gst/audiofx/audiochebband.c - mtk-gst-plugins-good-debian - Git at Google

 /*
  * GStreamer
  * Copyright (C) 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., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */

 /*
  * Chebyshev type 1 filter design based on
  * "The Scientist and Engineer's Guide to DSP", Chapter 20.
  * http://www.dspguide.com/
  *
  * For type 2 and Chebyshev filters in general read
  * http://en.wikipedia.org/wiki/Chebyshev_filter
  *
  * Transformation from lowpass to bandpass/bandreject:
  * http://docs.dewresearch.com/DspHelp/html/IDH_LinearSystems_LowpassToBandPassZ.htm
  * http://docs.dewresearch.com/DspHelp/html/IDH_LinearSystems_LowpassToBandStopZ.htm
  *
  */

 /**
  * SECTION:element-audiochebband
  *
  * Attenuates all frequencies outside (bandpass) or inside (bandreject) of a frequency
  * band. The number of poles and the ripple parameter control the rolloff.
  *
  * This element has the advantage over the windowed sinc bandpass and bandreject filter that it is
  * much faster and produces almost as good results. It's only disadvantages are the highly
  * non-linear phase and the slower rolloff compared to a windowed sinc filter with a large kernel.
  *
  * For type 1 the ripple parameter specifies how much ripple in dB is allowed in the passband, i.e.
  * some frequencies in the passband will be amplified by that value. A higher ripple value will allow
  * a faster rolloff.
  *
  * For type 2 the ripple parameter specifies the stopband attenuation. In the stopband the gain will
  * be at most this value. A lower ripple value will allow a faster rolloff.
  *
  * As a special case, a Chebyshev type 1 filter with no ripple is a Butterworth filter.
  *
  * <note>
  * Be warned that a too large number of poles can produce noise. The most poles are possible with
  * a cutoff frequency at a quarter of the sampling rate.
  * </note>
  *
  * <refsect2>
  * <title>Example launch line</title>
  * |[
  * gst-launch audiotestsrc freq=1500 ! audioconvert ! audiochebband mode=band-pass lower-frequency=1000 upper-frequenc=6000 poles=4 ! audioconvert ! alsasink
  * gst-launch filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiochebband mode=band-reject lower-frequency=1000 upper-frequency=4000 ripple=0.2 ! audioconvert ! alsasink
  * gst-launch audiotestsrc wave=white-noise ! audioconvert ! audiochebband mode=band-pass lower-frequency=1000 upper-frequency=4000 type=2 ! audioconvert ! alsasink
  * ]|
  * </refsect2>
  */

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

 #include <string.h>

 #include <gst/gst.h>
 #include <gst/base/gstbasetransform.h>
 #include <gst/audio/audio.h>
 #include <gst/audio/gstaudiofilter.h>

 #include <math.h>

 #include "math_compat.h"

 #include "audiochebband.h"

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

 #define GST_CAT_DEFAULT gst_audio_cheb_band_debug
 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

 enum
 {
   PROP_0,
   PROP_MODE,
   PROP_TYPE,
   PROP_LOWER_FREQUENCY,
   PROP_UPPER_FREQUENCY,
   PROP_RIPPLE,
   PROP_POLES
 };

 #define gst_audio_cheb_band_parent_class parent_class
 G_DEFINE_TYPE (GstAudioChebBand, gst_audio_cheb_band,
     GST_TYPE_AUDIO_FX_BASE_IIR_FILTER);

 static void gst_audio_cheb_band_set_property (GObject * object,
     guint prop_id, const GValue * value, GParamSpec * pspec);
 static void gst_audio_cheb_band_get_property (GObject * object,
     guint prop_id, GValue * value, GParamSpec * pspec);
 static void gst_audio_cheb_band_finalize (GObject * object);

 static gboolean gst_audio_cheb_band_setup (GstAudioFilter * filter,
     const GstAudioInfo * info);

 enum
 {
   MODE_BAND_PASS = 0,
   MODE_BAND_REJECT
 };

 #define GST_TYPE_AUDIO_CHEBYSHEV_FREQ_BAND_MODE (gst_audio_cheb_band_mode_get_type ())
 static GType
 gst_audio_cheb_band_mode_get_type (void)
 {
   static GType gtype = 0;

   if (gtype == 0) {
     static const GEnumValue values[] = {
       {MODE_BAND_PASS, "Band pass (default)",
           "band-pass"},
       {MODE_BAND_REJECT, "Band reject",
           "band-reject"},
       {0, NULL, NULL}
     };

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

 /* GObject vmethod implementations */

 static void
 gst_audio_cheb_band_class_init (GstAudioChebBandClass * klass)
 {
   GObjectClass *gobject_class = (GObjectClass *) klass;
   GstElementClass *gstelement_class = (GstElementClass *) klass;
   GstAudioFilterClass *filter_class = (GstAudioFilterClass *) klass;

   GST_DEBUG_CATEGORY_INIT (gst_audio_cheb_band_debug, "audiochebband", 0,
       "audiochebband element");

   gobject_class->set_property = gst_audio_cheb_band_set_property;
   gobject_class->get_property = gst_audio_cheb_band_get_property;
   gobject_class->finalize = gst_audio_cheb_band_finalize;

   g_object_class_install_property (gobject_class, PROP_MODE,
       g_param_spec_enum ("mode", "Mode",
           "Low pass or high pass mode", GST_TYPE_AUDIO_CHEBYSHEV_FREQ_BAND_MODE,
           MODE_BAND_PASS,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));
   g_object_class_install_property (gobject_class, PROP_TYPE,
       g_param_spec_int ("type", "Type", "Type of the chebychev filter", 1, 2, 1,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));

