gst/audiofx/audiowsinclimit.c - imx-gst-plugins-good - Git at Google

 /* -*- c-basic-offset: 2 -*-
  *
  * GStreamer
  * Copyright (C) 1999-2001 Erik Walthinsen <omega@cse.ogi.edu>
  *               2006 Dreamlab Technologies Ltd. <mathis.hofer@dreamlab.net>
  *               2007-2009 Sebastian Dröge <sebastian.droege@collabora.co.uk>
  *
  * 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., 51 Franklin St, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  *
  * this windowed sinc filter is taken from the freely downloadable DSP book,
  * "The Scientist and Engineer's Guide to Digital Signal Processing",
  * chapter 16
  * available at http://www.dspguide.com/
  *
  * For the window functions see
  * http://en.wikipedia.org/wiki/Window_function
  */

 /**
  * SECTION:element-audiowsinclimit
  *
  * Attenuates all frequencies above the cutoff frequency (low-pass) or all frequencies below the
  * cutoff frequency (high-pass). The length parameter controls the rolloff, the window parameter
  * controls rolloff and stopband attenuation. The Hamming window provides a faster rolloff but a bit
  * worse stopband attenuation, the other way around for the Blackman window.
  *
  * This element has the advantage over the Chebyshev lowpass and highpass filter that it has
  * a much better rolloff when using a larger kernel size and almost linear phase. The only
  * disadvantage is the much slower execution time with larger kernels.
  *
  * <refsect2>
  * <title>Example launch line</title>
  * |[
  * gst-launch-1.0 audiotestsrc freq=1500 ! audioconvert ! audiowsinclimit mode=low-pass cutoff=1000 length=501 ! audioconvert ! alsasink
  * gst-launch-1.0 filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiowsinclimit mode=high-pass cutoff=15000 length=501 ! audioconvert ! alsasink
  * gst-launch-1.0 audiotestsrc wave=white-noise ! audioconvert ! audiowsinclimit mode=low-pass cutoff=1000 length=10001 window=blackman ! audioconvert ! alsasink
  * ]|
  * </refsect2>
  */

 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif

 #include <string.h>
 #include <math.h>
 #include <gst/gst.h>
 #include <gst/audio/gstaudiofilter.h>

 #include "audiowsinclimit.h"

 #include "gst/glib-compat-private.h"

 #define GST_CAT_DEFAULT gst_audio_wsinclimit_debug
 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

 enum
 {
   PROP_0,
   PROP_LENGTH,
   PROP_FREQUENCY,
   PROP_MODE,
   PROP_WINDOW
 };

 enum
 {
   MODE_LOW_PASS = 0,
   MODE_HIGH_PASS
 };

 #define GST_TYPE_AUDIO_WSINC_LIMIT_MODE (gst_audio_wsinclimit_mode_get_type ())
 static GType
 gst_audio_wsinclimit_mode_get_type (void)
 {
   static GType gtype = 0;

   if (gtype == 0) {
     static const GEnumValue values[] = {
       {MODE_LOW_PASS, "Low pass (default)",
           "low-pass"},
       {MODE_HIGH_PASS, "High pass",
           "high-pass"},
       {0, NULL, NULL}
     };

     gtype = g_enum_register_static ("GstAudioWSincLimitMode", values);
   }
   return gtype;
 }

 enum
 {
   WINDOW_HAMMING = 0,
   WINDOW_BLACKMAN,
   WINDOW_GAUSSIAN,
   WINDOW_COSINE,
   WINDOW_HANN
 };

 #define GST_TYPE_AUDIO_WSINC_LIMIT_WINDOW (gst_audio_wsinclimit_window_get_type ())
 static GType
 gst_audio_wsinclimit_window_get_type (void)
 {
   static GType gtype = 0;

   if (gtype == 0) {
     static const GEnumValue values[] = {
       {WINDOW_HAMMING, "Hamming window (default)",
           "hamming"},
       {WINDOW_BLACKMAN, "Blackman window",
           "blackman"},
       {WINDOW_GAUSSIAN, "Gaussian window",
           "gaussian"},
       {WINDOW_COSINE, "Cosine window",
           "cosine"},
       {WINDOW_HANN, "Hann window",
           "hann"},
       {0, NULL, NULL}
     };

     gtype = g_enum_register_static ("GstAudioWSincLimitWindow", values);
   }
   return gtype;
 }

