<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>levelmeter.cpp Example File | Qt Multimedia 5.9</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.9</td><td ><a href="qtmultimedia-index.html">Qt Multimedia</a></td><td ><a href="qtmultimedia-multimedia-spectrum-example.html">Spectrum Example</a></td><td >levelmeter.cpp Example File</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"><div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">levelmeter.cpp Example File</h1> <span class="subtitle">multimedia/spectrum/app/levelmeter.cpp</span> <!-- $$$multimedia/spectrum/app/levelmeter.cpp-description --> <div class="descr"> <a name="details"></a> <pre class="cpp"> <span class="comment">/**************************************************************************** ** ** Copyright (C) 2017 The Qt Company Ltd. ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the examples of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:BSD$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and The Qt Company. For licensing terms ** and conditions see https://www.qt.io/terms-conditions. For further ** information use the contact form at https://www.qt.io/contact-us. ** ** BSD License Usage ** Alternatively, 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 The Qt Company Ltd 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." ** ** $QT_END_LICENSE$ ** ****************************************************************************/</span> <span class="preprocessor">#include "levelmeter.h"</span> <span class="preprocessor">#include <math.h></span> <span class="preprocessor">#include <QPainter></span> <span class="preprocessor">#include <QTimer></span> <span class="preprocessor">#include <QDebug></span> <span class="comment">// Constants</span> <span class="keyword">const</span> <span class="type">int</span> RedrawInterval <span class="operator">=</span> <span class="number">100</span>; <span class="comment">// ms</span> <span class="keyword">const</span> <span class="type">qreal</span> PeakDecayRate <span class="operator">=</span> <span class="number">0.001</span>; <span class="keyword">const</span> <span class="type">int</span> PeakHoldLevelDuration <span class="operator">=</span> <span class="number">2000</span>; <span class="comment">// ms</span> LevelMeter<span class="operator">::</span>LevelMeter(<span class="type">QWidget</span> <span class="operator">*</span>parent) : <span class="type">QWidget</span>(parent) <span class="operator">,</span> m_rmsLevel(<span class="number">0.0</span>) <span class="operator">,</span> m_peakLevel(<span class="number">0.0</span>) <span class="operator">,</span> m_decayedPeakLevel(<span class="number">0.0</span>) <span class="operator">,</span> m_peakDecayRate(PeakDecayRate) <span class="operator">,</span> m_peakHoldLevel(<span class="number">0.0</span>) <span class="operator">,</span> m_redrawTimer(<span class="keyword">new</span> <span class="type">QTimer</span>(<span class="keyword">this</span>)) <span class="operator">,</span> m_rmsColor(<span class="type">Qt</span><span class="operator">::</span>red) <span class="operator">,</span> m_peakColor(<span class="number">255</span><span class="operator">,</span> <span class="number">200</span><span class="operator">,</span> <span class="number">200</span><span class="operator">,</span> <span class="number">255</span>) { setSizePolicy(<span class="type">QSizePolicy</span><span class="operator">::</span>Fixed<span class="operator">,</span> <span class="type">QSizePolicy</span><span class="operator">::</span>Preferred); setMinimumWidth(<span class="number">30</span>); connect(m_redrawTimer<span class="operator">,</span> SIGNAL(timeout())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(redrawTimerExpired())); m_redrawTimer<span class="operator">-</span><span class="operator">></span>start(RedrawInterval); } LevelMeter<span class="operator">::</span><span class="operator">~</span>LevelMeter() { } <span class="type">void</span> LevelMeter<span class="operator">::</span>reset() { m_rmsLevel <span class="operator">=</span> <span class="number">0.0</span>; m_peakLevel <span class="operator">=</span> <span class="number">0.0</span>; update(); } <span class="type">void</span> LevelMeter<span class="operator">::</span>levelChanged(<span class="type">qreal</span> rmsLevel<span class="operator">,</span> <span class="type">qreal</span> peakLevel<span