179 lines
4 KiB
C
179 lines
4 KiB
C
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/* (C) Guenter Geiger <geiger@epy.co.at> */
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/*
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These filter coefficients computations are taken from
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http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
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written by Robert Bristow-Johnson
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*/
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#include "m_pd.h"
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#ifdef NT
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#pragma warning( disable : 4244 )
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#pragma warning( disable : 4305 )
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#endif
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#include <math.h>
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#include "filters.h"
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/* ------------------- lowpass ----------------------------*/
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static t_class *lowpass_class;
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void lowpass_bang(t_rbjfilter *x)
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{
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t_atom at[5];
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t_float omega = e_omega(x->x_freq,x->x_rate);
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t_float alpha = e_alpha(x->x_bw*0.01,omega);
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t_float b1 = 1 - cos(omega);
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t_float b0 = b1/2.;
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t_float b2 = b0;
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t_float a0 = 1 + alpha;
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t_float a1 = -2.*cos(omega);
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t_float a2 = 1 - alpha;
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/* post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
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if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
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post("lowpass: filter unstable -> resetting");
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a0=1.;a1=0.;a2=0.;
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b0=1.;b1=0.;b2=0.;
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}
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SETFLOAT(at,-a1/a0);
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SETFLOAT(at+1,-a2/a0);
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SETFLOAT(at+2,b0/a0);
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SETFLOAT(at+3,b1/a0);
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SETFLOAT(at+4,b2/a0);
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outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
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}
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void lowpass_float(t_rbjfilter *x,t_floatarg f)
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{
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x->x_freq = f;
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lowpass_bang(x);
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}
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static void *lowpass_new(t_floatarg f,t_floatarg bw)
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{
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t_rbjfilter *x = (t_rbjfilter *)pd_new(lowpass_class);
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x->x_rate = 44100.0;
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outlet_new(&x->x_obj,&s_float);
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/* floatinlet_new(&x->x_obj, &x->x_gain); */
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floatinlet_new(&x->x_obj, &x->x_bw);
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if (f > 0.) x->x_freq = f;
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if (bw > 0.) x->x_bw = bw;
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return (x);
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}
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void lowpass_setup(void)
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{
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lowpass_class = class_new(gensym("lowpass"), (t_newmethod)lowpass_new, 0,
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sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,0);
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class_addbang(lowpass_class,lowpass_bang);
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class_addfloat(lowpass_class,lowpass_float);
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}
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/* (C) Guenter Geiger <geiger@epy.co.at> */
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/*
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These filter coefficients computations are taken from
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http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
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written by Robert Bristow-Johnson
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*/
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#include "m_pd.h"
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#ifdef NT
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#pragma warning( disable : 4244 )
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#pragma warning( disable : 4305 )
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#endif
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#include <math.h>
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#include "filters.h"
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/* ------------------- lowpass ----------------------------*/
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static t_class *lowpass_class;
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void lowpass_bang(t_rbjfilter *x)
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{
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t_atom at[5];
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t_float omega = e_omega(x->x_freq,x->x_rate);
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t_float alpha = e_alpha(x->x_bw*0.01,omega);
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t_float b1 = 1 - cos(omega);
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t_float b0 = b1/2.;
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t_float b2 = b0;
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t_float a0 = 1 + alpha;
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t_float a1 = -2.*cos(omega);
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t_float a2 = 1 - alpha;
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/* post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
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if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
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post("lowpass: filter unstable -> resetting");
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a0=1.;a1=0.;a2=0.;
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b0=1.;b1=0.;b2=0.;
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}
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SETFLOAT(at,-a1/a0);
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SETFLOAT(at+1,-a2/a0);
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SETFLOAT(at+2,b0/a0);
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SETFLOAT(at+3,b1/a0);
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SETFLOAT(at+4,b2/a0);
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outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
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}
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void lowpass_float(t_rbjfilter *x,t_floatarg f)
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{
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x->x_freq = f;
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lowpass_bang(x);
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}
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static void *lowpass_new(t_floatarg f,t_floatarg bw)
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{
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t_rbjfilter *x = (t_rbjfilter *)pd_new(lowpass_class);
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x->x_rate = 44100.0;
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outlet_new(&x->x_obj,&s_float);
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/* floatinlet_new(&x->x_obj, &x->x_gain); */
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floatinlet_new(&x->x_obj, &x->x_bw);
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if (f > 0.) x->x_freq = f;
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if (bw > 0.) x->x_bw = bw;
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return (x);
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}
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void lowpass_setup(void)
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{
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lowpass_class = class_new(gensym("lowpass"), (t_newmethod)lowpass_new, 0,
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sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,0);
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class_addbang(lowpass_class,lowpass_bang);
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class_addfloat(lowpass_class,lowpass_float);
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}
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