   /* FIXME: Don't use the complete possible range but restrict the upper boundary
    * so automatically generated UIs can use a slider without */
   g_object_class_install_property (gobject_class, PROP_LOWER_FREQUENCY,
       g_param_spec_float ("lower-frequency", "Lower frequency",
           "Start frequency of the band (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_UPPER_FREQUENCY,
       g_param_spec_float ("upper-frequency", "Upper frequency",
           "Stop frequency of the band (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_RIPPLE,
       g_param_spec_float ("ripple", "Ripple", "Amount of ripple (dB)", 0.0,
           200.0, 0.25,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));
   /* FIXME: What to do about this upper boundary? With a frequencies near
    * rate/4 32 poles are completely possible, with frequencies very low
    * or very high 16 poles already produces only noise */
   g_object_class_install_property (gobject_class, PROP_POLES,
       g_param_spec_int ("poles", "Poles",
           "Number of poles to use, will be rounded up to the next multiply of four",
           4, 32, 4,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));

   gst_element_class_set_static_metadata (gstelement_class,
       "Band pass & band reject filter", "Filter/Effect/Audio",
       "Chebyshev band pass and band reject filter",
       "Sebastian Dröge <sebastian.droege@collabora.co.uk>");

   filter_class->setup = GST_DEBUG_FUNCPTR (gst_audio_cheb_band_setup);
 }

 static void
 gst_audio_cheb_band_init (GstAudioChebBand * filter)
 {
   filter->lower_frequency = filter->upper_frequency = 0.0;
   filter->mode = MODE_BAND_PASS;
   filter->type = 1;
   filter->poles = 4;
   filter->ripple = 0.25;

   g_mutex_init (&filter->lock);
 }

 static void
 generate_biquad_coefficients (GstAudioChebBand * filter,
     gint p, gint rate, gdouble * b0, gdouble * b1, gdouble * b2, gdouble * b3,
     gdouble * b4, gdouble * a1, gdouble * a2, gdouble * a3, gdouble * a4)
 {
   gint np = filter->poles / 2;
   gdouble ripple = filter->ripple;

   /* pole location in s-plane */
   gdouble rp, ip;

   /* zero location in s-plane */
   gdouble iz = 0.0;

   /* transfer function coefficients for the z-plane */
   gdouble x0, x1, x2, y1, y2;
   gint type = filter->type;

   /* Calculate pole location for lowpass at frequency 1 */
   {
     gdouble angle = (G_PI / 2.0) * (2.0 * p - 1) / np;

     rp = -sin (angle);
     ip = cos (angle);
   }

   /* If we allow ripple, move the pole from the unit
    * circle to an ellipse and keep cutoff at frequency 1 */
   if (ripple > 0 && type == 1) {
     gdouble es, vx;

     es = sqrt (pow (10.0, ripple / 10.0) - 1.0);

     vx = (1.0 / np) * asinh (1.0 / es);
     rp = rp * sinh (vx);
     ip = ip * cosh (vx);
   } else if (type == 2) {
     gdouble es, vx;

     es = sqrt (pow (10.0, ripple / 10.0) - 1.0);
     vx = (1.0 / np) * asinh (es);
     rp = rp * sinh (vx);
     ip = ip * cosh (vx);
   }

   /* Calculate inverse of the pole location to move from
    * type I to type II */
   if (type == 2) {
     gdouble mag2 = rp * rp + ip * ip;

     rp /= mag2;
     ip /= mag2;
   }

   /* Calculate zero location for frequency 1 on the
    * unit circle for type 2 */
   if (type == 2) {
     gdouble angle = G_PI / (np * 2.0) + ((p - 1) * G_PI) / (np);
     gdouble mag2;

     iz = cos (angle);
     mag2 = iz * iz;
     iz /= mag2;
   }

   /* Convert from s-domain to z-domain by
    * using the bilinear Z-transform, i.e.
    * substitute s by (2/t)*((z-1)/(z+1))
    * with t = 2 * tan(0.5).
    */
   if (type == 1) {
     gdouble t, m, d;

     t = 2.0 * tan (0.5);
     m = rp * rp + ip * ip;
     d = 4.0 - 4.0 * rp * t + m * t * t;

     x0 = (t * t) / d;
     x1 = 2.0 * x0;
     x2 = x0;
     y1 = (8.0 - 2.0 * m * t * t) / d;
     y2 = (-4.0 - 4.0 * rp * t - m * t * t) / d;
   } else {
     gdouble t, m, d;

     t = 2.0 * tan (0.5);
     m = rp * rp + ip * ip;
     d = 4.0 - 4.0 * rp * t + m * t * t;

     x0 = (t * t * iz * iz + 4.0) / d;
     x1 = (-8.0 + 2.0 * iz * iz * t * t) / d;
     x2 = x0;
     y1 = (8.0 - 2.0 * m * t * t) / d;
     y2 = (-4.0 - 4.0 * rp * t - m * t * t) / d;
   }

   /* Convert from lowpass at frequency 1 to either bandpass
    * or band reject.
    *
    * For bandpass substitute z^(-1) with:
    *
    *   -2            -1
    * -z   + alpha * z   - beta
    * ----------------------------
    *         -2            -1
    * beta * z   - alpha * z   + 1
    *
    * alpha = (2*a*b)/(1+b)
    * beta = (b-1)/(b+1)
    * a = cos((w1 + w0)/2) / cos((w1 - w0)/2)
    * b = tan(1/2) * cot((w1 - w0)/2)
    *
    * For bandreject substitute z^(-1) with:
    *
    *  -2            -1
    * z   - alpha * z   + beta
    * ----------------------------
    *         -2            -1
    * beta * z   - alpha * z   + 1
    *
    * alpha = (2*a)/(1+b)
    * beta = (1-b)/(1+b)
    * a = cos((w1 + w0)/2) / cos((w1 - w0)/2)
    * b = tan(1/2) * tan((w1 - w0)/2)
    *
    */
   {
     gdouble a, b, d;
     gdouble alpha, beta;
     gdouble w0 = 2.0 * G_PI * (filter->lower_frequency / rate);
     gdouble w1 = 2.0 * G_PI * (filter->upper_frequency / rate);

     if (filter->mode == MODE_BAND_PASS) {
       a = cos ((w1 + w0) / 2.0) / cos ((w1 - w0) / 2.0);
       b = tan (1.0 / 2.0) / tan ((w1 - w0) / 2.0);

       alpha = (2.0 * a * b) / (1.0 + b);
       beta = (b - 1.0) / (b + 1.0);

       d = 1.0 + beta * (y1 - beta * y2);

