Qt Reference Documentation

# spectrum.h Example File

demos/spectrum/app/spectrum.h

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     #ifndef SPECTRUM_H
     #define SPECTRUM_H

     #include <QtCore/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