I hooked my MacBook Pro to a Panasonic 58″ 3D plasma display today and fed it a 3D video in the form of side-by-side video content. The good news is that the display showed a perfectly good 3D image when told to expect side-by-side content (yay!). However, there was a problem with my stereo 3D video: for some reason, all of the 3D content was pushed way back past the stereo window. The only way this would happen is if the left and right video content were diverged; upon closer inspection, it was obvious that this was the case.

At first, I though I might have screwed up my video export, so I exported it again. The problem remained. On a whim, I fired up Quicktime 7 to play the side-by-side video, and the problem went away! I ran some more tests, and it turns out that by default, Quicktime X overscans! That’s right — it cuts off video content all around the edges.

Quicktime output of side-by-side content

Zoomed: overscan is obvious

Inner red rectangle is Quicktime X’s cropped output

Normally, one might not notice a small percentage of video content disappearing (in fact, it is standard practice in TV), but in side-by-side stereo 3D content, overscanning has the effect of diverging the image, pushing it back through the stereo window. The left part of the left eye’s video (on the left side of the screen) is cut off, the right part of the right eye’s video is cut off, and the new full images are overlaid, resulting in an introduced horizontal divergence.

Combined with Quicktime X’s propensity to screw up anaglyph 3D video colors, stereographers should just stay away from Quicktime X altogether. I would just delete it from my system, but when I do that, double clicking on a Quicktime movie opens Final Cut Pro instead of Quicktime 7. There is no apparent way to change the default application for file types in Mac OS X¹, and opening Final Cut Pro is not good default behavior.

In hindsight, Quicktime X’s overscan was obvious all along. When I open a 1920×1080 video and hit cmd-i for video info, I see this:

I always wondered what the “1888 x 1062 (Actual)” current size meant. Now I know that Quicktime X is throwing away 32 horizontal pixels and 18 vertical pixels (1.67% of each axis). If you change the display size of the video, the current size changes, but it never shows more than 1888 x 1062 of the actual content — it just scales up the existing crop.

Once again, Quicktime X proves itself as a huge waste of time for professional users.