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Using compression
As mentioned previously, one second of video can easily require as much
as 30 MB of disk space. No conventional hard drive can transfer that
much data with sufficient speed, and it is only through compression that
desktop systems can manage to work with video. In all, there are two
types of compression you can use when you capture: hardware-based
and software-based.
Hardware-based compression, such as MJPEG or MPEG, relies on
additional memory on the video capture board to compress video. This
provides the smallest file sizes with the best quality. The downside is that
video with hardware-compression can only be played back on machines
with a similar setup.
Software-based compression, such as Cinepak and Indeo, is handled by
your system which has to share the job of compressing with anything else
running. While software-based compression is unable to match the com-
pression ratios of hardware-based compression, it is device independent
and therefore can be played back on a variety of machines. This makes
software-based compression the ideal choice for video intended for
distribution on other machines via CD-ROM or the Internet.
Techniques for improving your video captures
Even if you don't have the ideal system for capturing video, you can still
achieve good results by working around the limitations of what you do
have. For example, you can:
• Close all other programs that may be running in the background to free
up as much CPU resources as possible.
• Regularly defragment your hard drive with a utility such as Windows
Disk Defragmenter from the Systems Tools menu. (Fragmented drives
force the hard drive to slow down as it has to seek available free space
to save a file.)
• Dedicate a separate hard drive for your video captures, or a separate
partition on an existing hard drive.
• Capture at the best quality possible and then resample down if neces-
sary. Resampling up creates (interpolates) new data which results in
lower quality than the original.
VIDEO CAPTURE: CHAPTER TWO
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