Composite

Composite video is the format of an analog television (picture only) signal before it is combined with a sound signal and modulated onto an RF carrier. Composite video is often designated by the CVBS acronym, meaning any of "Color, Video, Blank and Sync", "Composite Video Baseband Signal", "Composite Video Burst Signal", or "Composite Video with Burst and Sync". It is a composite of three source signals called Y, U and V (together referred to as YUV) with sync pulses. Since Y is a baseband signal and UV has been mixed with a carrier, this addition is equivalent to frequency-division multiplexing. Composite video can easily be directed to any broadcast channel simply by modulating the proper RF carrier frequency with it. Most analog home video equipment records a signal in (roughly) composite format: LaserDiscs store a true composite signal, while VHS tapes use a slightly modified composite signal. In typical home applications, the composite video signal is typically connected using an RCA jack, normally yellow, which is often accompanied with red and white for right and left audio channels respectively. In Europe, SCART connections are often used instead of RCA jacks (and to a lesser extent, S-Video), so where available, RGB is used instead of composite video with computers, video game consoles, and DVD players. Some devices that connect to a TV, such as VCRs, older video game consoles and home computers of the 1980s, naturally output a composite signal. VCRs and similar devices already have to deal with RF signals in their tuners, so the modulator is located inside the box. The process of modulating RF with the original video signal, and then demodulating the original signal again in the TV, introduces several losses. RF is also "noisy" because of all of the video and radio signals already being broadcast, so this conversion also typically adds noise or interference to the signal as well. Almost all modern video equipment has at least composite connectors, so this typically isn't a problem; however, older video equipment and some very low-end modern televisions have only RF input, which essentially used the antenna jack, while RF modulators are no longer common, they are still widely available to translate baseband signals for older equipment. However, just as the modulation and demodulation of RF loses quality, the mixing of the various signals into the original composite signal does the same, causing a checkerboard video artifact known as dot crawl. Dot crawl is an infamous defect that results from crosstalk due to the inter-modulation of the chrominance and luminance components of the signal. This has led to a proliferation of systems such as S-Video and component video to separate out one or more of the mixed signals. When used for connecting a video source to a video display where both support 4:3 and 16:9 display formats, the PAL television standard provides for signaling pulses that will automatically switch the display from one format to the other. The Composite video connection supports this operation. Since many TV screens have cropped part of the output of a composite video signal, extensions have been implemented by taking advantage of this unseen plane of output, and examples of these extensions include closed captioning, digital information regarding the show title, etc. Other extensions to the standard include S-video; S-video is an extension to the standard because it uses 2 parallel monochrome composite video signals, one for luminance and one for chroma or the colour.