public static void SetResonantLowpassCoefficients(
ResonantLowpassRec Filter,
double Cutoff,
double Bandwidth,
double Gain,
double SamplingRate)
{
if ((Cutoff == Filter.OldCutoff) && (Bandwidth == Filter.OldBandwidth) && (Gain == Filter.OldGain))
{
return;
}
Filter.OldCutoff = Cutoff;
Filter.OldBandwidth = Bandwidth;
Filter.OldGain = Gain;
if (Filter.NumLowpassSections != 0)
{
/* initialize first one */
ButterworthLowpassRec.ComputeButterworthLowpassCoefficients(
ref Filter.iir[0],
Cutoff,
SamplingRate);
/* copy to the others */
for (int i = 1; i < Filter.NumLowpassSections; i += 1)
{
Filter.iir[i].A0 = Filter.iir[0].A0;
Filter.iir[i].A1 = Filter.iir[0].A1;
Filter.iir[i].A2 = Filter.iir[0].A2;
Filter.iir[i].B1 = Filter.iir[0].B1;
Filter.iir[i].B2 = Filter.iir[0].B2;
}
}
if (Filter.NumBandpassSections != 0)
{
/* initialize first one */
ButterworthBandpassRec.ComputeButterworthBandpassCoefficients(
ref Filter.iir[Filter.NumLowpassSections + 0],
Cutoff,
Bandwidth,
SamplingRate);
/* copy to the others */
for (int i = 1; i < Filter.NumBandpassSections; i += 1)
{
Filter.iir[Filter.NumLowpassSections + i].A0 = Filter.iir[Filter.NumLowpassSections + 0].A0;
Filter.iir[Filter.NumLowpassSections + i].A1 = Filter.iir[Filter.NumLowpassSections + 0].A1;
Filter.iir[Filter.NumLowpassSections + i].A2 = Filter.iir[Filter.NumLowpassSections + 0].A2;
Filter.iir[Filter.NumLowpassSections + i].B1 = Filter.iir[Filter.NumLowpassSections + 0].B1;
Filter.iir[Filter.NumLowpassSections + i].B2 = Filter.iir[Filter.NumLowpassSections + 0].B2;
}
}
Filter.BandpassGain = (float)Gain;
}
/* apply filter to an array of values, adding result to output array */
public void Apply(
float[] XinVector,
int XInVectorOffset,
float[] YoutVector,
int YoutVectorOffset,
int VectorLength,
float OutputScaling,
SynthParamRec SynthParams)
{
ResonantLowpassRec Filter = this;
// ScratchWorkspace1* is used in ApplyUnifiedFilterArray()
#if DEBUG
Debug.Assert(!SynthParams.ScratchWorkspace2InUse);
SynthParams.ScratchWorkspace2InUse = true;
#endif
float[] ScratchVector1 = XinVector /*sic*/; // SourceCopy
int ScratchVector1Offset = SynthParams.ScratchWorkspace2LOffset;
float[] ScratchVector2 = XinVector /*sic*/; // Workspace
int ScratchVector2Offset = SynthParams.ScratchWorkspace2ROffset;
FloatVectorCopy(
XinVector,
XInVectorOffset,
ScratchVector1, // SourceCopy
ScratchVector1Offset,
VectorLength);
FloatVectorZero(
YoutVector,
YoutVectorOffset,
VectorLength);
/* lowpass section */
if (Filter.NumLowpassSections == 0)
{
}
else if (Filter.NumLowpassSections == 1)
{
IIR2DirectIMAcc(
ref Filter.iir[0],
ScratchVector1, // SourceCopy
ScratchVector1Offset,
YoutVector,
YoutVectorOffset,
VectorLength,
OutputScaling);
}
else
{
IIR2DirectI(
ref Filter.iir[0],
ScratchVector1, // SourceCopy
ScratchVector1Offset,
ScratchVector2, // Workspace
ScratchVector2Offset,
VectorLength);
int i;
for (i = 1; i < Filter.NumLowpassSections - 1; i += 1)
{
IIR2DirectI(
ref Filter.iir[i],
ScratchVector2, // Workspace
ScratchVector2Offset,
ScratchVector2, // Workspace
ScratchVector2Offset,
VectorLength);
}
IIR2DirectIMAcc(
ref Filter.iir[i],
ScratchVector2, // Workspace
ScratchVector2Offset,
YoutVector,
YoutVectorOffset,
VectorLength,
OutputScaling);
}
/* bandpass section */
if (Filter.NumBandpassSections == 0)
{
}
else if (Filter.NumBandpassSections == 1)
{
IIR2DirectIMAcc(
ref Filter.iir[Filter.NumLowpassSections + 0],
ScratchVector1, // SourceCopy
ScratchVector1Offset,
YoutVector,
YoutVectorOffset,
VectorLength,
Filter.BandpassGain * OutputScaling);
}
else
{
IIR2DirectI(
ref Filter.iir[Filter.NumLowpassSections + 0],
ScratchVector1, // SourceCopy
ScratchVector1Offset,
ScratchVector2, // Workspace
ScratchVector2Offset,
VectorLength);
int i;
for (i = 1; i < Filter.NumBandpassSections - 1; i += 1)
{
IIR2DirectI(
ref Filter.iir[Filter.NumLowpassSections + i],
ScratchVector2, // Workspace
ScratchVector2Offset,
ScratchVector2, // Workspace
ScratchVector2Offset,
VectorLength);
}
IIR2DirectIMAcc(
ref Filter.iir[Filter.NumLowpassSections + i],
ScratchVector2, // Workspace
ScratchVector2Offset,
YoutVector,
YoutVectorOffset,
VectorLength,
Filter.BandpassGain * OutputScaling);
}
#if DEBUG
SynthParams.ScratchWorkspace2InUse = false;
#endif
}
