Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 619

About data rate
With some video and audio codecs, you can specify the data rate, also called the bit rate, which controls the amount
of video information that must be processed each second during playback. Specifying a data rate actually sets the
maximum data rate, because the actual data rate varies depending on the visual content of each frame.
To maximize the quality of encoded video, set the data rate as high as the target delivery medium can support. If you
plan to stream video to an audience using dial-up Internet access, this may be as low as 20 kilobits per second;
however, if you plan to distribute video on DVD, it may be as high as 7 megabits per second. The data rate you specify
depends on the purpose of the video. The following list describes data rate guidelines for some uses:
The data rate should maximize quality while fitting the entire program within the space available
DVD production
on the DVD.
Non-DV videotape production
perform the final playback to tape.
If the final video will be played back from hard disks, determine the typical data transfer rate of
Hard-disk playback
your audience's hard disks and set the data rate accordingly. If you're exporting video to be used in another editing
system or to be imported into a compositing application, you'll want to export at the maximum quality. Use a lossless
codec or the codec supported by your video capture card, and specify the data rate that the editing system supports
for video capture and editing.
The data rate for video played from a CD-ROM depends on the speed of the drive. For example,
CD-ROM playback
if you're preparing a final video file for a quad-speed CD-ROM drive (600 kilobytes per second), you might specify
between 300 and 500 kilobytes per second to account for both the data rate of the drive and for the system overhead
required to move the data.
The data rate can be 1 megabit per second or faster, depending on the speed of the intranet.
Intranet playback
Streaming video over the web
example, the data rate for streaming video designed for a 56-kilobit-per-second connection is often set to 40 kilobits
per second. The difference accounts for factors such as data volume and line quality that often prevent telephone-
based Internet connections from consistently achieving their stated data rate. For broadband connections, set the
data rate for streaming video to 128 kilobits per second.
Downloading a video file over the web
the main concern is how long it takes to download the file. However, it still may be desirable to reduce the data rate
for downloaded video because doing so reduces the size of the video file, making it download faster.
In Adobe Premiere Pro, use the File > Get Properties For command to analyze the data rate of files you export.
Specify QuickTime compression settings
In the Render Queue panel, click the underlined name of the output module.
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2 For Format, choose QuickTime.
Click Format Options in the Video Output section.
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4 In the Compression Settings dialog box, choose a compressor.
Note: Set the color depth in the Compression Settings dialog box instead of in the Output Module Settings dialog box.
This ensures that non-Adobe plug-ins receive color depth information from After Effects. See step 8.
Select a Quality level from Least to Best.
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The data rate should fall within the capabilities of the computer and hard disk that
The data rate should account for real-world performance at the target data rate. For
The data rate is less important than the size of the video file on disk, because
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