 #define gst_audio_wsinclimit_parent_class parent_class
 G_DEFINE_TYPE (GstAudioWSincLimit, gst_audio_wsinclimit,
     GST_TYPE_AUDIO_FX_BASE_FIR_FILTER);

 static void gst_audio_wsinclimit_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec);
 static void gst_audio_wsinclimit_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec);
 static void gst_audio_wsinclimit_finalize (GObject * object);

 static gboolean gst_audio_wsinclimit_setup (GstAudioFilter * base,
     const GstAudioInfo * info);


 #define POW2(x)  (x)*(x)

 static void
 gst_audio_wsinclimit_class_init (GstAudioWSincLimitClass * klass)
 {
   GObjectClass *gobject_class = (GObjectClass *) klass;
   GstElementClass *gstelement_class = (GstElementClass *) klass;
   GstAudioFilterClass *filter_class = (GstAudioFilterClass *) klass;

   GST_DEBUG_CATEGORY_INIT (gst_audio_wsinclimit_debug, "audiowsinclimit", 0,
       "Low-pass and High-pass Windowed sinc filter plugin");

   gobject_class->set_property = gst_audio_wsinclimit_set_property;
   gobject_class->get_property = gst_audio_wsinclimit_get_property;
   gobject_class->finalize = gst_audio_wsinclimit_finalize;

   /* FIXME: Don't use the complete possible range but restrict the upper boundary
    * so automatically generated UIs can use a slider */
   g_object_class_install_property (gobject_class, PROP_FREQUENCY,
       g_param_spec_float ("cutoff", "Cutoff",
           "Cut-off Frequency (Hz)", 0.0, 100000.0, 0.0,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));
   g_object_class_install_property (gobject_class, PROP_LENGTH,
       g_param_spec_int ("length", "Length",
           "Filter kernel length, will be rounded to the next odd number",
           3, 256000, 101,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));

   g_object_class_install_property (gobject_class, PROP_MODE,
       g_param_spec_enum ("mode", "Mode",
           "Low pass or high pass mode", GST_TYPE_AUDIO_WSINC_LIMIT_MODE,
           MODE_LOW_PASS,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));

   g_object_class_install_property (gobject_class, PROP_WINDOW,
       g_param_spec_enum ("window", "Window",
           "Window function to use", GST_TYPE_AUDIO_WSINC_LIMIT_WINDOW,
           WINDOW_HAMMING,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));

   gst_element_class_set_static_metadata (gstelement_class,
       "Low pass & high pass filter", "Filter/Effect/Audio",
       "Low pass and high pass windowed sinc filter",
       "Thomas Vander Stichele <thomas at apestaart dot org>, "
       "Steven W. Smith, "
       "Dreamlab Technologies Ltd. <mathis.hofer@dreamlab.net>, "
       "Sebastian Dröge <sebastian.droege@collabora.co.uk>");

   filter_class->setup = GST_DEBUG_FUNCPTR (gst_audio_wsinclimit_setup);
 }

 static void
 gst_audio_wsinclimit_init (GstAudioWSincLimit * self)
 {
   self->mode = MODE_LOW_PASS;
   self->window = WINDOW_HAMMING;
   self->kernel_length = 101;
   self->cutoff = 0.0;

   g_mutex_init (&self->lock);
 }

 static void
 gst_audio_wsinclimit_build_kernel (GstAudioWSincLimit * self,
     const GstAudioInfo * info)
 {
   gint i = 0;
   gdouble sum = 0.0;
   gint len = 0;
   gdouble w;
   gdouble *kernel = NULL;
   gint rate, channels;

   len = self->kernel_length;

   if (info) {
     rate = GST_AUDIO_INFO_RATE (info);
     channels = GST_AUDIO_INFO_CHANNELS (info);
   } else {
     rate = GST_AUDIO_FILTER_RATE (self);
     channels = GST_AUDIO_FILTER_CHANNELS (self);
   }

   if (rate == 0) {
     GST_DEBUG ("rate not set yet");
     return;
   }

   if (channels == 0) {
     GST_DEBUG ("channels not set yet");
     return;
   }

   /* Clamp cutoff frequency between 0 and the nyquist frequency */
   self->cutoff = CLAMP (self->cutoff, 0.0, rate / 2);

   GST_DEBUG ("gst_audio_wsinclimit_: initializing filter kernel of length %d "
       "with cutoff %.2lf Hz "
       "for mode %s",
       len, self->cutoff,
       (self->mode == MODE_LOW_PASS) ? "low-pass" : "high-pass");

