- Qt 5.5
- Qt Multimedia
- Spectrum Example
- spectrumanalyser.h Example File
- Qt 5.5.1 Reference Documentation

# spectrumanalyser.h Example File

spectrum/app/spectrumanalyser.h

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
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    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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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