Qt 5.9 | Qt Multimedia | Spectrum Example | spectrumanalyser.h Example File

Qt 5.9.4 Reference Documentation

# spectrumanalyser.h Example File

multimedia/spectrum/app/spectrumanalyser.h

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      #ifndef SPECTRUMANALYSER_H
      #define SPECTRUMANALYSER_H

      #include <QByteArray>
      #include <QObject>
      #include <QVector>

      #ifdef DUMP_SPECTRUMANALYSER
      #include <QDir>
      #include <QFile>
      #include <QTextStream>
      #endif

      #include "frequencyspectrum.h"
      #include "spectrum.h"

      #ifndef DISABLE_FFT
      #include "FFTRealFixLenParam.h"
      #endif

      QT_FORWARD_DECLARE_CLASS(QAudioFormat)
      QT_FORWARD_DECLARE_CLASS(QThread)

      class FFTRealWrapper;

      class SpectrumAnalyserThreadPrivate;

      /**
       * Implementation of the spectrum analysis which can be run in a
       * separate thread.
       */
      class SpectrumAnalyserThread : public QObject
      {
          Q_OBJECT

      public:
          SpectrumAnalyserThread(QObject *parent);
          ~SpectrumAnalyserThread();

      public slots:
          void setWindowFunction(WindowFunction type);
          void calculateSpectrum(const QByteArray &buffer,
                                 int inputFrequency,
                                 int bytesPerSample);

      signals:
          void calculationComplete(const FrequencySpectrum &spectrum);

      private:
          void calculateWindow();

      private:
      #ifndef DISABLE_FFT
          FFTRealWrapper*                             m_fft;
      #endif

          const int                                   m_numSamples;

          WindowFunction                              m_windowFunction;

      #ifdef DISABLE_FFT
          typedef qreal                               DataType;
      #else
          typedef FFTRealFixLenParam::DataType        DataType;
      #endif
          QVector<DataType>                           m_window;

          QVector<DataType>                           m_input;
          QVector<DataType>                           m_output;

          FrequencySpectrum                           m_spectrum;

      #ifdef SPECTRUM_ANALYSER_SEPARATE_THREAD
          QThread*                                    m_thread;
      #endif
      };

      /**
       * Class which performs frequency spectrum analysis on a window of
       * audio samples, provided to it by the Engine.
       */
      class SpectrumAnalyser : public QObject
      {
          Q_OBJECT

      public:
          SpectrumAnalyser(QObject *parent = 0);
          ~SpectrumAnalyser();

      #ifdef DUMP_SPECTRUMANALYSER
          void setOutputPath(const QString &outputPath);
      #endif

      public:
          /*
           * Set the windowing function which is applied before calculating the FFT
           */
          void setWindowFunction(WindowFunction type);

          /*
           * Calculate a frequency spectrum
           *
           * \param buffer       Audio data
           * \param format       Format of audio data
           *
           * Frequency spectrum is calculated asynchronously.  The result is returned
           * via the spectrumChanged signal.
           *
           * An ongoing calculation can be cancelled by calling cancelCalculation().
           *
           */
          void calculate(const QByteArray &buffer, const QAudioFormat &format);

          /*
           * Check whether the object is ready to perform another calculation
           */
          bool isReady() const;

          /*
           * Cancel an ongoing calculation
           *
           * Note that cancelling is asynchronous.
           */
          void cancelCalculation();

      signals:
          void spectrumChanged(const FrequencySpectrum &spectrum);

      private slots:
          void calculationComplete(const FrequencySpectrum &spectrum);

      private:
          void calculateWindow();

      private:

          SpectrumAnalyserThread*    m_thread;

          enum State {
              Idle,
              Busy,
              Cancelled
          };

          State              m_state;

      #ifdef DUMP_SPECTRUMANALYSER
          QDir                m_outputDir;
          int                 m_count;
          QFile               m_textFile;
          QTextStream         m_textStream;
      #endif
      };

      #endif // SPECTRUMANALYSER_H