qtmultimedia/src/multimedia/video/qvideoprobe.cpp

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/*!
    \class QVideoProbe
    \inmodule QtMultimedia

    \ingroup multimedia
    \ingroup multimedia_video

    \brief The QVideoProbe class allows you to monitor video frames being played or recorded.

    \code
        QMediaPlayer *player = new QMediaPlayer();
        QVideoProbe *probe = new QVideoProbe;

        connect(probe, SIGNAL(videoFrameProbed(QVideoFrame)), this, SLOT(processFrame(QVideoFrame)));

        probe->setSource(player); // Returns true, hopefully.

        player->setVideoOutput(myVideoSurface);
        player->setMedia(QUrl::fromLocalFile("observation.mp4"));
        player->play(); // Start receving frames as they get presented to myVideoSurface
    \endcode

    This same approach works with the QCamera object as well, to receive viewfinder or video
    frames as they are captured.

    \sa QAudioProbe, QMediaPlayer, QCamera
*/

#include "qvideoprobe.h"
#include "qmediavideoprobecontrol.h"
#include "qmediaservice.h"
#include "qmediarecorder.h"
#include "qsharedpointer.h"
#include "qpointer.h"

QT_BEGIN_NAMESPACE

class QVideoProbePrivate {
public:
    QPointer<QMediaObject> source;
    QPointer<QMediaVideoProbeControl> probee;
};

/*!
    Creates a new QVideoProbe class with \a parent. After setting the
    source to monitor with \l setSource(), the \l videoFrameProbed()
    signal will be emitted when video frames are flowing in the
    source media object.
 */
QVideoProbe::QVideoProbe(QObject *parent)
    : QObject(parent)
    , d(new QVideoProbePrivate)
{

}

/*!
    Destroys this probe and disconnects from any
    media object.
 */
QVideoProbe::~QVideoProbe()
{
    if (d->source) {
        // Disconnect
        if (d->probee) {
            disconnect(d->probee.data(), SIGNAL(videoFrameProbed(QVideoFrame)), this, SIGNAL(videoFrameProbed(QVideoFrame)));
            disconnect(d->probee.data(), SIGNAL(flush()), this, SIGNAL(flush()));
        }
        d->source.data()->service()->releaseControl(d->probee.data());
    }
}

/*!
    Sets the media object to monitor to \a source.

    If \a source is zero, this probe will be deactivated
    and this function wil return true.

    If the media object does not support monitoring
    video, this function will return false.

    Any previously monitored objects will no longer be monitored.
    Passing in the same object will be ignored, but
    monitoring will continue.
 */
bool QVideoProbe::setSource(QMediaObject *source)
{
    // Need to:
    // 1) disconnect from current source if necessary
    // 2) see if new one has the probe control
    // 3) connect if so

    // in case source was destroyed but probe control is still valid
    if (!d->source && d->probee) {
        disconnect(d->probee.data(), SIGNAL(videoFrameProbed(QVideoFrame)), this, SIGNAL(videoFrameProbed(QVideoFrame)));
        disconnect(d->probee.data(), SIGNAL(flush()), this, SIGNAL(flush()));
        d->probee.clear();
    }

    if (source != d->source.data()) {
        if (d->source) {
            Q_ASSERT(d->probee);
            disconnect(d->probee.data(), SIGNAL(videoFrameProbed(QVideoFrame)), this, SIGNAL(videoFrameProbed(QVideoFrame)));
            disconnect(d->probee.data(), SIGNAL(flush()), this, SIGNAL(flush()));
            d->source.data()->service()->releaseControl(d->probee.data());
            d->source.clear();
            d->probee.clear();
        }

        if (source) {
            QMediaService *service = source->service();
            if (service) {
                d->probee = service->requestControl<QMediaVideoProbeControl*>();
            }

            if (d->probee) {
                connect(d->probee.data(), SIGNAL(videoFrameProbed(QVideoFrame)), this, SIGNAL(videoFrameProbed(QVideoFrame)));
                connect(d->probee.data(), SIGNAL(flush()), this, SIGNAL(flush()));
                d->source = source;
            }
        }
    }

    return (!source || d->probee != 0);
}

/*!
    Starts monitoring the given \a mediaRecorder.

    If there is no mediaObject associated with \a mediaRecorder, or if it is
    zero, this probe will be deactivated and this function wil return true.

    If the media recorder instance does not support monitoring
    video, this function will return false.

    Any previously monitored objects will no longer be monitored.
    Passing in the same object will be ignored, but
    monitoring will continue.
 */
bool QVideoProbe::setSource(QMediaRecorder *mediaRecorder)
{
    QMediaObject *source = mediaRecorder ? mediaRecorder->mediaObject() : 0;
    bool result = setSource(source);

    if (!mediaRecorder)
        return true;

    if (mediaRecorder && !source)
        return false;

    return result;
}

/*!
    Returns true if this probe is monitoring something, or false otherwise.

    The source being monitored does not need to be active.
 */
bool QVideoProbe::isActive() const
{
    return d->probee != 0;
}

/*!
    \fn QVideoProbe::videoFrameProbed(const QVideoFrame &frame)

    This signal should be emitted when a video \a frame is processed in the
    media service.
*/

/*!
    \fn QVideoProbe::flush()

    This signal should be emitted when it is required to release all frames.
    Application must release all outstanding references to video frames.
*/

QT_END_NAMESPACE