12.5. The Video Codecs: A Catalog When you decide to export your iMovie production as a QuickTime movie, you can get a great deal of control out of how the Mac produces the resulting movie file by choosing Expert from the dialog box shown in Figure 12-1, then clicking Options (Figure 12-5), and then clicking Settings (Figure 12-6). You get access to a long list of codecs. As you can read in this listing, few of these codecs are very useful for everyday use. Many of them are designed for saving still frames (not movies), for storing your movies (not playing them), or for compatibility with very old versions of the QuickTime software. Most of the time, the Sorenson Video 3 compressor (for CD or hard drive playback) or Apple H.263 (for Internet playback) are the ones that will make you and your audience the happiest.
Note: The list of codecs that pop up in your dialog boxes may not match what you see here. Your codecs reflect the version of QuickTime that you have installed, which may be older or newer than the 6.5.2 version described here.
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Animation. This codec is significant because, at its Best quality setting, it maintains all of the original DV picture quality, while still managing to convert files so that they're smaller than files with no compression at all. (As the name implies, this codec was originally designed to process video composed of large blocks of solid colorsthat is, cartoons.) The resulting file is therefore huge when compared with the other codecs described here, but not as huge as it would be if you used the None choice in this pop-up menu. As a result, the Animation codec is a popular format for storing or transferring QuickTime footage from one piece of video-editing software to another. Because the files are so huge, however, it's not so great as a finished movie file format. -
Apple H.263, Apple VC H.263, H.261. These codecs were designed for video teleconferencing (VC), in which a tiny, jerky image of you is transmitted over a telephone line to somebody who's also equipped with a video telephone. Apple's version, however, does a very good job at maintaining a good picture, while keeping the file size very small. In fact, Apple H.263 should be one of your first choices if you plan to send your video by email or post it on a Web page.
Tip: These codecs work best in footage where very little is going onlike a person sitting in front of a video telephone. The more that the frame remains the same, the better the picture quality, which is yet another argument for using a tripod whenever you can.
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Apple Pixlet Video. Pixlet was designed for use by a professional film companyPixar, to be exact. Film and TV editors want to be able to edit movies with perfect frame quality and perfect frame accuracywithout having to ship gargantuan, full-resolution, multi-gigabyte files across the network or across the country. Pixlet is the answer. It compresses the original, film-resolution movie down to about a twentieth of its original file size, without introducing any artifacts (specks or blockiness). Unlike other codecs, Pixlet doesn't compress video over time; that is, it doesn't memorize one key frame and then, for the following frames, store only the information for the pixels that have changed. Pixlet stores all of the color information for every single frame. (It achieves its compression solely by compressing the color information within each frame.) The point of all this is to permit editors to scrub back and forth through a scene, stepping frame by frame if they like, and viewing full, instantaneous, half-high-definition resolution at every step. The bottom line: It's not intended for compressing iMovie masterpieces. -
Cinepak. This compressor produces very tiny QuickTime files. Until the invention of the Sorenson codec described below, almost all CD-ROM-bound QuickTime movies were compressed using this codec. Unfortunately, the compromises are severe: The picture quality is often greatly degraded, and the compression and saving process takes a very long time. -
BMP, PNG, Photo-JPEG, JPEG 2000, PNG, TIFF. You may recognize these formats as popular still image file formats. Remember that QuickTime is designed to be a Grand Central Station for multimedia files of all kindsnot just movies, but sound files and graphics files as well. These graphics-format options are largely irrelevant to movies. (They appear in your Compressor list because they're among QuickTime's master list of codecs, all of which are made available to QuickTime savvy software programs like iMovie.) -
Component Video. In the era before digital video, you could convert footage from your camcorder into a digital file only if you had a digitizing card, an expensive circuit board for this purpose. Component Video is the format these digitizing cards used, because it could store video extremely quickly on your hard drive during the digitizing (capturing) process. It was designed for real-time recording speed, not for compression. The files it creates require huge tracts of disk space. -
DV-PAL, DVCPRO-PAL. These options are here so that you can export your iMovie masterpiece in the European video format (PAL), while retaining full DV size and frame rate. (DVCPRO is a slight variant of the DV format, intended for use with super-expensive professional broadcast TV video gear.) Unfortunately, the quality of the video suffers when you make this kind of conversion, especially in action scenes. -