   /* fill the kernel */
   w = 2 * G_PI * (self->cutoff / rate);

   kernel = g_new (gdouble, len);

   for (i = 0; i < len; ++i) {
     if (i == (len - 1) / 2.0)
       kernel[i] = w;
     else
       kernel[i] = sin (w * (i - (len - 1) / 2)) / (i - (len - 1) / 2.0);

     /* windowing */
     switch (self->window) {
       case WINDOW_HAMMING:
         kernel[i] *= (0.54 - 0.46 * cos (2 * G_PI * i / (len - 1)));
         break;
       case WINDOW_BLACKMAN:
         kernel[i] *= (0.42 - 0.5 * cos (2 * G_PI * i / (len - 1)) +
             0.08 * cos (4 * G_PI * i / (len - 1)));
         break;
       case WINDOW_GAUSSIAN:
         kernel[i] *= exp (-0.5 * POW2 (3.0 / len * (2 * i - (len - 1))));
         break;
       case WINDOW_COSINE:
         kernel[i] *= cos (G_PI * i / (len - 1) - G_PI / 2);
         break;
       case WINDOW_HANN:
         kernel[i] *= 0.5 * (1 - cos (2 * G_PI * i / (len - 1)));
         break;
     }
   }

   /* normalize for unity gain at DC */
   for (i = 0; i < len; ++i)
     sum += kernel[i];
   for (i = 0; i < len; ++i)
     kernel[i] /= sum;

   /* convert to highpass if specified */
   if (self->mode == MODE_HIGH_PASS) {
     for (i = 0; i < len; ++i)
       kernel[i] = -kernel[i];

     if (len % 2 == 1) {
       kernel[(len - 1) / 2] += 1.0;
     } else {
       kernel[len / 2 - 1] += 0.5;
       kernel[len / 2] += 0.5;
     }
   }

   gst_audio_fx_base_fir_filter_set_kernel (GST_AUDIO_FX_BASE_FIR_FILTER (self),
       kernel, self->kernel_length, (len - 1) / 2, info);
 }

 /* GstAudioFilter vmethod implementations */

 /* get notified of caps and plug in the correct process function */
 static gboolean
 gst_audio_wsinclimit_setup (GstAudioFilter * base, const GstAudioInfo * info)
 {
   GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (base);

   gst_audio_wsinclimit_build_kernel (self, info);

   return GST_AUDIO_FILTER_CLASS (parent_class)->setup (base, info);
 }

 static void
 gst_audio_wsinclimit_finalize (GObject * object)
 {
   GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (object);

   g_mutex_clear (&self->lock);

   G_OBJECT_CLASS (parent_class)->finalize (object);
 }

 static void
 gst_audio_wsinclimit_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec)
 {
   GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (object);

   g_return_if_fail (GST_IS_AUDIO_WSINC_LIMIT (self));

   switch (prop_id) {
     case PROP_LENGTH:{
       gint val;

       g_mutex_lock (&self->lock);
       val = g_value_get_int (value);
       if (val % 2 == 0)
         val++;

       if (val != self->kernel_length) {
         gst_audio_fx_base_fir_filter_push_residue (GST_AUDIO_FX_BASE_FIR_FILTER
             (self));
         self->kernel_length = val;
         gst_audio_wsinclimit_build_kernel (self, NULL);
       }
       g_mutex_unlock (&self->lock);
       break;
     }
     case PROP_FREQUENCY:
       g_mutex_lock (&self->lock);
       self->cutoff = g_value_get_float (value);
       gst_audio_wsinclimit_build_kernel (self, NULL);
       g_mutex_unlock (&self->lock);
       break;
     case PROP_MODE:
       g_mutex_lock (&self->lock);
       self->mode = g_value_get_enum (value);
       gst_audio_wsinclimit_build_kernel (self, NULL);
       g_mutex_unlock (&self->lock);
       break;
     case PROP_WINDOW:
       g_mutex_lock (&self->lock);
       self->window = g_value_get_enum (value);
       gst_audio_wsinclimit_build_kernel (self, NULL);
       g_mutex_unlock (&self->lock);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 static void
 gst_audio_wsinclimit_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec)
 {
   GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (object);

