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About data rate
With
some video codecs, you can specify the data rate, which
controls the amount of video information that is processed each
second during playback. Specifying a data rate in Adobe Premiere Elements sets the maximum data
rate because the actual data rate varies according to 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:
- DVD production
- The
data rate should maximize quality while fitting the entire program
within the space available on the DVD. By default, Adobe Premiere Elements automatically adjusts the DVD
data rate.
- Non-DV videotape production
- The
data rate should be well within the data transfer rate of your hard
disk because the video will be played back from the hard disk to
the recording device. Check your documentation for information on the
data transfer rate of your hard disk.
- Hard disk playback
- Determine the typical data transfer rate of your audience’s hard
disks and set the data rate accordingly. Generally, 7200 rpm hard
disks have sustained data rates of 20 to 35 MB per second, which
is high. In comparison, the average data rate of digital video is
3.6 MB per second. So, to achieve high-quality playback, you may
not need to set the data rate as high as 20 to 35 MB per second.
However, if you are exporting video for use in another editing system
or in a compositing application, such as Adobe After Effects, export
at the maximum quality. Use a lossless codec, which is one that
compresses without discarding information, and specify the data
rate that the editing system supports for video capture and editing.
- CD-ROM playback
- The
data rate depends on the speed of the CD drive. For example, if
you are preparing a final video file for a double‑speed CD‑ROM drive (300
kilobytes per second) you might specify between 150 kilobytes and 200 kilobytes
per second to account for both the data rate of the drive and the system
overhead required to move the data.
- Intranet playback
- The
data rate can be 100 kilobytes 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
communications lines than standard telephone lines, so they are
usually much faster than the Internet.
- Streaming video over the web
- Though there
are fewer users with dial‑up connections than in previous years,
you should still consider tailoring your data rate to users still
employing this method of accessing the Internet if you want your
file to be viewable to the largest number of users. Streaming video
on the web is constrained by the limited bandwidth (56 KB or less)
of most consumer modems. Use a higher bitrate if you know your audience
has broadband Internet access, such as DSL or cable modem service.
- Playing back from a handheld device
- The
data rate is very important due to the relatively small size, capacity,
and lesser speed of handheld devices. The data rate can range from
8 to 90 kilobits per second, depending upon the device. You can
choose preset QuickTime export options in Adobe Premiere Elements to
export a file optimized for playback on a handheld device.
- Downloading a video file over the web
- The data rate is less important than the size of the video
file because 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.
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