After spending several days editing footage for your nonprofit organization's outreach video, you're ready to distribute the finished movie. You'll need to burn a few copies to CDs (for both Macs and PCs) that you can hand out at a meeting, and you want to put the movie on your Web site for a worldwide audience. You could shell out big bucks for the $449 Sorenson Squeeze 3 Compression Suite or $599 Discreet Cleaner 6, but if you're on a budget, Apple's $30 QuickTime 6 Pro can do the job.
Although iMovie, Final Cut Express, and Final Cut Pro (all based on QuickTime) provide default settings for generating files appropriate for various uses, you'll find that by tweaking QuickTime's Export settings, you can create movies that are more compact and better looking than the movies your video-editing application automatically outputs.
To give your movies manageable file sizes, you must compress them. QuickTime includes a variety of compressors/decompressors (or codecs) designed to do just that -- we'll focus on two that produce movies of both reasonable size and good quality: the Sorenson 3 and MPEG-4 video codecs.
However, the codec you choose is only one factor in creating superior movies. The size of your movie, the number of frames per second (fps), and the frequency of keyframes also affect the final product.
You can manipulate codecs, filters, and movie settings via the Export command in iMovie, Final Cut Express and Pro, and QuickTime Pro. Doing so in your video application saves the time (and disk space) required if you export the movie in an uncompressed form and then compress it within QuickTime.
To access iMovie's Expert Settings, select File: Export. In the resulting window, choose To QuickTime from the Export pop-up menu and Expert Settings from the Formats pop-up menu. Click on the Export button to reveal the Save Exported File As window. Select Movie To QuickTime Movie from the Export pop-up menu, and click on the Options button. In the resulting Movie Settings window, click on Settings, Filter, or Size to adjust those settings. You can change the same settings in Final Cut Pro by choosing File: Export: QuickTime and then clicking on the Options button in the Save window. In QuickTime Player, choose File: Export.
Movies for Modems
Any movie that will be accessed via a dial-up modem connection requires sacrifices in the movie's frame size (number of pixels) and quality.
Begin by reducing the size. Though a modem connection that delivers data at between 48 and 52 Kbps may be able to play movies as large as 256 by 192 pixels, you're safer with 160 by 120. To adjust screen size, click on the Size button in the Movie Settings window and enter the width and height values you desire.
To adjust the frame rate, frequency of keyframes, and maximum data rate, click on the Settings button in the Movie Settings window. In the top pop-up menu, choose the codec you'll use. The Sorenson Video 3 codec is a good choice if people viewing your movie are likely to have Macs or PCs made in the past five years. (Decoding a movie compressed with the Sorenson 3 codec requires a reasonably powerful processor, such as a PowerPC G3 or Pentium II. And Sorenson 3 works only with QuickTime 5 and 6.)
You should set frame rates to a common divisor of the original frame rate -- 5, 7.5, 10, or 15 fps for a 30-fps movie, for example. For this low-bandwidth movie, set frame rate to 7.5 or 10 fps. (Compress at the higher frame rate first; if the movie you create plays back smoothly over a test connection similar to your intended audience's, use that version.)
Keyframe rates for Sorenson-encoded video are typically 10 times the frame rate you've chosen -- a keyframe every 10 seconds -- so use either 75 or 100, depending on whether you've entered a frame rate of 7.5 or 10 fps.
To determine your data rate, divide the download speed by 10, and then change bits to bytes. So, for example, if you expect download speeds of 48 Kbps over a dial-up connection, aim for a data rate of 4.8 KBps. This results in a conservative value that you can use as a starting point. Once you've entered a data rate in this window, the Quality setting has no effect -- leave the slider where it is.
Now compress the audio track. Click on the Settings button under the Audio heading in the Movie Settings window. Select QDesign Music 2 from the Compressor pop-up menu and 22.050kHz from the Rate pop-up menu, select the 16-Bit and Mono options, and click on OK.
Finally, in the Movie Settings window, select the Prepare For Internet Streaming option and choose Fast Start-Compressed Header from the pop-up menu below that. These options allow your movie to begin playing back before it has completely downloaded (this scheme is called progressive download).
The Broadband Movie
With movies intended for progressive download over a broadband connection, you can safely make the proportions bigger, increase the frame rate, and bump up the data rate.
If you expect your movie to be downloaded over a 256-Kbps DSL connection, make its size 240 by 180 pixels. If it's longer than 5 minutes, choose a frame rate of 10 fps. If it's shorter, or if you suspect that your viewers will have a connection faster than 256 Kbps (or that they'll be patient while your movie downloads), choose 15 fps. When using the Sorenson 3 codec, choose a keyframe rate of 100 or 150, depending on the fps value you've entered. Using the "divide by 10" rule, enter 25 KBps for the data rate.
As you did with the modem movie, use the QDesign Music 2 codec set to 22.050kHz, 16-Bit, Mono. Select the Prepare For Internet Streaming option and choose Fast Start-Compressed Header from the pop-up menu at the bottom of the Movie Settings window.
Alternatively, if you're sure your viewers have QuickTime 6, create an MPEG-4 movie (prior versions of QuickTime don't support MPEG-4). Such movies can be smaller and better-looking than those compressed with the Sorenson 3 codec. Another advantage of MPEG-4 movies is that they compensate for differences in standard brightness, so they look the same played on Macs and Windows PCs.
It's easy to create MPEG-4 movies. Go to File: Export, and select Movie To MPEG-4 from the Export pop-up menu (this option appears only if you have installed QuickTime 6) and DSL/Cable-Medium from the Use pop-up menu. Click on Save to save your movie as an MPEG-4 file. If you click on the Option button instead, you can edit the movie settings in the MPEG-4 Settings window -- increase the data rate, change the fps number, alter the frequency of keyframes, and change the audio resolution. This window offers another benefit: it tells you when you've chosen an invalid selection of settings (and therefore risk producing a movie that will play poorly).
Before significantly altering these values, you should consider using either the DSL/Cable-Low or DSL/ Cable-High settings in the Use pop-up menu. As you'd expect, the Low setting creates a smaller, lower-quality movie than the Medium setting. The High setting creates a movie that takes longer to download but looks better than Low or Medium movies.
Movie on Disc
Thanks to the speed of today's media drives, you can open the data floodgates when producing video intended for CD-ROM or DVD-ROM distribution. To begin, create a 320-by-240-pixel movie, and leave the fps field blank -- this ensures that the exported movie will use the same frame rate as the original.
If you need to fit a lot of video onto your disc, reduce the frame rate to 15 fps.
If you compress your movie with the Sorenson 3 codec and the original movie plays at 30 fps, choose a keyframe frequency of 300 (the frame rate times 10). Because the Sorenson 3 codec can make fine-looking disc-based movies at data rates lower than 100 KBps, test your movie at a data rate of 85 KBps and increase that number if you're unhappy with the results. You have enough available bandwidth for better-sounding audio, too, so choose the IMA 4:1, 44.1kHz, 16-Bit, and Stereo options. Alternatively, select the Movie To MPEG-4 option from File: Export and choose LAN from the Use pop-up menu. This creates a 320-by-240 movie that plays smoothly on media drives made in the past three years.