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Info about... NTSC - Anamorphicly Encoded Images

Video images are stored on an DVD 'anamorphically'. If you look up the meaning of the word 'anamorphic' in the dictionary. It will say something like: "a distorted image that appears to look normal when viewed".

In the case of a DVD image, this means that although the image you see looks normal on your TV or PC screen. It is not stored like this on the disc!

NTSC - Widescreen 16:9 - Anamorphic Images

 

When an NTSC 'widescreen' (1.77:1) image is stored on an DVD, it's actually distorted (ie: squashed up width-ways).

 

Just to confuse you more, although the image has an Pixel Aspect Ratio (PAR) of 1.77:1, the image pixel frame size is, 720x480. Which means the Frame Aspect Ratio (FAR) is actually 1.50:1 : -

 


 

However, when that same image is viewed via an 4:3 TV or PC monitor it should look normal (ie: circles look perfectly round), like this: -

 

And if that same image is viewed via an 16:9 TV or PC monitor it should look normal (ie: circles look perfectly round), like this: -


NTSC - Full/Standard Frame 4:3 - (Anamorphic) Images

 

When an NTSC 'Full Frame/Standard Frame' (1.33:1) image is stored on an DVD (using all of it's 720x480 pixels), it actually looks distorted (ie: slightly expanded up), like this: -

 


 

However, when that same image is viewed via an 4:3 TV or PC monitor it should look normal (ie: circles look perfectly round), like this: -




And if that same image is viewed via an 16:9 TV or PC monitor it should look normal (ie: circles look perfectly round), like this: -


Anamorphic Signalling

Another thing you should try and understand is that an Mpeg2 DVD stream is very clever, as it's able to store 'anamorphic signalling' information within it's video stream. And it's this signalling information that's able to tell your software media player/stand-alone player or to adjust the shape of the picture, automatically.