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S-Video

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S-Video (also known as Y/C) is a baseband analog video format offering a higher quality signal than composite video, but a lower quality than RGB and component video. This mid-level format divides the signal into two channels - luminance and chrominance.

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, VCRs, and modern game consoles. It is also available on some professional equipment and computer video capture and playback cards.

See also