Qt 5.7 | Qt Multimedia | Spectrum Example | spectrum.h Example File

Qt 5.7.1 Reference Documentation

# spectrum.h Example File

multimedia/spectrum/app/spectrum.h

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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