IIRCoefficients IIRCoefficients::makeHighPass (const double sampleRate,
const double frequency) noexcept
{
const double n = tan (double_Pi * frequency / sampleRate);
const double nSquared = n * n;
const double c1 = 1.0 / (1.0 + std::sqrt (2.0) * n + nSquared);
return IIRCoefficients (c1,
c1 * -2.0f,
c1,
1.0,
c1 * 2.0 * (nSquared - 1.0),
c1 * (1.0 - std::sqrt (2.0) * n + nSquared));
}
IIRCoefficients IIRCoefficients::makeLowPass (const double sampleRate,
const double frequency) noexcept
{
jassert (sampleRate > 0);
const double n = 1.0 / tan (double_Pi * frequency / sampleRate);
const double nSquared = n * n;
const double c1 = 1.0 / (1.0 + std::sqrt (2.0) * n + nSquared);
return IIRCoefficients (c1,
c1 * 2.0f,
c1,
1.0,
c1 * 2.0 * (1.0 - nSquared),
c1 * (1.0 - std::sqrt (2.0) * n + nSquared));
}
IIRCoefficients BiquadFilter::makeHighPass (const double sampleRate,
const double frequency,
const double Q) noexcept
{
const double oneOverCurrentSampleRate = 1.0 / sampleRate;
float w0 = (float) (2.0f * float_Pi * frequency * oneOverCurrentSampleRate);
float cos_w0 = cos (w0);
float sin_w0 = sin (w0);
float alpha = sin_w0 / (2.0f * (float) Q);
return IIRCoefficients ((1.0f + cos_w0) * 0.5f,
-(1.0f + cos_w0),
(1.0f + cos_w0) * 0.5f,
(1.0f + alpha),
-2.0f * cos_w0,
(1.0f - alpha));
}
IIRCoefficients IIRCoefficients::makeHighPass (const double sampleRate,
const double frequency,
const double Q) noexcept
{
jassert (sampleRate > 0.0);
jassert (frequency > 0.0 && frequency <= sampleRate * 0.5);
jassert (Q > 0.0);
const double n = std::tan (double_Pi * frequency / sampleRate);
const double nSquared = n * n;
const double c1 = 1.0 / (1.0 + 1.0 / Q * n + nSquared);
return IIRCoefficients (c1,
c1 * -2.0,
c1,
1.0,
c1 * 2.0 * (nSquared - 1.0),
c1 * (1.0 - 1.0 / Q * n + nSquared));
}
IIRCoefficients IIRCoefficients::makeNotchFilter (const double sampleRate,
const double frequency,
const double Q) noexcept
{
jassert (sampleRate > 0.0);
jassert (frequency > 0.0 && frequency <= sampleRate * 0.5);
jassert (Q > 0.0);
const double n = 1.0 / std::tan (double_Pi * frequency / sampleRate);
const double nSquared = n * n;
const double c1 = 1.0 / (1.0 + n / Q + nSquared);
return IIRCoefficients (c1 * (1.0 + nSquared),
2.0 * c1 * (1.0 - nSquared),
c1 * (1.0 + nSquared),
1.0,
c1 * 2.0 * (1.0 - nSquared),
c1 * (1.0 - n / Q + nSquared));
}
IIRCoefficients BiquadFilter::makeAllpass (const double sampleRate,
const double frequency,
const double Q) noexcept
{
const double qFactor = jlimit(0.00001, 1000.0, Q);
const double oneOverCurrentSampleRate = 1.0 / sampleRate;
float w0 = (float) (2.0f * float_Pi * frequency * oneOverCurrentSampleRate);
float cos_w0 = cos(w0);
float sin_w0 = sin(w0);
float alpha = (float) (sin_w0 / (2 * qFactor));
return IIRCoefficients (1.0f - alpha,
-2 * cos_w0,
1.0f + alpha,
1.0f + alpha,
-2.0f * cos_w0,
1.0f - alpha);
}
IIRCoefficients BiquadFilter::makeBandPass (const double sampleRate,
const double frequency,
const double Q) noexcept
{
const double qFactor = jlimit (0.00001, 1000.0, Q);
const double oneOverCurrentSampleRate = 1.0 / sampleRate;
float w0 = (float) (2.0f * float_Pi * frequency * oneOverCurrentSampleRate);
float cos_w0 = cos (w0);
float sin_w0 = sin (w0);
float alpha = sin_w0 / (2.0f * (float) qFactor);
// float alpha = sin_w0 * sinh( (log(2.0)/2.0) * bandwidth * w0/sin_w0 );
return IIRCoefficients (alpha,
0.0f,
-alpha,
1.0f + alpha,
-2.0f * cos_w0,
1.0f - alpha);
}
IIRCoefficients IIRCoefficients::makePeakFilter (const double sampleRate,
const double centreFrequency,
const double Q,
const float gainFactor) noexcept
{
jassert (sampleRate > 0);
jassert (Q > 0);
const double A = jmax (0.0f, std::sqrt (gainFactor));
const double omega = (double_Pi * 2.0 * jmax (centreFrequency, 2.0)) / sampleRate;
const double alpha = 0.5 * std::sin (omega) / Q;
const double c2 = -2.0 * std::cos (omega);
const double alphaTimesA = alpha * A;
const double alphaOverA = alpha / A;
return IIRCoefficients (1.0 + alphaTimesA,
c2,
1.0 - alphaTimesA,
1.0 + alphaOverA,
c2,
1.0 - alphaOverA);
}
IIRCoefficients IIRCoefficients::makeLowShelf (const double sampleRate,
const double cutOffFrequency,
const double Q,
const float gainFactor) noexcept
{
jassert (sampleRate > 0);
jassert (Q > 0);
const double A = jmax (0.0f, std::sqrt (gainFactor));
const double aminus1 = A - 1.0;
const double aplus1 = A + 1.0;
const double omega = (double_Pi * 2.0 * jmax (cutOffFrequency, 2.0)) / sampleRate;
const double coso = std::cos (omega);
const double beta = std::sin (omega) * std::sqrt (A) / Q;
const double aminus1TimesCoso = aminus1 * coso;
return IIRCoefficients (A * (aplus1 - aminus1TimesCoso + beta),
A * 2.0 * (aminus1 - aplus1 * coso),
A * (aplus1 - aminus1TimesCoso - beta),
aplus1 + aminus1TimesCoso + beta,
-2.0 * (aminus1 + aplus1 * coso),
aplus1 + aminus1TimesCoso - beta);
}