calculateSpectralFlux()

float fl::audio::detector::Beat::calculateSpectralFlux ( const fft::Bins & fft )

private

Definition at line 80 of file beat.cpp.hpp.

                                                    {
    float flux = 0.0f;
    size numBins = fl::min(fft.raw().size(), mPreviousMagnitudes.size());
 
    // Use the bass half of fft::FFT bins for beat detection.
    // Musical beats (kick drums) have energy at 60-200 Hz.
    // With 16 CQ log-spaced bins from 30-4698 Hz:
    //   bins 0-3 cover ~30-82 Hz (sub-bass)
    //   bins 4-7 cover ~82-226 Hz (bass/low-mid, kick fundamentals)
    // Using numBins/2 = 8 bins covers the full kick drum range (~30-226 Hz).
    // Treble transients (hi-hats, cymbals) in bins 8-15 are excluded.
    size bassBins = numBins / 2;
    if (bassBins < 1) bassBins = 1;
 
    for (size i = 0; i < bassBins; i++) {
        float diff = fft.raw()[i] - mPreviousMagnitudes[i];
        if (diff > 0.0f) {
            flux += diff;
        }
    }
 
    return flux / static_cast<float>(bassBins);
}

References fl::min(), and mPreviousMagnitudes.

Referenced by update().

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