Qt Reference Documentation

# spectrumanalyser.h Example File

demos/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