update()

template<typename T = float>

T fl::detail::SpectralVarianceImpl< T >::update ( fl::span< const T > bins )

inline

Feed a new frame of multi-channel data.

Returns mean relative deviation. First call initializes internal state and returns 0.

Definition at line 36 of file spectral_variance_impl.h.

                                   {
        const int n = static_cast<int>(bins.size());
        if (n == 0) return T(0);
 
        // Initialize on first call or if channel count changes
        if (mSmoothed.size() != static_cast<fl::size>(n)) {
            mSmoothed.resize(n);
            for (int i = 0; i < n; ++i) {
                mSmoothed[i] = bins[i];
            }
            mVariance = T(0);
            return T(0);
        }
 
        T sumRelChange = T(0);
        int activeCount = 0;
 
        for (int i = 0; i < n; ++i) {
            T smoothed = mSmoothed[i];
            T denom = (smoothed > mFloor) ? smoothed : mFloor;
 
            // Only count channels with meaningful energy
            if (smoothed > mFloor) {
                T diff = bins[i] - smoothed;
                T absDiff = (diff >= T(0)) ? diff : -diff;
                sumRelChange += absDiff / denom;
                ++activeCount;
            }
 
            // Update EMA: smoothed = alpha * current + (1-alpha) * smoothed
            mSmoothed[i] = mAlpha * bins[i] + (T(1) - mAlpha) * smoothed;
        }
 
        mVariance = (activeCount >= 2)
                        ? sumRelChange / static_cast<T>(activeCount)
                        : T(0);
        return mVariance;
    }

References mAlpha, mFloor, mSmoothed, mVariance, and fl::span< T, Extent >::size().

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