       *b0 = (x0 + beta * (-x1 + beta * x2)) / d;
       *b1 = (alpha * (-2.0 * x0 + x1 + beta * x1 - 2.0 * beta * x2)) / d;
       *b2 =
           (-x1 - beta * beta * x1 + 2.0 * beta * (x0 + x2) +
           alpha * alpha * (x0 - x1 + x2)) / d;
       *b3 = (alpha * (x1 + beta * (-2.0 * x0 + x1) - 2.0 * x2)) / d;
       *b4 = (beta * (beta * x0 - x1) + x2) / d;
       *a1 = (alpha * (2.0 + y1 + beta * y1 - 2.0 * beta * y2)) / d;
       *a2 =
           (-y1 - beta * beta * y1 - alpha * alpha * (1.0 + y1 - y2) +
           2.0 * beta * (-1.0 + y2)) / d;
       *a3 = (alpha * (y1 + beta * (2.0 + y1) - 2.0 * y2)) / d;
       *a4 = (-beta * beta - beta * y1 + y2) / d;
     } else {
       a = cos ((w1 + w0) / 2.0) / cos ((w1 - w0) / 2.0);
       b = tan (1.0 / 2.0) * tan ((w1 - w0) / 2.0);

       alpha = (2.0 * a) / (1.0 + b);
       beta = (1.0 - b) / (1.0 + b);

       d = -1.0 + beta * (beta * y2 + y1);

       *b0 = (-x0 - beta * x1 - beta * beta * x2) / d;
       *b1 = (alpha * (2.0 * x0 + x1 + beta * x1 + 2.0 * beta * x2)) / d;
       *b2 =
           (-x1 - beta * beta * x1 - 2.0 * beta * (x0 + x2) -
           alpha * alpha * (x0 + x1 + x2)) / d;
       *b3 = (alpha * (x1 + beta * (2.0 * x0 + x1) + 2.0 * x2)) / d;
       *b4 = (-beta * beta * x0 - beta * x1 - x2) / d;
       *a1 = (alpha * (-2.0 + y1 + beta * y1 + 2.0 * beta * y2)) / d;
       *a2 =
           -(y1 + beta * beta * y1 + 2.0 * beta * (-1.0 + y2) +
           alpha * alpha * (-1.0 + y1 + y2)) / d;
       *a3 = (alpha * (beta * (-2.0 + y1) + y1 + 2.0 * y2)) / d;
       *a4 = -(-beta * beta + beta * y1 + y2) / d;
     }
   }
 }

 static void
 generate_coefficients (GstAudioChebBand * filter, const GstAudioInfo * info)
 {
   gint rate;

   if (info) {
     rate = GST_AUDIO_INFO_RATE (info);
   } else {
     rate = GST_AUDIO_FILTER_RATE (filter);
   }

   if (rate == 0) {
     gdouble *a = g_new0 (gdouble, 1);
     gdouble *b = g_new0 (gdouble, 1);

     a[0] = 1.0;
     b[0] = 1.0;
     gst_audio_fx_base_iir_filter_set_coefficients (GST_AUDIO_FX_BASE_IIR_FILTER
         (filter), a, 1, b, 1);
     GST_LOG_OBJECT (filter, "rate was not set yet");
     return;
   }

   if (filter->upper_frequency <= filter->lower_frequency) {
     gdouble *a = g_new0 (gdouble, 1);
     gdouble *b = g_new0 (gdouble, 1);

     a[0] = 1.0;
     b[0] = (filter->mode == MODE_BAND_PASS) ? 0.0 : 1.0;
     gst_audio_fx_base_iir_filter_set_coefficients (GST_AUDIO_FX_BASE_IIR_FILTER
         (filter), a, 1, b, 1);

     GST_LOG_OBJECT (filter, "frequency band had no or negative dimension");
     return;
   }

   if (filter->upper_frequency > rate / 2) {
     filter->upper_frequency = rate / 2;
     GST_LOG_OBJECT (filter, "clipped upper frequency to nyquist frequency");
   }

   if (filter->lower_frequency < 0.0) {
     filter->lower_frequency = 0.0;
     GST_LOG_OBJECT (filter, "clipped lower frequency to 0.0");
   }

   /* Calculate coefficients for the chebyshev filter */
   {
     gint np = filter->poles;
     gdouble *a, *b;
     gint i, p;

     a = g_new0 (gdouble, np + 5);
     b = g_new0 (gdouble, np + 5);

     /* Calculate transfer function coefficients */
     a[4] = 1.0;
     b[4] = 1.0;

     for (p = 1; p <= np / 4; p++) {
       gdouble b0, b1, b2, b3, b4, a1, a2, a3, a4;
       gdouble *ta = g_new0 (gdouble, np + 5);
       gdouble *tb = g_new0 (gdouble, np + 5);

       generate_biquad_coefficients (filter, p, rate,
           &b0, &b1, &b2, &b3, &b4, &a1, &a2, &a3, &a4);

       memcpy (ta, a, sizeof (gdouble) * (np + 5));
       memcpy (tb, b, sizeof (gdouble) * (np + 5));

       /* add the new coefficients for the new two poles
        * to the cascade by multiplication of the transfer
        * functions */
       for (i = 4; i < np + 5; i++) {
         b[i] =
             b0 * tb[i] + b1 * tb[i - 1] + b2 * tb[i - 2] + b3 * tb[i - 3] +
             b4 * tb[i - 4];
         a[i] =
             ta[i] - a1 * ta[i - 1] - a2 * ta[i - 2] - a3 * ta[i - 3] -
             a4 * ta[i - 4];
       }
       g_free (ta);
       g_free (tb);
     }

