DVD resolution/Aspect Ratio question

[Diablo_75]

I'm in the process of captureing video at 640x480 and plan to edit, and then export the results to a DVD. The import video is at a 4:3 ratio, and if I go to 720x480, I either have to crop of some stuff, or the results will look a little stretched.

I doubt there's a way around this, but I'm just wondering if there is either a 4:3 ratio resolution that DVD will accept.

[House de Kris]

You didn't say what application you are using for the conversion, but in general, just specify "keep aspect ratio" and everything will work out fine. The thing to keep in mind here is that video does not have to (and rarely does) use square pixels. For example, SVCD is typically 480x480 yet it is displayed just fine on a 4:3 TV.

[mikk]

yes, number of pixels is not related to resolution. but when you resize 640 to 720, the 640 pixels are smeared across 720 pixels, blurring it a little bit. the best way would be if u could capture at 720x480

[Diablo_75]

I'll be using Adobe After Effects for the most part to do the editing/converting. Export the results back out to lossless, and then convert those files to MPEG-2. It has several default resolutions in it already (with minor descriptions such as "D1 widescreen" or some HDTV res's, and even higher stuff for film.

What resolutions should I export the video out as before I convert it to mpeg-2?

[dvddarren]

mikk, you say that upping the resolution would smear the picture slightly, would it be better to reduce the resolution to 352 x 288 or 352 x 576.

Would this give a better picture or worse.

cheers

[mikk]

D1 is gonna be either 704x480 or 720x480... not sure which because i've seen it quoted both ways.

dvdarren reducing the resolution will definitely make it worse... when resizing, think of it this way:
let's say you have a 2x2 grid of pixels with one black one and the rest white like this:
XO
OO
if you try to resize it to 3x2, how do u do it? the X has to go across 1.5 pixels... so what would happen is that you would get something like this:
XxO
OOO
the x represents a grey pixel. so now the image is blurred... this is basically what happens when u resize... but it doesn't have to be that way. instead, lets resize to 4x2:
XXOO
OOOO
no grey pixels, just pure black and white. if u resize by whole number multiples, u won't get nearly as much blurring as if u resize by a fraction. also, the more you fragment the multiple, the more u blur the image. e.g. 1.5 is better than 1.2013. i hope i made myself understood... same sort of rules apply to shrinking an image, but u get better results if u divide by factorials of the image dimensions. i hope i made myself clear

[dvddarren]

Thanks for your explanation mikk, nicely explained.

So for an image of 480 x 576 @ 25fps i am best expanding it to 720 x 576 instead of 352 x 576 as 720 is 1.5 times 480 whereas 352 is multiplied by 0.7333.

Is this right

cheers

[mikk]

yep, good call