   switch (prop_id) {
     case PROP_LENGTH:
       g_value_set_int (value, self->kernel_length);
       break;
     case PROP_FREQUENCY:
       g_value_set_float (value, self->cutoff);
       break;
     case PROP_MODE:
       g_value_set_enum (value, self->mode);
       break;
     case PROP_WINDOW:
       g_value_set_enum (value, self->window);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }
	/* -- c-basic-offset: 2 --
	*
	* GStreamer
	* Copyright (C) 1999-2001 Erik Walthinsen <omega@cse.ogi.edu>
	* 2006 Dreamlab Technologies Ltd. <mathis.hofer@dreamlab.net>
	* 2007-2009 Sebastian Dröge <sebastian.droege@collabora.co.uk>
	*
	* 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., 51 Franklin St, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*
	*
	* this windowed sinc filter is taken from the freely downloadable DSP book,
	* "The Scientist and Engineer's Guide to Digital Signal Processing",
	* chapter 16
	* available at http://www.dspguide.com/
	*
	* For the window functions see
	* http://en.wikipedia.org/wiki/Window_function
	*/

	/**
	* SECTION:element-audiowsinclimit
	*
	* Attenuates all frequencies above the cutoff frequency (low-pass) or all frequencies below the
	* cutoff frequency (high-pass). The length parameter controls the rolloff, the window parameter
	* controls rolloff and stopband attenuation. The Hamming window provides a faster rolloff but a bit
	* worse stopband attenuation, the other way around for the Blackman window.
	*
	* This element has the advantage over the Chebyshev lowpass and highpass filter that it has
	* a much better rolloff when using a larger kernel size and almost linear phase. The only
	* disadvantage is the much slower execution time with larger kernels.
	*
	* <refsect2>
	* <title>Example launch line</title>
	* \|[
	* gst-launch-1.0 audiotestsrc freq=1500 ! audioconvert ! audiowsinclimit mode=low-pass cutoff=1000 length=501 ! audioconvert ! alsasink
	* gst-launch-1.0 filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiowsinclimit mode=high-pass cutoff=15000 length=501 ! audioconvert ! alsasink
	* gst-launch-1.0 audiotestsrc wave=white-noise ! audioconvert ! audiowsinclimit mode=low-pass cutoff=1000 length=10001 window=blackman ! audioconvert ! alsasink
	* ]\|
	* </refsect2>
	*/

	#ifdef HAVE_CONFIG_H
	#include "config.h"
	#endif

	#include <string.h>
	#include <math.h>
	#include <gst/gst.h>
	#include <gst/audio/gstaudiofilter.h>

	#include "audiowsinclimit.h"

	#include "gst/glib-compat-private.h"

	#define GST_CAT_DEFAULT gst_audio_wsinclimit_debug
	GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

	enum
	{
	PROP_0,
	PROP_LENGTH,
	PROP_FREQUENCY,
	PROP_MODE,
	PROP_WINDOW
	};

	enum
	{
	MODE_LOW_PASS = 0,
	MODE_HIGH_PASS
	};

	#define GST_TYPE_AUDIO_WSINC_LIMIT_MODE (gst_audio_wsinclimit_mode_get_type ())
	static GType
	gst_audio_wsinclimit_mode_get_type (void)
	{
	static GType gtype = 0;

	if (gtype == 0) {
	static const GEnumValue values[] = {
	{MODE_LOW_PASS, "Low pass (default)",
	"low-pass"},
	{MODE_HIGH_PASS, "High pass",
	"high-pass"},
	{0, NULL, NULL}
	};

	gtype = g_enum_register_static ("GstAudioWSincLimitMode", values);
	}
	return gtype;
	}

	enum
	{
	WINDOW_HAMMING = 0,
	WINDOW_BLACKMAN,
	WINDOW_GAUSSIAN,
	WINDOW_COSINE,
	WINDOW_HANN
	};

	#define GST_TYPE_AUDIO_WSINC_LIMIT_WINDOW (gst_audio_wsinclimit_window_get_type ())
	static GType
	gst_audio_wsinclimit_window_get_type (void)
	{
	static GType gtype = 0;

	if (gtype == 0) {
	static const GEnumValue values[] = {
	{WINDOW_HAMMING, "Hamming window (default)",
	"hamming"},
	{WINDOW_BLACKMAN, "Blackman window",
	"blackman"},
	{WINDOW_GAUSSIAN, "Gaussian window",
	"gaussian"},
	{WINDOW_COSINE, "Cosine window",
	"cosine"},
	{WINDOW_HANN, "Hann window",
	"hann"},
	{0, NULL, NULL}
	};

	gtype = g_enum_register_static ("GstAudioWSincLimitWindow", values);
	}
	return gtype;
	}

