calculateConfidence() [2/2]

float fl::audio::detector::Pitch::calculateConfidence ( const vector< float > & autocorr, int peakLag ) const

private

Definition at line 171 of file pitch.cpp.hpp.

                                                                                 {
    // Confidence based on:
    // 1. Strength of the autocorrelation peak
    // 2. Ratio of peak to nearby values (peak clarity)
 
    if (peakLag <= 0 || peakLag >= static_cast<int>(autocorr.size())) {
        return 0.0f;
    }
 
    float peakValue = autocorr[static_cast<size>(peakLag)];
 
    // Confidence is primarily based on peak strength
    // Autocorrelation ranges from -1 to 1, but we only care about positive peaks
    float confidence = fl::max(0.0f, fl::min(1.0f, peakValue));
 
    // Calculate clarity by comparing peak to surrounding values
    // Look at ±10% of the period
    int windowSize = fl::max(2, peakLag / 10);
    float neighborSum = 0.0f;
    int neighborCount = 0;
 
    for (int offset = -windowSize; offset <= windowSize; offset++) {
        if (offset == 0) continue;  // Skip the peak itself
 
        int lag = peakLag + offset;
        if (lag >= mMinPeriod && lag <= mMaxPeriod && lag < static_cast<int>(autocorr.size())) {
            neighborSum += fl::max(0.0f, autocorr[static_cast<size>(lag)]);
            neighborCount++;
        }
    }
 
    if (neighborCount > 0) {
        float neighborAvg = neighborSum / static_cast<float>(neighborCount);
 
        // Peak should be significantly higher than neighbors
        // If peak is 2x higher, that's good; if it's similar, reduce confidence
        if (neighborAvg > 1e-6f) {
            float clarity = fl::min(1.0f, (peakValue - neighborAvg) / neighborAvg);
            confidence *= (0.7f + 0.3f * clarity);  // Weight clarity at 30%
        }
    }
 
    return confidence;
}

References fl::max(), fl::min(), mMaxPeriod, mMinPeriod, offset(), and fl::vector_basic::size().

Referenced by calculateAutocorrelation().

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