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Separate Video, more commonly known as S-Video and Y/C, is often referred to by JVC (who introduced the DIN-connector pictured) as both an S-VHS connector and as Super Video. It is an analog video transmission scheme, in which video information is encoded on two channels: luma (luminance, intensity, "Y") and chroma (colour, "C"). This separation is in contrast with lower-quality composite video, in which all video information is encoded on one channel, and higher-quality component video, in which video information is encoded on three channels. S-Video carries standard definition video (typically at 480i or 576i resolution), but does not carry audio on the same cable.
The four-pin mini-DIN connector (shown at right) is the most common of several S-Video connector types. Other connector variants include seven-pin locking "dub" connectors used on many professional S-VHS machines, and dual "Y" and "C" BNC connectors, often used for S-Video patch panels. Early Y/C video monitors often used phono (RCA connector) that were switchable between Y/C and composite video input. Though the connectors are different, the Y/C signals for all types are compatible.
S-Video, with its two signals for video, is a compromise in terms of quality and convenience between composite video with one, and three-wire (or more) component video schemes. Using two video lines will, for example, use two inputs of video processing Integrated Circuits where two composite video inputs could have been accommodated, e.g. in the TVP5154A.
Compared with component video schemes where separate Red, Green and Blue (or luminance and two colour-difference signals) are given their own cables, S-Video is:
- poorer quality, because the colour information encoding (with a subcarrier frequency of perhaps 3.57 to 4.43 Megahertz, depending on standard) limits the maximum theoretical chrominance bandwidth possible, although the signal source may have its own limitations. [comment mention 4:2:2 etc?]
- Carrying the colour information as one signal means that the colour has to be encoded in some way, and as such, NTSC, PAL, and SECAM signals are all decidedly different through S-Video. Thus, for full compatibility, the connected devices not only have to be S-Video compatible, but also compatible in colour encoding. In addition, S-Video suffers from reduced colour resolution. NTSC S-Video colour resolution is typically 120 lines horizontal (approximately 160 pixels edge-to-edge), versus 250 lines horizontal for the Rec. 601-encoded signal of a DVD, or 30 lines horizontal for standard VCRs.
Compared with Digital video systems, S-Video:
- requires less processing to feed analog televisions but more complex processing (and hence quality loss) to interact with digital systems, including computer storage and processing, as well as most modern televisions.
- Depth of colour depends in S-Video, and other analog video systems, on the Signal-to-noise ratio, but in digital systems it depends on the number of bits allocated (e.g. 2 bits to each colour-difference signal in 8-bit ITU-R BT.656 may mean S-Video has more realistic colours, even if the resolution and noise performance is worse than the digital system).
ABOUT AUDIO VIDEOEdit
In 1987, JVC's release of S-VHS introduced the S-Video cable standard. With these cables, the S-VHS video cassette systems play with their full potential, completing the improved definition and resolution into a compatible TV. Due to low market penetration of television sets and video devices equipped with S-Video ports, the format failed to become a mainstream image standard and remained in the niche high-end home cinema market.
In the late 1990s, big-screen television sets began shipping with S-Video option in input ports, thus increasing the number of supportable electronic devices such as DVD players, satellite receivers, and video game consoles. The format gained some popularity as a better alternative to composite video inputs. S-Video was also adopted in the graphics card market in the early 2000s to provide a video output from computers to TVs.
The introduction of component video, offering a better image and backward compatibility, replaced S-Video as the default alternative to the composite video on many high-end cards. Laptops commonly included an S-Video output, but since the mid-2000s, this function on new models has been replaced by DisplayPort or HDMI outputs.
Etymologically, the word S-Video has several denotations: Super Video (complementing Super VHS), Separated Video, and S-VHS cable.