ADOBE AFTER EFFECTS 7.0
User Guide
620
Non-DV videotape production The data rate should fall within the capabilities of the computer and hard disk that
perform the final playback to tape.
Hard-disk playback If the final video will be played back from a hard disk, determine the typical data transfer rate
of your audience’s hard disks and set the data rate accordingly. If you are 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.
CD-ROM playback The data rate for video played from a CD-ROM depends on the speed of the drive. For example,
if you are 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.
Intranet playback The data rate can be 1 megabit per second or faster, depending on the speed of your intranet.
Because they are limited in scope, intranets generally use higher quality communications lines than standard
telephone lines, so they are usually much faster than the Internet.
Streaming video over the web The data rate should account for real-world performance at the target data rate. For
example, the data rate for streaming video designed for a 56-kilobit-per-second connection is often set to 40 kilobits
per second. That’s because factors such as data volume and line quality 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 Thedatarateislessimportantthanthesizeofthevideofileondisk,because
themainconcernishowlongittakestodownloadthefile.However,itstillmaybedesirabletoreducethedatarate
for downloaded video because doing so reduces the size of the video file, making it download faster.
If you use Adobe Premiere Pro, use the Get Properties For command to analyze the data rate of files you export.
To specify QuickTime compression options
1 In the Render Queue panel, click the underlined name of the output module.
2 For Format, choose QuickTime.
3 Click Format Options in the Video Output section.
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.
5 Select a Quality level from Least to Best.
Note: (Mac OS only): If you intend to use keyframes in the movie, hold down Option and adjust the Quality slider to
control the temporal compression of the movie. Temporal compression compresses a movie by comparing successive
frames and keeping only changed data. High temporal quality maintains smoothness of motion. Low temporal quality
tends to produce jerkiness of motion because a pixel doesn’t change unless the difference between frames is great.
6 If you want the smallest possible files, and your compressor choice allows for a key frame rate, select the box and
type a number in the Key Frame Every box. Generally, you should type a number equal to the frame rate. For
example, if you set a frame rate of 30 fps, type 30 in the Key Frame box. This sets one key frame every 30 frames of
your movie.
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