diff options
| -rw-r--r-- | gst/equalizer/gstiirequalizer.c | 200 |
1 files changed, 145 insertions, 55 deletions
diff --git a/gst/equalizer/gstiirequalizer.c b/gst/equalizer/gstiirequalizer.c index b671b247..0e481c68 100644 --- a/gst/equalizer/gstiirequalizer.c +++ b/gst/equalizer/gstiirequalizer.c @@ -121,10 +121,6 @@ struct _GstIirEqualizerBandClass static GType gst_iir_equalizer_band_get_type (void); -static void setup_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band); - -static void set_passthrough (GstIirEqualizer * equ); - static void gst_iir_equalizer_band_set_property (GObject * object, guint prop_id, const GValue * value, GParamSpec * pspec) @@ -357,12 +353,6 @@ gst_iir_equalizer_finalize (GObject * object) G_OBJECT_CLASS (parent_class)->finalize (object); } -static inline gdouble -arg_to_scale (gdouble arg) -{ - return (pow (10.0, arg / 20.0)); -} - /* Filter taken from * * The Equivalence of Various Methods of Computing @@ -372,66 +362,163 @@ arg_to_scale (gdouble arg) * * http://www.aes.org/e-lib/browse.cfm?elib=6326 * http://www.musicdsp.org/files/EQ-Coefficients.pdf + * http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt * * The bandwidth method that we use here is the preferred * one from this article transformed from octaves to frequency * in Hz. */ +static inline gdouble +arg_to_scale (gdouble arg) +{ + return (pow (10.0, arg / 40.0)); +} + +static gdouble +calculate_omega (gdouble freq, gint rate) +{ + gdouble omega; + + if (freq / rate >= 0.5) + omega = M_PI; + else if (freq <= 0.0) + omega = 0.0; + else + omega = 2.0 * M_PI * (freq / rate); + + return omega; +} + +static gdouble +calculate_bw (GstIirEqualizerBand * band, gint rate) +{ + gdouble bw = 0.0; + + if (band->width / rate >= 0.5) { + /* If bandwidth == 0.5 the calculation below fails as tan(M_PI/2) + * is undefined. So set the bandwidth to a slightly smaller value. + */ + bw = M_PI - 0.00000001; + } else if (band->width <= 0.0) { + /* If bandwidth == 0 this band won't change anything so set + * the coefficients accordingly. The coefficient calculation + * below would create coefficients that for some reason amplify + * the band. + */ + band->a0 = 1.0; + band->a1 = 0.0; + band->a2 = 0.0; + band->b1 = 0.0; + band->b2 = 0.0; + } else { + bw = 2.0 * M_PI * (band->width / rate); + } + return bw; +} + static void -setup_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band) +setup_peak_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band) +{ + g_return_if_fail (GST_AUDIO_FILTER (equ)->format.rate); + + { + gdouble gain, omega, bw; + gdouble alpha, alpha1, alpha2, b0; + + gain = arg_to_scale (band->gain); + omega = calculate_omega (band->freq, GST_AUDIO_FILTER (equ)->format.rate); + bw = calculate_bw (band, GST_AUDIO_FILTER (equ)->format.rate); + if (bw == 0.0) + goto out; + + alpha = tan (bw / 2.0); + + alpha1 = alpha * gain; + alpha2 = alpha / gain; + + b0 = (1.0 + alpha2); + + band->a0 = (1.0 + alpha1) / b0; + band->a1 = (-2.0 * cos (omega)) / b0; + band->a2 = (1.0 - alpha1) / b0; + band->b1 = (2.0 * cos (omega)) / b0; + band->b2 = -(1.0 - alpha2) / b0; + + out: + GST_INFO + ("gain = %5.1f, width= %7.2f, freq = %7.2f, a0 = %7.5g, a1 = %7.5g, a2=%7.5g b1 = %7.5g, b2 = %7.5g", + band->gain, band->width, band->freq, band->a0, band->a1, band->a2, + band->b1, band->b2); + } +} + +static void +setup_low_shelf_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band) { g_return_if_fail (GST_AUDIO_FILTER (equ)->format.rate); - /* FIXME: we need better filters - * - we need shelf-filter for 1st and last band - */ { gdouble gain, omega, bw; - gdouble edge_gain, gamma; - gdouble alpha, beta; + gdouble alpha, delta, b0; + gdouble egp, egm; gain = arg_to_scale (band->gain); + omega = calculate_omega (band->freq, GST_AUDIO_FILTER (equ)->format.rate); + bw = calculate_bw (band, GST_AUDIO_FILTER (equ)->format.rate); + if (bw == 0.0) + goto out; + + egm = gain - 1.0; + egp = gain + 1.0; + alpha = tan (bw / 2.0); + + delta = 2.0 * sqrt (gain) * alpha; + b0 = egp + egm * cos (omega) + delta; + + band->a0 = ((egp - egm * cos (omega) + delta) * gain) / b0; + band->a1 = ((egm - egp * cos (omega)) * 2.0 * gain) / b0; + band->a2 = ((egp - egm * cos (omega) - delta) * gain) / b0; + band->b1 = ((egm + egp * cos (omega)) * 2.0) / b0; + band->b2 = -((egp + egm * cos (omega) - delta)) / b0; - if (band->freq / GST_AUDIO_FILTER (equ)->format.rate >= 0.5) - omega = M_PI; - else if (band->freq <= 0.0) - omega = 0.0; - else - omega = 2.0 * M_PI * (band->freq / GST_AUDIO_FILTER (equ)->format.rate); - - if (band->width / GST_AUDIO_FILTER (equ)->format.rate >= 0.5) { - /* If bandwidth == 0.5 the calculation below fails as tan(M_PI/2) - * is undefined. So set the bandwidth to a slightly smaller value. - */ - bw = M_PI - 0.00000001; - } else if (band->width <= 0.0) { - /* If bandwidth == 0 this band won't change anything so set - * the coefficients accordingly. The coefficient calculation - * below would create coefficients that for some reason amplify - * the band. - */ - band->a0 = 1.0; - band->a1 = 0.0; - band->a2 = 0.0; - band->b1 = 0.0; - band->b2 = 0.0; - gain = 1.0; + + out: + GST_INFO + ("gain = %5.1f, width= %7.2f, freq = %7.2f, a0 = %7.5g, a1 = %7.5g, a2=%7.5g b1 = %7.5g, b2 = %7.5g", + band->gain, band->width, band->freq, band->a0, band->a1, band->a2, + band->b1, band->b2); + } +} + +static void +setup_high_shelf_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band) +{ + g_return_if_fail (GST_AUDIO_FILTER (equ)->format.rate); + + { + gdouble gain, omega, bw; + gdouble alpha, delta, b0; + gdouble egp, egm; + + gain = arg_to_scale (band->gain); + omega = calculate_omega (band->freq, GST_AUDIO_FILTER (equ)->format.rate); + bw = calculate_bw (band, GST_AUDIO_FILTER (equ)->format.rate); + if (bw == 0.0) goto out; - } else { - bw = 2.0 * M_PI * (band->width / GST_AUDIO_FILTER (equ)->format.rate); - } - edge_gain = sqrt (gain); - gamma = tan (bw / 2.0); + egm = gain - 1.0; + egp = gain + 1.0; + alpha = tan (bw / 2.0); - alpha = gamma * edge_gain; - beta = gamma / edge_gain; + delta = 2.0 * sqrt (gain) * alpha; + b0 = egp - egm * cos (omega) + delta; + + band->a0 = ((egp + egm * cos (omega) + delta) * gain) / b0; + band->a1 = ((egm + egp * cos (omega)) * -2.0 * gain) / b0; + band->a2 = ((egp + egm * cos (omega) - delta) * gain) / b0; + band->b1 = ((egm - egp * cos (omega)) * -2.0) / b0; + band->b2 = -((egp - egm * cos (omega) - delta)) / b0; - band->a0 = (1.0 + alpha) / (1.0 + beta); - band->a1 = (-2.0 * cos (omega)) / (1.0 + beta); - band->a2 = (1.0 - alpha) / (1.0 + beta); - band->b1 = (2.0 * cos (omega)) / (1.0 + beta); - band->b2 = -(1.0 - beta) / (1.0 + beta); out: GST_INFO @@ -459,11 +546,14 @@ set_passthrough (GstIirEqualizer * equ) static void update_coefficients (GstIirEqualizer * equ) { - gint i; + gint i, n = equ->freq_band_count; - for (i = 0; i < equ->freq_band_count; i++) { - setup_filter (equ, equ->bands[i]); + setup_low_shelf_filter (equ, equ->bands[0]); + for (i = 1; i < n - 1; i++) { + setup_peak_filter (equ, equ->bands[i]); } + setup_high_shelf_filter (equ, equ->bands[n - 1]); + equ->need_new_coefficients = FALSE; } |