Section 12.3. The Share Presets: What They Mean

12.3. 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 hear any difference except when you listen through headphones or stereo speakers . When the sound plays through the built-in speaker on the standard Macintosh, most people can't tell the difference between 44.1 and 22 kHz.

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  Tip: All of the canned export presets preserve the stereo sound present in your original camcorder footage. Unfortunately, most computers don't have stereo speakers. (Some Mac models do, but not all.) Meanwhile, saving two independent soundtracks makes your QuickTime file larger than it would be if it were saved in mono.Therefore, if creating a compact QuickTime Movie file is important to you, consider using the Expert settings, described later in this chapter, to eliminate the duplicate soundtrack.

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• Time to compress one minute of video . The "Time to Compress" statistic provided below indicates how long it took a PowerBook G4 to compress a standard sample movie that's exactly one minute long. (Compressing a 10-minute movie, of course, would take about ten times as long.) Of course, the time it will take your movie to get compressed and saved depends on the codec you've chosen , the length of the movie, how much motion is visible on the screen, and your Mac's speed, but the next section offers a rough guide.

• File size . The final statistic provided for each option shows you how big the resulting QuickTime file might be (in megabytes). These numbers , too, refer to the sample one-minute DV movie described in the previous paragraph.

12.3.1. Email

Video codec: H.263

Size: 160 x 120

Frame rate: 10 per second

Audio codec: QDesign Music 2, mono, 22 kHz

Time to compress one minute of video: 1 minute

File size: 1.2 MB

The movie you export with these settings is fairly blurry, and the size of the QuickTime screen is closer in size to a Wheat Thin than a Cineplex.

Still, the H.263 video codec has two important benefits. First, it makes the exporting much faster than if you used, say, the MPEG-4 codec (which takes nearly twice as long). Second, the resulting QuickTime file is relatively tiny; at just over 1 MB for a minute-long movie, it's actually within the realm of possibility that you could email this thing to somebody without incurring their wrath. (The MPEG-4 codec produces a better-looking movie. But its movies are 3.3 MB per minutefar too large for casual emailing.)

12.3.2. Web

Video codec: H.263

Size: 240 x 180

Frame rate: 12 per second

Audio codec: QDesign Music 2, stereo, 22 kHz

Time to compress one minute of video: 1 minute, 35 seconds

File size: 2.4 MB

This kind of movie is much more satisfying to watch than the Email type. The image is over twice as big, and the higher frame rate produces smoother motion.

Once again, the MPEG-4 codec could provide far better image quality; but at 2.4 MB per minute, the product of the H.263 codec is small enough to download from a Web page without a high-speed Internet connection.

12.3.3. Web Streaming

In quality and size, this preset is identical to the Web preset described above. The only difference is that this kind of movie comes set up for streaming delivery from the Web, meaning it's played on your audience's screens as it's being sent from the Web. In other words, your viewers don't have to download the entire movie before playing it.

Streaming means that your movies can be extremely long, even if they're therefore extremely large files. Only a tiny bit at a time is sent to your spectators' computers.

For details on putting your QuickTime movies on the Web, see Chapter 13.

12.3.4. CD-ROM

Video codec: H.263

Size: 320 x 240

Frame rate: 15 per second

Audio codec: IMA 4:1, Stereo, 44.1 kHz

Time to compress one minute of video: 1 minute, 30 seconds

File size: 6 MB

As you can see by the specs above, a movie with the CD-ROM setup generally contains too much data to be suitable for live Web delivery. But saving your QuickTime productions into this kind of QuickTime file is ideal if you plan to play it from a hard drive or a CD-ROM that you record yourself, as described later this chapter. The high frame rate means that motion will seem smooth, and the 320 x 240 dimensions of the window mean that the movie will fill a decent fraction of the computer screen. That's big enough to see a good amount of detail.

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Tip: If you're willing to endure more compressing time and a larger resulting file, you can give your CD-ROM movies a dramatic picture-quality upgrade by substituting the MPEG-4 codec for the H.263 codec. (Use the Expert settings described on the next page to do so; duplicate the settings described here, but choose the MPEG-4 codec instead of H.263.)The only down side is that the resulting QuickTime movie contains too much data for older, slower CD-ROM drives , such as those rated below 12X, to deliver to the computer's brain. The movie will play on slower CD-ROM drives, but it will skip a lot.

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12.3.5. Full Quality

Video codec: Depends on project format. HDV project uses Apple Intermediate Codec; DV uses DV; iSight uses Motion JPEG; MPEG4 uses MPEG4 .

Size: 720 x 480

Frame rate: 29.97 per second (for NTSC; 25 for PAL)

Audio codec: No compression; stereo, 32 or 48 kHz (depending on source audio)

Time to compress one minute of video: 1 minute

File size: 411 MB

As the numbers (and the example in Figure 12-3) show you, this is the QuickTime format for people whose equipment doesn't mess around. The file size is massivemuch too large for playback from a CD-ROM drive.

That's because this setting isn't intended for playback; it's intended to offer you a means of storing your iMovie production without sacrificing any video quality. The Full Quality DV setting applies no compression at all to your audio or video.

Yet preserving your iMovie work as a giant, single DV clip on the hard drive is still a useful exercise. It can save hard drive space, for one thing, since the resulting Quick-Time file is still far smaller than the collection of DV clips in your project's Media folder from which it was made. After creating a Full Quality DV movie, you could delete the project folder to free up some disk space, confident that you've got your entire movie safely preserved with 100 percent of its original DV quality intact.