half biquad~

svn path=/trunk/externals/zexy/; revision=17213

3 files changed, 124 insertions, 0 deletions

diff --git a/src/doublepole~.c b/src/doublepole~.c
new file mode 100644
index 0000000..93a2a74
--- /dev/null
+++ b/src/doublepole~.c
@@ -0,0 +1,122 @@
+/* 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);
+}
diff --git a/src/z_zexy.c b/src/z_zexy.c
index 4efc3d8..0a6c5b5 100644
--- a/src/z_zexy.c
+++ b/src/z_zexy.c
@@ -27,6 +27,7 @@ void z_zexy_setup(void)
 	demultiplex_setup(); /* demultiplex */
 	dfreq_tilde_setup(); /* dfreq~ */
 	dirac_tilde_setup(); /* dirac~ */
+	doublepole_tilde_setup(); /* doublepole~ */
 	drip_setup(); /* drip */
 	envrms_tilde_setup(); /* envrms~ */
 	fifop_setup(); /* fifop */
diff --git a/src/z_zexy.h b/src/z_zexy.h
index 2699361..f8f6c55 100644
--- a/src/z_zexy.h
+++ b/src/z_zexy.h
@@ -25,6 +25,7 @@ void demultiplex_tilde_setup(void); /* demultiplex~ */
 void demultiplex_setup(void); /* demultiplex */
 void dfreq_tilde_setup(void); /* dfreq~ */
 void dirac_tilde_setup(void); /* dirac~ */
+void doublepole_tilde_setup(void); /* doublepole~ */
 void drip_setup(void); /* drip */
 void envrms_tilde_setup(void); /* envrms~ */
 void fifop_setup(void); /* fifop */