Newbie question about 720 x 480 dvd resolution

[siratfus]

Some movies will fill up the screen completely, while some will have horizontal black bars. Can someone explain the relationship between horizontal black bars and resolution? I guess I'm wondering if a movie is still 480 length wise if it has black bars?

Secondly, when converting dvds to divx, xvid, mp4, etc... Lets use Fairuse Wizard for example since I'm currently using/learning this program. How come there is never a choice for an output resolution of 720 x 480, it's always 720 x 384, 704 x 400, 640 x whatever, etc and etc? Yet the newly made file will display just like the dvd. I figured if the dvd is 720 x480 and the converted file is 720 x 384, then maybe I would see thicker black bars? How come that's not the case?

Please advise, I really want to learn this stuff. Thank you.

[manono]

Hi-

I guess I'm wondering if a movie is still 480 length wise if it has black bars?

Length wise? 720 is the width. 480 is the height. That's the resolution before being resized. It gets resized to roughly 854x480 at playback time. 480 is still the height, but if there are black bars above and below, then the active video's height is less.

How come there is never a choice for an output resolution of 720 x 480...

Because that's the non-square pixel resolution. Usually AVIs are 1:1 (as opposed the 16:9 or 4:3 DVDs), and have been already resized, often to the resolutions you mentioned. If you tried to watch an unresized 720x480 AVI from a 16:9 DVD, people would look tall and thin - have bad aspect ratio. Here, read this:

http://www.doom9.org/aspectratios.htm

Yet the newly made file will display just like the dvd.

DVDs get resized. AVIs if made as 1:1 just get scaled. It's possible to make unresized AVIs and then you'd let the player do the resize. You can make 720x480 AVIs, but not all player will respect the flag added into the video that tells how it's to be resized.

[yoda313]

Resolution is not identical to aspect ratio.

Resolution is the frame of the picture. Bluray and hdtv is 1920x1080. Dvd is 720x480.

Aspect Ratio is how the picture looks inside the frame.

4:3 is the square picture most tv programs used up until the late 90's with the emergence of dvd sales and high def tv.

16:9 is widescreen. That is the horizontal bars. There are two main flavors: 1.77:1 and 2.35:1. There are some funky exceptions to this for certain movies and some bluray/hddvd releases that have nonstandard ratios.

1.77:1 will have small bars on the top and bottoms. Most of the tv shows today that are widescreen TEND to be 1.77:1. Movie comedies and lesser action pics will use 1.77:1. Those tend to fill up a widescreen tv when used in fill mode.

2.35:1 is used by BIG movies like Star Wars, Ben Hur, Lord Of The Rings, Titanic, etc... Any thing that uses landscapes and vistas to draw in an audience. Those aspect ratios will still have a black bar even on a widescreen tv. However they will be relatively small black bars depending on the sclaing features your dvd player and tv uses.

Those aspect ratios for divx are the cropped output of dvd. This is a "forced" widescreen output I believe. However others here are by far more knowledegable in the mathmatics of the cropping of dvd resolution into widescreen for compressed video puproses.

[filmboss80]

NTSC (North America, Japan) video at 720 by 480 can apply to both a standard 4:3 aspect ratio and widescreen 16:9 aspect ratio. In the case of widescreen, the 720 x 480 frame has a squeezed, anamorphic image, making everything look narrow, but it gets stretched out to normal-looking widescreen by an instruction the DVD disc tells the player. Without trying to sound too technical, basically your DVDs will be encoded with flags that tell the DVD player whether to play the 720 x 480 image as square pixels (4:3) or stretched out rectangular pixels (16:9). On a standard 4:3 TV, the DVD player will add bars to the top and bottom, but the same disc on a widescreen TV will fill out the frame, end to end. The exception is when someone makes a pseudo-widescreen, "letterboxed" movie; that is, the black bars are incorporated into an actual 4:3, square-pixel video.

Yep, it's about that convoluted. That is why it's good to use GSpot to analyze the video, as to whether it is actually a 16:9 widescreen video or a 4:3 letterboxed (psuedo-widescreen) video.

[siratfus]

Thanx everyone! I was hoping there was a simple answer, but I guess I'll have to really really really really read up on this. When you got programs that automatically configures these things, you tend to not learn anything. I've been making great divx files with fairuse wizard. The layman thinks I'm a genius. However, I absolutely don't understand how or why these programs work.

[jagabo]

The fundamental relationship between the displayed aspect ratio and the frame size is:

DAR = SAR * PAR

DAR is the Display Aspect ratio, the final shape of the picture
SAR is storage aspect ratio, the relative frame dimensions
PAR is the pixel aspect ratio, the shape of individual pixels