new filter subdir for standard audio filters first filter uses code from vorbis to implement an iir filter not optimi...

Original commit message from CVS:
new filter subdir for standard audio filters
first filter uses code from vorbis to implement an iir filter
not optimized yet, iir code uses doubles and plugin uses float

6 files changed, 762 insertions, 0 deletions

diff --git a/gst/filter/Makefile.am b/gst/filter/Makefile.am
new file mode 100644
index 00000000..4204955f
--- /dev/null
+++ b/gst/filter/Makefile.am
@@ -0,0 +1,10 @@
+plugindir = $(libdir)/gst
+
+plugin_LTLIBRARIES = libgstfilter.la
+
+libgstfilter_la_SOURCES = gstfilter.c gstiir.c iir.c
+libgstfilter_la_CFLAGS = $(GST_CFLAGS)
+libgstfilter_la_LIBADD =
+libgstfilter_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS)
+
+noinst_HEADERS = gstfilter.h iir.h
diff --git a/gst/filter/gstfilter.c b/gst/filter/gstfilter.c
new file mode 100644
index 00000000..2ed416c1
--- /dev/null
+++ b/gst/filter/gstfilter.c
@@ -0,0 +1,120 @@
+/* GStreamer
+ * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
+ *                    2000 Wim Taymans <wtay@chello.be>
+ *
+ * gstfilter.c: element for filter plug-ins
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "gstfilter.h"
+
+
+struct _elements_entry {
+  gchar *name;
+  GType (*type) (void);
+  GstElementDetails *details;
+  gboolean (*factoryinit) (GstElementFactory *factory);
+};
+
+static struct _elements_entry _elements[] = {
+  { "iir",  gst_iir_get_type,  &gst_iir_details,  NULL },
+  { NULL, 0 },
+};
+
+GstPadTemplate* 
+gst_filter_src_factory (void)
+{
+  static GstPadTemplate *templ = NULL;
+  if (!templ) {
+    templ = GST_PAD_TEMPLATE_NEW ( 
+  		"src",
+  		GST_PAD_SRC,
+  		GST_PAD_ALWAYS,
+  		GST_CAPS_NEW (
+  		  "filter_src",
+  		  "audio/raw",
+  		    "format",		GST_PROPS_STRING ("float"),
+  		    "rate",            	GST_PROPS_INT_RANGE (1, G_MAXINT),
+		    "layout",     	GST_PROPS_STRING ("gfloat"),
+		    "intercept",  	GST_PROPS_FLOAT(0.0),
+		    "slope",      	GST_PROPS_FLOAT(1.0),
+		    "channels",   	GST_PROPS_INT (1)
+		)
+  	     );
+  }
+  return templ;
+}
+
+GstPadTemplate* 
+gst_filter_sink_factory (void)
+{
+  static GstPadTemplate *templ = NULL;
+  if (!templ) {
+    templ = GST_PAD_TEMPLATE_NEW ( 
+  		"sink",
+  		GST_PAD_SINK,
+  		GST_PAD_ALWAYS,
+  		GST_CAPS_NEW (
+  		  "filter_src",
+  		  "audio/raw",
+  		    "format",		GST_PROPS_STRING ("float"),
+  		    "rate",            	GST_PROPS_INT_RANGE (1, G_MAXINT),
+		    "layout",     	GST_PROPS_STRING ("gfloat"),
+		    "intercept",  	GST_PROPS_FLOAT(0.0),
+		    "slope",      	GST_PROPS_FLOAT(1.0),
+		    "channels",   	GST_PROPS_INT (1)
+		)
+  	     );
+  }
+  return templ;
+}
+
+static gboolean
+plugin_init (GModule * module, GstPlugin * plugin)
+{
+  GstElementFactory *factory;
+  gint i = 0;
+
+  while (_elements[i].name) {
+    factory = gst_element_factory_new (_elements[i].name,
+                                      (_elements[i].type) (),
+                                       _elements[i].details);
+
+    if (!factory) {
+      g_warning ("gst_filter_new failed for `%s'",
+                 _elements[i].name);
+      continue;
+    }
+    gst_element_factory_add_pad_template (factory, gst_filter_src_factory ());
