- Qt 5.5
- Qt Multimedia
- Spectrum Example
- waveform.cpp Example File
- Qt 5.5.1 Reference Documentation

# waveform.cpp Example File

spectrum/app/waveform.cpp

    /****************************************************************************
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    ** This file is part of the examples of the Qt Toolkit.
    **
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    #include "waveform.h"
    #include "utils.h"
    #include <QPainter>
    #include <QResizeEvent>
    #include <QDebug>

    //#define PAINT_EVENT_TRACE
    #ifdef PAINT_EVENT_TRACE
    #   define WAVEFORM_PAINT_DEBUG qDebug()
    #else
    #   define WAVEFORM_PAINT_DEBUG nullDebug()
    #endif

    Waveform::Waveform(QWidget *parent)
        :   QWidget(parent)
        ,   m_bufferPosition(0)
        ,   m_bufferLength(0)
        ,   m_audioPosition(0)
        ,   m_active(false)
        ,   m_tileLength(0)
        ,   m_tileArrayStart(0)
        ,   m_windowPosition(0)
        ,   m_windowLength(0)
    {
        setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
        setMinimumHeight(50);
    }

    Waveform::~Waveform()
    {
        deletePixmaps();
    }

    void Waveform::paintEvent(QPaintEvent * /*event*/)
    {
        QPainter painter(this);

        painter.fillRect(rect(), Qt::black);

        if (m_active) {
            WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                 << "windowPosition" << m_windowPosition
                                 << "windowLength" << m_windowLength;
            qint64 pos = m_windowPosition;
            const qint64 windowEnd = m_windowPosition + m_windowLength;
            int destLeft = 0;
            int destRight = 0;
            while (pos < windowEnd) {
                const TilePoint point = tilePoint(pos);
                WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "pos" << pos
                                     << "tileIndex" << point.index
                                     << "positionOffset" << point.positionOffset
                                     << "pixelOffset" << point.pixelOffset;

                if (point.index != NullIndex) {
                    const Tile &tile = m_tiles[point.index];
                    if (tile.painted) {
                        const qint64 sectionLength = qMin((m_tileLength - point.positionOffset),
                                                         (windowEnd - pos));
                        Q_ASSERT(sectionLength > 0);

                        const int sourceRight = tilePixelOffset(point.positionOffset + sectionLength);
                        destRight = windowPixelOffset(pos - m_windowPosition + sectionLength);

                        QRect destRect = rect();
                        destRect.setLeft(destLeft);
                        destRect.setRight(destRight);

                        QRect sourceRect(QPoint(), m_pixmapSize);
                        sourceRect.setLeft(point.pixelOffset);
                        sourceRect.setRight(sourceRight);

                        WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "tileIndex" << point.index
                                             << "source" << point.pixelOffset << sourceRight
                                             << "dest" << destLeft << destRight;

                        painter.drawPixmap(destRect, *tile.pixmap, sourceRect);

                        destLeft = destRight;

                        if (point.index < m_tiles.count()) {
                            pos = tilePosition(point.index + 1);
                            WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "pos ->" << pos;
                        } else {
                            // Reached end of tile array
                            WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "reached end of tile array";
                            break;
                        }
                    } else {
                        // Passed last tile which is painted
                        WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "tile" << point.index << "not painted";
                        break;
                    }
                } else {
                    // pos is past end of tile array
                    WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "pos" << pos << "past end of tile array";
                    break;
                }
            }

            WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "final pos" << pos << "final x" << destRight;
        }
    }

    void Waveform::resizeEvent(QResizeEvent *event)
    {
        if (event->size() != event->oldSize())
            createPixmaps(event->size());
    }

    void Waveform::initialize(const QAudioFormat &format, qint64 audioBufferSize, qint64 windowDurationUs)
    {
        WAVEFORM_DEBUG << "Waveform::initialize"
                       << "audioBufferSize" << audioBufferSize
                       << "windowDurationUs" << windowDurationUs;

        reset();

        m_format = format;

        // Calculate tile size
        m_tileLength = audioBufferSize;

        // Calculate window size
        m_windowLength = audioLength(m_format, windowDurationUs);

        // Calculate number of tiles required
        int nTiles;
        if (m_tileLength > m_windowLength) {
            nTiles = 2;
        } else {
            nTiles = m_windowLength / m_tileLength + 1;
            if (m_windowLength % m_tileLength)
                ++nTiles;
        }

