static void
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);
}
}
void AVFEqualizerBand::RecalculateParams() {
double rate = mEQ->GetSampleRate();
mBypass = (rate == 0.0);
if (mBypass) {
// can't calculate until we have a sample rate
return;
}
// recalculate coefficients based on new parameters
double bw = calculate_bandwidth(m_Bandwidth, rate);
if (bw <= 0.0) {
// no bandwidth, no filter...
mBypass = true;
return;
}
double absGain = pow(10, m_Gain / 40); // convert dB to scale
double omega = calculate_omega(mFrequency, rate);
switch (mFilterType) {
case Peak:
SetupPeakFilter(omega, bw, absGain);
break;
case LowShelf:
SetupLowShelfFilter(omega, bw, absGain);
break;
case HighShelf:
SetupHighShelfFilter(omega, bw, absGain);
break;
}
}
static void
setup_high_shelf_filter (GstIirEqualizer * equ, GstIirEqualizerBand * band)
{
gint rate = GST_AUDIO_FILTER_RATE (equ);
g_return_if_fail (rate);
{
gdouble gain, omega, bw;
gdouble alpha, delta, b0;
gdouble egp, egm;
gain = arg_to_scale (band->gain);
omega = calculate_omega (band->freq, rate);
bw = calculate_bw (band, 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;
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);
}
}