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+/****************************************************************************
+**
+** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+** * Redistributions of source code must retain the above copyright
+** notice, this list of conditions and the following disclaimer.
+** * Redistributions in binary form must reproduce the above copyright
+** notice, this list of conditions and the following disclaimer in
+** the documentation and/or other materials provided with the
+** distribution.
+** * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
+** of its contributors may be used to endorse or promote products derived
+** from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#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, SIGNAL(timeout()), this, SLOT(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);
+}