audiolevelsiodevice.cpp Example File

audiolevels/audiolevelsiodevice.cpp
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#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; }