aspectratio 16:9

[kheperi]

Hi,

I'm not shure if this is the best thread to post my question, but since the problem rises while setting the sizes in Vdub i try here first :- )

In Doom9's aspectratio story 2 sizes are mentioned which appears to be the same. That puzzles me a bit.
I mean the 16:9 size, which alse is regarded as 1:1.85

The point is that 19/9 is not 1.85 but its 1.78. That may seem a small difference but its not.

For example Doom9 uses the example of Austin Powers and he recalculates the aspectratio by using
480 (dvd-size) * 16/8 = ~850

But in his suggested resolutions he uses aspects trying close as possible to 1.85

Now 480 * 1.85 = 888!

See? thats not really a neglectable difference.
So i wonder: what is the factor that is really used?

[UHT]

check out the article on aspect ratios, u gotta take the black bars which are often encoded as part of the image into account too

[kheperi]

no it has nothing to do with the black bars.
I only want to know what factor is used for DAR3

is it 1.78 or is it 1.85

A dvd player does not crop it just widens the picture by this factor.

[kheperi]

to add to my own story:

If indeed a factor of 1,78 (16/9) is used in DAR 3, as Doom9 implies, then the suggested ratio's, with all due respect to Doom9's great work done for all of us, are wrong.

Doom9 suggests these:
720x384, 640x352, 576x304, 512x272, 480x256, 400x224

but better would be (IF it is 1.78)
720x400, 640x352 (or 368), 576x320, 512x288, 480x272, 400x224

(still maintaining a multiple 16)


Oh by the way... the same goes for the so called 2.11:1 ratio, that is also mentioned as 2.35:1

[Wilbert]

As I understand it (but I warn you I don't), there are two aspect ratio's. One of the dvd and one of the movie itself. For example a dvd can have an ar of 16x9 (as can be read at the back of the dvd) but the movie can be recorded in 1.78x1. On this site you can download "DVtool.zip" which gives the actual ar (I believe).

[rechteHandDesTeufels]

Maybe the information on this site clears the question about the aspect ratio up a bit: What's an anamorphic DVD (http://gregl.net/videophile/anamorphic.htm)

--
Until the waves quit rollin'

[kheperi]

All i ask is: what are the right aspect ratios for resizing different movies when backing them up using divx.

Ok reading this site you suggested made me clear that there are lots of ways to put a movie on dvd. So maybe there is no easy answer.

Anyway,
I noticed (as i wrote earlyer) that the sizes Doom9 suggests do not really good cover the way my software player (WinDVD) displays it. WinDVD displays the picture somewhat more vertically stretched.

Doom9, for instance, suggests using 512x272 for a 1:1.85 movie when resizing a dvd in virtual dub. And that is after cutting all black bars off the picture.
But when i compare the picture with WinDVD output (of course taking visible black bars into account) it doesnt look like the best choice. Resizing to 512x288 looks much closer to it (thats an aspectratio of 1.78).

Now, this can only mean 2 things. OR WinDVD doesnt display the dvd as it should OR the suggested a.r. by Doom9 is not the best one to choose.

[rechteHandDesTeufels]

What has worked best for me is this:

1. Find out the original aspectratio of the movie. (i.e. using the amazon)

2. Load the movie into VirtualDub and crop the upper and the lower black bar.

3. Devide the width by the aspectratio found in 1 (So if ar. is 1:2,35 and the desired width is 720 the height has to be 306)

4. If the calculated height is not a multiple of 8 you have 2 coices

- Use the next height thats a multiple of 8 as "New height" (in this case it would be 304). You'll get a very small distortion so.

- Use the exact calculated height as "New height" and set "Expand frame and letterbox image" and use the next multiple of 8 to the calculated height as "Frame height" (in this case 312). The image will not be distortet but you'll get tiny black bars again.

I haven't experienced any problems so far using this method, and the resulting DivX movie always looked exactly like the original WinDVD playback.

--
Until the waves quit rollin'

[kheperi]

So the picture as WinDVD shows it is the right aspectratio? In that case i will use that as reference to get an ar close as possible to that (and still maintaining a multiple of 16).

Hmmm i think i understand now... (ok i'm slow :- )

Doom9 leaves the left and right black bars (if there) where they are. So that will make the effective horizontal size lower. Probably something like 484. the rest (512-484= 28) are the black bars left and right of the movie.

But since i cut them of the story changes. Ah, i reread Doom9's guide about this and indeed he doesnt mention cutting off the left and right black bars.

Ok, its clear now :- ) thanks for your time