1 files changed, 56 insertions, 0 deletions
diff --git a/sigdelta.c b/sigdelta.c
new file mode 100644
index 0000000..92ed69c
--- /dev/null
+++ b/sigdelta.c
@@ -0,0 +1,56 @@
+#include "m_pd.h"
+#include <math.h>
+#ifdef NT
+#pragma warning( disable : 4244 )
+#pragma warning( disable : 4305 )
+#endif
+
+/* ------------------------ delta~ ----------------------------- */
+
+/* tilde object to take difference value. */
+
+static t_class *delta_class;
+
+typedef struct _delta
+{
+  t_object x_obj;
+  t_sample x_last;
+} t_delta;
+
+static t_int *delta_perform(t_int *w)
+{
+  t_delta *x  = (t_delta *)(w[1]);
+  t_float *in = (t_float *)(w[2]);
+  t_float *out = (t_float *)(w[3]);
+  int n = (int)(w[4]);
+  while (n--)
+    {
+      float f = *(in++);
+      // *out++ = (f > 0 ? f : -f);	
+      *out++ = (f > x->x_last ? fabs(f - x->x_last) : -fabs(f - x->x_last));
+      x->x_last = f;
+    }
+  return (w+5);
+}
+
+static void delta_dsp(t_delta *x, t_signal **sp)
+{
+  dsp_add(delta_perform, 4, x, sp[0]->s_vec, sp[1]->s_vec, sp[0]->s_n);
+}
+
+static void *delta_new(void)
+{
+  t_delta *x = (t_delta *)pd_new(delta_class);
+  x->x_last = 0.;
+  outlet_new(&x->x_obj, gensym("signal"));
+  return (x);
+}
+
+void delta_tilde_setup(void)
+{
+  delta_class = class_new(gensym("delta~"), (t_newmethod)delta_new, 0,
+			  sizeof(t_delta), 0, A_DEFFLOAT, 0);
+  class_addmethod(delta_class, nullfn, gensym("signal"), 0);
+  class_addmethod(delta_class, (t_method)delta_dsp, gensym("dsp"), 0);
+  class_sethelpsymbol(delta_class, gensym("cxc/delta.pd"));
+}