engine.h Example File

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 #ifndef ENGINE_H
 #define ENGINE_H

 #include "spectrum.h"
 #include "spectrumanalyser.h"
 #include "wavfile.h"

 #include <QObject>
 #include <QByteArray>
 #include <QBuffer>
 #include <QVector>
 #include <QtMultimedia/QAudioDeviceInfo>
 #include <QtMultimedia/QAudioFormat>

 #ifdef DUMP_CAPTURED_AUDIO
 #define DUMP_DATA
 #endif

 #ifdef DUMP_SPECTRUM
 #define DUMP_DATA
 #endif

 #ifdef DUMP_DATA
 #include <QDir>
 #endif

 class FrequencySpectrum;
 QT_FORWARD_DECLARE_CLASS(QAudioInput)
 QT_FORWARD_DECLARE_CLASS(QAudioOutput)
 QT_FORWARD_DECLARE_CLASS(QFile)

 /**
  * This class interfaces with the QtMultimedia audio classes, and also with
  * the SpectrumAnalyser class.  Its role is to manage the capture and playback
  * of audio data, meanwhile performing real-time analysis of the audio level
  * and frequency spectrum.
  */
 class Engine : public QObject {
     Q_OBJECT
 public:
     Engine(QObject *parent = 0);
     ~Engine();

     const QList<QAudioDeviceInfo>& availableAudioInputDevices() const
                                     { return m_availableAudioInputDevices; }

     const QList<QAudioDeviceInfo>& availableAudioOutputDevices() const
                                     { return m_availableAudioOutputDevices; }

     QAudio::Mode mode() const       { return m_mode; }
     QAudio::State state() const     { return m_state; }

     /**
      * \return Current audio format
      * \note May be QAudioFormat() if engine is not initialized
      */
     const QAudioFormat& format() const  { return m_format; }

     /**
      * Stop any ongoing recording or playback, and reset to ground state.
      */
     void reset();

     /**
      * Load data from WAV file
      */
     bool loadFile(const QString &fileName);

     /**
      * Generate tone
      */
     bool generateTone(const Tone &tone);

     /**
      * Generate tone
      */
     bool generateSweptTone(qreal amplitude);

     /**
      * Initialize for recording
      */
     bool initializeRecord();

     /**
      * Position of the audio input device.
      * \return Position in bytes.
      */
     qint64 recordPosition() const   { return m_recordPosition; }

     /**
      * RMS level of the most recently processed set of audio samples.
      * \return Level in range (0.0, 1.0)
      */
     qreal rmsLevel() const          { return m_rmsLevel; }

     /**
      * Peak level of the most recently processed set of audio samples.
      * \return Level in range (0.0, 1.0)
      */
     qreal peakLevel() const         { return m_peakLevel; }

     /**
      * Position of the audio output device.
      * \return Position in bytes.
      */
     qint64 playPosition() const     { return m_playPosition; }

     /**
      * Length of the internal engine buffer.
      * \return Buffer length in bytes.
      */
     qint64 bufferLength() const;

     /**
      * Amount of data held in the buffer.
      * \return Data length in bytes.
      */
     qint64 dataLength() const       { return m_dataLength; }

     /**
      * Set window function applied to audio data before spectral analysis.
      */
     void setWindowFunction(WindowFunction type);

 public slots:
     void startRecording();
     void startPlayback();
     void suspend();
     void setAudioInputDevice(const QAudioDeviceInfo &device);
     void setAudioOutputDevice(const QAudioDeviceInfo &device);

 signals:
     void stateChanged(QAudio::Mode mode, QAudio::State state);

     /**
      * Informational message for non-modal display
      */
     void infoMessage(const QString &message, int durationMs);

     /**
      * Error message for modal display
      */
     void errorMessage(const QString &heading, const QString &detail);

     /**
      * Format of audio data has changed
      */
     void formatChanged(const QAudioFormat &format);

     /**
      * Length of buffer has changed.
      * \param duration Duration in microseconds
      */
     void bufferLengthChanged(qint64 duration);

     /**
      * Amount of data in buffer has changed.
      * \param Length of data in bytes
      */
     void dataLengthChanged(qint64 duration);

     /**
      * Position of the audio input device has changed.
      * \param position Position in bytes
      */
     void recordPositionChanged(qint64 position);

     /**
      * Position of the audio output device has changed.
      * \param position Position in bytes
      */
     void playPositionChanged(qint64 position);

     /**
      * Level changed
      * \param rmsLevel RMS level in range 0.0 - 1.0
      * \param peakLevel Peak level in range 0.0 - 1.0
      * \param numSamples Number of audio samples analyzed
      */
     void levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples);

     /**
      * Spectrum has changed.
      * \param position Position of start of window in bytes
      * \param length   Length of window in bytes
      * \param spectrum Resulting frequency spectrum
      */
     void spectrumChanged(qint64 position, qint64 length, const FrequencySpectrum &spectrum);

     /**
      * Buffer containing audio data has changed.
      * \param position Position of start of buffer in bytes
      * \param buffer   Buffer
      */
     void bufferChanged(qint64 position, qint64 length, const QByteArray &buffer);

 private slots:
     void audioNotify();
     void audioStateChanged(QAudio::State state);
     void audioDataReady();
     void spectrumChanged(const FrequencySpectrum &spectrum);

 private:
     void resetAudioDevices();
     bool initialize();
     bool selectFormat();
     void stopRecording();
     void stopPlayback();
     void setState(QAudio::State state);
     void setState(QAudio::Mode mode, QAudio::State state);
     void setFormat(const QAudioFormat &format);
     void setRecordPosition(qint64 position, bool forceEmit = false);
     void setPlayPosition(qint64 position, bool forceEmit = false);
     void calculateLevel(qint64 position, qint64 length);
     void calculateSpectrum(qint64 position);
     void setLevel(qreal rmsLevel, qreal peakLevel, int numSamples);

 #ifdef DUMP_DATA
     void createOutputDir();
     QString outputPath() const { return m_outputDir.path(); }
 #endif

 #ifdef DUMP_CAPTURED_AUDIO
     void dumpData();
 #endif

 private:
     QAudio::Mode        m_mode;
     QAudio::State       m_state;

     bool                m_generateTone;
     SweptTone           m_tone;

     WavFile*            m_file;
     // We need a second file handle via which to read data into m_buffer
     // for analysis
     WavFile*            m_analysisFile;

     QAudioFormat        m_format;

     const QList<QAudioDeviceInfo> m_availableAudioInputDevices;
     QAudioDeviceInfo    m_audioInputDevice;
     QAudioInput*        m_audioInput;
     QIODevice*          m_audioInputIODevice;
     qint64              m_recordPosition;

     const QList<QAudioDeviceInfo> m_availableAudioOutputDevices;
     QAudioDeviceInfo    m_audioOutputDevice;
     QAudioOutput*       m_audioOutput;
     qint64              m_playPosition;
     QBuffer             m_audioOutputIODevice;

     QByteArray          m_buffer;
     qint64              m_bufferPosition;
     qint64              m_bufferLength;
     qint64              m_dataLength;

     int                 m_levelBufferLength;
     qreal               m_rmsLevel;
     qreal               m_peakLevel;

     int                 m_spectrumBufferLength;
     QByteArray          m_spectrumBuffer;
     SpectrumAnalyser    m_spectrumAnalyser;
     qint64              m_spectrumPosition;

     int                 m_count;

 #ifdef DUMP_DATA
     QDir                m_outputDir;
 #endif

 };

 #endif // ENGINE_H