Composite video adapts the format of an analog picture signal which is then combined with sound signals and subsequently modulated through an R F Carrier. It is a composite signal from three different sources called the Y, U and V, which are combined with sync pulses. Y represents luminance; U and V carry the hue and saturation, which together constitutes the chrominance. So, U and V together carry the information on the color signals. Composite video is also often called the CVBS, which is an abbreviation for Colour, Video, Blank and Sync.
S-video is known as "separate video" and sometimes also wrongly addressed as the "super video". This is also a video analog signal that carries the information in two different signals, namely the chroma, which means colour; and luma, which means luminance. It carries standard definition video in a single cable, and does not combine it with audio signals. Both S-video and Composite Video are different from each other in various aspects.
edit History and Evolution
Composite video was extensively used in the 1980s, in older versions of game consoles, VCRs and television sets. In the year 1987, the S-Video cable standard was used for the first time in JVC's S-VHS. In the late 1990s larger television sets started incorporating S-Video, making it compatible with video game consoles, DVD players and satellite receivers.
The cost of installing composite video is far cheaper than the more advanced S- Video. The cables and adapters required for installing the latter, are substantially dearer.
edit Functional Differences and Picture Quality
Composite video is an analog signal, and carries the video or picture through a single, low quality signal. In comparison, S-video carries the picture through two signals, namely the chroma (colour) and luma (luminance). This video signal is of far better quality than what composite video has to offer. In composite video, the luminance signal is low pass filtered to prevent any cross talk between the color sub carrier and the luminance information. This luminance information is essentially high frequency. However, S-video keeps the two signals separate, so that this act of low pass filtering is not required. This automatically provides a wider bandwidth for luminance and also brings down the intensity of the colour cross talk issue. This helps in offering better picture clarity by keeping the information from the original video source intact.
edit Composite and S-video Connectors
Both S-video and composite video depend on analog based video signals. Both of them work on PAL, NTSC, and SECAM coding standards. However, their connectors are different from each other.
S-video signal generally uses a cable with 4-pin mini-DIN connector which is somewhat similar to the regular mini-DIN cables. Alternatively, simple cables can also be used, but they do not offer superior picture quality. The prices of connectors are pretty reasonable, however the quality of the pins are weak and may bend with extensive usage. Before the advent of these cables, simple plugs capable of carrying S Video signals were used for the same purpose.
Composite video, on the other hand, uses typical yellow RCA connector or a 1/8 inch jack plug, especially when used in consumer durables. When the same signal is used in gaming devices, there is a single composite output cable with 4 connectors.
There are special cables that can connect to an S-video output jack (for example, from a laptop) and feed the signal to a TV that has a composite input port.
Initially, composite video was used in larger television sets and earlier versions of VCRs. This was steadily replaced by S-Video, due to its better picture quality , It is being extensively used as a popular alternative for televisions, high end VCD players, video game consoles and graphic cards. Though composite video offers good signals, S-video is more popular for its better picture clarity.