Component video
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Component video is a type of video information that is transmitted or stored as two or more separate signals (as opposed to composite video, such as NTSC or PAL, which is a single signal).
Most component video systems are variations of the red, green and blue signals that make up a television image. The simplest type, RGB, consists of the three discrete red, green and blue signals sent down three wires, usually accompanied by one or two synchronising signals on additional wires. This type is commonly used in Europe through SCART connectors. Outside Europe, it is generally used for computer monitors, but rarely for TV-type applications.
Another type consists of R-Y, B-Y and Y, delivered the same way. This is the signal type that is usually meant when people talk of component video today. Y is the luminance channel, B-Y (also called U) is the blue component minus the luminance information, and R-Y (also called V) is the red component minus the luminance information. See YUV and YIQ for more information on this color space.
Component digital video signals are sometimes referred to as 4:2:2, meaning that for every 4 bits that are dedicated to the Y component, 2 bits each are dedicated to the U & V components on both even (second 2) and odd lines (third 2) of the image. The luminance or Y channel carries most of the image detail and is, therefore, assigned more bits. Another common method, 4:2:0, is used on DVDs. In this case, only the even lines have color information; for the odd lines it is approximated by interpolation. This signal is often converted to 4:2:2 inside the player before it is sent out to other devices.
S-Video is also considered a component signal, because the luminance and chrominance (color) signals are transmitted on separate wires.
Examples of international component video standards are: