Finding correct aspect ratio

[Scanline]

I've recently started doing a little DiVX encoding just for fun, and I've ran into a little problem that I couldn't find a good answer to. How do I find the correct ratio for a DVD? IMDb says it's 2.35:1, but when I do a screen cap in WinDVD I find that the AR of that cap is closer to 2.219:1. I understand that I can't get exactly the correct aspect ratio since I have to create a DiVX with a width and height that can be divided by 16, but the difference between 2.35 and 2.219 is large enough to warrant a different DiVX size.

So, what's the best way to find the correct aspect ratio of a certain DVD?

[UncasMS]

the answer is GORDIONKNOT

[Scanline]

Thanks for your reply, Gordian Knot looks rather nice. I usually don't like all-in-one tools because they often hide functionality. It seems that the aspect ratio I got when viewing the vob in WinDVD was a bit off.

[UncasMS]

GK is NOT an all-in-one tool!

it IS a gui for the best tools one could use!!

[benderman]

First of all there are only 2 differnet aspect ratios for dvd. 16:9 and 4:3. All other ratios are made by black bars at the top and bottom. If you want to do it "by hand" here ist the formula. I use it for PAL-DVDs, but it will wotk for all others:


width[DVD] = width of the DVD-video, normaly 720
hight[DVD] = hight of the DVD-video, PAL is normaly 576
width[cutDVD] = width of the DVD-video after cutting the black bars off
hight[cutDVD] = hight of the DVD-video after cutting the black bars off
width[avi] = width of the resulting avi, normaly 640 or 512
hight[avi] = hight of the resulting avi
aspectratio = 16:9 (1,778) or 4:3 (1,333)

Now here's the formula:

hight[avi] = (width[DVD]/hight[DVD]) * (hight[cutDVD]/width[cutDVD]) / aspectratio * width[avi]

That would give you the most precise result. I make my videos only devidable by 2 in the hight, and they work fine on every computer/graphicsadapter I know, but it may depend on the codec.

[Scanline]

I am not talking about that aspect ratio, I'm talking about the aspect ratio of the movie. The movie may have a different aspect ration than what is output by the DVD-player, in which case the DVD-player adds black bars to get a 16:9 or 4:3 aspect ratio. But since I am cropping and resizing an anamorphic source I need to know the correct aspect ratio of the movie.

[Brain-Arts]

If you don't want to worry about formulas you should use MPEG4CRT!

You only have to mark th actual movie in a DVD screenshot (make one with DVD2AVI, VirtualDub,...) and MPEG4CRT calculates all settings needed...

Link for MPEG4CRT

[benderman]

If you use the formula above you, you don't need any other informations about the aspect ratio. If you want to get the original aspect ratio you only ned to use this difficult formula:

width[avi] / hight[avi] = aspectratio[avi]

That's all, folk.