Res for 16x9 enhanced DVDs

[Jonma Tifa]

4x3 DVD mode is 720x480 NTSC right? what is the 16x9 resolution for NTSC DVDs?

[Donny661]

Read this guide http://www.vcdhelp.com/forum/userguides/94382.php

[Smart Dumb Guy]

I don't believe that guide addresses it very well.

Here's my understanding of it (keep in mind that I'm just a newb myself so I could be dead wrong).

I believe that the resolution for MPEG2 DVD is 720x480 NTSC for both 4:3 and 16:9.
The trick is that rectangular pixels are used, instead of square ones.

4:3 = 4/3 = 1.3333333 times wider than it is high.
720:480 = 720/480 = 1.5 times wider than it is high (with square pixels).
So when 720x480 is displayed on TV in 4:3 mode, the pixel width is :
(4/3) / (720/480) = 0.888888 times wider than the pixel is high.
This means that it is displaying the 720x480 pixels as if it were 640x480 pixels.

Now for 16:9

16:9 = 16/9 = 1.7777777 times wider than it is high.
720:480 = 720/480 = 1.5 times wider than it is high (with square pixels).
So when 720x480 is displayed on TV in 4:3 mode, the pixel width is :
(16/9) / (720/480) = 1.185185185 times wider than the pixel is high.
This means that it is displaying the 720x480 pixels as if it were 853x480 pixels.

What this means for transcoding.
Let's say you have an AVI file with square pixels (are they always?) and has a 640x360 resolution.
640/360 = 1.77777 so that's 16:9

480/360 = 1.33333 that's how much we've got to increase the height by to get to 480.
Now if you multiply the width by this (as if square pixels were going to be used by DVD), then you'd get:
640 * 1.33333 = 853.3333.
Now DVD doesn't use square pixels so you divide that number by the width of the pixel used : ((16/9) / (720/480) = 1.185185185) :
853.333 / 1.185185185 = 720.

So 640x360 (16:9) using square pixels is 720x480 in DVD 16:9.

I'm sure there's a calculator out there that does all that stuff for you, check the tools section.

[sterno]

That's pretty much right, though I didn't read through all your math. 16:9 and 4:3 DVDs use the same resolution. 16:9 DVDs are "anamorphic" - they're flagged as using a 16:9 display aspect ratio instead of 4:3. If your DVD player is set for 4:3 output it resizes and letterboxes the 16:9 video before sending it to the TV, but if it's set for 16:9 output it sends the video through as-is. That's why the DVD player setup menus will have a 4:3/16:9 setting somewhere.

AVI files always use square pixels because your computer uses square pixels. AVI files aren't made to display on anything else.

I think FitCD includes an aspect ratio calculator.