Puzzled over aspect ratios.. help!!

[AndyP]

I have been reading the guides on aspect ratios and a couple of things puzzle me...

(1) All PAL DVDs are encoded in 720x576 but when viewed unresized in Gknot look vertically stretched. This because it is squashed horizontally to fit in the above resolution. When the DVD player reads it it resizes it horizontally to look correct. Is this true for 16:9, 2.35 and 4:3 films???

(2) I have been looking at 3 DVD movies:
a - blair witch (R2) 4:3 in DVD2AVI
b - scary movie 2 (R2) 16:9 in DVD2AVI
c - pitch black (R1) 16:9 in DVD2AVI but 2.35:1 on the back cover

Both (b) and (c) are reported as 720x576. (b) fills most of the image (smart crop takes about 10-15 off each edge) while (c) has a black border of about 70 on the top and bottom. Does this mean that mean with the border removed the remaining image will be 2.35:1 and the whole image (with borders) is 16:9??

As a divx avi of (c) only occupies 1/3 of the screen (with borders cropped - ie 2.35:1 i assume) I would like to crop some off each side to simulate true 16:9 (or should I say 1.85:1). What values should I use to still keep aspect ratio for the remaining picture??

(a) reports the image size as 704x576. Is that because it is 4:3?? Can 4:3 come on 720x576 as well?? As the image is completely filled (as in (b)) I assume the only difference is the resizing by the player

Summary (am I correct??)
16:9 (1.85:1) and 4:3 always fill the entire 720x576 frame and are resized differently to look right
2.35:1 always has top/bottom black borders to make remaining image 2.35:1

As asked above how do I convert 2.35:1 to 1.85:1 for divx?

Thanks if you are still here and thanks for any replies.

Andy

[Messerjockel]

Hi

When using resize filters in Nandub/Virtualdub completely crop the black lines and set the desired/calculated size(check the DVD-box). This always worked fine for me.

[MvB]

(1) All PAL DVDs are encoded in 720x576 but when viewed unresized in Gknot look vertically stretched. This because it is squashed horizontally to fit in the above resolution. When the DVD player reads it it resizes it horizontally to look correct. Is this true for 16:9, 2.35 and 4:3 films???

First: It's true that all PAL DVDs are encoded in 720x576. A lot of them are encoded anamorphic, that means 16:9 enhanced.
2.35 and 16:9 are formats that can be recorded anamorph on a DVD.
If you have a TV that is 16:9 enhanced , you can tell your DVD-player to send the picture in anamorphic (2.35 or 16:9, stretched in height about 25%) format to your television. The TV then reduces the picture vertically (in height) by changing the spacing between the lines of the picture without loosing resolution resulting in a significant sharper picture than in widescreen.
If your TV is not able to resize to 16:9 or 2.35 correctly, you can tell your DVD Player to switch to widescreen (16:9) mode, resulting in a picture similar to 16:9 on an 16:9 enhanced TV. But the vertikal stretch is reduced by the player b loosing every 4th line in the picture.
If you have a 4:3 movie, it is recorded as is, without stretching.

a - blair witch (R2) 4:3 in DVD2AVI
b - scary movie 2 (R2) 16:9 in DVD2AVI
c - pitch black (R1) 16:9 in DVD2AVI but 2.35:1 on the back cover

Both (b) and (c) are reported as 720x576. (b) fills most of the image (smart crop takes about 10-15 off each edge) while (c) has a black border of about 70 on the top and bottom. Does this mean that mean with the border removed the remaining image will be 2.35:1 and the whole image (with borders) is 16:9??

First: a R1 Disk is recorded in NTSC. That means it has a resolution of 720x480. If you have you display resolution set to 720x576 the black borders will be much greater than ntsc. The borders in anamorphic format are reduced because the space they would use ist occupied by the stretched picture of the movie. They come to normal height by reducing the picture in height resulting in a 16:9 oder 2.35:1 picture.
if you compress anamorphic to divx, you shoud set the aspect ration in Flask manually to 4:3. Then you see the stretched picture. You can then cut the black borders off (when they exist) and encode a anamorphic divx. Otherwise set the aspect ration the movie should have (when not anamorphic) and encode this one. The result is a divx-movie in the correct aspect ratio.

Please look at this comparison page (http://home.t-online.de/home/stefan.sk/dv3.htm). It's in German but has the formats in easy to understand pictures on it.

16:9 (1.85:1) and 4:3 always fill the entire 720x576 frame and are resized differently to look right

Yes. But 4:3 is the aspect ratio of your TV so it won't be resized anymore.

2.35:1 always has top/bottom black borders to make remaining image 2.35:1

Yes. It will be reduced like 16:9 anamorphic, but because it's smaller it fills not the whole picture on the DVD.

For the conversion matter: Try Flaskmpeg (cropping at the sides of the movie) But you'll never get real 16:9 because you would have to stretch the picture in height for this and i don't think flask can handle this :(

Hope I could help you a bit.
Good night.

[AndyP]

Wow! I'd forgotten about this thread. Thanks for the comprehensive reply.

Andy