Method doFFTAnalysis

src/core/RealtimeAnalyser.cpp:112–162

}

void RealtimeAnalyser::doFFTAnalysis()
{
    // Unroll the input buffer into a temporary buffer, where we'll apply an analysis window followed by an FFT.
    uint32_t fftSize = this->fftSize();

    AudioFloatArray temporaryBuffer(fftSize);
    float * inputBuffer = m_inputBuffer.data();
    float * tempP = temporaryBuffer.data();

    // Take the previous fftSize values from the input buffer and copy into the temporary buffer.
    size_t writeIndex = m_writeIndex;
    if (writeIndex < fftSize)
    {
        memcpy(tempP, inputBuffer + writeIndex - fftSize + InputBufferSize, sizeof(*tempP) * (fftSize - writeIndex));
        memcpy(tempP + fftSize - writeIndex, inputBuffer, sizeof(*tempP) * writeIndex);
    }
    else
    {
        memcpy(tempP, inputBuffer + writeIndex - fftSize, sizeof(*tempP) * fftSize);
    }

    // Window the input samples.
    ApplyWindowFunctionInplace(WindowFunction::blackman, tempP, fftSize);

    // Do the analysis.
    m_analysisFrame->computeForwardFFT(tempP);

    float * realP = m_analysisFrame->realData();
    float * imagP = m_analysisFrame->imagData();

    // Erase the packed nyquist component.
    imagP[0] = 0;

    // Normalize so than an input sine wave at 0dBfs registers as 0dBfs (undo FFT scaling factor).
    const double magnitudeScale = 1.0 / DefaultFFTSize;

    // A value of 0 does no averaging with the previous result.  Larger values produce slower, but smoother changes.
    double k = m_smoothingTimeConstant;
    k = max(0.0, k);
    k = min(1.0, k);

    // Convert the analysis data from complex to magnitude and average with the previous result.
    float * destination = magnitudeBuffer().data();
    size_t n = magnitudeBuffer().size();
    for (size_t i = 0; i < n; ++i)
    {
        std::complex<double> c(realP[i], imagP[i]);
        double scalarMagnitude = abs(c) * magnitudeScale;
        destination[i] = float(k * destination[i] + (1 - k) * scalarMagnitude);
    }
}

void RealtimeAnalyser::getFloatFrequencyData(std::vector<float> & destinationArray)
{