What is the pixel count on a widescreen standard definition DVD @ 720 * 480 ?

Z

ZerosInfinite

New member
o-k can someone explain this to me like I'm new please...
720 * 480 is a 3:2 or 1.5:1 ratio right?
and my television (also SD) is 4:3 or 1.33:1

So when you squeeze a 1.5:1 image onto a 1.33:1 display you should lose about 11% off the top and bottom together in the form of black bars... thats about 6% on the top and 6% on the bottom....
so why does it look like nearly half of my screen is black bars?

thanks ..was always curious about that ... is the content there and things are scaling down? or is the content missing and things are scaling up ?
 
S

sullivan

Member
DVD is indeed 720x480 and that is indeed a ratio of 3:2.

When playing a DVD containing 4:3 content on a 4:3 screen, this should fill the screen. There should be no black bars. This works because the pixels on such a DVD are not square. They are taller than they are wide when displayed in this way.

Conversely, when playing a DVD containing 16:9 content on a 16:9 screen, this should also fill the screen with no black bars. In this case the pixels on the DVD are non-square in the opposite direction. 16:9 at 480 high is 853x480. In this case the pixels from the DVD, as displayed on the screen, are wider than they are tall.

The "pixel aspect ratio", as it is called, is encoded into the DVD, and the DVD player scales things accordingly before sending the video to the display.

Now if you're getting black bars top and bottom, you must be playing content that is a wider format than 4:3. This has nothing directly to do with the pixel aspect ratio recorded on the DVD. It has to do with the fact that your content is 16:9 and when you put it on a 4:3 screen, it has to be either squashed horizontally (everybody will look skinny) or else there are going to be some black bars top and bottom.

Suppose it is 16:9 content. An SDTV would have a 640x480 display. So the "16" occupies 640 pixels. Then the "9" will only fill 360 pixels vertically. This leaves 25% of your screen unused. If you want to watch the disc at the original aspect ratio (so circles stay circular, etc.) it's either that or cut off the left and right sides (pan and scan).

If this is confusing, take two pieces of paper. In one cut a window that is in 4:3 ratio. Cut the other piece to a 16:9 rectangle. Now look at that one through the hole in the other. Is there any way to see all of the 16:9 rectangle while using all of the 4:3? Nope.

To make matters worse, a lot of movies are shot even wider than 16:9. Those have black bars top and bottom even when shown on an HDTV.

Hope this helps.
 
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