why are dvd's 720x480?

[draggoon01]

i got to wondering, why was dvd made with 720x480 ratio? if it's intended for 4:3 or 16:9, why not define it in a resolution corresponding to one of those resolutions (for example ~853x480 natively instead of stretching it to that resolution)?

is there any information on how high definition videos will be set at in the future (resolution and aspect ratio)? like hd-dvd or hdtv? will all future videos always use some 4:3 intermediate that will be stretched to 16:9 (anamorphic)?

lastly is 1080i the upper limit defined? will there never be 1080p? i ask because been reading that many people say 720p looks better than 1080i. seems like waste to even have a 1080i.

 

[imgod2u]

Originally, widescreen format was defined to be 3:1. This changed with the introduction of 16:9 and HDTV just happen to use that format.

As for 1080i. The current stretch of technology (economically for TV's) is 1080i. In the future, we may get 1080p but currently, we're still trying to get pas 480i

 

[Erasmus-X]

Toshiba unleashed a flat panel LCOS (read: not plasma....) display at CES that supports 1080p resolution. It'll take a 1080i picture and upconvert it.

The whole idea of anamorphic widescreen is to provide the best possible picture quality regardless of the display being used. For example, if you (like 95% of all TV owners) own a 4:3 set, the DVD player will downsample the widescreen presentation by digitally rendering the letterboxing on the top and bottom of the screen. This way, you loose no picture quality and the image doesn't have the "stretched" appearance. When the same program is being presented on a 16:9 monitor, the DVD will know to render the image to fit the entire screen without picture loss.

Now, the big dilemma is that not all DVDs are mastered as anamorphic transfers! This is why even on widescreen TVs, a 2.35:1 presentation will still show some black letterboxing. You can tell your display to electronically magnify the picture, but image quality will suffer. Here's a link to a great comparison between anamorphic and non-anamorphic widescreen presentations if you're still confused. Sometimes it's easier to observe this visually.

Hope that helps.

 

[draggoon01]

imgod2u: 3:1? really? that'd feel funny i'd think in your living room.

Erasmus-X: are you sure about that? 16:9 is 1.77:1. some films are shot in 2.35:1 as you said. so if you're going to preserve aspect ratio, there has to be black bars. not so much that it's not anamorphic. or at least that's my understanding.

 

[Spicedaddy]

Originally posted by: draggoon01
imgod2u: 3:1? really? that'd feel funny i'd think in your living room.

Erasmus-X: are you sure about that? 16:9 is 1.77:1. some films are shot in 2.35:1 as you said. so if you're going to preserve aspect ratio, there has to be black bars. not so much that it's not anamorphic. or at least that's my understanding.

You're right, a wider aspect ratio just means the director wanted it that way, it has nothing to do with anamorphic vs. non-anamorphic. An example of non-anamorphic would be a widescreen movie (1.85:1 or 2.35:1, doesn't matter) encoded with big black bars as to fill a 4:3 screen. That's totally pointless since you waste lines of res. for the black bars outside of the 16x9 image, when they can be generated by the DVD player... This is very rare these days, but it's more common with older DVDs, probably because the first DVD players couldn't generate the black bars.


To get back to the original question, my guess is they use that res. because it's a compromise between 4:3 and 16:9. Horizontal resolution is less important than vertical res., and you can define the aspect ratio using a flag on the DVD anyways.

BTW, a bunch of different aspect ratios exist. Here's good info on that.