+    gst_element_factory_add_pad_template (factory, gst_filter_sink_factory ());
+
+    gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));
+    if (_elements[i].factoryinit) {
+      _elements[i].factoryinit (factory);
+    }
+    i++;
+  }
+
+  return TRUE;
+}
+
+GstPluginDesc plugin_desc = {
+  GST_VERSION_MAJOR,
+  GST_VERSION_MINOR,
+  "filter",
+  plugin_init
+};
diff --git a/gst/filter/gstfilter.h b/gst/filter/gstfilter.h
new file mode 100644
index 00000000..a806bb4d
--- /dev/null
+++ b/gst/filter/gstfilter.h
@@ -0,0 +1,34 @@
+/* GStreamer
+ * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
+ *                    2000 Wim Taymans <wtay@chello.be>
+ *
+ * gstfilter.h: element for filter plug-ins
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+
+#ifndef __GST_FILTER_H__
+#define __GST_FILTER_H__
+
+#include <gst/gst.h>
+GType gst_iir_get_type (void);
+extern GstElementDetails gst_iir_details;
+
+extern GstPadTemplate *gst_filter_sink_factory ();
+extern GstPadTemplate *gst_filter_src_factory ();
+
+#endif /* __GST_FILTER_H__ */
diff --git a/gst/filter/gstiir.c b/gst/filter/gstiir.c
new file mode 100644
index 00000000..811b6a12
--- /dev/null
+++ b/gst/filter/gstiir.c
@@ -0,0 +1,259 @@
+/* -*- c-basic-offset: 2 -*-
+ * GStreamer
+ * Copyright (C) 1999-2001 Erik Walthinsen <omega@cse.ogi.edu>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include <gst/gst.h>
+#include "gstfilter.h"
+#include "iir.h"
+
+GstElementDetails gst_iir_details = {
+  "IIR",
+  "Filter/Audio/Effect",
+  "IIR filter based on vorbis code",
+  VERSION,
+  "Monty <monty@xiph.org>, "\
+  "Thomas <thomas@apestaart.org>",
+  "(C) 2001",
+};
+
+enum {
+  /* FILL ME */
+  LAST_SIGNAL
+};
+
+enum {
+  ARG_0,
+  ARG_A,
+  ARG_B,
+  ARG_GAIN,
+  ARG_STAGES,
+};
+
+#define GST_TYPE_IIR \
+  (gst_iir_get_type())
+#define GST_IIR(obj) \
+      (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_IIR,GstIIR))
+#define GST_IIR_CLASS(klass) \
+      (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_ULAW,GstIIR))
+#define GST_IS_IIR(obj) \
+      (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_IIR))
+#define GST_IS_IIR_CLASS(obj) \
+      (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_IIR))
+
+typedef struct _GstIIR GstIIR;
+typedef struct _GstIIRClass GstIIRClass;
+
+struct _GstIIR
+{
+  GstElement element;
+
+  GstPad *sinkpad, *srcpad;
+
+  double A, B;
+  double gain;
+  int stages;
+  IIR_state *state;
+};
+
+struct _GstIIRClass
+{
+    GstElementClass parent_class;
+};
+
+static void gst_iir_class_init		(GstIIRClass * klass);
+static void gst_iir_init               	(GstIIR * filter);
+
+static void gst_iir_set_property	(GObject * object, guint prop_id,
+                                         const GValue * value, 
+					 GParamSpec * pspec);
+static void gst_iir_get_property	(GObject * object, guint prop_id,
+                                         GValue * value, GParamSpec * pspec);
+
+static void gst_iir_chain		(GstPad * pad, GstBuffer * buf);
+static GstPadConnectReturn
+       gst_iir_sink_connect 		(GstPad * pad, GstCaps * caps);
+
+static GstElementClass *parent_class = NULL;
+/*static guint gst_iir_signals[LAST_SIGNAL] = { 0 }; */
+
+GType gst_iir_get_type (void)
+{
+  static GType iir_type = 0;
+
+  if (!iir_type) {
+    static const GTypeInfo iir_info = {
