spectrumanalyser.cpp Example File

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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;
  }