     /* Move coefficients to the beginning of the array to move from
      * the transfer function's coefficients to the difference
      * equation's coefficients */
     for (i = 0; i <= np; i++) {
       a[i] = a[i + 4];
       b[i] = b[i + 4];
     }

     /* Normalize to unity gain at frequency 0 and frequency
      * 0.5 for bandreject and unity gain at band center frequency
      * for bandpass */
     if (filter->mode == MODE_BAND_REJECT) {
       /* gain is sqrt(H(0)*H(0.5)) */

       gdouble gain1 =
           gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b, np + 1,
           1.0, 0.0);
       gdouble gain2 =
           gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b, np + 1,
           -1.0, 0.0);

       gain1 = sqrt (gain1 * gain2);

       for (i = 0; i <= np; i++) {
         b[i] /= gain1;
       }
     } else {
       /* gain is H(wc), wc = center frequency */

       gdouble w1 = 2.0 * G_PI * (filter->lower_frequency / rate);
       gdouble w2 = 2.0 * G_PI * (filter->upper_frequency / rate);
       gdouble w0 = (w2 + w1) / 2.0;
       gdouble zr = cos (w0), zi = sin (w0);
       gdouble gain =
           gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b, np + 1, zr,
           zi);

       for (i = 0; i <= np; i++) {
         b[i] /= gain;
       }
     }

     gst_audio_fx_base_iir_filter_set_coefficients (GST_AUDIO_FX_BASE_IIR_FILTER
         (filter), a, np + 1, b, np + 1);

     GST_LOG_OBJECT (filter,
         "Generated IIR coefficients for the Chebyshev filter");
     GST_LOG_OBJECT (filter,
         "mode: %s, type: %d, poles: %d, lower-frequency: %.2f Hz, upper-frequency: %.2f Hz, ripple: %.2f dB",
         (filter->mode == MODE_BAND_PASS) ? "band-pass" : "band-reject",
         filter->type, filter->poles, filter->lower_frequency,
         filter->upper_frequency, filter->ripple);

     GST_LOG_OBJECT (filter, "%.2f dB gain @ 0Hz",
         20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b,
                 np + 1, 1.0, 0.0)));
     {
       gdouble w1 = 2.0 * G_PI * (filter->lower_frequency / rate);
       gdouble w2 = 2.0 * G_PI * (filter->upper_frequency / rate);
       gdouble w0 = (w2 + w1) / 2.0;
       gdouble zr, zi;

       zr = cos (w1);
       zi = sin (w1);
       GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
           20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1,
                   b, np + 1, zr, zi)), (int) filter->lower_frequency);
       zr = cos (w0);
       zi = sin (w0);
       GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
           20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1,
                   b, np + 1, zr, zi)),
           (int) ((filter->lower_frequency + filter->upper_frequency) / 2.0));
       zr = cos (w2);
       zi = sin (w2);
       GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
           20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1,
                   b, np + 1, zr, zi)), (int) filter->upper_frequency);
     }
     GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
         20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b,
                 np + 1, -1.0, 0.0)), rate / 2);
   }
 }

 static void
 gst_audio_cheb_band_finalize (GObject * object)
 {
   GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (object);

   g_mutex_clear (&filter->lock);

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

 static void
 gst_audio_cheb_band_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec)
 {
   GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (object);

   switch (prop_id) {
     case PROP_MODE:
       g_mutex_lock (&filter->lock);
       filter->mode = g_value_get_enum (value);
       generate_coefficients (filter, NULL);
       g_mutex_unlock (&filter->lock);
       break;
     case PROP_TYPE:
       g_mutex_lock (&filter->lock);
       filter->type = g_value_get_int (value);
       generate_coefficients (filter, NULL);
       g_mutex_unlock (&filter->lock);
       break;
     case PROP_LOWER_FREQUENCY:
       g_mutex_lock (&filter->lock);
       filter->lower_frequency = g_value_get_float (value);
       generate_coefficients (filter, NULL);
       g_mutex_unlock (&filter->lock);
       break;
     case PROP_UPPER_FREQUENCY:
       g_mutex_lock (&filter->lock);
       filter->upper_frequency = g_value_get_float (value);
       generate_coefficients (filter, NULL);
       g_mutex_unlock (&filter->lock);
       break;
     case PROP_RIPPLE:
       g_mutex_lock (&filter->lock);
       filter->ripple = g_value_get_float (value);
       generate_coefficients (filter, NULL);
       g_mutex_unlock (&filter->lock);
       break;
     case PROP_POLES:
       g_mutex_lock (&filter->lock);
       filter->poles = GST_ROUND_UP_4 (g_value_get_int (value));
       generate_coefficients (filter, NULL);
       g_mutex_unlock (&filter->lock);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 static void
 gst_audio_cheb_band_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec)
 {
   GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (object);

   switch (prop_id) {
     case PROP_MODE:
       g_value_set_enum (value, filter->mode);
       break;
     case PROP_TYPE:
       g_value_set_int (value, filter->type);
       break;
     case PROP_LOWER_FREQUENCY:
       g_value_set_float (value, filter->lower_frequency);
       break;
     case PROP_UPPER_FREQUENCY:
       g_value_set_float (value, filter->upper_frequency);
       break;
     case PROP_RIPPLE:
       g_value_set_float (value, filter->ripple);
       break;
     case PROP_POLES:
       g_value_set_int (value, filter->poles);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 /* GstAudioFilter vmethod implementations */

 static gboolean
 gst_audio_cheb_band_setup (GstAudioFilter * base, const GstAudioInfo * info)
 {
   GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (base);

   generate_coefficients (filter, info);

   return GST_AUDIO_FILTER_CLASS (parent_class)->setup (base, info);
 }
	/*
	* GStreamer
	* Copyright (C) 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., 59 Temple Place - Suite 330,
	* Boston, MA 02111-1307, USA.
	*/

