title: Python QT Application with vlc does not show fullscreen
body: <p>I am working on an application where several vlc streams (rtsp) are shown and by double-clicking one of them, the stream should be displayed fullscreen.
  The application is python 3.7 using pyqt5 and vlc-qt.</p>
  
  <p>Code as follows:</p>
  
  <pre><code>import sys
  import vlc
  from PyQt5.QtCore import *
  from PyQt5.QtWidgets import *
  from PyQt5.QtGui import *
  from PyQt5.QtWebEngineWidgets import *
  from PyQt5.QtPrintSupport import *
  
  class MainWindow(QMainWindow):
      def __init__(self, *args, **kwargs):
          super(MainWindow, self).__init__(*args, **kwargs)
  
          self.sizeHint = lambda: QSize(1280, 900)
          self.move(100, 10)
  
          self.videoFrame = QFrame()
          self.setCentralWidget(self.videoFrame)
  
          self.vlcInstance = vlc.Instance(['--video-on-top'])
          self.videoPlayer = self.vlcInstance.media_player_new()
          self.videoPlayer.set_mrl("rtsp://xxx.xxx.xxx.xxx", "network-caching=300")
          self.videoPlayer.audio_set_mute(True)
          if sys.platform.startswith('linux'): # for Linux using the X Server
              self.videoPlayer.set_xwindow(self.videoFrame.winId())
          elif sys.platform == "win32": # for Windows
              self.videoPlayer.set_hwnd(self.videoFrame.winId())
          elif sys.platform == "darwin": # for MacOS
              self.videoPlayer.set_nsobject(int(self.videoFrame.winId()))
  
          self.videoPlayer.play()
          self.show()
  
  if __name__ == "__main__":
      app = QApplication(sys.argv)
      app.setApplicationName("VLC Test")
  
      window = MainWindow()
      app.exec_()
  </code></pre>
  
  <p>When double clicking the video, the following console message appears:</p>
  
  <blockquote>
    <p>[000001e0a128e630] mmdevice audio output error: cannot initialize COM (error 0x80010106)
    [000001e0a12c8710] mmdevice audio output error: cannot initialize COM (error 0x80010106)
    [000001e0a2927420] main vout display error: Failed to set fullscreen</p>
  </blockquote>
  
  <p>The message "Failed to set fullscreen" appears as soon as I double-click.
  Does anyone have an idea what the problem might be?</p>
  
  <p>Thanks in advance</p>