While playing a video you press the ok button, to get the onscreen controls. You press the icon to the left, then you go to the Stats for Nerds (if I remember correctly).
At last

!!! You are a genius tmihai20. Thank you.
For anyone else struggling:
1. Start the video
2. Switch OFF the mouse. (That's why I could not get it working!)
3. Press the central OK button
4. Use the 'left arrow' key to select 'more options', press OK
5. The 'stats for nerds' icon is on the last on the right, press OK
6. To switch it off, reverse the procedure.