--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/demos/spectrum/app/levelmeter.cpp	Fri Jun 11 14:24:45 2010 +0300
@@ -0,0 +1,143 @@
+/****************************************************************************
+**
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#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);
+}