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 component video. This mid-level format divides the signal into two channels - luminance and chrominance.
The luminance signal and modulated chrominance subcarrier information are carried on separate signal/ground pairs. The luminance signal is effectively a black-and-white television signal with the timing of a colour composite video signal. Because the luminance signal is carried on a separate wire, it does not need to be low-pass filtered to prevent crosstalk between high-frequency luminance information and the colour subcarrier.
This allows a higher bandwidth to be used for the luminance information, and also eliminates the colour crosstalk problem.
The luminance performance of S-Video is similar to analog component video, but the chrominance performance retains most of the other defects of composite video, apart from the crosstalk problem.
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.
S-Video is commonly used on consumer DVD players, VTRss, and modern game consoles. It is also available on some professional equipment and computer video capture and playback cards.