	/*
	* Chebyshev type 1 filter design based on
	* "The Scientist and Engineer's Guide to DSP", Chapter 20.
	* http://www.dspguide.com/
	*
	* For type 2 and Chebyshev filters in general read
	* http://en.wikipedia.org/wiki/Chebyshev_filter
	*
	* Transformation from lowpass to bandpass/bandreject:
	* http://docs.dewresearch.com/DspHelp/html/IDH_LinearSystems_LowpassToBandPassZ.htm
	* http://docs.dewresearch.com/DspHelp/html/IDH_LinearSystems_LowpassToBandStopZ.htm
	*
	*/

	/**
	* SECTION:element-audiochebband
	*
	* Attenuates all frequencies outside (bandpass) or inside (bandreject) of a frequency
	* band. The number of poles and the ripple parameter control the rolloff.
	*
	* This element has the advantage over the windowed sinc bandpass and bandreject filter that it is
	* much faster and produces almost as good results. It's only disadvantages are the highly
	* non-linear phase and the slower rolloff compared to a windowed sinc filter with a large kernel.
	*
	* For type 1 the ripple parameter specifies how much ripple in dB is allowed in the passband, i.e.
	* some frequencies in the passband will be amplified by that value. A higher ripple value will allow
	* a faster rolloff.
	*
	* For type 2 the ripple parameter specifies the stopband attenuation. In the stopband the gain will
	* be at most this value. A lower ripple value will allow a faster rolloff.
	*
	* As a special case, a Chebyshev type 1 filter with no ripple is a Butterworth filter.
	*
	* <note>
	* Be warned that a too large number of poles can produce noise. The most poles are possible with
	* a cutoff frequency at a quarter of the sampling rate.
	* </note>
	*
	* <refsect2>
	* <title>Example launch line</title>
	* \|[
	* gst-launch audiotestsrc freq=1500 ! audioconvert ! audiochebband mode=band-pass lower-frequency=1000 upper-frequenc=6000 poles=4 ! audioconvert ! alsasink
	* gst-launch filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiochebband mode=band-reject lower-frequency=1000 upper-frequency=4000 ripple=0.2 ! audioconvert ! alsasink
	* gst-launch audiotestsrc wave=white-noise ! audioconvert ! audiochebband mode=band-pass lower-frequency=1000 upper-frequency=4000 type=2 ! audioconvert ! alsasink
	* ]\|
	* </refsect2>
	*/

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

	#include <string.h>

	#include <gst/gst.h>
	#include <gst/base/gstbasetransform.h>
	#include <gst/audio/audio.h>
	#include <gst/audio/gstaudiofilter.h>

	#include <math.h>

	#include "math_compat.h"

	#include "audiochebband.h"

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

	#define GST_CAT_DEFAULT gst_audio_cheb_band_debug
	GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

	enum
	{
	PROP_0,
	PROP_MODE,
	PROP_TYPE,
	PROP_LOWER_FREQUENCY,
	PROP_UPPER_FREQUENCY,
	PROP_RIPPLE,
	PROP_POLES
	};

	#define gst_audio_cheb_band_parent_class parent_class
	G_DEFINE_TYPE (GstAudioChebBand, gst_audio_cheb_band,
	GST_TYPE_AUDIO_FX_BASE_IIR_FILTER);

	static void gst_audio_cheb_band_set_property (GObject * object,
	guint prop_id, const GValue * value, GParamSpec * pspec);
	static void gst_audio_cheb_band_get_property (GObject * object,
	guint prop_id, GValue * value, GParamSpec * pspec);
	static void gst_audio_cheb_band_finalize (GObject * object);

	static gboolean gst_audio_cheb_band_setup (GstAudioFilter * filter,
	const GstAudioInfo * info);

	enum
	{
	MODE_BAND_PASS = 0,
	MODE_BAND_REJECT
	};

	#define GST_TYPE_AUDIO_CHEBYSHEV_FREQ_BAND_MODE (gst_audio_cheb_band_mode_get_type ())
	static GType
	gst_audio_cheb_band_mode_get_type (void)
	{
	static GType gtype = 0;

	if (gtype == 0) {
	static const GEnumValue values[] = {
	{MODE_BAND_PASS, "Band pass (default)",
	"band-pass"},
	{MODE_BAND_REJECT, "Band reject",
	"band-reject"},
	{0, NULL, NULL}
	};

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

	/* GObject vmethod implementations */

	static void
	gst_audio_cheb_band_class_init (GstAudioChebBandClass * klass)
	{
	GObjectClass gobject_class = (GObjectClass ) klass;
	GstElementClass gstelement_class = (GstElementClass ) klass;
	GstAudioFilterClass filter_class = (GstAudioFilterClass ) klass;

	GST_DEBUG_CATEGORY_INIT (gst_audio_cheb_band_debug, "audiochebband", 0,
	"audiochebband element");

	gobject_class->set_property = gst_audio_cheb_band_set_property;
	gobject_class->get_property = gst_audio_cheb_band_get_property;
	gobject_class->finalize = gst_audio_cheb_band_finalize;

	g_object_class_install_property (gobject_class, PROP_MODE,
	g_param_spec_enum ("mode", "Mode",
	"Low pass or high pass mode", GST_TYPE_AUDIO_CHEBYSHEV_FREQ_BAND_MODE,
	MODE_BAND_PASS,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));
	g_object_class_install_property (gobject_class, PROP_TYPE,
	g_param_spec_int ("type", "Type", "Type of the chebychev filter", 1, 2, 1,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));

