720x576 is the DV PAL pixel ratio, with non-square pixels. 768x576 would be the square pixels equivalent to this, generally used for motion graphics, so you can make a square in photoshop in 768x576, and then render to 720x576 so on the vga monitor it looks distorted, but then on TV it's square again.
So no pixels are really lost, they are just re-rendered to accomodate the non-square pixels of TV sets
HTH
Barend
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