	#define gst_audio_wsinclimit_parent_class parent_class
	G_DEFINE_TYPE (GstAudioWSincLimit, gst_audio_wsinclimit,
	GST_TYPE_AUDIO_FX_BASE_FIR_FILTER);

	static void gst_audio_wsinclimit_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec);
	static void gst_audio_wsinclimit_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec);
	static void gst_audio_wsinclimit_finalize (GObject * object);

	static gboolean gst_audio_wsinclimit_setup (GstAudioFilter * base,
	const GstAudioInfo * info);


	#define POW2(x) (x)*(x)

	static void
	gst_audio_wsinclimit_class_init (GstAudioWSincLimitClass * klass)
	{
	GObjectClass gobject_class = (GObjectClass ) klass;
	GstElementClass gstelement_class = (GstElementClass ) klass;
	GstAudioFilterClass filter_class = (GstAudioFilterClass ) klass;

	GST_DEBUG_CATEGORY_INIT (gst_audio_wsinclimit_debug, "audiowsinclimit", 0,
	"Low-pass and High-pass Windowed sinc filter plugin");

	gobject_class->set_property = gst_audio_wsinclimit_set_property;
	gobject_class->get_property = gst_audio_wsinclimit_get_property;
	gobject_class->finalize = gst_audio_wsinclimit_finalize;

	/* FIXME: Don't use the complete possible range but restrict the upper boundary
	* so automatically generated UIs can use a slider */
	g_object_class_install_property (gobject_class, PROP_FREQUENCY,
	g_param_spec_float ("cutoff", "Cutoff",
	"Cut-off Frequency (Hz)", 0.0, 100000.0, 0.0,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));
	g_object_class_install_property (gobject_class, PROP_LENGTH,
	g_param_spec_int ("length", "Length",
	"Filter kernel length, will be rounded to the next odd number",
	3, 256000, 101,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));

	g_object_class_install_property (gobject_class, PROP_MODE,
	g_param_spec_enum ("mode", "Mode",
	"Low pass or high pass mode", GST_TYPE_AUDIO_WSINC_LIMIT_MODE,
	MODE_LOW_PASS,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));

	g_object_class_install_property (gobject_class, PROP_WINDOW,
	g_param_spec_enum ("window", "Window",
	"Window function to use", GST_TYPE_AUDIO_WSINC_LIMIT_WINDOW,
	WINDOW_HAMMING,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));

	gst_element_class_set_static_metadata (gstelement_class,
	"Low pass & high pass filter", "Filter/Effect/Audio",
	"Low pass and high pass windowed sinc filter",
	"Thomas Vander Stichele <thomas at apestaart dot org>, "
	"Steven W. Smith, "
	"Dreamlab Technologies Ltd. <mathis.hofer@dreamlab.net>, "
	"Sebastian Dröge <sebastian.droege@collabora.co.uk>");

	filter_class->setup = GST_DEBUG_FUNCPTR (gst_audio_wsinclimit_setup);
	}

	static void
	gst_audio_wsinclimit_init (GstAudioWSincLimit * self)
	{
	self->mode = MODE_LOW_PASS;
	self->window = WINDOW_HAMMING;
	self->kernel_length = 101;
	self->cutoff = 0.0;

	g_mutex_init (&self->lock);
	}

	static void
	gst_audio_wsinclimit_build_kernel (GstAudioWSincLimit * self,
	const GstAudioInfo * info)
	{
	gint i = 0;
	gdouble sum = 0.0;
	gint len = 0;
	gdouble w;
	gdouble *kernel = NULL;
	gint rate, channels;

	len = self->kernel_length;

	if (info) {
	rate = GST_AUDIO_INFO_RATE (info);
	channels = GST_AUDIO_INFO_CHANNELS (info);
	} else {
	rate = GST_AUDIO_FILTER_RATE (self);
	channels = GST_AUDIO_FILTER_CHANNELS (self);
	}

	if (rate == 0) {
	GST_DEBUG ("rate not set yet");
	return;
	}

	if (channels == 0) {
	GST_DEBUG ("channels not set yet");
	return;
	}

	/* Clamp cutoff frequency between 0 and the nyquist frequency */
	self->cutoff = CLAMP (self->cutoff, 0.0, rate / 2);

	GST_DEBUG ("gst_audio_wsinclimit_: initializing filter kernel of length %d "
	"with cutoff %.2lf Hz "
	"for mode %s",
	len, self->cutoff,
	(self->mode == MODE_LOW_PASS) ? "low-pass" : "high-pass");

