sclass JFFMPEGVideoPlayer is Swingable {
  SurfaceShowingAutoZoomedImage imageSurface;
  JPanel buttons = rightAlignedLine();
  JButton btnPlayPause = jbutton("Pause", r playPause);
  
  ImageStreamFromVideoFile stream;
  long playStartTime;
  new BoolVar paused;
  
  void init {
    imageSurface = swing(-> new SurfaceShowingAutoZoomedImage);
    buttons.add(btnPlayPause);
    buttons.add(jbutton("Open video...", rThread openDialog));
    bindToComponent(imageSurface, null, rThread closeStream);
  }
  
  *() { init(); }
  
  *(File videoFile) {
    init();
    if (videoFile != null)
      onFirstShow(imageSurface, rThread { play(videoFile) });
  }
  
  visual
    centerAndSouth(
      imageSurface,
      withMargin(buttons)
    );
    
  void openDialog swing {
    new JFileChooser fc;
    fc.setDialogTitle("Open video");
    play(execFileChooser(fc));
  }
  
  void play(File videoFile) {
    if (videoFile == null) ret;
    pcall-infobox {
      closeStream();
      stream = new ImageStreamFromVideoFile;
      stream.open(videoFile);
      stream.onHaveImage((image, pos) -> {
        waitWhileTrue(paused);
        
        if (playStartTime == 0 || playStartTime+pos.toMillis() < sysNow())
          playStartTime = sysNow()-pos.toMillis();
        else
          sleepUntilSysTime(playStartTime+pos.toMillis());
        imageSurface.setImage(image);
      });
      paused.set(false);
      stream.startDecodeThread();
    }
  }
  
  void closeStream {
    imageSurface.noImage();
    dispose stream;
    playStartTime = 0;
  }
  
  void playPause() swing {
    paused.set(!paused!);
    setText(btnPlayPause, paused! ? "Play" : "Pause");
  }
}