goertzel()

MAYAFLUX_API double MayaFlux::Kinesis::Discrete::goertzel ( std::span< const double >  window, std::span< const double >  coefs  )

noexcept

Weighted energy of the window at chosen frequencies.

coefs: pairs (frequency in cycles per sample, weight). Each frequency is measured with the Goertzel recurrence over the whole window and gives the squared amplitude of the sinusoid there (a sine of amplitude A on the frequency gives A^2 when it fits the window in whole cycles); the result is the weighted sum.

Definition at line 451 of file Kernels.cpp.

{
    const size_t n = window.size();
    if (n == 0)
        return 0.0;
 
    const double scale = 4.0 / (static_cast<double>(n) * static_cast<double>(n));
    double total = 0.0;
 
    for (size_t j = 0; j + 1 < coefs.size(); j += 2) {
        const double coeff = 2.0 * std::cos(two_pi * coefs[j]);
        double s1 = 0.0;
        double s2 = 0.0;
        for (const double x : window) {
            const double s = x + coeff * s1 - s2;
            s2 = s1;
            s1 = s;
        }
        total += coefs[j + 1] * scale * (s1 * s1 + s2 * s2 - coeff * s1 * s2);
    }
    return total;
}

References MayaFlux::Kinesis::scale(), total, and window.

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