That is true about the pixel aspect ratio, and your math is spot on.
I hadn't taken into account the square versus non-square factors when
doing my math!!
It's easy to forget that our images are more or less converted on the
fly from a 0.9 pixel aspect ratio to a 1.0 pixel aspect ratio when
outputting to NTSC.
So, for more fun math:
NTSC - 4:3 aspect ratio or 1.3333 non-terminating
D1 NTSC - 720 x 486 with a 0.9 pixel aspect ratio - if we undo this
0.9 ratio, and work as if it were a 1.0 pixel aspect ratio - which is
what happens (more or less) when displaying a D1 NTSC image on an
NTSC monitor, we arrive at.....
486 / 0.9 = 540
So, our 16:9 relationship would work as follows:
720 : x = 16 : 9
720 * 9 = 16x
6480 = 16x
x = 405
But, this would be if we were working with SQUARE PIXELS, and since
we are working with NON-SQUARE PIXELS in the DS (D1 NTSC), we have to
account for the 0.9 pixel aspect ratio....
Therefore, 405 * 0.9 = 365 (rounded from 364.5).
And, 486 - 365 = 121, divided evenly - we get 60 for a top crop and
61 for a bottom... SPOT ON SPENCER!!
Nice catch!!
Cheers,
Ryan
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