private float[] GenerateFilterCoeff(double fc, double q)
{
fc = SynthHelper.ClampD(fc, SynthConstants.DenormLimit, .49);
float[] coeff = new float[4];
switch (FilterMethod)
{
case FilterType.BiquadLowpass:
{
double w0 = SynthConstants.TwoPi * fc;
double cosw0 = Math.Cos(w0);
double alpha = Math.Sin(w0) / (2.0 * q);
double a0inv = 1.0 / (1.0 + alpha);
coeff[0] = (float)(-2.0 * cosw0 * a0inv);
coeff[1] = (float)((1.0 - alpha) * a0inv);
coeff[2] = (float)((1.0 - cosw0) * a0inv * (1.0 / Math.Sqrt(q)));
coeff[3] = _b1 * 0.5f;
}
break;
case FilterType.BiquadHighpass:
{
double w0 = SynthConstants.TwoPi * fc;
double cosw0 = Math.Cos(w0);
double alpha = Math.Sin(w0) / (2.0 * q);
double a0inv = 1.0 / (1.0 + alpha);
double qinv = 1.0 / Math.Sqrt(q);
coeff[0] = (float)(-2.0 * cosw0 * a0inv);
coeff[1] = (float)((1.0 - alpha) * a0inv);
coeff[2] = (float)((-1.0 - cosw0) * a0inv * qinv);
coeff[3] = (float)((1.0 + cosw0) * a0inv * qinv * 0.5);
}
break;
case FilterType.OnePoleLowpass:
coeff[0] = 1.0f - (float)Math.Exp(-2.0 * Math.PI * fc);
break;
}
return(coeff);
}
/// <inheritdoc />
public void SetChannelVolume(int channel, double volume)
{
volume = SynthHelper.ClampD(volume, SynthConstants.MinVolume, SynthConstants.MaxVolume);
_synth.PostMessage(new { cmd = AlphaSynthWebWorker.CmdSetChannelVolume, channel = channel, volume = volume });
}
/// <inheritdoc />
public void SetChannelVolume(int channel, double volume)
{
volume = SynthHelper.ClampD(volume, SynthConstants.MinVolume, SynthConstants.MaxVolume);
_synthesizer.SetChannelVolume(channel, volume);
}
