Different display aspect ratios between Mac and PC

Question

I am working with some NTSC DV .mov files (720x480). When I view them in OS X Lion (Quicktime 10.1), the Quicktime Movie Inspector shows the video correclty at 4:3 Aspect Ratio with the correct dimensions of 640x480 (using square pixels).
However, when I open the same video in Windows 7 using Quicktime 7.7.2, It shows the video as 720x480 (I guess it is interpreting the pixesls as square instead of 0.9091). Also, on the pc, there are black bars on the left and right margins. These don't appear on the mac.
Any ideas about why these are being interpreted differently by Quicktime on OS X and Windows?
Thanks.

Answer 1

I assure you that I can open the same file from an external drive with my Windows PC or my Mac and get the above results. I have over 500 of these videos, and they all behave the same way.
And I assure you that the files are not the same if the file display internals were chagned by your copy work flow.
I did discover in QT 7 that if I go to the "Presentation" tab in the "Show Movie Properties", that I can set the "Conform aperture to:" to "Clean" and it sets the movie to 640x480 and removes the black bars.
Underscan issues are separate from aspect ratio issues. They can be eliminated by masking or cropping along with the re-scaling—the latter of which I've have been pointing out would correct your 720x480 (3:2 aspect ratio) to 640x480 (4:3 aspect ratio) which was the original title subject of your topic.
I believe this is the difference.
http://support.apple.com/kb/HT4265
All NTSC SD DV content is encoded 720x480 matrix content whether the aspect ratio is 4:3 or 16:9. To properly trim and scale the content as described by this article, the file must contain a valid setting flagging whether the original content was recoded with a 16:9 or 4:3 aspect ratio. This has yet to be proven to be the case of your copied file which the media info window states is now playing as a simple non-anamorphic 720x480 whereas your current example reads as a simple non-anamorphic 640x480 file. In most cases this does not matter if the source content was 4:3 aspect. However, any file with a "lost" flag setting will be treated as 4:3 aspect file whether the original content was recorded as 4:3 or 16:9 so there is a potential for problems here.