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Component video is ananalog video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video (CAV) information that istransmitted or stored as three separate signals. Component video can be contrasted withcomposite video in which all the video information is combined into a single signal that is used inanalog television. Like composite, component cables do not carryaudio and are often paired withaudio cables.
When used without any other qualifications, the termcomponent video usually refers to analogYPBPR component video withsync onluma (Y) found on analoghigh-definition televisions and associated equipment from the 1990s through the 2000s when they were largely replaced withHDMI and other all-digital standards. Component video cables and theirRCA jack connectors on equipment are normally color-coded red, green and blue, although the signal is not inRGB. YPbPr component video can belosslessly converted to the RGB signal that internally drives the monitor; the encoding is useful as the Y signal will also work on black and white monitors.
Reproducing a video signal on a display device (for example, acathode-ray tube; CRT) is a straightforward process complicated by the multitude of signal sources.DVD,VHS, computers and video game consoles all store, process and transmit video signals using different methods, and often each will provide more than one signal option. One way of maintaining signal clarity is by separating the components of a video signal so that they do not interfere with each other. A signal separated in this way is called "component video".S-Video,RGB andYPBPR signals comprise two or more separate signals and thus are all component-video signals. For most consumer-level video applications, the common three-cable system using BNC or RCA connectorsanalog component video was used. Typical formats are480i (480 lines visible, 525 full for NTSC) and576i (576 lines visible, 625 full for PAL). Forpersonal computer displays the 15-pin DIN connector (IBM VGA) provided screen resolutions including 640×480, 800×600, 1024×768, 1152×864, 1280×1024.
The various RGB (red, green, blue) analog component video standards (e.g., RGBS, RGBHV, RGsB) use no compression and impose no real limit oncolor depth or resolution, but require largebandwidth to carry the signal and contain a lot ofredundant data since each channel typically includes much of the same black-and-white image. Early personal computers such as theIBM PS/2 offered this signal via aVGA port. Many televisions, especially in Europe, can utilize RGB via theSCART connector.[citation needed]
In addition to the red, green and blue color signals, RGB requires two additional signals to synchronize the video display. Several methods are used:
Composite sync is common in the European SCART connection scheme (using pins 17 [ground] and 19 [composite-out] or 20 [composite-in]). RGBS requires four wires – red, green, blue and sync. If separate cables are used, the sync cable is usually colored yellow (as is the standard for composite video) or white.
Separate sync is most common withVGA, used worldwide for analogcomputer monitors. This is sometimes known as RGBHV, as the horizontal andvertical synchronization pulses are sent in separate channels. This mode requires five conductors. If separate cables are used, the sync lines are usually yellow (H) and white (V), yellow (H) and black (V), or gray (H) and black (V).
Sync on Green (SoG) is less common, and while some VGA monitors support it, most do not.Sony is a big proponent of SoG, and most of their monitors (and theirPlayStation line of video game consoles) use it. Like devices that use composite video or S-video, SoG devices require additional circuitry to remove the sync signal from the green line. A monitor that is not equipped to handle SoG will display an image with an extreme green tint, if any image at all, when given a SoG input.
Sync on red and sync on blue are even rarer than sync on green and are typically used only in certain specialized equipment.
Sync on composite, not to be confused with composite sync, is commonly used on devices that output both composite video and RGB over SCART. The RGB signal is used for color information, while the composite video signal is only used to extract the sync information. This is generally an inferior sync method, as this often causes checkerboards to appear on an image, but the image quality is still much sharper than standalone composite video.
Sync on luma is much similar to sync on composite but uses the Y signal from S-Video instead of a composite video signal. This is sometimes used on SCART since both composite video and S-Video luma ride along the same pins. This generally does not suffer from the same checkerboard issue as sync on composite, and is generally acceptable on devices that do not feature composite sync, such as the Sony PlayStation and some modded Nintendo 64 models.
Further types of component analog video signals do not use separate red, green and blue components but rather a colorless component, termedluma, which provides brightness information (as in black-and-white video). This combines with one or more color-carrying components, termedchroma, that give only color information. Both theS-Video component video output (two separate signals) and theYPBPR component video output (three separate signals) seen on DVD players are examples of this method.
Converting video into luma and chroma allows forchroma subsampling, a method used byJPEG andMPEG compression schemes to reduce the storage requirements for images and video (respectively).
Many consumer TVs, DVD players, monitors, video projectors and other video devices at one time used YPBPR output or input.
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.
Component video requires an extrasynchronization signal to be sent along with the video.Component video sync signals can be sent in several different ways:
Digital component video makes use of single cables with signal lines/connector pins dedicated to digital signals, transmitting digital color space values allowing higher resolutions up to1080p.[1]
RGB component video has largely been replaced by modern digital formats, such asDisplayPort orDigital Visual Interface (DVI) digital connections, while home theater systems increasingly favorHigh-Definition Multimedia Interface (HDMI), which support higher resolutions,[2] higher dynamic range, and can be made to supportdigital rights management. The demise of analog is largely due to screens moving to large flat digital panels as well as the desire for having a single cable for both audio and video, but also due to a slight loss of clarity when converting from a digital media source to analog and back again for a flat digital display, particularly when used at higher resolutions where analog signals are highly susceptible to noise.
Examples of international component video standards are:
In a composite signal, such asNTSC,PAL orSECAM, theluminance (Y) andchrominance (C) signals are encoded together into one signal. When the color components are kept as separate signals, the video is called component analog video (CAV), which requires three separate signals: the luminance signal (Y) and the color difference signals (R-Y andB-Y).
Since component video does not undergo the encoding process, the color quality is noticeably better than composite video.[3]
Component video connectors are not unique in that the same connectors are used for several different standards; hence, making a component video connection often does not lead to a satisfactory video signal being transferred. Many DVD players and TVs may need to be set to indicate the type of input/output being used, and if set incorrectly the image may not be properly displayed.Progressive scan, for example, is often not enabled by default, even when component video output is selected.