[vazamb]

There are real-time sensors in the balls. Players are tracked with cameras and ,I think, also sensors in their shoes. We read about a systems developed by a German uni in an event processing class (they generated millions of events per minute) but I cannot recall the name right now.

[nodofox]

I'm not sure if they're tracking it from the ball or the shoes. I don't think they have sensors in their shoes.

This could be from offline analysis of the video.

[poloniculmov]

Players usually wear their own shoes, so I doubt they have sensors.