class="operator">,</span> <span class="type">int</span> numSamples) { <span class="comment">// Smooth the RMS signal</span> <span class="keyword">const</span> <span class="type">qreal</span> smooth <span class="operator">=</span> pow(<span class="type">qreal</span>(<span class="number">0.9</span>)<span class="operator">,</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type">qreal</span><span class="operator">></span>(numSamples) <span class="operator">/</span> <span class="number">256</span>); <span class="comment">// TODO: remove this magic number</span> m_rmsLevel <span class="operator">=</span> (m_rmsLevel <span class="operator">*</span> smooth) <span class="operator">+</span> (rmsLevel <span class="operator">*</span> (<span class="number">1.0</span> <span class="operator">-</span> smooth)); <span class="keyword">if</span> (peakLevel <span class="operator">></span> m_decayedPeakLevel) { m_peakLevel <span class="operator">=</span> peakLevel; m_decayedPeakLevel <span class="operator">=</span> peakLevel; m_peakLevelChanged<span class="operator">.</span>start(); } <span class="keyword">if</span> (peakLevel <span class="operator">></span> m_peakHoldLevel) { m_peakHoldLevel <span class="operator">=</span> peakLevel; m_peakHoldLevelChanged<span class="operator">.</span>start(); } update(); } <span class="type">void</span> LevelMeter<span class="operator">::</span>redrawTimerExpired() { <span class="comment">// Decay the peak signal</span> <span class="keyword">const</span> <span class="type">int</span> elapsedMs <span class="operator">=</span> m_peakLevelChanged<span class="operator">.</span>elapsed(); <span class="keyword">const</span> <span class="type">qreal</span> decayAmount <span class="operator">=</span> m_peakDecayRate <span class="operator">*</span> elapsedMs; <span class="keyword">if</span> (decayAmount <span class="operator"><</span> m_peakLevel) m_decayedPeakLevel <span class="operator">=</span> m_peakLevel <span class="operator">-</span> decayAmount; <span class="keyword">else</span> m_decayedPeakLevel <span class="operator">=</span> <span class="number">0.0</span>; <span class="comment">// Check whether to clear the peak hold level</span> <span class="keyword">if</span> (m_peakHoldLevelChanged<span class="operator">.</span>elapsed() <span class="operator">></span> PeakHoldLevelDuration) m_peakHoldLevel <span class="operator">=</span> <span class="number">0.0</span>; update(); } <span class="type">void</span> LevelMeter<span class="operator">::</span>paintEvent(<span class="type">QPaintEvent</span> <span class="operator">*</span>event) { Q_UNUSED(event) <span class="type">QPainter</span> painter(<span class="keyword">this</span>); painter<span class="operator">.</span>fillRect(rect()<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>black); <span class="type">QRect</span> bar <span class="operator">=</span> rect(); bar<span class="operator">.</span>setTop(rect()<span class="operator">.</span>top() <span class="operator">+</span> (<span class="number">1.0</span> <span class="operator">-</span> m_peakHoldLevel) <span class="operator">*</span> rect()<span class="operator">.</span>height()); bar<span class="operator">.</span>setBottom(bar<span class="operator">.</span>top() <span class="operator">+</span> <span class="number">5</span>); painter<span class="operator">.</span>fillRect(bar<span class="operator">,</span> m_rmsColor); bar<span class="operator">.</span>setBottom(rect()<span class="operator">.</span>bottom()); bar<span class="operator">.</span>setTop(rect()<span class="operator">.</span>top() <span class="operator">+</span> (<span class="number">1.0</span> <span class="operator">-</span> m_decayedPeakLevel) <span class="operator">*</span> rect()<span class="operator">.</span>height()); painter<span class="operator">.</span>fillRect(bar<span class="operator">,</span> m_peakColor); bar<span class="operator">.</span>setTop(rect()<span class="operator">.</span>top() <span class="operator">+</span> (<span class="number">1.0</span> <span class="operator">-</span> m_rmsLevel) <span class="operator">*</span> rect()<span class="operator">.</span>height()); painter<span class="operator">.</span>fillRect(bar<span class="operator">,</span> m_rmsColor); } </pre> </div> <!-- @@@multimedia/spectrum/app/levelmeter.cpp --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2017 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>