spectrumanalyser.cpp Example File

spectrum/app/spectrumanalyser.cpp
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#include "spectrumanalyser.h"
#include "utils.h"
#include "fftreal_wrapper.h"

#include <qmath.h>
#include <qmetatype.h>
#include <QAudioFormat>
#include <QThread>

SpectrumAnalyserThread::SpectrumAnalyserThread(QObject *parent)
    :   QObject(parent)
#ifndef DISABLE_FFT
    ,   m_fft(new FFTRealWrapper)
#endif
    ,   m_numSamples(SpectrumLengthSamples)
    ,   m_windowFunction(DefaultWindowFunction)
    ,   m_window(SpectrumLengthSamples, 0.0)
    ,   m_input(SpectrumLengthSamples, 0.0)
    ,   m_output(SpectrumLengthSamples, 0.0)
    ,   m_spectrum(SpectrumLengthSamples)
#ifdef SPECTRUM_ANALYSER_SEPARATE_THREAD
    ,   m_thread(new QThread(this))
#endif
{
#ifdef SPECTRUM_ANALYSER_SEPARATE_THREAD
    // moveToThread() cannot be called on a QObject with a parent
    setParent(0);
    moveToThread(m_thread);
    m_thread->start();
#endif
    calculateWindow();
}

SpectrumAnalyserThread::~SpectrumAnalyserThread()
{
#ifndef DISABLE_FFT
    delete m_fft;
#endif
}

void SpectrumAnalyserThread::setWindowFunction(WindowFunction type)
{
    m_windowFunction = type;
    calculateWindow();
}

void SpectrumAnalyserThread::calculateWindow()
{
    for (int i=0; i<m_numSamples; ++i) {
        DataType x = 0.0;

        switch (m_windowFunction) {
        case NoWindow:
            x = 1.0;
            break;
        case HannWindow:
            x = 0.5 * (1 - qCos((2 * M_PI * i) / (m_numSamples - 1)));
            break;
        default:
            Q_ASSERT(false);
        }

        m_window[i] = x;
    }
}

void SpectrumAnalyserThread::calculateSpectrum(const QByteArray &buffer,
                                                int inputFrequency,
                                                int bytesPerSample)
{
#ifndef DISABLE_FFT
    Q_ASSERT(buffer.size() == m_numSamples * bytesPerSample);

    // Initialize data array
    const char *ptr = buffer.constData();
    for (int i=0; i<m_numSamples; ++i) {
        const qint16 pcmSample = *reinterpret_cast<const qint16*>(ptr);
        // Scale down to range [-1.0, 1.0]
        const DataType realSample = pcmToReal(pcmSample);
        const DataType windowedSample = realSample * m_window[i];
        m_input[i] = windowedSample;
        ptr += bytesPerSample;
    }

    // Calculate the FFT
    m_fft->calculateFFT(m_output.data(), m_input.data());

    // Analyze output to obtain amplitude and phase for each frequency
    for (int i=2; i<=m_numSamples/2; ++i) {
        // Calculate frequency of this complex sample
        m_spectrum[i].frequency = qreal(i * inputFrequency) / (m_numSamples);

        const qreal real = m_output[i];
        qreal imag = 0.0;
        if (i>0 && i<m_numSamples/2)
            imag = m_output[m_numSamples/2 + i];

        const qreal magnitude = qSqrt(real*real + imag*imag);
        qreal amplitude = SpectrumAnalyserMultiplier * qLn(magnitude);

        // Bound amplitude to [0.0, 1.0]
        m_spectrum[i].clipped = (amplitude > 1.0);
        amplitude = qMax(qreal(0.0), amplitude);
        amplitude = qMin(qreal(1.0), amplitude);
        m_spectrum[i].amplitude = amplitude;
    }
#endif

    emit calculationComplete(m_spectrum);
}

//=============================================================================
// SpectrumAnalyser
//=============================================================================

SpectrumAnalyser::SpectrumAnalyser(QObject *parent)
    :   QObject(parent)
    ,   m_thread(new SpectrumAnalyserThread(this))
    ,   m_state(Idle)
#ifdef DUMP_SPECTRUMANALYSER
    ,   m_count(0)
#endif
{
    CHECKED_CONNECT(m_thread, SIGNAL(calculationComplete(FrequencySpectrum)),
                    this, SLOT(calculationComplete(FrequencySpectrum)));
}