        WAVEFORM_DEBUG << "Waveform::initialize"
                       << "tileLength" << m_tileLength
                       << "windowLength" << m_windowLength
                       << "nTiles" << nTiles;

        m_pixmaps.fill(0, nTiles);
        m_tiles.resize(nTiles);

        createPixmaps(rect().size());

        m_active = true;
    }

    void Waveform::reset()
    {
        WAVEFORM_DEBUG << "Waveform::reset";

        m_bufferPosition = 0;
        m_buffer = QByteArray();
        m_audioPosition = 0;
        m_format = QAudioFormat();
        m_active = false;
        deletePixmaps();
        m_tiles.clear();
        m_tileLength = 0;
        m_tileArrayStart = 0;
        m_windowPosition = 0;
        m_windowLength = 0;
    }

    void Waveform::bufferChanged(qint64 position, qint64 length, const QByteArray &buffer)
    {
        WAVEFORM_DEBUG << "Waveform::bufferChanged"
                       << "audioPosition" << m_audioPosition
                       << "bufferPosition" << position
                       << "bufferLength" << length;
        m_bufferPosition = position;
        m_bufferLength = length;
        m_buffer = buffer;
        paintTiles();
    }

    void Waveform::audioPositionChanged(qint64 position)
    {
        WAVEFORM_DEBUG << "Waveform::audioPositionChanged"
                       << "audioPosition" << position
                       << "bufferPosition" << m_bufferPosition
                       << "bufferLength" << m_bufferLength;

        if (position >= m_bufferPosition) {
            if (position + m_windowLength > m_bufferPosition + m_bufferLength)
                position = qMax(qint64(0), m_bufferPosition + m_bufferLength - m_windowLength);
            m_audioPosition = position;
            setWindowPosition(position);
        }
    }

    void Waveform::deletePixmaps()
    {
        QPixmap *pixmap;
        foreach (pixmap, m_pixmaps)
            delete pixmap;
        m_pixmaps.clear();
    }

    void Waveform::createPixmaps(const QSize &widgetSize)
    {
        m_pixmapSize = widgetSize;
        m_pixmapSize.setWidth(qreal(widgetSize.width()) * m_tileLength / m_windowLength);

        WAVEFORM_DEBUG << "Waveform::createPixmaps"
                       << "widgetSize" << widgetSize
                       << "pixmapSize" << m_pixmapSize;

        Q_ASSERT(m_tiles.count() == m_pixmaps.count());

        // (Re)create pixmaps
        for (int i=0; i<m_pixmaps.size(); ++i) {
            delete m_pixmaps[i];
            m_pixmaps[i] = 0;
            m_pixmaps[i] = new QPixmap(m_pixmapSize);
        }

        // Update tile pixmap pointers, and mark for repainting
        for (int i=0; i<m_tiles.count(); ++i) {
            m_tiles[i].pixmap = m_pixmaps[i];
            m_tiles[i].painted = false;
        }
    }

    void Waveform::setWindowPosition(qint64 position)
    {
        WAVEFORM_DEBUG << "Waveform::setWindowPosition"
                       << "old" << m_windowPosition << "new" << position
                       << "tileArrayStart" << m_tileArrayStart;

        const qint64 oldPosition = m_windowPosition;
        m_windowPosition = position;

        if ((m_windowPosition >= oldPosition) &&
            (m_windowPosition - m_tileArrayStart < (m_tiles.count() * m_tileLength))) {
            // Work out how many tiles need to be shuffled
            const qint64 offset = m_windowPosition - m_tileArrayStart;
            const int nTiles = offset / m_tileLength;
            shuffleTiles(nTiles);
        } else {
            resetTiles(m_windowPosition);
        }

        if (!paintTiles() && m_windowPosition != oldPosition)
            update();
    }

    qint64 Waveform::tilePosition(int index) const
    {
        return m_tileArrayStart + index * m_tileLength;
    }

