levelmeter.cpp Example File

multimedia/spectrum/app/levelmeter.cpp
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#include "levelmeter.h" #include <math.h> #include <QPainter> #include <QTimer> #include <QDebug> // Constants const int RedrawInterval = 100; // ms const qreal PeakDecayRate = 0.001; const int PeakHoldLevelDuration = 2000; // ms LevelMeter::LevelMeter(QWidget *parent) : QWidget(parent) , m_rmsLevel(0.0) , m_peakLevel(0.0) , m_decayedPeakLevel(0.0) , m_peakDecayRate(PeakDecayRate) , m_peakHoldLevel(0.0) , m_redrawTimer(new QTimer(this)) , m_rmsColor(Qt::red) , m_peakColor(255, 200, 200, 255) { setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Preferred); setMinimumWidth(30); connect(m_redrawTimer, &QTimer::timeout, this, &LevelMeter::redrawTimerExpired); m_redrawTimer->start(RedrawInterval); } LevelMeter::~LevelMeter() { } void LevelMeter::reset() { m_rmsLevel = 0.0; m_peakLevel = 0.0; update(); } void LevelMeter::levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples) { // Smooth the RMS signal const qreal smooth = pow(qreal(0.9), static_cast<qreal>(numSamples) / 256); // TODO: remove this magic number m_rmsLevel = (m_rmsLevel * smooth) + (rmsLevel * (1.0 - smooth)); if (peakLevel > m_decayedPeakLevel) { m_peakLevel = peakLevel; m_decayedPeakLevel = peakLevel; m_peakLevelChanged.start(); } if (peakLevel > m_peakHoldLevel) { m_peakHoldLevel = peakLevel; m_peakHoldLevelChanged.start(); } update(); } void LevelMeter::redrawTimerExpired() { // Decay the peak signal const int elapsedMs = m_peakLevelChanged.elapsed(); const qreal decayAmount = m_peakDecayRate * elapsedMs; if (decayAmount < m_peakLevel) m_decayedPeakLevel = m_peakLevel - decayAmount; else m_decayedPeakLevel = 0.0; // Check whether to clear the peak hold level if (m_peakHoldLevelChanged.elapsed() > PeakHoldLevelDuration) m_peakHoldLevel = 0.0; update(); } void LevelMeter::paintEvent(QPaintEvent *event) { Q_UNUSED(event) QPainter painter(this); painter.fillRect(rect(), Qt::black); QRect bar = rect(); bar.setTop(rect().top() + (1.0 - m_peakHoldLevel) * rect().height()); bar.setBottom(bar.top() + 5); painter.fillRect(bar, m_rmsColor); bar.setBottom(rect().bottom()); bar.setTop(rect().top() + (1.0 - m_decayedPeakLevel) * rect().height()); painter.fillRect(bar, m_peakColor); bar.setTop(rect().top() + (1.0 - m_rmsLevel) * rect().height()); painter.fillRect(bar, m_rmsColor); }