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/* Copyright (c) 1997-1999 Miller Puckette.
* For information on usage and redistribution, and for a DISCLAIMER OF ALL
* WARRANTIES, see the file, "LICENSE.txt," in this distribution. */
/* "filters", both linear and nonlinear.
*/
#include "m_pd.h"
#include <math.h>
//* ---------------- doublepole~ - raw doublepole filter ----------------- */
typedef struct doublepolectl {
t_sample c_x1;
t_sample c_x2;
t_sample c_fb1;
t_sample c_fb2;
} t_doublepolectl;
typedef struct sigdoublepole {
t_object x_obj;
t_float x_f;
t_doublepolectl x_cspace;
t_doublepolectl *x_ctl;
} t_sigdoublepole;
static t_class *sigdoublepole_class = NULL;
static void sigdoublepole_list(t_sigdoublepole *x, t_symbol *s, int argc,
t_atom *argv);
static void *sigdoublepole_new(t_symbol *s, int argc, t_atom *argv)
{
t_sigdoublepole *x = (t_sigdoublepole *)pd_new(sigdoublepole_class);
outlet_new(&x->x_obj, &s_signal);
x->x_ctl = &x->x_cspace;
x->x_cspace.c_x1 = x->x_cspace.c_x2 = 0;
sigdoublepole_list(x, s, argc, argv);
x->x_f = 0;
return (x);
}
static t_int *sigdoublepole_perform(t_int *w)
{
t_sample *in = (t_sample *)(w[1]);
t_sample *out = (t_sample *)(w[2]);
t_doublepolectl *c = (t_doublepolectl *)(w[3]);
int n = (t_int)(w[4]);
int i;
t_sample last = c->c_x1;
t_sample prev = c->c_x2;
t_sample fb1 = c->c_fb1;
t_sample fb2 = c->c_fb2;
for (i = 0; i < n; i++) {
t_sample output = *in++ + fb1 * last + fb2 * prev;
if (PD_BIGORSMALL(output)) {
output = 0;
}
*out++ = output;
prev = last;
last = output;
}
c->c_x1 = last;
c->c_x2 = prev;
return (w+5);
}
static void sigdoublepole_list(t_sigdoublepole *x, t_symbol *s, int argc,
t_atom *argv)
{
t_float fb1 = atom_getfloatarg(0, argc, argv);
t_float fb2 = atom_getfloatarg(1, argc, argv);
t_float discriminant = fb1 * fb1 + 4 * fb2;
t_doublepolectl *c = x->x_ctl;
if (discriminant < 0) { /* imaginary roots -- resonant filter */
/* they're conjugates so we just check that the product
is less than one */
if (fb2 >= -1.0f) {
goto stable;
}
} else { /* real roots */
/* check that the parabola 1 - fb1 x - fb2 x^2 has a
vertex between -1 and 1, and that it's nonnegative
at both ends, which implies both roots are in [1-,1]. */
if (fb1 <= 2.0f && fb1 >= -2.0f &&
1.0f - fb1 -fb2 >= 0 && 1.0f + fb1 - fb2 >= 0) {
goto stable;
}
}
/* if unstable, just bash to zero */
fb1 = fb2 = 0;
stable:
c->c_fb1 = fb1;
c->c_fb2 = fb2;
}
static void sigdoublepole_set(t_sigdoublepole *x, t_symbol *s, int argc,
t_atom *argv)
{
t_doublepolectl *c = x->x_ctl;
c->c_x1 = atom_getfloatarg(0, argc, argv);
c->c_x2 = atom_getfloatarg(1, argc, argv);
}
static void sigdoublepole_dsp(t_sigdoublepole *x, t_signal **sp)
{
dsp_add(sigdoublepole_perform, 4,
sp[0]->s_vec, sp[1]->s_vec,
x->x_ctl, sp[0]->s_n);
}
void doublepole_tilde_setup(void)
{
sigdoublepole_class = class_new(gensym("doublepole~"),
(t_newmethod)sigdoublepole_new,
0, sizeof(t_sigdoublepole), 0, A_GIMME, 0);
CLASS_MAINSIGNALIN(sigdoublepole_class, t_sigdoublepole, x_f);
class_addmethod(sigdoublepole_class, (t_method)sigdoublepole_dsp,
gensym("dsp"), 0);
class_addlist(sigdoublepole_class, sigdoublepole_list);
class_addmethod(sigdoublepole_class, (t_method)sigdoublepole_set,
gensym("set"),
A_GIMME, 0);
class_addmethod(sigdoublepole_class, (t_method)sigdoublepole_set,
gensym("clear"),
A_GIMME, 0);
}
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