Qt Reference Documentation

spectrumanalyser.cpp Example File

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

 #include <QtCore/qmath.h>
 #include <QtCore/qmetatype.h>
 #include <QtMultimedia/QAudioFormat>
 #include <QThread>

 #include "fftreal_wrapper.h"

 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(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());

     // Analyse 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 = sqrt(real*real + imag*imag);
         qreal amplitude = SpectrumAnalyserMultiplier * log(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.channels() / 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.frequency()),
                                   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;
 }
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