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    41 

    42 #include "levelmeter.h"

    43 

    44 #include <math.h>

    45 

    46 #include <QPainter>

    47 #include <QTimer>

    48 #include <QDebug>

    49 

    50 

    51 // Constants

    52 const int RedrawInterval = 100; // ms

    53 const qreal PeakDecayRate = 0.001;

    54 const int PeakHoldLevelDuration = 2000; // ms

    55 

    56 

    57 LevelMeter::LevelMeter(QWidget *parent)

    58     :   QWidget(parent)

    59     ,   m_rmsLevel(0.0)

    60     ,   m_peakLevel(0.0)

    61     ,   m_decayedPeakLevel(0.0)

    62     ,   m_peakDecayRate(PeakDecayRate)

    63     ,   m_peakHoldLevel(0.0)

    64     ,   m_redrawTimer(new QTimer(this))

    65     ,   m_rmsColor(Qt::red)

    66     ,   m_peakColor(255, 200, 200, 255)

    67 {

    68     setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Preferred);

    69     setMinimumWidth(30);

    70 

    71     connect(m_redrawTimer, SIGNAL(timeout()), this, SLOT(redrawTimerExpired()));

    72     m_redrawTimer->start(RedrawInterval);

    73 }

    74 

    75 LevelMeter::~LevelMeter()

    76 {

    77 

    78 }

    79 

    80 void LevelMeter::reset()

    81 {

    82     m_rmsLevel = 0.0;

    83     m_peakLevel = 0.0;

    84     update();

    85 }

    86 

    87 void LevelMeter::levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples)

    88 {

    89     // Smooth the RMS signal

    90     const qreal smooth = pow(qreal(0.9), static_cast<qreal>(numSamples) / 256); // TODO: remove this magic number

    91     m_rmsLevel = (m_rmsLevel * smooth) + (rmsLevel * (1.0 - smooth));

    92 

    93     if (peakLevel > m_decayedPeakLevel) {

    94         m_peakLevel = peakLevel;

    95         m_decayedPeakLevel = peakLevel;

    96         m_peakLevelChanged.start();

    97     }

    98 

    99     if (peakLevel > m_peakHoldLevel) {

   100         m_peakHoldLevel = peakLevel;

   101         m_peakHoldLevelChanged.start();

   102     }

   103 

   104     update();

   105 }

   106 

   107 void LevelMeter::redrawTimerExpired()

   108 {

   109     // Decay the peak signal

   110     const int elapsedMs = m_peakLevelChanged.elapsed();

   111     const qreal decayAmount = m_peakDecayRate * elapsedMs;

   112     if (decayAmount < m_peakLevel)

   113         m_decayedPeakLevel = m_peakLevel - decayAmount;

   114     else

   115         m_decayedPeakLevel = 0.0;

   116 

   117     // Check whether to clear the peak hold level

   118     if (m_peakHoldLevelChanged.elapsed() > PeakHoldLevelDuration)

   119         m_peakHoldLevel = 0.0;

   120 

   121     update();

   122 }

   123 

   124 void LevelMeter::paintEvent(QPaintEvent *event)

   125 {

   126     Q_UNUSED(event)

   127 

   128     QPainter painter(this);

   129     painter.fillRect(rect(), Qt::black);

   130 

   131     QRect bar = rect();

   132 

   133     bar.setTop(rect().top() + (1.0 - m_peakHoldLevel) * rect().height());

   134     bar.setBottom(bar.top() + 5);

   135     painter.fillRect(bar, m_rmsColor);

   136     bar.setBottom(rect().bottom());

   137 

   138     bar.setTop(rect().top() + (1.0 - m_decayedPeakLevel) * rect().height());

   139     painter.fillRect(bar, m_peakColor);

   140 

   141     bar.setTop(rect().top() + (1.0 - m_rmsLevel) * rect().height());

   142     painter.fillRect(bar, m_rmsColor);

   143 }