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gst/equalizer/gstiirequalizer.c: Replace filters with a bit better filters for which we can actually find documentati...
Original commit message from CVS: * gst/equalizer/gstiirequalizer.c: (gst_iir_equalizer_band_set_property), (gst_iir_equalizer_band_get_property), (gst_iir_equalizer_band_class_init), (arg_to_scale), (setup_filter), (gst_iir_equalizer_compute_frequencies): Replace filters with a bit better filters for which we can actually find documentation, which don't change anything on zero gain, etc. Make the frequency property of the bands writable, rename the band-width property to bandwidth and change the meaning to the frequency difference between bandedges, change the meaning of the gain property to dB instead of a weird scale between -1 and 1 that has no real meaning.
This commit is contained in:
Sebastian Dröge
parent
b3f1b71446
commit
7c8653f596
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@ -83,7 +83,7 @@ enum
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{
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ARG_GAIN = 1,
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ARG_FREQ,
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ARG_BAND_WIDTH
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ARG_BANDWIDTH
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};
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typedef struct _GstIirEqualizerBandClass GstIirEqualizerBandClass;
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@ -110,9 +110,8 @@ struct _GstIirEqualizerBand
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gdouble width;
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/* second order iir filter */
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gdouble alpha; /* IIR coefficients for outputs */
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gdouble beta; /* IIR coefficients for inputs */
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gdouble gamma; /* IIR coefficients for inputs */
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gdouble b1, b2; /* IIR coefficients for outputs */
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gdouble a0, a1, a2; /* IIR coefficients for inputs */
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};
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struct _GstIirEqualizerBandClass
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@ -148,7 +147,25 @@ gst_iir_equalizer_band_set_property (GObject * object, guint prop_id,
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}
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break;
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}
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case ARG_BAND_WIDTH:{
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case ARG_FREQ:{
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gdouble freq;
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freq = g_value_get_double (value);
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GST_DEBUG_OBJECT (band, "freq = %lf -> %lf", band->freq, freq);
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if (freq != band->freq) {
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GstIirEqualizer *equ =
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GST_IIR_EQUALIZER (gst_object_get_parent (GST_OBJECT (band)));
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band->freq = freq;
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if (GST_AUDIO_FILTER (equ)->format.rate) {
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setup_filter (equ, band);
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}
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gst_object_unref (equ);
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GST_DEBUG_OBJECT (band, "changed freq = %lf ", band->freq);
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}
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break;
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}
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case ARG_BANDWIDTH:{
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gdouble width;
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width = g_value_get_double (value);
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@ -185,7 +202,7 @@ gst_iir_equalizer_band_get_property (GObject * object, guint prop_id,
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case ARG_FREQ:
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g_value_set_double (value, band->freq);
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break;
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case ARG_BAND_WIDTH:
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case ARG_BANDWIDTH:
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g_value_set_double (value, band->width);
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break;
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default:
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@ -204,18 +221,18 @@ gst_iir_equalizer_band_class_init (GstIirEqualizerBandClass * klass)
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g_object_class_install_property (gobject_class, ARG_GAIN,
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g_param_spec_double ("gain", "gain",
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"gain for the frequency band ranging from -1.0 to +1.0",
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-1.0, 1.0, 0.0, G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE));
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"gain for the frequency band ranging from -24.0 dB to +12.0 dB",
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-24.0, 12.0, 0.0, G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE));
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g_object_class_install_property (gobject_class, ARG_FREQ,
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g_param_spec_double ("freq", "freq",
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"center frequency of the band",
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0.0, 100000.0, 0.0, G_PARAM_READABLE));
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0.0, 100000.0, 0.0, G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE));
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g_object_class_install_property (gobject_class, ARG_BAND_WIDTH,
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g_param_spec_double ("band-width", "band-width",
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"band width calculated as distance between bands * this value", 0.1,
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10.0, 1.0, G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE));
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g_object_class_install_property (gobject_class, ARG_BANDWIDTH,
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g_param_spec_double ("bandwidth", "bandwidth",
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"difference between bandedges in Hz",
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1.0, 100000.0, 1.0, G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE));
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}
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static void
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@ -330,53 +347,57 @@ gst_iir_equalizer_finalize (GObject * object)
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G_OBJECT_CLASS (parent_class)->finalize (object);
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}
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/*
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* converts gain values to scale factors.
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*
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* we map -1 ... 1 to a db range.
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* A suitable range would be -12db ... 0 ... + 6db which expressed as
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* a factor is about 0.06 ... 1 ... 4.0
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*
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* We need to subtract one so that gain is centered around zero
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*
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* visualize via gnuplot:
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* set xrange [-1:1]
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* plot 10.0 ** (12*x/10.0)
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*/
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static gdouble
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static inline gdouble
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arg_to_scale (gdouble arg)
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{
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return (pow (10.0, (6.0 * fabs (arg)) / 10.0) - 1.0);
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return (pow (10.0, arg / 20.0));
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}
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/* Filter taken from
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*
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* The Equivalence of Various Methods of Computing
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* Biquad Coefficients for Audio Parametric Equalizers
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*
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* by Robert Bristow-Johnson
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*
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* http://www.aes.org/e-lib/browse.cfm?elib=6326
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* http://www.musicdsp.org/files/EQ-Coefficients.pdf
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*
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* The bandwidth method that we use here is the preferred
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* one from this article transformed from octaves to frequency
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* in Hz.
