S-Video
S-Video (also known as Y/C and SVHS) is an analog video signal, though many retail packages of s-video cables are incorrectly labeled as digital video, probably to impress the retail customer. S-Video will appear better than composite video since the TV does not have to decode the brightness and color information that are found together on composite video.
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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 with some s-video cables.
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 can bend easily but this is usually not a problem when properly inserting it to the s-video receptacle. If a pin is bent the result could be 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. The S-Video connector is the most common video-out connector on laptop computers.
Today, S-Video signals can be transferred through SCART connections as well. However the device that has the SCART connector must support S-Video as it is not part of the original SCART standard. For instance, a VCR that has a SCART connector may not support S-Video, so if you try to connect an S-Video signal through a SCART connector you will get black and white signal.
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.
See also
References
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
Categories: Video and movie technology | Electrical connectors