    Waveform::TilePoint Waveform::tilePoint(qint64 position) const
    {
        TilePoint result;
        if (position >= m_tileArrayStart) {
            const qint64 tileArrayEnd = m_tileArrayStart + m_tiles.count() * m_tileLength;
            if (position < tileArrayEnd) {
                const qint64 offsetIntoTileArray = position - m_tileArrayStart;
                result.index = offsetIntoTileArray / m_tileLength;
                Q_ASSERT(result.index >= 0 && result.index <= m_tiles.count());
                result.positionOffset = offsetIntoTileArray % m_tileLength;
                result.pixelOffset = tilePixelOffset(result.positionOffset);
                Q_ASSERT(result.pixelOffset >= 0 && result.pixelOffset <= m_pixmapSize.width());
            }
        }

        return result;
    }

    int Waveform::tilePixelOffset(qint64 positionOffset) const
    {
        Q_ASSERT(positionOffset >= 0 && positionOffset <= m_tileLength);
        const int result = (qreal(positionOffset) / m_tileLength) * m_pixmapSize.width();
        return result;
    }

    int Waveform::windowPixelOffset(qint64 positionOffset) const
    {
        Q_ASSERT(positionOffset >= 0 && positionOffset <= m_windowLength);
        const int result = (qreal(positionOffset) / m_windowLength) * rect().width();
        return result;
    }

    bool Waveform::paintTiles()
    {
        WAVEFORM_DEBUG << "Waveform::paintTiles";
        bool updateRequired = false;

        for (int i=0; i<m_tiles.count(); ++i) {
            const Tile &tile = m_tiles[i];
            if (!tile.painted) {
                const qint64 tileStart = m_tileArrayStart + i * m_tileLength;
                const qint64 tileEnd = tileStart + m_tileLength;
                if (m_bufferPosition <= tileStart && m_bufferPosition + m_bufferLength >= tileEnd) {
                    paintTile(i);
                    updateRequired = true;
                }
            }
        }

        if (updateRequired)
            update();

        return updateRequired;
    }

    void Waveform::paintTile(int index)
    {
        const qint64 tileStart = m_tileArrayStart + index * m_tileLength;

        WAVEFORM_DEBUG << "Waveform::paintTile"
                       << "index" << index
                       << "bufferPosition" << m_bufferPosition
                       << "bufferLength" << m_bufferLength
                       << "start" << tileStart
                       << "end" << tileStart + m_tileLength;

        Q_ASSERT(m_bufferPosition <= tileStart);
        Q_ASSERT(m_bufferPosition + m_bufferLength >= tileStart + m_tileLength);

        Tile &tile = m_tiles[index];
        Q_ASSERT(!tile.painted);

        const qint16* base = reinterpret_cast<const qint16*>(m_buffer.constData());
        const qint16* buffer = base + ((tileStart - m_bufferPosition) / 2);
        const int numSamples = m_tileLength / (2 * m_format.channelCount());

        QPainter painter(tile.pixmap);

        painter.fillRect(tile.pixmap->rect(), Qt::black);

        QPen pen(Qt::white);
        painter.setPen(pen);

        // Calculate initial PCM value
        qint16 previousPcmValue = 0;
        if (buffer > base)
            previousPcmValue = *(buffer - m_format.channelCount());

        // Calculate initial point
        const qreal previousRealValue = pcmToReal(previousPcmValue);
        const int originY = ((previousRealValue + 1.0) / 2) * m_pixmapSize.height();
        const QPoint origin(0, originY);

        QLine line(origin, origin);

        for (int i=0; i<numSamples; ++i) {
            const qint16* ptr = buffer + i * m_format.channelCount();

            const int offset = reinterpret_cast<const char*>(ptr) - m_buffer.constData();
            Q_ASSERT(offset >= 0);
            Q_ASSERT(offset < m_bufferLength);
            Q_UNUSED(offset);

            const qint16 pcmValue = *ptr;
            const qreal realValue = pcmToReal(pcmValue);

            const int x = tilePixelOffset(i * 2 * m_format.channelCount());
            const int y = ((realValue + 1.0) / 2) * m_pixmapSize.height();

            line.setP2(QPoint(x, y));
            painter.drawLine(line);
            line.setP1(line.p2());
        }

        tile.painted = true;
    }

    void Waveform::shuffleTiles(int n)
    {
        WAVEFORM_DEBUG << "Waveform::shuffleTiles" << "n" << n;

        while (n--) {
            Tile tile = m_tiles.first();
            tile.painted = false;
            m_tiles.erase(m_tiles.begin());
            m_tiles += tile;
            m_tileArrayStart += m_tileLength;
        }

        WAVEFORM_DEBUG << "Waveform::shuffleTiles" << "tileArrayStart" << m_tileArrayStart;
    }

    void Waveform::resetTiles(qint64 newStartPos)
    {
        WAVEFORM_DEBUG << "Waveform::resetTiles" << "newStartPos" << newStartPos;

        QVector<Tile>::iterator i = m_tiles.begin();
        for ( ; i != m_tiles.end(); ++i)
            i->painted = false;

        m_tileArrayStart = newStartPos;
    }