Why does the function expand the horizontal resolution by a factor of 4? What I mean is that if you look at the result of the stack horizontal then you end up with an avi with a resolution of 2880xht (ht= 480 or 576) just prior to the resize to 720xht.
Could'nt we have just calculated rezize horzontal values for each wedge ( a,b....g ) such that the total already is 720xht?