+      sizeof (GstIIRClass), NULL, NULL,
+      (GClassInitFunc) gst_iir_class_init, NULL, NULL,
+      sizeof (GstIIR), 0,
+      (GInstanceInitFunc) gst_iir_init,
+    };
+
+    iir_type = g_type_register_static (GST_TYPE_ELEMENT, "GstIIR", 
+	                                   &iir_info, 0);
+  }
+  return iir_type;
+}
+
+static void
+gst_iir_class_init (GstIIRClass * klass)
+{
+  GObjectClass *gobject_class;
+  GstElementClass *gstelement_class;
+
+  gobject_class = (GObjectClass *) klass;
+  gstelement_class = (GstElementClass *) klass;
+
+  parent_class = g_type_class_ref (GST_TYPE_ELEMENT);
+
+  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_A,
+      g_param_spec_double ("A", "A", "A filter coefficient", 
+	                   -G_MAXDOUBLE, G_MAXDOUBLE, 
+	                   0, G_PARAM_READWRITE));
+  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_B,
+      g_param_spec_double ("B", "B", "B filter coefficient", 
+	                   -G_MAXDOUBLE, G_MAXDOUBLE, 
+	                   0, G_PARAM_READWRITE));
+  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_GAIN,
+      g_param_spec_double ("gain", "Gain", "Filter gain", 
+	                   -G_MAXDOUBLE, G_MAXDOUBLE, 
+	                   0, G_PARAM_READWRITE));
+  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_STAGES,
+      g_param_spec_int ("stages", "Stages", "Number of filter stages", 
+	                   1, G_MAXINT, 
+	                   0, G_PARAM_READWRITE));
+
+  gobject_class->set_property = gst_iir_set_property;
+  gobject_class->get_property = gst_iir_get_property;
+}
+
+static void
+gst_iir_init (GstIIR * filter)
+{
+  filter->sinkpad = gst_pad_new_from_template (gst_filter_sink_factory (), "sink");
+  gst_pad_set_chain_function (filter->sinkpad, gst_iir_chain);
+  gst_pad_set_connect_function (filter->sinkpad, gst_iir_sink_connect);
+  gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
+
+  filter->srcpad = gst_pad_new_from_template (gst_filter_src_factory (), "src");
+  gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
+
+  filter->A = 0.0;
+  filter->B = 0.0;
+  filter->gain = 1.0;	/* unity gain as default */
+  filter->stages = 1;
+  filter->state = NULL;
+}
+
+static GstPadConnectReturn
+gst_iir_sink_connect (GstPad * pad, GstCaps * caps)
+{
+  GstIIR *filter;
+  
+  filter = GST_IIR (gst_pad_get_parent (pad));
+  
+  if (!GST_CAPS_IS_FIXED (caps))
+    return GST_PAD_CONNECT_DELAYED;
+    
+  if (gst_pad_try_set_caps (filter->srcpad, caps)) {
+    /* connection works, so init the filter */
+    /* FIXME: remember to free it */
+    filter->state = (IIR_state *) g_malloc (sizeof (IIR_state));
+    IIR_init (filter->state, filter->stages, 
+	      filter->gain, &(filter->A), &(filter->B));
+    return GST_PAD_CONNECT_OK;
+  }
+
+  return GST_PAD_CONNECT_REFUSED;
+}
+
+static void
+gst_iir_chain (GstPad * pad, GstBuffer * buf)
+{
+  GstIIR *filter;
+  gfloat *src;
+  int i;
+
+  filter = GST_IIR (gst_pad_get_parent (pad));
+
+  src = (gfloat *) GST_BUFFER_DATA (buf);
+
+  /* do an in-place edit */
+  for (i = 0; i < GST_BUFFER_SIZE (buf) / sizeof (gfloat); ++i)
+    *(src + i) = (gfloat) IIR_filter (filter->state, (double) *(src + i));
+
+  gst_pad_push (filter->srcpad, buf);
+}
+
+static void
+gst_iir_set_property (GObject * object, guint prop_id, const GValue * value, GParamSpec * pspec)
