From fc3d3c0a4f110a23335398c327ac0a4fc949d5cb Mon Sep 17 00:00:00 2001
From: Guenter  Geiger <ggeiger@users.sourceforge.net>
Date: Mon, 17 Jun 2002 10:13:57 +0000
Subject: This commit was generated by cvs2svn to compensate for changes in
 r12, which included commits to RCS files with non-trunk default branches.

svn path=/trunk/externals/ggee/; revision=13
---
 filters/highpass.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100755 filters/highpass.c

(limited to 'filters/highpass.c')

diff --git a/filters/highpass.c b/filters/highpass.c
new file mode 100755
index 0000000..e7e0443
--- /dev/null
+++ b/filters/highpass.c
@@ -0,0 +1,87 @@
+/* (C) Guenter Geiger <geiger@epy.co.at> */
+
+
+/*
+
+ These filter coefficients computations are taken from
+ http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt  
+
+ written by Robert Bristow-Johnson
+
+*/
+
+#include <m_pd.h>
+#ifdef NT
+#pragma warning( disable : 4244 )
+#pragma warning( disable : 4305 )
+#endif
+#include <math.h>
+#include "filters.h"
+
+
+/* ------------------- highpass ----------------------------*/
+
+static t_class *highpass_class;
+
+void highpass_bang(t_rbjfilter *x)
+{
+     t_atom at[5];
+     t_float omega = e_omega(x->x_freq,x->x_rate);
+     t_float alpha = e_alpha(x->x_bw* 0.01,omega);
+     t_float b1 = -(1 + cos(omega));
+     t_float b0 = -b1/2.;
+     t_float b2 = b0;
+     t_float a0 = 1 + alpha;
+     t_float a1 = -2.*cos(omega);
+     t_float a2 = 1 - alpha;
+
+/*     post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
+     
+     if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
+       post("highpass: filter unstable -> resetting");
+       a0=1.;a1=0.;a2=0.;
+       b0=1.;b1=0.;b2=0.;
+     }
+
+     SETFLOAT(at,-a1/a0);
+     SETFLOAT(at+1,-a2/a0);
+     SETFLOAT(at+2,b0/a0);
+     SETFLOAT(at+3,b1/a0);
+     SETFLOAT(at+4,b2/a0);
+     
+     outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
+}
+
+
+void highpass_float(t_rbjfilter *x,t_floatarg f)
+{
+     x->x_freq = f;
+     highpass_bang(x);
+}
+
+
+static void *highpass_new(t_floatarg f,t_floatarg bw)
+{
+    t_rbjfilter *x = (t_rbjfilter *)pd_new(highpass_class);
+
+    x->x_rate = 44100.0;
+    outlet_new(&x->x_obj,&s_float);
+/*    floatinlet_new(&x->x_obj, &x->x_gain);    */
+    floatinlet_new(&x->x_obj, &x->x_bw);
+    if (f > 0.) x->x_freq = f;
+    if (bw > 0.) x->x_bw = bw;
+    return (x);
+}
+
+
+void highpass_setup(void)
+{
+    highpass_class = class_new(gensym("highpass"), (t_newmethod)highpass_new, 0,
+				sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,0);
+    class_addbang(highpass_class,highpass_bang);
+    class_addfloat(highpass_class,highpass_float);
+}
+
+
+
+
-- 
cgit v1.2.1