resolveModeEnums()

void fl::audio::fft::Args::resolveModeEnums ( Mode & mode, Window & window, int bands, int samples, float fmin, float fmax )

static

Definition at line 265 of file fft.cpp.hpp.

                                                                     {
    // Resolve mode first
    if (mode == Mode::AUTO) {
        if (bands <= 32) {
            mode = Mode::LOG_REBIN;
        } else {
            // Check kernel conditioning: N_window = N * fmin / fmax.
            // When >= 2, CQ_NAIVE (single FFT + kernels) works well.
            // When < 2, kernels degenerate and we need octave-wise CQT.
            int winMin = static_cast<int>(
                static_cast<float>(samples) * fmin / fmax);
            mode = (winMin >= 2) ? Mode::CQ_NAIVE : Mode::CQ_OCTAVE;
        }
    }
 
    // Resolve window based on resolved mode
    if (window == Window::AUTO) {
        switch (mode) {
        case Mode::LOG_REBIN:
        case Mode::CQ_HYBRID:
            // These paths apply time-domain windowing before fft::FFT.
            // BLACKMAN_HARRIS: -92 dB sidelobe rejection (vs -31 dB HANNING).
            // Sidelobes produce only mag=0-1 quantization noise, ensuring
            // distant output bins have near-zero energy (≤2) for pure tones.
            // Main lobe is 8 FFT bins wide (~690 Hz at 512/44100), so
            // output bins narrower than ~130 Hz may see main lobe leakage
            // at distance 3+ — a fundamental resolution limit.
            window = Window::BLACKMAN_HARRIS;
            break;
        case Mode::CQ_NAIVE:
        case Mode::CQ_OCTAVE:
            // CQ kernels already apply Hamming windowing in frequency domain.
            // No time-domain window is applied on these paths, so this is
            // cosmetic. HANNING is the lighter/cheaper default.
            window = Window::HANNING;
            break;
        default:
            window = Window::BLACKMAN_HARRIS;
            break;
        }
    }
}

References fl::audio::fft::AUTO, bands, fl::audio::fft::BLACKMAN_HARRIS, fl::audio::fft::CQ_HYBRID, fl::audio::fft::CQ_NAIVE, fl::audio::fft::CQ_OCTAVE, fmax, fmin, fl::audio::fft::HANNING, fl::audio::fft::LOG_REBIN, mode, samples, and window.

Referenced by fl::audio::fft::Context::Context().

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