videoFrame.toImage() does not work in a different thread than the video rendering thread

#include <QApplication>
#include <QMediaPlayer>
#include <QVideoFrame>
#include <QVideoWidget>
#include <QVideoSink>
#include <QWindow>
#include <QThread>
#include <QTimer>
#include <QLabel>
#include <QPixmap>

class SecondThread : public QThread
{
    Q_OBJECT

public slots:
    void convertFrame(const QVideoFrame &frame) 
    {
      emit newImage(frame.toImage()); 
    }
signals:
    void newImage(const QImage &img);
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);    
    QLabel label;
    label.show();
    QVideoWidget widget;
    widget.show();
    QMediaPlayer player;
    player.setVideoOutput(&widget);
    QTimer::singleShot(500, [&](){
      player.setSource(QUrl("somemovie.mp4"));
      player.play();
    });    

    SecondThread t2;
    t2.start();
    t2.moveToThread(&t2);
    QObject::connect(widget.videoSink(), &QVideoSink::videoFrameChanged, &t2, &SecondThread::convertFrame);
    QObject::connect(&t2, &SecondThread::newImage, &a, [&](const QImage &img){
        label.setPixmap(QPixmap::fromImage(img));
    });
     return a.exec();
}

#include "main.moc"