audiolevelsiodevice.cpp Example File

/**************************************************************************** ** ** Copyright (C) 2016 The Qt Company Ltd. ** Contact: ** ** This file is part of the Qt Data Visualization module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:GPL$ ** 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 For further ** information use the contact form at ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 3 or (at your option) any later version ** approved by the KDE Free Qt Foundation. The licenses are as published by ** the Free Software Foundation and appearing in the file LICENSE.GPL3 ** included in the packaging of this file. Please review the following ** information to ensure the GNU General Public License requirements will ** be met: ** ** $QT_END_LICENSE$ ** ****************************************************************************/
#include "audiolevelsiodevice.h" #include <QtCore/QDebug> using namespace QtDataVisualization; static const int resolution = 8; static const int rowSize = 800; static const int rowCount = 7; // Must be odd number static const int middleRow = rowCount / 2; AudioLevelsIODevice::AudioLevelsIODevice(QBarDataProxy *proxy, QObject *parent) : QIODevice(parent), m_proxy(proxy), m_array(new QBarDataArray) { // We reuse the existing array for maximum performance, so construct the array here m_array->reserve(rowCount); for (int i = 0; i < rowCount; i++) m_array->append(new QBarDataRow(rowSize)); qDebug() << "Total of" << (rowSize * rowCount) << "items in the array."; } // Implementation required for this pure virtual function qint64 AudioLevelsIODevice::readData(char *data, qint64 maxSize) { Q_UNUSED(data) Q_UNUSED(maxSize) return -1; } qint64 AudioLevelsIODevice::writeData(const char *data, qint64 maxSize) { // The amount of new data available. int newDataSize = maxSize / resolution; // If we get more data than array size, we need to adjust the start index for new data. int newDataStartIndex = qMax(0, (newDataSize - rowSize)); // Move the old data ahead in the rows (only do first half of rows + middle one now). // If the amount of new data was larger than row size, skip copying. if (!newDataStartIndex) { for (int i = 0; i <= middleRow; i++) { QBarDataItem *srcPos = m_array->at(i)->data(); QBarDataItem *dstPos = srcPos + newDataSize; memmove((void *)dstPos, (void *)srcPos, (rowSize - newDataSize) * sizeof(QBarDataItem)); } } // Insert data in reverse order, so that newest data is always at the front of the row. int index = 0; for (int i = newDataSize - 1; i >= newDataStartIndex; i--) { // Add 0.01 to the value to avoid gaps in the graph (i.e. zero height bars). // Also, scale to 0...100 float value = float(quint8(data[resolution * i]) - 128) / 1.28f + 0.01f; (*m_array->at(middleRow))[index].setValue(value); // Insert a fractional value into front half of the rows. for (int j = 1; j <= middleRow; j++) { float fractionalValue = value / float(j + 1); (*m_array->at(middleRow - j))[index].setValue(fractionalValue); } index++; } // Copy the front half of rows to the back half for symmetry. index = 0; for (int i = rowCount - 1; i > middleRow; i--) { QBarDataItem *srcPos = m_array->at(index++)->data(); QBarDataItem *dstPos = m_array->at(i)->data(); memcpy((void *)dstPos, (void *)srcPos, rowSize * sizeof(QBarDataItem)); } // Reset the proxy array now that data has been updated to trigger a redraw. m_proxy->resetArray(m_array); return maxSize; }

© 2018 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. 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.