Unreal Engine Livestream - Media Framework 4.18 Preview - Sept 28 - Live from Epic HQ

I have one question: I want to reproduce the webcam streaming shown in the video. In the Mediaplayer I can find and select my webcam as shown (select video capture device). But there seem to be two streams. By default stream 1 is displayed which is just black. If I choose Track 0 (PlayBack Options -> Tracks -> Video) the webcam stream is visible as expected. So how can I choose this track in BP? Any hint?
Webcam: Logitech HD C310


[Edit] If I use the Select Track node this doesn´t help, the correct URL is displayed