Method update

src/fl/audio/detector/tempo_analyzer.cpp.hpp:37–93

TempoAnalyzer::~TempoAnalyzer() FL_NOEXCEPT = default;

void TempoAnalyzer::update(shared_ptr<Context> context) {
    mRetainedFFT = context->getFFT16();
    const fft::Bins& fft = *mRetainedFFT;
    u32 timestamp = context->getTimestamp();

    // Calculate spectral flux for onset detection
    float flux = calculateSpectralFlux(fft);

    // Update adaptive threshold
    updateAdaptiveThreshold();

    // Detect onsets
    if (detectOnset(timestamp)) {
        mOnsetTimes.push_back(timestamp);
        if (mOnsetTimes.size() > MAX_ONSET_HISTORY) {
            mOnsetTimes.pop_front();
        }

        // Update tempo hypotheses
        updateHypotheses(timestamp);
    }

    mPreviousFlux = flux;

    // Update per-bin magnitudes for next frame's spectral flux calculation
    size numBins = fl::min(static_cast<size>(8), fft.raw().size());
    for (size i = 0; i < numBins && i < mPreviousMagnitudes.size(); i++) {
        mPreviousMagnitudes[i] = fft.raw()[i];
    }

    // Prune weak hypotheses
    pruneHypotheses();

    // Update current tempo based on best hypothesis
    updateCurrentTempo();

    // Update stability analysis
    updateStability();

    // Silence gate: fade confidence toward 0 during silence. The BPM estimate
    // itself survives unchanged so beat sync is seamless on audio re-entry.
    // dt derived from timestamp deltas (ms→s). First frame: dt=0 → pass-through.
    float dt = 0.0f;
    if (mHasPrevTimestamp && timestamp >= mPrevTimestamp) {
        dt = static_cast<float>(timestamp - mPrevTimestamp) * 0.001f;
    }
    mPrevTimestamp = timestamp;
    mHasPrevTimestamp = true;

    const bool isSilent = context->isSilent();
    mConfidence = mConfidenceEnvelope.update(isSilent, mConfidence, dt);

    // Track state changes for fireCallbacks()
    float bpmDiff = fl::abs(mCurrentBPM - mPreviousBPM);
    mBpmChanged = (bpmDiff > 5.0f);
    mPreviousBPM = mCurrentBPM;
}