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pixel aspect ratio in editting softwares

 
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compusic



Joined: 22 Sep 2006
Posts: 35

PostPosted: Fri 17 Nov 2006, 1:40    Post subject: pixel aspect ratio in editting softwares Reply with quote

say I have captured a hdv video file, that's Pal 1080i, we all know it's 1920X1080 in square pixels. but as you know, in fact the physical resolution is 1440X1080. does the editting softwares should resample the file to 1920X1080 in square pixels first to edit or process the video file? when export as hdv files, will the editting softwares resample the file back to 1440X1080? then there are 2 converstions of pixel aspect ratio. I think it will degrade the quality. since all the editting softwares process square pixels natively, then it's unavoidable, right?

btw, as for graphic softwares, such as Photoshop, does it also natively deal with square pixels only?
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Fri 17 Nov 2006, 7:19    Post subject: Reply with quote

Since all SD (standard definition) broadcast video formats use non-square pixels, most video editing software can deal with non-square pixels just fine, and doesn't need to do any resizing (except for the preview window, but tht doesn't affect any of the processing; in fact, it's usually done simply by telling the graphics card to stretch the image).

Some codecs might resize the image (or keep the original size but report a different one - Canopus' DV codec did this with 16:9 files), but codecs supported directly by the editing application should just work at the native resolution. Double resizing isn't just bad due to the loss of quality; it would also make editing and processing significantly slower.

Photoshop CS (version 8) and above has support for non-square pixels (under Image -> Pixel Aspect Ratio). If you load a file without aspect ratio information, it will assume the file uses square pixels, but you can always change it manually.

RMN
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