Method runHybrid

src/fl/audio/fft/fft_impl.cpp.hpp:867–963

    }

    void runHybrid(span<const i16> buffer, Bins *out) {
        const int N = mInputSamples;
        const int numRawBins = N / 2 + 1;

        out->setParams(mFmin, mFmax, mSampleRate);

        // Use thread-local scratch buffers
        FftScratch &s = scratch();
        s.re.resize(numRawBins);
        s.im.resize(numRawBins);
        s.mag.resize(numRawBins);
        s.windowed.resize(N);
        s.rawBinsI.resize(mTotalBands);

        // Phase 1: Windowed 512pt FFT → LOG_REBIN for upper bins
        applyWindow(buffer.data(), mWindowBuf.data(), s.windowed.data(), N);

        fl_fft_real_forward(mFftrCfg, mInputSamples, s.windowed.data(), mFftOut.data());

        deinterleave(mFftOut.data(), s.re.data(), s.im.data(), numRawBins);
        batchMag(s.re.data(), s.im.data(), s.mag.data(), numRawBins);

        computeLinearBins(s.mag.data(), N, out);

        // Integer accumulation for log-rebin
        fl::memset(s.rawBinsI.data(), 0, sizeof(u32) * mTotalBands);

        // Upper tier: LOG_REBIN for bins [mHybridMidSplitBin, mTotalBands)
        logRebinRange(s.mag.data(), N,
                      static_cast<float>(mSampleRate),
                      mHybridMidSplitBin, mTotalBands, s.rawBinsI.data(),
                      mLogBinLut);

        // Decimate signal: 512 → 256 → 128 (2 steps for mid tier)
        int workLen = N;
        for (int i = 0; i < N; i++) {
            mWorkBuf[i] =
                (i < static_cast<int>(buffer.size())) ? buffer[i] : 0;
        }
        decimateBy2(mWorkBuf.data(), workLen);
        workLen /= 2;
        decimateBy2(mWorkBuf.data(), workLen);
        workLen /= 2;

        // Phase 2: Zero-padded 256pt FFT (128 windowed + 128 zeros) → LOG_REBIN for mid bins
        if (mHybridMidSplitBin > mHybridSplitBin && mHybridMidFft) {
            int midFftN = mHybridMidN * 2;
            int midRawBins = midFftN / 2 + 1;
            s.windowed.resize(midFftN);
            applyWindow(mWorkBuf.data(), mHybridMidWindow.data(),
                           s.windowed.data(), mHybridMidN);
            for (int i = mHybridMidN; i < midFftN; ++i) {
                s.windowed[i] = 0;
            }
            fl_fft_real_forward(mHybridMidFft, mHybridMidN * 2,
                                s.windowed.data(),
                                mHybridMidFftOut.data());
            deinterleave(mHybridMidFftOut.data(), s.re.data(), s.im.data(), midRawBins);