	/* fill the kernel */
	w = 2 * G_PI * (self->cutoff / rate);

	kernel = g_new (gdouble, len);

	for (i = 0; i < len; ++i) {
	if (i == (len - 1) / 2.0)
	kernel[i] = w;
	else
	kernel[i] = sin (w * (i - (len - 1) / 2)) / (i - (len - 1) / 2.0);

	/* windowing */
	switch (self->window) {
	case WINDOW_HAMMING:
	kernel[i] = (0.54 - 0.46 cos (2 * G_PI * i / (len - 1)));
	break;
	case WINDOW_BLACKMAN:
	kernel[i] = (0.42 - 0.5 cos (2 * G_PI * i / (len - 1)) +
	0.08 * cos (4 * G_PI * i / (len - 1)));
	break;
	case WINDOW_GAUSSIAN:
	kernel[i] = exp (-0.5 POW2 (3.0 / len * (2 * i - (len - 1))));
	break;
	case WINDOW_COSINE:
	kernel[i] = cos (G_PI i / (len - 1) - G_PI / 2);
	break;
	case WINDOW_HANN:
	kernel[i] = 0.5 (1 - cos (2 * G_PI * i / (len - 1)));
	break;
	}
	}

	/* normalize for unity gain at DC */
	for (i = 0; i < len; ++i)
	sum += kernel[i];
	for (i = 0; i < len; ++i)
	kernel[i] /= sum;

	/* convert to highpass if specified */
	if (self->mode == MODE_HIGH_PASS) {
	for (i = 0; i < len; ++i)
	kernel[i] = -kernel[i];

	if (len % 2 == 1) {
	kernel[(len - 1) / 2] += 1.0;
	} else {
	kernel[len / 2 - 1] += 0.5;
	kernel[len / 2] += 0.5;
	}
	}

	gst_audio_fx_base_fir_filter_set_kernel (GST_AUDIO_FX_BASE_FIR_FILTER (self),
	kernel, self->kernel_length, (len - 1) / 2, info);
	}

	/* GstAudioFilter vmethod implementations */

	/* get notified of caps and plug in the correct process function */
	static gboolean
	gst_audio_wsinclimit_setup (GstAudioFilter * base, const GstAudioInfo * info)
	{
	GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (base);

	gst_audio_wsinclimit_build_kernel (self, info);

	return GST_AUDIO_FILTER_CLASS (parent_class)->setup (base, info);
	}

	static void
	gst_audio_wsinclimit_finalize (GObject * object)
	{
	GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (object);

	g_mutex_clear (&self->lock);

	G_OBJECT_CLASS (parent_class)->finalize (object);
	}

	static void
	gst_audio_wsinclimit_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec)
	{
	GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (object);

	g_return_if_fail (GST_IS_AUDIO_WSINC_LIMIT (self));

	switch (prop_id) {
	case PROP_LENGTH:{
	gint val;

	g_mutex_lock (&self->lock);
	val = g_value_get_int (value);
	if (val % 2 == 0)
	val++;

	if (val != self->kernel_length) {
	gst_audio_fx_base_fir_filter_push_residue (GST_AUDIO_FX_BASE_FIR_FILTER
	(self));
	self->kernel_length = val;
	gst_audio_wsinclimit_build_kernel (self, NULL);
	}
	g_mutex_unlock (&self->lock);
	break;
	}
	case PROP_FREQUENCY:
	g_mutex_lock (&self->lock);
	self->cutoff = g_value_get_float (value);
	gst_audio_wsinclimit_build_kernel (self, NULL);
	g_mutex_unlock (&self->lock);
	break;
	case PROP_MODE:
	g_mutex_lock (&self->lock);
	self->mode = g_value_get_enum (value);
	gst_audio_wsinclimit_build_kernel (self, NULL);
	g_mutex_unlock (&self->lock);
	break;
	case PROP_WINDOW:
	g_mutex_lock (&self->lock);
	self->window = g_value_get_enum (value);
	gst_audio_wsinclimit_build_kernel (self, NULL);
	g_mutex_unlock (&self->lock);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	static void
	gst_audio_wsinclimit_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec)
	{
	GstAudioWSincLimit *self = GST_AUDIO_WSINC_LIMIT (object);

	switch (prop_id) {
	case PROP_LENGTH:
	g_value_set_int (value, self->kernel_length);
	break;
	case PROP_FREQUENCY:
	g_value_set_float (value, self->cutoff);
	break;
	case PROP_MODE:
	g_value_set_enum (value, self->mode);
	break;
	case PROP_WINDOW:
	g_value_set_enum (value, self->window);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}