People here on videohelp have said that Quicktime has lots of quirks. I certainly have observed quirks with Quicktime Player 7 and 10 on Snow Leopard.
When I was using Mac O.S. 10.4 (Tiger), Quicktime Player 7 behaved predictably when adjusting the display of DV-NTSC 4:3 video (720×480) on my monitor according to Presentation settings in Properties. Upon switching conform aperture between Encoded Pixels, Production, and Clean, I could observe changes before my eyes, and it all made perfect sense. With conform aperture set to Encoded Pixels, the video appeared horizontally stretched, as it should. With conform aperture set to Production, the video was horizontally scaled to 655x480, without hiding transition samples on the left and right sides (common with digitized analog video). With conform aperture set to Clean, the video was displayed at 640x480, the horizontal scaling the same as Production, and the transition samples appropriately cropped on the left and right sides. The results were consistent with the Rec. 601 guidelines for horizontally cropping the source raster from 720 to 704 pixels, and scaling per the pixel aspect ratio, that I've learned on this forum.
However, since I started using Mac 10.6 (Snow Leopard) on a new iMac, Quicktime Player 7 no longer produces consistent results between the aforementioned Presentation settings. Egregious errors occur such as the source raster being cropped per clean aperture, with the cropped image horizontally stretched to a width of 655 pixels, upon Production aperture presentation; or the source raster not being cropped, and the video horizontally squeezed into a width of 640 pixels, upon Clean aperture presentation. I've even seen the display spontaneously and rapidly alternating back and forth between proper and squeezed, and/or proper and stretched, during playback, as reported by MyCometG3 on YouTube. I can no longer use Quicktime Player 7 as a guidepost for the proper scaling and cropping of DV-NTSC 4:3 video, and can no longer use it to demonstrate the Rec. 601 guidelines to someone.
I've noticed another phenomenon that is somewhat more subtle. Quicktime Player 10, which offers only Clean aperture presentation, appears to crop the source raster more tightly on the left and right sides than the default Clean aperture presentation I've seen of the same video in Quicktime Player 7. The tighter cropping means the image gets horizontally stretched to fill the width of 640 pixels. Later, I noticed a seemingly related phenomenon in Quicktime Player 7, upon fooling with Visual Settings of the Video Track in Properties. With the Deinterlace box checked, I observed that checking the High Quality box causes the video to become more tightly cropped, matching the Quicktime Player 10 presentation. In fact, I observed the video changing back and forth before my eyes, upon checking and unchecking the box. Then, I observed the same differences, back and forth, starting with the High Quality box checked, and checking or unchecking the Single Field or Deinterlace boxes. (I am clueless regarding whether any of this is repeatable phenomenon.)
Has anyone noticed any of the aforementioned phenomenon? Can anyone speculate on a possible reason for tighter cropping? Can anyone verify that Quicktime Player 10 crops DV-NTSC 4:3 video too tightly?
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helo just a short answer
make a search on BBC site about "pseudo-square pixels" (they have a very intersesting sheet about broadcasting needs, no idea about its link, I lose it). You will find that broadcasting does not display "real square pixels" (and a friend -working in a french national broadcaster- had the same conclusion ).
So you have to add some pixels more to keep final geometry (to not-normally stretch your src to obtain the good display). This is weird but "normal" (and the aperture>production now produces a stretched file compliant with this final broadcasting )
[…]a seemingly related phenomenon in Quicktime Player 7[…]
One version … one (different) default behavior, no constant behavior
PS (personal taste): after a lot of tries, I finally don't mind about real specifications/hacks for professional broadcasting, even broadcasters make some years to notice the "approwximative display"!!! So I continue to think with "real square pixels" (easier and simpler)