SpectrumAnalyser::~SpectrumAnalyser()
{

}

#ifdef DUMP_SPECTRUMANALYSER
void SpectrumAnalyser::setOutputPath(const QString &outputDir)
{
    m_outputDir.setPath(outputDir);
    m_textFile.setFileName(m_outputDir.filePath("spectrum.txt"));
    m_textFile.open(QIODevice::WriteOnly | QIODevice::Text);
    m_textStream.setDevice(&m_textFile);
}
#endif

//-----------------------------------------------------------------------------
// Public functions
//-----------------------------------------------------------------------------

void SpectrumAnalyser::setWindowFunction(WindowFunction type)
{
    const bool b = QMetaObject::invokeMethod(m_thread, "setWindowFunction",
                              Qt::AutoConnection,
                              Q_ARG(WindowFunction, type));
    Q_ASSERT(b);
    Q_UNUSED(b) // suppress warnings in release builds
}

void SpectrumAnalyser::calculate(const QByteArray &buffer,
                         const QAudioFormat &format)
{
    // QThread::currentThread is marked 'for internal use only', but
    // we're only using it for debug output here, so it's probably OK :)
    SPECTRUMANALYSER_DEBUG << "SpectrumAnalyser::calculate"
                           << QThread::currentThread()
                           << "state" << m_state;

    if (isReady()) {
        Q_ASSERT(isPCMS16LE(format));

        const int bytesPerSample = format.sampleSize() * format.channelCount() / 8;

#ifdef DUMP_SPECTRUMANALYSER
        m_count++;
        const QString pcmFileName = m_outputDir.filePath(QString("spectrum_%1.pcm").arg(m_count, 4, 10, QChar('0')));
        QFile pcmFile(pcmFileName);
        pcmFile.open(QIODevice::WriteOnly);
        const int bufferLength = m_numSamples * bytesPerSample;
        pcmFile.write(buffer, bufferLength);

        m_textStream << "TimeDomain " << m_count << "\n";
        const qint16* input = reinterpret_cast<const qint16*>(buffer);
        for (int i=0; i<m_numSamples; ++i) {
            m_textStream << i << "\t" << *input << "\n";
            input += format.channels();
        }
#endif

        m_state = Busy;

        // Invoke SpectrumAnalyserThread::calculateSpectrum using QMetaObject.  If
        // m_thread is in a different thread from the current thread, the
        // calculation will be done in the child thread.
        // Once the calculation is finished, a calculationChanged signal will be
        // emitted by m_thread.
        const bool b = QMetaObject::invokeMethod(m_thread, "calculateSpectrum",
                                  Qt::AutoConnection,
                                  Q_ARG(QByteArray, buffer),
                                  Q_ARG(int, format.sampleRate()),
                                  Q_ARG(int, bytesPerSample));
        Q_ASSERT(b);
        Q_UNUSED(b) // suppress warnings in release builds

#ifdef DUMP_SPECTRUMANALYSER
        m_textStream << "FrequencySpectrum " << m_count << "\n";
        FrequencySpectrum::const_iterator x = m_spectrum.begin();
        for (int i=0; i<m_numSamples; ++i, ++x)
            m_textStream << i << "\t"
                         << x->frequency << "\t"
                         << x->amplitude<< "\t"
                         << x->phase << "\n";
#endif
    }
}

bool SpectrumAnalyser::isReady() const
{
    return (Idle == m_state);
}

void SpectrumAnalyser::cancelCalculation()
{
    if (Busy == m_state)
        m_state = Cancelled;
}

//-----------------------------------------------------------------------------
// Private slots
//-----------------------------------------------------------------------------

void SpectrumAnalyser::calculationComplete(const FrequencySpectrum &spectrum)
{
    Q_ASSERT(Idle != m_state);
    if (Busy == m_state)
        emit spectrumChanged(spectrum);
    m_state = Idle;
}

© 2016 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.