What is S-Video?

Separate Video (S-Video, sometimes referred to as Y/C Video, or S-VHS) is a video signal transmission in which the luminance signal and the chrominance signal are transmitted separately to achieve superior picture clarity. The luminance signal (Y) carries brightness information, which defines the black and white portion, and the chrominance signal (C) carries color information, which defines hue and saturation. Traditional or composite video, the way that video signals have traditionally been transmitted, sends both (along with synchronization data) as one signal.

Television sets are actually designed to display luminance and chrominance signals separately. Composite signals must be separated before they can be displayed. When the signals are sent as a composite, they overlap at a frequency range above 2.1 megahertz (MHz). The overlapping areas are difficult to separate entirely, and the remnants of either signal within the other creates video errors. Vestiges of chrominance data remaining in the luminance data cause a cross-luminance effect that creates a dot structure pattern (this is sometimes referred to as "dot crawl"), and vestiges of luminance data remaining in the chrominance data create "rainbow" effects in detailed patterns called "cross-color". Sending the signals separately, as in S-Video, circumvents this error-prone process.

What are the advantages of S-Video over composite video?

The luminance (Y; gray-scale) signal and modulated chrominance (C; color) information are carried on separate synchronized signal and ground pairs.

In composite video, the luminance signal is low-pass filtered to prevent crosstalk between high-frequency luminance information and the color sub-carrier. S-Video separates the two, and detrimental low-pass filtering is unnecessary. This increases bandwidth for the luminance information, and also subdues the color crosstalk problem. The infamous dot crawl is eliminated. This means that S-Video leaves more information from the original video intact, thus having a much-improved image reproduction compared to composite video.

Due to the separation of the video into brightness and color components, S-Video is sometimes considered a type of component video signal, although it is also the most inferior of them, quality-wise, being far surpassed by the more complex component video schemes (like RGB). What differentiates S-Video from these higher component video schemes is that S-Video carries the color information as one signal.

S-Video Modes

S-Video, as most commonly implemented, carries 480i or 576i resolution video, i.e. standard definition video.

What is the life expectancy of S-Video?

S-Video is commonly used throughout the world. It is found on consumer TVs, DVD players, high-end video cassette recorders, Digital TV receivers, DVRs, and game consoles. Almost all TV-out connectors on graphics cards can support S-video. But due to a lack of bandwidth, S-Video connections are generally not considered suitable for high-definition video signals and as high definition becomes more available in sources and devices, it will reqire the component, dvi and hdmi cables.