Specifications

Video Cards for Multimedia
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Table 15.22 Television Versus Computer Monitors
Standard Year Est. Country Lines Rate
Television
NTSC 1953 (color) U.S., Japan 525 60 fields/sec
1941 (b&w)
PAL 1941 Europe
1
625 50 fields/sec
SECAM 1962 France 625 25 fields/sec
Computer
VGA 1987 U.S. 640×480
2
72Hz
Field = 1/2 (.5 frame)
1. England, Holland, and West Germany.
2. VGA is based on more lines and uses pixels (480) versus lines; genlocking is used to lock pixels into lines and syn-
chronize computers with TV standards.
A video-output (or VGA-to-NTSC) adapter enables you to display computer screens on a TV set or
record them onto videotape for easy distribution. These products fall into two categories: those with
genlocking (which enables the board to synchronize signals from multiple video sources or video with
PC graphics) and those without. Genlocking provides the signal stability necessary to obtain adequate
results when recording to tape, but it isn’t necessary for using a television as a video display.
VGA-to-NTSC converters are available as internal expansion boards, external boxes that are portable
enough to use with a laptop for presentations on the road, and TV-out ports on the rear of most video
cards using chipsets from NVIDIA, ATI, and others. Indeed, many laptop and notebook systems these
days come equipped with a built-in VGA-to-NTSC converter.
The converter does not replace your existing video adapter but instead connects to the adapter using
an external cable. In addition to VGA input and output ports, a video output board has a video out-
put interface for S-video and composite video.
Most VGA-to-TV converters support the standard NTSC television format and might also support the
European PAL format. The resolution these devices display on a TV set or record on videotape often is
limited to straight VGA at 640×480 pixels, although some TV-out ports on recent video cards can also dis-
play 800×600 resolution. The converter also might contain an antiflicker circuit to help stabilize the pic-
ture because VGA-to-TV products, as well as TV-to-VGA solutions, often suffer from a case of the jitters.
Video Capture Devices
You can capture individual screen images or full-motion video for reuse in several ways, including:
■ 3D accelerator cards with TV-in ports
■ TV tuner cards
■ USB- or parallel port–based devices such as TV tuner/capture devices discussed earlier or a dedi-
cated device such as the SnapMAGIC (available from
www.snapnsend.com)
■ Webcams with video input ports
These units capture still or moving images from NTSC video sources, such as camcorders and VCRs.
Although image quality is limited by the input signal, the results are still good enough for presenta-
tions and desktop publishing applications. These devices work with 8-, 16-, and 24-bit VGA cards and
usually accept video input from VHS, Super VHS, and Hi-8 devices. As you might expect, however,
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