robgraham gurgled happily, sounding much like
they were saying:

I've brought it home to play with but what is there different about
adverts on TV from normal transmission ?

Probably the adverts are transmitted in a different aspect ratio, and the
box is trying to shift - our TV does that, chucking up an on-screen
display to tell you, so it's quite noticable. Seems to be most prevalent
on C4.