Qt 5.9 | Qt Multimedia | Spectrum Example | levelmeter.h Example File

Qt 5.9.9 Reference Documentation

# levelmeter.h Example File

multimedia/spectrum/app/levelmeter.h

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      #ifndef LEVELMETER_H
      #define LEVELMETER_H

      #include <QTime>
      #include <QWidget>

      /**
       * Widget which displays a vertical audio level meter, indicating the
       * RMS and peak levels of the window of audio samples most recently analyzed
       * by the Engine.
       */
      class LevelMeter : public QWidget
      {
          Q_OBJECT

      public:
          explicit LevelMeter(QWidget *parent = 0);
          ~LevelMeter();

          void paintEvent(QPaintEvent *event) override;

      public slots:
          void reset();
          void levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples);

      private slots:
          void redrawTimerExpired();

      private:
          /**
           * Height of RMS level bar.
           * Range 0.0 - 1.0.
           */
          qreal m_rmsLevel;

          /**
           * Most recent peak level.
           * Range 0.0 - 1.0.
           */
          qreal m_peakLevel;

          /**
           * Height of peak level bar.
           * This is calculated by decaying m_peakLevel depending on the
           * elapsed time since m_peakLevelChanged, and the value of m_decayRate.
           */
          qreal m_decayedPeakLevel;

          /**
           * Time at which m_peakLevel was last changed.
           */
          QTime m_peakLevelChanged;

          /**
           * Rate at which peak level bar decays.
           * Expressed in level units / millisecond.
           */
          qreal m_peakDecayRate;

          /**
           * High watermark of peak level.
           * Range 0.0 - 1.0.
           */
          qreal m_peakHoldLevel;

          /**
           * Time at which m_peakHoldLevel was last changed.
           */
          QTime m_peakHoldLevelChanged;

          QTimer *m_redrawTimer;

          QColor m_rmsColor;
          QColor m_peakColor;

      };

      #endif // LEVELMETER_H