Pixels squared V non squared

[phaseman]

When would you use squared and non squared pixels?

If my understanding is correct non squared are used predominantly for wide screen

[Trevor Andrew]

Hi

Most video uses Non Square Pixel Rendering

Many/all video destined for the internet use square pixels, Flash Video for instance, Probably WMV types as well

Standard definition 4:3 and 16:9 both use NSPR
Pal is 720 x 576 but this is neither 4:3 or 16:9 unless we stretch it using NSPR
NTSC uses 720 x 480 again this is neither 4:3 or 16:9 unless we stretch it using NSPR

HD using 1920 x 1080 now this may use square pixels, This aspect ratio is 16:9
1280 x 720 gas an aspect ratio of 16:9
HD 1440 x 1080 is not 16:9 and uses NSPR to create the 16:9 frame.

Simply using a calculator will identify the video frame aspect ratios.

Generally you should leave Non Square Pixel Rendering selected

[phaseman]

Ok , so HD 1440 x 1080 is stretch using NSPR to create 16:9, would it matter if it was interlaced or progressive, or is this the great debate?

[Trevor Andrew]

Hi


Interlaced or progressive is the way in which the frame is viewed/transmitted. It is not related to the shape/aspect ratio of the video frame.

Interlaced ----the frame is split into two halves, one upper and one lower so Pal would use 25fps or 50 half frames, deciding on which is transmitted first depends on the source, Analogue and HD use Upper Field first , DV-Avi use Lower Field first, the two halves being shown in the correct sequence.

Progressive or Frame Based use full frames, the internet, you tube use frame based.
WMV, Flash, some Mpeg4 use frame based.

High Definition video can use both progressive and interlaced.

I'm sure its more involved than that, but should give you the idea of whats happening.

Try reading wikipedia

http://en.wikipedia.org/wiki/Interlaced_video

[phaseman]

Found this, thought worth sharing.

[Ken Berry]

Thanks for finding that, phaseman -- a good and easily understood explanation of a rather complex subject...