QtMultimedia.videooverview

Video Features

Qt Multimedia offers both high and low level C++ classes for playing and manipulating video data, and QML types for playback and control. Some of these classes also overlap with both camera and audio classes, which can be useful.

Video Implementation Details

Playing Video in C++

You can use the QMediaPlayer class to decode a video file, and display it using QVideoWidget, QGraphicsVideoItem, or a custom class.

Here's an example of using QVideoWidget:

player = new QMediaPlayer;
playlist = new QMediaPlaylist(player);
playlist->addMedia(QUrl(class="string">"http://example.com/myclip1.mp4"));
playlist->addMedia(QUrl(class="string">"http://example.com/myclip2.mp4"));
videoWidget = new QVideoWidget;
player->setVideoOutput(videoWidget);
videoWidget->show();
playlist->setCurrentIndex(1);
player->play();

And an example with QGraphicsVideoItem:

player = new QMediaPlayer(this);
QGraphicsVideoItem item = new QGraphicsVideoItem;
player->setVideoOutput(item);
graphicsView->scene()->addItem(item);
graphicsView->show();
player->setMedia(QUrl(class="string">"http://example.com/myclip4.ogv"));
player->play();

class MyVideoSurface : public QAbstractVideoSurface
{
QList<QVideoFrame::PixelFormat> supportedPixelFormats(
QAbstractVideoBuffer::HandleType handleType = QAbstractVideoBuffer::NoHandle) const
{
Q_UNUSED(handleType);
// Return the formats you will support
return QList<QVideoFrame::PixelFormat>() << QVideoFrame::Format_RGB565;
}
bool present(const QVideoFrame &frame)
{
Q_UNUSED(frame);
// Handle the frame and do your processing
return true;
}
};

player->setVideoOutput(myVideoSurface);

class MyVideoProducer : public QObject
{
Q_OBJECT
Q_PROPERTY(QAbstractVideoSurface videoSurface READ videoSurface WRITE setVideoSurface)
public:
QAbstractVideoSurface videoSurface() const { return m_surface; }
void setVideoSurface(QAbstractVideoSurface surface)
{
if (m_surface != surface && m_surface && m_surface->isActive()) {
m_surface->stop();
}
m_surface = surface;
if (m_surface)
m_surface->start(m_format);
}
// ...
public slots:
void onNewVideoContentReceived(const QVideoFrame &frame)
{
if (m_surface)
m_surface->present(frame);
}
private:
QAbstractVideoSurface *m_surface;
QVideoSurfaceFormat m_format;
};

Recording Video

You can use the QMediaRecorder class in conjunction with other classes to record video to disk. Primarily this is used with the camera, so consult the Camera Overview for more information.

Monitoring Video Frames

You can use the QVideoProbe class to access video frames as they flow through different parts of a media pipeline when using other classes like QMediaPlayer, QMediaRecorder or QCamera. After creating the high level media class, you can set the source of the video probe to that instance. This can be useful for performing some video processing tasks (like barcode recognition, or object detection) while the video is rendered normally. You can not affect the video frames using this class, and they may arrive at a slightly different time than they are being rendered.

Here's an example of installing a video probe while recording the camera:

camera = new QCamera;
viewfinder = new QCameraViewfinder();
camera->setViewfinder(viewfinder);
camera->setCaptureMode(QCamera::CaptureVideo);
videoProbe = new QVideoProbe(this);
if (videoProbe->setSource(camera)) {
// Probing succeeded, videoProbe->isValid() should be true.
connect(videoProbe, SIGNAL(videoFrameProbed(QVideoFrame)),
this, SLOT(detectBarcodes(QVideoFrame)));
}
camera->start();
// Viewfinder frames should now also be emitted by
// the video probe, even in still image capture mode.
// Another alternative is to install the probe on a
// QMediaRecorder connected to the camera to get the
// recorded frames, if they are different from the
// viewfinder frames.

Examples

There are both C++ and QML examples available.

C++ Examples

QML Examples

Reference Documentation

C++ Classes

QML Types