Composite video

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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. In contrast to component video (YPbPr) it contains all required video information, including colors in a single line-level signal. Like component video, composite-video cables do not carry audio and are often paired with audio cables.

Composite video is often designated by the CVBS initialism, meaning "Composite Video, Blanking, and Sync."

It is usually in standard formats such as NTSC, PAL, and SECAM.

Contents

Signal components

It is a composite of three source signals called Y, U and V (together referred to as YUV) with sync pulses. Y represents the brightness or luminance of the picture and includes synchronizing pulses, so that by itself it could be displayed as a monochrome picture. U and V represent hue and saturation or chrominance; between them they carry the color information. They are first modulated on two orthogonal phases of a color carrier signal to form a signal called the chrominance. Y and UV are then combined. Since Y is a baseband signal and UV has been mixed with a carrier, this addition is equivalent to frequency-division multiplexing.

Signal modulation

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 record a signal in (roughly) composite format: LaserDiscs store a true composite signal, while VHS tapes use a slightly modified composite signal. These devices then give the user the option of outputting the raw signal, or modulating it onto a VHF or UHF frequency to appear on a selected TV channel.

Standard connectors

In typical home applications, the composite video signal is typically connected using an RCA jack (called a phono plug in the UK), normally yellow (often accompanied with red and white for right and left audio channels respectively). BNC connectors and higher quality co-axial cable are often used in more professional applications.

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