> I wonder what video signal I would have got on my 4:3 TV... "stretch the sides", then > cut off the sides?
It might have letter boxed it with top and bottom black bars.
On a programme that mixes new widescreen content with 4:3 I can see why they would want to fill in the space either side. Often they do it with a blurred & distorted copy of the edges, just so you get a vague sense that it's the same colour. But if the entire programme is 4:3 then they should just broadcast it like that.