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par / sar / dar
I am attempting to develop a comprehensive understanding of Aspect Ratios as they apply to displays, pixels, and storage. So far… it’s pretty confusing.
This came about because I am trying to create a .mov from a .mpg2 source file that is 720×480, SAR = 3:2, PAR = 8:9, DAR = 4:3 (according to Gspot).
It seems like the only way to match these two files so the aspect ratio matches to the naked eye is to make the .mov 640×480. Gspot confirms that, with those settings, the DAR = 4:3 on both files.
My question is – What is the right formula to create a .mov that most closely matches the .mpg2 settings I listed above? Is there a way to make the .mov 720×480 and still have the proportions match to the eye?
It seems when I automatically changed the Pixel Aspect Ratio in the .mov settings to .889, it has no affect. Is there a reason .mpg2 settings let you choose a 4:3 display but other containers don’t?
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4 Replies
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[Sam Caino] “It seems when I automatically changed the Pixel Aspect Ratio in the .mov settings to .889, it has no affect. Is there a reason .mpg2 settings let you choose a 4:3 display but other containers don’t?”
QuickTime is pretty useless when it comes to pixel aspect ratios (at least on the PC). You always want to feed QuickTime PAR 1.0. For example, if you source is NTSC DV which 720×480 PAR 0.9091, you have to multiply the width by the PAR to get the equivalent square pixels. The width of 720 x 0.9091 = 654.552 rounded up is 655. So to match a 720×480 PAR 0.9091 file in QuickTime you should render 655×480 PAR 1.0.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
John – that is very valuable information. Thank you! Does the same concept apply to a Sony AVC .mp4 file?
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[Sam Caino] “Does the same concept apply to a Sony AVC .mp4 file?”
Only if you play it with the QuickTime player. This is problem with the QuickTime player. Since MP4 files can be played with other players you might not have this problem.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
Oh wow, that is an important distinction, thank you.
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