Hi -
> From: Selva Nair <[EMAIL PROTECTED]>
> The general advice is to avoid vertical scaling mainly because vertical
> scalers should be interlacing-aware -- also for interlaced frames the
and y4mscaler is, I believe, interlacing aware ;)
Downscaling feels more correct. Removing information is preferable
to synthesizing it.
> may not matter much, though. In any case, you will get proper aspect ratio
> only if you scale by the correct SAR value: 10:11 in case of NTSC. So
Ah, but if you read Martin Sitter's DVD Studio Pro book (or take a look
at books on Adobe Photoshop) it would seem that NTSC TVs use 9:10
pixels and there are a couple NTSC frame sizes to contend with. The
use of 720x534 when designing menus and overlays is mentioned several
times with a note that 720x540 is not correct unless you're going to
D1 NTSC (720x486).
> 640x480 --> 704x480 or 720x540 --> 704x480, if you prefer 540. This need
> to scale in both directions is another reason to keep away from 720x540.
But since DVDs are 720x480 there's no scaling in the horizontal
dimension - that stays at 720.
> 720x534 makes no sense to me. Apparently, the popularity of 720x540 is
> because it appears related to both PAL and NTSC by a vertical scaling
> factor -- scale to 720x480 in one case and 720x576 in the other. But that
It's a bit more complicated than that I think.
.9 * 534 = 480.6 while 540*.9 = 486
So D1 NTSC at 720x486 would use 720x540 scaled to 720x486 and then
crop 6 pixels (usually the top 6 but it can vary) to get to DVD frame
size. 720x534 would scale to 720x480 with no cropping.
> > and overlays (something about "D1 NTSC" vs "DVD/DV NTSC"). It's
> > all very confusing ;)
>
> Very confusing indeed;) Take a look at Aho's page (the link above), you
> may find some logic behind all those convoluted and confusing standards.
I've seen that - it didn't say anything about the source of my
confusion (where'd 9:10 and 720x486 come from? ;)) and Matto's
http://www.mir.com/DMG/aspect.html
Guess I'll have to try both sizes with a DVD using overlay highlights
and see if the books are correct about a misalignment when using
720x540 instead of 720x534 ;)
Cheers,
Steven Schultz
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