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*/
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static void
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setup_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band)
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{
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g_return_if_fail (GST_AUDIO_FILTER (equ)->format.rate);
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/* FIXME: we need better filters
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* - the band-width control is not good
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* - we need shelf-filter for 1st and last band
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*/
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{
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gdouble gain = arg_to_scale (band->gain);
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gdouble frequency = band->freq / GST_AUDIO_FILTER (equ)->format.rate;
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gdouble q = pow (HIGHEST_FREQ / LOWEST_FREQ,
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1.0 / (equ->freq_band_count - 1)) * band->width;
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gdouble omega = 2.0 * M_PI * frequency;
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gdouble bw =
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2.0 * M_PI * (band->width / GST_AUDIO_FILTER (equ)->format.rate);
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gdouble theta = frequency * 2 * M_PI;
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gdouble edge_gain = sqrt (gain);
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gdouble gamma = tan (bw / 2.0);
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band->beta = (q - theta / 2) / (2 * q + theta);
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band->gamma = (0.5 + band->beta) * cos (theta);
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band->alpha = (0.5 - band->beta) / 2;
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gdouble alpha = gamma * edge_gain;
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gdouble beta = gamma / edge_gain;
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band->beta *= 2.0;
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band->alpha *= 2.0 * gain;
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band->gamma *= 2.0;
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band->a0 = (1.0 + alpha) / (1.0 + beta);
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band->a1 = (-2.0 * cos (omega)) / (1.0 + beta);
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band->a2 = (1.0 - alpha) / (1.0 + beta);
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band->b1 = (2.0 * cos (omega)) / (1.0 + beta);
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band->b2 = -(1.0 - beta) / (1.0 + beta);
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GST_INFO
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("gain = %7.5g, frequency = %7.5g, alpha = %7.5g, beta = %7.5g, gamma=%7.5g",
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gain, frequency, band->alpha, band->beta, band->gamma);
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("gain = %7.5g, , bandwidth= %7.5g, frequency = %7.5g, a0 = %7.5g, a1 = %7.5g, a2=%7.5g b1 = %7.5g, b2 = %7.5g",
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gain, band->width, frequency, band->a0, band->a1, band->a2, band->b1,
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band->b2);
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}
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}
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@ -425,11 +446,13 @@ gst_iir_equalizer_compute_frequencies (GstIirEqualizer * equ, guint new_count)
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* FIXME: arg! we can't change the name of parented objects :(
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* application should read band->freq to get the name
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*/
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step = pow (HIGHEST_FREQ / LOWEST_FREQ, 1.0 / new_count);
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freq0 = LOWEST_FREQ;
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for (i = 0; i < new_count; i++) {
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freq1 = freq0 * step;
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equ->bands[i]->freq = freq0 + ((freq1 - freq0) / 2.0);
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equ->bands[i]->width = freq1 - freq0;
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GST_DEBUG ("band[%2d] = '%lf'", i, equ->bands[i]->freq);
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/*
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if(equ->bands[i]->freq<10000.0)
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@ -442,6 +465,7 @@ gst_iir_equalizer_compute_frequencies (GstIirEqualizer * equ, guint new_count)
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freq0 = freq1;
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}
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if (GST_AUDIO_FILTER (equ)->format.rate) {
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for (i = 0; i < new_count; i++) {
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setup_filter (equ, equ->bands[i]);
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@ -462,16 +486,16 @@ one_step_ ## TYPE (GstIirEqualizerBand *filter, \
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SecondOrderHistory ## TYPE *history, TYPE input) \
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{ \
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/* calculate output */ \
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TYPE output = filter->alpha * (input - history->x2) + \
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filter->gamma * history->y1 - filter->beta * history->y2; \
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TYPE output = filter->a0 * input + filter->a1 * history->x1 + \
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filter->a2 * history->x2 + filter->b1 * history->y1 + \
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filter->b2 * history->y2; \
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/* update history */ \
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history->y2 = history->y1; \
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history->y1 = output; \
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history->x2 = history->x1; \
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history->x1 = input; \
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\
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/* for negative gains we subtract */ \
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return (filter->gain>0.0) ? output : -output; \
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return output; \
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} \
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\
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static const guint \
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@ -484,17 +508,15 @@ guint size, guint channels) \
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guint frames = size / channels / sizeof (TYPE); \
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guint i, c, f; \
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BIG_TYPE cur; \
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TYPE val; \
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\
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for (i = 0; i < frames; i++) { \
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for (c = 0; c < channels; c++) { \
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SecondOrderHistory ## TYPE *history = equ->history; \
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val = *((TYPE *) data); \
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cur = 0.25 * val; /* FIXME: should be without factor*/ \
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cur = *((TYPE *) data); \
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for (f = 0; f < equ->freq_band_count; f++) { \
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GstIirEqualizerBand *filter = equ->bands[f]; \
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\
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cur += one_step_ ## TYPE (filter, history, val); \
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cur = one_step_ ## TYPE (filter, history, cur); \
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history++; \
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} \
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cur = CLAMP (cur, MIN_VAL, MAX_VAL); \
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