On Tue, 15 Feb 2005, Trent Piepho wrote:
> There is no need to do anything special for 720x480 instead of 704x480, you
> can use the same math.
What about the difference in SAR between D1 and DV/DVD? If it's not
a fiction doesn't that need to be taken into account? I have seen
(in a couple different books and programs) 9:10 and 720x486 vs 720x480
mentioned.
If that's so then to get 720x480 you need to create the graphics
at 720x534 and scale to 720x480.
Pick up a book on FCP-HD or Adobe's "Premiere" (Photoshop even has
a NTSC DV preset that uses 9:10 and 720x534).
> If you are going from a non-anamorphic DVD to a computer, the input SAR is
He's going, as I recall from computer to DVD so it'd be from 1:1 to
non-square.
What does seem to be confusing me (perhaps others too) is that there
is the SAR of 10:11 (ratio of 12.272727 and 13.5MHz) and the
"NTSC DV" SAR of 9:10 which is used by some fairly highend video
editors.
> If you are going from a non-anamorphic DVD to a computer, the input SAR is
> 10/11, and the output is 1/1. The input height is 480 and the input width is
Or 9/10 depending which book was last consulted :)
> 704 or 720.
I'm not sure if fiddling with the numbers (if I put 720x528 in I can
get 720x480 out) instead of padding 704 to 720 is the right thing to
do.
If you look at a DVD created from digitizing a analog source you will
PLAINLY see a 704x480 frame centered inside the DVD 720x480 frame!
> Want to scale vertically and get 720x480?
> 480 / (10/11) * (1/1) = 528, use 720x528
> Want to scale vertically and get 704x480?
> 480 / (10/11) * (1/1) = 528, use 704x528
Huh? The same vertical size being used? That's making the assumption
that the 720x480 image is a 4:3 image and I thought that was not
the case unless the SAR is 9:10!
IF you have Wx480 being a 4:3 image then W can only be 704 for a SAR
of 10:11. Only way I see of getting 720 is to fudge things with the
assumption that 720x480 represents a 4:3 image OR use a SAR of 9:10.
Now IF you use 9:10 THEN you can get 720x480 from 720x534.
Matt's page does make mention of the 720x480 frame not representing
the 4:3 image - that's true for 10:11 but what about 9:10 which is
a number I've seen used. Wouldn't that make 720x534 -> 720x480
the right thing to do? Either that or pad 704x480 to 720x480.
NOTE:
If you look at a DVD created from digitizing a analog source you will
PLAINLY see a 704x480 frame centered inside the DVD 720x480 frame!
It's done by padding, not scaling.
It's all sooooo confusing! ;)
At any rate there is the need for scaling - I think we can agree
on that much at least.
Cheers,
Steven Schultz
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