	/* FIXME: Don't use the complete possible range but restrict the upper boundary
	* so automatically generated UIs can use a slider without */
	g_object_class_install_property (gobject_class, PROP_LOWER_FREQUENCY,
	g_param_spec_float ("lower-frequency", "Lower frequency",
	"Start frequency of the band (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_UPPER_FREQUENCY,
	g_param_spec_float ("upper-frequency", "Upper frequency",
	"Stop frequency of the band (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_RIPPLE,
	g_param_spec_float ("ripple", "Ripple", "Amount of ripple (dB)", 0.0,
	200.0, 0.25,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));
	/* FIXME: What to do about this upper boundary? With a frequencies near
	* rate/4 32 poles are completely possible, with frequencies very low
	* or very high 16 poles already produces only noise */
	g_object_class_install_property (gobject_class, PROP_POLES,
	g_param_spec_int ("poles", "Poles",
	"Number of poles to use, will be rounded up to the next multiply of four",
	4, 32, 4,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));

	gst_element_class_set_static_metadata (gstelement_class,
	"Band pass & band reject filter", "Filter/Effect/Audio",
	"Chebyshev band pass and band reject filter",
	"Sebastian Dröge <sebastian.droege@collabora.co.uk>");

	filter_class->setup = GST_DEBUG_FUNCPTR (gst_audio_cheb_band_setup);
	}

	static void
	gst_audio_cheb_band_init (GstAudioChebBand * filter)
	{
	filter->lower_frequency = filter->upper_frequency = 0.0;
	filter->mode = MODE_BAND_PASS;
	filter->type = 1;
	filter->poles = 4;
	filter->ripple = 0.25;

	g_mutex_init (&filter->lock);
	}

	static void
	generate_biquad_coefficients (GstAudioChebBand * filter,
	gint p, gint rate, gdouble * b0, gdouble * b1, gdouble * b2, gdouble * b3,
	gdouble * b4, gdouble * a1, gdouble * a2, gdouble * a3, gdouble * a4)
	{
	gint np = filter->poles / 2;
	gdouble ripple = filter->ripple;

	/* pole location in s-plane */
	gdouble rp, ip;

	/* zero location in s-plane */
	gdouble iz = 0.0;

	/* transfer function coefficients for the z-plane */
	gdouble x0, x1, x2, y1, y2;
	gint type = filter->type;

	/* Calculate pole location for lowpass at frequency 1 */
	{
	gdouble angle = (G_PI / 2.0) * (2.0 * p - 1) / np;

	rp = -sin (angle);
	ip = cos (angle);
	}

	/* If we allow ripple, move the pole from the unit
	* circle to an ellipse and keep cutoff at frequency 1 */
	if (ripple > 0 && type == 1) {
	gdouble es, vx;

	es = sqrt (pow (10.0, ripple / 10.0) - 1.0);

	vx = (1.0 / np) * asinh (1.0 / es);
	rp = rp * sinh (vx);
	ip = ip * cosh (vx);
	} else if (type == 2) {
	gdouble es, vx;

	es = sqrt (pow (10.0, ripple / 10.0) - 1.0);
	vx = (1.0 / np) * asinh (es);
	rp = rp * sinh (vx);
	ip = ip * cosh (vx);
	}

	/* Calculate inverse of the pole location to move from
	* type I to type II */
	if (type == 2) {
	gdouble mag2 = rp * rp + ip * ip;

	rp /= mag2;
	ip /= mag2;
	}

	/* Calculate zero location for frequency 1 on the
	* unit circle for type 2 */
	if (type == 2) {
	gdouble angle = G_PI / (np * 2.0) + ((p - 1) * G_PI) / (np);
	gdouble mag2;

	iz = cos (angle);
	mag2 = iz * iz;
	iz /= mag2;
	}

	/* Convert from s-domain to z-domain by
	* using the bilinear Z-transform, i.e.
	* substitute s by (2/t)*((z-1)/(z+1))
	* with t = 2 * tan(0.5).
	*/
	if (type == 1) {
	gdouble t, m, d;

	t = 2.0 * tan (0.5);
	m = rp * rp + ip * ip;
	d = 4.0 - 4.0 * rp * t + m * t * t;

	x0 = (t * t) / d;
	x1 = 2.0 * x0;
	x2 = x0;
	y1 = (8.0 - 2.0 * m * t * t) / d;
	y2 = (-4.0 - 4.0 * rp * t - m * t * t) / d;
	} else {
	gdouble t, m, d;

	t = 2.0 * tan (0.5);
	m = rp * rp + ip * ip;
	d = 4.0 - 4.0 * rp * t + m * t * t;

	x0 = (t * t * iz * iz + 4.0) / d;
	x1 = (-8.0 + 2.0 * iz * iz * t * t) / d;
	x2 = x0;
	y1 = (8.0 - 2.0 * m * t * t) / d;
	y2 = (-4.0 - 4.0 * rp * t - m * t * t) / d;
	}

	/* Convert from lowpass at frequency 1 to either bandpass
	* or band reject.
	*
	* For bandpass substitute z^(-1) with:
	*
	* -2 -1
	* -z + alpha * z - beta
	* ----------------------------
	* -2 -1
	* beta * z - alpha * z + 1
	*
	* alpha = (2ab)/(1+b)
	* beta = (b-1)/(b+1)
	* a = cos((w1 + w0)/2) / cos((w1 - w0)/2)
	* b = tan(1/2) * cot((w1 - w0)/2)
	*
	* For bandreject substitute z^(-1) with:
	*
	* -2 -1
	* z - alpha * z + beta
	* ----------------------------
	* -2 -1
	* beta * z - alpha * z + 1
	*
	* alpha = (2*a)/(1+b)
	* beta = (1-b)/(1+b)
	* a = cos((w1 + w0)/2) / cos((w1 - w0)/2)
	* b = tan(1/2) * tan((w1 - w0)/2)
	*
	*/
	{
	gdouble a, b, d;
	gdouble alpha, beta;
	gdouble w0 = 2.0 * G_PI * (filter->lower_frequency / rate);
	gdouble w1 = 2.0 * G_PI * (filter->upper_frequency / rate);

