Qt 5.6 | Qt Multimedia | Spectrum Example | spectrumanalyser.cpp Example File

Qt 5.6.2 Reference Documentation

# spectrumanalyser.cpp Example File

multimedia/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;
      }