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Old 25th November 2011, 04:17   #1  |  Link
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Determining Pixel Aspect Ratio (PAR)

This is a replacement for this discussion which was so zany and nonsensical. When scaling video to another size, it is essential to determine the pixel aspect ratio (PAR) of the source in order to do it properly.

If your source looks stretched or squeezed horizontally (objects look too fat or too skinny) then it most likely it has non-square pixels. If you don't know where your clip originated, determining PAR can be difficult.

Fortunately, only certain dimensions tend to have non-square pixels and most sources of these sizes tend to follow one of the standards.

If your image is not of the dimensions listed below, it is most likely square pixels (PAR = 1) and requires no special consideration. [such as 1920x1080, 1280x720, 1024x768, 640x480, 640x360, 480x360, etc.]

In addition to common DVD formats, I have also included SVCD and a few oddball "internet" resolutions with decent guesses as to their possible PAR. Please remember that, unless your source comes directly from a DVD or some known standard format, these are only "educated guesses", but educated guesses can often be better than stabbing in the dark.

For each resolution there are two possible PAR values listed: The "normal" (4:3) aspect, and "widescreen" (16:9)

Common non-square pixel formats and their Pixel Aspect Ratio (PAR)

720x486   \
720x480    \ image appears slightly stretched -----> PAR = (10/11)
704x480    / image appears squeezed ---------------> PAR = (40/33)
352x240   /
480x480   \
360x360    \ image appears squeezed ---------------> PAR = (15/11)
352x360    / image appears extremely squeezed -----> PAR = (60/33)
360x480   \
352x480    \ image appears extremely squeezed------> PAR = (20/11)
           / image appears ridiculously squeezed --> PAR = (80/33)
720x576   \
704x576    \ image appears slightly squeezed ------> PAR = (59/54)
352x288    / image appears extremely squeezed -----> PAR = (118/81)
360x288   /
480x576 --- image appears extremely squeezed ------> PAR = (59/36)
        --- image appears ridiculously squeezed ---> PAR = (59/27)
480x384 --- image appears slightly squeezed -------> PAR = (59/54)
        --- image appears extremely squeezed ------> PAR = (118/81)
360x576   \
352x576    \ image appears ridiculously squeezed---> PAR = (118/54)
           / image appears insanely squeezed-------> PAR = (236/81)
HD (either NTSC or PAL)
1440x1080 \ 
960x720    \ --------------------------------------> PAR = (4/3)
1280x1080 -----------------------------------------> PAR = (3/2)

Last edited by vampiredom; 27th November 2011 at 20:41. Reason: corrected SVCD PARs, expanded tables
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conversion, par, pixel aspect ratio, standards

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