (t_rbjfilter *)pd_new(equ_class); x->x_rate = 44100.0; outlet_new(&x->x_obj,&s_float); floatinlet_new(&x->x_obj, &x->x_gain); floatinlet_new(&x->x_obj, &x->x_bw); if (f > 0.) x->x_freq = f; if (bw > 0.) x->x_bw = bw; if (g != 0.) x->x_gain = g; return (x); } void equalizer_setup(void) { equ_class = class_new(gensym("equalizer"), (t_newmethod)equ_new, 0, sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,A_DEFFLOAT,0); class_addbang(equ_class,equ_bang); class_addfloat(equ_class,equ_float); } ``````