Specifications

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Chapter 15 Video Hardware
Super VHS and Hi-8 video sources give better results, as do configurations using more than 256
colors. For the best results, use DV camcorders equipped with IEEE 1394 (i.LINK/FireWire) connectors;
these can output high-quality digital video direct to your computer without the need to perform an
analog-to-digital conversion. If your computer doesn’t include an IEEE 1394a or 1394b port, you must
install an IEEE 1394 add-in card if you want to capture output from a DV camcorder.
Desktop Video Boards
You can also capture NTSC (television) signals to your computer system for display or editing. In
other words, you can literally watch TV in a window on your computer. When capturing video, you
should think in terms of digital versus analog. The biggest convenience of an analog TV signal is effi-
ciency; it is a compact way to transmit video information through a low-bandwidth pipeline. The dis-
advantage is that although you can control how the video is displayed, you can’t edit it.
Actually capturing and recording video from external sources and saving the files onto your PC
requires special technology. To do this, you need a device called a video capture board (also called a TV
tuner, video digitizer, or video grabber).
Note
In this context, the technical nomenclature again becomes confusing because the term video here has its usual connotation;
that is, it refers to the display of full-motion photography on the PC monitor. When evaluating video hardware, be sure to dis-
tinguish between devices that capture still images from a video source and those that capture full-motion video streams.
Today, video sources come in two forms:
■ Analog
■ Digital
Analog video can be captured from traditional sources such as broadcast or cable TV, VCRs, and cam-
corders using VHS or similar tape standards. This process is much more demanding of storage space
and system performance than still images are. Here’s why:
The typical computer screen was designed to display mainly static images. The storing and retrieving
of these images requires managing huge files. Consider this: A single, full-screen color image in an
uncompressed format can require as much as 2MB of disk space; a 1-second video would therefore
require 45MB. Likewise, any video transmission you want to capture for use on your PC must be con-
verted from an analog NTSC signal to a digital signal your computer can use. On top of that, the
video signal must be moved inside your computer at 10 times the speed of the conventional ISA bus
structure. You need not only a superior video card and monitor, but also an excellent expansion bus,
such as PCI or AGP.
Considering that full-motion video can consume massive quantities of disk space, it becomes appar-
ent that data compression is all but essential. Compression and decompression apply to both video
and audio. Not only does a compressed file take up less space, it also performs better simply because
less data must be processed. When you are ready to replay the video/audio, the application decom-
presses the file during playback. In any case, if you are going to work with video, be sure that your
hard drive is large enough and fast enough to handle the huge files that can result.
Compression/decompression programs and devices are called codecs. Two types of codecs exist:
hardware-dependent codecs and software (or hardware-independent) codecs. Hardware codecs typi-
cally perform better; however, they require additional hardware—either an add-on card or a high-end
video card with hardware codecs built in. Software codes do not require hardware for compression or
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