CHAPTER 11
300
Producing Final Video
Setting the data rate
Some video codecs let you specify the
data rate
, which controls the amount of video
information that must be processed each second during playback. Specifying a data rate
in Premiere actually sets the maximum data rate, because the actual data rate varies
depending on the visual content of each frame.
The data rate you specify depends on the purpose of the video. The following list describes
data rate guidelines for some uses:
Videotape production
The data rate should fall within the capabilities of the computer that
will play the Timeline or clip during videotape recording.
Hard disk playback
If your 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 edited further at maximum quality, use a lossless codec 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 double-speed CD-ROM drive
(300 KB per second) you might specify between 150 to 200 KB 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 100 KB per second or faster, depending on the speed
of your
intranet
. An intranet is an in-house or private network that uses Internet network
protocols. Because they are limited in scope, intranets generally use higher-quality communi-
cations lines than standard telephone lines, so they are usually much faster than the Internet.
Streaming video over the World Wide Web
The data rate should account for real-world perfor-
mance at the target data rate. For example, the data rate for streaming video designed for a
28,800 bps (bits per second) connection is often set to 20,000 bps. That’s because factors such
as data volume and line quality often prevent telephone-based Internet connections from
consistently achieving their stated data rate.
c11.fm Page 300 Wednesday, April 1, 1998 10:08 AM
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