+{
+  GstIIR *filter;
+
+  /* it's not null if we got it, but it might not be ours */
+  g_return_if_fail (GST_IS_IIR (object));
+
+  filter = GST_IIR (object);
+
+  switch (prop_id) {
+    case ARG_A:
+     filter->A = g_value_get_double (value);
+     break; 
+    case ARG_B:
+     filter->B = g_value_get_double (value);
+     break; 
+    case ARG_GAIN:
+     filter->gain = g_value_get_double (value);
+     break; 
+    case ARG_STAGES:
+     filter->stages = g_value_get_int (value);
+     break; 
+    default:
+      break;
+  }
+}
+
+static void
+gst_iir_get_property (GObject * object, guint prop_id, GValue * value, GParamSpec * pspec)
+{
+  GstIIR *filter;
+
+  /* it's not null if we got it, but it might not be ours */
+  g_return_if_fail (GST_IS_IIR (object));
+  
+  filter = GST_IIR (object);
+
+  switch (prop_id) {
+    case ARG_A:
+      g_value_set_double (value, filter->A);
+      break;
+    case ARG_B:
+      g_value_set_double (value, filter->B);
+      break;
+    case ARG_GAIN:
+      g_value_set_double (value, filter->gain);
+      break;
+    case ARG_STAGES:
+      g_value_set_int (value, filter->stages);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+} 
+
diff --git a/gst/filter/iir.c b/gst/filter/iir.c
new file mode 100644
index 00000000..1ef31540
--- /dev/null
+++ b/gst/filter/iir.c
@@ -0,0 +1,302 @@
+/********************************************************************
+ *                                                                  *
+ * THIS FILE IS PART OF THE Ogg Vorbis SOFTWARE CODEC SOURCE CODE.  *
+ * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
+ * THE GNU PUBLIC LICENSE 2, WHICH IS INCLUDED WITH THIS SOURCE.    *
+ * PLEASE READ THESE TERMS DISTRIBUTING.                            *
+ *                                                                  *
+ * THE OggSQUISH SOURCE CODE IS (C) COPYRIGHT 1994-2000             *
+ * by Monty <monty@xiph.org> and The XIPHOPHORUS Company            *
+ * http://www.xiph.org/                                             *
+ *                                                                  *
+ ********************************************************************
+
+  function: Direct Form I, II IIR filters, plus some specializations
+  last mod: $Id$
+
+ ********************************************************************/
+
+/* LPC is actually a degenerate case of form I/II filters, but we need
+   both */
+
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include "iir.h"
+
+void IIR_init(IIR_state *s,int stages,double gain, double *A, double *B){
+  memset(s,0,sizeof(IIR_state));
+  s->stages=stages;
+  s->gain=gain;
+  s->coeff_A=malloc(stages*sizeof(double));
+  s->coeff_B=malloc((stages+1)*sizeof(double));
+  s->z_A=calloc(stages*2,sizeof(double));
+  s->z_B=calloc(stages*2,sizeof(double));
+
+  memcpy(s->coeff_A,A,stages*sizeof(double));
+  memcpy(s->coeff_B,B,(stages+1)*sizeof(double));
+}
+
+void IIR_clear(IIR_state *s){
+  if(s){
+    free(s->coeff_A);
+    free(s->coeff_B);
+    free(s->z_A);
+    free(s->z_B);
+    memset(s,0,sizeof(IIR_state));
+  }
+}
+
+double IIR_filter(IIR_state *s,double in){
+  int stages=s->stages,i;
+  double newA;
+  double newB=0;
+  double *zA=s->z_A+s->ring;
+
+  newA=in/=s->gain;
+  for(i=0;i<stages;i++){
