LOL I had to re-watch & pay attention to the Audience
School for Def Maybe ?
This Guy was at least Alive. His Head was bobbin' !
he even reacted and smiled at one point.
Seen two propping their heads up with their Hands under their Chin
like this

someone was baby sitting
Maybe they were all scared of the Long-Hairs
everyone they are Filming are Behind the Band.
perhaps this is why. I was behind the Band for Jethro Tull.
Was definitely a disadvantage as far as Getting the full effect.
only other thing I can think is volume was turned way down
so people could talk while recording , and the audience was hired from a local school
for scenery. the two girls behind the children look like they are whispering to each other.
not normally possible at a Deep Purple concert.