Although iTunes can play a variety of .mp4, .m4v, and .mov video formats, Apple TV and the iPod require more specific formats.
The iPod supports up to 640 x 480, while Apple TV supports up to 1280 x 720. To optimize for both platforms, it is recommended that your source file is at least 640 pixels wide and that you use the built-in iPod converters in Compressor (“H.264 for iPod”), QuickTime Pro (“Movie to iPod”), or iTunes (“Convert Selection for iPod”). Each of these maintains the aspect ratio of your source file and results in an M4V file containing H.264 video (Low Complexity version of the Baseline profile) and AAC-LC audio. If you want to maximize the screen area of a wide-screen TV, your source file should have an aspect ratio of 16:9 (for example, 640 x 360). If you want to maximize the screen area on the iPod, your source file should have an aspect ratio of 4:3 (for example, 640 x 480).
To use specific artwork for individual tracks within a video, use QuickTime Pro to set the video’s poster frame. A poster frame is a still image from a video that represents the video. The default poster frame is the first frame in the video. iTunes U displays the track artwork in places such as track links and the Get Info Summary pane upon download.
© 2009 Apple Inc. All Rights Reserved. (Last updated: 2009-11-04)