+    newA+= s->coeff_A[i] * zA[i];
+    newB+= s->coeff_B[i] * zA[i];
+  }
+  newB+=newA*s->coeff_B[stages];
+
+  zA[0]=zA[stages]=newA;
+  if(++s->ring>=stages)s->ring=0;
+
+  return(newB);
+}
+
+/* this assumes the symmetrical structure of the feed-forward stage of
+   a Chebyshev bandpass to save multiplies */
+double IIR_filter_ChebBand(IIR_state *s,double in){
+  int stages=s->stages,i;
+  double newA;
+  double newB=0;
+  double *zA=s->z_A+s->ring;
+
+  newA=in/=s->gain;
+
+  newA+= s->coeff_A[0] * zA[0];
+  for(i=1;i<(stages>>1);i++){
+    newA+= s->coeff_A[i] * zA[i];
+    newB+= s->coeff_B[i] * (zA[i]-zA[stages-i]);
+  }
+  newB+= s->coeff_B[i] * zA[i];
+  for(;i<stages;i++)
+    newA+= s->coeff_A[i] * zA[i];
+
+  newB+= newA-zA[0];
+
+  zA[0]=zA[stages]=newA;
+  if(++s->ring>=stages)s->ring=0;
+
+  return(newB);
+}
+
+#ifdef _V_SELFTEST
+
+/* z^-stage, z^-stage+1... */
+static double cheb_bandpass_B[]={-1.,0.,5.,0.,-10.,0.,10.,0.,-5.,0.,1};
+static double cheb_bandpass_A[]={-0.6665900311,
+				  1.0070146601,
+				 -3.1262875409,
+			 	  3.5017171569,
+				 -6.2779211945,
+				  5.2966481740,
+				 -6.7570216587,
+				  4.0760335768,
+				 -3.9134284363,
+				  1.3997338886};
+
+static double data[128]={  
+  0.0426331,
+  0.0384521,
+  0.0345764,
+  0.0346069,
+  0.0314636,
+  0.0310059,
+  0.0318604,
+  0.0336304,
+  0.036438,
+  0.0348511,
+  0.0354919,
+  0.0343628,
+  0.0325623,
+  0.0318909,
+  0.0263367,
+  0.0225525,
+  0.0195618,
+  0.0160828,
+  0.0168762,
+  0.0145569,
+  0.0126343,
+  0.0127258,
+  0.00820923,
+  0.00787354,
+  0.00558472,
+  0.00204468,
+  3.05176e-05,
+  -0.00357056,
+  -0.00570679,
+  -0.00991821,
+  -0.0101013,
+  -0.00881958,
+  -0.0108948,
+  -0.0110168,
+  -0.0119324,
+  -0.0161438,
+  -0.0194702,
+  -0.0229187,
+  -0.0260315,
+  -0.0282288,
+  -0.0306091,
+  -0.0330505,
+  -0.0364685,
+  -0.0385742,
+  -0.0428772,
+  -0.043457,
+  -0.0425415,
+  -0.0462341,
+  -0.0467529,
+  -0.0489807,
+  -0.0520325,
+  -0.0558167,
+  -0.0596924,
+  -0.0591431,
+  -0.0612793,
+  -0.0618591,
+  -0.0615845,
+  -0.0634155,
+  -0.0639648,
+  -0.0683594,
+  -0.0718079,
+  -0.0729675,
+  -0.0791931,
+  -0.0860901,
+  -0.0885315,
+  -0.088623,
+  -0.089386,
+  -0.0899353,
+  -0.0886841,
+  -0.0910645,
+  -0.0948181,
+  -0.0919495,
+  -0.0891418,
+  -0.0916443,
+  -0.096344,
+  -0.100464,
+  -0.105499,
+  -0.108612,
+  -0.112213,
+  -0.117676,
+  -0.120911,
+  -0.124329,
+  -0.122162,
+  -0.120605,
+  -0.12326,
+  -0.12619,
+  -0.128998,
+  -0.13205,
+  -0.134247,
+  -0.137939,
+  -0.143555,
+  -0.14389,
+  -0.14859,
+  -0.153717,
+  -0.159851,
+  -0.164551,
+  -0.162811,
+  -0.164276,
+  -0.156952,
+  -0.140564,
+  -0.123291,
+  -0.10321,
+  -0.0827637,
+  -0.0652466,
+  -0.053772,
+  -0.0509949,
+  -0.0577698,
+  -0.0818176,
+  -0.114929,
+  -0.148895,
+  -0.181122,
+  -0.200714,
+  -0.21048,
+  -0.203644,
+  -0.179413,
+  -0.145325,
+  -0.104492,
+  -0.0658264,
+  -0.0332031,
+  -0.0106201,
+  -0.00363159,
+  -0.00909424,
+  -0.0244141,
+  -0.0422058,
+  -0.0537415,
+  -0.0610046,
+  -0.0609741,
+  -0.0547791};
+
+/* comparison test code from http://www-users.cs.york.ac.uk/~fisher/mkfilter/
+   (the above page kicks ass, BTW)*/
+
+#define NZEROS 10
+#define NPOLES 10
+#define GAIN   4.599477515e+02
+
+static float xv[NZEROS+1], yv[NPOLES+1];