	if (filter->mode == MODE_BAND_PASS) {
	a = cos ((w1 + w0) / 2.0) / cos ((w1 - w0) / 2.0);
	b = tan (1.0 / 2.0) / tan ((w1 - w0) / 2.0);

	alpha = (2.0 * a * b) / (1.0 + b);
	beta = (b - 1.0) / (b + 1.0);

	d = 1.0 + beta * (y1 - beta * y2);

	b0 = (x0 + beta (-x1 + beta * x2)) / d;
	b1 = (alpha (-2.0 * x0 + x1 + beta * x1 - 2.0 * beta * x2)) / d;
	*b2 =
	(-x1 - beta * beta * x1 + 2.0 * beta * (x0 + x2) +
	alpha * alpha * (x0 - x1 + x2)) / d;
	b3 = (alpha (x1 + beta * (-2.0 * x0 + x1) - 2.0 * x2)) / d;
	b4 = (beta (beta * x0 - x1) + x2) / d;
	a1 = (alpha (2.0 + y1 + beta * y1 - 2.0 * beta * y2)) / d;
	*a2 =
	(-y1 - beta * beta * y1 - alpha * alpha * (1.0 + y1 - y2) +
	2.0 * beta * (-1.0 + y2)) / d;
	a3 = (alpha (y1 + beta * (2.0 + y1) - 2.0 * y2)) / d;
	a4 = (-beta beta - beta * y1 + y2) / d;
	} else {
	a = cos ((w1 + w0) / 2.0) / cos ((w1 - w0) / 2.0);
	b = tan (1.0 / 2.0) * tan ((w1 - w0) / 2.0);

	alpha = (2.0 * a) / (1.0 + b);
	beta = (1.0 - b) / (1.0 + b);

	d = -1.0 + beta * (beta * y2 + y1);

	b0 = (-x0 - beta x1 - beta * beta * x2) / d;
	b1 = (alpha (2.0 * x0 + x1 + beta * x1 + 2.0 * beta * x2)) / d;
	*b2 =
	(-x1 - beta * beta * x1 - 2.0 * beta * (x0 + x2) -
	alpha * alpha * (x0 + x1 + x2)) / d;
	b3 = (alpha (x1 + beta * (2.0 * x0 + x1) + 2.0 * x2)) / d;
	b4 = (-beta beta * x0 - beta * x1 - x2) / d;
	a1 = (alpha (-2.0 + y1 + beta * y1 + 2.0 * beta * y2)) / d;
	*a2 =
	-(y1 + beta * beta * y1 + 2.0 * beta * (-1.0 + y2) +
	alpha * alpha * (-1.0 + y1 + y2)) / d;
	a3 = (alpha (beta * (-2.0 + y1) + y1 + 2.0 * y2)) / d;
	a4 = -(-beta beta + beta * y1 + y2) / d;
	}
	}
	}

	static void
	generate_coefficients (GstAudioChebBand * filter, const GstAudioInfo * info)
	{
	gint rate;

	if (info) {
	rate = GST_AUDIO_INFO_RATE (info);
	} else {
	rate = GST_AUDIO_FILTER_RATE (filter);
	}

	if (rate == 0) {
	gdouble *a = g_new0 (gdouble, 1);
	gdouble *b = g_new0 (gdouble, 1);

	a[0] = 1.0;
	b[0] = 1.0;
	gst_audio_fx_base_iir_filter_set_coefficients (GST_AUDIO_FX_BASE_IIR_FILTER
	(filter), a, 1, b, 1);
	GST_LOG_OBJECT (filter, "rate was not set yet");
	return;
	}

	if (filter->upper_frequency <= filter->lower_frequency) {
	gdouble *a = g_new0 (gdouble, 1);
	gdouble *b = g_new0 (gdouble, 1);

	a[0] = 1.0;
	b[0] = (filter->mode == MODE_BAND_PASS) ? 0.0 : 1.0;
	gst_audio_fx_base_iir_filter_set_coefficients (GST_AUDIO_FX_BASE_IIR_FILTER
	(filter), a, 1, b, 1);

	GST_LOG_OBJECT (filter, "frequency band had no or negative dimension");
	return;
	}

	if (filter->upper_frequency > rate / 2) {
	filter->upper_frequency = rate / 2;
	GST_LOG_OBJECT (filter, "clipped upper frequency to nyquist frequency");
	}

	if (filter->lower_frequency < 0.0) {
	filter->lower_frequency = 0.0;
	GST_LOG_OBJECT (filter, "clipped lower frequency to 0.0");
	}

	/* Calculate coefficients for the chebyshev filter */
	{
	gint np = filter->poles;
	gdouble a, b;
	gint i, p;

	a = g_new0 (gdouble, np + 5);
	b = g_new0 (gdouble, np + 5);

	/* Calculate transfer function coefficients */
	a[4] = 1.0;
	b[4] = 1.0;

	for (p = 1; p <= np / 4; p++) {
	gdouble b0, b1, b2, b3, b4, a1, a2, a3, a4;
	gdouble *ta = g_new0 (gdouble, np + 5);
	gdouble *tb = g_new0 (gdouble, np + 5);

	generate_biquad_coefficients (filter, p, rate,
	&b0, &b1, &b2, &b3, &b4, &a1, &a2, &a3, &a4);

	memcpy (ta, a, sizeof (gdouble) * (np + 5));
	memcpy (tb, b, sizeof (gdouble) * (np + 5));

	/* add the new coefficients for the new two poles
	* to the cascade by multiplication of the transfer
	* functions */
	for (i = 4; i < np + 5; i++) {
	b[i] =
	b0 * tb[i] + b1 * tb[i - 1] + b2 * tb[i - 2] + b3 * tb[i - 3] +
	b4 * tb[i - 4];
	a[i] =
	ta[i] - a1 * ta[i - 1] - a2 * ta[i - 2] - a3 * ta[i - 3] -
	a4 * ta[i - 4];
	}
	g_free (ta);
	g_free (tb);
	}

