iMovie 6 & iDVD: The Missing Manual

The Share Presets: What They Mean

iMovie offers several ready-to-use QuickTime compression settings that govern the quality, file size, and playback-window size of the movie you’re exporting. Here’s a guide to these presets to help you choose the one that’s appropriate for your movie-distribution plans.

Each of the descriptions below includes the following information:

• Video codec. As noted earlier, iMovie offers access to QuickTime’s long list of codecs, each offering a different tradeoff in compression speed, file size, picture quality, and so on. These codecs are described in detail in the next section.

• Size. These dimensions, in pixels (of which there are 72 per inch on your computer screen), indicate how big the finished QuickTime movie “screen” window will be. Use Figure 12-3 to guide you.

• Frame rate. This number tells you how many frames (individual pictures) you’ll see per second when the QuickTime Movie plays back. Thirty frames per second is standard NTSC television quality (in PAL countries, it’s 25 per second). Ten to fifteen frames per second begins to look less smooth, and anything under ten yields a flickering, old-time movie effect.

  Trivia: Old-time silent movies actually played at eighteen frames per second.

• Audio codec. This statistic is the sonic equivalent of the frame rate, in that it tells you what kind of sound quality you’ll get. At 44.1 kHz, the quality is exactly the same as that of a commercial music CD. At 22 kHz, it’s half as good, but you won’t ...