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Reprinted from Wikipedia
Three RCA cables are often used to carry analog component video
Component video is a type of analog video information that is transmitted or stored as two or more separate signals. Component video can be contrasted with composite video (such as NTSC or PAL) in which all the video information is combined into a single signal such as a TV broadcast. Currently, component video connections are being rivaled by digital DVI and HDMI interfaces.
Analog video signals (also called components) must provide information about the amount of red, green, and blue to create a television image. The simplest type, RGB, consists of three discrete red, green and blue signals sent down three coaxial cables. There are a number of schemes which vary according to how synchronization is handled. If a synchronisation signal is sent on the green channel, it is called sync-on-green. Some schemes use a separate sync channel, for instance the European SCART connection scheme in which the video signal occupies four (R,G,B + sync) of the 21 pins in the interface. SVGA, another RGB scheme, is used worldwide for computer monitors (this is sometimes known as RGBHV, as the horizontal and vertical synchronisation pulses are sent on separate lines).
An alternative type of componentization does not use R,G,B components but rather a colorless component, termed luminance combined with one or more color-carrying components, termed chrominance, that give only color information. Multiple chrominance channels allow for more precision and speed in mapping the RGB colour space. This componentization scheme is a transformation (in some cases linear, in others not) of the sRGB color space. This type of signal is usually what is meant when people talk of component video today. The most common variant, the Component Video port found on many consumer DVD players, plasma displays, video projectors and the like, uses the [[YPbPr]] format of color coding. Other three-wire-variants which once were used in professional equipment were transferring formats like YUV (PAL) and YIQ (NTSC), but never [[YCbCr]] since this is a digital-only color coding format, namely the digital child of the analog [[YPbPr]].
In component video systems, additional synchronization signals may need to be sent along with the images. The synchronization signals are commonly transmitted on one or two separate wires, or embedded in the blanking period of one or all of the components. In computing, the common standard is for two extra wires to carry the horizontal and vertical components ('separate syncs'), whereas in video applications it is more usual to embed the sync signal in the Y component ('sync on luminance').
S-Video is another type of component video signal (transferring YUV when used for PAL video and YIQ when used for NTSC video), because the luminance (Y) and chrominance (UV or IQ) signals are transmitted on separate wires. This connection type, however, cannot produce high definition pictures with more than 480 interlaced lines of video for NTSC or more than 576 lines of interlaced video for PAL.
Component video is capable of producing signals such as 480p, 576p, 720p, 1080i, and 1080p, but, according to some, digital connections such as DVI (video only) and HDMI (which can also include up to 8 channels of audio) generally give better results at the higher resolutions (up to 1080p). HDMI also includes both a video and audio signal in a single cable.
Examples of international component video standards are:
- RS-170 RGB (525 lines, based on NTSC timings, now EIA/TIA-343)
- RS-343 RGB (525, 625 or 875 lines)
- STANAG 3350 Analogue Video Standard (NATO military version of RS-343 RGB)
The digital component video is sometimes referred to as 4:2:2. This means that for every 4 pixels of luminance (Y) information, only 2 pixels of Cb (blue-luminance signal), and 2 pixels of Cr (red-luminance signal) are encoded. This is the scheme used for the DVD format. The numbers also represent the relative number of bits (but not the actual number) used to carry the three pieces of information at each pixel. The colour information is spread across the pixels it represents.
Another scheme encountered will be 4:1:1. This is the scheme used on the (digital) NTSC version of the DV (and hence miniDV) tape formats for camcorder use. In this case for every 4 pixels of luminance, only 1 pixel of the Cb and Cr color deviation information is encoded for each line.
To provide apparent confusion, the (digital) PAL version of the DV and miniDV tape format use 4:2:0 which would appear to suggest the absence of the Cr signal altogether. In fact, the system takes advantage of features of the PAL colour system, and encodes 2 pixels of Cb colour deviation for every 4 luminance pixels on odd lines only. On even lines, 2 pixels of Cr colour deviation are encoded for every 4 luminance pixels. In each case the missing information is recovered from the previous line (and is thus closer to the French SECAM system than PAL). This doubles the horizontal resolution but halves the vertical resolution. This is acceptable, because the PAL analogue colour system does in fact have half the vertical resolution of the NTSC system.
The settings on many DVD players and TVs may require that you designate the type of input/output being used, or the image may not be properly displayed. Progressive scan is often not enabled by default, even when component video output is selected.
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