Science Fair Project Encyclopedia
S-Video
S-Video (also known as Y/C) is a digital video format offering a higher quality signal than RGB and component video. This mid-level format divides the signal into two channels—luminance (Y) and chrominance (C).
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Method
The luminance signal and modulated chrominance subcarrier information are carried on separate synchronized signal/ground pairs.
In composite video, the luminance signal is low-pass filtered to prevent crosstalk between high-frequency luminance information and the color subcarrier. S-Video, however, separates the two, so low-pass filtering is not necessary. This increases bandwidth for the luminance information, and also subdues the color crosstalk problem.
While the luminance performance of S-Video compares favorably to analog component video, the chrominance performance—aside from reduced crosstalk—does not show notable improvement over composite video.
S-Video signals tend to degrade considerably when transmitted across more than 5 meters of cable. For long distances, component or composite video may provide better quality.
Connector
Today, S-Video signals are generally connected using 4-pin mini-DIN connectors using a 75 ohm termination impedance. The pins in the connectors bend easily, hence care must be taken when plugging the cables in—else a pin is likely to bend, causing the loss of color, corruption of the signal, or complete loss of the signal.
Before the mini-DIN plug became standard, S-Video signals were often carried through different types of plugs. For example, the Commodore 64 home computer of the 1980s, one of the first widely available devices to feature S-Video output, used an 8-pin standard size DIN plug on the computer end and a pair of RCA plugs on the monitor end.
Today, S-Video signals can be transferred through SCART connections as well. However the SCART connector must explicitly support S-Video as it is not part of the original SCART standard.
Usage
S-Video is commonly used on consumer DVD players, VTRs, and modern game consoles. It is also available on some professional equipment and computer video capture and playback cards. However, S-Video cannot transmit HDTV signals since there is not enough available bandwidth to carry the video.
See also
References
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