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Add EBU R128 k-weighting filter implementation to Biquad.

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This commit is contained in:
Max Maisel 2019-03-15 16:27:32 +01:00
parent c3d25cfb44
commit c002165952
2 changed files with 50 additions and 0 deletions
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49
src/effects/Biquad.cpp
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@ -304,6 +304,55 @@ ArrayOf<Biquad> Biquad::CalcChebyshevType2Filter(int order, double fn, double fc
return std::move(pBiquad);
}
// fs: sample rate
// returns array of two Biquads
//
// EBU R128 parameter sampling rate adaption after
// Mansbridge, Stuart, Saoirse Finn, and Joshua D. Reiss.
// "Implementation and Evaluation of Autonomous Multi-track Fader Control."
// Paper presented at the 132nd Audio Engineering Society Convention,
// Budapest, Hungary, 2012."
ArrayOf<Biquad> Biquad::CalcEBUR128WeightingFilter(float fs)
{
ArrayOf<Biquad> pBiquad(size_t(2), true);
//
// HSF pre filter
//
double db = 3.999843853973347;
double f0 = 1681.974450955533;
double Q = 0.7071752369554196;
double K = tan(M_PI * f0 / fs);
double Vh = pow(10.0, db / 20.0);
double Vb = pow(Vh, 0.4996667741545416);
double a0 = 1.0 + K / Q + K * K;
pBiquad[0].fNumerCoeffs[Biquad::B0] = (Vh + Vb * K / Q + K * K) / a0;
pBiquad[0].fNumerCoeffs[Biquad::B1] = 2.0 * (K * K - Vh) / a0;
pBiquad[0].fNumerCoeffs[Biquad::B2] = (Vh - Vb * K / Q + K * K) / a0;
pBiquad[0].fDenomCoeffs[Biquad::A1] = 2.0 * (K * K - 1.0) / a0;
pBiquad[0].fDenomCoeffs[Biquad::A2] = (1.0 - K / Q + K * K) / a0;
//
// HPF weighting filter
//
f0 = 38.13547087602444;
Q = 0.5003270373238773;
K = tan(M_PI * f0 / fs);
pBiquad[1].fNumerCoeffs[Biquad::B0] = 1.0;
pBiquad[1].fNumerCoeffs[Biquad::B1] = -2.0;
pBiquad[1].fNumerCoeffs[Biquad::B2] = 1.0;
pBiquad[1].fDenomCoeffs[Biquad::A1] = 2.0 * (K * K - 1.0) / (1.0 + K / Q + K * K);
pBiquad[1].fDenomCoeffs[Biquad::A2] = (1.0 - K / Q + K * K) / (1.0 + K / Q + K * K);
return std::move(pBiquad);
}
void Biquad::ComplexDiv (double fNumerR, double fNumerI, double fDenomR, double fDenomI,
double* pfQuotientR, double* pfQuotientI)
{

1
src/effects/Biquad.h
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@ -66,6 +66,7 @@ struct Biquad
static ArrayOf<Biquad> CalcButterworthFilter(int order, double fn, double fc, int type);
static ArrayOf<Biquad> CalcChebyshevType1Filter(int order, double fn, double fc, double ripple, int type);
static ArrayOf<Biquad> CalcChebyshevType2Filter(int order, double fn, double fc, double ripple, int type);
static ArrayOf<Biquad> CalcEBUR128WeightingFilter(float fs);
static void ComplexDiv (double fNumerR, double fNumerI, double fDenomR, double fDenomI,
double* pfQuotientR, double* pfQuotientI);