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

# spectrum.h Example File

spectrum/app/spectrum.h

    /****************************************************************************
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    ** This file is part of the examples of the Qt Toolkit.
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    #ifndef SPECTRUM_H
    #define SPECTRUM_H

    #include <qglobal.h>
    #include "utils.h"
    #include "fftreal_wrapper.h" // For FFTLengthPowerOfTwo

    //-----------------------------------------------------------------------------
    // Constants
    //-----------------------------------------------------------------------------

    // Number of audio samples used to calculate the frequency spectrum
    const int    SpectrumLengthSamples  = PowerOfTwo<FFTLengthPowerOfTwo>::Result;

    // Number of bands in the frequency spectrum
    const int    SpectrumNumBands       = 10;

    // Lower bound of first band in the spectrum
    const qreal  SpectrumLowFreq        = 0.0; // Hz

    // Upper band of last band in the spectrum
    const qreal  SpectrumHighFreq       = 1000.0; // Hz

    // Waveform window size in microseconds
    const qint64 WaveformWindowDuration = 500 * 1000;

    // Length of waveform tiles in bytes
    // Ideally, these would match the QAudio*::bufferSize(), but that isn't
    // available until some time after QAudio*::start() has been called, and we
    // need this value in order to initialize the waveform display.
    // We therefore just choose a sensible value.
    const int   WaveformTileLength      = 4096;

    // Fudge factor used to calculate the spectrum bar heights
    const qreal SpectrumAnalyserMultiplier = 0.15;

    // Disable message timeout
    const int   NullMessageTimeout      = -1;

    //-----------------------------------------------------------------------------
    // Types and data structures
    //-----------------------------------------------------------------------------

    enum WindowFunction {
        NoWindow,
        HannWindow
    };

    const WindowFunction DefaultWindowFunction = HannWindow;

    struct Tone
    {
        Tone(qreal freq = 0.0, qreal amp = 0.0)
        :   frequency(freq), amplitude(amp)
        { }

        // Start and end frequencies for swept tone generation
        qreal   frequency;

        // Amplitude in range [0.0, 1.0]
        qreal   amplitude;
    };

    struct SweptTone
    {
        SweptTone(qreal start = 0.0, qreal end = 0.0, qreal amp = 0.0)
        :   startFreq(start), endFreq(end), amplitude(amp)
        { Q_ASSERT(end >= start); }

        SweptTone(const Tone &tone)
        :   startFreq(tone.frequency), endFreq(tone.frequency), amplitude(tone.amplitude)
        { }

        // Start and end frequencies for swept tone generation
        qreal   startFreq;
        qreal   endFreq;

        // Amplitude in range [0.0, 1.0]
        qreal   amplitude;
    };

    //-----------------------------------------------------------------------------
    // Macros
    //-----------------------------------------------------------------------------

    // Macro which connects a signal to a slot, and which causes application to
    // abort if the connection fails.  This is intended to catch programming errors
    // such as mis-typing a signal or slot name.  It is necessary to write our own
    // macro to do this - the following idiom
    //     Q_ASSERT(connect(source, signal, receiver, slot));
    // will not work because Q_ASSERT compiles to a no-op in release builds.

    #define CHECKED_CONNECT(source, signal, receiver, slot) \
        if (!connect(source, signal, receiver, slot)) \
            qt_assert_x(Q_FUNC_INFO, "CHECKED_CONNECT failed", __FILE__, __LINE__);

    // Handle some dependencies between macros defined in the .pro file

    #ifdef DISABLE_WAVEFORM
    #undef SUPERIMPOSE_PROGRESS_ON_WAVEFORM
    #endif

    #endif // SPECTRUM_H