	/* Move coefficients to the beginning of the array to move from
	* the transfer function's coefficients to the difference
	* equation's coefficients */
	for (i = 0; i <= np; i++) {
	a[i] = a[i + 4];
	b[i] = b[i + 4];
	}

	/* Normalize to unity gain at frequency 0 and frequency
	* 0.5 for bandreject and unity gain at band center frequency
	* for bandpass */
	if (filter->mode == MODE_BAND_REJECT) {
	/* gain is sqrt(H(0)H(0.5)) /

	gdouble gain1 =
	gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b, np + 1,
	1.0, 0.0);
	gdouble gain2 =
	gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b, np + 1,
	-1.0, 0.0);

	gain1 = sqrt (gain1 * gain2);

	for (i = 0; i <= np; i++) {
	b[i] /= gain1;
	}
	} else {
	/* gain is H(wc), wc = center frequency */

	gdouble w1 = 2.0 * G_PI * (filter->lower_frequency / rate);
	gdouble w2 = 2.0 * G_PI * (filter->upper_frequency / rate);
	gdouble w0 = (w2 + w1) / 2.0;
	gdouble zr = cos (w0), zi = sin (w0);
	gdouble gain =
	gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b, np + 1, zr,
	zi);

	for (i = 0; i <= np; i++) {
	b[i] /= gain;
	}
	}

	gst_audio_fx_base_iir_filter_set_coefficients (GST_AUDIO_FX_BASE_IIR_FILTER
	(filter), a, np + 1, b, np + 1);

	GST_LOG_OBJECT (filter,
	"Generated IIR coefficients for the Chebyshev filter");
	GST_LOG_OBJECT (filter,
	"mode: %s, type: %d, poles: %d, lower-frequency: %.2f Hz, upper-frequency: %.2f Hz, ripple: %.2f dB",
	(filter->mode == MODE_BAND_PASS) ? "band-pass" : "band-reject",
	filter->type, filter->poles, filter->lower_frequency,
	filter->upper_frequency, filter->ripple);

	GST_LOG_OBJECT (filter, "%.2f dB gain @ 0Hz",
	20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b,
	np + 1, 1.0, 0.0)));
	{
	gdouble w1 = 2.0 * G_PI * (filter->lower_frequency / rate);
	gdouble w2 = 2.0 * G_PI * (filter->upper_frequency / rate);
	gdouble w0 = (w2 + w1) / 2.0;
	gdouble zr, zi;

	zr = cos (w1);
	zi = sin (w1);
	GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
	20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1,
	b, np + 1, zr, zi)), (int) filter->lower_frequency);
	zr = cos (w0);
	zi = sin (w0);
	GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
	20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1,
	b, np + 1, zr, zi)),
	(int) ((filter->lower_frequency + filter->upper_frequency) / 2.0));
	zr = cos (w2);
	zi = sin (w2);
	GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
	20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1,
	b, np + 1, zr, zi)), (int) filter->upper_frequency);
	}
	GST_LOG_OBJECT (filter, "%.2f dB gain @ %dHz",
	20.0 * log10 (gst_audio_fx_base_iir_filter_calculate_gain (a, np + 1, b,
	np + 1, -1.0, 0.0)), rate / 2);
	}
	}

	static void
	gst_audio_cheb_band_finalize (GObject * object)
	{
	GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (object);

	g_mutex_clear (&filter->lock);

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

	static void
	gst_audio_cheb_band_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec)
	{
	GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (object);

	switch (prop_id) {
	case PROP_MODE:
	g_mutex_lock (&filter->lock);
	filter->mode = g_value_get_enum (value);
	generate_coefficients (filter, NULL);
	g_mutex_unlock (&filter->lock);
	break;
	case PROP_TYPE:
	g_mutex_lock (&filter->lock);
	filter->type = g_value_get_int (value);
	generate_coefficients (filter, NULL);
	g_mutex_unlock (&filter->lock);
	break;
	case PROP_LOWER_FREQUENCY:
	g_mutex_lock (&filter->lock);
	filter->lower_frequency = g_value_get_float (value);
	generate_coefficients (filter, NULL);
	g_mutex_unlock (&filter->lock);
	break;
	case PROP_UPPER_FREQUENCY:
	g_mutex_lock (&filter->lock);
	filter->upper_frequency = g_value_get_float (value);
	generate_coefficients (filter, NULL);
	g_mutex_unlock (&filter->lock);
	break;
	case PROP_RIPPLE:
	g_mutex_lock (&filter->lock);
	filter->ripple = g_value_get_float (value);
	generate_coefficients (filter, NULL);
	g_mutex_unlock (&filter->lock);
	break;
	case PROP_POLES:
	g_mutex_lock (&filter->lock);
	filter->poles = GST_ROUND_UP_4 (g_value_get_int (value));
	generate_coefficients (filter, NULL);
	g_mutex_unlock (&filter->lock);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	static void
	gst_audio_cheb_band_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec)
	{
	GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (object);

	switch (prop_id) {
	case PROP_MODE:
	g_value_set_enum (value, filter->mode);
	break;
	case PROP_TYPE:
	g_value_set_int (value, filter->type);
	break;
	case PROP_LOWER_FREQUENCY:
	g_value_set_float (value, filter->lower_frequency);
	break;
	case PROP_UPPER_FREQUENCY:
	g_value_set_float (value, filter->upper_frequency);
	break;
	case PROP_RIPPLE:
	g_value_set_float (value, filter->ripple);
	break;
	case PROP_POLES:
	g_value_set_int (value, filter->poles);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	/* GstAudioFilter vmethod implementations */

	static gboolean
	gst_audio_cheb_band_setup (GstAudioFilter * base, const GstAudioInfo * info)
	{
	GstAudioChebBand *filter = GST_AUDIO_CHEB_BAND (base);

	generate_coefficients (filter, info);

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