Later on at midnight a five hour documentation about the festival will be broadcasted through their TV channel. (You should also be able to see this through the webstream of the TV station at http://www.ndr.de/fernsehen/livestream217.html).
For more details on this event like the exact timetable for the mentioned interviews and live-recordings go to www.ndr.de/unterhaltung/events/wacken/wackennacht101.html (sorry, only in german available).
Update 2013/09/16: If you missed the documentation "Alles auf schwarz - Wacken!!!: Sarnau & Hübner bei den Metalheads" then you've got a second chance to see this by checking out this site.
It holds the documentation divided into three parts plus several interviews with well known musicians.
Update 2013/09/13: Some more details in german language about the documentation entitled "Alles auf schwarz -Wacken!!!: Sarnau & Hübner bei den Metalheads" that will be broadcasted tonight plus a trailer can be viewed on this site of the TV station NDR.