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MEDIASTUDIO PRO USER GUIDE
Inside digital video
There are three components that go into the makeup of digital video: frame
rate, frame size, and data type. The frame rate refers to the number of
frames that appear each second, while the frame size is the actual physical
size of each frame. The data type determines the number of colors allowed
to appear at one time. How you work with these three elements is deter-
mined by the type of video capture board available and your preferred
method of distribution. For instance, if you have a high-end capture board
and plan to output your data into a video tape, then you need the best quality
possible, like 640x480, 30 frames per second 24-bit color, for NTSC
devices. If you have a less expensive capture board, and plan to output your
video in a CD-ROM or over the Internet, then your decision on the type of
video is determined by the machine or medium it will be played back from.
This is because different machines and mediums have different abilities at
moving amounts of video data. This ability is referred to as the data rate,
which measures how much data can be moved within one second.
Working with the data rate
The problem with most venues where video is transmitted and viewed (e.g.
DVD players, computer disc players, the Internet, etc.) is that they have
trouble moving large amounts of data continuously. The specifications of a
majority of these devices give you an indication of how many kilobytes can
be moved at any one time. A DVD with a capacity of 4.7 to 17GB, has a
data rate of approximately 600kbps to 1.3mbps. Compare that to the
Internet where many people still operate with 56kb dial-up modems with a
data transfer rate of less than 57.6kbps!
Another point to consider is that while devices promote a specific data
transfer rate, very few can maintain that rate over an extended period. As
such, if your video comes in just under 600kbps, it doesn't necessarily
mean that most DVDs can play it smoothly. There are four factors that
affect the data transfer rate for video files: frame rate, frame size, data
type, and compression.
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