The problem was that with a maximum resolution of 640 x 480, only traditional television content, with its standard-definition TV 4:3 aspect ratio, actually took advantage of the full 480 lines of vertical resolution. Apple called the 640 x 480 resolution “near-DVD quality,” which to be fair was not far off, depending upon the aspect ratio of the source material. Until very recently, most of the video content available on the iTunes Store was encoded in a 640 x 480 maximum resolution, matching the published on-TV output capabilities of the fifth-generation iPod, as well as the rough limitations of standard-definition television sets. A standard DVD uses a resolution of 720 x 480-enough dots to create images that looked at least little more detailed than most pre-2000 vintage TVs were capable of displaying, and over four times as detailed as the 320 x 240 screens of 2005-2006 iPods could display. Resolution-or the number of dots that make up an on-screen image, measured in horizontal dots by vertical dots-is critically important in understanding how detailed or ‘defined’ a picture or movie will be. Semantics: An Introduction to How Apple Markets its Video Formats and Resolutions In this second part of our series on iTunes movie rentals, we examine the actual video formats that Apple now uses for its files, and the devices those files will and won’t play on.
Unfortunately, Apple has changed its approach somewhat with the release of video rental support and the Apple TV 2.0: certain iTunes Store files, specifically movie rentals, don’t work on certain Apple devices.
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