+
+static double filterloop(double next){ 
+  xv[0] = xv[1]; xv[1] = xv[2]; xv[2] = xv[3]; xv[3] = xv[4]; xv[4] = xv[5]; 
+  xv[5] = xv[6]; xv[6] = xv[7]; xv[7] = xv[8]; xv[8] = xv[9]; xv[9] = xv[10]; 
+  xv[10] = next / GAIN;
+  yv[0] = yv[1]; yv[1] = yv[2]; yv[2] = yv[3]; yv[3] = yv[4]; yv[4] = yv[5]; 
+  yv[5] = yv[6]; yv[6] = yv[7]; yv[7] = yv[8]; yv[8] = yv[9]; yv[9] = yv[10]; 
+  yv[10] =   (xv[10] - xv[0]) + 5 * (xv[2] - xv[8]) + 10 * (xv[6] - xv[4])
+    + ( -0.6665900311 * yv[0]) + (  1.0070146601 * yv[1])
+    + ( -3.1262875409 * yv[2]) + (  3.5017171569 * yv[3])
+    + ( -6.2779211945 * yv[4]) + (  5.2966481740 * yv[5])
+    + ( -6.7570216587 * yv[6]) + (  4.0760335768 * yv[7])
+    + ( -3.9134284363 * yv[8]) + (  1.3997338886 * yv[9]);
+  return(yv[10]);
+}
+
+#include <stdio.h>
+int main(){
+
+  /* run the pregenerated Chebyshev filter, then our own distillation
+     through the generic and specialized code */
+  double *work=malloc(128*sizeof(double));
+  IIR_state iir;
+  int i;
+
+  for(i=0;i<128;i++)work[i]=filterloop(data[i]);
+  {
+    FILE *out=fopen("IIR_ref.m","w");
+    for(i=0;i<128;i++)fprintf(out,"%g\n",work[i]);
+    fclose(out);
+  }
+
+  IIR_init(&iir,NPOLES,GAIN,cheb_bandpass_A,cheb_bandpass_B);
+  for(i=0;i<128;i++)work[i]=IIR_filter(&iir,data[i]);
+  {
+    FILE *out=fopen("IIR_gen.m","w");
+    for(i=0;i<128;i++)fprintf(out,"%g\n",work[i]);
+    fclose(out);
+  }
+  IIR_clear(&iir);  
+
+  IIR_init(&iir,NPOLES,GAIN,cheb_bandpass_A,cheb_bandpass_B);
+  for(i=0;i<128;i++)work[i]=IIR_filter_ChebBand(&iir,data[i]);
+  {
+    FILE *out=fopen("IIR_cheb.m","w");
+    for(i=0;i<128;i++)fprintf(out,"%g\n",work[i]);
+    fclose(out);
+  }
+  IIR_clear(&iir);  
+
+  return(0);
+}
+
+#endif
diff --git a/gst/filter/iir.h b/gst/filter/iir.h
new file mode 100644
index 00000000..241cc1d2
--- /dev/null
+++ b/gst/filter/iir.h
@@ -0,0 +1,37 @@
+/********************************************************************
+ *                                                                  *
+ * THIS FILE IS PART OF THE Ogg Vorbis SOFTWARE CODEC SOURCE CODE.  *
+ * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
+ * THE GNU PUBLIC LICENSE 2, WHICH IS INCLUDED WITH THIS SOURCE.    *
+ * PLEASE READ THESE TERMS DISTRIBUTING.                            *
+ *                                                                  *
+ * THE OggSQUISH SOURCE CODE IS (C) COPYRIGHT 1994-2000             *
+ * by Monty <monty@xiph.org> and The XIPHOPHORUS Company            *
+ * http://www.xiph.org/                                             *
+ *                                                                  *
+ ********************************************************************
+
+  function: Direct Form I, II IIR filters, plus some specializations
+  last mod: $Id$
+
+ ********************************************************************/
+
+#ifndef _V_IIR_H_
+#define _V_IIR_H_
+
+typedef struct {
+  int stages;
+  double *coeff_A;
+  double *coeff_B;
+  double *z_A;
+  double *z_B;
+  int ring;
+  double gain;
+} IIR_state;
+
+void IIR_init(IIR_state *s,int stages,double gain, double *A, double *B);
+void IIR_clear(IIR_state *s);
+double IIR_filter(IIR_state *s,double in);
+double IIR_filter_ChebBand(IIR_state *s,double in);
+
+#endif