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() 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 = 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;
     }