S-Video (Separated Video often referred to as "Super-Video") is a video interface standard found on most audiovisual equipment today. S-Video is a step up from standard composite video, which uses a yellow RCA jack and RCA cable, while S-Video utilizes a mini-DIN plug and S-Video cable. When connecting equipment that has both options, one can choose to use S-Video.
S-Video connectors are four or seven-pin mini-DIN plugs. To ensure correct orientation of the pins the connector has a notched, metal sleeve that must align properly with the female jack before it can be inserted. S-Video cables are more expensive than RCA cables and are not always included with products, but can be purchased separately.
S-Video delivers a superior picture to composite video by avoiding some of the processing that composite video requires. A video signal is a mixture of two separate data streams: brightness or luminescence, known as the Y stream, and chrominance or color, known as the C stream. The C signal carries values for red and blue, while green values are deduced. Hence, RGB, or red, green and blue, occupies just two data streams within the C signal.
In the original analog video standard in use since the 1950s, the Y/C signals are compressed into a single stream, passed through a single RCA wire, and decoded by a television filter into its Y and C elements. Although enduring and convenient, the process of compressing and decoding video signals results in some degradation of data integrity. This translates directly to the screen in loss of picture quality. S-Video preserves greater signal integrity by housing two wires in a single sheath, dedicating one to each of the Y and C signals and eliminating much of the filtering process. Greater preservation of signal integrity results in a sharper picture.
As with composite video, S-Video only transfers visual data. Audio cables are required for transferring sound. These can be standard RCA cables, or in the case of high-end CD and DVD players, digital audio connections might be preferred.
There are people who claim to see no appreciable difference between composite video and S-Video, while others believe the transition from composite to S-Video is akin to getting a system upgrade for the cost of a cable. Some of the confusion might lie in the fact that aside from HDTV, television signals and VHS tapes are encoded with composite video. DVDs, however, are encoded using a higher standard, so an increase in picture quality should be more evident when using S-Video to view DVDs. But before running out for S-Video cables, check to see if your equipment supports either component video or High-Definition Multimedia Interface (HDMI), both of which are superior to S-Video.