How could I add multiple players to play videos at the same time?

Hi, related to #100, could someone instruct me how to play multiple videos at the same time using MediaManager.Forms?
I tried to add 4 in Xaml like this,

```

```

And in .xaml.cs, I have code like this,

```
private IPlaybackController PlaybackController => CrossMediaManager.Current.PlaybackController;
...
PlaybackController.Play();
```

But while running, only the last one is playing. Other three show black screen.
Is it possible to achieve this?

Is it because that I only defined one PlaybackController? But I tried to define more than one PlaybackController, it didn't work. Is there some example code for this?

Thank you very much. @martijn00 @SimonSimCity @modplug

The reason I want to do this is that, I want to monitor and play rtsp streams from several IP cameras at the same time. I've tested, it's okay to play a rtsp stream from a camera.