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-rwxr-xr-xfilters/highshelf.c90
1 files changed, 90 insertions, 0 deletions
diff --git a/filters/highshelf.c b/filters/highshelf.c
new file mode 100755
index 0000000..ee6006c
--- /dev/null
+++ b/filters/highshelf.c
@@ -0,0 +1,90 @@
+/* (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"
+
+
+/* ------------------- highshelf ----------------------------*/
+
+static t_class *highshelf_class;
+
+void highshelf_bang(t_rbjfilter *x)
+{
+ t_atom at[5];
+ t_float omega = e_omega(x->x_freq,x->x_rate);
+ t_float A = e_A(x->x_gain);
+ t_float cs = cos(omega);
+ t_float sn = sin(omega);
+ t_float beta = e_beta(A,x->x_bw* 0.01);
+
+ t_float b0 = A*((A+1) + (A-1)*cs + beta*sn);
+ t_float b1 =-2.*A*((A-1) + (A+1)*cs);
+ t_float b2 = A*((A+1) + (A-1)*cs - beta*sn);
+ t_float a0 = ((A+1) - (A-1)*cs + beta*sn);
+ t_float a1 = 2.*((A-1) - (A+1)*cs);
+ t_float a2 = ((A+1) - (A-1)*cs - beta*sn);
+
+/* 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("highshelf: 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 highshelf_float(t_rbjfilter *x,t_floatarg f)
+{
+ x->x_freq = f;
+ highshelf_bang(x);
+}
+
+
+static void *highshelf_new(t_floatarg f,t_floatarg g,t_floatarg bw)
+{
+ t_rbjfilter *x = (t_rbjfilter *)pd_new(highshelf_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;
+ if (g != 0.) x->x_gain = g;
+ return (x);
+}
+
+
+void highshelf_setup(void)
+{
+ highshelf_class = class_new(gensym("highshelf"), (t_newmethod)highshelf_new, 0,
+ sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,A_DEFFLOAT,0);
+ class_addbang(highshelf_class,highshelf_bang);
+ class_addfloat(highshelf_class,highshelf_float);
+}
+
+