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/* Copyright (c) 2003 krzYszcz and others.
* For information on usage and redistribution, and for a DISCLAIMER OF ALL
* WARRANTIES, see the file, "LICENSE.txt," in this distribution. */
/* The general two-pole resonator (csound's lp2). For a nice analysis
see section 9.1.3 of ``Introduction to Digital Filters'' by Smith. */
/* CHECKME if creation args (or defaults) restored after signal disconnection */
#include <math.h>
#include "m_pd.h"
#include "shared.h"
#include "sickle/sic.h"
#if defined(_WIN32) || defined(__APPLE__)
/* cf pd/src/x_arithmetic.c */
#define expf exp
#define cosf cos
#endif
/* CHECKME negative resonance */
/* CHECKME max resonance, esp. at low freqs (watch out, gain not normalized) */
#define LORES_MAXRESONANCE (1. - 1e-20)
#define LORES_MINOMEGA .0001 /* CHECKME */
#define LORES_MAXOMEGA SHARED_PI /* CHECKME */
typedef struct _lores
{
t_sic x_sic;
float x_srcoef;
float x_ynm1;
float x_ynm2;
} t_lores;
static t_class *lores_class;
static void lores_clear(t_lores *x)
{
x->x_ynm1 = x->x_ynm2 = 0.;
}
/* LATER make ready for optional audio-rate modulation
(separate scalar case routines, use sic_makecostable(), etc.) */
static t_int *lores_perform(t_int *w)
{
t_lores *x = (t_lores *)(w[1]);
int nblock = (int)(w[2]);
t_float *xin = (t_float *)(w[3]);
t_float fin0 = *(t_float *)(w[4]);
t_float rin0 = *(t_float *)(w[5]);
t_float *out = (t_float *)(w[6]);
float ynm1 = x->x_ynm1;
float ynm2 = x->x_ynm2;
/* CHECKME sampled once per block */
float omega = fin0 * x->x_srcoef;
float radius, c1, c2, b0;
if (omega < LORES_MINOMEGA)
omega = LORES_MINOMEGA;
else if (omega > LORES_MAXOMEGA)
omega = LORES_MAXOMEGA;
if (rin0 > LORES_MAXRESONANCE)
rin0 = LORES_MAXRESONANCE;
/* radius = pow(base, rin0 - 1), which maps rin0 of 0..1 to radius
of 1/base..1, where base=exp(.125), and 1/base=.882496902585 */
radius = expf(rin0 * .125) * .882496902585;
c1 = 2. * radius * cos(omega);
c2 = radius * radius;
b0 = 1. - c1 + c2;
while (nblock--)
{
float yn;
*out++ = yn = b0 * *xin++ + c1 * ynm1 - c2 * ynm2;
ynm2 = ynm1;
ynm1 = yn;
}
/* LATER rethink */
x->x_ynm1 = (PD_BIGORSMALL(ynm1) ? 0. : ynm1);
x->x_ynm2 = (PD_BIGORSMALL(ynm2) ? 0. : ynm2);
return (w + 7);
}
static void lores_dsp(t_lores *x, t_signal **sp)
{
x->x_srcoef = SHARED_2PI / sp[0]->s_sr;
lores_clear(x);
dsp_add(lores_perform, 6, x, sp[0]->s_n,
sp[0]->s_vec, sp[1]->s_vec, sp[2]->s_vec, sp[3]->s_vec);
}
static void *lores_new(t_floatarg f1, t_floatarg f2)
{
t_lores *x = (t_lores *)pd_new(lores_class);
x->x_srcoef = SHARED_2PI / sys_getsr();
sic_newinlet((t_sic *)x, f1);
sic_newinlet((t_sic *)x, f2);
outlet_new((t_object *)x, &s_signal);
lores_clear(x);
return (x);
}
void lores_tilde_setup(void)
{
lores_class = class_new(gensym("lores~"),
(t_newmethod)lores_new, 0,
sizeof(t_lores), 0,
A_DEFFLOAT, A_DEFFLOAT, 0);
sic_setup(lores_class, lores_dsp, SIC_FLOATTOSIGNAL);
class_addmethod(lores_class, (t_method)lores_clear, gensym("clear"), 0);
}
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