# Why is SD video always in 4:3 aspect ratio?



## Tyrone Burton (Aug 24, 2012)

I know that that SD is always 4:3, but can also be stretched to 16:9 properly by a player (anamorphic). But really, the SD video is still really only 4:3. My question is, why? My best go at it would be because there isn't enough pixels to fill the 16:9 screen and thus it's squashed in the middle? 

My curiosity has stricken again...:uhoh:


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## JimE (Apr 16, 2009)

For the record, "HD" includes 480P, 720P, and 1080P. So basically, any resolution below 480P (DVD resolution) is considered SD. See here (scroll down to the bottom of the page) What is DVD? - VideoHelp.com

Screen size/format is mostly irrelevant, as any input (resolution) to a TV that isn't at the screens native resolution, is scaled by the TV to match the screens native resolution. 

By spec, "SD" is 4:3. But you could have SD widescreen material. In any case, it's a combination of the technology available at the time, both of the media and the hardware (monitors/TV's) built for playback. When referencing movies, there are numerous AR's that have, and still are used (16:9 is just one of many). Television and movies are two different entities, which are both sharing a common format (consumer TV's).

widescreen.org - The Letterbox and Widescreen Advocacy Page


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## Tyrone Burton (Aug 24, 2012)

So basically what your saying is that although SD is 4:3, on the medias side of things they can manipulate it to widescreen depending on the technology they have at the time? 

But if they film something in HD, and then they compress it down for DVD resolution, does it have to be 4:3 unless they add anamorphic? Or have I totally lost the point here lol.


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## JimE (Apr 16, 2009)

I'm saying the terms were added along the way as technology was changing. DVD was already around for awhile before the term "HD" even came up.

AR and quality have nothing to do with each other. You can have 4:3 AR video in SD or HD format. 

SD and HD denote the quality. And based on the specs, the standard resolutions established for said content.

AR is set/decided by the creator of the material.

I used to have a good link with lots of information, but I can't find it at the moment. In any case, more info:

Aspect Ratios Explained: Part One - Articles - DVDActive

What is Anamorphic DVD ?

Anamorphic format - Wikipedia, the free encyclopedia


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## Tyrone Burton (Aug 24, 2012)

Gah! I get it now yes, thank you for the links.


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