QGCQVideoSinkController.h

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#pragma once
 
#include <QtCore/QList>
#include <QtCore/QMetaObject>
#include <QtCore/QMutex>
#include <QtCore/QObject>
#include <QtCore/QPointer>
#include <QtCore/QSize>
#include <QtCore/QString>
#include <QtCore/QTimer>
#include <gst/gst.h>
 
class QQuickVideoOutput;
class QVideoSink;
 
class QGCQVideoSinkController : public QObject
{
    Q_OBJECT
 
    Q_PROPERTY(quint64 frameCount READ frameCount NOTIFY frameCountsChanged)
    Q_PROPERTY(QString negotiatedFormat READ negotiatedFormat NOTIFY negotiationChanged)
    Q_PROPERTY(QSize negotiatedResolution READ negotiatedResolution NOTIFY negotiationChanged)
 
public:
    QGCQVideoSinkController(GstElement* element, QObject* parent = nullptr);
    ~QGCQVideoSinkController() override;
 
    static QList<QGCQVideoSinkController*> controllersOf(const QObject* receiver);
 
    static void syncActiveToWindowVisibility(QObject* receiver, QQuickVideoOutput* videoOutput);
 
    // setActive(false) drops frames at the element; setVideoSink swaps the destination under
    // GST_OBJECT_LOCK. QPointer so a caller-thread destruction race is caught here, not in GObject.
    void setActive(bool active);
    void setVideoSink(QPointer<QVideoSink> sink);
 
    void prepareForRelease();
 
    const GstElement* element() const noexcept;
    void updateNegotiation(const QString& format, const QSize& resolution);
 
    quint64 frameCount() const noexcept;
    QString negotiatedFormat() const;
    QSize negotiatedResolution() const;
 
public slots:
    void refreshLatency();
 
signals:
    void frameCountsChanged();
    void negotiationChanged();
 
private:
    void _releaseElementBinding() noexcept;
    void _onEmitTimer();
 
    GstElement* _element = nullptr;  // owned ref
    QMetaObject::Connection _sinkDestroyedConnection;
    bool _bindingReleased = false;
    QTimer _emitTimer;
 
    mutable QMutex _stateMutex;
    QString _negotiatedFormat;
    QSize _negotiatedResolution;
    quint64 _lastEmittedFrameTotal = 0;
};