Aspect ratio

[ngc7088]

What is pixel aspect ratio?
How does it relate to screen resolution?

If I'm using NTSC, what are my choices?

I think 1920x1080 is a ratio of 1.78 and so is 1280x720 and so is 16:9. Does that mean the pixels cannot be "Square". So what happens if I choose square pixels in rendering?

Now if I start with 1920x1080 and would like a 4:3 (1.33) is it a viable choice, does it imply a loss of quality? What does a codec actually do with a request like that?

How can DVD's be 720x480 (1.5) be also 4:3 (1.33) or 16:9 (1.78)?

What is the best aspect ratio choice for dvd?...for HD video?
Why does Vimeo prefer we choose square pixel ratio?

[edDV]

Big subject that has been explained often. Use forum search.

For your specific questions, ATSC uses square pixels for 1920x1080 and 1280x720. ATSC SD resolutions are all 704x480 with differnt PAR for 4:3 and 16:9 same as DVD.

Camcorders use a variety of PAR (e.g. 1.333 PAR 1440x1080 for HDV and AVCHD) so sources vary.

See
https://forum.videohelp.com/threads/316284-What-is-the-mathematical-formula-to-figure-o...=1#post1957501

https://forum.videohelp.com/threads/317206-Fairuse-wizard-Resolution-AR-question%21?p=1...=1#post1964437

[jagabo]

DAR = SAR * PAR

DAR = Display Aspect Ratio -- the final shape of the picture
PAR = Pixel Aspect Ratio -- the shape of individual pixels
SAR = Storage Aspect Ratio -- the frame dimensions

https://forum.videohelp.com/threads/316284-What-is-the-mathematical-formula-to-figure-o...=1#post1957501

https://forum.videohelp.com/threads/317206-Fairuse-wizard-Resolution-AR-question!?p=196...=1#post1964437

[Baldrick]

Start read http://en.wikipedia.org/wiki/Pixel_aspect_ratio


And if you would like to convert from 1920x1080 16:9 to 4:3 you must CROP the video or else it will look stretched. You wont lose quality but image.

[ngc7088]

So when I find these choices in the editor, aiming to keep my PAR square while avoiding cropping or streching sounds like the thing to do right?

It is not clear to me which "aspect ratio" the software has in mind when it is simply called "aspect ratio".

[poisondeathray]

It depends which software, what your input format is , what your project settings are, and what your export format is

The terms can differ between software

Provide more details (what software are you using). "aspect ratio" in most software usually refers to DAR or the display aspect ratio

(Not to confuse you even more, but even PAR, DAR, SAR, FAR can have different meanings and stand for different things. Even official published standards disagree on what the acronyms should stand for)

[edDV]

DVD will always be non-square.

[poisondeathray]

Online sites like vimeo, youtube, blip.tv and flash based sites will always be square

[ngc7088]

How about my screen, it has a maximum resolution of 1920x1200, but I have it set to 1920x1080.
Is it square pixels when at maximum? is it square when at 1920X1080? how can I tell?
If set to 1920x1200 and I play a 1920x1080 video, what does it do with the pixels?...the frames?....the image?
If set to 1920x1080, how come I can still see the whole screen and there are no pillars or letterbox effect?

[jagabo]

1920x1200 screens are 16:10 AR, not 16:9. If you have your graphics card set to 1920x1080 and the monitor stretches that to fill the screen you will not have square pixels. Individual pixels will be 1200/1080 taller than they are wide, 9:10 pixel AR. This aspect ratio error will be noticeable.

If your monitor is running at 1920x1200 and you play at 1920x1080 video the player should add black letterbox bars top and bottom, each 60 pixels wide.