DV/DVCPRO -NTSC. Suppose you've just completed a masterful movie, and the thought of compressing it to some much smaller, image-degraded QuickTime movie breaks your heart. You can use this codec to turn your finished, effect-enhanced, fully edited iMovie production into a new, raw DV clip, exactly like the DV clips in the Media folder in your project folder. You might do so if, for example, you wanted to import your entire movie into another DV-editing program, such as Final Cut Express or Final Cut Pro, or if you wanted to turn it into a Video CD or DVD, as described at the end of this chapter. ( DV, of course, means digital video; NTSC is the format used in the Western Hemisphere and Japan.) -
Graphics. Uses a maximum of 256 colors to depict each frame. The result is grainy and blotchy. Use it only if your movie contains nothing but solid-colored images, such as cartoons, pie charts , or other computer-generated simple images. Even then, this aging codec doesn't compress the video very much. -
Motion JPEG A, Motion JPEG B. These codecs don't perform any temporal (frame-to-frame) compression. Each movie frame is saved as an individual, full- sized color picture. The disadvantage is, of course, that the resulting files are extremely large. In fact, you need to buy a special circuit board for your computer just to play back this kind of movie. In other words, motion JPEG is occasionally useful when editing video, but never for distributing it. So what good is it? Motion JPEG is the format used by many professional DV-editing machines (such as those from Avid, Accom, and Discreet). Because there's no key-frame business going on, editors can make cuts at any frame. (Doing so isn't always possible in a file created by a codec that stores only the difference between one frame and the next . A particular frame might contain data that describes only new information, as shown in Figure 12-4.)
Tip: Motion JPEG is not the same thing as MPEG, which is the format used to store movies on the DVD discs you can rent from Blockbuster. Despite the similarity of names , the differences are enormous . For example, MPEG uses temporal compression and requires special software to create.
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None. If quality is everything to you, and disk space and Internet-ability are nothing, you can use this option, which (like the DV codecs) doesn't compress the video at all. The resulting QuickTime file may contain so much data that your computer can't even play it back smoothly. You can, however, put it in a cryogenic tank in anticipation of the day when superfast computers come your way. -
Planar RGB. This format is another one that's designed for use with still images, not with video. This one preserves the alpha channel of the graphic (a transparency feature), so that, if you owned a fancier editing program, you could superimpose a photo on top of the video. POWER USERS' CLINIC
Secrets of the Sorenson Codec | | Because the Sorenson Video 3 codec offers such high quality at such small file sizes, getting the most out of it has become the subject of many a Web page and Internet discussion group . A few highlights: -
When you play back a Sorenson movie in QuickTime Player (Chapter 14), you can use the Movie  Double Size command to enlarge the "movie screen." Technically, all QuickTime Player does is double the size of each pixel of each framebut the result looks very good when compared with movies prepared by other codecs. -
Don't create key frames any more often than one per second: They take up a lot of disk space and degrade the movie quality. If your movie plays at 12 frames per second, therefore, use a number that's twelve or higher in the Key Frames box shown in Figure 12-6. -
If you're a professional, or soon to become one, $300 buys you something called the Sorenson Video Pro codec. It offers a number of extremely technical added options that, in the right hands, lead to even better quality QuickTime movies. For example, the Pro version generates key frames automatically at the beginning of each new cut, and offers variable bitrate encoding a compression scheme whereby frames filled with motion or transitions get the most "attention" by the data in the movie, and less active frames get correspondingly less. The result is more efficient use of the movie's dataand better visual quality. (Note, though, that only high- powered software like Cleaner and Sorenson's own Squeeze software can apply the Sorenson Pro codec. iMovie and QuickTime Player alone cannot.) If you've ever wondered why your iMovie films , when exported as QuickTime movies, don't look quite as good as the Hollywood movie ads on the Apple Web site, now you know part of the story. |
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Sorenson Video, Sorenson Video 3. Here it isthe codec that gives you very high quality with very good compression, and files so small that you can play them from a CD-ROM or even over the Internet. Sorenson-compressed movies play back on either Macs or Windows computers, too. (Use Sorenson Video 3 if possible. Use the older Sorenson Videowithout a numberonly if your audience might still be using some ancient version of QuickTime to play back your opus.) -
Video. You might think of this, one of the original QuickTime codecs, as the "fat Sorenson." The quality is very high, and it doesn't take very long to compress and save the movie in this formatbut the compression is light. The resulting files aren't suitable, therefore, for transmitting on the Internet.
Tip: The Video compressor doesn't take very long to save a QuickTime file. For that reason, it's a great choice of format when you want to test your finished iMovie. You can see how it will look as a QuickTime movie, see how your transitions and titles will look, experiment with different frame rates, and so on.
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