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View Full Version : 720x576 displayed as 1024x576 => how does a DVD player know (how to choose AR ratio)?

Irigy
15th November 2004, 18:20
With some DVD movies the player automatically changes the screen size from 720x576 to 1024x576. This does make since since the picture would look distorted when viewing it at 720x576.

But how does the DVD player know? Where on the DVD is the information stored that it needs to be viewed in a 1024x576 format?

And how do you account for this when encoding it with programs like Gordian Knot? The source material is still in 720x576 format and the encoded movie will look distorted - how do you set the correct aspect ratio?
Soulhunter
15th November 2004, 18:52
The stream has a "AR flag" thats specifys if its 4:3 or 16:9... ;)

In GordianKnot you can set the AR @ the "Resolution" tab !!!

Bye
Irigy
15th November 2004, 19:02
That's not my problem. Normally 16:9 movies have those black bars at top and bottom. This movie doesn't have them. So it looks distorted when viewing the vobs with Avisynth. And it still looks distorted after encoding (AR is set correctly, i think).
killingspree
15th November 2004, 19:10
what did you set it to?
Irigy
15th November 2004, 19:19
Input res: PAL
Input Pixel AR: Pal Anamorphic (16:9)

(as Avisynth showed)
jggimi
15th November 2004, 20:01
Irigy:

You'll find that all commercial PAL DVDs are 720x576. Your PC has square pixels. If you were to play back this video without resizing, you'd have an aspect ratio of 1.25:1. But unlike PCs, DVDs do not have square pixels.

The DVD's Display Aspect Ratio (DAR) flag will be set to one of two choices -- 4:3 (1.33:1) or 16:9 (1.78:1). All TVs are one of those two shapes.

But, movies can have all sorts of aspect ratios, such 2.35:1, 2.55:1, 2.66:1, 2.77:1, 3:1, etc. The DVD producers, when authoring, add letterboxing (or pillarboxing) as needed to correct the aspect ratio. If you have no letterboxing, your content is probably 1.78:1 or 1.33:1.

You would think that all widescreen content would be authored with a 16:9 DAR, which leaves more resolution for content. But there is no guarantee of this. I have a collection of 2.20:1 films (shot in Todd-AO) that were stupidly authored with 4:3 DARs.